KR20190113654A - Method and apparatus for processing video signal - Google Patents

Abstract

A method for decoding an image according to the present invention may include: a step of determining whether a coding block undergoes triple tree division; a step of determining the division direction of the coding block, if it is determined that the coding block undergoes triple tree division; and a step of dividing the coding block into three sub-coding blocks according to the determined division direction. At this time, a quad tree division method and a triple tree division method may not be allowed in the sub-coding block. It is possible to perform inter prediction efficiently.

Description

Method and apparatus for processing video signal {METHOD AND APPARATUS FOR PROCESSING VIDEO SIGNAL}

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

Recently, the demand for high resolution and high quality images such as high definition (HD) and ultra high definition (UHD) images is increasing in various applications. As the video data becomes higher resolution and higher quality, the amount of data increases relative to the existing video data. Therefore, when the video data is transmitted or stored using a medium such as a conventional wired / wireless broadband line, The storage cost will increase. High efficiency image compression techniques can be used to solve these problems caused by high resolution and high quality image data.

An inter-screen prediction technique for predicting pixel values included in the current picture from a picture before or after the current picture using an image compression technique, an intra prediction technique for predicting pixel values included in a current picture using pixel information in the current picture, Various techniques exist, such as an entropy encoding technique for allocating a short code to a high frequency of appearance and a long code to a low frequency of appearance, and the image data can be effectively compressed and transmitted or stored.

Meanwhile, as the demand for high resolution video increases, the demand for stereoscopic video content also increases as a new video service. There is a discussion about a video compression technology for effectively providing high resolution and ultra high resolution stereoscopic image contents.

An object of the present invention is to provide a method and apparatus for effectively dividing an encoding / decoding target block in encoding / decoding a video signal.

An object of the present invention is to provide a method and apparatus for dividing an encoding / decoding target block into a symmetrical or asymmetrical block in encoding / decoding a video signal.

An object of the present invention is to provide a method and apparatus for setting a prediction target or a transform target block to a size / shape different from a coding block in encoding / decoding a video signal.

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 above will be clearly understood by those skilled in the art from the following description. Could be.

The video signal decoding method and apparatus according to the present invention determine whether a coding block is triple tree split, and when it is determined that the coding block is triple tree split, determine a split direction of the coding block and determine the split According to the direction, the coding block may be divided into three sub-coding blocks. In this case, a quad tree division method and a triple tree division method may not be allowed in the sub-coded block.

The video signal encoding method and apparatus according to the present invention determine whether a coding block is triple tree split, and when it is determined that the coding block is triple tree split, determine a split direction of the coding block and determine the split According to the direction, the coding block may be divided into three sub-coding blocks. In this case, a quad tree division method and a triple tree division method may not be allowed in the sub-coded block.

In the video signal encoding / decoding method and apparatus according to the present invention, a binary tree partitioning method identical to the partitioning direction may not be allowed in a subblock having the largest size among the sub-coding blocks.

In the video signal encoding / decoding method and apparatus according to the present invention, the transform unit of the sub-coding blocks may be set identically to the coding block.

In the video signal encoding / decoding method and apparatus according to the present invention, when the size of at least one of the sub-coding blocks is the minimum size or the at least one splitting depth is the maximum splitting depth, the transform unit of the sub-coding blocks May be set to be the same as the coding block.

In the video signal encoding / decoding method and apparatus according to the present invention, the transform unit of the sub coding blocks may include the sub coding blocks.

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

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

According to the present invention, the encoding / decoding efficiency can be increased by dividing the encoding / decoding target block into symmetrical or asymmetrical blocks.

According to the present invention, the encoding / decoding efficiency can be increased by setting the prediction target or transform target block to a size / shape different from that of the coding block.

The effects obtainable in the present invention are not limited to the above-mentioned effects, and other effects not mentioned above may be clearly understood by those skilled in the art from the following description. will be.

1 is a block diagram illustrating an image encoding apparatus according to an embodiment of the present invention.
2 is a block diagram illustrating an image decoding apparatus according to an embodiment of the present invention.
3 is a diagram illustrating a partition mode candidate that can be applied to a coding block when the coding block is encoded by inter-screen prediction.
FIG. 4 illustrates an example in which coding blocks are hierarchically divided based on a tree structure according to an embodiment to which the present invention is applied.
FIG. 5 is a diagram illustrating a partition form in which binary tree based partitioning is allowed as an embodiment to which the present invention is applied.
6 illustrates an example in which only a specific type of binary tree based partitioning is allowed.
FIG. 7 is a diagram for describing an example in which information related to a binary tree split permission number is encoded / decoded according to an embodiment to which the present invention is applied.
8 is a flowchart illustrating a process of determining a split type of a coding unit based on hierarchically coded split information.
9 is a flowchart illustrating a process of determining a split type of a non-square type coding unit based on split information.
10 illustrates a partitioned form of a coding block based on asymmetric binary tree partitioning.
11 is a diagram illustrating an example in which a coding block is divided into a plurality of coding blocks based on quad tree splitting, symmetric binary tree splitting, and asymmetric binary tree splitting.
12 is a diagram illustrating a quad tree-based splitting form of a coding block.
FIG. 13 is a diagram illustrating a quad tree splitting form using a plurality of vertical lines or a plurality of horizontal lines.
14 shows a triple tree split form.
FIG. 15 is a diagram illustrating an additional partition form of a coding block generated as a result of triple tree partitioning.
16 illustrates a division type that may be applied to a coding block.
17 is a diagram illustrating a transform unit of triple tree partitioned coding blocks.
18 is a flowchart illustrating a process of obtaining a residual sample according to an embodiment to which the present invention is applied.

As the invention allows for various changes and numerous embodiments, particular embodiments will be illustrated in the drawings and described in detail in the written description. However, this is not intended to limit the present invention to specific embodiments, it should be understood to include all modifications, equivalents, and substitutes included in the spirit and scope of the present invention. In describing the drawings, similar reference numerals are used for similar elements.

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

When a component is referred to as being "connected" or "connected" to another component, it may be directly connected to or connected to that other component, but it may be understood that other components may exist in the middle. Should be. On the other hand, when a component is referred to as being "directly connected" or "directly connected" to another component, it should be understood that there is no other component in between.

The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting of the present invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this application, the terms "comprise" or "have" are intended to indicate that there is a feature, number, step, operation, component, part, or combination thereof described in the specification, and one or more other features. It is to be understood that the present invention does not exclude the possibility of the presence or the addition of numbers, steps, operations, components, components, or a combination thereof.

Hereinafter, with reference to the accompanying drawings, it will be described in detail a preferred embodiment of the present invention. Hereinafter, the same reference numerals are used for the same components in the drawings, and duplicate descriptions of the same components are omitted.

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

Referring to FIG. 1, the image encoding apparatus 100 may include a picture splitter 110, a predictor 120 and 125, a transformer 130, a quantizer 135, a realigner 160, and an entropy encoder. 165, an inverse quantizer 140, an inverse transformer 145, a filter 150, and a memory 155.

Each of the components shown in FIG. 1 is independently illustrated to represent different characteristic functions in the image encoding apparatus, and does not mean that each of the components is made of separate hardware or one software component unit. In other words, each component is included in each component for convenience of description, and at least two of the components may be combined into one component, or one component may be divided into a plurality of components to perform a function. Integrated and separate embodiments of the components are also included within the scope of the present invention without departing from the spirit of the invention.

In addition, some of the components may not be essential components for performing essential functions in the present invention, but may be optional components for improving performance. The present invention can be implemented including only the components essential for implementing the essentials of the present invention except for the components used for improving performance, and the structure including only the essential components except for the optional components used for improving performance. Also included in the scope of the present invention.

The picture dividing unit 110 may divide the input picture into at least one processing unit. In this case, the processing unit may be a prediction unit (PU), a transform unit (TU), or a coding unit (CU). The picture dividing 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 on a predetermined basis (eg, a cost function). You can select to encode the picture.

For example, one picture may be divided into a plurality of coding units. In order to split a coding unit in a picture, a recursive tree structure such as a quad tree structure may be used, and coding is divided into other coding units by using one image or a largest coding unit as a root. The unit may be split with as many child nodes as the number of split coding units. Coding units that are no longer split according to certain restrictions become leaf nodes. That is, when it is assumed that only square division is possible for one coding unit, one coding unit may be split into at most four other coding units.

Hereinafter, in an embodiment of the present invention, a coding unit may be used as a unit for encoding or may be used as a unit for decoding.

The prediction unit may be split in the form of at least one square or rectangle having the same size in one coding unit, or the prediction unit of any one of the prediction units split in one coding unit is different from one another. It may be divided to have a different shape and / or size than the unit.

When generating a prediction unit that performs intra prediction based on the coding unit, the intra prediction may be performed without splitting into a plurality of prediction units NxN when the prediction unit is not the minimum coding unit.

The predictors 120 and 125 may include an inter predictor 120 that performs inter prediction and an intra predictor 125 that performs intra prediction. Whether to use inter prediction or intra prediction on the prediction unit may be determined, and specific information (eg, an intra prediction mode, a motion vector, a reference picture, etc.) according to each prediction method may be determined. In this case, the processing unit in which the prediction is performed may differ from the processing unit in which the prediction method and the details are determined. For example, the method of prediction and the prediction mode may be determined in the prediction unit, and the prediction may be performed in the transform unit. The residual value (residual block) between the generated prediction block and the original block may be input to the transformer 130. In addition, prediction mode information and motion vector information used for prediction may be encoded by the entropy encoder 165 together with the residual value and transmitted to the decoder. When a specific encoding mode is used, the original block may be encoded as it is and transmitted to the decoder without generating the prediction block through the prediction units 120 and 125.

