KR20200096537A - Video decoding method and apparatus thereof, and video encoding method and apparatus thereof - Google Patents

Abstract

A scan area including all effective transform coefficients in the current block is determined, information on transform coefficients in the scan area is scanned according to a predetermined scan order, and binary arithmetic decoding is performed based on information on the scanned transform coefficients. To generate binary arithmetic-decoded information, inverse binarization is performed on the binary arithmetic-decoded information to obtain information on transform coefficients of the current block, and inverse quantization based on information on transform coefficients of the current block And a video decoding method of performing inverse transformation to generate a residual block of a current block, and reconstructing the current block based on the generated residual block. According to the disclosed video decoding method, the binary arithmetic decoding may be performed using a context model determined based on at least one of a size and shape of a current block.

Description

Video decoding method and apparatus thereof, and video encoding method and apparatus thereof

It relates to a video decoding method and video encoding. In detail, it relates to entropy decoding and entropy encoding.

With the development and dissemination of hardware capable of reproducing and storing high-resolution or high-definition video content, the need for a video codec for effectively encoding or decoding high-resolution or high-definition video content is increasing. According to the existing video codec, video is encoded according to a limited coding method based on coding units having a tree structure.

Image data in the spatial domain is transformed into coefficients in the frequency domain using frequency transformation. The video codec divides an image into blocks of a predetermined size in order to perform frequency transformation quickly, performs DCT transformation for each block, and encodes frequency coefficients in units of blocks. Compared to image data in the spatial domain, coefficients in the frequency domain are more easily compressed. In particular, since an image pixel value in a spatial domain is expressed as a prediction error through inter prediction or intra prediction of a video codec, a lot of data may be converted to zero when frequency conversion is performed on the prediction error. The video codec reduces the amount of data by replacing continuously and repeatedly generated data with data of a small size.

According to various embodiments, entropy encoding and decoding efficiency may be improved by determining a scan area based on various factors, scanning information on coefficients, and performing binary arithmetic encoding/decoding based on binarization/inverse binarization and context models. .

According to various embodiments, in the process of entropy encoding and decoding a transform coefficient, a rectangular scan area including all effective transform coefficients in the current block is determined, and effective transform coefficients in the rectangular scan area are scanned to reduce unnecessary scans, and interrelationships are possible. Entropy encoding and decoding efficiency can be improved by scanning adjacent effective transform coefficients. Entropy encoding and decoding efficiency can be improved by determining a context model for the syntax for a transform coefficient based on various factors. In particular, entropy encoding and decoding efficiency can be improved by determining a context model for a syntax element related to a transform coefficient in consideration of at least one of a block size and a block shape. In addition, entropy encoding and decoding efficiency can be improved by determining a context model for a syntax regarding a transform coefficient in consideration of a scan area. In addition, without independently encoding and decoding information on horizontal coordinates specifying the scan area and information on vertical coordinates, information on coordinates specifying the scan area is provided in consideration of the relationship between horizontal coordinates and vertical coordinates. By encoding and decoding, the encoding and decoding efficiency can be improved.

A computer-readable recording medium in which a program for implementing a method according to various embodiments is recorded may be included.

Of course, the technical problems of various embodiments are not limited to the features mentioned above, and other technical problems that are not mentioned will be clearly understood by those skilled in the art from the following description.

The technical problems of the present invention are not limited to the features mentioned above, and other technical problems that are not mentioned will be clearly understood by those skilled in the art from the following description.

A video decoding method according to various embodiments may include determining a scan area including all effective transform coefficients in a current block; Scanning information on transform coefficients in the scan area according to a predetermined scan order; Generating binary arithmetic-decoded information by performing binary arithmetic decoding based on the information on the scanned transform coefficients; Obtaining information on transform coefficients of the current block by performing inverse binarization on the binary arithmetic-decoded information; Generating a residual block of the current block by performing inverse quantization and inverse transformation based on information on the transform coefficients of the current block; And restoring a current block based on the generated residual block,

The binary arithmetic decoding may be performed using a context model determined based on at least one of the size and shape of the current block.

In the rectangular scan area, all effective transform coefficients in the current block may be included, and the remaining areas in the current block excluding the rectangular scan area may include only 0, not the effective transform coefficient.

The scan area is a rectangular scan area,

The step of determining the scan area

Obtaining information about coordinates specifying the rectangular scan area from a bitstream; And

Determining a rectangular scan area of a transform coefficient in a current block based on information on coordinates specifying the rectangular scan area,

The horizontal coordinates specifying the rectangular scan area represent coordinates of an effective transform coefficient pixel located at the rightmost position in the current block,

The vertical coordinates specifying the rectangular scan area represent coordinates of an effective transform coefficient pixel located at the bottom of the current block,

Flag information indicating whether information on coordinates specifying the rectangular scan area includes a difference between coordinate values in a horizontal direction and a vertical direction specifying the rectangular scan area is included in the bitstream,

Information on coordinates specifying the rectangular scan area is

When it is indicated that the flag information includes a difference between coordinate values in a horizontal direction and a vertical direction specifying the rectangular scan area,

Information indicating coordinates in one direction among horizontal coordinates for a pixel of an effective transform coefficient positioned at the rightmost side in the current block and vertical coordinates for a pixel of an effective transform coefficient positioned at the bottom of the current block; and It may include information indicating a difference between the coordinates for one direction and the coordinates for the other direction.

The size of the current block is determined based on at least one of a minimum value and a maximum value of the height and width of the current block,

The shape of the current block may be determined based on whether the height and width of the current block are the same, the height is greater than the width, or the width is greater than the height.

Determining a scan area including all transform coefficients in the current block,

If the height and width of the current block are different from each other, generating a swapped current block by swapping horizontal and vertical coordinates representing positions of transform coefficients in the current block; And

And determining a scan area including all effective transform coefficients in the swapped current block,

The step of determining a scan area including all effective transform coefficients in the swapped current block,

When the height and width of the current block are different from each other, horizontal coordinates and vertical coordinates specifying the scan area are changed (swap), and based on the swapped horizontal coordinates and vertical coordinates, the It may include the step of determining the scan area.

The bitstream includes information indicating whether flag information indicating whether a difference between coordinate values in a horizontal direction and a vertical direction specifying a scan area is included, and information about coordinates specifying the scan area,

The information on coordinates specifying the scan area includes information on horizontal coordinates and information on vertical coordinates specifying the scan area,

When it is indicated that the flag information includes a difference between coordinate values in a horizontal direction and a vertical direction specifying the rectangular scan area,

The information on the horizontal coordinates specifying the scan area and the information on the vertical coordinates are information indicating coordinates related to one of the horizontal coordinates and vertical coordinates, and the coordinates related to the one direction and the other directions. It contains information indicating the difference (difference) between the relative coordinates,

The step of determining a scan area including all effective transform coefficients in the swapped current block,

If the height and width of the current block are different,

Swapping horizontal coordinates and vertical coordinates obtained from information on coordinates specifying the scan area, and determining the scan area based on the swapped horizontal coordinates and vertical coordinates It may include steps.

Among the context models, the context model related to flag information of the current transform coefficient includes the size of the scan area, the number of coefficients scanned before the current transform coefficient according to a predetermined scan order within the scan area, and the scan area. It may be further determined based on at least one of a relative position of the current transform coefficient and whether the current effective transform coefficient is a first transform coefficient among transform coefficients scanned according to the predetermined scan order in the scan area.

When the context model for the flag information of the current transform coefficient is determined based on the size of the scan area and the number of flag information of the transform coefficient scanned before the current coefficient according to the predetermined scan order,

Context model regarding flag information of the current transform coefficient based on a predetermined context offset corresponding to a case where the number of flag information of the transform coefficient scanned before the current coefficient is smaller than a predetermined value based on the size of the scan area Can be determined.

When the context model for the flag information of the current transform coefficient is determined based on the relative position of the current transform coefficient in the scan area,

A context model relating to the current transform coefficient may be determined based on a predetermined context offset corresponding to a case where the coordinate of the current transform coefficient is smaller than a predetermined value based on a coordinate specifying the position of the scan area.

Information about the transformation coefficient,

Flag information indicating whether the transform coefficient is greater than a predetermined value, remaining level information regarding the absolute value of the effective transform coefficient, code information of the transform coefficient, and binarization used for inverse binarization of the transform coefficient It includes at least one of parameter information,

The predetermined value may be at least one of 0, 1, and 2.

A video encoding method according to various embodiments includes obtaining transform coefficients of a current block; Determining a scan area including all effective transform coefficients in the current block; Scanning information about transform coefficients included in the scan area according to a predetermined scan order and performing binarization based on the information about the scanned transform coefficients to generate binarized information; Generating entropy-encoded information by performing binary arithmetic encoding on the binarized information; And generating a bitstream including the entropy-encoded information,

The binary arithmetic encoding may be performed using a context model determined based on at least one of the size and shape of the current block.

The scan area is a rectangular scan area,

The horizontal coordinates specifying the rectangular scan area represent coordinates of an effective transform coefficient pixel located at the rightmost position in the current block,

The vertical coordinates specifying the rectangular scan area represent coordinates of an effective transform coefficient pixel located at the bottom of the current block,

The flag information indicating whether the information on coordinates specifying the rectangular scan area and the coordinates specifying the rectangular scan area includes a difference between coordinate values in the horizontal direction and the vertical direction specifying the rectangular scan area is the bit Is included in the stream,

When it is indicated that the flag information includes a difference between coordinate values in a horizontal direction and a vertical direction specifying the rectangular scan area,

The information on the coordinates specifying the rectangular scan area is a horizontal coordinate for a pixel of an effective transform coefficient positioned at the rightmost position in the current block and a vertical direction for a pixel of an effective transform coefficient positioned at the bottom of the current block. It may include information indicating a coordinate of one direction among the coordinates and information indicating a difference between the coordinates of the one direction and the coordinates of the other direction.

A video decoding apparatus according to various embodiments determines a scan area including all effective transform coefficients in a current block, scans information on transform coefficients in the scan area according to a predetermined scan order, and scans the scanned transform coefficients. An entropy decoder for generating binary arithmetic-decoded information by performing binary arithmetic decoding on the basis of the information on, and obtaining information on transform coefficients of the current block by performing inverse binarization on the binary arithmetic-decoded information ; And

Inverse quantization and inverse transformation are performed based on information on the transform coefficients of the current block to generate a residual block of the current block, and an image restoration unit reconstructing the current block based on the generated residual block,

The binary arithmetic decoding may be performed using a context model determined based on at least one of the size and shape of the current block.

A video encoding apparatus according to various embodiments may obtain transform coefficients of a current block, determine a scan area including all effective transform coefficients in the current block, and determine information on transform coefficients included in the scan area. Entropy encoding that scans according to the scan order, performs binarization based on the information on the scanned transform coefficients to generate binarized information, and performs binary arithmetic coding on the binarized information to generate entropy-encoded information part; And a bitstream generator for generating a bitstream including the entropy-encoded information, wherein the binary arithmetic encoding is performed using a context model determined based on at least one of the size and shape of the current block. I can.

A computer-readable recording medium in which a program for implementing a method according to various embodiments is recorded may be included.

1A is a block diagram of a video decoding apparatus according to various embodiments.
1B is a flowchart of a video decoding method according to various embodiments.
1C is a block diagram of a video encoding apparatus according to various embodiments.
1D is a flowchart of a video encoding method according to various embodiments.
1E is a block diagram of an image decoder according to various embodiments.
1F is a block diagram of an image encoder according to various embodiments.
FIG. 2 is a diagram for describing a method of scanning an intra-block transform coefficient according to an exemplary embodiment.
3A is a diagram for describing a method of scanning an intra-block transform coefficient according to an exemplary embodiment.
3B is a diagram for describing an operation of determining a coefficient group (subblock) within a block and an operation performed for each coefficient group, according to an exemplary embodiment.
FIG. 4 is a diagram for describing a process of determining a context model for context-based binary arithmetic encoding and decoding information on transform coefficients, according to an embodiment.
FIG. 5 is a diagram for describing a process of determining a context model for context-based binary arithmetic encoding and decoding information on transform coefficients according to another embodiment.
6A is a diagram for explaining a horizontal-first zigzag scan sequence for scanning information on transform coefficients in a block, according to an exemplary embodiment.
6B is a diagram illustrating a vertical priority zigzag scan sequence for scanning information on transform coefficients in a block, according to an exemplary embodiment.
6C is a diagram for explaining a horizontal scan sequence for scanning information about transform coefficients in a block according to an embodiment.
6D is a diagram for describing a vertical scan sequence for scanning information on transform coefficients in a block according to an embodiment.
6E is a diagram for explaining a diagonal scan order for scanning information about transform coefficients in a block according to an embodiment.
7A is a diagram for explaining a process of changing a scan area by changing horizontal and vertical coordinates of transform coefficient pixels in a rectangular scan area according to an exemplary embodiment.
FIG. 7B is a diagram for explaining a process of changing a scan area by swapping coordinates in a horizontal direction and a vertical direction of transform coefficient pixels in the scan area according to another embodiment.
FIG. 8 is a diagram for describing a process of determining a context model for syntax element information of a transform coefficient in a current block based on at least one of a size of a current block and a shape of the current block, according to an embodiment.
9A to 9C are diagrams for explaining a residual encoding syntax structure according to an embodiment.
9D to 9F are diagrams for explaining a residual encoding syntax structure according to another embodiment.
10 illustrates a process in which at least one coding unit is determined by splitting a current coding unit according to an embodiment.
11 illustrates a process in which at least one coding unit is determined by splitting coding units having a non-square shape according to an embodiment.
12 illustrates a process in which a coding unit is split based on at least one of block type information and split type information, according to an embodiment.
13 illustrates a method of determining a predetermined coding unit among odd coding units, according to an embodiment.
14 illustrates an order in which a plurality of coding units are processed when a current coding unit is split to determine a plurality of coding units, according to an embodiment.
15 illustrates a process of determining that a current coding unit is divided into odd number of coding units when coding units cannot be processed in a predetermined order according to an embodiment.
16 illustrates a process in which at least one coding unit is determined by splitting a first coding unit according to an embodiment.
FIG. 17 illustrates that when a second coding unit of a non-square shape determined by splitting a first coding unit satisfies a predetermined condition, a form in which the second coding unit can be split is limited. .
FIG. 18 is a diagram illustrating a process in which a square type coding unit is divided when it is not possible to indicate that split type information is divided into four square type coding units, according to an embodiment.
19 illustrates that a processing order between a plurality of coding units may vary according to a splitting process of a coding unit, according to an embodiment.
FIG. 20 illustrates a process in which a depth of a coding unit is determined according to a change in a shape and size of a coding unit when a coding unit is recursively split to determine a plurality of coding units according to an embodiment.
21 illustrates a depth that may be determined according to a shape and size of coding units and a part index (hereinafter referred to as PID) for classifying coding units according to an embodiment.
22 illustrates that a plurality of coding units are determined according to a plurality of predetermined data units included in a picture, according to an embodiment.
23 illustrates a processing block that serves as a reference for determining an order of determining reference coding units included in a picture, according to an embodiment.

Hereinafter,'image' may represent a still image of a video or a moving picture, that is, the video itself.

Hereinafter, “sample” refers to data allocated to a sampling position of an image and to be processed. For example, pixels in an image of a spatial domain may be samples.

Hereinafter, the'Current Block' may mean a block of an image to be encoded or decoded.

1A is a block diagram of a video decoding apparatus according to various embodiments.

The video decoding apparatus 100 according to various embodiments may include an entropy decoding unit 105 and an image reconstruction unit 120.

The entropy decoding unit 105 may acquire syntax element information received from a bitstream and perform entropy decoding on the syntax element information. In this case, the syntax element information received from the bitstream may be information on various syntax elements related to an image.

The entropy decoder 105 may obtain syntax element information about a transform coefficient in a current block from a bitstream, and may entropy decode syntax element information about a transform coefficient in a current block. In this case, the current block may be a data unit that can be used in the process of encoding/decoding an image described with reference to FIGS. 10 to 23.

The entropy decoder 105 may obtain information about transform coefficients in the current block by scanning syntax element information about transform coefficients in the current block, which is entropy-decoded, according to a predetermined scan order. The predetermined scan order may be various scan orders in the reverse direction. Here, the reverse scan order may be an order of scanning from the lower right pixel in the block to the transform coefficient pixel at the upper left in the block. The order of scanning the transform coefficients from the upper left transform coefficient pixel to the lower right transform coefficient can be referred to as the forward scan order, and scan the transform coefficients in the order of the last transform coefficient located at the lower right to the upper left transform coefficient. If so, it may be referred to as a reverse scan order. The syntax element information about the transform coefficient in the current block may be flag information indicating whether the transform coefficient in the current block is greater than a predetermined value. In this case, the predetermined value may be an integer value greater than or equal to 0. For example, it may be 0, 1 or 2.

In addition, the syntax element information on the transform coefficient in the current block may be syntax element information indicating a remaining level absolute value. The residual level absolute value may mean a difference between the absolute value of the level of the transform coefficient and the absolute value of the base level. The absolute value of the base level may be determined based on syntax element information indicating whether the absolute value of the transform coefficient is greater than a predetermined value. For example, a flag indicating whether the absolute value of the transform coefficient is greater than 0 (or whether the transform coefficient is an effective transform coefficient; here, the effective transform coefficient means a transform coefficient whose absolute value is greater than 0.) The value of information (Greater than 0 flag or sig_coeff_flag; hereinafter referred to as GT0 flag) and flag information indicating whether it is greater than 1 (Greater than 1 flag or coeff_abs_level_greater1_flag; hereinafter referred to as GT1 flag) and whether it is greater than 2 The sum of the values of flag information indicated (Greater than 2 flag or coeff_abs_level_greater2_flag; referred to as GT2 flag) may be an absolute value of the base level. Here, when flag information indicating whether the absolute value of the transform coefficient is greater than a predetermined value is greater than a predetermined value, the value of the flag information may be 1, and when it indicates that it is less than a predetermined value, the flag information The value of may be 0. Meanwhile, some of the flag information related to the size of the transform coefficient may not be obtained from the bitstream. According to an embodiment, a flag indicating whether the size of the transform coefficient is greater than n (n is an integer) is GTn, a flag indicating whether the size of the transform coefficient is greater than (n+1) GT(n+1), and transform When a flag indicating whether the coefficient size is greater than (n+2) is GT(n+2), it is converted from the relatively smaller value of n or n+1 among the reference values of n, n+1 and n+2. Only flags indicating whether the absolute value of the coefficient is larger, that is, GTn and GT(n+1) are transmitted, and GT(n+2) may not be included in the bitstream.

For example, when the GT0 flag information and the GT1 flag information indicate that the absolute values of the transform coefficients are greater than 0 and 1, respectively, when the GT2 flag is not included in the bitstream, the entropy decoding unit 105 excludes the GT2 flag, Since the absolute value of the transform coefficient is greater than 1 by using only the GT0 flag information and the GT1 flag information, the remaining absolute value of the transform coefficient by subtracting 2 can be determined as the residual level absolute value of the transform coefficient.

When the GT0 flag information, the GT1 flag information, and the GT2 flag information indicate that they are greater than 0, 1, and 2, respectively, the entropy decoding unit 105 subtracts 3 from the absolute value of the transform coefficient because the absolute value of the transform coefficient is greater than 2. The absolute value can be determined as the absolute value of the residual level of the transform coefficient. That is, the residual level absolute value may represent an absolute value difference between a predetermined absolute value determined based on information indicating whether an absolute value of a transform coefficient is greater than a predetermined value and an absolute value of an effective transform coefficient. Entropy decoding unit 105 ) Acquires syntax element information received from the bitstream, performs binary arithmetic decoding on the syntax element information, and performs binary arithmetic decoding, inversely with respect to a bin string, which is an output generated by performing binary arithmetic decoding. Inverse binarization can be performed. The binary arithmetic decoding operation may be performed by the binary arithmetic decoding unit 110, and the inverse binarization operation may be performed by the inverse binarization unit 115.

The binary arithmetic decoder 110 may perform binary arithmetic decoding based on a predetermined context model on the syntax element information obtained from the bitstream. Here, the context model may be information on a probability of occurrence of a bin. The information on the probability of occurrence of a bin includes information (valMPS) indicating one symbol of the least propbable symbol (LPS), which is a symbol with a relatively low probability of occurrence among the two symbols 0 and 1, and the least probable symbol (MPS), which is a high symbol. It may include information on the probability of occurrence of one symbol. The probability of occurrence has a value between 0 and 1. Therefore, when the probability of one symbol among MPS and LPS is determined, the probability of occurrence of one symbol is determined because information about the probability of occurrence of another symbol is information about the probability of subtracting the probability of occurrence of a predetermined symbol from 1 If so, the binary arithmetic decoder 110 may determine the probability of occurrence of the remaining symbols. In this case, the probability of occurrence of one symbol determined first may be the probability of occurrence of a least probable symbol (LPS). Meanwhile, the occurrence probabilities of symbols corresponding to the index values may be determined in advance in the table, and the occurrence probability information on the symbol may be information indicating an index (pStateIdx) indicating the occurrence probabilities of symbols determined in the table.

The predetermined context model may be determined based on a bin index indicating a location of a bin, a probability of occurrence of a bin included in a block adjacent to a block including the bin, and various factors of the current block or the adjacent block.

Alternatively, the binary arithmetic decoder 110 may perform binary arithmetic decoding on the syntax element information acquired from the bitstream according to a bypass mode. In this case, the probability of generating 0 or 1 for the bin that is currently binary arithmetic decoding is fixed to 0.5, and based on this probability, binary arithmetic decoding may be performed on the syntax element information.

The inverse binarization unit 115 may perform inverse binarization on a bin string that is an output value generated by performing binary arithmetic decoding. The inverse binarization unit 115 may perform inverse binarization on an empty string based on an inverse binarization method corresponding to a predetermined binarization method. The predetermined binarization method may include a fixed length binarization method, a Rice binarization method, an Exponential-Golomb binarization method, and a Gollum-Rice binarization method. Alternatively, the predetermined binarization method may be a binarization method in which a first binarization method and a second binarization method are combined. For example, the inverse binarization unit 115 performs inverse binarization on a first bin string, which is a part of the empty string of the syntax element, based on the inverse binarization method corresponding to the first binarization method, and performs a second binarization, which is a part of the empty string of the syntax element. For an empty string, inverse binarization may be performed based on an inverse binarization method corresponding to the second binarization method. The part of the empty string may be a prefix or suffix of the empty string of the syntax element.

Both the binarization method and the inverse binarization method are related to a kind of code word that defines a 1:1 correspondence relationship of a binstring including at least one bin corresponding to the value of the syntax element. In terms of encoding, a binstring including at least one bin corresponding to a value of a syntax element is determined according to one of the aforementioned various binarization methods, and in terms of decoding, a syntax element corresponding to a binstring according to an inverse binarization method The value of can be determined. For example, when the empty string A corresponding to the value a of the syntax element (a is a real number) is determined according to a predetermined binarization/inverse binarization method, the process of determining the empty string A based on the value a of the syntax element is binarized. It is referred to as a process, and the process of determining the value a of the syntax element based on the binstring A may be referred to as an inverse binarization process. However, as described above, binarization and inverse binarization essentially define a mapping relationship between a value of a syntax element and a binstring, and it can be easily understood by those skilled in the art that binarization/inverse binarization are substantially the same.

The entropy decoder 105 may obtain information on transform coefficients in the current block by scanning syntax element information about transform coefficients in the current block according to a predetermined scan order and performing entropy decoding. The predetermined scan order may be an order according to a zigzag scan in the reverse direction or an order according to a diagonal scan in the reverse direction. This is not limited thereto, and the predetermined scan order may be various scan orders such as an order according to a horizontal scan in a reverse direction and a scan order according to a vertical scan. The predetermined scan order is the horizontal coordinate (e.g., x-coordinate (x is an integer) of the Cartesian coordinate system) of the effective transform coefficient pixel located at the rightmost position in the current block and the effective transform coefficient located at the bottom of the current block. It may be determined based on at least one of the vertical coordinates of the pixel (eg, y-coordinate (y is an integer) of a Cartesian coordinate system). For example, the entropy decoder 105 may determine a predetermined scan order based on the size of the horizontal coordinate value and the size of the vertical coordinate value. When the horizontal coordinate value is greater than the vertical coordinate value, the entropy decoder 105 may determine a reverse vertical scan order as a predetermined scan order. When the vertical coordinate value is greater than the horizontal coordinate value, the entropy decoder 105 may determine the reverse horizontal scan order as a predetermined scan order.

Alternatively, when the horizontal coordinate value is greater than the vertical coordinate value, the entropy decoder 105 may determine a vertical first zigzag scan order in the reverse direction as a predetermined scan order. Detailed contents of the vertical-first zigzag scan sequence will be described with reference to FIG. 6B. When the vertical coordinate value is greater than the horizontal coordinate value, the entropy decoder 105 may determine a horizontal first zigzag scan order in the reverse direction as a predetermined scan order. Details of the horizontal first zigzag scan order will be described with reference to FIG. 6A. When the vertical coordinate value is the same as the horizontal coordinate value, the entropy decoder 105 may determine one of a vertical first zigzag scan order and a horizontal first zigzag scan order in a predetermined scan order.

Alternatively, when the horizontal coordinate value is greater than the vertical coordinate value, the entropy decoder 105 may determine a horizontal first zigzag scan order in the reverse direction as a predetermined scan order. Meanwhile, when the horizontal coordinate value is not greater than the vertical coordinate value, the entropy decoder 105 may determine a vertical first zigzag scan order in the reverse direction as a predetermined scan order.

The entropy decoder 105 may determine a scan area including all effective transform coefficients in the current block before scanning information on the transform coefficient. In this case, all effective transform coefficients in the current block may be included in the scan area, and the remaining areas in the current block excluding the scan area may include only transform coefficients of 0, not effective transform coefficients. At this time, the scan area includes transform coefficients from the upper left of the scan area to the last effective transform coefficient (hereinafter referred to as the last effective transform coefficient) when scanned according to a predetermined forward scan order. It may be an area to do. In this case, the coordinates specifying the scan area may be the coordinates of the last scanned effective transform coefficient pixel.

The entropy decoder 105 may obtain information about coordinates representing the last effective transform coefficient from the bitstream, and determine a scan area based on information about coordinates representing the last effective transform coefficient. For example, the entropy decoder 105 may obtain information indicating a horizontal coordinate value of the last effective transform coefficient and information indicating a vertical coordinate value of the last effective transform coefficient from the bitstream. At this time, binary arithmetic decoding is performed on each information to obtain an empty string for each information, and the horizontal coordinate value of the last effective transform coefficient by using an inverse binarization method corresponding to a predetermined binarization method for each empty string And a vertical coordinate value of the last effective transform coefficient.

The entropy decoder 105 obtains a first value by performing a first inverse binarization method on a first empty string that is a part of the empty string, and performs a second inverse binarization method on a second empty string that is another part of the empty string. Thus, the second value can be obtained. Based on the first value and the second value, a horizontal coordinate value of the last effective transform coefficient and a vertical coordinate value of the last effective transform coefficient may be obtained. In this case, the first empty string may be a prefix, and the first inverse binarization method may be an inverse binarization method corresponding to a fixed-length binarization method. The second empty string may be a suffix, and the second inverse binarization method may be an inverse binarization method corresponding to the truncated unary binarization method.

Alternatively, the scan area may be a rectangular scan area, and the rectangular scan area is a horizontal coordinate of an effective transform coefficient pixel positioned at the rightmost among all effective transform coefficients in the current block and an effective transform coefficient positioned at the bottom of the current block. It may be an area specified by the vertical coordinates of the pixel.

The entropy decoder 105 may obtain information on coordinates specifying the rectangular scan area from the bitstream, and determine the rectangular scan area based on information about coordinates specifying the acquired rectangular scan area. For example, the entropy decoder 105 includes information representing a horizontal coordinate value of an effective transform coefficient pixel located at the rightmost among all effective transform coefficients in the current block from the bitstream and among all effective transform coefficients in the current block. Information indicating a vertical coordinate value of an effective transform coefficient pixel positioned at the lowermost side may be obtained. At this time, the entropy decoder 105 performs binary arithmetic decoding on each information to obtain an empty string for each information, and uses an inverse binarization method corresponding to a predetermined binarization method for the empty string. Among the effective transform coefficients, a horizontal coordinate value of an effective transform coefficient pixel positioned at the rightmost position and a vertical coordinate value of an effective transform coefficient pixel positioned at the lowermost side of the effective transform coefficients may be obtained. The entropy decoder 105 obtains a first value by performing a first inverse binarization method on a first empty string that is a part of the empty string, and performs a second inverse binarization method on a second empty string that is another part of the empty string. Thus, the second value can be obtained. Based on the first value and the second value, the horizontal coordinate value of the rightmost effective transform coefficient pixel among all the effective transform coefficients in the current block and the vertical coordinate value of the lowest effective transform coefficient pixel Can be obtained. In this case, the first empty string may be a prefix, and the first inverse binarization method may be an inverse binarization method corresponding to a fixed-lenth binarization method. The second empty string may be a suffix, and the second inverse binarization method may be an inverse binarization method corresponding to the truncated unary binarization method.

Alternatively, the entropy decoding unit 105 is a horizontal coordinate value of an effective transform coefficient pixel located at the rightmost among all effective transform coefficients in the current block from the bitstream, or the lowest among all effective transform coefficients in the current block. Information indicating a coordinate value in one direction among vertical coordinate values of an effective transform coefficient pixel and information indicating a difference between the coordinate value in the one direction and the coordinate value in the other direction may be obtained. The entropy decoder 105 may determine the one direction based on the height and width of the current block.

The entropy decoder 105 may obtain flag information indicating whether to obtain information indicating a difference between a coordinate value in one direction and a coordinate value in the other direction from the bitstream. When the flag information indicates that information indicating a difference between a coordinate value in one direction and a coordinate value in the other direction is obtained from the bitstream, the entropy decoding unit 105 is selected from among all effective transform coefficients in the current block from the bitstream. The horizontal coordinate value of the rightmost effective transform coefficient pixel (or the horizontal coordinate value of the last effective transform coefficient pixel) or the vertical coordinate of the lowest effective transform coefficient pixel among all the effective transform coefficients in the current block. Information indicating a coordinate value in one direction among values (or a vertical coordinate value of the last effective transform coefficient pixel) and information indicating a difference between the coordinate value in the one direction and the coordinate value in the other direction may be obtained.

When the flag information indicates that information indicating a difference between a coordinate value in one direction and a coordinate value in the other direction is not obtained from the bitstream, the entropy decoding unit 105 includes all effective transform coefficients in the current block from the bitstream. Information indicating a horizontal coordinate value of an effective transform coefficient pixel positioned at the rightmost of the, and information indicating a vertical coordinate value of an effective transform coefficient pixel positioned at the bottom of all effective transform coefficients in the current block may be obtained. .

On the other hand, whether to acquire flag information indicating whether the entropy decoder 105 acquires information indicating the difference between the coordinate value of one direction and the coordinate value of the other direction from the bitstream based on the width and height of the current block. Can be determined. For example, when the width and height of the current block are different (ie, rectangular), the entropy decoding unit 105 obtains information indicating the difference between the coordinate value in one direction and the coordinate value in the other direction from the bitstream. It may be determined to obtain flag information indicating whether or not.

For example, the entropy decoder 105 may obtain a coordinate value SR_x indicating a horizontal direction for specifying a scan area and a coordinate value SR_y indicating a vertical direction according to the following pseudo code 1.

[Water Code 1]

According to the pseudo code 1, the entropy decoding unit 105 indicates whether to first decode the variable isXfirst indicating whether information on the coordinate value in the horizontal direction is to be decoded first and the information about the coordinate value in the vertical direction. You can initialize the value of isYfirst to 0. In addition, the entropy decoder 105 may initialize flag information srDeltaFlag to 0, indicating whether information indicating a difference between a coordinate value in one direction and a coordinate value in the other direction is acquired.

When the width W of the current block is greater than the height H of the current block or the height H of the current block is greater than the width W of the current block, the entropy decoder 105 may acquire srDeltFlag from the bitstream and decode srDeltaFlag. have.

When the value of the decoded srDeltaFlag is 1 (that is, when it indicates that information indicating the difference between the coordinate value in one direction and the coordinate value in the other direction is obtained), the entropy decoding unit 105 has a width W of the current block. If the height of the current block is smaller than H, the value of IsXfirst can be determined as 1.

When the value of the decoded srDeltaFlag is 1 (that is, when it indicates that information indicating the difference between the coordinate value in one direction and the coordinate value in the other direction is received), the width W of the current block is If the height of the block is greater than H, the value of IsYfirst can be determined as 1.

When the value of IsXfirst is 1 (indicating that information on the coordinate value in the horizontal direction is to be decoded first), the entropy decoding unit 105 includes information indicating the coordinate value in the horizontal direction Sr_x and the coordinate value in the vertical direction and the horizontal direction. Information (Sr_delta) (Sr_y-Sr_x) indicating the difference of the coordinate values of is obtained from the bitstream and decoded. In this case, the vertical coordinate value Sr_y may be determined as Sr_x+Sr_delta.

When the value of IsYfirst is 1 (indicating that information on the coordinate value in the vertical direction is first decoded), the entropy decoding unit 105 provides information indicating the coordinate value in the vertical direction, Sr_y, and the coordinate value in the horizontal direction and the vertical direction. Information (Sr_delta) (Sr_x-Sr_y) indicating the difference of the coordinate values of is obtained from the bitstream and decoded. In this case, the vertical coordinate value Sr_x may be determined as Sr_y+Sr_delta.

When the value of the decoded srDeltaFlag is 0 (i.e., it indicates that information indicating the difference between the coordinate value in one direction and the coordinate value in the other direction is not obtained), the entropy decoding unit 105 Information Sr_x indicating a and information Sr_y indicating a coordinate value in a vertical direction may be obtained from a bitstream and decoded.

The entropy decoder 105 may determine a context model used for binary arithmetic decoding of all syntax element information used for coefficient decoding based on at least one of the size of the current block and the shape of the current block. have. For example, the size of the current block may be determined according to at least one of minimum and maximum values of the height and width of the current block. The shape of the current block may be determined according to whether the width and height of the current block are the same. All syntax element information used for coefficient decoding may include syntax element information for specifying the scan area and information on transform coefficients within the scan area.

For example, the entropy decoder 105 may determine information size_tu1 about the size of the current block based on Equation 1 below.

In this case, log2_width may be a value obtained by taking log2 to the width W of the current block, and log2_height may be a value obtained by taking log2 to the height H of the current block.

The entropy decoder 105 determines a context model corresponding to information size_tu1 about the size of the current block, determines a context model for syntax element information used for coefficient decoding, and uses the context model for coefficient decoding. It is possible to perform binary arithmetic decoding on syntax element information.

Alternatively, the video decoding apparatus 100 may determine information size_tu2 about the size of the current block based on Equation 2 below.

The entropy decoder 105 determines a context model based on information size_tu2 about the size of the current block, determines a context model for syntax element information used for coefficient decoding, and uses the context model for coefficient decoding. It is possible to perform binary arithmetic decoding on syntax element information.

Alternatively, the entropy decoder 105 determines a context model based on information size_tu1 and size_tu2 on the size of the current block, determines a context model for syntax element information used for coefficient decoding, and uses the context model It is possible to perform binary arithmetic decoding on syntax element information used for decoding.

The entropy decoding unit 105 determines what is the minimum value and the maximum value among the sizes and heights of the current block, determines a context model based on the minimum and maximum values among the sizes and heights of the current block, and decodes coefficients. A context model for the syntax element information used for is determined, and the syntax element information used for coefficient decoding may be binary arithmetic decoding using the context model.

Meanwhile, the entropy decoder 105 may determine a context model used for binary arithmetic decoding of all syntax elements used for coefficient decoding based on the shape of the current block.

For example, the entropy decoder 105 may determine information shape_tu on the shape of the current block based on Equation 3 below.

According to [Equation 3], the entropy decoding unit 105 determines shape_tu as 2 when the width of the current block is greater than the height and height, and determines shape_tu as 1 when the width of the current block is smaller than the height and height. And, if the width of the current block is equal to the height and height, shape_tu may be determined as 0. That is, for a rectangle having a width greater than the height, shape_tu may be determined as 2, for a rectangle having a height greater than the width, shape_tu may be determined as 1, and in the case of a square, shape_tu may be determined as 0.

The entropy decoding unit 105 determines a context model based on information shape_tu about the size of the current block, determines a context model for syntax element information used for coefficient decoding, and uses the context model for coefficient decoding. It is possible to perform binary arithmetic decoding on syntax element information.

The entropy decoder 105 may determine a context model for syntax element information used for coefficient decoding based on the size of the current block and the shape of the current block. For example, the video decoding apparatus 100 determines a context model for syntax element information used for coefficient decoding based on at least one of information about the size of the current block size_tu1 and size_tu2 and information about the shape of the current block shape_tu. And, using the context model, it is possible to perform binary arithmetic decoding on the syntax element information used for coefficient decoding.

