KR102349435B1 - The method of encoding and decoding of quantization matrix and the apparatus for using the same - Google Patents

Abstract

The present invention relates to a method for encoding and decoding a quantization matrix and an apparatus using the same, and the method for decoding a quantization matrix according to the present invention includes decoding information on whether a quantization matrix is used and information on whether or not there is a quantization matrix. Decoding information related to a prediction method of , decoding a quantization matrix identifier for prediction between quantization matrices and using a base matrix, predicting and decoding coefficients in a quantization matrix, and restoring a quantization matrix. .

Description

The method of encoding and decoding of quantization matrix and the apparatus for using the same

The present invention relates to image encoding and decoding technology, and more particularly, to a method and apparatus for encoding/decoding a quantization matrix.

Recently, a broadcasting service having a high definition (HD) resolution is expanding not only in Korea but also worldwide. Accordingly, many users are accustomed to high-resolution and high-definition images, and many organizations are spurring the development of next-generation imaging devices.

Along with HDTV, as interest in Ultra High Definition (UHD) having a resolution four times higher than that of HDTV increases, a compression technology for higher resolution and high-definition images is required.

For image compression, pixel information of a current picture may be encoded by prediction. For example, an inter prediction technique that predicts a pixel value included in the current picture from temporally previous and/or later pictures, an intra prediction technique that predicts a pixel value included in the current picture using pixel information in the current picture ) prediction techniques can be applied.

In addition, by applying an entropy encoding technique in which a short code is assigned to a symbol having a high frequency of occurrence and a long code is assigned to a symbol having a low frequency of occurrence, it is possible to increase the encoding efficiency and reduce the amount of transmitted information.

In this case, there is a problem in how to more effectively quantize the transform coefficients for the residual block generated by prediction.

The present invention provides a quantization matrix prediction encoding/decoding method and apparatus for performing quantization matrix prediction from a quantization matrix having the same size as the quantization matrix during encoding/decoding in order to improve encoding efficiency and increase the degree of freedom in prediction of a quantization matrix.

An embodiment of the present invention includes the steps of decoding the use and presence or absence of a quantization matrix, decoding quantization matrix prediction method information, decoding a quantization matrix identifier for prediction between quantization matrices and using a base matrix, coefficients in a quantization matrix Predictive decoding of , and restoring a quantization matrix, wherein the decoding of the quantization matrix identifier for prediction between quantization matrices and the use of the base matrix includes the quantization matrix prediction from the quantization matrix equal to the size of the quantization matrix at the time of decoding. A quantization matrix prediction decoding method and apparatus characterized in that it performs.

According to the present invention, it is possible to improve encoding efficiency and increase the degree of freedom in quantization matrix prediction by providing a quantization matrix prediction encoding/decoding method and apparatus for performing prediction of a quantization matrix from a quantization matrix having the same size as the quantization matrix at the time of encoding/decoding.

1 is a block diagram illustrating a configuration of an image encoding apparatus to which the present invention is applied according to an embodiment.
2 is a block diagram illustrating a configuration of an image decoding apparatus to which the present invention is applied according to an embodiment.
3 is a conceptual diagram schematically illustrating an embodiment in which one unit is divided into a plurality of sub-units.
4 is a conceptual diagram illustrating an encoding operation according to an embodiment of the present invention.
5 is a conceptual diagram illustrating a conventional quantization matrix prediction encoding/decoding method.
6 illustrates a method of performing quantization matrix prediction from a quantization matrix having the same size as the quantization matrix during encoding/decoding according to an embodiment of the present invention.
7 is a flowchart illustrating a decoding method according to an embodiment of the present invention.
8 is a conceptual diagram illustrating upsampling of a quantization matrix according to an embodiment of the present invention.
9 is a conceptual diagram illustrating a method of generating a quantization matrix used for a non-square transform coefficient block according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In describing the embodiments of the present specification, if it is determined that a detailed description of a related known configuration or function may obscure the gist of the present specification, the corresponding description may be omitted.

In this specification, when a component is referred to as being “connected” or “connected” to another component, it may mean that it is directly connected or connected to the other component, or another component in the middle. It can also mean that the element is present. In addition, the description of “including” a specific configuration in the present specification does not exclude configurations other than the corresponding configuration, and it means that additional configurations may be included in the practice of the present invention or the scope of the technical spirit of the present invention.

Terms such as first, second, etc. may be used to describe various components, but the components are not limited by the terms. The terms are used for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, a first configuration may be named as a second configuration, and similarly, a second configuration may also be called a first configuration.

In addition, the components shown in the embodiment of the present invention are shown independently to represent different characteristic functions, and it does not mean that each component is formed of separate hardware or a single software component. That is, each component is listed as each component for convenience of description, and at least two components among each component may form one component, or one component may be divided into a plurality of components to perform a function. Integrated embodiments and separate embodiments of each component are also included in the scope of the present invention without departing from the essence of the present invention.

In addition, some of the components are not essential components for performing essential functions in the present invention, but may be optional components for merely improving performance. The present invention can be implemented by including only essential components to implement the essence of the present invention, except for components used for performance improvement, and a structure including only essential components excluding optional components used for performance improvement Also included in the scope of the present invention.

First, for convenience of description and understanding of the invention, terms used herein will be briefly described.

A unit means a unit of video encoding and decoding. In other words, in image encoding/decoding, a coding unit or a decoding unit refers to a divided unit when an image is divided into subdivided units for encoding or decoding. A block, a macro block, a coding unit or a prediction unit or a transform unit or a coding block or a prediction block or a transform block, etc. can be called as One unit may be divided into smaller sub-units.

A transform unit is a basic unit or unit unit in performing encoding/decoding of a residual block such as transform, inverse transform, quantization, inverse quantization, and transform coefficient encoding/decoding, and one transform unit is divided It can be divided into a number of small transformation units in size. In addition, it can be used in the same meaning as the transform block, and a form in which a syntax element related to a transform block for luminance and chrominance signals is included may be referred to as a transform unit.

A quantization matrix refers to a matrix used in a quantization or inverse quantization process to improve subjective or objective image quality of an image. The quantization matrix is also called a scaling list.

A quantization matrix used for quantization/dequantization may be transmitted as a bitstream, or a default matrix already possessed by the encoder and/or decoder may be used. The transmitted quantization matrix information may be transmitted collectively for each size of a quantization matrix or a transform block size to which the quantization matrix is applied through a sequence parameter set (SPS) or a picture parameter set (PPS). For example, 4x4 quantization matrices for a 4x4 transform block may be transmitted, 8x8 matrices for an 8x8 transform block may be transmitted, 16x16 matrices may be transmitted for a 16x16 transform block, and 32x32 matrices may be transmitted for a 32x32 transform block. .

The quantization matrix applied to the current block may (1) be obtained by copying a quantization matrix of the same size, or (2) may be generated by prediction from a previous matrix coefficient in the quantization matrix. The matrix of the same size may be a quantization matrix previously encoded, decoded, or used, may be a reference quantization matrix, or may be a basic quantization matrix. Alternatively, it may be selectively determined from a combination including at least two of a quantization matrix, a reference quantization matrix, and a basic quantization matrix previously encoded or decoded or used.

