WO2018155983A1

WO2018155983A1 - Video signal processing method and device

Info

Publication number: WO2018155983A1
Application number: PCT/KR2018/002340
Authority: WO
Inventors: 이배근
Original assignee: 주식회사 케이티
Priority date: 2017-02-24
Filing date: 2018-02-26
Publication date: 2018-08-30
Also published as: KR20180098158A

Abstract

The present invention relates to a video signal processing method and device. An image decoding method, according to the present invention, can comprise the steps of: confirming whether a current coding block is a current parallel processing block adjacent to a neighboring parallel processing block in at least any one of horizontal, vertical, and diagonal directions, by using block partition information on the current coding block; and decoding the current parallel processing block in parallel with the neighboring parallel processing block. According to the present invention, a block to be encoded/decoded is independently processed in parallel, thereby enabling the encoding/decoding efficiency of an image signal to be increased.

Description

Video signal processing method and apparatus

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 multi-tree partitioning method and apparatus capable of effectively dividing an encoding / decoding target block in encoding / decoding a video signal.

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

An object of the present invention is to provide a method and apparatus for parallel encoding and / or decoding a coding block divided by multi-tree partitioning.

An object of the present invention is to provide a recording medium including a video signal bitstream encoded by the encoding method.

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

The image decoding method according to the present invention uses the block partition information on the current coding block to determine whether the current coding block is a current parallel processing block adjacent to the neighboring parallel processing block in at least one of horizontal, vertical, or diagonal directions. And parallel decoding with the neighbor parallel processing block for the current parallel processing block.

In addition, if at least one reference sample reconstructed around the current parallel processing block does not exist, the method may further include obtaining a reference sample of the current parallel processing block by using the reconstructed reference sample around the neighbor parallel processing block. .

In addition, obtaining a reference sample of the current parallel processing block may include obtaining a difference between a reference point sample value of the current parallel processing block and a reference point sample of the neighbor parallel processing block as an offset, and restoring around the neighbor parallel processing block. Subtracting the offset from the received reference sample to obtain a reference sample of the current parallel processing block.

In addition, when the width w size of the current parallel processing block is smaller than the height h size, the reference point sample position of the current parallel processing block utilizes the restored top sample.

Further, when the current parallel processing block has a height h smaller than the width w, the reference sample position of the current parallel processing block utilizes the reconstructed left sample.

In addition, the reference sample of the current parallel processing block utilizes the restored reference sample of the neighbor parallel processing block as it is.

If the current coding block is located in the parallel coding unit unit PCUR region, the current coding block is determined as the current parallel processing block.

In addition, the form of the parallel coding unit unit PCUR can be selected among square or non-square in the encoding process, and obtains a syntax element indicating the form of the selected PCUR, and confirms the form of the PCUR.

In addition, when the parallel coding unit unit PCUR has a square shape, a syntax element indicating the size of the selected square PCUR is obtained to check the size of the square PCUR.

In addition, the parallel decoding step independently performs decoding without sharing at least motion information and a reference picture list among parallel processing blocks.

Further, the parallel decoding step independently performs decoding without sharing at least intra reference samples between parallel processing blocks.

The current parallel processing block also includes a block divided by multi-tree partitioning.

According to an embodiment of the present invention, a method of encoding an image may include determining whether a current coding block is a current parallel processing block adjacent to a neighboring parallel processing block in at least one of horizontal, vertical, or diagonal directions by using block partition information on the current coding block. And parallel encoding the current parallel processing block with the neighboring parallel processing block.

In addition, when at least one reference sample reconstructed around the current parallel processing block does not exist, the reconstructed reference sample around the neighbor parallel processing block is used to obtain a reference sample of the current parallel processing block.

In addition, if the current coding block is located in the predetermined parallel coding unit unit PCUR region, the current coding block is determined as the current parallel processing block.

Further, the form of the parallel coding unit unit PCUR is selectable between square or non-square, and signals a syntax element indicating the form of the selected PCUR.

In addition, when the shape of the parallel coding unit unit PCUR is selected as a square, a syntax element indicating the size of the selected square PCUR is signaled.

The image decoding apparatus according to the present invention uses block partition information on the current coding block to determine whether the current coding block is a current parallel processing block adjacent to the neighboring parallel processing block in at least one of horizontal, vertical, or diagonal directions, And a decoder for performing parallel decoding on the current parallel processing block together with the neighbor parallel processing block.

In a recording medium including a video signal bitstream according to the present invention, the video signal bitstream included in the recording medium may include at least a current coding block and a neighboring parallel processing block using block partition information about the current coding block. Determining whether the current parallel processing block is adjacent to one of the horizontal, vertical, and diagonal directions, and performing parallel encoding on the current parallel processing block together with the neighboring parallel processing block. It features.

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, by efficiently dividing an encoding / decoding target block, the encoding / decoding efficiency of a video signal can be increased.

According to the present invention, the encoding / decoding efficiency of an image signal can be increased by dividing an encoding / decoding target block into a symmetrical or asymmetrical block.

According to the present invention, the encoding / decoding efficiency of the video signal can be increased by independently processing the encoding / decoding target blocks in parallel.

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 that can be applied to a coding block when the coding block is encoded by inter-screen prediction.

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

FIG. 5 illustrates an example of hierarchically splitting a coding block based on quad tree and binary tree splitting as an embodiment to which the present invention is applied.

FIG. 6 illustrates an example of hierarchically partitioning coding blocks based on quad tree and symmetric binary tree splitting as an embodiment to which the present invention is applied.

7 is a diagram illustrating a partition form in which an asymmetric binary tree split is allowed as an embodiment to which the present invention is applied.

FIG. 8 illustrates a split form of a coding block based on quad tree and symmetric / asymmetric binary tree splitting as an embodiment to which the present invention is applied.

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

FIG. 10 illustrates, as an embodiment to which the present invention is applied, a syntax element included in a network abstraction layer (NAL) to which quadtree and binary tree splits are applied.

FIG. 11 is a diagram illustrating a partition type in which asymmetric quad tree division is allowed as another embodiment to which the present invention is applied.

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

FIG. 13 illustrates, as another embodiment to which the present invention is applied, a syntax element included in a network abstraction layer (NAL) to which asymmetric quadtree splitting is applied.

FIG. 14 is a diagram illustrating a partition type allowing quad tree and triple tree division as another embodiment to which the present invention is applied.

15 is a flowchart illustrating a coding block partitioning method based on quadtree and tripletree partitioning as another embodiment to which the present invention is applied.

FIG. 16 illustrates, as another embodiment to which the present invention is applied, a syntax element included in a network abstraction layer (NAL) to which quad tree and triple tree splits are applied.

FIG. 17 is a diagram illustrating a basic partition type in which multi-tree partitioning is allowed as another embodiment to which the present invention is applied.

18 is a diagram illustrating an extended partition type in which multi-tree partitioning is allowed as another embodiment to which the present invention is applied.

19 is a flowchart illustrating a coding block partitioning method based on multi-tree partitioning according to another embodiment to which the present invention is applied.

FIG. 20 is a diagram for explaining a parallel processing method of a first type coding block partitioned by multi-tree partitioning as another embodiment to which the present invention is applied.

FIG. 21 is a diagram for describing a parallel processing method of a second type coding block partitioned by multi-tree partitioning as another embodiment to which the present invention is applied.

FIG. 22 is a diagram for describing a parallel processing coding block partitioned by multi-tree partitioning as another embodiment to which the present invention is applied.

FIG. 23 is a diagram for describing a parallel processing unit processing region (PCUR: Parallel Coding Unit Processing Region) divided by multi-tree partitioning according to another embodiment to which the present invention is applied.

FIG. 24 is a diagram for describing a parallel processing encoding method of a coding block divided by multitree division, according to another embodiment to which the present invention is applied.

FIG. 25 is a diagram for explaining a parallel processing decoding method of a coding block divided by multitree partitioning, according to another embodiment to which the present invention is applied.

26 and 27 illustrate a method of obtaining a reference sample for parallel processing of a first type coding block according to another embodiment to which the present invention is applied.

28 and 29 are diagrams for explaining a method of obtaining a reference sample for parallel processing of a second type coding block as another embodiment to which the present invention is applied.

FIG. 30 illustrates, as another embodiment to which the present invention is applied, a syntax element included in a network abstraction layer (NAL) to which a parallel processing coding block divided to multi-tree partitions 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.

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.

In addition, the term “unit” used in the present application may be replaced with a “block”, and thus, the term “coding tree unit” and “coding tree block”, “coding unit” and “coding block” are used herein. ”,“ Prediction unit ”and“ prediction block ”,“ transform unit ”and“ transform block ”can be interpreted in the same sense.

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.

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

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.

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 by 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 present on the left side, the pixel present on the upper left side, and the upper part exist 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.

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 the largest coding unit allowed in a sequence or slice. Information regarding whether the coding tree unit is square or non-square or the size of the coding tree unit may be signaled through a sequence parameter set, a picture parameter set or a slice header. 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.

3 is a diagram illustrating a partition mode that may be applied to a coding block when a coding block is encoded by intra picture prediction or inter picture prediction. An arbitrary size partition generated as a coding tree unit is split is defined as a coding unit. can do. For example, Figure 3 (a) shows the coding unit is 2Nx2N size. The coding unit may be split recursively or split into basic units for performing prediction, quantization, transform, or in-loop filtering. For example, a partition of any size generated as a coding unit is divided may be defined as a coding unit, or a transform unit (TU) or a prediction unit that is a basic unit for performing prediction, quantization, transform, or in-loop filtering. (PU: Prediction Unit) can be defined.

