KR20190142750A - Image encoding/decoding method and apparatus - Google Patents

Abstract

Provided are a method for encoding/decoding an image and an apparatus thereof. According to the present invention, the method for encoding/decoding an image can comprise the steps of: restoring reference pixel line information; selecting at least one reference pixel line among a plurality of reference pixel lines based on the reference pixel line information; and generating a prediction block for a current block by performing intra-screen prediction on the current block based on the selected reference pixel line.

Description

Image Encoding / Decoding Method and Apparatus {IMAGE ENCODING / DECODING METHOD AND APPARATUS}

The present invention relates to an image encoding / decoding method and apparatus, and more particularly, to an image encoding / decoding method and apparatus for performing intra prediction using a plurality of reconstructed pixel lines.

Recently, the demand for multimedia data such as moving pictures is rapidly increasing on the Internet. However, the speed at which the bandwidth of a channel develops is difficult to keep up with the rapidly increasing amount of multimedia data. Accordingly, the ITU-T's Video Coding Expert Group (VCEG) and ISO / IEC's Moving Picture Expert Group (MPEG) launched the video compression standard HEVC (High Efficiency Video Coding) version 1 in February 2014. Enacted.

HEVC defines techniques such as intra prediction (or intra prediction), inter prediction (or inter prediction), transformation, quantization, entropy coding, and in-loop filter.

An object of the present invention is to provide an image encoding / decoding method and apparatus for performing intra prediction using a plurality of reference pixel lines.

Moreover, an object of this invention is to provide the recording medium which stored the bitstream produced | generated by the video encoding method or apparatus of this invention.

It is also an object of the present invention to provide a recording medium storing a bitstream to be decoded by the video decoding method or apparatus of the present invention.

The technical problems to be achieved in the present invention are not limited to the technical problems mentioned above, and other technical problems not mentioned above will be clearly understood by those skilled in the art from the following description. Could be.

An image decoding method according to an aspect of the present invention may include reconstructing reference pixel line information, selecting at least one reference pixel line among a plurality of reference pixel lines based on the reference pixel line information, and selecting the selected pixel. The method may include generating a prediction block for the current block by performing intra prediction on the current block based on a reference pixel line.

In the image decoding method according to the present invention, the reference pixel line information may be decoded in units of blocks.

In the image decoding method according to the present invention, the prediction block may be generated by performing a weighted summation between an upper reference pixel of the current block and a left reference pixel of the current block.

In the image decoding method according to the present invention, the upper reference pixel and the left reference pixel may be selected based on a prediction direction of the current block.

In the image decoding method according to the present invention, the upper reference pixel and the left reference pixel are present on a first reference pixel line adjacent to the current block, and the upper reference pixel and the left reference pixel are current pixels in the current block. It may be selected based on the coordinate of.

In the image decoding method according to the present invention, when the coordinate of the upper left pixel in the current block is (0, 0) and the coordinate of the current pixel is (x, y), the coordinate of the upper reference pixel is (x + y + 1, -1), and the coordinates of the left reference pixel may be (-1, x + y + 1).

In the image decoding method according to the present invention, a weight used for the weighted sum may be determined based on a distance from a current pixel in the current block to the upper reference pixel and the left reference pixel.

In the image decoding method according to the present invention, a greater weight may be applied to a reference pixel having a distance from the current pixel among the upper reference pixel and the left reference pixel.

According to another aspect of the present invention, there is provided a method of encoding an image, selecting at least one reference pixel line among a plurality of reference pixel lines, and performing intra prediction on the current block based on the selected reference pixel line. Generating a prediction block for the block, and encoding reference pixel line information about the selected reference pixel line.

In the image encoding method according to the present invention, the reference pixel line information may be encoded in units of blocks.

In the image encoding method according to the present invention, the prediction block may be generated by performing a weighted summation between an upper reference pixel of the current block and a left reference pixel of the current block.

