KR20200139116A - Encoding And Decoding Methods For Video Information - Google Patents

Abstract

The present invention relates to an image information encoding method and decoding method and to a device using the same. According to one aspect of the present invention, the decoding method of image information comprises the steps of: dividing a prediction region into a first prediction region and a second prediction region according to an intra prediction mode; performing intra prediction and restoration on the first prediction region; and performing prediction and restoration on the second prediction region. In the step of predicting and restoring the second prediction region, intra prediction on the second prediction region can be performed by referring to a reference sample for the first prediction region or a predetermined sample in the first prediction region.

Description

Video information encoding method and decoding method {Encoding And Decoding Methods For Video Information}

The present invention relates to video information compression technology, and more particularly, to a video region segmentation method and apparatus dependent on an intra prediction mode.

Recently, as broadcasting services having high definition (HD) resolution are expanded not only domestically but also globally, many users are getting accustomed to high-definition and high-definition images, and accordingly, many organizations are spurring the development of next-generation imaging devices. In addition, as interest in UHD (Ultra High Definition) having a resolution of 4 or more times higher than that of HDTV in addition to HDTV is increasing, a compression technology for higher resolution and high quality images is required.

Image compression technology includes inter prediction technology that temporally predicts pixel values included in the current picture from previous and/or subsequent pictures, and intra prediction technology that predicts pixel values included in the current picture using pixel information in the current picture. (intra) prediction technology, weight prediction technology to prevent deterioration of image quality due to changes in lighting, entropy coding technology that assigns short codes to symbols with high frequency of appearance and long codes to symbols with low frequency of appearance, etc. There is this. In particular, when prediction is performed on the current block in the skip mode, a prediction block is generated using only the predicted value from the previously encoded region, and separate motion information or residual signal Is not transmitted from the encoder to the decoder. Image data can be efficiently compressed by these image compression techniques.

On the other hand, among video information compression techniques, various intra prediction modes are used for intra prediction. Depending on the prediction mode, a pixel value of the current block may be predicted using different reference samples. Therefore, it is possible to consider a method of obtaining optimal compression efficiency by adaptively changing a prediction method according to different prediction modes, that is, different reference samples.

The technical problem according to the present invention is to provide a method of increasing the efficiency of intra encoding and reducing the complexity of an image information processing process.

Another technical problem according to the present invention is to provide a method of dividing a prediction unit (PU) and a transform unit (TU) differently according to an intra prediction mode.

Another technical problem according to the present invention is to provide a method for solving the problem of complexity caused by dividing a prediction region and a transform region regardless of a prediction mode.

Another technical problem according to the present invention is to provide a method of determining a prediction mode for each prediction region divided according to the prediction mode.

Another technical problem according to the present invention is to provide a prediction region and a transform region partitioning method for improving the performance of intra prediction and reducing the complexity required to determine an optimal prediction region partition structure and an optimal transform region partition structure. .

(1) According to an embodiment of the present invention, a method of decoding image information is provided, comprising: dividing a prediction region into a first prediction region and a second prediction region according to an intra prediction mode, intra prediction of the first prediction region, and And performing a restoration and prediction and restoration for the second prediction area, and in the prediction and restoration step for the second prediction area, a reference sample for the first prediction area or the restored Intra prediction on the second prediction area may be performed by referring to a predetermined sample in the first prediction area.

(2) In (1), information on the intra prediction mode may be received from an encoder, and in the prediction region division step, a region in which a residual signal equal to or greater than a reference value exists when the intra prediction mode is used is determined. It can be set as a second prediction area.

(3) In (1), information on the intra prediction mode may be received from an encoder, and the second prediction region may be a region at a position farthest from the reference sample of the intra prediction mode in the current block.

(4) In (1), information on the intra prediction mode may be received from an encoder, and the first prediction region and the second prediction region may be preset for each intra prediction mode.

(5) In (1), in the intra prediction and reconstruction step of the second prediction area, a residual signal is generated based on a transform coefficient of a transform area corresponding to the second prediction area, and the second prediction area A reconstructed signal may be generated by combining the prediction result of is with the generated residual signal.

(6) In (1), the second prediction region may be further divided into a plurality of prediction regions, and for a prediction region divided from the second prediction region, a reference sample for the first prediction region or another reconstructed Intra prediction may be performed by referring to a predetermined sample in the prediction region.

(7) In (1), the prediction mode applied to the second prediction area may be selected from a prediction mode applied to the first prediction area and a prediction mode having an angle similar to that of the prediction mode applied to the first prediction area. have.

(8) In (7), the intra prediction for the second prediction region may be performed by referring to the reconstructed sample in the first region.

(9) In (1), the prediction mode applied to the second prediction area may be selected from candidate prediction modes for the first prediction area.

(10) In (1), the prediction mode applied to the second prediction area is a prediction mode applied to a block adjacent to the second prediction area and a prediction mode having a similar angle to a prediction mode applied to a block adjacent to the second prediction area Can be selected from.

(11) Another embodiment of the present invention is a method of encoding video information, comprising dividing a prediction region into a first prediction region and a second prediction region according to an intra prediction mode, intra prediction of the first prediction region, and Performing restoration, performing prediction and restoration on the second prediction region, and transmitting information on a prediction mode of a current block, and in the prediction and restoration step on the second prediction region, Intra prediction on the second prediction area may be performed by referring to a reference sample for the first prediction area or a predetermined sample in the reconstructed first prediction area.

(12) In (11), in the step of dividing the prediction region, a region in which a residual signal equal to or greater than a reference value exists when the intra prediction mode is used may be set as the second prediction region.

(13) In (11), the second prediction region may be a region at a position farthest from the reference sample of the intra prediction mode in the current block.

(14) In (11), in the intra prediction and restoration step of the second prediction area, a residual signal is generated based on a transform coefficient of a transform area corresponding to the second prediction area, and the second prediction area A reconstructed signal may be generated by combining the prediction result of is with the generated residual signal.

(15) In (14), the transform region may be an area having the same size as the first prediction area and the second prediction area, or an area in which the first prediction area or the second prediction area is divided into a square or amorphous shape. .

(16) In (11), in the step of dividing the first prediction region and the second prediction region, the second prediction region is further divided into a plurality of prediction regions, and the prediction region divided from the second prediction region is Intra prediction may be performed by referring to a reference sample for the first prediction area or a predetermined sample in another reconstructed prediction area.

(17) In (11), a prediction mode applied to the second prediction area may be selected from a prediction mode applied to the first prediction area and a prediction mode having an angle similar to the prediction mode applied to the first prediction area. .

(18) In (11), the prediction mode applied to the second prediction area is a prediction mode of a block adjacent to the second prediction area and a prediction mode having an angle similar to that of a block adjacent to the second prediction area. You can choose from.

According to the present invention, it is possible to increase the efficiency of intra coding and reduce the complexity of a process of processing image information.

According to the present invention, it is possible to solve the problem of complexity caused by partitioning the prediction region and the transform region regardless of the prediction mode.

According to the present invention, by dividing the prediction region and the transform region differently according to the intra prediction mode, prediction and transformation can be performed based on the optimal prediction region partition structure and the optimal transformation region partition structure.

According to the present invention, performance of intra prediction can be improved by applying an optimal prediction mode to a prediction region and a transform region divided according to the intra prediction mode.