The inter prediction unit 120 may predict the prediction unit based on the information of at least one of the previous picture or the next picture of the current picture. In some cases, the inter prediction unit 120 may predict the prediction unit based on the information of the partial region in which the encoding is completed in the current picture. You can also predict units. The inter predictor 120 may include a reference picture interpolator, a motion predictor, and a motion compensator.

The reference picture interpolator may receive reference picture information from the memory 155 and generate pixel information of an integer pixel or less in the reference picture. In the case of luminance pixels, a DCT based 8-tap interpolation filter having different filter coefficients may be used to generate pixel information of integer pixels or less in units of 1/4 pixels. In the case of a chrominance signal, a DCT-based interpolation filter having different filter coefficients may be used to generate pixel information of an integer pixel or less in units of 1/8 pixels.

The motion predictor may perform motion prediction based on the reference picture interpolated by the reference picture interpolator. As a method for calculating a motion vector, various methods such as full search-based block matching algorithm (FBMA), three step search (TSS), and new three-step search algorithm (NTS) may be used. The motion vector may have a motion vector value of 1/2 or 1/4 pixel units based on the interpolated pixels. The motion prediction unit may predict the current prediction unit by using a different motion prediction method. As the motion prediction method, various methods such as a skip method, a merge method, an advanced motion vector prediction (AMVP) method, an intra block copy method, and the like may be used.

The intra predictor 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 that has performed inter prediction, and the reference pixel is a pixel that has performed inter prediction, the reference pixel of the block that has performed intra prediction around the reference pixel included in the block where the inter prediction has been performed Can be used as a substitute for information. That is, when the reference pixel is not available, the unavailable reference pixel information may be replaced with at least one reference pixel among the available reference pixels.

In intra prediction, a prediction mode may have a directional prediction mode using reference pixel information according to a prediction direction, and a non-directional mode using no directional information when performing prediction. The mode for predicting the luminance information and the mode for predicting the color difference information may be different, and the intra prediction mode information or the predicted luminance signal information used for predicting the luminance information may be utilized to predict the color difference information.

When performing intra prediction, if the size of the prediction unit and the size of the transform unit are the same, the intra prediction on the prediction unit is performed based on the pixels on the left of the prediction unit, the pixels on the upper left, and the pixels on the top. Can be performed. However, when performing intra prediction, if the size of the prediction unit is different from that of the transform unit, intra prediction may be performed using a reference pixel based on the transform unit. In addition, intra prediction using NxN division may be used only for a minimum coding unit.

The intra prediction method may generate a prediction block after applying an adaptive intra smoothing (AIS) filter to a reference pixel according to a prediction mode. The type of AIS filter applied to the reference pixel may be different. In order to perform the intra prediction method, the intra prediction mode of the current prediction unit may be predicted from the intra prediction mode of the prediction unit existing around the current prediction unit. When the prediction mode of the current prediction unit is predicted by using the mode information predicted from the neighboring prediction unit, if the intra prediction mode of the current prediction unit and the neighboring prediction unit is the same, the current prediction unit and the neighboring prediction unit using the predetermined flag information If the prediction modes of the current prediction unit and the neighboring prediction unit are different, entropy encoding may be performed to encode the prediction mode information of the current block.

Also, a residual block may include a prediction unit performing prediction based on the prediction units generated by the prediction units 120 and 125 and residual information including residual information that is a difference from an original block of the prediction unit. The generated residual block may be input to the transformer 130.

The transform unit 130 converts the residual block including residual information of the original block and the prediction unit generated by the prediction units 120 and 125 into a discrete cosine transform (DCT), a discrete sine transform (DST), and a KLT. You can convert using the same conversion method. Whether to apply DCT, DST, or KLT to transform the residual block may 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 by the transformer 130 into the frequency domain. 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 reordering unit 160.

The reordering unit 160 may reorder coefficient values with respect to the quantized residual value.

The reordering unit 160 may change the two-dimensional block shape coefficients into a one-dimensional vector form through a coefficient scanning method. For example, the reordering unit 160 may scan from DC coefficients to coefficients in the high frequency region by using a Zig-Zag scan method and change them into one-dimensional vectors. Depending on the size of the transform unit and the intra prediction mode, a vertical scan that scans two-dimensional block shape coefficients in a column direction instead of a zig-zag scan may be used, and a horizontal scan that scans two-dimensional block shape coefficients in a row direction. That is, according to the size of the transform unit and the intra prediction mode, it is possible to determine which scan method among the zig-zag scan, the vertical scan, and the horizontal scan is used.

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

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

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

The inverse quantizer 140 and the inverse transformer 145 inverse quantize the quantized values in the quantizer 135 and inversely transform the transformed values in the transformer 130. The residual value generated by the inverse quantizer 140 and the inverse transformer 145 is reconstructed by combining the prediction units predicted by the motion estimator, the motion compensator, and the intra predictor included in the predictors 120 and 125. You can create a 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 may remove block distortion caused by boundaries between blocks in the reconstructed picture. In order to determine whether to perform deblocking, it may be determined 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 the deblocking filter is applied to the block, a strong filter or a weak filter may be applied according to the required deblocking filtering strength. In addition, in applying the deblocking filter, horizontal filtering and vertical filtering may be performed in parallel when vertical filtering and horizontal filtering are performed.

The offset correction unit may correct the offset with respect to the original image on a pixel-by-pixel basis for the deblocking image. In order to perform offset correction for a specific picture, the pixels included in the image are divided into a predetermined number of areas, and then, an area to be offset is determined, an offset is applied to the corresponding area, or offset considering the edge information of each pixel. You can use this method.

Adaptive Loop Filtering (ALF) may be performed based on a value obtained by comparing the filtered reconstructed image with the original image. After dividing the pixels included in the image into a predetermined group, one filter to be applied to the group may be determined and filtering may be performed for each group. For information related to whether to apply ALF, a luminance signal may be transmitted for each coding unit (CU), and the shape and filter coefficient of an ALF filter to be applied may vary according to each block. In addition, regardless of the characteristics of the block to be applied, the same type (fixed form) of the ALF filter may be applied.

The memory 155 may store the reconstructed block or picture calculated by the filter unit 150, and the stored reconstructed block or picture may be provided to the predictors 120 and 125 when performing inter prediction.

2 is a block diagram illustrating an image decoding apparatus 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 quantizer 220, an inverse transformer 225, a predictor 230, 235, and a filter unit ( 240, a memory 245 may be included.

When an image bitstream is input from the image encoder, the input bitstream may be decoded by a procedure opposite to that of the image encoder.

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

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

The reordering unit 215 may reorder the entropy decoded bitstream in the entropy decoding unit 210 based on a method of rearranging the bitstream. Coefficients expressed in the form of a one-dimensional vector may be reconstructed by reconstructing the coefficients in a two-dimensional block form. The reordering unit 215 may be realigned by receiving information related to coefficient scanning performed by the encoder and performing reverse scanning based on the scanning order performed by the corresponding encoder.

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

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

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

As described above, when performing the intra prediction in the same manner as the operation in the image encoder, when the size of the prediction unit and the size of the transformation unit are the same, the pixel existing on the left side, the pixel present on the upper left side, and the upper side Intra prediction is performed on a prediction unit based on a pixel, but when intra prediction is performed, when the size of the prediction unit and the size of the transformation unit are different, intra prediction may be performed using a reference pixel based on the transformation unit. Can be. In addition, intra prediction using NxN division may be used only for a minimum coding unit.

The predictors 230 and 235 may include a prediction unit determiner, an inter predictor, and an intra predictor. The prediction unit determiner 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, and distinguishes the prediction unit from the current coding unit, and predicts It may be determined whether the unit performs inter prediction or intra prediction. The inter prediction unit 230 predicts the current prediction based on information included in at least one of a previous picture or a subsequent picture of the current picture including the current prediction unit by using information required for inter prediction of the current prediction unit provided by the image encoder. Inter prediction may be performed on a unit. Alternatively, inter prediction may be performed based on information of some regions pre-restored in the current picture including the current prediction unit.

In order to perform inter prediction, a motion prediction method of a prediction unit included in a coding unit based on a coding unit includes a skip mode, a merge mode, an AMVP mode, and an intra block copy mode. It can be determined whether or not it is a method.

The intra predictor 235 may generate a prediction block based on pixel information in the current picture. When the prediction unit is a prediction unit that has performed intra prediction, intra prediction may be performed based on intra prediction mode information of the prediction unit provided by the image encoder. The intra predictor 235 may include an adaptive intra smoothing (AIS) filter, a reference pixel interpolator, and a DC filter. The AIS filter is a part of filtering the reference pixel of the current block and determines whether to apply the filter according to the prediction mode of the current prediction unit. AIS filtering may be performed on the reference pixel of the current block by using the prediction mode and the AIS filter information of the prediction unit provided by the image 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.

When the prediction mode of the prediction unit is a prediction unit that performs intra prediction based on a pixel value interpolating the reference pixel, the reference pixel interpolator may generate a reference pixel having an integer value or less by interpolating the reference pixel. If the prediction mode of the current prediction unit is a prediction mode for generating a prediction block without interpolating the reference pixel, the reference pixel may not be interpolated. The DC filter may generate the prediction block through filtering when the prediction mode of the current block is the DC mode.