Alternatively, when the coding block is determined, a prediction block having the same size as the coding block or a size smaller than the coding block may be determined through prediction division of the coding block. Predictive partitioning of a coding block may be performed by a partition mode (Part_mode) indicating a partition type of a coding block. The size or shape of the prediction block may be determined according to the partition mode of the coding block. The division type of the coding block may be determined through information specifying any one of partition candidates. In this case, the partition candidates available to the coding block may include an asymmetric partition shape (eg, nLx2N, nRx2N, 2NxnU, 2NxnD) according to the size, shape, or coding mode of the coding block. As an example, a partition candidate available to a coding block may be determined according to an encoding mode of the current block. For example, when the coding block is encoded by inter-screen prediction, any one of eight partition modes may be applied to the coding block, as shown in the example illustrated in FIG. On the other hand, when a coding block is encoded by intra prediction, PART_2Nx2N or PART_NxN among the eight partition modes of FIG. 3 (b) 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 is signaled through the slice header, and accordingly, the minimum size of the coding block may be defined for each slice.

As another example, the partition candidates available to the coding block may be determined differently according to at least one of the size or shape of the coding block. For example, the number or type of partition 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 candidates among partition candidates available to the coding block may be limited according to the size or shape of the coding block. As an example, the number or type of asymmetric partition 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.

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.

It is also possible to recursively split a coding block using the partition mode. That is, the coding block may be divided according to the partition mode indicated by the partition index, and each partition generated as the coding block is divided may be defined as the coding block.

Hereinafter, a method of recursively dividing a coding unit will be described in more detail. For convenience of description, hereinafter, it is assumed that a coding tree unit is included in a category of a coding unit. That is, in an embodiment to be described later, the coding unit may refer to a coding tree unit or may mean a coding unit generated as the coding tree unit is divided. In addition, when a coding block is recursively split, 'partition' generated as the coding block is split may be understood as meaning 'coding block'.

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

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

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

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

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

When the coding tree unit or 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.

In the embodiments described below, it is assumed that a coding unit is divided into four partitions as a quad tree-based partition, and that a coding unit is divided into two partitions is assumed to be a binary tree-based partition. In addition, it is assumed that the coding unit is divided into three partitions as triple tree based partitioning. In addition, it is assumed that the partitioning is performed by applying the at least two partitioning schemes.

In the drawings to be described below, to divide the coding unit, a predetermined number of vertical lines or a predetermined number of horizontal lines will be shown to be used, but using a larger number of vertical lines or a larger number of horizontal lines than shown, the coding unit It will also be within the scope of the present invention to divide the partition into more partitions than shown or fewer partitions than shown.

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 and a binary tree. Here, quad tree-based partitioning divides a 2Nx2N coding block into four NxN coding blocks (Fig. 4 (a)), and binary tree-based partitioning divides one coding block into two coding blocks. Each can mean. Even if binary tree-based partitioning is performed, there may be a square coding block at a lower depth.

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

Binary tree-based partitioning may be limitedly limited to either symmetric or asymmetric partitions. In this case, configuring the coding tree unit into square blocks may correspond to quad tree CU partitioning, and configuring the coding tree unit into symmetric non-square blocks may correspond to binary tree CU partitioning. Configuring the coding tree unit into square blocks and symmetric non-square blocks may correspond to quad and binary tree CU partitioning.

Hereinafter, the partitioning method based on the quad tree and the binary tree will be referred to as quad-tree & binary-tree (QTBT) partitioning.

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, in a Quad-Tree & Binary-Tree (QTBT) splitting method based on a quad tree and a binary tree, a coding block may be a prediction block, and the prediction block may be a transform block. For example, when the QTBT segmentation method is used, 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. Here, generating the prediction image in units of coding blocks may mean that motion information is determined based on the coding block or one intra prediction mode is determined based on the coding block. Accordingly, the coding block may be encoded using at least one of a skip mode, an intra prediction or an inter prediction.

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

In the QTBT division method, BT may be set such that only symmetric division 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, in the present invention, to improve coding efficiency, a method of partitioning coding blocks asymmetrically will be described later in another embodiment. Asymetric Binary Tree Partitioning refers to splitting a coding block into two smaller coding blocks. As a result of the asymmetric binary tree partitioning, the coding block may be divided into two asymmetrical coding blocks.

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

In addition, the division of the lower depth may be determined depending on the division type of the upper depth. For example, when binary tree-based partitioning is allowed in two or more depths, only a binary tree-based partitioning of the same type as a binary tree partitioning of an upper depth may be allowed in a lower depth. For example, when the binary tree based splitting is performed in the 2NxN form at the upper depth, the binary tree based splitting in the 2NxN form may be performed at the lower depth. Alternatively, when binary tree-based partitioning is performed in an Nx2N form at an upper depth, Nx2N-type binary tree-based partitioning may be allowed in a lower depth.

Conversely, it is also possible to allow only binary tree-based partitioning of a form different from the binary tree splitting form of the upper depth in the lower depth.

For sequences, slices, coding tree units, or coding units, only certain types of binary tree based partitioning may be used. For example, the 2NxN or Nx2N type binary tree based partitioning may be limited to the coding tree unit. The allowed partition type may be predefined in the encoder or the decoder, and information about the allowed partition type or the not allowed partition type may be encoded and signaled through a bitstream.

As illustrated in FIG. 5, 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 information about the size / depth of the coding block that is not.

The size of the coding block may be limited to a predetermined number, or the size of the coding block in the predetermined unit may have a fixed value. As an example, the size of the coding block in the sequence or the size of the coding block in the picture may be limited to 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.

6 is a diagram illustrating an example in which only a specific form, for example, a partition based on a symmetric binary tree is allowed. FIG. 6A illustrates an example in which only Nx2N type binary tree based partitioning is allowed. For example, the depth 1 coding block 601 may be divided into two

Nx2N blocks

601a and 601b at depth 2, and the depth 2 coding block 602 may be divided into two

Nx2N blocks

602a and 602b at depth 3. .

6 (b) shows an example in which only 2N × N type binary tree based partitioning is allowed. For example, the depth 1 coding block 603 may be divided into two

2NxN blocks

603a and 603b at depth 2, and the depth 2 coding block 604 may be divided into two

2NxN blocks

604a and 604b at depth 3. .

FIG. 6C illustrates an example of dividing a block divided into a symmetric binary tree into a symmetric binary tree. For example, the depth 1 coding block 605 is divided into two

Nx2N blocks

605a and 605b at depth 2, and the depth 2 coding block 605a generated after the division is divided into two Nx2N blocks 605a1, at depth 3. 605a2). The partitioning scheme is equally applicable to 2N × N coding blocks generated by symmetric binary tree partitioning.

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 Information about whether the image is in the horizontal direction may be used. For example, quad_split_flag may indicate whether a coding block is divided into four coding blocks, and binary_split_flag may indicate whether a coding block is divided into two coding blocks. When the coding block is split into two coding blocks, is_hor_split_flag indicating whether the splitting direction of the coding block is vertical or horizontal may be signaled.

In addition, for the coding tree unit or the predetermined coding unit, the number of times that binary tree splitting is allowed, the depth for which binary tree splitting is allowed or the number of depths for which binary tree splitting is allowed may be obtained. The information may be encoded in a coding tree unit or a coding unit and 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.

In addition, referring to the example of FIG. 6C, the result of performing binary tree splitting on the coding units having depth 2 (eg, 605a and 605b) and the coding units having depth 3 (eg, 605a1 and 605a2) is illustrated. . Accordingly, information indicating the number of times binary tree splitting has been performed in the coding tree unit (for example, two times), information indicating the maximum depth (eg, depth 3) allowed for binary tree splitting in the coding tree unit, or in the coding tree unit. At least one of information representing the number of depths (eg, two, depth 2, and depth 3) allowed for binary tree splitting 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 a binary tree split allows, may be differently set according to a temporal identifier (Temporal_ID) of a slice or a picture. have. Here, the temporal level identifier Temporal_ID 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.

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

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

When applying the transform skip to at least one of the horizontal direction and the vertical direction, it is also possible to signal in which direction the transform skip is applied depending on the type of the CU. Specifically, for example, in the case of a 2NxN type CU The transform may be performed in the horizontal direction and the transform skip may be applied in the vertical direction. In the case of an Nx2N type CU, the transform skip may be applied in the horizontal direction and the transform may be performed in the vertical direction. Here, the transform may be at least one of DCT or DST.

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

FIG. 7 is a diagram illustrating a partition form in which an asymmetric binary tree split is allowed according to an embodiment to which the present invention is applied. A 2Nx2N coding block includes two coding blocks having a width ratio of n: (1-n) or a height ratio of n It may be split into two coding blocks: (1-n). Here, n may represent a real number greater than 0 and less than 1.

In FIG. 7, for example, as asymmetric binary tree partitioning is applied to a coding block, two

coding blocks

701, 702 having a width ratio of 1: 3, or two

coding blocks

703, 704 having a 3: 1, Or two

coding blocks

705, 706 with a height ratio of 1: 3 or two

coding blocks

707, 708 with a 3: 1 are shown.

Specifically, as the coding block having the WxH size is divided in the vertical direction, a left partition having a width of 1 / 4W and a right partition having a width of 3 / 4W 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 3 / 4W and a right partition having a width of 1 / 4W 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, a top partition having a height of 1 / 4H and a bottom partition having a height of 3 / 4H 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 3 / 4H and a lower partition having a height of 1 / 4H 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.

In FIG. 7, the width ratio or height ratio between two coding blocks is 1: 3 or 3: 1. However, the width ratio or height ratio between two coding blocks generated by asymmetric binary tree partitioning is not limited thereto. The coding block may be divided into two coding blocks having a different width ratio or a different height ratio than that shown in FIG. 7.

