KR20140120396A - Fast Video coding method - Google Patents

Abstract

The present invention relates to a method for determining coding of a coding unit which comprises the steps of: checking an optimal mode of the coded current coding unit; setting a depth range selection mechanism (DRSM) of the coded coding unit after checking the optimal mode of the current coding unit; and determining a depth range of a coding unit to be coded using the DRSM, thereby rapidly determining whether to code a coding block.

Description

[0001] The present invention relates to a fast video coding method,

The present invention relates to an image encoding method and an apparatus using the same, and more particularly, to an image encoding method for block setting and block mode determination for coding an image and an apparatus using the same.

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

An inter picture prediction technique for predicting a pixel value included in a current picture from a previous or a subsequent picture of a current picture by an image compression technique, an intra picture prediction technique for predicting a pixel value included in a current picture using pixel information in the current picture, There are various techniques such as an entropy encoding technique in which a short code is assigned to a value having a high appearance frequency and a long code is assigned to a value having a low appearance frequency. Image data can be effectively compressed and transmitted or stored using such an image compression technique.

An object of the present invention is to provide an image coding method and apparatus capable of quickly determining whether coding is to be performed on a coding block.

An object of the present invention is to provide an image coding method and apparatus capable of effectively dividing a coding block.

An object of the present invention is to provide an image encoding method and apparatus capable of reducing the amount of computation when determining a prediction mode.

It is another object of the present invention to provide an image coding method and apparatus capable of reducing unnecessary inter-picture coding prediction mode calculation.

According to an embodiment of the present invention, there is provided a coding determination method of a coding unit, comprising: confirming an optimal mode of a current coding unit in which coding has been completed; checking a best mode of the current coding unit; Selection Mechanism), and determining a depth range of a coding unit that performs coding using the DRSM.

According to an embodiment of the present invention, there is provided an image encoding method and apparatus capable of quickly determining whether to perform coding on a coding block.

According to an embodiment of the present invention, an image encoding method and an encoding apparatus capable of effectively dividing a coding block are provided. As a result, the complexity can be reduced.

According to an embodiment of the present invention, there is provided an image encoding method and an encoding apparatus capable of reducing a computation amount when a prediction mode is determined.

According to an embodiment of the present invention, there is provided an image encoding method and apparatus capable of reducing unnecessary inter-picture encoding prediction mode calculation.

1 is a block diagram illustrating a configuration of an image encoding apparatus according to an embodiment of the present invention.
2 is a block diagram illustrating a configuration of an image decoding apparatus according to an embodiment of the present invention.
3 is a conceptual diagram schematically showing an embodiment in which one unit is divided into a plurality of lower units.
4 is a control flowchart for explaining a method of determining a mode of an image according to an embodiment of the present invention.
5 is a diagram illustrating an example in which a coding block is divided according to an embodiment of the present invention.
6 is a diagram for explaining an early coding determination method of a coding unit according to an embodiment of the present invention.
7 is a diagram for explaining an early coding determination method of a coding unit according to another embodiment of the present invention.
8 is a diagram for explaining an early coding determination method of a coding unit according to another embodiment of the present invention.
9 is a diagram for explaining an early coding determination method of a coding unit according to an embodiment of the present invention.
FIG. 10 is a diagram for explaining a coding early determination method of a coding unit according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In describing the embodiments of the present invention, if the detailed description of related known structures or functions is deemed to obscure the subject matter of the present specification, the description may be omitted.

When an element is referred to herein as being "connected" or "connected" to another element, it may mean directly connected or connected to the other element, Element may be present. In addition, the content of " including " a specific configuration in this specification does not exclude a configuration other than the configuration, and means that additional configurations can be included in the scope of the present invention or the scope of the present invention.

The terms first, second, etc. may be used to describe various configurations, but the configurations are not limited by the term. The terms are used for the purpose of distinguishing one configuration from another. For example, without departing from the scope of the present invention, the first configuration may be referred to as the second configuration, and similarly, the second configuration may be named as the first configuration.