In the image encoding method according to the present invention, the upper reference pixel and the left reference pixel may be selected based on a prediction direction of the current block.

In the image encoding method according to the present invention, the upper reference pixel and the left reference pixel are present on a first reference pixel line adjacent to the current block, and the upper reference pixel and the left reference pixel are current pixels in the current block. It may be selected based on the coordinate of.

In the image encoding method according to the present invention, when the coordinate of the upper left pixel in the current block is (0, 0) and the coordinate of the current pixel is (x, y), the coordinate of the upper reference pixel is (x + y + 1, -1), and the coordinates of the left reference pixel may be (-1, x + y + 1).

In the image encoding method according to the present invention, a weight used for the weighted sum may be determined based on a distance from a current pixel in the current block to the upper reference pixel and the left reference pixel.

In the image encoding method according to the present invention, a greater weight may be applied to a reference pixel having a distance from the current pixel among the upper reference pixel and the left reference pixel.

A computer readable recording medium according to another aspect of the present invention may store a bitstream generated by the video encoding method and / or apparatus according to the present invention.

A computer readable recording medium according to another aspect of the present invention may store a bitstream decoded by an image decoding method and / or apparatus according to the present invention.

According to the present invention, an image encoding / decoding method and apparatus for performing intra prediction using a plurality of reference pixel lines may be provided.

According to the present invention, a method and apparatus for predicting a current block using a plurality of prediction blocks generated based on a plurality of prediction information may be provided.

In addition, according to the present invention, a computer-readable recording medium for storing a bitstream generated by the video encoding method / apparatus according to the present invention can be provided.

Further, according to the present invention, a computer-readable recording medium for storing a bitstream decoded by the image decoding method and / or apparatus according to the present invention can be provided.

1 is an exemplary view briefly illustrating a configuration of a video encoding apparatus.
2 is a diagram illustrating an embodiment of a prediction unit of an image encoding apparatus.
3 is a diagram for describing an embodiment of encoding encoding information by a video encoding apparatus.
4 is a diagram illustrating a configuration of an image decoding apparatus.
5 is an exemplary diagram illustrating a configuration of a prediction unit of an image decoding device.
FIG. 6 is a diagram for describing an embodiment of decoding encoding information by a video decoding apparatus. FIG.
FIG. 7 illustrates an example of intra prediction using a plurality of reference pixel lines.
8 is a diagram for describing another embodiment of intra prediction using a plurality of reference pixel lines.
9 is an exemplary diagram illustrating an intra prediction unit of an image encoding apparatus using one or more reference pixel lines.
10 is an exemplary diagram illustrating an intra prediction unit of an image decoding apparatus using one or more reference pixel lines.
11 is a diagram for describing a method of encoding prediction mode information according to an embodiment of the present invention.
12 is a diagram for describing a method of decoding prediction mode information according to an embodiment of the present invention.
FIG. 13 is a diagram for describing an intra prediction unit of a video encoding apparatus according to another embodiment. FIG.
FIG. 14 is a diagram for describing an intra prediction unit of an image decoding apparatus according to another exemplary embodiment.
15 is a diagram for describing a method of encoding prediction mode information according to an embodiment of the present invention.
16 is a diagram for describing a method of decoding prediction mode information according to an embodiment of the present invention.
17 is a diagram for describing a method of performing intra prediction according to another embodiment of the present invention.
18 is a diagram for explaining an intra prediction unit of a video encoding apparatus according to another embodiment.
FIG. 19 is a diagram for describing an intra prediction unit of a video decoding apparatus according to another exemplary embodiment.
20 is a diagram for describing a method of encoding prediction mode information according to an embodiment of the present invention.
21 is a diagram for describing a method of decoding prediction mode information according to an embodiment of the present invention.

DETAILED DESCRIPTION Embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. In the drawings, parts irrelevant to the description are omitted in order to clearly describe the present invention, and like reference numerals designate like parts throughout the specification.

In the present specification, when a part is 'connected' to another part, this includes not only a case where the part is directly connected, but also a case where the part is electrically connected with another element in between.

