KR20170132036A - Method for coding unit partitioning, video encoding and decoding thereof - Google Patents

Abstract

The present invention relates to a block partitioning method for image processing and an image encoding and decoding method using the same, which can improve coding efficiency on a high-resolution image. The block partitioning method comprises the steps of: partitioning a picture of an image into a plurality of coding units which are a basic unit for performing inter prediction or intra prediction; and partitioning the partitioned coding units into one or more transform units for performing transformation on a residual block. The step of partitioning the coding unit includes a step of partitioning the picture or the partitioned coding unit into a binary tree structure. The step of partitioning the transform units includes a step of partitioning the coding unit into the binary tree structure.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a block division method for image processing, a method for coding and decoding the image,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to image encoding and decoding, and more particularly, to a method and apparatus for encoding and decoding a motion picture by dividing a picture into a plurality of blocks.

In the image compression method, a picture is divided into a plurality of blocks each having a predetermined size to perform coding. Further, inter prediction and intra prediction techniques for eliminating redundancy between pictures are used to increase compression efficiency.

In this case, intra prediction and inter prediction are used to generate a residual signal. The reason why the residual signal is obtained is that when the coding is performed using the residual signal, the amount of data is small, so that the data compression rate is high. Is small.

The intraprediction method predicts the data of the current block by using the pixels around the current block. The difference between the actual value and the predicted value is called a residual signal block. In case of HEVC, the intra prediction method increases to 35 prediction modes in nine prediction modes used in the existing H.264 / AVC, and further subdivided prediction is performed.

In the case of the inter prediction method, the current block is compared with the blocks in the neighboring pictures to find the closest block. At this time, the position information (Vx, Vy) of the found block is referred to as a motion vector. The difference between the intra-block pixel values of the current block and the prediction block predicted by the motion vector is called a residual-signal block (motion-compensated residual block).

In this way, although intra prediction and inter prediction are further refined, the amount of data of the residual signal is decreasing, but the amount of computation for processing a moving image is greatly increased.

Particularly, there is a difficulty in pipeline implementation due to the increase in complexity in the process of determining a intra-picture partitioning structure for image encoding and decoding, and the existing block dividing method and accordingly, It may not be suitable for encoding.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and it is an object of the present invention to provide a coding unit dividing method suitable for coding and decoding a high-resolution image, and a video coding and decoding method using the same.

According to an aspect of the present invention, there is provided a method of dividing a picture into blocks, the method comprising the steps of: dividing a picture into a plurality of blocks, each of which is a basic unit in which inter prediction or intra prediction is performed; Into coding units (Coding Units); And dividing the divided coding unit into one or two or more transform units that are basic units for performing a conversion on a residual block, Or partitioning the divided coding unit into a binary tree structure, wherein the transforming unit partitioning step comprises dividing the coding unit into a binary tree structure.

According to an aspect of the present invention, there is provided a method of encoding an image, the method comprising: dividing a picture of an image into a plurality of coding units; Performing inter prediction or intra prediction on the basis of the divided coding units as a basic unit; Dividing the divided coding unit into one or more conversion units; And performing a transform on the residual block according to the inter prediction or intra prediction using the divided transform unit as a basic unit, wherein the coding unit dividing step includes a step of transforming the picture or the divided coding unit into a binary tree Structure, and the transform unit splitting step includes splitting the coding unit into a binary tree structure.

According to an embodiment of the present invention, there is provided an image decoding method including: receiving an encoded bitstream; Performing inverse quantization and inverse transform on the input bitstream to obtain a residual block; Performing inter-prediction or intra-prediction to obtain a prediction block; And reconstructing an image by summing the obtained residual block and a prediction block, wherein a coding unit, which is a basic unit in which the inter prediction or intra prediction is performed, is a block divided from a coding tree unit using a binary tree structure, The conversion unit, which is the basic unit in which the inverse transformation is performed, is a block divided from the coding unit using a binary tree structure.

Meanwhile, the above-described methods may be embodied as a computer-readable recording medium on which a program for execution by a computer is recorded.

According to the embodiment of the present invention, a coding unit, which is a basic unit in which inter prediction or intra prediction is performed, and a conversion unit, which is a basic unit in which conversion is performed, are divided into a binary tree structure and used for coding and decoding an image. Thereby improving the coding efficiency.

1 is a block diagram illustrating a configuration of an image encoding apparatus according to an embodiment of the present invention.
FIGS. 2 to 5 are diagrams for explaining a first embodiment of a method for dividing and processing an image into blocks.
6 is a block diagram for explaining an embodiment of a method of performing inter-prediction in the image encoding apparatus.
7 is a block diagram illustrating a configuration of an image decoding apparatus according to an embodiment of the present invention.
8 is a block diagram for explaining an embodiment of a method of performing inter-prediction in an image decoding apparatus.
FIG. 9 is a diagram for explaining a second embodiment of a method of dividing and processing an image into blocks.
10 is a diagram showing an embodiment of a syntax structure used for dividing and processing an image into blocks.
11 is a diagram for explaining a third embodiment of a method for dividing and processing an image into blocks.
12 is a diagram for explaining an embodiment of a method of dividing a coding unit into a binary tree structure to construct a conversion unit.
FIG. 13 is a diagram for explaining a fourth embodiment of a method of dividing and processing an image into blocks.
FIGS. 14 to 16 are diagrams for explaining still another embodiment of a method of dividing and processing an image into blocks.
FIGS. 17 and 18 are diagrams for explaining embodiments of a method of performing a rate distortion optimization (RDO) to determine a division structure of a conversion unit.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the following description of the embodiments of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present disclosure rather unclear.

It is to be understood that when an element is referred to as being "connected" or "connected" to another element, it may be directly connected or connected to the other element, . In addition, the description of "including" a specific configuration in the present invention does not exclude a configuration other than the configuration, and means that additional configurations can be included in the practice of the present invention or the technical scope of the present invention.

The terms first, second, etc. 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 a second component, and similarly, the second component may also be referred to as a first component.

In addition, the components shown in the embodiments of the present invention are shown independently to represent different characteristic functions, which does not mean that each component is composed of separate hardware or software constituent units. That is, each constituent unit is included in each constituent unit for convenience of explanation, and at least two constituent units of the constituent units may be combined to form one constituent unit, or one constituent unit may be divided into a plurality of constituent units to perform a function. The integrated embodiments and separate embodiments of the components are also included within the scope of the present invention, unless they depart from the essence of the present invention.

