WO2016072777A1

WO2016072777A1 - Combined intra prediction encoding/decoding method and device

Info

Publication number: WO2016072777A1
Application number: PCT/KR2015/011882
Authority: WO
Inventors: 박찬율
Original assignee: 삼성전자 주식회사
Priority date: 2014-11-06
Filing date: 2015-11-06
Publication date: 2016-05-12

Abstract

Disclosed is a combined intra prediction encoding/decoding method and device. A disclosed method and device for decoding a video according to one embodiment parses, from a bitstream, combination prediction information indicating whether a predicted value of a current block is acquired, by applying a plurality of intra prediction modes; determines whether to perform combination prediction for the current block, on the basis of the combination prediction information; when performing the combination prediction, acquires a plurality of predicted luminance values by applying a plurality of luminance prediction modes to a luminance component of the current block; determines a predicted final luminance value by weighted-summing the plurality of the predicted luminance values; acquires a plurality of predicted chrominance values by applying a plurality of chrominance prediction modes to a chrominance component of the current block; and determines a predicted final chrominance value by weighted-summing the plurality of the predicted chrominance values.

Description

Intra joint predictive coding, decoding method and apparatus

The present invention relates to a method of encoding and decoding an image, and more particularly, to a method and an apparatus for intra prediction encoding and decoding of an image for improving compression efficiency of an image by applying a plurality of intra prediction modes.

In video compression schemes such as MPEG-1, MPEG-2 and MPEG-4 H.264 / MPEG-4 AVC (Advanced Video coding), a picture is divided into macro blocks to encode an image. Each macro block is encoded using inter prediction and intra prediction. Then, the optimal encoding mode is selected in consideration of the data size of the encoded macroblock and the distortion degree of the original macroblock, and the macroblock is encoded. Meanwhile, HEVC, the most recent video standard, has a quadtree partitioning coding unit having a hierarchical recursion structure instead of a macroblock having a fixed size used in the existing video standard. CU) was introduced. HEVC significantly improves the compression efficiency by adopting the quadtree structure compared with the existing image standard, but the computational complexity is greatly increased.

Intra prediction does not refer to a reference picture in order to encode a block of a current picture, but encodes using a pixel value spatially adjacent to a block to be encoded. First, a prediction value for a block to be encoded is calculated by using adjacent pixel values. Next, only the difference between the predicted value and the pixel value of the actual block is encoded. Intra prediction modes are classified into 4 × 4 intra prediction modes of luminance components, 8 × 8 intra prediction modes, 16 × 16 intra prediction modes, and intra prediction modes of chrominance components. The intra prediction encoding apparatus performs all intra prediction in 16 × 16, 8 × 8, and 4 × 4 intra prediction modes, and then selects an optimal intra prediction mode among three cases.

The technical problem to be solved by the present invention is to improve the compression efficiency of the overall image by increasing the accuracy of intra prediction by applying a plurality of intra prediction modes.

An image decoding method according to an embodiment includes parsing joint prediction information indicating whether a prediction value of a current block is obtained from a bitstream by applying a plurality of intra prediction modes; Determining whether to perform joint prediction on a current block based on the joint prediction information; When performing the joint prediction: obtaining a plurality of luminance prediction values by applying a plurality of luminance prediction modes to the luminance component of the current block; Weighting the plurality of luminance prediction values to determine a final luminance prediction value; Obtaining a plurality of color difference prediction values by applying a plurality of color difference prediction modes to the color difference components of the current block; And weighting the plurality of color difference prediction values to determine a final color difference prediction value.

Further, in the image decoding method according to an embodiment, the obtaining of the plurality of brightness prediction values may include classifying a plurality of available brightness prediction modes into candidate groups of the plurality of brightness prediction modes; And obtaining the plurality of luminance prediction values by applying a luminance prediction mode selected from a candidate group of each luminance prediction mode to the luminance components of the current block, wherein the obtaining of the plurality of color difference prediction values comprises: Classifying the plurality of available color difference prediction modes into candidate groups of the plurality of color difference prediction modes; And applying the color difference prediction mode selected from the candidate group of each color difference prediction mode to the color difference components of the current block, to obtain the plurality of color difference prediction values.

Further, in the image decoding method according to an embodiment, the luminance prediction mode available in the candidate group of each luminance prediction mode is determined by the information of neighboring blocks or the correlation between each luminance prediction mode and the respective color difference prediction The color difference prediction mode available in the candidate group of the mode may be determined by the information of the neighboring blocks or the correlation between each color difference prediction mode.

Further, in the image decoding method according to an embodiment, of the candidate groups of the plurality of luminance prediction modes, the candidate group of the first luminance prediction mode includes all available luminance prediction modes, and the candidate group of the remaining luminance prediction modes It may preferentially include a prediction mode that does not include an interpolation process.

Also, in the image decoding method according to an embodiment, among the candidate groups of the plurality of luminance prediction modes, the luminance prediction mode selected from the candidate group of the first luminance prediction mode may be excluded from the candidate group of the remaining luminance prediction modes.

Further, in the image decoding method according to an embodiment, when the luminance prediction mode selected from the candidate group of the first luminance prediction mode among the candidate groups of the plurality of luminance prediction modes is also included in the candidate group of the remaining luminance prediction modes, The selected luminance prediction mode may be replaced with another luminance prediction mode in the candidate group of the remaining luminance prediction modes.

Further, in the image decoding method according to an embodiment, the candidate group of the plurality of color difference prediction modes may include a prediction mode selected from the candidate group of the plurality of luminance prediction modes.

In the image decoding method according to an embodiment, among the candidate groups of the plurality of luminance prediction modes, the luminance prediction mode included in the candidate group of the first luminance prediction mode is the luminance prediction included in the candidate group of the remaining luminance prediction modes. It may be different from the mode.

Further, in the image decoding method according to an embodiment, each of the candidate groups of the luminance prediction mode is a candidate group of a prediction mode having no direction, a candidate group of a prediction mode having horizontal direction or a candidate of a prediction mode having vertical direction. May correspond to one of the groups.

According to an embodiment, an apparatus for decoding an image may include: a receiver configured to apply a plurality of intra prediction modes to parse combined prediction information indicating whether a prediction value of a current block is obtained from a bitstream; Based on the joint prediction information, it is determined whether to perform joint prediction on the current block, obtain a plurality of luminance prediction values by applying a plurality of luminance prediction modes to the luminance component of the current block, and A final luminance prediction value is determined by weighting the luminance prediction values, a plurality of color difference prediction values are obtained by applying a plurality of color difference prediction modes to the color difference components of the current block, and the final color difference is weighted by adding the plurality of color difference prediction values. It includes a decoder for determining the prediction value.

According to an exemplary embodiment, an image encoding method includes: obtaining a plurality of luminance prediction values by applying a plurality of luminance prediction modes to luminance components of a current block; Weighting the plurality of luminance prediction values to determine a final luminance prediction value; Obtaining a plurality of color difference prediction values by applying a plurality of color difference prediction modes to the color difference components of the current block; Determining a final color difference prediction value by weighting the plurality of color difference prediction values; Determining joint prediction information indicating whether to perform joint prediction on the current block; And transmitting a bitstream including the combined prediction information.

Also, in the image encoding method, the obtaining of the plurality of luminance prediction values may include classifying a plurality of available luminance prediction modes into candidate groups of the plurality of luminance prediction modes; And obtaining the plurality of luminance prediction values by applying a luminance prediction mode selected from a candidate group of each luminance prediction mode to the luminance components of the current block, wherein the obtaining of the plurality of color difference prediction values comprises: Classifying the plurality of available color difference prediction modes into candidate groups of the plurality of color difference prediction modes; And applying the color difference prediction mode selected from the candidate group of each color difference prediction mode to the color difference components of the current block, to obtain the plurality of color difference prediction values.

Further, in the image encoding method according to an embodiment, the luminance prediction modes available in the candidate group of the respective luminance prediction modes are determined by the information of neighboring blocks or the correlation between the luminance prediction modes, and the respective color difference predictions. The color difference prediction mode available in the candidate group of the mode may be determined by the information of the neighboring blocks or the correlation between each color difference prediction mode.

An image encoding apparatus according to an embodiment obtains a plurality of luminance prediction values by applying a plurality of luminance prediction modes to luminance components of a current block, weights up the plurality of luminance prediction values, and determines a final luminance prediction value, Obtain a plurality of color difference prediction values by applying a plurality of color difference prediction modes to the color difference components of the current block, determine a final color difference prediction value by weighting the plurality of color difference prediction values, and perform joint prediction on the current block. An encoding unit to determine joint prediction information indicating whether to perform; And a transmitter for transmitting a bitstream including the combined prediction information.

FIG. 1 is a diagram for describing a method of performing intra prediction by applying intra modes in different directions.

2A is a schematic block diagram of an image encoding apparatus 20 according to an embodiment.

2B is a flowchart illustrating an image encoding method, according to an exemplary embodiment.

3A is a schematic block diagram of an image decoding apparatus 30 according to an embodiment.

3B is a flowchart illustrating an image decoding method, according to an exemplary embodiment.

4 is a reference diagram for describing a process of obtaining a prediction value of a current block by applying a plurality of intra prediction modes according to an embodiment.

5 is a flowchart illustrating an intra prediction method using a plurality of intra prediction modes, according to an exemplary embodiment.

6 is a flowchart illustrating an intra prediction method using a plurality of intra prediction modes according to various embodiments.

7 is a flowchart illustrating a syntax parsing process for joint intra prediction according to an embodiment.

8 illustrates a method of setting a candidate group of a prediction mode according to an embodiment.

9 illustrates a method of setting a candidate group of a prediction mode according to various embodiments.

10 is a block diagram of an image encoding apparatus, according to an embodiment.

11 is a block diagram of an image decoding apparatus, according to an embodiment.

12 illustrates a concept of coding units, according to an embodiment.

13 is a block diagram of an image encoder based on coding units, according to an embodiment.

14 is a block diagram of an image decoder based on coding units, according to an embodiment.

15 is a diagram of deeper coding units according to depths, and partitions, according to an embodiment.

16 illustrates a relationship between a coding unit and transformation units, according to an embodiment.

17 is a diagram of deeper encoding information, according to an embodiment.

18 is a diagram of deeper coding units according to depths, according to an exemplary embodiment.

19, 20, and 21 illustrate a relationship between a coding unit, a prediction unit, and a frequency transformation unit, according to an embodiment.

FIG. 22 illustrates a relationship between a coding unit, a prediction unit, and a transformation unit, according to encoding mode information of Table 1. FIG.

23 illustrates the number of intra prediction modes according to the size of a prediction unit, according to an embodiment.

24 is a reference diagram for describing intra prediction modes having various directionalities, according to an exemplary embodiment.

FIG. 25 is a diagram for describing a relationship between a neighboring pixel located on an extension line having a directionality of (dx, dy) and a current pixel, according to an exemplary embodiment.

26 and 27 are diagrams illustrating an intra prediction mode direction, according to an embodiment.

FIG. 28 is a diagram illustrating a direction of intra prediction modes having 33 orientations according to an embodiment. FIG.

The terms "... unit", "module", and the like described herein refer to a unit for processing at least one function or operation, which may be implemented in hardware or software, or a combination of hardware and software.

As used herein, the term "one embodiment" or "an embodiment" refers to a particular feature, structure, feature, etc. described with an embodiment included in at least one embodiment. Thus, the appearances of the phrases “in one embodiment” or “in an embodiment” appearing in various places throughout this specification are not necessarily all referring to the same embodiment.

In performing intra prediction, first, an intra prediction direction is determined for each unit block, and thus a prediction block is obtained, and a residue subtracted from the original block is encoded. The residue is transformed by DCT (discrete consine transform), quantized to generate a bitstream, and information about an intra prediction direction of each unit block is inserted into the bitstream. Further, the criteria for selecting an optimal intra prediction mode in consideration of residue and distortion among the intra prediction modes may be different for each type of data to be encoded and the encoding apparatus.

In FIG. 1,

intra prediction

1010 and 1020 are performed in two prediction modes with respect to a block to be encoded, and each prediction result is combined 1030.

Hereinafter, referring to FIGS. 2A to 9, an encoding method and a decoding method of an image for performing intra prediction by applying a plurality of intra prediction modes according to various embodiments will be described.

Also, with reference to FIGS. 10 to 22, an image encoding technique and an image decoding technique based on coding units having a tree structure according to various embodiments are disclosed. Hereinafter, the 'image' may be a still image of the image or a video, that is, the image itself.

In addition, the intra prediction mode according to various embodiments will be described with reference to FIGS. 23 to 28.

Referring to FIG. 2A, the image encoding apparatus 20 according to an embodiment includes an encoder 21 and a transmitter 22.

The image encoding apparatus 20 according to an embodiment receives images in units of slices, pictures, and the like, divides each image into blocks, and encodes each block. The type of block may be square or rectangular, and may be any geometric shape. It is not limited to data units of a certain size. A block according to an embodiment may include a largest coding unit (LCU), a coding unit (CU), a prediction unit, or a transform unit among coding units having a tree structure. ) And the like. Video encoding and decoding methods based on coding units having a tree structure will be described later with reference to FIGS. 10 to 22.