The reconstructed 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 about whether a deblocking filter is applied to a corresponding block or picture, and when the deblocking filter is applied to the corresponding block or picture, may be provided with information about whether a strong filter or a weak filter is applied. In the deblocking filter of the image decoder, the deblocking filter related information provided by the image encoder may be provided and the deblocking filtering of the corresponding block may be performed in the image decoder.

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

The ALF may be applied to a coding unit based on ALF application information, ALF coefficient information, and the like provided from the encoder. Such ALF information may be provided included in a specific parameter set.

The memory 245 may store the reconstructed picture or block to use as a reference picture or reference block, and may provide the reconstructed picture to the output unit.

As described above, in the embodiment of the present invention, a coding unit is used as a coding unit for convenience of description, but may also be a unit for performing decoding as well as encoding.

In addition, the current block represents a block to be encoded / decoded, and according to the encoding / decoding step, a coding tree block (or a coding tree unit), an encoding block (or a coding unit), a transform block (or a transform unit), or a prediction block. (Or prediction unit) or the like. In the present specification, 'unit' may indicate a basic unit for performing a specific encoding / decoding process, and 'block' may indicate a sample array having a predetermined size. Unless otherwise specified, 'block' and 'unit' may be used interchangeably. For example, in the embodiments described below, the coding block (coding block) and the coding unit (coding unit) may be understood to have the same meaning.

One picture may be divided into square or non-square basic blocks and encoded / decoded. In this case, the basic block may be referred to as a coding tree unit. A coding tree unit may be defined as a coding unit of the largest size allowed in a sequence or slice. Information indicating whether the coding tree unit is square or non-square or information related to the size of the coding tree unit may be signaled through a sequence parameter set, a picture parameter set or a slice header. The coding tree unit may be divided into smaller sized partitions. In this case, when the partition generated by dividing the coding tree unit is called depth 1, the partition generated by dividing the partition having depth 1 may be defined as depth 2. That is, a partition generated by dividing a partition that is a depth k in a coding tree unit may be defined as having a depth k + 1.

A partition of any size generated as the coding tree unit is split may be defined as a coding unit. The coding unit may be split recursively or split into basic units for performing prediction, quantization, transform, or in-loop filtering. For example, an arbitrary size partition generated as a coding unit is divided may be defined as a coding unit or a transform unit or a prediction unit that is a basic unit for performing prediction, quantization, transform, or in-loop filtering.

Alternatively, a prediction block having the same size as that of the coding block or a size smaller than the coding block may be determined through prediction division of the coding block. For prediction division of the coding block, one of partition mode (Part_mode) candidates indicating a partitioning form of the coding block may be specified. Information for determining a partition index indicating any one of the partition mode candidates may be signaled through the bitstream. Alternatively, the partition index of the coding block may be determined based on at least one of the size, shape, or coding mode of the coding block. The size or shape of the predictive block may be determined based on the partition mode specified by the partition index. Partition mode candidates may include asymmetric partition types (eg, nLx2N, nRx2N, 2NxnU, 2NxnD). The number or type of asymmetric partition mode candidates that a coding block may use may be determined based on at least one of the size, shape, or coding mode of the coding block.

3 is a diagram illustrating a partition mode candidate that can be applied to a coding block when the coding block is encoded by inter-screen prediction.

When the coding block is encoded by inter prediction, any one of eight partition mode candidates illustrated in FIG. 3 may be applied to the coding block.

On the other hand, when a coding block is encoded by intra prediction, only square partition division may be applied to the coding block. That is, when the coding block is encoded by intra prediction, partition mode PART_2Nx2N or PART_NxN may be applied to the coding block.

PART_NxN may 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 the decoder. Alternatively, information about the minimum size of the coding block may be signaled through the bitstream. As an example, the minimum size of the coding block may be signaled through the slice header. Accordingly, the minimum size of the coding block for each slice may be determined differently.

As another example, the partition mode candidates available to the coding block may be determined differently according to at least one of the size or shape of the coding block. As an example, the number or type of partition mode candidates that a coding block may use may be differently determined according to at least one of the size or shape of the coding block.

Alternatively, the type or number of asymmetric partition mode candidates that the coding block may use may be determined based on the size or shape of the coding block. The number or type of asymmetric partition mode candidates that a coding block may use may be determined differently according to at least one of the size or shape of the coding block. For example, when a coding block has a non-square shape whose width is larger than a height, at least one of PART_2NxN, PART_2NxnU, or PART_2NxnD may not be used as a partition mode candidate of the coding block. When the coding block has a non-square shape whose height is greater than the width, at least one of PART_Nx2N, PART_nLx2N, and PART_nRx2N may not be used as a partition mode candidate of the coding block.

In general, the size of the prediction block may have a size of 64x64 to 4x4. However, when the coding block is encoded by inter prediction, when the motion compensation is performed, the prediction block may not have a 4x4 size in order to reduce the memory bandwidth.

Based on the partition mode, it is also possible to recursively split the coding blocks. That is, based on the partition mode determined by the partition index, a plurality of partitions may be generated by dividing coding blocks, and each partition may be defined as a coding block.

Hereinafter, a method of recursively dividing a coding unit will be described in more detail. In an embodiment to be described below, a coding unit may mean a coding tree unit or a coding unit included in a coding tree unit. In addition, 'partition' generated as the coding block is divided may mean 'coding block'.

The coding unit may be divided by at least one line. In this case, the angle of the line dividing the coding unit may be a value within a range of 0 degrees to 360 degrees. For example, the angle of the horizontal line may be 0 degrees, the angle of the vertical line may be 90 degrees, the angle of the diagonal line in the upper right direction may be 45 degrees, and the angle of the upper left diagonal line may be 135 degrees.

When the 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 than the other lines. Alternatively, the coding tree unit or the plurality of lines dividing the coding unit may have a predefined angle difference (eg, 90 degrees).

Information about a line dividing the coding unit may be determined by the partition mode. Alternatively, information about at least one of the number, direction, angle, or position of a line in a block may be encoded.

For convenience of description, in the following embodiments, it is assumed that a coding unit is divided into a plurality of coding units using 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 unit may be divided into two partitions by using one vertical line or one horizontal line. Alternatively, the coding unit may be divided into three partitions by 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 that are 1/2 smaller in width and height than the coding unit.

When the coding unit is divided into a plurality of partitions using at least one vertical line or at least one horizontal line, the partitions may have a uniform size. Alternatively, either partition may have a different size than the remaining partitions, or each partition may have a different size. For example, when splitting a coding unit into two horizontal lines or two vertical lines, the coding unit may be divided into three partitions. In this case, the width ratio or height ratio of the three partitions may be n: 2n: n, 2n: n: n, or n: n: 2n.

In the embodiments described below, a division of a coding unit into four partitions will be referred to as a quad tree-based partition, and a division of a coding unit into two partitions will be referred to as a binary tree-based partition.

In the drawings described below, one vertical line and / or one horizontal line will be shown to be used to divide the coding unit, but with more vertical lines and / or more horizontal lines than shown, It would also be within the scope of the present invention to divide the coding unit into more partitions than shown or fewer partitions than shown.

FIG. 4 illustrates an example of hierarchically dividing a coding block based on a tree structure according to an embodiment to which the present invention is applied.

The input video signal is decoded in predetermined block units, and the basic unit for decoding the input video signal in this way is called a coding block. The coding block may be a unit for performing intra / inter prediction, transformation, and quantization. In addition, a prediction mode (eg, an intra prediction mode or an inter prediction mode) is determined on a coding block basis, and prediction blocks included in the coding block may share the determined prediction mode. The coding block can be a square or non-square block with any size in the range 8x8 to 64x64, and can be a square or non-square block with a size of 128x128, 256x256 or more.

In detail, the coding block may be hierarchically divided based on at least one of a quad tree splitting method and a binary tree splitting method. Here, quad tree-based partitioning may mean a method in which 2Nx2N coding blocks are divided into four NxN coding blocks, and binary tree-based partitioning may mean a method in which one coding block is divided into two coding blocks. Even if binary tree-based partitioning is performed, there may be a square coding block at a lower depth.

Partitions created due to binary tree based partitioning may be symmetrical or asymmetrical. In addition, the coding block divided based on the binary tree may be a square block or a non-square block (eg, a rectangle).

5 is a diagram illustrating a split form of a coding block based on binary tree splitting. The partition form of a coding block based on binary tree partitioning is a large symmetric type such as 2NxN (horizontal non-square coding unit) or Nx2N (vertical non-square coding unit) or asymmetric such as nLx2N, nRx2N, 2NxnU or 2NxnD. It may include an (asymmetric) type. Only one of the symmetric type or the asymmetric type may be allowed in the split form of the coding block.

Only division of square or non-square symmetry can be allowed for the coding unit. In this case, dividing the coding unit into square partitions may constitute quad-tree CU partitioning, and dividing the coding unit into symmetric non-square partitions may correspond to binary tree partitioning. have. Dividing the coding tree unit into square partitions and symmetric non-square partitions may correspond to quad and binary tree CU partitioning (QTBT).

Binary tree-based partitioning may be performed on coding blocks in which quadtree-based partitioning is no longer performed. Quad tree-based partitioning may no longer be performed on a coding block partitioned based on a binary tree.

In addition, the division of the lower depth partition may be determined depending on the division type of the upper depth partition. For example, when the upper partition and the lower partition are partitioned based on the binary tree, only the partition based on the binary tree of the same type as the binary tree partition of the upper depth partition may be allowed in the lower depth partition. For example, when the binary tree splitting shape of the upper depth partition is 2NxN type, the binary tree splitting shape of the lower depth partition may also be set to 2NxN shape. Alternatively, when the binary tree partition type of the upper depth partition is Nx2N type, the partition shape of the lower depth partition may also be set to Nx2N type.

