KR20210013279A - Method and apparatus for video coding/decoding using intra prediction - Google Patents

Abstract

Disclosed are a method and an apparatus for improving encoding/decoding efficiency by improving the accuracy of intra-prediction. A method for decoding a video comprises the steps of: decoding a received bit stream to generate reconstructed information including a residual value for a current pixel and intra-prediction information; generating a first prediction value by using a first reference pixel and an upper-right pixel (T) of a current block including the current pixel based on the intra-prediction information; generating a second prediction value by using a second reference pixel and a lower-left pixel (L) of the current block including the current pixel based on the intra-prediction information; and generating a final prediction value for the current pixel by using the first prediction value and the second prediction value. In applying a planar mode, the accuracy of intra-prediction can be improved by using a reference pixel having higher correlation or applying a weight based on the directionality of the current block.

Description

Video encoding/decoding method and apparatus using intra prediction {METHOD AND APPARATUS FOR VIDEO CODING/DECODING USING INTRA PREDICTION}

The present invention relates to encoding and decoding of video, and more particularly, to a method and apparatus for improving encoding/decoding efficiency by improving intra prediction accuracy.

Recently, due to the advent of smart phones and smart TVs, the use of video data through wired and wireless communication networks is explosively increasing. While moving picture data has superior information transmission capability compared to plain text data, it has a very large capacity, so it is difficult to transmit, reproduce, and store data in a network channel having a limited bandwidth. In addition, since a vast amount of video information must be properly processed according to the request of an application, a system for processing video is also required to have high specifications.

There are two types of video encoding: Loss Coding and Lossless Coding. H.264/AVC supports lossless coding as well as lossless coding. In particular, for lossless coding, a more efficient lossless coding technique was adopted in the H.264/AVC Fidelity Range Extension (FRExt) standardization. The lossless coding technique adopted in FRExt is implemented by simply not performing transformation and quantization to avoid data loss. That is, lossless compression can be performed by directly entropy encoding, without transforming and quantizing residual signals obtained through intra prediction and inter prediction.

In addition, standardization of HEVC (High Efficiency Video Coding) has been recently completed as a next-generation video compression standard technology known to have a compression efficiency of about twice or more compared to the conventional H.264/AVC.

HEVC defines a coding unit (CU), a prediction unit (PU), and a transform unit (TU) having a quadtree structure, and is a sample adaptive offset (SAO). Offset) and deblocking filters, such as additional in-loop filters are applied. In addition, compression coding efficiency is improved by improving existing intra prediction and inter prediction.

In intra prediction, encoding is performed by using a pixel around a pixel to be currently encoded directly or by using a value generated through filtering using several pixels as a predicted value for the current pixel. In addition, the difference between the value generated through prediction and the current pixel value is transmitted with additional information (information on the intra prediction mode, such as DC mode, vertical direction mode, or horizontal direction mode) to perform encoding. Proceed.

However, in the case of the planar mode according to HEVC, the distance from the reference pixel increases as the current pixel moves into the current block, and thus the accuracy of prediction decreases.

An object of the present invention for solving the above problems is to provide an intra prediction method that improves coding efficiency by increasing the accuracy of intra prediction.

Another object of the present invention for solving the above problems is to provide a method of decoding an encoded video by increasing the accuracy of intra prediction.

Another object of the present invention for solving the above problems is to provide an apparatus for decoding an encoded video by increasing the accuracy of intra prediction.

In an intra prediction method according to an embodiment of the present invention for achieving the above object, in intra prediction for a current block including a current pixel, a pixel T at an upper right of the current block and a first reference pixel are used. Generating a first predicted value, generating a second predicted value using the lower left pixel (L) and a second reference pixel of the current block, and using the first predicted value and the second predicted value for the current pixel. Generating a final predicted value.