The entropy decoder 105 may change the height and width of the current block when either the height or the width is larger among the cases in which the height and width of the current block are different from each other. That is, horizontal coordinates and vertical coordinates of pixels included in the current block may be swapped. For example, when the width of the current block is greater than the height, the entropy decoder 105 may change the height and width of the current block. That is, values of horizontal coordinates and vertical coordinates of pixels included in the current block may be swapped. In addition, when the width of the current block is not larger than the height, the entropy decoder 105 may not swap horizontal coordinates and vertical coordinates of pixels included in the current block. The present invention is not limited thereto, and the entropy decoder 105 may change the height and width of the current block when the height of the current block is greater than the width. That is, values of horizontal coordinates and vertical coordinates of pixels included in the current block may be swapped. When the horizontal and vertical coordinates of the pixels included in the current block are swapped, the entropy decoding unit 105 transmits information on the horizontal and vertical coordinates specifying the scan area from the bitstream. It is possible to acquire and swap the coordinates of the horizontal direction coordinates and the vertical direction coordinates specifying the scan area. The entropy decoder 105 may determine the first scan area in the swapped current block based on coordinates specifying the swapped scan area. The entropy decoding unit 105 may scan information about transform coefficients included in the first scan area, and obtain a first transform coefficient of a changed current block based on the information about the scanned transform coefficient. have. When the horizontal and vertical coordinates of the pixels included in the current block are swapped, the entropy decoding unit 105 calculates the horizontal and vertical coordinates of the first transformation coefficient of the changed current block. By changing, the second transform coefficient in the current block can be obtained. The entropy decoder 105 may generate a residual block of the current block by performing inverse quantization and inverse transformation on the second transform coefficient of the current block.

For example, the entropy decoding unit 105 may change the horizontal coordinate (Sr_x or last_x) and the vertical coordinate (Sr_y or last_y) specifying the scan area according to the pseudocode 2 from each other.

[Water code 2]

According to the pseudo code 2, the entropy decoding unit 105, when the width (TU_width) of the current block TU (Transform Unit) is greater than the height (TU_height) of the current block TU (Transform Unit), the current block TU (Transform Unit) The width of (TU_width) and the height (TU_height) of the current block TU (Transform Unit) can be changed. In the process of changing the height and width of the TU, horizontal coordinates and vertical coordinates of the four corners of the TU determined based on the height and width of the TU may be changed. Also, horizontal coordinates and vertical coordinates of pixels included in the TU may be swapped. In this case, the entropy decoder 105 may determine a value of swap_flag indicating whether the height and width of the TU are changed as 1.

If the width (TU_width) of the current block TU (Transform Unit) is not greater than the height (TU_height) of the current block TU (Transform Unit), the entropy decoding unit 105 is the width of the current block TU (Transform Unit) (TU_width) And the height (TU_height) of the current block TU (Transform Unit) may not be changed.

In this case, the entropy decoder 105 may determine a value of swap_flag indicating whether the height and width of the TU are changed as 0.

In order to specify the scan area, the entropy decoding unit 105 includes coordinates [Sr_x, Sr_y] for specifying a rectangular scan area from a bitstream or coordinates of an effective transform coefficient that is last scanned in the TU according to a forward scan order [last_x, last_y] can be parsed.

When the value of swap_flag is 1, the entropy decoding unit 105 changes the coordinates [Sr_x,Sr_y] for specifying the rectangular scan area to each other, or the coordinates of the effective transform coefficients that are scanned last in the TU according to the scan order in the forward direction [last_x,last_y] can be changed to each other.

For example, the entropy decoder 105 may change the horizontal coordinate (Sr_x or last_x) and the vertical coordinate (Sr_y or last_y) specifying the scan area according to the capital code 3 to each other.

[Water Code 3]

According to the pseudo code 3, the entropy decoding unit 105, when the width (TU_width) of the current block TU (Transform Unit) is greater than the height (TU_height) of the current block TU (Transform Unit), the current block TU (Transform Unit) The width of (TU_width) and the height (TU_height) of the current block TU (Transform Unit) can be changed. In the process of changing the height and width of the TU, horizontal coordinates and vertical coordinates of the four corners of the TU determined based on the height and width of the TU may be changed. Also, horizontal coordinates and vertical coordinates of pixels included in the TU may be swapped. In this case, the entropy decoder 105 may determine a value of swap_flag indicating whether the height and width of the TU are changed as 1.

If the width (TU_width) of the current block TU (Transform Unit) is not greater than the height (TU_height) of the current block TU (Transform Unit), the entropy decoding unit 105 is the width of the current block TU (Transform Unit) (TU_width) And the height (TU_height) of the current block TU (Transform Unit) may not be changed. In this case, the entropy decoder 105 may determine a value of swap_flag indicating whether the height and width of the TU are changed as 0.

The entropy decoding unit 105 determines whether to obtain a coordinate value in a horizontal direction and a coordinate value in a vertical direction for specifying the scan area by using difference information between the coordinate value in the horizontal direction and the coordinate value in the vertical direction for specifying the scan area. The indicated flag (deltaXYflag) can be parsed from the bitstream. The flag (deltaXYflag) may be generated to have a value of 1 when the coordinate value in the vertical direction is greater than the coordinate value in the horizontal direction in the video encoding apparatus, otherwise it may be generated to have a value of 0. If deltaXYflag is 0, the entropy decoding unit 105 separately acquires information on the horizontal coordinate value and the information on the vertical coordinate value to decode entropy, and to specify the scan area based on the entropy-decoded information. Can be obtained.

When the value of deltaXYflag is 1, the entropy decoder 105 may parse coordinate information for specifying the scan area from the bitstream. For example, the entropy decoding unit 105 parses information about a horizontal coordinate value Sr_x for specifying a rectangular scan area, and information about a difference between information about a horizontal coordinate value and a vertical coordinate value Sr_xy_delta from a bitstream. can do. Alternatively, the entropy decoding unit 105 includes information about the horizontal coordinate value of the effective transform coefficient last scanned in the TU according to the scan order in the forward direction to specify the scan area, last_x, information about the horizontal coordinate value, and the vertical direction. Information on the difference between coordinate values last_xy_delta can be parsed.

The entropy decoder 105 may determine the horizontal coordinate value Sr_x for specifying the rectangular scan area as information Sr_x about the horizontal coordinate value parsed from the bitstream. The entropy decoder 105 may determine a vertical coordinate value Sr_y for specifying a rectangular scan area as a sum of Sr_xy_delta parsed from the bitstream and information Sr_x on a horizontal coordinate value parsed from the bitstream.

Alternatively, when the value of deltaXYflag is 1, the entropy decoding unit 105 parses the horizontal coordinate value last_x of the effective transform coefficient last scanned in the TU according to the scan order in the forward direction for specifying the scan area from the bitstream. It can be determined as information last_x about the horizontal coordinate value. The entropy decoding unit 105 uses the vertical coordinate value last_y of the effective transform coefficient scanned last in the TU according to the scan order in the forward direction for specifying the scan area, and the horizontal direction parsed from the bitstream in information last_xy_delta parsed from the bitstream. Information about the coordinate value can be determined as a sum of last_x

When the value of swap_flag is 1, the entropy decoding unit 105 changes the coordinates [Sr_x,Sr_y] for specifying the rectangular scan area with each other, or scans the last in the TU according to the scan order in the forward direction for specifying the scan area. It is possible to change the coordinates [last_x, last_y] of the effective transform coefficients to each other.

The entropy decoding unit 105 may perform binary arithmetic decoding based on a context model on information on coordinates specifying a rectangular scan area. The entropy decoding unit 105 may perform inverse binarization on the binary arithmetic-decoded information based on an inverse binarization method corresponding to a predetermined binarization method to obtain inverse binarization information about coordinates specifying a rectangular scan area, From the inverse binarization information on the coordinates, coordinates specifying the rectangular scan area may be obtained. In this case, the context model may be determined based on at least one of the size of the current block, a color component of the current block, and a bin index. The color component may include a luminance component and a color difference component. The bin index may be information indicating a position of a bin currently binary arithmetic-decoded among bin strings related to the syntax element. The inverse binarization method corresponding to the predetermined binarization method may be at least one of a fixed length inverse binarization method and a truncated unary inverse binarization method. For example, the entropy decoder 105 obtains first inverse binarization information by performing inverse binarization using a fixed-length inverse binarization method on a first bin string among the binary arithmetic decoded information, and Inverse binarization using a truncated unary inverse binarization method may be performed on the second empty string to obtain second inverse binarization information. The entropy decoding unit 105 may obtain coordinates specifying the rectangular scan area based on the first inverse binarization information and the second inverse binarization information.

The entropy decoder 105 may obtain binary arithmetic-decoded information by performing binary arithmetic decoding on the basis of information on transform coefficients scanned in the scan area within the current block. In this case, the binary arithmetic decoding may be performed using a context model determined based on at least one of the size and shape of the current block.

The entropy decoder 105 may obtain information on transform coefficients of the current block by performing inverse binarization on the binary arithmetic-decoded information.

The entropy decoding unit 105 may obtain transform coefficients of the current block by performing at least one of binary arithmetic decoding and inverse binarization based on a context model for the transform coefficients based on information on the transform coefficients scanned in the scan area. I can.

When the information about the transform coefficients is information indicating whether the absolute value of the current transform coefficient is greater than a predetermined value, information about the absolute value of the residual level, and the sign information of the current transform coefficient, the entropy decoder 105 includes the scanned transform coefficients. Binary arithmetic decoding based on a context model may be performed on the information about. The entropy decoder 105 may obtain transform coefficients of the current block by performing inverse binarization on information about the transform coefficients that are binary arithmetic-decoded. The first information on the transform coefficients is information indicating whether the absolute value of the current transform coefficient is greater than a predetermined value, information on the absolute value of the residual level, and sign information of the current transform coefficient, and the second information about the transform coefficients is current transform In the case of coefficient-related binarization parameter information, the entropy decoder 105 may perform binary arithmetic decoding based on the context model on the first information about the transform coefficient.

The entropy decoder 105 may obtain transform coefficients of the current block by performing inverse binarization based on the binarization parameter information included in the second information on the binary arithmetic-decoded first information. The binarization parameter information may be Rice parameter information for the current transform coefficient. The Rice parameter may be information for determining the length of the prefix included in the binstring. The present invention is not limited thereto, and the binarization parameter information may be various binarization parameter information for the current transform coefficient.

When the first information about the transform coefficients is information about the absolute residual level of the current transform coefficient, the entropy decoding unit 105 uses a (truncated) Rice binarization method for the absolute residual level information of the current transform coefficient. A value of the residual level absolute value of the current transform coefficient may be obtained by using a corresponding inverse binarization method and an inverse binarization method corresponding to the exponential Gollum binarization method. For example, the entropy decoder 105 performs inverse binarization using an inverse binarization method corresponding to the Rice binarization method based on the Rice parameter on the prefix of the empty string of the residual level absolute value information of the current transform coefficient. Acquire a first value for the absolute residual level of the current transform coefficient, and perform inverse binarization using an inverse binarization method corresponding to the exponential Gollum binarization method on the suffix of the empty string of the residual level absolute value information. A current block is obtained based on a second value relating to the absolute residual level value of the current transform coefficient and a first value relating to the absolute residual level value of the current transform coefficient and a second value relating to the absolute residual level value of the current transform coefficient It is possible to obtain a value about the absolute value of the residual level of.

The context model for the first transform coefficient among the context models for the transform coefficients includes information on at least one second transform coefficient previously scanned according to a predetermined scan order, the position and color of the first transform coefficient in the current block. It may be determined based on at least one of a component, information about a right or a lower peripheral transform coefficient, and a scan position of the first transform coefficient.

For example, the context model regarding flag information indicating whether the first transform coefficient is greater than 0 is based on the number of transform coefficients on the right or lower side whose absolute value is greater than 0 among transform coefficients on the right or the bottom of a predetermined position. Can be determined.

The context model regarding flag information indicating whether the first transform coefficient is greater than 0 is not limited thereto, and the absolute value of the n transform coefficients previously scanned according to a predetermined scan order (n is a positive integer) is greater than 0. It can be determined based on the number of large effective transform coefficients.

Alternatively, the context model regarding flag information indicating whether the first transform coefficient is greater than 0 may be determined based on the position of the first transform coefficient in the coefficient group and the corresponding effective coefficient group flags on the right or lower side of the corresponding coefficient group.

The entropy decoder 105 may determine a context model regarding flag information indicating whether the first transform coefficient is greater than 0 based on the position of the first transform coefficient in the current block. For example, if the sum of the horizontal coordinate value pos_x of the first transform coefficient in the current block and the vertical position pos_y in the current block is less than a predetermined threshold value thred1, the entropy decoding unit 105 determines the context index by a predetermined value. The context offset may be increased by offset1, and the context model may be determined based on the increased context index. When the sum of the horizontal coordinate value pos_x of the first transform coefficient in the current block and the vertical position pos_y in the current block is less than a predetermined threshold value thred2, the entropy decoding unit 105 sets the context index by a predetermined context offset offset2. The context model may be determined based on the increased and increased context index. When the sum of the horizontal coordinate value pos_x of the first transform coefficient in the current block and the vertical position pos_y in the current block is less than a predetermined threshold value thred3, the entropy decoding unit 105 sets the context index by a predetermined context offset offset3. The context model may be determined based on the increased and increased context index.

The entropy decoder 105 includes the size of the scan area, the number of transform coefficients already scanned in the scan area, the relative position of the first transform coefficient in the scan area, and the first position in which the first transform coefficient is scanned according to a predetermined scan order. A context model regarding flag information indicating whether the first transform coefficient is greater than 0 may be determined based on at least one of the coefficients.

For example, the entropy decoder 105 may determine the size_sr of the rectangular scan area based on Equation 4 below. That is, the size_sr of the rectangular scan area may mean the number of transform coefficients included in the rectangular scan area.

However, the present invention is not limited thereto, and when the scan area is specified by the coordinates of the last effective transform coefficient pixel, size_sr may be the number of transform coefficient pixels included in the scan area.

The entropy decoder 105 may determine the number cnt_pos of all the transform coefficients scanned before scanning the first transform coefficient among the transform coefficients in the rectangular scan area. In this case, cnt_pos may indicate the position of the first transform coefficient among all transform coefficients in the scan area scanned according to a predetermined scan order.

When cnt_pos is less than a predetermined threshold value thred1, the entropy decoder 105 may increase the context index by a predetermined context offset offset1 and determine a context model based on the increased context index. At this time, thred1 may be 1. Alternatively, thred1 may be 1/4*size_sr.

When cnt_pos is less than a predetermined threshold value thred2, the entropy decoder 105 may increase the context index by a predetermined context offset offset2 and determine a context model based on the increased context index. In this case, thred2 may be 1/4*size_sr. Alternatively, thred2 may be 1/2*size_sr.

When cnt_pos is not smaller than the predetermined threshold values thred1 and thred2, the entropy decoder 105 may increase the context index by a predetermined context offset offset3 and determine a context model based on the increased context index. However, the threshold values thred1 and thred2 are only examples, and it can be easily understood by those skilled in the art that various values may be determined based on size_sr.

The entropy decoder 105 may determine a context model for flag information indicating whether the first transform coefficient is greater than 0 based on the relative position of the first transform coefficient in the scan area.

The entropy decoding unit 105 indicates whether the first transform coefficient is greater than 0 based on the horizontal coordinate value pos_x and the vertical coordinate value pos_y of the first transform coefficient in the current block and the coordinates Sr_x and Sr_y specifying the rectangular scan area. A context model for flag information can be determined.

When pos_x is smaller than thred1_x and pos_y is smaller than thred1_y, the entropy decoder 105 may increase the context index by a predetermined context offset offset1, and determine the context model based on the increased context index. In this case, [thred1_x, thred1_y] may be [1,1]. Alternatively, [thred1_x, thred1_y] may be [sr_x/4,sr_y/4] or [(sr_x+1)/4, (sr_y+1)/4].

When pos_x is smaller than thred2_x and pos_y is smaller than thred2_y, the entropy decoder 105 may increase the context index by a predetermined context offset offset2 and determine a context model based on the increased context index. In this case, [thred2_x,thred2_y] may be [thred1_x, thred1_y], [sr_x/2,sr_y/2] or [(sr_x+1)/2, (sr_y+1)/2].

However, the threshold values thred1_x, thred1_y, and thred2_y, thred2_y are only examples, and a person skilled in the art can easily understand that various values may be determined based on sr_x and sr_y.

The entropy decoder 105 may determine a context model for flag information indicating whether the first transform coefficient is greater than 0 based on whether the first transform coefficient is a transform coefficient of a first position scanned according to a reverse scan order. . That is, the entropy decoder 105 determines a first context model for flag information indicating whether the first transform coefficient is greater than 0 when the first transform coefficient is the first position scanned according to the reverse scan order, and If one transform coefficient is not the first position scanned according to the reverse scan order, a second context model regarding flag information indicating whether the first transform coefficient is greater than 0 may be determined. In this case, the transform coefficient of the pixel positioned at the lower right corner of the rectangular scan area may be a transform coefficient of the first position scanned according to the reverse scan order.

Alternatively, flag information indicating whether the first transform coefficient is greater than 0 (GT0 flag information) is GT0 flag information of n (n is a positive integer) transform coefficients previously scanned according to a predetermined scan order, and the information in the current block. 1 The position of the transform coefficient, the color component, and GT0 flag information of n (n is a positive integer) transform coefficients adjacent to the right or the lower side, whether the first transform coefficient in the scan order is the transform coefficient at the first position in the scan area, In the scan order, the first transform coefficient may be determined based on at least one of whether the first transform coefficient is a transform coefficient of a final position in the scan area.

The context model regarding flag information indicating whether the absolute value of the first transform coefficient is greater than 1 is determined based on the number of effective transform coefficients on the right or the lower side of which the absolute value is greater than 1 among transform coefficients on the right or the bottom of a predetermined position. I can.

The entropy decoder 105 may determine a context model regarding flag information indicating whether the first transform coefficient is greater than 1 based on the position of the first transform coefficient in the current block. For example, if the sum of the horizontal coordinate value pos_x of the first transform coefficient in the current block and the vertical position pos_y in the current block is less than a predetermined threshold value thred1, the entropy decoding unit 105 determines the context index by a predetermined value. The context offset may be increased by offset1, and the context model may be determined based on the increased context index. When the sum of the horizontal coordinate value pos_x of the first transform coefficient in the current block and the vertical position pos_y in the current block is less than a predetermined threshold value thred2, the entropy decoding unit 105 sets the context index by a predetermined context offset offset2. The context model may be determined based on the increased and increased context index.

When the sum of the horizontal coordinate value pos_x of the first transform coefficient in the current block and the vertical position pos_y in the current block is less than a predetermined threshold value thred3, the entropy decoding unit 105 sets the context index by a predetermined context offset offset3. The context model may be determined based on the increased and increased context index. At this time, offsets 1, 2, and 3 related to the context model regarding flag information indicating whether the first transform coefficient is greater than 1 and predetermined threshold values thred 1,2 and 3 are flag information indicating whether the first transform coefficient is greater than 0 Offsets offsets 1, 2, and 3 related to the context model for and predetermined threshold values thred 1, 2, and 3 may be different from each other.

The entropy decoder 105 determines the size of the scan area, the number of transform coefficients already scanned in the scan area, the relative position of the first transform coefficient in the scan area, and the first zero in which the first transform coefficient is scanned according to a predetermined scan order. A context model for flag information indicating whether the first transform coefficient is greater than 1 may be determined based on at least one of whether the transform coefficient of a non-location position is not.

For example, the entropy decoder 105 may determine the size_sr of the rectangular scan area based on Equation 5 below. That is, the size_sr of the rectangular scan area may mean the number of transform coefficients included in the rectangular scan area.

The entropy decoder 105 may determine the number cnt_pos of all the transform coefficients scanned before scanning the first transform coefficient among the transform coefficients in the rectangular scan area. In this case, cnt_pos may indicate the position of the first transform coefficient among all transform coefficients in the scan area scanned according to a predetermined scan order. However, the present invention is not limited thereto, and cnt_pos may be the number of transform coefficients greater than all zeros scanned before scanning the first transform coefficient among transform coefficients in the rectangular scan area.

When cnt_pos is less than a predetermined threshold value thred1, the entropy decoder 105 may increase the context index by a predetermined context offset offset1 and determine a context model based on the increased context index. At this time, thred1 may be 1. Alternatively, thred1 may be 1/4*size_sr.

When cnt_pos is less than a predetermined threshold value thred2, the entropy decoder 105 may increase the context index by a predetermined context offset offset2 and determine a context model based on the increased context index. In this case, thred2 may be 1/4*size_sr. Alternatively, thred2 may be 1/2*size_sr.

When cnt_pos is not smaller than the predetermined threshold values thred1 and thred2, the entropy decoder 105 may increase the context index by a predetermined context offset offset3 and determine a context model based on the increased context index.

However, the threshold values thred1 and thred2 are only examples, and it can be easily understood by those skilled in the art that various values may be determined based on size_sr. At this time, offsets 1, 2, and 3 related to the context model regarding flag information indicating whether the first transform coefficient is greater than 1 and predetermined threshold values thred 1 and thred2 are related to flag information indicating whether the first transform coefficient is greater than 0. Those skilled in the art can easily understand that the offsets offset1, 2, and 3 related to the context model and the predetermined threshold values thred 1 and thred2 and their values may be different.

The entropy decoder 105 may determine a context model of flag information indicating whether the first transform coefficient is greater than 1 based on the relative position of the first transform coefficient in the scan area.

The entropy decoding unit 105 indicates whether the first transform coefficient is greater than 1 based on the horizontal coordinate value pos_x and the vertical coordinate value pos_y of the first transform coefficient in the current block and the coordinates Sr_x and Sr_y specifying the rectangular scan area. A context model for flag information can be determined.

When pos_x is smaller than thred1_x and pos_y is smaller than thred1_y, the video decoding apparatus 100 may increase the context index by a predetermined context offset offset1, and determine the context model based on the increased context index. In this case, [thred1_x,thred1_y] may be [1,1]. Alternatively, [thred1_x,thred1_y] may be [sr_x/4,sr_y/4] or [(sr_x+1)/4, (sr_y+1)/4].

When pos_x is smaller than thred2_x and pos_y is smaller than thred2_y, the entropy decoder 105 may increase the context index by a predetermined context offset offset2 and determine a context model based on the increased context index. In this case, [thred2_x,thred2_y] may be [thred1_x, thred1_y], [sr_x/2,sr_y/2] or [(sr_x+1)/2, (sr_y+1)/2].

However, the threshold values thred1_x, thred1_y, and thred2_y, thred2_y are only examples, and a person skilled in the art can easily understand that various values may be determined based on sr_x and sr_y.

However, the threshold values thred1_x, thred1_y, thred2_x, and thred2_y are only examples, and a person skilled in the art can easily understand that various values may be determined based on size_sr. At this time, offsets offset1, 2, and 3 related to the context model regarding flag information indicating whether the first transform coefficient is greater than 1, and predetermined threshold values thred1_x, thred1_y, thred2_x, and thred2_y are flags indicating whether the first transform coefficient is greater than 0 Those skilled in the art can easily understand that offsets offset1, 2, and 3 related to the context model for information and predetermined threshold values thred1_x, thred1_y, thred2_x, and thred2_y and their values may be different.

The entropy decoder 105 uses flag information indicating whether the first transform coefficient is greater than 1 based on whether the first transform coefficient is a transform coefficient at the first position among transform coefficients larger than 0 scanned according to the reverse scan order. Can determine the context model for That is, when the first transform coefficient is a first position among transform coefficients larger than 0 scanned according to the reverse scan order, the video decoding apparatus 100 provides first information regarding flag information indicating whether the first transform coefficient is greater than 1 A second context model for flag information indicating whether the first transform coefficient is greater than 1 when the context model is determined and the first transform coefficient is not the first position among transform coefficients larger than 0 scanned according to the reverse scan order Can be determined.

Without being limited thereto, the context model for flag information indicating whether the absolute value of the first transform coefficient is greater than 1 is an absolute value among n (n is a positive integer) transform coefficients previously scanned according to a predetermined scan order. It can be determined based on the number of effective transform coefficients greater than one.

Alternatively, the context model for flag information indicating whether the absolute value of the first transform coefficient is greater than 1 may be determined based on previously decoded GT1 flag information in the corresponding coefficient group and GT1 flag information in the previously decoded group.

Alternatively, flag information indicating whether the absolute value of the first transform coefficient is greater than 1 (GT1 flag information) is the GT1 flag information of n (n is a positive integer) transform coefficients previously scanned according to a predetermined scan order and the current GT1 flag information of the position of the first transform coefficient in the block, the color component, and n (n is a positive integer) adjacent right or lower transform coefficients, whether the first transform coefficient is a transform coefficient at the first position in the scan area, The first transform coefficient may be determined based on at least one of whether the first transform coefficient is a transform coefficient of a final position in the scan area.

The context model for flag information indicating whether the absolute value of the first transform coefficient is greater than 2 may be determined based on the number of effective transform coefficients on the right or the lower side where the absolute value is greater than 2.

The entropy decoder 105 may determine a context model for flag information indicating whether the first transform coefficient is greater than 2 based on the position of the first transform coefficient in the current block. For example, if the sum of the horizontal coordinate value pos_x of the first transform coefficient in the current block and the vertical position pos_y in the current block is less than a predetermined threshold value thred1, the entropy decoding unit 105 determines the context index by a predetermined value. The context offset may be increased by offset1, and the context model may be determined based on the increased context index. When the sum of the horizontal coordinate value pos_x of the first transform coefficient in the current block and the vertical position pos_y in the current block is less than a predetermined threshold value thred2, the entropy decoding unit 105 sets the context index by a predetermined context offset offset2. The context model may be determined based on the increased and increased context index. When the sum of the horizontal coordinate value pos_x of the first transform coefficient in the current block and the vertical position pos_y in the current block is less than a predetermined threshold value thred3, the entropy decoding unit 105 sets the context index by a predetermined context offset offset3. The context model may be determined based on the increased and increased context index. At this time, offsets offset 1, 2, and 3 related to the context model regarding flag information indicating whether the first transform coefficient is greater than 2 and predetermined threshold values thred 1,2 and 3 indicate whether the first transform coefficient is greater than 0 and 1. Offsets offsets 1, 2, and 3 related to the context model for flag information and predetermined threshold values thred 1, 2, and 3 may be different from each other.

The entropy decoder 105 determines the size of the scan area, the number of transform coefficients already scanned in the scan area, the relative position of the first transform coefficient in the scan area, and the first zero in which the first transform coefficient is scanned according to a predetermined scan order. A context model regarding flag information indicating whether the first transform coefficient is greater than 1 may be determined based on at least one of whether the transform coefficient is a transform coefficient of a position that is not (or a first position among transform coefficients greater than 1).

For example, the entropy decoder 105 may determine the size_sr of the rectangular scan area based on Equation 6 below. That is, the size_sr of the rectangular scan area may mean the number of transform coefficients included in the rectangular scan area.

The entropy decoder 105 may determine the number cnt_pos of all the transform coefficients scanned before scanning the first transform coefficient among the transform coefficients in the rectangular scan area. In this case, cnt_pos may indicate the position of the first transform coefficient among all transform coefficients in the scan area scanned according to a predetermined scan order. However, the present invention is not limited thereto, and cnt_pos may be the number of all transform coefficients whose absolute values are scanned before scanning the first transform coefficient among the transform coefficients in the rectangular scan area is greater than 1.

When cnt_pos is less than a predetermined threshold value thred1, the entropy decoder 105 may increase the context index by a predetermined context offset offset1 and determine a context model based on the increased context index. At this time, thred1 may be 1. Alternatively, thred1 may be 1/4*size_sr.

When cnt_pos is less than a predetermined threshold value thred2, the entropy decoder 105 may increase the context index by a predetermined context offset offset2 and determine a context model based on the increased context index. In this case, thred2 may be 1/4*size_sr. Alternatively, thred2 may be 1/2*size_sr.

When cnt_pos is not smaller than the predetermined threshold values thred1 and thred2, the entropy decoder 105 may increase the context index by a predetermined context offset offset3 and determine a context model based on the increased context index.

However, the threshold values thred1 and thred2 are only examples, and it can be easily understood by those skilled in the art that various values may be determined based on size_sr. At this time, offsets 1, 2, and 3 related to the context model related to flag information indicating whether the first transform coefficient is greater than 0 or 1 and predetermined threshold values thred 1 and thred2 indicate whether the first transform coefficient is greater than 0 or 1. Those skilled in the art can easily understand that the offsets offset1, 2, and 3 related to the context model for the flag information and the predetermined threshold values thred 1 and thred2 and their values may be different.

The entropy decoder 105 may determine a context model of flag information indicating whether the first transform coefficient is greater than 2 based on the relative position of the first transform coefficient in the scan area.

The entropy decoding unit 105 indicates whether the first transform coefficient is greater than 2 based on the horizontal coordinate value pos_x and the vertical coordinate value pos_y of the first transform coefficient in the current block and the coordinates Sr_x and Sr_y specifying the rectangular scan area. A context model for flag information can be determined.

When pos_x is smaller than thred1_x and pos_y is smaller than thred1_y, the entropy decoder 105 may increase the context index by a predetermined context offset offset1, and determine the context model based on the increased context index. In this case, [thred1_x,thred1_y] may be [1,1]. Alternatively, [thred1_x,thred1_y] may be [sr_x/4,sr_y/4] or [(sr_x+1)/4, (sr_y+1)/4].

When pos_x is smaller than thred2_x and pos_y is smaller than thred2_y, the entropy decoder 105 may increase the context index by a predetermined context offset offset2 and determine a context model based on the increased context index. In this case, [thred2_x,thred2_y] may be [thred1_x, thred1_y], [sr_x/2,sr_y/2] or [(sr_x+1)/2, (sr_y+1)/2].

However, the threshold values thred1_x, thred1_y, and thred2_y, thred2_y are only examples, and a person skilled in the art can easily understand that various values may be determined based on sr_x and sr_y.

However, the threshold values thred1_x, thred1_y, thred2_x, and thred2_y are only examples, and a person skilled in the art can easily understand that various values may be determined based on size_sr. At this time, offsets 1, 2, and 3 related to the context model related to flag information indicating whether the first transform coefficient is greater than 0 or 1, and predetermined threshold values thred1_x, thred1_y, thred2_x, and thred2_y indicate whether the first transform coefficient is greater than 0. Those skilled in the art can easily understand that offsets offset1, 2, and 3 related to the context model for the indicated flag information, and predetermined threshold values thred1_x, thred1_y, thred2_x, and thred2_y, and their values may be different.

The entropy decoder 105 uses flag information indicating whether the first transform coefficient is greater than 2 based on whether the first transform coefficient is a transform coefficient at the first position among transform coefficients larger than 0 scanned according to the reverse scan order. Can determine the context model for That is, when the first transform coefficient is the first among transform coefficients larger than 0 scanned according to the reverse scan order, the entropy decoding unit 105 is the first flag information indicating whether the first transform coefficient is greater than 1 A second context model for flag information indicating whether the first transform coefficient is greater than 1 when the context model is determined and the first transform coefficient is not the first position among transform coefficients larger than 0 scanned according to the reverse scan order Can be determined.

However, the present invention is not limited thereto, and the entropy decoder 105 has a first transform coefficient of 2 based on whether the first transform coefficient is a transform coefficient of a first position among transform coefficients larger than 1 scanned according to the reverse scan order. It is possible to determine a context model for flag information indicating whether it is greater. That is, when the first transform coefficient is the first among transform coefficients greater than 1 scanned according to the reverse scan order, the entropy decoding unit 105 is the first of the flag information indicating whether the first transform coefficient is greater than 1 A second context model for flag information indicating whether the first transform coefficient is greater than 2 when the context model is determined and the first transform coefficient is not the first position among transform coefficients larger than 1 scanned according to the reverse scan order Can be determined.

The context model for flag information indicating whether the first transform coefficient is greater than 2 is not limited thereto, and the absolute value of the n transform coefficients previously scanned according to a predetermined scan order (n is a positive integer) is greater than 2 It can be determined based on the number of large effective transform coefficients.

Alternatively, the context model regarding flag information indicating whether the absolute value of the first transform coefficient is greater than 2 may be determined based on previously decoded GT2 flag information in the corresponding coefficient group and GT2 flag information in the previously decoded group.

Alternatively, flag information indicating whether the absolute value of the first transform coefficient is greater than 2 (hereinafter referred to as GT2 flag information) is a GT2 flag of n (n is a positive integer) transform coefficients previously scanned according to a predetermined scan order. Information and GT2 flag information of the position of the first transform coefficient in the current block, the color component, and n (n is a positive integer) adjacent right or lower transform coefficients, the first transform coefficient is the transform coefficient at the first position in the scan area It may be determined based on at least one of whether or not the first transform coefficient is a transform coefficient of a final position in the scan area.

Alternatively, flag information indicating whether the first transform coefficient is greater than m (m is an integer greater than 2) (hereinafter referred to as GTm flag information) is n (n is a positive integer) previously scanned according to a predetermined scan order. GTm flag information of the transform coefficients, the position of the first transform coefficient in the current block, the color component, and GTm flag information of n adjacent right or lower transform coefficients (n is a positive integer), the first transform coefficient is in the scan area It may be determined based on at least one of whether the first transform coefficient is a transform coefficient of the first position and whether the first transform coefficient is a transform coefficient of the final position in the scan area.

Meanwhile, the binarization parameter information about the residual level absolute value of the first transform coefficient may be determined based on the level absolute value of the peripheral effective transform coefficient to the right or lower side of the first transform coefficient.

For example, the binarization parameter information about the residual level absolute value of the first transform coefficient may be determined based on the sum of the level absolute values of the predetermined peripheral effective transform coefficients on the right or the lower side of the first transform coefficient.

Alternatively, the binarization parameter information regarding the absolute residual level value of the first transform coefficient may be determined based on a previously coded level value.

Alternatively, the binarization parameter information about the absolute value of the residual level of the first transform coefficient is the level of n (n is an integer) transform coefficients previously scanned according to a predetermined scan order, the position of the first transform coefficient in the current block, and the color. The level of the component and n (n is a positive integer) transform coefficients adjacent to the right or lower side, whether the first transform coefficient in the scan order is the transform coefficient at the first position in the scan area, and the first transform coefficient is scanned in the scan order It may be determined based on at least one of whether or not the transform coefficient of the final position in the region and whether the first transform coefficient is the coefficient of the first position in the coefficient group in the scan order.

The entropy decoding unit 105 has the position of the transform coefficient currently being scanned in the scan area [SRx,0] (SRx is an integer, SRx is the horizontal coordinate value of the right boundary pixel of the scan area based on the coordinates of the upper left corner of the scan area. Means), and [SRx,Y] previously scanned according to a predetermined scan order (Y is an integer greater than 0 and less than or equal to SRy, SRy is the lower boundary of the scan area based on the coordinates of the upper left corner of the scan area) Refers to the vertical coordinate value of the pixel) If the transform coefficients of the position are all 0s, the GT0 flag information value may be determined as 1 without obtaining GT0 flag information of the transform coefficient currently scanned from the bitstream.

Likewise, the entropy decoder 105 has the position of the transform coefficient currently being scanned in the scan area [0,SRy] (SRy is an integer, SRy is the vertical coordinate of the lower boundary of the scan area based on the coordinates of the upper left corner of the scan area. Value), and [X,SRy] previously scanned according to a predetermined scan order (X is an integer greater than 0 and less than or equal to SRx, SRx is the right side of the scan area based on the coordinates of the upper left corner of the scan area) Refers to the vertical coordinate value of the boundary pixel) If the transform coefficients of the position are all 0 coefficients, the GT0 flag information value can be determined as 1 without obtaining GT0 flag information of the transform coefficient currently scanned from the bitstream. .

Meanwhile, the entropy decoder 105 may determine the maximum number of GT1 flag information of the effective transform coefficient in the current block, and receive GT1 flag information in the current block from the bitstream within the maximum coefficient of the determined effective transform coefficient. . That is, when the entropy decoding unit 105 receives the maximum number of GT1 flag information of the effective transform coefficients received from the bitstream, the entropy decoding unit 105 later determines whether there is GT1 flag information of the effective transform coefficient in the bitstream. May not be checked any more.

The entropy decoder 105 may determine all non-zero effective transform coefficients as the maximum number of GT1 flag information in the current block. Alternatively, the entropy decoder 105 may determine the maximum number of GT1 flag information in the current block based on the size of the scan area. For example, the entropy decoder 105 may determine the maximum number of GT1 flag information MaxCount_GT1 based on Equation 7 below.

Here, sizeSR may mean the size (width) of the rectangular scan area, and sizeSR may be (Sr_x+1)*(Sr_y+1). Sr_x may mean the horizontal coordinate of the rightmost effective transform coefficient pixel based on the coordinate of the upper left corner of the scan area. In other words, Sr_x may mean horizontal coordinates of the right boundary pixel based on the coordinates of the upper left corner of the scan area. Sr_y may mean the vertical coordinate of the lowest effective transform coefficient pixel based on the coordinate of the upper left corner of the scan area. In other words, Sr_y may mean the vertical coordinate of the lower boundary pixel based on the coordinate of the upper left corner of the scan area.