In addition, when any part of the present specification 'includes' a certain component, this means that it may further include other components, without excluding other components unless otherwise stated.

In addition, terms such as first and second may be used to describe various components, but the components should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from another.

In addition, in the embodiments of the apparatus and method described herein, some of the configuration of the apparatus or some of the steps of the method may be omitted. In addition, the order of some of the components of the apparatus or some of the steps of the method may be changed. In addition, other configurations or other steps may be inserted into part of the device or part of the steps of the method.

In addition, some components or some steps of the first embodiment of the present invention may be added to, or may replace some elements or some steps of the second embodiment.

In addition, the components shown in the embodiments of the present invention are shown independently to represent different characteristic functions, and do not mean that each component is composed of separate hardware or one software unit. That is, each component is described by listing each component for convenience of description, and at least two of the components may be combined to form one component, or one component may be divided into a plurality of components to perform a function. The integrated and separated embodiments of each of these components are also included within the scope of the present invention without departing from the spirit of the invention.

First, the terms used in the present application will be briefly described as follows.

The video decoding apparatus (Video Decoding Apparatus) to be described below is a civil security camera, civil security system, military security camera, military security system, personal computer (PC, Personal Computer), notebook computer, portable multimedia player (PMP, Portable MultimediaPlayer), It may be a device included in a server terminal such as a wireless communication terminal, a smart phone, a TV application server and a service server, and a communication modem for communicating with a user terminal such as various devices or a wired or wireless communication network. It may mean a variety of devices including a communication device such as an image, a memory for storing various programs and data for inter- or intra-prediction for decoding or decoding an image, a microprocessor for executing and operating a program, and the like. Can be.

In addition, the image encoded in the bitstream by the encoder is real-time or non-real-time through the wired or wireless communication network, such as the Internet, local area wireless communication network, wireless LAN network, WiBro network, mobile communication network or the like, cable, universal serial bus (USB, It can be transmitted to a video decoding apparatus through various communication interfaces such as a universal serial bus), decoded, reconstructed, and played back. Alternatively, the bitstream generated by the encoder may be stored in the memory. The memory may include both a volatile memory and a nonvolatile memory. In the present specification, a memory may be represented as a recording medium storing a bitstream.

Typically, a video may be composed of a series of pictures, and each picture may be divided into a coding unit such as a block. In addition, it will be understood by those of ordinary skill in the art that the term 'picture' described below may be used interchangeably with other terms having equivalent meanings such as an image, a frame, and the like. will be. And it will be understood by those skilled in the art that the term coding unit may be used interchangeably with other terms having equivalent meanings such as unit blocks, blocks, and the like.

Hereinafter, with reference to the accompanying drawings, it will be described in detail an embodiment of the present invention. In describing the present invention, duplicate descriptions of the same components will be omitted.

1 is an exemplary view briefly illustrating a configuration of a video encoding apparatus.

The image encoding apparatus 100 may include an image splitter 101, an intra prediction unit 102, an inter prediction unit 103, a subtractor 104, a transform unit 105, a quantization unit 106, and entropy encoding. The unit 107, an inverse quantization unit 108, an inverse transform unit 109, an adder 110, a filter unit 111, and a memory 112 may be included.

RateDistortion-Cost (RD-Cost) can be compared to select the best information for each device. The RD-Cost refers to a cost value calculated by using distortion information between the original block and the reconstructed block and the amount of bits generated when the prediction mode is transmitted. In this case, a sum of absolute difference (SAD), a sum of absolute transformed difference (SATD), a sum of square for error (SSE) may be used to calculate the cost value.

Each of the components shown in FIG. 1 is independently shown to represent different characteristic functions in the image encoding apparatus, and does not mean that each of the components is made of separate hardware or one software component unit. In other words, each component is included in each component for convenience of description and at least two of the components are combined to form one component, or one component may be divided into a plurality of components to perform a function. Integrated and separate embodiments of the components are also included within the scope of the present invention without departing from the spirit of the invention.