Alternatively, the split type of the lower depth partition may be determined in consideration of the split type of the upper depth partition and the split type of the neighboring lower depth partition. Specifically, when the upper depth partition is partitioned based on the binary tree, the partition type of the lower depth partition may be determined so that the same result as that of partitioning the upper depth partition based on the quad tree does not occur. For example, when the partition type of the upper depth partition is 2NxN and the partition type of the neighboring lower depth partition is Nx2N, the partition type of the current lower depth partition cannot be set to Nx2N. This is because, when the partition type of the current lower depth partition has Nx2N, the same result as that of the quadtree partition of the upper depth partition of the NxN type is caused. When the partition type of the upper depth partition is Nx2N and the partition shape of the neighboring lower depth partition is 2NxN, the partition type of the current lower depth partition cannot be set to 2NxN. That is, when the binary tree splitting shape of the upper depth partition and the binary tree splitting shape of the neighboring lower depth partition are different, the binary tree splitting shape of the current lower depth partition may be set to be the same as the binary tree splitting shape of the upper depth partition.

Alternatively, the binary tree split type of the lower depth partition may be set differently from the binary tree split type of the upper depth partition.

In units of sequence, slice, or coding unit, the allowed binary tree splitting forms may be determined. For example, the binary tree splitting type allowed for a coding tree unit may be limited to 2NxN or Nx2N type. The allowed partition type may be predefined in the encoder or the decoder. Alternatively, information about an allowed split type or a not allowed split type may be encoded and signaled through a bitstream.

6 illustrates an example in which only a specific type of binary tree based partitioning is allowed.

FIG. 6A illustrates an example in which only Nx2N type binary tree based partitioning is allowed, and FIG. 6B illustrates an example in which only 2NxN type binary tree based partitioning is allowed.

Information indicating a quad tree based partition, information about a size / depth of a coding block allowing quad tree based partitioning, and binary tree based partitioning to implement the quad tree or binary tree based adaptive partitioning Information about the size / depth of coding blocks that allow binary tree based splitting, information about the size / depth of coding blocks that do not allow binary tree based splitting, or whether the binary tree based splitting is vertical, or At least one of information about whether the image is in a landscape direction may be used.

In addition, for the coding tree unit or the coding unit, at least one of the number of times that binary tree splitting is allowed, the depth that allows binary tree splitting, or the number of depths that allow binary tree splitting may be obtained. The above information may be encoded in a coding tree unit or a coding unit and may be transmitted to a decoder through a bitstream.

For example, a syntax 'max_binary_depth_idx_minus1' indicating a maximum depth that allows binary tree splitting may be encoded / decoded through the bitstream through the bitstream. In this case, max_binary_depth_idx_minus1 + 1 may indicate the maximum depth allowed for binary tree splitting.

Alternatively, the number of times that the binary tree split is allowed, the depth that allows the binary tree split, or the number of the depths that allow the binary tree split may be predefined in the encoder and the decoder. Alternatively, the number of times binary tree splitting is allowed, the depth in which binary tree splitting is allowed, or the number of depths in which binary tree splitting is allowed may be determined based on at least one of an index of a sequence or slice or a size / type of a coding unit. . For example, in the first slice, binary tree splitting may be allowed at one depth, and in the second slice, binary tree splitting may be allowed at two depths.

Referring to the example illustrated in FIG. 7, in FIG. 7, binary tree splitting is performed on a coding unit having a depth of 2 and a coding unit having a depth of 3. Accordingly, information indicating the number of times binary tree splitting has been performed in the coding tree unit (2 times), information indicating the maximum depth (depth 3) of the partition generated by the binary tree splitting in the coding tree unit, or the binary tree in the coding tree unit. At least one of information indicating the number of partition depths (2, depth 2, and depth 3) to which division is applied may be encoded / decoded through a bitstream.

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

As another example, at least one of the number of times that a binary tree split is allowed, the depth that allows a binary tree split, or the number of depths that allow a binary tree split may be differently set according to a temporal ID (TemporalID) of a slice or a picture. have. Here, the temporal level identifier TemporalID may be used to identify each of a plurality of layers of an image having at least one scalability among a view, a spatial, a temporal, or a quality. will be.

Information for determining the division type of the coding unit may be signaled through the bitstream. The decoder may partition the coding unit by decoding the information from the bitstream.

8 is a flowchart illustrating a process of determining a split type of a coding unit based on hierarchically coded split information.

Based on the split_flag, it may be determined whether to split the current coding unit into lower depth coding units (S810). split_flag indicates whether to split the current coding unit into lower depth coding units. If split_flag is true, QT_flag or BT_flag for determining the split type of the coding unit may be decoded (S820). QT_flag indicates whether a coding unit is quad tree split. BT_flag indicates whether a coding unit is binary tree split. Only either QT_flag or BT_flag may be selectively encoded. If QT_flag is true or BT_flag is false, the coding unit may be split into four coding units (S830). If QT_flag is false or BT_flag is true, the coding unit may be split into two coding units. When QT_flag is false or BT_flag is true, BT_hor_flag or BT_ver_flag indicating the split direction of the coding unit may be decoded (S840). BT_hor_flag indicates whether a coding unit is split in the horizontal direction. BT_ver_flag indicates whether the coding unit is split in the vertical direction. Only either BT_hor_flag or BT_ver_flag may be selectively encoded. If BT_hor_flag is true or if BT_ver_flag is false, the coding unit may be split in the horizontal direction 2N × N (S850). If BT_hor_flag is false or BT_ver_flag is true, the coding unit may be split in the vertical direction Nx2N (S860).

A process of splitting a coding unit into a plurality of lower depth coding units and determining a split form for each lower depth coding unit may be performed recursively. In this case, quad tree partitioning may be set to not be allowed in a non-square type coding unit or a coding unit generated as a result of binary tree partitioning. Whether to split the coding unit generated as a result of the non-square form or binary tree partitioning may follow FIG. 9.

9 is a flowchart illustrating a process of determining a split type of a non-square type coding unit based on split information.

Based on the split_flag, it may be determined whether to split the current coding unit into lower depth coding units (S910). If split_flag is true, BT_hor_flag or BT_ver_flag indicating the split direction of the coding unit may be decoded (S920). Only either BT_hor_flag or BT_ver_flag may be selectively encoded. If BT_hor_flag is true or BT_ver_flag is false, the coding unit may be split in the horizontal direction 2N × N (S930). If BT_hor_flag is false or BT_ver_flag is true, the coding unit may be split in the vertical direction Nx2N (S940).

In the above-described embodiment, it has been described that split_flag is used to determine whether to split a coding block. As another example, encoding of the split_flag may be omitted, and whether to split the coding block may be determined based on at least one of the QT_flag and the BT_flag. As an example, when QT_flag is true, the coding block may be divided into four partitions. If QT_flag is false and BT_flag is true, the coding block may be split into two partitions. If QT_flag and BT_flag are false, the coding block is no longer split.

As shown in FIG. 4, the first coding block 300 having 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 having half the width and the height of the first coding block, and the split depth of the second coding block may be increased to k + 1.

The second coding block 310 having the division depth k + 1 may be divided into a plurality of third coding blocks having the division depth k + 2. Partitioning of the second coding block 310 may be selectively performed using either a quart tree or a binary tree according to a partitioning scheme. Here, the splitting scheme may be determined based on at least one of information indicating splitting based on the quad tree or information indicating splitting based on the binary tree.

When the second coding block 310 is divided on the basis of the quart tree, the second coding block 310 is divided into four third coding blocks 310a having half the width and the height of the second coding block, The split depth can be increased to k + 2. On the other hand, when the second coding block 310 is divided on a binary tree basis, the second coding block 310 may be split into two third coding blocks. In this case, each of the two third coding blocks is a non-square block having one half of the width and the height of the second coding block, and the split depth may be increased to k + 2. The second coding block may be determined as a non-square block in the horizontal direction or the vertical direction according to the division direction, and the division direction may be determined based on information about whether the binary tree-based division is the vertical direction or the horizontal direction.

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

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

Meanwhile, the third coding block 310b split 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 corresponding coding The partition depth of the block can be increased to k + 3. Alternatively, the third coding block 310b may be determined as an end coding block 310b-1 that is no longer split based on the binary tree, in which case the coding block 310b-1 may be used as a prediction block or a transform block. Can be. However, the above-described partitioning process allows information about the size / depth of a coding block that allows quad-tree based partitioning, information about the size / depth of the coding block that allows binary tree-based partitioning, or binary-tree based partitioning. It may be limitedly performed based on at least one of the information about the size / depth of the coding block that is not.

A size candidate that a coding block may have is limited to a predetermined number, or the size of a coding block in a predetermined unit may have a fixed value. For example, the size of the coding block in the sequence or the size of the coding block in the picture may be limited to have any one of 256x256, 128x128, or 32x32. Information representing the size of a coding block in a sequence or picture may be signaled through a sequence header or picture header.

As a result of the splitting based on the quad tree and binary tree, the coding unit may take a square or a rectangle of any size.