In addition, some of the components are not essential components to perform essential functions in the present invention, but may be optional components only to improve performance. The present invention can be implemented only with components essential for realizing the essence of the present invention, except for the components used for the performance improvement, and can be implemented by only including the essential components except the optional components used for performance improvement Are also included in the scope of the present invention.

FIG. 1 is a block diagram illustrating a configuration of an image encoding apparatus according to an exemplary embodiment of the present invention. The image encoding apparatus 10 includes a picture division unit 110, a transform unit 120, a quantization unit 130, An entropy encoding unit 140, an intra prediction unit 150, an inter prediction unit 160, an inverse quantization unit 135, an inverse transformation unit 125, a post-processing unit 170, a picture storage unit 180 A subtracting unit 190, and an adding unit 195. [

Referring to FIG. 1, a picture dividing unit 110 analyzes an input video signal, divides a picture into coding units to determine a prediction mode, and determines a size of a prediction unit for each coding unit.

The picture division unit 110 also sends the prediction unit to be encoded to the intra prediction unit 150 or the inter prediction unit 160 according to a prediction mode (or a prediction method). Further, the picture division unit 110 sends the prediction unit to be encoded to the subtraction unit 190.

Here, a picture of an image is composed of a plurality of slices, and a slice can be divided into a plurality of coding tree units (CTU), which is a basic unit for dividing a picture.

The coding tree unit may be divided into one or two or more coding units (CUs), which are basic units for performing inter prediction or intra prediction.

The coding unit (CU) can be divided into one or more prediction units (PU), which are basic units on which prediction is performed.

In this case, the coding apparatus 10 determines one of the inter prediction and intra prediction as the prediction method for each of the divided coding units (CUs), but differently for each prediction unit (PU) Can be generated.

On the other hand, the coding unit CU may be divided into one or two or more Transform Units (TUs), which are basic units for performing a conversion on a residual block.

In this case, the picture dividing unit 110 may deliver the image data to the subtracting unit 190 in a block unit (for example, a prediction unit (PU) or a conversion unit (TU)) which is divided as described above.

Referring to FIG. 2, a coding tree unit (CTU) having a maximum size of 256x256 pixels may be divided into a quad tree structure and divided into four coding units (CUs) having a square shape.

Each of the four coding units (CUs) having the square shape can be divided into quad tree structures. The depth of the coding unit (CU) It can have one integer value.

The coding unit (CU) may be divided into one or more prediction units (PU) according to the prediction mode.

In the case of the intra prediction mode, when the size of the coding unit CU is 2Nx2N, the prediction unit PU can have the size of 2Nx2N shown in Fig. 3A or the size of NxN shown in Fig. 3B have.

On the other hand, in the case of the inter prediction mode, when the size of the coding unit CU is 2Nx2N, the prediction unit PU is 2Nx2N shown in Fig. 4A, 2NxN shown in Fig. 4D, 2NxnU shown in FIG. 4E, 2NxnD shown in FIG. 4F, and FIG. 4G shown in FIG. 4G, And nRx2N shown in FIG. 4 (h).

Referring to FIG. 5, a coding unit (CU) may be divided into a quad tree structure and divided into four transformation units (TUs) having a square shape.

Each of the four transformation units TU having the square shape can be divided into quad tree structures. The depth of the transformation unit TU divided into the quad tree structure can be set to any one of 0 to 3 It can have one integer value.

Here, when the coding unit (CU) is in the inter prediction mode, the prediction unit (PU) and the conversion unit (TU) divided from the coding unit (CU) may have a division structure independent of each other.

When the coding unit CU is in the intra prediction mode, the conversion unit TU divided from the coding unit CU can not be larger than the size of the prediction unit PU.

In addition, the conversion unit TU divided as described above can have a maximum size of 64x64 pixels.

The transforming unit 120 transforms the residual block, which is a residual signal between the original block of the input prediction unit PU, and the prediction block generated by the intra prediction unit 150 or the inter prediction unit 160, Unit TU as a basic unit.

In the conversion process, different conversion matrices can be determined according to the intra or inter prediction mode. Since the residual signal of the intra prediction has directionality according to the intra prediction mode, the conversion matrix can be adaptively determined according to the intra prediction mode. have.

The transformation unit can be transformed by two (horizontal, vertical) one-dimensional transformation matrices, for example in the case of interprediction, one predetermined transformation matrix can be determined.

On the other hand, in the case of intra prediction, when the intra prediction mode is horizontal, the probability that the residual block has the directionality in the vertical direction becomes higher. Therefore, the DCT-based integer matrix is applied in the vertical direction and the DST- Apply a KLT-based integer matrix. When the intra prediction mode is vertical, a DST-based or KLT-based integer matrix can be applied in the vertical direction, and a DCT-based integer matrix can be applied in the horizontal direction.

In the case of the DC mode, a DCT-based integer matrix can be applied to both directions.

And, in the case of intraprediction, the transformation matrix may be adaptively determined based on the size of the transformation unit TU.

The quantization unit 130 determines a quantization step size for quantizing the coefficients of the residual block transformed by the transform matrix, and the quantization step size can be determined for each quantization unit larger than a predetermined size.

The size of the quantization unit may be 8x8 or 16x16, and the quantization unit 130 quantizes the coefficients of the transform block using the quantization matrix determined according to the quantization step size and the prediction mode.

Further, the quantization unit 130 can use the quantization step size of the quantization unit adjacent to the current quantization unit as a quantization step size predictor of the current quantization unit.

The quantization unit 130 searches the left quantization unit, the upper quantization unit, and the upper left quantization unit of the current quantization unit in order, and can generate a quantization step size predictor of the current quantization unit using one or two effective quantization step sizes have.

For example, the quantization unit 130 may determine the valid first quantization step size searched in the above order as a quantization step size predictor, determine an average value of two valid quantization step sizes searched in the above order as a quantization step size predictor, or If only one quantization step size is valid, it can be determined as a quantization step size predictor.

When the quantization step size predictor is determined, the quantization unit 130 transmits the difference value between the quantization step size of the current quantization unit and the quantization step size predictor to the entropy encoding unit 140.

On the other hand, neither the left coding unit, the upper coding unit nor the upper left coding unit of the current coding unit exists. Or there may be a coding unit that was previously present on the coding order within the maximum coding unit.

Therefore, the quantization step sizes of the quantization units adjacent to the current coding unit and the quantization unit immediately before the coding order in the maximum coding unit can be candidates.

In this case, 1) the left quantization unit of the current coding unit, 2) the upper quantization unit of the current coding unit, 3) the upper left side quantization unit of the current coding unit, and 4) . The order may be changed, and the upper left side quantization unit may be omitted.