In the case of using asymmetric binary tree partitioning, an asymmetric binary partition shape of a coding block may be determined based on information signaled through a bitstream. For example, a partitioning type of a coding block may include information indicating a partitioning direction of a coding block and a coding block. The partition may be determined based on information indicating whether the first partition generated as the partition is smaller 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, hor_binary_flag may indicate whether a coding block is divided in a horizontal direction. A value of hor_binary_flag equal to 1 indicates that the coding block is divided in the horizontal direction, and a value of hor_binary_flag equal to 0 may indicate that the coding block is divided in the vertical direction. Alternatively, ver_binary_flag indicating whether the coding block is divided in the vertical direction may be used.

The information indicating whether the first partition has a smaller size than the second partition may be a 1-bit flag. As an example, is_left_above_small_part_flag may indicate whether the size of the left or top partition generated as the coding block is split is smaller than the right or bottom partition. The value of is_left_above_small_part_flag equal to 1 may mean that the size of the left or top partition is smaller than the right or bottom partition, and the value of is_left_above_small_part_flag equal to 0 may mean that the size of the left or top partition is larger than the right or bottom partition. Alternatively, is_right_bottom_small_part_flag may be used indicating whether the size of the right or bottom partition is smaller than the left or top 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.

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 may 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 may indicate a 2NxnD binary partition.

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

	Asymetric partition indexAsymetric partition index	BinarizationBinarization

nLx2NnLx2N	00	00
nRx2N nRx2N		1One	1010
2NxnU 2NxnU	22	100100
2NxnD 2NxnD	33	111111

Asymmetric binary tree partitioning may be used depending on the QTBT partitioning method. For example, if quad tree partitioning or binary tree partitioning is no longer applied to a coding block, whether to apply asymmetric binary tree partitioning to the coding block. Can be determined. Here, whether to apply asymmetric binary tree splitting to the coding block may be determined by information signaled through the bitstream. For example, the information may be a 1-bit flag 'asymmetric_binary_tree_flag', and based on the flag, it may be determined whether asymmetric binary tree splitting is applied to the coding block. Alternatively, the coding block may be split into two blocks. If so, it may be determined whether the partition type is binary tree split or asymmetric binary tree split. Here, whether the partition type of the coding block is binary tree partitioning or asymmetric binary tree partitioning may be determined by information signaled through the bitstream. For example, the information may be a one-bit flag 'is_asymmetric_split_flag', and based on the flag, it may be determined whether the coding block is divided into symmetrical or asymmetrical forms. Different indexes may be allocated and according to the index information, it may be determined whether a coding block is divided into a symmetrical form or an asymmetrical form. As an example, Table 2 shows an example in which different indices are assigned to a symmetric binary partition and an asymmetric binary partition.

	Binary partition indexBinary partition index	BinarizationBinarization
2NxN (수평 방향 바이너리 파티션)2NxN (horizontal binary partition)	00	00
Nx2N(수직 방향 바이너리 파티션)Nx2N (vertical binary partition)	1One	1010
nLx2N nLx2N	22	110110
nRx2NnRx2N	33	11101110
2NxnU 2NxnU	44	1111011110
2NxnD 2NxnD	55	1111111111

The coding tree block or coding block may be subdivided into a plurality of coding blocks through quad tree splitting, binary tree splitting or asymmetric binary tree splitting. For example, FIG. 8 is a diagram illustrating an example in which a coding block is divided into a plurality of coding blocks using QTBT and asymmetric binary tree splitting. Referring to FIG. 9, it can be seen that asymmetric binary tree splits are performed in depth 2 partitioning of the first grip, depth 3 partitioning of the second figure, and depth 3 partitioning of the third figure. Coding blocks divided by asymmetric binary tree partitioning are performed. May be restricted so that it is no longer split. For example, quad-tree, binary tree, or asymmetric binary tree related information may not be encoded / decoded in a coding block generated through asymmetric binary tree partitioning. 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 binary tree is split, a binary tree, or an asymmetric binary tree split direction is specified. Encoding / decoding of syntax, such as an indicating flag or index information indicating an asymmetric binary partition, may be omitted. As another example, whether to allow binary tree partitioning may be determined depending on whether to allow QTBT. As an example, asymmetric binary tree partitioning may be restricted from a picture or slice in which a split method based on QTBT is not used.

Information indicating whether asymmetric binary tree partitioning is allowed may be encoded and signaled in units of blocks, slices, or pictures. Here, the information indicating whether asymmetric binary tree partitioning is allowed may be a 1-bit flag. As an example, the value of is_used_asymmetric_QTBT_enabled_flag equal to 0 may indicate that asymmetric binary tree partitioning is not used. When binary tree partitioning is not used on a picture basis or a slice basis, the value may be set to 0 without signaling is_used_asymmetric_QTBT_enabled_flag.

8 (a) shows an example in which nLx2N type asymmetric binary tree based partitioning is allowed. For example, depth 1 coding block 801 is divided into two

asymmetrical nLx2N blocks

801a and 801b at depth 2, and depth 2 coding block 801b is also divided into two symmetrical Nx2N blocks 801b1 and 801b2 at depth 3. The divided example is shown.

8 (b) shows an example in which nRx2N type asymmetric binary tree based partitioning is allowed. For example, the depth 2 coding block 802 illustrates an example divided into two

asymmetric nRx2N blocks

802a and 802b at depth 3.

8 (c) shows an example in which 2NxnU type asymmetric binary tree based partitioning is allowed. For example, the depth 2 coding block 803 shows an example divided into two asymmetric two 2N ×

nU blocks

803a and 803b at depth 3.

Based on the size, shape, split depth or split type of the coding block, the split 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, when the coding block is generated by quad tree splitting, the coding block may allow both quad tree splitting, binary tree splitting, and asymmetric binary tree splitting. That is, when the coding block is generated based on quad tree partitioning, all the partition types shown in FIG. 10 may be applied to the coding block. For example, a 2N × 2N partition indicates a case in which the coding block is no longer partitioned and NxN. Denotes a case in which a coding block is quadtree-divided, and Nx2N and 2NxN may indicate a case in which a coding block is binary-tree divided. Also, nLx2N, nRx2N, 2NxnU, and 2NxnD may represent a case where a coding block is asymmetric binary tree split.

On the other hand, when the coding block is generated by binary tree splitting, the asymmetric binary tree splitting may be limited to the coding block. That is, when the coding block is generated based on binary tree partitioning, it may be restricted to apply an asymmetric partition type (nLx2N, nRx2N, 2NxnU, 2NxnD) among the partition types shown in FIG. 7 to the coding block.

Assume that the depth k coding block is divided into the depth k + 1 coding blocks. First, it is determined whether quad tree splitting is applied to the depth k current block (S910). If quad tree splitting is applied, the current block is split into four square blocks (S920). On the other hand, if quad tree splitting is not applied, it is determined whether binary tree splitting is applied to the current block (S930). If binary tree splitting is not applied, then the current block becomes a depth k + 1 coding block without splitting. As a result of the determination of S930, if binary tree partitioning is applied to the current block, it is checked whether either symmetrical binary partitioning or asymmetrical binary partitioning is applied (S940). According to the determination result of S940, the partition type applied to the current block is determined (S950). For example, the partition type applied to the step S950 may be any one of the form of FIG. 4 (b) in the case of symmetry, or one of the form of FIG. 4 (c) in case of the asymmetry. In step S950, the current block is divided into two depth k + 1 coding blocks according to the determined partition type (S960).

The compressed image to which the present invention is applied may be packetized in units of a network abstract layer (hereinafter, referred to as NAL) and transmitted through a transmission medium. However, the present invention is not limited to the NAL, but may be applied to various data transmission schemes to be developed in the future. NAL unit to which the present invention is applied, for example, as shown in Figure 10, video parameter set (VPS), sequence parameter set (SPS), picture parameter set (PPS) and at least one slice set (Slice) It may include.

For example, although the syntax elements included in the sequence parameter set (SPS) are illustrated in FIG. 10, the syntax elements may be included in the picture parameter set (PPS) or the slice set (Slice). In addition, syntax elements to be commonly applied to sequence units or picture units for each syntax element may be included in a sequence parameter set (SPS) or a picture parameter set (PPS). On the other hand, the syntax element applied only to the slice is preferably included in the slice set (Slice). Therefore, this can be selected in consideration of encoding performance and efficiency.

In this regard, the syntax elements to which quad tree and binary tree splits are applied are as follows. Although all syntax elements shown in FIG. 10 may be set as essential elements, dual syntax elements may be selectively set in consideration of encoding efficiency and performance.

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

In another alternative, 'isUseBinaryTreeFlag' indicates whether binary tree partitioning is applied to the current block, and is also a syntax element indicating a split direction of the coding block, and 'hor_binary_flag' indicates whether the coding block has been split in the horizontal direction. Can be represented. For example, when “hor_binary_flag = 1”, this may indicate that the coding block is split in the horizontal direction, and when “hor_binary_flag = 0”, it may indicate that the coding block is split in the vertical direction. Or, instead of 'hor_binary_flag', ver_binary_flag indicating whether or not the coding block is divided in the vertical direction may be set in the same manner.

In addition, 'max_binary_depth_idx_minus1' may be defined as a syntax element indicating the maximum depth allowed for binary tree splitting. For example, "max_binary_depth_idx_minus1 + 1" may indicate the maximum depth allowed for binary tree splitting.

In addition, 'ver_transform_skip_flag' may be set as a syntax element indicating whether to apply the horizontal transform skip and 'hor_transform_skip_flag' and a syntax element indicating whether to apply the vertical transform skip.

