KR102601268B1 - Method and apparatus for processing a video signal - Google Patents

Abstract

The present invention relates to a video signal processing method and device. The video decoding method according to the present invention includes the steps of checking transform block coding indicator information from an encoded syntax element, if the transform block coding indicator information indicates that at least one valid transform coefficient exists in the transform block, the transform block It includes the step of decoding the inner transform coefficient. According to the present invention, the encoding/decoding efficiency of the video signal can be increased by efficiently processing the encoding/decoding target transform block.

Description

Video signal processing method and apparatus {METHOD AND APPARATUS FOR PROCESSING A VIDEO SIGNAL}

The present invention relates to a video signal processing method and device.

Recently, demand for high-resolution, high-quality images such as HD (High Definition) images and UHD (Ultra High Definition) images is increasing in various application fields. As video data becomes higher resolution and higher quality, the amount of data increases relative to existing video data. Therefore, when video data is transmitted using media such as existing wired or wireless broadband lines or stored using existing storage media, transmission costs and Storage costs increase. High-efficiency video compression technologies can be used to solve these problems that arise as video data becomes higher resolution and higher quality.

Inter-screen prediction technology that predicts the pixel value included in the current picture from pictures before or after the current picture using video compression technology, intra-screen prediction technology that predicts the pixel value included in the current picture using pixel information in the current picture, There are various technologies, such as entropy coding technology, which assigns short codes to values with a high frequency of occurrence and long codes to values with a low frequency of occurrence. Using these video compression technologies, video data can be effectively compressed and transmitted or stored.

Meanwhile, as the demand for high-resolution video increases, the demand for three-dimensional video content as a new video service is also increasing. Discussions are underway regarding video compression technology to effectively provide high-resolution and ultra-high-resolution stereoscopic video content.

The purpose of the present invention is to provide a multi-tree partitioning method and device that can effectively divide encoding/decoding target blocks when encoding/decoding video signals.

The purpose of the present invention is to provide a multi-tree partitioning method and device for dividing an encoding/decoding target block into symmetric or asymmetric blocks when encoding/decoding a video signal.

The purpose of the present invention is to provide a method and device for encoding and/or decoding transform coefficients in a transform block corresponding to a coding block divided by multi-tree partitioning.

The purpose of the present invention is to provide a recording medium containing a video signal bitstream encoded by the above encoding method.

The technical problems to be achieved in the present invention are not limited to the technical problems mentioned above, and other technical problems not mentioned will be clearly understood by those skilled in the art from the description below. You will be able to.

The video decoding method according to the present invention includes the steps of checking transform block coding indicator information from an encoded syntax element, and if the transform block coding indicator information indicates that at least one valid transform coefficient exists in a transform block, It includes the step of decoding the transform coefficients in the transform block.

Additionally, if the transform block coding indicator information does not indicate that at least one valid transform coefficient exists in the transform block, all transform coefficients in the transform block are set to predetermined values.

Additionally, only when the transform block is determined to be a block generated by inter prediction mode, the transform block coding indicator information is checked.

In addition, the step of decoding the transform coefficient involves using a luminance signal component indicator syntax element ( cbf_luma) is detected and decrypted.

Additionally, when at least one of the chrominance signal component indicator syntax elements (cbf_cb, cbf_cr) corresponding to the transform block is '0', the luminance signal component indicator syntax element (cbf_luma) corresponding to the transform block is not considered.

Additionally, the size of the coding block is compared with a predetermined reference size, and the transform block coding indicator information is checked only for coding blocks whose size is larger than the reference size as a result of the comparison.

Additionally, the shape of the coding block is checked, and only when the coding block is square, the transform block coding indicator information is checked.

Additionally, the partitioning type of the coding block is checked, and only when the coding block is divided by quad tree partitioning, the transform block coding indicator information is checked.

Another video decoding method according to the present invention involves dividing a transform block into at least one sub-transform block from an encoded syntax element, and checking sub-block coding indicator information (CSBF) corresponding to each divided sub-transform block. and, when the sub-block coding indicator information (CSBF) indicates that at least one valid transform coefficient exists in the sub-transform block, decoding the transform coefficient in the sub-transform block.

In addition, the size of the coding block is compared with a predetermined reference size, and the sub-block coding indicator information (CSBF) is checked only for coding blocks whose size is larger than the reference size as a result of the comparison.

In addition, the size of the coding block is compared with a predetermined reference size, and for coding blocks that are larger than the standard size as a result of the comparison, sub-block coding indicator information (CSBF) is checked for each NxN sub-transform block unit, and the standard size as a result of the comparison is checked. For smaller coding blocks, sub-block coding indicator information (CSBF) is checked for each MxM (M<N) sub-transform block unit.

Additionally, the shape of the coding block is checked, and if the coding block is square, the sub-block coding indicator information (CSBF) is checked.

In addition, the type of the coding block is confirmed, and if the coding block is non-square and minimally asymmetric, the sub-transform block unit to which the sub-block coding indicator information (CSBF) is applied is confirmed, and each confirmed sub-transform block unit is checked. , check the sub-block coding indicator information (CSBF).

In addition, when the coding block is non-square and minimally asymmetric, the sub-transform block unit to which the sub-block coding indicator information (CSBF) is applied has at least one of width or height smaller than the predetermined size. The predetermined size may be defined as 4 or less.

In addition, when the coding block is non-square and minimally asymmetric, the sub-transform block unit to which the sub-block coding indicator information (CSBF) is applied has at least one of width or height having a value of 1.

In addition, when the coding block is non-square and minimally asymmetric, the sub-transform block unit to which the sub-block coding indicator information (CSBF) is applied is divided based on the number of samples included in the sub-transform block.

The video encoding method according to the present invention includes, when the size of the partitioned current coding block is larger than the reference size, encoding a transform block in the current coding block, and determining whether a valid transform coefficient exists in the encoded transform block. Thus, it includes signaling transform block coding indicator information for each transform block, wherein the transform block coding indicator information indicates whether at least one valid transform coefficient exists in the transform block.

Another video encoding method according to the present invention includes, when the size of the partitioned current coding block is larger than the reference size, dividing the transform block in the current coding block into at least one sub-transform block, and valid for the sub-transform block. Determining whether a transform coefficient exists and signaling sub-block coding indicator information (CSBF) for each of the divided sub-transform blocks, wherein the sub-transform block coding indicator information is present in at least one sub-transform block in the sub-transform block. Indicates whether a valid conversion coefficient exists.

The video decoding device according to the present invention checks transform block coding indicator information from an encoded syntax element, and if the transform block coding indicator information indicates that at least one valid transform coefficient exists in the transform block, It includes a decoder that decodes the transform coefficient.

Another video decoding device according to the present invention divides a transform block into at least one sub-transform block from an encoded syntax element, checks sub-block coding indicator information (CSBF) corresponding to each divided sub-transform block, and When the sub-block coding indicator information (CSBF) indicates that at least one valid transform coefficient exists in the sub-transform block, it includes a decoder that decodes the transform coefficient in the sub-transform block.

According to the present invention, in a recording medium including a video signal bitstream, the video signal bitstream included in the recording medium is a transform block in the current coding block when the size of the partitioned current coding block is larger than the reference size. Encoding, and determining whether a valid transform coefficient exists in the encoded transform block, and signaling transform block coding indicator information for each transform block, wherein the transform block coding indicator information is stored in the transform block. It is characterized by being encoded using an image encoding method that indicates whether at least one valid transformation coefficient exists.

In another recording medium including a video signal bitstream according to the present invention, the video signal bitstream included in the recording medium is, when the size of the partitioned current coding block is larger than the reference size, the video signal bitstream within the current coding block. Dividing a transform block into at least one sub-transform block, determining whether a valid transform coefficient exists in the sub-transform block, and signaling sub-block coding indicator information (CSBF) for each of the divided sub-transform blocks. Including, wherein the sub-transform block coding indicator information is characterized in that it is encoded by a video encoding method that indicates whether at least one valid transform coefficient exists in the sub-transform block.

The features briefly summarized above with respect to the present invention are merely exemplary aspects of the detailed description of the present invention that follows, and do not limit the scope of the present invention.

According to the present invention, the encoding/decoding efficiency of a video signal can be increased by efficiently dividing the encoding/decoding target block.

According to the present invention, the encoding/decoding efficiency of a video signal can be increased by dividing the encoding/decoding target block into symmetric or asymmetric blocks.

According to the present invention, the encoding/decoding efficiency of a video signal can be increased by efficiently processing the conversion block to be encoded/decoded.

The effects that can be obtained from the present invention are not limited to the effects mentioned above, and other effects not mentioned can be clearly understood by those skilled in the art from the description below. will be.

Figure 1 is a block diagram showing a video encoding device according to an embodiment of the present invention.
Figure 2 is a block diagram showing an image decoding device according to an embodiment of the present invention.
Figure 3 is a diagram illustrating a partition mode that can be applied to a coding block when the coding block is encoded with inter-screen prediction.
FIG. 4 is a diagram illustrating a partition type in which quad tree and binary tree partitioning is allowed, as an embodiment to which the invention is applied.
Figure 5 is an embodiment to which the present invention is applied, showing an example of hierarchically dividing a coding block based on quad tree and binary tree division.
Figure 6 is an embodiment to which the present invention is applied, showing an example of hierarchically partitioning a coding block based on quad tree and symmetric binary tree partitioning.
Figure 7 is an embodiment to which the present invention is applied, and is a diagram showing a partition type in which asymmetric binary tree division is permitted.
Figure 8 is an embodiment to which the present invention is applied, illustrating the division form of a coding block based on quad tree and symmetric/asymmetric binary tree division.
Figure 9 is a flowchart of a coding block partitioning method based on quad tree and binary tree partitioning as an embodiment to which the present invention is applied.
Figure 10 is an embodiment to which the present invention is applied, showing as an example a syntax element included in a network abstraction layer (NAL) to which quad tree and binary tree partitioning is applied.
Figure 11 is another embodiment to which the present invention is applied, a diagram showing a partition type in which asymmetric quad tree partitioning is permitted.
Figure 12 is a flowchart of a coding block partitioning method based on asymmetric quad tree partitioning as another embodiment to which the present invention is applied.
Figure 13 is another embodiment to which the present invention is applied, showing as an example a syntax element included in a network abstraction layer (NAL) to which asymmetric quad tree partitioning is applied.
Figure 14 is another embodiment to which the present invention is applied, a diagram showing a partition type in which quad tree and triple tree division is permitted.
Figure 15 is another embodiment to which the present invention is applied, a flowchart of a coding block partitioning method based on quad tree and triple tree partitioning.
Figure 16 is another embodiment to which the present invention is applied, showing as an example a syntax element included in a network abstraction layer (NAL) to which quad tree and triple tree partitioning is applied.
Figure 17 is another embodiment to which the present invention is applied, and is a diagram showing a basic partition type to which multi-tree division is permitted.
Figure 18 is another embodiment to which the present invention is applied, a diagram showing an extended partition form that allows multi-tree division.
Figure 19 is a flowchart of a coding block division method based on multi-tree division as another embodiment to which the present invention is applied.
Figure 20 is another embodiment to which the present invention is applied, and is shown to explain transform block coding indicator information of a transform block corresponding to a coding block divided by multi-tree division.
Figures 21 and 22 are another embodiment to which the present invention is applied, showing an image decoding method using transform block coding indicator information of a transform block.
Figures 23 to 26 show another embodiment to which the present invention is applied and illustrate an image encoding method using transform block coding indicator information of a transform block.
Figures 27 and 28 are another embodiment to which the present invention is applied, showing another image decoding method using transform block coding indicator information of a transform block.
Figure 29 is another embodiment to which the present invention is applied, dividing a transform block into a plurality of sub-transform blocks and illustrating sub-block coding indicator information provided for each sub-transform block.
Figures 30 to 32 are another embodiment to which the present invention is applied, showing various embodiments of dividing a transform block into a plurality of sub-transform blocks and a sub-block coding indicator for each divided sub-transform block.
Figure 33 is another embodiment to which the present invention is applied, showing an image encoding method using a sub-block coding indicator for each sub-transformation block.
Figure 34 is another embodiment to which the present invention is applied, showing an image encoding method using a sub-block coding indicator for each sub-transform block corresponding to a non-square coding block.
Figure 35 is another embodiment to which the present invention is applied, showing an image encoding method using a sub-block coding indicator for each sub-transform block corresponding to a very asymmetric coding block.
Figure 36 is another embodiment to which the present invention is applied, showing an image decoding method using a sub-block coding indicator for each sub-transform block corresponding to a very asymmetric coding block.
Figure 37 is another embodiment to which the present invention is applied, showing as an example a syntax element included in a network abstraction layer (NAL) applied to a transform block.

Since the present invention can make various changes and have various embodiments, specific embodiments will be illustrated in the drawings and described in detail in the detailed description. However, this is not intended to limit the present invention to specific embodiments, and should be understood to include all changes, equivalents, and substitutes included in the spirit and technical scope of the present invention. While describing each drawing, similar reference numerals are used for similar components.

Terms such as first, second, etc. may be used to describe various components, but the components should not be limited by the terms. The above terms are used only for the purpose of distinguishing one component from another. For example, a first component may be named a second component, and similarly, the second component may also be named a first component without departing from the scope of the present invention. The term and/or includes any of a plurality of related stated items or a combination of a plurality of related stated items.

The terms used in this application are only used to describe specific embodiments and are not intended to limit the invention. Singular expressions include plural expressions unless the context clearly dictates otherwise. In this application, terms such as “comprise” or “have” are intended to designate the presence of features, numbers, steps, operations, components, parts, or combinations thereof described in the specification, but are not intended to indicate the presence of one or more other features. It should be understood that this does not exclude in advance the possibility of the existence or addition of elements, numbers, steps, operations, components, parts, or combinations thereof.

In addition, “unit” used in this application can be replaced with “block,” and therefore, in this specification, “coding tree unit” and “coding tree block”, “coding unit” and “coding block”. ”, “Prediction unit” and “Prediction block”, “Conversion unit” and “Conversion block” can each be interpreted to have the same meaning.

Hereinafter, preferred embodiments of the present invention will be described in more detail with reference to the attached drawings. Hereinafter, the same reference numerals will be used for the same components in the drawings, and duplicate descriptions of the same components will be omitted.

Figure 1 is a block diagram showing a video encoding device according to an embodiment of the present invention.

Referring to FIG. 1, the image encoding device 100 includes a picture segmentation unit 110, prediction units 120 and 125, a conversion unit 130, a quantization unit 135, a reordering unit 160, and an entropy encoding unit ( 165), an inverse quantization unit 140, an inverse transform unit 145, a filter unit 150, and a memory 155.

Each component shown in FIG. 1 is shown independently to represent different characteristic functions in the video encoding device, and does not mean that each component is comprised of separate hardware or a single software component. That is, each component is listed and included as a separate component for convenience of explanation, and at least two of each component can be combined to form one component, or one component can be divided into a plurality of components to perform a function, and each of these components can be divided into a plurality of components. Integrated embodiments and separate embodiments of the constituent parts are also included in the scope of the present invention as long as they do not deviate from the essence of the present invention.

Additionally, some components may not be essential components that perform essential functions in the present invention, but may simply be optional components to improve performance. The present invention can be implemented by including only essential components for implementing the essence of the present invention excluding components used only to improve performance, and a structure including only essential components excluding optional components used only to improve performance. is also included in the scope of rights of the present invention.

The picture division unit 110 may divide the input picture into at least one processing unit. At this time, the processing unit may be a prediction unit (PU), a transformation unit (TU), or a coding unit (CU). The picture division unit 110 divides one picture into a combination of a plurality of coding units, prediction units, and transformation units, and combines one coding unit, prediction unit, and transformation unit based on a predetermined standard (for example, a cost function). You can encode the picture by selecting .