As a result of the division based on the quad tree and the binary tree, coding blocks that are no longer split may be used as prediction blocks or transform blocks. That is, it can be used as a coding block, prediction block, or transform block generated as a result of quad tree partitioning or binary tree partitioning. For example, a prediction image may be generated in units of coding blocks, and a residual signal that is a difference between the original image and the prediction image may be converted in units of coding blocks. In order to generate a prediction image in units of coding blocks, motion information may be determined based on a coding block, or an intra prediction mode may be determined based on a coding block. Accordingly, the coding block may be encoded using at least one of a skip mode, an intra prediction or an inter prediction.

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

The binary tree based splitting form of the coding block may be set such that only symmetric splitting is allowed. However, even when the object and the background are divided at the block boundary, if only symmetric binary division is allowed, the coding efficiency may be lowered. Accordingly, the present invention proposes a method of dividing a coding block into asymmetric partitions in order to improve encoding / decoding efficiency.

As a result of Asymmetric Binary Tree Partitioning, the coding block may be split into two smaller coding blocks. The two coding blocks may differ in size. Partitioning a coding block into two partitions of the same size may be defined as symmetric binary tree partitioning. Splitting a coding block into two partitions of different sizes can be defined as asymmetric binary tree partitioning. The binary tree splitting form may include at least one of a symmetric binary tree splitting form or an asymmetric binary tree splitting form.

10 illustrates a partitioned form of a coding block based on asymmetric binary tree partitioning.

The 2N × 2N coding block may be divided into two coding blocks having a width ratio of n: (1-n) or two coding blocks having a height ratio of n: (1-n). Here, n may represent a real number greater than 0 and less than 1.

As an example, the width ratio or height ratio of coding blocks generated as a result of asymmetric binary tree partitioning may be 1: 3 or 3: 1.

Specifically, as the coding block having the WxH size is divided in the vertical direction, a left partition having a width of W / 4 and a right partition having a width of 3W / 4 may be generated. As described above, a partitioned form in which the width of the left partition is smaller than the width of the right partition may be referred to as an nLx2N binary partition.

As the WxH sized coding block is divided in the vertical direction, a left partition having a width of 3W / 4 and a right partition having a width of W / 4 may be generated. As described above, the partition type whose width of the right partition is smaller than the width of the left partition may be referred to as nRx2N binary partition.

As the WxH sized coding block is divided in the horizontal direction, an upper partition having a height of H / 4 and a lower partition having a height of 3H / 4 may be generated. As described above, a partition type in which the height of the upper partition is smaller than the height of the lower partition may be referred to as a 2NxnU binary partition.

As the coding block of the WxH size is divided in the horizontal direction, an upper partition having a height of 3H / 4 and a lower partition having a height of H / 4 may be generated. As described above, a partitioned form in which the height of the lower partition is smaller than the height of the upper partition may be referred to as a 2NxnD binary partition.

The width ratio or height ratio of the two coding blocks generated as a result of the asymmetric binary tree splitting may be predefined in the encoder and the decoder. Alternatively, information representing the width ratio or height ratio of the two coding blocks may be signaled through the bitstream. Alternatively, the width ratio or the height ratio of two coding blocks may be determined based on at least one of the shape, size, coding mode, scan order, or intra prediction mode of the coding block.

The asymmetric binary partition form of the coding block may be determined based on information signaled through the bitstream. As an example, the split type of the coding block may be determined based on information indicating the split direction of the coding block and information indicating whether the first partition generated as the coding block is split has a smaller size than the second partition.

The information indicating the splitting direction of the coding block may be a 1-bit flag indicating whether the coding block is split in the vertical direction or in the horizontal direction. For example, any one of hor_binary_flag or ver_binary_flag may be signaled through the bitstream. hor_binary_flag may indicate whether the coding block is split in the horizontal direction, and ver_binary_flag may indicate whether the coding block is split in the vertical direction. When the value of hor_binary_flag is 1 or the value of ver_binary_flag is 0, the coding block may be split in the horizontal direction. When the value of hor_binary_flag is 0 or the value of ver_binary_flag is 1, the coding block may be split in the vertical direction.

The information indicating whether the first partition has a smaller size than the second partition may be a 1-bit flag. For example, one of is_left_above_small_part_flag or is_right_bottom_small_part_flag may be signaled through the bitstream. is_left_above_small_part_flag indicates whether the size of the left or top partition created as the coding block is split is smaller than the right or bottom partition, and is_right_bottom_small_part_flag indicates that the size of the right or bottom partition resulting from splitting the coding block is larger than the left or top partition. Indicates whether it is small. When the value of is_left_above_small_part_flag is 1 or the value of is_right_bottom_small_part_flag is 0, the size of the left or top partition is set smaller than that of the right or bottom partition. When the value of is_left_above_small_part_flag is 0 or the value of is_right_bottom_small_part_flag is 1, the size of the left or top partition is set larger than the right or bottom partition.

For example, a value of hor_binary_flag equal to 0 and a value of is_left_above_small_part_flag equal to 1 indicate an nLx2N binary partition, a value of hor_binary_flag equal to 0, and a value of is_left_above_small_part_flag equal to 0 indicate an nRx2N binary partition. In addition, a value of hor_binary_flag equal to 1 and a value of is_left_above_small_part_flag equal to 1 indicate a 2NxnU binary partition, a value of hor_binary_flag equal to 1, and a value of is_left_above_small_part_flag equal to 0 indicate a 2NxnD binary partition.

Alternatively, the size of the first partition and the second partition may be determined using information representing a width ratio, a height ratio, or a width ratio between the first partition and the second partition.

Alternatively, the index information for determining the asymmetric binary partition shape of the coding block may be signaled, and the coding block may be divided based on the asymmetric binary partition shape indicated by the index information. Each of the asymmetric binary partition types may be assigned a different index, and the index information may indicate either index. The index information may be encoded with a fixed length (ie, a fixed number of bits) or a variable length. For example, Table 1 below shows binary codes of partition indexes and corresponding index information.

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

Whether to use the asymmetric binary tree partitioning method may be determined depending on whether to use the quad tree partitioning method and the symmetric binary tree partitioning method. For example, when it is determined not to apply quad tree splitting or symmetric binary tree splitting to a coding block, it may be determined whether to apply asymmetric binary tree splitting to the coding block. For example, when both QT_flag and BT_flag are false, information indicating whether asymmetric binary tree split is applied to a coding block may be encoded / decoded. The information may be a 1-bit flag 'asymmetric_binary_tree_flag'. A value of asymmetric_binary_tree_flag of 1 indicates that asymmetric binary tree splitting is applied to a coding block, and a value of asymmetric_binary_tree_flag of 0 indicates that asymmetric binary tree splitting is not applied to a coding block.

Alternatively, when it is determined that binary tree partitioning is applied to a coding block, it may be determined whether a partitioned form of the coding block is symmetrical or asymmetrical. For example, when split_flag is true and QT_flag is false or split_flag is true and BT_flag is true, information representing a split type of a coding block may be encoded / decoded. The information may be a 1-bit flag 'is_asymmetric_split_flag'. A value of is_asymmetric_split_flag of 1 indicates that a split type of a coding block is asymmetric, and a value of 0 is_asymmetric_split_flag indicates that a split type of a coding block is symmetric.

Alternatively, different indexes may be assigned to each of the symmetric binary partition type and the asymmetric binary partition type, and the partition type of the coding block may be determined based on index information indicating one of the plurality of partition types. As an example, Table 2 shows a binary code of a partition index and corresponding index information.

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

The coding block may be divided into a plurality of coding blocks through quad tree splitting, symmetric binary tree splitting, or asymmetric binary tree splitting. 11 is a diagram illustrating an example in which a coding block is divided into a plurality of coding blocks based on quad tree division, symmetric binary tree division, and asymmetric binary tree division. Referring to FIG. 11, it can be seen that asymmetric binary tree splitting is performed in depth 2 partitioning of the first picture, depth 3 partitioning of the second picture, and depth 3 partitioning of the third picture.

A coding block divided through asymmetric binary tree partitioning may be set not to be split into smaller coding blocks. For example, for a coding block generated through asymmetric binary tree partitioning, information indicating whether a partition is divided, information indicating whether a quad tree is split, information indicating whether a symmetric binary tree is split, information indicating whether or not a split is asymmetric binary tree, and split direction At least one of the information indicating or the information indicating the partition type may not be encoded / decoded. That is, for a coding block generated through asymmetric binary tree partitioning, a flag indicating whether a quad tree is split, a flag indicating whether a binary tree is split, a flag indicating whether a symmetric binary tree is split, a flag indicating whether a split asymmetric binary tree is split, The encoding / decoding of the syntaxes related to the flag indicating the binary tree partitioning direction or the index information indicating the partition type may be omitted.

Asymmetric binary tree partitioning may not be allowed in a picture, slice, or coding tree unit for which QTBT is not allowed. Alternatively, information indicating whether to allow asymmetric binary tree partitioning may be encoded and signaled in units of blocks, slices, or pictures. The information may be a flag of 1 bit. As an example, the value of is_used_asymmetric_QTBT_enabled_flag equal to 0 may indicate that asymmetric binary tree partitioning is not allowed. Alternatively, after determining whether to allow a binary tree, whether to allow asymmetric binary tree splitting may be determined. For example, when it is determined that binary tree splitting is allowed at the picture level or the slice level, whether to split an asymmetric binary tree through the is_used_asymmetric_QTBT_enabled_flag may be determined. Or, if it is determined that binary tree splitting is not allowed at the picture level or the slice level, the value may be set to 0 without signaling is_used_asymmetric_QTBT_enabled_flag.