Here, the pixel T at the upper right of the current block is a pixel TR at the upper right of the current block, a pixel selected from among pixels located on the same horizontal line as the pixel TR at the upper right of the current block, and the current block. One of the pixels generated by filtering the pixels located on the same horizontal line as the pixel TR at the upper right of the current block, and the pixel L at the lower left of the current block is the pixel LB at the lower left of the current block. ), a pixel generated by filtering selected pixels among pixels located on the same vertical line as the lower left pixel LB of the current block and pixels located on the same vertical line as the lower left pixel LB of the current block It can be any one of.

Here, the first reference pixel may belong to the same horizontal line as the current pixel and are adjacent to the current pixel, and the second reference pixel may belong to the same vertical line as the current pixel and may be a pixel adjacent to the current pixel.

Here, the intra prediction method may divide the current block into at least two regions, and sequentially perform intra prediction for each partitioned region.

Here, in the generating of the first prediction value, a first prediction value is generated by applying a weight to each of the pixel TR at the upper right of the current block and the pixel belonging to the same horizontal line as the current pixel and adjacent to the current block, respectively, In the generating of the second prediction value, a second prediction value may be generated by applying a weight to each of the pixel LB at the lower left of the current block and a pixel belonging to the same vertical line as the current pixel and adjacent to the current block.

Here, the weight may be determined based on the direction of the current block.

Here, the directionality of the current block may be divided into a horizontal directionality and a vertical directionality.

Here, in the generating of the final predicted value, the final predicted value may be generated by averaging the first predicted value and the second predicted value.

A video decoding method according to an embodiment of the present invention for achieving the above other object includes the steps of decoding a received bitstream to generate restoration information including a residual value for a current pixel and intra prediction information, and intra prediction information Generating a first prediction value using a first reference pixel and a pixel T at the upper right of the current block including the current pixel based on the information, and the left side of the current block including the current pixel based on the intra prediction information And generating a second predicted value using a lower pixel L and a second reference pixel, and generating a final predicted value for the current pixel using the first predicted value and the second predicted value.

Here, the video decoding method may further include generating a reconstructed image by adding a residual value for a current pixel to a final prediction value.

A video decoding apparatus according to an embodiment of the present invention for achieving the above another object includes an entropy decoding unit for decoding a received bitstream to generate restoration information including a residual value for a current pixel and intra prediction information; Based on the intra prediction information, a first prediction value is generated using a pixel (T) at the upper right of the current block including the current pixel and a first reference pixel, and the current block including the current pixel is generated based on the intra prediction information. An intra prediction unit generates a second prediction value using the lower left pixel L and the second reference pixel, and generates a final prediction value for the current pixel by using the first prediction value and the second prediction value.

The video encoding/decoding method and apparatus using intra prediction according to the present invention as described above can improve the accuracy of intra prediction by performing intra prediction using a reference pixel having a higher correlation.

In addition, in applying the planar mode, accuracy of intra prediction may be improved by applying a weight based on the direction of the current block.

1 is a conceptual diagram illustrating an intra prediction mode according to the HEVC standard.
2 is a conceptual diagram for describing a planar mode according to the HEVC standard.
3 is a conceptual diagram illustrating intra prediction according to an embodiment of the present invention.
4 is a conceptual diagram illustrating intra prediction according to another embodiment of the present invention.
5 is a conceptual diagram illustrating intra prediction according to another embodiment of the present invention.
6 is a conceptual diagram illustrating intra prediction according to another embodiment of the present invention.
7 is a block diagram illustrating a video encoding apparatus that performs an intra prediction method according to an embodiment of the present invention.
8 is a block diagram illustrating a video decoding apparatus that performs an intra prediction method according to an embodiment of the present invention.

In the present invention, various modifications may be made and various embodiments may be provided, and specific embodiments will be illustrated in the drawings and described in detail in the detailed description. However, this is not intended to limit the present invention to a specific embodiment, it is to be understood to include all changes, equivalents, and substitutes included in the spirit and scope of the present invention. In describing each drawing, similar reference numerals have been used for similar elements.