For example, one picture may be divided into a plurality of coding units. To split the coding unit in a picture, a recursive tree structure such as the Quad Tree Structure can be used. Coding is split into other coding units with one image or the largest coding unit as the root. A unit can be divided into child nodes equal to the number of divided coding units. A coding unit that is no longer divided according to certain restrictions becomes a leaf node. That is, assuming that only square division is possible for one coding unit, one coding unit can be divided into up to four different coding units.

Hereinafter, in the embodiments of the present invention, the coding unit may be used to mean a unit that performs encoding, or may be used to mean a unit that performs decoding.

A prediction unit may be divided into at least one square or rectangular shape of the same size within one coding unit, and any one of the prediction units divided within one coding unit may be a prediction unit of another prediction unit. It may be divided to have a different shape and/or size than the unit.

If the prediction unit for which intra prediction is performed based on the coding unit is not the minimum coding unit when generated, intra prediction can be performed without dividing the prediction unit into a plurality of prediction units NxN.

The prediction units 120 and 125 may include an inter prediction unit 120 that performs inter prediction and an intra prediction unit 125 that performs intra prediction. It is possible to determine whether to use inter prediction or intra prediction for a prediction unit, and determine specific information (eg, intra prediction mode, motion vector, reference picture, etc.) according to each prediction method. At this time, the processing unit in which the prediction is performed and the processing unit in which the prediction method and specific contents are determined may be different. For example, the prediction method and prediction mode are determined in prediction units, and prediction may be performed in transformation units. The residual value (residual block) between the generated prediction block and the original block may be input to the conversion unit 130. Additionally, prediction mode information, motion vector information, etc. used for prediction may be encoded in the entropy encoder 165 together with the residual value and transmitted to the decoder. When using a specific encoding mode, it is possible to encode the original block as is and transmit it to the decoder without generating a prediction block through the prediction units 120 and 125.

The inter prediction unit 120 may predict a prediction unit based on information on at least one picture among the pictures before or after the current picture, and in some cases, prediction based on information on a partially encoded region within the current picture. Units can also be predicted. The inter prediction unit 120 may include a reference picture interpolation unit, a motion prediction unit, and a motion compensation unit.

The reference picture interpolation unit may receive reference picture information from the memory 155 and generate pixel information of an integer number of pixels or less from the reference picture. In the case of luminance pixels, a DCT-based 8-tap interpolation filter with different filter coefficients can be used to generate pixel information of an integer pixel or less in 1/4 pixel units. In the case of color difference signals, a DCT-based 4-tap interpolation filter with different filter coefficients can be used to generate pixel information of an integer pixel or less in 1/8 pixel units.

The motion prediction unit may perform motion prediction based on a reference picture interpolated by the reference picture interpolation unit. Various methods such as FBMA (Full search-based Block Matching Algorithm), TSS (Three Step Search), and NTS (New Three-Step Search Algorithm) can be used to calculate the motion vector. The motion vector may have a motion vector value in units of 1/2 or 1/4 pixels based on the interpolated pixels. The motion prediction unit can predict the current prediction unit by using a different motion prediction method. As a motion prediction method, various methods such as the skip method, the merge method, the Advanced Motion Vector Prediction (AMVP) method, and the intra block copy method can be used.

The intra prediction unit 125 may generate a prediction unit based on reference pixel information around the current block, which is pixel information in the current picture. If the neighboring block of the current prediction unit is a block on which inter prediction has been performed and the reference pixel is a pixel on which inter prediction has been performed, the reference pixel included in the block on which inter prediction has been performed is the reference pixel of the block on which intra prediction has been performed. It can be used in place of information. That is, when a reference pixel is not available, the unavailable reference pixel information can be replaced with at least one reference pixel among available reference pixels.

In intra prediction, the prediction mode can include a directional prediction mode that uses reference pixel information according to the prediction direction and a non-directional mode that does not use directional information when performing prediction. The mode for predicting luminance information and the mode for predicting chrominance information may be different, and intra prediction mode information used to predict luminance information or predicted luminance signal information may be used to predict chrominance information.

When performing intra prediction, if the size of the prediction unit and the size of the transformation unit are the same, intra prediction for the prediction unit is made based on the pixel on the left, the pixel on the top left, and the pixel on the top of the prediction unit. can be performed. However, when performing intra prediction, if the size of the prediction unit and the size of the transformation unit are different, intra prediction can be performed using a reference pixel based on the transformation unit. Additionally, intra prediction using NxN partitioning can be used only for the minimum coding unit.

The intra prediction method can generate a prediction block after applying an Adaptive Intra Smoothing (AIS) filter to the reference pixel according to the prediction mode. The type of AIS filter applied to the reference pixel may be different. To perform the intra prediction method, the intra prediction mode of the current prediction unit can be predicted from the intra prediction mode of prediction units existing around the current prediction unit. When predicting the prediction mode of the current prediction unit using predicted mode information from neighboring prediction units, if the intra prediction mode of the current prediction unit and neighboring prediction units are the same, predetermined flag information is used to predict the current prediction unit and neighboring prediction units. Information that the prediction modes of are the same can be transmitted, and if the prediction modes of the current prediction unit and neighboring prediction units are different, entropy encoding can be performed to encode the prediction mode information of the current block.

Additionally, based on the prediction units generated by the prediction units 120 and 125, a residual block may be generated that includes residual information that is the difference between the prediction unit on which prediction was performed and the original block of the prediction unit. The generated residual block may be input to the conversion unit 130.

The transform unit 130 transforms the residual block, including the original block and the residual value information of the prediction unit generated through the prediction units 120 and 125, into DCT (Discrete Cosine Transform), DST (Discrete Sine Transform), KLT and It can be converted using the same conversion method. Whether to apply DCT, DST, or KLT to transform the residual block can be determined based on intra prediction mode information of the prediction unit used to generate the residual block.

The quantization unit 135 may quantize the values converted to the frequency domain by the conversion unit 130. The quantization coefficient may change depending on the block or the importance of the image. The value calculated by the quantization unit 135 may be provided to the inverse quantization unit 140 and the realignment unit 160.

The rearrangement unit 160 may rearrange coefficient values for the quantized residual values.

The rearrangement unit 160 can change the coefficients in a two-dimensional block form into a one-dimensional vector form through a coefficient scanning method. For example, the realignment unit 160 can scan from DC coefficients to coefficients in the high frequency region using a zig-zag scan method and change it into a one-dimensional vector form. Depending on the size of the transformation unit and the intra prediction mode, a vertical scan that scans the two-dimensional block-type coefficients in the column direction or a horizontal scan that scans the two-dimensional block-type coefficients in the row direction may be used instead of the zig-zag scan. That is, depending on the size of the transformation unit and the intra prediction mode, it can be determined which scan method among zig-zag scan, vertical scan, and horizontal scan will be used.

The entropy encoding unit 165 may perform entropy encoding based on the values calculated by the reordering unit 160. Entropy coding can use various coding methods, such as Exponential Golomb, Context-Adaptive Variable Length Coding (CAVLC), and Context-Adaptive Binary Arithmetic Coding (CABAC).

The entropy encoding unit 165 receives the residual value coefficient information and block type information of the coding unit, prediction mode information, division unit information, prediction unit information and transmission unit information, and motion information from the reordering unit 160 and the prediction units 120 and 125. Various information such as vector information, reference frame information, block interpolation information, and filtering information can be encoded.

The entropy encoding unit 165 may entropy encode the coefficient value of the coding unit input from the reordering unit 160.

The inverse quantization unit 140 and the inverse transformation unit 145 inversely quantize the values quantized in the quantization unit 135 and inversely transform the values transformed in the transformation unit 130. The residual value generated in the inverse quantization unit 140 and the inverse transform unit 145 is restored by combining the prediction units predicted through the motion estimation unit, motion compensation unit, and intra prediction unit included in the prediction units 120 and 125. You can create a block (Reconstructed Block).

The filter unit 150 may include at least one of a deblocking filter, an offset correction unit, and an adaptive loop filter (ALF).

The deblocking filter can remove block distortion caused by boundaries between blocks in the restored picture. To determine whether to perform deblocking, it is possible to determine whether to apply a deblocking filter to the current block based on the pixels included in several columns or rows included in the block. When applying a deblocking filter to a block, a strong filter or a weak filter can be applied depending on the required deblocking filtering strength. Additionally, when applying a deblocking filter, horizontal filtering and vertical filtering can be processed in parallel when vertical filtering and horizontal filtering are performed.

The offset correction unit may correct the offset of the deblocked image from the original image in pixel units. In order to perform offset correction for a specific picture, the pixels included in the image are divided into a certain number of areas, then the area to perform offset is determined and the offset is applied to that area, or the offset is performed by considering the edge information of each pixel. You can use the method of applying .

Adaptive Loop Filtering (ALF) can be performed based on a comparison between the filtered restored image and the original image. After dividing the pixels included in the image into predetermined groups, filtering can be performed differentially for each group by determining one filter to be applied to that group. Information related to whether to apply ALF may be transmitted for each coding unit (CU), and the shape and filter coefficients of the ALF filter to be applied may vary for each block. Additionally, an ALF filter of the same type (fixed type) may be applied regardless of the characteristics of the block to which it is applied.

The memory 155 may store a reconstructed block or picture calculated through the filter unit 150, and the stored reconstructed block or picture may be provided to the prediction units 120 and 125 when inter prediction is performed.

Figure 2 is a block diagram showing an image decoding device according to an embodiment of the present invention.

Referring to FIG. 2, the image decoder 200 includes an entropy decoder 210, a reordering unit 215, an inverse quantization unit 220, an inverse transform unit 225, a prediction unit 230, 235, and a filter unit ( 240) and memory 245 may be included.

When a video bitstream is input from a video encoder, the input bitstream can be decoded in a procedure opposite to that of the video encoder.

The entropy decoding unit 210 may perform entropy decoding in a procedure opposite to the procedure in which entropy encoding is performed in the entropy encoding unit of the video encoder. For example, various methods such as Exponential Golomb, CAVLC (Context-Adaptive Variable Length Coding), and CABAC (Context-Adaptive Binary Arithmetic Coding) can be applied in response to the method performed in the image encoder.

The entropy decoder 210 can decode information related to intra prediction and inter prediction performed by the encoder.

The reordering unit 215 may rearrange the bitstream entropy-decoded by the entropy decoding unit 210 based on the method in which the encoder rearranges the bitstream. Coefficients expressed in the form of a one-dimensional vector can be restored and rearranged as coefficients in the form of a two-dimensional block. The reordering unit 215 may receive information related to coefficient scanning performed by the encoder and perform reordering by reverse scanning based on the scanning order performed by the encoder.

The inverse quantization unit 220 may perform inverse quantization based on the quantization parameters provided by the encoder and the coefficient values of the rearranged blocks.

The inverse transform unit 225 may perform inverse transform, that is, inverse DCT, inverse DST, and inverse KLT, on the transform performed by the transformer, that is, DCT, DST, and KLT, on the quantization result performed by the image encoder. Inverse transformation can be performed based on the transmission unit determined by the video encoder. The inverse transform unit 225 of the video decoder may selectively perform a transformation technique (eg, DCT, DST, KLT) according to a plurality of information such as a prediction method, the size of the current block, and the prediction direction.

The prediction units 230 and 235 may generate a prediction block based on prediction block generation-related information provided by the entropy decoder 210 and previously decoded block or picture information provided by the memory 245.

As described above, when performing intra prediction in the same manner as in the operation of the video encoder, when the size of the prediction unit and the size of the transformation unit are the same, the pixel that exists on the left of the prediction unit, the pixel that exists in the upper left, and the pixel that exists on the top Intra prediction is performed for the prediction unit based on the pixel, but when performing intra prediction, if the size of the prediction unit and the size of the transformation unit are different, intra prediction is performed using a reference pixel based on the transformation unit. You can. Additionally, intra prediction using NxN partitioning only for the minimum coding unit can be used.

The prediction units 230 and 235 may include a prediction unit determination unit, an inter prediction unit, and an intra prediction unit. The prediction unit discriminator receives various information such as prediction unit information input from the entropy decoder 210, prediction mode information of the intra prediction method, and motion prediction-related information of the inter prediction method, distinguishes the prediction unit from the current coding unit, and makes predictions. It is possible to determine whether a unit performs inter-prediction or intra-prediction. The inter prediction unit 230 uses the information required for inter prediction of the current prediction unit provided by the video encoder to make current prediction based on information included in at least one picture of the picture before or after the current picture including the current prediction unit. Inter prediction for units can be performed. Alternatively, inter prediction may be performed based on information on a pre-restored partial region within the current picture including the current prediction unit.

To perform inter prediction, based on the coding unit, the motion prediction method of the prediction unit included in the coding unit is Skip Mode, Merge Mode, AMVP Mode, and Intra Block Copy Mode. You can judge whether it is a certain method or not.

The intra prediction unit 235 may generate a prediction block based on pixel information in the current picture. If the prediction unit is a prediction unit that has performed intra prediction, intra prediction can be performed based on the intra prediction mode information of the prediction unit provided by the video encoder. The intra prediction unit 235 may include an Adaptive Intra Smoothing (AIS) filter, a reference pixel interpolation unit, and a DC filter. The AIS filter is a part that performs filtering on the reference pixels of the current block, and can be applied by determining whether or not to apply the filter according to the prediction mode of the current prediction unit. AIS filtering can be performed on the reference pixel of the current block using the prediction mode and AIS filter information of the prediction unit provided by the video encoder. If the prediction mode of the current block is a mode that does not perform AIS filtering, the AIS filter may not be applied.

If the prediction mode of the prediction unit is a prediction unit that performs intra prediction based on pixel values obtained by interpolating the reference pixel, the reference pixel interpolator may interpolate the reference pixel to generate a reference pixel in pixel units of an integer value or less. If the prediction mode of the current prediction unit is a prediction mode that generates a prediction block without interpolating the reference pixel, the reference pixel may not be interpolated. The DC filter can generate a prediction block through filtering when the prediction mode of the current block is DC mode.

The restored block or picture may be provided to the filter unit 240. The filter unit 240 may include a deblocking filter, an offset correction unit, and an ALF.

Information on whether a deblocking filter has been applied to the corresponding block or picture can be received from the video encoder, and when a deblocking filter has been applied, information on whether a strong filter or a weak filter has been applied. In the deblocking filter of the video decoder, information related to the deblocking filter provided by the video encoder is provided and the video decoder can perform deblocking filtering on the corresponding block.

The offset correction unit may perform offset correction on the reconstructed image based on the type of offset correction applied to the image during encoding and offset value information.

ALF can be applied to the coding unit based on ALF application availability information, ALF coefficient information, etc. provided from the encoder. This ALF information may be included and provided in a specific parameter set.

The memory 245 can store the restored picture or block so that it can be used as a reference picture or reference block, and can also provide the restored picture to an output unit.

As described above, hereinafter, in the embodiments of the present invention, the term coding unit is used as a coding unit for convenience of explanation, but it may also be a unit that performs not only encoding but also decoding.

In addition, the current block represents an encoding/decoding target block and, depending on the encoding/decoding stage, is a coding tree block (or coding tree unit), a coding block (or coding unit), a transform block (or transform unit), or a prediction block. (or prediction unit), etc. In this specification, 'unit' may represent a basic unit for performing a specific encoding/decoding process, and 'block' may represent a sample array of a predetermined size. Unless otherwise specified, ‘block’ and ‘unit’ can be used with the same meaning. For example, in embodiments described later, a coding block (coding block) and a coding unit (coding unit) may be understood to have equivalent meanings.

One picture can be divided into square or non-square basic blocks and encoded/decoded. At this time, the basic block may be called a Coding Tree Unit. A coding tree unit may be defined as the largest size coding unit allowed by a sequence or slice. Information regarding whether the coding tree unit is square or non-square or the size of the coding tree unit may be signaled through a sequence parameter set, a picture parameter set, or a slice header. Coding tree units can be divided into partitions of smaller sizes. At this time, if the partition created by splitting the coding tree unit is referred to as depth 1, the partition created by splitting the partition of depth 1 may be defined as depth 2. That is, a partition created by dividing a partition with depth k within a coding tree unit can be defined as having depth k+1.