K1 may be an adjustment coefficient between the size of the scan area and the GT1 flag. For example, it may be an integer greater than 1. Th1 may be a predetermined threshold. For example, Th1 may be 16,8. However, it is not limited thereto, and those skilled in the art can easily understand that K1 and Th1 may have various values.

The entropy decoding unit 105 may determine the maximum number of GT2 flag information in the current block and receive GT2 flag information in the current block within the determined maximum coefficient of the effective transform coefficient from the bitstream. That is, when the entropy decoding unit 105 receives the maximum number of GT2 flag information of the effective transform coefficients received from the bitstream, the entropy decoder 105 later determines whether there is GT2 flag information of the effective transform coefficient in the bitstream. May not be checked any more.

The entropy decoder 105 may determine all non-zero effective transform coefficients as the maximum number of GT2 flag information in the current block. Alternatively, the entropy decoder 105 may determine the maximum number of GT2 flag information in the current block based on the size of the scan area. For example, the entropy decoder 105 may determine the maximum number of GT2 flag information MaxCount_GT2 based on Equation 8 below.

Here, sizeSR may mean the size (width) of the rectangular scan area, and sizeSR may be (Sr_x+1)*(Sr_y+1). Sr_x may mean the horizontal coordinate of the rightmost effective transform coefficient pixel based on the coordinate of the upper left corner of the scan area. In other words, Sr_x may mean horizontal coordinates of the right boundary pixel based on the coordinates of the upper left corner of the scan area. Sr_y may mean the vertical coordinate of the lowest effective transform coefficient pixel based on the coordinate of the upper left corner of the scan area. In other words, Sr_y may mean the vertical coordinate of the lower boundary pixel based on the coordinate of the upper left corner of the scan area. K2 may be an adjustment coefficient between the size of the scan area and the GT2 flag. For example, it may be an integer greater than 1. K2 may be a predetermined threshold. For example, Th2 may be 16,8. However, it is not limited thereto, and those skilled in the art can easily understand that K2 and Th2 may have various values.

The entropy decoder 105 may obtain information on a coefficient group in the current block from the bitstream. Here, the information on the coefficient group may be flag information indicating whether the coefficient group includes at least one effective transform coefficient (or whether the coefficient group includes only zero transform coefficients). The flag information may be referred to as significant coefficient group flag information. The entropy decoder 105 may scan information about transform coefficients in the current coefficient group based on information about the current coefficient group obtained from the bitstream. For example, if the information on the coefficient group indicates that the coefficient group does not include at least one effective transform coefficient, the entropy decoding unit 105 calculates the value of the transform coefficient within the coefficient group without scanning the information about the transform coefficient. It can be derived to zero. When the information on the coefficient group indicates that the coefficient group includes at least one effective transform coefficient, the entropy decoder 105 scans the information on the transform coefficient according to a predetermined scan order to obtain the transform coefficient within the coefficient group. I can.

In this case, the entropy decoder 105 may determine one coefficient group for every K (K is an integer) transform coefficients scanned according to a predetermined scan order of the transform coefficients included in the scan area. That is, one coefficient group may include K transform coefficients. In this case, the scan order may be a forward scan order that is opposite to a predetermined reverse scan order.

Accordingly, the entropy decoder 105 may determine a coefficient group by scanning in a forward scan order from a DC coefficient that is a coefficient adjacent to the upper left corner of the current block. In this case, when the number of transform coefficients included in the current block is not an integer multiple of K, the final coefficient group among the groups of coefficients scanned according to the forward scan order may include a number of transform coefficients smaller than K.

However, the present invention is not limited thereto, and the entropy decoding unit 105 scans from a coefficient located at the lower right of the transform coefficients included in the current block to a coefficient located at the upper left of the transform coefficients included in the current block. It can be easily understood by those skilled in the art that coefficient groups can be determined by scanning according to.

However, the present invention is not limited thereto, and those skilled in the art can easily understand that the entropy decoder 105 may determine the coefficient group according to a predetermined scan order without obtaining information on the coefficient group in the current block from the bitstream. The reason for determining the coefficient group is that the entropy decoder 105 performs an operation (an operation such as sign data hiding) according to the coefficient group. The entropy decoding unit 105 does not obtain information on the coefficient group from the bitstream when one coefficient group among the groups of coefficients scanned according to a predetermined scan order includes only one transform coefficient, and a GT0 flag Information can be obtained from the bitstream.

The entropy decoder 105 may determine whether to hide the sign of at least one transform coefficient for each coefficient group included in the current block. For example, in some cases, the entropy decoder may determine to hide the signs of one or two transform coefficients for each coefficient group included in the current block.

The entropy decoder 105 may scan information about transform coefficients in the rectangular scan area according to a predetermined scan order. The predetermined scan order may include a reverse zigzag scan order, a reverse diagonal scan order, a reverse vertical scan order, and a horizontal scan order. However, it will be easily understood by those skilled in the art that the predetermined scan order is not limited to the above-mentioned reverse scan order, and may include various reverse scan orders.

The entropy decoder 105 may obtain transform coefficients of the current block based on information on the scanned transform coefficients.

The image reconstructor 120 may generate a residual block of the current block by performing inverse quantization and inverse transformation on transform coefficients of the current block.

The image reconstructor 120 may restore the current block based on the residual block of the current block.

The image reconstructor 120 may generate a prediction block of the current block by performing inter prediction or intra prediction on the current block. The image restoration unit 120 may reconstruct the current block based on the prediction block of the current block and the residual block of the current block. That is, the image restoration unit 120 may restore values of pixels included in the current block by adding values of pixels included in the prediction block and values of pixels included in the residual block.

The entropy decoding unit 105 may perform binary arithmetic decoding based on a context model on information on coordinates specifying a rectangular scan area. The entropy decoding unit 105 may perform inverse binarization using a predetermined inverse binarization method on the binary arithmetic decoded information to obtain inverse binarization information about coordinates specifying a rectangular scan area, and inverse binarization about the coordinates. Coordinates specifying the rectangular scan area may be acquired based on the information. In this case, the context model may be determined based on at least one of a size of the current block, a color component of the current block, and a blank index. The color component may include a luminance component and a color difference component. The bin index may be information indicating a position of a bin currently binary arithmetic-decoded among bin strings related to the syntax element. Here, the predetermined inverse binarization method may be at least one of a fixed length inverse binarization method and a cutting-type unary inverse binarization method.

The entropy decoder 105 may obtain transform coefficients of the current block by performing at least one of binary arithmetic decoding and inverse binarization based on a context model for the effective transform coefficients based on information on the scanned effective transform coefficients. have. When the information on the effective transform coefficients is information indicating whether the absolute value of the current effective transform coefficient is greater than a predetermined value, residual level information, and sign information of the current effective transform coefficient, the entropy decoding unit 105 performs the scanned effective transform. Binary arithmetic decoding based on a context model may be performed on information about coefficients. The entropy decoder 105 may obtain transform coefficients of the current block by performing inverse binarization on information about the effective transform coefficients that have been binary arithmetic-decoded. The first information about the effective transform coefficients is information indicating whether the information about the effective transform coefficients is greater than the absolute value of the current effective transform coefficient, residual level information, and sign information of the current effective transform coefficient, and the effective transform When the second information about the coefficients is the binarization parameter information, the entropy decoder 105 may perform binary arithmetic decoding based on the context model on the first information about the effective transform coefficient. The entropy decoder 105 may obtain transform coefficients of the current block by performing inverse binarization based on the binarization parameter information included in the second information on the binary arithmetic-decoded first information. The binarization parameter information may be Rice parameter information for the current transform coefficient. The context model for the first transform coefficient among the context models for flag information of the transform coefficients is previously scanned according to a predetermined scan order. It may be determined based on at least one of information on at least one second transform coefficient, a position and a color component of the first transform coefficient in the current block, information on a right or lower peripheral transform coefficient, and a scan position of the first transform coefficient. have.

The context model for flag information indicating whether the first transform coefficient is greater than 0 may be determined based on the number of effective transform coefficients on the right side and the bottom side having an absolute value greater than 0.

The context model for flag information indicating whether the first transform coefficient is greater than 0 is not limited thereto, and the absolute value of the n transform coefficients previously scanned according to a predetermined scan order (n is a positive integer) is greater than 0. It can be determined based on the number of large effective transform coefficients.

Alternatively, flag information indicating whether the first transform coefficient is greater than 0 (hereinafter referred to as GT0 flag information) is GT0 flag information of n (n is a positive integer) transform coefficients previously scanned according to a predetermined scan order and the current GT0 flag information of the position of the first transform coefficient in the block, the color component, and n (n is a positive integer) adjacent right or lower transform coefficients, whether the first transform coefficient is a transform coefficient at the first position in the scan area, The first transform coefficient may be determined based on at least one of whether the first transform coefficient is a transform coefficient of a final position in the scan area.

The context model for flag information indicating whether the first transform coefficient is greater than 1 may be determined based on the number of effective transform coefficients on the right side and the bottom side having an absolute value greater than 1.

The context model regarding flag information indicating whether the first transform coefficient is greater than 1 is not limited thereto, and the absolute value of the n transform coefficients previously scanned according to a predetermined scan order (n is a positive integer) is greater than 1. It can be determined based on the number of large effective transform coefficients.

Alternatively, flag information indicating whether the first transform coefficient is greater than 1 (hereinafter referred to as GT1 flag information) is GT1 flag information of n (n is a positive integer) transform coefficients previously scanned according to a predetermined scan order and the current GT1 flag information of the position of the first transform coefficient in the block, the color component, and n (n is a positive integer) adjacent right or lower transform coefficients, whether the first transform coefficient is a transform coefficient at the first position in the scan area, The first transform coefficient may be determined based on at least one of whether the first transform coefficient is a transform coefficient of a final position in the scan area.

The context model for flag information indicating whether the first transform coefficient is greater than 2 may be determined based on the number of effective transform coefficients on the right side and the bottom side having an absolute value greater than 2. 2 In this case, the context model for flag information indicating whether the first transform coefficient is greater than 2 is not limited to the second tooth, among n (n is a positive integer) transform coefficients previously scanned according to a predetermined scan order. The absolute value may be determined based on the number of effective transform coefficients greater than 2.

Alternatively, flag information indicating whether the first transform coefficient is greater than 2 (hereinafter referred to as GT2 flag information) is GT1 flag information of n (n is a positive integer) transform coefficients previously scanned according to a predetermined scan order and the current GT1 flag information of the position of the first transform coefficient in the block, the color component, and n (n is a positive integer) adjacent right or lower transform coefficients, whether the first transform coefficient is a transform coefficient at the first position in the scan area, The first transform coefficient may be determined based on at least one of whether the first transform coefficient is a transform coefficient of a final position in the scan area.

Alternatively, flag information indicating whether the first transform coefficient is greater than m (m is an integer greater than 2) (hereinafter referred to as GTm flag information) is n (n is a positive integer) previously scanned according to a predetermined scan order. GTm flag information of the transform coefficients, the position of the first transform coefficient in the current block, the color component, and GTm flag information of n adjacent right or lower transform coefficients (n is a positive integer), the first transform coefficient is in the scan area It may be determined based on at least one of whether the first transform coefficient is a transform coefficient of the first position and whether the first transform coefficient is a transform coefficient of the final position in the scan area.

Meanwhile, the binarization parameter information about the residual level absolute value of the first transform coefficient may be determined based on the absolute level values of the adjacent effective transform coefficients on the right side and the lower side of the first transform coefficient.

For example, the binarization parameter information about the residual level absolute value of the first transform coefficient may be determined based on the sum of the level absolute values of the right and lower peripheral effective transform coefficients of the first transform coefficient.

The context model for flag information indicating whether the first transform coefficient is greater than 2 is not limited thereto, and the absolute value of the n transform coefficients previously scanned according to a predetermined scan order (n is a positive integer) is greater than 2 It can be determined based on the number of large effective transform coefficients.

The context model for flag information indicating whether the first transform coefficient is greater than 1 may be determined based on the number of effective transform coefficients on the right side and the bottom side having an absolute value greater than 1.

The context model for flag information indicating whether the first transform coefficient is greater than 2 may be determined based on the number of effective transform coefficients on the right side and the bottom side having an absolute value greater than 2.

Meanwhile, the binarization parameter information about the residual level absolute value of the first transform coefficient may be determined based on the absolute level values of the adjacent effective transform coefficients on the right side and the lower side of the first transform coefficient. For example, the binarization parameter information about the residual level absolute value of the first transform coefficient may be determined based on the sum of the level absolute values of the right and lower peripheral effective transform coefficients of the first transform coefficient.

The binarization parameter information about the absolute residual level of the first transform coefficient includes the levels of n (n is an integer) transform coefficients previously scanned according to a predetermined scan order, the position of the first transform coefficient in the current block, a color component, and The level of n (n is a positive integer) transform coefficients adjacent to the right or lower side, whether the first transform coefficient in the scan order is the transform coefficient at the first position in the scan area, and the first transform coefficient in the scan order It may be determined based on at least one of whether the transform coefficient of the final position is or whether the first transform coefficient is the coefficient of the first position in the coefficient group in the scan order.

The entropy decoding unit 105 has the position of the transform coefficient currently being scanned in the scan area [SRx,0] (SRx is an integer, SRx is the horizontal coordinate value of the right boundary pixel of the scan area based on the coordinates of the upper left corner of the scan area. Means), and [SRx,Y] previously scanned according to a predetermined scan order (Y is an integer greater than 0 and less than or equal to SRy, SRy is the lower boundary of the scan area based on the coordinates of the upper left corner of the scan area) Refers to the vertical coordinate value of the pixel) If the transform coefficients of the position are all 0s, the GT0 flag information value may be determined as 1 without obtaining GT0 flag information of the transform coefficient currently scanned from the bitstream.

Likewise, the entropy decoder 105 has the position of the transform coefficient currently being scanned in the scan area [0,SRy] (SRy is an integer, SRy is the vertical coordinate of the lower boundary of the scan area based on the coordinates of the upper left corner of the scan area. Value), and [X,SRy] previously scanned according to a predetermined scan order (X is an integer greater than 0 and less than or equal to SRx, SRx is the right side of the scan area based on the coordinates of the upper left corner of the scan area) Refers to the vertical coordinate value of the boundary pixel) If the transform coefficients of the position are all 0 coefficients, the GT0 flag information value can be determined as 1 without obtaining GT0 flag information of the transform coefficient currently scanned from the bitstream. .

Meanwhile, the entropy decoder 105 may determine the maximum number of GT1 flag information of the effective transform coefficient in the current block, and receive GT1 flag information in the current block from the bitstream within the maximum coefficient of the determined effective transform coefficient. . That is, when the entropy decoding unit 105 receives the maximum number of GT1 flag information of the effective transform coefficients received from the bitstream, the entropy decoding unit 105 later determines whether there is GT1 flag information of the effective transform coefficient from the bitstream. May not be checked any more.

The entropy decoder 105 may determine all non-zero effective transform coefficients as the maximum number of GT1 flag information in the current block. Alternatively, the entropy decoder 105 may determine the maximum number of GT1 flag information in the current block based on the size of the scan area. For example, the entropy decoder 105 may determine the maximum number of GT1 flag information MaxCount_GT1 based on Equation 9 below.

Here, sizeSR may mean the size (width) of the rectangular scan area, and sizeSR may be (Sr_x+1)*(Sr_y+1). Sr_x may mean the horizontal coordinate of the rightmost effective transform coefficient pixel based on the coordinate of the upper left corner of the scan area. In other words, Sr_x may mean horizontal coordinates of the right boundary pixel based on the coordinates of the upper left corner of the scan area. Sr_y may mean the vertical coordinate of the lowest effective transform coefficient pixel based on the coordinate of the upper left corner of the scan area. In other words, Sr_y may mean the vertical coordinate of the lower boundary pixel based on the coordinate of the upper left corner of the scan area. K1 may be an adjustment coefficient between the size of the scan area and the GT1 flag. For example, it may be an integer greater than 1. Th1 may be a predetermined threshold. For example, Th1 may be 16,8. However, it is not limited thereto, and those skilled in the art can easily understand that K1 and Th1 may have various values.

The entropy decoding unit 105 may determine the maximum number of GT2 flag information in the current block and receive GT2 flag information in the current block within the determined maximum coefficient of the effective transform coefficient from the bitstream. That is, when the entropy decoding unit 105 receives the maximum number of GT2 flag information of the effective transform coefficients received from the bitstream, the entropy decoding unit 105 later determines whether there is GT2 flag information of the effective transform coefficient from the bitstream. May not be checked any more.

The entropy decoder 105 may determine all non-zero effective transform coefficients as the maximum number of GT2 flag information in the current block. Alternatively, the entropy decoder 105 may determine the maximum number of GT2 flag information in the current block based on the size of the scan area. For example, the entropy decoder 105 may determine the maximum number of GT2 flag information MaxCount_GT2 based on Equation 10 as follows.

Here, sizeSR may mean the size (width) of the rectangular scan area, and sizeSR may be (Sr_x+1)*(Sr_y+1). Sr_x may mean the horizontal coordinate of the rightmost effective transform coefficient pixel based on the coordinate of the upper left corner of the scan area. In other words, Sr_x may mean horizontal coordinates of the right boundary pixel based on the coordinates of the upper left corner of the scan area. Sr_y may mean the vertical coordinate of the lowest effective transform coefficient pixel based on the coordinate of the upper left corner of the scan area. In other words, Sr_y may mean the vertical coordinate of the lower boundary pixel based on the coordinate of the upper left corner of the scan area. K2 may be an adjustment factor. For example, it may be an integer greater than 1. K2 may be a predetermined threshold. For example, Th2 may be 16,8. However, it is not limited thereto, and those skilled in the art can easily understand that K2 and Th2 may have various values.

The entropy decoder 105 may obtain information on a coefficient group in the current block from the bitstream. The information on the coefficient group may be flag information indicating whether the coefficient group includes at least one effective transform coefficient. In this case, the entropy decoder 105 may determine one coefficient group for each K (K is an integer) transform coefficients scanned according to the scan order of the transform coefficients included in the scan region. That is, one coefficient group may include K transform coefficients. In this case, the scan order may be a forward scan order that is opposite to a predetermined reverse scan order. The predetermined reverse scan order referred to herein may mean an order of scanning from a coefficient positioned at the lower right of the transform coefficients included in the current block to a coefficient positioned at the upper left of the transform coefficients included in the current block.

Accordingly, the entropy decoder 105 may determine a coefficient group by scanning from a DC coefficient, which is a coefficient adjacent to the upper left corner of the current block, in a forward scan order. In this case, when the number of transform coefficients included in the current block is not an integer multiple of K, the final coefficient group among the groups of coefficients scanned according to the forward scan order may include a number of transform coefficients smaller than K. However, the present invention is not limited thereto, and the entropy decoding unit 105 scans from a coefficient located at the lower right of the transform coefficients included in the current block to a coefficient located at the upper left of the transform coefficients included in the current block. It can be easily understood by those skilled in the art that coefficient groups can be determined by scanning according to.

The entropy decoding unit 105 does not obtain information on the coefficient group from the bitstream, but only GT0 flag information, when the final coefficient group among the coefficient groups scanned according to a predetermined scan order includes only one transform coefficient. It can be obtained from the bitstream.

The entropy decoder 105 may determine whether to hide the sign of at least one transform coefficient for each coefficient group included in the current block. For example, in some cases, the entropy decoder may determine to hide the signs of one or two transform coefficients for each coefficient group included in the current block.

The entropy decoding unit 105 may scan information about an effective transform coefficient in a rectangular scan area according to a predetermined scan order. The predetermined scan order may include a reverse zigzag scan order, a reverse diagonal scan order, a reverse vertical scan order, and a horizontal scan order. However, it will be easily understood by those skilled in the art that the predetermined scan order is not limited to the above-mentioned reverse scan order, and may include various reverse scan orders.

The entropy decoder 105 may obtain transform coefficients of the current block based on information about the scanned effective transform coefficients.

The image reconstructor 120 may generate a residual block of the current block by performing inverse quantization and inverse transformation on transform coefficients of the current block.

The image reconstructor 120 may restore the current block based on the residual block of the current block.

The image reconstructor 120 may generate a prediction block of the current block by performing inter prediction or intra prediction on the current block. The image restoration unit 120 may reconstruct the current block based on the prediction block of the current block and the residual block of the current block. That is, the image restoration unit 120 may restore values of pixels included in the current block by adding values of pixels included in the prediction block and values of pixels included in the residual block. The optical flow will be described later in the description related to FIG. 3A.

The video decoding apparatus 100 may include an image decoding unit (not shown), and the image decoding unit (not shown) may include an entropy decoding unit 105 and an image restoration unit 120. An image decoding unit will be described with reference to FIG. 1E. FIG. 1B is a flowchart of a video decoding method according to various embodiments.

In step S105, the video decoding apparatus 100 may determine a scan area including all effective transform coefficients in the current block. At this time, the scan area includes transform coefficients from the upper left of the scan area to the last effective transform coefficient (hereinafter referred to as the last effective transform coefficient) when scanned according to a predetermined forward scan order. It may be an area to do. In this case, the coordinates specifying the scan area may be the coordinates of the last scanned effective transform coefficient pixel. The video decoding apparatus 100 may obtain information about coordinates representing a last effective transform coefficient from a bitstream, and determine a scan area based on information about coordinates representing the obtained last effective transform coefficient.

Alternatively, the scan area may be a rectangular scan area, and the rectangular scan area is a horizontal coordinate of an effective transform coefficient pixel positioned at the rightmost among all effective transform coefficients in the current block and an effective transform coefficient pixel positioned at the bottom of the current block. It may be an area specified by the vertical coordinate of. The video decoding apparatus 100 may obtain information about coordinates specifying the rectangular scan area from the bitstream, and determine the rectangular scan area based on information about coordinates specifying the obtained rectangular scan area.

In step S110, the video decoding apparatus 100 may scan information about transform coefficients in the scan area according to a predetermined scan order. The predetermined scan order may include a reverse zigzag scan order or a reverse diagonal scan order. The zigzag scan order may include a vertical first zigzag scan order or a horizontal first zigzag scan order. In step S115, the video decoding apparatus 100 performs binary arithmetic decoding on the basis of information on the scanned transform coefficients It is possible to generate arithmetic-decoded information. In this case, the video decoding apparatus 100 may perform binary arithmetic decoding by using a context model determined based on at least one of the size and shape of the current block.

In step S120, the video decoding apparatus 100 scans information on transform coefficients included in the scan area according to a predetermined scan order, performs inverse binarization on the binary arithmetic decoded information, and converts the transform coefficients of the current block. You can get information about it.

In step S125, the video decoding apparatus 100 may generate a residual block of the current block by performing inverse quantization and inverse transformation based on information on transform coefficients of the current block. That is, the video decoding apparatus 100 obtains transform coefficients of the current block based on information on the transform coefficients of the current block, and performs inverse quantization and inverse transform of the transform coefficients of the current block to obtain a residual block of the current block. Can be created.

In step S130, the video decoding apparatus 100 may reconstruct the current block based on the residual block. The video decoding apparatus 100 performs inter prediction or intra prediction to generate a prediction block of the current block, and the video decoding apparatus 100 adds a pixel value included in the prediction block of the current block and the pixel value of the residual block. A pixel value of a reconstructed block of the current block can be generated.

1C is a block diagram of a video encoding apparatus according to various embodiments.

The video encoding apparatus 150 according to various embodiments includes an entropy encoding unit 155 and a bitstream generation unit 170.

The entropy encoder 155 may entropy-encode a syntax element related to a transform coefficient in a current block. The entropy encoder 155 scans 2D array information about transform coefficients in the current block according to a predetermined scan order to generate 1D array information about transform coefficients in the current block, and generates transform coefficients in the current block. Entropy encoding can be performed on the one-dimensional array information of.

The syntax element for the transform coefficient may be a flag indicating whether the transform coefficient is greater than a predetermined value. In this case, the predetermined value may be greater than or equal to 0. For example, it may be 0, 1 or 2. In addition, it may be a syntax element indicating an absolute value of a remaining level for a transform coefficient. That is, the absolute value of the remaining level may represent an absolute value difference between the absolute value of the transform coefficient and a predetermined absolute value determined based on whether it is greater than the predetermined value. Also, the syntax element related to the effective transform coefficient may be a syntax element related to the sign of the effective transform coefficient.

First, the entropy encoder 155 may perform binarization on the syntax element to generate an empty string, and perform binary arithmetic encoding on the empty string to generate entropy-encoded information on the syntax element. In this case, binarization may be performed by the binarization unit 160, and binary arithmetic encoding may be performed by the binary arithmetic encoding unit 165.

The binarization unit 160 may generate an empty string by performing binarization on a predetermined syntax element. The binarization unit 160 may perform binarization on a predetermined syntax element based on a predetermined binarization method. The predetermined binarization method may include a fixed length binarization method, a Rice binarization method, an Exponential Golomb binarization method, and a Gollum-Rice binarization method. Alternatively, the predetermined binarization method may be a binarization method in which a first binarization method and a second binarization method are combined. For example, the binarization unit 160 may generate a first bin string by binarizing a part of the syntax element based on a first binarization method, and a second binarizing method for another part of the syntax element. A second bin string may be generated by performing binarization based on. In this case, the first empty string may be a part of the empty string of the syntax element, and the second empty string may be another part of the empty string of the syntax element. A part of the empty string may be a prefix or a suffix.

The binary arithmetic encoding unit 165 may perform binary arithmetic encoding based on a predetermined context model on an empty string for a predetermined syntax element. Alternatively, the binary arithmetic encoding unit 165 may perform binary arithmetic encoding on an empty string for a predetermined syntax element without a predetermined context model. At this time, the probability of generating 0 or 1 for a bin currently binary arithmetic coding is fixed at 0,5, and binary arithmetic coding may be performed based on this probability.

The entropy encoder 155 may obtain transform coefficients of the current block. That is, the video encoding apparatus 150 may perform inter prediction or intra prediction to generate a prediction block of the current block, and generate a residual block of the current block based on the original block of the current block and the prediction block of the current block. can do. The video encoding apparatus 150 may generate transform coefficients of the current block by performing transform and quantization on the residual block of the current block. The entropy encoder 155 may obtain transform coefficients of the generated current block.

The entropy encoder 155 determines information on the transform coefficients of the current block, scans information on the transform coefficients of the current block according to a predetermined scan order, and generates 1D array information about the transform coefficients of the current block. , Entropy encoding may be performed on 1D array information. The predetermined scan order may be an inverse zigzag scan or an inverse diagonal scan. The present invention is not limited thereto, and may be various scan orders, such as an inverse horizontal scan and an inverse vertical scan. The predetermined scan order may be determined based on at least one of a horizontal coordinate of an effective transform coefficient pixel positioned at the rightmost position in the current block and a vertical direction of an effective transform coefficient pixel positioned at the lowermost side of the current block. The entropy encoder 155 may determine a predetermined scan order based on the size of the horizontal coordinate value and the size of the vertical coordinate value. For example, when the horizontal coordinate value is greater than the vertical coordinate value, the entropy encoder 155 may determine a reverse vertical scan order as a predetermined scan order. When the vertical coordinate value is greater than the horizontal coordinate value, the entropy encoder 155 may determine the reverse horizontal scan order as a predetermined scan order.

Alternatively, when the horizontal coordinate value is greater than the vertical coordinate value, the entropy encoder 155 may determine a reverse vertical priority zigzag scan order as a predetermined scan order. When the vertical coordinate value is greater than the horizontal coordinate value, the entropy encoder 155 may determine a reverse horizontal first zigzag scan order as a predetermined scan order. When the vertical coordinate value is the same as the horizontal coordinate value, the entropy encoder 155 may determine one of a reverse vertical first zigzag scan order and a horizontal first zigzag scan order as a predetermined scan order.

Alternatively, when the horizontal coordinate value is greater than the vertical coordinate value, the entropy encoder 155 may determine the reverse horizontal priority zigzag scan order as a predetermined scan order. When the horizontal coordinate value is not greater than the vertical coordinate value, the entropy encoder 155 may determine a horizontal first zigzag scan order in the reverse direction as a predetermined scan order.

First, the entropy encoder 155 may determine a scan area including all effective transform coefficients in the current block. In this case, all effective transform coefficients in the current block may be included in the scan area, and the remaining areas in the current block excluding the scan area may include only transform coefficients having a value of 0, not the effective transform coefficient. At this time, the scan area includes transform coefficients from the upper left of the scan area to the last effective transform coefficient (hereinafter referred to as the last effective transform coefficient) when scanned according to a predetermined forward scan order. It may be an area to do. In this case, the coordinates specifying the scan area may be the coordinates of the last scanned effective transform coefficient pixel.

The entropy encoder 155 may generate information on coordinates representing the last effective transform coefficient. For example, the entropy decoder 105 may generate syntax element information indicating a horizontal coordinate value of the last effective transform coefficient and syntax element information indicating a vertical coordinate value of the last effective transform coefficient. In this case, entropy The encoding unit 155 generates an empty string by binarizing the syntax element representing the horizontal coordinate value of the last effective transform coefficient and the syntax element representing the vertical coordinate value of the last effective transform coefficient, and performs binary arithmetic on the empty string. By performing decoding, syntax element information indicating a horizontal coordinate value of the last effective transform coefficient and syntax element information indicating a vertical coordinate value of the last effective transform coefficient may be generated.

The entropy encoder 155 generates a first bin string by performing a first binarization method on some first values of the syntax element values, and performing a second binarization method on some other second values of the syntax element values. 2 You can create an empty string. An empty string including the first empty string and the second empty string may be generated. In this case, the first empty string may be a prefix, and the first binarization method may be a fixed-length binarization method. The second empty string may be a suffix, and the second inverse binarization method may be a truncated unary binarization method.

Alternatively, the entropy encoding unit 155 includes information indicating a coordinate value in one direction of a horizontal coordinate value of the last effective transform coefficient pixel or a vertical coordinate value of the last effective transform coefficient pixel among all effective transform coefficients in the current block, and Information indicating a difference between the coordinate value of one direction and the coordinate value of the other direction may be generated.

Alternatively, the scan area may be a rectangular scan area, and the rectangular scan area is a horizontal coordinate of an effective transform coefficient pixel positioned at the rightmost among all effective transform coefficients in the current block and an effective transform coefficient positioned at the bottom of the current block. It may be an area specified by the vertical coordinates of the pixel.

The entropy encoder 155 may generate syntax element information about coordinates specifying a rectangular scan area. For example, the entropy encoder 155 includes syntax element information indicating a horizontal coordinate value of an effective transform coefficient pixel located at the rightmost among all effective transform coefficients in the current block, and the most effective transform coefficient among all effective transform coefficients in the current block. Syntax element information indicating a vertical coordinate value of an effective transform coefficient pixel located at the lower side may be generated. At this time, the entropy encoding unit 155 is a syntax element representing a horizontal coordinate value of an effective transform coefficient pixel positioned at the rightmost among all effective transform coefficients in the current block and a lowermost position among all effective transform coefficients in the current block. Syntax element information representing the horizontal coordinate value of the last effective transform coefficient by binarizing the syntax element representing the vertical coordinate value of the effective transform coefficient pixel to generate an empty string, and performing binary arithmetic decoding on the empty string, and Syntax element information indicating the vertical coordinate value of the last effective transform coefficient may be generated.

The entropy encoder 155 generates a first bin string by performing a first binarization method on some first values of the syntax element values, and performing a second binarization method on some other second values of the syntax element values. 2 You can create an empty string. An empty string including the first empty string and the second empty string may be generated. In this case, the first empty string may be a prefix, and the first binarization method may be a fixed-length binarization method. The second empty string may be a suffix, and the second inverse binarization method may be a truncated unary binarization method.

Alternatively, the entropy encoding unit 155 is a horizontal coordinate value of an effective transform coefficient pixel positioned at the rightmost among all effective transform coefficients in the current block, or an effective transform coefficient positioned at the bottom of all effective transform coefficients in the current block. Information indicating a coordinate value in one direction among vertical coordinate values of a pixel and information indicating a difference between the coordinate value in the one direction and the coordinate value in the other direction may be generated. The entropy encoder 155 may determine the one direction based on the height and width of the current block.

The entropy encoder 155 may generate flag information indicating whether to obtain information indicating a difference between a coordinate value in one direction and a coordinate value in the other direction.

Meanwhile, the entropy encoder 155 may determine whether to generate flag information indicating whether to obtain information indicating a difference between a coordinate value in one direction and a coordinate value in the other direction based on the width and height of the current block. have. For example, when the width and height of the current block are different (i.e., in the case of a rectangle), the entropy encoder 155 determines whether to obtain information indicating the difference between a coordinate value in one direction and a coordinate value in the other direction. It is determined to generate the indicated flag information, and the flag information can be generated.

The entropy encoder 155 may determine a context model used for binary arithmetic encoding of all syntax elements used for coefficient encoding based on at least one of the size of the current block and the shape of the current block. . For example, the size of the current block may be determined according to at least one of minimum and maximum values of the height and width of the current block. The shape of the current block may be determined according to whether the width and height of the current block are the same. All syntax elements used for coefficient coding may include a syntax element for specifying a scan area and a syntax element for transform coefficients within the scan area.

For example, the entropy encoder 155 may determine information size_tu1 about the size of the current block based on Equation 11 below.

The entropy encoder 155 determines a context model corresponding to information size_tu1 about the size of the current block, determines a context model for a syntax element used for coefficient encoding, and uses the context model to determine a syntax used for coefficient encoding. Elements can be binary arithmetic coding.

Alternatively, the entropy encoder 155 may determine information size_tu2 about the size of the current block based on Equation 12 below.

The entropy encoder 155 determines a context model based on information size_tu2 on the size of the current block, determines a context model for a syntax element used for coefficient encoding, and uses the context model to determine a syntax used for coefficient encoding. Elements can be binary arithmetic coding.

Alternatively, the entropy encoder 155 determines a context model based on information size_tu1 and size_tu2 on the size of the current block, determines a context model for a syntax element used for coefficient encoding, and encodes coefficients using the context model. The syntax element used for can be subjected to binary arithmetic coding.

The entropy encoder 155 determines what is the minimum value and the maximum value among the sizes and heights of the current block, determines a context model based on the minimum and maximum values among the sizes and heights of the current block, and encodes the coefficients. A context model for a syntax element used for is determined, and a syntax element used for coefficient coding may be subjected to binary arithmetic coding using the context model.

Meanwhile, the entropy encoder 155 may determine a context model used for binary arithmetic coding of all syntax elements used for coefficient coding based on the shape of the current block.

For example, the entropy encoder 155 may determine information shape_tu on the shape of the current block based on Equation 13 below.

According to [Equation 13], the entropy encoder 155 determines shape_tu as 2 when the width of the current block is greater than the height and height, and determines shape_tu as 1 when the width of the current block is smaller than the height and height. And, if the width of the current block is equal to the height and height, shape_tu may be determined as 0. That is, for a rectangle having a width greater than the height, shape_tu may be determined as 2, for a rectangle having a height greater than the width, shape_tu may be determined as 1, and in the case of a square, shape_tu may be determined as 0.

The entropy encoder 155 determines a context model based on information shape_tu on the size of the current block, determines a context model for a syntax element used for coefficient encoding, and uses the context model to determine a syntax used for coefficient encoding. Elements can be binary arithmetic coding.

The entropy encoder 155 may determine a context model for a syntax element used for coefficient encoding based on the size of the current block and the shape of the current block. For example, the entropy decoder 155 determines a context model for a syntax element used for coefficient encoding based on at least one of size_tu1 and size_tu2 on the size of the current block and shape_tu on the shape of the current block, and , A syntax element used for coefficient coding may be subjected to binary arithmetic coding using the context model.

The entropy encoder 155 may change the height and width of the current block when either the height or the width is large among the cases in which the height and width of the current block are different. That is, the coordinates in the horizontal direction and the coordinates in the vertical direction of pixels included in the current block may be swapped. For example, when the width of the current block is greater than the height, the entropy encoder 155 may change the height and width of the current block. That is, values of horizontal coordinates and vertical coordinates of pixels included in the current block may be swapped. In addition, when the width of the current block is not greater than the height, the entropy encoder 155 may not swap horizontal coordinates and vertical coordinates of pixels included in the current block. This is not limited thereto, and the entropy encoder 155 may change the height and width of the current block when the height of the current block is greater than the width. That is, values of horizontal coordinates and vertical coordinates of pixels included in the current block may be swapped. When the horizontal and vertical coordinates of the pixels included in the current block are swapped, the entropy encoder 155 specifies the horizontal coordinates and vertical coordinates that specify the current block scan area. It is possible to change (swap) the coordinates of the horizontal and vertical coordinates to each other. The entropy encoder 155 may determine the first scan area in the swapped current block based on coordinates specifying the swapped scan area. The entropy encoder 155 may scan information about transform coefficients included in the first scan area, and perform entropy encoding on the information about the scanned transform coefficient. The entropy encoder 155 may perform a rectangular scan area. It is possible to determine the coordinates for specifying a, and entropy encoding information on the coordinates for specifying the rectangular scan area. That is, the entropy encoder 155 may generate a bin string by performing binarization based on a predetermined binarization method on a syntax element relating to coordinates specifying a rectangular scan area. Here, the predetermined binarization method may be at least one of a fixed length binarization method and a cutting-type unary binarization method.