Terms such as first, second, A, and B may be used to describe various elements, but the elements 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. The term and/or includes a combination of a plurality of related listed items or any of a plurality of related listed items.

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. On the other hand, when a component is referred to as being "directly connected" or "directly connected" to another component, it should be understood that there is no other component in the middle.

The terms used in the present application are only used to describe specific embodiments, and are not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In the present application, terms such as "comprise" or "have" are intended to designate the presence of features, numbers, steps, actions, components, parts, or combinations thereof described in the specification, but one or more other features. It is to be understood that the presence or addition of elements or numbers, steps, actions, components, parts, or combinations thereof, does not preclude in advance.

Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention belongs. Terms as defined in a commonly used dictionary should be interpreted as having a meaning consistent with the meaning in the context of the related technology, and should not be interpreted as an ideal or excessively formal meaning unless explicitly defined in this application. Does not.

The video encoding apparatus (Video Encoding Apparatus) and the video decoding apparatus (Video Decoding Apparatus), which will be described later, include a personal computer (PC), a notebook computer, a personal digital assistant (PDA), and a portable multimedia player (PMP). : Portable Multimedia Player), PlayStation Portable (PSP), Wireless Communication Terminal, Smart Phone, TV application server and service server, and other server terminals. It is a user terminal or a communication device such as a communication modem for performing communication with a wired/wireless communication network, a memory for storing various programs and data for inter- or intra-screen prediction for encoding or decoding an image, or for encoding or decoding. It may mean a variety of devices including a microprocessor or the like for executing calculation and control.

In addition, the image encoded as a bitstream by the image encoding device can be transmitted through wired or wireless communication networks such as the Internet, short-range wireless communication network, wireless LAN network, WiBro network, mobile communication network, etc. Serial Bus) can be transmitted to an image decoding device through various communication interfaces, decoded by the image decoding device, and reconstructed and reproduced as an image.

Typically, a moving picture may be composed of a series of pictures, and each picture may be divided into a predetermined area such as a frame or a block.

In addition, the High Efficiency Video Coding (HEVC) standard defines concepts of a coding unit (CU), a prediction unit (PU), and a transform unit (TU). The encoding unit is similar to an existing macroblock, but encoding can be performed while variably adjusting the size of the coding unit. The prediction unit is determined in a coding unit that is no longer split, and may be determined through a prediction type and a prediction unit splitting (PU splitting) process. The transformation unit is a transformation unit for transformation and quantization, and may be larger than the size of the prediction unit, but cannot be larger than the coding unit. Therefore, in the present invention, a block may be understood to mean equivalent to a unit.

Also, a block or pixel referred to for encoding or decoding a current block or a current pixel is referred to as a reference block or a reference pixel. In addition, those of ordinary skill in the art to which the present embodiment pertains that the term "picture" described below may be substituted with other terms having an equivalent meaning such as image, frame, etc. When you grow up, you can understand.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a conceptual diagram illustrating an intra prediction mode according to the HEVC standard, and FIG. 2 is a conceptual diagram illustrating a planar mode according to the HEVC standard.

* Referring to FIG. 1, the HEVC standard provides 35 intra prediction modes. As the number of prediction modes increases, overhead bits for transmitting mode information increase, but by using various prediction modes, more accurate prediction can be performed and prediction errors can be reduced.

Mode 0 represents a planar mode, mode 1 represents a DC mode, and modes 2 to 34 represent an angular mode. A brief description of each intra prediction mode is as follows.

The planar mode is a method designed to efficiently encode a visually smooth image. It is effective in predicting a region in which pixel values gradually change, and the DC mode uses an average value of neighboring pixels of the current prediction block as a prediction value.