Figure 3 is a diagram illustrating a partition mode that can be applied to a coding block when the coding block is encoded by intra-prediction or inter-picture prediction. A partition of arbitrary size created as a coding tree unit is divided is defined as a coding unit. can do. For example, Figure 3(a) shows that the coding unit is 2Nx2N in size. Coding units can be divided recursively or into basic units for performing prediction, quantization, transformation, or in-loop filtering. As an example, a partition of arbitrary size created as a coding unit is divided is defined as a coding unit, or a transform unit (TU: Transform Unit) or prediction unit, which is a basic unit for performing prediction, quantization, transformation, or in-loop filtering. It can be defined as (PU: Prediction Unit).

Alternatively, once the coding block is determined, a prediction block having the same size as the coding block or a size smaller than the coding block can be determined through prediction division of the coding block. Prediction division of a coding block can be performed by a partition mode (Part_mode) indicating the division type of the coding block. The size or shape of the prediction block may be determined according to the partition mode of the coding block. The division type of the coding block can be determined through information specifying one of the partition candidates. At this time, partition candidates that can be used by the coding block may include an asymmetric partition type (eg, nLx2N, nRx2N, 2NxnU, 2NxnD) depending on the size, shape, or encoding mode of the coding block. As an example, a partition candidate that a coding block can use may be determined according to the encoding mode of the current block. For example, when a coding block is encoded by inter-prediction, any one of eight partition modes may be applied to the coding block, as in the example shown in FIG. 3(b). On the other hand, when the coding block is encoded by intra-picture prediction, PART_2Nx2N or PART_NxN among the eight partition modes in FIG. 3 (b) may be applied to the coding block.

PART_NxN can be applied when the coding block has a minimum size. Here, the minimum size of the coding block may be predefined in the encoder and decoder. Alternatively, information about the minimum size of a coding block may be signaled through a bitstream. As an example, the minimum size of a coding block is signaled through a slice header, and accordingly, the minimum size of a coding block may be defined for each slice.

As another example, partition candidates that can be used by a coding block may be determined differently depending on at least one of the size or shape of the coding block. As an example, the number or type of partition candidates that a coding block can use may be determined differently depending on at least one of the size or shape of the coding block.

Alternatively, the type or number of asymmetric partition candidates among partition candidates that a coding block can use may be limited depending on the size or shape of the coding block. As an example, the number or type of asymmetric partition candidates that a coding block can use may be determined differently depending on at least one of the size or shape of the coding block.

Generally, the size of the prediction block can range from 64x64 to 4x4. However, when a coding block is encoded with inter-screen prediction, the prediction block may not have a size of 4x4 to reduce memory bandwidth when performing motion compensation.

Using partition mode, it is also possible to recursively partition coding blocks. That is, the coding block can be divided according to the partition mode indicated by the partition index, and each partition created as the coding block is divided can be defined as a coding block.

Hereinafter, a method for recursively dividing a coding unit will be described in more detail. For convenience of explanation, hereinafter, it is assumed that coding tree units are also included in the category of coding units. That is, in an embodiment described later, the coding unit may refer to a coding tree unit or may mean a coding unit created as the coding tree unit is divided. Additionally, when a coding block is divided recursively, the 'partition' created as the coding block is divided may be understood to mean a 'coding block'.

A coding unit may be divided by at least one line. At this time, the line dividing the coding unit may have a predetermined angle. Here, the predetermined angle may be a value within the range of 0 degrees to 360 degrees. For example, a 0 degree line may mean a horizontal line, a 90 degree line may mean a vertical line, and a 45 degree or 135 degree line may mean a diagonal line.

When a coding unit is divided by a plurality of lines, the plurality of lines may all have the same angle. Alternatively, at least one of the plurality of lines may have a different angle from other lines. Alternatively, the coding tree unit or a plurality of lines dividing the coding unit may be set to have a predefined angle difference (eg, 90 degrees).

Information about lines dividing a coding tree unit or a coding unit may be defined and encoded in a partition mode. Alternatively, information about the number of lines, direction, angle, position of the line within the block, etc. may be encoded.

For convenience of explanation, in the embodiment described later, it is assumed that the coding tree unit or coding unit is divided into a plurality of coding units using at least one of a vertical line and a horizontal line.

Assuming that partitioning of the coding unit is performed based on at least one of a vertical line or a horizontal line, the number of vertical or horizontal lines partitioning the coding unit may be at least one. For example, a coding tree unit or a coding unit can be divided into two partitions using one vertical line or one horizontal line, or a coding unit can be divided into three partitions using two vertical lines or two horizontal lines. . Alternatively, one vertical line and one horizontal line may be used to divide the coding unit into four partitions whose length and width are 1/2.

When dividing a coding tree unit or a coding unit into a plurality of partitions using at least one vertical line or at least one horizontal line, the partitions may have uniform sizes. Alternatively, one partition may have a different size from the remaining partitions, or each partition may have a different size.

In embodiments described later, it is assumed that the coding unit is divided into four partitions as quad tree-based division, and that the coding unit is divided into two partitions is assumed to be binary tree-based division. Additionally, it is assumed that the coding unit is divided into three partitions as a triple tree-based division. Additionally, it is assumed that division by applying at least two of the above division methods is multi-tree based division.

In the drawings described later, it will be shown that a predetermined number of vertical lines or a predetermined number of horizontal lines are used to divide the coding unit, but by using a larger number of vertical lines or a larger number of horizontal lines than shown, the coding unit Dividing into a larger number of partitions than shown or into a smaller number of partitions than shown will also be included within the scope of the present invention.

FIG. 4 is a diagram illustrating a partition type in which quad tree and binary tree partitioning is allowed, as an embodiment to which the invention is applied.

The input video signal is decoded in units of predetermined blocks, and the basic unit for decoding the input video signal is called a coding block. A coding block can be a unit that performs intra/inter prediction, transformation, and quantization. Additionally, a prediction mode (eg, intra-prediction mode or inter-screen prediction mode) is determined on a coding block basis, and prediction blocks included in the coding block may share the determined prediction mode. Coding blocks can be square or non-square blocks of any size ranging from 8x8 to 64x64, or square or non-square blocks with sizes of 128x128, 256x256 or larger.

Specifically, the coding block may be hierarchically divided based on at least one of a quad tree and a binary tree. Here, the quad tree-based splitting is a method in which a 2Nx2N coding block is split into four NxN coding blocks (Figure 4(a)), and the binary tree-based splitting is a method in which one coding block is split into two coding blocks. Each can mean something. Even if binary tree-based segmentation is performed, square coding blocks may exist at lower depths.

Binary tree-based partitioning may be performed symmetrically or asymmetrically. Additionally, coding blocks divided based on a binary tree may be square blocks or non-square blocks such as rectangles. As an example, the partition type that allows binary tree-based division is symmetric 2NxN (horizontal non-square coding unit) or Nx2N (vertical non-square coding unit), as shown in the example shown in FIG. 4 (b). ) can be. Additionally, as an example, the partition type that allows binary tree-based partitioning may include at least one of asymmetric nLx2N, nRx2N, 2NxnU, or 2NxnD, as shown in the example shown in FIG. 4 (c). .

Binary tree-based partitioning may only allow one of symmetric or asymmetric partitions. In this case, configuring the coding tree unit with square blocks may correspond to quad tree CU partitioning, and configuring the coding tree unit with symmetric non-square blocks may correspond to binary tree CU partitioning. Constructing a coding tree unit into square blocks and symmetric non-square blocks may correspond to quad and binary tree CU partitioning.

Hereinafter, the partitioning method based on the quad tree and binary tree is called QTBT (Quad-Tree & Binary-Tree) partition.

As a result of division based on quad tree and binary tree, coding blocks that are no longer divided can be used as prediction blocks or transformation blocks. That is, in the QTBT (Quad-Tree & Binary-Tree) partitioning method based on quad tree and binary tree, the coding block can be a prediction block, and the prediction block can be a transformation block. For example, when using the QTBT segmentation method, a predicted image can be generated in units of coding blocks, and a residual signal, which is the difference between the original image and the predicted image, can be converted in units of coding blocks. Here, generating a prediction image in units of coding blocks may mean that motion information is determined based on the coding block, or one intra prediction mode is determined based on the coding block. Accordingly, the coding block may be encoded using at least one of skip mode, intra prediction, or inter prediction.

As another example, it is possible to divide the coding block and use a prediction block or transform block with a smaller size than the coding block.

In the QTBT partitioning method, BT can be set to allow only symmetric partitioning. However, even when the object and background are divided at the block boundary, if only symmetric binary segmentation is allowed, encoding efficiency may be lowered. Accordingly, in the present invention, in order to increase coding efficiency, a method of asymmetrically partitioning coding blocks will be described later as another embodiment. Asymmetric Binary Tree Partitioning refers to splitting a coding block into two smaller coding blocks. As a result of asymmetric binary tree partitioning, a coding block can be divided into two asymmetric coding blocks.

Binary tree-based partitioning may be performed on coding blocks for which quad-tree-based partitioning is no longer performed. Quad-tree-based partitioning may no longer be performed on coding blocks partitioned based on binary trees.

Additionally, the division of the lower depth may be determined dependent on the division type of the upper depth. For example, when binary tree-based partitioning is allowed at two or more depths, only binary tree-based partitioning of the same type as the binary tree partitioning form of the upper depth may be allowed at the lower depth. For example, if binary tree-based segmentation in the form of 2NxN is performed at the upper depth, binary tree-based segmentation in the form of 2NxN may also be performed at the lower depth. Alternatively, if binary tree-based partitioning in Nx2N format is performed at the upper depth, Nx2N binary tree-based partitioning may be allowed at lower depths.

Conversely, at lower depths, it is also possible to allow only binary tree-based partitioning in a form different from the binary tree partitioning form at higher depths.

For a sequence, slice, coding tree unit, or coding unit, only a specific type of binary tree-based partitioning may be restricted to be used. As an example, coding tree units may be restricted to allow only binary tree-based division in the form of 2NxN or Nx2N. The allowable partition type may be predefined in the encoder or decoder, or information regarding the allowable or unacceptable partition type may be encoded and signaled through a bitstream.

Figure 5 is an embodiment to which the present invention is applied, showing an example of hierarchically dividing a coding block based on quad tree and binary tree division.

As shown in FIG. 5, the first coding block 300 with a split depth of k may be divided into a plurality of second coding blocks based on a quad tree. For example, the second coding blocks 310 to 340 are square blocks with half the width and height of the first coding block, and the division depth of the second coding block can be increased to k+1.

The second coding block 310 with a split depth of k+1 may be divided into a plurality of third coding blocks with a split depth of k+2. Division of the second coding block 310 may be performed selectively using either a quot tree or a binary tree depending on the division method. Here, the division method may be determined based on at least one of information indicating quad tree-based division or information indicating binary tree-based division.

When the second coding block 310 is divided based on a quot tree, the second coding block 310 is divided into four third coding blocks 310a with a size of half the width and height of the second coding block, and the third coding block 310a The division depth can be increased to k+2. On the other hand, when the second coding block 310 is divided based on a binary tree, the second coding block 310 may be divided into two third coding blocks. At this time, each of the two third coding blocks is a non-square block whose width or height is half the size of the second coding block, and the division depth can be increased to k+2. The second coding block may be determined to be a horizontal or vertical non-square block depending on the division direction, and the division direction may be determined based on information about whether the binary tree-based division is vertical or horizontal.

Meanwhile, the second coding block 310 may be determined to be an end coding block that is no longer divided based on a quad tree or binary tree, and in this case, the corresponding coding block can be used as a prediction block or a transform block.

The third coding block 310a may be determined as an end coding block similar to the division of the second coding block 310, or may be additionally divided based on a quad tree or binary tree.

Meanwhile, the third coding block 310b divided based on the binary tree may be further divided into a vertical coding block 310b-2 or a horizontal coding block 310b-3 based on the binary tree, and the corresponding coding The division depth of a block can be increased to k+3. Alternatively, the third coding block 310b may be determined to be the terminal coding block 310b-1 that is no longer divided based on the binary tree, and in this case, the coding block 310b-1 may be used as a prediction block or transform block. You can. However, the above-described division process requires information about the size/depth of the coding block for which quad-tree-based division is allowed, information about the size/depth of the coding block for which binary tree-based division is allowed, or binary tree-based division is allowed. It may be performed limitedly based on at least one of information about the size/depth of a coding block that is not used.

The size that a coding block can have may be limited to a predetermined number, or the size of a coding block within a predetermined unit may have a fixed value. For example, the size of a coding block within a sequence or a size of a coding block within a picture may be limited to 256x256, 128x128, or 32x32. Information indicating the size of a coding block within a sequence or picture may be signaled through a sequence header or picture header.

As a result of partitioning based on quad tree and binary tree, the coding unit may be square or rectangular in shape.

Figure 6 is an embodiment to which the present invention is applied, showing an example of hierarchically partitioning a coding block based on quad tree and symmetric binary tree partitioning.

Figure 6 is a diagram illustrating an example in which only division based on a specific type, for example, a symmetric binary tree, is allowed. Figure 6(a) shows an example where only Nx2N binary tree-based division is allowed. For example, depth 1 coding block 601 can be split into two Nx2N blocks (601a, 601b) at depth 2, and depth 2 coding block 602 can be split into two Nx2N blocks (602a, 602b) at depth 3. .

Figure 6(b) shows an example where only 2NxN binary tree-based division is allowed. For example, the depth 1 coding block 603 can be split into two 2NxN blocks (603a, 603b) at depth 2, and also the depth 2 coding block 604 can be split into two 2NxN blocks (604a, 604b) at depth 3. .

Figure 6(c) shows an example of dividing a block divided into a symmetric binary tree again into a symmetric binary tree. For example, the depth 1 coding block 605 is divided into two Nx2N blocks (605a, 605b) at depth 2, and the depth 2 coding block 605a generated after the division is divided into two Nx2N blocks (605a1, 605b) at depth 3. 605a2) can be divided. The above partitioning method is equally applicable to 2NxN coding blocks generated by symmetric binary tree partitioning.

In order to implement the quad-tree or binary tree-based adaptive partitioning, information indicating quad-tree-based partitioning, information regarding the size/depth of the coding block for which quad-tree-based partitioning is allowed, and indicating binary tree-based partitioning information about the size/depth of coding blocks for which binary tree-based splitting is allowed, information about the size/depth of coding blocks for which binary tree-based splitting is not allowed, or whether the binary tree-based splitting is vertical, or Information about whether it is horizontally oriented can be used. As an example, quad_split_flag may indicate whether the coding block is split into four coding blocks, and binary_split_flag may indicate whether the coding block is split into two coding blocks. When a coding block is split into two coding blocks, is_hor_split_flag indicating whether the split direction of the coding block is vertical or horizontal may be signaled.

Additionally, for a coding tree unit or a predetermined coding unit, the number of times binary tree splitting is allowed, the depth at which binary tree splitting is allowed, or the number of depths at which binary tree splitting is allowed, etc. can be obtained. The information may be encoded in coding tree units or coding units and transmitted to the decoder through a bitstream.

As an example, the syntax 'max_binary_depth_idx_minus1' indicating the maximum depth at which binary tree division is allowed may be encoded/decoded through the bitstream. In this case, max_binary_depth_idx_minus1+1 may indicate the maximum depth at which binary tree division is allowed.

In addition, looking at the example of FIG. 6 (c) described above, the results of binary tree division are shown for coding units with a depth of 2 (e.g., 605a, 605b) and coding units with a depth of 3 (e.g., 605a1, 605a2). . Accordingly, information indicating the number of times the binary tree split within the coding tree unit was performed (e.g., twice), information indicating the maximum depth allowed for the binary tree split within the coding tree unit (e.g., depth 3), or information indicating the number of times the binary tree split within the coding tree unit was performed (e.g., 2 times). At least one of the information indicating the number of depths (e.g., 2, depth 2, and depth 3) permitted for binary tree division may be encoded/decoded through a bitstream.