In addition, some of the components may not be essential components for performing essential functions in the present invention, but may be optional components for improving performance. The present invention can be implemented including only the components necessary to implement the essentials of the present invention except for the components used for improving performance, and includes only the essential components except for the optional components used for improving performance. The structure is also included in the scope of the present invention.

The image divider 100 may divide the input image into at least one block. In this case, the input image may have various shapes and sizes, such as a picture, a slice, a tile, and a segment. A block may mean a coding unit (CU), a prediction unit (PU), or a transformation unit (TU). The partitioning may be performed based on at least one of a quadtree, a binary tree, and a ternary tree. Quad tree is a method of dividing an upper block into lower blocks having a width and a height of half of the upper block. Binary tree is a method of dividing the upper block into lower blocks, either half of the upper block of width or height. The ternary tree divides an upper block into lower blocks based on either a width or a height. Through partitioning based on the binary tree and the ternary tree described above, a block may have a square as well as a non-square shape.

The prediction units 102 and 103 may include an inter prediction unit 103 that performs inter prediction and an intra prediction unit 102 that performs intra prediction. It is possible to determine whether to use inter-prediction prediction or intra-prediction prediction for the prediction unit, and determine specific information (eg, intra prediction prediction mode, motion vector, reference picture, etc.) according to each prediction method. have. In this case, the processing unit in which the prediction is performed may differ from the processing unit in which the prediction method and the details are determined. For example, the method of prediction and the prediction mode may be determined in the prediction unit, and the prediction may be performed in the transform unit.

The residual value (residual block) between the generated prediction block and the original block may be input to the transformer 105. In addition, prediction mode information and motion vector information used for prediction may be encoded by the entropy encoder 107 together with the residual value and transmitted to the decoder. When a specific encoding mode is used, the original block may be encoded as it is and transmitted to the decoder without generating the prediction block through the prediction units 102 and 103.

The intra prediction unit 102 may generate a prediction block based on reference pixel information around the current block, which is pixel information in the current picture. When the prediction mode of the neighboring block of the current block on which the intra prediction prediction is to be performed is the inter prediction prediction, the reference pixel included in the neighboring block to which the inter prediction prediction is applied is referred to a reference pixel in the other block around the intra prediction prediction applied. Can be replaced with pixels. That is, when the reference pixel is not available, the unavailable reference pixel information may be replaced with at least one reference pixel among the available reference pixels.

In intra prediction, a prediction mode may have a directional prediction mode using reference pixel information according to a prediction direction and a non-directional mode using no directional information. The mode for predicting the luminance information and the mode for predicting the color difference information may be different. In order to predict the color difference information, intra prediction mode information or predicted luminance signal information used for the prediction of the luminance information may be utilized.

The intra prediction unit 102 may include an adaptive intra smoothing (AIS) filter, a reference pixel interpolator, and a DC filter. The AIS filter is a filter for filtering the reference pixels of the current block and may adaptively determine whether to apply the filter according to the prediction mode of the current prediction unit. If the prediction mode of the current block is a mode that does not perform AIS filtering, the AIS filter may not be applied.

The reference pixel interpolation unit of the intra prediction unit 102 refers to the fractional unit position by interpolating the reference pixel when the intra prediction mode of the prediction unit is a mode for performing intra prediction based on the pixel value interpolated with the reference pixel. Pixels can be generated. If the prediction mode of the current prediction unit is a prediction mode for generating a prediction block without interpolating the reference pixel, the reference pixel may not be interpolated. The DC filter may generate the prediction block through filtering when the prediction mode of the current block is the DC mode.

The inter prediction unit 103 generates a prediction block using the reconstructed reference image and motion information stored in the memory 112. The motion information may include, for example, a motion vector, a reference picture index, a list 1 prediction flag, a list 0 prediction flag, and the like.