As a result, asymmetric binary tree partitioning cannot be applied to coding blocks included in a picture, slice, or coding tree unit for which QTBT or asymmetric binary tree partitioning is not allowed. Accordingly, encoding / decoding of information related to asymmetric binary tree splitting for the coding blocks may be omitted. Alternatively, a syntax value related to asymmetric binary tree splitting may be set such that asymmetric binary tree splitting is not applied to the coding blocks.

Based on the size, shape, division depth of the coding block, or the division type of the parent node coding block, etc., the division type allowed 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 the quad tree split and the coding block generated by the binary tree split may be different.

For example, any one of quad tree division, binary tree division, or asymmetric binary tree division may be selectively applied to a coding block generated by quad tree division. That is, when the coding block is generated based on quad tree splitting, the splitting method candidates applicable to the coding block may include quad tree splitting, binary tree splitting, and asymmetric binary tree splitting. As a result, at least one partition type of 2Nx2N, Nx2N, 2NxN, NxN, nLx2N, nRx2N, 2NxnU, or 2NxnD may be applied to the coding block. The 2N × 2N partition represents the case where the coding block is no longer split. NxN represents a case where a coding block is quadtree split. Nx2N and 2NxN represent the case where the coding block is symmetric binary tree split. nLx2N, nRx2N, 2NxnU or 2NxnD represent a case where the coding block is asymmetric binary tree split.

For example, asymmetric binary tree splitting may not be allowed in a coding block generated by binary tree splitting. That is, an asymmetric partition type such as nLx2N, nRx2N, 2NxnU, or 2NxnD may not be applied to the coding block.

Various division forms of the coding block have been described through the above-described embodiments. Hereinafter, various division forms other than the above-described division forms will be further described.

In addition to the partitioning method of dividing the coding block into four square blocks, asymmetric quad tree CU partitioning can be allowed. Asymmetric quad tree splitting may be performed by at least one of a horizontal line dividing the coding block or a vertical line dividing the coding block by dividing the coding block into an asymmetric form. For example, a horizontal line divides a coding block into an asymmetric form, whereas a vertical line divides a coding block into a symmetric form, and a horizontal line divides a coding block into a symmetric form, whereas a vertical line divides a coding block into an asymmetric form. A partition form, or a partition form for dividing the coding block into an asymmetric shape in both horizontal and vertical lines, may be applied to the coding block. As a result of the asymmetric quad tree splitting, the width or height of one partition may be different from the width or height of the other partition.

12 is a diagram illustrating a quad tree-based splitting form of a coding block.

FIG. 12A illustrates a partition form in which horizontal lines and vertical lines symmetrically divide a coding block. 12 (b) and 12 (c) show horizontal partitions symmetrically partitioning coding blocks, while vertical lines are partition shapes that asymmetrically partition coding blocks. 12 (d) and 12 (e) show partition shapes in which a vertical line symmetrically divides a coding block, while a horizontal line asymmetrically divides a coding block.

Information related to the quad tree division type may be encoded in the bitstream. The information may be index information indicating any one of a plurality of partition type candidates. For example, a different index may be allocated to each of the plurality of partition type candidates shown in FIG. 12. The quadtree splitting shape of the coding block may be determined based on the index information indicating one index among the plurality of partition type candidates. Alternatively, the information may include an indicator indicating whether the quad tree split form is symmetrical or asymmetrical. The indicator may be coded in block units. For example, when the indicator is true, the quad tree splitting form of the coding block may be determined as symmetric splitting (FIG. 12A). When the indicator is false, the splitting form of the coding block may be determined by any one of asymmetric splitting forms ((b), (c), (d) and (e) of FIG. 12). If the indicator is false, index information indicating any one of the asymmetric division forms may be further encoded / decoded. Alternatively, when the indicator is false, at least one of vertical division information or horizontal division information described below may be further encoded / decoded.

Alternatively, at least one of the vertical direction splitting information indicating whether the vertical line symmetrically splits the coding block or the horizontal direction splitting information indicating whether the horizontal line symmetrically splits the coding block may be encoded / decoded. The quadtree splitting type of the coding block may be determined based on at least one of the vertical splitting information or the vertical splitting information.

Alternatively, one of the horizontal division information and the vertical division information may be determined based on the other value. That is, only one of the horizontal direction splitting information or the vertical direction splitting information is encoded, and the other value may be determined based on the value of the encoded information. As an example, the horizontal direction splitting information and the vertical direction splitting information may have different values. When the horizontal direction split information indicates an asymmetric split, the vertical direction split information may be determined as symmetric split. Alternatively, when the vertical division information indicates asymmetric division, the horizontal division information may be determined as symmetric division.

When the horizontal direction splitting information indicates asymmetric splitting, at least one of information about a position of a horizontal line for dividing the coding block or a height of coding blocks generated by horizontal splitting may be further encoded / decoded. When the vertical direction splitting information indicates asymmetric splitting, at least one of information about a position of a vertical line dividing the coding block or information about widths of coding blocks generated by vertical splitting may be further encoded / decoded.

In addition to the quad tree splitting method using one vertical line and one horizontal line, a quadtree splitting method using a plurality of vertical lines or a plurality of horizontal lines may be used. For example, a quad tree splitting form using a plurality of vertical lines and one horizontal line or a plurality of horizontal lines and a vertical line or a quadtree splitting form using a plurality of vertical lines or a plurality of horizontal lines may be applied to a coding block.

FIG. 13 is a diagram illustrating a quad tree splitting form using a plurality of vertical lines or a plurality of horizontal lines.

The quad tree splitting form may include splitting a coding block into three blocks using two vertical lines, and then splitting any one of the three divided blocks into one horizontal line. In this case, the horizontal line may be used to divide any one of the three blocks into a symmetrical form or an asymmetrical form. In addition, the quad tree splitting form may include splitting a coding block into three blocks using two horizontal lines, and then splitting any one of the three divided blocks into one vertical line. In this case, the vertical line may be used to divide any one of the three blocks into a symmetrical form or an asymmetrical form.

As in the example illustrated in FIG. 13, a block located in the middle of three blocks generated by dividing a coding block into two vertical lines or two horizontal lines may be further divided. Alternatively, the quad tree splitting form may include a form of further dividing a block located at the edge of the coding block among three blocks.

A partition which is further divided among three partitions may be predefined in the encoder and the decoder. For example, the width ratio or height ratio of the three partitions generated by dividing the coding block into two horizontal lines or two vertical lines may be n: 2n: n, 2n: n: n or n: n: 2n. The partition with the largest width or height among the three partitions can be determined for further partitioning. Alternatively, information (eg, partition index) for specifying a partition that is further divided among three partitions may be signaled through the bitstream.

As in the example shown in FIG. 13, the quad tree splitting type divides a coding block by combining a plurality of vertical lines and one horizontal line, or a split type splitting a coding block by combining a plurality of horizontal lines and one vertical line. It may include at least one of. By the quad tree partitioning, a coding block may be divided into two partitions having a first size / first shape and two partitions having a second size / second shape. Alternatively, by the quad tree partitioning, the coding block may include one partition having a first size / first shape, one partition having a second size / second shape, and two partitions having a third size / third shape. It can be divided into As described above, a quad tree partition type having two or three size or shape numbers of four partitions may be defined as three types of asymmetric quad-tree CU partitioning.

Information about three asymmetric quad tree partitionings may be encoded through a bitstream. The information includes at least one of information indicating whether three asymmetric quad tree partitioning is allowed, information indicating whether a coding block is three asymmetric quad tree partitioning, or information indicating a split form of three asymmetric quad tree partitioning. can do. The information indicating the partition type may include index information indicating any one of a plurality of partition type candidates, information about the number of horizontal lines or vertical lines, information about the position of horizontal lines or vertical lines, or information indicating width ratios or height ratios of partitions. It may include at least one of.

Quad tree splitting refers to splitting a coding block into four coding blocks, and binary tree splitting refers to splitting a coding block into two coding blocks. Three coding blocks or five or more coding blocks The division type to divide by may be defined. Splitting a coding block into three partitions may be defined as triple tree partitioning. The triple tree splitting form may include at least one of splitting a coding block into two vertical lines or splitting the coding block into two horizontal lines. Three non-square partitions can be created by triple tree partitioning.

14 shows a triple tree split form.

Triple tree splitting may include splitting a coding block into two horizontal lines or splitting a coding block into two vertical lines. The width ratio or height ratio of the partitions resulting from the splitting of the coding block may be n: 2n: n, 2n: n: n or n: n: 2n.

The location of the partition having the largest width or height among the three partitions may be predefined in the encoder and the decoder. Alternatively, information indicating a partition having the largest width or height among the three partitions may be signaled through the bitstream.

The coding block generated as a result of the triple tree splitting may be divided into smaller coding blocks. Alternatively, for prediction or transformation, the coding block generated as a result of triple tree splitting may be split into prediction blocks or transform blocks of smaller size. Alternatively, only the coding block having the largest size among the three coding blocks generated as a result of the triple tree split may be split into coding blocks having a smaller size.

As another example, the coding block generated as a result of the triple tree split may be set not to be further split.

Alternatively, at least one of quad tree splitting, triple tree splitting, or binary tree splitting may be applied to a coding block generated as a result of triple tree splitting. For example, quad-tree splitting and triple-tree splitting may not be allowed in a coding block generated as a result of triple tree splitting. Only binary tree splitting may be allowed in the coding block.

FIG. 15 is a diagram illustrating an additional partition form of a coding block generated as a result of triple tree partitioning.