In addition, the constituent elements shown in the embodiments of the present invention are shown independently to represent different characteristic functions, which do not mean that each constituent element is composed of separate hardware or a single software constituent unit. That is, each constituent unit is included in each constituent unit for convenience of explanation, and at least two constituent units of each constituent unit may 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 the separate embodiments of each component are also included in 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.

First, in order to facilitate the description and to facilitate understanding of the invention, terms used in this specification will be briefly described.

A unit is a unit of image encoding and decoding. In other words, a coding unit or a decoding unit in image coding / decoding refers to a divided unit when one image is divided into subdivided units and is then encoded or decoded. A block, a macroblock, a coding unit or a prediction unit, a transform unit, a coding block, a prediction block or a transform block, etc. . One unit may be divided into smaller-sized lower units.

A transform unit is a basic unit or a unit unit for performing coding / decoding of residual blocks such as transform, inverse transform, quantization, inverse quantization, and transform coefficient coding / decoding, and one transform unit is divided So that the size can be divided into a plurality of small conversion units. In addition, it can be used in the same sense as a conversion block, and a form including a syntax element related to a conversion block for luminance and chrominance signals may be referred to as a conversion unit.

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

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

The quantization matrix applied to the current block may be obtained by (1) copying a quantization matrix of the same size, or (2) by prediction from a previous matrix coefficient in the quantization matrix. A matrix of the same size may be a previously quantized, decoded, or used quantization matrix, a reference quantization matrix, or a basic quantization matrix. Or a combination including at least two of a quantization matrix, a reference quantization matrix, and a basic quantization matrix which have been previously encoded or decoded or used.

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

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

The basic matrix may denote a predetermined quantization matrix predefined in the image encoding apparatus and / or the image decoding apparatus, and the basic quantization matrix to be described later in this specification may be used in the same meaning as the basic matrix. The non-default matrix means a quantization matrix that is not previously defined in the image encoding apparatus and / or the image decoding apparatus, but is transmitted from the image encoding apparatus to the image decoding apparatus, that is, transmitted / received by the user And a non-basic quantization matrix to be described later in this specification can be used in the same sense as a non-basic matrix.

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

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

The image encoding apparatus 100 may encode an input image in an intra mode or an inter mode and output a bit stream. Intra prediction is intra prediction, and inter prediction is inter prediction. In the intra mode, the switch 115 is switched to the intra mode, and in the inter mode, the switch 115 can be switched to the inter mode. The image encoding apparatus 100 may generate a prediction block for an input block of the input image, and may then code the difference between the input block and the prediction block. At this time, the input image may mean an original picture.

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

In the inter mode, the motion predicting unit 111 may obtain a motion vector by searching an area of the reference image stored in the reference image buffer 190, which is best matched with the input block, in the motion estimation process. The motion compensation unit 112 may generate a prediction block by performing motion compensation using a motion vector. Here, the motion vector is a two-dimensional vector used for inter prediction, and can represent an offset between a current block and a block in the reference image.

The subtractor 125 can generate the residual block by the difference between the input block and the generated prediction block. The transforming unit 130 may perform a transform on the residual block to output a transform coefficient. The quantization unit 140 may quantize the input transform coefficient using at least one of a quantization parameter and a quantization matrix to output a quantized coefficient. At this time, the quantization matrix may be input to the image encoding apparatus, and the input quantization matrix may be determined to be used in the image encoding apparatus.

The entropy encoding unit 150 may output a bit stream by performing entropy encoding based on the values calculated by the quantization unit 140 or the encoding parameter values calculated in the encoding process. When entropy encoding is applied, a small number of bits are allocated to a symbol having a high probability of occurrence, and a large number of bits are allocated to a symbol having a low probability of occurrence, thereby expressing symbols, The size of the column can be reduced. Therefore, the compression performance of the image encoding can be enhanced through the entropy encoding. The entropy encoding unit 150 may use an encoding method such as Exponential-Golomb Code, Context-Adaptive Variable Length Coding (CAVLC), and Context-Adaptive Binary Arithmetic Coding (CABAC) for entropy encoding.