As another example, at least one of the number of times binary tree division is allowed, the depth at which binary tree division is allowed, or the number of depths at which binary tree division is allowed may be obtained for each sequence and slice. As an example, the information may be encoded in units of sequences, pictures, or slices and transmitted through a bitstream. Accordingly, at least one of the number of binary tree divisions, the maximum depth at which binary tree division is allowed, or the number of depths at which binary tree division is allowed for the first slice and the second slice may be different. For example, in a first slice, binary tree splitting may be allowed only at one depth, while in a second slice, binary tree splitting may be allowed at two depths.

As another example, at least one of the number of times binary tree division is allowed, the depth at which binary tree division is allowed, or the number of depths at which binary tree division is allowed may be set differently depending on the temporal level identifier (Temporal_ID) of the slice or picture. there is. Here, the temporal level identifier (Temporal_ID) is used to identify each of a plurality of layers of the image with at least one scalability of view, spatial, temporal, or quality. will be.

Additionally, the use of Transform skip can be restricted in CUs partitioned using binary partitioning. Alternatively, in a non-square partitioned CU, transformskip may be applied only in at least one of the horizontal or vertical directions. Applying only the horizontal transform skip indicates performing only scaling and quantization without performing the transform in the horizontal direction, and performing transformation by specifying at least one transform such as DCT or DST in the vertical direction.

Likewise, applying only the vertical transform skip indicates performing transformation by specifying at least one transform, such as DCT or DST, in the horizontal direction, and only scaling and quantization without performing the transform in the vertical direction. The syntax hor_transform_skip_flag, which indicates whether to apply horizontal transform skip, and the syntax ver_transform_skip_flag, which indicates whether to apply vertical transform skip, may be signaled.

When applying transform skip to at least one of the horizontal or vertical directions, signaling may be performed in which direction to apply transform skip depending on the type of CU. Specifically, for example, in the case of a CU in the form of 2NxN. You can perform transform in the horizontal direction and apply transform skip in the vertical direction. In the case of an Nx2N type CU, you can also apply transform skip in the horizontal direction and perform transform in the vertical direction. Here, the transform may be at least one of DCT or DST.

For another example, in the case of a 2NxN type CU, transform can be performed in the vertical direction and transform skip can be applied in the horizontal direction, and in the case of an Nx2N type CU, transform skip can be applied in the vertical direction and transform in the horizontal direction. You can also perform . Here, the transform may be at least one of DCT or DST.

Figure 7 is an embodiment to which the present invention is applied and is a diagram showing a partition form in which asymmetric binary tree partitioning is allowed. A 2Nx2N coding block is two coding blocks with a width ratio of n:(1-n) or a height ratio of n. It can be divided into two coding blocks: :(1-n). Here, n can represent a real number greater than 0 and less than 1.

In Figure 7, for example, as asymmetric binary tree partitioning is applied to the coding blocks, two coding blocks (701, 702) with a width ratio of 1:3, or two coding blocks (703, 704) with a width ratio of 3:1, Alternatively, it is shown that two coding blocks (705, 706) with a height ratio of 1:3 or two coding blocks (707, 708) with a height ratio of 3:1 are generated.

Specifically, as a coding block of size WxH is divided in the vertical direction, a left partition with a width of 1/4W and a right partition with a width of 3/4W can be created. As shown above, a partition type in which the width of the left partition is smaller than the width of the right partition can be called an nLx2N binary partition.

As a coding block of size WxH is divided in the vertical direction, a left partition with a width of 3/4W and a right partition with a width of 1/4W may be created. As shown above, a partition type in which the width of the right partition is smaller than the width of the left partition can be called an nRx2N binary partition.

As a coding block of size WxH is divided in the horizontal direction, an upper partition with a height of 1/4H and a lower partition with a height of 3/4H can be created. As shown above, a partition type in which the height of the upper partition is smaller than the height of the lower partition can be called a 2NxnU binary partition.

As a coding block of size WxH is divided in the horizontal direction, an upper partition with a height of 3/4H and a lower partition with a height of 1/4H can be created. As shown above, a partition type in which the height of the lower partition is smaller than the height of the upper partition can be called a 2NxnD binary partition.

FIG. 7 illustrates a case where the width or height ratio between two coding blocks is 1:3 or 3:1, but the width or height ratio between two coding blocks generated by asymmetric binary tree partitioning is not limited to this. A coding block may be split into two coding blocks with a different width ratio or a different height ratio than shown in Figure 7.

When using asymmetric binary tree partitioning, the asymmetric binary partition type of the coding block can be determined based on information signaled through the bitstream. For example, the division type of the coding block includes information indicating the division direction of the coding block and the coding block. It may be determined based on information indicating whether the first partition created as a result of this division has a smaller size than the second partition.

Information indicating the division direction of the coding block may be a 1-bit flag indicating whether the coding block is divided in the vertical or horizontal direction. As an example, hor_binary_flag may indicate whether a coding block is divided in the horizontal direction. A value of hor_binary_flag of 1 may indicate that the coding block is divided in the horizontal direction, and a value of hor_binary_flag of 0 may indicate that the coding block is divided in the vertical direction. Alternatively, ver_binary_flag may be used, indicating whether the coding block is divided in the vertical direction.

Information indicating whether the first partition has a smaller size than the second partition may be a 1-bit flag. As an example, is_left_above_small_part_flag may indicate whether the size of the left or upper partition created as a coding block is divided is smaller than the right or lower partition. A value of is_left_above_small_part_flag of 1 means that the size of the left or top partition is smaller than the right or bottom partition, and a value of is_left_above_small_part_flag of 0 may mean that the size of the left or top partition is larger than the right or bottom partition. Alternatively, is_right_bottom_small_part_flag can be used, which indicates whether the size of the right or bottom partition is smaller than the left or top partition.

Alternatively, the sizes of the first partition and the second partition may be determined using information indicating the width ratio, height ratio, or area ratio between the first partition and the second partition.

A value of hor_binary_flag of 0 and a value of is_left_above_small_part_flag of 1 may indicate an nLx2N binary partition, and a value of hor_binary_flag of 0 and a value of is_left_above_small_part_flag of 0 may indicate an nRx2N binary partition. Additionally, a value of hor_binary_flag of 1 and a value of is_left_above_small_part_flag of 1 may indicate a 2NxnU binary partition, and a value of hor_binary_flag of 1 and a value of is_left_above_small_part_flag of 0 may indicate a 2NxnD binary partition.

As another example, the asymmetric binary partition type of the coding block may be determined by index information indicating the partition type of the coding block. Here, the index information is information signaled through a bitstream, and may be encoded with a fixed length (i.e., a fixed number of bits) or a variable length. As an example, Table 1 below shows the partition index for each asymmetric binary partition.

Asymetric partition index Binarization nLx2N 0 0 nRx2N One 10 2NxnU 2 100 2NxnD 3 111

Asymmetric binary tree partitioning may be used depending on the QTBT partitioning method. For example, when quad tree partitioning or binary tree partitioning is no longer applied to a coding block, whether to apply asymmetric binary tree partitioning to the coding block. can be decided. Here, whether to apply asymmetric binary tree partitioning to the coding block can be determined by information signaled through the bitstream. For example, the information may be a 1-bit flag 'asymmetric_binary_tree_flag', and based on the flag, it may be determined whether asymmetric binary tree division is applied to the coding block. Alternatively, the coding block may be divided into two blocks. When determined, it may be determined whether the division type is binary tree division or asymmetric binary tree division. Here, whether the division type of the coding block is binary tree division or asymmetric binary tree division can be determined by information signaled through the bitstream. For example, the information may be a 1-bit flag 'is_asymmetric_split_flag', and based on the flag, it may be determined whether the coding block is split symmetrically or asymmetrically.

As another example, different indexes may be assigned to the symmetric binary partition and the asymmetric binary partition, and depending on the index information, it may be determined whether the coding block is divided into a symmetric or asymmetric form. As an example, Table 2 shows an example in which different indexes are assigned to a symmetric binary partition and an asymmetric binary partition.

Binary partition index Binarization 2NxN (horizontal binary partition) 0 0 Nx2N (vertically oriented binary partition) One 10 nLx2N 2 110 nRx2N 3 1110 2NxnU 4 11110 2NxnD 5 11111

A coding tree block or coding block may be subdivided into a plurality of coding blocks through quad tree partitioning, binary tree partitioning, or asymmetric binary tree partitioning. As an example, FIG. 8 is a diagram showing an example in which a coding block is divided into a plurality of coding blocks using QTBT and asymmetric binary tree partitioning. Referring to Figure 9, it can be seen that asymmetric binary tree partitioning was performed in the depth 2 partitioning of the first grip, the depth 3 partitioning of the second picture, and the depth 3 partitioning of the third picture. Coding blocks divided through asymmetric binary tree partitioning may be restricted from further division. As an example, information related to a quad tree, binary tree, or asymmetric binary tree may not be encoded/decoded in a coding block generated through asymmetric binary tree partitioning. That is, for coding blocks generated through asymmetric binary tree partitioning, a flag indicating whether to split the quad tree, a flag indicating whether to split the binary tree, a flag indicating whether to split the asymmetric binary tree, and the direction of splitting the binary tree or asymmetric binary tree. Encoding/decoding of syntax, such as a flag indicating a flag or index information indicating an asymmetric binary partition, may be omitted.

As another example, whether to allow binary tree partitioning may be determined dependent on whether to allow QTBT. As an example, asymmetric binary tree partitioning may be restricted from being used in pictures or slices in which a QTBT-based partitioning method is not used.

Information indicating whether asymmetric binary tree partitioning is allowed may be encoded and signaled on a block, slice, or picture basis. Here, information indicating whether asymmetric binary tree partitioning is allowed may be a 1-bit flag. As an example, a value of is_used_asymmetric_QTBT_enabled_flag of 0 may indicate that asymmetric binary tree partitioning is not used. If binary tree partitioning is not used on a picture or slice basis, is_used_asymmetric_QTBT_enabled_flag may not be signaled and its value may be set to 0.

Figure 8 is an embodiment to which the present invention is applied, illustrating the division form of a coding block based on quad tree and symmetric/asymmetric binary tree division.

Figure 8(a) shows an example in which splitting based on an asymmetric binary tree in the nLx2N format is allowed. For example, depth 1 coding block 801 is split into two asymmetric nLx2N blocks (801a, 801b) at depth 2, and also depth 2 coding block 801b is split into two symmetric Nx2N blocks (801b1, 801b2) at depth 3. An example of division is shown.

Figure 8(b) shows an example in which splitting based on an asymmetric binary tree in the nRx2N format is allowed. For example, the depth 2 coding block 802 is divided into two asymmetric nRx2N blocks 802a and 802b at depth 3.

Figure 8 (c) shows an example in which splitting based on an asymmetric binary tree in the form of 2NxnU is allowed. For example, the depth 2 coding block 803 shows an example of being divided into two asymmetric 2NxnU blocks (803a, 803b) at depth 3.

Based on the size, shape, division depth, or division type of the coding block, an allowable division type for the coding block may be determined. As an example, at least one of the partition type, partition type, or number of partitions allowed between the coding block generated by quad tree partition and the coding block generated by binary tree partition may be different.

For example, when a coding block is generated by quad-tree partitioning, quad-tree partitioning, binary tree partitioning, and asymmetric binary tree partitioning may all be allowed for the coding block. That is, if the coding block is generated based on quad tree partitioning, all partition types shown in Figure 10 can be applied to the coding block. For example, a 2Nx2N partition indicates a case where the coding block is no longer partitioned, and NxN indicates a case where a coding block is divided into a quad tree, and Nx2N and 2NxN may indicate a case where a coding block is divided into a binary tree. Additionally, nLx2N, nRx2N, 2NxnU, and 2NxnD may indicate a case where a coding block is divided into an asymmetric binary tree.

On the other hand, if the coding block is generated by binary tree partitioning, asymmetric binary tree partitioning may be restricted to the corresponding coding block. That is, if the coding block is generated based on binary tree division, application of the asymmetric partition type (nLx2N, nRx2N, 2NxnU, 2NxnD) among the partition types shown in FIG. 7 to the coding block may be limited.

Figure 9 is a flowchart of a coding block partitioning method based on quad tree and binary tree partitioning as an embodiment to which the present invention is applied.

It is assumed that the depth k coding block is divided into depth k+1 coding blocks. First, it is determined whether quad tree division is applied to the current block with depth k (S910). If quad tree partitioning is applied, the current block is partitioned into four square blocks (S920). On the other hand, if quad tree division is not applied, it is determined whether binary tree division is applied to the current block (S930). If binary tree splitting is also not applied, the current block becomes a depth k+1 coding block without splitting. As a result of the determination at S930, if binary tree partitioning has been applied to the current block, it is checked whether symmetric binary partitioning or asymmetric binary partitioning is applied (S940). According to the determination result at S940, the partition type applied to the current block is determined (S950). For example, the partition shape applied in step S950 may be any one of the shapes of FIG. 4(b) if it is symmetrical, or the shape of FIG. 4(c) if it is asymmetric. Through S950, the current block is divided into two depth k+1 coding blocks according to the determined partition type (S960).

Figure 10 is an embodiment to which the present invention is applied, showing as an example a syntax element included in a network abstraction layer (NAL) to which quad tree and binary tree partitioning is applied.

Compressed video to which the present invention is applied can be, for example, packetized in units of Network Abstract Layer (hereinafter referred to as 'NAL') and transmitted through a transmission medium. However, the present invention is not limited to NAL and can be applied to various data transmission methods to be developed in the future. For example, the NAL unit to which the present invention is applied includes a video parameter set (VPS), a sequence parameter set (SPS), a picture parameter set (PPS), and at least one slice set (Slice), as shown in FIG. 10. It can be included.

For example, Figure 10 shows syntax elements included in a sequence parameter set (SPS), but it is also possible to include syntax elements in a picture parameter set (PPS) or slice set (Slice). Additionally, for each syntax element, syntax elements to be commonly applied to the sequence unit or picture unit can be included in the sequence parameter set (SPS) or picture parameter set (PPS). On the other hand, it is desirable that syntax elements that apply only to the corresponding slice are included in the slice set (Slice). Therefore, it can be selected considering coding performance and efficiency.

In relation to this, the syntax elements to which quad tree and binary tree partitioning are applied are described as follows. Although it is possible to set all syntax elements shown in FIG. 10 as essential elements, it is also possible to selectively set dual syntax elements in consideration of coding efficiency and performance.

As an example, 'quad_split_flag' indicates whether a coding block is split into four coding blocks. 'binary_split_flag' may indicate whether a coding block is split into two coding blocks. When a coding block is split into two coding blocks, 'is_hor_split_flag' indicating whether the split direction of the coding block is vertical or horizontal may be signaled. “is_hor_split_flag = 1” can be defined as horizontal direction, and “is_hor_split_flag = 0” can be defined as vertical direction.

Additionally, as another alternative, 'isUseBinaryTreeFlag' indicates whether binary tree partitioning is applied to the current block, and as a syntax element indicating the division direction of the coding block, 'hor_binary_flag' indicates whether the coding block is divided in the horizontal direction. It can be expressed. For example, “hor_binary_flag = 1” may indicate that the coding block is divided in the horizontal direction, and “hor_binary_flag = 0” may indicate that the coding block is divided in the vertical direction. Alternatively, it can be set in the same way by using ver_binary_flag, which indicates whether the coding block is divided in the vertical direction, instead of 'hor_binary_flag'.

Additionally, 'max_binary_depth_idx_minus1' can be defined as a syntax element indicating the maximum depth at which binary tree division is allowed. For example, “max_binary_depth_idx_minus1 + 1” may indicate the maximum depth at which binary tree splitting is allowed.

Additionally, 'hor_transform_skip_flag' can be set as a syntax element indicating whether to apply horizontal transform skip, and 'ver_transform_skip_flag' can be set as a syntax element indicating whether to apply vertical transform skip.