The residual block may include a prediction unit generated by the prediction units 102 and 103 and residual information which is a difference value between the prediction unit and the original block. The generated residual block may be input to the transform unit 105 and converted.

The inter prediction unit 103 may induce a prediction block based on information of at least one of a previous picture or a subsequent picture of the current picture. In addition, a prediction block of the current block may be derived based on information of a partial region in which encoding in the current picture is completed. The inter prediction unit 103 according to an embodiment of the present invention may include a reference picture interpolator, a motion predictor, and a motion compensator.

The reference picture interpolation unit may receive reference picture information from the memory 112 and generate pixel information of less than an integer pixel in the reference picture. In the case of luminance pixels, a DCT based 8-tap interpolation filter having different filter coefficients may be used to generate pixel information of integer pixels or less in units of 1/4 pixels. In the case of a chrominance signal, a DCT-based interpolation filter having different filter coefficients may be used to generate pixel information of an integer pixel or less in units of 1/8 pixels.

The motion predictor may perform motion prediction based on the reference picture interpolated by the reference picture interpolator. As a method for calculating a motion vector, various methods such as full search-based block matching algorithm (FBMA), three step search (TSS), and new three-step search algorithm (NTS) may be used. The motion vector may have a motion vector value of 1/2 or 1/4 pixel units based on the interpolated pixels. The motion prediction unit may predict the prediction block of the current block by using a different motion prediction method. As the motion prediction method, various methods such as a skip method, a merge method, and an advanced motion vector prediction (AMVP) method may be used.

The subtraction unit 104 generates a residual block of the current block by subtracting the block to be currently encoded from the prediction block generated by the intra prediction unit 102 or the inter prediction unit 103.

The transform unit 105 may transform the residual block including the residual data by using a transformation method such as DCT, DST, or Karhunen Loeve Transform (KLT). In this case, the conversion method may be determined based on an intra prediction mode of the prediction unit used to generate the residual block. For example, according to the intra prediction mode, DCT may be used in the horizontal direction and DST may be used in the vertical direction. Alternatively, different transformation techniques may be used in the horizontal and vertical directions depending on the aspect ratio, size, and the like of the current block.

The quantization unit 106 may quantize the values converted in the frequency domain by the transformer 105. The quantization coefficient may change depending on the block or the importance of the image. The value calculated by the quantization unit 106 may be provided to the inverse quantization unit 108 and the entropy encoding unit 107.

The transform unit 105 and / or the quantization unit 106 may be selectively included in the image encoding apparatus 100. That is, the image encoding apparatus 100 may encode the residual block by performing at least one of transform or quantization on the residual data of the residual block, or skipping both transform and quantization. Even if neither the transformation nor the quantization is performed or neither the transformation nor the quantization is performed in the image encoding apparatus 100, a block entering the input of the entropy encoder 107 is generally referred to as a transform block.

The entropy encoder 107 entropy encodes the input data. Entropy coding may use various coding methods such as, for example, Exponential Golomb, Context-Adaptive Variable Length Coding (CAVLC), and Context-Adaptive Binary Arithmetic Coding (CABAC).

The entropy encoder 107 may be configured to perform various operations such as coefficient information, block type information, prediction mode information, split unit information, prediction unit information, transmission unit information, motion vector information, reference frame information, interpolation information of a transform block, filtering information, and the like. Information can be encoded. The coefficients of the transform block may be encoded in units of sub blocks within the transform block.

Last_sig, a syntax element that informs the position of the first non-zero coefficient in reverse scan order for coding of coefficients of the transform block, Coded_sub_blk_flag, which is a flag indicating whether there is at least one non-zero coefficient in a subblock, Sig_coeff_flag, a flag that indicates whether the coefficient is non-zero, Abs_greater1_flag, which indicates whether the coefficient is greater than 1, Abs_greater2_flag, which indicates whether the coefficient is greater than 2, and Sign_flag, which indicates the sign of the coefficient. Syntax elements may be encoded. Residual values of coefficients not encoded with only the syntax elements may be encoded through the syntax element remaining_coeff.