Since the image encoding apparatus 100 according to the embodiment of FIG. 1 performs inter-prediction encoding, that is, inter-view prediction encoding, the currently encoded image needs to be decoded and stored for use as a reference image. Accordingly, the quantized coefficients are inversely quantized in the inverse quantization unit 160 and inversely transformed in the inverse transformation unit 170. The inverse quantized and inverse transformed coefficients become reconstructed residual blocks and added to the prediction block through an adder 175 to generate reconstructed blocks.

The restoration block passes through the filter unit 180 and the filter unit 180 applies at least one of a deblocking filter, a sample adaptive offset (SAO), and an adaptive loop filter (ALF) can do. The filter unit 180 may be referred to as an in-loop filter. The deblocking filter can remove block distortion occurring at the boundary between the blocks. The SAO may add a proper offset value to the pixel value to compensate for coding errors. ALF can perform filtering based on the comparison between the reconstructed image and the original image. The restoration block having passed through the filter unit 180 may be stored in the reference image buffer 190.

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

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

The video decoding apparatus 200 receives the bit stream output from the video encoding apparatus, decodes the video stream into the intra mode or the inter mode, and outputs the reconstructed video, that is, the reconstructed video. In the intra mode, the switch is switched to the intra mode, and in the inter mode, the switch can be switched to the inter mode. The image decoding apparatus 200 may obtain a reconstructed residual block from the input bitstream, generate a prediction block, and add the reconstructed residual block and the prediction block to generate a reconstructed block, i.e., a reconstructed block .

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

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

The quantized coefficients are inversely quantized in the inverse quantization unit 220 using the quantization parameters and inversely transformed in the inverse transformation unit 230. The reconstructed residual blocks can be generated as a result of inverse quantization / inverse transformation of the quantized coefficients.

The quantization matrix used for inverse quantization is also called a scaling list. The inverse quantization unit 220 may generate a dequantized coefficient by applying a quantization matrix to the quantized coefficients.

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

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

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

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

3 is a conceptual diagram schematically showing an embodiment in which one unit is divided into a plurality of lower units. In the figure, for convenience of explanation, the processing unit of the image is described by taking a coding unit (CU) as an example.

The coding unit CU is a processing unit for processing the above-described video signal, for example intra / inter prediction, transform, quantization and / or entropy coding In this paper, The size of the coding unit used in coding one image may not be constant.

The coding unit may have a rectangular shape, and one coding unit may be divided into several coding units again. For example, one coding unit having a size of 2N x 2N may again be divided into coding units having four NxN sizes. The division of such a coding unit can be made recursively, and not all the coding units need be divided into the same form. However, there may be restrictions on the maximum or minimum size of the coding unit for convenience in coding and processing. If the maximum size of the coding unit is determined, it is called the maximum coding unit size, and if the minimum size is specified, it is called the minimum coding unit size.

For one coding unit, information indicating whether or not the coding unit is divided may be specified. For example, if the flag indicating the division is 1, the block corresponding to the corresponding node is divided into four blocks again. If the flag is 0, the processing process for the corresponding coding unit can be performed without further division.

The structure of the coding unit described above can be represented using a recursive tree structure. That is, a coding unit that is divided into other coding units, with one image or a maximum size coding unit root, has as many child nodes as the number of the divided coding units. Thus, the coding unit which is not further divided becomes a leaf node. Assuming that only one square division is possible for one coding unit, one coding unit may be divided into a maximum of four different coding units, so that the tree representing the coding unit structure will be in the form of a quad tree. For simplicity's sake, in the present document, a coding unit having a maximum coding unit size is referred to as a maximum coding unit (LCU), and a coding unit having a minimum coding unit size is referred to as a minimum coding unit (SCU).