In addition, the angular mode performs prediction based on a total of 33 directions, including vertical and horizontal directions. In the vertical mode or horizontal mode, surrounding pixel values are copied in a vertical or horizontal direction and used as a predicted value. On the other hand, directional prediction modes other than the vertical and horizontal modes perform intra prediction in a direction divided into 32 at 45 degrees, and are divided by the same angle based on the centrifugal 10, so that the pixels in each prediction direction have equal intervals. Because it is not, predicted values are generated through linear interpolation.

According to the planar mode with reference to FIG. 2, first, a first prediction value may be obtained by using a pixel TR positioned at an upper right of the current block and a pixel belonging to the same horizontal line as the current pixel and adjacent to the current block. In addition, a second prediction value may be obtained by using a pixel LB at the lower left of the current block and a pixel belonging to the same vertical line as the current pixel and adjacent to the current block. In addition, the average value of the first predicted value and the second predicted value may be determined as the predicted value of the current pixel.

In FIG. 2, a pixel corresponding to a dark area may mean a pixel adjacent to the current block. That is, the current block can be represented as an 8×8 size block in a bright area. However, the size of the current block is not limited to 8×8. Accordingly, the current pixel may mean a pixel included in the current block and subjected to encoding/decoding.

However, in the planar mode, the pixel TR located at the top right of the current block and the current pixel belong to the same horizontal line and are far from the pixel adjacent to the current block, and the pixel LB and the current pixel at the bottom left of the current block In the case of a current pixel belonging to the same vertical line and a distance from a pixel adjacent to the current block, accuracy of prediction may be degraded.

3 is a conceptual diagram illustrating intra prediction according to an embodiment of the present invention.

In the planar mode according to HEVC, the pixel TR at the upper right of the current block and the pixel LB at the lower left of the current block shown in FIG. 2 are used as reference pixels.

In comparison, referring to FIG. 3, in the modified Planar mode according to the exemplary embodiment of the present invention, a selected pixel among pixels located on the same horizontal line as the pixel TR at the upper right of the current block may be used as a reference pixel. Also, a pixel generated by filtering pixels located on the same horizontal line as the pixel TR on the upper right of the current block may be used as a reference pixel. For example, in FIG. 3, one of the pixels located at T ₁ to T _n may be determined as a reference pixel, or a pixel generated by applying filtering to T ₁ to T _n may be determined as the reference pixel.

Here, a pixel generated by filtering a selected pixel among pixels located on the same horizontal line as the upper right pixel TR of the current block or the pixels located on the same horizontal line as the upper right pixel TR of the current block May be defined as the pixel T at the upper right of the current block. Furthermore, the pixel T at the upper right of the current block may be a concept including the pixel TR at the upper right of the current block.

Meanwhile, in the modified planar mode according to the exemplary embodiment of the present invention, a selected pixel from among pixels located on the same vertical line as the pixel LB at the lower left of the current block may be used as a reference pixel. Also, a pixel generated by filtering pixels located on the same vertical line as the lower left pixel TR of the current block may be used as a reference pixel. For example, in FIG. 3, one of the pixels located at L ₁ to L _n may be determined as a reference pixel, or a pixel generated by applying filtering to L ₁ to L _n may be determined as the reference pixel.

Here, a pixel generated by filtering selected one of the pixels located on the same vertical line as the lower left pixel LB of the current block or the pixels located on the same vertical line as the lower left pixel LB of the current block May be defined as the pixel T at the upper right of the current block. Furthermore, the pixel L at the lower left of the current block may be a concept including the pixel L at the lower left of the current block.

Accordingly, embodiments to be described later will be described using the concept of the pixel T at the upper right of the current block and the pixel L at the lower left of the current block.

4 is a conceptual diagram for explaining intra prediction according to another embodiment of the present invention, and FIG. 5 is a conceptual diagram for explaining intra prediction according to another embodiment of the present invention. In FIGS. 4 and 5, the current block may appear as an 8×8 size block in a bright area. However, the size of the current block is not limited to 8×8.