1 is a block diagram illustrating a configuration of an image encoding apparatus according to an embodiment.
2 is a block diagram showing a configuration of an image decoding apparatus according to an embodiment.
3 is a diagram for explaining each mode of intra prediction.
4 schematically shows samples that can be referenced by a current block in an intra prediction mode.
5 is a diagram schematically illustrating a distribution of a residual signal according to directional prediction.
6 schematically shows examples of a first prediction area and a second prediction area that are predetermined according to an intra prediction mode in a system to which the present invention is applied.
7 is a flowchart schematically illustrating an example of intra prediction in a system to which the present invention is applied.
8 is a flowchart schematically illustrating an operation of an encoder that performs the above-described intra prediction method in a system to which the present invention is applied.
9 is a flowchart schematically illustrating an operation of a decoder performing the above-described intra prediction method in a system to which the present invention is applied.
10 schematically illustrates an example of a split structure of a coding region CU, a prediction region PU, and a transform region TU.
11 schematically shows an example of dividing a current block (a block to be encoded) into two prediction regions according to prediction modes in a system to which the present invention is applied.
12 schematically shows another example of dividing a current block (a block to be encoded) into two prediction regions according to prediction modes in a system to which the present invention is applied.
13 schematically illustrates examples of dividing a current block (a block to be encoded) into three prediction regions according to an intra prediction mode in a system to which the present invention is applied.
14 schematically shows examples of transformation of an amorphous transformation region in a system to which the present invention is applied.
FIG. 15 is a schematic diagram illustrating examples of performing prediction on a lower order prediction region using a reconstructed sample of the priority prediction region based on a correlation between a priority prediction region and a lower priority prediction region within a current block in a system to which the present invention is applied It is shown as.
16 schematically illustrates examples of determining a prediction mode of a current prediction region in a system to which the present invention is applied.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In describing the embodiments of the present specification, if it is determined that a detailed description of a related known configuration or function may obscure the subject matter of the present specification, a detailed description thereof will be omitted.

When a component is referred to as being “connected” or “connected” to another component, it is understood that it may be directly connected or connected to the other component, but other components may exist in the middle. Should be. In addition, the description of "including" a specific configuration in the present invention does not exclude configurations other than the corresponding configuration, and means that additional configurations may be included in the scope of the implementation of the present invention or the technical idea of the present invention.

Terms such as first and second may be used to describe various components, but the components should not be limited by the terms. These terms are used only for the purpose of distinguishing one component from another component. For example, without departing from the scope of the present invention, a first element may be referred to as a second element, and similarly, a second element may be referred to as a first element.

In addition, the components shown in the embodiments of the present invention are shown independently to represent different characteristic functions, and it does not mean that each component is formed of separate hardware or a single software component. That is, each constituent part is listed and included as a respective constituent part for convenience of explanation, and at least two of the constituent parts are combined to form one constituent part, or one constituent part is divided into a plurality of constituent parts to perform a function. Integrated embodiments and separate embodiments of the components are also included in the scope of the present invention unless departing from the essence of the present invention.

In addition, some of the components are not essential components that perform essential functions in the present invention, but may be optional components only for improving performance. The present invention can be implemented by including only the components essential to implement the essence of the present invention excluding components used for performance improvement, and a structure including only essential components excluding optional components used for performance improvement Also included in the scope of the present invention.

1 is a block diagram showing a configuration of an image encoding apparatus according to an embodiment.

Referring to FIG. 1, the image encoding apparatus 100 includes a motion prediction unit 110, a motion compensation unit 115, an intra prediction unit 120, a subtractor 125, a transform unit 130, and a quantization unit 135. ), an entropy encoding unit 140, an inverse quantization unit 145, an inverse transform unit 150, an adder 155, a filter unit 160, and a reference image buffer 165.

The image encoding apparatus 100 may encode an input image in an intra mode or an inter mode and output a bit stream. In the case of the intra mode, prediction may be performed by the intra prediction unit 120, and in the case of the inter mode, the prediction may be performed through the motion prediction unit 110, the motion compensation unit 115, or the like. The image encoding apparatus 100 may generate a prediction block for an input block of an input image and then encode a difference between the input block and the prediction block.

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

In the case of the inter mode, the motion prediction unit 110 may obtain a motion vector by finding a region that best matches the input block in the reference image stored in the reference image buffer 165 in the motion prediction process. The motion compensation unit 115 may generate a prediction block by performing motion compensation using a motion vector and a reference image stored in the reference image buffer 165.

The subtractor 125 may generate a residual block based on a difference between the input block and the generated prediction block. The transform unit 130 may transform the residual block and output a transform coefficient. The residual signal may mean the difference between the original signal and the predicted signal, and a signal in which the difference between the original signal and the predicted signal is transformed, or the difference between the original signal and the predicted signal is transformed and quantized. It can also mean. In block units, the residual signal may be referred to as a residual block.

The quantization unit 135 may output a quantized coefficient obtained by quantizing a transform coefficient according to a quantization parameter.

The entropy encoding unit 140 entropy-encodes a symbol corresponding to values calculated by the quantization unit 135 or an encoding parameter value calculated in the encoding process according to a probability distribution, and outputs a bit stream. I can.

When entropy encoding is applied, a small number of bits is allocated to a symbol having a high probability of occurrence and a large number of bits is allocated to a symbol having a low probability of occurrence, thereby improving compression performance of image encoding.

For entropy encoding, encoding methods such as Context-Adaptive Variable Length Coding (CAVLC) and Context-Adaptive Binary Arithmetic Coding (CABAC) may be used. For example, the entropy encoding unit 140 may perform entropy encoding using a variable length encoding (VLC) table. The entropy encoder 140 derives a binarization method of a target symbol and a probability model of a target symbol/bin, and then performs entropy encoding using the derived binarization method or a probability model. May be.

The quantized coefficients may be inverse quantized in the inverse quantization unit 145 and inverse transformed in the inverse transform unit 150. The inverse quantized and inverse transformed coefficients are generated as a reconstructed residual block, and the adder 155 may generate a reconstructed block using the prediction block and the reconstructed residual block.

The filter unit 160 may apply at least one of a deblocking filter, a sample adaptive offset (SAO), and an adaptive loop filter (ALF) to a reconstructed block or a reconstructed picture. The reconstructed block that has passed through the filter unit 160 may be stored in the reference image buffer 165.

2 is a block diagram showing a configuration of an image decoding apparatus according to an embodiment.

Referring to FIG. 2, the image decoding apparatus 200 includes an entropy decoding unit 210, an inverse quantization unit 220, an inverse transform unit 230, an intra prediction unit 240, a motion compensation unit 250, and a filter unit. 260, a reference image buffer 270, and an adder 280.

The image decoding apparatus 200 may receive a bit stream output from an encoder, perform decoding in an intra mode or an inter mode, and output a reconstructed image, that is, a reconstructed image. In the case of the intra mode, prediction may be performed by the intra prediction unit 240, and in the case of the inter mode, the prediction may be performed through the motion compensation unit 250. The image decoding apparatus 200 may generate a reconstructed block, that is, a reconstructed block, by obtaining a reconstructed residual block from an input bitstream, generating a prediction block, and adding the reconstructed residual block and the prediction block. have.

The entropy decoding unit 210 may entropy-decode the input bit stream according to a probability distribution to generate symbols in the form of quantized coefficients. The entropy decoding method may be performed corresponding to the entropy encoding method described above.