The encoder 21 according to an embodiment performs intra prediction to find a predicted value of a current block within a current picture. In performing the prediction, the encoder 21 may perform intra prediction using an intra prediction mode according to the prior art, and may also obtain a prediction value of the current block by applying a plurality of intra prediction modes.

The encoder 21 according to an embodiment obtains a plurality of brightness prediction values by applying a plurality of brightness prediction modes to the brightness components of the current block, and weights the obtained plurality of brightness prediction values to obtain a final brightness prediction value. Decide In addition, the encoder 21 obtains a plurality of color difference prediction values by applying a plurality of color difference prediction modes to the color difference components of the current block, and weights the obtained plurality of color difference prediction values to determine a final color difference prediction value. The encoder 21 may determine joint prediction information indicating whether to perform joint prediction on the current block.

As such, the intra prediction operation performed by the encoder 21 includes performing intra prediction on the current block two or more times, and reconstructing the intra prediction result into one prediction result. For example, the encoder 21 performs n intra predictions (n is an integer) on the luminance component of the current block to obtain the first to n th luminance prediction values and obtains them based on the weight information. The final luminance prediction value may be determined by weighting the first to n th luminance prediction values. In addition, the encoder 21 performs k intra predictions (k is an integer) on the color difference components of the current block, obtains first to k th color difference prediction values, and obtains the first based on the weight information. The final color difference prediction value may be determined by weighting the first color difference prediction value to the k th color difference prediction value. In this case, the weight information may be determined through training, or may be determined by information of neighboring blocks or correlation between the prediction modes.

According to an embodiment, the transmitter 22 transmits the joint prediction information determined by the encoder 21 in the form of a bitstream. In addition, the transmitter 22 may insert and transmit information regarding n luminance prediction modes and k color difference prediction modes into a bitstream in the form of a flag or an index to transmit the information to the image decoding apparatus. .

When the image encoding apparatus 20 according to an embodiment uses an encoding method having a large number of intra prediction modes such as HEVC, the candidate coding unit for prediction may be configured using various combinations of prediction modes, so that the intra prediction may be performed. By increasing the accuracy of the overall image compression efficiency can be improved.

The image encoding method performed by the image encoding apparatus 20 according to an embodiment may include obtaining a plurality of luminance prediction values by applying a plurality of luminance prediction modes to luminance components of a current block (S2001). Determining a final luminance prediction value by weighting the luminance prediction values (S2002), obtaining a plurality of color difference prediction values by applying a plurality of color difference prediction modes to the color difference components of the current block (S2003), and a plurality of color difference predictions Determining a final chrominance prediction value by weighting the values (S2004), determining joint prediction information indicating whether to perform joint prediction on the current block (S2005), and transmitting a bitstream including the joint prediction information It includes the step (S2006).

In detail, the plurality of luminance prediction values may be obtained as follows. First, the image encoding apparatus 20 may classify a plurality of available luminance prediction modes into candidate groups of the plurality of luminance prediction modes. In this case, the luminance prediction mode available in the candidate group of the plurality of luminance prediction modes may be determined by the information of neighboring blocks or the correlation between the luminance prediction modes. The candidate group of each luminance prediction mode may be set differently, and the entropy encoding method may also be set differently. For example, the candidate group of the luminance prediction mode may be classified into k candidate groups. Of the candidate groups of the plurality of luminance prediction modes, the candidate group of the first luminance prediction mode includes all available luminance prediction modes (eg, prediction modes 0 to 34 in the case of HEVC), and candidates of the second luminance prediction mode. The group may include prediction modes that do not include an interpolation process (eg, planner (0), DC (1), horizontal (10), and vertical (26) prediction modes for HEVC). Can be. In addition, the candidate group of each luminance prediction mode may be encoded through an arithmetic coding method, a 2-bit fixed length coding method, or the like. The image encoding apparatus 20 may obtain a plurality of luminance prediction values by applying the luminance prediction mode selected from the candidate group of each luminance prediction mode to the luminance component of the current block.

The process of obtaining a plurality of color difference prediction values is also similar to the process of obtaining a plurality of luminance prediction values. First, the image encoding apparatus 20 may classify a plurality of available color difference prediction modes into candidate groups of the plurality of color difference prediction modes. In this case, the color difference prediction mode available in the candidate group of the plurality of color difference prediction modes may be determined by information of neighboring blocks or correlation between each color difference prediction mode. The candidate group of each color difference prediction mode may be set differently, and the entropy encoding method may also be set differently. For example, the candidate group of the color difference prediction mode may be classified into n candidate groups. The candidate group of the first color difference prediction mode among the candidate groups of the plurality of color difference prediction modes includes all available color difference prediction modes (for example, prediction modes 0 to 34 for HEVC) and candidates for the second color difference prediction mode. The group may include prediction modes that do not include an interpolation process (eg, planner (0), DC (1), horizontal (10), and vertical (26) prediction modes for HEVC). Can be. The candidate group of each color difference prediction mode may be encoded through an arithmetic coding method, a 2-bit fixed length coding method, or the like. The image encoding apparatus 20 may obtain a plurality of color difference prediction values by applying a color difference prediction mode selected from candidate groups of each color difference prediction mode to the color difference components of the current block.

Referring to FIG. 3A, an image decoding apparatus 30 according to an embodiment includes a receiver 31 and a decoder 32.

The image decoding apparatus 30 according to an embodiment may perform an image decoding operation by operating in conjunction with an internal image decoding processor or an external image decoding processor to reconstruct an image through image decoding. The internal video decoding processor of the video decoding apparatus 30 according to an embodiment may implement a basic video decoding operation as a separate processor. In addition, the image decoding apparatus 30, the central processing unit, or the graphic processing unit may include a case of implementing a basic image decoding operation by including an image decoding processing module. The video decoding apparatus 30 obtains a residual regarding the current block by decoding the bitstream. The type of block may be square or rectangular, and may be any geometric shape. It is not limited to data units of a certain size.

The receiver 31 according to an embodiment applies a plurality of intra prediction modes to parse combined prediction information indicating whether a prediction value of a current block is obtained from a bitstream. In addition, the receiver 31 may parse information about the plurality of luminance prediction modes and the plurality of color difference prediction modes from the bitstream.

The decoder 32 according to an embodiment performs intra prediction that finds the prediction value of the current block within the current picture. In performing prediction, the decoder 32 may perform intra prediction using an intra prediction mode according to the prior art, and may also obtain a prediction value of a current block by applying a plurality of intra prediction modes.

The decoder 32 according to an embodiment determines whether to perform joint prediction on the current block based on the joint prediction information parsed from the bitstream. In addition, the decoder 32 obtains a plurality of brightness prediction values by applying a plurality of brightness prediction modes to the brightness components of the current block, and weights the obtained plurality of brightness prediction values to determine a final brightness prediction value. The decoder 32 obtains a plurality of color difference prediction values by applying a plurality of color difference prediction modes to the color difference components of the current block, and weights the obtained plurality of color difference prediction values to determine a final color difference prediction value.

As such, the intra prediction operation performed by the decoder 32 includes performing intra prediction on the current block two or more times, and reconstructing the intra prediction result into one prediction result. For example, the decoder 32 performs intra prediction on the luminance component of the current block n times (n is an integer) to obtain the first to n th luminance prediction values, and the flag or index of the bitstream. The final luminance prediction value may be determined by weighting the first luminance prediction value to the nth luminance prediction value based on the weight information obtained from the. In addition, the decoder 32 performs intra prediction on the color difference component of the current block k times (k is an integer) to obtain a first color difference prediction value to a kth color difference prediction value, and obtains it from a flag or index of the bitstream. The final color difference prediction value may be determined by weighting the first to k th color difference prediction values based on the weighted information.

When the image decoding apparatus 30 according to an embodiment uses an encoding method having a large number of intra prediction modes such as HEVC, the intra prediction may be formed by using various combinations of prediction modes. By increasing the accuracy of the overall image compression efficiency can be improved.

3B is a flowchart illustrating an image encoding method, according to an exemplary embodiment.

In an image decoding method performed by the image decoding apparatus 30 according to an embodiment, parsing joint prediction information indicating whether a prediction value of a current block is obtained by applying a plurality of intra prediction modes ( S3001), based on the joint prediction information, determining whether to perform joint prediction on the current block (S3002), when performing joint prediction: by applying a plurality of luminance prediction modes to the luminance components of the current block Obtaining a plurality of luminance prediction values (S3003), determining a final luminance prediction value by weighting the plurality of luminance prediction values (S3004), and applying a plurality of color difference prediction modes to the color difference components of the current block Obtaining a color difference prediction value (S3005), and determining a final color difference prediction value by weighting a plurality of color difference prediction values (S3006) is included.

In detail, the plurality of luminance prediction values may be obtained as follows. First, the image decoding apparatus 30 may classify a plurality of available luminance prediction modes into candidate groups of the plurality of luminance prediction modes. In this case, the luminance prediction mode available in the candidate group of the plurality of luminance prediction modes may be determined by the information of neighboring blocks or the correlation between the luminance prediction modes. The candidate group of each luminance prediction mode may be set differently, and the entropy encoding method may also be set differently. For example, the candidate group of the luminance prediction mode may be classified into k candidate groups. Of the candidate groups of the plurality of luminance prediction modes, the candidate group of the first luminance prediction mode includes all available luminance prediction modes (eg, prediction modes 0 to 34 in the case of HEVC), and candidates of the second luminance prediction mode. The group may include prediction modes that do not include an interpolation process (eg, planner (0), DC (1), horizontal (10), and vertical (26) prediction modes for HEVC). Can be. The candidate group of each luminance prediction mode may be decoded through an arithmetic decoding method, a 2-bit fixed length decoding method, or the like. The image decoding apparatus 30 may obtain a plurality of luminance prediction values by applying the luminance prediction mode selected from the candidate group of each luminance prediction mode to the luminance component of the current block.

The process of obtaining a plurality of color difference prediction values is also similar to the process of obtaining a plurality of luminance prediction values. First, the image decoding apparatus 30 may classify a plurality of available color difference prediction modes into candidate groups of the plurality of color difference prediction modes. In this case, the color difference prediction mode available in the candidate group of the plurality of color difference prediction modes may be determined by information of neighboring blocks or correlation between each color difference prediction mode. The candidate group of each color difference prediction mode may be set differently, and the entropy encoding method may also be set differently. For example, the candidate group of the color difference prediction mode may be classified into n candidate groups. The candidate group of the first color difference prediction mode among the candidate groups of the plurality of color difference prediction modes includes all available color difference prediction modes (for example, prediction modes 0 to 34 for HEVC) and candidates for the second color difference prediction mode. The group may include prediction modes that do not include an interpolation process (eg, planner (0), DC (1), horizontal (10), and vertical (26) prediction modes for HEVC). Can be. The candidate group of each color difference prediction mode may be decoded through an arithmetic decoding method, a 2-bit fixed length decoding method, or the like. The image decoding apparatus 30 may obtain a plurality of color difference prediction values by applying a color difference prediction mode selected from candidate groups of each color difference prediction mode to the color difference components of the current block.

Although the method for setting the candidate group of the prediction mode and the entropy encoding / decoding method are different in the image encoding apparatus 20 and the image decoding apparatus 30, the basic prediction method is the same.

When the image decoding apparatus 30 performs joint prediction, the image decoding apparatus 30 performs a first luminance intra prediction 4010 on the luminance component of the current block to obtain a first luminance prediction value X1. . Here, the prediction mode applied in the first luminance intra prediction 4010 may be a prediction mode selected from a candidate group of the first luminance prediction mode. In addition, the candidate group of the first luminance prediction mode may include arbitrary prediction modes. The image decoding apparatus 30 obtains the first luminance prediction value X1 and then performs the second luminance intra prediction 4020 on the luminance component of the current block to obtain the second luminance prediction value X2. Here, the prediction mode applied in the second luminance intra prediction 4020 may be a prediction mode selected from a candidate group of the second luminance prediction mode. In addition, the candidate group of the second luminance prediction mode may include arbitrary prediction modes, and may include prediction modes different from those of the prediction mode included in the candidate group of the first luminance prediction mode. The image decoding apparatus 30 determines a final luminance prediction value X by weighting the obtained first luminance prediction value X1 and the second luminance prediction value X2. Here, if each sample value has a weighting factor defined in advance, and the first luminance prediction value X1 is multiplied by the weighting factor WL, the second luminance prediction value X2 has a weight of (1-WL). The factor is multiplied to derive the final luminance prediction value X.