The coding block generated as a result of the triple tree split may be set such that at least one of the quad tree split method and the triple tree split method is not allowed. In the coding block generated as a result of the triple tree split, only the binary tree splitting method may be set.

FIG. 15A illustrates an example in which binary partitioning in the vertical direction is applied to two coding blocks 1510 and 1530 having a smaller width among coding blocks generated as a result of triple tree division. FIG. 15B illustrates an example in which horizontal partitioning is applied to a coding block 1520 having the largest width among coding blocks generated as a result of triple tree splitting. FIG. 15C illustrates an example in which binary partitioning in the horizontal direction is applied to two coding blocks 1510 and 1530 having smaller widths among coding blocks generated as a result of triple tree division.

A binary tree split in the same direction as the triple tree split may not be allowed in the coding block having the largest size among the coding blocks generated as a result of the triple tree split. For example, as in the example illustrated in FIG. 15B, only the binary tree split in the vertical direction may be allowed in the coding block having the largest width among the coding blocks generated as the result of the triple tree split in the vertical direction. . Accordingly, encoding / decoding of information indicating a binary tree split direction may be omitted for the coding block.

Whether to allow triple tree splitting may be determined according to the width, height, width and height ratio, size, or shape of the coding block. For example, when at least one of the width or height of the coding block is greater than or equal to the predefined value, or when at least one of the case where the size of the coding block is greater than or equal to the predefined value or the width and height ratio of the coding block is greater than or equal to the predefined value Triple tree splitting may not be allowed. Alternatively, triple tree splitting may be allowed only when the size of the coding block is M × N. Here, N and M may be natural numbers having the same value or different values. For example, N and M may have a value of 4, 8, 16, 32, 64 or more.

Alternatively, information representing a width, a height, a size, a width and a height ratio, or a shape of a coding block that allows triple tree splitting may be encoded and transmitted through a bitstream. The information may indicate a maximum or minimum value. For example, if the width, height, size or width and height ratio of the coding block is greater than or equal to the minimum value indicated by the information, or if the width, height, size or width and height ratio of the coding block is less than or equal to the maximum value indicated by the information, Triple tree splitting may be allowed for the above. Alternatively, the size or shape of a block that allows triple tree splitting may have a fixed value contracted by the encoder / decoder.

Alternatively, information indicating whether triple tree splitting is allowed may be signaled through the bitstream. The information may be signaled at a picture level, slice level, tile group level, tile level, or block level. The information may be a 1-bit flag. When a coding block is included in a higher level where triple tree splitting is not allowed, encoding and decoding of information related to triple tree splitting for the coding block may be omitted. When a coding block is included in a higher level in which triple tree split is allowed, information related to triple tree split may be included in information related to a split type that is encoded / decoded for the coding block.

Information indicating whether the coding block is triple tree split may be signaled through the bitstream. The information may be a 1-bit flag. For example, TT_flag indicating whether a coding block is triple tree split may be encoded / decoded. A value of TT_flag is true indicates that the coding block is divided into three coding blocks. A false value of TT_flag indicates that triple tree splitting is not applied to the coding block.

Or, it may be determined whether triple tree split is applied to the coding block using QT_flag or BT_flag. For example, if QT_flag is true, it means that the coding block is quad tree split, and if QT_flag is false, it can indicate that the coding block is triple tree split.

Alternatively, the fact that BT_flag is true may indicate that the coding block is binary tree split, and when BT_flag is false may indicate that the coding block is triple tree split. BT_flag may be encoded / decoded when QT_flag is false, or when the coding block is a non-square partition and split_flag is 1.

When triple tree splitting is applied to a coding block, at least one of information indicating a split direction of the coding block or information indicating the size of partitions generated as a result of splitting the coding block may be additionally signaled. The information indicating the division direction indicates whether the division direction of the coding block is the horizontal direction or whether the division direction of the coding block is the vertical direction. When the splitting direction of the coding block is the horizontal direction, the coding block may be divided into three coding blocks by two horizontal lines. When the splitting direction of the coding block is the vertical direction, the coding block may be divided into three coding blocks by two vertical lines.

When the coding block is triple tree divided, partitions included in the coding block may share motion information, a merge candidate, a reference sample, or an intra prediction mode according to the size or shape of the coding block. For example, when the current coding block is divided into triple tree partitioning and the size or shape of the current coding block satisfies a predetermined condition, the coding blocks in the current coding block are spatial, temporal neighboring block candidates, screens for inter prediction. At least one of a reference sample for prediction and an intra prediction mode may be shared. Alternatively, only some of the coding blocks in the current coding block may share the information, and the remaining coding block may be configured not to share the information.

Summarizing the above-described embodiments, the coding block splitting method may include at least one of a quadtree splitting method, a binary tree splitting method, or a triple tree splitting method. The quad tree split includes at least one of symmetric quad tree split, asymmetric quad tree split, or three asymmetric quad tree split, and the binary tree split includes at least one of symmetric binary tree split or asymmetric binary tree split. The method of partitioning coding blocks using at least one of the quad tree partitioning method, the binary tree partitioning method, or the triple tree partitioning method described above is called a multi-tree partitioning (or multiple tree partitioning) method. This can be called.

16 illustrates a division type that may be applied to a coding block.

If symmetric quad tree splitting, symmetric binary tree splitting, asymmetric binary tree splitting, and triple tree splitting are allowed, the splitting shape of the coding block may be determined by any one of nine splitting shapes shown in FIG.

At least one of whether to allow quad tree split, whether to allow binary tree split, or whether to allow triple tree split may be determined at a sequence level, a picture level, a slice level, a tile group level, or a tile level. Information indicating whether to allow each division method may be signaled through the bitstream. The information may be a flag of 1 bit. For example, at least one of isUseQuadTreeFlag indicating whether the quad tree splitting method is allowed or at least one of isUseBinaryTreeFlag indicating whether the binary tree splitting method is allowed or isUseTripleTreeFlag indicating whether the triple tree splitting method is allowed may be signaled through the bitstream. Depending on whether each partitioning method is allowed, the coding blocks included in the higher level can be partitioned using both quad tree partitioning, binary tree partitioning, and triple tree partitioning, or one or two of quad tree partitioning, binary tree partitioning, or triple tree partitioning. The coding blocks included in the higher level may be divided using a partitioning method of.

Alternatively, some partitioning methods such as quad tree partitioning, binary tree partitioning, and triple tree partitioning are allowed by default, and whether to allow the remaining partitioning method may be selectively determined. For example, the quad tree split method is basically allowed, but whether the binary tree split method or the triple tree split method is allowed may be selectively determined. Alternatively, the quad tree split method and the triple tree split method are basically allowed, but whether the binary tree split method is allowed may be selectively determined. Alternatively, the quad tree splitting method and the binary tree splitting method are basically allowed, but whether to use triple tree splitting may be selectively determined. The information indicating whether the binary tree splitting method is allowed or the information indicating whether the triple tree splitting method is allowed may be a 1-bit flag. For example, at least one of isUseBinaryTreeFlag indicating whether the binary tree splitting method is allowed or isUseTripleTreeFlag indicating whether the triple tree splitting method is allowed may be signaled through the bitstream. The information may be signaled at a sequence header, picture level, slice level, tile group level, or tile level. As an example, an isUseBinaryTreeFlag value of 1 indicates that coding blocks in a sequence may be split by a binary tree splitting method. An isUseBinaryTreeFlag value of 0 indicates that coding blocks included in a sequence cannot be split by the binary tree splitting method. If the binary tree splitting method is not allowed, encoding / decoding of information related to binary tree splitting may be omitted for the coding blocks.

Alternatively, a value of isUseTripleTreeFlag of 1 indicates that coding blocks included in a sequence may be split by a triple tree splitting method. A value of isUseTripleTreeFlag of 0 indicates that coding blocks included in a sequence cannot be split by the triple tree splitting method. If the triple tree splitting method is not allowed, encoding / decoding of information related to triple tree splitting may be omitted for the coding blocks.

The coding block generated as a result of quad tree division, binary tree division, or triple tree division may be set as a basic unit for prediction or transformation. That is, by setting a coding block as a prediction block or a transform block, prediction, transform, or quantization may be performed on the coding block.

Alternatively, the size and / or shape of at least one of the prediction block or the coding block may be set differently from the coding block size and / or shape. For example, the coding block may be divided to generate prediction blocks or transform blocks having a smaller size than the coding block. Alternatively, a plurality of coding blocks may be set as one prediction block or a transform block. For example, a transform unit for coding blocks generated as a result of triple tree splitting may be determined as an upper partition region. The upper partition area may be a non-square or square area including at least one of three blocks generated as a result of triple tree partitioning. That is, an upper node block including the coding blocks may be set as a transform unit for the coding blocks.

17 is a diagram illustrating a transform unit of triple tree partitioned coding blocks.

In FIG. 17A, a transform unit of CU0, CU1, and CU2 generated as a result of triple tree splitting may be set to an upper node block including CU0, CU1, and CU2. That is, transformation and / or quantization for CU0, CU1, and CU2 may be performed based on an upper node block including CU0, CU1, and CU2.

In FIG. 17B, a transform unit of CU3, CU4, and CU5 generated as a result of triple tree division may be set to an upper node block including CU3, CU4, and CU5. That is, transformation and / or quantization for CU3, CU4, and CU5 may be performed based on an upper node block including CU3, CU4, and CU5.

