KR102327318B1 - 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 intra prediction accuracy. The video decoding method comprises the steps of: decoding a received bitstream to generate restoration information including a residual value for a current pixel and intra prediction information; generating a first prediction value using the pixel (T) and the first reference pixel; and using the pixel (L) at the lower left of the current block including the current pixel and the second reference pixel based on the intra prediction information generating a second prediction value; and generating a final prediction value for the current pixel by using the first prediction value and the second prediction value. In applying the planar mode, the accuracy of intra prediction can be improved by using a reference pixel having a higher correlation or by applying a weight based on the directionality of the current block.

Description

Video encoding/decoding method and apparatus using intra prediction

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

Recently, due to the advent of smartphones and smart TVs, the use of video data through wired/wireless communication networks is explosively increasing. While video data has superior information delivery ability 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 with limited bandwidth. In addition, since vast amounts of video information must be appropriately processed according to application requirements, a system for processing video also requires high specifications.

Video coding includes loss coding and lossless coding. H.264/AVC supports not only lossy coding but also lossless coding. In particular, lossless coding is a more efficient lossless coding technique in H.264/AVC FRExt (Fidelity Range Extension) standardization. The lossless encoding technique adopted in FRExt was achieved by simply not performing transformation and quantization in order 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, the standardization of HEVC (High Efficiency Video Coding) as a next-generation video compression standard technology known to have about two times or more compression efficiency compared to the conventional H.264/AVC has recently been completed.

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

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

However, in the case of the planar mode according to HEVC, as the current pixel moves toward the inside of the current block, the distance from the reference pixel increases, resulting in poor prediction accuracy.

SUMMARY OF THE INVENTION An object of the present invention to solve the above problems is to provide an intra prediction method for improving encoding efficiency by increasing intra prediction accuracy.

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

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

Here, the pixel T at the upper right of the current block is the pixel TR at the upper right of the current block, a selected pixel 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 is any one of the pixels generated by filtering pixels located on the same horizontal line as the upper right pixel TR of the current block, and the lower left pixel L of the current block is the lower left pixel LB ), a pixel generated by performing filtering on a selected pixel 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 may be any one of

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

Here, the generating of the first predicted value includes applying a weight to 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 to generate the first predicted value, The generating of the second predicted value may include applying a weight to the pixel LB at the lower left of the current block and the pixel belonging to the same vertical line as the current pixel and adjacent to the current block to generate the second predicted value.

Here, the weight may be determined based on the directionality 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 another object comprises the steps of: decoding a received bitstream to generate restoration information including a residual value of a current pixel and intra prediction information; generating a first prediction value using the first reference pixel and the upper right pixel T of the current block including the current pixel based on the intra prediction information, and the left side of the current block including the current pixel based on intra prediction information generating a second predicted value using the lower pixel L and a second reference pixel; and generating a final predicted value for the current pixel by 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 of the current pixel to the 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 that decodes a received bitstream and generates restoration information including a residual value of a current pixel and intra prediction information; Based on the intra prediction information, a first prediction value is generated using the upper right pixel (T) and the first reference pixel of the current block including the current pixel, and based on the intra prediction information of the current block including the current pixel and an intra prediction unit that 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.

As described above, the video encoding/decoding method and apparatus using intra prediction according to the present invention can improve the accuracy of intra prediction by performing intra prediction using reference pixels with higher correlation.

In addition, when applying the planar mode, the accuracy of intra prediction can be improved by applying a weight based on the directionality of the current block.

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

Since the present invention can have various changes and can have various embodiments, specific embodiments are illustrated in the drawings and described in detail in the detailed description. However, this is not intended to limit the present invention to specific embodiments, and it should be understood to include all modifications, equivalents and substitutes included in the spirit and scope of the present invention. In describing each figure, like reference numerals have been used for like 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. The above terms are used only for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, a first component may be referred to as a second component, and similarly, a second component may also be referred to as a first component. 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 the other component may be directly connected or connected to the other component, but other components may exist in between. it should be On the other hand, when it is said that a certain element is "directly connected" or "directly connected" to another element, it should be understood that no other element is present 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. The singular expression includes the plural expression unless the context clearly dictates otherwise. In the present application, terms such as “comprise” or “have” are intended to designate that a feature, number, step, operation, component, part, or combination thereof described in the specification exists, but one or more other features It should be understood that this does not preclude the existence or addition of numbers, steps, operations, components, parts, or combinations thereof.