In addition, as an syntax element indicating whether asymmetric binary tree partitioning is allowed, 'is_used_asymmetric_QTBT_enabled_flag' may be defined. For example, "is_used_asymmetric_QTBT_enabled_flag = 1" indicates that asymmetric binary tree partitioning is used, and "is_used_asymmetric_QTBT_enabled_flag = 0" may indicate that asymmetric binary tree partitioning is not used. On the other hand, when binary tree partitioning is not used in picture units or slice units, the value may be set to 0 without signaling is_used_asymmetric_QTBT_enabled_flag. Alternatively, 'asymmetric_binary_tree_flag' may indicate whether asymmetric binary tree partitioning is applied to the current block.

In addition, as a syntax element indicating asymmetric binary tree partitioning, 'is_left_above_small_part_flag' may indicate whether the size of the left or top partition generated as the coding block is split is smaller than the right or bottom partition. For example, if “is_left_above_small_part_flag = 1” means the size of the left or top partition is smaller than the right or bottom partition, and if “is_left_above_small_part_flag = 0”, the size of the left or top partition is larger than the right or bottom partition Can mean. Alternatively, instead of 'is_left_above_small_part_flag', 'is_right_bottom_small_part_flag' indicating whether the size of the right or bottom partition is smaller than the left or top partition may be used.

In this regard, it is possible to combine the syntax elements to define an asymmetric binary partition form of a coding block. For example, “hor_binary_flag = 0” and “is_left_above_small_part_flag = 1” can be set to indicate nLx2N binary partitions, and “hor_binary_flag = 0” and “is_left_above_small_part_flag = 0” to indicate nRx2N binary partitions. In addition, if "hor_binary_flag = 1" and "is_left_above_small_part_flag = 1", it can represent a 2NxnU binary partition. If "hor_binary_flag = 1" and "is_left_above_small_part_flag = 0", it can represent a 2NxnD binary partition. Similarly, the combination of the 'ver_binary_flag' and the 'is_right_bottom_small_part_flag' may indicate an asymmetric binary partition form.

Alternatively, it is possible to define an asymmetric binary partition form of a coding block by indicating the index of Table 1 described above by Asymetric_partition_index 'or by indicating the index of table 2 described above by' Binary_partition_index '. Do.

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

When the current block is quad tree split, at least one of the horizontal line or the vertical line may split the coding block into an asymmetric shape. Here, the asymmetry may mean a case in which the heights of the blocks divided by the horizontal lines are not the same or the widths of the blocks divided by the vertical lines are not the same. 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, while a horizontal line divides a coding block into a symmetric form, whereas a vertical line divides a coding block into an asymmetric form. It may be. Alternatively, both horizontal and vertical lines may split the coding block into an asymmetric shape.

11 (a) shows a symmetric quad tree split form of a coding block, and (b) to (k) shows an asymmetric quad tree split form of a coding block. 11 (a) shows an example in which both horizontal and vertical lines are used for symmetrical division. 11 (b) and 11 (c) show an example in which horizontal lines are used for symmetrical division, while vertical lines are used for asymmetrical division. 11 (d) and (e) show an example in which vertical lines are used for symmetrical division, while horizontal lines are used for asymmetrical division.

In order to specify the divisional form of the coding block, information related to the divisional form of the coding block may be encoded. In this case, the information may include a first indicator indicating whether the partitioned form of the coding block is symmetrical or asymmetrical. The first indicator may be encoded in units of blocks or may be encoded for each vertical line or horizontal line. For example, the first indicator may include information indicating whether a vertical line is used for symmetric division and information indicating whether a horizontal line is used for symmetric division.

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

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

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

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

Referring to FIGS. 11F and 11K, quadtree splitting divides a coding block into three blocks by two vertical lines or two horizontal lines, and any one of the divided three blocks into two blocks. By dividing. At this time, as in the example shown in Figs. 11 (f) to (k), a block located in the middle of the blocks divided by two vertical lines or two horizontal lines may be divided by one horizontal line or vertical line. In addition to the illustrated example, a block located at one boundary of a coding block may be divided by one horizontal line or a vertical line. Alternatively, information (eg, partition index) for specifying a partition among three partitions may be signaled through the bitstream.

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

For example, FIG. 11 (f) illustrates a partition form in which a middle coding block divided into two asymmetrical shapes by two vertical lines is divided into two symmetrical coding blocks by a horizontal line. In addition, FIG. 11 (g) illustrates a partition form in which a middle coding block divided into two asymmetrical shapes by two horizontal lines is divided into two symmetrical coding blocks by a vertical line.

On the other hand, Figure 11 (h) and (i) shows a partition form in which the middle coding block divided into two asymmetrical forms by two vertical lines divided into two asymmetrical coding blocks by a horizontal line again. 11 (j) and 11 (k) show a partition form in which a middle coding block divided into two asymmetrical shapes by two horizontal lines is further divided into two asymmetrical coding blocks by a vertical line.

When combining a plurality of vertical / horizontal lines and one horizontal / vertical line, the coding block is divided into four partitions (i.e., four coding blocks) of at least two different sizes. The partitioning of a coding block into four partitions of at least two different sizes may be referred to as three types of asymmetric quad-tree partitioning.

The information about the three asymmetric quad tree partitionings may be encoded based on at least one of the aforementioned first indicator or second indicator. As an example, the first indicator may indicate whether the splitting form of the coding block is symmetrical or asymmetrical. The first indicator may be encoded in units of blocks or may be encoded for each vertical line or horizontal line. For example, the first indicator may include information indicating whether one or more vertical lines are used for symmetric division and information indicating whether one or more horizontal lines are used for symmetric division.

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

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

Assume that the depth k coding block is divided into the depth k + 1 coding blocks. First, it is determined whether the quad tree split is applied to the depth k current block (S1210). As a result of the determination of step S1210, if quad tree splitting is not applied, the current block becomes a depth k + 1 coding block without splitting. If it is determined in step S1210 that the quad tree split is applied, it is determined whether the asymmetric quad tree split is applied to the current block (S1220). If the asymmetric quad tree split is not applied and the symmetric quad tree split is applied, the current block is split into four square blocks (S1230).

On the other hand, if an asymmetric quad tree split is applied, it is determined whether three asymmetric quad tree splits are applied to the current block (S1240). If three kinds of asymmetric quad tree splits are not applied, the current block is divided into four two kinds of asymmetric blocks (S1250). In this case, the partition information may be divided into any one partition form of FIGS. 11 (b) to (e).

On the other hand, if three kinds of asymmetric quad tree splits are applied, the current block is divided into four kinds of three asymmetric blocks (S1260). In this case, the partition information may be partitioned into one of the partitions of FIGS. 11 (f) to 11 (k).

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

For example, although FIG. 13 illustrates syntax elements included in a sequence parameter set (SPS), syntax elements may be included in a picture parameter set (PPS) or a slice set (Slice). In addition, syntax elements to be commonly applied to sequence units or picture units for each syntax element may be included in a sequence parameter set (SPS) or a picture parameter set (PPS). On the other hand, the syntax element applied only to the slice is preferably included in the slice set (Slice). Therefore, this can be selected in consideration of encoding performance and efficiency.

The syntax element 'Is_used_asymmertic_quad_tree_flag' indicates whether quad tree splitting is performed asymmetrically. In addition, 'Is_used_triple_asymmertic_quad_tree_flag' indicates whether quad tree splitting is performed asymmetrically. Therefore, if "Is_used_asymmertic_quad_tree_flag = 0" means symmetric quad tree split, 'Is_used_triple_asymmertic_quad_tree_flag' is not signaled. On the other hand, if "Is_used_asymmertic_quad_tree_flag = 1" and "Is_used_triple_asymmertic_quad_tree_flag = 1", it means three types of asymmetric quad tree splits. In addition, if "Is_used_asymmertic_quad_tree_flag = 1" and "Is_used_triple_asymmertic_quad_tree_flag = 0", it means two types of asymmetric quad tree splits.

The syntax element 'hor_asymmetric_flag' indicates the direction of asymmetric quad tree splitting. That is, when “Is_used_asymmertic_quad_tree_flag = 1”, this may indicate whether the asymmetric division is performed in the horizontal direction or the vertical direction. For example, "hor_asymmetric_flag = 1" indicates asymmetry in the horizontal direction, and "hor_asymmetric_flag = 0" indicates asymmetry in the vertical direction. Alternatively, it is also possible to utilize 'ver_asymmetric_flag'.

The syntax element 'width_left_asymmetric_flag' indicates another direction of asymmetric quad tree splitting. That is, when “Is_used_asymmertic_quad_tree_flag = 1”, this may indicate whether the asymmetric division is performed in the width direction left or right direction. For example, "width_left_asymmetric_flag '= 1" indicates asymmetry in the width left direction, and "width_left_asymmetric_flag = 0" indicates asymmetry in the width right direction.

In addition, the syntax element 'height_top_asymmetric_flag' indicates another direction of asymmetric quad tree splitting. That is, in the case of “Is_used_asymmertic_quad_tree_flag = 1”, this may indicate whether the asymmetric division is performed in the upper direction or the lower direction in the height direction. For example, "height_top_asymmetric_flag '= 1" indicates asymmetry in the upper direction of height, and "height_top_asymmetric_flag = 0" indicates asymmetry in the lower direction of height.

In addition, the syntax element 'is_used_symmetric_line_flag' indicates whether the block is symmetric with respect to the center block in the case of three asymmetric quad tree splits. That is, when "Is_used_asymmertic_quad_tree_flag = 1" and "Is_used_triple_asymmertic_quad_tree_flag = 1", this indicates whether the middle block is symmetrically divided.