* Intra prediction according to a modified Planar mode according to an embodiment of the present invention will be described with reference to FIGS. 4 and 5. The first prediction value may be generated by using the pixel T at the upper right of the current block and a first reference pixel that is a pixel adjacent to the current pixel and belonging to the same horizontal line as the current pixel. In addition, the pixel L at the lower left of the current block and the second reference pixel belonging to the same vertical line as the current pixel and adjacent to the current pixel may be used. For example, interpolation using the upper right pixel (T) and a first reference pixel to generate a first predicted value, and interpolation using the lower left pixel (L) and a second reference pixel to generate a second predicted value can do.

Meanwhile, a final predicted value for the current pixel may be generated by using the first predicted value and the second predicted value. For example, a final predicted value may be generated by averaging the first predicted value and the second predicted value.

First, referring to FIG. 4A, intra prediction may be performed on a current pixel located at the upper left of the current block. That is, intra prediction may start from the current pixel located at the upper left of the current block.

Here, the current pixel included in the current block and used as the starting point of the intra prediction may be subjected to intra prediction by the same method as the conventional planar mode. That is, the first reference pixel and the second reference pixel may be pixels included in a block adjacent to the current block.

4B and 4C, the intra prediction direction may be sequentially performed in the horizontal direction. For example, after intra prediction for a current pixel included in a row positioned at the top of the current block is completed, intra prediction for a next (downward) row may be performed. That is, intra prediction may be performed in a raster scan order.

Next, referring to FIG. 5A, intra prediction may be performed on a current pixel located at the upper left of the current block. That is, intra prediction may start from the current pixel located at the upper left of the current block.

Here, the current pixel included in the current block and used as the starting point of the intra prediction may be subjected to intra prediction by the same method as the conventional planar mode. That is, the first reference pixel and the second reference pixel may be pixels included in a block adjacent to the current block.

5B and 5C, the intra prediction direction may be sequentially performed in the vertical direction. For example, after intra prediction for a current pixel included in a leftmost row of the current block is completed, intra prediction for a next (rightward) column may be performed.

According to the embodiments of FIGS. 4 and 5, it has been described that intra prediction is started from a current pixel positioned at the upper left of the current block, but it is of course possible to start intra prediction from a current pixel positioned at a different location in the current block. . In addition, although an embodiment in which sequential intra prediction is performed in a horizontal direction or a vertical direction has been described, it is obvious that sequential intra prediction may be performed in a diagonal direction. Here, the diagonal direction may mean an up-right digonal direction.

According to an embodiment of the present invention, a pixel belonging to the same horizontal line as the current pixel and adjacent to the current pixel and a pixel belonging to the same vertical line as the current pixel and adjacent to the current pixel are used as reference pixels, thereby improving accuracy of intra prediction. I can.

6 is a conceptual diagram illustrating intra prediction according to another embodiment of the present invention.

Referring to FIG. 6, a planar mode may be performed by dividing a current block into at least two regions. That is, after intra prediction for the first region 10 is performed, intra prediction for the second region 20 may be performed. Since the pixel located in the first region in which intra prediction has been completed may be used as a reference pixel, accuracy of intra prediction may be further improved.

For example, intra prediction may be first performed on a row located at the bottom of the current block and a column located at the rightmost side of the current block, and intra prediction may be performed on the remaining region 20. have.

In this case, intra prediction may start from a current pixel located at a location other than the current pixel located at the upper left of the current block. For example, intra prediction may be performed from a current pixel located at the lower right of the current block.

Accordingly, according to an embodiment of the present invention, the accuracy of intra prediction may be improved by sequentially performing intra prediction by partitioning the current block as shown in FIG. 6. However, the present invention may sequentially perform intra prediction by partitioning the current block into various regions, and the present invention is not limited to the partition according to FIG. 6.

Intra prediction according to the Planar mode according to FIG. 2 can be expressed as Equation 1 below.