A parameter set corresponds to header information in a structure in a bitstream, and has the meaning of collectively calling a sequence parameter set, a picture parameter set, an adaptation parameter set, and the like.

A quantization parameter is a value used in quantization and inverse quantization, and the quantization parameter may be a value mapped to a quantization step size.

The default matrix may mean a predetermined quantization matrix predefined in the encoder and/or decoder, and the default quantization matrix to be described later in this specification may be used in the same meaning as the default matrix. A non-default matrix may mean a quantization matrix that is not predefined in the encoder and/or decoder, and is transmitted from the encoder to the decoder, that is, transmitted/received by the user, which will be described later in this specification. A non-basic quantization matrix to be used may be used in the same sense as a non-basic matrix.

1 is a block diagram illustrating a configuration of an image encoding apparatus to which the present invention is applied according to an embodiment.

Referring to FIG. 1 , the image encoding apparatus 100 includes a motion prediction unit 111 , a motion compensation unit 112 , an intra prediction unit 120 , a switch 115 , a subtractor 125 , and a transform unit 130 . , a quantizer 140 , an entropy encoder 150 , an inverse quantizer 160 , an inverse transform unit 170 , an adder 175 , a filter unit 180 , and a reference image buffer 190 .

The image encoding apparatus 100 may encode an input image in an intra mode or an inter mode and output a bitstream. Intra prediction refers to intra prediction, and inter prediction refers to inter prediction. In the intra mode, the switch 115 may be switched to the intra mode, and in the inter mode, the switch 115 may be switched to the inter mode. The image encoding apparatus 100 may generate a prediction block for an input block of an input image, and then encode a difference between the input block and the prediction block. In this case, the input image may mean an original picture.

In the intra mode, the intra prediction unit 120 may generate a prediction block by performing spatial prediction using pixel values of an already coded block around the current block.

In the inter mode, the motion prediction unit 111 may obtain a motion vector by finding a region that best matches the input block in the reference image stored in the reference image buffer 190 during the motion prediction process. The motion compensator 112 may generate a prediction block by performing motion compensation using a motion vector. Here, the motion vector is a two-dimensional vector used for inter prediction, and may indicate an offset between the current block and a block in the reference image.

The subtractor 125 may generate a residual block by the difference between the input block and the generated prediction block. The transform unit 130 may perform transform on the residual block to output a transform coefficient. In addition, the quantization unit 140 may quantize the input transform coefficient using at least one of a quantization parameter and a quantization matrix to output a quantized coefficient. In this case, the quantization matrix may be input to the encoder, and the input quantization matrix may be determined to be used in the encoder.

The entropy encoding unit 150 may output a bit stream by performing entropy encoding based on the values calculated by the quantization unit 140 or encoding parameter values calculated during the encoding process. When entropy encoding is applied, a small number of bits are allocated to a symbol having a high probability of occurrence and a large number of bits are allocated to a symbol having a low probability of occurrence to express the symbol, so that bits for symbols to be encoded The size of the column may be reduced. Accordingly, compression performance of image encoding may be improved through entropy encoding. The entropy encoder 150 may use an encoding method such as an exponential-Golomb code, a context-adaptive variable length coding (CAVLC), or a context-adaptive binary arithmetic coding (CABAC) for entropy encoding.

Since the image encoding apparatus according to the embodiment of FIG. 1 performs inter prediction encoding, that is, inter prediction encoding, the currently encoded image needs to be decoded and stored to be used as a reference image. Accordingly, the quantized coefficients are inverse quantized by the inverse quantization unit 160 and inversely transformed by the inverse transformation unit 170 . The inverse-quantized and inverse-transformed coefficients become a reconstructed residual block and are added to the prediction block through the adder 175 to generate a reconstructed block.

The reconstructed block passes through the filter unit 180, and the filter unit 180 applies at least one of a deblocking filter, a sample adaptive offset (SAO), and an adaptive loop filter (ALF) to the reconstructed block or the reconstructed picture. can do. The filter unit 180 may be referred to as an in-loop filter. The deblocking filter can remove block distortion caused at the boundary between blocks. The SAO may add an appropriate offset value to a pixel value to compensate for a coding error. The ALF may perform filtering based on a value obtained by comparing the reconstructed image and the original image. The reconstructed block passing through the filter unit 180 may be stored in the reference image buffer 190 .

2 is a block diagram illustrating a configuration of an image decoding apparatus to which the present invention is applied according to an embodiment.

2, the image decoding apparatus 200 includes an entropy decoding unit 210, an inverse quantization unit 220, an inverse transform unit 230, an intra prediction unit 240, a motion compensator 250, an adder ( 255), a filter unit 260 and a reference image buffer 270 .

The image decoding apparatus 200 may receive a bitstream output from the encoder, perform decoding in an intra mode or an inter mode, and output a reconstructed image, that is, a reconstructed image. In the case of the intra mode, the switch may be switched to the intra mode, and in the case of the inter mode, the switch may be switched to the inter mode. The image decoding apparatus 200 obtains a reconstructed residual block from the received bitstream, generates a prediction block, and then adds the reconstructed residual block and the prediction block to generate a reconstructed block, that is, a reconstructed block. .

The entropy decoding unit 210 may entropy-decode the input bitstream according to a probability distribution to generate symbols including symbols in the form of quantized coefficients. The entropy decoding method is similar to the entropy encoding method described above.

When the entropy decoding method is applied, a small number of bits are allocated to a symbol having a high occurrence probability and a large number of bits are allocated to a symbol having a low occurrence probability to represent the symbol, so that the size of the bit stream for each symbol is can be reduced.

The quantized coefficient is inverse quantized using the quantization parameter in the inverse quantization unit 220 and inverse transformed in the inverse transformation unit 230. As a result of inverse quantization/inverse transformation of the quantized coefficient, a reconstructed residual block may be generated.

A quantization matrix used for inverse quantization is also called a scaling list. The inverse quantizer 220 may generate an inverse quantized coefficient by applying a quantization matrix to the quantized coefficient.

In this case, the inverse quantization unit 220 may perform inverse quantization in response to the quantization applied by the encoder. For example, the inverse quantization unit 220 may perform inverse quantization by inversely applying the quantization matrix applied by the encoder to the quantized coefficients.

The quantization matrix used for inverse quantization in the image decoding apparatus 200 may be received from a bitstream, or a default matrix already possessed by the encoder and/or decoder may be used. The transmitted quantization matrix information may be collectively received for each size of a quantization matrix or a size of a transform block to which the quantization matrix is applied through a sequence parameter set or a picture parameter set. For example, 4x4 quantization matrices for a 4x4 transform block may be received, 8x8 matrices for an 8x8 transform block may be received, 16x16 matrices for a 16x16 transform block may be received, and 32x32 matrices may be received for a 32x32 transform block.