Meanwhile, the quantized transform block is transferred to the inverse quantization unit 135 and the scanning unit 131.

The scanning unit 131 scans the coefficients of the quantized transform block and converts the coefficients into one-dimensional quantization coefficients. In this case, since the coefficient distribution of the transformed block after quantization may be dependent on the intra prediction mode, Can be determined accordingly.

Also, the coefficient scanning method may be determined depending on the size of the conversion unit, and the scan pattern may be changed according to the directional intra prediction mode. In this case, the scanning order of the quantization coefficients may be scanned in the reverse direction.

When the quantized coefficients are divided into a plurality of sub-sets, the same scan pattern may be applied to the quantization coefficients in each sub-set, and a scan pattern between the sub-sets may be zigzag scan or diagonal scan.

Meanwhile, the scan pattern is preferably scanned from the main subset including the DC to the remaining subset in the forward direction, but the reverse direction is also possible.

In addition, a scan pattern between subset can be set in the same manner as a scan pattern of quantized coefficients in a subset, and a scan pattern between subset can be determined according to an intra prediction mode.

On the other hand, the encoding apparatus 10 includes information indicating the position of the last non-zero quantization coefficient in the conversion unit PU and the position of the last non-zero quantization coefficient in each subset, 10).

The inverse quantization unit 135 dequantizes the quantized coefficients as described above. The inverse transform unit 125 performs an inverse transform on the basis of the transform unit (TU), restores the inversely quantized transform coefficients into a residual block in the spatial domain can do.

The adder 195 may generate a reconstruction block by summing the residual block reconstructed by the inverse transformer 125 and the prediction block received from the intra prediction unit 150 or the inter prediction unit 160. [

In addition, the post-processing unit 170 performs a deblocking filtering process to remove a blocking effect generated in the reconstructed picture, a sample adaptive offset (hereinafter, referred to as " sample adaptive offset " SAO) application process and an Adaptive Loop Filtering (ALF) process to compensate a difference value between the original image and a coding unit.

The deblocking filtering process can be applied to a boundary of a prediction unit (PU) or a conversion unit (TU) having a size larger than a predetermined size.

For example, the deblocking filtering process may include determining a boundary to be filtered, determining a bounary filtering strength to be applied to the boundary, determining whether to apply a deblocking filter, And if the deblocking filter is determined to be applied, selecting a filter to be applied to the boundary.

Whether or not the deblocking filter is applied depends on whether i) the border filtering strength is greater than 0 and ii) whether the pixel values at the boundary of two blocks (P block, Q block) May be determined by whether the value represented is less than a first reference value determined by the quantization parameter.

The filter is preferably at least two or more. If the absolute value of the difference between two pixels located at the block boundary is greater than or equal to the second reference value, a filter that performs relatively weak filtering is selected.

And the second reference value is determined by the quantization parameter and the boundary filtering strength.

In addition, the application of the sample adaptive offset (SAO) process is intended to reduce the distortion between pixels in an image to which a deblocking filter is applied and a source pixel, and a process of applying a sample adaptive offset (SAO) Can be determined.

The picture or slice may be divided into a plurality of offset regions, and an offset type may be determined for each of the offset regions. The offset type may include a predetermined number (for example, four) of edge offset types and two band offsets Type.

For example, when the offset type is an edge offset type, the edge type to which each pixel belongs is determined and the corresponding offset is applied. The edge type can be determined based on the distribution of two pixel values adjacent to the current pixel have.

The adaptive loop filtering (ALF) process may perform filtering on the basis of a value obtained by comparing a reconstructed image and an original image through a deblocking filtering process or an adaptive offset applying process.

The picture storage unit 180 receives the post-processed image data from the post-processing unit 170 and restores and stores the picture in units of pictures. The picture may be a frame-based image or a field-based image.

The inter-prediction unit 160 may perform motion estimation using at least one reference picture stored in the picture storage unit 180, and may determine a reference picture index and a motion vector indicating a reference picture.

In this case, the prediction block corresponding to the prediction unit to be coded can be extracted from the reference picture used for motion estimation among the plurality of reference pictures stored in the picture storage unit 180, according to the determined reference picture index and motion vector have.

The intraprediction unit 150 can perform intraprediction encoding using the reconstructed pixel values in the picture including the current prediction unit.

The intra prediction unit 150 receives the current prediction unit to be predictively encoded and can perform intra prediction by selecting one of a predetermined number of intra prediction modes according to the size of the current block.

The intraprediction unit 150 may adaptively filter the reference pixels to generate an intra prediction block, and may generate reference pixels using available reference pixels when the reference pixels are not available.

The entropy encoding unit 140 may entropy encode quantization coefficients quantized by the quantization unit 130, intra prediction information received from the intra prediction unit 150, motion information received from the inter prediction unit 160, and the like .

6 is a block diagram of an embodiment of a configuration for performing inter-prediction in the encoding apparatus 10. The inter-prediction encoder shown in FIG. 6 includes a motion information determination unit 161, a motion information encoding mode determination unit 162, A motion information coding unit 163, a prediction block generating unit 164, a residual block generating unit 165, a residual block coding unit 166 and a multiplexer 167.

Referring to FIG. 6, the motion information determination unit 161 determines motion information of a current block, the motion information includes a reference picture index and a motion vector, and the reference picture index includes any one of previously coded and reconstructed pictures Lt; / RTI >

When the current block is unidirectionally predictive-coded, indicates one of the reference pictures belonging to the list 0 (L0). When the current block is bidirectional predictive-coded, the reference picture indicating one of the reference pictures of the list 0 (L0) Index and a reference picture index indicating one of the reference pictures of the list 1 (L1).

In addition, when the current block is bi-directionally predictive-coded, it may include an index indicating one or two pictures among the reference pictures of the composite list LC generated by combining the list 0 and the list 1.

The motion vector indicates the position of a prediction block in a picture indicated by each reference picture index, and the motion vector may be a pixel unit (integer unit) or a sub-pixel unit.

For example, the motion vector may have a resolution of 1/2, 1/4, 1/8, or 1/16 pixels, and if the motion vector is not an integer unit, the prediction block may be generated from pixels of an integer unit .

The motion information encoding mode determination unit 162 may determine the encoding mode for the motion information of the current block to be one of a skip mode, a merge mode, and an AMVP mode.

The skip mode is applied when a skip candidate having motion information the same as the motion information of the current block exists and the residual signal is 0. The skip mode is a mode in which the current block which is the prediction unit (PU) Can be applied.