In Equation 1, x and y denote coordinate values of a pixel, and nTbS denotes the size of a block. Also, p[x][y] may represent a pixel value of a pixel located at x and y coordinates, and predSamples[x][y] may represent a predicted pixel value.

According to an embodiment of the present invention, a first predicted value may be generated by applying a weight to a pixel TR at an upper right of the current block and a pixel belonging to the same horizontal line as the current pixel and adjacent to the current block, respectively. In addition, a second prediction value may be generated by applying a weight to a pixel LB at the lower left of the current block and a pixel belonging to the same vertical line as the current pixel and adjacent to the current block, respectively.

Meanwhile, a final predicted value for the current pixel may be generated by using the first predicted value and the second predicted value. For example, a final predicted value may be generated by averaging the first predicted value and the second predicted value.

That is, according to an embodiment of the present invention, the pixel TR at the upper right of the current block, the pixel belonging to the same horizontal line as the current pixel and adjacent to the current block, the pixel LB at the lower left of the current block, and the current pixel A weight may be applied to each pixel belonging to the same vertical line and adjacent to the current block. Here, the weights applied to each may be the same or different from each other.

In addition, each weight may be determined based on the direction of the current block, and the direction of the current block may be divided into a horizontal direction and a vertical direction.

For example, when prediction is performed to obtain an optimal mode of intra prediction for the current block, the direction of the current block can be checked. In this case, when prediction is performed using a planar mode, a prediction value may be generated by assigning an appropriate weight according to the direction pattern of the current block obtained previously.

However, the direction of the current block is not limited to the horizontal and vertical directions.

A planar mode modified by applying a weight to a reference pixel according to an embodiment of the present invention may be expressed as Equation 2 below.

In Equation 2, ω _A , ω _B , ω _C , and ω _D may represent weights. Thus, ω _A , ω _B , ω _C , and ω _D can be determined based on the direction of the current block. For example, when the current block has horizontal directionality, ω _A and ω _B may be larger than ω _C and ω _D. In addition, when the current block has horizontal directionality, ω _A and ω _B may be smaller than ω _C and ω _D.

Meanwhile, the weight can be set by the encoding device, and can be set in various units. That is, the weights may be different for each block or the same for each picture. The information on the weight may be set under an agreement between the encoding device and the decoding device. In addition, the encoding device may send information about the weight in units of a sequence, picture, or block to the decoding device.

7 is a block diagram for describing a video encoding apparatus that performs an intra prediction method according to an embodiment of the present invention.

Referring to FIG. 7, a video encoding apparatus for performing an intra prediction method according to an embodiment of the present invention includes a subtractor 110, an entropy encoder 120, an adder 130, an inter prediction unit 140, and an intra prediction unit. Includes 150.

* In the case of a lossy encoding apparatus, entropy encoding is performed through transformation and quantization, but in the case of lossless encoding, entropy encoding may be directly performed. When an input image is received, a residual value obtained through intra prediction or inter prediction may be transmitted to an entropy encoder. However, the encoding apparatus 100 according to an embodiment of the present invention is not limited to a lossless encoding apparatus.

The intra predictor 150 according to an exemplary embodiment of the present invention may generate a first predicted value using a pixel T at an upper right of the current block and a first reference pixel. In addition, the intra prediction unit 150 may generate a second prediction value by using the lower left pixel L and the second reference pixel of the current block. Here, the first reference pixel may be a pixel belonging to the same horizontal line as the current pixel and adjacent to the current pixel, and the second reference pixel may be a pixel belonging to the same vertical line as the current pixel and adjacent to the current pixel.

Here, the pixel T at the upper right of the current block is a pixel TR at the upper right of the current block, a pixel selected among pixels located on the same horizontal line as the pixel TR at the upper right of the current block, and the right side of the current block. It may be any one of pixels generated by filtering pixels located on the same horizontal line as the upper pixel TR.