In the encoder, the maximum and minimum coding unit sizes may be determined according to the characteristics (for example, resolution) of the video image or the efficiency of coding, and information about the maximum and minimum coding unit sizes may be included in the bitstream.

For example, when the maximum coding unit size and the maximum depth of the tree are defined, if the square division is performed, the height and width of the coding unit are half the height and width of the coding unit of the parent node, You can get the minimum coding unit size. Conversely, the minimum coding unit size and the maximum depth of the tree can be predefined and utilized, and the maximum coding unit size can be derived and used if necessary. Since the size of a unit changes in a square of 2 in a square partition, the size of the actual coding unit is expressed as a log value of 2 or less, which can increase the transmission efficiency.

The decoder may obtain information indicating whether the current coding unit is partitioned. This information can only be obtained (sent) under certain conditions to increase efficiency. For example, if the current coding unit is an SCU, it is no longer divided into smaller coding units, so in this case, it is not necessary to acquire information indicating that it is divided.

If the information indicates that the coding unit has been divided, the size of the divided coding unit is half of the current coding unit, and is divided into four square coding units based on the current processing position. The above processing can be repeated for each divided coding unit.

A unit or block can be hierarchically partitioned with depth information based on a tree structure. Each divided subunit may have depth information. The depth information may include information on the size of the lower unit, as the unit indicates the number and / or degree of division.

Referring to 310 of FIG. 3, the uppermost node may be referred to as a root node and may have the smallest depth value. At this time, the uppermost node may have a depth of level 0, and may represent the first unpartitioned unit.

A lower node having a depth of level 1 may represent a unit in which the first unit is divided once and a lower node having a depth of level 2 may represent the unit in which the first unit is divided twice. For example, in FIG. 3, the unit a corresponding to the node a in 320 is a unit that has been divided once in the initial unit and can have a depth of level 1.

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

Currently, JCT-VC is working on standards for High Efficiency Video Coding (HEVC) technology as the next generation video standard. HEVC aims at compression efficiency of more than 50% compared to H.264 / AVC which provides the best compression ratio. Many coding tools have been proposed for this purpose. Conventional video codecs are coded in macroblocks (16x16), while HEVC is optimized for CU (Coding Unit), PU (Prediction Unit) and TU (Transform Unit) Of the block size.

On the other hand, the image encoding method according to the HEVC requires a large amount of computation to calculate the inter picture coding mode. This is because the basic size of the block coding process is divided into the child CUs of the same size as the tree structure, and the calculation is performed on the PU and TU each time the image coding method according to the HEVC is H.264 / AVC. It is because.

The CU is divided into 32x32, 16x16, and 8x8 blocks from a maximum size 64x64 (LCU: Largest Coding Unit), and each CU calculates the optimum block size of the optimal PU and TU. Therefore, SKIP, Inter_2Nx2N, Inter_2NxN, Inter_N2N, Inter_2NxnU, Inter_2NxnD, Inter_nRx2N, Inter_nLx2N, and Intra_PCM modes are supported in one CU size.

If the current CU size is 8x8, Rate-Distortion Optimization (RDO) is performed for Inter_NxN and Intra_NxN modes to determine the most optimal block mode in one CU size.

There is a need for a method capable of efficiently terminating the inter-picture coding mode efficiently because the complexity of inter picture coding itself is considerably larger than that of intra picture coding.

Accordingly, the present invention provides a method of reducing the complexity of an encoder by early determining a block division process in a current CU (Coding Unit) during video coding, and an apparatus using the method.

In order to apply this early termination method, when performing from the largest one block (CTU: Coding Tree Unit) to the smallest block (SCU: Smallest Coding Unit), the parent block and the child block We propose a method to terminate the block partitioning process early by analyzing the SKIP mode correlation.