The image decoding apparatus 30 obtains the prediction value with respect to the color difference component of the current block in a similar manner to the luminance component. The image decoding apparatus 30 obtains a first color difference prediction value Y1 by performing first color difference intra prediction 4030 on the color difference component of the current block. Here, the prediction mode applied in the first color difference intra prediction 4030 may be a prediction mode selected from a candidate group of the first color difference prediction mode. The candidate group of the first color difference prediction mode may include arbitrary prediction modes. The image decoding apparatus 30 obtains the first color difference prediction value Y1 and then performs a second color difference intra prediction 4040 on the color difference component of the current block to obtain a second color difference prediction value Y2. Here, the prediction mode applied in the second color difference intra prediction 4040 may be a prediction mode selected from a candidate group of the second color difference prediction mode. The candidate group of the second chrominance prediction mode may include arbitrary prediction modes, and may include different prediction modes from the prediction mode included in the candidate group of the first chrominance prediction mode. The image decoding apparatus 30 determines a final color difference prediction value Y by weighting the obtained first color difference prediction value Y1 and the second color difference prediction value Y2. Here, if each weighting factor is previously defined in each prediction value, and the first color difference prediction value Y1 is multiplied by the weighting factor WC, the second color difference prediction value Y2 has a weight of (1-WC). The factor is multiplied to derive the final color difference prediction value Y.

The correlation between the candidate groups of the first and second luminance prediction modes and the candidate groups of the first and second color difference prediction modes will be described in more detail with reference to FIGS. 8 to 9.

The image decoding apparatus 30 according to an embodiment determines whether to perform prediction by applying an intra mode (5001). When the intra mode is not applied, the image decoding apparatus 30 performs prediction through the inter mode (5005). If an intra mode is applied, the image decoding apparatus 30 may determine whether to perform intra prediction using a plurality of intra prediction modes (that is, joint intra prediction or duplicate intra prediction). The on / off flag of the prediction is decoded (5010). The image decoding apparatus 30 determines whether to perform joint intra prediction based on a result of decoding the joint intra prediction flag (5015). When joint intra prediction is not performed, the image decoding apparatus 30 performs intra prediction once on the luminance component and the chrominance component of the current block, respectively, according to a conventional scheme. That is, the image decoding apparatus 30 performs a first luminance intra prediction mode to obtain a luminance prediction value (5020), and performs a first chrominance intra prediction mode to obtain a color difference prediction value (5025). However, when performing joint intra prediction, the image decoding apparatus 30 obtains N luminance prediction values by applying N

luminance prediction modes

5030, 5035, and 5040, and obtains K color difference prediction modes 5050, 5055. ) To obtain K color difference prediction values. N luminance prediction modes are each selected from the candidate group of N luminance prediction modes, and K color difference prediction modes are each selected from the candidate group of K color difference prediction modes. In this case, K and N are integers, K may be less than or equal to N. As described above, in the case of performing joint intra prediction, the candidate group of the plurality of luminance / color difference prediction modes may include various combinations of prediction modes, thereby compressing the entire image by increasing the accuracy of intra prediction in decoding the image. The efficiency can be improved.

The image decoding apparatus 30 according to various embodiments may not perform joint intra prediction on the color difference component of the current block. In this case, the overall operation of intra prediction is as follows. The image decoding apparatus 30 according to various embodiments determines whether to perform prediction by applying an intra mode (6001). When the intra mode is not applied, the image decoding apparatus 30 performs prediction through the inter mode (6005). If an intra mode is applied, the image decoding apparatus 30 may determine whether to perform intra prediction using a plurality of intra prediction modes (that is, joint intra prediction or duplicate intra prediction). The on / off flag of the prediction is decoded (6010). The image decoding apparatus 30 determines whether to perform joint intra prediction based on a result of decoding the joint intra prediction flag (6015). When joint intra prediction is not performed, the image decoding apparatus 30 performs intra prediction once on the luminance component and the chrominance component of the current block, respectively, according to a conventional scheme. That is, the image decoding apparatus 30 performs a first luminance intra prediction mode to obtain a luminance prediction value (6020), and performs a first chrominance intra prediction mode to obtain a color difference prediction value (6025). However, when performing joint intra prediction, the image decoding apparatus 30 obtains N luminance prediction values by applying N

luminance prediction modes

6030, 6035, and 6040. The image decoding apparatus 30 obtains one color difference prediction value by applying one color difference prediction mode 6045 after obtaining N brightness prediction values. N luminance prediction modes are each selected from the candidate group of N luminance prediction modes, and one chrominance prediction mode is each selected from the candidate group of one chrominance prediction mode.

The video decoding apparatus 30 according to an embodiment decodes whether the slice type is 7001, and determines whether the decoding target slice is an intra slice (7005). If the decoding target slice is not an intra slice, the image decoding apparatus 30 decodes whether the block within the slice is an intra / inter type (7010), and determines whether the decoding target block is an intra block (7015). ). If the decoding target block is not an intra block, the image decoding apparatus 30 performs inter block decoding (7020). However, when the decoding target slice is an intra slice or the decoding target block is an intra block, the image decoding apparatus 30 decodes an on / off flag of joint intra prediction to determine whether to perform joint intra prediction (7025). . The image decoding apparatus 30 determines whether to perform joint intra prediction based on a result of decoding the joint intra prediction flag (7030). When joint intra prediction is not performed, the image decoding apparatus 30 performs intra prediction once on the luminance component and the chrominance component of the current block, respectively, in a conventional manner (7035). When performing joint intra prediction, the image decoding apparatus 30 performs joint intra prediction using a plurality of intra prediction modes on the luminance component and the chrominance component of the current block (7040).

The candidate group of the plurality of luminance / color difference prediction modes according to an embodiment may include various combinations of prediction modes. For example, in HEVC, the candidate group of the first luminance prediction mode includes all 35 intra prediction modes, and the candidate group of the second luminance prediction mode is a DC mode (Mode 1) and a planar mode (Mode 0). It may include.

In addition, in HEVC, the candidate group of the first luminance prediction mode includes all 35 intra prediction modes, and the candidate group of the second luminance prediction mode is a horizontal mode (Mode 10) and a vertical mode (Mode 26). ) May be included.

Further, in HEVC, the candidate group of the first luminance prediction mode includes all 35 intra prediction modes, and the candidate group of the second luminance prediction mode includes the bottom left mode (Mode 2) and the upper right (Above Right). It may include a mode (Mode 34).

In addition, in HEVC, the candidate group of the first luminance prediction mode includes all 35 intra prediction modes, and the candidate group of the second luminance prediction mode includes a planner mode (Mode 0), a DC mode (Mode 1), and a horizontal mode (Mode). 10) and vertical mode (Mode 26).

In addition, in HEVC, the candidate group of the first luminance prediction mode includes all 35 intra prediction modes, and the candidate group of the second luminance prediction mode includes a prediction mode (eg, horizontal, Vertical and diagonal prediction modes) may be included first.

In addition, the luminance prediction mode selected from the candidate group of the first luminance prediction mode in HEVC may be excluded from the candidate group of the second luminance prediction mode.

In addition, when the luminance prediction mode selected from the candidate group of the first luminance prediction mode in the HEVC is also included in the candidate group of the second luminance prediction mode, the luminance prediction mode selected from the candidate group of the first luminance prediction mode is the second luminance prediction. It may be replaced by another luminance prediction mode in the candidate group of modes.

Referring to FIG. 8, when the luminance prediction mode selected from the candidate group of the first luminance prediction mode is Mode 10 (8010), except for Mode 10 in the candidate group 8020 of the second luminance prediction mode, instead of Mode 34 Mode 8050 may be added. That is, the luminance prediction mode selected from the candidate group of the first luminance prediction mode may influence the configuration of the candidate group of the second luminance prediction mode. Referring to FIG. 8, since Mode 10 is selected from the candidate group of the first luminance prediction mode, the candidate group of the second luminance prediction mode is Mode 0 in the candidate group 8020 including

Mode

0, 1, 10, and 26. Shown as being changed to a candidate group 8040, which includes 1, 26, and 34.

The candidate group of the plurality of luminance / color difference prediction modes according to an embodiment may include more various combinations of prediction modes.

For example, in HEVC, the candidate group of the first luminance prediction mode includes all 35 intra prediction modes, and the candidate group of the second luminance prediction mode includes planner mode (Mode 0), DC mode (Mode 1), and horizontal mode. (Mode 10), vertical mode (Mode 26), upper right mode (Mode 34), lower left mode (Mode 2), upper left mode (Mode 18), and Mode 6. Here Mode 6 can be replaced with one of the other modes.

Further, in HEVC, the candidate group of the first luminance prediction mode includes all 35 intra prediction modes, and the candidate group of the second luminance prediction mode is 34 intra except for the prediction mode selected from the candidate group of the first luminance prediction mode. It can include all prediction modes.

In addition, in HEVC, the candidate group of the first and second luminance prediction modes may limit the number of available prediction modes to 19, including a planner mode, a DC mode, and an even mode.

Further, in HEVC, the candidate group of the first luminance prediction mode includes 19 intra prediction modes including a planner mode, a DC mode, and an even mode, and the candidate group of the second luminance prediction mode is a DC mode (Mode 1) and a planner. Mode 0 may be included.

In addition, the candidate group of the first luminance prediction mode in HEVC includes 19 intra prediction modes including a planner mode, a DC mode, and an even mode, and the candidate group of the second luminance prediction mode is a horizontal mode (Mode 10) and a vertical. Mode 26 may be included.

Further, in HEVC, the candidate group of the first luminance prediction mode includes 19 intra prediction modes including a planner mode, a DC mode, and an even mode, and the candidate group of the second luminance prediction mode is a DC mode (Mode 1), a planner. It may include a mode (Mode 0), a horizontal mode (Mode 10) and a vertical mode (Mode 26).

Further, in HEVC, the candidate group of the first luminance prediction mode includes 19 intra prediction modes including a planner mode, a DC mode, and an even mode, and the candidate group of the second luminance prediction mode is a planner mode (Mode 0), DC. Mode (Mode 1), horizontal mode (Mode 10), vertical mode (Mode 26), upper right mode (Mode 34), lower left mode (Mode 2), upper left mode (Mode 18), and Mode 6 have. Here Mode 6 can be replaced with one of the other modes.

Further, in HEVC, the candidate group of the first luminance prediction mode includes 19 intra prediction modes including a planner mode, a DC mode, and an even mode, and the candidate group of the second luminance prediction mode is a candidate group of the first luminance prediction mode. All 34 intra prediction modes may be included except the prediction mode selected in FIG.

Further, in HEVC, the candidate group of the first luminance prediction mode includes 19 intra prediction modes including a planner mode, a DC mode, and an even mode, and the candidate group of the second luminance prediction mode is a candidate group of the first luminance prediction mode. It may include the remaining 16 intra prediction modes except the prediction mode available in.

In addition, the candidate group of the chrominance prediction mode in HEVC may include all intra prediction modes available in the candidate group of the first and second luminance prediction modes.

In addition, the candidate group of the chrominance prediction mode in HEVC may include intra prediction modes selected from candidate groups of the first and second luminance prediction modes.

Referring to FIG. 9, when the luminance prediction mode selected from the candidate group of the first luminance prediction mode is Mode 1 and the luminance prediction mode selected from the candidate group of the second luminance prediction mode is Mode 10 (9010), the chrominance prediction mode is determined. In the candidate group 9020, except for Mode 1 and Mode 10, an alternative candidate mode 9050 of Mode 34 and Mode 2 may be added instead. Here, there may be a priority between candidate modes to be replaced. For example, Mode 34 may have a higher priority than Mode 2 and may be replaced first. As in the embodiment of FIG. 9, the luminance prediction modes selected from the candidate groups of the first and second luminance prediction modes may influence the configuration of the candidate group of the chrominance prediction mode. 9, since Mode 1 and Mode 10 are selected from candidate groups of the first and second luminance prediction modes, the candidate group of the color difference prediction mode includes

Mode

0, 1, 10, and 26 (9020). Is changed to a candidate group 9040 including

Modes

0, 2, 26, and 34.

In addition, the intra prediction mode included in the candidate group of the first luminance prediction mode in HEVC may be different from the intra prediction mode included in the candidate group of the second luminance prediction mode. For example, when classifying candidate groups of the first and second luminance prediction modes, each candidate group may be grouped so as not to include the same prediction mode.

Further, in HEVC, the candidate group of each luminance prediction mode is a candidate group of prediction mode without direction (eg, planner, DC mode), and a candidate group of prediction mode having horizontal direction (eg, Mode 2 ~). 18) or a candidate group of prediction modes having vertical directionality (for example, Modes 18 to 34). Here, Mode 18 may belong to a candidate group having a horizontal orientation and may also belong to a candidate group having a vertical orientation.

In addition, the context models of candidate groups of the plurality of luminance / color difference prediction modes may be individually set. For example, the context model of the intra prediction mode in the current block may be obtained using the intra prediction mode of the neighboring block (eg, upper left, upper, upper right, left, lower left blocks).

In addition, in predicting the luminance component of the current block in HEVC, the luminance component prediction mode of the upper block among the neighboring blocks and the luminance component prediction mode of the left block may be used for context modeling. The first luminance prediction mode for the current block determines the context model using the first luminance prediction mode of the neighboring block, and the second luminance prediction mode for the current block uses the second luminance prediction mode of the neighboring block. Can be determined. The luminance and chrominance prediction mode of the intra block predicted by the general intra prediction method may be regarded as the first luminance and chrominance prediction mode.