The entropy encoder 155 may perform binary arithmetic encoding based on a context model on an empty string for a syntax element related to a coordinate specifying a rectangular scan area. In this case, the context model may be determined based on at least one of a size of the current block, a color component of the current block, and a blank index. The color component may include a luminance component and a color difference component. The bin index may be information indicating a position of a bin currently subjected to binary arithmetic coding among bin strings related to the syntax element.

The entropy encoder 155 may generate entropy-encoded information by performing at least one of binarization and binary arithmetic encoding based on a context model for the transform coefficients based on information about the scanned transform coefficients.

The first information about the transform coefficients is information indicating whether the absolute value of the current transform coefficient is greater than a predetermined value, information about the absolute value of the residual level, and sign information of the current transform coefficient, and the second information about the transform coefficients is the residual level. In the case of the absolute value of the binarization parameter information, the entropy encoder 155 may generate a bin string for the first information by performing binarization based on the second information on the first information on the transform coefficients. have. The entropy encoder 155 may generate entropy-encoded information by performing binary arithmetic encoding on a bin string related to the first information.

The second information includes information on at least one second transform coefficient previously scanned according to a predetermined scan order, a position of the first transform coefficient in the current block, a color component, information on the right or lower peripheral transform coefficient, and the second information. It may be determined based on at least one of the scan positions of one transform coefficient. For example, the binarization parameter information about the residual level absolute value of the first transform coefficient may be determined based on the level absolute value of the surrounding effective transform coefficients on the right or lower side of the first transform coefficient. The binarization parameter information about the residual level absolute value of the first transform coefficient may be determined based on the sum of the level absolute values of the peripheral effective transform coefficients on the right or lower side of the first transform coefficient.

Alternatively, the binarization parameter information about the absolute value of the residual level of the first transform coefficient is the level of n (n is an integer) transform coefficients previously scanned according to a predetermined scan order, the position of the first transform coefficient in the current block, and the color. The level of the component and n (n is a positive integer) transform coefficients adjacent to the right or lower side, whether the first transform coefficient in the scan order is the transform coefficient at the first position in the scan area, and the first transform coefficient is scanned in the scan order It may be determined based on at least one of whether a transform coefficient at a final position in the region or whether the first transform coefficient is a coefficient at a first position in a coefficient group in a scan order.

When the information about the transform coefficients is information indicating whether the absolute value of the current transform coefficient is greater than a predetermined value, information about the absolute value of the residual level, and the sign information of the current transform coefficient, the entropy encoder 155 Binaryization can be performed on information to generate a bin string. The entropy encoder 155 may generate binary arithmetic-encoded information by performing binary arithmetic encoding based on a context model for transform coefficients on a bin string. Among the context models for the transform coefficients, the context model for the first transform coefficient includes information on at least one second transform coefficient previously scanned according to a predetermined scan order, the position of the first transform coefficient in the current block, and a color. It may be determined based on at least one of a component, information about a right or a lower peripheral transform coefficient, and a scan position of the first transform coefficient.

The context model for flag information indicating whether the first transform coefficient is greater than 0 may be determined based on the number of effective transform coefficients on the right or the lower side having an absolute value greater than 0.

The entropy encoder 155 may determine a context model for flag information indicating whether the first transform coefficient is greater than 0 based on the position of the first transform coefficient in the current block. For example, when the sum of the horizontal coordinate value pos_x of the first transform coefficient in the current block and the vertical position pos_y in the current block is less than a predetermined threshold value thred1, the entropy encoder 155 sets the context index to a predetermined value. The context offset may be increased by offset1, and the context model may be determined based on the increased context index. When the sum of the horizontal coordinate value pos_x of the first transform coefficient in the current block and the vertical position pos_y in the current block is less than a predetermined threshold value thred2, the entropy encoder 155 sets the context index by a predetermined context offset offset2. The context model may be determined based on the increased and increased context index. When the sum of the horizontal coordinate value pos_x of the first transform coefficient in the current block and the vertical position pos_y in the current block is less than a predetermined threshold value thred3, the entropy encoder 155 sets the context index by a predetermined context offset offset3. The context model may be determined based on the increased and increased context index.

The entropy encoder 155 includes the size of the scan area, the number of transform coefficients already scanned in the scan area, the relative position of the first transform coefficient in the scan area, and the first position in which the first transform coefficient is scanned according to a predetermined scan order. A context model regarding flag information indicating whether the first transform coefficient is greater than 0 may be determined based on at least one of the coefficients.

For example, the entropy encoder 155 may determine the size_sr of the rectangular scan area based on Equation 14 below. That is, the size_sr of the rectangular scan area may mean the number of transform coefficients included in the rectangular scan area.

However, the present invention is not limited thereto, and when the scan area is a scan area specified by the coordinates of the last effective transform coefficient pixel, size_sr may mean the number of transform coefficients included in the scan area.

The entropy encoder 155 may determine the number cnt_pos of all transform coefficients scanned before scanning the first transform coefficient among the transform coefficients in the rectangular scan area. In this case, cnt_pos may indicate the position of the first transform coefficient among all transform coefficients in the scan area scanned according to a predetermined scan order.

When cnt_pos is less than a predetermined threshold value thred1, the entropy encoder 155 may increase the context index by a predetermined context offset offset1 and determine a context model based on the increased context index. At this time, thred1 may be 1. Alternatively, thred1 may be 1/4*size_sr.

When cnt_pos is less than a predetermined threshold value thred2, the entropy encoder 155 may increase the context index by a predetermined context offset offset2 and determine a context model based on the increased context index. In this case, thred2 may be 1/4*size_sr. Alternatively, thred2 may be 1/2*size_sr.

When cnt_pos is not smaller than the predetermined threshold values thred1 and thred2, the entropy encoder 155 may increase the context index by a predetermined context offset offset3 and determine a context model based on the increased context index. However, the threshold values thred1 and thred2 are only examples, and it can be easily understood by those skilled in the art that various values may be determined based on size_sr.

The entropy encoder 155 may determine a context model for flag information indicating whether the first transform coefficient is greater than 0 based on the relative position of the first transform coefficient in the scan area.

The entropy encoding unit 155 indicates whether the first transform coefficient is greater than 0 based on the horizontal coordinate value pos_x and the vertical coordinate value pos_y of the first transform coefficient in the current block and the coordinates Sr_x and Sr_y specifying the rectangular scan area. A context model for flag information can be determined.

When pos_x is smaller than thred1_x and pos_y is smaller than thred1_y, the entropy encoder 155 may increase the context index by a predetermined context offset offset1 and determine a context model based on the increased context index. In this case, [thred1_x, thred1_y] may be [1,1]. Alternatively, [thred1_x, thred1_y] may be [sr_x/4,sr_y/4] or [(sr_x+1)/4, (sr_y+1)/4].

When pos_x is smaller than thred2_x and pos_y is smaller than thred2_y, the entropy encoder 155 may increase the context index by a predetermined context offset offset2 and determine a context model based on the increased context index. In this case, [thred2_x,thred2_y] may be [thred1_x, thred1_y], [sr_x/2,sr_y/2] or [(sr_x+1)/2, (sr_y+1)/2].

However, the threshold values thred1_x, thred1_y, and thred2_y, thred2_y are only examples, and a person skilled in the art can easily understand that various values may be determined based on sr_x and sr_y.

The entropy encoder 155 may determine a context model for flag information indicating whether the first transform coefficient is greater than 0 based on whether the first transform coefficient is a transform coefficient of a first position scanned according to a reverse scan order. . That is, the entropy decoding unit 155 determines a first context model for flag information indicating whether the first transform coefficient is greater than 0 when the first transform coefficient is a first position scanned according to the reverse scan order, and If one transform coefficient is not the first position scanned according to the reverse scan order, a second context model regarding flag information indicating whether the first transform coefficient is greater than 0 may be determined. In this case, the transform coefficient of the pixel positioned at the lower right corner of the rectangular scan area may be a transform coefficient of the first position scanned according to the reverse scan order.

The context model for flag information indicating whether the first transform coefficient is greater than 0 is not limited thereto, and the absolute value of the n transform coefficients previously scanned according to a predetermined scan order (n is a positive integer) is greater than 0. It can be determined based on the number of large effective transform coefficients.

The context model for flag information indicating whether the first transform coefficient is greater than 1 may be determined based on the number of effective transform coefficients on the right or the lower side having an absolute value greater than 1.

The entropy encoder 155 may determine a context model regarding flag information indicating whether the first transform coefficient is greater than 1 based on the position of the first transform coefficient in the current block. For example, when the sum of the horizontal coordinate value pos_x of the first transform coefficient in the current block and the vertical position pos_y in the current block is less than a predetermined threshold value thred1, the entropy encoder 155 sets the context index to a predetermined value. The context offset may be increased by offset1, and the context model may be determined based on the increased context index. When the sum of the horizontal coordinate value pos_x of the first transform coefficient in the current block and the vertical position pos_y in the current block is less than a predetermined threshold value thred2, the entropy encoder 155 sets the context index by a predetermined context offset offset2. The context model may be determined based on the increased and increased context index.

When the sum of the horizontal coordinate value pos_x of the first transform coefficient in the current block and the vertical position pos_y in the current block is less than a predetermined threshold value thred3, the entropy encoder 155 sets the context index by a predetermined context offset offset3. The context model may be determined based on the increased and increased context index. At this time, offsets 1, 2, and 3 related to the context model regarding flag information indicating whether the first transform coefficient is greater than 1 and predetermined threshold values thred 1,2 and 3 are flag information indicating whether the first transform coefficient is greater than 0 Offsets offsets 1, 2, and 3 related to the context model for and predetermined threshold values thred 1, 2, and 3 may be different from each other.

The entropy encoder 155 determines the size of the scan area, the number of transform coefficients already scanned in the scan area, the relative position of the first transform coefficient in the scan area, and the first zero in which the first transform coefficient is scanned according to a predetermined scan order. A context model for flag information indicating whether the first transform coefficient is greater than 1 may be determined based on at least one of whether the transform coefficient of a non-location position is not.

For example, the entropy encoder 155 may determine the size_sr of the rectangular scan area based on Equation 15 below. That is, the size_sr of the rectangular scan area may mean the number of transform coefficients included in the rectangular scan area.

The entropy encoder 155 may determine the number cnt_pos of all transform coefficients scanned before scanning the first transform coefficient among the transform coefficients in the rectangular scan area. In this case, cnt_pos may indicate the position of the first transform coefficient among all transform coefficients in the scan area scanned according to a predetermined scan order. However, the present invention is not limited thereto, and cnt_pos may be the number of transform coefficients greater than all zeros scanned before scanning the first transform coefficient among transform coefficients in the rectangular scan area.

When cnt_pos is less than a predetermined threshold value thred1, the entropy encoder 155 may increase the context index by a predetermined context offset offset1 and determine a context model based on the increased context index. At this time, thred1 may be 1. Alternatively, thred1 may be 1/4*size_sr.

When cnt_pos is less than a predetermined threshold value thred2, the entropy encoder 155 may increase the context index by a predetermined context offset offset2 and determine a context model based on the increased context index. In this case, thred2 may be 1/4*size_sr. Alternatively, thred2 may be 1/2*size_sr.

When cnt_pos is not smaller than the predetermined threshold values thred1 and thred2, the entropy encoder 155 may increase the context index by a predetermined context offset offset3 and determine a context model based on the increased context index.

However, the threshold values thred1 and thred2 are only examples, and it can be easily understood by those skilled in the art that various values may be determined based on size_sr. At this time, offsets 1, 2, and 3 related to the context model regarding flag information indicating whether the first transform coefficient is greater than 1 and predetermined threshold values thred 1 and thred2 are related to flag information indicating whether the first transform coefficient is greater than 0. Those skilled in the art can easily understand that the offsets offset1, 2, and 3 related to the context model and the predetermined threshold values thred 1 and thred2 and their values may be different.

The entropy encoder 155 may determine a context model for flag information indicating whether the first transform coefficient is greater than 1 based on the relative position of the first transform coefficient in the scan area.

The entropy encoder 155 indicates whether the first transform coefficient is greater than 1 based on the horizontal coordinate value pos_x and the vertical coordinate value pos_y of the first transform coefficient in the current block and the coordinates Sr_x and Sr_y specifying the rectangular scan area. A context model for flag information can be determined.

When pos_x is smaller than thred1_x and pos_y is smaller than thred1_y, the entropy encoder 155 may increase the context index by a predetermined context offset offset1 and determine a context model based on the increased context index. In this case, [thred1_x,thred1_y] may be [1,1]. Alternatively, [thred1_x,thred1_y] may be [sr_x/4,sr_y/4] or [(sr_x+1)/4, (sr_y+1)/4].

When pos_x is smaller than thred2_x and pos_y is smaller than thred2_y, the entropy encoder 155 may increase the context index by a predetermined context offset offset2 and determine a context model based on the increased context index. In this case, [thred2_x,thred2_y] may be [thred1_x, thred1_y], [sr_x/2,sr_y/2] or [(sr_x+1)/2, (sr_y+1)/2].

However, the threshold values thred1_x, thred1_y, and thred2_y, thred2_y are only examples, and a person skilled in the art can easily understand that various values may be determined based on sr_x and sr_y.

However, the threshold values thred1_x, thred1_y, thred2_x, and thred2_y are only examples, and a person skilled in the art can easily understand that various values may be determined based on size_sr. At this time, offsets offset1, 2, and 3 related to the context model regarding flag information indicating whether the first transform coefficient is greater than 1, and predetermined threshold values thred1_x, thred1_y, thred2_x, and thred2_y are flags indicating whether the first transform coefficient is greater than 0 Those skilled in the art can easily understand that offsets offset1, 2, and 3 related to the context model for information and predetermined threshold values thred1_x, thred1_y, thred2_x, and thred2_y and their values may be different.

The entropy encoder 155 uses flag information indicating whether the first transform coefficient is greater than 1 based on whether the first transform coefficient is a transform coefficient at the first position among transform coefficients larger than 0 scanned according to the reverse scan order. Can determine the context model for That is, when the first transform coefficient is a first position among transform coefficients larger than 0 scanned according to the reverse scan order, the video decoding apparatus 100 provides first information regarding flag information indicating whether the first transform coefficient is greater than 1 A second context model for flag information indicating whether the first transform coefficient is greater than 1 when the context model is determined and the first transform coefficient is not the first position among transform coefficients larger than 0 scanned according to the reverse scan order Can be determined.

The context model regarding flag information indicating whether the first transform coefficient is greater than 1 is not limited thereto, and the absolute value of the n transform coefficients previously scanned according to a predetermined scan order (n is a positive integer) is greater than 1. It can be determined based on the number of large effective transform coefficients.

The context model for flag information indicating whether the first transform coefficient is greater than 2 may be determined based on the number of effective transform coefficients on the right or the lower side having an absolute value greater than 2.

The entropy encoder 155 may determine a context model for flag information indicating whether the first transform coefficient is greater than 2 based on the position of the first transform coefficient in the current block. For example, when the sum of the horizontal coordinate value pos_x of the first transform coefficient in the current block and the vertical position pos_y in the current block is less than a predetermined threshold value thred1, the entropy encoder 155 sets the context index to a predetermined value. The context offset may be increased by offset1, and the context model may be determined based on the increased context index. When the sum of the horizontal coordinate value pos_x of the first transform coefficient in the current block and the vertical position pos_y in the current block is less than a predetermined threshold value thred2, the entropy encoder 155 sets the context index by a predetermined context offset offset2. The context model may be determined based on the increased and increased context index. When the sum of the horizontal coordinate value pos_x of the first transform coefficient in the current block and the vertical position pos_y in the current block is less than a predetermined threshold value thred3, the entropy encoder 155 sets the context index by a predetermined context offset offset3. The context model may be determined based on the increased and increased context index. At this time, offsets offset 1, 2, and 3 related to the context model regarding flag information indicating whether the first transform coefficient is greater than 2 and predetermined threshold values thred 1,2 and 3 indicate whether the first transform coefficient is greater than 0 and 1. Offsets offsets 1, 2, and 3 related to the context model for flag information and predetermined threshold values thred 1, 2, and 3 may be different from each other.

The entropy encoder 155 determines the size of the scan area, the number of transform coefficients already scanned in the scan area, the relative position of the first transform coefficient in the scan area, and the first zero in which the first transform coefficient is scanned according to a predetermined scan order. A context model regarding flag information indicating whether the first transform coefficient is greater than 1 may be determined based on at least one of whether the transform coefficient is a transform coefficient of a position that is not (or a first position among transform coefficients greater than 1).

For example, the entropy encoder 155 may determine the size_sr of the rectangular scan area based on Equation 16 below. That is, the size_sr of the rectangular scan area may mean the number of transform coefficients included in the rectangular scan area.

The entropy encoder 155 may determine the number cnt_pos of all transform coefficients scanned before scanning the first transform coefficient among the transform coefficients in the rectangular scan area. In this case, cnt_pos may indicate the position of the first transform coefficient among all transform coefficients in the scan area scanned according to a predetermined scan order. However, the present invention is not limited thereto, and cnt_pos may be the number of all transform coefficients whose absolute values are scanned before scanning the first transform coefficient among the transform coefficients in the rectangular scan area is greater than 1.

When cnt_pos is less than a predetermined threshold value thred1, the entropy encoder 155 may increase the context index by a predetermined context offset offset1 and determine a context model based on the increased context index. At this time, thred1 may be 1. Alternatively, thred1 may be 1/4*size_sr.

When cnt_pos is less than a predetermined threshold value thred2, the entropy encoder 155 may increase the context index by a predetermined context offset offset2 and determine a context model based on the increased context index. In this case, thred2 may be 1/4*size_sr. Alternatively, thred2 may be 1/2*size_sr.

When cnt_pos is not smaller than the predetermined threshold values thred1 and thred2, the entropy encoder 155 may increase the context index by a predetermined context offset offset3 and determine a context model based on the increased context index.

However, the threshold values thred1 and thred2 are only examples, and it can be easily understood by those skilled in the art that various values may be determined based on size_sr. At this time, offsets 1, 2, and 3 related to the context model related to flag information indicating whether the first transform coefficient is greater than 0 or 1 and predetermined threshold values thred 1 and thred2 indicate whether the first transform coefficient is greater than 0 or 1. Those skilled in the art can easily understand that the offsets offset1, 2, and 3 related to the context model for the flag information and the predetermined threshold values thred 1 and thred2 and their values may be different.

The entropy encoder 155 may determine a context model for flag information indicating whether the first transform coefficient is greater than 2 based on the relative position of the first transform coefficient in the scan area.

The entropy encoding unit 155 indicates whether the first transform coefficient is greater than 2 based on the horizontal coordinate value pos_x and the vertical coordinate value pos_y of the first transform coefficient in the current block and the coordinates Sr_x and Sr_y specifying the rectangular scan area. A context model for flag information can be determined.

When pos_x is smaller than thred1_x and pos_y is smaller than thred1_y, the entropy encoder 155 may increase the context index by a predetermined context offset offset1 and determine a context model based on the increased context index. In this case, [thred1_x,thred1_y] may be [1,1]. Alternatively, [thred1_x,thred1_y] may be [sr_x/4,sr_y/4] or [(sr_x+1)/4, (sr_y+1)/4].

When pos_x is smaller than thred2_x and pos_y is smaller than thred2_y, the entropy encoder 155 may increase the context index by a predetermined context offset offset2 and determine the context model based on the increased context index. In this case, [thred2_x,thred2_y] may be [thred1_x, thred1_y], [sr_x/2,sr_y/2] or [(sr_x+1)/2, (sr_y+1)/2].

However, the threshold values thred1_x, thred1_y, and thred2_y, thred2_y are only examples, and a person skilled in the art can easily understand that various values may be determined based on sr_x and sr_y.

However, the threshold values thred1_x, thred1_y, thred2_x, and thred2_y are only examples, and a person skilled in the art can easily understand that various values may be determined based on size_sr. At this time, offsets 1, 2, and 3 related to the context model related to flag information indicating whether the first transform coefficient is greater than 0 or 1, and predetermined threshold values thred1_x, thred1_y, thred2_x, and thred2_y indicate whether the first transform coefficient is greater than 0. Those skilled in the art can easily understand that offsets offset1, 2, and 3 related to the context model for the indicated flag information, and predetermined threshold values thred1_x, thred1_y, thred2_x, and thred2_y, and their values may be different.

The entropy encoder 155 uses flag information indicating whether the first transform coefficient is greater than 2 based on whether the first transform coefficient is a transform coefficient at the first position among transform coefficients larger than 0 scanned according to the reverse scan order. Can determine the context model for That is, when the first transform coefficient is the first among transform coefficients larger than 0 scanned according to the reverse scan order, the entropy encoding unit 155 is configured to provide a first flag information indicating whether the first transform coefficient is greater than 1. A second context model for flag information indicating whether the first transform coefficient is greater than 1 when the context model is determined and the first transform coefficient is not the first position among transform coefficients larger than 0 scanned according to the reverse scan order Can be determined.

However, the present invention is not limited thereto, and the entropy encoder 155 has a first transform coefficient of 2 based on whether the first transform coefficient is a transform coefficient of a first position among transform coefficients larger than 1 scanned according to the reverse scan order. It is possible to determine a context model for flag information indicating whether it is greater. That is, when the first transform coefficient is the first among transform coefficients larger than 1 scanned according to the reverse scan order, the entropy encoding unit 155 performs first information regarding flag information indicating whether the first transform coefficient is greater than 1 A second context model for flag information indicating whether the first transform coefficient is greater than 2 when the context model is determined and the first transform coefficient is not the first position among transform coefficients larger than 1 scanned according to the reverse scan order Without being limited thereto, the context model for flag information indicating whether the first transform coefficient is greater than 2 is among n (n is a positive integer) transform coefficients previously scanned according to a predetermined scan order. The absolute value may be determined based on the number of effective transform coefficients greater than 2.

The entropy encoder 155 determines the position of the currently scanned transform coefficient in the scan area [SRx,0] (SRx is an integer, SRx is the horizontal coordinate value of the right boundary pixel of the scan area based on the coordinates of the upper left corner of the scan area. Means), and [SRx,Y] previously scanned according to a predetermined scan order (Y is an integer greater than 0 and less than or equal to SRy, SRy is the lower boundary of the scan area based on the coordinates of the upper left corner of the scan area) Refers to the vertical coordinate value of the pixel) If the transform coefficients of the position are all zeros, GT0 flag information of the transform coefficient currently being scanned may not be generated.

Similarly, the entropy encoder 155 determines the position of the currently scanned transform coefficient in the scan area [0,SRy] (SRy is an integer, SRy is the vertical coordinate of the lower boundary of the scan area based on the coordinates of the upper left corner of the scan area. Value), and [X,SRy] previously scanned according to a predetermined scan order (X is an integer greater than 0 and less than or equal to SRx, SRx is the right side of the scan area based on the coordinates of the upper left corner of the scan area) Refers to the vertical coordinate value of the boundary pixel) If the transform coefficients of the position are all zeros, GT0 flag information of the transform coefficient currently being scanned may not be generated.

Meanwhile, the entropy encoder 155 may determine the maximum number of GT1 flag information of the effective transform coefficient in the current block, and generate GT1 flag information in the current block within the maximum coefficient of the determined effective transform coefficient. That is, when the entropy encoder 155 generates the maximum number of GT1 flag information of the effective transform coefficients, the entropy encoder 155 may no longer generate GT1 flag information of the effective transform coefficient.

The entropy encoder 155 may determine all non-zero effective transform coefficients as the maximum number of GT1 flag information in the current block. Alternatively, the entropy encoder 155 may determine the maximum number of GT1 flag information in the current block based on the size of the scan area. For example, the entropy encoder 155 may determine the maximum number of GT1 flag information MaxCount_GT1 based on Equation 17 below.

Here, sizeSR may mean the size (width) of the rectangular scan area, and sizeSR may be (Sr_x+1)*(Sr_y+1). Sr_x may mean the horizontal coordinate of the rightmost effective transform coefficient pixel based on the coordinate of the upper left corner of the scan area. In other words, Sr_x may mean horizontal coordinates of the right boundary pixel based on the coordinates of the upper left corner of the scan area. Sr_y may mean the vertical coordinate of the lowest effective transform coefficient pixel based on the coordinate of the upper left corner of the scan area. In other words, Sr_y may mean the vertical coordinate of the lower boundary pixel based on the coordinate of the upper left corner of the scan area. K1 may be an adjustment coefficient between the size of the scan area and the GT1 flag. For example, K1 may be an integer greater than 1. Th1 may be a predetermined threshold. For example, Th1 may be 16,8. However, it is not limited thereto, and those skilled in the art can easily understand that K1 and Th1 may have various values.

The entropy encoder 155 may determine the maximum number of GT2 flag information in the current block and generate GT2 flag information in the current block within the maximum coefficient of the determined effective transform coefficient. That is, if the entropy encoder 155 generates the maximum number of GT2 flag information of the effective transform coefficients, the entropy encoder 155 may no longer generate GT2 flag information of the effective transform coefficient.

The entropy encoder 155 may determine all non-zero effective transform coefficients as the maximum number of GT2 flag information in the current block. Alternatively, the entropy encoder 155 may determine the maximum number of GT2 flag information in the current block based on the size of the scan area. For example, the entropy encoder 155 may determine the maximum number of GT2 flag information MaxCount_GT2 based on Equation 18 below.

Here, sizeSR may mean the size (width) of the rectangular scan area, and sizeSR may be (Sr_x+1)*(Sr_y+1). Sr_x may mean the horizontal coordinate of the rightmost effective transform coefficient pixel based on the coordinate of the upper left corner of the scan area. In other words, Sr_x may mean horizontal coordinates of the right boundary pixel based on the coordinates of the upper left corner of the scan area. Sr_y may mean the vertical coordinate of the lowest effective transform coefficient pixel based on the coordinate of the upper left corner of the scan area. In other words, Sr_y may mean the vertical coordinate of the lower boundary pixel based on the coordinate of the upper left corner of the scan area. K2 may be an adjustment coefficient between the size of the scan area and the GT2 flag. For example, K2 may be an integer greater than 1. Th2 may be a predetermined threshold. For example, Th2 may be 16,8. However, it is not limited thereto, and those skilled in the art can easily understand that K2 and Th2 may have various values.

The entropy encoder 155 may generate information on a coefficient group within the current block. The information on the coefficient group may be flag information indicating whether the coefficient group includes at least one effective transform coefficient. In this case, the entropy encoder 155 may determine one coefficient group for every K (K is an integer) transform coefficients scanned according to the scan order of the transform coefficients included in the scan area. That is, one coefficient group may include K transform coefficients. In this case, the scan order may be a forward scan order that is opposite to a predetermined reverse scan order. The predetermined reverse scan order referred to herein may mean an order of scanning from a coefficient positioned at the lower right of the transform coefficients included in the current block to a coefficient positioned at the upper left of the transform coefficients included in the current block.

Accordingly, the entropy encoder 155 may determine a coefficient group by scanning from a DC coefficient that is a coefficient adjacent to the upper left corner of the current block in a forward scan order. In this case, when the number of transform coefficients included in the current block is not an integer multiple of K, the final coefficient group among the groups of coefficients scanned according to the forward scan order may include a number of transform coefficients smaller than K. However, the present invention is not limited thereto, and the entropy encoder 155 scans from a coefficient positioned at the lower right of the transform coefficients included in the current block to a coefficient positioned at the upper left of the transform coefficients included in the current block. It can be easily understood by those skilled in the art that coefficient groups can be determined by scanning according to.

The entropy encoding unit 155 does not generate information on the coefficient group and immediately stores GT0 flag information when one coefficient group among the groups of coefficients scanned according to a predetermined scan order includes only one transform coefficient. Can be generated.

The entropy encoder 155 may determine whether to hide the sign of at least one transform coefficient for each coefficient group included in the current block. For example, in some cases, the entropy encoder 155 may determine to hide the signs of one or two transform coefficients for each coefficient group included in the current block.

The entropy encoder 155 may scan information about transform coefficients in the rectangular scan area according to a predetermined scan order. The predetermined scan order may include a reverse zigzag scan order, a reverse diagonal scan order, a reverse vertical scan order, and a horizontal scan order. However, it will be easily understood by those skilled in the art that the predetermined scan order is not limited to the above-mentioned reverse scan order, and may include various reverse scan orders.

The bitstream generator 170 may generate a bitstream including entropy-encoded information. That is, the bitstream generator 170 may scan information about a transform coefficient in the entropy encoder 160 and generate a bitstream including entropy-encoded information based on the information about the scanned transform coefficient. .

The bitstream generation unit 170 may generate a bitstream including information about coordinates specifying an area scan area for scanning information about transform coefficients.

The video encoding apparatus 150 may include an image encoder (not shown), and the image encoder (not shown) may include an entropy encoder 155 and a bitstream generator 170. The video encoder will be described with reference to FIG. 1F.

1D is a flowchart of a video encoding method according to various embodiments.

Referring to FIG. 1D, in step S150, the video encoding apparatus 150 may obtain transform coefficients of a current block. The current block may be a data unit that can be used in a process of encoding/decoding an image described with reference to FIGS. 10 to 23. The video encoding apparatus 150 may perform inter prediction or intra prediction to generate a prediction block of the current block, and may generate a residual block of the current block based on an original block of the current block and a prediction block of the current block. have. The video encoding apparatus 150 may generate transform coefficients of the current block by performing transform and quantization on the residual block of the current block.

In step S155, the video encoding apparatus 150 may determine a scan area including all effective transform coefficients in the current block. In this case, all effective transform coefficients in the current block may be included in the scan area, and the remaining areas in the current block excluding the scan area may include only 0, not the effective transform coefficient.

In step S160, the video encoding apparatus 150 may scan information on transform coefficients included in the scan area according to a predetermined scan order. The information on the transform coefficient may include flag information indicating whether the transform coefficient is greater than a predetermined value. In this case, the predetermined value may be at least one of 0, 1, and 2. It may include at least one of residual level information about the absolute value of the transform coefficient, code information of the transform coefficient, and binarization parameter information of the residual level absolute value. The predetermined scan order may include a reverse zigzag scan order, a reverse diagonal scan order, a reverse vertical scan order, and a horizontal scan order. However, it will be easily understood by those skilled in the art that the predetermined scan order is not limited to the above-mentioned reverse scan order, and may include various reverse scan orders.

In step S165, the video encoding apparatus 150 may generate binarized information by performing binarization based on information on the scanned transform coefficient.

In step S170, the video encoding apparatus 150 may generate entropy-encoded information by performing binary arithmetic encoding on the binarized information. In this case, the video encoding apparatus 150 may perform binary arithmetic encoding using a context model determined based on at least one of the size and shape of the current block.

In step S175, the video encoding apparatus 150 may generate a bitstream including entropy-encoded information. The video encoding apparatus 150 may scan information about a transform coefficient in the entropy encoder 160 and generate a bitstream including entropy-encoded information based on the information about the scanned transform coefficient. The video encoding apparatus 150 may generate a bitstream including information about coordinates specifying a scan area, which is an area for scanning information about transform coefficients.

1E is a block diagram of an image decoder 6000 according to various embodiments.

The image decoder 6000 according to various embodiments of the present disclosure performs tasks performed by an image decoder (not shown) of the video decoding apparatus 100 to encode image data.

Referring to FIG. 1E, an entropy decoder 6150 parses encoded image data to be decoded and encoding information necessary for decoding from a bitstream 6050. The encoded image data is a quantized transform coefficient, and the inverse quantization unit 6200 and the inverse transform unit 6250 restore residual data from the quantized transform coefficient. The entropy decoding unit 6150 of FIG. 1E may correspond to the entropy decoding unit 105 of FIG. 1A.

The intra prediction unit 6400 performs intra prediction for each block. The inter prediction unit 6350 performs inter prediction for each block by using a reference image acquired from the reconstructed picture buffer 6300. By adding the prediction data for each block generated by the intra prediction unit 6400 or the inter prediction unit 6350 and the residual data, data in the spatial domain of the block of the current image 6050 is restored, and the deblocking unit ( 6450 and the SAO performing unit 6500 may perform loop filtering on the reconstructed spatial domain data to output the filtered reconstructed image 6600. Also, reconstructed pictures stored in the reconstructed picture buffer 6300 may be output as reference pictures.

In order to decode image data in a decoder (not shown) of the video decoding apparatus 100, step-by-step operations of the image decoder 6000 according to various embodiments may be performed for each block.

1F is a block diagram of an image encoder according to various embodiments.

The image encoder 7000 according to various embodiments performs tasks performed by an image encoder (not shown) of the video encoding apparatus 150 to encode image data.

That is, the intra prediction unit 7200 performs intra prediction for each block of the current image 7050, and the inter prediction unit 7150 calculates the current image 7050 and the reference image acquired from the reconstructed picture buffer 7100 for each block. Inter prediction is performed by using.

The residual data is generated by subtracting the prediction data for each block output from the intra prediction unit 7200 or the inter prediction unit 7150 from the data for the block to be encoded in the current image 7050, and the transform unit 7250 And the quantization unit 7300 may perform transform and quantization on the residual data to output quantized transform coefficients for each block. The inverse quantization unit 7450 and the inverse transform unit 7500 may restore residual data in the spatial domain by performing inverse quantization and inverse transformation on the quantized transform coefficient. The residual data of the reconstructed spatial domain is restored to data of the spatial domain of the block of the current image 7050 by adding prediction data for each block output from the intra prediction unit 7200 or the inter prediction unit 7150. . The deblocking unit 7550 and the SAO performing unit perform in-loop filtering on the reconstructed spatial domain data to generate a filtered reconstructed image. The generated reconstructed image is stored in the reconstructed picture buffer 7100. The reconstructed pictures stored in the reconstructed picture buffer 7100 may be used as a reference picture for inter prediction of other pictures. The entropy encoding unit 7350 may entropy-encode the quantized transform coefficients and output the entropy-encoded coefficients as the bitstream 7400. The entropy encoder 7350 of FIG. 1F may correspond to the entropy encoder 155 of FIG. 1C.

In order to apply the image encoder 7000 according to various embodiments to the video encoding apparatus 150, step-by-step operations of the image encoder 7000 according to various embodiments may be performed for each block.

Hereinafter, it is assumed that '0' and '1' shown for pixels in the current block of FIGS. 2 and 3A to 3B are the values of the effective transform coefficient flag (a flag indicating whether the absolute value of the coefficient is greater than 0). A method of scanning the transform coefficients in a block will be described in detail.

FIG. 2 is a diagram for describing a method of scanning an intra-block transform coefficient according to an exemplary embodiment.

Referring to FIG. 2, the current block 200 is a block including a plurality of transform coefficients. The current block 200 is a data unit that performs an inverse transform operation, and may be a block having a size of MxN (M and N are positive integers). For example, as shown in FIG. 2, the current block 200 may be a 16×16 block.

The video decoding apparatus 100 may divide the current block 200 into coefficient groups (or sub-blocks) 205 having a predetermined size. The coefficient group may be a block having a size of XxY (X and Y are positive integers). For example, as shown in FIG. 2, the coefficient group 205 may be a 4x4 block.

The video decoding apparatus 100 scans the current block 200 from the upper left transform coefficient to the lower right transform coefficient according to the forward scan order. Among all the effective transform coefficients scanned, the pixel of the final effective transform coefficient ( 210) can be obtained from the bitstream. The information about the coordinates of the pixel 210 of the final effective transform coefficient may include information about the horizontal coordinate of the pixel of the final effective transform coefficient and information about the vertical coordinate of the pixel of the final effective transform coefficient.

The video decoding apparatus 100 acquires the coordinates of the pixel 210 of the final effective transform coefficient based on the information on the coordinates of the pixel 210 of the final effective transform coefficient, and the coordinates of the pixel 210 of the final effective transform coefficient The information of the transform coefficient may be scanned according to a predetermined reverse scan order 215 from the effective transform coefficient for the final effective transform coefficient 210. For example, as shown in FIG. 2, a predetermined reverse scan order 215 may be a reverse diagonal scan order.

The video decoding apparatus 100 may scan the coefficient groups 205 according to a predetermined scan order, and scan each coefficient group 205 according to a predetermined scan order. The video decoding apparatus 100 may scan information on a coefficient group with respect to the coefficient groups according to a predetermined scan order. Information about the coefficient group may be obtained or derived from the bitstream. The information on the coefficient group may be derived to indicate that at least one effective transform coefficient is included for the first coefficient group and the last coefficient group scanned according to the forward (reverse) scan order. That is, information about the coefficient group may not be included in the bitstream for the first coefficient group and the last coefficient group scanned according to the forward (reverse) scan order.

In this case, the video decoding apparatus 100 may determine a predetermined reverse scan order based on at least one of a block size and a prediction mode. For example, when the size of the current block is 4x4 and the prediction mode of the current block is the intra prediction mode, the video decoding apparatus 100 selects one of a reverse horizontal scan order, a vertical scan order, or a diagonal scan order. It can be determined in reverse scan order. In addition, when the size of the current block is 8x8 and the prediction mode of the current block is the intra prediction mode, the video decoding apparatus 100 performs one of a reverse horizontal scan order, a vertical scan order, or a diagonal scan order. You can decide in order.