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

A video encoding apparatus (Video Encoding Apparatus) and a video decoding apparatus (Video Decoding Apparatus), which will be described later, are a personal computer (PC), a notebook computer, a personal digital assistant (PDA), and a portable multimedia player (PMP). : Portable Multimedia Player), PlayStation Portable (PSP: PlayStation Portable), Wireless Communication Terminal, Smart Phone, TV application server and service server, etc. 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 encoding or decoding an image, or inter- or intra-screen prediction for encoding or decoding; It may refer to various devices having a microprocessor for executing, calculating, and controlling the operation.

In addition, the video encoded in the bitstream by the video encoding device is transmitted in real time or in non-real time through a wired/wireless communication network such as the Internet, a local area network, a wireless LAN network, a WiBro network, or a mobile communication network, or through a cable, a universal serial bus (USB: Universal Serial Bus), etc., may be transmitted to the image decoding apparatus through various communication interfaces, decoded in the image decoding apparatus, and restored as an image and reproduced.

In general, 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 HEVC (High Efficiency Video Coding) standard defines the 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 enables encoding to be performed while variably adjusting the size of the coding unit. A prediction unit is determined from a coding unit that is no longer split, and may be determined through a prediction type and a PU splitting process. A transformation unit is a transformation unit for transformation and quantization, and may be larger than a size of a prediction unit, but may not be larger than a coding unit. Accordingly, in the present invention, a block may be understood as equivalent to a unit.

In addition, a block or pixel referenced for encoding or decoding the current block or current pixel is referred to as a reference block or reference pixel. In addition, it is common knowledge in the art that the term “picture” described below may be used instead of other terms having the same meaning, such as an image, a frame, and the like. You can understand it when you grow up.

Hereinafter, preferred embodiments according to 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. However, more accurate prediction can be performed by using various prediction modes to reduce prediction errors.

Mode 0 indicates a planar mode, mode 1 indicates a DC mode, and modes 2 to 34 indicate a directional mode (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 and is effective in predicting a region in which pixel values change gradually. In the DC mode, the average value of neighboring pixels of the current prediction block is used as a prediction value.

In addition, Angular mode performs prediction based on a total of 33 directions including vertical and horizontal directions. In a vertical mode or a horizontal mode, a neighboring pixel value is copied in a vertical or horizontal direction and used as a prediction value. On the other hand, in directional prediction modes other than vertical and horizontal modes, intra prediction is performed in a direction in which 45 degrees are divided into 32, and since they are divided at the same angle based on the centrifugal 10, pixels according to each prediction direction are equally spaced. Therefore, predictive values are generated through linear interpolation.

According to the planar mode with reference to FIG. 2 , first, a first prediction value may be obtained using a pixel TR located 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. In addition, the second predicted value may be obtained by using the pixel LB at the lower left of the current block and the pixel belonging to the same vertical line as the current pixel and adjacent to the current block. In addition, an 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 may 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 upper right of the current block belongs to the same horizontal line as the current pixel, the distance is far from the pixel adjacent to the current block, and the pixel LB and the current pixel located at the lower left of the current block In the case of a current pixel belonging to the same vertical line as and far from a pixel adjacent to the current block, prediction accuracy may be reduced.

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

The planar mode according to HEVC uses 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 as reference pixels.

In comparison, referring to FIG. 3 , in the planar mode modified according to the 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 performing filtering on pixels positioned on the same horizontal line as the upper right pixel TR of the current block may be used as a reference pixel. For example, _{one of the pixels located at T 1} to T _n in FIG. 3 may be determined as the 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 from among pixels located on the same horizontal line as the upper right pixel TR of the current block or 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 planar mode modified according to the embodiment of the present invention, a selected pixel 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 performing filtering on pixels located on the same vertical line as the pixel TR at the lower left of the current block may be used as a reference pixel. For example, _{one of the pixels located in L 1} to L _n in FIG. 3 may be determined as the 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 a selected pixel from among pixels located on the same vertical line as the lower left pixel LB of the current block or 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 a pixel T at the upper right of the current block and a 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. 4 and 5 , the current block may be displayed 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 the planar mode modified according to an embodiment of the present invention will be described with reference to FIGS. 4 and 5 . The first predicted value may be generated using the pixel T at the upper right of the current block and the first reference pixel that is adjacent to the current pixel and belongs to the same horizontal line as the current pixel. Also, it may be generated using the pixel L at the lower left of the current block and the second reference pixel, which is a pixel belonging to the same vertical line as the current pixel and adjacent to the current pixel. For example, the first predicted value is generated by performing interpolation using the upper right pixel T and the first reference pixel, and the second predicted value is generated by performing interpolation using the lower left pixel L and the second reference pixel can do.