In the intra mode, the intra prediction unit 240 may generate a prediction block by performing spatial prediction using pixel values of an already decoded block around the current block. In the inter mode, the motion compensator 250 may generate a prediction block by performing motion compensation using a motion vector and a reference image stored in the reference image buffer 270 .

The reconstructed residual block and the prediction block may be added through the adder 255 , and the added block may pass through the filter unit 260 . The filter unit 260 may apply at least one of a deblocking filter, SAO, and ALF to a reconstructed block or a reconstructed picture. The filter unit 260 may output a reconstructed image, that is, a reconstructed image. The reconstructed image may be stored in the reference image buffer 270 and used for inter prediction.

Meanwhile, the block division information may include information about the depth of the unit. The depth information may indicate the number and/or degree to which a unit is divided.

3 is a conceptual diagram schematically illustrating an embodiment in which one unit is divided into a plurality of sub-units.

One unit or block may be hierarchically divided with depth information based on a tree structure. Each divided sub-unit may have depth information. Since the depth information indicates the number and/or degree of division of the unit, it may include information on the size of the sub-unit.

Referring to 310 of FIG. 3 , the highest node may be referred to as a root node and may have the smallest depth value. In this case, the highest node may have a depth of level 0, and may represent an undivided first unit.

A lower node having a depth of level 1 may indicate a unit in which the initial unit is divided once, and a lower node having a depth of level 2 may indicate a unit in which the initial unit is divided twice. For example, unit a corresponding to node a in 320 of FIG. 3 is a unit divided once from the initial unit, and may have a depth of level 1.

A leaf node of level 3 may indicate a unit in which the initial unit is divided three times. For example, in 320 of FIG. 3 , a unit d corresponding to a node d is a unit divided three times in the initial unit, and may have a depth of level 3 . Accordingly, the leaf node of level 3, which is the lowest node, may have the deepest depth.

A quantization matrix may be used to improve the subjective or objective image quality of an image. The encoder may use the quantization matrix when quantizing the transform coefficients using different values for each spatial frequency in the quantization process. The decoder may use a quantization matrix when dequantizing transform coefficients by using different values for each spatial frequency in the dequantization process.

In the quantization and dequantization process, a default matrix predefined in the encoder and the decoder may be used as the quantization matrix. As another method, a quantization matrix individually defined by the encoder and the decoder may be used. In this case, the quantization matrix defined by the user may be referred to as a non-default matrix. The encoder may encode the non-basic matrix into a bitstream and transmit it to the decoder.

The conventional quantization matrix prediction encoding/decoding method and apparatus performed quantization matrix copying based on the size of the quantization matrix during quantization and dequantization, rather than the size of the quantization matrix during encoding/decoding. Accordingly, since the quantization matrix is copied from a limited number of quantization matrices, there is a limit to improving encoding efficiency when encoding/decoding a quantization matrix.

Hereinafter, in order to solve this problem, a method of predicting a quantization matrix based on a quantization matrix equal to the size of the quantization matrix during encoding/decoding is disclosed.

4 is a conceptual diagram illustrating an encoding operation according to an embodiment of the present invention.

Referring to FIG. 4 , a quantization matrix is determined (step S400 ).

In the step of determining the quantization matrix, a quantization matrix to be used for each transform coefficient block in the quantization process may be determined. A quantization matrix required for a quantization process may be determined by using a default matrix predefined in the encoder and decoder. Alternatively, a quantization matrix necessary for a quantization process may be determined based on a non-default matrix that is not predefined in the encoder.

The quantization matrix may be determined by various variables. For example, the quantization matrix may include a prediction mode (such as an intra prediction mode or an inter prediction mode) of a transform coefficient block, a color component (such as a luminance or chrominance), and a block size (4x4, 8x8, 16x16, 32x32, 16x4, 4x16, 32x8, 8x32, etc.).

When the determined quantization matrix is encoded, it may be encoded based on various formats. For example, a quantization matrix to be used for quantization of a transform coefficient block corresponding to 16x16 and 32x32 sizes may be a quantization matrix of 16x16 and 32x32 sizes during quantization. The 16x16 and 32x32 quantization matrices can be encoded and expressed as an 8x8 quantization matrix during encoding. More specifically, quantization is performed based on a quantization matrix having a size of 16x16 or 32x32, and when encoding is performed on the quantization matrix, the encoder performs subsampling or downsampling based on a 16x16 method. Alternatively, a quantization matrix having a size of 32x32 may be encoded as a quantization matrix having a size of 8x8.

As another method, a quantization matrix of a large size may be generated based on a quantization matrix of a small size. For example, the encoder may generate a quantization matrix of a size of 16x16 or 32x32 by using upsampling or interpolation, etc. based on a quantization matrix of size 8x8 in the encoder, and may be used for quantization. During encoding, an 8x8 quantization matrix may be encoded.

Table 1 shows an example of a set quantization matrix.

<Table 1>

Referring to Table 1, different matrices may be used according to the prediction method (whether intra prediction or inter prediction), the type of pixel included in the block, and the size of the block.

Table 1 is an example, and quantization matrices used by various methods may be determined.

Information on whether or not a quantization matrix is used and whether a quantization matrix exists is encoded (step S410).

Information indicating the use and existence of the quantization matrix may be encoded in a parameter set. The parameter set may be, for example, a sequence parameter set or a picture parameter set.

Table 2 below shows information on whether a quantization matrix included in a sequence parameter set and a picture parameter set is used and whether a quantization matrix exists.

<Table 2>

In Table 2, scaling_list_enable_flag is information indicating whether a quantization matrix is used, and sps_scaling_list_data_present_flag is information indicating whether a quantization matrix is present in a sequence parameter. pps_scaling_list_data_present_flag is information indicating whether a quantization matrix exists in a picture parameter.

As in the example of the syntax element in Table 2, scaling_list_enable_flag, which is information indicating whether a quantization matrix is used or not, can be coded into a sequence parameter set. For example, when scaling_list_enable_flag is 0, it may indicate that the quantization matrix is not used in the quantization/dequantization process, and when scaling_list_enable_flag is 1, it may indicate that the quantization matrix is used in the quantization/dequantization process.

In addition, sps_scaling_list_data_present_flag, which is information indicating whether the quantization matrix exists in the sequence parameter, may be coded into the sequence parameter set. For example, when sps_scaling_list_data_present_flag is 0, it may indicate that the quantization matrix does not exist in the sequence parameter, and when sps_scaling_list_data_present_flag is 1, it may indicate that the quantization matrix exists in the sequence parameter.

In addition, pps_scaling_list_data_present_flag, which is information indicating whether the quantization matrix exists in the picture parameter, may be coded into the picture parameter set. When pps_scaling_list_data_present_flag is 0, since the quantization matrix does not exist in the picture parameter set, it may be indicated to refer to the quantization matrix of the sequence parameter set. When pps_scaling_list_data_present_flag is 1, it may indicate that the quantization matrix is present in the picture parameter to replace the quantization matrix in the sequence parameter set.