As described above, the image encoding apparatus 20 according to an embodiment and the image decoding apparatus 30 according to an embodiment may obtain a prediction value of the current block by applying a plurality of intra prediction modes. Hereinafter, an embodiment of an image encoding method and an image decoding method based on coding units having a tree structure according to various embodiments will be described with reference to FIGS. 10 to 22. Also, an embodiment of an intra prediction mode scheme according to various embodiments is described with reference to FIGS. 23 through 28.

10 is a block diagram of an image encoding apparatus, according to an embodiment. The image encoding apparatus 100 illustrated in FIG. 10 may correspond to the image encoding apparatus 20 of FIG. 2A described above, and determine the maximum coding unit splitter 110 and the coding unit included in the image encoding apparatus 100. The unit 120 may be included as a part of the encoder 21 to perform a function thereof.

The image encoding apparatus 100 according to an embodiment includes a maximum coding unit splitter 110, a coding unit determiner 120, and an outputter 130.

The maximum coding unit splitter 110 may partition the current picture based on the maximum coding unit that is a coding unit of the maximum size for the current picture of the image. If the current picture is larger than the maximum coding unit, image data of the current picture may be split into at least one maximum coding unit. The maximum coding unit according to an embodiment may be a data unit having a size of 32x32, 64x64, 128x128, 256x256, etc., and may be a square data unit having a square power of 2 with a horizontal and vertical size greater than eight. The image data may be output to the coding unit determiner 120 for at least one maximum coding unit.

The coding unit according to an embodiment may be characterized by a maximum size and depth. The depth indicates the number of times the coding unit is spatially divided from the maximum coding unit, and as the depth increases, the coding unit for each depth may be split from the maximum coding unit to the minimum coding unit. The depth of the largest coding unit is the highest depth and the minimum coding unit may be defined as the lowest coding unit. As the maximum coding unit decreases as the depth increases, the size of the coding unit for each depth decreases, and thus, the coding unit of the higher depth may include coding units of a plurality of lower depths.

As described above, the image data of the current picture may be divided into maximum coding units according to the maximum size of the coding unit, and each maximum coding unit may include coding units divided by depths. Since the maximum coding unit is divided according to depths, image data of a spatial domain included in the maximum coding unit may be hierarchically classified according to depths.

The maximum depth and the maximum size of the coding unit that limit the total number of times of hierarchically dividing the height and the width of the maximum coding unit may be preset.

The coding unit determiner 120 encodes at least one divided region obtained by dividing the region of the largest coding unit for each depth, and determines a depth at which the final encoding result is output for each of the at least one divided region. That is, the coding unit determiner 120 encodes the image data in coding units according to depths for each maximum coding unit of the current picture, and selects a depth at which the smallest coding error occurs to determine the coding depth. The determined coded depth and the image data for each maximum coding unit are output to the outputter 130.

Image data in the largest coding unit is encoded based on coding units according to depths according to at least one depth less than or equal to the maximum depth, and encoding results based on the coding units for each depth are compared. As a result of comparing the encoding error of the coding units according to depths, a depth having the smallest encoding error may be selected. At least one coding depth may be determined for each maximum coding unit.

As the depth of the maximum coding unit increases, the coding unit is divided into hierarchically and the number of coding units increases. In addition, even in the case of coding units having the same depth included in one largest coding unit, a coding error of each data is measured, and whether or not division into a lower depth is determined. Therefore, even in the data included in one largest coding unit, since the encoding error for each depth is different according to the position, the coding depth may be differently determined according to the position. Accordingly, one or more coding depths may be set for one maximum coding unit, and data of the maximum coding unit may be partitioned according to coding units of one or more coding depths.

Accordingly, the coding unit determiner 120 according to an embodiment may determine coding units having a tree structure included in the current maximum coding unit. The coding units having a tree structure according to an embodiment include coding units having a depth determined as a coding depth among all deeper coding units included in the maximum coding unit. The coding unit of the coding depth may be hierarchically determined according to the depth in the same region within the maximum coding unit, and may be independently determined for the other regions. Similarly, the coded depth for the current region may be determined independently of the coded depth for the other region.

The maximum depth according to an embodiment is an index related to the number of divisions from the maximum coding unit to the minimum coding unit. The first maximum depth according to an embodiment may represent the total number of divisions from the maximum coding unit to the minimum coding unit. The second maximum depth according to an embodiment may represent the total number of depth levels from the maximum coding unit to the minimum coding unit. For example, when the depth of the largest coding unit is 0, the depth of the coding unit obtained by dividing the largest coding unit once may be set to 1, and the depth of the coding unit divided twice may be set to 2. In this case, if the coding unit divided four times from the maximum coding unit is the minimum coding unit, since depth levels of 0, 1, 2, 3, and 4 exist, the first maximum depth is set to 4 and the second maximum depth is set to 5. Can be.

Predictive coding and frequency transform of the largest coding unit may be performed. Similarly, the prediction encoding and the frequency transformation are performed based on depth-wise coding units for each maximum coding unit and for each depth below the maximum depth.

Since the number of coding units for each depth increases each time the maximum coding unit is divided for each depth, encoding including prediction coding and frequency transformation should be performed on all the coding units for each depth generated as the depth deepens. For convenience of explanation, the prediction encoding and the frequency transformation will be described based on the coding unit of the current depth among at least one maximum coding unit.

The image encoding apparatus 100 according to an embodiment may variously select a size or shape of a data unit for encoding image data. The encoding of the image data is performed through prediction encoding, frequency conversion, entropy encoding, and the like. The same data unit may be used in every step, or the data unit may be changed in steps.

For example, the image encoding apparatus 100 may select not only a coding unit for encoding the image data, but also a data unit different from the coding unit in order to perform predictive encoding of the image data in the coding unit.

For prediction encoding of the largest coding unit, prediction encoding may be performed based on a coding unit of a coding depth, that is, a more strange undivided coding unit, according to an embodiment. Hereinafter, a more strange undivided coding unit that is the basis of prediction coding is referred to as a 'prediction unit'. The partition in which the prediction unit is divided may include a data unit in which at least one of the prediction unit and the height and the width of the prediction unit are divided.

For example, when a coding unit having a size of 2Nx2N (where N is a positive integer) is no longer split, it becomes a prediction unit of size 2Nx2N, and the size of a partition may be 2Nx2N, 2NxN, Nx2N, NxN, or the like. According to an embodiment, the partition type includes not only symmetric partitions in which the height or width of the prediction unit is divided by a symmetrical ratio, but also partitions divided in an asymmetrical ratio, such as 1: n or n: 1, by a geometric form. It may optionally include partitioned partitions, arbitrary types of partitions, and the like.

The prediction mode of the prediction unit may be at least one of an intra mode, an inter mode, and a skip mode. For example, the intra mode and the inter mode may be performed on partitions having sizes of 2N × 2N, 2N × N, N × 2N, and N × N. In addition, the skip mode may be performed only for partitions having a size of 2N × 2N. The encoding may be performed independently for each prediction unit within the coding unit to select a prediction mode having the smallest encoding error.

Also, the image encoding apparatus 100 according to an embodiment may perform frequency conversion of image data of a coding unit based on not only a coding unit for encoding the image data but also a data unit different from the coding unit.

For frequency conversion of a coding unit, frequency conversion may be performed based on a data unit having a size smaller than or equal to the coding unit. For example, the data unit for frequency conversion may include a data unit for an intra mode and a data unit for an inter mode.

Hereinafter, the data unit on which the frequency conversion is based may be referred to as a 'conversion unit'. In a manner similar to the coding unit, while the transform unit in the coding unit is recursively divided into smaller transform units, the residual data of the coding unit may be partitioned according to the transform unit having a tree structure according to the transform depth.

For a transform unit according to an embodiment, a transform depth indicating a number of divisions between the height and the width of the coding unit divided to the transform unit may be set. For example, if the size of the transform unit of the current coding unit of size 2Nx2N is 2Nx2N, the transform depth is 0, the transform depth 1 if the size of the transform unit is NxN, and the transform depth 2 if the size of the transform unit is N / 2xN / 2. Can be. That is, the transformation unit having a tree structure may also be set for the transformation unit according to the transformation depth.

The encoded information for each coded depth requires not only the coded depth but also prediction related information and frequency transform related information. Accordingly, the coding unit determiner 120 may determine not only a coding depth that generates a minimum coding error, but also a partition type obtained by dividing a prediction unit into partitions, a prediction mode for each prediction unit, and a size of a transformation unit for frequency transformation. .

A method of determining a coding unit and a partition according to a tree structure of a maximum coding unit according to an embodiment will be described later in detail with reference to FIGS. 12 to 21.

The coding unit determiner 120 may measure a coding error of coding units according to depths using a Lagrangian Multiplier-based rate-distortion optimization technique.

The output unit 130 outputs the image data of the maximum coding unit encoded based on the at least one coded depth determined by the coding unit determiner 120 and the information about the encoding modes according to depths in the form of a bit stream.

The encoded image data may be a result of encoding residual data of the image.

The information about the encoding modes according to depths may include encoding depth information, partition type information of a prediction unit, prediction mode information, size information of a transformation unit, and the like.

The coded depth information may be defined using depth-specific segmentation information indicating whether to encode to a coding unit of a lower depth without encoding to the current depth. If the current depth of the current coding unit is a coding depth, since the current coding unit is encoded in a coding unit of the current depth, split information of the current depth may be defined so that it is no longer divided into lower depths. On the contrary, if the current depth of the current coding unit is not the coding depth, encoding should be attempted using the coding unit of the lower depth, and thus split information of the current depth may be defined to be divided into coding units of the lower depth.

If the current depth is not the coded depth, encoding is performed on the coding unit divided into the coding units of the lower depth. Since at least one coding unit of a lower depth exists in the coding unit of the current depth, encoding may be repeatedly performed for each coding unit of each lower depth, and recursive coding may be performed for each coding unit of the same depth.

Since coding units having a tree structure are determined in one largest coding unit and information about at least one coding mode should be determined for each coding unit of a coding depth, information about at least one coding mode may be determined for one maximum coding unit. Can be. In addition, since the data of the largest coding unit is divided hierarchically according to the depth, the coding depth may be different for each location, and thus information about the coded depth and the coding mode may be set for the data.

Accordingly, the output unit 130 according to an embodiment may allocate encoding information about a corresponding coding depth and an encoding mode to at least one of a coding unit, a prediction unit, and a minimum unit included in the maximum coding unit. .

According to an embodiment, a minimum unit is a square data unit having a minimum coding unit, which is a lowest coding depth, divided into four pieces, and has a maximum size that may be included in all coding units, prediction units, and transformation units included in the maximum coding unit. It may be a square data unit.

For example, the encoding information output through the output unit 130 may be classified into encoding information according to depth coding units and encoding information according to prediction units. The encoding information for each coding unit according to depth may include prediction mode information and partition size information. The encoding information transmitted for each prediction unit includes information about an estimation direction of the inter mode, information about a reference image index of the inter mode, information about a motion vector, information about a chroma component of an intra mode, and information about an inter mode of an intra mode. And the like. In addition, information about a maximum size and information about a maximum depth of a coding unit defined for each picture, slice, or GOP may be inserted in a header of a bitstream.

According to an embodiment of the simplest form of the image encoding apparatus 100, a coding unit according to depths is a coding unit having a size in which a height and a width of a coding unit of one layer higher depth are divided by half. That is, if the size of the coding unit of the current depth is 2Nx2N, the size of the coding unit of the lower depth is NxN. In addition, the current coding unit having a size of 2N × 2N may include up to four lower depth coding units having a size of N × N.

Accordingly, the image encoding apparatus 100 according to an embodiment determines a coding unit having an optimal shape and size for each maximum coding unit based on the size and the maximum depth of the maximum coding unit determined in consideration of characteristics of the current picture. In this case, coding units having a tree structure may be configured. In addition, since each of the maximum coding units may be encoded in various prediction modes, frequency transform schemes, or the like, an optimal coding mode may be determined in consideration of image characteristics of coding units having various image sizes.

Therefore, if an image having a very high resolution or a very large data amount is encoded in an existing macroblock unit, the number of macroblocks per picture is excessively increased. Accordingly, since the compressed information generated for each macroblock increases, the transmission burden of the compressed information increases, and the data compression efficiency tends to decrease. Therefore, the image encoding apparatus according to an embodiment may adjust the coding unit in consideration of the image characteristics while increasing the maximum size of the coding unit in consideration of the size of the image, thereby increasing image compression efficiency.

11 is a block diagram of an image decoding apparatus, according to an embodiment. The image decoding apparatus 200 illustrated in FIG. 11 may correspond to the image decoding apparatus 30 of FIG. 3A, and the image data and decoding information extracting unit 220 and the image included in the image decoding apparatus 200. The data decoder 230 may be included as a part of the decoder 32 to perform a function thereof.

The image decoding apparatus 200 according to an embodiment includes a receiver 210, image data and encoding information extractor 220, and image data decoder 230. Definitions of various terms such as coding units, depths, prediction units, transformation units, and information about various encoding modes for various processings of the image decoding apparatus 200 according to an exemplary embodiment may be described with reference to FIG. 10 and the image encoding apparatus 100. Same as described above with reference.