In addition, during the coding process for an arbitrary block, the CU division process can be terminated early using the optimal mode of the current block to be coded and the skip mode correlation for neighboring blocks, and the skip mode of the previous coded block can be terminated And calculating RDO only for a CU estimated as an optimal block (CU) size in the next encoding in one CTU, thereby providing a method and an apparatus capable of reducing a large amount of computation in inter picture coding.

It will be described in more detail that the optimum block size is estimated. The coding unit (CU), which is a basic unit for encoding a video signal, has a square size and has a size of 64x64 (CU depth 0), 32x32 (CU depth 1), 16x16 (CU depth 2), and 8x8 (CU depth 3) It can be divided. As described above, 64x64 corresponding to the coding unit of the largest size can be expressed as CTU.

When coding these CTUs, it is necessary to calculate the RDO for each size and find a coding unit structure that can code the best, that is, the best quality for the smallest bit amount. For example, the coding unit structure may be determined to be 64x64, the coding unit may be determined to be 32x32, or a more complex structure may be split. In this specification, a coding unit estimated with an optimal block size means having a coding unit structure that is divided into coding units of various sizes for the best coding among arbitrary CTUs. It is also intended to reduce the complexity by computing RDO only in a coding unit estimated with an optimal block size, rather than calculating RDO for all coding unit sizes.

4 is a control flowchart for explaining a method of determining a mode of an image according to an embodiment of the present invention.

First, the optimal mode of the current coding unit in which coding has been completed is confirmed (S401).

5 is a diagram illustrating an example in which a coding block is divided according to an embodiment of the present invention. According to an embodiment of the present invention, a coding unit to be coded currently has a divided structure as shown in FIG. This division structure is similar to a tree structure, and the coding units have strong depth similarity according to the depth.

For example, if a coding unit of depth 2 is referred to as a current coding unit (CU), a coding unit of depth 1 may be referred to as a parent CU, and a coding unit of depth 3 may be referred to as a child CU. At this time, if the prediction mode for the coding is determined to be the skip mode (SKIP mode) by calculating the ROD in the parent CU, the probability of the current coding block (current CU) is also determined to be the skip mode.

When the coding unit is divided and the inter prediction is performed, the calculation amount for one CTU is 1, 4, 16, 64, and the calculation amount for the prediction unit and the conversion unit is enormous.

Therefore, it is possible to use the skip mode information for the current coding unit to estimate the optimal mode of the coding unit to be encoded in order to effectively reduce the enormous amount of computation that occurs through block division for one coding unit.

According to an embodiment of the present invention, when the optimal mode of a current block to be coded is a skip mode, coding can be terminated early without performing a dividing process to a child CU of a current coded block

After confirming the optimal mode of the current coding unit, a DRSM (Depth Range Selection Mechanism) of the coding unit in which the coding is completed is set (S402).

When the optimum mode of the coding unit currently coded in step S401 is determined as the skip mode, the coding unit of the depth to be encoded when the coding unit of another tree is encoded from the CTU by setting the depth of the coding unit to DRSM has a skip mode Or the optimal coding unit, thereby determining the depth of the block to be currently encoded.

Since the coding units in one CTU have strong depth correlation and spatial correlation, when the coding unit to be currently coded is the skip mode, the coding units having the same depth and their child CUs are also skipped .

In addition, when the coding unit to be currently coded is a skip mode, in the four subtrees (the tree in which the 32X32 coding unit of Fig. 5 is the root) generated from the CTU, the other coding unit having the same size as the parent coding unit of the coding unit A coding unit of a sub-tree (coding unit of detph-1), a coding unit of another subtree having the same size as a child CU of a coding unit in which a skip mode is generated (a coding unit of detph +1) The coding unit (same detph) of another subtree having the same size is also likely to be a skip mode.

For example, if a coding unit having a depth of 2 and a size of 16x16 is referred to as a CU, as shown in FIG. 5, a coding unit having a size of 32x32 at a depth of 1 includes a parent CU, a coding having a depth of 3, A unit becomes a child CU. At this time, if the current CU is in the skip mode, the parent CU and the child CU are also likely to be in the skip mode.