The parameter disclosed in Table 2 is an example of a parameter for indicating use and presence of a quantization matrix, and other parameters may be used to indicate use and presence of a quantization matrix.

The quantization matrix prediction method information is encoded (step S420).

In order to encode information on a method of predicting a quantization matrix, a type of a prediction encoding method of a quantization matrix may be determined, and the determined prediction encoding method information of the quantization matrix may be encoded in a parameter set. The parameter set may be, for example, a sequence parameter or a picture parameter set.

Table 3 below is a table showing a method of encoding quantization matrix prediction method information.

<Table 3>

The scaling_list_pred_mode_flag disclosed in Table 3 is flag information for a quantization matrix prediction method. scaling_list_pred_size_matrix_id_delta may be a syntax element including identifier information on a reference quantization matrix of a quantization matrix.

Referring to Table 3, scaling_list_pred_mode_flag, which is information on a method of predicting and encoding a quantization matrix, can be coded into a parameter set. When scaling_list_pred_mode_flag is 1, it may indicate a case in which the quantization matrix is scanned for predictive encoding of the coefficients in the quantization matrix and encoded using DPCM (Differential Pulse Code Modulation) and Exponential-Golomb codes. When scaling_list_pred_mode_flag is 0, it may indicate a case in which a reference quantization matrix used for prediction between quantization matrices and a quantization matrix to be coded have the same value or a case in which a default matrix is used as the quantization matrix. Determining that the reference quantization matrix and the quantization matrix to be encoded have the same value may be a quantization matrix prediction method in which a coefficient value of the reference quantization matrix is copied to a quantization matrix coefficient value to be encoded. Scaling_list_pred_size_matrix_id_data will be additionally described below.

sizeID may mean the size of the transform coefficient block or the size of a quantization matrix as shown in Table 4 below, and the matrixID value is a quantization matrix that means a prediction mode and a color component as shown in Table 5 below. It can mean kind.

<Table 4>

<Table 5>

A quantization matrix identifier for inter-quantization matrix prediction and use of a base matrix is encoded (step S430).

5 is a conceptual diagram illustrating a conventional quantization matrix prediction encoding/decoding method.

Referring to FIG. 5 , the quantization matrix copy is performed using the quantization matrix size during quantization and inverse quantization, not the size of the quantization matrix during encoding/decoding.

As in the example of Figure 5, the 8x8 inter-screen color difference Cb quantization matrix (sizeID == 1, matrixID == 5) can be predicted from the 8x8 inter-screen color difference Cr quantization matrix (sizeID == 1, matrixID == 4), but The 32x32 inter-screen luminance Y quantization matrix (sizeID == 3, matrixID == 1) cannot be predicted from the 8x8 intra-screen luminance Y quantization matrix (sizeID == 1, matrixID == 0), and the 16x16 inter-screen chrominance Cr quantization matrix (sizeID == 2, matrixID == 4) cannot be predicted from the color difference Cr quantization matrix (sizeID == 1, matrixID == 1) in the 8x8 screen.

That is, it is impossible to predict between quantization matrices having different sizeIDs that distinguish sizes of quantization matrices during quantization and dequantization. Therefore, the conventional quantization matrix prediction encoding/decoding method and apparatus copy the quantization matrix from a limited number of quantization matrices, so there is a limit in the degree of freedom of copying the quantization matrix, and there is a limit in improving the encoding efficiency when encoding/decoding the quantization matrix.

Hereinafter, a method of performing quantization matrix prediction from a quantization matrix having the same size as the quantization matrix size during encoding in order to solve the problems of the existing quantization matrix prediction encoding method and apparatus is disclosed.

A quantization matrix having a size of 4x4 during encoding has a size of 4x4 even during quantization/inverse quantization, but a quantization matrix having a size of 8x8 during encoding may have a size of 8x8, 16x16, or 32x32 during quantization/inverse quantization. Accordingly, since quantization matrices having a size of 8x8, 16x16, or 32x32 during quantization/dequantization have the same size as 8x8 during encoding, inter-quantization matrix prediction can be performed. That is, when quantization matrices of the same size (8x8) are transmitted during encoding, but quantization matrices of different sizes (8x8, 16x16, or 32x32) are induced during quantization/dequantization, when encoding, between quantization matrices of the same size ( Prediction between quantization matrices of different sizes during encoding (between sizes of 4x4 and size of 8x8 during decoding) may not be allowed while prediction is allowed only between sizes of 8x8 during encoding.

If the prediction encoding method of the quantization matrix is the same as the reference quantization matrix for inter-quantization matrix prediction or the method using the default matrix (scaling_list_pred_mode_flag = 0), scaling_list_pred_size_matrix_id_delta, which is the quantization matrix identifier of the quantization matrix to be encoded, is added to the parameter set. can be coded. The parameter set may be, for example, a sequence parameter set or a picture parameter set.

Referring back to the syntax elements of Table 3 above, when the encoding target quantization matrix coefficient value is determined to be the same as the reference quantization matrix coefficient value or when the encoding target quantization matrix coefficient value is determined to be the same as the basic matrix coefficient value, the encoding target quantization Scaling_list_pred_size_matrix_id_delta, which is a reference quantization matrix identifier of a matrix, can be coded in the parameter set.

In this case, matrixID, which is matrix information of a quantization matrix to be coded, RefMatrixID, which is matrix information of a reference quantization matrix and a base matrix, sizeID, which is size information of a quantization matrix to be coded, RefSizeID, which is size information of a reference quantization matrix and a base matrix, to be quantized matrix to be coded It is possible to determine the quantization matrix identifier, scaling_list_pred_size_matrix_id_delta, by using Size_Matrix_ID, which is the size and matrix information of , and the following equation.

<Equation 1>

In this case, RefMap is a mapping table indicating the relationship between Size_Matrix_ID and RefSizeID and RefMatrixID as in the example of Table 6.

<Table 6>

In this case, although the sizes of the quantization matrices during quantization/dequantization are different, the sizes of the quantization matrices during encoding are the same.

The method using RefMap may be applied to a quantization matrix having a size of 8x8 during encoding, and may not be applied to a quantization matrix having a size of 4x4 during encoding. For a quantization matrix having a size of 4x4 during encoding, scaling_list_pred_size_matrix_id_delta, which is a quantization matrix identifier, may be determined based on Equation 2 below. That is, a method of predicting a quantization matrix may be different according to a size of a quantization matrix during encoding, and a method of determining a quantization matrix identifier may also be different.

<Equation 2>

It is a quantization matrix with a size of 8x8 during encoding, and when the quantization matrix coefficient value to be encoded is determined to be the same as the default matrix coefficient value predetermined in the encoder/decoder, the value of scaling_list_pred_size_matrix_id_delta is encoded as 0, so that the RefMatrixID value and the matrixID value are the same. and make the RefSizeID value and sizeID value the same. In this case, the basic matrix means a basic matrix corresponding to sizeID and matrixID.