Therefore, it is possible to express the partition form shown in Figs. 11A to 11K through the combination of the syntax elements. For example, if "Is_used_asymmertic_quad_tree_flag = 0", it means that the partition is divided into four symmetric blocks as shown in FIG. 11 (a).

In addition, if "Is_used_asymmertic_quad_tree_flag = 1" and "Is_used_triple_asymmertic_quad_tree_flag = 0", it corresponds to any one of partition types of FIGS. 11 (b) to (e). In this case, if “hor_asymmetric_flag = 1” and “width_left_asymmetric_flag '= 1”, this means a partition type of FIG. 11 (b). In addition, when "hor_asymmetric_flag = 1" and "width_left_asymmetric_flag '= 0", it means a partition form of FIG. 11 (c). In addition, when "hor_asymmetric_flag = 0" and "height_top_asymmetric_flag '= 1", it means a partition type of FIG. 11 (d). In addition, when "hor_asymmetric_flag = 0" and "height_top_asymmetric_flag '= 0", it means the partition type of FIG. 11 (e).

In addition, if "Is_used_asymmertic_quad_tree_flag = 1" and "Is_used_triple_asymmertic_quad_tree_flag = 1", it corresponds to any one of partition types of FIGS. 11 (f) to (k). In this case, if "is_used_symmetric_line_flag = 1", it corresponds to any one of FIG. 11 (f), (g) partition type, and if "is_used_symmetric_line_flag = 0", it corresponds to any one of FIG. 11 (h) ~ (k) partition type. Yes. In addition, if "is_used_symmetric_line_flag = 1" and "hor_asymmetric_flag = 1", it may be defined in FIG. 11 (f) partition form, and in the case of "hor_asymmetric_flag 0", it may be defined in FIG. 11 (g) partition form.

In addition, when "Is_used_asymmertic_quad_tree_flag = 1", "Is_used_triple_asymmertic_quad_tree_flag = 1" and "is_used_symmetric_line_flag = 0", "hor_asymmetric_flag" and "width_left_asymmetric_flag" can be defined by "hehe_a_symmetric_flag" and "aheight_flag". For example, when “hor_asymmetric_flag = 1” and “height_top_asymmetric_flag = 0”, this means a partition type of FIG. 11 (h). In addition, when "hor_asymmetric_flag = 1" and "height_top_asymmetric_flag = 1", it means the partition type of FIG. 11 (i). In addition, when "hor_asymmetric_flag = 0" and "width_left_asymmetric_flag '= 0", it means the partition type of FIG. 11 (j). In addition, when "hor_asymmetric_flag = 0" and "width_left_asymmetric_flag '= 1", it means the partition type of FIG. 11 (k).

Alternatively, the partition types of FIGS. 11A to 11K may be represented as indexes by 'asymmetric_quadtree_partition_index'.

The coding block may be hierarchically divided based on at least one of a quad tree and a triple tree. Here, quad tree-based partitioning divides a 2Nx2N coding block into four NxN coding blocks (FIG. 14 (a)), and triple tree-based partitioning divides one coding block into three coding blocks. Each can mean. Even if triple tree-based partitioning is performed, there may be a square coding block at a lower depth.

Triple tree based splitting may be performed symmetrically (FIG. 14B) or may be performed asymmetrically (FIG. 14C). In addition, the coding block divided based on the triple tree may be a square block or a non-square block such as a rectangle. For example, a partition type that allows triple tree-based partitioning is a 2Nx (2N / 3) (horizontal non-square coding unit) that is symmetric with the same width or height, as in the example shown in FIG. 14 (b). ) Or (2N / 3) x2N (a vertical non-square coding unit). In addition, as an example, a partition type that allows triple tree-based partitioning may be an asymmetric partition type including coding blocks having different widths or heights, as shown in the example illustrated in FIG. 14C. have. For example, in the form of an asymmetric triple tree partition according to FIG. 14 (c), at least two

coding blocks

1401 and 1403 are defined to be located at both sides with k values having the same width (or height) size, and the rest. One block 1402 may be defined to have a value of 2k as a width (or height) size and be located between the same size blocks 1401 and 1403.

In relation to this, a method of dividing a CTU or a CU into three sub-partitions having a non-square shape as shown in FIG. 14 is called a triple tree CU partitioning method. A CU divided into triple tree partitioning may be further restricted to not perform partitioning.

Assume that the depth k coding block is divided into the depth k + 1 coding blocks. First, it is determined whether the quad tree split is applied to the depth k current block (S1510). If quad tree splitting is applied, the current block is split into four square blocks (S1520). On the other hand, if the quad tree split has not been applied, it is determined whether the triple tree split is applied to the current block (S1530). If triple tree splitting is not applied, the current block becomes a depth k + 1 coding block without splitting.

As a result of the determination in S1530, if triple tree splitting is applied to the current block, it is checked whether either of symmetric triple splitting or asymmetric triple splitting is applied (S1540). The partition type applied to the current block is determined according to the determination result of S1540 (S1550). For example, the partition type applied to the step S1550 may be any one of the shape of FIG. 14 (b) in the case of symmetry, and one of the shape of FIG. 14 (c) in the case of the asymmetry. In operation S1550, the current block is divided into three depth k + 1 coding blocks according to the determined partition type in operation S1560.

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

For example, although FIG. 16 illustrates syntax elements included in a sequence parameter set (SPS), syntax elements may be included in a picture parameter set (PPS) or a slice set (Slice). In addition, syntax elements to be commonly applied to sequence units or picture units for each syntax element may be included in a sequence parameter set (SPS) or a picture parameter set (PPS). On the other hand, the syntax element applied only to the slice is preferably included in the slice set (Slice). Therefore, this can be selected in consideration of encoding performance and efficiency.

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

In another alternative, 'isUseTripleTreeFlag' indicates whether triple tree partitioning is applied to the current block, and is also a syntax element indicating a split direction of the coding block, and 'hor_triple_flag' indicates whether the coding block has been split in the horizontal direction. Can be represented. For example, when “hor_triple_flag = 1”, this may indicate that the coding block is split in the horizontal direction, and when “hor_triple_flag = 0”, it may indicate that the coding block is split in the vertical direction. Alternatively, instead of 'hor_triple_flag', ver_triple_flag indicating whether a coding block is divided in the vertical direction may be used in the same manner.

In addition, 'asymmetric_triple_tree_flag' may be defined as a syntax element indicating whether asymmetric triple tree partitioning is allowed. For example, "asymmetric_triple_tree_flag = 1" indicates that asymmetric triple tree partitioning is used, and "asymmetric_triple_tree_flag = 0" indicates that asymmetric triple tree partitioning is not used. On the other hand, when triple tree partitioning is not used in picture units or slice units, the value may be set to 0 without signaling 'asymmetric_triple_tree_flag'.

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

In addition, if "isUseTripleTreeFlag = 1" and "asymmetric_triple_tree_flag = 0", it corresponds to any one of partition types of FIG. 14 (b). In this case, if "hor_triple_flag = 1", it is defined as meaning (b) (2N / 3) x2N partition type of FIG. If “hor_triple_flag = 0”, FIG. 14B may be defined to mean a 2Nx (2N / 3) partition type.

In addition, if "isUseTripleTreeFlag = 1" and "asymmetric_triple_tree_flag = 1", it corresponds to any one of partition types of FIG. 14 (c). At this time, if "hor_triple_flag = 1", it is defined to mean the partition shape of Figure 14 (c). If “hor_triple_flag = 0”, it may be defined as meaning the right partition form of FIG. 14 (c).

Alternatively, the partition types of FIGS. 14A to 14C may be represented as indexes by 'asymmetric_tripletree_partition_index'.

FIG. 17 is a diagram illustrating a partition type in which multi-tree partitioning is allowed as another embodiment to which the present invention is applied.

A method of partitioning a CTU or CU using at least one of the aforementioned quad tree partitioning, binary partitioning, or triple tree partitioning is called multi-tree CU partitioning. Any of the N partitions described above may be used to partition a CTU or a CU. Specifically, for example, as shown in FIG. 17, nine partitions may be used to partition a CTU or a CU.

Partitioning may be performed using quad-tree partitioning, binary tree partitioning, or triple-tree partitioning, either in sequence units or in picture units, or the CTU or CU may be partitioned using any one or two partitionings.

Quad tree partitioning is used by default, and binary tree partitioning and triple tree partitioning are optional. In this case, it may be signaled whether to use binary tree partitioning and / or triple tree partitioning in a sequence parameter set or a picture parameter set.

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

The partition form divided by multi-tree partitioning can be limited to nine basic partitions shown in Figs. 17A to 17I, for example. (A) shows a quad tree partition form, (b)-(c) shows a symmetric binary tree partition form, (d)-(e) shows an asymmetric triple tree partition form, and (f)- (i) shows an asymmetric binary tree partition type. Regarding each partition type shown in FIG. 17 in connection with the above description, detailed descriptions thereof will be omitted.

Alternatively, it may be extended to further include 12 partitions shown in FIGS. 18 (j) to (u), for example, in the form of partitions divided by multi-tree partitioning. 18 (j) to (m) show an asymmetric quad tree partition form, (n) to (s) show three asymmetric quad tree partition forms, and (t) to (u) show a symmetric triple tree partition form. Express. Regarding each partition type shown in FIG. 18 in the same manner as described above, a detailed description thereof will be omitted.

Assume that the depth k coding block is divided into the depth k + 1 coding blocks. First, it is determined whether the quad tree split is applied to the depth k current block (S1910). If the quad tree split has not been applied, it is determined whether the binary tree split is applied to the current block (S1950). In addition, if binary tree splitting is not applied, it is determined whether triple tree splitting is applied to the current block (S1990). If triple tree splitting is not applied as a result of the step S1950, the current block becomes a depth k + 1 coding block without splitting.