The merge mode is applied when there is a merge candidate having the same motion information as the motion information of the current block. The merge mode has a residual signal when the current block is different in size from the coding unit (CU) . On the other hand, the merge candidate and the skip candidate can be the same.

The AMVP mode is applied when the skip mode and the merge mode are not applied, and the AMVP candidate having the motion vector most similar to the motion vector of the current block can be selected as the AMVP predictor.

The motion information encoding unit 163 can encode the motion information according to the mode determined by the motion information encoding mode deciding unit 162. [

For example, the motion information encoding unit 163 performs a merge motion vector encoding process when the motion information encoding mode is the skip mode or the merge mode, and performs the AMVP encoding process when the motion information encoding mode is the AMVP mode.

When a motion vector is an integer unit, the prediction block generator 164 copies a block corresponding to a position indicated by a motion vector in a picture indicated by a reference picture index, and outputs the current block Lt; / RTI >

On the other hand, when the motion vector is not an integer unit, the prediction block generator 164 can generate the pixels of the prediction block from the integer unit pixels in the picture indicated by the reference picture index.

In this case, a predictive pixel is generated using an 8-tap interpolation filter for a luminance pixel, and a predictive pixel can be generated using a 4-tap interpolation filter for a chrominance pixel.

The residual block generating unit 165 generates a residual block using the current block and the current block. If the current block is 2Nx2N, the residual block generating unit 165 generates a residual block using a 2Nx2N- Blocks can be created.

On the other hand, if the size of the current block used for prediction is 2NxN or Nx2N, a prediction block for each of the 2NxN blocks constituting 2Nx2N is obtained, and a 2Nx2N final prediction block using the 2NxN prediction blocks is obtained Lt; / RTI >

In addition, a residual block of 2Nx2N size may be generated using the 2Nx2N prediction block, and overlap smoothing is applied to the pixels of the boundary portion to solve the discontinuity of the boundary of two prediction blocks having 2NxN size .

The residual block coding unit 166 divides the residual block into one or more conversion units (TU), and each of the conversion units (TU) can be transcoded, quantized, and entropy encoded.

The residual block coding unit 166 may transform the residual block generated by the inter prediction method using an integer-based transform matrix, and the transform matrix may be an integer-based DCT matrix.

On the other hand, the residual block coding unit 166 uses a quantization matrix to quantize the coefficients of the residual block transformed by the transformation matrix, and the quantization matrix can be determined by the quantization parameter.

Wherein the quantization parameter is determined for each coding unit (CU) of a predetermined size or more, and when the current coding unit (CU) is smaller than the predetermined size, the coding unit (CU) CU) and the quantization parameters of the remaining coding units (CUs) are the same as those of the above-mentioned parameters, and thus can not be encoded.

In addition, coefficients of the transform block may be quantized using a quantization matrix determined according to the quantization parameter and the prediction mode.

The quantization parameter determined for each coding unit (CU) larger than the predetermined size can be predictively encoded using the quantization parameter of the coding unit (CU) adjacent to the current coding unit (CU).

A quantization parameter predictor of the current coding unit (CU) can be generated by searching in the order of the left coding unit (CU), the upper coding unit (CU) of the current coding unit (CU) and using one or two valid quantization parameters have.

For example, a valid first quantization parameter retrieved in the above order can be determined as a quantization parameter predictor, and a valid first quantization parameter is quantized by searching in the order of a left coding unit (CU) and a coding unit (CU) It can be determined as a parameter predictor.

The coefficients of the quantized transform block are scanned and converted into one-dimensional quantization coefficients, and the scanning method can be set differently according to the entropy encoding mode.

For example, when encoded by CABAC, inter-prediction-encoded quantized coefficients can be scanned in a predetermined manner (zigzag or diagonal raster scan), and when encoded by CAVLC, .

For example, the scanning method may be determined according to the intra-prediction mode in the case of interlacing, or the intra-prediction mode in the case of intra, and the coefficient scanning method may be determined differently depending on the size of the conversion unit.

Meanwhile, the scan pattern may vary according to the directional intra prediction mode, and the scan order of the quantization coefficients may be scanned in the reverse direction.

The multiplexer 167 multiplexes the motion information encoded by the motion information encoding unit 163 and the residual signals encoded by the residual block encoding unit 166.

The motion information may be changed according to the encoding mode. For example, in the case of skip or merge, the motion information may include only an index indicating a predictor. In case of AMVP, the motion information may include a reference picture index, a difference motion vector, and an AMVP index of a current block .

Hereinafter, an embodiment of the operation of the intra predictor 150 shown in FIG. 1 will be described in detail.

The intra prediction unit 150 receives the prediction mode information and the size of the prediction unit PU from the picture division unit 110 and stores the reference pixels in the picture storage unit 110 to determine the intra prediction mode of the prediction unit PU. (180). ≪ / RTI >

The intra prediction unit 150 determines whether a reference pixel is generated by examining whether or not a reference pixel that is not available exists, and the reference pixels can be used to determine an intra prediction mode of the current block.

If the current block is located at the upper boundary of the current picture, pixels adjacent to the upper side of the current block are not defined. If the current block is located at the left boundary of the current picture, pixels adjacent to the left side of the current block are not defined, It can be determined that the pixels are not usable pixels.

Also, even if the current block is located at the slice boundary and the pixels adjacent to the upper side or the left side of the slice are not encoded and reconstructed, it can be determined that they are not usable pixels.

As described above, if there are no pixels adjacent to the left or upper side of the current block, or if there are no pixels that have been previously coded and reconstructed, the intra prediction mode of the current block may be determined using only available pixels.

On the other hand, a reference pixel at an unavailable position may be generated using the available reference pixels of the current block. For example, when pixels of the upper block are not available, , And vice versa.

That is, when a reference pixel is generated by copying an available reference pixel at a position closest to a predetermined direction from a reference pixel at an unavailable position, or when there is no reference pixel available in a predetermined direction, A reference pixel can be generated by copying an available reference pixel of the position.

On the other hand, even if the upper or left pixels of the current block exist, the reference pixel may be determined as an unavailable reference pixel according to the encoding mode of the block to which the pixels belong.

For example, if the block to which the reference pixel adjacent to the upper side of the current block belongs is inter-coded to be the reconstructed block, the pixels can be determined as unavailable pixels.

In this case, usable reference pixels can be generated using pixels belonging to the restored block by intra-coded blocks adjacent to the current block, and information indicating that the encoding device 10 determines available reference pixels according to the encoding mode To the decryption apparatus 20.