When decoding, it is a quantization matrix with a size of 4x4, and when the quantization matrix coefficient value to be encoded is determined to be the same as the default matrix coefficient value predetermined in the encoder/decoder, the scaling_list_pred_size_matrix_id_delta value is encoded as 0, so that the RefMatrixID value and the matrixID value are the same . In this case, the basic matrix means a basic matrix corresponding to sizeID and matrixID.

When encoding, it is a quantization matrix with a size of 8x8, and if the quantization matrix coefficient value to be encoded is determined to be the same as the reference quantization matrix coefficient value, the value of scaling_list_pred_size_matrix_id_delta is encoded as a non-zero value and a reference corresponding to the value of RefMatrixID and RefSizeID Allows to perform inter-matrix prediction from a quantization matrix. When the matrix size is 16x16 or 32x32 during quantization/inverse quantization, DC matrix coefficients may be included. Accordingly, when predicting from a quantization matrix having a matrix size of 16x16 or 32x32 during quantization/inverse quantization, DC matrix coefficients can also be predicted.

When encoding, it is a quantization matrix with a size of 4x4, and if the quantization matrix coefficient value to be encoded is determined to be the same as the reference quantization matrix coefficient value, the scaling_list_pred_size_matrix_id_delta value is encoded as a non-zero value, and inter-matrix prediction from the reference quantization matrix corresponding to the RefMatrixID value can be made to perform

In addition, inter-matrix prediction may not be performed from a quantization matrix having a larger value than Size_Matrix_ID of the quantization matrix to be coded, and the quantization matrix identifier scaling_list_pred_size_matrix_id_delta is a specific value (eg, 0 to 13). can be set to have. When the maximum value of the quantization matrix identifier is specified, encoding efficiency may be improved by using a truncated unary rather than an exponential-Golomb code.

If the quantization matrix copy is performed using the quantization matrix size during quantization and inverse quantization, the quantization matrix identifier of the quantization matrix having a size of 4x4, 8x8, or 16x16 during quantization and inverse quantization has a value between 0 and 5. In the case of quantization and dequantization, the quantization matrix identifier of a quantization matrix having a size of 32x32 may be constrained to have a value between 0 and 1. Since the maximum value of the quantization matrix identifier is limited by size during quantization and inverse quantization, encoding efficiency can be improved by using a truncated unary rather than an Exponential-Golomb code.

6 illustrates a method of performing quantization matrix prediction from a quantization matrix having the same size as the quantization matrix during encoding/decoding according to an embodiment of the present invention.

Referring to FIG. 6 , quantization matrix copying may be performed using the size of the quantization matrix during encoding/decoding.

As in the example of Figure 6, the 8x8 inter-screen color difference Cb quantization matrix (sizeID == 1, matrixID == 5) can be predicted from the 8x8 inter-screen color difference Cr quantization matrix (sizeID == 1, matrixID == 4), A 32x32 inter-screen luminance Y quantization matrix (sizeID == 3, matrixID == 1) can be predicted from an 8x8 intra-screen luminance Y quantization matrix (sizeID == 1, matrixID == 0), and a 16x16 inter-screen chrominance Cr quantization matrix (sizeID == 2, matrixID == 4) can be predicted from the color difference Cr quantization matrix (sizeID == 1, matrixID == 1) in the 8x8 screen.

That is, when the sizeID that distinguishes the size of the quantization matrix during quantization and dequantization is different, but the size of the quantization matrix during encoding/decoding is the same, prediction between quantization matrices is possible.

Therefore, based on a method of performing quantization matrix prediction from a quantization matrix having the same size as the quantization matrix at the time of coding/decoding, it is possible to predict the quantization matrix from the quantization matrix having the same size as the quantization matrix at the time of coding/decoding. It is possible to increase the degree of freedom of prediction.

The coefficients in the quantization matrix are predictively encoded (step S440).

If the predictive encoding method of the quantization matrix is a method of encoding the coefficients in the quantization matrix with scan, DPCM, and exponential-Golomb codes for predictive encoding (scaling_list_pred_mode_flag = 1), the previously encoded quantization matrix coefficient values in the quantization matrix and the encoding target A difference value of a quantization matrix coefficient value may be encoded in a parameter set. The parameter set may be, for example, a sequence parameter set or a picture parameter set.

Table 7 shows a method of encoding DC coefficients in a quantization matrix.

<Table 7>

As in the syntax element example of Table 7, when the size of the quantization matrix to be encoded is 16x16 (sizeID=2) or 32x32 (sizeID=3), the DC matrix coefficient scaling_list_dc_coef_minus8 can be coded into the parameter set. The value of scaling_list_dc_coef_minus8 can be limited to a value between -8 and 247, and can be coded using a Signed Exponental-Golomb code with a value between -8 and 247.

As in the example of the syntax element in Table 7, scaling_list_delta_coef, which is a difference value between a quantization matrix coefficient value previously encoded in a quantization matrix and a quantization matrix coefficient value to be encoded, can be encoded in the parameter set. At this time, scaling_list_delta_coef encodes a total of 16 coefficients, which is the number of coefficients in a 4x4 quantization matrix when encoding a 4x4 quantization matrix, and when encoding a quantization matrix used for a transform coefficient block of 8x8 or larger size, the number of coefficients in the 8x8 quantization matrix A total of 64 phosphors can be encoded.

As a first process, a scan for aligning coefficients in a two-dimensional quantization matrix into a one-dimensional coefficient array may be performed.

As a second process, scaling_list_delta_coef, which is a difference value between a quantization matrix coefficient to be encoded and a quantization matrix coefficient positioned in a previous order in a one-dimensional coefficient array, can be generated by the scan method. In this case, the difference value may be a value calculated using DPCM, and the quantization matrix coefficient located in the previous order may be a coefficient that exists immediately before the quantization matrix coefficient to be encoded. In addition, since the first coefficient in the one-dimensional coefficient array does not have a quantization matrix coefficient positioned in the previous order to be predicted, a difference value can be generated using a predetermined constant value, and when sizeID is greater than 1, A difference value can be generated using the DC matrix coefficients. In this case, the predetermined constant value may be a value between 1 and 255, in particular 8 or 16.

As a third process, scaling_list_delta_coef, which is the calculated difference value, is encoded into an Exponential-Golomb code. In this case, since the difference value has sign information, it may be encoded as a signed Exponental-Golomb code. The value of scaling_list_delta_coef can be limited to a value between -254 and 254, and can be coded as a value between -254 and 254.

7 is a flowchart illustrating a decoding method according to an embodiment of the present invention.

Referring to FIG. 7 , the use and existence of a quantization matrix are decoded (step S700).

In the step of decoding the use and presence of the quantization matrix, information indicating the use and presence of the quantization matrix in the bitstream may be decoded from the parameter set. In this case, the parameter set may be a sequence parameter set or a picture parameter set.

As in the example of the syntax element in Table 2, scaling_list_enable_flag, which is information indicating whether a quantization matrix is used or not, can be decoded from the sequence parameter set. In this case, when scaling_list_enable_flag is 0, the quantization matrix is not used in the inverse quantization process, and when scaling_list_enable_flag is 1, the quantization matrix can be used in the inverse quantization process.