The quantized coefficients are inverse quantized by the inverse quantization unit 220 and inversely transformed by the inverse transform unit 230, and a residual block reconstructed as a result of inverse quantization/inverse transformation of the quantized coefficients may be generated.

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

The adder 280 may generate a reconstructed block based on the reconstructed residual block and the prediction block. The filter unit 260 may apply at least one of a deblocking filter, SAO, and ALF to the reconstructed block. The filter unit 260 outputs a reconstructed image, that is, a reconstructed image. The reconstructed image may be stored in the reference image buffer 270 and used for inter prediction.

In the aforementioned intra prediction mode, directional prediction or non-directional prediction is performed using one or more reconstructed reference samples.

3 is a diagram for explaining each mode of intra prediction. Referring to FIG. 3, except for a DC mode (Intra_DC), a planar mode (Intra_Planar), and a mode applying a luma mode to chroma (Intra_FromLuma), the modes 0, 1, 3 to 33 are defined according to directions. I can confirm.

The number of modes that can be used for prediction of the current block among the prediction modes shown in FIG. 3 may be determined according to the size of the current block.

Table 1 shows an example of the number of prediction modes usable according to the size of the current block.

<Table 1>

At this time, the size of the prediction target block, that is, the current block, may be a rectangular block such as 2x8, 4x8, 2x16, 4x16, 8x16, as well as squares such as 2x2, 4x4, 8x8, 16x16, 32x32, and 64x64 illustrated in Table 1. have.

The size of the prediction target block may be the size of at least one of a coding region (CU), a prediction region (PU), and a transform region (TU).

In intra prediction, information of a reference sample may be used according to each mode as shown in FIG. 3.

4 schematically shows samples that can be referenced by a current block in an intra prediction mode. Referring to FIG. 4, when intra prediction is applied to the current blocks C and 410, reconstructed reference samples around the current block 410, that is, an upper left reference sample 420, and an upper ) The reference sample selected according to the prediction mode among the reference sample 430, the upper-right reference sample 440, the left reference sample 450, and the lower-left reference sample 460 is the current block ( 410) can be used for prediction.

For example, when the prediction mode of the current block 410 is a vertical mode of mode 0 (mode=0) in FIG. 3, an upper reference sample 430 of the current block 410 may be used. When the prediction mode of the current block 410 is a horizontal direction mode of mode 1 (mode=1), a left reference sample 450 of the current block 410 may be used.

In addition, when the prediction mode of the current block 410 is mode 13 (mode=13), an upper (above) reference sample 430 or an upper right (above_right) reference sample 440 may be used. Similarly, when the prediction mode of the current block 410 is mode 7 (mode=7), a left reference sample 450 or a lower left reference sample 460 may be used.

As described above, in the directional prediction (intra prediction mode, 0, 1, 3 to 33) used for intra prediction, the prediction-based pixel value (reference sample value) is directly predicted according to the prediction direction, that is, according to the prediction mode. Or the average value of the prediction-based pixel values as the prediction value. In addition, it is possible to use a residential quadtree (RQT) method that signals a split structure of the transform region after splitting the transform region separately from the partitioning of the prediction region. However, in this case, the characteristic that the distribution of the residual signal is different according to the intra prediction mode cannot be used. Accordingly, the improvement in encoding efficiency is limited, and the complexity of the encoder increases in order to determine the optimal transform region division structure.

Specifically, in directional prediction used for encoding/decoding of image information, as the distance from the reference sample increases, the accuracy of prediction decreases.

5 is a diagram schematically illustrating a distribution of a residual signal according to directional prediction.

FIG. 5(A) schematically shows a residual signal distribution when diagonal prediction is performed from an upper left to a lower right. In the example of FIG. 5A, an intra prediction mode is applied to a current block 500 that is a prediction target block, and prediction 530 in the lower right direction is performed using reference samples 510 and 520. As shown, the residual signal 540 is largely distributed in the lower right direction far from the reference sample.

FIG. 5(B) schematically shows a residual signal division when prediction is performed in a vertical direction. In the example of FIG. 5(B), the intra prediction mode is applied to the current block 550, which is a block to be predicted, and prediction 580 in the vertical direction using the upper reference sample 560 among the reference samples 560 and 570. ) Is being executed. As shown, the residual signal 540 is distributed far from the reference sample 560 on the upper side.

As shown in FIGS. 5A and 5B, in general, the magnitude of the residual signal increases as the distance from the reference sample increases. In addition, the distribution of the residual signal is different depending on the prediction mode.

As described above, in directional prediction, the accuracy of prediction decreases as the distance from the reference sample increases. Therefore, considering that the size of the residual signal increases as the distance from the reference sample increases and the residual signal is distributed more, depending on the direction of intra prediction, the area where the residual signal is estimated to be distributed more is closer to each other. By using the reconstructed sample as a reference sample, prediction efficiency can be further improved.

In this case, a region in which a large number of residual signals are distributed may be determined according to the intra prediction mode. By determining the division region of the residual signal according to the intra prediction mode, it is possible to reduce the signaling overhead required to separately encode the region division information and minimize the complexity required to determine the structure of the region division.

In this specification, an area in which a large number of residual signals are estimated to be distributed is referred to as a'second prediction area' for convenience of description, and a region other than the second prediction area in the current block, that is, a region in which a residual signal is not distributed much The estimated area is referred to as a'first prediction area'.

In this case, a region in which a residual signal having a size greater than or equal to a predetermined reference value is distributed in the current block may be set as the second prediction region. Also, a predetermined area determined in advance according to each prediction mode may be set as the second prediction area. For example, a region located farthest from the sample referenced in each prediction mode in the current block may be set as the second prediction block.

In addition, at this time, the second prediction region may have the same size as the transform region, as shown in the drawings to be described later.

* FIG. 6 schematically illustrates an example of a first prediction region and a second prediction region predetermined according to an intra prediction mode in a system to which the present invention is applied. In the examples of Figs. 6A and 6B, the transform block is set to be a quarter size of the prediction target block (current block).

Referring to FIG. 6A, intra prediction is performed on the first prediction region 610 of the current block 600 by using the reconstructed reference samples 605 around the current block 600. In the example of FIG. 6A, the prediction mode 615 in the lower right direction is applied to the first prediction region 610 of the current block 600.

In FIG. 6(A), after prediction and transformation/reconstruction of the first prediction area 610 is performed, for prediction of the second prediction area 620, the reconstructed sample 625 of the first prediction area is used. It is possible to increase the encoding efficiency of the second prediction region 620 in which a large number of residual signals are estimated to be generated. The prediction mode 630 for the second prediction area 620 may be determined after restoration of the first prediction area 610 is performed.

Referring to FIG. 6B, intra prediction is performed on the first prediction region 650 of the current block 640 by using the reconstructed reference samples 645 around the current block 640. In the example of FIG. 6B, a prediction mode 655 in the vertical direction is applied to the first prediction region 640 of the current block 640.

In FIG. 6(B), after prediction and transformation/reconstruction of the first prediction area 650 is performed, for prediction of the second prediction area 660, the reconstructed sample 665 of the first prediction area is used. It is possible to increase the encoding efficiency of the second prediction region 660 that is estimated to generate a large number of residual signals. The prediction mode 670 for the second prediction area 660 may be determined after restoration of the first prediction area 650 is performed.