When the DRSM is set, the range of the depth for performing the encoding using the DRSM is limited (S403). Through this step, the inter picture encoding mode of the coding unit to be currently encoded can be terminated early.

If the skip mode is selected in the optimum mode for the first time in the encoding process, the DRSM is set to the target depth (target detph) of the depth of the coding unit selected in the skip mode.

(DRSM -1 (target detph -1) and DRSM +1 (target detph +1) in order to reduce the loss according to the similarity of the depth when encoding is performed for the remaining coding units after the DRSM is determined, Lt; = DRSM + 1) of the coding unit to be currently coded.

That is, after the DRSM is determined, if the coding unit that performs the remaining coding process satisfies the condition of Equation (1), the coding process is performed, and if the condition is not satisfied, the coding process is skipped.

≪ Formula 1 >

DRSM -1 ≤ depth of the coding unit to be currently coded ≤ DRSM +1

Through this early determination process, 85 operations for the coding unit can be reduced to at least 5 operations and 80 operations can be reduced. Including the amount of calculation for the prediction unit and the conversion unit according to the early determination of the coding unit can also reduce a considerable amount of computation.

6 is a diagram for explaining an early coding determination method of a coding unit according to an embodiment of the present invention.

FIG. 6 shows a coding unit divided into a tree structure from depth 0 to depth 3. Each coding unit may comprise a plurality of prediction units (PUs).

The coding units can be expressed in depth and code order. For example, the coding unit 601 corresponding to the largest coding unit may be represented by 0 since it corresponds to the depth 0, and the coding unit 611, 612, 613 with a depth of 1 divided from the largest coding unit 601 , 614) can be expressed as 1-0, 1-1, 1-2, and 1-3 depending on the depth 1 and the coding order.

Likewise, depth 2 coding units 620 and 621 and depth 3 coding units 630 and 631 are also 2-0, 2-1, 2-2, 2-3 and 3-0 according to their depth and coding order. , 3-1, 3-2, 3-3.

The coding unit indicated by the solid line means a coding unit for performing an encoding process and the coding unit indicated by a dotted line means a coding unit for omitting the encoding process.

If the optimum mode of the coding unit 601 having the depth 0 is checked and the optimal mode of the coding unit 601 is the skip mode, the DRSM (Depth Range Selection Mechanism) of the coding unit in which the coding is completed is set. According to this embodiment, depth 0 is set to DRSM.

When DRSM is set, it determines whether the depth of the next coding unit to be coded satisfies Equation 1 and determines the depth range of the coding unit to perform coding.

Since DRSM is set to 0, the depths satisfying Equation 1 are 0 and 1, respectively. Therefore, since the coding unit for depth 0 is encoded, the coding units 611, 612, 613 and 614 belonging to the depth 1 perform the coding process and the coding units 620, 621 and 630 belonging to the depths 2 and 3 , 631) may be omitted.

7 is a diagram for explaining an early coding determination method of a coding unit according to another embodiment of the present invention.

FIG. 7 shows a coding unit divided into a tree structure from the depth (detph) 0 to the depth 3 as shown in FIG. 6, and each coding unit may include a plurality of prediction units (PUs).

The coding units can be represented according to the depth and coding order. For example, the coding unit 601 corresponding to the largest coding unit can be represented by 0 since it corresponds to the depth 0, and the coding unit 711, 712, 713 with a depth of 1 divided from the largest coding unit 701 , 714) can be expressed as 1-0, 1-1, 1-2, and 1-3 depending on the depth 1 and the encoding order.

Similarly, the depth 2 coding units 720 and 721 and the depth 3 coding units 730 and 731 are also 2-0, 2-1, 2-2, 2-3, 3-0 , 3-1, 3-2, 3-3.

The coding unit indicated by the solid line means a coding unit for performing an encoding process and the coding unit indicated by a dotted line means a coding unit for omitting the encoding process.