The receiver 205 receives and parses a bitstream of an encoded video. The image data and encoding information extractor 220 extracts image data encoded for each coding unit from the parsed bitstream according to coding units having a tree structure for each maximum coding unit, and outputs the encoded image data to the image data decoder 230. The image data and encoding information extractor 220 may extract information about a maximum size of a coding unit of the current picture from a header for the current picture.

Also, the image data and encoding information extractor 220 extracts information about a coded depth and an encoding mode for the coding units having a tree structure for each maximum coding unit, from the parsed bitstream. The extracted information about the coded depth and the coding mode is output to the image data decoder 230. That is, the image data of the bit string may be divided into maximum coding units so that the image data decoder 230 may decode the image data for each maximum coding unit.

The information about the coded depth and the encoding mode for each largest coding unit may be set with respect to one or more coded depth information, and the information about the coding mode according to the coded depths may include partition type information, prediction mode information, and transformation unit of the corresponding coding unit. May include size information and the like. In addition, split information for each depth may be extracted as the coded depth information.

The information about the coded depth and the encoding mode according to the maximum coding units extracted by the image data and the encoding information extractor 220 may be encoded according to the depth according to the maximum coding unit, as in the image encoding apparatus 100 according to an exemplary embodiment. Information about a coded depth and an encoding mode determined to repeatedly perform encoding for each unit to generate a minimum encoding error. Therefore, the image decoding apparatus 200 may reconstruct the image by decoding the data according to an encoding method that generates a minimum encoding error.

Since the encoded information about the coded depth and the encoding mode according to an embodiment may be allocated to a predetermined data unit among the corresponding coding unit, the prediction unit, and the minimum unit, the image data and the encoding information extractor 220 may determine the predetermined data. Information about a coded depth and an encoding mode may be extracted for each unit. If the information about the coded depth and the coding mode of the maximum coding unit is recorded for each of the predetermined data units, the predetermined data units having the information about the same coded depth and the coding mode are inferred as data units included in the same maximum coding unit. Can be.

The image data decoder 230 reconstructs the current picture by decoding image data of each maximum coding unit based on the information about the coded depth and the encoding mode for each maximum coding unit. That is, the image data decoder 230 may decode the encoded image data based on the read partition type, the prediction mode, and the transformation unit for each coding unit among the coding units having the tree structure included in the maximum coding unit. Can be. The decoding process may include a prediction process including intra prediction and motion compensation, and a frequency inverse transform process.

The image data decoder 230 may perform intra prediction or motion compensation according to each partition and prediction mode for each coding unit based on partition type information and prediction mode information of the prediction unit of the coding unit for each coding depth. .

In addition, the image data decoder 230 may perform frequency inverse transformation according to each transformation unit for each coding unit based on size information of the transformation unit of the coding unit for each coding depth, for a frequency inverse transformation for each maximum coding unit. have.

The image data decoder 230 may determine the coded depth of the current maximum coding unit by using the split information for each depth. If the split information indicates that the split information is no longer split at the current depth, the current depth is the coded depth. Therefore, the image data decoder 230 may decode the coding unit of the current depth using the partition type, the prediction mode, and the transformation unit size information of the prediction unit with respect to the image data of the current maximum coding unit.

In other words, by observing the encoding information set for a predetermined data unit among the coding unit, the prediction unit, and the minimum unit, the data units having the encoding information including the same split information are gathered, and the image data decoder 230 It may be regarded as one data unit to be decoded in the same encoding mode.

The image decoding apparatus 200 according to an exemplary embodiment may obtain information about a coding unit that generates a minimum coding error by recursively encoding each maximum coding unit in an encoding process, and use the same to decode the current picture. have. That is, decoding of encoded image data of coding units having a tree structure determined as an optimal coding unit for each maximum coding unit can be performed.

Therefore, even if a high resolution image or an excessively large amount of data is used, the image data can be efficiently used according to the coding unit size and the encoding mode that are adaptively determined according to the characteristics of the image by using the information about the optimum encoding mode transmitted from the encoding end. Can be decoded and restored.

Hereinafter, a method of determining coding units, a prediction unit, and a transformation unit according to a tree structure according to an embodiment will be described with reference to FIGS. 12 to 22.

12 illustrates a concept of hierarchical coding units.

As an example of a coding unit, a size of a coding unit may be expressed by a width x height, and may include 32x32, 16x16, and 8x8 from a coding unit having a size of 64x64. Coding units of size 64x64 may be partitioned into partitions of size 64x64, 64x32, 32x64, and 32x32, coding units of size 32x32 are partitions of size 32x32, 32x16, 16x32, and 16x16, and coding units of size 16x16 are 16x16. Coding units of size 8x8 may be divided into partitions of size 8x8, 8x4, 4x8, and 4x4, into partitions of 16x8, 8x16, and 8x8.

As for the video data 310, the resolution is set to 1920x1080, the maximum size of the coding unit is 64, and the maximum depth is 2. For the video data 320, the resolution is set to 1920x1080, the maximum size of the coding unit is 64, and the maximum depth is 3. As for the video data 330, the resolution is set to 352x288, the maximum size of the coding unit is 16, and the maximum depth is 1. The maximum depth illustrated in FIG. 12 represents the total number of divisions from the maximum coding unit to the minimum coding unit.

When the resolution is high or the amount of data is large, it is preferable that the maximum size of the coding size is relatively large not only to improve the coding efficiency but also to accurately shape the image characteristics. Accordingly, the

video data

310 or 320 having a higher resolution than the video data 330 may be selected to have a maximum size of 64.

Since the maximum depth of the video data 310 is 2, the coding unit 315 of the video data 310 is divided twice from a maximum coding unit having a long axis size of 64, and the depth is deepened by two layers, so that the long axis size is 32, 16. Up to coding units may be included. On the other hand, since the maximum depth of the video data 330 is 1, the coding unit 335 of the video data 330 is divided once from coding units having a long axis size of 16, and the depth is deepened by one layer to increase the long axis size to 8. Up to coding units may be included.

Since the maximum depth of the video data 320 is 3, the coding unit 325 of the video data 320 is divided three times from the largest coding unit having a long axis size of 64, and the depth is three layers deep, so that the long axis size is 32, 16. , Up to 8 coding units may be included. As the depth increases, the expressive power of the detailed information may be improved.

13 is a block diagram of an image encoder based on coding units, according to an embodiment. The image encoder 400 illustrated in FIG. 13 may correspond to the encoder 21 of FIG. 2A described above.

The image encoder 400 according to an embodiment includes operations performed by the encoding unit determiner 120 of the image encoding apparatus 100 to encode image data. That is, the intra predictor 410 performs intra prediction on the coding unit of the intra mode among the current frame 405, and the motion estimator 420 and the motion compensator 425 are the current frame 405 of the inter mode. And the inter frame estimation and motion compensation using the reference frame 495.

Data output from the intra predictor 410, the motion estimator 420, and the motion compensator 425 is output as a quantized transform coefficient through the frequency converter 430 and the quantizer 440. The quantized transform coefficients are restored to the data of the spatial domain through the inverse quantizer 460 and the frequency inverse transformer 470, and the recovered data of the spatial domain is passed through the deblocking block 480 and the loop filtering unit 490. It is post-processed and output to the reference frame 495. The quantized transform coefficients may be output to the bitstream 455 via the entropy encoder 450.

In order to be applied to the image encoding apparatus 100 according to an embodiment, an intra predictor 410, a motion estimator 420, a motion compensator 425, and a frequency converter that are components of the image encoder 400 may be used. 430, quantization unit 440, entropy encoding unit 450, inverse quantization unit 460, frequency inverse transform unit 470, deblocking unit 480, and loop filtering unit 490 are all the maximum coding units. In each case, a task based on each coding unit among coding units having a tree structure should be performed in consideration of the maximum depth.

In particular, the intra predictor 410, the motion estimator 420, and the motion compensator 425 partition each coding unit among coding units having a tree structure in consideration of the maximum size and the maximum depth of the current maximum coding unit. And a prediction mode, and the frequency converter 430 should determine the size of a transform unit in each coding unit among the coding units having a tree structure.

14 is a block diagram of an image decoder based on coding units, according to an embodiment. The image decoder 500 illustrated in FIG. 14 may correspond to the decoder 32 of FIG. 3A.

The bitstream 505 is parsed through the parsing unit 510, and the encoded image data to be decoded and information about encoding necessary for decoding are parsed. The encoded image data is output as inverse quantized data through the entropy decoder 520 and the inverse quantizer 530, and the image data of the spatial domain is restored through the frequency inverse transformer 540.

For the image data of the spatial domain, the intra prediction unit 550 performs intra prediction on the coding unit of the intra mode, and the motion compensator 560 uses the reference frame 585 together to apply the coding unit of the inter mode. Perform motion compensation for the

Data in the spatial domain that has passed through the intra predictor 550 and the motion compensator 560 may be post-processed through the deblocking unit 570 and the loop filtering unit 580 to be output to the reconstructed frame 595. In addition, the post-processed data through the deblocking unit 570 and the loop filtering unit 580 may be output as the reference frame 585.

In order to decode the image data by the image data decoder 230 of the image decoding apparatus 200, step-by-step operations after the parser 510 of the image decoder 500 may be performed.

In order to be applied to the image decoding apparatus 200 according to an exemplary embodiment, the components of the image decoder 500 include a parser 510, an entropy decoder 520, an inverse quantizer 530, and a frequency inverse transform unit ( 540, the intra predictor 550, the motion compensator 560, the deblocking unit 570, and the loop filtering unit 580 all perform operations based on coding units having a tree structure for each largest coding unit. shall.

In particular, the intra predictor 550 and the motion compensator 560 determine partitions and prediction modes for each coding unit having a tree structure, and the frequency inverse transform unit 540 must determine the size of the transform unit for each coding unit. do.

The image encoding apparatus 100 and the image decoding apparatus 200 according to an embodiment use hierarchical coding units to consider image characteristics. The maximum height, width, and maximum depth of the coding unit may be adaptively determined according to the characteristics of the image, and may be variously set according to a user's request. According to the maximum size of the preset coding unit, the size of the coding unit for each depth may be determined.

The hierarchical structure 600 of a coding unit according to an embodiment illustrates a case in which a maximum height and a width of a coding unit are 64 and a maximum depth is four. Since the depth deepens along the vertical axis of the hierarchical structure 600 of the coding unit according to an embodiment, the height and the width of the coding unit for each depth are divided. In addition, a prediction unit and a partition on which the prediction encoding of each depth-based coding unit is shown along the horizontal axis of the hierarchical structure 600 of the coding unit are illustrated.

That is, the coding unit 610 has a depth of 0 as the largest coding unit of the hierarchical structure 600 of the coding unit, and the size, ie, the height and width, of the coding unit is 64x64. The depth is deeper along the vertical axis, the coding unit 620 of depth 1 having a size of 32x32, the coding unit 630 of depth 2 having a size of 16x16, the coding unit 640 of depth 3 having a size of 8x8, and the depth 4 of depth 4x4. The coding unit 650 exists. A coding unit 650 having a depth of 4 having a size of 4 × 4 is a minimum coding unit.

Prediction units and partitions of the coding unit are arranged along the horizontal axis for each depth. That is, if the coding unit 610 of size 64x64 having a depth of zero is a prediction unit, the prediction unit may include a partition 610 of size 64x64, partitions 612 of size 64x32, and size included in the coding unit 610 of size 64x64. 32x64 partitions 614, 32x32 partitions 616.

Similarly, the prediction unit of the coding unit 620 having a size of 32x32 having a depth of 1 includes a partition 620 of size 32x32, partitions 622 of size 32x16 and a partition of size 16x32 included in the coding unit 620 of size 32x32. 624, partitions 626 of size 16x16.

Similarly, the prediction unit of the coding unit 630 of size 16x16 having a depth of 2 includes a partition 630 of size 16x16, partitions 632 of size 16x8, and a partition of size 8x16 included in the coding unit 630 of size 16x16. 634, partitions 636 of size 8x8.

Similarly, the prediction unit of the coding unit 640 of size 8x8 having a depth of 3 includes a partition 640 of size 8x8, partitions 642 of size 8x4 and a partition of size 4x8 included in the coding unit 640 of size 8x8. 644, partitions 646 of size 4x4.

Finally, the coding unit 650 of size 4x4 having a depth of 4 is the minimum coding unit and the coding unit of the lowest depth, and the corresponding prediction unit may also be set only as the partition 650 having a size of 4x4.

The coding unit determiner 120 of the image encoding apparatus 100 according to an exemplary embodiment may determine a coding depth of the maximum coding unit 610. The coding unit of each depth included in the maximum coding unit 610. Encoding must be performed every time.

The number of deeper coding units according to depths for including data having the same range and size increases as the depth increases. For example, four coding units of depth 2 are required for data included in one coding unit of depth 1. Therefore, in order to compare the encoding results of the same data for each depth, each of the coding units having one depth 1 and four coding units having four depths 2 should be encoded.