Additionally, 'is_used_asymmetric_QTBT_enabled_flag' can be defined as a syntax element indicating whether asymmetric binary tree partitioning is allowed. For example, if “is_used_asymmetric_QTBT_enabled_flag = 1”, it may indicate that asymmetric binary tree partitioning was used, and if “is_used_asymmetric_QTBT_enabled_flag = 0”, it may indicate that asymmetric binary tree partitioning was not used. On the other hand, if binary tree partitioning is not used on a picture or slice basis, is_used_asymmetric_QTBT_enabled_flag may not be signaled and its value may be set to 0. Additionally, as another alternative, 'asymmetric_binary_tree_flag' can be used to indicate whether asymmetric binary tree partitioning is applied to the current block.

Additionally, as a syntax element indicating asymmetric binary tree division, 'is_left_above_small_part_flag' may indicate whether the size of the left or upper partition created as the coding block is divided is smaller than the right or lower partition. For example, if “is_left_above_small_part_flag = 1”, it means that the size of the left or top partition is smaller than the right or bottom partition, and if “is_left_above_small_part_flag = 0”, it means that the size of the left or top partition is larger than the right or bottom partition. It can mean something. Alternatively, instead of 'is_left_above_small_part_flag', you can use 'is_right_bottom_small_part_flag', which indicates whether the size of the right or bottom partition is smaller than the left or top partition.

In relation to this, it is possible to define an asymmetric binary partition form of a coding block by combining the above syntax elements. For example, if “hor_binary_flag = 0” and “is_left_above_small_part_flag =1”, it can be set to indicate an nLx2N binary partition, and if “hor_binary_flag = 0” and “is_left_above_small_part_flag = 0”, it can be set to indicate an nRx2N binary partition. Additionally, if “hor_binary_flag = 1” and “is_left_above_small_part_flag = 1”, it can indicate a 2NxnU binary partition, and if “hor_binary_flag = 1” and “is_left_above_small_part_flag = 0”, it can indicate a 2NxnD binary partition. Likewise, an asymmetric binary partition form can be indicated using a combination of 'ver_binary_flag' and 'is_right_bottom_small_part_flag'.

Additionally, as another alternative, it is possible to define an asymmetric binary partition form of the coding block by indicating the index of the above-described Table 1 by 'Asymetric_partition_index', or by indicating the index of the above-described Table 2 by 'Binary_partition_index'. do.

As seen in the above example, a coding unit (or coding tree unit) may be recursively divided by at least one vertical or horizontal line. As an example, quad tree partitioning can be summarized as a method of partitioning a coding block using horizontal and vertical lines, and binary tree partitioning can be summarized as a method of partitioning a coding block using horizontal or vertical lines. The partition form of the coding block that is divided into quad tree division and binary tree division is not limited to the examples shown in FIGS. 4 to 8, and extended partition forms other than those shown may be used. That is, the coding block may be recursively divided into a form different from that shown in FIGS. 4 to 8.

Figure 11 is another embodiment to which the present invention is applied, a diagram showing a partition type in which asymmetric quad tree partitioning is permitted.

When the current block is divided into a quad tree, at least one of the horizontal or vertical lines may divide the coding block in an asymmetric form. Here, asymmetry may mean that the heights of blocks divided by horizontal lines are not the same or the widths of blocks divided by vertical lines are not the same. For example, a horizontal line may divide a coding block in an asymmetrical form, while a vertical line may divide a coding block in a symmetrical form, and while a horizontal line may divide a coding block in a symmetrical form, a vertical line may divide a coding block in an asymmetrical form. It may be possible. Alternatively, the coding block may be divided in an asymmetric manner by both horizontal and vertical lines.

Figure 11 (a) shows a symmetrical quad-tree division form of a coding block, and (b) to (k) are diagrams showing an asymmetric quad-tree partition form of a coding block. Figure 11 (a) shows an example in which both horizontal and vertical lines are used for symmetrical division. Figures 11 (b) and (c) show examples where horizontal lines are used for symmetrical division, while vertical lines are used for asymmetrical division. Figures 11 (d) and (e) show examples where vertical lines are used for symmetrical division, while horizontal lines are used for asymmetrical division.

In order to specify the division type of the coding block, information related to the division type of the coding block may be encoded. Here, the information may include a first indicator indicating whether the division form of the coding block is symmetric or asymmetric. The first indicator may be encoded in blocks, or may be encoded in vertical or horizontal lines. As an example, the first indicator may include information indicating whether a vertical line is used for symmetric division and information indicating whether a horizontal line is used for symmetric division.

Alternatively, the first indicator may be encoded only for at least one of a vertical line or a horizontal line, and another segmentation form in which the first indicator is not encoded may be derived dependently by the first indicator. For example, another segmentation form in which the first indicator is not encoded may have a value opposite to that of the first indicator. That is, when the first indicator indicates that a vertical line is used for asymmetric division, the horizontal line may be set to be used for symmetric division opposite to the first indicator.

If the first indicator indicates asymmetric division, a second indicator may be additionally encoded for a vertical or horizontal line. Here, the second indicator may indicate at least one of the position of a vertical or horizontal line used for asymmetric division or a ratio between blocks divided by a vertical or horizontal line.

Quad tree division may be performed using a plurality of vertical lines or a plurality of horizontal lines. For example, it is possible to divide a coding block into four blocks by combining at least one of one or more vertical lines or one or more horizontal lines.

Figures 11 (f) to (k) are diagrams showing an example of asymmetrically dividing a coding block by combining a plurality of vertical/horizontal lines and one horizontal/vertical line.

Referring to Figures 11 (f) to (k), quad tree division divides a coding block into three blocks by two vertical lines or two horizontal lines, and divides any one of the three divided blocks into two blocks. This can be done by dividing. At this time, as in the example shown in FIGS. 11 (f) to (k), a block located in the middle of blocks divided by two vertical lines or two horizontal lines may be divided by one horizontal line or vertical line. In addition to the example shown, a block located on one boundary of a coding block may be divided by a single horizontal or vertical line. Alternatively, information (eg, partition index) for specifying which of the three partitions is divided may be signaled through a bitstream.

At least one of the horizontal or vertical lines may be used to divide the coding block in an asymmetric form, and the other line may be used to divide the coding block in a symmetric form. For example, a plurality of vertical or horizontal lines may be used to divide a coding block in a symmetrical form, or a single horizontal or vertical line may be used to divide a coding block in a symmetrical form. Alternatively, both horizontal and vertical lines may be used to divide the coding block in a symmetrical form or may be used to divide the coding block in an asymmetrical form.

For example, Figure 11(f) shows a partition form in which a central coding block is asymmetrically divided by two vertical lines and is divided into two symmetric coding blocks by a horizontal line. Additionally, FIG. 11(g) shows a partition form in which the middle coding block is asymmetrically divided by two horizontal lines and is divided into two symmetric coding blocks by a vertical line.

On the other hand, Figures 11(h) and (i) show a partition form in which the central coding block, which is asymmetrically divided by two vertical lines, is further divided into two asymmetric coding blocks by a horizontal line. In addition, Figures 11 (j) and (k) show a partition form in which the central coding block, which is asymmetrically divided by two horizontal lines, is further divided into two asymmetric coding blocks by a vertical line.

When combining multiple vertical/horizontal lines and one horizontal/vertical line, the coding block is divided into four partitions (i.e., four coding blocks) of at least two different sizes. In this way, dividing a coding block into four partitions of at least two different sizes can be called Triple Type Asymmetric Quad-treeCU partitioning.

Information about type 3 asymmetric quad tree partitioning may be encoded based on at least one of the above-described first indicator or second indicator. As an example, the first indicator may indicate whether the division form of the coding block is symmetric or asymmetric. The first indicator may be encoded in blocks, or may be encoded in vertical or horizontal lines. As an example, the first indicator may include information indicating whether one or more vertical lines are used for symmetric division and information indicating whether one or more horizontal lines are used for symmetric division.

Alternatively, the first indicator may be encoded only for at least one of a vertical line or a horizontal line, and another segmentation form in which the first indicator is not encoded may be derived dependently by the first indicator.

If the first indicator indicates asymmetric division, a second indicator may be additionally encoded for a vertical or horizontal line. Here, the second indicator may indicate at least one of the position of a vertical or horizontal line used for asymmetric division or a ratio between blocks divided by a vertical or horizontal line.

Figure 12 is a flowchart of a coding block partitioning method based on asymmetric quad tree partitioning as another embodiment to which the present invention is applied.

It is assumed that the depth k coding block is divided into depth k+1 coding blocks. First, it is determined whether quad tree division is applied to the current block with depth k (S1210). As a result of the determination in step S1210, if quad tree division is not applied, the current block becomes a depth k+1 coding block without division. If, as a result of the determination in step S1210, quad-tree partitioning has been applied, it is determined whether asymmetric quad-tree partitioning is applied to the current block (S1220). If asymmetric quad-tree partitioning is not applied and symmetric quad-tree partitioning is applied, the current block is divided into four square blocks (S1230).

On the other hand, if asymmetric quad-tree partitioning is applied, it is determined whether three types of asymmetric quad-tree partitioning are applied to the current block (S1240). If type 3 asymmetric quad tree partitioning is not applied, the current block is divided into four type 2 asymmetric blocks (S1250). At this time, it may be divided into any one of the partition types shown in Figures 11 (b) to (e) according to the partition information.

On the other hand, if type 3 asymmetric quad tree partitioning is applied, the current block is divided into 4 type 3 asymmetric blocks (S1260). At this time, it may be divided into any one of the partition types shown in Figures 11 (f) to (k) according to the partition information.

Figure 13 is another embodiment to which the present invention is applied, showing as an example a syntax element included in a network abstraction layer (NAL) to which asymmetric quad tree partitioning is applied. The NAL unit to which the present invention is applied may include, for example, a video parameter set (VPS), a sequence parameter set (SPS), a picture parameter set (PPS), and at least one slice set (Slice).

For example, Figure 13 shows syntax elements included in a sequence parameter set (SPS), but it is also possible to include syntax elements in a picture parameter set (PPS) or slice set (Slice). Additionally, for each syntax element, syntax elements to be commonly applied to the sequence unit or picture unit can be included in the sequence parameter set (SPS) or picture parameter set (PPS). On the other hand, it is desirable that syntax elements that apply only to the corresponding slice are included in the slice set (Slice). Therefore, it can be selected considering coding performance and efficiency.

The syntax element 'Is_used_asymmertic_quad_tree_flag' indicates whether quad tree partitioning is performed asymmetrically. Additionally, 'Is_used_triple_asymmertic_quad_tree_flag' indicates whether quad tree division is performed in three types of asymmetry. Therefore, if “Is_used_asymmertic_quad_tree_flag = 0”, it means symmetric quad tree division, so ‘Is_used_triple_asymmertic_quad_tree_flag’ is not signaled. On the other hand, if “Is_used_asymmertic_quad_tree_flag = 1” and “Is_used_triple_asymmertic_quad_tree_flag = 1”, it means 3 types of asymmetric quad tree splitting. Additionally, if “Is_used_asymmertic_quad_tree_flag = 1” and “Is_used_triple_asymmertic_quad_tree_flag = 0”, it means type 2 asymmetric quad tree splitting.

The syntax element 'hor_asymmetric_flag' indicates the direction of asymmetric quad tree partitioning. That is, when “Is_used_asymmertic_quad_tree_flag = 1”, it can indicate whether there is asymmetric division in the horizontal or vertical direction. For example, “hor_asymmetric_flag = 1” indicates asymmetry in the horizontal direction, and “hor_asymmetric_flag = 0” indicates asymmetry in the vertical direction. Also, as another alternative, it is also possible to use 'ver_asymmetric_flag'.

The syntax element 'width_left_asymmetric_flag' indicates another direction of asymmetric quad tree partitioning. That is, when “Is_used_asymmertic_quad_tree_flag = 1”, it can indicate whether there is asymmetric division in the left or right width direction. For example, if “width_left_asymmetric_flag' = 1”, it indicates asymmetry in the left direction of the width, and if “width_left_asymmetric_flag = 0”, it indicates asymmetry in the right direction of the width.

Additionally, the syntax element 'height_top_asymmetric_flag' indicates another direction of asymmetric quad tree partitioning. That is, when “Is_used_asymmertic_quad_tree_flag = 1”, it can indicate whether there is asymmetric division in the upper or lower height direction. For example, if “height_top_asymmetric_flag' = 1”, it indicates asymmetry in the upper direction of the height, and if “height_top_asymmetric_flag = 0”, it indicates asymmetry in the lower direction.

Additionally, the syntax element 'is_used_symmetric_line_flag' indicates whether or not the middle block is a symmetric block in the case of type 3 asymmetric quad tree partitioning. That is, when “Is_used_asymmertic_quad_tree_flag = 1” and “Is_used_triple_asymmertic_quad_tree_flag = 1”, it indicates whether the center block is symmetrically divided.

Therefore, it is possible to express the partition form shown in Figures 11 (a) to (k) through a combination of the above syntax elements. For example, if “Is_used_asymmertic_quad_tree_flag = 0”, it means that it is divided into 4 symmetrical blocks as shown in the partition form in Figure 11(a).

Additionally, if “Is_used_asymmertic_quad_tree_flag = 1” and “Is_used_triple_asymmertic_quad_tree_flag = 0”, it corresponds to any one of the partition types in Figures 11 (b) to (e). In this case, “hor_asymmetric_flag = 1” and “width_left_asymmetric_flag' = 1” means the partition type in Figure 11 (b). Additionally, if “hor_asymmetric_flag = 1” and “width_left_asymmetric_flag' = 0”, it means the partition type in Figure 11 (c). Additionally, if “hor_asymmetric_flag = 0” and “height_top_asymmetric_flag' = 1”, it means the partition type shown in Figure 11 (d). Additionally, if “hor_asymmetric_flag = 0” and “height_top_asymmetric_flag' = 0”, it means the partition type in Figure 11 (e).

Additionally, if “Is_used_asymmertic_quad_tree_flag = 1” and “Is_used_triple_asymmertic_quad_tree_flag = 1”, it corresponds to any one of the partition types in Figures 11 (f) to (k). In this case, if “is_used_symmetric_line_flag = 1”, it corresponds to any one of the partition types of Figures 11 (f) and (g), and if “is_used_symmetric_line_flag = 0”, it corresponds to any of the partition types of Figures 11 (h) to (k). It applies. In addition, if “is_used_symmetric_line_flag = 1” and “hor_asymmetric_flag = 1”, it can be defined as the partition type of Figure 11 (f), and if “hor_asymmetric_flag 0”, it can be defined as the partition type of Figure 11 (g).

Additionally, in the case of “Is_used_asymmertic_quad_tree_flag = 1”, “Is_used_triple_asymmertic_quad_tree_flag = 1” and “is_used_symmetric_line_flag = 0”, the partition type can be defined by “hor_asymmetric_flag”, “width_left_asymmetric_flag” and “height_top_asymmetric_flag”. For example, if “hor_asymmetric_flag = 1” and “height_top_asymmetric_flag = 0”, it means the partition type shown in Figure 11 (h). Additionally, if “hor_asymmetric_flag = 1” and “height_top_asymmetric_flag= 1”, it means the partition type in Figure 11 (i). Additionally, if “hor_asymmetric_flag = 0” and “width_left_asymmetric_flag' = 0”, it means the partition type of Figure 11 (j). Additionally, if “hor_asymmetric_flag = 0” and “width_left_asymmetric_flag' = 1”, it means the partition type shown in Figure 11 (k).

Additionally, as another alternative, it is also possible to display each of the partition types of FIGS. 11(a) to 11(k) as an index using 'asymmetric_quadtree_partition_index'.

Figure 14 is another embodiment to which the present invention is applied, a diagram showing a partition type in which quad tree and triple tree division is permitted.

Coding blocks may be hierarchically divided based on at least one of a quad tree and a triple tree. Here, the quad tree-based splitting is a method in which a 2Nx2N coding block is split into four NxN coding blocks (FIG. 14(a)), and the triple tree-based splitting is a method in which one coding block is split into three coding blocks. Each can mean something. Even if triple tree-based segmentation is performed, square coding blocks may exist at lower depths.