The inverse quantization unit 108 and the inverse transformer 109 inverse quantize the quantized values in the quantization unit 106 and inverse transform the transformed values in the transformer 105. The residual values generated by the inverse quantizer 108 and the inverse transformer 109 are predicted by the motion estimation unit, the motion compensator, and the intra prediction unit 102 included in the predictors 102 and 103. It may be combined with the prediction unit to generate a reconstructed block. The adder 110 generates a reconstructed block by adding the prediction blocks generated by the predictors 102 and 103 and the residual blocks generated by the inverse transform unit 109.

The filter unit 111 may include at least one of a deblocking filter, an offset corrector, and an adaptive loop filter (ALF).

The deblocking filter may remove block distortion caused by boundaries between blocks in the reconstructed picture. To determine whether to perform deblocking, it may be determined whether a deblocking filter is applied to the current block based on pixels included in several columns or rows included in the block. When the deblocking filter is applied to the block, a strong filter or a weak filter may be applied according to the required deblocking filtering strength. In addition, in applying the deblocking filter, horizontal filtering and vertical filtering may be performed in parallel when vertical filtering and horizontal filtering are performed.

The offset correction unit may correct the offset with respect to the original image on a pixel-by-pixel basis for the deblocking image. In order to perform offset correction for a specific picture, the pixels included in the image are divided into a predetermined number of areas, and then, an area to be offset is determined, an offset is applied to the corresponding area, or offset considering the edge information of each pixel. You can use this method.

Adaptive Loop Filtering (ALF) may be performed based on a value obtained by comparing the filtered reconstructed image with the original image. After dividing the pixels included in the image into a predetermined group, one filter to be applied to the group may be determined and filtering may be performed for each group. For information related to whether to apply ALF, a luminance signal may be transmitted for each coding unit (CU), and the shape and filter coefficient of an ALF filter to be applied may vary according to each block. In addition, regardless of the characteristics of the block to be applied, the same type (fixed form) of the ALF filter may be applied.

The memory 112 may store a reconstructed block or picture calculated by the filter unit 111, and the stored reconstructed block or picture may be provided to the predictors 102 and 103 when performing inter prediction.

2 is a diagram illustrating an embodiment of a prediction unit of an image encoding apparatus.

When the prediction mode of the current block is the intra prediction mode, the intra prediction unit 201 may generate the reference pixel by deriving a reference pixel from the periphery of the current block and filtering the reference pixel. The reference pixel is determined using the reconstructed pixels around the current block. If some restored pixels are not available or no restored pixels are in the vicinity of the current block, the available reference pixels may be padded in an area where the available reference pixels are not available or padded using an intermediate value of a range of values that the pixels may have. . After deriving all of the reference pixels, the reference pixels may be filtered using an adaptive intra smoothing (AIS) filter.

The intra prediction mode search unit 202 may determine one of the M intra prediction modes. M represents the total number of intra prediction modes. The intra prediction mode includes a directional prediction mode and a non-directional prediction mode.

The prediction block is generated using the determined prediction mode and the filtered reference pixel. By comparing the RD-Cost for each intra prediction mode, one of the lowest cost prediction modes may be selected.

The inter prediction unit 203 may be divided into a merge candidate search unit 204 and an AMVP candidate search unit 206 according to a method of deriving motion information. The Merger candidate searcher 204 sets a reference block in which inter prediction is used among blocks reconstructed around the current block as a merge candidate. Merge candidates are derived in the same manner in the encoding / decoding apparatus and use the same number. The number of merge candidates is transmitted from the encoding apparatus to the decoding apparatus or uses a predetermined number. When a predetermined number of Megre candidates are not derived from reference blocks reconstructed around the current block, motion information of blocks existing at the same position as the current block in pictures other than the current picture may be used as merge candidates. Alternatively, the motion information of the past direction and the motion information of the future direction may be combined with respect to the current picture to derive the insufficient merge candidate. Alternatively, a block at the same position of another reference picture may be set as a merge candidate.