As a result of the determination in step S1910, if quad tree splitting is applied, it is checked whether a symmetrical or asymmetric quadtree splitting is performed (S1920). Thereafter, the partition information is checked to determine the block partition type of the current block (S1930), and the current block is divided into four blocks according to the determined partition type (S1940). For example, when the symmetric quad tree is applied, it is divided into the partition form of FIG. 17 (a). In addition, when the asymmetric quad tree is applied, it is divided into any one partition form of FIGS. 18 (j) to (m). Alternatively, when three kinds of asymmetric quad trees are applied, they are divided into any one partition form of Figs. 18 (n) to (s). However, as described above, if only the basic partition type of FIG. 17 is applied to the multi-tree partition type, only the symmetric square block of FIG. 17 (a) may be applied without determining whether the quad tree is asymmetric.

In addition, as a result of the determination of step S1950, if binary tree splitting is applied, it is checked whether a symmetric or asymmetric binary tree splitting is performed (S1960). Thereafter, the partition information is determined to determine the block partition type of the current block (S1970), and the current block is divided into two blocks according to the determined partition type (S1980). For example, when the symmetric binary tree is applied, the partition is divided into one of the partitions of FIGS. 17B and 17C. In addition, when an asymmetric binary tree is applied, it divides into any partition form of FIG.17 (f)-(i).

In addition, as a result of the determination in step S1990, if triple tree splitting is applied, it is checked whether symmetric or asymmetric triple tree splitting is performed (S1960). Thereafter, the partition information is determined to determine a block partition type of the current block (S1970), and the current block is divided into three blocks according to the determined partition type (S1980). For example, when an asymmetric triple tree is applied, it is divided into any one partition form of FIGS. 17 (d) and (e). In addition, when the symmetric binary tree is applied, it divides into any partition form of FIG. 18 (t)-(u). However, as described above, if the multi-tree partition type applies only the basic partition type of FIG. 17, the asymmetric triple block defined in 17 (d) and (e) is not determined without determining whether the triple tree is asymmetric. Only applicable.

. As a syntax element representing multi-tree partitioning, 'is_used_Multitree_flag' indicating whether to split a multi-tree may be defined. In addition, it is possible to use the syntax elements shown and described with reference to FIGS. 10, 13, and 16 as information for determining a multi-tree partitioner shape.

20 and 21 are diagrams for explaining a parallel processing method of coding blocks divided by multi-tree division, as another embodiment to which the present invention is applied. For example, FIG. 20 illustrates a parallel processing method of a first type coding block partitioned by multi-tree partitioning, and FIG. 21 illustrates a parallel processing method of a second type coding block partitioned by multi-tree partitioning. will be. The first type coding block refers to a non-square block having a longer length in the vertical direction when the width (w) of the parallel processing block is smaller than the height (h). In addition, the second type coding block is a case where the height h of the parallel processing block is smaller than the width w, and means a non-square block having a longer length in the horizontal direction.

FIG. 20 illustrates a case where a coding block CU is divided into lower depth coding blocks CU0 to CU9. For example, the size of partitioned CU0 and CU1 is 2x4, the size of partitioned CU2, CU3 and CU4 is 4x4, the size of partitioned CU5 and CU6 is 2x8, the size of partitioned CU7 is 4x8, the size of partitioned CU8 and CU9 The size shows the case divided by 8x8.

21 illustrates a case where the coding block CU is divided into lower depth coding blocks CU10 to CU17, for example. For example, the size of the divided CU10 and CU11 is divided into 8x2, the size of the divided CU12, CU15 and CU16 is 8x4, the size of the divided CU13 and CU14 is 4x8, the size of the divided CU17 is 8x8. will be.

20 and 21 illustrate that the partition of FIG. 20 and FIG. 21 are applied by applying one of the above-described multi-tree partitioning methods, and various partition types different from those of FIGS. 20 and 21 may be possible according to the partition scheme.

In this regard, for example, when CU1 2002 illustrated in FIG. 20 is encoded in an intra prediction mode, CU1 2002 may be encoded after CU0 2001 is encoded by a conventional HEVC or a legacy legacy codec. That is, conventionally, since the image or samples reconstructed in CU0 2001 are used as an intra reference sample (ie, a reference sample) of CU1 2002, CU0 2001 and CU1 2002 cannot be simultaneously encoded. Similarly, conventionally, in order to encode the CU6 2004 shown in FIG. 20 in the intra prediction mode, the CU6 2004 can be encoded after the CU5 2003 is encoded. That is, conventionally, since the image or samples reconstructed in CU5 (2003) are used as an intra reference sample (ie, a reference sample) of CU6 (2004), CU5 (2003) and CU6 (2004) cannot be simultaneously encoded.

When applying the multi-tree partitioning of the present invention described above, a non-square coding unit having a small width or height, such as 2x16, 16x2, or 2x8, 8x2, can be used, which can effectively compress small objects or fine objects. However, the data dependency problem caused by the generation of a large number of non-square coding units when multi-tree partitioning is applied, causes a long latency in hardware or software implementation, thereby increasing implementation complexity and speed. This can be Accordingly, the present invention proposes an image decoding and encoding method for parallel processing a plurality of independent coding blocks in order to more effectively support the aforementioned multi-tree partitioning scheme.

Specifically, by the parallel processing method according to the present invention, the current CU may perform intra or inter prediction independently of the neighboring CU. The current CU may perform prediction without data dependencies sharing texture data (eg, reconstructed samples, residual samples, prediction samples, etc.) and / or encoding parameters of neighboring CUs. In this case, the independent prediction may mean that data with the neighboring CU is not used, or may mean that the current CU and the neighboring CU are performed in parallel according to an implementation method. Alternatively, the neighboring CU may be set as an unavailable block for encoding / decoding of the current CU.

In addition, when the coding unit is partitioned by multi-tree partitioning, the current CU and the neighboring CU may be independently encoded / decoded based on at least one of the width or the height of the coding unit. The number of neighboring CUs may be one or more. The position of the neighboring CU may be continuous in at least one of horizontal, vertical, or diagonal directions with respect to the current CU. In addition, the neighboring CU is based on at least one of the directionality of the prediction mode and / or the intra prediction mode of the current CU, the position of the current CU within the upper CU, the shape and size related information of the current CU, or the luminance / color difference component related information. Can be specified.

Whether a plurality of adjacent coding units are independent parallel processing CUs may be set according to various criteria. For example, a plurality of coding units may be independently encoded / decoded based on whether the width w or height h of the coding unit is smaller than a specific threshold. Alternatively, the plurality of coding units may be independently encoded / decoded based on whether the width w and height h ratios (ie, w / h or h / w) values of the coding unit are smaller than a specific threshold. Alternatively, the plurality of coding units may be independently encoded / decoded based on whether the sum of the width and height of the coding unit or the number of samples of the coding unit is smaller than a specific threshold. The specific threshold value may be a fixed value preset in the encoder / decoder, or may be determined by an encoder, and may be encoded and signaled by a decoder. In this case, the encoded threshold information may be signaled in at least one unit of a sequence, a picture, a slice, and a block.

Specifically, for example, two consecutive coding units when the width or height of the coding unit is smaller than 4 as shown in {CU0, CU1}, {CU5, CU6} of FIG. 20 and {CU10, CU11} of FIG. Can be coded / decoded independently.

Herein, a CU that precedes the coding scan order is referred to as a corresponding CU, and a CU that follows the coding scan order is defined as a target CU. Alternatively, among a plurality of blocks that are parallel processed together, the current coding block may be referred to as a current parallel processing block, and a coding block adjacent to the current parallel processing block may be called a neighbor parallel processing block. That is, referring to FIG. 20, CU0 2001 and CU5 2003 correspond to corresponding CUs, and CU1 2002 and CU6 2004 correspond to target CUs. In addition, referring to FIG. 21, a CU10 2101 corresponds to a corresponding CU, and a CU11 2102 corresponds to a target CU.

In detail, in order to perform parallel processing on the target CU (eg, CU1, CU6, CU11) that is the current parallel processing block, it is necessary to obtain a reference sample for decoding / coding the target CU. According to the present invention, the target CU reference sample is not derived from a corresponding CU (eg, CU0, CU5, CU10) region, which is a neighboring parallel processing block that has not yet been restored, and utilizes the reference sample used in the corresponding CU. do. Alternatively, the target CU reference sample may be derived by using a difference between the target CU reference point sample value and the corresponding CU reference point sample value.

Here, the reference point sample may be one or more samples adjacent to the target CU or the corresponding CU. Also, the reference point sample may be a sample adjacent to the top, left, or left-top corner of the target CU or the corresponding CU. The location of all or part of the reference point samples may be variably specified according to the size, shape, aspect ratio, location of the encoding / decoding target sample, or the like of the target CU or the corresponding CU. Alternatively, a sample of a fixed position may be used regardless of the target CU or the corresponding CU.

In addition, the difference may be derived through the difference between the reference point sample value of the target CU and the reference point sample value of the corresponding CU, or may be derived by applying a predetermined weight to each reference point sample value. Alternatively, the difference may be derived by scaling a value generated through the difference with a predetermined scaling factor. Alternatively, the difference may be derived as an offset mapped to a value generated through the difference. In relation to this, a detailed method of obtaining a reference sample for performing parallel processing encoding / decoding for a target CU will be described in detail later with reference to FIGS. 26 to 29.