For each depth coding, encoding may be performed for each prediction unit of a coding unit according to depths along a horizontal axis of the hierarchical structure 600 of the coding unit, and a representative coding error, which is the smallest coding error at a corresponding depth, may be selected. . In addition, a depth deeper along the vertical axis of the hierarchical structure 600 of the coding unit, the encoding may be performed for each depth, and the minimum coding error may be searched by comparing the representative coding error for each depth. The depth and the partition in which the minimum coding error occurs in the maximum coding unit 610 may be selected as the coding depth and the partition type of the maximum coding unit 610.

The image encoding apparatus 100 according to an embodiment or the image decoding apparatus 200 according to an embodiment encodes or decodes an image in coding units having a size smaller than or equal to the maximum coding unit for each maximum coding unit. The size of a transform unit for frequency transformation during the encoding process may be selected based on a data unit that is not larger than each coding unit.

For example, in the image encoding apparatus 100 or the image decoding apparatus 200 according to the embodiment, when the current coding unit 710 is 64x64 size, the 32x32 transform unit 720 may be selected. Frequency conversion can be performed using the above.

In addition, the data of the 64x64 coding unit 710 is encoded by performing frequency transformation on the 32x32, 16x16, 8x8, and 4x4 transform units having a size of 64x64 or less, and the transform unit having the least error with the original is obtained. Can be selected.

17 is a diagram of deeper encoding information, according to an embodiment.

The output unit 130 of the image encoding apparatus 100 according to an embodiment is information about an encoding mode. Information 800 regarding partition types and information 810 about prediction modes for each coding unit of each coding depth may be used. The information 820 about the size of the transformation unit may be encoded and transmitted.

The information about the partition type 800 is a data unit for predictive encoding of the current coding unit and indicates information about a partition type in which the prediction unit of the current coding unit is divided. For example, the current coding unit CU_0 of size 2Nx2N may be any one of a partition 802 of size 2Nx2N, a partition 804 of size 2NxN, a partition 806 of size Nx2N, and a partition 808 of size NxN. It can be divided and used. In this case, the information 800 about the partition type of the current coding unit represents one of a partition 802 of size 2Nx2N, a partition 804 of size 2NxN, a partition 806 of size Nx2N, and a partition 808 of size NxN. It is set to.

Information 810 relating to the prediction mode indicates the prediction mode of each partition. For example, through the information 810 about the prediction mode, whether the partition indicated by the information 800 about the partition type is performed in one of the intra mode 812, the inter mode 814, and the skip mode 816 is performed. Whether or not can be set.

In addition, the information about the transform unit size 820 indicates whether to transform the current coding unit based on the transform unit. For example, the transform unit may be one of a first intra transform unit size 822, a second intra transform unit size 824, a first inter transform unit size 826, and a second intra transform unit size 828. have.

The image data and encoding information extractor 210 of the image decoding apparatus 200 according to an embodiment may include information about a partition type 800, information 810 about a prediction mode, and transformation for each depth-based coding unit. Information 820 about the unit size may be extracted and used for decoding.

Segmentation information may be used to indicate a change in depth. The split information indicates whether a coding unit of a current depth is split into coding units of a lower depth.

The prediction unit 910 for predictive encoding of the coding unit 900 having depth 0 and 2N_0x2N_0 size includes a partition type 912 having a size of 2N_0x2N_0, a partition type 914 having a size of 2N_0xN_0, a partition type 916 having a size of N_0x2N_0, and a N_0xN_0 It may include a partition type 918 of size. Although only

partitions

912, 914, 916, and 918 in which the prediction unit is divided by a symmetrical ratio are illustrated, as described above, the partition type is not limited thereto, and asymmetric partitions, arbitrary partitions, geometric partitions, and the like. It may include.

For each partition type, prediction coding must be performed repeatedly for one 2N_0x2N_0 partition, two 2N_0xN_0 partitions, two N_0x2N_0 partitions, and four N_0xN_0 partitions. For partitions having a size 2N_0x2N_0, a size N_0x2N_0, a size 2N_0xN_0, and a size N_0xN_0, prediction encoding may be performed in an intra mode and an inter mode. The skip mode may be performed only for prediction encoding on partitions having a size of 2N_0x2N_0.

If the encoding error by one of the

partition types

912, 914, and 916 of sizes 2N_0x2N_0, 2N_0xN_0, and N_0x2N_0 is the smallest, it is no longer necessary to divide it into lower depths.

If the encoding error of the partition type 918 having the size N_0xN_0 is the smallest, the depth 0 is changed to 1 and split (920), and the encoding is repeatedly performed on the depth 2 and the coding units 930 of the partition type having the size N_0xN_0. We can search for the minimum coding error.

The prediction unit 940 for predictive encoding of the coding unit 930 having a depth of 1 and a size of 2N_1x2N_1 (= N_0xN_0) includes a partition type 942 having a size of 2N_1x2N_1, a partition type 944 having a size of 2N_1xN_1, and a partition type having a size of N_1x2N_1. 946, a partition type 948 of size N_1 × N_1 may be included.

In addition, if the encoding error due to the partition type 948 having the size N_1xN_1 is the smallest, the depth 1 is changed to the depth 2 and divided (950), and repeatedly for the depth 2 and the coding units 960 of the size N_2xN_2. The encoding may be performed to search for a minimum encoding error.

When the maximum depth is d, the split information for each depth may be set until the depth d-1, and the split information may be set up to the depth d-2. That is, when encoding is performed from the depth d-2 to the depth d-1 to the depth d-1, the prediction encoding of the coding unit 980 of the depth d-1 and the size 2N_ (d-1) x2N_ (d-1) The prediction unit for 990 is a partition type 992 of size 2N_ (d-1) x2N_ (d-1), partition type 994 of size 2N_ (d-1) xN_ (d-1), size A partition type 996 of N_ (d-1) x2N_ (d-1) and a partition type 998 of size N_ (d-1) xN_ (d-1) may be included.

Among the partition types, one partition 2N_ (d-1) x2N_ (d-1), two partitions 2N_ (d-1) xN_ (d-1), two sizes N_ (d-1) x2N_ Prediction encoding is repeatedly performed for each partition of (d-1) and four partitions of size N_ (d-1) xN_ (d-1), so that a partition type having a minimum encoding error may be searched. .

Even if the encoding error of the partition type 998 of size N_ (d-1) xN_ (d-1) is the smallest, the maximum depth is d, so the coding unit CU_ (d-1) of the depth d-1 is no longer The encoding depth of the current maximum coding unit 900 may be determined as the depth d-1, and the partition type may be determined as N_ (d-1) xN_ (d-1) without going through a division process into lower depths. In addition, since the maximum depth is d, split information is not set for the coding unit 952 having the depth d-1.

The data unit 999 may be referred to as a 'minimum unit' for the current maximum coding unit. According to an embodiment, the minimum unit may be a square data unit having a size obtained by dividing the minimum coding unit, which is the lowest coding depth, into four divisions. Through this iterative encoding process, the image encoding apparatus 100 compares the encoding errors for each depth of the coding unit 900, selects the depth at which the smallest encoding error occurs, and determines the encoding depth. The partition type and the prediction mode may be set to the encoding mode of the coded depth.

In this way, the depth with the smallest error can be determined by comparing the minimum coding errors for all depths of

depths

0, 1, ..., d-1, d, and can be determined as the coding depth. The coded depth, the partition type of the prediction unit, and the prediction mode may be encoded and transmitted as information about an encoding mode. In addition, since the coding unit must be split from the depth 0 to the coded depth, only the split information of the coded depth is set to '0', and the split information for each depth except the coded depth should be set to '1'.

The image data and encoding information extractor 220 of the image decoding apparatus 200 according to an embodiment may extract information about a coding depth and a prediction unit for the coding unit 900 and use the same to decode the coding unit 912. Can be. The image decoding apparatus 200 according to an exemplary embodiment may identify a depth having split information of '0' as a coding depth using split information according to depths, and may use the decoding depth by using information about an encoding mode for a corresponding depth. have.

The coding units 1010 are coding units according to coding depths determined by the image encoding apparatus 100 according to an embodiment with respect to the maximum coding unit. The prediction unit 1060 is partitions of prediction units of each coding depth of each coding depth among the coding units 1010, and the transformation unit 1070 is transformation units of each coding depth for each coding depth.

If the depth-based coding units 1010 have a depth of 0, the

coding units

1012 and 1054 have a depth of 1, and the

coding units

1014, 1016, 1018, 1028, 1050, and 1052 have depths. 2,

coding units

1020, 1022, 1024, 1026, 1030, 1032, and 1048 have a depth of three, and

coding units

1040, 1042, 1044, and 1046 have a depth of four.

Some of the

partitions

1014, 1016, 1022, 1032, 1048, 1050, 1052, and 1054 of the prediction units 1060 are obtained by splitting coding units. That is,

partitions

1014, 1022, 1050, and 1054 are partition types of 2NxN,

partitions

1016, 1048, and 1052 are partition types of Nx2N, and partitions 1032 are partition types of NxN. Prediction units and partitions of the coding units 1010 according to depths are smaller than or equal to each coding unit.

The image data of the part 1052 of the transformation units 1070 may be frequency transformed or inversely transformed in a data unit having a smaller size than the coding unit. In addition, the

transformation units

1014, 1016, 1022, 1032, 1048, 1050, 1052, and 1054 are data units having different sizes or shapes when compared to corresponding prediction units and partitions among the prediction units 1060. That is, the image encoding apparatus 100 according to an embodiment and the image decoding apparatus 200 according to the embodiment may be intra prediction / motion estimation / motion compensation operations and frequency conversion / inverse transformation operations for the same coding unit. Each can be performed based on separate data units.

Accordingly, encoding is performed recursively for each coding unit having a hierarchical structure for each largest coding unit, and thus, an optimal coding unit is determined. Accordingly, coding units having a recursive tree structure may be configured. Partition information, partition type information, prediction mode information, and transformation unit size information about a unit may be included. Table 1 below shows an example that can be set in the image encoding apparatus 100 and the image decoding apparatus 200 according to an embodiment.

Table 1

Segmentation information 0 (coding for coding units of size 2Nx2N of current depth d)					Split information 1
Prediction mode	Partition mode		Transformation unit size		Iterative coding for each coding unit of lower depth d + 1
Intra interskip (2Nx2N only)	Symmetric Partition Mode	Asymmetric Partition Mode	Conversion unit split information 0	Conversion unit split information 1
	2Nx2N2NxNNx2NNxN	2NxnU2NxnDnLx2NnRx2N	2Nx2N	NxN (symmetric partition mode) N / 2xN / 2 (asymmetric partition mode)

The output unit 130 of the image encoding apparatus 100 according to an embodiment outputs encoding information about coding units having a tree structure, and the encoding information extraction unit of the image decoding apparatus 200 according to an embodiment ( 220 may extract encoding information about coding units having a tree structure from the received bitstream.

The split information indicates whether the current coding unit is split into coding units of a lower depth. If the split information of the current depth d is 0, partition type information, prediction mode, and transform unit size information are defined for the coded depth because the depth in which the current coding unit is no longer divided into the lower coding units is a coded depth. Can be. If it is to be further split by the split information, encoding should be performed independently for each coding unit of the divided four lower depths.

The prediction mode may be represented by one of an intra mode, an inter mode, and a skip mode. Intra mode and inter mode can be defined in all partition types, and skip mode can be defined only in partition type 2Nx2N.

The partition type information indicates the symmetric partition types 2Nx2N, 2NxN, Nx2N and NxN, in which the height or width of the prediction unit is divided by the symmetrical ratio, and the asymmetric partition types 2NxnU, 2NxnD, nLx2N, nRx2N, which are divided by the asymmetrical ratio. Can be. The asymmetric partition types 2NxnU and 2NxnD are divided into heights 1: 3 and 3: 1, respectively, and the asymmetric partition types nLx2N and nRx2N are divided into 1: 3 and 3: 1 widths, respectively.

The conversion unit size may be set to two kinds of sizes in the intra mode and two kinds of sizes in the inter mode. That is, if the transformation unit split information is 0, the size of the transformation unit is set to the size 2Nx2N of the current coding unit. If the transform unit split information is 1, a transform unit having a size obtained by dividing the current coding unit may be set. In addition, if the partition type for the current coding unit having a size of 2Nx2N is a symmetric partition type, the size of the transform unit may be set to NxN, and if the asymmetric partition type is N / 2xN / 2.

Encoding information of coding units having a tree structure according to an embodiment may be allocated to at least one of a coding unit, a prediction unit, and a minimum unit unit of a coding depth. The coding unit of the coding depth may include at least one prediction unit and at least one minimum unit having the same encoding information.

Therefore, if the encoding information held by each adjacent data unit is checked, it may be determined whether the adjacent data units are included in the coding unit having the same coding depth. In addition, since the coding unit of the corresponding coding depth may be identified by using the encoding information held by the data unit, the distribution of the coded depths within the maximum coding unit may be inferred.