The intra prediction unit 150 determines the intra prediction mode of the current block using the reference pixels, and the number of intra prediction modes that can be accepted in the current block may vary according to the size of the block.

For example, if the current block size is 8x8, 16x16, or 32x32, there may be 34 intra prediction modes. If the current block size is 4x4, 17 intra prediction modes may exist.

The 34 or 17 intra prediction modes may include at least one non-directional mode and a plurality of directional modes.

The one or more non-directional modes may be a DC mode and / or a planar mode. When the DC mode and the planar mode are included in the non-directional mode, there may be 35 intra-prediction modes regardless of the size of the current block.

In this case, two non-directional modes (DC mode and planar mode) and 33 directional modes may be included.

In the planar mode, a prediction block of a current block is predicted using at least one pixel value (or a predicted value of the pixel value, hereinafter referred to as a first reference value) located on the bottom-right side of the current block and reference pixels .

The configuration of an image decoding apparatus according to an embodiment of the present invention can be derived from the configuration of the image encoding apparatus 10 described with reference to FIGS. 1 to 6, and for example, as described with reference to FIGS. 1 to 6 The image can be decoded by reversing the processes of the same image encoding method.

FIG. 7 is a block diagram of a moving picture decoding apparatus according to an embodiment of the present invention. The decoding apparatus 20 includes an entropy decoding unit 210, an inverse quantization / inverse transform unit 220, an adder 270, A de-blocking filter 250, a picture storage unit 260, an intra prediction unit 230, a motion compensation prediction unit 240, and an intra / inter changeover switch 280.

The entropy decoding unit 210 receives and decodes the bitstream encoded by the image encoding apparatus 10 and separates the bitstream into an intra prediction mode index, motion information, a quantization coefficient sequence, and the like, and outputs the decoded motion information to a motion compensation prediction unit 240).

The entropy decoding unit 210 transfers the intra prediction mode index to the intra prediction unit 230 and the inverse quantization / inverse transformation unit 220, and transmits the inverse quantization coefficient sequence to the inverse quantization / inverse transformation unit 220.

The inverse quantization / inverse transform unit 220 transforms the quantized coefficient sequence into a two-dimensional array of inverse quantization coefficients, and can select one of a plurality of scanning patterns for the transformation. For example, the inverse quantization / , Intra prediction or inter prediction) and the intra prediction mode.

The inverse quantization / inverse transform unit 220 applies quantization matrices selected from a plurality of quantization matrices to the inverse quantization coefficients of the two-dimensional array to restore the quantization coefficients.

The quantization matrix may be selected based on at least one of a prediction mode and an intra prediction mode of the current block with respect to a block of the same size, according to the size of the current block to be restored.

The inverse quantization / inverse transform unit 220 inversely transforms the reconstructed quantized coefficients to reconstruct residual blocks, and the inverse transform process may be performed using a transform unit (TU) as a basic unit.

The adder 270 combines the residual block reconstructed by the inverse quantization / inverse transform unit 220 and the prediction block generated by the intra prediction unit 230 or the motion compensation prediction unit 240 to reconstruct the image block.

The deblocking filter 250 may perform deblocking filter processing on the reconstructed image generated by the adder 270 to reduce deblocking artifacts due to video loss due to the quantization process.

The picture storage unit 260 is a frame memory for storing the local decoded picture subjected to the deblocking filter process by the deblocking filter 250. [

The intraprediction unit 230 restores the intra prediction mode of the current block based on the intra prediction mode index received from the entropy decoding unit 210 and generates a prediction block according to the reconstructed intra prediction mode.

The motion compensation prediction unit 240 generates a prediction block for the current block from the picture stored in the picture storage unit 260 based on the motion vector information and applies the interpolation filter selected when the motion compensation with the decimal precision is applied, Can be generated.

The intra / inter changeover switch 280 may provide the adder 270 with a prediction block generated in one of the intra prediction unit 230 and the motion compensation prediction unit 240 based on the encoding mode.

FIG. 8 is a block diagram of a configuration for performing inter-prediction in the image decoding apparatus 20. The inter-prediction decoder includes a demultiplexer 241, a motion information encoding mode determiner 242, An information decoding unit 243, an AMVP mode motion information decoding unit 244, a prediction block generating unit 245, a residual block decoding unit 246 and a restoration block generating unit 247.

8, the de-multiplexer 241 demultiplexes the currently encoded motion information and the encoded residual signals from the received bit stream, and transmits the demultiplexed motion information to the motion information encoding mode determination unit 242 And transmit the demultiplexed residual signal to the residual block decoding unit 246.

The motion information encoding mode determination unit 242 determines the motion information encoding mode of the current block. If the skip_flag of the received bitstream has a value of 1, it is determined that the motion information encoding mode of the current block is encoded in the skip encoding mode can do.

When the skip_flag of the received bitstream has a value of 0 and the motion information received from the de-multiplexer 241 has only a merge index, the motion information encoding mode determiner 242 determines the motion information encoding mode of the current block Can be determined to be encoded in the merge mode.

Also, the motion information encoding mode determination unit 242 determines that the skip_flag of the received bitstream has a value of 0, and the motion information received from the demultiplexer 241 includes the reference picture index, the differential motion vector, and the AMVP index , It can be determined that the motion information encoding mode of the current block is coded in the AMVP mode.

The merge mode motion information decoding unit 243 is activated when the motion information encoding mode determining unit 242 determines the motion information encoding mode of the current block as a skip or merge mode and the AMVP mode motion information decoding unit 244 decodes the motion Information encoding mode determination unit 242 determines that the motion information encoding mode of the current block is the AMVP mode.

The prediction block generation unit 245 generates a prediction block of the current block using the motion information reconstructed by the merge mode motion information decoding unit 243 or the AMVP mode motion information decoding unit 244. [

When a motion vector is an integer unit, a block corresponding to a position indicated by a motion vector in a picture indicated by a reference picture index may be copied to generate a prediction block of the current block.

On the other hand, when the motion vector is not an integer unit, pixels of the prediction block are generated from the pixels in the integer unit in the picture indicated by the reference picture index. In this case, an 8-tap interpolation filter is used for the luminance pixel, A prediction pixel can be generated using a 4-tap interpolation filter.

The residual block decoding unit 246 entropy-decodes the residual signal, inversely scans the entropy-decoded coefficients to generate a two-dimensional quantized coefficient block, and the inverse scanning method can be changed according to the entropy decoding method.