When the size of the current block is not 4x4 or 8x8, or the prediction mode of the current block is not the inter prediction mode, the video decoding apparatus 100 may determine a reverse diagonal scan order as a predetermined reverse scan order.

When the information on the coefficient group 205 indicates that the coefficient group 205 includes at least one effective coefficient, the video decoding apparatus 100 may reverse the information on the transform coefficients in the coefficient group 205 in the reverse direction. Information about transform coefficients in the coefficient group may be scanned according to a predetermined scan order 215.

Meanwhile, the video decoding apparatus 100 may determine whether to hide at least one sign among effective transform coefficients included in each coefficient group 205.

3A is a diagram for describing a method of scanning an intra-block transform coefficient according to another embodiment.

Referring to FIG. 3A, a current block 300 is a block including a plurality of transform coefficients. The current block 300 is a data unit that performs an inverse transform operation, and may be a block having a size of MxN (M,N are positive integers). For example, as shown in FIG. 3, the current block 300 may be a 16×16 block.

Referring to FIG. 3A, the video decoding apparatus 100 may determine a rectangular scan area 340 including all effective transform coefficients existing in the current block 300. In this case, the rectangular scan area 340 may be determined by the coordinates of the pixel 330 positioned at the lower right of the rectangular scan area 340. The horizontal coordinates of the pixel 330 positioned at the lower right of the scan area 340 may be the horizontal coordinates of the effective transform coefficient pixel 320 positioned at the rightmost among all the effective transform coefficients in the current block 300 have. The vertical coordinate of the pixel 330 positioned at the lower right of the scan area 340 may be the vertical coordinate of the effective transform coefficient pixel 310 positioned at the bottom of all effective transform coefficients in the current block 300 have. The information on the pixel 330 may include information on the position of the upper left corner of the pixel 330. However, the present invention is not limited thereto, and the information on the pixel 330 may include information on the position of the lower right corner of the pixel 330.

The video decoding apparatus 100 receives information on the coordinates of the pixel 330 specifying the rectangular scan area 340 from the bitstream, and the rectangular scan area 340 based on the received information on the pixel 330 Can be determined. The video decoding apparatus 100 may scan information on the transform coefficient from the pixel 330 to the pixel 345 at the upper left of the rectangular scan area 340 according to a predetermined reverse scan order 355. In this case, the coefficient group may be determined for each K scan coefficients (K is a positive integer) scanned according to a predetermined forward scan order from the transform coefficient at the upper left of the rectangular scan area 340. However, it is not limited thereto, and those skilled in the art can easily understand that it may be determined for each K scan coefficients (K is a positive integer) scanned according to a predetermined reverse scan order from the transform coefficient at the lower right. Details of the coefficient group will be described later with reference to FIG. 3B.

Meanwhile, the video decoding apparatus 100 may determine that a sign for at least one effective transform coefficient is hidden for each coefficient group, and may restore a sign for at least one effective transform coefficient that is hidden. . Details on performing the operation of restoring hidden codes for each coefficient group will be described later with reference to FIG. 3B.

3B is a diagram for describing an operation of determining a coefficient group (subblock) within a block and an operation performed for each coefficient group, according to an exemplary embodiment.

The video decoding apparatus 100 may determine a coefficient group for every K (K is a positive integer) transform coefficient pixels according to a predetermined scan order 355 in the forward direction in the current block 350. The video decoding apparatus 100 may determine a coefficient group including K transform coefficient pixels. For example, as shown in FIG. 3B, the video decoding apparatus 100 may determine a coefficient group 360 for every 16 pixels.

The video decoding apparatus 100 determines that a sign for at least one effective transform coefficient is hidden for each coefficient group 360, and a sign for at least one effective transform coefficient for each coefficient group 360 is You can decide that it is hidden. For example, the video decoding apparatus 100 may determine that a sign for at least one effective transform coefficient is hidden for the current coefficient group based on a distance of previously decoded effective transform coefficients in the current coefficient group. . In detail, the video decoding apparatus 100 uses a sign for at least one effective transform coefficient for the current coefficient group based on the distance between the first effective transform coefficient and the final effective transform coefficient scanned according to a predetermined reverse scan order. You can decide that is hidden. In this case, the distance may be a difference between the positions of the coefficients scanned according to the scan order in the reverse direction.

For example, when the distance between the first effective transform coefficient and the final effective transform coefficient scanned according to a predetermined reverse scan order is greater than a predetermined value, the video decoding apparatus 100 may determine at least one effective transform coefficient for the current coefficient group. It can be determined that the Sign is hidden. In this case, the predetermined value may be various integer values. For example, the predetermined value may be 3.

When it is determined that the sign for at least one effective transform coefficient is hidden for the current coefficient group, the video decoding apparatus 100 performs at least in the current coefficient group without obtaining information about the code from the bitstream for the current coefficient group. Hidden codes can be restored for one effective transform coefficient. For example, when the parity sum of the levels of the effective transform coefficients in the current coefficient group is odd or even, the video decoding apparatus 100 determines a code for at least one effective transform coefficient as 0 or 1. I can. In this case, the code of the restored effective transform coefficient may include a code related to the last effective transform coefficient scanned according to the reverse scan order. However, the present invention is not limited thereto, and those skilled in the art can easily understand that a code at a predetermined position in a coefficient group can be restored according to a predetermined scan order.

The video decoding apparatus 100 obtains information on a corresponding coefficient group from a bitstream according to a predetermined scan order in the reverse direction, and when the information on the coefficient group indicates that the coefficient group includes at least one transform coefficient, Information about transform coefficients within a coefficient group can be scanned. When the information on the coefficient group indicates that only the transform coefficients having a value of 0 are included in the coefficient group, all transform coefficients in the coefficient group may be determined as 0.

Meanwhile, when the number of transform coefficients included in the rectangular scan area in the current block 300 is not an integer multiple of K, the number of transforms less than K in the process of determining the last coefficient group according to the forward scan order There may be coefficient pixels. In this case, the video decoding apparatus 100 may determine a coefficient group 365 including a number of transform coefficient pixels less than K. For example, as shown in FIG. 3B, the video decoding apparatus 100 may determine a coefficient group 365 including two transform coefficients.

The video decoding apparatus 100 may obtain information on the coefficient groups 355 and 360 from the bitstream. Here, the information on the coefficient groups 355 and 360 is flag information indicating whether at least one of the transform coefficients included in the coefficient group 355 and 360 is an effective transform coefficient or whether only the transform coefficients having 0 in the coefficient group 355 and 360 are included (effective coefficient Group flag information).

Meanwhile, if a coefficient group including only one transform coefficient is determined, the video decoding apparatus 100 does not obtain information about the coefficient group (eg, effective coefficient group flag information) from the bitstream, Information about the coefficient can be obtained.

The video decoding apparatus 100 is a context for binary arithmetic decoding information on the current coefficient group based on information on the coefficient group of the coefficient group scanned before the current coefficient group according to a predetermined scan order 355 in the reverse direction. You can decide the model.

FIG. 4 is a diagram for describing a process of determining a context model for context-based binary arithmetic encoding and decoding information on transform coefficients, according to an embodiment.

Referring to FIG. 4, the video decoding apparatus 100 may determine a context model of information on the currently scanned transform coefficient pixel 405 based on the surrounding transform coefficient pixels 410. In FIG. 4, the peripheral transform coefficient pixels 405 may be five pixels existing at a predetermined position on the right or lower side of the currently scanned transform coefficient pixel 405. However, the present invention is not limited thereto, and those skilled in the art can easily understand that the peripheral transform coefficient pixels 405 may be n (n is a positive integer) pixels present at predetermined positions on the right or the lower side.

For example, the video decoding apparatus 100 uses a context model of flag information indicating whether the absolute level value of the currently scanned transform coefficient pixel 405 is greater than 0, and the absolute level value of the surrounding transform coefficient pixels 410 is 0. It can be determined based on the number of larger coefficient pixels.

Also, the video decoding apparatus 100 uses a context model of flag information indicating whether the absolute level of the currently scanned transform coefficient pixel 405 is greater than 1, and the absolute value of the neighboring transform coefficient pixels 410 is greater than 1. Can be determined based on the number of pixels

The video decoding apparatus 100 uses a context model of flag information indicating whether the absolute level of the currently scanned transform coefficient pixel 405 is greater than 2, among coefficient pixels having an absolute value greater than 2 among the surrounding transform coefficient pixels 410. It can be determined based on the number.

The video decoding apparatus 100 uses the context model of flag information indicating whether the level value of the currently scanned transform coefficient pixel 405 is greater than N (N is an integer greater than 2) as an absolute value among the surrounding transform coefficient pixels 410 It can be determined based on the number of coefficient pixels greater than N.

The video decoding apparatus 100 may determine a parameter for binarizing the residual level absolute value of the currently scanned transform coefficient pixel 405 based on the sum of the absolute level values of the surrounding transform coefficient pixels 410. In this case, the binarization parameter may be a Rice parameter.

FIG. 5 is a diagram for describing a process of determining a context model for context-based binary arithmetic encoding and decoding information on transform coefficients, according to an embodiment.

Referring to FIG. 5, the video decoding apparatus 100 determines a context model of information about a transform coefficient pixel 505 currently being scanned, and transform coefficient pixels 510 previously scanned according to a predetermined reverse scan order 515. Can be determined based on As illustrated in FIG. 5, the transform coefficient pixels 510 may be five pixels previously scanned according to a predetermined reverse reflection scan order 515 than the currently scanned transform coefficient pixel 505. However, the present invention is not limited thereto, and those skilled in the art can easily understand that the transform coefficient pixels 505 may be n (n is a positive integer) pixels previously scanned according to a predetermined reverse reflection scan order 515. . As shown in FIG. 5, a predetermined reverse scan sequence 515 may be a reverse zig-zag scan sequence, but is not limited thereto, and those skilled in the art that it may include a horizontal scan sequence, a vertical scan sequence, and a diagonal scan sequence. It can be easily understood. In particular, the predetermined reverse scan order may be determined as one of a plurality of scan orders based on the size of the horizontal coordinate value and the size of the vertical coordinate value specifying the scan area.

For example, the video decoding apparatus 100 uses a context model of flag information indicating whether the absolute level of the currently scanned transform coefficient pixel 505 is greater than 0, and the absolute value of the surrounding transform coefficient pixels 510 is greater than 0. It can be determined based on the number of large coefficient pixels.

In addition, the video decoding apparatus 100 converts the context model of flag information indicating whether the absolute level of the currently scanned transform coefficient pixel 505 is greater than 1, among the transform coefficient pixels 510 having an absolute value greater than 1. It can be determined based on the number of them.

The video decoding apparatus 100 uses a context model of flag information indicating whether the absolute level of the currently scanned transform coefficient pixel 505 is greater than 2, among coefficient pixels having an absolute value greater than 2 among the surrounding transform coefficient pixels 510. It can be determined based on the number.

The video decoding apparatus 100 converts the context model of flag information indicating whether the absolute level of the currently scanned transform coefficient pixel 505 is greater than N (N is an integer greater than 2) among the surrounding transform coefficient pixels 510. It may be determined based on the number of coefficient pixels having a value greater than N.

The video decoding apparatus 100 may determine a parameter for binarizing the residual level absolute value of the currently scanned transform coefficient pixel 505 based on the sum of the absolute value levels of the surrounding transform coefficient pixels 510. In this case, the binarization parameter may be a Rice parameter.

6A is a diagram for describing a zigzag scan sequence for scanning information on effective transform coefficients in a block according to an embodiment.

6A, in order to scan information on the transform coefficients of the current block 600, the video decoding apparatus 100 is left from the transform coefficient pixel at the lower right of the current block 600 according to a zigzag scan order 602. You can scan up to the top transform coefficient pixels.

Specifically, according to the zigzag scan sequence 602, the video decoding apparatus 100 scans the left pixel 606 of the pixel 604 after scanning the transform coefficient pixel 604 at the lower right, and then the pixel 606 After scanning is performed, the pixels 608 located in the diagonal direction of the upper right are scanned. The video decoding apparatus 100 scans a pixel 610 adjacent to an upper side of the pixel 608. The video decoding apparatus 100 scans pixels 612 located in a diagonal direction at the lower left of the pixel. The video decoding apparatus 100 scans a pixel 614 positioned to the left of a pixel adjacent to the boundary of the current block 600 among the pixels 612. In a similar manner, the video decoding apparatus 100 may scan information about the remaining transform coefficient pixels according to the zigzag scan order 602.

Meanwhile, in the zigzag scan sequence 602 according to an embodiment, since the left-facing pixel 606 positioned in the horizontal direction is scanned immediately after scanning the pixel 604, the zigzag scan sequence 602 is referred to as the horizontal first zigzag sequence. Can be called.

6B is a diagram for explaining a vertical priority zigzag scan sequence for scanning information on transform coefficients in a block according to another embodiment.

6B, in order to scan information on the transform coefficients of the current block 600, the video decoding apparatus 100 is left from a transform coefficient pixel at the lower right of the current block 600 according to a zigzag scan order 616. You can scan up to the top transform coefficient pixels.

Specifically, according to the zigzag scan order 616, the video decoding apparatus 100 scans the upper pixel 620 of the pixel 618 after scanning the transform coefficient pixel 618 at the lower right, and then the pixel 620 After scanning is performed, the pixels 622 located in the diagonal direction at the lower left are scanned. The video decoding apparatus 100 scans a pixel 624 adjacent to the left side of the pixel 622. The video decoding apparatus 100 scans pixels 626 located in the diagonal direction of the upper right of the pixel. The video decoding apparatus 100 scans a pixel 628 positioned above a pixel adjacent to the boundary of the current block 600 among the pixels 626. In a similar manner, the video decoding apparatus 100 may scan information on the remaining transform coefficient pixels according to the zigzag scan order 616.

Meanwhile, in the zigzag scan sequence 616 according to an embodiment, since the upward direction pixels 620 positioned in the vertical direction are scanned immediately after scanning the pixels 618, the zigzag scan sequence 616 is referred to as the vertical priority zigzag sequence Can be called.

6C is a diagram for explaining a horizontal scan sequence for scanning information about transform coefficients in a block according to an embodiment.

Referring to FIG. 6C, the video decoding apparatus 100 scans information on the transform coefficients of the current block 600 to the left from the transform coefficient pixels at the lower right of the current block 600 according to a horizontal scan order 630. You can scan up to the top transform coefficient pixels.

Specifically, according to the horizontal scan order 630, the video decoding apparatus 100 sequentially scans the pixels 634 positioned in the left direction in the horizontal direction after scanning the transform coefficient pixels 632 at the lower right. , After scanning a pixel adjacent to the left boundary of the current block 600 among the pixels 634, the rightmost pixel 636 of the row immediately above is scanned. The video decoding apparatus 100 scans the pixels 638 positioned in the left direction in the horizontal direction in the same manner as the pixels 634 of the previous row were scanned. In a similar manner, the video decoding apparatus 100 may scan information on the remaining transform coefficient pixels according to the horizontal scan order 630.

6D is a diagram for describing a vertical scan sequence for scanning information on transform coefficients in a block according to an embodiment.

6D, in order to scan information on the transform coefficients of the current block 600, the video decoding apparatus 100 is left from the transform coefficient pixel at the lower right of the current block 600 according to a vertical scan order 640. You can scan up to the top transform coefficient pixels.

Specifically, according to the vertical scan order 640, the video decoding apparatus 100 sequentially scans the pixels 644 positioned in the vertical direction upward after scanning the transform coefficient pixel 642 in the lower right. , After scanning a pixel adjacent to the upper boundary of the current block 600 among the pixels 644, the lowermost pixel 646 of the immediately left column is scanned. The video decoding apparatus 100 scans the pixels 648 positioned in the vertical direction upward in the same manner as the pixels 644 in the previous column were scanned. In a similar manner, the video decoding apparatus 100 may scan information on the remaining transform coefficient pixels according to the vertical scan order 640.

FIG. 6E is a diagram for explaining a diagonal scan sequence for scanning information about transform coefficients in a block according to an embodiment.

6E, in order to scan information on the transform coefficients of the current block 600, the video decoding apparatus 100 is left from a transform coefficient pixel at the lower right of the current block 600 according to a diagonal scan order 650. You can scan up to the top transform coefficient pixels.

Specifically, according to the diagonal scan sequence 650, the video decoding apparatus 100 scans the upper pixel 654 of the pixel 652 after scanning the transform coefficient pixel 652 at the lower right, and then the pixel 654 After scanning is performed, the pixels 656 located in the diagonal direction at the lower left are scanned. The video decoding apparatus 100 scans a pixel 658 adjacent to an upper side of the pixel 654. The video decoding apparatus 100 scans pixels 660 located diagonally at the lower left of the pixel 658. In a similar manner, the video decoding apparatus 100 may scan information on the remaining transform coefficient pixels according to the diagonal scan order 650.

Various scan sequences for scanning information on effective transform coefficients in a block have been described above with reference to FIGS. 6A to 6E. The scan orders described with reference to FIGS. 6A to 6E are reverse scan orders, but are not limited thereto, and those skilled in the art can easily understand the forward scan order in which the reverse scan order is performed.

FIG. 7A is a diagram for explaining a process of changing a scan area by changing (swap) coordinates in a horizontal direction and a vertical direction of transform coefficient pixels in the scan area according to an exemplary embodiment.

Referring to FIG. 7A, the current block 700 may be a rectangle having a width greater than a height.

The video decoding apparatus 100 may obtain a flag indicating that an operation of changing horizontal coordinates and vertical coordinates of a transform coefficient pixel included in the current block 700 is activated. When the flag indicates that an operation of changing horizontal coordinates and vertical coordinates of the transform coefficient pixels included in the current block 700 is activated, the width of the current block 700 is increased. You can decide whether it is greater than.

When the width of the current block is greater than the height, the video decoding apparatus 100 may determine a swapped block 710 by changing the width and height of the current block.

That is, the video decoding apparatus 100 may determine the pixel position of the transform coefficient included in the changed block 710 by changing the horizontal coordinate and the vertical coordinate of the transform coefficient pixel included in the current block 700. .

The video decoding apparatus 100 may obtain information about coordinates for specifying the rectangular scan area 705 including all effective transform coefficients from the bitstream. Here, the horizontal coordinates of the coordinates for specifying the rectangular scan area 705 may be the horizontal coordinates of the effective transform coefficient pixel located at the rightmost among all the effective transform coefficients in the current block. The vertical coordinates of the coordinates for specifying the rectangular scan area may be the vertical coordinates of the lowest effective transform coefficient pixel among all the effective transform coefficients in the current block. The information on the coordinates for specifying the rectangular scan area 705 is information on the horizontal coordinate value of the most right effective transform coefficient pixel among all the effective transform coefficients in the current block and all effective transform coefficients in the current block. It may include information on a vertical coordinate value of an effective transform coefficient pixel located at the lowest of the ones. Alternatively, the information on the coordinates for specifying the rectangular scan area 705 is the horizontal coordinate value of the effective transform coefficient pixel located at the rightmost among all the effective transform coefficients and the lowest among all the effective transform coefficients in the current block. It may include information about one coordinate value among vertical coordinate values of the located effective transform coefficient pixel and information indicating a difference between the one coordinate value and the other coordinate value.

When the width and height of the current block are different from each other, the video decoding apparatus 100 includes information about coordinates for specifying the rectangular scan area 705 from the bitstream, as a horizontal coordinate value for specifying the rectangular scan area 705 Flag information (hereinafter referred to as delta flag information) indicating whether information indicating a difference between the and vertical coordinate values is included may be obtained. The video decoding apparatus 100 includes information representing a coordinate value representing one of a horizontal coordinate value and a vertical coordinate value for specifying the rectangular scan area 705 from the bitstream based on the delta flag information, and one coordinate value. Information indicating a difference between different coordinate values may be obtained.

The video decoding apparatus 100 may acquire coordinates for specifying the rectangular scan area 705 based on information about coordinates for specifying the rectangular scan area 705 including all effective transform coefficients obtained from the bitstream. I can. At this time, the coordinates for specifying the rectangular scan area 705 acquired by the video decoding apparatus 100 are coordinates for specifying the rectangular scan area 705 in the current block 700, and specify the rectangular scan area 705 The video decoding apparatus 100 may obtain a coordinate value for specifying the rectangular scan area 715 of the changed block 710 by changing the horizontal coordinate value and the horizontal coordinate value of the coordinate to be used.

The video decoding apparatus 100 may scan information on a transform coefficient based on the rectangular scan area 715 of the changed block 710 according to a predetermined scan order. In this case, the predetermined scan order is a scan order corresponding to a predetermined scan order for the current block 700, and a horizontal coordinate value and a vertical coordinate value of the transform coefficient pixels scanned according to a predetermined scan order for the current block 700 It may be a scan order according to coordinate values obtained by changing coordinate values of directions. For example, the coordinate value of the transform coefficient pixels scanned according to a predetermined scan order for the current block 700 is (4,4)->(3,4)->(4,3)->... In the case of, the coordinate value of the transform coefficient pixels scanned in a predetermined order for the changed block 710 is (4,4)->(4,3)->(3,4)->?? Can be

The video decoding apparatus 100 may perform binary arithmetic decoding on information about the transform coefficients scanned in the changed block 710 based on a predetermined context model, and inverse binarization to obtain transform coefficients of the changed block 710. The video decoding apparatus 100 may obtain transform coefficients of the current block 700 by changing a horizontal coordinate value and a vertical direction of the transform coefficients of the changed block 710.

When the width of the current block is greater than the height, the video decoding apparatus 100 swaps horizontal coordinates and vertical coordinates of the transform coefficient pixels included in the current block, and changes the transform coefficients in the changed block 710. By entropy-decoding the information on the scanned transform coefficient by scanning the information, it is always possible to entropy-decode the information on the transform coefficient for the block whose height is greater than or equal to the width of the current block. Therefore, it is possible to reduce the complexity of entropy decoding by not using a separate context model for a case where the width of the current block is greater than the height, and only using a context model for a block whose height is greater than or equal to the width of the current block.

In the above, when the width and height of the current block are different from each other, the content of obtaining delta flag information has been described, but the present invention is not limited thereto, and the video encoding apparatus 150 and the video decoding apparatus 100 When the width and height of the blocks are different, information indicating the difference between the horizontal coordinate value and the vertical coordinate value for specifying the rectangular scan area 715 from the bitstream can be obtained without obtaining delta flag information. Those skilled in the art can easily understand.

Without being limited thereto, the video decoding apparatus 100 may obtain information indicating a difference between a horizontal coordinate value and a vertical coordinate value without generating delta flag information regardless of whether the width and height of the current block are the same or different. It can be readily understood by those skilled in the art.

Based on a flag indicating that the ideal video encoding apparatus 150 generates a change flag, and the video decoding apparatus 100 activates an operation of changing the horizontal coordinates and vertical coordinates of the transform coefficient pixels included in the current block with each other Thus, the content of determining whether to change the horizontal coordinates and vertical coordinates of the transform coefficient pixels included in the current block to each other has been described, but the present invention is not limited thereto, and the video decoding apparatus 100 includes: It can be easily understood by those skilled in the art that the horizontal direction coordinates and the vertical direction coordinates can always be changed from each other.

As described above, when the width of the current block is greater than the height of the current block, the video decoding apparatus 100 swaps the horizontal and vertical coordinates of the transform coefficient pixels included in the current block. Otherwise, the content is not changed. Has been described, but is not limited thereto, and conversely, when the height of the current block is greater than the width, it may be easily understood by those skilled in the art that horizontal and vertical coordinates of the transform coefficient pixels included in the current block can be changed.

As described above, the video decoding apparatus 100 changes the horizontal and vertical coordinates of the current block, changes the horizontal and vertical coordinates of the scan area to scan information on the transformation coefficient, and scans the scanned transformation coefficient. Contents for obtaining transformation coefficients in the current block by performing entropy decoding on the information about and changing the horizontal and vertical coordinates of the obtained transformation coefficients have been described, but are not limited thereto, and the horizontal direction of the current block Without changing the coordinates and vertical coordinates, by changing only the horizontal coordinates and the vertical coordinates of the scan area to each other, scan and entropy decoding information on the transform coefficients in the scan area to obtain the transform coefficients in the scan area, Those skilled in the art can easily understand that the transform coefficients in the current block can be obtained by changing the horizontal and vertical coordinates of the transform coefficients in the scan area.

As described above, the video decoding apparatus 100 changes the horizontal and vertical coordinates of the current block, changes the horizontal and vertical coordinates of the scan area to scan information on the transformation coefficient, and scans the scanned transformation coefficient. The information about entropy decoding is performed to obtain transformation coefficients in the current block, and the contents of changing the horizontal and vertical coordinates of the obtained transformation coefficients have been described, but are not limited thereto, and the horizontal direction of the transformation coefficients And decoding by changing only the horizontal coordinates and the vertical coordinates of the scan area without changing the vertical coordinates, scanning and entropy decoding information on the transform coefficients in the scan area to obtain the transform coefficients in the scan area, It can be easily understood by those skilled in the art that the transform coefficient within the current block can be obtained.

That is, when the width of the current block is greater than the height of the current block, the video encoding apparatus 150 may change coordinates in the horizontal direction and the vertical direction of the scan area of the current block with each other, and transmit information indicating this. At this time, in general, when the width of the current block is larger than the height, the width of the scan area is larger than the height, and the coordinates in the horizontal direction specifying the scan area become larger than the coordinates in the vertical direction. , The changed coordinate value in the horizontal direction becomes smaller than the changed coordinate value in the vertical direction. Accordingly, it is possible to reduce the number of bits by transmitting information about the changed coordinate value in the horizontal direction and difference information about the changed coordinate value in the horizontal direction and the changed coordinate value in the vertical direction. However, when the width of the current block is greater than the height and the height of the scan area is greater than the width, the video encoding apparatus 150 provides the changed coordinate value information in the horizontal direction, the changed coordinate value in the horizontal direction, and the changed coordinate value in the vertical direction. Information can be transmitted as it is. That is, difference information may not be transmitted. In this case, this is because the changed coordinate value in the horizontal direction is larger than the changed coordinate value in the vertical direction.

The video encoding apparatus 150 may also transmit a flag indicating whether to transmit difference information. When the width of the current block is greater than the height of the current block, the video decoding apparatus 100 may determine to change the horizontal coordinate value and the vertical coordinate value specifying the scan area to each other, obtain a flag from the bitstream, and the flag value is If it is 1 (indicating that the difference information is transmitted), information about the changed coordinate value in the horizontal direction and the difference information about the changed coordinate value in the horizontal direction and the changed coordinate value in the vertical direction are obtained, and based on this, the changed scan area is specified. It is possible to obtain a coordinate value.

If the flag value is 0 (indicating that the difference information is not transmitted), information about the changed horizontal coordinate value and the changed vertical coordinate value is obtained, and based on this, the coordinate value specifying the changed scan area Can be obtained.

The video decoding apparatus 100 may specify a final scan area by changing the acquired horizontal coordinate value and vertical coordinate value with each other, and scan information about transformation coefficients within the scan area.

However, it can be easily understood by those skilled in the art that the current block is not limited when the width is greater than the height, and a similar operation may be performed even when the current block height is greater than the width.

FIG. 7B is a diagram for explaining a process of changing a scan area by changing horizontal and vertical coordinates of transform coefficient pixels in a rectangular scan area according to another embodiment.

Referring to FIG. 7B, the current block 720 may be a rectangle whose width is greater than the height.

The video decoding apparatus 100 may obtain a flag indicating that an operation of changing horizontal coordinates and vertical coordinates of the transform coefficient pixels included in the current block 720 is activated. When the flag indicates that an operation of changing horizontal coordinates and vertical coordinates of a transform coefficient pixel included in the current block 720 is activated, the width of the current block 720 is increased. You can decide whether it is greater than.

When the width of the current block is greater than the height, the video decoding apparatus 100 may determine the swapped block 730 by changing the width and the height of the current block.

That is, the video decoding apparatus 100 may determine the pixel position of the transform coefficient included in the changed block 730 by changing the horizontal coordinate and the vertical coordinate of the transform coefficient pixel included in the current block 720. .

The video decoding apparatus 100 may obtain information about coordinates for specifying the scan area 725 including all effective transform coefficients from the bitstream. Here, the coordinates for specifying the scan area 725 may be horizontal and vertical coordinates of the last effective transform coefficient pixel when scanning is performed according to a predetermined forward scan order. Information about coordinates for specifying the scan area 725 may include information about horizontal coordinates of the last effective transform coefficient pixel 725 and information about vertical coordinates. Alternatively, the information on the coordinates for specifying the scan area 725 is information on one of the horizontal and vertical coordinates of the last effective transform coefficient pixel, and the difference between the one coordinate and the other coordinate value. It may include information indicating

When the width and height of the current block are different from each other, the video decoding apparatus 100 may obtain information about coordinates for specifying the scan area 725 from the bitstream, perpendicular to the horizontal coordinate value for specifying the scan area 725. Flag information (hereinafter referred to as delta flag information) indicating whether information indicating a difference in direction coordinate values is included may be obtained. The video decoding apparatus 100 includes information indicating a coordinate value indicating one of a horizontal coordinate value and a vertical coordinate value for specifying the scan area 725 from the bitstream based on the delta flag information, and information indicating a coordinate value different from one coordinate value. Information indicating a difference between coordinate values may be obtained.

The video decoding apparatus 100 may obtain coordinates for specifying the scan area 725 based on information about coordinates for specifying the scan area 725 including all effective transform coefficients obtained from the bitstream. . In this case, the coordinates for specifying the scan area 725 acquired by the video decoding apparatus 100 are coordinates for specifying the scan area 725 in the current block 720, and coordinates for specifying the scan area 725 The video decoding apparatus 100 may obtain a coordinate value for specifying the scan area 725 of the changed block 730 by changing the horizontal coordinate value and the horizontal coordinate value of.

The video decoding apparatus 100 may scan information about a transform coefficient based on the scan area 735 of the changed block 730 according to a predetermined scan order. In this case, the predetermined scan order is a scan order corresponding to a predetermined scan order for the current block 720, and a horizontal coordinate value and a vertical coordinate value of the transform coefficient pixels scanned according to a predetermined scan order for the current block 720 It may be a scan order according to coordinate values obtained by changing coordinate values of directions. For example, the coordinate value of the transform coefficient pixels scanned according to a predetermined scan order for the current block 720 is (4,4)->(3,4)->(4,3)->... In the case of, the coordinate value of the transform coefficient pixels scanned in a predetermined order for the changed block 730 is (4,4)->(4,3)->(3,4)->... have.

The video decoding apparatus 100 may perform binary arithmetic decoding on information about the transform coefficients scanned in the changed block 730 based on a predetermined context model, and inverse binarization to obtain transform coefficients of the changed block 730. The video decoding apparatus 100 may obtain transform coefficients of the current block 720 by changing a horizontal coordinate value and a vertical direction value of the transform coefficients of the changed block 730.

When the width of the current block is greater than the height, the video decoding apparatus 100 swaps horizontal coordinates and vertical coordinates of transform coefficient pixels included in the current block, and changes the transform coefficients in the changed block 720. By entropy-decoding the information on the scanned transform coefficient by scanning the information, it is always possible to entropy-decode the information on the transform coefficient for the block whose height is greater than or equal to the width of the current block. Therefore, it is possible to reduce the complexity of entropy decoding by not using a separate context model for the case where the width of the current block is greater than the height, and only using the context model for the block whose height is greater than or equal to the width of the current block.

In the above, when the width and height of the current block are different from each other, the content of obtaining delta flag information has been described, but the present invention is not limited thereto, and the video encoding apparatus 150 and the video decoding apparatus 100 If the width and height of the blocks are different, those skilled in the art can obtain information indicating the difference between the horizontal coordinate value and the vertical coordinate value for specifying the scan area 720 from the bitstream without obtaining delta flag information. Is easily understandable.

Without being limited thereto, the video decoding apparatus 100 may obtain information indicating a difference between a horizontal coordinate value and a vertical coordinate value without generating delta flag information regardless of whether the width and height of the current block are the same or different. It can be readily understood by those skilled in the art.

Based on a flag indicating that the ideal video encoding apparatus 150 generates a change flag, and the video decoding apparatus 150 activates an operation of changing horizontal coordinates and vertical coordinates of transform coefficient pixels included in the current block. Thus, the content of determining whether to change the horizontal coordinates and vertical coordinates of the transform coefficient pixels included in the current block to each other has been described, but the present invention is not limited thereto, and the video decoding apparatus 100 includes: It can be easily understood by those skilled in the art that the horizontal direction coordinates and the vertical direction coordinates can always be changed from each other.

As described above, when the width of the current block is greater than the height of the current block, the video decoding apparatus 100 swaps the horizontal and vertical coordinates of the transform coefficient pixels included in the current block. Otherwise, the content is not changed. Has been described, but is not limited thereto, and conversely, when the height of the current block is greater than the width, it may be easily understood by those skilled in the art that horizontal and vertical coordinates of the transform coefficient pixels included in the current block can be changed.

As described above, the video decoding apparatus 100 changes the horizontal and vertical coordinates of the current block, changes the horizontal and vertical coordinates of the scan area to scan information on the transformation coefficient, and scans the scanned transformation coefficient. The information about entropy decoding is performed to obtain transformation coefficients in the current block, and the contents of changing the horizontal and vertical coordinates of the obtained transformation coefficients have been described, but are not limited thereto, and the horizontal direction of the current block Without changing the coordinates and vertical coordinates, by changing only the horizontal coordinates and the vertical coordinates of the scan area to each other, scan and entropy decoding information on the transform coefficients in the scan area to obtain the transform coefficients in the scan area, Those skilled in the art can easily understand that the transform coefficients in the current block can be obtained by changing the horizontal and vertical coordinates of the transform coefficients in the scan area.

As described above, the video decoding apparatus 100 changes the horizontal and vertical coordinates of the current block, changes the horizontal and vertical coordinates of the scan area to scan information on the transformation coefficient, and scans the scanned transformation coefficient. The information about entropy decoding is performed to obtain transformation coefficients in the current block, and the contents of changing the horizontal and vertical coordinates of the obtained transformation coefficients have been described, but are not limited thereto, and the horizontal direction of the transformation coefficients And decoding by changing only the horizontal coordinates and the vertical coordinates of the scan area without changing the vertical coordinates, scanning and entropy decoding information on the transform coefficients in the scan area to obtain the transform coefficients in the scan area, It can be easily understood by those skilled in the art that the transform coefficient within the current block can be obtained.

That is, when the width of the current block is greater than the height of the current block, the video encoding apparatus 150 may change coordinates in the horizontal direction and the vertical direction of the scan area of the current block with each other, and transmit information indicating this. At this time, in general, when the width of the current block is larger than the height, the width of the scan area is larger than the height, and the coordinates in the horizontal direction specifying the scan area become larger than the coordinates in the vertical direction. , The changed coordinate value in the horizontal direction becomes smaller than the changed coordinate value in the vertical direction. Accordingly, it is possible to reduce the number of bits by transmitting information about the changed coordinate value in the horizontal direction and difference information about the changed coordinate value in the horizontal direction and the changed coordinate value in the vertical direction. However, when the width of the current block is greater than the height and the height of the scan area is greater than the width, the video encoding apparatus 150 provides the changed coordinate value information in the horizontal direction, the changed coordinate value in the horizontal direction, and the changed coordinate value in the vertical direction. Information can be transmitted as it is. That is, difference information may not be transmitted. In this case, this is because the changed coordinate value in the horizontal direction is larger than the changed coordinate value in the vertical direction.

The video encoding apparatus 150 may also transmit a flag indicating whether to transmit difference information. When the width of the current block is greater than the height of the current block, the video decoding apparatus 100 may determine to change the horizontal coordinate value and the vertical coordinate value specifying the scan area to each other, obtain a flag from the bitstream, and the flag value is If it is 1 (indicating that the difference information is transmitted), information about the changed coordinate value in the horizontal direction and the difference information about the changed coordinate value in the horizontal direction and the changed coordinate value in the vertical direction are obtained, and based on this, the changed scan area is specified. It is possible to obtain a coordinate value.

If the flag value is 0 (indicating that the difference information is not transmitted), information about the changed horizontal coordinate value and the changed vertical coordinate value is obtained, and based on this, the coordinate value specifying the changed scan area Can be obtained.

The video decoding apparatus 100 may specify a final scan area by changing the acquired horizontal coordinate value and vertical coordinate value with each other, and scan information about transformation coefficients within the scan area.

However, it can be easily understood by those skilled in the art that the current block is not limited when the width is greater than the height, and a similar operation may be performed even when the current block height is greater than the width.

FIG. 8 is a diagram for describing a process of determining a context model for syntax element information of a transform coefficient in a current block based on at least one of a size of a current block and a shape of a current block, according to an embodiment.