Meanwhile, a final predicted value for the current pixel may be generated using the first predicted value and the second predicted value. For example, the 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 the current pixel located at the upper left in 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 serving as the starting point of the intra prediction may be intra-predicted by the same method as in the existing 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 direction of intra prediction may be sequentially performed in a horizontal direction. For example, after intra prediction for a current pixel included in a row located 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 the 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 serving as the starting point of the intra prediction may be intra-predicted by the same method as in the existing 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 direction of intra prediction may be sequentially performed in a vertical direction. For example, after intra prediction of a current pixel included in a leftmost column of the current block is completed, intra prediction of a next (right direction) column may be performed.

4 and 5 , although it has been described that intra prediction starts from a current pixel located at the upper left of the current block, it goes without saying that intra prediction may start from a current pixel located at another position in the current block. . In addition, although an embodiment in which intra prediction is sequentially performed in a horizontal direction or a vertical direction has been described, it goes without saying that sequential intra prediction may be performed in a diagonal direction. Here, the diagonal direction may mean an up-right diagonal direction.

According to an embodiment of the present invention, the accuracy of intra prediction can be improved by using 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 as a reference pixel. can

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

Referring to FIG. 6 , the planar mode may be performed by partitioning the current block into at least two regions. That is, after performing intra prediction on the first region 10 , intra prediction on the second region 20 may be performed. Since the pixel located in the first area where the intra prediction has been completed can be used as a reference pixel, the accuracy of the intra prediction can 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 then intra prediction may be performed on the remaining area 20 . have.

In this case, intra prediction may be started from a current pixel located at a position other than the current pixel located at the upper left in 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 can be improved by sequentially performing intra prediction by partitioning the current block as shown in FIG. 6 . However, the present invention can sequentially perform intra prediction by partitioning the current block into various regions, and is not limited to the partitioning illustrated in 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 may represent coordinate values of a pixel, and nTbS may represent the size of a block. Also, p[x][y] may represent a pixel value of a pixel located at x,y coordinates, and predSamples[x][y] may represent a predicted pixel value.

According to an embodiment of the present invention, the first predicted value may be generated by applying a weight to the pixel TR of 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 second predicted value may be generated by applying a weight to the pixel LB at the lower left of the current block and the 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 using the first predicted value and the second predicted value. For example, the final predicted value may be generated by averaging the first predicted value and the second predicted value.

That is, according to the 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 as or different from each other.

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

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

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

According to an embodiment of the present invention, a planar mode modified by applying a weight to a reference pixel can be expressed as Equation 2 below.

In Equation 2, ω _A , ω _B , ω _C , and ω _D may represent weights. Accordingly, ω _A , ω _B , ω _C , ω _D may be determined based on the directionality of the current block. For example, when the directionality of the current block has a horizontal directionality, ω _A and ω _B may be greater than ω _C and ω _{D .} Also, when the directionality of the current block has a horizontal directionality, ω _A and ω _B may be smaller than ω _C and ω _{D .}

Meanwhile, the weight can be set in the encoding apparatus and can be set in various units. That is, various cases are possible, such as different weights for each block or the same for each picture. The weight information may be set by the encoding apparatus and the decoding apparatus under mutual agreement. Also, the encoding apparatus may transmit information on weights in units of sequences, pictures, blocks, etc. to the decoding apparatus.

7 is a block diagram illustrating a video encoding apparatus performing an intra prediction method according to an embodiment of the present invention.

Referring to FIG. 7 , a video encoding apparatus performing an intra prediction method according to an embodiment of the present invention includes a subtractor 110 , an entropy encoding unit 120 , an adder 130 , an inter prediction unit 140 , and an intra prediction unit. (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 the 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 prediction unit 150 according to an embodiment of the present invention may generate a first prediction value using the pixel T at the upper right of the current block and the first reference pixel. Also, the intra prediction unit 150 may generate a second prediction value using the lower left pixel L of the current block and the second reference pixel. 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 the pixel TR at the upper right of the current block, a selected pixel 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 performing filtering on pixels positioned on the same horizontal line as the upper pixel TR.