For example, in case of decoding based on CABAC, raster inverse scanning method in diagonal direction, and in case of decoding based on CAVLC, the inverse scanning method can be applied in a zigzag reverse scan method. In addition, the inverse scanning method may be determined differently depending on the size of the prediction block.

The residual block decoding unit 246 may dequantize the generated coefficient block using an inverse quantization matrix and restore the quantization parameter to derive the quantization matrix. Here, the quantization step size can be restored for each coding unit of a predetermined size or more.

The residual block decoding unit 260 inversely transforms the dequantized coefficient block to recover the residual block.

The reconstruction block generation unit 270 adds the prediction blocks generated by the prediction block generation unit 250 and the residual blocks generated by the residual block decoding unit 260 to generate reconstruction blocks.

Hereinafter, an embodiment of a process of restoring a current block through intraprediction will be described with reference to FIG.

First, the intra-prediction mode of the current block is decoded from the received bitstream. To this end, the entropy decoding unit 210 restores the first intra-prediction mode index of the current block by referring to one of the plurality of intra- .

One table selected according to the distribution of intra-prediction modes for a plurality of blocks adjacent to the current block may be applied as a table shared by the intra-prediction mode tables encoding apparatus 10 and the decoding apparatus 20 .

For example, if the intra prediction mode of the left block of the current block is the same as the intra prediction mode of the upper block of the current block, the first intra prediction mode table of the current block is restored by applying the first intra prediction mode table, The second intra prediction mode table may be applied to restore the first intra prediction mode index of the current block.

As another example, when the intra prediction modes of the upper block and the left block of the current block are all the directional intra prediction modes, the direction of the intra prediction mode of the upper block and the direction of the intra prediction mode of the left block The first intra prediction mode table of the current block is restored by restoring the first intra prediction mode index of the current block and the second intra prediction mode table of the current block is applied to the first intra prediction mode index .

The entropy decoding unit 210 transmits the first intra-prediction mode index of the restored current block to the intra-prediction unit 230.

The intraprediction unit 230 receiving the index of the first intraprediction mode can determine the maximum possible mode of the current block as the intra prediction mode of the current block when the index has the minimum value (i.e., when the index is 0) .

Meanwhile, if the index has a value other than 0, the intra predictor 230 compares the index indicated by the maximum possible mode of the current block with the first intra prediction mode index, The intra prediction mode corresponding to the second intra prediction mode index obtained by adding 1 to the first intra prediction mode index is determined as the intra prediction mode of the current block if the index is not smaller than the index indicated by the maximum possible mode of the current block. The intra prediction mode corresponding to the first intra prediction mode index may be determined as the intra prediction mode of the current block.

The intra prediction mode acceptable for the current block may be composed of at least one non-directional mode and a plurality of directional modes.

The one or more non-directional modes may be a DC mode and / or a planar mode. In addition, either the DC mode or the planar mode may be adaptively included in the allowable intra prediction mode set.

To this end, information specifying the non-directional mode included in the allowable intra prediction mode set may be included in the picture header or slice header.

Next, in order to generate an intra prediction block, the intra predictor 230 rotors the reference pixels stored in the picture storage unit 260, and determines whether there is a reference pixel that is not available.

The determination may be made according to the presence or absence of the reference pixels used to generate the intra prediction block by applying the decoded intra prediction mode of the current block.

Next, when it is necessary to generate a reference pixel, the intra-prediction unit 230 may generate reference pixels at positions that are not available by using previously reconstructed available reference pixels.

The definition of a non-available reference pixel and the method of generating a reference pixel may be the same as those of the intra prediction unit 150 shown in FIG. 1, but an intra prediction block may be generated according to a decoded intra prediction mode of the current block The reference pixels used for the reference pixel may be selectively restored.

In addition, the intra-prediction unit 230 determines whether to apply a filter to the reference pixels to generate a prediction block, i.e., whether to apply filtering to the reference pixels to generate an intra-prediction block of the current block And may be determined based on the decoded intra prediction mode and the size of the current prediction block.

Since the problem of the blocking artifact increases as the size of the block increases, the number of prediction modes for filtering the reference pixel can be increased as the size of the block increases. However, if the block is larger than a predetermined size, It may not filter the reference pixel for the reference pixel.

If it is determined that the filter needs to be applied to the reference pixel, the intra predictor 230 filters the reference pixels using a filter.

At least two or more filters may be adaptively applied according to the difference in level difference between the reference pixels. The filter coefficient of the filter is preferably symmetrical.

In addition, the above two or more filters may be adaptively applied according to the size of the current block, and when a filter is applied, a filter having a narrow bandwidth for a block having a small size, a filter having a wide bandwidth for a block having a large size, May be applied.

In the DC mode, since a prediction block is generated by an average value of reference pixels, there is no need to apply a filter. In a vertical mode in which correlation is vertical, there is no need to apply a filter to a reference pixel. It may not be necessary to apply the filter to the reference pixel even in the horizontal mode which is related to the direction.

Since the filtering is applied to the intra-prediction mode of the current block, the reference pixel can be adaptively filtered based on the intra-prediction mode of the current block and the size of the prediction block.

Next, the intra-prediction unit 230 generates a prediction block using the reference pixel or the filtered reference pixels according to the reconstructed intra-prediction mode, and the generation of the prediction block is the same as the operation in the coding apparatus 10 A detailed description thereof will be omitted.

The intraprediction unit 230 may determine whether to filter the generated prediction block, and the filtering may be determined based on the information included in the slice header or the encoding unit header or according to the intra prediction mode of the current block.

If it is determined that the generated prediction block is to be filtered, the intra prediction unit 230 may generate a new pixel by filtering pixels at a specific position of the prediction block generated using the available reference pixels adjacent to the current block .

For example, in the DC mode, a prediction pixel in contact with reference pixels among prediction pixels may be filtered using a reference pixel in contact with the prediction pixel.

Accordingly, the prediction pixels are filtered using one or two reference pixels according to the positions of the prediction pixels, and the filtering of the prediction pixels in the DC mode can be applied to the prediction blocks of all sizes.

On the other hand, in the vertical mode, the prediction pixels adjacent to the left reference pixel among the prediction pixels of the prediction block can be changed using reference pixels other than the upper pixel used to generate the prediction block.

Likewise, in the horizontal mode, the prediction pixels adjacent to the upper reference pixel among the generated prediction pixels may be changed using reference pixels other than the left pixel used to generate the prediction block.

The current block can be restored using the predicted block of the current block restored in this manner and the residual block of the decoded current block.