When the prediction region is further divided in addition to the first prediction region and the second prediction region, as described above, the first prediction in which the prediction for the second prediction region is restored after prediction/transformation/restore for the first prediction region. It is possible to sequentially repeat the assumptions made using the samples of the region. For example, in the case of a third prediction area obtained by dividing the second prediction area or when the first prediction area is divided into a second prediction area and a third prediction area, the prediction for the third prediction area is a reconstructed second prediction area. This can be done using samples of.

In this specification, the term “prediction region” refers to a region in which pixel value prediction is performed according to various intra prediction modes. In addition, in the present specification, the term'transformation region' refers to a region in which sample value restoration is performed through transcoding while being composed of part or all of the prediction region, and having the same prediction mode as the prediction region including itself. .

7 is a flowchart schematically illustrating an example of intra prediction in a system to which the present invention is applied. The intra prediction method of FIG. 7 may be performed by an encoder or a decoder.

Referring to FIG. 7, according to an intra prediction mode for a current block, a prediction region is divided into two or more (S710).

Next, the transform region is divided into two or more according to the intra prediction mode (S720).

The processing order of the prediction region and the transform region is determined according to the intra prediction mode (S730).

In accordance with the determined processing order, intra prediction/reconstruction is performed on the first prediction area (the first prediction area) (S740).

After restoring the first prediction area, intra prediction/reconstruction is performed on the second prediction area (the second prediction area) according to the processing order (S750).

8 is a flowchart schematically illustrating an operation of an encoder that performs the above-described intra prediction method in a system to which the present invention is applied.

Referring to FIG. 8, the encoder determines an optimal prediction mode for a plurality of prediction regions (S810). When the method of determining the optimal prediction mode is described for the n-th prediction region predetermined for each prediction mode within the current block, prediction and transformation/transformation/prediction according to the structure of the transformation region predetermined for each prediction mode and the order of transformation/restore Perform restoration. In addition, a prediction error and/or a prediction bit amount for the n-th prediction region may be calculated, and an optimal intra prediction mode for the n-th prediction region may be determined based on the calculation.

The partition structure and processing order for the current block are determined (S820). According to the optimal intra prediction mode for the first (n=1) prediction region of the current block determined in S810, the partition structure of the prediction region and the transform region for the current block, and the processing order of the prediction region and the transform region are determined. It is possible to determine the number N of the total prediction regions together with the split structure of the prediction region and the transform region for the current block.

Subsequently, an intra prediction mode of the prediction region is signaled (S830). The optimal intra prediction mode of the n-th prediction region is signaled. Using the prediction modes available for prediction of the second and subsequent (n>1) prediction regions, and the prediction modes of a region adjacent to the n-th prediction region among the reconstructed regions of the second and subsequent (n>1) prediction regions, The prediction mode candidate(s) for prediction of the n-th prediction region may be determined.

Transcoding is performed on the prediction region (S840). For each transform region(s) belonging to the n-th prediction region, each transform region for the prediction error signal according to the optimal intra prediction mode of the n-th prediction region according to the partition structure and processing order of the transform region determined in step S820. Transcoding can be performed on the n-th prediction region by encoding the transform coefficient of.

When each of the steps described above is performed for the entire prediction region (n==N), the execution of each step is terminated. If the above steps have not yet been performed for the entire prediction area (n<N), the following steps may be performed again from step S810 for the next prediction area (ie, a prediction area in which n=n+1).

Accordingly, the entire operation of FIG. 8 may proceed in the order of a first prediction region (a first prediction region), a second prediction region (a second prediction region), and then a third prediction region (a third prediction region). In this case, operation S820, which is an operation for the first prediction region, may not be performed from the second prediction region.

9 is a flowchart schematically illustrating an operation of a decoder performing the above-described intra prediction method in a system to which the present invention is applied.

Referring to FIG. 9, the decoder parses a bit stream received from an encoder to obtain a prediction mode for a first prediction region (a first prediction region) (S910).

The decoder determines the partition structure and processing order for the current block (S920). The decoder determines a partition structure of a prediction region and a transform region for the current block (block to be decoded), and a processing order of the prediction region and the transform region according to the prediction mode obtained in step S910. It is possible to determine the number N of the total prediction regions together with the partition structure of the prediction region and the transform region.

Transform coefficients are decoded for each transform region in the prediction region (S930). For example, for each of the N prediction regions in the current block, transform coefficients of each transform region belonging to the prediction region may be parsed from a bit stream and decoded. For the prediction area after the second prediction area (the second prediction area), the prediction modes usable for prediction of the first prediction area (the first prediction area) and the first prediction area (the first prediction area) are excluded. Prediction mode candidate(s) for prediction of the n-th prediction area may be determined by using prediction modes of an area adjacent to the n-th prediction area among the already reconstructed prediction areas.

Thereafter, a reconstructed signal for each transform region is generated (S940). Looking at the n-th prediction region, for each transform region(s) belonging to the n-th prediction region, the residual signal by inverse transforming the transform coefficients of each transform region according to the partition structure and processing order of the transform region determined in step S910. Restore. The n-th prediction region may be reconstructed by generating a reconstructed signal for each transform region by summing the reconstructed residual signal and a prediction result performed according to the prediction mode for the n-th prediction region.

When each of the steps described above is performed for the entire prediction region (n==N), the execution of each step is terminated. If the above steps have not yet been performed for the entire prediction area (n<N), the following steps may be performed again from step S910 for the next prediction area (ie, a prediction area in which n=n+1).

Accordingly, the entire operation of FIG. 9 may proceed in the order of a first prediction area (first prediction area), a second prediction area (second prediction area), and then a third prediction area (third prediction area). In this case, step S930, which is an operation for the first prediction region, may not be performed from the second prediction region.

10 schematically illustrates an example of a split structure of a coding region CU, a prediction region PU, and a transform region TU.

In FIG. 10, an example of division of a 64x64-sized encoding region 1010, a 32x32-sized encoding region 1020, a 16x16-sized encoding region 1030, and an 8x8-sized encoding region 1040 in order from the uppermost column. Schematically shows.

Referring to FIG. 10, a split structure of a prediction region PU and a transform region TU with respect to the size of each coding region CU can be confirmed.

In addition, a short distance intraprediction (SDIP) region may be defined for a predetermined coding region size. SDIP is a method in which a rectangle and a line segmentation structure are added to the conventional segmentation structure.In the case of SDIP, the coding region is not divided into a square prediction region and is non-square, e.g., the height (or width) is the same as the coding region. , The width (or height) may be divided into a rectangular prediction area that is 1/2 or 1/4 of the encoding area.

In addition, as shown, prediction by Mode Dependent Intra Prediction (MDIP) may be performed. In MDIP, as described above, the partition structure is changed according to the prediction mode. FIG. 10 schematically illustrates two methods of using an upper reference sample and a left reference sample among methods of differently dividing a division structure according to an intra prediction mode or additionally dividing a divided region in the present specification. As illustrated, in addition to directional prediction, prediction on a current block may be performed using a non-directional intra prediction mode such as a DC mode and a planar mode.

Referring to FIG. 10, in the case of general intra prediction other than MDIP and the case of SDIP, a method of dividing a prediction region and a transform region may vary according to the size of a current block. On the other hand, when MDIP is applied, the partition structure does not change according to the size of the block except for the size of the minimum prediction region/minimum transform region (4x4) that cannot be partitioned any more. In the case of applying MDIP, the split structure may vary depending on the prediction mode.