As described, a plurality of coding blocks may be set as one transform unit. In other words, a transform process of setting a set of a plurality of coding blocks into one transform unit may be performed. The conversion process may be performed on not only blocks generated by triple tree division but also coding blocks generated by binary tree division or quad tree division. The transform process may be performed in consideration of at least one of a shape of a coding block, a size of a coding block, a split depth of a coding block, or a split shape of an upper node block. For example, when the size of the coding block is the minimum size, when the splitting depth of the coding block is the maximum splitting depth, when the coding block is non-square, or when the size of the coding block is less than the predetermined size satisfies at least one The conversion process can be performed. When at least one of the plurality of coding blocks satisfies the above condition, the transform process may be performed. The minimum size or the maximum division depth may be predefined in the encoder and the decoder. In addition, information for determining the minimum size or the maximum division depth may be signaled through a bitstream. The predetermined size may be preset in the encoder and the decoder.

Alternatively, when the shape of the coding block is a preset form in the encoder and the decoder, the conversion process may be set. The preset form may be square (eg, 2x2 or 4x4) or rectangular (eg, 2x4, 4x2, 2x8 or 8x2).

Alternatively, information indicating whether to perform the conversion process may be signaled through the bitstream. For example, a flag indicating whether to perform transform processing on any one of a plurality of coding blocks may be signaled through a bitstream. Alternatively, information specifying the first coding block and the last coding block on which the transform process is performed may be signaled through the bitstream.

Alternatively, information indicating a condition for performing the conversion process may be signaled through the bitstream. The information may relate to at least one of a shape of a coding block, a size of a coding block, or a depth of a coding block that allows transform processing.

Prediction may be performed on each of a plurality of coding blocks, and transform or quantization may be performed on a transform block including the coding blocks.

18 is a flowchart illustrating a process of obtaining a residual sample according to an embodiment to which the present invention is applied.

First, a residual coefficient of the current block may be obtained (S1810). The decoder may acquire the residual coefficients through the coefficient scanning method. For example, the decoder may perform coefficient scanning using diagonal scan, zigzag scan, up-write scan, vertical scan, or horizontal scan, and as a result, obtain a residual coefficient in the form of a two-dimensional block.

Inverse quantization may be performed on the residual coefficient of the current block (S1820).

It may be determined whether to inverse transform the skipped inverse quantized residual coefficient of the current block (S1830). In detail, the decoder may determine whether to skip an inverse transform in at least one of the horizontal direction and the vertical direction of the current block. When it is determined to apply an inverse transform to at least one of a vertical or horizontal direction of the current block, a residual sample of the current block may be obtained by inversely transforming an inverse quantized residual coefficient of the current block (S1840). Here, the inverse transform may be performed using at least one of DCT, DST, or KLT.

If the inverse transform is skipped in both the horizontal and vertical directions of the current block, the inverse transform is not performed in the horizontal and vertical directions of the current block. In this case, the residual quantized residual coefficient may be scaled to a preset value to obtain a residual sample of the current block (S1850).

Omitting the inverse transform in the horizontal direction means performing the inverse transform in the vertical direction without performing the inverse transform in the horizontal direction. In this case, scaling may be performed in the horizontal direction.

Omitting the inverse transform in the vertical direction means not performing the inverse transform in the vertical direction but performing the inverse transform in the horizontal direction. In this case, scaling may be performed in the vertical direction.

According to the partition type of the current block, it may be determined whether an inverse transform skip technique may be used for the current block. For example, when the current block is generated through binary tree-based partitioning, the inverse transform skip technique may not be used for the current block. Accordingly, when the current block is generated through binary tree-based partitioning, a residual sample of the current block may be obtained by inversely transforming the current block. In addition, when the current block is generated through binary tree-based partitioning, encoding / decoding of information (eg, transform_skip_flag) indicating whether an inverse transform is skipped may be omitted.

Alternatively, when the current block is generated through binary tree based partitioning, the inverse transform skip technique may be limited to only at least one of the horizontal direction and the vertical direction. Here, the direction in which the inverse transform skip technique is limited may be determined based on information decoded from the bitstream or adaptively determined based on at least one of the size of the current block, the shape of the current block, or the intra prediction mode of the current block. have.

For example, when the current block is a non-square block having a width greater than the height, the inverse skip skip technique may be allowed only in the vertical direction, and the use of the inverse skip skip technique may be restricted in the horizontal direction. That is, when the current block is 2N × N, inverse transform may be performed in the horizontal direction of the current block, and inverse transform may be selectively performed in the vertical direction.

On the other hand, if the height of the current block is a non-square block larger than the width, the inverse skip skip technique can be allowed only in the horizontal direction, the use of the inverse transform skip technique can be restricted in the vertical direction. That is, when the current block is Nx2N, inverse transform may be performed in the vertical direction of the current block, and inverse transform may be selectively performed in the horizontal direction.

In contrast to the above example, if the current block is a non-square block with a width greater than its height, the inverse skipping scheme is allowed only for the horizontal direction; if the current block is a non-square block with a height greater than the width, an inverse transform for the vertical direction only The skip technique may be allowed.

Information on whether to skip the inverse transform in the horizontal direction or information indicating whether to skip the inverse transform in the vertical direction may be signaled through the bitstream. For example, information indicating whether to skip the inverse transform in the horizontal direction is a 1-bit flag, 'hor_transform_skip_flag', and information indicating whether to skip the inverse transform in the vertical direction is a 1-bit flag and 'ver_transform_skip_flag'. Can be '. The encoder may encode at least one of 'hor_transform_skip_flag' or 'ver_transform_skip_flag' according to the shape of the current block. In addition, the decoder may determine whether an inverse transform in the horizontal direction or the vertical direction is skipped using at least one of 'hor_transform_skip_flag' or 'ver_transform_skip_flag'.

Depending on the division form of the current block, in either direction, the inverse transform may be set to be omitted. For example, when the current block is generated through a binary tree based partitioning, an inverse transform in the horizontal direction or the vertical direction may be omitted. That is, if the current block is generated by partitioning based on a binary tree, the horizontal or vertical direction with respect to the current block may be performed without encoding / decoding of information indicating whether the inverse transform of the current block is skipped (for example, transform_skip_flag, hor_transform_skip_flag, ver_transform_skip_flag). It may be determined to skip the inverse transformation for at least one of the following.

The names of the syntaxes used in the above-described embodiments are merely named for convenience of description.

Application of the embodiments described mainly on the decoding process or the encoding process to the encoding process or the decoding process is included in the scope of the present invention. It is also within the scope of the present invention to change the embodiments described in a certain order in a different order than described.

Although the above-described embodiments are described based on a series of steps or flowcharts, this does not limit the time-series order of the invention and may be performed simultaneously or in a different order as necessary. In addition, in the above-described embodiment, each component (for example, a unit, a module, etc.) constituting the block diagram may be implemented as a hardware device or software, and a plurality of components are combined into one hardware device or software. It may be implemented. The above-described embodiments may be implemented in the form of program instructions that may be executed by various computer components, and may be recorded in a computer-readable recording medium. The computer-readable recording medium may include program instructions, data files, data structures, etc. alone or in combination. Examples of computer-readable recording media include magnetic media such as hard disks, floppy disks and magnetic tape, optical recording media such as CD-ROMs, DVDs, and magneto-optical media such as floptical disks. media), and hardware devices specifically configured to store and execute program instructions, such as ROM, RAM, flash memory, and the like. The hardware device may be configured to operate as one or more software modules to perform the process according to the invention, and vice versa.

Claims (12)

Determining whether the coding block is triple tree split;
If it is determined that the coding block is triple tree split, determining a split direction of the coding block; And
Dividing the coding block into three sub-coding blocks according to the determined division direction,
Quad tree division and triple tree division are not allowed in the sub-coded block. The method of claim 1,
The same method as the splitting direction is not allowed for the subblock having the largest size among the sub-coding blocks. The method of claim 1,
And the transform unit of the sub-coded blocks is set to be the same as the coding block. The method of claim 1,
When the size of at least one of the sub-coding blocks is the minimum size or at least one splitting depth is the maximum splitting depth, the transform unit of the sub-coding blocks is set to be the same as the coding block, Decryption method. The method of claim 1,
And the transformation unit of the sub coding blocks is set to a square region including the sub coding blocks. Determining whether the coding block is triple tree split;
If it is determined that the coding block is triple tree split, determining a split direction of the coding block; And
Dividing the coding block into three sub-coding blocks according to the determined division direction,
Quad tree splitting and triple tree splitting are not allowed in the sub-coding block. The method of claim 6,
The binary coding method of the same subdivision direction as the division direction is not allowed in the subblock having the largest size among the sub-coding blocks. The method of claim 6,
And the transform unit of the sub-coding blocks is set equal to the coding block. The method of claim 6,
When the size of at least one of the sub-coding blocks is the minimum size or at least one splitting depth is the maximum splitting depth, the transform unit of the sub-coding blocks is set to be the same as the coding block, Coding method. The method of claim 6,
And the transform unit of the sub coding blocks is set to a square region including the sub coding blocks. Determine whether a coding block is triple tree split, and if it is determined that the coding block is triple tree split, determine a split direction of the coding block, and according to the determined split direction, subcode the coded block into three sub-codes. And a picture dividing unit for dividing into blocks, wherein the quad-tree dividing method and the triple-tree dividing method are not allowed in the sub-coded block. Determine whether a coding block is triple tree split, and if it is determined that the coding block is triple tree split, determine a split direction of the coding block, and according to the determined split direction, subcode the coded block into three sub-codes. And a picture dividing unit for dividing into blocks, wherein a quad tree dividing method and a triple tree dividing method are not allowed in the sub-coded block.

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