As in the example of the syntax element of Table 2, sps_scaling_list_data_present_flag, which is information indicating whether the quantization matrix exists in the sequence parameter, can be decoded from the sequence parameter set. In this case, when sps_scaling_list_data_present_flag is 0, the quantization matrix does not exist in the sequence parameter, and when sps_scaling_list_data_present_flag is 1, the quantization matrix may exist in the sequence parameter.

As in the example syntax element of Table 2, pps_scaling_list_data_present_flag, which is information indicating whether a quantization matrix exists in a picture parameter, can be decoded from the picture parameter set. At this time, if pps_scaling_list_data_present_flag is 0, the quantization matrix does not exist in the picture parameter set and the quantization matrix of the sequence parameter set is referred to. can be substituted for

The quantization matrix prediction method information is decoded (step S710).

By decoding the prediction decoding method information of the quantization matrix from the parameter set, the type of the prediction decoding method of the quantization matrix may be determined. The parameter set may be, for example, a sequence parameter set or a picture parameter set.

As in the example of the syntax element of Table 3, scaling_list_pred_mode_flag, which is information on the prediction decoding method of the quantization matrix, can be decoded from the parameter set. In this case, if scaling_list_pred_mode_flag is 1, the quantization matrix coefficients can be decoded using an Exponential-Golomb code, Inverse Differential Pulse Code Modulation (DPCM) and scan to predict and decode the coefficients in the quantization matrix. If scaling_list_pred_mode_flag is 0, the quantization matrix coefficient value to be decoded may be determined to have the same value as the reference quantization matrix coefficient value for inter-quantization matrix prediction, or the quantization matrix coefficient value to be decoded may be determined to be the same as the default matrix coefficient value. In this case, determining to have the same value may mean a quantization matrix prediction method of copying a specific quantization matrix coefficient value to a quantization matrix coefficient value to be decoded.

A quantization matrix identifier for inter-quantization matrix prediction and use of a base matrix is decoded (step S720).

In order to solve the problems of the existing quantization matrix prediction decoding method and apparatus, quantization matrix prediction may be performed from a quantization matrix having the same size as the quantization matrix during decoding.

A quantization matrix having a size of 4x4 during decoding has a size of 4x4 even during inverse quantization, but a quantization matrix having a size of 8x8 during decoding may have a size of 8x8, 16x16, or 32x32 during inverse quantization. Accordingly, since quantization matrices having a size of 8x8, 16x16, or 32x32 during inverse quantization have the same 8x8 size during decoding, inter-quantization matrix prediction can be performed. That is, when quantization matrices of the same size (8x8) are decoded, but quantization matrices of different sizes (8x8, 16x16, or 32x32) are derived during quantization/dequantization, between quantization matrices of the same size (8x8 in decoding) Prediction is allowed only between sizes), and prediction between quantization matrices of different sizes (between 4x4 and 8x8 sizes during decoding) may not be allowed during decoding.

If the prediction decoding method of the quantization matrix is a method of determining the same as the reference quantization matrix for prediction between quantization matrices or a method using a default matrix (scaling_list_pred_mode_flag=0), the quantization matrix identifier scaling_list_pred_size_matrix_id_delta of the quantization matrix to be decoded is decoded from the parameter set. can do. In this case, the parameter set may be a sequence parameter set or a picture parameter set.

As in the syntax element example of Table 3, when the quantization matrix coefficient value to be decoded is determined to be the same as the reference quantization matrix coefficient value or when the quantization matrix coefficient value to be decoded is determined to be the same as the default matrix coefficient value, the reference of the quantization matrix to be decoded The quantization matrix identifier scaling_list_pred_size_matrix_id_delta can be decoded from the parameter set.

At this time, using the quantization matrix identifier scaling_list_pred_size_matrix_id_delta, Size_Matrix_ID, which is the size and matrix information of the quantization matrix to be decoded, and the following equations, RefMatrixID, which is matrix information of the reference quantization matrix and base matrix, and RefSizeID, which is size information of the reference quantization matrix and default matrix, are obtained. can decide

<Equation 3>

<Equation 4>

In this case, RefMap is a mapping table indicating the relationship between Size_Matrix_ID and RefSizeID and RefMatrixID as in the example of Table 6. In this case, since the size of the quantization matrix during inverse quantization is different, but the size of the quantization matrix during decoding is the same, quantization matrix identifiers may be sequentially assigned according to the type of the quantization matrix having an 8x8 size during decoding.

The method using the RefMap may be applied to a quantization matrix having a size of 8x8 during decoding, and may not be applied to a quantization matrix having a size of 4x4 during decoding. During decoding, RefMatrixID, which is matrix information of a reference quantization matrix and a base matrix, can be determined for a quantization matrix having a size of 4x4 by using the following equation. That is, a method of predicting a quantization matrix may be different depending on a size of a quantization matrix during decoding, and a method of determining a reference quantization matrix may also be different.

<Equation 5>

In the case of a quantization matrix having a size of 8x8 during decoding, if the RefMatrixID value is the same as the matrixID value and the RefSizeID value is the same as the sizeID value, the quantization matrix coefficient value to be decoded corresponding to sizeID and matrixID is a default matrix coefficient predetermined in the encoder/decoder determined to be the same as the value. In this case, the basic matrix means a basic matrix corresponding to sizeID and matrixID. And, if the scaling_list_pred_matrix_id_delta value is 0, it means that the RefMatrixID value and the matrixID value are the same, and the RefSizeID value is the same as the sizeID value.

In the case of a quantization matrix having a size of 4x4 during decoding, if the RefMatrixID value is the same as the matrixID value, the quantization matrix coefficient values to be decoded corresponding to the sizeID and matrixID are determined to be the same as the default matrix coefficient values predetermined in the encoder/decoder. In this case, the basic matrix means a basic matrix corresponding to sizeID and matrixID. And, if the scaling_list_pred_matrix_id_delta value is 0, it means that the RefMatrixID value and the matrixID value are the same.

In the case of a quantization matrix having a size of 8x8 during decoding, if the RefMatrixID value is not the same as the matrixID value and the RefSizeID value is not the same as the sizeID value, the quantization matrices corresponding to RefMatrixID and RefSizeID are determined as the reference quantization matrix of the quantization matrix to be decoded; A quantization matrix coefficient value to be decoded is determined to be the same as a reference quantization matrix coefficient value. Determining the quantization matrix coefficient value to be decoded to be the same as the reference quantization matrix coefficient value is determining the reference quantization matrix corresponding to RefMatrixID and RefSizeID as the reference quantization matrix of the quantization matrix to be decoded, and determining the reference quantization matrix coefficient value to the quantization matrix to be decoded It may refer to a method of predicting a quantization matrix that is copied as a coefficient value. When the matrix size is 16x16 or 32x32 during inverse quantization, DC matrix coefficients may be included. Accordingly, when predicting from a quantization matrix having a matrix size of 16x16 or 32x32 during inverse quantization, DC matrix coefficients can also be predicted.