On the other hand, for the prediction region in the coding region, a large number of partition structures of the transformation region can be presented based on a quad tree structure. If the optimal transformation structure is selected after comparing all the results of compression for such various partition structures, The complexity of the coding becomes high. In addition, signaling overhead increases in order to signal various split structures of the transform region.

In this regard, if the partitioning of the current block is determined according to the intra prediction mode as presented in the present invention, the partition structure of the prediction region and the partition structure of the transform region are fixed to one or two according to the prediction mode and are optimized. , Encoding performance can be improved and complexity can be reduced. In addition, it is possible to reduce a candidate set of prediction modes according to a split structure for each prediction mode, thereby further reducing coding complexity.

Hereinafter, the division of a transform region according to a prediction mode proposed in the present invention will be described in detail with reference to the drawings.

11 schematically shows an example of dividing a current block (a block to be encoded) into two prediction regions according to prediction modes in a system to which the present invention is applied. In the example of Fig. 11, the case where the coding region is divided into square prediction regions is shown.

In FIGS. 11(A), (B) and (C), the segmented first prediction region P1 in the coding regions 1100, 1135, and 1170 is intra-intra based on the decoded samples 1115, 1150, and 1185 around them. It can be predicted. The encoding of the divided prediction region may be performed in a manner of performing prediction/reconstruction on the first prediction region P1 and then performing prediction/reconstruction on the second prediction region P2. Accordingly, when prediction is performed on the second prediction area P2 in which a large number of residual signals exist, prediction efficiency can be increased by using the sample of the reconstructed first prediction area P1 as a reference sample.

Referring to FIG. 11A, a first prediction region 1105 of a current block 1100 may be predicted based on a reference sample capable of obtaining excellent compression efficiency. In the example of FIG. 11(A), it is assumed that the sample 1120 on the upper/above-right side of the current block is a reference sample that can obtain the best extrusion efficiency for the first prediction block 1105. Then, prediction on the first prediction region 1105 may be performed using the reference sample 1120. For example, in FIG. 3, a prediction mode {20, 11, 21, 0, 22, 12, 23, 5, 24, 13, 25, 6}, etc. may be the reference sample 1120. The prediction of the second prediction area 1110 may be performed using a sample of the reconstructed first prediction area 1105.

Even in the example of FIG. 11B, the first prediction region 1135 of the current block 1135 may be predicted based on a reference sample capable of obtaining excellent compression efficiency. In the example of FIG. 11(B), it is assumed that the sample 1155 to the left/below-left of the current block is a reference sample that can obtain the best extrusion efficiency for the first prediction block 1140. Then, prediction on the first prediction region 1140 may be performed using the reference sample 1155. For example, in FIG. 3, a prediction mode {28, 15, 29, 1, 30, 16, 31, 8, 32, 17, 33, 9}, etc. may be the reference sample 1155. The prediction of the second prediction area 1145 may be performed using a sample of the reconstructed first prediction area 1140.

Also in the example of FIG. 11C, the first prediction region 1175 of the current block 1170 may be predicted based on a reference sample capable of obtaining excellent compression efficiency. In the example of FIG. 11C, unlike the examples of FIGS. 11A and 11B, a case in which one of the DC mode and the planar mode is used as a prediction mode is illustrated. That is, the sample 1190-1 of the upper/above-left and the sample 1190-2 of the left/above-left of the current block is the first prediction block ( Assuming that 1175 is a reference sample capable of obtaining the best extrusion efficiency, prediction for the first prediction region 1175 may be performed using the reference samples 11190-1 and 1190-2. For example, in FIG. 3, prediction modes {2, 34, 4, 19, 10, 18, 3, 26, 14, 27, 7}, etc. may be reference samples 11190-1 and 1190-2. The prediction of the second prediction area 1180 may be performed using a sample of the reconstructed first prediction area 1175.

Meanwhile, in the regions 1125, 1160, and 1195 corresponding to the current blocks in FIGS. 11(A), (B), and (C), T1, T2, T3, and T4 represent respective transform regions, and transform/restore is performed. The order of doing so may be T1→T2→T3→T4 or T1→T3→T2→T4, depending on the prediction order. Accordingly, the transform region T4 corresponding to the second prediction region can be processed last. In the example of FIG. 11, an example in which each of the transform regions T1 to T4 is divided in the forward direction as can be seen in the divided structures 1125, 1160, and 1195 of the transform region has been described.

11(A), (B) and (C) assume that the reference sample as shown is the most effective reference sample, but this is only an assumption for convenience of explanation, and the reference sample that can obtain the best effect is predicted. May vary depending on the block.

12 schematically shows another example of dividing a current block (a block to be encoded) into two prediction regions according to prediction modes in a system to which the present invention is applied. In the example of Fig. 12, the case where the coding region is divided into non-square prediction regions is shown.

In Figs. 12(A), (B) and (C), the divided first prediction area P1 in the coding areas 1120, 1230, and 1260 is based on the decoded samples 1209, 1239, and 1269 around the intra It can be predicted. The encoding of the divided prediction region may be performed in a manner of performing prediction/reconstruction on the first prediction region P1 and then performing prediction/reconstruction on the second prediction region P2. Accordingly, when prediction is performed on the second prediction area P2 in which a large number of residual signals exist, prediction efficiency can be increased by using the sample of the reconstructed first prediction area P1 as a reference sample.

In the example of FIG. 12(A), samples 1210-1 and 1210-2 of the top/top-left or left/above-left of the current block 1200 Assuming that the first prediction region 1203 is a reference sample capable of obtaining the best extrusion efficiency, the first prediction region 1203 is performed through the prediction mode 1213 using the reference samples 1210-1 and 1210-2. ) Can be predicted. The case of using the reference samples 1210-1 and 1210-2 includes a case of using one of a DC mode and a planar mode as a prediction mode. In addition, assuming that the sample 1216 above/above-right of the current block is a reference sample capable of obtaining the best compression efficiency for the first prediction region 1203, the reference sample 1216 Prediction on the first prediction region 1203 may be performed through the prediction mode 1219 using ). The prediction of the second prediction area 1206 may be performed using a sample of the reconstructed first prediction area 1103.

In the example of FIG. 12(B), samples 1241-1 and 1240-2 of the top/top-left or left/above-left of the current block 1230 Assuming that the first prediction region 1233 is a reference sample capable of obtaining the highest extrusion efficiency, the first prediction region 1233 is performed through the prediction mode 1243 using the reference samples 1241-1 and 1240-2. ) Can be predicted. The case of using the reference samples 1241-1 and 1240-2 includes a case of using either a DC mode or a planar mode as a prediction mode. In addition, assuming that the left/low-left samples 1246 of the current block are reference samples capable of obtaining the best compression efficiency for the first prediction region 1233, the reference sample 1246 Prediction on the first prediction region 1233 may be performed through the prediction mode 1249 using ). The prediction of the second prediction area 1236 may be performed using a sample of the reconstructed first prediction area 1233.

On the other hand, the prediction mode 1213, using the upper/upper-left reference samples (1210-1, 1240-1, 1270-1) and the left/upper-left reference samples (1210-2, 1240-2, 1270-2). 1243) is applicable to both the cases of Figs. 12(A) and 12(B). Therefore, when the prediction modes 1213 and 1243 in the screen are the prediction modes, among Figs. 12(A) and 12(B), It is also possible to signal which partition structure has an indicator.