Triple tree-based partitioning may be performed symmetrically (Figure 14(b)) or asymmetrically (Figure 14(c)). Additionally, the coding block divided based on the triple tree may be a square block or a non-square block such as a rectangle. As an example, the partition type that allows triple tree-based partitioning is 2Nx(2N/3) (horizontal non-square coding unit), which is symmetric with the same width or height, as shown in the example shown in FIG. 14 (b). ) or (2N/3)x2N (vertically non-square coding unit). Additionally, as an example, a partition form that allows triple tree-based partitioning may be an asymmetric partition form that includes coding blocks with at least different widths or heights, as shown in the example shown in Figure 14 (c). there is. For example, in the asymmetric triple tree partition form shown in Figure 14 (c), at least two coding blocks 1401 and 1403 are defined to be located on both sides with the same width (or height) size and k value, and the remaining One block 1402 has a width (or height) of 2k and can be defined to be located between the blocks 1401 and 1403 of the same size.

In relation to this, the method of dividing the CTU or CU into three non-square sub-partitions as shown in FIG. 14 is called triple tree partitioning method (triple tree CU partitioning). CUs divided by triple tree partitioning may be restricted from performing additional partitioning.

Figure 15 is another embodiment to which the present invention is applied, a flowchart of a coding block partitioning method based on quad tree and triple tree partitioning.

It is assumed that the depth k coding block is divided into depth k+1 coding blocks. First, it is determined whether quad tree division is applied to the current block with depth k (S1510). If quad tree partitioning is applied, the current block is partitioned into four square blocks (S1520). On the other hand, if quad tree division is not applied, it is determined whether triple tree division is applied to the current block (S1530). If triple tree partitioning is not applied, the current block becomes a depth k+1 coding block without partitioning.

As a result of the determination in S1530, if triple tree division has been applied to the current block, it is checked whether symmetric triple division or asymmetric triple division is applied (S1540). According to the determination result in S1540, the partition type applied to the current block is determined (S1550). For example, the partition shape applied in step S1550 may be any one of the shapes in FIG. 14(b) if it is symmetrical, and any one of the shapes in FIG. 14(c) if it is asymmetric. Through step S1550, the current block is divided into three depth k+1 coding blocks according to the determined partition type (S1560).

Figure 16 is another embodiment to which the present invention is applied, showing as an example a syntax element included in a network abstraction layer (NAL) to which quad tree and triple tree partitioning is applied. The NAL unit to which the present invention is applied may include, for example, a video parameter set (VPS), a sequence parameter set (SPS), a picture parameter set (PPS), and at least one slice set (Slice).

For example, Figure 16 shows syntax elements included in a sequence parameter set (SPS), but it is also possible to include syntax elements in a picture parameter set (PPS) or slice set (Slice). Additionally, for each syntax element, syntax elements to be commonly applied to the sequence unit or picture unit can be included in the sequence parameter set (SPS) or picture parameter set (PPS). On the other hand, it is desirable that syntax elements that apply only to the corresponding slice are included in the slice set (Slice). Therefore, it can be selected considering encoding performance and efficiency.

The syntax element 'quad_split_flag' indicates whether the coding block is split into four coding blocks. 'triple_split_flag' may indicate whether a coding block is split into three coding blocks. When a coding block is split into three coding blocks, 'is_hor_split_flag' indicating whether the split direction of the coding block is vertical or horizontal may be signaled. “is_hor_split_flag = 1” can be defined as horizontal direction, and “is_hor_split_flag = 0” can be defined as vertical direction.

Additionally, as another alternative, 'isUseTripleTreeFlag' indicates whether triple tree partitioning is applied to the current block, and as a syntax element indicating the division direction of the coding block, 'hor_triple_flag' indicates whether the coding block is divided in the horizontal direction. It can be expressed. For example, “hor_triple_flag = 1” may indicate that the coding block is divided in the horizontal direction, and “hor_triple_flag = 0” may indicate that the coding block is divided in the vertical direction. Alternatively, it can be set in the same way by using ver_triple_flag, which indicates whether the coding block is divided in the vertical direction, instead of 'hor_triple_flag'.

Additionally, 'asymmetric_triple_tree_flag' can be defined as a syntax element indicating whether asymmetric triple tree partitioning is allowed. For example, “asymmetric_triple_tree_flag = 1” may indicate that asymmetric triple tree partitioning was used, and “asymmetric_triple_tree_flag = 0” may indicate that asymmetric triple tree partitioning was not used. On the other hand, if triple tree partitioning is not used on a picture or slice basis, 'asymmetric_triple_tree_flag' may not be signaled and its value may be set to 0.

Therefore, it is possible to express the partition form shown in Figures 14 (a) to (c) through a combination of the above syntax elements. For example, if “isUseTripleTreeFlag = 0”, it means that it is divided into four symmetrical blocks as shown in the partition form in Figure 14(a).

Additionally, if “isUseTripleTreeFlag = 1” and “asymmetric_triple_tree_flag = 0”, it corresponds to any one of the partition types in Figure 14 (b). At this time, if “hor_triple_flag = 1”, it is defined to mean the (2N/3)x2N partition type in Figure 14 (b). If “hor_triple_flag = 0”, it can be defined to mean the 2Nx (2N/3) partition type in Figure 14 (b).

Additionally, if “isUseTripleTreeFlag = 1” and “asymmetric_triple_tree_flag = 1”, it corresponds to any one of the partition types in Figure 14 (c). At this time, if “hor_triple_flag = 1”, it is defined to mean the left partition type in Figure 14 (c). If “hor_triple_flag = 0”, it can be defined to mean the right partition type of Figure 14 (c).

Additionally, as another alternative, it is also possible to display each of the partition shapes of FIGS. 14(a) to 14(c) as an index using 'asymmetric_tripletree_partition_index'.

Figure 17 is another embodiment to which the present invention is applied, a diagram showing a partition type in which multi-tree division is permitted.

A method of partitioning a CTU or CU using at least one of the aforementioned quad tree partitioning, binary partitioning, or triple tree partitioning is called multi tree partitioning. A CTU or CU can be partitioned using any of the N partitions in the examples described above. Specifically, for example, a CTU or CU can be partitioned using 9 partitions as shown in FIG. 17.

Partitioning may be performed on a sequence or picture basis using all of quad tree partitioning, binary tree partitioning, or triple tree partitioning, or a CTU or CU may be partitioned using any one or both of them.

Quad tree partitioning is used by default, and binary tree partitioning and triple tree partitioning can be used optionally. At this time, whether binary tree partitioning and/or triple tree partitioning is used may be signaled in the sequence header (sequence parameter set) or picture header (picture parameter set).

Alternatively, quad tree partitioning and triple tree partitioning can be used by default, and binary tree partitioning can be used optionally. For example, the syntax isUseBinaryTreeFlag can be signaled in the sequence header to indicate whether binary tree partitioning is used. If the isUseBinaryTreeFlag value is 1, the CTU or CU can be partitioned using binary tree partitioning in the current sequence. The syntax isUseTripleTreeFlag may be signaled in the sequence header to indicate whether triple tree partitioning is used. If the isUseTripleTreeFlag value is 1, the CTU or CU can be partitioned using triple tree partitioning in the current sequence header.

The partition type divided by multi-tree partitioning can be limited to, for example, the 9 basic partitions shown in Figures 17 (a) to (i). 17 (a) shows a quad tree partition form, (b) to (c) show a symmetric binary tree partition form, (d) to (e) show an asymmetric triple tree partition form, and (f) ~ (i) represents an asymmetric binary tree partition form. In relation to this, each partition type shown in FIG. 17 is the same as described above, so detailed description below will be omitted.

Additionally, as another alternative, it can be expanded to further include 12 partitions as shown in Figures 18 (j) to (u), for example, as a partition type divided by multi-tree partitioning. 18 (j) to (m) represent an asymmetric quad tree partition type, (n) to (s) represent three types of asymmetric quad tree partition types, and (t) to (u) represent a symmetric triple tree partition type. Express. In relation to this, each partition type shown in FIG. 18 is the same as described above, so detailed description below will be omitted.

Figure 19 is a flowchart of a coding block division method based on multi-tree division as another embodiment to which the present invention is applied.

It is assumed that the depth k coding block is divided into depth k+1 coding blocks. First, it is determined whether quad tree division is applied to the current block with depth k (S1910). If quad tree partitioning is not applied, it is determined whether binary tree partitioning is applied to the current block (S1950). Additionally, if binary tree partitioning is not applied, it is determined whether triple tree partitioning is applied to the current block (S1990). If, as a result of the determination in step S1950, triple tree partitioning is not applied, the current block becomes a depth k+1 coding block without partitioning.

Here, as a result of the determination in step S1910, if quad tree division is applied, it is checked whether symmetric or asymmetric quad tree division is performed (S1920). Afterwards, the partition information is checked to determine the block partition type of the current block (S1930), and the current block is divided into four blocks according to the determined partition type (S1940). For example, when a symmetrical quad tree is applied, it is divided in the partition format shown in Figure 17 (a). Additionally, when an asymmetric quad tree is applied, it is divided into one of the partition types shown in Figures 18 (j) to (m). Alternatively, when a three-type asymmetric quad tree is applied, it is divided into one of the partition types shown in Figures 18 (n) to (s). However, as described above, if only the basic partition type of FIG. 17 is applied as the multi-tree partition type, only the symmetrical square block of FIG. 17 (a) can be applied without determining whether the quad tree is asymmetric.

Additionally, as a result of the determination in step S1950, if binary tree division is applied, it is checked whether symmetric or asymmetric binary tree division is performed (S1960). Afterwards, the partition information is checked to determine the block partition type of the current block (S1970), and the current block is divided into two blocks according to the determined partition type (S1980). For example, when a symmetric binary tree is applied, it is divided into one of the partition types shown in Figures 17 (b) and (c). Additionally, when an asymmetric binary tree is applied, it is divided into one of the partition types shown in Figures 17 (f) to (i).

Additionally, as a result of the determination in step S1990, if triple tree division is applied, it is checked whether symmetric or asymmetric triple tree division is performed (S1960). Afterwards, the partition information is checked to determine the block partition type of the current block (S1970), and the current block is divided into three blocks according to the determined partition type (S1980). For example, when an asymmetric triple tree is applied, it is divided into one of the partition types shown in Figure 17 (d) and (e). Additionally, when a symmetric binary tree is applied, it is divided into one of the partition types shown in Figures 18 (t) to (u). However, as described above, if only the basic partition form of FIG. 17 is applied to the multi-tree partition form, it is not determined whether the triple tree is asymmetric, and the predefined asymmetric triple block of 17 (d) and (e) is used. It can only be applied.

. As a syntax element expressing multi-tree partitioning, 'is_used_Multitree_flag', which indicates whether multi-tree partitioning, can be defined. Additionally, it is possible to use the syntax elements shown and described in FIGS. 10, 13, and 16 described above as information for determining the multi-tree partitioner type.

Figure 20 is another embodiment to which the present invention is applied, and is shown to explain transform block coding indicator information of a transform block corresponding to a coding block divided by multi-tree division.

The transform unit 130 and quantization unit 135 described above in FIG. 1 may generate residual coefficients by performing transformation and/or quantization on the residual signal based on a predetermined block unit for transformation and/or quantization. . Hereinafter, the residual coefficient may be referred to as a quantized transform coefficient or transform coefficient. The predetermined block unit may be defined differently for each component of the residual signal (eg, luminance component, chrominance component). The residual coefficient can be encoded/decoded in independent block units corresponding to the luminance component (Luma), the chrominance component Cb, and the chrominance component Cr. At this time, the basic block that performs conversion is called the “conversion block” or “conversion unit” described above. Transform blocks can be square or non-square.

Specifically, for example, a square-type conversion block such as a 4x4 conversion block, an 8x8 conversion block, a 16x16 conversion block, a 32x32 conversion block, and a 64x64 conversion block, as well as a 4x8 conversion block, an 8x4 conversion block, an 8x16 conversion block, a 16x8 conversion block, and a 16x32 conversion block. Transformation encoding/decoding can be performed using non-square transform blocks such as transform blocks, 32x16 transform blocks, 32x64 transform blocks, 64x32 transform blocks, 4x16 transform blocks, 4x32 transform blocks, and 8x32 transform blocks.

As described above, the CU determined through multi-tree partitioning can be used as a transform block. Alternatively, the transform block may be determined by performing additional partitioning on the corresponding CU, or the transform block may be determined by merging a plurality of CUs divided through multi-tree partitioning. This may be based on the minimum size of the transform block determined by the encoder/decoder, or it may be based on the minimum block unit for transform coefficient scanning.

Referring to FIG. 20, for example, a coding block or coding tree block 2010 may be divided into a plurality of coding blocks according to the multi-tree partitioning method described above. Additionally, each divided coding block has at least one corresponding transform block. For example, FIG. 20 shows a case where the divided coding block 2011 includes an 8x8 transform block 2011a, and the divided coding block 2012 includes two 4x8 transform blocks 2012a and 2012b.

In the decoding step, a residual signal can be generated by performing inverse quantization and/or inverse transformation on the quantized and/or transformed residual coefficients, and this process is called residual coefficient decoding or transformation coefficient decoding.

In relation to this, it can be defined by signaling the transform block coding indicator (rqt_root_cbf) as a syntax element indicating whether there is at least one valid transform coefficient other than '0' belonging to the transform blocks (2011a, 2012a, 2012b). For example, if “rqt_root_cbf = 1”, it is defined to indicate that there is at least one valid non-zero conversion coefficient in the conversion block. On the other hand, if “rqt_root_cbf = 0”, all conversion coefficients in the conversion block are It is defined as indicating that the transform coefficient has the value of '0'. Therefore, it is possible to selectively decide whether to decode the transform coefficient in the transform block according to the value of the signaled transform block coding indicator (rqt_root_cbf).

Figures 21 and 22 are another embodiment to which the present invention is applied, showing an image decoding method using transform block coding indicator information of a transform block.

First, referring to FIG. 21, a decoder (eg, 200) receives an encoded bitstream and parses syntax elements included in the bitstream (S2110). The parsed syntax element includes all syntax elements for video signal decoding. In particular, syntax elements for the above-described multi-tree partitioning and syntax elements related to transform block decoding to be described later are included.

Among the syntax elements, the transform block coding indicator (rqt_root_cbf) flag value is detected and confirmed (S2120). That is, when the rqt_root_cbf value is '1', transform coefficient decoding within the transform block is performed (S2130). On the other hand, when the rqt_root_cbf value is '0', decoding of the transform coefficient within the transform block is not performed, and the transform coefficient within the corresponding transform block is set to a predetermined value (S2140). For example, if the rqt_root_cbf value is '0', all transform coefficients in the transform block can be set to '0'.

Alternatively, referring to FIG. 22, the decoder (eg, 200) receives the encoded bitstream and parses syntax elements included in the bitstream (S2210). The parsed syntax element includes all syntax elements for video signal decoding. In particular, the parsed syntax element includes not only the syntax elements and transform block syntax elements for multi-tree partitioning described above, but also prediction mode information corresponding to the coding block. In relation to this, the transform block coding indicator rqt_root_cbf can be limited to use only when the prediction block corresponding to the transform block is encoded by inter prediction.

Therefore, it is checked whether the prediction block is inter prediction (S2220), and if the prediction block is not inter prediction, decoding is performed without detecting the transform block coding indicator rqt_root_cbf information. On the other hand, if the prediction block is inter prediction, the transform block coding indicator rqt_root_cbf information is detected and decoding is performed in the same manner as the flowchart of FIG. 21 (S2230). That is, when the rqt_root_cbf value is '1', transform coefficient decoding within the transform block is performed (S2240). On the other hand, when the rqt_root_cbf value is '0', decoding of the transform coefficient within the transform block is not performed, and the transform coefficient within the corresponding transform block is set to a predetermined value, for example, '0' (S2250).