In the case of a quantization matrix having a size of 4x4 during decoding, if the RefMatrixID value is not the same as the matrixID value, the quantization matrix corresponding to RefMatrixID is determined as the reference quantization matrix of the quantization matrix to be decoded, and the quantization matrix coefficient value to be decoded is the reference quantization matrix coefficient determined to be the same as the value.

In addition, inter-matrix prediction can be restricted from a quantization matrix having a larger value than Size_Matrix_ID of the quantization matrix to be decoded, and when the quantization matrix identifier scaling_list_pred_size_matrix_id_delta has a value between 0 and 13, inter-quantization matrix prediction and You can use the default matrix. Since the maximum value of the quantization matrix identifier is limited, it is possible to use a truncated unary code rather than an Exponential-Golomb code.

If the quantization matrix copy is performed using the quantization matrix size during inverse quantization, when the quantization matrix identifier of a quantization matrix having a size of 4x4, 8x8, or 16x16 during inverse quantization has a value between 0 and 5, between quantization matrices Prediction and default matrices can be used, and when the quantization matrix identifier of a quantization matrix having a size of 32x32 has a value between 0 and 1 during inverse quantization, the prediction and default matrix between quantization matrices can be used. Since the maximum value of the quantization matrix identifier is limited by size during inverse quantization, a truncated unary code can be used instead of an Exponential-Golomb code.

The coefficients in the quantization matrix are predicted and decoded (step S730).

If the predictive decoding method of the quantization matrix is a method of decoding the coefficients in the quantization matrix using the exponential-Golomb code, inverse DPCM, and scan (scaling_list_pred_mode_flag=1) to predictively decode the coefficients in the quantization matrix, the quantization matrix coefficient values previously decoded in the quantization matrix A difference value between a coefficient value of a quantization matrix to be decoded and a value of a quantization matrix to be decoded may be decoded from the parameter set. In this case, the parameter set may be a sequence parameter set or a picture parameter set.

As in the syntax element example of Table 7, when the size of the quantization matrix to be decoded is 16x16 (sizeID=2) or 32x32 (sizeID=3), the DC matrix coefficient scaling_list_dc_coef_minus8 can be decoded from the parameter set. The value of scaling_list_dc_coef_minus8 may be a value limited to between -8 and 247, and it can be decoded into a value between -8 and 247 using a Signed Exponental-Golomb code. The DC matrix coefficient value is calculated as a value of scaling_list_dc_coef_minus8 + 8 later, and the calculated value may be a value between 1 and 255.

As in the example of the syntax element of Table 7, scaling_list_delta_coef, which is a difference value between the quantization matrix coefficient value previously decoded in the quantization matrix and the quantization matrix coefficient value to be decoded, can be decoded from the parameter set. At this time, scaling_list_delta_coef decodes a total of 16 coefficients in a 4x4 quantization matrix when decoding a 4x4 quantization matrix, and when decoding a quantization matrix used for a transform coefficient block of 8x8 or larger size, the number of coefficients in an 8x8 quantization matrix Decrypt a total of 64 phosphors. The following shows the detailed process of decoding scaling_list_delta_coef.

As the first process, scaling_list_delta_coef is decoded using Exponential-Golomb code. The value of scaling_list_delta_coef can be a value limited to -254 to 254, and since the difference value has sign information, a value between -254 and 254 using a signed Exponental-Golomb code. can be decrypted as The decoded difference values may be stored in the order of decoding in a one-dimensional coefficient array.

As a second process, nextCoef or scalingList[i], which is a quantization matrix coefficient to be decoded, is restored by calculating the sum of the decoded difference value with the quantization matrix coefficient located in the previous order in the one-dimensional coefficient array. In this case, i means an order in the one-dimensional coefficient array. The quantization matrix coefficient to be decoded may be a value calculated using inverse DPCM (inverse DPCM), and the quantization matrix coefficient positioned in the previous order may be a coefficient that exists immediately before the quantization matrix coefficient to be decoded. Also, since the first coefficient in the one-dimensional coefficient array does not have a quantization matrix coefficient positioned in the previous order to be predicted, it can be restored using a predetermined constant value, and when sizeID is greater than 1, the DC matrix It can be restored using coefficients. In this case, the predetermined constant value may be a value between 1 and 255, in particular 8 or 16. The reconstructed quantization matrix coefficient may be a value between 1 and 255.

As a third process, a scan is performed to align the one-dimensional reconstructed quantization matrix coefficient array into a two-dimensional quantization matrix.

The quantization matrix is restored (step S740).

The reconstructed quantization matrix coefficients arranged in the 2D quantization matrix are reconstructed into a 2D quantization matrix to be used in inverse quantization. In this case, the two-dimensional quantization matrix may be restored using upsampling, interpolation, DC matrix coefficient replacement, subsampling, or the like, and an embodiment of restoring the quantization matrix is as follows.

For example, a quantization matrix used for inverse quantization of a square transform coefficient block such as 4x4, 8x8, 16x16, or 32x32 can be restored in the following way.

As shown in Equation 6, as a quantization matrix used for inverse quantization of a transform coefficient block having a size of 4x4, the aligned two-dimensional quantization matrix having a size of 4x4 may be used as it is.

<Equation 6>

As shown in Equation 7, as a quantization matrix used for inverse quantization of an 8x8 transform coefficient block, the aligned two-dimensional 8x8 quantization matrix may be used as it is.

<Equation 7>

8 is a conceptual diagram illustrating upsampling of a quantization matrix according to an embodiment of the present invention.

Referring to FIG. 8, as shown in Equation 8, the quantization matrix used for inverse quantization of a transform coefficient block having a size of 16x16 is upsampling that copies the aligned two-dimensional quantization matrix of size 8x8 from the nearest neighbor coefficient as shown in FIG. can be restored to a quantization matrix having a size of 16x16 by performing . In addition, a quantization matrix coefficient existing at a DC position in the quantization matrix, that is, a (0, 0) position may be replaced with a value of scaling_list_dc_coef_minus8 + 8, which is a DC matrix coefficient value.

<Equation 8>

As shown in Equation 9, the quantization matrix used for inverse quantization of the transform coefficient block of size 32x32 is 32x32 by performing upsampling by copying the aligned two-dimensional quantization matrix of size 8x8 from the nearest neighbor coefficient in the same manner as in FIG. 8 . It can be restored to a quantization matrix of size. In addition, a quantization matrix coefficient existing at a DC position in the quantization matrix, that is, a (0, 0) position may be replaced with a value of scaling_list_dc_coef_minus8 + 8, which is a DC matrix coefficient value.

<Equation 9>

9 is a conceptual diagram illustrating a method of generating a quantization matrix used for a non-square transform coefficient block according to an embodiment of the present invention.

Referring to FIG. 9 , a quantization matrix used for a non-square transform coefficient block such as 16x4, 4x16, 32x8, or 8x32 may be restored by the following method.