FIG. 22 is a diagram for describing a parallel processing coding block partitioned by multi-tree partitioning as another embodiment to which the present invention is applied. When the coding unit is partitioned with multi-tree partitioning, it is possible to independently parallel the current CU and the neighboring CU based on at least one of the width or the height of the coding unit. Also. The position of the neighbor parallel CU may be continuous to at least one of horizontal, vertical, or diagonal directions with respect to the current parallel CU. For example, Fig. 22 (a) shows a horizontal parallel processing block, Fig. 22 (b) shows a vertical parallel processing block, Fig. 22 (c) shows a diagonal parallel processing block, and Fig. 22 (d) shows a horizontal parallel processing block. In this case, the vertical and diagonal parallel processing blocks are included.

Here, the determination of the parallel processing block can be selected at the time of encoding / decoding according to the encoding / decoding performance and efficiency of the coding unit. Alternatively, the determination of the parallel processing block may be performed at the time of encoding according to the encoding performance and the efficiency of the corresponding coding unit, and the selected parallel processing information may be signaled and transmitted to the decoder to perform parallel processing on the determined block at the time of decoding. .

FIG. 22A illustrates a case where a coding unit is divided into lower depth coding units CU18 to CU29, for example. Here, {CU27, CU28} divided by the third depth may be determined as the horizontally adjacent parallel processing block based on the width or the height of the adjacent horizontal coding unit among the above-described determination methods of the parallel processing blocks. Further, by the same criterion, {CU18, CU19} and {CU21, CU22} divided by the third depths of different positions can be determined as parallel processing blocks adjacent in the horizontal direction, respectively.

FIG. 22B illustrates a case where a coding unit is divided into lower depth coding units CU30 to CU40, for example. Here, {CU36, CU37} divided by the third depth may be determined as the vertically adjacent parallel processing block based on the width or the height of the adjacent vertical coding unit among the above-described determination methods of the parallel processing blocks. Further, by the same criterion, {CU30, CU31} divided by the third depths of different positions can be determined as parallel processing blocks adjacent to each other in the horizontal direction.

FIG. 22C illustrates a case where, for example, the coding unit is divided into lower depth coding units CU41 to CU54. Here, {CU41, CU44} divided by the third depth may be determined as the diagonally adjacent parallel processing blocks based on the width or the height of the adjacent diagonal coding unit among the above-described determination methods of the parallel processing blocks. Further, by the same criterion, {CU42, CU43} may be determined as diagonally adjacent parallel processing blocks.

FIG. 22D illustrates a case where the coding unit is divided into lower depth coding units CU41 to CU54, similarly to FIG. 22C. Here, the parallel processing block may be simultaneously determined based on the width or height size of the coding unit adjacent to at least one of horizontal, vertical, and diagonal directions among the above-described determination methods of the various parallel processing blocks. For example, {CU52, CU53} divided by the third depth may be determined as the parallel processing block adjacent to the horizontal direction, and {CU49, CU50} divided by the third depth of the other position may be determined as the parallel processing block adjacent to the vertical direction. In addition, {CU41, CU44} divided by the third depth of another position may be determined as diagonally adjacent parallel processing blocks.

FIG. 23 is a diagram for describing a parallel processing unit processing region (PCUR: Parallel Coding Unit Processing Region) divided by multi-tree partitioning according to another embodiment to which the present invention is applied. In order to reduce encoding and / or decoding processing latency, a predetermined block may be limited to process a prediction block (a prediction block generated through an inter prediction encoding mode and an intra prediction encoding mode) in parallel. . The predefined specific region is called a "Parallel Coding Unit Processing Region (PCUR)".

That is, data (eg, sample values, intra reference samples, motion information, reference picture lists, etc.) in a coding region within an N × M PCUR unit may be limited to not refer to each other. Here, N and M may be 4, 8, 16, 32 or more, and N and M may be the same or different. Specifically, FIG. 23 illustrates a case where the size of the PCUR is 8x8. In coding units {CU10, CU11, CU12} and {CU15, CU16} present in an 8x8 PCUR block, data (e.g., sample values, intra reference samples, motion information, reference picture lists, etc.) are restricted from being referenced to each other. Independent parallel processing between CUs can be enabled.

In this case, a coding unit larger than a PCUR size set as a 16x16 coding unit, or an 8x16 coding unit not completely included in the PCUR, such as CU13 to CU14 of FIG. 23, may not be processed in parallel, but may be processed sequentially or in a neighboring block. encoding can be performed with a dependency. That is, encoding may be performed using the peripheral data (eg, sample value, intra reference sample, motion information, reference picture list, etc.).

However, the parallel coding unit unit PCUR may be a square region or a non-square region. A syntax element isRect_PCUR_flag indicating whether it is a square or non-square area may be signaled in a sequence parameter header, a picture parameter header, a slice header, or the like.

For example, if the parallel coding unit PCUR is 8x8, data (eg, sample value, intra reference sample, motion information, reference picture list, etc.) in the coding unit in the 8x8 region may be defined not to be referred to. have. If "isRect_PCUR_flag = 1", this means that the parallel coding unit PCUR is square, and if "isRect_PCUR_flag = 0", the parallel coding unit PCUR can be defined as non-square.

In detail, when “isRect_PCUR_flag = 1”, the syntax “log2_PCUR_width_minus1” indicating the width and height of the parallel coding unit may be further signaled. In this case, the width and height of the parallel coding unit may be defined as 1 << (log2_PCUR_width_minus1 + 1). Where << represents a bit shift operation. For example, if "log2_PCUR_width_minus1 = 1", the size of the minimum parallel coding unit unit is 4x4 unit.

In addition, when "isRect_PCUR_flag = 0", each of the syntaxes representing the width and the height of the parallel coding unit may be signaled. Alternatively, regardless of isRect_PUCR_flag, the encoder may determine the size of an optimal parallel coding unit for each sequence, picture, or slice, and encode and signal the same. Alternatively, a fixed sized parallel coding unit pre-defined with the encoder / decoder may be used.

FIG. 24 is a diagram for explaining a parallel processing encoding method of a coding block divided by multi-tree division, according to another embodiment to which the present invention is applied.

First, a partition shape of a coding block divided by a multi-partitioning method is determined (S2410). The partition type may be any one of the partition types of FIGS. 11 and 12 described above. The prediction mode of the split coding block is determined (S2420). The prediction mode includes intra prediction or inter prediction. However, the parallel coding method can be applied only to the intra prediction block.

According to the determined partition type and prediction mode, a block capable of parallel processing is determined (S2430). The parallel processing block determination criteria may be determined by various methods as described above. For example, it can be determined by the width and height size (below threshold) of the coding block sample, and the position (horizontal, vertical, diagonally adjacent) with adjacent parallel coding blocks. In addition, the parallel coding block may be determined by the above-described parallel coding unit unit PCUR setting.

If, in step S2430, it is not determined to be a parallel processing block, reference samples for each coding block are determined (S2460), and encoding is performed in units of coding blocks (S2470). On the other hand, if it is determined as a parallel processing block by the step S2430, the parallel processing blocks are independently processed simultaneously. To this end, reference samples for each parallel block are determined (S2440), and parallel processing blocks are simultaneously encoded (S2450). Reference sample determination of the parallel block of step S2440 will be described later in detail with reference to FIGS. 26 to 29.

First, encoding information is parsed from an input encoded video bitstream (S2510). From the parsed encoding information, a partition type of a coding block divided by a multi-partitioning scheme and a prediction mode of each split coding block are checked (S2520). In addition, from the parsed encoding information, whether or not the above-described parallel coding unit unit PCUR is set and the set PCUR size may be checked (S2520). In this regard, the partition type may be any one of the partition types of FIGS. 11 and 12 described above. In addition, the prediction mode of the coding block includes intra prediction or inter prediction. However, the parallel decoding method can be applied only to the intra prediction block.

A block capable of parallel processing is determined according to the determined partition type and prediction mode (S2530). The parallel processing block determination criteria may be determined by various methods as described above. For example, it can be determined by the width and height size (below threshold) of the coding block sample, and the position (horizontal, vertical, diagonally adjacent) with adjacent parallel coding blocks. In addition, the parallel coding block may be determined by the above-described parallel coding unit unit PCUR setting.

If, in step S2530, it is not determined to be a parallel processing block, a reference sample for each coding block is determined (S2560), and decoding is performed in units of coding blocks (S2570). On the other hand, if it is determined as a parallel processing block by the step S2530, the parallel processing blocks are independently processed simultaneously. To this end, reference samples for each parallel block are determined (S2540), and the parallel processing blocks are simultaneously decoded (S2550). Reference sample determination of the parallel block of step S2540 will be described later in detail with reference to FIGS. 26 to 29.

26 and 27 illustrate a method of obtaining a reference sample for parallel processing of the first type coding block illustrated in FIG. 20 described above. First, neighboring coding units CU5 and CU6 illustrated in FIGS. 26 and 27 correspond to the above-described parallel processing block criteria, and mean coding units in which independent parallel processing decoding and / or encoding is performed. For example, 2x8 size CU5 and CU6 correspond to coding units of the same size horizontally adjacent among the various parallel processing criteria described above, and the width (w) of the coding unit is 4 or less, and the width (w) and height (h) may be determined as a parallel processing block based on the ratio, i.e., whether the w / h value is less than a certain threshold (e.g., 1/2). However, as described above, the parallel processing block determination criteria may be selectively set in consideration of encoding performance and efficiency.

As illustrated in FIG. 26, when there is already a reconstructed region around the 2x8 coding unit CU5, which is a parallel processing target, a reference sample may be configured by using sample values of the reconstructed region. In addition, if there are some sample values of the unreconstructed region around CU5, the reference sample may be configured by using the reconstructed neighboring sample values.