Therefore, in this case, when the current coding unit is predicted with reference to the neighboring data unit, the encoding information of the data unit in the depth-specific coding unit adjacent to the current coding unit may be directly referenced and used.

In another embodiment, when the prediction coding is performed by referring to the neighboring coding unit, the data adjacent to the current coding unit in the coding unit according to depths is encoded by using the encoding information of the adjacent coding units according to depths. The neighboring coding unit may be referred to by searching.

The maximum coding unit 1300 includes

coding units

1302, 1304, 1306, 1312, 1314, 1316, and 1318 of a coded depth. Since one coding unit 1318 is a coding unit of a coded depth, split information may be set to zero. The partition type information of the coding unit 1318 having a size of 2Nx2N is partition type 2Nx2N 1322, 2NxN 1324, Nx2N 1326, NxN 1328, 2NxnU 1332, 2NxnD 1334, nLx2N (1336). And nRx2N 1338.

When partition type information is set to one of symmetric partition types 2Nx2N (1322), 2NxN (1324), Nx2N (1326), and NxN (1328), the conversion unit of size 2Nx2N when the conversion unit partition information (TU size flag) is 0 1134 is set, and if the transform unit split information is 1, a transform unit 1344 of size NxN may be set.

When the partition type information is set to one of the asymmetric partition types 2NxnU (1332), 2NxnD (1334), nLx2N (1336), and nRx2N (1338), if the conversion unit partition information (TU size flag) is 0, a conversion unit of size 2Nx2N ( 1352 is set, and if the transform unit split information is 1, a transform unit 1354 of size N / 2 × N / 2 may be set.

The conversion unit splitting information (TU size flag) described above with reference to FIG. 15 is a flag having a value of 0 or 1, but the conversion unit splitting information according to an embodiment is not limited to a 1-bit flag and is set to 0 according to a setting. , 1, 2, 3., etc., and may be divided hierarchically. The transformation unit partition information may be used as an embodiment of the transformation index.

In this case, when the transformation unit split information according to an embodiment is used together with the maximum size of the transformation unit and the minimum size of the transformation unit, the size of the transformation unit actually used may be expressed. The image encoding apparatus 100 according to an embodiment may encode maximum transform unit size information, minimum transform unit size information, and maximum transform unit split information. The encoded maximum transform unit size information, minimum transform unit size information, and maximum transform unit split information may be inserted into the SPS. The image decoding apparatus 200 according to an embodiment may use the maximum transformation unit size information, the minimum transformation unit size information, and the maximum transformation unit split information to use for image decoding.

For example, (a) if the current coding unit is 64x64 in size and the maximum transform unit size is 32x32, (a-1) when the transform unit split information is 0, the size of the transform unit is 32x32, (a-2) When the split information is 1, the size of the transform unit may be set to 16 × 16, and (a-3) when the split unit information is 2, the size of the transform unit may be set to 8 × 8.

As another example, (b) if the current coding unit is size 32x32 and the minimum transform unit size is 32x32, (b-1) when the transform unit split information is 0, the size of the transform unit may be set to 32x32. Since the size cannot be smaller than 32x32, no further conversion unit split information can be set.

As another example, (c) if the current coding unit is 64x64 and the maximum transform unit split information is 1, the transform unit split information may be 0 or 1, and no other transform unit split information may be set.

Therefore, when the maximum transform unit split information is defined as 'MaxTransformSizeIndex', the minimum transform unit size is 'MinTransformSize', and the transform unit split information is 0, the minimum transform unit possible in the current coding unit is defined as 'RootTuSize'. The size 'CurrMinTuSize' can be defined as in relation (1) below.

CurrMinTuSize = max (MinTransformSize, RootTuSize / (2 ^ MaxTransformSizeIndex)) ... (1)

Compared to the minimum transform unit size 'CurrMinTuSize' possible in the current coding unit, 'RootTuSize', which is a transform unit size when the transform unit split information is 0, may indicate a maximum transform unit size that can be adopted in the system. That is, according to relation (1), 'RootTuSize / (2 ^ MaxTransformSizeIndex)' is a transformation obtained by dividing 'RootTuSize', which is the size of the transformation unit when the transformation unit division information is 0, by the number of times corresponding to the maximum transformation unit division information. Since the unit size is 'MinTransformSize' is the minimum transform unit size, a smaller value among them may be the minimum transform unit size 'CurrMinTuSize' possible in the current coding unit.

According to an embodiment, the maximum transform unit size RootTuSize may vary depending on a prediction mode.

For example, if the current prediction mode is the inter mode, RootTuSize may be determined according to the following relation (2). In relation (2), 'MaxTransformSize' represents the maximum transform unit size and 'PUSize' represents the current prediction unit size.

RootTuSize = min (MaxTransformSize, PUSize) ......... (2)

That is, when the current prediction mode is the inter mode, 'RootTuSize', which is a transform unit size when the transform unit split information is 0, may be set to a smaller value among the maximum transform unit size and the current prediction unit size.

If the prediction mode of the current partition unit is a mode when the prediction mode is an intra mode, 'RootTuSize' may be determined according to Equation (3) below. 'PartitionSize' represents the size of the current partition unit.

RootTuSize = min (MaxTransformSize, PartitionSize) ........... (3)

That is, if the current prediction mode is the intra mode, the conversion unit size 'RootTuSize' when the conversion unit split information is 0 may be set to a smaller value among the maximum conversion unit size and the current partition unit size.

However, it should be noted that the current maximum conversion unit size 'RootTuSize' according to an embodiment that changes according to the prediction mode of the partition unit is only an embodiment, and a factor determining the current maximum conversion unit size is not limited thereto.

Hereinafter, the intra prediction unit 410 of the image encoding apparatus 100 and the intra prediction unit 550 of the image decoding apparatus 200 of FIG. 14 may perform intra prediction on the prediction unit. It demonstrates concretely.

The

intra prediction units

410 and 550 perform intra prediction that obtains the prediction value of the current prediction unit by using the neighboring pixels of the current prediction unit.

Intra prediction units

410 and 550 according to an exemplary embodiment consider that the prediction unit has a large size of 16 × 16 or more, and the intra prediction units having various directions using the (dx, dy) parameter in addition to the intra prediction mode having limited directionality according to the prior art may be used. Perform the prediction mode additionally. An intra prediction mode having various directions according to an embodiment will be described later.

In addition, the

intra predictors

410 and 550 may generate the predictor P1 through linear interpolation in the horizontal direction of the current pixel, and obtain the predictor P1 in order to obtain a predictor of the current pixel. A predictor P2 may be generated through interpolation to use the average values of the predictors P1 and P2 as predictors of the current pixel. An intra prediction mode that combines the predictors obtained through the linear interpolation in the horizontal direction and the linear interpolation in the vertical direction to generate the predictor of the current pixel is defined as a planar mode. In particular, the

intra predictors

410 and 550 generate virtual pixels used for horizontal linear interpolation using at least one or more peripheral pixels positioned on the upper right side of the current prediction unit in planner mode, and lower left side At least one peripheral pixel located at is used to generate a virtual pixel used for linear interpolation in the vertical direction.

The

intra prediction units

410 and 550 may variously set the number of intra prediction modes to be applied to the prediction unit according to the size of the prediction unit. For example, referring to FIG. 23, when the size of the intra prediction unit is NxN, the number of intra prediction modes that are actually performed for each of the prediction units having 2x2, 4x4, 8x8, 16x16, 32x32, 64x64, and 128x128 size is respectively. 5, 9, 9, 17, 33, 5, 5 (in the case of Example 2) can be set. The reason for differentiating the number of intra prediction modes that are actually performed according to the size of the prediction unit is that overhead for encoding prediction mode information varies according to the size of the prediction unit. That is, in the case of the prediction unit, although the portion of the entire image is small, the overhead for transmitting additional information such as the prediction mode of the small prediction unit may increase. Therefore, in the case of encoding a small prediction unit in too many prediction modes, the bit amount may increase, thereby reducing the compression efficiency. In addition, since a prediction unit having a large size, for example, a prediction unit having a size of 64x64 or more is generally selected as a prediction unit for a flat region of an image, a large size that is largely selected to encode such a flat region is often selected. Encoding the prediction unit in too many prediction modes may also be inefficient in terms of compression efficiency. Therefore, when the size of the prediction unit is too large or small than the predetermined size, only a relatively small number of intra prediction modes may be applied. The number of intra prediction modes applied according to the size of the prediction unit is not limited to FIG. 23 and may be variously set. The number of prediction modes applied according to the size of each prediction unit illustrated in FIG. 23 is only an example, and the number of prediction modes according to the size of each prediction unit may be changed. In addition, the number of intra prediction modes applied to each prediction unit may be constantly set regardless of the size of the prediction unit.

The

intra predictor

410 or 550 according to an embodiment is an intra prediction mode applied to a prediction unit to determine a peripheral reference pixel by using a line having a predetermined slope with respect to the pixel in the prediction unit, and determine the determined peripheral reference pixel of the pixel. Intra prediction modes used as predictors may be included. The slope of this line may be set using the (dx, dy) parameter (dx, dy is an integer). For example, when 33 prediction modes are defined as mode N (N is an integer from 0 to 32), mode 0 is a vertical mode, mode 1 is a horizontal mode, mode 2 is a DC mode, mode 3 is a plane mode, mode 32 is set to planar mode, and modes 4 to mode31 are each represented by (1, -1), (1,1), (1,2), and (2,1) as shown in Table 1 below. , (1, -2), (2,1), (1, -2), (2, -1), (2, -11), (5, -7), (10, -7), ( 11,3), (4,3), (1,11), (1, -1), (12, -3), (1, -11), (1, -7), (3, -10 ), (5, -6), (7, -6), (7, -4), (11,1), (6,1), (8,3), (5,3), (5, A line having a directionality of tan ⁻¹ (dy / dx) using (dx, dy) represented by one of 7), (2,7), (5, -7), and (4, -3) By using the neighboring reference pixels may be determined, and the determined neighboring reference pixels may be defined as an intra prediction mode.

TABLE 2

mode #	dx	dy	mode #	dx	dy
mode
4	One	-One	mode 18	One	-11
mode 5	One	One	mode 19	One	-7
mode 6	One	2	mode 20	3	-10
mode 7	2	One	mode 21	5	-6
mode 8	One	-2	mode 22	7	-6
mode 9	2	-One	mode 23	7	-4
mode 10	2	-11	mode 24	11	One
mode 11	5	-7	mode 25	6	One
mode 12	10	-7	mode 26	8	3
mode 13	11	3	mode 27	5	3
mode 14	4	3	mode 28	5	7
mode 15	One	11	mode 29	2	7
mode 16	One	-One	mode 30	5	-7
mode 17	12	-3	mode 31	4	-3
mode 0 is vertical mode, mode 1 is horizontal mode, mode 2 is DC mode, mode 3 is plane mode, and mode 32 is planar mode.

The number of intra prediction modes used by the

intra prediction units

410 and 550 is not limited to Table 2, and is variously set based on information such as whether the current prediction unit is a chrominance component or a luminance component and the size of the current prediction unit. In addition, whether or not each mode N indicates which intra prediction mode may be variously set. For example, the total number of intra prediction modes is set to 36, mode 0 is a planar mode, mode 1 is a DC mode, and modes 2 to 34 are intra prediction modes having 33 directionalities, as in the example described below. The mode 35 may be defined as a mode In_FromLuma using the prediction unit of the luminance component corresponding to the prediction unit of the chrominance component. The intra prediction mode In_FromLuma, which performs the prediction unit of the corresponding color difference component from the prediction unit of the luminance component of Mode 35, is applied only to the prediction unit of the color difference component, and is not used in the intra prediction of the prediction unit of the luminance component.

As described above, the

intra predictor

410 or 550 according to an exemplary embodiment uses a line having a slope of tan ⁻¹ (dy / dx) determined using a plurality of (dx, dy) parameters to select a peripheral reference pixel. The prediction may be performed using the determined peripheral reference pixels.

Referring to FIG. 24, an angle of tan ⁻¹ (dy / dx) determined according to the mode-specific (dx, dy) values shown in Table 2 around the current pixel P to be predicted in the current prediction unit is determined. Peripheral pixels A and B positioned on the extension line 150 may be used as predictors of the current pixel P. In this case, the peripheral pixel used as the predictor is preferably the pixel of the previous prediction unit of the upper side, the left side, the upper right side, and the lower left side of the current prediction unit, previously encoded and reconstructed. As described above, prediction encoding is performed according to intra prediction modes having various directionalities, thereby enabling more efficient compression according to characteristics of an image.

In FIG. 24, when generating the predictor of the current pixel P using neighboring pixels located at or close to the extension line 150, the extension line 150 actually has a directionality of tan ⁻¹ (dy / dx). Since the dividing operation of (dy / dx) is required to determine the neighboring pixel using the extension line 150, it may include a decimal point operation when implemented in hardware or software, thereby increasing the amount of computation. . Therefore, when setting the prediction direction for selecting the reference pixel using the dx and dy parameters, it is necessary to set dx and dy so as to reduce the amount of computation.