In relation to this, the step of performing transform coefficient decoding within a transform block by steps S2130 and S2240 uses “cbf_cb”, “cbf_cr”, and “cbf_luma” values as syntax elements corresponding to the corresponding transform block or coding block. Thus, decryption can be performed. Here, “cbf_cb” refers to a syntax element indicating whether a conversion coefficient of the color difference component Cb that is not ‘0’ exists, and “cbf_cr” refers to a syntax element that indicates whether a conversion coefficient of the color difference component Cr that is not ‘0’ exists, , “cbf_luma” refers to a syntax element that indicates whether a conversion coefficient for a luminance component other than ‘0’ exists.

Hereinafter, an encoding method or signaling method in which the syntax elements (“rqt_root_cbf”, “cbf_cb”, “cbf_cr”, and “cbf_luma”) are included in the encoded bitstream will be described.

Figures 23 to 26 show another embodiment to which the present invention is applied and illustrate an image encoding method using transform block coding indicator information of a transform block. In particular, it shows a method of signaling syntax elements related to transform block decoding.

Referring to FIG. 23, first, the rqt_root_cbf value is signaled (S2310). The rqt_root_cbf value is signaled by checking whether at least one valid transform coefficient other than '0' exists in the encoded transform block as described above. The signaled rqt_root_cbf value is checked (S2320). If the rqt_root_cbf value is '0', it terminates without signaling other syntax elements cbf_cb, cbf_cr, and cbf_luma. On the other hand, when the signaled rqt_root_cbf value is '1', the cbf_cb and cbf_cr values among the syntax elements are signaled (S2330, S2340). If both the signaled cbf_cb and cbf_cr values are not '0' (S2350), the other syntax element cbf_luma is signaled (S2360). On the other hand, if at least one of the signaled cbf_cb and cbf_cr values has the value '0', the syntax element cbf_luma is not signaled. Quit. Relatedly, if both the cbf_cb and cbf_cr values are not '0', the cbf_luma value may be set to a pre-defined default value (defualt value, ex, '1').

That is, according to the present invention, it is possible to determine whether to signal the syntax elements cbf_cb and cbf_cr values indicating the presence of color difference components Cb and Cr as lower syntax elements, depending on the value of the transform block coding indicator rqt_root_cbf, which is the upper syntax element. there is. Additionally, only when both the lower syntax element cbf_cb and cbf_cr values have '1', the syntax element cbf_luma indicating the presence of the luminance component in the transform block is signaled. Therefore, by eliminating the need to include unnecessary syntax elements in the bitstream through sequential signaling, overall coding efficiency can be improved.

Additionally, as another alternative to steps S2350 and S2360, if any of the signaled cbf_cb and cbf_cr values is not '0', the other syntax element cbf_luma may be signaled. Alternatively, the cbf_luma value may be signaled when at least one of the cbf_cb or cbf_cr values is '0'.

Or, conversely, the cbf_cb and/or cbf_cr values may be selectively signaled based on the cbf_luma value. For example, if the cbf_luma value is 0, the cbf_cb and/or cbf_cr value may be set to a pre-defined default value (defual value, ex, '0'). Therefore, cbf_cb and/or cbf_cr can be signaled only when the cbf_luma value is 1.

In relation to this, the unit in which cbf_luma is first signaled and the unit in which cbf_cb and/or cbf_cr are first signaled may be the same or different from each other. Alternatively, for one coding block (or transform block), the unit in which cbf_luma is finally signaled and the unit in which cbf_cb and/or cbf_cr are finally signaled may be the same or different from each other. That the signaling units are different may mean that at least one of the size, depth, or shape of the signaling units is different.

Figure 24 presents an encoding method for selectively signaling lower-order syntax elements according to the size of the coding block. That is, the syntax element rqt_root_cbf can be selectively encoded according to the size of the coding block. Additionally, signaling of the lower syntax elements cbf_cb, cbf_cr, and cbf_luma may be determined depending on the value of the upper syntax element rqt_root_cbf. That is, steps S2410 to S2460 of FIG. 24 consist of substantially the same process as steps S2310 to S2360 of FIG. 23 described above.

For example, referring to FIG. 24, the size of the coding block is compared with a preset reference size value (eg, MxN) (S2400). If the size of the coding block is larger than the standard size, the syntax elements rqt_root_cbf, cbf_cb, cbf_cr, and cbf_luma can be signaled sequentially through steps S2410 to S2460. On the other hand, if the size of the coding block is smaller than the standard size, the syntax elements cbf_cb, cbf_cr, and cbf_luma can be signaled through steps S2470 to S2490, respectively.

Here, the size of the coding block can be expressed as width, height, the sum of the width and height, the number of samples belonging to the coding block, etc. Additionally, the reference size value may be based on a predefined square NxN block size. However, the present invention is not limited to this.

Or, as another alternative, through step S2400, signaling of rqt_root_cbf may be restricted, conversely, when the size of the coding block is smaller than a preset reference size value.

Figure 25 presents an encoding method for selectively signaling lower-order syntax elements according to the type of coding block. That is, the syntax element rqt_root_cbf can be selectively encoded according to the type of coding block. Additionally, signaling of the lower syntax elements cbf_cb, cbf_cr, and cbf_luma may be determined depending on the value of the upper syntax element rqt_root_cbf. That is, steps S2510 to S2560 of FIG. 25 consist of substantially the same process as steps S2310 to S2360 of FIG. 23 described above.

That is, rqt_root_cbf may be selectively encoded depending on the type of coding block. For example, rqt_root_cbf may be selectively encoded depending on whether the coding block is a non-square coding block or a square coding block. Specifically, for example, in a square coding block, rqt_root_cbf can be selectively signaled based on the shape and prediction mode of the block, and in a non-square coding block, cbf_luma, cbf_cb, and cbf_cr can be signaled without signaling rqt_root_cbf. there is.

Specifically, referring to FIG. 25, it is confirmed whether the shape of the coding block is non-square (S2500). If the shape of the coding block is square, the syntax elements rqt_root_cbf, cbf_cb, cbf_cr, and cbf_luma can be signaled sequentially through steps S2510 to S2560. On the other hand, if the shape of the coding block is non-square, the syntax elements cbf_cb, cbf_cr, and cbf_luma can be signaled through steps S2570 to S2590, respectively.

Figure 26 presents an encoding method that selectively signals syntax elements according to the partitioning method according to the type of coding block. That is, the syntax element rqt_root_cbf can be selectively encoded according to the partitioning method of the coding block. Additionally, signaling of the lower syntax elements cbf_cb, cbf_cr, and cbf_luma may be determined depending on the value of the upper syntax element rqt_root_cbf. That is, steps S2610 to S2660 of FIG. 26 consist of substantially the same process as steps S2310 to S2360 of FIG. 23 described above.

That is, rqt_root_cbf can be selectively encoded according to the partitioning method of the coding block. For example, in a coding block divided by quad tree partitioning, rqt_root_cbf can be signaled, and in a coding block divided by binary tree partitioning or triple tree partitioning, cbf_luma, cbf_cb, and cbf_cr can be signaled without signaling rqt_root_cbf.

Specifically, referring to FIG. 26, it is confirmed whether the current coding block is divided by quad tree partitioning (S2600). If the current coding block is divided by quad tree partitioning, the syntax elements rqt_root_cbf, cbf_cb, cbf_cr, and cbf_luma can be signaled sequentially through steps S2610 to S2660. On the other hand, if the coding block is partitioned in a manner other than quad tree partitioning, the syntax elements cbf_cb, cbf_cr, and cbf_luma can be signaled through steps S2670 to S2690, respectively.

Figures 27 and 28 are another embodiment to which the present invention is applied, showing another image decoding method using transform block coding indicator information of a transform block. In relation to this, the decoding method of FIG. 27 corresponds to the encoding method of FIG. 23 described above, and the decoding method of FIG. 28 corresponds to the encoding method of FIGS. 24 to 26 described above.

Referring to FIG. 27, the decoder (eg, 200) receives the encoded bitstream and parses syntax elements included in the bitstream (S2710). The parsed syntax element includes all syntax elements for video signal decoding. In particular, it includes at least one syntax element rqt_root_cbf, cbf_cb, cbf_cr, and cbf_luma required for transform block decoding.

Among the syntax elements, the transform block coding indicator (rqt_root_cbf) flag value is detected and confirmed (S2720). That is, when the rqt_root_cbf value is '0', transform coefficient decoding within the transform block is not performed, and the residual signal within the corresponding transform block is set to a predetermined value (S2730). For example, if the rqt_root_cbf value is '0', all transform coefficients in the transform block can be set to '0'.

On the other hand, when the rqt_root_cbf value is '1', transform coefficient decoding within the transform block is performed. That is, when the parsed syntax element rqt_root_cbf value is '1', it is checked whether the parsed lower syntax element cbf_cb and cbf_cr values are both '0' (S2740). If both the parsed syntax element cbf_cb and cbf_cr values are not '0', another syntax element cbf_luma is detected (S2750). Thereafter, when the cbf_cb, cbf_cr, and cbf_luma values indicate the existence of each corresponding transform coefficient (ex. '1'), the corresponding transform coefficient is detected and decoding is performed (S2760). Alternatively, if both the cbf_cb and cbf_cr values are not '0', the cbf_luma value may be automatically set to a pre-defined default value (defualt value, ex, '1'). In this case, the cbf_luma value can be immediately set to '1' even if it is not parsed from the bitstream.

On the other hand, if at least one of the signaled cbf_cb and cbf_cr values has the value '0', it means that the syntax element cbf_luma is not signaled in the bitstream, so the corresponding conversion is performed without the need to detect cbf_luma. The coefficient is detected and decoding is performed (S2760).

Referring to FIG. 28, the decoder (eg, 200) receives the encoded bitstream and parses syntax elements included in the bitstream (S2810). The parsed syntax element includes all syntax elements for video signal decoding. In addition, in particular, the parsed syntax element includes syntax elements indicating the size, shape, and partitioning method of the coding block. In addition, according to the conditions of syntax elements regarding the size, shape, and partitioning method of the coding block, it includes at least one syntax element rqt_root_cbf, cbf_cb, cbf_cr, and cbf_luma required for transform block decoding.

Through the parsed syntax element, the size, shape, and/or partitioning method of the coding block can be confirmed. That is, through the parsed syntax element, the size, shape, and/or partitioning method of the coding block can be compared with a predefined reference value (S2810) to determine whether to detect the syntax element rqt_root_cbf. For example, through step S2810, the case where it is determined that the syntax element rqt_root_cbf exists can be defined as the first type, and the case where it is determined that the syntax element rqt_root_cbf does not exist can be defined as the second type.

For example, referring to the rqt_root_cbf signaling method of FIGS. 24 to 26 described above, if the current coding block is larger than the standard size, is square, or is a block divided by quad tree partitioning, the first type Correspondingly, the syntax element rqt_root_cbf is detected (S2850). Since step S2850(A) is the same as the process of performing steps S2720 to S2770 of FIG. 27 described above, the detailed description below is omitted.

On the other hand, if the current coding block does not correspond to the first type but to the second type, it means that the syntax element rqt_root_cbf is not included in the bitstream. Therefore, without detecting rqt_root_cbf, other syntax element cbf_cb, cbf_cr, and cbf_luma values are detected from the bitstream (S2830). Afterwards, when the detected syntax element cbf_cb, cbf_cr, and cbf_luma values indicate the existence of each corresponding transform coefficient (ex. '1'), the corresponding transform coefficient is detected and decoding is performed (S2840). Alternatively, if both the cbf_cb and cbf_cr values are not '0', the cbf_luma value may be automatically set to a pre-defined default value (defualt value, ex, '1'). In this case, the cbf_luma value can be immediately set to '1' even if it is not parsed from the bitstream.

Figure 29 is another embodiment to which the present invention is applied, dividing a transform block into a plurality of sub-transform blocks and illustrating sub-block coding indicator information provided for each sub-transform block.

When decoding a transform block, if the size of the transform block is larger than the standard size, for example, 4x4, there is at least one transform coefficient other than '0' for each subblock unit (e.g., 4x4), as shown in FIG. 29. Encoding and decoding efficiency can be improved by using the sub-block coding indicator “coded_sub_block_flag” (CSBF) value indicating the flag as a syntax element.

For example, after dividing the 8x8 transform block 2900 into four 4x4 sub-transform blocks (2901 to 2904), the value of the syntax element “coded_sub_block_flag” (hereinafter CSBF) is set for each sub-transform block. For example, if there is at least one coefficient other than '0' in the sub-transformation block, the CSBF value is set to '1' (2901, 2902, 2903), and if all coefficients in the sub-transformation block are '0' The CSBF value is set to '0' (2904).

Therefore, as the current transform block is divided into further sub-transform blocks and CSBF is applied to each sub-transform block, investment signaling and decoding are not required for the sub-block with “CSBF = 0”, resulting in further encoding. And decoding efficiency can be increased.

That is, the transform coefficients can be encoded based on a transform coefficient level flag (significant flag) indicating whether each transform coefficient in the block is '0' or not '0'. If Coded_sub_block_flag is non-0, there is at least one non-zero transform coefficient, and the transform coefficient levels of all transform coefficients in the block can be encoded. All transform coefficient levels within a block are called a transform coefficient level map (significant map). After encoding the significant map, the absolute value and sign of the non-zero transformation coefficient can be encoded.

Figures 30 to 32 are another embodiment to which the present invention is applied, showing various embodiments of dividing a transform block into a plurality of sub-transform blocks and a sub-block coding indicator for each divided sub-transform block.

When using the above-described binary partitioning or triple tree partitioning, at least one of the width or height of the coding block is smaller than a predetermined constant (for example, 4 or more) or the ratio of the width and height of the block (w/ A case may occur where h or h/w (where w represents the width of the coding block and h represents the height of the coding block) is smaller than a predetermined constant, and this is called a minimally asymmetric coding block.

For example, if at least one of the width or height of the coding block is less than 4, the CSBF flag may be signaled in at least one of 2x2 block units, 2x4 block units, and 2x8 block units.

Or, in a very small asymmetric coding block where the size of the coding block is 2xN, CSBF is signaled in at least one of (a) 2x2 block, (b) 2x4 block, or (c) 2x8 block, as shown in FIG. can do. Additionally, similarly, in the extremely asymmetric coding block where the size of the coding block is Nx2, as shown in FIG. 31, it is divided into at least one of (a) 8x2 block, (b) 4x2 block, or (c) 2x2 block. CSBF can be signaled.

In relation to this, a syntax element representing a unit for encoding CSBF in a very small asymmetric coding block may be signaled in the sequence header, picture header, or slice header. The unit encoding the CSBF may be encoded in the form of a minimum unit encoding the CSBF, a maximum unit, or a difference between the minimum and maximum units.

Alternatively, the CSBF flag may be signaled in units of samples with a predetermined number regardless of block type. Here, the predetermined number may be 4, 8, 16 or more. The encoder can determine the optimal number of units for encoding CSBF and encode it. The information regarding the number may be encoded in the form of the minimum/maximum sample number of the CSBF encoding unit or the difference between the minimum/maximum sample number.

For example, as shown in FIG. 32, when CU0 and CU2 are minimally asymmetric coding blocks in the form of 1x16, and CU1 is a minimally asymmetric coding block in the form of 2x16, CSBF can be signaled in units of 16 samples. Specifically, CSBF may be signaled in CU0 and CU2, and the CSBF flag may be signaled in 2x8 units in CU1.

Additionally, the size of the block that encodes the CSBF can be selectively set according to the size of the coding block. Specifically, for example, if the size of the coding block is larger than a preset reference value, CSBF may be signaled in NxN units, and if the size of the coding unit is smaller than the preset reference value, CSBF may be signaled in MxM units. You may. Here, N and M can be 2, 4, 8, 16 or more. N may be the same as M or may be a value greater than M. For example, if it is a 64x64 block, CSBF can be signaled in 8x8 units, and if it is a 32x32 block, CSBF can be signaled in 4x4 units. The block encoding the CSBF is not limited to the square form and may also be in a non-square form. In the case of a very small coding unit, CSBF may be signaled in at least one unit among 2x8, 8x2, 2x4, 4x2, or 2x2.