In addition, the pixel L at the lower left of the current block is selected from among pixels located on the same vertical line as the pixel LB at the lower left of the current block, the pixel LB at the lower left of the current block, and the left side of the current block. It may be any one of the pixels generated by filtering pixels located on the same vertical line as the lower pixel LB.

The intra prediction unit 150 may partition the current block into at least two regions and perform sequential intra prediction for each partitioned region.

Furthermore, the intra prediction unit 150 may generate a first prediction value by applying a weight to each of the pixel TR at the upper right of the current block and the pixel belonging to the same horizontal line as the current pixel and adjacent to the current block, respectively. In addition, the intra prediction unit 150 may generate a second prediction value by applying a weight to each of the pixel LB at the lower left of the current block and a pixel belonging to the same vertical line as the current pixel and adjacent to the current block, respectively.

Here, the weight may be determined based on the direction of the current block, and the direction of the current block may be divided into a horizontal direction and a vertical direction.

As a result, the intra predictor 150 may generate a final predicted value for the current pixel by using the first predicted value and the second predicted value. For example, a final predicted value may be generated by averaging the first predicted value and the second predicted value.

The subtractor 110 may generate a difference value between the final predicted value and the pixel value of the current pixel as a residual value.

In addition, the encoding apparatus 100 may transmit information on the weight in units such as a sequence, a picture, and a block to the decoding apparatus.

In addition, since the lossless encoding device is similar to the lossy encoding device, it will be briefly described. The entropy encoder 120 performs entropy encoding on the residual image, the adder 130 generates a reconstructed image by adding the residual image and the prediction image, and the inter prediction unit 140 performs inter prediction through motion estimation. Can be done.

8 is a block diagram illustrating a video decoding apparatus that performs an intra prediction method according to an embodiment of the present invention.

Referring to FIG. 8, a decoding apparatus according to an embodiment of the present invention includes an entropy decoding unit 210, an adder 220, an intra prediction unit 230, and an inter prediction unit 240.

In the case of the lossy decoding apparatus, inverse quantization and inverse transformation are performed after entropy decoding is performed, but in the case of lossless decoding, inverse quantization and inverse transformation may not be performed. That is, a reconstructed image may be generated by decoding the bitstream to obtain a residual value for a current pixel, and adding a final prediction value to the residual value for the current pixel. However, the decoding apparatus according to an embodiment of the present invention is not limited to a lossless decoding apparatus.

The entropy decoder 210 may decode the received bitstream to generate restoration information including a residual value for a current pixel and intra prediction information. Here, the intra prediction information may include information on a modified Planar mode according to an embodiment of the present invention.

The intra prediction unit 230 may generate a first prediction value using a first reference pixel and a pixel T at an upper right of the current block including the current pixel based on the intra prediction information. In addition, the intra prediction unit 230 may generate a second prediction value using the lower left pixel L of the current block including the current pixel and the second reference pixel based on the intra prediction information.

Here, the pixel T at the upper right of the current block is a pixel TR at the upper right of the current block, a pixel selected among pixels located on the same horizontal line as the pixel TR at the upper right of the current block, and the right side of the current block. It may be any one of pixels generated by filtering pixels located on the same horizontal line as the upper pixel TR.

In addition, the pixel L at the lower left of the current block is a pixel selected from among pixels located on the same vertical line as the pixel LB at the lower left of the current block, the pixel LB at the lower left of the current block, and the left side of the current block. It may be any one of the pixels generated by filtering pixels located on the same vertical line as the lower pixel LB.

The intra prediction unit 230 may partition the current block into at least two regions and perform sequential intra prediction for each partitioned region.

Here, the first reference pixel may be a pixel belonging to the same horizontal line as the current pixel and adjacent to the current pixel, and the second reference pixel may be a pixel belonging to the same vertical line as the current pixel and adjacent to the current pixel.