Referring to FIG. 25, the current pixel located at (j, i) is P 1610 and an upper periphery located on an extension line having a direction, ie, slope, tan ⁻¹ (dy / dx) passing through the current pixel P 1610. A pixel is defined as A 1611 and a left peripheral pixel is referred to as B 1612. The size of the prediction unit including the current pixel P 1610 is nSxnS (nS is a positive integer), and the position of each pixel in the prediction unit is one of (0,0) to (nS-1, nS-1). Assume that the position of the upper peripheral pixel on the x-axis is (m, -1) (m is an integer) and the position of the left peripheral pixel on the y-axis is (-1, n) (n is an integer). The position of the upper peripheral pixel A 1611 that meets the extension line passing through the current pixel P 1610 is (j + i * dx / dy, -1), and the position of the left peripheral pixel B 1612 is (-1, i + j * dy / dx). Accordingly, a division operation such as dx / dy or dy / dx is required to determine the upper peripheral pixel A 1611 or the left peripheral pixel B 1612 for prediction of the current pixel P 1610. As described above, since the division operation has high computational complexity, it may cause a decrease in computational speed in software or hardware implementation. Therefore, at least one of dx and dy indicating the direction of the prediction mode for determining the neighboring pixels may be determined by an exponential power of 2. That is, when n and m are integers, dx and dy may be 2 ^ n and 2 ^ m, respectively.

When the left peripheral pixel B 1612 is used as the predictor of the current pixel P 1610 and dx has a value of 2 ^ n, the position of the left peripheral pixel B 1612 (-1, i + j * dy) The j * dy / dx operation required to determine / dx) is (i * dy) / (2 ^ n), and the operation to divide by this power of 2 is (i * dy) >> n. Since it can be implemented through shift operation, the amount of calculation is reduced.

Similarly, when the upper peripheral pixel A 1611 is used as the predictor of the current pixel P 1610 and dy has a value of 2 ^ m, the position of the upper peripheral pixel A (j + i * dx / dy, The i * dx / dy operation required to determine -1) is (i * dx) / (2 ^ m), and the operation to divide by this power of 2 is (i * dx) >> m. It can be implemented through a shift operation.

In general, straight patterns appearing in an image or a video signal are often vertical or horizontal. Therefore, when defining an intra prediction mode having various directions using the parameters of (dx, dy), coding efficiency of an image can be improved by defining values of dx and dy as follows.

Specifically, when dy has a fixed value of 2 ^ m, the absolute value of dx is set such that the interval between prediction directions closer to the vertical direction is narrower, and the interval between prediction modes is closer to the prediction direction closer to the horizontal direction. Can be set to be wider. For example, referring to FIG. 26, when dy has a value of 2 ^ 5, that is, 32, the value of dx is 2,5,9,13,17,21,26,32, -2, -5, By setting as -9, -13, -17, -21, -26, -32, the interval between prediction directions closer to the vertical direction is set to be relatively narrow, and the interval between prediction modes is closer to the prediction direction closer to the horizontal direction. This can be set to be relatively wider.

Similarly, when dx has a fixed value of 2 ^ n, the absolute value of dy is set so that the interval between prediction directions close to the horizontal direction is narrow, and the interval between prediction modes is closer to the prediction direction closer to the vertical direction. It can be set to be wider. For example, referring to FIG. 27, when dx has a value of 2 ^ 5, that is, 32, a value of dy is 2,5,9,13,17,21,26,32, -2, -5, By setting as -9, -13, -17, -21, -26, -32, the interval between the prediction directions close to the horizontal direction is set to be narrow, and the interval between the prediction modes is wider for the prediction direction closer to the vertical direction. Can be set to lose.

In addition, when any one of dx and dy is fixed, the remaining non-fixed value may be set to increase for each prediction mode. For example, when dy is fixed, the interval between dx may be set to increase by a predetermined value. In addition, the increment may be divided by a predetermined unit to the angle between the horizontal direction and the vertical direction, it may be set for each divided angle. For example, if dy is fixed, the value of dx has an increase of a in the section within 15 degrees of the vertical axis, and an increase of b between 15 and 30 degrees, and c at 30 degrees or more. It can be set to have an increment.

For example, prediction modes having a directionality of tan ⁻¹ (dy / dx) using (dx, dy) may define (dx, dy) parameters shown in Tables 3 to 5 below.

TABLE 3

dx	Dy	dx	dy	dx	dy
-32	32	21	32	32	13
-26	32	26	32	32	17
-21	32	32	32	32	21
-17	32	32	-26	32	26
-13	32	32	-21	32	32
-9	32	32	-17
-5	32	32	-13
-2	32	32	-9
0	32	32	-5
2	32	32	-2
5	32	32	0
9	32	32	2
13	32	32	5
17	32	32	9

Table 4

dx	Dy	dx	dy	dx	dy
-32	32	19	32	32	10
-25	32	25	32	32	14
-19	32	32	32	32	19
-14	32	32	-25	32	25
-10	32	32	-19	32	32
-6	32	32	-14
-3	32	32	-10
-One	32	32	-6
0	32	32	-3
One	32	32	-One
3	32	32	0
6	32	32	One
10	32	32	3
14	32	32	6

Table 5

dx	Dy	dx	dy	dx	dy
-32	32	23	32	32	15
-27	32	27	32	32	19
-23	32	32	32	32	23
-19	32	32	-27	32	27
-15	32	32	-23	32	32
-11	32	32	-19
-7	32	32	-15
-3	32	32	-11
0	32	32	-7
3	32	32	-3
7	32	32	0
11	32	32	3
15	32	32	7
19	32	32	11

As described above, each of the intra prediction modes using the (dx, dy) parameters is the predictor of the pixel located at (j, i) and the left peripheral pixel (-1, i + j * dy / dx) or the upper peripheral pixel. (j + i * dx / dy, -1). When at least one of the values of dx or dy has an exponential power of 2, as shown in Table 2, the left peripheral pixel (-1, i + j * dy / dx) and the upper peripheral pixel (j + i * dx / dy The position of -1) can be obtained by only multiplication and shift operations without division operations. Since dx has a value of 2 ^ n as in the case of (dx, dy) of (dx, dy) values according to Table 2 above, the division operation using dx can be replaced by a right shift operation, so that the left peripheral pixel The position of may be obtained without a division operation based on the value of (i * dy) >> n. Similarly, when dy has a value of 2 ^ m, such as the case of (dx, dy) of (dx, dy) according to Table 2, the division operation using dy can be replaced by the right shift operation, so that the upper periphery The position of the pixel can be obtained without division operation based on the value of (i * dx) >> m.

Referring to FIG. 28, the

intra predictors

410 and 550 may determine a neighboring pixel to be used as a predictor of the current pixel according to the intra prediction modes having 33 directionalities as shown. As described above, the distance between the prediction modes is set to be narrower as the direction according to each intra prediction mode is closer to the horizontal direction or the vertical direction, and the distance between the prediction modes is wider as the distance is closer to the vertical direction or the horizontal direction. Can be.

The invention can also be embodied as computer readable code on a computer readable recording medium. The computer-readable recording medium includes all kinds of recording devices in which data that can be read by a computer system is stored. Examples of computer-readable recording media include ROM, RAM, CD-ROM, magnetic tape, floppy disk, optical data storage device, and the like. The computer readable recording medium can also be distributed over network coupled computer systems so that the computer readable code is stored and executed in a distributed fashion.

So far I looked at the center of the preferred embodiment for the present invention. Those skilled in the art will appreciate that the present invention can be implemented in a modified form without departing from the essential features of the present invention. The scope of the present invention is shown in the claims rather than the foregoing description, and all differences within the scope will be construed as being included in the present invention.

Claims

Parsing joint prediction information from the bitstream indicating whether a prediction value of a current block is obtained by applying a plurality of intra prediction modes;

Determining whether to perform joint prediction on a current block based on the joint prediction information;

When performing the joint prediction, obtaining a plurality of luminance prediction values by applying a plurality of luminance prediction modes to the luminance component of the current block;

Weighting the plurality of luminance prediction values to determine a final luminance prediction value;

Obtaining a plurality of color difference prediction values by applying a plurality of color difference prediction modes to the color difference components of the current block;

And weighting the plurality of color difference prediction values to determine a final color difference prediction value.
The method of claim 1,

Acquiring the plurality of luminance prediction values,

Classifying the plurality of available brightness prediction modes into candidate groups of the plurality of brightness prediction modes; And

Obtaining a plurality of luminance prediction values by applying a luminance prediction mode selected from a candidate group of each luminance prediction mode to the luminance component of the current block,

Acquiring the plurality of color difference prediction values,

Classifying the plurality of available color difference prediction modes into candidate groups of the plurality of color difference prediction modes; And

And applying the color difference prediction mode selected from the candidate group of each color difference prediction mode to the color difference component of the current block, to obtain the plurality of color difference prediction values.
The method of claim 2,

The luminance prediction mode available in the candidate group of each luminance prediction mode is determined by information of neighboring blocks or correlation between each luminance prediction mode,

The color difference prediction mode available in the candidate group of each color difference prediction mode is determined by the information of the neighboring blocks or the correlation between each color difference prediction mode.
The method of claim 2,

Among the candidate groups of the plurality of luminance prediction modes, the candidate group of the first luminance prediction mode includes all available luminance prediction modes, and the candidate groups of the remaining luminance prediction modes include a prediction mode that does not include an interpolation process. First, the video decoding method.
The method of claim 2,

And among the candidate groups of the plurality of luminance prediction modes, the luminance prediction mode selected from the candidate group of the first luminance prediction mode is excluded from the candidate group of the remaining luminance prediction modes.
The method of claim 2,

When the luminance prediction mode selected from the candidate group of the first luminance prediction mode is included in the candidate group of the remaining luminance prediction mode among the candidate groups of the plurality of luminance prediction modes, the selected luminance is selected from the candidate group of the remaining luminance prediction mode. The prediction mode is replaced with another luminance prediction mode.
The method of claim 2,

And the candidate group of the plurality of color difference prediction modes includes a prediction mode selected from the candidate group of the plurality of luminance prediction modes.
The method of claim 2,

And among the candidate groups of the plurality of luminance prediction modes, the luminance prediction mode included in the candidate group of the first luminance prediction mode is different from the luminance prediction mode included in the candidate group of the remaining luminance prediction modes.
The method of claim 2,

And the candidate group of each of the luminance prediction modes corresponds to one of the candidate group of the prediction mode without direction, the candidate group of the prediction mode with horizontal direction, or the candidate group of the prediction mode with vertical direction.
A computer-readable recording medium having recorded thereon a program for implementing the image decoding method according to any one of claims 1 to 9.
A receiver for parsing combined prediction information indicating whether a prediction value of a current block is obtained by applying a plurality of intra prediction modes;

Based on the joint prediction information, it is determined whether to perform joint prediction on the current block, obtain a plurality of luminance prediction values by applying a plurality of luminance prediction modes to the luminance component of the current block, and A final luminance prediction value is determined by weighting the luminance prediction values, a plurality of color difference prediction values are obtained by applying a plurality of color difference prediction modes to the color difference components of the current block, and the final color difference is weighted by adding the plurality of color difference prediction values. And a decoder configured to determine a prediction value.
Obtaining a plurality of luminance prediction values by applying a plurality of luminance prediction modes to the luminance component of the current block;

Weighting the plurality of luminance prediction values to determine a final luminance prediction value;

Obtaining a plurality of color difference prediction values by applying a plurality of color difference prediction modes to the color difference components of the current block;

Determining a final color difference prediction value by weighting the plurality of color difference prediction values;

Determining joint prediction information indicating whether to perform joint prediction on the current block; And

And transmitting a bitstream including the joint prediction information.
The method of claim 12,

Acquiring the plurality of luminance prediction values,

Classifying the plurality of available brightness prediction modes into candidate groups of the plurality of brightness prediction modes; And

Obtaining a plurality of luminance prediction values by applying a luminance prediction mode selected from a candidate group of each luminance prediction mode to the luminance component of the current block,

Acquiring the plurality of color difference prediction values,

Classifying the plurality of available color difference prediction modes into candidate groups of the plurality of color difference prediction modes; And

And applying the color difference prediction mode selected from the candidate group of each color difference prediction mode to the color difference components of the current block to obtain the plurality of color difference prediction values.
The method of claim 13,

The luminance prediction mode available in the candidate group of each luminance prediction mode is determined by information of neighboring blocks or correlation between each luminance prediction mode,

The chrominance prediction mode available in the candidate group of each chrominance prediction mode is determined by the information of the neighboring blocks or the correlation between the chrominance prediction modes.
A plurality of luminance prediction values are obtained by applying a plurality of luminance prediction modes to the luminance components of the current block, the final luminance prediction value is determined by weighting the plurality of luminance prediction values, and a plurality of the color difference components of the current block are obtained. Apply a plurality of color difference prediction modes to obtain a plurality of color difference prediction values, weight the sum of the plurality of color difference prediction values to determine a final color difference prediction value, and perform joint prediction information indicating whether to perform joint prediction on the current block. An encoding unit to determine; And

And a transmitter configured to transmit a bitstream including the joint prediction information.