FIG. 9 is a view for explaining a second embodiment of a method of dividing and processing an image into blocks.

Referring to FIG. 9, a coding tree unit (CTU) having a maximum size of 256x256 pixels is divided into a quad tree structure and divided into four coding units (CUs) having a square shape.

At least one of the coding units divided into the quad tree structure may be divided into two coding units (CUs) having a rectangular shape by being divided into a binary tree structure.

At least one of the coding units divided into the quad tree structure may be divided into four coding units (CUs) having a quad tree structure.

And at least one of the subdivided coding units into the binary tree structure may be divided into two coding units (CUs) having a square or rectangular shape, divided again into a binary tree structure.

At least one of the coding units re-divided into the quad-tree structure may be divided into a quad-tree structure or a binary-cry structure and divided into coding units (CUs) having a square or rectangular shape.

Coding blocks (CBs) divided into a binary tree structure as described above can be used for prediction and conversion without being further divided. That is, the size of the prediction unit PU and the conversion unit TU belonging to the coding block CB as shown in FIG. 9 may be the same as the size of the coding block CB.

As described above, the coding unit divided into the quad tree structure can be divided into one or more prediction units (PUs) using the method as described with reference to FIGS.

In addition, the coding unit divided into the quad tree structure as described above may be divided into one or two or more conversion units (TU) using the method as described with reference to FIG. 5, and the divided conversion unit (TU) Can have a maximum size of 64x64 pixels.

FIG. 10 shows an embodiment of a syntax structure used for dividing and processing an image into blocks.

Referring to FIG. 10, the division of a coding unit (CU) as described with reference to FIG. 9 is expressed using split_cu_flag, and the depth of a coding unit (CU) divided using a binary tree is represented using binary_depth It can be done.

In addition, whether or not the coding unit CU is divided into a binary tree structure may be represented by a separate binary_split_flag.

1 to 8 for blocks (e.g., a coding unit (CU), a prediction unit (PU), and a conversion unit (TU)) divided by a method as described with reference to Figs. 9 and 10 The encoding and decoding of the image can be performed by applying the methods as described above.

Hereinafter, with reference to Figs. 11 to 16, still another embodiment of a method of dividing a coding unit (CU) into one or two or more conversion units (TU) will be described.

According to the embodiment of the present invention, the coding unit (CU) can be divided into conversion units (TU) which are basic units in which a conversion to a residual block is divided into a binary tree structure.

11, at least one of the rectangular coding blocks CB ₀ and CB ₁ divided into a binary tree structure and having a size of Nx2N or 2NxN is divided into a binary tree structure again to form a square having a size of NxN Conversion units TU ₀ and TU ₁ .

As described above, the block-based image encoding method can perform prediction, transformation, quantization, and entropy encoding steps.

In the prediction step, a prediction signal is generated by referring to a current encoding block and an existing encoded image or a surrounding image, thereby calculating a difference signal with the current block.

Meanwhile, in the conversion step, the differential signal is input to perform conversion using various conversion functions. The converted signal is classified into DC coefficients and AC coefficients and energy compaction is performed to enhance the coding efficiency .

Also, in the quantization step, quantization is performed by inputting transform coefficients, and then entropy encoding is performed on the quantized signal, so that the image can be encoded.

On the other hand, the image decoding method proceeds in the reverse order of the encoding process as described above, and the image quality distortion phenomenon may occur in the quantization step.

As a method for improving the coding efficiency and reducing the image quality distortion, it is possible to vary the size or shape of the conversion unit (TU) and the type of the conversion function to be applied according to the distribution of the differential signal input to the input in the conversion step, have.

For example, when a block similar to the current block is found through the block-based motion estimation process in the prediction step, a cost measurement method such as SAD (Sum of Absolute Difference) or MSE (Mean Square Error) The distribution of the signal can be varied in various forms depending on the characteristics of the image.

Accordingly, effective encoding can be performed by selectively determining the size or shape of the conversion unit (CU) based on the distribution of the various difference signals and performing the conversion.

Referring to FIG. 12, when a difference signal is generated as shown in (a) in a certain coding block CBx, the coding block CBx is divided into a binary tree structure 2 (b) Lt; RTI ID = 0.0 > TUs < / RTI >

For example, it can be said that the DC value generally represents the average value of the input signal. Therefore, when the difference signal as shown in FIG. 12A is received as the input of the conversion process, the coding block CBx is divided into two By dividing into the conversion units (TUs), the DC value can be effectively represented.

13, a square coding unit CU ₀ having a size of 2Nx2N is divided into binary tree structures and can be divided into rectangular transform units TU ₀ and TU ₁ having a size of Nx2N or 2NxN .

According to another embodiment of the present invention, the step of dividing the coding unit (CU) into the binary tree structure as described above may be repeatedly performed twice or more to divide it into a plurality of conversion units (TU).

Referring to FIG. 14, a rectangular coding block CB ₁ having a size of Nx2N is divided into a binary tree structure, a block having the size of the divided NxN is divided into a binary tree structure again to form N / 2xN or NxN / 2xN or NxN / 2 is further divided into binary tree structures to form square transform units TU ₁ (N / 2xN / 2) having a size of N / 2xN / 2, , TU ₂ , TU ₄ , TU ₅ ).

15, a square coding block CB ₀ having a size of 2Nx2N is divided into a binary tree structure, a block having the size of the divided Nx2N is divided into a binary tree structure, and a square having a size of NxN The block having the size of NxN may be divided into a binary tree structure and divided into rectangular transform units TU ₁ and TU ₂ having a size of N / 2xN.

Referring to FIG. 16, a rectangular coding block CB ₀ having a size of 2NxN is divided into a binary tree structure, a block having the size of the divided NxN is divided into a quad tree structure again to obtain N / 2xN / 2 (TU ₁ , TU ₂ , TU ₃ , TU ₄ ) having a predetermined size.

1 to 8 for blocks (e.g., a coding unit (CU), a prediction unit (PU), and a conversion unit (TU)) divided by the method described with reference to Figs. 11 to 16 The encoding and decoding of the image can be performed by applying the methods as described above.

Hereinafter, embodiments of a method by which the encoding apparatus 10 according to the present invention determines a block division structure will be described.

The picture dividing unit 110 included in the image coding apparatus 10 performs Rate Distortion Optimization (RDO) in accordance with a predetermined order and outputs the division unit CU, the prediction unit PU, The division structure of the unit TU can be determined.