However, when there is no reconstructed region on the left side of another parallel processing target coding unit CU6 as shown in FIG. 27, the left reference sample R (-1, i) of the CU6 is selected and the reference sample value of the neighboring coding unit CU5 is set. Or offsets representing the difference in sample values between reference point samples.

Specifically, each of the upper left or upper samples of the coding units CU5 and CU6 may be set as reference point samples, and the difference value between these reference point samples may be set as an offset. For example, in FIG. 27, the reference point of CU5 is set to P (0, -1) 2702, and the reference point of CU6 is set to P (2, -1) 2704, and the two coding units CU5 and CU6 are set. The difference of the sample value between the reference point samples of may be set as an offset. That is, the offset f can be set as in the following equation (1).

In Equation (1), w represents the width of the coding unit, and f represents the difference between the reference point sample value of the target CU and the reference point sample value of the corresponding CU.

However, the reference point position can be determined by various methods. For example, the reference point of CU5 is P (-1, -1) 2701 and the reference point of CU6 is P (1, -1) (2703). It is also possible to obtain the offset f by setting The reference points of CU5 are the average values of P (-1, -1) 2701 and P (0, -1) 2702, and the reference points of CU6 are P (1, -1) 2703 and P (2). It is also possible to set the average value of (-2704) and obtain the offset f.

Accordingly, unreconstructed left reference samples R (-1, i) among the reference samples of CU5 may derive the offset f from the left reference sample of CU6 as a differential value, as follows: Can be expressed as

28 and 29 are diagrams for describing a method of obtaining a reference sample for parallel processing of the second type coding block as another embodiment. First, neighboring coding units CU10 and CU11 illustrated in FIGS. 28 and 29 correspond to the above-described parallel processing block criteria and refer to coding units in which independent parallel processing decoding and / or encoding is performed. For example, CU10 and CU11 of 8x2 size correspond to coding units of the same size vertically adjacent among the various parallel processing criteria described above, and the coding unit has a height h of 4 or less, width w and height. (h) The ratio may be determined as a parallel processing block based on whether the h / w value is less than a specific threshold (eg, 1/2). However, as described above, the parallel processing block determination criteria may be selectively set in consideration of encoding performance and efficiency.

As illustrated in FIG. 28, when there is already a reconstructed region around the 8x2 coding unit CU10, which is a parallel processing object, a reference sample may be configured by using sample values of the reconstructed region. In addition, if there are some sample values of the unreconstructed region around the CU10, the reference sample may be configured by using the reconstructed neighboring sample values.

However, when there is no reconstructed region at the top of another parallel processing target CU11 as shown in FIG. 29, the upper reference sample R (i, -1) of the CU11 is selected and the reference sample value of the neighboring coding unit CU10. Or offsets representing the difference in sample values between reference point samples.

Specifically, each of the upper left or left samples of the coding units CU10 and CU11 may be set as reference point samples, and the difference value between these reference point samples may be set as an offset. For example, in FIG. 29, the reference point of CU10 is set to P (-1,0) 2902 and the reference point of CU11 is set to P (-1,2) 2904, and the two coding units CU10 and CU11 are used. The difference of the sample value between the reference point samples of may be set as an offset. That is, the offset f can be set as in the following equation (3).

In Equation (3), h represents the height of the coding unit, and f represents the difference between the reference point sample value of the target CU and the reference point sample value of the corresponding CU.

However, the reference point position can be determined by various methods. For example, the reference point of CU10 is P (-1, -1) 2901 and the reference point of CU11 is P (-1,1) (2903). It is also possible to obtain the offset f by setting In addition, the reference points of CU10 are the average values of P (-1, -1) 2901 and P (-1,0) 2902, and the reference points of CU11 are P (-1,1) (2903) and P (-). 1,2) It is also possible to set to the average value of 2904 and obtain the offset f.

Accordingly, unreconstructed upper reference samples R (i, -1) among the reference samples of CU11 may derive the offset f from the upper reference sample of CU10 as a differential value, as shown in Equation 4 below. Can be expressed as

FIG. 30 illustrates, as another embodiment to which the present invention is applied, a syntax element included in a network abstraction layer (NAL) to which a parallel processing coding block having multi-tree partitions is applied.

The NAL unit to which the present invention is applied may include, for example, a video parameter set (VPS), a sequence parameter set (SPS), a picture parameter set (PPS), and at least one slice set (Slice).

For example, although FIG. 30 illustrates an included syntax element included in a picture parameter set (PPS), the syntax element may be included in a sequence parameter set (SPS) or a slice set (Slice). In addition, syntax elements to be commonly applied to sequence units or picture units for each syntax element may be included in a sequence parameter set (SPS) or a picture parameter set (PPS). On the other hand, the syntax element applied only to the slice is preferably included in the slice set (Slice). Therefore, this can be selected in consideration of encoding performance and efficiency.

The syntax element 'isRect_PCUR_flag' indicates whether the parallel coding unit unit PCUR is a square area or a non-square area. For example, if "isRect_PCUR_flag = 1", the parallel coding unit PCUR may be square, and if "isRect_PCUR_flag = 0", the parallel coding unit PCUR may be defined to be non-square.

In addition, the syntax element 'log2_PCUR_width_minus1' indicates the size of the PCUR when the parallel coding unit PCUR is square. For example, if "log2_PCUR_width_minus1 = 1", the size of the minimum parallel coding unit unit may be defined to indicate that the size of the 4x4 unit.

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 processing according to the present invention.

The present invention can be applied to an electronic device capable of encoding / decoding an image.

Claims

Using block partition information for the current coding block, identifying whether the current coding block is a current parallel processing block adjacent to a neighboring parallel processing block in at least one of a horizontal, vertical or diagonal direction, and

Parallel decoding the current parallel processing block together with the neighboring parallel processing block.
According to claim 1,

If there is at least one reference sample reconstructed around the current parallel processing block, further comprising obtaining a reference sample of the current parallel processing block by utilizing the reconstructed reference sample around the neighbor parallel processing block. Way.
The method of claim 2,

Obtaining a reference sample of the current parallel processing block,

Obtaining a difference between a reference point sample value of the current parallel processing block and a reference point sample of the neighboring parallel processing block as an offset, and

Subtracting the offset from the reconstructed reference samples around the neighbor parallel processing block to obtain a reference sample of the current parallel processing block.
The method of claim 3, wherein

And if the width (w) of the current parallel processing block is smaller than the height (h), the reference point sample position of the current parallel processing block utilizes the reconstructed top sample.
The method of claim 3, wherein

And when the height (h) of the current parallel processing block is smaller than the width (w), the reference point sample position of the current parallel processing block utilizes the reconstructed left sample.
According to claim 1,

The reference sample of the current parallel processing block utilizes the reconstructed reference sample of the neighbor parallel processing block as it is.
According to claim 1,

And if the current coding block is located in a parallel coding unit unit PCUR region, determining that the current coding block is a current parallel processing block.
The method of claim 7, wherein

The form of the parallel coding unit unit PCUR can be selected among square or non-square in the encoding process, and obtains a syntax element indicating the form of the selected PCUR, and confirms the form of the PCUR.
The method of claim 8,

And if the parallel coding unit unit PCUR has a square shape, obtains a syntax element indicating the size of the selected square PCUR, and checks the size of the square PCUR.
According to claim 1,

And the parallel decoding step performs decoding independently without sharing at least motion information and a reference picture list among parallel processing blocks.
According to claim 1,

And the parallel decoding step performs decoding independently without sharing at least intra reference samples between parallel processing blocks.
According to claim 1,

The current parallel processing block includes a block divided by multi-tree partitioning.
Using block partition information for the current coding block, determining whether the current coding block is a current parallel processing block adjacent to a neighboring parallel processing block in at least one of a horizontal, vertical or diagonal direction, and

And performing parallel encoding on the current parallel processing block together with the neighbor parallel processing block.
The method of claim 13,

If at least one reference sample reconstructed around the current parallel processing block does not exist, further comprising obtaining a reference sample of the current parallel processing block by using the reconstructed reference sample around the neighbor parallel processing block. Way.
The method of claim 14,

Obtaining a reference sample of the current parallel processing block,

Obtaining a difference between a reference point sample value of the current parallel processing block and a reference point sample of the neighboring parallel processing block as an offset, and

And subtracting the offset from a reconstructed reference sample around the neighbor parallel processing block to obtain a reference sample of the current parallel processing block.
The method of claim 14,

And if the width (w) of the current parallel processing block is smaller than the height (h), the reference point sample position of the current parallel processing block utilizes the reconstructed top sample.
The method of claim 14,

And the reference point sample position of the current parallel processing block utilizes the reconstructed left sample when the height h size is smaller than the width w size.
The method of claim 13,

And when the current coding block is located in a predetermined parallel coding unit unit PCUR region, determining the current coding block as a current parallel processing block.
The method of claim 18,

The form of the parallel coding unit unit PCUR is selectable between square or non-square, and an image encoding method for signaling a syntax element representing the form of the selected PCUR.
The method of claim 19,

And if a shape of the parallel coding unit unit PCUR is selected as a square, signaling a syntax element representing the size of the selected square PCUR.
Use block partition information for the current coding block to determine whether the current coding block is a current parallel processing block adjacent to a neighboring parallel processing block in at least one of a horizontal, vertical, or diagonal direction, and the neighbor to the current parallel processing block. And a decoder for performing parallel decoding together with the parallel processing block.
A recording medium comprising a video signal bitstream, wherein the video signal bitstream included in the recording medium uses block partition information for a current coding block so that the current coding block is at least horizontally, vertically, or adjacent to a neighboring parallel processing block. Determining whether the current parallel processing block is adjacent to one of the diagonal directions, and performing parallel encoding on the current parallel processing block together with the neighboring parallel processing block. media.