Alternatively, information indicating the size, depth, and/or shape of the block for which the CSBF is signaled may be signaled. The information may be signaled at at least one level among sequence, picture, slice, tile, CTU, CU, and TU. For example, an index indicating whether the size of the block for which CSBF is signaled in TU units is 4x4, 8x8, or 16x16 may be signaled. Or, for a TU of size 2Nx2N, if the depth value of the block for which CSBF is signaled is 0, CSBF is signaled in units of 2Nx2N, and if the depth value is 2, (N/2)x(N/2) CSBF may be signaled in units. Alternatively, the block unit in which CSBF is signaled may be determined by dividing the TU into a predetermined number of vertical/horizontal lines. At this time, information about the number and spacing of vertical/horizontal lines may be signaled.

Figure 33 shows an image encoding method using a sub-block coding indicator for each sub-transformation block. Referring to Figure 33, it is checked whether the size of the current coding block CU is larger than the reference size (S3310). For example, the standard size can be defined as PxP (ex, P=set to a predefined value among 8, 16, 32, 64, 126). If the current coding block size is smaller than the standard size, Sub-transform blocks are divided into MxM sizes, encoding is performed for each divided MxM sub-transform block unit, and then the CSBF#i (i=1,2...m) value is signaled (S3320). On the other hand, if the current coding block size is larger than the reference size, sub-transform blocks are divided into NxN (N>M) sizes, and coding is performed for each divided NxN sub-transform block unit, then CSBF#i (i=1 ,2…n) value is signaled (S3330).

Figure 34 is another embodiment to which the present invention is applied, showing an image encoding method using a sub-block coding indicator for each sub-transform block corresponding to a non-square coding block. Referring to FIG. 34, it is checked whether the current coding block CU is in a non-square form (S3410). If the current coding block is a square form, the encoding method (B: 3310, 3320, 3330) of FIG. 33 described above is used. Applicable (S3440). On the other hand, if the form of the current coding block CU is non-square, a new sub-transform block unit to which CSBF is applied is determined (S3430). That is, for non-square coding blocks, it is necessary to define a sub-transform block of a new size rather than using the NxN or MxM sub-transform block size defined in FIG. 33 as is. For example, the new sub-transformation block unit may be square (ex, 2x2, 4x4, 8x8,...) or non-square (ex, 2x4, 2x8, 4x2, 8x2,...). Alternatively, the new sub-transformation block unit may be determined based on the number of samples rather than a specific block type.

When the sub-transform block unit is determined through step S3430, encoding is performed for each determined sub-transform block, and the CSBF#i (i=1,2...n) value is signaled according to the encoded result (S3440).

Figure 35 is another embodiment to which the present invention is applied, showing an image encoding method using a sub-block coding indicator for each sub-transform block corresponding to a very asymmetric coding block. Referring to Figure 35, first check whether the current coding block CU is in a non-square form (S3510).

If the current coding block is in a square form, the encoding method (B: 3310, 3320, 3330) of FIG. 33 described above can be applied. On the other hand, if the form of the current coding block CU is non-square, it is further checked whether it corresponds to a minimally asymmetric coding block (S3520). For example, the extremely asymmetric coding block is a block in which at least one of the width or height of the coding block divided by binary partitioning or triple tree partitioning is smaller than a predetermined constant (for example, 4 or more) or It can be defined as a case where the width-to-height ratio (w/h or h/w, where w represents the width of the coding block and h represents the height of the coding block) is smaller than a predetermined constant. However, the present invention is not limited to this, and it is possible to define various types of extremely asymmetric coding blocks.

However, as another alternative, it is also possible to immediately perform the next step S3520 without confirming the non-square CU in step S3510. That is, for example, steps S3510 and S3520 may be integrated and applied as one process.

If the form of the current coding block CU does not correspond to a minimally asymmetric coding block, the coding method (B: 3310, 3320, 3330) of FIG. 33 described above can be applied (S3560). That is, as described in steps S3310, S3320, and S3330 of FIG. 33, the size of the CU is compared with the reference size, and according to the result, encoding is performed in units of MxM or NxN (N>M) sub-transformation blocks.

On the other hand, if the form of the current coding block CU is non-square and corresponds to a minimally asymmetric coding block, a new sub-transform block unit to which CSBF is applied is determined (S3530). That is, for extremely asymmetric coding blocks, it is necessary to define a sub-transform block of a new size rather than using the NxN or MxM sub-transform block size defined in FIG. 33 as is. For example, the new sub-transformation block unit may be square (ex, 2x2, 4x4, 8x8,...) or non-square (ex, 2x4, 2x8, 4x2, 8x2,...). Alternatively, the new sub-transformation block unit may be determined based on the number of samples rather than a specific block type. In addition, when determining a sub-transform block based on the number of samples, as shown in FIG. 32, one extremely asymmetric coding block (e.g., CU1 in FIG. 32) is divided into sub-transform blocks of different types including the same number of samples. It becomes possible.

When the sub-transform block unit is determined through step S3530, encoding is performed for each determined sub-transform block, and the CSBF#i (i=1,2...n) value is signaled according to the encoded result (S3540).

Figure 36 is another embodiment to which the present invention is applied, showing an image decoding method using a sub-block coding indicator for each sub-transform block corresponding to the coding block type.

Referring to FIG. 36, the decoder (eg, 200) receives the encoded bitstream and parses syntax elements included in the bitstream (S3610). The parsed syntax element includes all syntax elements for video signal decoding. In particular, the parsed syntax element includes syntax elements that indicate the size, shape, and partitioning method of the current coding block. Additionally, the parsed syntax element includes the sub-transform block coding indicator CSBF information under specific conditions.

Through the parsed syntax element, the size and/or shape of the current coding block can be compared with a predefined reference size or shape (S3620) to determine whether to detect the syntax element CSBF#i. For example, through step S3620, the case where it is determined that the syntax element CSBF#i exists in the current coding block is defined as the third type, and the case where it is determined that the syntax element CSBF#i does not exist is defined as the fourth type. It can be defined as a type. For example, referring to the CSBF#i signaling method of FIGS. 33 to 35 described above, if the current coding block is in a square shape larger than the standard size or is in a non-square shape regardless of the size, the third type is used. You can judge. However, the condition for determining whether the current coding block corresponds to the third type can be set to various conditions other than the above method depending on the definition between the encoder and decoder.

On the other hand, if the current coding block does not correspond to the third type but corresponds to the fourth type, it means that the transform block is not divided into sub-transform blocks and the syntax element CSBF#i is not included in the bitstream. . Therefore, without detecting CSBF#i, other syntax elements, such as the above-described rqt_root_cbf, cbf_cb, cbf_cr, and cbf_luma values, are detected from the bitstream to decode the transform coefficients in the transform block (S3630).

If the current coding block is determined to be a third type including the syntax element CSBF#i through step S3620, the sub-transformation block unit to which the syntax element CSBF#i is applied is confirmed (S3640). For example, the sub-transform block unit may be square, such as NxN or MxM (M<N), as described above, or may be non-square, such as 2x4, 2x8, 4x2, or 8x2. Or, for example, sub-transformation block units may be divided by the number of samples (e.g., 16 samples, 8 samples) rather than block units of the same size.

For example, if there are n sub-conversion block units to which the syntax element CSBF#i is applied through step S3640, set i=1 and then CSBF#i signaled for each sub-conversion block (i=1,2 …n) Check the values, i.e. CSBF#1, CSBF#2, CSBF#3,… ,CSBF#n, can be checked in that order.

For example, it is checked whether the signaled CSBF#1 value corresponding to the first sub-conversion block is '1' (S3650). If “CSBF#1 = 1”, it means that a transform coefficient other than ‘0’ exists in the first sub-transform block, and the transform coefficient is decoded (S3670). In step S3670 of decoding the transform coefficient, the signaled syntax element cbf_cb, cbf_cr, and cbf_luma values corresponding to each sub-transform block can be detected and utilized for decoding.

On the other hand, if “CSBF#1 = 0”, all transformation coefficient values in the first sub-transformation block are set to ‘0’ (S3660). The steps S3650, S3660, and S3670 are repeated until the CSBF#n value corresponding to the last sub-conversion block is detected (S3680, S3690).

Figure 37 is another embodiment to which the present invention is applied, showing as an example a syntax element included in the network abstraction layer (NAL) applied to the transform block.

The NAL unit to which the present invention is applied may include, for example, a video parameter set (VPS), a sequence parameter set (SPS), a picture parameter set (PPS), and at least one slice set (Slice). For example, Figure 37 shows syntax elements included in a slice set (Slice), but it is also possible to include the corresponding syntax elements in a sequence parameter set (SPS) or picture parameter set (PPS). In addition, for each syntax element, syntax elements that will be commonly applied to sequence units or picture units are included in the sequence parameter set (SPS) or picture parameter set (PPS), and syntax elements that apply only to specific slices are included in the slice set (Slice). It is also possible to differentiate them as much as possible. Therefore, this can be selected considering encoding performance and efficiency.

The syntax element rqt_root_cbf is a transformation block coding indicator. If “rqt_root_cbf = 1”, it indicates that at least one non-zero transformation coefficient exists in the transformation block. On the other hand, if “rqt_root_cbf = 0”, all transformations in the transformation block. Indicates that the coefficient has the value of '0'.

Additionally, the syntax elements cbf_cb, cbf_cr, and cbf_luma mean coding indicators of the chrominance component Cb, the chrominance component Cr, or the luminance component luma in the transform block.

In addition, the syntax element coded_sub_block_flag[i] (CSBF#i) is a sub-transform block coding indicator. If “coded_sub_block_flag[i] = 1”, at least one non-‘0’ transform coefficient exists in the i-th sub-transform block. Indicates. On the other hand, if coded_sub_block_flag[i] = 1”, it indicates that all transformation coefficients in the i-th sub-transformation block have the value of ‘0’.

Additionally, the syntax elements idx_coded_sub_block, width_coded_sub_block, and NumSample_in_coded_sub_block can be used as information to check the size or shape of the sub-conversion block.

For example, the syntax element idx_coded_sub_block can be used to index and indicate the sub-transform block to which CSBF#i is applied. Additionally, the syntax element width_coded_sub_block defines the width size of the sub-transform block to which CSBF#i is applied. In addition, the syntax element NumSample_in_coded_sub_block can be used to define the number of samples included in the sub-conversion block to which CSBF#i is applied.

Although the above-described embodiments are explained based on a series of steps or flowcharts, this does not limit the chronological order of the invention, and may be performed simultaneously or in a different order as needed. Additionally, in the above-described embodiment, each of the components (e.g., units, modules, etc.) constituting the block diagram may be implemented as a hardware device or software, and a plurality of components may be combined to form a single hardware device or software. It may be implemented. The above-described embodiments may be implemented in the form of program instructions that can be executed through various computer components and recorded on a computer-readable recording medium. The computer-readable recording medium may include program instructions, data files, data structures, etc., singly or in combination. Examples of computer-readable recording media include magnetic media such as hard disks, floppy disks and magnetic tapes, optical recording media such as CD-ROMs and DVDs, and magneto-optical media such as floptical disks. media), and hardware devices specifically configured to store and perform program instructions, such as ROM, RAM, flash memory, etc. The hardware device may be configured to operate as one or more software modules to perform processing according to the invention.

100: Encoder 110: Picture division unit
120, 230: Inter prediction unit 125, 235: Intra prediction unit
130: conversion unit 135: quantization unit
200: decoder 210: entropy decoder
215: rearrangement unit 220: inverse quantization unit
225: Inverse conversion unit

Claims (22)

Decoding a coding indicator of a transform block from a bitstream; and
When the coding indicator indicates that at least one valid transform coefficient exists in the transform block, determining, for a sub-transform block in the transform block, whether a valid transform coefficient exists in the sub-transform block, The size of the sub-transform block is equal to or smaller than the size of the transform block;
When it is determined that a valid transform coefficient exists in the sub-transform block, decoding the transform coefficient in the sub-transform block,
When the transform block is a minimally asymmetric block and when the transform block is not the minimally asymmetric block, at least one of the size and shape of the sub-transform block is different, and at least one of the width and height of the transform block is different. If is less than 4, the transform block is the minimal asymmetric block,
If the transform block is the minimal asymmetric block, the sub-transform block is determined to be a square of 2x2 size, or a non-square shape of 8x2 or 2x8. On the other hand, if the transform block is not the minimal asymmetric block, The sub-transformation block is characterized in that it is determined in a square shape of 4x4 size,
When the transform block is one of two partitions created by dividing a coding block, the coding indicator is not included in the bitstream. delete According to claim 1,
The image decoding method further includes determining whether to skip inverse transformation for the transform block,
When the transform block is one of two partitions created by dividing a coding block, skipping the inverse transform for the transform block is not allowed. According to clause 3,
Whether to split the coding block in a symmetrical or asymmetrical form is determined based on a first flag signaled through the bitstream,
When the first flag indicates that the coding block is divided in an asymmetric form, the coding block has a first partition with a size of 1/4 of the coding block and a second partition with a size of 3/4 of the coding block. Divided into partitions,
An image decoding method, wherein the transform block is the first partition. According to clause 4,
A video decoding method, characterized in that the positions of the first partition and the second partition are determined based on a second flag signaled through the bitstream. According to clause 5,
When the coding block is divided in the horizontal direction, it is determined whether the first partition is located at the top or bottom of the second partition based on the second flag,
When the coding block is divided in the vertical direction, it is determined whether the first partition is located on the left or right of the second partition based on the second flag. . Encoding transform coefficients within a transform block; and
Comprising the step of encoding a coding indicator indicating whether a valid transform coefficient is included in the transform block,
If there is at least one valid transform coefficient in the transform block, the transform coefficient is encoded for each sub-transform block, and the size of the sub-transform block is smaller than or equal to the size of the transform block,
When the transform block is a minimally asymmetric block and when the transform block is not the minimally asymmetric block, at least one of the size and shape of the sub-transform block is different, and at least one of the width and height of the transform block is different. If is less than 4, the transform block is the minimal asymmetric block,
If the transform block is the minimal asymmetric block, the sub-transform block is determined to be a square of 2x2 size, or a non-square shape of 8x2 or 2x8. On the other hand, if the transform block is not the minimal asymmetric block, The sub-transformation block is determined to be a square of 4x4 size,
When the transform block is one of two partitions created by dividing a coding block, encoding the coding indicator in the bitstream is omitted. delete According to clause 7,
The image encoding method further includes determining whether to skip transformation for the transform block,
When the transform block is one of two partitions created by dividing a coding block, skipping the transform for the transform block is not allowed. According to clause 9,
A first flag indicating whether the coding block is divided symmetrically or asymmetrically is explicitly encoded,
When the coding block is divided in an asymmetric form, the coding block is divided into a first partition with a size of 1/4 of the coding block and a second partition with a size of 3/4 of the coding block,
An image encoding method, wherein the transform block is the first partition. According to claim 10,
A video encoding method, characterized in that a second flag indicating the positions of the first partition and the second partition is explicitly encoded. Encoding transform coefficients within a transform block; and
Comprising the step of encoding a coding indicator indicating whether a valid transform coefficient is included in the transform block,
If there is at least one valid transform coefficient in the transform block, the transform coefficient is encoded for each sub-transform block, and the size of the sub-transform block is equal to or smaller than the size of the transform block,
When the transform block is a minimally asymmetric block and when the transform block is not the minimally asymmetric block, at least one of the size and shape of the sub-transform block is different, and at least one of the width and height of the transform block is different. If is less than 4, the transform block is the minimal asymmetric block,
If the transform block is the minimal asymmetric block, the sub-transform block is determined to be a square of 2x2 size, or a non-square shape of 8x2 or 2x8. On the other hand, if the transform block is not the minimal asymmetric block, The sub-transformation block is determined to be a square of 4x4 size,
When the transform block is one of two partitions created by dividing a coding block, encoding the coding indicator in the bitstream is omitted. A computer that records a bitstream encoded by an image encoding method. A readable recording medium. delete delete delete delete delete delete delete delete delete delete

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