As shown in Equation 10, the quantization matrix used for the 16x4 transform coefficient block is 16x4 by subsampling the 16x16 reconstructed quantization matrix at the y position (row, vertical direction) as shown in FIG. 9(A). It can be restored to a quantization matrix of size.

<Equation 10>

As shown in Equation 11, the quantization matrix used for the 4x16 transform coefficient block is 4x16 by subsampling the 16x16 reconstructed quantization matrix at the x position (column, horizontal direction) as shown in FIG. 9B. It can be restored to a quantization matrix of size.

<Equation 11>

As shown in Equation 12, the quantization matrix used for the transform coefficient block of size 32x8 subsampling the reconstructed quantization matrix of size 32x32 with respect to the y position (row, vertical direction) in the same manner as in FIG. 9(A). Thus, it can be restored to a quantization matrix having a size of 32x8.

<Equation 12>

As shown in Equation 13, the quantization matrix used for the transform coefficient block of size 8x32 subsampling the reconstructed quantization matrix of size 32x32 with respect to the x position (column, horizontal direction) in the same manner as in FIG. 9B. Thus, it can be restored to a quantization matrix having a size of 8x32.

<Equation 13>

If the default matrix predefined in the encoder and decoder is used for inverse quantization of the 16x16/32x32 size transform coefficient block in order to reduce the memory storage space, the 8x8 size basic matrix exists as the closest It can be restored to a quantization matrix having a size of 16x16/32x32 by performing upsampling that is copied from the neighboring coefficients.

As shown in Equation 14, the base matrix used for inverse quantization of the transform coefficient block of 16x16 size is converted to a quantization matrix of size 16x16 by performing upsampling by copying the base matrix of size 8x8 from the nearest neighbor coefficient in the same way as in FIG. can be restored

<Equation 14>

As shown in Equation 15, the default matrix used for inverse quantization of a transform coefficient block of 32x32 size is a quantization matrix of 32x32 size by performing upsampling by copying the base matrix of size 8x8 from the nearest neighbor coefficient in the same way as in FIG. can be restored

<Equation 15>

In the above equations, QM(x, y) denotes an aligned two-dimensional 4x4 quantization matrix, RQM(x, y) denotes a reconstructed quantization matrix, and DQM(x, y) denotes a basic matrix means

The upsampling method of copying from the nearest neighbor coefficients may be called a method of nearest neighbor interpolation or zeroth order interpolation.

In the above-described embodiment, when quantization/inverse quantization, the non-square 16x4 or 4x16 quantization matrix is derived from the square 16x16 quantization matrix. In addition to the quantization matrix, it can mean a non-square 16x4 or 4x16 quantization matrix. During quantization/inverse quantization, the non-square 32x8 or 8x32 quantization matrix is derived from a square 32x32 quantization matrix. A quantization matrix having a size of 32x32 may mean not only a quantization matrix having a size of a square 32x32, but also a quantization matrix having a size of a non-square 32x8 or 8x32.

The quantization matrix information refers to a quantization matrix or information from which a quantization matrix can be derived. In this case, the information capable of deriving the quantization matrix may mean whether a default matrix is used, a type of prediction encoding/decoding method, a reference quantization matrix identifier, a reference quantization matrix, or the like.

In the above-described embodiments, the methods are described on the basis of a flowchart as a series of steps or units, but the present invention is not limited to the order of steps, and some steps may occur in a different order or concurrently with other steps as described above. can In addition, those of ordinary skill in the art will recognize that the steps shown in the flowchart are not exclusive, other steps may be included, or that one or more steps in the flowchart may be deleted without affecting the scope of the present invention. you will understand

The above-described embodiments include examples of various aspects. It is not possible to describe every possible combination for representing the various aspects, but one of ordinary skill in the art will recognize that other combinations are possible. Accordingly, it is intended that the present invention cover all other substitutions, modifications and variations falling within the scope of the following claims.

Claims (3)

decoding information of a current quantization matrix;
reconstructing a current quantization matrix based on information on the current quantization matrix;
performing inverse quantization on the current block based on the restored current quantization matrix; and
Inverse transforming the inverse quantized current block,
The information on the current quantization matrix includes at least one of current quantization matrix prediction method information and information indicating a reference quantization matrix of the current quantization matrix,
Restoring the current quantization matrix comprises:
determining a reference quantization matrix according to the information indicating the reference quantization matrix when the quantization matrix prediction method information indicates that a current quantization matrix is determined to have the same coefficient value as a reference quantization matrix; and
Restoring the current quantization matrix according to the reference quantization matrix,
The restored current quantization matrix is characterized in that it is a square,
Performing inverse quantization on the current block based on the restored current quantization matrix comprises:
When the current block is a non-square block, non-square quantization corresponding to the height and width of the current block is performed by subsampling the current quantization matrix according to the height and width of the current block and the height and width of the current quantization matrix. generating a matrix; and
and performing inverse quantization on the current block based on the non-square quantization matrix.
determining a current quantization matrix;
determining information on a current quantization matrix based on the current quantization matrix, and encoding the determined information on the current quantization matrix;
performing transformation on the current block; and
performing quantization on the transformed current block based on the current quantization matrix,
The information on the current quantization matrix includes at least one of current quantization matrix prediction method information and information indicating a reference quantization matrix of the current quantization matrix,
The step of encoding the information of the current quantization matrix comprises:
When the current quantization matrix is determined to have the same coefficient values as the reference quantization matrix, determining information indicating the reference quantization matrix according to a reference quantization matrix of the current quantization matrix,
The current quantization matrix is characterized in that the square,
Performing quantization on the current block based on the current quantization matrix comprises:
When the current block is a non-square block, non-square quantization corresponding to the height and width of the current block is performed by subsampling the current quantization matrix according to the height and width of the current block and the height and width of the current quantization matrix. generating a matrix; and
and performing quantization on the current block based on the non-square quantization matrix.
A computer-readable recording medium storing a bitstream generated by a video encoding method, the video encoding method comprising:
determining a current quantization matrix;
determining information on a current quantization matrix based on the current quantization matrix, and encoding the determined information on the current quantization matrix;
performing transformation on the current block; and
performing quantization on the transformed current block based on the current quantization matrix,
The information on the current quantization matrix includes at least one of current quantization matrix prediction method information and information indicating a reference quantization matrix of the current quantization matrix,
The step of encoding the information of the current quantization matrix comprises:
When the current quantization matrix is determined to have the same coefficient values as the reference quantization matrix, determining information indicating the reference quantization matrix according to a reference quantization matrix of the current quantization matrix,
The current quantization matrix is characterized in that the square,
Performing quantization on the current block based on the current quantization matrix comprises:
When the current block is a non-square block, non-square quantization corresponding to the height and width of the current block is performed by subsampling the current quantization matrix according to the height and width of the current block and the height and width of the current quantization matrix. generating a matrix; and
and performing quantization on the current block based on the non-square quantization matrix.

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