This embodiment is an example of a case in which the skip mode occurs in the optimum mode in the coding unit 711 of the first tree 1-0 derived from the CTU and the depth of 1-0 is set to DRSM.

The DRSM is determined to be a depth 1, and the coding unit 720a to which the DRSM is determined next determines the condition from the coding unit 720a to perform coding.

The range of DRSM satisfying Eq. 1 is 0 and 2 in depth. Therefore, the coding process is performed for the coding units 701, 711, 712, 713, 714, 720 and 721 belonging to the depths 0 to 2, and the coding process is omitted for the coding units 730 and 731 belonging to the depths 3 can do.

8 is a diagram for explaining an early coding determination method of a coding unit according to another embodiment of the present invention.

According to the present embodiment, the skip mode is determined to be the optimal mode in the first coding unit 820a with the depth of 2 in the first tree derived from the CTU.

At this time, the depth 2 is set to DRSM, and the coding unit 830 which codes the DRSM in the next order of the determined coding unit 820a checks the condition for Equation 1. [

In this case, the range of the depth satisfying the condition is 1 and 3. Therefore, the coding process is performed on the coding units 811, 812, 813, 814, 820, 821, 830, and 831 belonging to the depths 1 to 3.

That is, when DRSM is set to 2, all the coding units are performed for all the coding units.

9 is a diagram for explaining an early coding determination method of a coding unit according to an embodiment of the present invention.

According to the present embodiment, the skip mode is determined as the best mode in the first coding unit 930a of depth 3 of the first tree derived from the CTU.

In this case, at this time, the depth 3 is set to DRSM, and the condition for Equation 1 is checked from the coding unit 930b for coding in the next order of the coding unit 930a determined by the DRSM.

At this time, the range of the depth satisfying the condition is 2 and 3. Since the depth 4 is not set, the encoding conditions are not determined in this embodiment.

Therefore, the coding process is performed on the coding units 920, 921, 930 and 931 belonging to the depths 2 to 3, and the coding unit 911 belonging to the depth 1 excluding the coding unit 911 corresponding to 1-0 of the CTU subtree The coding process is omitted for the coding units 912, 913, and 914.

FIG. 10 is a diagram for explaining a coding early determination method of a coding unit according to an embodiment of the present invention.

According to the present embodiment, the skip mode is determined as the best mode in the third coding unit 1013 of depth 1 of the first tree derived from the CTU.

In this case, at this time, the condition for Equation 1 is checked from the subcoding unit 2-0 of the coding unit in which the depth of 1-2 is set to DRSM and the DRSM codes in the next order of the coding unit 1013 determined by the DRSM .

At this time, the range of the depth satisfying the condition is 0 and 2. Therefore, the coding process is performed for the coding unit 1030 encoded before the coding units 1001, 1011, 1012, 1013, 1014, 1020 and 1021 belonging to the depths 0 to 2 and the coding unit 1013 are judged as the skip mode And the coding process for the coding units 1031 and 1032 belonging to the depth 3 is omitted.

In the above-described exemplary system, the methods are described on the basis of a flowchart as a series of steps or blocks, but the present invention is not limited to the order of the steps, and some steps may occur in different orders or simultaneously . In addition, the above-described embodiments include examples of various aspects. For example, combinations of the embodiments are also to be understood as one embodiment of the present invention.

100: image encoding device 111: motion prediction unit
112: motion compensation unit 120: intra prediction unit
115: Switch 125:
130: conversion unit 140: quantization unit
150: an entropy encoding unit 160: an inverse quantization unit
170: inverting section 180: filter section

Claims (1)

A coding method of a coding unit,
Confirming an optimal mode of the current coding unit in which the coding is completed;
Setting a DRSM (Depth Range Selection Mechanism) of a coding unit that has been coded after confirming the optimal mode of the current coding unit;
And determining a depth range of a coding unit that performs coding using the DRSM.

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