The example of FIG. 12(C) shows an example of using a partition structure different from the examples of FIGS. 12(A) and 12(B) for prediction modes using upper/top left or left/top left reference samples. Is shown. In the example of FIG. 12(C), the sample 1271-1 of the upper/above-left or the sample of the left/above-left of the current block 1260 ( Assuming that 1270-2) is a reference sample capable of obtaining the best extrusion efficiency for the first prediction block 1263, the first prediction mode 1273 using the reference samples 1271-1 and 1270-2 is used. The prediction area 1263 may be predicted. The case of using the reference samples 1271-1 and 1270-2 includes a case of using either a DC mode or a planar mode as a prediction mode. The prediction for the second prediction area 1266 may be performed using samples of the reconstructed first prediction area 1263.

On the other hand, in the regions 1220 and 1250 corresponding to the current blocks 1200 and 1230 of FIGS. 12A and 12B, T1, T2, T3, and T4 represent respective transformation regions, and transform/restore. The order of execution may be T1→T2→T3→T4. Accordingly, the transform region T4 corresponding to the second prediction region can be processed last.

In FIG. 12C, regions 1270, 1280, and 1290 are regions corresponding to the current block 1260, and are examples of various division structures and transformation orders of the transformation region. T1 to T16 of regions 1270 and 1280 and T1 to T10 of regions 1290 represent respective transform regions. T1 to T9 can always be transformed/restored before the transformed region after T10. In this case, in order to use a closer reconstructed sample as a reference sample, it is preferable that the changed area adjacent to the upper and left sides of the target transform area is restored first.

The region 1270 is an example in which the transform regions T1 to T9 corresponding to the first prediction region P1 are transformed/restored in a zig-zag order, and the region 1280 is a first prediction region P1 This is an example in which the transformed regions T1 to T9 corresponding to) are transformed/restored in the order of a left-above corner to a right-below corner. In the region 1280, the transform regions T1 to T9 corresponding to the first prediction region P1 are transformed/restored in the order of a left-above corner to a right-below corner. Maybe yes. Further, the region 1290 shows an example in which a plurality of transform regions belonging to the same prediction region are combined into one transform region and processed. In the region 1290, compared with the regions 1270 and 1280, the four upper left and lower four transform regions of the regions 1270 and 1280 are each processed as one transform region.

In the example of FIG. 12, as can be seen in the divided structures 1220 and 1250 of the transformed regions shown in FIGS. 12A and 12B, each transformed region T1 to T4 is divided in an amorphous direction. As can be seen in the divided structures 1270, 1280, and 1290 of the transform region shown in FIG. 12C, an example in which each transform region Ts may be divided into an amorphous shape has been described.

On the other hand, in FIGS. 12(A), (B), and (C), it is assumed that the reference sample as shown is the most effective reference sample, but this is only an assumption for convenience of explanation, and a reference sample capable of obtaining the most excellent effect. May vary depending on the prediction block.

13 schematically illustrates examples of dividing a current block (a block to be encoded) into three prediction regions according to an intra prediction mode in a system to which the present invention is applied. For example, FIG. 13 illustrates a case where the current block is divided into a square prediction region and an amorphous prediction region.

In FIGS. 13A and 13B, the divided first prediction region P1 within the encoding regions 1300 and 1330 may be intra predicted based on the decoded samples 1310 and 1340 around them. The encoding of the divided prediction region is performed in a manner of performing prediction/reconstruction for the first prediction region P1 and then predicting/recovering the second prediction region P2 and the third prediction region P3. I can. Therefore, when prediction is performed on the second prediction area P2 and the third prediction area P3 in which a large number of residual signals are present, prediction is performed by using the sample of the reconstructed first prediction area P1 as a reference sample. It can increase the efficiency. Between the second prediction area P2 and the third prediction area P3, the second prediction area P2 may be processed first, or the third prediction area P3 may be processed first.

In the example of FIG. 13A, samples 1313-1 and 1313-2 of left/above-left or above/above-left of the current block 1300 Assuming that the first prediction region 1303 is a reference sample capable of obtaining the highest extrusion efficiency, the first prediction region 1303 is performed through the prediction mode 1315 using the reference samples 1313-1 and 1313-2. ) Can be predicted. The case of using the reference samples 1313-1 and 1313-2 includes a case of using either a DC mode or a planar mode as a prediction mode. In addition, assuming that the sample 1317 above/above-right of the current block 1300 is a reference sample that can obtain the best compression efficiency for the first prediction region 1303, reference Prediction on the first prediction region 1303 may be performed through the prediction mode 1320 using the sample 1317. Prediction of the second prediction area 1305 and the third prediction area 1307 may be performed using samples of the reconstructed first prediction area 1303.

In the example of FIG. 13(B), samples 1343-1 and 1343-2 on the left/above-left or above/above-left of the current block 1330 Assuming that the first prediction region 1333 is a reference sample capable of obtaining the best extrusion efficiency, the first prediction region 1333 is performed through the prediction mode 1345 using the reference samples 1343-1 and 1343-2. ) Can be predicted. The case of using the reference samples 1343-1 and 1343-2 includes a case of using one of a DC mode and a planar mode as a prediction mode. In addition, assuming that the left/below-left samples 1347 of the current block 1330 are reference samples that can obtain the best compression efficiency for the first prediction region 1333, reference Prediction on the first prediction region 1333 may be performed through the prediction mode 1350 using the sample 1347. Prediction of the second prediction area 1335 and the third prediction area 1335 may be performed using samples of the reconstructed first prediction area 1333.

Meanwhile, in the regions 1323 and 1353 corresponding to the current blocks 1300 and 1330 of FIGS. 13A and 13B, T1, T2, T3, and T4 denote respective transformation regions, and transform/restore. The order of execution may be T1→T2→T3→T4 or T1→T2→T4→T3. Accordingly, the transform regions T3 and T4 corresponding to the second and third prediction regions can be processed last. As can be seen from the divided structures 1323 and 1353 of the transformed region shown in the examples of FIGS. 13A and 13B, in FIG. 13, a case in which the transformed region is divided into a mixed form of a square and amorphous is described. Explained as an example.

In FIGS. 13A and 13B, it is assumed that the reference sample as shown is the most effective reference sample, but this is only an assumption for convenience of explanation, and the reference sample that can obtain the best effect varies according to the prediction block. I can.

The above-described embodiments of FIGS. 11 to 13 may each be used independently, only a part may be used in the processing process according to each embodiment, and some or all of each embodiment may be used in combination with some or all of other embodiments. have. For example, FIGS. 13A and 13B and FIG. 12C may be used in combination. In this case, if a case in which one prediction mode can have multiple block splitting structures occurs, a separate indicator may be signaled to indicate which of the multiple block splitting structures the corresponding mode is for.

For the amorphous transform region, a non-square transform, for example, a rectangular transform may be applied, or a square transform may be applied after reordering a signal value, such as a residual signal, into a square shape.

14 schematically shows examples of transformation of an amorphous transformation region in a system to which the present invention is applied. In FIG. 14, a signal value rearrangement process in the encoder is described by taking an 8x2 amorphous transform region as an example.

14(A) shows an example in which the residual signal values of the amorphous transform region having a size of 8x2 are scanned horizontally first. 14(B) shows an example of vertically scanning the residual signal values of an amorphous transform region having a size of 8x2. In addition, FIG. 14C shows an example of zigzag scanning a residual signal value of an amorphous transform region having a size of 8x2.