For example, in order to determine a block division structure, the picture division unit 110 performs an optimal block division structure in terms of bit rate and distortion while performing Rate distortion Optimization-Quantization (RDO-Q) You can decide.

17, when the coding unit CU has the form of 2Nx2N pixel size, the 2Nx2N pixel size shown in (a), the NxN pixel size shown in (b), the Nx2N pixel size shown in (c) , RDO may be performed in order of the 2NxN pixel size conversion unit (PU) division structure shown in (d) to determine the optimum division structure of the conversion unit (PU).

Referring to Fig. 18, when the coding unit CU has the form of Nx2N or 2NxN pixel size, the pixel size of Nx2N (or 2NxN) shown in (a), the pixel size of NxN shown in (b) (x) shown in (e) shown in (e), a pixel size of N / 2xN (or NxN / 2) and NxN shown in / 2xN pixel size conversion unit (PU) division structure sequence in order to determine the optimum division structure of the conversion unit (PU).

Although the block division method of the present invention has been described with reference to the case where the block division structure is determined by performing Rate Distortion Optimization (RDO) in the above description, the picture division unit 110 may use a Sum of Absolute Difference (SAD) ), It is possible to maintain a proper efficiency while reducing the complexity.

The method according to the present invention may be implemented as a program for execution on a computer and stored in a computer-readable recording medium. Examples of the computer-readable recording medium include a ROM, a RAM, a CD- , A floppy disk, an optical data storage device, and the like, and may also be implemented in the form of a carrier wave (for example, transmission over the Internet).

The computer readable recording medium may be distributed over a networked computer system so that computer readable code can be stored and executed in a distributed manner. And, functional programs, codes and code segments for implementing the above method can be easily inferred by programmers of the technical field to which the present invention belongs.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, but, on the contrary, It should be understood that various modifications may be made by those skilled in the art without departing from the spirit and scope of the present invention.

Claims (23)

A method for dividing a block for image processing,
Dividing a picture of the picture into a plurality of coding units which are basic units in which inter prediction or intra prediction is performed; And
Dividing the divided coding units into one or more than one transform units, which is a basic unit in which a conversion for a residual block is performed,
Wherein the dividing the coding unit comprises dividing the picture or the divided coding unit into a binary tree structure and the transforming unit partitioning step comprises dividing the coding unit into a binary tree structure A Block Segmentation Method for Image Processing. The method according to claim 1,
Wherein the coding unit has a square or rectangular shape. The method according to claim 1,
The two or more slices constituting the picture are each divided into a plurality of coding tree units,
The coding unit partitioning step
And dividing the coding tree unit into one or more coding units, wherein the coding tree unit has a maximum size of 256x256 pixels. 4. The method of claim 3,
Dividing the coding tree unit into four coding units having a square shape; And
And subdividing at least one of the divided square coding units into two coding units having a rectangular shape. The method according to claim 1,
Wherein the conversion unit has a square or rectangular shape and has a maximum size of 64x64 pixels. The method according to claim 1,
And dividing the coding unit divided into the binary tree structure into two conversion units. The method according to claim 1,
And dividing the coding unit into a binary tree structure repeatedly at least twice. 8. The method according to claim 7,
Dividing the rectangular coding unit into two transformation units having a square shape; And
And re-segmenting at least one of the square transform units into two transform units having a rectangular shape. 8. The method according to claim 7,
Dividing the coding unit of the square into two conversion units having a rectangular shape; And
And re-partitioning at least one of the rectangular transform units into two transform units having a square shape. 8. The method according to claim 7,
Dividing the rectangular coding unit into two transformation units having a square shape; And
And dividing at least one of the square conversion units into four conversion units having a square shape. A method of encoding an image,
Dividing a picture of the picture into a plurality of coding units;
Performing inter prediction or intra prediction on the basis of the divided coding units as a basic unit;
Dividing the divided coding unit into one or more conversion units; And
And performing a transform on a residual block according to the inter prediction or intra prediction with the divided transform unit as a basic unit,
The coding unit dividing step includes dividing the picture or the divided coding unit into a binary tree structure, and the converting unit dividing step includes dividing the coding unit into a binary tree structure. 12. The method of claim 11,
The two or more slices constituting the picture are each divided into a plurality of coding tree units,
The coding unit partitioning step
And dividing the coding tree unit into one or more coding units, wherein the coding tree unit has a maximum pixel size of 256x256 pixels. 13. The method of claim 12,
Dividing the coding tree unit into four coding units having a square shape; And
And dividing at least one of the divided square coding units into two coding units having a rectangular shape. 12. The method of claim 11,
Wherein the transform unit has a square or rectangular shape and has a maximum size of 64x64 pixels. 12. The method according to claim 11,
And dividing the coding unit divided into the binary tree structure into two transformation units. 12. The method according to claim 11,
Wherein the step of dividing the coding unit into a binary tree structure is repeated two or more times. 12. The method of claim 11,
If the coding unit has a form of 2Nx2N pixel size,
Wherein the transform unit dividing step comprises performing Rate Distortion Optimization (RDO) in the order of transform units of 2Nx2N, NxN, Nx2N, and 2NxN pixel sizes to determine a division structure of the transform unit. 12. The method of claim 11,
If the coding unit has a form of Nx2N or 2NxN pixel size,
Wherein said converting unit dividing step comprises performing RDO in the order of the conversion units of Nx2N or 2NxN, NxN, N / 2xN or NxN / 2, N / 2xN / 2 pixel size to determine the division structure of said conversion unit Encoding method. A method for decoding an image,
Receiving an encoded bitstream;
Performing inverse quantization and inverse transform on the input bitstream to obtain a residual block;
Performing inter-prediction or intra-prediction to obtain a prediction block; And
And reconstructing an image by summing the obtained residual block and a prediction block,
A coding unit, which is a basic unit on which the inter prediction or intra prediction is performed, is a block divided from a coding tree unit using a binary tree structure, and the conversion unit, which is a basic unit on which the inverse transformation is performed, Wherein the block is a block divided from the block. 20. The method of claim 19,
Wherein the coding tree unit has a maximum size of 256x256 pixels and the conversion unit has a maximum size of 64x64 pixels. 20. The method of claim 19,
Wherein the coding tree unit is divided into four coding units having a square shape and at least one of the divided square coding units is subdivided into two coding units having a rectangular shape. 20. The method of claim 19,
Wherein the rectangular coding unit divided into the binary tree structure is divided into two transformation units having a square shape. 20. The apparatus of claim 19, wherein the conversion unit
Wherein the step of dividing the coding unit into a binary tree structure is repeated two or more times.

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