Referring to FIG. 8, the current block may have a shape of one of a first block 805, a second block 810, and a third block 815. The first block may be a rectangular block having a height greater than the width, the second block may be a rectangular block having a width greater than the height, and the third block 815 may be a square block having the same width and height. Can be

The video decoding apparatus 100 may determine a context model for syntax element information of a transform coefficient in a current block based on size_tu0 determined according to Equation 19.

Here, log2_width may be a value obtained by taking log 2 from the width of the current block, and log2_height may be a value obtained by taking log 2 from the height of the current block. Referring to FIG. 8, when the current block is the first block 805, size_tu may be (log ₂ a+ log ₂ b)/2 (a, b are positive integers). When the current block is the second block 810, size_tu may be (log ₂ c+log- ₂ d)/2 (c,d are positive integers). When the current block is the third block 815, size_tu may be log ₂ e (e is a positive integer).

Alternatively, the video decoding apparatus 100 may determine a value for the size of the current block, which is an element determining the context model, based on a minimum value among the width of the current block and the height of the current block. For example, the video decoding apparatus may determine a value size_tu1 relating to the size of the current block, which is an element determining the context model, based on Equation 20 below.

Here, the Min() function may be a function that outputs a minimum value among input values. Referring to FIG. 8, when the current block is the first block 805, size_tu may be log ₂ a (a is a positive integer). When the current block is the second block 810, size_tu may be log- ₂ d (d is a positive integer). When the current block is the third block 815, size_tu may be log ₂ e (e is a positive integer).

The video decoding apparatus 100 may determine a context model for syntax element information of a transform coefficient in a current block based on size_tu1 determined according to [Equation 20].

Alternatively, the video decoding apparatus 100 may determine a value for the size of the current block, which is an element determining the context model, based on a maximum value among the width of the current block and the height of the current block. For example, the video decoding apparatus may determine a value size_tu2 relating to the size of the current block, which is an element determining the context model, based on Equation 21 below.

Here, the Max() function may be a function that outputs a maximum value among function input values.

The video decoding apparatus 100 may determine a context model for syntax element information of a transform coefficient in a current block based on size_tu2 determined according to [Equation 21].

If a is 4, b is 16, and e is 8, size_tu for the first block 805 and size_tu0 for the third block 815 may be equal to 3.

The video decoding apparatus 100 determines the same context model for the first block 805 and the third block 815 based on size_tu0 even though the transform coefficient tends to be distributed to the wider of the height and width of the current block. I can. However, if the video decoding apparatus 100 determines the context models for the first block 805 and the third block 815 based on size_tu1 or size_tu2, the context models may be different from each other, and therefore, based on size_tu0 The efficiency of binary arithmetic decoding can be improved compared to when determining the context model.

The video decoding apparatus 100 may determine a value of the size of the current block, which is an element determining the context model, based on the shape of the current block. For example, the video decoding apparatus 100 may determine a value shape_tu for the shape of the current block, which is an element determining the context model, based on Equation 22 below.

For example, when the current block is the first block 805, shape_tu may be 1, and when the current block is the second block 810, shape_tu may be 2. When the current block is the third block 815, shape_tu may be 0. That is, if the shape of the current block has a rectangular shape with a width greater than the height of the current block, size_tu may be 2, and if the shape of the current block has a rectangular shape with a height greater than the width of the current block, size_tu may be 1. In addition, when the shape of the current block has a square shape having the same width and height of the current block, size_tu may be 0.

In [Equation 22], the height of the current block and the width of the current block are used, but are not limited thereto, and those skilled in the art can easily understand that it can be determined based on log2_width and log2_height as in [Equation 21]. have. In addition, in [Equation 22], shape_tu is determined to be one of 0 to 2, but it is not limited thereto, and other values may be assigned, and the shape of the current block represented by each value may be changed. I can understand.

If a is 4, b is 16, and e is 8, size_tu for the first block 805 may be 3 and size_tu for the third block 815 may be the same as 3.

Although the transform coefficient tends to be distributed to the wider of the height and width of the current block, the video decoding apparatus 100 may determine the same context model for the first block and the third block based on size_tu0. However, if the video decoding apparatus 100 determines the context models for the first block 805 and the third block 815 based on shape_tu, the context models may be different from each other, and therefore, the context model based on size_tu0 The efficiency of binary arithmetic decoding can be improved compared to when determining.

Meanwhile, the video decoding apparatus 100 may determine a context model for a transform coefficient based on a ratio between the minimum value and the maximum value of the current block calculated based on the minimum value size_tu1 and the maximum value size_tu2 of the height and width of the current block. For example, when the ratio between the minimum value and the maximum value is within a predetermined value range, the video decoding apparatus 100 may determine a context index corresponding to the corresponding range, and determine a context model for a transformation coefficient based on the determined context index. have. For example, if the height of the current block is larger than the width, if the value of the ratio between the minimum value (width) and the maximum value (height) is in the range between 1 and 2, the corresponding context index is determined, and the minimum and maximum values When the value of the liver ratio is in the range of 2 or more, a context index corresponding thereto may be determined.

Meanwhile, the video decoding apparatus 100 may determine a context model for a transform coefficient based on the shape and size of the current block. That is, the video decoding apparatus 100 may determine a context model for a transform coefficient based on the size of the current block and the shape of the current block.

The video decoding apparatus 100 determines a context index for a transform coefficient based on at least one of size_tu1 and size_tu2 for the size of the current block and shape_tu for the shape of the current block, and a context model corresponding to the determined context index Can be determined.

9A to 9C are diagrams for explaining a residual encoding syntax structure according to an embodiment.

9A to 9C, the video decoding apparatus 100 may scan syntax element information about a transform coefficient to restore the transform coefficient, and decode the transform coefficient based on the scanned syntax element information.

First, the video decoding apparatus 100 may obtain, from a bitstream, syntax element information scan_region_x and scan_region_y indicating coordinates for specifying a rectangular scan region. At this time, the syntax element information scan_region_x may represent a value of the horizontal coordinate (x-axis direction) of the effective transform coefficient located at the rightmost position in the current block based on the upper left corner coordinate of the current block, and the syntax element information scan_region_y A value of a coordinate value in the vertical direction (y-axis direction) of an effective transform coefficient positioned at the bottom of the current block based on the coordinates of the upper left corner of the block. The video decoding apparatus 100 may determine coordinates srX and srY for specifying the scan region based on the syntax element information scan_region_x and scan_region_y.

The video decoding apparatus 100 may determine a scan order (ScanOrder(srX+1, srY+1)) based on coordinates srX and srY for specifying the scan area.

The video decoding apparatus 100 may determine index information (lastSet) indicating a coefficient group that is last scanned in a forward scan order based on coordinates srX and srY for specifying a scan area. That is, the video decoding apparatus 100 performs an operation (>>4) of bit shifting a value of (srX+1)*(srY+1)) -1 which is the size of the scan area to the right by 4, and finally Index information (lastSet) of the coefficient group to be scanned may be determined. That is, the output value of the operation shifted to the right by 4 may be the same as the quotient determined according to the division by 16. That is, since the video decoding apparatus 100 determines one coefficient group for every 16 transform coefficients, when the total transform coefficients scanned in the scan area are divided by 16, the total number of coefficient groups (or the last in the forward scan order A value obtained by adding 1 to the index value representing the coefficient group to be scanned) may be determined.

The video decoding apparatus 100 determines the position of the last scanned coefficient (lastScanPos) in the forward scan order based on coordinates srX and srY for specifying the scan area, and scans the position of the current transform coefficient (Pos) in the forward direction. It can be determined by the position (lastScanPos) of the coefficient to be scanned last in the sequence.

The video decoding apparatus 100 may initialize i to lastset, decrease i by 1 when i is greater than 0, and perform an operation included in the loop (for statement) 905. The video decoding apparatus 100 may perform an operation included in the for statement 905 until a value less than 0 is reached. In this case, i may be an index indicating a coefficient group. That is, the video decoding apparatus 100 may perform an operation for one coefficient group each time an operation included in the for statement 905 is performed.

The video decoding apparatus 100 may determine setPos by multiplying i by 16 (i<<4). setPos may represent index information of a transform coefficient positioned at the first of a transform group.

When i is the last coefficient group (i==lastSet), the video decoding apparatus 100 determines n as a value obtained by subtracting setPos from lastScanPos (lastScanPos-setPos), and if not, n is determined as 15, and n is 0. If it is greater than or equal to, i may be decreased by 1, and the operation included in the for statement 910 may be performed. The video decoding apparatus 100 may perform an operation (operation related to sig_flag) included in the for statement 910 until a value less than 0 is reached. In this case, n may be index information indicating the position of the transform coefficient in the coefficient group according to the scan order in the forward direction.

For example, if the total number of transform coefficients included in the scan area is not an integer multiple of 16, the value obtained by subtracting setPos from lastScanPos for the last coefficient group (i=lastset) scanned according to the forward scan is greater than 0. It is equal to or has a value less than or equal to 15, and the value is determined as n, and a for statement 910 may be performed.

The video decoding apparatus 100 may determine the position blkpos of the current transform coefficient as a value obtained by adding n to the index information setPos indicating the position of the first coefficient of the current coefficient group in the ScanOrder array. The ScanOrder array may be an array indicating positions of transform coefficients according to a scan order in the forward direction.

The video decoding apparatus 100 may determine a value sx of coordinates in the currently scanned horizontal direction (x-axis direction) based on the position blkpos of the current transform coefficient and the width of the scan area. In addition, the video decoding apparatus 100 may determine a value sy of a coordinate in a vertical direction (y-axis direction) based on a location (blkpos) of a transform coefficient currently being decoded and a width (log2width) of a scan area.

When sx is 0, sy is srY, and is_last_y is 0 (sx==0 && sy==srY&&is_last_y==0), or sy is 0, sx is srX, and is_last_x is If 0 (sy==0 && sx==srX&&is_last_x==0), the video decoding apparatus 100 does not obtain the effective transform coefficient flag sig_flag(sig_flag[blkpos]) for the current transform coefficient from the bitstream, A value of sig_flag for the transform coefficient may be determined as 1. Here, is_last_x may be a value indicating whether there is an effective transform coefficient having an absolute value greater than 0 among transform coefficients scanned before the current transform coefficient among transform coefficients included in the lowermost row in the scan area. is_last_y may be a value indicating whether there is an effective transform coefficient whose absolute value is greater than 0 among transform coefficients scanned before the current transform coefficient among transform coefficients included in the rightmost column in the scan area.

When sx is 0, sy is srY, and is_last_y is 0 (sx==0 && sy==srY&&is_last_y==0) or sy is 0, sx is srX, and is_last_x is 0. If not (sy==0 && sx==srX&&is_last_x==0), an effective transform coefficient flag sig_flag[blkpos] for a transform coefficient currently decoded from the bitstream may be obtained.

The video decoding apparatus 100 sets is_last_x to 1 if the coordinate value sx of the current transform coefficient in the x-axis direction is equal to srX (sx==srX) when the effective transform coefficient flag sig_flag of the current transform coefficient is 1, and , If the coordinate value sy of the current transform coefficient in the y-axis direction is equal to srY (sy==srY), is_last_y may be set to 1.

Also, when lastSigScanPos is -1 (ie, an initial value), the video decoding apparatus 100 may determine lastSigScanPos as n. In other words, lastSigScanPos is an index indicating the position of the last effective transform coefficient in the coefficient group in the forward scan order because the index n indicating the location of the first effective transform coefficient in the coefficient group is determined as lastSigScanPos. It could be information. Meanwhile, the video decoding apparatus 100 may determine firstSigScanPos as n. If the effective transform coefficient flag sig_flag of the current transform coefficient is 1, the value of firstSigScanPos is continuously updated to n, which is index information indicating the position of the current transform coefficient, so the operation is finally performed on the transform coefficients included in the specific coefficient group i. When performed, firstSigScanPos may be index information indicating a position where the first effective transform coefficient exists in the coefficient group in the forward scan order.

The video decoding apparatus 100 increases cnt_nz by 1. That is, cnt_nz representing the number of coefficients having a non-zero value in the current block (or scan area) is updated whenever the current transform coefficient is an effective transform coefficient. Also, the video decoding apparatus 100 increases cg_nz[i] indicating the number of coefficients having a non-zero value in the current coefficient group i by one. That is, cg_nz[i] representing the number of coefficients having a non-zero value in the current coefficient group i is updated whenever the current transform coefficient is an effective transform coefficient.

When i is the last coefficient group (i==lastSet), the video decoding apparatus 100 determines n as a value obtained by subtracting setPos from lastScanPos (lastScanPos-setPos), and if not, n is determined as 15, and n is 0. If it is greater than or equal to, i may be decreased by 1 and an operation included in the for statement 915 may be performed. The video decoding apparatus 100 may perform operations (operations related to coeff_abs_level_greater1_flag and coeff_abs_level_greater2_flag) included in the for statement 915 until a value less than 0 is reached.

The video decoding apparatus 100 may determine the position blkpos of the current transform coefficient as a value obtained by adding n to the index information setPos indicating the position of the first coefficient of the current coefficient group in the ScanOrder array.

The video decoding apparatus 100 may obtain the absolute value abs_coef for the current transform coefficient based on information on the current transform coefficient gt0 flag, gt1 flag, gt2 flag, and remainining_abolute value level.

When the effective transform coefficient flag (sig_flag[blkpos]) of the current transform coefficient is 1, the video decoding apparatus 100 transforms the transform coefficient having an absolute value greater than 1 among transform coefficients included in previously scanned coefficient groups. The sum of the number of coefficients cnt_g1 and the number of transform coefficients c1 that obtains coeff_abs_level_greater1_flag from the bitstream among the previously scanned transform coefficients in the current coefficient group is obtained from the bitstream among the transform coefficients whose absolute value is greater than 1 (coeff_abs_level_greater_flag) If it is less than num_gt1, which is the maximum number of transform coefficients that can be performed, the video decoding apparatus 100 may obtain coeff_abs_level_greater1_flag[blkpos] for the current transform coefficient from the bitstream. coeff_abs_level_greater1_flag may be a flag indicating whether the absolute value of the current transform coefficient is greater than 1. The video decoding apparatus 100 may determine a flag gt1_flag (gt1flag[blkpos]) of the current transform coefficient based on coeff_abs_level_greater1_flag obtained from the bitstream.

When the value of the flag gt1_flag of the current transform coefficient is 1, the video decoding apparatus 100 may increase c1 by 1. If the flag gt1_flag of the current transform coefficient is 1, the value of c1 increases by 1 and the value of c1 is updated. Therefore, when the for statement () operation is performed on the next transform coefficients, c1 is the current coefficient. It may represent the number of transform coefficients obtained by obtaining coeff_abs_level_greater1_flag from a bitstream among transform coefficients previously scanned in the group.

When the effective transform coefficient flag (sig_flag[blkpos]) of the current transform coefficient is 1, the video decoding apparatus 100 includes a transform coefficient whose absolute value is greater than 2 among transform coefficients in previously scanned coefficient groups. The sum of the number cnt_g2 and the number of transform coefficients that have obtained coeff_abs_level_greater2_flag from the previously scanned bitstream in the current coefficient group is the sum of the transform coefficients that can obtain coeff_abs_level_greater_flag from the bitstream among the transform coefficients whose absolute value is greater than 2 If the number is less than the maximum number num_gt2, the video decoding apparatus 100 may obtain coeff_abs_level_greater2_flag for the current transform coefficient from the bitstream. coeff_abs_level_greater2_flag may be a flag indicating whether the absolute value of the current transform coefficient is greater than 2. The video decoding apparatus 100 may determine the flag gt2_flag of the current transform coefficient based on coeff_abs_level_greater2_flag obtained from the bitstream.

When the value of the flag gt2_flag of the current transform coefficient is 1, the video decoding apparatus 100 may increase the number c2 of the current gt2 flag by 1. If the flag gt2_flag of the current transform coefficient is 1, the value of c2 increases by 1 and the value of c2 is updated. Therefore, when the for statement () operation is performed on the next transform coefficients, c2 is the current coefficient. It may represent the number of transform coefficients obtained by obtaining coeff_abs_level_greater1_flag from a bitstream among transform coefficients previously scanned in the group.

In addition, the video decoding apparatus 100 may determine escapeDataPresent as 1. The escapeDataPresent may be information indicating that there is additionally acquired information (eg, residual level absolute value information coeff_abs_level_remaining) to determine the value of the transform coefficient in the current transform group.

When the effective transform coefficient flag (sig_flag[blkpos]) of the current transform coefficient is 1, the video decoding apparatus 100 includes a transform coefficient whose absolute value is greater than 2 among transform coefficients in previously scanned coefficient groups. The sum of the number cnt_g2 and the number of transform coefficients that have obtained coeff_abs_level_greater2_flag from the previously scanned bitstream in the current coefficient group is the sum of the transform coefficients that can obtain coeff_abs_level_greater_flag from the bitstream among the transform coefficients whose absolute value is greater than 2 If the maximum number is not less than num_gt2, the video decoding apparatus 100 may determine escapeDataPresent as 1.

The video decoding apparatus 100 includes the number of transform coefficients cnt_g1 having an absolute value greater than 1 among transform coefficients included in previously scanned coefficient groups, and a bitstream among transform coefficients previously scanned in the current coefficient group. If the sum of the number c1 of the transform coefficients that have obtained coeff_abs_level_greater1_flag from is not less than num_gt1, which is the maximum number of transform coefficients that can obtain coeff_abs_level_greater_flag from the bitstream among the transform coefficients whose absolute value is greater than 1, the video decoding apparatus ( 100) may determine escapeDataPresent to 1.

When the escapeDataPresent is 1, when i represents the last coefficient group (i==lastSet), the video decoding apparatus 100 determines n as a value obtained by subtracting setPos from lastScanPos (lastScanPos-setPos), and if not, n is 15 And, if n is greater than or equal to 0, i is decreased by 1, and the operation included in the for statement 920 may be performed. The video decoding apparatus 100 may perform an operation (coeff_abs_level_reamining related operation) included in the for statement 920 until a value less than 0 is reached.

The video decoding apparatus 100 may determine the position blkpos of the current transform coefficient as a value obtained by adding n to the index information setPos indicating the position of the first coefficient of the current coefficient group in the ScanOrder array.

When the absolute value of the current transform coefficient is greater than 1 (sig_flag[blkpos]), the video decoding apparatus 100 may determine the base level. The number of transform coefficients whose absolute values are greater than 1 among transform coefficients scanned before the current transform coefficient in the current coefficient group cnt_gt1 can acquire coeff_abs_level_greater_flag from the bitstream among transform coefficients whose absolute value is greater than 2 If the maximum number of existing transform coefficients is less than num_gt1, the number of transform coefficients whose absolute values are greater than 2 among transform coefficients scanned before the current transform coefficient in the current coefficient group cnt_gt2 is a transform whose absolute value is greater than 2 If among the coefficients, the maximum number of transform coefficients capable of obtaining coeff_abs_level_greater_flag from the bitstream is smaller than num_gt2, the video decoding apparatus 100 may determine the base level as 3. When cnt_gt1 is smaller than num_gt1 that can be obtained from the bitstream, if cnt_gt2 is smaller than num_gt2, the video decoding apparatus 100 may determine the base level as 2. When cnt_gt1 is not less than num_gt1, the video decoding apparatus 100 may determine the base level as 1.

The video decoding apparatus 100 may determine the absolute value level abs_coef of the current transform coefficient as a value obtained by adding 1 to the value obtained by adding the value of gt1flag and the value of gt2flag to the current transform coefficient. When the absolute value of the current transform coefficient has the same value as the base level (abs_coef[blkpos]==base_level), the video decoding apparatus 100 may obtain the residual absolute value level coeff_abs_level_remaining for the current transform coefficient from the bitstream. . The video decoding apparatus 100 may determine the absolute value level abs_coef for the current transform coefficient by adding the residual absolute value level level_remaining for the current transform coefficient to abs_coef.

If the absolute value level abs_coef for the current transform coefficient is greater than 2, the video decoding apparatus 100 may increase cnt_gt2 by 1. Also, if the absolute value level abs_coef for the current transform coefficient is greater than 1, the video decoding apparatus 100 may increase cnt_gt1 by 1.

If escapeDataPresent is 0, if i represents the last coefficient group (i==lastSet), n is determined as lastScanPos minus setPos (lastScanPos-setPos), and if not, n is determined as 15, and n is 0. If it is greater than or equal to, i may be decreased by 1 and the operation included in the for statement 925 may be performed. The video decoding apparatus 100 may perform an operation (an abs_coef related operation) included in the for statement 925 until a value less than 0 is reached. In the ScanOrder array, it may be determined as a value obtained by adding n to index information (setPos) indicating the position of the first coefficient in the current coefficient group.

When the effective transform coefficient flag for the current transform coefficient is 1, the video decoding apparatus 100 may increase cnt_gt2 by 1 if abs_coef, which is an absolute value for the current transform coefficient, is greater than or equal to 2. When the effective transform coefficient flag for the current transform coefficient is 1, if abs_coef, which is an absolute value for the current transform coefficient, is greater than or equal to 1, cnt_gt1 may be increased by 1.

When the difference between the position of the last effective transform coefficient lastSigScanPos and the position of the first effective transform coefficient firstSigScanPos in the current coefficient group i scanned according to the forward scan order is greater than 3, at least one in the current coefficient group i A value of signHidden (signHidden[i]) indicating that the sign of is hidden may be determined as 1. When the difference between the position of the last effective transform coefficient lastSigScanPos and the position of the first effective transform coefficient firstSigScanPos in the current coefficient group scanned according to the forward scan order is not greater than 3, at least one in the current coefficient group i A value of signHidden (signHidden[i]) indicating that the sign of is hidden may be determined as 0.

The video decoding apparatus 100 may initialize i to 0, increase i by 1 when i is less than or equal to lateSet, and perform an operation included in the for statement 930. The video decoding apparatus 100 may perform an operation included in the for statement 930 until i becomes a value greater than lateSet. In this case, i may be an index indicating a coefficient group. That is, the video decoding apparatus 100 may perform an operation for one coefficient group each time an operation included in the repetition statement (for statement) 930 is performed once.

If rsp (residual sign prediction) is applied (rsp_apply),

When i is the last coefficient group (i==lastSet), the video decoding apparatus 100 determines n as a value obtained by subtracting setPos from lastScanPos (lastScanPos-setPos), and if not, n is determined as 15, and n is 0. If it is greater than or equal to, i may be decreased by 1 and the operation included in the for statement 935 may be performed. The video decoding apparatus 100 may perform an operation included in the for statement 935 until a value less than 0 is reached.

The video decoding apparatus 100 may determine the location (blkpos) of the currently decoded transform coefficient as a value obtained by adding the current n to the index information setPos indicating the location of the first coefficient in the current coefficient group in the ScanOrder array according to the scan order in the forward direction. .

When the location blkpos of the currently decoded transform coefficient is not rsp_pos, the video decoding apparatus 100 includes information on the sign of the currently decoded transform coefficient (sign[blkpos]) if the code of the transform coefficient is hidden_pos. May be determined as information about the sign of the hidden transform coefficient hidden_sign.

If the sign of the transform coefficient is not the location of the hidden transform coefficient hidden_pos, the video decoding apparatus 100 may obtain information (sign[blkpos]) about the sign of the transform coefficient currently being decoded from the bitstream.

When the location blkpos of the currently decoded transform coefficient is rsp_pos, the video decoding apparatus 100 may obtain information (sign_rsp[blkpos]) about the rsp code of the currently decoded transform coefficient from the bitstream.

If rsp is not applied, the video decoding apparatus 100 determines n as a value obtained by subtracting setPos from lastScanPos (lastScanPos-setPos) when i is the last coefficient group (i==lastSet), and if not, n is 15 And, if n is greater than or equal to 0, i is decreased by 1, and the operation included in the for statement 940 may be performed. The video decoding apparatus 100 may perform an operation included in the for statement 940 until a value less than 0 is reached.

The video decoding apparatus 100 may determine the location of the current transform coefficient blkpos as a value obtained by adding the current n to the index information setPos indicating the location of the first coefficient of the current coefficient group in the ScanOrder array according to the forward scan order.

If the value of the effective transform coefficient flag of the current transform coefficient is 1, the value of the flag sign_data_hiding_enabled_flag) indicating whether hiding the sign data is activated is 0, there is no hidden sign for the current group (!signHidden[i]), or the forward direction When the position of the current transform coefficient in the current coefficient group in the scan order is not the position of the first effective transform coefficient firstSigScanPos, information about the sign of the current transform coefficient (sign[blkpos]) may be obtained from the bitstream.

9D to 9F are diagrams for explaining a residual encoding syntax structure according to another embodiment.

9B to 9F, the video decoding apparatus 100 may scan syntax element information about a transform coefficient to restore the transform coefficient, and decode the transform coefficient based on the scanned syntax element information.

First, the video decoding apparatus 100 may obtain syntax element information last_sig_coeff_x and last_sig_coeff_y indicating coordinates for specifying a scan area from a bitstream. At this time, the syntax element information last_sig_coeff_x may represent the value of the horizontal coordinate (x-axis direction) of the last effective transform coefficient in the forward scan order based on the upper left corner coordinate of the current block, and the syntax element information last_sig_coeff_y may represent a value of a vertical coordinate (y-axis direction) of an effective transform coefficient positioned at the end of a current block according to a scan order in a forward direction based on the coordinates of the upper left corner of the current block. The video decoding apparatus 100 may determine coordinates LastSigcoeffX and LastSigCoeffY for specifying the scan area based on the syntax element information last_sig_coeff_x and last_sig_coeff_y.

The video decoding apparatus 100 may initialize a position lastScanPos of the last effective transform coefficient to 16 according to a scan order in the forward direction within the subblock. The video decoding apparatus 100 may initialize a lastSubBlock indicating a sub-block in which the last effective transform coefficient is located according to a forward scan order in the sub-block. In this case, the initialized value may indicate a subblock positioned at the last among subblocks of the current block scanned according to the scan order in the forward direction. That is, the lastSubBlock may be initialized to a value indicating the last sub-block among sub-blocks scanned according to the scan order in the forward direction based on the height and width of the current block.

When the horizontal position xC of the current coefficient is not LastSigcoeffX or the vertical position yC of the current coefficient is not LastSigcoeffY, the video decoding apparatus 100 performs an operation within the Do-while loop statement 950, and xC is If it is LastSigcoeffX, and the vertical position yC of the current coefficient is LastSigcoeffY, the operation within the do-while loop statement 950 may no longer be performed.

If lastScanPos is 0, the video decoding apparatus 100 may determine lastScanPos as 16 and decrease the lastSubblock by 1. In other words, when the scan in one sub-block is completed according to the reverse scan order (lastScanPos is 0), the lastScanPos is initialized to 16 to scan the next sub-block according to the reverse scan order, and for the next sub-block scan. You can decrease the lastSubblock by 1. The video decoding apparatus 100 may scan transform coefficients in the current subblock lastSubblock according to the reverse scan order while decreasing lastScanPos by 1.

The video decoding apparatus 100 may determine a horizontal position xS and a vertical position yS of the current sub-block. The video decoding apparatus 100 may determine the location of the current sub-block based on the ScanOrder arrangement determined according to a predetermined forward scan order with respect to the current block. That is, the video decoding apparatus 100 may determine the location of the current subblock based on the height (log2height) and width (log2width) of the current block, the scan index scanIdx representing a predetermined scan order, and the value lastSubBlock representing the current subblock. have. In this case, xS and yS may not be actual positions of sub-blocks, but may be positions of sub-blocks when sub-blocks are treated as one pixel. That is, the width and height of the sub-blocks are ignored, and the difference in the horizontal direction and the vertical direction of the sub-blocks between adjacent sub-blocks may be 1.

Also, the video decoding apparatus 100 may determine a horizontal position xC and a vertical position yC of the current transform coefficient based on the ScanOrder arrangement determined according to a predetermined forward scan order for the current sub-block. That is, the video decoding apparatus 100 includes the height (log ₂ 4=2) and width (log ₂ 4=2) of the current sub-block, the scan index scanIdx indicating a predetermined scan order, and the position of the current sub-block (xS, yS). ) And a value lastScanPos indicating the position of the current transform coefficient in the current sub-block, the position (xC, yC) of the current transform coefficient may be determined.

Since the video decoding device 100 no longer performs the operation within the do-while loop statement 950 when the vertical position yC of the current transform coefficient is LastSigcoeffY, it is determined through the do-while loop statement 950. lastScanPos may be index information indicating the position of the last effective transform coefficient in the sub-block including the last effective transform coefficient in the current block scanned according to the forward scan order, and lastSubBlock is the sub where the last effective transform coefficient in the current block is located. It may be index information indicating a block.

The video decoding apparatus 100 may initialize i as lastSubBlock, decrease i by 1 when i is greater than 0, and perform an operation included in the for statement 960. The video decoding apparatus 100 may perform an operation included in the for statement 960 until a value less than 0 is reached. In this case, i may be an index indicating a coefficient group. That is, the video decoding apparatus 100 may perform an operation for one sub-block each time an operation included in the for statement 960 is performed once.

The video decoding apparatus 100 may determine a horizontal position xS and a vertical position yS of the current sub-block.

The video decoding apparatus 100 indicates that i, which represents the current sub-block, indicates a sub-block having a value smaller than the value (lastSubBlock) representing a sub-block in which the last effective transform coefficient is located, or represents a sub-block including a DC coefficient. When a subblock having a value greater than the value (0) is indicated, coded_sub_block_flag[xS][yS] for the current subblock i may be obtained. coded_sub_block_flag[xS][yS] may be flag information indicating whether at least one effective transform coefficient in the current subblock i is included.

The video decoding apparatus 100 initializes n to lastScanPos-1 if the current subblock is a subblock including the last effective transform coefficient (lastSubBlock), otherwise it initializes to 15, and n is greater than or equal to 0. In case n is reduced by 1, the operation included in the loop (for statement)() can be performed. The video decoding apparatus 100 may perform the operation included in the for statement 960 until n becomes a value less than 0. In this case, n is an index indicating the position of the current transform coefficient in the sub-block. Can be That is, the video decoding apparatus 100 may perform an operation for one coefficient group each time an operation included in the for statement () is performed once. That is, the video decoding apparatus 100 may perform an operation (operation related to sig_coeff_flag) on one sub-block whenever an operation included in the repetition statement (for statement) 960 is performed once.

The video decoding apparatus 100 may determine positions xC and yC of the current transform coefficient n.

When the coded_sub_block_flag[xS][yS] for the current subblock is 1 and n is greater than 0 or inferSbDcSigCoeffFlag is 0, the video decoding apparatus 100 bit the flag sig_coeff_flag[xC][yC] for the current transform coefficient. It can be obtained from the stream. sig_coeff_flag[xC][yC] may be a flag indicating whether the current transform coefficient is an effective transform coefficient.

If the value of sig_coeff_flag[xC][yC] is 1, inferSbDcSigCoeffFlag may be determined as 0.

The video decoding apparatus 100 initializes the position of the transform coefficient firstScanPos that is first scanned in the current sub-block according to the forward scan order, and the position of the transform coefficient that is last scanned in the current sub-block according to the forward scan order. You can initialize the value of lastSigScanPos. The video decoding apparatus 100 may initialize a value of numGreater1Flag indicating the number of Greater1Flags, and initialize a value of lastGreater1ScanPos at a last location where Greater1Flag is obtained according to a forward scan order.

The video decoding apparatus 100 may initialize cg_nz[i] indicating the number of non-zero transform coefficients in sub-block i.

The video decoding apparatus 100 may initialize n to 15, and if n is greater than or equal to 0, decrease n by 1 and perform an operation in the loop (for statement) 965 until n is less than 0.

The video decoding apparatus 100 may determine positions xC and Yc of the current transform coefficient n.

When the effective transform coefficient flag sig_coeff_flag for the current transform coefficient is 1, the video decoding apparatus 100 acquires coeff_level_greater1_flag[n] for the current transform coefficient n when numGreater1Flag is less than 8, and increases the value of numGreater1Flag by 1 I can make it. coeff_level_greater1_flag[n] may be flag information indicating whether the absolute value of the level of the transform coefficient n is greater than 1. The video decoding apparatus 100 may determine Greater1Flag[n] based on coeff_level_greater1_flag[n]d.

If the value of coeff_abs_level_greater_flag for the current transform coefficient is 1 and the value of lastreater1ScanPos is an initial value, the video decoding apparatus 100 may determine lastGreater1ScanPos as the position n of the current transform coefficient in the current subblock. Accordingly, lastGreater1ScanPos may be index information indicating a position of a coefficient having a value of coeff_abs_level_greater_flag located last in the current subblock according to the forward scan order. Otherwise (not the case where the value of coeff_abs_level_greater1_flag for the current transform coefficient is 1 and the value of lastreater1ScanPos is the initial value), and if coeff_abs_level_greater1_flag is 1, escapeDataPresent may be determined as 1.

The video decoding apparatus 100 may determine escapeDataPresent as 1 if numGreater1Flag is not less than 8.

The video decoding apparatus 100 may determine lastSigScanPos as the position n of the transform coefficient in the current sub-block when lastSigScanPos indicating the position of the last effective transform coefficient in the current sub-block according to the forward scan order has an initial value. .

The video decoding apparatus 100 may determine firstSigScanPos, which represents the position of the first effective transform coefficient in the current sub-block, as the position n of the transform coefficient in the current sub-block according to the forward scan order. If the effective transform coefficient flag sig_coeff_flag[xC][yC] of the current transform coefficient is 1, the value of firstSigScanPos is continuously updated to n, which is index information indicating the position of the current transform coefficient in the current sub-block. When an operation is performed on the transform coefficients included in, firstSigScanPos may be index information indicating a position where the first effective transform coefficient in the subblock exists in the forward scan order.

When the difference between lastSigScanPos and firstSigScanPos is greater than 3, the video decoding apparatus 100 may determine the sigHidden value as 1, and when the difference between lastSigScanPos and firstSigScanPos is not greater than 3, the sigHidden value may be determined as 0. In this case, sigHidden may be a value indicating that the sign of at least one transform coefficient is hidden for the current subblock.

If the position of the transform coefficient at which the last coeff_abs_level_greater1_flag is obtained among coeff_abs_level_greater1_flag (Greater1Flag) for the transform coefficients obtained from the bitstream scanned according to the forward scan order, lastGreater1ScanPos is not an initial value (ie, at least one Greater1Flag from the bitstream). Is acquired in the current sub-block), the video decoding apparatus 100 may obtain a flag coeff_abs_level_greater2_flag[lastGreater1ScanPos] for a transform coefficient at the position of lastGreater1ScanPos from the bitstream. coeff_abs_level_greater2_flag may be a flag indicating whether the absolute value of the transform coefficient is greater than 2. If the value of the flag coeff_abs_level_greater2_flag[lastGreater1ScanPos] for the transform coefficient at the lastGreater1ScanPos position is 1, the video decoding apparatus 100 may determine the escapeDataPresent as 1. The video decoding apparatus 100 may determine Greater2Flag[n] based on coeff_level_greater2_flag[n].

The video decoding apparatus 100 may initialize numSigCoeff. In this case, numSigCoeff may mean the number of effective transform coefficients among transform coefficients scanned before the current transform coefficient according to the scan order in the reverse direction.

The video decoding apparatus 100 initializes n to 15, decreases n by 1 when n is greater than or equal to 0, and performs an operation within the for statement 970, and when n is less than 0, the for statement 970 ) I may no longer perform my actions. The video decoding apparatus 100 may perform an operation of scanning information on transform coefficients in a current subblock according to a reverse scan order.

The video decoding apparatus 100 may determine the positions xC and yC of the current transform coefficient based on the position n of the current transform coefficient in the current sub-block.

When the value of the effective transform coefficient flag sig_coeff_flag[xC][yC] related to the current transform coefficient is 1, the video decoding apparatus 100 includes the value of the flag coeff_abs_level_greater1_flag related to the current transform coefficient and the value of the flag coeff_abs_level_greater2_flag related to the current transform coefficient. The sum of 1 can be determined as baseLevel.

If numSigCoeff is less than 8 and the position n of the current transform coefficient is lastGreater1ScanPos, and the base level is 3, the video decoding apparatus 100 obtains residual level information coeff_abs_level_remaining[n] for the current transform coefficient n from the bitstream. Can be obtained.

If numSigCoeff is less than 8 and the position n of the current transform coefficient is not lastGreater1ScanPos, and the base level is 2, the video decoding apparatus 100 provides information on residual level values for the current transform coefficient n from the bitstream coeff_abs_level_remaining[n ] Can be obtained. If numSigCoeff is greater than 8, if the base level is 1, the video decoding apparatus 100 may obtain residual level information coeff_abs_level_remaining[n] for the current transform coefficient n from the bitstream.

The video decoding apparatus 100 adds TransCoeffLevel[x0][y0][cIdx][xC][yC], which is the level value of the current transform coefficient in the current block by summing the base level for the current transform coefficient and the residual level value for the current transform coefficient. Can be determined. Here, cIdx may be an index indicating a color component.

If i increases from 0 to 1 and becomes a value less than or equal to lastSubBlock, the operation included in the for statement 975 may be performed. In this case, i may be an index indicating a sub-block. That is, the video decoding apparatus 100 may perform an operation for one coefficient group each time the syntax in the for statement 975 is executed once.