In addition, the pixel L at the lower left of the current block includes the pixel LB at the lower left of the current block, a selected pixel among pixels located on the same vertical line as 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 pixels generated by performing filtering on 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 sequentially perform intra prediction for each partitioned region.

Furthermore, the intra prediction unit 150 may generate the first prediction value by applying a weight to 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. Also, the intra prediction unit 150 may generate the second prediction value by applying a weight to the pixel LB at the lower left of the current block and the 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 directionality of the current block, and the directionality of the current block may be divided into a horizontal directionality and a vertical directionality.

As a result, the intra prediction unit 150 may generate a final prediction value for the current pixel by using the first prediction value and the second prediction value. For example, the 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.

Also, the encoding apparatus 100 may transmit information on weights to the decoding apparatus in units of sequences, pictures, blocks, and the like.

In addition, since the lossless encoding apparatus is similar to the lossy encoding apparatus, it will be briefly described. The entropy encoding unit 120 performs entropy encoding on the residual image, the adder 130 generates a reconstructed image by adding the residual image and the predicted 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 performing an intra prediction method according to an embodiment of the present invention.

Referring to FIG. 8 , the 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, 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 of the current pixel and adding a final predicted value to the residual value of the current pixel. However, the decoding apparatus according to the embodiment of the present invention is not limited to the lossless decoding apparatus.

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

The intra prediction unit 230 may generate a first prediction value based on the intra prediction information by using the upper right pixel T of the current block including the current pixel and the first reference pixel. Also, the intra prediction unit 230 may generate a second prediction value by 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 the pixel TR at the upper right of the current block, a selected pixel 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 performing filtering on pixels positioned on the same horizontal line as the upper pixel TR.

In addition, the pixel L at the lower left of the current block includes the pixel LB at the lower left of the current block, a selected pixel among pixels located on the same vertical line as 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 pixels generated by performing filtering on 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 sequentially perform 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 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. Also, the intra prediction unit 230 may generate a second prediction value by applying a weight to the pixel LB at the lower left of the current block and the 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 directionality of the current block, and the directionality of the current block may be divided into a horizontal directionality and a vertical directionality.

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

Also, 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 the residual value of 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, a detailed description thereof will be omitted.

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

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

In addition, when applying the planar mode, the accuracy of intra prediction can be improved by applying a weight based on the directionality 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 can variously modify and change the present invention within the scope without departing from the spirit and scope of the present invention as set forth in the claims below. You will understand that it can be done.

100: encoding device 110: subtractor
120: entropy encoder 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 of 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 in the current block by using the first prediction pixel of the first area as a reference pixel; and
Decoding the current block based on the first prediction pixel and the second prediction pixel,
The first area includes a pixel located at the lower right of the current block,
A pixel located at the lower right corner in the current block is predicted using a neighboring pixel adjacent to the current block as a reference pixel,
The first prediction pixel is obtained without using another prediction pixel in the first area obtained before the first prediction pixel as a reference pixel. According to claim 1,
The first area in the current block includes pixels belonging to at least one of a row located at the lowermost side of the current block or a column located at the rightmost side of the current block,
The second area in the current block is a remaining area in the current block except for the first area. 3. The method of claim 2,
The second prediction pixel of the second area in 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. 3. The method of claim 2,
The image decoding method, wherein 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. 5. The method of claim 4,
and a pixel located at the lower right of the current block is predicted before a pixel located at the upper left of the current block. 5. The method of claim 4,
The method of claim 1, wherein intra prediction is performed on a second region in the current block after intra prediction of the first region in the current block is completed. In the video encoding method based on intra prediction,
obtaining a first prediction pixel of 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 in the current block by using the first prediction pixel of the first area as a reference pixel; and
encoding the current block based on the first prediction pixel and the second prediction pixel;
The first area includes a pixel located at the lower right of the current block,
A pixel located at the lower right corner in the current block is predicted using a neighboring pixel adjacent to the current block as a reference pixel,
The first prediction pixel is obtained without using another prediction pixel in the first area obtained before the first prediction pixel as a reference pixel. delete

Images