The scan method as shown in FIGS. 14A to 14C may be predetermined according to a prediction mode of the first prediction area (first prediction area) in the encoding area.

As shown in FIGS. 14A to 14C, signal values of the scanned transform region may be rearranged in the square transform region. For example, as shown in FIG. 14(D), the signal value in the 8x2 amorphous transform region may be rearranged in the 4x4 square transform region. The rearranged signal value can be transformed into the frequency domain by a transformation method such as Discrete Cosine Transform (DST) and/or Discrete Sine Transform (DST).

Meanwhile, in the decoder, the transform coefficients arranged in the square transform region are inversely transformed. The inverse transform can be performed by inversely applying the transform method applied when generating the transform coefficient. For example, Inverse Discrete Cosine Transform (IDCT) and/or Inverse Discrete Sine Transform (IDST) may be applied to the transform coefficient. The decoder scans the inverse transform coefficient in the reverse direction of FIG. 14(D) and rearranges the inverse transform coefficient in the reverse direction of FIGS. 14(A) to 14(C), thereby relocating the inverse transform coefficient in the 8×2 amorphous transform region. I can.

When the encoding target block (current block) is divided into two or more prediction regions PU, a prediction mode of a subsequent prediction region and a prediction mode of a prior prediction region may have a high correlation in the order of the prediction regions. Therefore, by using this characteristic, it is possible to reduce the signaling overhead required for encoding the prediction mode for each prediction region, and improve the encoding performance.

15 schematically illustrates examples of performing prediction on a lower order prediction region using a reconstructed sample of the priority prediction region, based on the correlation between a priority prediction region and a lower priority prediction region within a current block in a system to which the present invention is applied It is shown as.

In the example of FIG. 15A, prediction is performed on the first prediction region 1503 of the current block 1500 by using the upper/right reference samples 1507. For the second prediction region 1505, prediction may be performed using the left/lower left reference samples 1510 and/or some samples 1513 of the previously reconstructed first prediction region 1503. In this case, a partial sample 1513 of the first prediction area 1503 used for prediction of the second prediction area 1505 is a sample of the first prediction area 1503 adjacent to the second prediction area 1505 and the second prediction This is a sample reconstructed before prediction for the region 1505 is performed.

In the example of FIG. 15B, for the first prediction region 1517 of the current block 1515, an upper/upper left reference sample 1523-1 or a left/upper left reference sample 1523-2 is used. Make predictions. For the second prediction area 1520, prediction may be performed using some samples 1525 of the first prediction area 1517 that have already been reconstructed. In this case, a partial sample 1525 of the first prediction area 1517 used for prediction of the second prediction area 1520 is a sample of the first prediction area 1517 adjacent to the second prediction area 1520 and the second prediction This is a sample reconstructed before prediction of the region 1520 is performed.

In the example of FIG. 15C, for the first prediction region 1533 of the current block 1530, an upper/upper left reference sample 1537-1 or a left/upper left reference sample 1537-2 is used. You can make predictions. In addition, prediction on the first prediction region 1533 may be performed using the upper/right upper reference samples 1540. For the second prediction region 1535, prediction may be performed by using the left/lower left reference samples 1543 and/or some samples 1545 of the previously reconstructed first prediction region 1533. In this case, a partial sample 1545 of the first prediction area 1533 used for prediction of the second prediction area 1535 is a sample of the first prediction area 1533 adjacent to the second prediction area 1535 and the second prediction This is a sample reconstructed before prediction for the region 1535 is performed.

In the example of FIG. 15(D), for the first prediction region 1553 of the current block 1550, an upper/top left reference sample 1557-1 or a left/top left reference sample 1557-2 is used. You can make predictions. For the second prediction region 1555, an upper/right side reference sample 1563-1, a left/lower left reference sample 1560-2, and/or a partial sample 1563 of the previously reconstructed first prediction region 1553 ) Can be used to perform prediction. In this case, a partial sample 1563 of the first prediction area 1553 used for prediction of the second prediction area 1555 is a sample of the first prediction area 1553 adjacent to the second prediction area 1555, and the second prediction This is a sample reconstructed before prediction for the region 1555 is performed.

In the example of FIG. 15(E), for the first prediction region 1567 of the current block 1565, an upper/top left reference sample 1575-1 or a left/top left reference sample 1575-2 is used. You can make predictions. In addition, prediction on the first prediction region 1567 may be performed using the upper/right upper reference samples 1577. For the second prediction region 1570, prediction may be performed using the left/lower left and upper/upper left reference samples 1580 and/or some samples 1583 of the previously restored first prediction region 1567. have. Also, for the third prediction area 1573, prediction may be performed using the upper/right side reference samples 1589 and/or some samples 1587 of the previously reconstructed first prediction area 1567. In this case, some samples 1583 and 1587 of the first prediction area 1567 used for prediction of the second prediction area 1570 and the third prediction area 1567 are respectively the second prediction area 1570 and the third prediction area. As a sample of the first prediction area 1567 adjacent to the area 1573, this is a sample reconstructed before prediction of the second prediction area 1570 and the third prediction area 1573 is performed.

Referring to FIG. 15, a second prediction area P2 in FIGS. 15A to 15D and a second prediction area P2 and a third prediction area P3 in FIG. 15E are Since it is more adjacent to the first prediction area P1 than other reconstructed samples, in this case, prediction mode candidates of the second prediction area P2 and the third prediction area P3 are used for prediction of the first prediction area P1. The prediction modes that were available (reference samples (1507, 1523-1, 1523-2, 1537-1, 1537-2, 1540, 1557-1, 1557-2, 1575-1, 1575-2, 1577, etc.) It can be limited to the prediction mode used).

Alternatively, only the prediction modes used for prediction of the area adjacent to the second prediction area P2 and the third prediction area P3 of FIGS. 15A to 15E are used for the second prediction area P2 and the third prediction area. A prediction mode candidate may be configured for the prediction region P3.

In addition, by combining the above two examples, prediction modes that were available for prediction of the first prediction region P1 (reference samples 1507, 1523-1, 1523-2, 1537-1, 1537-2, 1540, 1557 -1, 1557-2, 1575-1, 1575-2, 1577, etc.) and the second prediction area P2 or the third prediction area (out of the remaining areas excluding the first prediction area P1) ( Prediction mode candidates of the second prediction area P2 or the third prediction area P3 may be formed by prediction modes of a region adjacent to P3).

Meanwhile, as illustrated in FIG. 15, the shape and range of samples that can be used for prediction for the prediction area vary according to the shape and position of the prediction area. As in the case of the second prediction area P2 of FIGS. 15A and 15E, when the reference samples substantially surround the prediction area, bidirectional prediction, for example, the weighted sum of both prediction values Performing prediction on the region may result in better prediction efficiency.

According to the method described with reference to FIG. 15, a candidate prediction mode for each prediction region may be set, and the encoder may perform prediction on the prediction region by selecting one of the prediction modes. The selection of the prediction mode may be determined in consideration of compression efficiency such as Rate Distortion Optimization (RDO). The encoder may transmit information on the selected prediction mode to the decoder.

In addition, the decoder may select a prediction mode to be applied to the current prediction region after setting the candidate prediction mode by the same method as the encoder, or may apply a prediction mode indicated by information transmitted from the encoder to the current prediction block. have.