If the flag coded_sub_block_flag[xS][yS] for the current subblock i is 1, if rsp is applied (rsp_apply), the video decoding apparatus 100 determines n as 15, and n is greater than 0 or If it is the same, an operation within the for statement 980 is performed, and after n is decreased by 1, if n is greater than or equal to 0, the operation of the for statement 980 may be performed again. If n is less than 0, the operation in the for statement 980 may no longer be performed.

The video decoding apparatus 100 may determine a horizontal position and a vertical position xC and yC of the current transform coefficient corresponding to the position n of the current transform coefficient in the current sub-block. The video decoding apparatus 100 may determine the position blkpos of the current transform coefficient based on xC and yC.

When the location blkpos of the current transform coefficient is not rsp_pos, the video decoding apparatus 100 may determine the sign of the current transform coefficient as the sign hidden_sign of the hidden transform coefficient, if the location of the transform coefficient hidden_pos is hidden.

If not (the code is not the location of the hidden transform coefficient hidden_pos), the video decoding apparatus 100 may obtain information sign[xC][yC] about the code of the current transform coefficient from the bitstream.

When the location of the current transform coefficient is rsp_pos, the video decoding apparatus 100 may obtain information sign_rsp[xC][yC] about the rsp code of the current transform coefficient from the bitstream.

If rsp is not applied, the video decoding apparatus 100 determines n as 15, and if n is greater than 0, performs the operation in the for statement 985, and decreases n by 1, and then n is greater than 0. If it is greater than or equal to, the operation of the for statement 985 may be performed again, and if n is less than 0, the operation within the for statement 985 may no longer be performed.

The video decoding apparatus 100 may determine a horizontal position and a vertical position xC and yC of the current transform coefficient corresponding to the position n of the current transform coefficient in the current sub-block. The video decoding apparatus 100 may determine the position blkpos of the current transform coefficient based on xC and yC.

If the value of the effective transform coefficient flag sig_coeff_flag[xC][yC] of the current transform coefficient is 1, the value of the flag sign_data_hiding_enabled_flag indicating whether hiding the sign data is enabled is 0, or there is no hidden sign for the current sub-block (!signHidden) [i]), if the position of the current transform coefficient in the current sub-block in the forward scan order is the position of the first effective transform coefficient firstSigScanPos is not 0, the sign information sign[xC][yC] of the current transform coefficient from the bitstream is obtained. Can be obtained.

Hereinafter, a method of determining a data unit that can be used in a process of decoding an image by the video decoding apparatus 100 according to an exemplary embodiment will be described with reference to FIGS. 10 to 23. The operation of the video encoding apparatus 150 may be an operation similar or opposite to that of various embodiments of the operation of the video decoding apparatus 100 to be described later.

10 illustrates a process in which the video decoding apparatus 100 determines at least one coding unit by dividing a current coding unit according to an embodiment.

According to an embodiment, the video decoding apparatus 100 may determine a type of a coding unit using block type information, and may determine in what type a coding unit is divided using the split type information. That is, a method of dividing a coding unit indicated by the division type information may be determined according to which block type the block type information used by the video decoding apparatus 100 represents.

According to an embodiment, the video decoding apparatus 100 may use block type information indicating that a current coding unit is a square shape. For example, the video decoding apparatus 100 may determine whether to split a square coding unit, split it vertically, split it horizontally, split it into four coding units, or the like according to split type information. Referring to FIG. 10, when block shape information of the current coding unit 1000 indicates a square shape, the video decoding apparatus 100 has the same size as the current coding unit 1000 according to split type information indicating that the division is not divided. The coding unit 1010a having a is not split, or split coding units 1010b, 1010c, 1010d, etc. may be determined based on split type information indicating a predetermined splitting method.

Referring to FIG. 10, according to an exemplary embodiment, the video decoding apparatus 100 determines two coding units 1010b obtained by vertically splitting the current coding unit 1000 based on split type information indicating vertical splitting. I can. The video decoding apparatus 100 may determine two coding units 1010c obtained by splitting the current coding unit 1000 in the horizontal direction based on split type information indicating splitting in the horizontal direction. The video decoding apparatus 100 may determine four coding units 1010d obtained by splitting the current coding unit 1000 vertically and horizontally based on split type information indicating splitting in the vertical and horizontal directions. However, the split form in which the square coding unit can be split is limited to the above-described form and should not be interpreted, and various forms that can be represented by split form information may be included. Predetermined splitting forms in which the square coding unit is split will be described in detail through various embodiments below.

11 illustrates a process in which the video decoding apparatus 100 determines at least one coding unit by splitting coding units having a non-square shape, according to an embodiment.

According to an embodiment, the video decoding apparatus 100 may use block type information indicating that a current coding unit is a non-square type. The video decoding apparatus 100 may determine whether to split the non-square current coding unit or split it by a predetermined method according to the split type information. Referring to FIG. 11, when block type information of a current coding unit 1100 or 1150 indicates a non-square type, the video decoding apparatus 100 may display the current coding unit 1100 according to split type information indicating that the current coding unit 1100 or 1150 is not divided. Alternatively, coding units 1110 or 1160 having the same size as 1150) are not split, or coding units 1120a, 1120b, 1130a, 1130b, 1130c, 1170a, which are split based on split type information indicating a predetermined splitting method. 1170b, 1180a, 1180b, 1180c) may be determined. A predetermined splitting method in which a non-square coding unit is split will be described in detail through various embodiments below.

According to an embodiment, the video decoding apparatus 100 may determine a form in which a coding unit is split using split form information, and in this case, the split form information indicates the number of at least one coding unit generated by splitting the coding unit. Can be indicated. Referring to FIG. 11, when split type information indicates that a current coding unit (1100 or 1150) is split into two coding units, the video decoding apparatus 100 includes a current coding unit (1100 or 1150) based on split type information. The two coding units 1120a and 11420b or 1170a and 1170b included in the current coding unit may be determined by dividing.

According to an embodiment, when the video decoding apparatus 100 splits a non-square type of current coding unit (1100 or 1150) based on the split type information, a non-square type of current coding unit (1100 or 1150) is The current coding unit may be split in consideration of the position of the long side. For example, the video decoding apparatus 100 splits the current coding unit 1100 or 1150 in a direction for dividing the long side of the current coding unit 1100 or 1150 in consideration of the shape of the current coding unit 1100 or 1150 Thus, a plurality of coding units may be determined.

According to an embodiment, when the split type information indicates that coding units are split into odd blocks, the video decoding apparatus 100 may determine an odd number of coding units included in the current coding unit 1100 or 1150. For example, when the split type information indicates that the current coding unit (1100 or 1150) is split into three coding units, the video decoding apparatus 100 converts the current coding unit (1100 or 1150) into three coding units (1130a). , 1130b, 1130c, 1180a, 1180b, 1180c). According to an embodiment, the video decoding apparatus 100 may determine an odd number of coding units included in the current coding unit 1100 or 1150, and all sizes of the determined coding units may not be the same. For example, the size of a predetermined coding unit (1130b or 1180b) among the determined odd number of coding units (1130a, 1130b, 1130c, 1180a, 1180b, 1180c) is different from other coding units (1130a, 1130c, 1180a, 1180c) You can also have That is, a coding unit that can be determined by splitting the current coding unit 1100 or 1150 may have a plurality of types of sizes, and in some cases, an odd number of coding units 1130a, 1130b, 1130c, 1180a, 1180b, and 1180c May each have a different size.

According to an embodiment, when the split type information indicates that coding units are split into odd blocks, the video decoding apparatus 100 may determine an odd number of coding units included in the current coding unit 1100 or 1150, and further The video decoding apparatus 100 may place a predetermined limit on at least one coding unit among odd coding units generated by splitting. Referring to FIG. 11, the video decoding apparatus 100 is a coding unit located at the center of three coding units 1130a, 1130b, 1130c, 1180a, 1180b, and 1180c generated by splitting a current coding unit 1100 or 1150. A decoding process for (1130b, 1180b) may be different from other coding units (1130a, 1130c, 1180a, 1180c). For example, unlike other coding units 1130a, 1130c, 1180a, 1180c, the video decoding apparatus 100 limits the coding units 1130b and 1180b located at the center so that they are not further divided, or limited to a predetermined number of times. Can be restricted to be divided.

12 illustrates a process in which the video decoding apparatus 100 splits a coding unit based on at least one of block type information and split type information, according to an embodiment.

According to an embodiment, the video decoding apparatus 100 may determine that the square-shaped first coding unit 1200 is split into coding units or not split based on at least one of block type information and split type information. According to an embodiment, when the split type information indicates that the first coding unit 1200 is split in the horizontal direction, the video decoding apparatus 100 splits the first coding unit 1200 in the horizontal direction to obtain a second coding unit. (1210) can be determined. A first coding unit, a second coding unit, and a third coding unit used according to an embodiment are terms used to understand a relationship before and after splitting between coding units. For example, when the first coding unit is split, a second coding unit may be determined, and when the second coding unit is split, a third coding unit may be determined. Hereinafter, it may be understood that the relationship between the used first coding unit, the second coding unit, and the third coding unit follows the above-described characteristics.

According to an embodiment, the video decoding apparatus 100 may determine that the determined second coding unit 1210 is split into coding units or not split based on at least one of block type information and split type information. Referring to FIG. 12, the video decoding apparatus 100 divides the first coding unit 1200 based on at least one of block type information and split type information to determine a non-square type second coding unit 1210. It may be split into at least one third coding unit 1220a, 1220b, 1220c, 1220d, etc., or the second coding unit 1210 may not be split. The video decoding apparatus 100 may obtain at least one of block type information and split type information, and the video decoding apparatus 100 may obtain a first coding unit 1200 based on at least one of the obtained block type information and split type information. ) Can be divided into a plurality of second coding units (eg, 1210) of various types, and the second coding unit 1210 is a first coding based on at least one of block type information and split type information The unit 1200 may be divided according to the division method. According to an embodiment, when the first coding unit 1200 is split into the second coding unit 1210 based on at least one of block type information and split type information for the first coding unit 1200, the second coding unit 1200 The coding unit 1210 may also be divided into third coding units (eg, 1220a, 1220b, 1220c, 1220d, etc.) based on at least one of block type information and split type information for the second coding unit 1210. have. That is, the coding units may be recursively split based on at least one of split type information and block type information related to each coding unit. Accordingly, the coding unit of the square may be determined from the coding units of the non-square shape, and the coding unit of the square shape may be recursively divided to determine the coding unit of the non-square shape. Referring to FIG. 12, a predetermined coding unit (for example, among odd-numbered third coding units 1220b, 1220c, 1220d) determined by splitting a second coding unit 1210 in a non-square shape Coding units or square-shaped coding units) may be recursively divided. According to an embodiment, a square-shaped third coding unit 1220c, which is one of the odd number of third coding units 1220b, 1220c, and 1220d, may be split in a horizontal direction and split into a plurality of fourth coding units. The fourth coding unit 1240 having a non-square shape, which is one of the plurality of fourth coding units, may be divided into a plurality of coding units. For example, the fourth coding unit 1240 having a non-square shape may be divided into odd number of coding units 1250a, 1250b, and 1250c.

A method that can be used for recursive splitting of coding units will be described later through various embodiments.

According to an embodiment, the video decoding apparatus 100 divides each of the third coding units 1220a, 1220b, 1220c, 1220d, etc. into coding units based on at least one of block type information and split type information, or second encoding It can be determined that the unit 1210 is not divided. The video decoding apparatus 100 may split the second coding unit 1210 of a non-square shape into odd number of third coding units 1220b, 1220c, and 1220d according to an embodiment. The video decoding apparatus 100 may place a predetermined limit on a predetermined third coding unit among the odd number of third coding units 1220b, 1220c, and 1220d. For example, the video decoding apparatus 100 should be limited to a coding unit 1220c positioned in the middle of the odd number of third coding units 1220b, 1220c, and 1220d, or divided by a settable number of times. It can be limited to what you do. Referring to FIG. 12, the video decoding apparatus 100 includes an odd number of third coding units 1220b, 1220c, and 1220d included in the second coding unit 1210 of a non-square type. 1220c) is not further divided or is divided into a predetermined division (for example, divided into four coding units or divided into a shape corresponding to the divided second coding unit 1210), or a predetermined It can be limited to dividing only by the number of times (for example, dividing only n times, n>0). However, since the limitation on the central coding unit 1220c is merely exemplary embodiments, it is limited to the above-described exemplary embodiments and should not be interpreted, and the central coding unit 1220c is different from the other coding units 1220b and 1220d. It should be interpreted as including various restrictions that can be decrypted differently from ).

According to an embodiment, the video decoding apparatus 100 may obtain at least one of block type information and split type information used to divide a current coding unit at a predetermined position in the current coding unit.

13 illustrates a method for the video decoding apparatus 100 to determine a predetermined coding unit among odd coding units, according to an embodiment. Referring to FIG. 13, at least one of block type information and split type information of the current coding unit 1300 is a sample at a predetermined position among a plurality of samples included in the current coding unit 1300 (eg, It may be obtained in sample 1340). However, a predetermined position in the current coding unit 1300 in which at least one of the block type information and the split type information can be obtained should not be interpreted as being limited to the center position shown in FIG. 13, and the current coding unit 1300 It should be construed that various locations that may be included within (eg, top, bottom, left, right, top left, bottom left, top right or bottom right, etc.) can be included. The video decoding apparatus 100 may determine that the current coding unit is divided into coding units of various types and sizes or not divided by obtaining at least one of block type information and split type information obtained from a predetermined location.

According to an embodiment, when the current coding unit is divided into a predetermined number of coding units, the video decoding apparatus 100 may select one of the coding units. Methods for selecting one of a plurality of coding units may be various, and a description of these methods will be described later through various embodiments below.

According to an embodiment, the video decoding apparatus 100 may divide a current coding unit into a plurality of coding units and determine a coding unit at a predetermined location.

13 illustrates a method for the video decoding apparatus 100 to determine a coding unit at a predetermined position among odd coding units, according to an embodiment.

According to an embodiment, the video decoding apparatus 100 may use information indicating a location of each of the odd number of coding units to determine a coding unit located in the middle of the odd number of coding units. Referring to FIG. 13, the video decoding apparatus 100 may determine odd number of coding units 1320a, 1320b, and 1320c by dividing a current coding unit 1300. The video decoding apparatus 100 may determine a central coding unit 1320b by using information on the positions of the odd number of coding units 1320a, 1320b, and 1320c. For example, the video decoding apparatus 100 determines the location of the coding units 1320a, 1320b, and 1320c based on information indicating the location of a predetermined sample included in the coding units 1320a, 1320b, and 1320c. The coding unit 1320b positioned at may be determined. In more detail, the video decoding apparatus 100 includes the coding units 1320a, 1320b, and 1320c based on information indicating the positions of the samples 1330a, 1330b, and 1330c at the upper left of the coding units 1320a, 1320b, and 1320c. By determining the position, the coding unit 1320b positioned in the center may be determined.

According to an embodiment, information indicating the position of the upper left sample 1330a, 1330b, and 1330c included in the coding units 1320a, 1320b, and 1320c, respectively, is the position in the picture of the coding units 1320a, 1320b, and 1320c. Alternatively, it may include information about coordinates. According to an embodiment, information indicating the location of the upper left sample 1330a, 1330b, and 1330c included in the coding units 1320a, 1320b, and 1320c, respectively, is the coding units 1320a and 1320b included in the current coding unit 1300. , 1320c) may include information indicating the width or height, and the width or height may correspond to information indicating a difference between coordinates within a picture of the coding units 1320a, 1320b, and 1320c. That is, the video decoding apparatus 100 directly uses information on a position or coordinates within a picture of the coding units 1320a, 1320b, and 1320c, or provides information on a width or height of a coding unit corresponding to a difference value between coordinates. By using it, the coding unit 1320b positioned in the center may be determined.

According to an embodiment, information indicating the position of the upper left sample 1330a of the upper coding unit 1320a may represent (xa, ya) coordinates, and the upper left sample 1330b of the center coding unit 1320b Information indicating the location of) may indicate (xb, yb) coordinates, and information indicating the location of the upper left sample 1330c of the lower coding unit 1320c may indicate (xc, yc) coordinates. The video decoding apparatus 100 may determine the middle coding unit 1320b by using coordinates of the upper left samples 1330a, 1330b, and 1330c included in the coding units 1320a, 1320b, and 1320c, respectively. For example, when the coordinates of the upper left samples 1330a, 1330b, and 1330c are arranged in ascending or descending order, the coding unit 1320b including (xb, yb), which is the coordinates of the sample 1330b located in the middle, is May be determined as a coding unit positioned at the center of the coding units 1320a, 1320b, and 1320c determined by splitting the current coding unit 1300. However, the coordinates indicating the position of the upper left samples 1330a, 1330b, 1330c may indicate the coordinates indicating the absolute position in the picture, and furthermore, the position of the upper left sample 1330a of the upper coding unit 1320a As a reference, (dxb, dyb) coordinates, which is information indicating the relative position of the upper left sample 1330b of the center coding unit 1320b, indicating the relative position of the upper left sample 1330c of the lower coding unit 1320c Information (dxc, dyc) coordinates can also be used. In addition, as information indicating the location of a sample included in the coding unit, the method of determining the coding unit of a predetermined location by using the coordinates of the sample should not be interpreted limited to the above-described method. Should be interpreted in a way.

According to an embodiment, the video decoding apparatus 100 may split the current coding unit 1300 into a plurality of coding units 1320a, 1320b, and 1320c, and a predetermined criterion among coding units 1320a, 1320b, and 1320c The coding unit may be selected according to the following. For example, the video decoding apparatus 100 may select coding units 1320b having different sizes among coding units 1320a, 1320b, and 1320c.

According to an embodiment, the video decoding apparatus 100 includes (xa, ya) coordinates, which is information indicating the location of the upper left sample 1330a of the upper coding unit 1320a, and the upper left sample of the center coding unit 1320b. The coding unit 1320a, using (xb, yb) coordinates, which is information indicating the position of (1330b), and (xc, yc) coordinates, which are information indicating the position of the upper left sample 1330c of the lower coding unit 1320c. 1320b, 1320c) Each width or height may be determined. The video decoding apparatus 100 uses (xa, ya), (xb, yb), and (xc, yc) which are coordinates representing the positions of the coding units 1320a, 1320b, and 1320c. ) You can decide the size of each.

According to an embodiment, the video decoding apparatus 100 may determine the width of the upper coding unit 1320a as xb-xa and the height as yb-ya. According to an embodiment, the video decoding apparatus 100 may determine the width of the center coding unit 1320b as xc-xb and the height as yc-yb. According to an embodiment, the video decoding apparatus 100 may determine the width or height of the lower coding unit using the width or height of the current coding unit and the width and height of the upper coding unit 1320a and the center coding unit 1320b. . The video decoding apparatus 100 may determine a coding unit having a size different from other coding units based on the determined width and height of the coding units 1320a, 1320b, and 1320c. Referring to FIG. 13, the video decoding apparatus 100 may determine a coding unit 1320b having a size different from the size of the upper coding unit 1320a and the lower coding unit 1320c as the coding unit at a predetermined position. However, in the above-described process of determining a coding unit having a size different from other coding units, the video decoding apparatus 100 determines a coding unit at a predetermined location by using a size of a coding unit determined based on sample coordinates. Therefore, various processes of determining a coding unit at a predetermined location by comparing sizes of coding units determined according to predetermined sample coordinates may be used.

However, the location of the sample considered to determine the location of the coding unit should not be interpreted by being limited to the upper left corner described above, and it may be interpreted that information on the location of an arbitrary sample included in the coding unit can be used.

According to an embodiment, the video decoding apparatus 100 may select a coding unit at a predetermined position from among odd number of coding units determined by splitting the current coding unit in consideration of a shape of a current coding unit. For example, if the current coding unit has a non-square shape whose width is longer than the height, the video decoding apparatus 100 may determine the coding unit at a predetermined position according to the horizontal direction. That is, the video decoding apparatus 100 may determine one of coding units having different positions in the horizontal direction and place restrictions on the corresponding coding unit. If the current coding unit has a non-square shape whose height is longer than the width, the video decoding apparatus 100 may determine a coding unit at a predetermined position according to the vertical direction. That is, the video decoding apparatus 100 may determine one of coding units that have different positions in the vertical direction and place restrictions on the corresponding coding unit.

According to an embodiment, the video decoding apparatus 100 may use information indicating a position of each of the even number of coding units to determine a coding unit of a predetermined position among even number of coding units. The video decoding apparatus 100 may determine an even number of coding units by dividing the current coding unit, and may determine a coding unit at a predetermined position by using information on positions of the even number of coding units. A detailed process for this may be a process corresponding to a process of determining a coding unit at a predetermined location (eg, a center location) among the odd numbered coding units described above in FIG. 13, and thus will be omitted.

According to an embodiment, when a current coding unit in a non-square shape is divided into a plurality of coding units, a predetermined coding unit at a predetermined position is determined during the splitting process to determine a coding unit at a predetermined position among the plurality of coding units. Information of is available. For example, the video decoding apparatus 100 may determine the block type information and the split type stored in a sample included in the middle coding unit during the splitting process in order to determine a coding unit located in the middle of the coding units divided into a plurality of the current coding unit. At least one of the information can be used.

Referring to FIG. 13, the video decoding apparatus 100 may split a current coding unit 1300 into a plurality of coding units 1320a, 1320b, and 1320c based on at least one of block type information and split type information. A coding unit 1320b positioned in the middle of the plurality of coding units 1320a, 1320b, and 1320c may be determined. Furthermore, the video decoding apparatus 100 may determine a coding unit 1320b positioned at the center in consideration of a position at which at least one of block type information and split type information is obtained. That is, at least one of block type information and split type information of the current coding unit 1300 may be obtained from a sample 1340 located in the center of the current coding unit 1300, and the block type information and the split type information When the current coding unit 1300 is divided into a plurality of coding units 1320a, 1320b, and 1320c based on at least one of, the coding unit 1320b including the sample 1340 is used as a coding unit positioned at the center. You can decide. However, the information used to determine the centered coding unit should not be interpreted as being limited to at least one of block type information and split type information, and various types of information will be used in the process of determining the centered coding unit. I can.

According to an embodiment, predetermined information for identifying a coding unit at a predetermined location may be obtained from a predetermined sample included in a coding unit to be determined. Referring to FIG. 13, the video decoding apparatus 100 includes coding units (eg, split into a plurality of coding units 1320a, 1320b, and 1320c) of a plurality of coding units determined by splitting the current coding unit 1300. Block type information obtained from a sample (eg, a sample located in the center of the current coding unit 1300) at a predetermined position in the current coding unit 1300 in order to determine a coding unit located in the middle of the coding units, and At least one of the division type information may be used. . That is, the video decoding apparatus 100 may determine the sample at the predetermined position in consideration of the block block shape of the current coding unit 1300, and the video decoding apparatus 100 may determine the current coding unit 1300 by splitting it. From among the plurality of coding units 1320a, 1320b, 1320c, a coding unit 1320b including a sample from which predetermined information (eg, at least one of block type information and split type information) can be obtained is determined Certain restrictions can be placed. Referring to FIG. 13, according to an embodiment, the video decoding apparatus 100 may determine a sample 1340 positioned in the center of the current coding unit 1300 as a sample from which predetermined information can be obtained, and the video decoding apparatus The coding unit 1320b including the sample 1340 may be limited in a decoding process. However, the location of the sample from which predetermined information can be obtained should not be interpreted as being limited to the above-described location, but may be interpreted as samples at an arbitrary location included in the coding unit 1320b to be determined to impose restrictions.

According to an embodiment, the location of a sample from which predetermined information can be obtained may be determined according to the shape of the current coding unit 1300. According to an embodiment, the block shape information may determine whether the shape of a current coding unit is a square or a non-square shape, and a location of a sample from which predetermined information can be obtained may be determined according to the shape. For example, the video decoding apparatus 100 uses at least one of information about the width and height of the current coding unit to be positioned on a boundary that divides at least one of the width and height of the current coding unit in half. The sample may be determined as a sample from which predetermined information can be obtained. For another example, when the block type information related to the current coding unit indicates that the block type information is a non-square type, the video decoding apparatus 100 determines one of the samples adjacent to the boundary dividing the long side of the current coding unit in half. It can be determined as a sample from which the information of can be obtained.

According to an embodiment, when a current coding unit is split into a plurality of coding units, in order to determine a coding unit at a predetermined position among the plurality of coding units, the video decoding apparatus 100 may perform at least one of block type information and split type information. You can use one. According to an embodiment, the video decoding apparatus 100 may obtain at least one of block type information and split type information from a sample at a predetermined position included in a coding unit, and the video decoding apparatus 100 splits a current coding unit The generated coding units may be split by using at least one of split form information and block form information obtained from samples at a predetermined position included in each of the plurality of coding units. That is, the coding unit may be recursively split using at least one of block type information and split type information obtained from a sample at a predetermined location included in each coding unit. Since the recursive splitting process of the coding unit has been described above with reference to FIG. 12, a detailed description will be omitted.

According to an embodiment, the video decoding apparatus 100 may determine at least one coding unit by dividing a current coding unit, and determine an order in which the at least one coding unit is decoded by a predetermined block (eg, a current coding unit). ) Can be determined.

14 illustrates an order in which a plurality of coding units are processed when the video decoding apparatus 100 determines a plurality of coding units by dividing a current coding unit according to an embodiment.

According to an embodiment, the video decoding apparatus 100 may determine the second coding units 1410a and 1410b by vertically splitting the first coding unit 1400 according to the block type information and the split type information, or Second coding units 1450a, 1450b, 1450c, 1450d by splitting 1400 in the horizontal direction to determine second coding units 1430a and 1430b, or splitting the first coding unit 1400 in vertical and horizontal directions Can be determined.

Referring to FIG. 14, the video decoding apparatus 100 may determine an order so that the second coding units 1410a and 1410b determined by dividing the first coding unit 1400 in the vertical direction are processed in the horizontal direction 1410c. . The video decoding apparatus 100 may determine a processing order of the second coding units 1430a and 1430b determined by dividing the first coding unit 1400 in the horizontal direction as the vertical direction 1430c. After the video decoding apparatus 100 divides the first coding unit 1400 in the vertical and horizontal directions, the second coding units 1450a, 1450b, 1450c, and 1450d determined by processing the coding units located in one row are processed. The coding units located in the next row may be determined according to a predetermined order (eg, a raster scan order or a z scan order 1450e).

According to an embodiment, the video decoding apparatus 100 may recursively split coding units. Referring to FIG. 14, the video decoding apparatus 100 may divide the first coding unit 1400 to determine a plurality of coding units 1410a, 1410b, 1430a, 1430b, 1450a, 1450b, 1450c, 1450d, and Each of the determined coding units 1410a, 1410b, 1430a, 1430b, 1450a, 1450b, 1450c, and 1450d may be recursively divided. A method of dividing the plurality of coding units 1410a, 1410b, 1430a, 1430b, 1450a, 1450b, 1450c, and 1450d may correspond to a method of dividing the first coding unit 1400. Accordingly, the plurality of coding units 1410a, 1410b, 1430a, 1430b, 1450a, 1450b, 1450c, and 1450d may be independently divided into a plurality of coding units. Referring to FIG. 14, the video decoding apparatus 100 may determine second coding units 1410a and 1410b by dividing the first coding unit 1400 in a vertical direction, and further, each of the second coding units 1410a and 1410b. It can be decided to divide independently or not to divide.

According to an embodiment, the video decoding apparatus 100 may split the second coding unit 1410a on the left side in a horizontal direction and split it into third coding units 1420a and 1420b, and the second coding unit 1410b on the right side. ) May not be divided.

According to an embodiment, the processing order of coding units may be determined based on a splitting process of the coding units. In other words, the processing order of the divided coding units may be determined based on the processing order of the coding units immediately before being divided. The video decoding apparatus 100 may independently determine an order in which the third coding units 1420a and 1420b determined by splitting the second coding unit 1410a on the left side are processed, independently from the second coding unit 1410b on the right side. Since the second coding unit 1410a on the left is split in the horizontal direction to determine the third coding units 1420a and 1420b, the third coding units 1420a and 1420b may be processed in the vertical direction 1420c. In addition, since the order in which the left second coding unit 1410a and the right second coding unit 1410b are processed corresponds to the horizontal direction 1410c, the third coding unit included in the left second coding unit 1410a After the 1420a and 1420b are processed in the vertical direction 1420c, the right coding unit 1410b may be processed. Since the above description is for explaining a process in which the processing order of coding units is determined according to the coding unit before division, each coding unit should not be interpreted as being limited to the above-described embodiment, and coding units determined by being divided into various forms It should be construed as being used in a variety of ways that can be processed independently in sequence.

FIG. 15 illustrates a process of determining that a current coding unit is divided into odd number of coding units when coding units cannot be processed in a predetermined order, according to an embodiment.

According to an embodiment, the video decoding apparatus 100 may determine that the current coding unit is divided into odd number of coding units based on the obtained block type information and split type information. Referring to FIG. 15, a first coding unit 1500 having a square shape may be divided into second coding units 1510a and 1510b having a non-square shape, and the second coding units 1510a and 1510b are each independently It may be divided into 3 coding units 1520a, 1520b, 1520c, 1520d, and 1520e. According to an embodiment, the video decoding apparatus 100 may determine a plurality of third coding units 1520a and 1520b by splitting a left coding unit 1510a among the second coding units in a horizontal direction, and determining a plurality of third coding units 1520a and 1520b, and the right coding unit 1510b ) May be divided into odd number of third coding units 1520c, 1520d, and 1520e.

According to an embodiment, the video decoding apparatus 100 determines whether or not the third coding units 1520a, 1520b, 1520c, 1520d, and 1520e can be processed in a predetermined order to determine whether there are coding units divided into odd numbers. You can decide. Referring to FIG. 15, the video decoding apparatus 100 may determine third coding units 1520a, 1520b, 1520c, 1520d, and 1520e by recursively splitting the first coding unit 1500. The video decoding apparatus 100 may include a first coding unit 1500, a second coding unit 1510a, 1510b, or a third coding unit 1520a, 1520b, 1520c, based on at least one of block type information and split type information. It may be determined whether the 1520d and 1520e) are split into odd number of coding units among the split types. For example, a coding unit positioned to the right of the second coding units 1510a and 1510b may be divided into odd number of third coding units 1520c, 1520d, and 1520e. The order in which the plurality of coding units included in the first coding unit 1500 are processed may be a predetermined order (eg, z-scan order 1530), and the video decoding apparatus ( 100) may determine whether the third coding units 1520c, 1520d, and 1520e determined by dividing the right second coding units 1510b into odd numbers satisfies a condition capable of being processed according to the predetermined order.

According to an embodiment, the video decoding apparatus 100 satisfies a condition in which the third coding units 1520a, 1520b, 1520c, 1520d, and 1520e included in the first coding unit 1500 can be processed in a predetermined order. Whether or not at least one of the widths and heights of the second coding units 1510a and 1510b is divided in half according to the boundary of the third coding units 1520a, 1520b, 1520c, 1520d, and 1520e, and Related. For example, the third coding units 1520a and 1520b determined by dividing the height of the left second coding unit 1510a in a non-square shape in half satisfy the condition, but the second coding unit 1510b on the right is 3 Since the boundary of the third coding units 1520c, 1520d, and 1520e determined by dividing into two coding units cannot split the width or height of the right second coding unit 1510b in half, the third coding unit 1520c, 1520d, 1520e) may be determined not to satisfy the condition, and the video decoding apparatus 100 determines that the scan order is disconnected when the condition is not satisfied, and based on the determination result, the right second coding unit 1510b is It may be determined to be split into odd number of coding units. According to an embodiment, when the video decoding apparatus 100 is divided into an odd number of coding units, the video decoding apparatus 100 may place a predetermined restriction on a coding unit at a predetermined position among the divided coding units. Since it has been described above through the embodiment, detailed description will be omitted.

16 illustrates a process in which the video decoding apparatus 100 determines at least one coding unit by dividing the first coding unit 1600 according to an embodiment. According to an embodiment, the video decoding apparatus 100 may divide the first coding unit 1600 based on at least one of block type information and split type information acquired through the acquirer 110. The first coding unit 1600 having a square shape may be divided into four coding units having a square shape, or may be divided into a plurality of coding units having a non-square shape. For example, referring to FIG. 16, when the block type information indicates that the first coding unit 1600 is a square and the split type information is divided into non-square coding units, the video decoding apparatus 100 (1600) may be divided into a plurality of non-square coding units. Specifically, when the split type information indicates that an odd number of coding units is determined by splitting the first coding unit 1600 in a horizontal direction or a vertical direction, the video decoding apparatus 100 includes a first coding unit 1600 having a square shape. ) May be divided into odd-numbered coding units, divided into second coding units 1610a, 1610b, and 1610c determined by splitting in the vertical direction or second coding units 1620a, 1620b, and 1620c splitting in the horizontal direction and determined.

According to an embodiment, the video decoding apparatus 100 may process the second coding units 1610a, 1610b, 1610c, 1620a, 1620b, and 1620c included in the first coding unit 1600 according to a predetermined order. Is satisfied, and the condition is whether at least one of the width and height of the first coding unit 1600 is divided in half according to the boundary of the second coding units 1610a, 1610b, 1610c, 1620a, 1620b, and 1620c. It is related to whether or not. Referring to FIG. 16, the boundary of the second coding units 1610a, 1610b, and 1610c determined by dividing the square-shaped first coding unit 1600 in a vertical direction divides the width of the first coding unit 1600 in half. Therefore, it may be determined that the first coding unit 1600 does not satisfy a condition capable of being processed according to a predetermined order. Also, since the boundaries of the second coding units 1620a, 1620b, and 1620c determined by dividing the square-shaped first coding unit 1600 in the horizontal direction cannot divide the width of the first coding unit 1600 It may be determined that one coding unit 1600 does not satisfy a condition capable of being processed according to a predetermined order. In the case of dissatisfaction with this condition, the video decoding apparatus 100 may determine that the scan order is disconnected, and determine that the first coding unit 1600 is divided into odd number of coding units based on the determination result. According to an embodiment, when the video decoding apparatus 100 is divided into an odd number of coding units, the video decoding apparatus 100 may place a predetermined restriction on a coding unit at a predetermined position among the divided coding units. Since it has been described above through the embodiment, detailed description will be omitted.

According to an embodiment, the video decoding apparatus 100 may determine various types of coding units by dividing the first coding unit.

Referring to FIG. 16, the video decoding apparatus 100 may split a square type first coding unit 1600 and a non-square type first coding unit 1630 or 1650 into various types of coding units. .

17 illustrates a second coding unit in a non-square shape determined by splitting a first coding unit 1700 according to an embodiment, and when a second coding unit satisfies a predetermined condition, a second coding unit is split. It shows that the possible forms are limited.

According to an embodiment, the video decoding apparatus 100 uses the first coding unit 1700 in a square shape based on at least one of block shape information and split type information acquired through the acquisition unit 105 to be in a non-square shape. It may be determined to divide into second coding units 1710a, 1710b, 1720a, and 1720b. The second coding units 1710a, 1710b, 1720a, and 1720b may be independently split. Accordingly, the video decoding apparatus 100 determines that the second coding units 1710a, 1710b, 1720a, and 1720b are divided into a plurality of coding units or not divided based on at least one of block type information and split type information related to each of the second coding units 1710a, 1710b, 1720a, and 1720b. I can. According to an embodiment, the video decoding apparatus 100 splits the left second coding unit 1710a of a non-square shape determined by splitting the first coding unit 1700 in a vertical direction in a horizontal direction, and splitting the third coding unit ( 1712a, 1712b) can be determined. However, when the video decoding apparatus 100 splits the left second coding unit 1710a in the horizontal direction, the right second coding unit 1710b is in the horizontal direction in the same direction as the left second coding unit 1710a. It can be restricted so that it cannot be divided into. If the right second coding unit 1710b is split in the same direction to determine the third coding units 1714a and 1714b, the left second coding unit 1710a and the right second coding unit 1710b are respectively The third coding units 1712a, 1712b, 1714a, and 1714b may be determined by being split independently. However, this is because the video decoding apparatus 100 divides the first coding unit 1700 into four square-shaped second coding units 1730a, 1730b, 1730c, and 1730d based on at least one of block type information and split type information. This is the same result as the one, and this may be inefficient in terms of image decoding.

According to an embodiment, the video decoding apparatus 100 divides the second coding unit 1720a or 1720b in a non-square shape determined by dividing the first coding unit 11300 in a horizontal direction in a vertical direction to obtain a third coding unit. (1722a, 1722b, 1724a, 1724b) can be determined. However, when the video decoding apparatus 100 splits one of the second coding units (for example, the upper second coding unit 1720a) in the vertical direction, another second coding unit (for example, the lower The coding unit 1720b may be limited so that the upper second coding unit 1720a cannot be split in the vertical direction in the same way as the split direction.

FIG. 18 illustrates a process in which the video decoding apparatus 100 splits a square coding unit when it is not possible to indicate that split type information is split into four square coding units according to an embodiment.