Furthermore, the intra prediction unit 230 may generate a first prediction value by applying a weight to each of the pixel TR at the upper right of the current block and a pixel belonging to the same horizontal line as the current pixel and adjacent to the current block, respectively. In addition, the intra prediction unit 230 may generate a second prediction value by applying a weight to each of the pixel LB at the lower left of the current block and a pixel belonging to the same vertical line as the current pixel and adjacent to the current block, respectively.

Here, the weight may be determined based on the direction of the current block, and the direction of the current block may be divided into a horizontal direction and a vertical direction.

As a result, the intra predictor 230 may generate a final predicted value for the current pixel by using the first predicted value and the second predicted value. For example, a final predicted value may be generated by averaging the first predicted value and the second predicted value.

In addition, the adder 220 may generate a reconstructed image by adding the residual image and the predicted image. That is, the adder 220 may generate a reconstructed image by adding a residual value for the current pixel to the final predicted value.

Meanwhile, the inter prediction unit 240 may perform inter prediction through motion estimation.

In addition, since the lossless decoding apparatus is similar to the lossless encoding apparatus, detailed descriptions are omitted.

The above-described encoding and decoding apparatuses according to the embodiment of the present invention may perform intra prediction according to the descriptions of FIGS. 3 and 4.

The video encoding/decoding method and apparatus using intra prediction according to the above-described embodiment of the present invention can improve the accuracy of intra prediction by performing intra prediction using reference pixels having a higher correlation.

In addition, in applying the planar mode, accuracy of intra prediction may be improved by applying a weight based on the direction of the current block.

Accordingly, by improving the accuracy of intra prediction, it is possible to increase the encoding/decoding efficiency.

Although the above has been described with reference to preferred embodiments of the present invention, those skilled in the art will variously modify and change the present invention within the scope not departing from the spirit and scope of the present invention described in the following claims. You will understand that you can do it.

100: encoding device 110: subtractor
120: entropy encoding unit 130, 220: adder
140, 240: inter prediction unit 150, 230: intra prediction unit
200: decryption device

Claims (8)

In the video decoding method based on intra prediction,
Obtaining a first prediction pixel in a first area in the current block by using a neighboring pixel adjacent to the current block as a reference pixel;
Obtaining a second prediction pixel in a second area in the current block by using the first prediction pixel in the first area as a reference pixel; And
And decoding the current block based on the first prediction pixel and the second prediction pixel. The method of claim 1,
The first area in the current block includes pixels belonging to at least one of a row located at the bottom of the current block or a column located at the rightmost side of the current block,
The second area in the current block is an area remaining in the current block except for the first area. The method of claim 2,
The second prediction pixel in the second area of the current block is obtained by further using a pixel located on the same vertical line as the second prediction pixel among neighboring pixels adjacent to an upper end of the current block. The method of claim 2,
The intra prediction is performed from a pixel located at a position other than the pixel located at the upper left of the current block. The method of claim 4,
The image decoding method, wherein a pixel located at a lower right of the current block is predicted before a pixel located at an upper left of the current block. The method of claim 4,
The image decoding method, wherein intra prediction is performed on the second area in the current block after the intra prediction on the first area in the current block is completed. In the video encoding method based on intra prediction,
Obtaining a first prediction pixel in a first area in the current block by using a neighboring pixel adjacent to the current block as a reference pixel;
Obtaining a second prediction pixel of a second area of the current block by using the first prediction pixel of the first area as a reference pixel; And
And encoding the current block based on the first prediction pixel and the second prediction pixel. A computer-readable recording medium storing a bitstream generated by a video encoding method, comprising:
The video encoding method,
Obtaining a first prediction pixel in a first area within the current block by using a neighboring pixel adjacent to the current block as a reference pixel;
Obtaining a second prediction pixel of a second area of the current block by using the first prediction pixel of the first area as a reference pixel; And
And encoding the current block based on the first prediction pixel and the second prediction pixel.

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