In FIG. 15, reference samples (prediction modes) for prediction regions are selected as shown, but these are only examples for convenience of explanation, and reference samples (prediction modes) for each prediction region are based on the characteristics of the prediction regions. It can be selected in a variety of ways.

16 schematically illustrates examples of determining a prediction mode of a current prediction region in a system to which the present invention is applied.

16(A) shows the prediction mode 1610 of the first prediction area P1 and the second prediction area P2 for the first prediction area P1 and the second prediction area P2 in the current block 1600. ) Schematically shows an example of use in the prediction mode 1620. In this case, instead of using the prediction mode 1610 of the first prediction area P1 as the prediction mode of the second prediction area P2 as it is, an angle similar to the prediction mode 1610 of the first prediction area P1 A prediction mode having a may be used as a prediction mode of the second prediction region 1620. In addition, when the prediction mode of the first prediction area P1 is a DC mode or a planar mode, a DC mode or a planar mode may be used as the prediction mode of the second prediction area P2.

16(B) shows a prediction mode of a block adjacent to the second prediction area P2 with respect to the first prediction area P1 and the second prediction area P2 in the current block 1630 as a second prediction area P2. ) Schematically shows an example of using the prediction mode 1660. For example, of the prediction mode 1650 of the left area of the second prediction area P2 or the prediction mode 1640 of the first prediction area P1 in contact with the second prediction area P2. A prediction mode 1660 may be determined.

Fig. 16(C) shows an example in which Figs. 16(A) and 16(B) are combined. In FIG. 16C, a prediction mode of the second prediction region P2 among prediction modes 1680 and 1690 of a block adjacent to the second prediction region P2 and prediction modes 1680 and 1690 of the adjacent block. (1699) can be determined.

As described in the example of FIG. 16, the encoder may select a prediction mode to be applied to the current prediction region. When a prediction mode is selected from a candidate group including a prediction mode having a similar angle to a prediction mode of a neighboring block (including the first prediction region), it may be determined in consideration of compression efficiency such as Rate Distortion Optimization (RDO). The encoder may transmit information on the selected prediction mode to the decoder.

In addition, the decoder may select a prediction mode to be applied to the current prediction region after setting the candidate prediction mode by the same method as the encoder. Therefore, the prediction mode to be selected for the prediction area (the third prediction area, the fourth prediction area, ...) after the second prediction area (the second prediction area) is determined by the prediction mode and/or the prediction area for the first prediction area. It may be set in advance between the encoder and the decoder according to the split structure of Also, the decoder may apply the prediction mode indicated by information transmitted from the encoder to the current prediction block.

In the exemplary system described above, the methods are described on the basis of a flowchart as a series of steps or blocks, but the present invention is not limited to the order of the steps, and certain steps may occur in a different order or concurrently with the steps described above. I can. In addition, the above-described embodiments include examples of various aspects. Accordingly, the present invention will be said to cover all other replacements, modifications and changes falling within the scope of the following claims.

Until now, in the description of the present invention, when one component is referred to as being "connected" or "connected" to another component, the other component is directly connected or connected to the other component. Although there may be, it should be understood that other components may exist between the two components. On the other hand, when it is mentioned that one component is "directly connected" or "directly connected" to another component, it should be understood that no other component exists between the two components.

Claims (13)

Determining a prediction mode for the current block as an intra prediction mode;
Dividing the current block into at least two sub-blocks including a first sub-block and a second sub-block;
Performing intra prediction on the first sub-block;
Performing intra prediction on the second sub-block; And
And obtaining a prediction block for the current block by using intra prediction results for the first sub-block and the second sub-block,
In the intra prediction step for the second sub-block,
Intra prediction for the second sub-block is performed with reference to a reference sample for the first sub-block or a predetermined sample in the reconstructed first sub-block,
An intra prediction mode applied to the second sub-block is one of an intra prediction mode applied to the first sub-block and an intra prediction mode having a similar angle to the intra prediction mode applied to the first sub-block,
The at least two sub-blocks are blocks obtained by dividing the current block only in a horizontal direction. The method of claim 1, wherein information on the intra prediction mode is received from an encoder,
In the current block division step, when the intra prediction mode is used, a region in which a residual signal equal to or greater than a reference value exists is set as the second sub-block. The method of claim 1, wherein information on the intra prediction mode is received from an encoder,
And the second sub-block is a region at a position farthest from the reference sample of the intra prediction mode in the current block. The method of claim 1, wherein information on the intra prediction mode is received from an encoder,
The first sub-block and the second sub-block are preset for each intra prediction mode. The method of claim 1, wherein intra prediction for the second sub-block is performed by referring to samples within the first sub-block. The method of claim 1, wherein an intra prediction mode applied to the second sub-block is selected from among candidate intra prediction modes for the first sub-block. The intra prediction mode of claim 1, wherein the intra prediction mode applied to the second sub-block is an intra prediction mode applied to a block adjacent to the second sub-block and an intra prediction mode applied to a block adjacent to the second sub-block. Video information decoding method, characterized in that one of the prediction modes. Determining a prediction mode of the current block as an intra prediction mode;
Dividing the current block into at least two sub-blocks including a first sub-block and a second sub-block;
Performing intra prediction on the first sub-block;
Performing intra prediction on the second sub-block; And
And transmitting information on the intra prediction mode of the current block,
In the intra prediction step for the second sub-block,
Intra prediction for the second sub-block is performed with reference to a reference sample for the first sub-block or a predetermined sample in the reconstructed first sub-block,
An intra prediction mode applied to the second sub-block is one of an intra prediction mode applied to the first sub-block and an intra prediction mode having a similar angle to the intra prediction mode applied to the first sub-block,
The at least two sub-blocks are blocks obtained by dividing the current block only in a horizontal direction. The method of claim 8, wherein in the current block division step, when the intra prediction mode is used, a region in which a residual signal equal to or greater than a reference value exists is set as the second sub-block. 9. The method of claim 8, wherein the second sub-block is a region at a position farthest from the reference sample of the intra prediction mode in the current block. The method of claim 10, wherein the transform region is a region having the same size as the first sub-block and the second sub-block, or a region in which the first sub-block or the second sub-block is divided into a square or amorphous shape. Video information encoding method. The method of claim 10, wherein the intra prediction mode applied to the second sub-block is an intra prediction mode of a block adjacent to the second sub-block and an intra prediction mode of a block adjacent to the second sub-block. Image information encoding method, characterized in that one of the prediction modes. In the non-transitory computer readable recording medium storing a bitstream,
Determining a prediction mode of the current block as an intra prediction mode;
Dividing the current block into at least two sub-blocks including a first sub-block and a second sub-block;
Performing intra prediction on the first sub-block;
Performing intra prediction on the second sub-block; And
And transmitting information on the intra prediction mode of the current block,
In the intra prediction step for the second sub-block,
Intra prediction for the second sub-block is performed with reference to a reference sample for the first sub-block or a predetermined sample in the reconstructed first sub-block,
An intra prediction mode applied to the second sub-block is one of an intra prediction mode applied to the first sub-block and an intra prediction mode having a similar angle to the intra prediction mode applied to the first sub-block,
The at least two or more sub-blocks are blocks obtained by dividing the current block only in a horizontal direction. A non-transitory computer-readable recording medium for storing a bitstream generated by the image information encoding method.

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