According to an embodiment, the video decoding apparatus 100 divides the first coding unit 1800 based on at least one of block type information and split type information to generate second coding units 1810a, 1810b, 1820a, 1820b, etc. You can decide. Split type information may include information on various types in which a coding unit can be divided, but information on various types may not include information for dividing into four coding units in a square shape. According to the split type information, the video decoding apparatus 100 cannot split the square-shaped first coding unit 1800 into four square-shaped second coding units 1830a, 1830b, 1830c, and 1830d. The video decoding apparatus 100 may determine the non-square type of second coding units 1810a, 1810b, 1820a, 1820b, etc. based on the split type information.

According to an embodiment, the video decoding apparatus 100 may independently split the second coding units 1810a, 1810b, 1820a, 1820b, etc. of a non-square shape. Each of the second coding units 1810a, 1810b, 1820a, 1820b, etc. may be split in a predetermined order through a recursive method, and this is based on at least one of block type information and split type information. ) May be a division method corresponding to the division method.

For example, the video decoding apparatus 100 may determine the third coding units 1812a and 1812b in a square shape by splitting the left second coding unit 1810a in a horizontal direction, and the second coding unit 1810b on the right The third coding units 1814a and 1814b having a square shape may be determined by being split in a horizontal direction. Furthermore, the video decoding apparatus 100 may determine the third coding units 1816a, 1816b, 1816c, and 1816d in a square shape by splitting both the left second coding unit 1810a and the right second coding unit 1810b in the horizontal direction. have. In this case, the coding unit may be determined in the same form as the first coding unit 1800 is divided into four square second coding units 1830a, 1830b, 1830c, and 1830d.

For another example, the video decoding apparatus 100 may determine the third coding units 1822a and 1822b in a square shape by splitting the upper second coding unit 1820a in a vertical direction, and the lower second coding unit 1820b ) Is divided in a vertical direction to determine the third coding units 1824a and 1824b having a square shape. Furthermore, the video decoding apparatus 100 may determine the third coding units 1822a, 1822b, 1824a, and 1824b in a square shape by splitting both the upper second coding units 1820a and the lower second coding units 1820b in the vertical direction. have. In this case, the coding unit may be determined in the same form as the first coding unit 1800 is divided into four square second coding units 1830a, 1830b, 1830c, and 1830d.

19 illustrates that a processing order between a plurality of coding units may vary according to a splitting process of a coding unit, according to an embodiment.

According to an embodiment, the video decoding apparatus 100 may split the first coding unit 1900 based on block type information and split type information. When the block shape information indicates a square shape and the split type information indicates that the first coding unit 1900 is divided in at least one of a horizontal direction and a vertical direction, the video decoding apparatus 100 may perform the first coding unit 1900. ) May be split to determine a second coding unit (eg, 1910a, 1910b, 1920a, 1920b, 1930a, 1930b, 1930c, 1930d, etc.). Referring to FIG. 19, the second coding units 1910a, 1910b, 1920a, and 1920b of a non-square shape determined by splitting a first coding unit 1900 only in a horizontal direction or a vertical direction are block type information and split type information for each Can be divided independently based on. For example, the video decoding apparatus 100 splits the second coding units 1910a and 1910b generated by splitting the first coding unit 1900 in the vertical direction and splitting the second coding units 1910a and 1910b in the horizontal direction, 1916c and 1916d) may be determined, and the second coding units 1920a and 1920b generated by splitting the first coding unit 1900 in the horizontal direction are split in the horizontal direction, respectively, and the third coding units 1926a, 1926b, and 1926c , 1926d). Since the dividing process of the second coding units 1910a, 1910b, 1920a, and 1920b has been described above with reference to FIG. 17, a detailed description thereof will be omitted.

According to an embodiment, the video decoding apparatus 100 may process coding units according to a predetermined order. Features of processing of coding units according to a predetermined order have been described above with reference to FIG. 14, and thus detailed descriptions will be omitted. Referring to FIG. 19, the video decoding apparatus 100 divides the first coding unit 1900 in a square shape to form four square-shaped third coding units 1916a, 1916b, 1916c, 1916d, 1926a, 1926b, 1926c, 1926d. ) Can be determined. According to an embodiment, the video decoding apparatus 100 performs a processing order of the third coding units 1916a, 1916b, 1916c, 1916d, 1926a, 1926b, 1926c, and 1926d according to the form in which the first coding unit 1900 is split. You can decide.

According to an embodiment, the video decoding apparatus 100 determines third coding units 1916a, 1916b, 1916c, and 1916d by dividing the second coding units 1910a and 1910b generated by being split in a vertical direction, respectively, in a horizontal direction. The video decoding apparatus 100 may first process the third coding units 1916a and 1916b included in the left second coding unit 1910a in the vertical direction, and then process the third coding units 1916a and 1916b included in the right second coding unit 1910b. The third coding units 1916a, 1916b, 1916c, and 1916d may be processed according to an order 1917 of processing the third coding units 1916c and 1916d in the vertical direction.

According to an embodiment, the video decoding apparatus 100 determines third coding units 1926a, 1926b, 1926c, and 1926d by dividing the second coding units 1920a and 1920b generated by being split in a horizontal direction in a vertical direction, respectively. The video decoding apparatus 100 may first process the third coding units 1926a and 1926b included in the upper second coding unit 1920a in the horizontal direction, and then, the lower second coding unit 1920b. The third coding units 1926a, 1926b, 1926c, and 1926d may be processed according to an order 1927 of processing the third coding units 1926c and 1926d in the horizontal direction.

Referring to FIG. 19, second coding units 1910a, 1910b, 1920a, and 1920b are respectively divided to determine square-shaped third coding units 1916a, 1916b, 1916c, 1916d, 1926a, 1926b, 1926c, and 1926d. have. The second coding units 1910a and 1910b determined by splitting in the vertical direction and the second coding units 1920a and 1920b determined by splitting in the horizontal direction are split into different forms, but the third coding unit 1916a determined later , 1916b, 1916c, 1916d, 1926a, 1926b, 1926c, 1926d), eventually, the first coding unit 1900 is divided into coding units of the same type. Accordingly, the video decoding apparatus 100 recursively divides coding units through different processes based on at least one of block type information and split type information, and consequently determines coding units of the same type, The coding units may be processed in different orders.

FIG. 20 illustrates a process of determining a depth of a coding unit according to a change in a shape and size of a coding unit when coding units are recursively split to determine a plurality of coding units, according to an embodiment.

According to an embodiment, the video decoding apparatus 100 may determine a depth of a coding unit according to a predetermined criterion. For example, the predetermined criterion may be the length of the long side of the coding unit. When the length of the long side of the current coding unit is split by 2n (n>0) times the length of the long side of the coding unit before splitting, the depth of the current coding unit is greater than the depth of the coding unit before splitting. It can be determined that the depth is increased by n. Hereinafter, a coding unit having an increased depth is expressed as a coding unit having a lower depth.

Referring to FIG. 20, according to an embodiment, based on block shape information indicating a square shape (for example, block shape information may indicate '0: SQUARE'), the video decoding apparatus 100 One coding unit 2000 may be split to determine a second coding unit 2002 and a third coding unit 2004 having a lower depth. If the size of the square-shaped first coding unit 2000 is 2Nx2N, the second coding unit 2002 determined by dividing the width and height of the first coding unit 2000 by 1/21 times may have a size of NxN. have. Furthermore, the third coding unit 2004 determined by dividing the width and height of the second coding unit 2002 into 1/2 size may have a size of N/2xN/2. In this case, the width and height of the third coding unit 2004 are 1/22 times that of the first coding unit 2000. When the depth of the first coding unit 2000 is D, the depth of the second coding unit 2002, which is 1/21 times the width and height of the first coding unit 2000, may be D+1, and the first coding unit The depth of the third coding unit 2004, which is 1/22 times the width and height of (2000), may be D+2.

According to an embodiment, block shape information indicating a non-square shape (for example, block shape information is '1: NS_VER' indicating that the height is a non-square that is longer than the width, or ′ indicating that the width is a non-square shape that is longer than the height. 2: NS_HOR′), the video decoding apparatus 100 splits a first coding unit (2010 or 2020) having a non-square shape and a second coding unit (2012 or 2022) having a lower depth, A third coding unit 2014 or 2024 may be determined.

The video decoding apparatus 100 may determine a second coding unit (eg, 2002, 2012, 2022, etc.) by splitting at least one of the width and height of the first coding unit 2010 having a size of Nx2N. That is, the video decoding apparatus 100 may split the first coding unit 2010 in a horizontal direction to determine a second coding unit 2002 having a size of NxN or a second coding unit 2022 having a size of NxN/2, A second coding unit 2012 having a size of N/2xN may be determined by dividing in a horizontal direction and a vertical direction.

According to an embodiment, the video decoding apparatus 100 determines a second coding unit (for example, 2002, 2012, 2022, etc.) by dividing at least one of a width and a height of the first coding unit 2020 having a size of 2NxN. May be. That is, the video decoding apparatus 100 may determine a second coding unit 2002 having a size of NxN or a second coding unit 2012 having a size of N/2xN by splitting the first coding unit 2020 in a vertical direction, The second coding unit 2022 having a size of NxN/2 may be determined by dividing in the horizontal direction and the vertical direction.

According to an embodiment, the video decoding apparatus 100 determines a third coding unit (eg, 2004, 2014, 2024, etc.) by dividing at least one of a width and a height of the second coding unit 2002 having a size of NxN. May be. That is, the video decoding apparatus 100 determines the third coding unit 2004 having a size of N/2xN/2 by splitting the second coding unit 2002 in a vertical direction and a horizontal direction, or determining the third coding unit 2004 having a size of N/22xN/2. 3 coding units 2014 may be determined or a third coding unit 2024 having a size of N/2xN/22 may be determined.

According to an embodiment, the video decoding apparatus 100 divides at least one of a width and a height of the second coding unit 2012 having a size of N/2xN to a third coding unit (eg, 2004, 2014, 2024, etc.) You can also decide. In other words, the video decoding apparatus 100 splits the second coding unit 2012 in a horizontal direction to determine the third coding unit 2004 having a size of N/2xN/2 or a third coding unit 2024 having a size of N/2xN/22. ) May be determined or divided in a vertical direction and a horizontal direction to determine the third coding unit 2014 having a size of N/22xN/2.

According to an embodiment, the video decoding apparatus 100 divides at least one of a width and a height of the second coding unit 2014 having a size of NxN/2 to a third coding unit (eg, 2004, 2014, 2024, etc.). You can also decide. That is, the video decoding apparatus 100 splits the second coding unit 2012 in a vertical direction to determine the third coding unit 2004 having a size of N/2xN/2 or a third coding unit having a size of N/22xN/2. ) May be determined or divided in a vertical direction and a horizontal direction to determine the third coding unit 2024 having a size of N/2xN/22.

According to an embodiment, the video decoding apparatus 100 may split square coding units (for example, 2000, 2002, 2004) in a horizontal direction or a vertical direction. For example, the first coding unit 2000 having a size of 2Nx2N is split in a vertical direction to determine a first coding unit 2010 having a size of Nx2N, or a first coding unit having a size of 2NxN is determined by splitting in the horizontal direction. I can. According to an embodiment, when the depth is determined based on the length of the longest side of the coding unit, the depth of the coding unit determined by splitting a 2Nx2N sized first coding unit (2000, 2002 or 2004) in a horizontal direction or a vertical direction May be the same as the depth of the first coding unit (2000, 2002, or 2004).

According to an embodiment, the width and height of the third coding unit 2014 or 2024 may correspond to 1/22 times the first coding unit 2010 or 2020. When the depth of the first coding unit (2010 or 2020) is D, the depth of the second coding unit (2012 or 2014) which is 1/2 times the width and height of the first coding unit (2010 or 2020) may be D+1 In addition, the depth of the third coding unit 2014 or 2024, which is 1/22 times the width and height of the first coding unit 2010 or 2020, may be D+2.

21 illustrates a depth that may be determined according to a shape and size of coding units and a part index (hereinafter referred to as PID) for classifying coding units, according to an embodiment.

According to an embodiment, the video decoding apparatus 100 may determine various types of second coding units by splitting the first coding unit 2100 having a square shape. Referring to FIG. 21, the video decoding apparatus 100 divides a first coding unit 2100 in at least one of a vertical direction and a horizontal direction according to split type information, and divides the second coding units 2102a, 2102b, and 2104a. 2104b, 2106a, 2106b, 2106c, 2106d) can be determined. That is, the video decoding apparatus 100 may determine the second coding units 2102a, 2102b, 2104a, 2104b, 2106a, 2106b, 2106c, and 2106d based on split type information on the first coding unit 2100.

According to an embodiment, the second coding units 2102a, 2102b, 2104a, 2104b, 2106a, 2106b, 2106c, and 2106d determined according to split type information for the first coding unit 2100 in a square shape are Based on the depth can be determined. For example, since the length of one side of the first coding unit 2100 in a square shape and the length of the long side of the second coding units 2102a, 2102b, 2104a, 2104b in a non-square shape are the same, the first coding unit ( 2100) and the non-square second coding units 2102a, 2102b, 2104a, and 2104b may have the same depth as D. On the other hand, when the video decoding apparatus 100 divides the first coding unit 2100 into four square second coding units 2106a, 2106b, 2106c, 2106d based on the split type information, Since the length of one side of the 2 coding units 2106a, 2106b, 2106c, 2106d is 1/2 times the length of one side of the first coding unit 2100, the depth of the second coding units 2106a, 2106b, 2106c, 2106d May be a depth of D+1 that is one depth lower than the depth of D of the first coding unit 2100.

According to an embodiment, the video decoding apparatus 100 splits a first coding unit 2110 having a height longer than a width in a horizontal direction according to split type information, and a plurality of second coding units 2112a, 2112b, 2114a, 2114b, 2114c) can be divided. According to an embodiment, the video decoding apparatus 100 divides a first coding unit 2120 having a width longer than a height in a vertical direction according to the split type information to obtain a plurality of second coding units 2122a, 2122b, 2124a, 2124b, 2124c) can be divided.

According to an embodiment, the second coding units 2112a, 2112b, 2114a, 2114b, 2116a, 2116b, 2116c, 2116d, which are determined according to split type information for the first non-square type coding unit 2110 or 2120, are The depth may be determined based on the length of the long side. For example, since the length of one side of the second coding units 2112a and 2112b in a square shape is 1/2 times the length of one side of the first coding unit 2110 in a non-square shape whose height is longer than the width, the square The depth of the second coding units 2102a, 2102b, 2104a, and 2104b of the form is D+1, which is one depth lower than the depth D of the first coding unit 2110 of the non-square form.

Furthermore, the video decoding apparatus 100 may split the first coding unit 2110 of the non-square shape into odd number of second coding units 2114a, 2114b, 2114c based on the split type information. The odd number of second coding units 2114a, 2114b, and 2114c may include second coding units 2114a and 2114c having a non-square shape and a second coding unit 2114b having a square shape. In this case, the length of the long side of the second coding units 2114a and 2114c of the non-square form and the length of one side of the second coding unit 2114b of the square form are 1/ of the length of one side of the first coding unit 2110 Since it is twice as large, the depth of the second coding units 2114a, 2114b, and 2114c may be a depth of D+1 that is one depth lower than the depth of D of the first coding unit 2110. The video decoding apparatus 100 is a method corresponding to the method of determining the depth of coding units related to the first coding unit 2110, and is related to the first coding unit 2120 in a non-square shape having a width greater than a height. The depth of the coding units may be determined.

According to an embodiment, in determining an index (PID) for classifying divided coding units, if the coding units divided into odd numbers are not the same size, the size ratio between the coding units is Based on the index can be determined. Referring to FIG. 21, among the coding units 2114a, 2114b, and 2114c divided into odd numbers, a coding unit 2114b positioned in the middle is a coding unit having the same width as other coding units 2114a and 2114c, but different heights. It may be twice the height of the fields 2114a and 2114c. That is, in this case, the coding unit 2114b positioned in the center may include two of the other coding units 2114a and 2114c. Accordingly, if the index (PID) of the coding unit 2114b located in the middle according to the scan order is 1, the coding unit 2114c located in the next order may have an index of 3 with an increase of 2. That is, there may be discontinuities in the index value. According to an embodiment, the video decoding apparatus 100 may determine whether or not the odd-numbered coding units are of the same size based on whether there is discontinuity in an index for distinguishing between the split coding units.

According to an embodiment, the video decoding apparatus 100 may determine whether to be split into a specific split type based on an index value for classifying a plurality of coding units determined by being split from a current coding unit. Referring to FIG. 21, the video decoding apparatus 100 determines an even number of coding units 2112a and 2112b by dividing a rectangular first coding unit 2110 having a height greater than a width, or an odd number of coding units 2114a and 2114b. , 2114c) can be determined. The video decoding apparatus 100 may use an index (PID) representing each coding unit to distinguish each of a plurality of coding units. According to an embodiment, the PID may be obtained from a sample (eg, an upper left sample) at a predetermined position of each coding unit.

According to an embodiment, the video decoding apparatus 100 may determine a coding unit at a predetermined position among coding units that are split and determined using an index for classifying coding units. According to an embodiment, when it is indicated that split type information for the first coding unit 2110 having a rectangular shape having a height longer than a width is divided into three coding units, the video decoding apparatus 100 may determine the first coding unit 2110. It can be divided into three coding units 2114a, 2114b, and 2114c. The video decoding apparatus 100 may allocate indexes for each of the three coding units 2114a, 2114b, and 2114c. The video decoding apparatus 100 may compare an index for each coding unit to determine a coding unit among coding units divided into odd numbers. The video decoding apparatus 100 encodes a coding unit 2114b having an index corresponding to a middle value among the indices based on the indexes of the coding units, and a center position among coding units determined by splitting the first coding unit 2110 It can be determined as a unit. In determining an index for classifying divided coding units, according to an embodiment, when the coding units are not the same size, the video decoding apparatus 100 may determine the index based on a size ratio between coding units. . Referring to FIG. 21, a coding unit 2114b generated by splitting the first coding unit 2110 is the same as the other coding units 2114a and 2114c, but the coding units 2114a and 2114c having different heights. It can be twice the height. In this case, if the index (PID) of the coding unit 2114b positioned in the middle is 1, the coding unit 2114c positioned in the next order may have an index of 3 with an increase of 2. As in this case, when the index increases evenly and then the increase width varies, the video decoding apparatus 100 may determine that the index is divided into a plurality of coding units including coding units having different sizes from other coding units. According to this, when it indicates that the split type information is split into odd number of coding units, the video decoding apparatus 100 includes a coding unit (for example, a center coding unit) at a predetermined position among odd coding units having a different size from other coding units. The current coding unit can be split by. In this case, the video decoding apparatus 100 may determine a coding unit having a different size using an index (PID) for a coding unit. However, the above-described index and the size or position of the coding unit at a predetermined position to be determined are specific for describing an embodiment and should not be interpreted as being limited thereto, and various indexes and positions and sizes of the coding unit may be used. It must be interpreted.

According to an embodiment, the video decoding apparatus 100 may use a predetermined data unit in which recursive division of a coding unit starts.

22 illustrates that a plurality of coding units are determined according to a plurality of predetermined data units included in a picture, according to an embodiment.

According to an embodiment, a predetermined data unit may be defined as a data unit in which a coding unit starts to be recursively split using at least one of block type information and split type information. That is, it may correspond to a coding unit of a highest depth used in a process in which a plurality of coding units for splitting a current picture are determined. Hereinafter, for convenience of description, such a predetermined data unit is referred to as a reference data unit.

According to an embodiment, the reference data unit may represent a predetermined size and shape. According to an embodiment, the reference coding unit may include MxN samples. Here, M and N may be identical to each other, and may be integers expressed as a multiplier of 2. That is, the reference data unit may represent a square or non-square shape, and may be divided into an integer number of coding units thereafter.

According to an embodiment, the video decoding apparatus 100 may divide a current picture into a plurality of reference data units. According to an embodiment, the video decoding apparatus 100 may divide a plurality of reference data units for dividing a current picture using split information for each reference data unit. The partitioning process of the reference data unit may correspond to the partitioning process using a quad-tree structure.

According to an embodiment, the video decoding apparatus 100 may determine in advance a minimum size that a reference data unit included in a current picture can have. Accordingly, the video decoding apparatus 100 may determine a reference data unit of various sizes having a size equal to or greater than the minimum size, and determine at least one coding unit using block type information and split type information based on the determined reference data unit. You can decide.

Referring to FIG. 22, the video decoding apparatus 100 may use a reference coding unit 2200 having a square shape or a non-square reference coding unit 2202. According to an embodiment, the shape and size of a reference coding unit is various data units that may include at least one reference coding unit (e.g., a sequence, a picture, a slice, and a slice segment ( slice segment), maximum coding unit, etc.).

According to an embodiment, the acquirer 105 of the video decoding apparatus 100 may obtain at least one of information on a shape of a reference coding unit and information on a size of a reference coding unit from the bitstream for each of the various data units. have. The process of determining at least one coding unit included in the square-shaped reference coding unit 2200 has been described above through the process of dividing the current coding unit 300 of FIG. 10, and the non-square-shaped reference coding unit 2200 The process of determining at least one coding unit included in) has been described above through a process in which the current coding unit 1100 or 1150 of FIG. 11 is split, so a detailed description thereof will be omitted.

According to an embodiment, the video decoding apparatus 100 determines the size and shape of a reference coding unit according to some data units that are predetermined based on a predetermined condition, and an index for identifying the size and shape of the reference coding unit You can use That is, the acquisition unit 105 is a data unit having a size less than or equal to a slice among the various data units (eg, sequence, picture, slice, slice segment, maximum coding unit, etc.) from the bitstream. As a data unit satisfying ), only an index for identifying the size and shape of the reference coding unit may be obtained for each slice, slice segment, and maximum coding unit. The video decoding apparatus 100 may determine the size and shape of the reference data unit for each data unit that satisfies the predetermined condition by using the index. When information about the shape of the reference coding unit and information about the size of the reference coding unit are obtained from a bitstream for each relatively small data unit, the use efficiency of the bitstream may not be good, so the type of the reference coding unit Instead of directly obtaining information on and information on the size of the reference coding unit, only the index may be obtained and used. In this case, at least one of the size and shape of the reference coding unit corresponding to the index indicating the size and shape of the reference coding unit may be predetermined. That is, the video decoding apparatus 100 selects at least one of the size and shape of the predetermined reference coding unit according to the index, so that at least one of the size and shape of the reference coding unit included in the data unit that is the reference for obtaining the index is selected. You can decide.

According to an embodiment, the video decoding apparatus 100 may use at least one reference coding unit included in one largest coding unit. That is, at least one reference coding unit may be included in the largest coding unit for dividing an image, and a coding unit may be determined through a recursive splitting process of each reference coding unit. According to an embodiment, at least one of the width and height of the largest coding unit may correspond to an integer multiple of at least one of the width and height of the reference coding unit. According to an embodiment, the size of the reference coding unit may be a size obtained by dividing a maximum coding unit n times according to a quad tree structure. That is, the video decoding apparatus 100 may determine the reference coding unit by dividing the maximum coding unit n times according to the quad tree structure, and according to various embodiments, the reference coding unit is at least one of block type information and split type information. Can be divided based on

23 illustrates a processing block that serves as a reference for determining an order of determining reference coding units included in the picture 2300 according to an embodiment.

According to an embodiment, the video decoding apparatus 100 may determine at least one processing block for dividing a picture. A processing block is a data unit including at least one reference coding unit that divides an image, and at least one reference coding unit included in the processing block may be determined in a specific order. That is, the order of determination of at least one reference coding unit determined in each processing block may correspond to one of a variety of order types in which the reference coding unit may be determined, and the order of determination of the reference coding unit determined in each processing block May be different for each processing block. The order of determination of the reference coding units determined for each processing block is raster scan, Z-scan, N-scan, up-right diagonal scan, and horizontal scan ( Horizontal scan) and vertical scan may be one of various orders, but the order that can be determined is limited to the scan orders and should not be interpreted.

According to an embodiment, the video decoding apparatus 100 may determine the size of at least one processing block included in the image by obtaining information on the size of the processing block. The video decoding apparatus 100 may determine the size of at least one processing block included in the image by obtaining information on the size of the processing block from the bitstream. The size of the processing block may be a predetermined size of a data unit indicated by information about the size of the processing block.

According to an embodiment, the acquisition unit 105 of the video decoding apparatus 100 may acquire information on the size of a processing block from a bitstream for each specific data unit. For example, information on the size of a processing block may be obtained from a bitstream in data units such as an image, a sequence, a picture, a slice, and a slice segment. That is, the acquisition unit 105 may obtain information on the size of the processing block from the bitstream for each of the several data units, and the video decoding apparatus 100 divides a picture using the information on the size of the obtained processing block. The size of at least one processing block may be determined, and the size of such a processing block may be an integer multiple of the reference coding unit.

According to an embodiment, the video decoding apparatus 100 may determine the sizes of the processing blocks 2302 and 2312 included in the picture 2300. For example, the video decoding apparatus 100 may determine the size of the processing block based on information on the size of the processing block obtained from the bitstream. Referring to FIG. 23, according to an embodiment, the video decoding apparatus 100 sets the horizontal size of the processing blocks 2302 and 2312 to 4 times the horizontal size of the reference coding unit and the vertical size to 4 times the vertical size of the reference coding unit. You can decide. The video decoding apparatus 100 may determine an order in which at least one reference coding unit is determined in at least one processing block.

According to an embodiment, the video decoding apparatus 100 may determine each of the processing blocks 2302 and 2312 included in the picture 2300 based on the size of the processing block, and are included in the processing blocks 2302 and 2312. It is possible to determine an order of determining at least one of the reference coding units. According to an embodiment, determining the reference coding unit may include determining the size of the reference coding unit.

According to an embodiment, the video decoding apparatus 100 may obtain information on a decision order of at least one reference coding unit included in at least one processing block from a bitstream, and based on the obtained decision order information Thus, an order in which at least one reference coding unit is determined may be determined. The information on the order of determination may be defined as an order or direction in which reference coding units are determined in a processing block. That is, the order in which the reference coding units are determined may be independently determined for each processing block.

According to an embodiment, the video decoding apparatus 100 may obtain information about a determination order of a reference coding unit for each specific data unit from a bitstream. For example, the acquirer 105 may obtain information on the determination order of the reference coding unit from the bitstream for each data unit such as an image, a sequence, a picture, a slice, a slice segment, and a processing block. Since the information on the determination order of the reference coding unit indicates the determination order of the reference coding unit within the processing block, the information on the determination order may be obtained for each specific data unit including an integer number of processing blocks.

The video decoding apparatus 100 may determine at least one reference coding unit based on an order determined according to an embodiment.

According to an embodiment, the acquisition unit 105 is information related to the processing blocks 2302 and 2312 from a bitstream, and may obtain information on an order of determining a reference coding unit, and the video decoding apparatus 100 An order of determining at least one reference coding unit included in 2302 and 2312 may be determined, and at least one reference coding unit included in the picture 2300 may be determined according to the determining order of the coding units. Referring to FIG. 23, the video decoding apparatus 100 may determine a determination order 2304 and 2314 of at least one reference coding unit related to each of the processing blocks 2302 and 2312. For example, when information about a determination order of a reference coding unit is obtained for each processing block, the order of determining a reference coding unit related to each of the processing blocks 2302 and 2312 may be different for each processing block. When the reference coding unit determination order 2304 related to the processing block 2302 is a raster scan order, the reference coding units included in the processing block 2302 may be determined according to the raster scan order. On the other hand, when a reference coding unit determination order 2314 related to another processing block 2312 is in the reverse order of the raster scan order, the reference coding units included in the processing block 2312 may be determined according to the reverse order of the raster scan order.

The video decoding apparatus 100 may decode at least one determined reference coding unit according to an embodiment. The video decoding apparatus 100 may decode an image based on the reference coding unit determined through the above-described embodiment. The method of decoding the reference coding unit may include various methods of decoding the image.

According to an embodiment, the video decoding apparatus 100 may obtain and use block type information indicating a type of a current coding unit or split type information indicating a method of dividing a current coding unit from a bitstream. Block type information or split type information may be included in a bitstream related to various data units. For example, the video decoding apparatus 100 includes a sequence parameter set, a picture parameter set, a video parameter set, a slice header, and a slice segment header. Segment header) may use block type information or segmentation type information. Furthermore, the video decoding apparatus 100 may obtain and use a syntax corresponding to block type information or split type information from a bitstream for each maximum coding unit, reference coding unit, and processing block.

So far, we have looked at the center of various embodiments. Those of ordinary skill in the art to which the present disclosure pertains will appreciate that the present disclosure may be implemented in a modified form without departing from the essential characteristics of the present disclosure. Therefore, the disclosed embodiments should be considered from an illustrative point of view rather than a limiting point of view. The scope of the present disclosure is shown in the claims rather than the foregoing description, and all differences within the scope equivalent thereto should be construed as being included in the present disclosure.

Meanwhile, the above-described embodiments of the present disclosure can be written as a program that can be executed on a computer, and can be implemented in a general-purpose digital computer that operates the program using a computer-readable recording medium. The computer-readable recording medium includes a storage medium such as a magnetic storage medium (eg, ROM, floppy disk, hard disk, etc.), and an optical reading medium (eg, CD-ROM, DVD, etc.).

Claims (15)

Determining a scan area including all effective transform coefficients in the current block;
Scanning information on transform coefficients in the scan area according to a predetermined scan order;
Generating binary arithmetic-decoded information by performing binary arithmetic decoding based on the information on the scanned transform coefficients;
Obtaining information on transform coefficients of the current block by performing inverse binarization on the binary arithmetic-decoded information;
Generating a residual block of the current block by performing inverse quantization and inverse transformation based on information on the transform coefficients of the current block; And
Including the step of restoring the current block based on the generated residual block,
The video decoding method, wherein the binary arithmetic decoding is performed by using a context model determined based on at least one of a size and a shape of the current block. The method of claim 1,
All effective transform coefficients in the current block are included in the rectangular scan area,
The video decoding method according to claim 1, wherein the remaining areas in the current block excluding the rectangular scan area include only 0, not an effective transform coefficient. The method of claim 1,
The scan area is a rectangular scan area,
The step of determining the scan area
Obtaining information about coordinates specifying the rectangular scan area from a bitstream; And
Determining a rectangular scan area of a transform coefficient in a current block based on information on coordinates specifying the rectangular scan area,
The horizontal coordinates specifying the rectangular scan area represent coordinates of an effective transform coefficient pixel located at the rightmost position in the current block,
The vertical coordinates specifying the rectangular scan area represent coordinates of an effective transform coefficient pixel located at the bottom of the current block,
Flag information indicating whether information on coordinates specifying the rectangular scan area includes a difference between coordinate values in a horizontal direction and a vertical direction specifying the rectangular scan area is included in the bitstream,
Information on coordinates specifying the rectangular scan area is
When it is indicated that the flag information includes a difference between coordinate values in a horizontal direction and a vertical direction specifying the rectangular scan area,
Information indicating coordinates in one direction among horizontal coordinates for a pixel of an effective transform coefficient positioned at the rightmost side in the current block and vertical coordinates for a pixel of an effective transform coefficient positioned at the bottom of the current block; and And information indicating a difference between the coordinates for the one direction and the coordinates for the other direction. The method of claim 1,
The size of the current block is determined based on at least one of a minimum value and a maximum value of the height and width of the current block,
The shape of the current block is determined based on whether the height and width of the current block are the same, the height is greater than the width, or the width is greater than the height. The method of claim 1,
Determining a scan area including all transform coefficients in the current block,
If the height and width of the current block are different from each other, generating a swapped current block by swapping horizontal and vertical coordinates representing positions of transform coefficients in the current block; And
And determining a scan area including all effective transform coefficients in the swapped current block,
The step of determining a scan area including all effective transform coefficients in the swapped current block,
When the height and width of the current block are different from each other, horizontal coordinates and vertical coordinates specifying the scan area are changed (swap), and based on the swapped horizontal coordinates and vertical coordinates, the And determining a scan area. The method of claim 5,
The bitstream includes information indicating whether flag information indicating whether a difference between coordinate values in a horizontal direction and a vertical direction specifying a scan area is included, and information about coordinates specifying the scan area,
The information on coordinates specifying the scan area includes information on horizontal coordinates and information on vertical coordinates specifying the scan area,
When it is indicated that the flag information includes a difference between coordinate values in a horizontal direction and a vertical direction specifying the rectangular scan area,
The information on the horizontal coordinates specifying the scan area and the information on the vertical coordinates are information indicating coordinates related to one of the horizontal coordinates and vertical coordinates, and the coordinates related to the one direction and the other directions. It contains information indicating the difference (difference) between the relative coordinates,
The step of determining a scan area including all effective transform coefficients in the swapped current block,
If the height and width of the current block are different,
Swapping horizontal and vertical coordinates obtained from information about coordinates specifying the scan area, and determining the scan area based on the swapped horizontal and vertical coordinates Video decoding method comprising the step. The method of claim 1,
Among the context models, the context model related to flag information of the current transform coefficient includes the size of the scan area, the number of coefficients scanned before the current transform coefficient according to a predetermined scan order within the scan area, and the scan area. A video, characterized in that it is further determined based on at least one of a relative position of the current transform coefficient within and whether the current effective transform coefficient is the first transform coefficient among transform coefficients scanned according to the predetermined scan order in the scan area Decryption method. The method of claim 7,
When the context model for the flag information of the current transform coefficient is determined based on the size of the scan area and the number of flag information of the transform coefficient scanned before the current coefficient according to the predetermined scan order,
Context model regarding flag information of the current transform coefficient based on a predetermined context offset corresponding to a case where the number of flag information of the transform coefficient scanned before the current coefficient is smaller than a predetermined value based on the size of the scan area A video decoding method, characterized in that is determined. The method of claim 7,
When the context model for the flag information of the current transform coefficient is determined based on the relative position of the current transform coefficient in the scan area,
A video, characterized in that the context model for the current transform coefficient is determined based on a predetermined context offset corresponding to a case in which the coordinates of the current transform coefficient are smaller than a predetermined value based on a coordinate specifying the position of the scan area. Decryption method. The method of claim 1,
Information about the transformation coefficient,
Flag information indicating whether the transform coefficient is greater than a predetermined value, remaining level information regarding the absolute value of the effective transform coefficient, code information of the transform coefficient, and binarization used for inverse binarization of the transform coefficient It includes at least one of parameter information,
The video decoding method, wherein the predetermined value is at least one of 0, 1, and 2. Obtaining a transform coefficient of the current block;
Determining a scan area including all effective transform coefficients in the current block;
Scanning information about transform coefficients included in the scan area according to a predetermined scan order and performing binarization based on the information about the scanned transform coefficients to generate binarized information;
Generating entropy-encoded information by performing binary arithmetic encoding on the binarized information; And
And generating a bitstream including the entropy-encoded information,
The video encoding method, wherein the binary arithmetic encoding is performed using a context model determined based on at least one of a size and a shape of the current block. The method of claim 9,
The scan area is a rectangular scan area,
The horizontal coordinates specifying the rectangular scan area represent coordinates of an effective transform coefficient pixel located at the rightmost position in the current block,
The vertical coordinates specifying the rectangular scan area represent coordinates of an effective transform coefficient pixel located at the bottom of the current block,
The flag information indicating whether the information on coordinates specifying the rectangular scan area and the coordinates specifying the rectangular scan area includes a difference between coordinate values in the horizontal direction and the vertical direction specifying the rectangular scan area is the bit Is included in the stream,
When it is indicated that the flag information includes a difference between coordinate values in a horizontal direction and a vertical direction specifying the rectangular scan area,
The information on the coordinates specifying the rectangular scan area is a horizontal coordinate for a pixel of an effective transform coefficient positioned at the rightmost position in the current block and a vertical direction for a pixel of an effective transform coefficient positioned at the bottom of the current block. And information indicating a coordinate in one direction among the coordinates and information indicating a difference between the coordinates in the one direction and the coordinates in the other direction. Determine a scan area including all effective transform coefficients in the current block, scan information on the transform coefficients in the scan area according to a predetermined scan order, and perform binary arithmetic decoding based on the information on the scanned transform coefficients An entropy decoder for generating binary arithmetic-decoded information by performing, and obtaining information on transform coefficients of the current block by performing inverse binarization on the binary arithmetic-decoded information; And
Inverse quantization and inverse transformation are performed based on information on the transform coefficients of the current block to generate a residual block of the current block, and an image restoration unit reconstructing the current block based on the generated residual block,
The video decoding apparatus, wherein the binary arithmetic decoding is performed using a context model determined based on at least one of a size and a shape of the current block. Obtaining transform coefficients of the current block, determining a scan area including all effective transform coefficients in the current block, scanning information on transform coefficients included in the scan area according to a predetermined scan order, and scanning the scanned area An entropy encoder for generating binarized information by performing binarization on the basis of information on transform coefficients, and generating entropy-encoded information by performing binary arithmetic coding on the binarized information; And
A bitstream generator for generating a bitstream including the entropy-encoded information,
The video encoding apparatus, wherein the binary arithmetic encoding is performed using a context model determined based on at least one of a size and a shape of the current block. A computer-readable recording medium on which a program for implementing the video decoding method of claim 1 is recorded.

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