The AMVP candidate searcher 206 determines the motion information of the current block by the motion estimation unit 207. The motion estimator 207 finds the predicted block most similar to the current block from the reconstructed pictures.

When inter prediction is performed, motion information of the current block is determined using one of the merge candidate searcher 204 and the AMVP candidate searcher 206, and the motion compensation 208 predicts the motion based on the determined motion information. Create a block.

3 is a diagram for describing an embodiment of encoding encoding information by a video encoding apparatus.

In step S301, operation information of the SKIP mode is encoded. The prediction of the current block in the skip mode uses the merge mode, and the decoding apparatus uses the prediction block of the current block as a reconstruction block. In step S302 of inter prediction, it is determined whether the SKIP mode is operated. If the SKIP mode operates in step S302 (Yes), after the MERGE candidate index information for the SKIP mode is encoded in step S307, the flowchart ends. If the SKIP mode does not operate in step S302 (No), the prediction mode is encoded in step S303. In step S304, it is determined whether the prediction mode is inter prediction or intra prediction. If the prediction mode is the inter prediction mode in step S304 (Yes), operation information of the MERGE mode is encoded in step S305. In step S306 it is determined whether the MERGE mode operation. If the MERGE mode operates in step S306 (Yes), the flow proceeds to step S307 after encoding the MERGE candidate index information for the MERGE mode, and ends the flowchart. If the MERGE mode does not operate in step S306 (No), the prediction direction is encoded in step S308. The prediction direction may be one of a past direction, a future direction, and a bidirectional direction. In step S309 it is determined whether the prediction direction is the future direction. If the prediction direction is not the future direction in step S309 (Yes), the reference picture index information of the past direction is encoded in step S310. In step S311, MVD (Motion Vector Difference) information of the past direction is encoded. In step S312, MVP (Motion Vector Predictor) information of the past direction is encoded. In step S309, if the prediction direction is a future direction or bidirectional (No), or after step S312, it is determined in step S313 whether the prediction direction is a past direction. If the prediction direction is not the past direction in step S313 (Yes), the future direction reference picture index information is encoded in step S314. In step S315, MVD information of a future direction is encoded. In step S316, after encoding the MVP information of the future direction, the flowchart ends. The encoding of the information performed in steps S305 to S316 may be referred to as inter picture prediction unit mode information encoding.

If the prediction mode is the intra prediction mode at step S304 (No), at operation S317, operation information of the Most Probable Mode (MPM) mode is encoded. In the MPM mode, the prediction mode in the MPM candidate screen is configured by using the reconstructed intra prediction mode around the current block, and then the information of the optimal intra prediction mode of the current block determined by the image encoding apparatus is in the prediction mode in the MPM candidate screen. If present, it means a method of transmitting the prediction mode index information in the MPM candidate screen. In operation S318, it is determined whether the MPM mode is operated. The MPM mode is a mode for encoding index information when there is a same mode as that of the current block among prediction modes of a reconstructed block around the current block. If the MPM mode operation is true (Yes) in step S318, index information of the prediction mode in the MPM candidate screen is encoded in step S319. If the operation of the MPM mode is false in step S318 (No), in step S320, luma optimal intra prediction mode information is encoded among luma prediction modes other than the prediction mode in the MPM candidate screen.

After the steps S319 and S320 are finished, after encoding the optimal intra prediction mode information of Chroma, the flowchart may be terminated. In this case, the module performing the steps S308 to S316 may be referred to as a motion information encoder. In addition, the module performing the steps S317 to S320 may be referred to as a luma picture prediction mode encoder.

4 is a diagram illustrating a configuration of an image decoding apparatus 400.

The image decoding apparatus 400 includes an entropy decoder 401, an inverse quantizer 402, an inverse transformer 403, an adder 404, a filter 405, a memory 406, and a predictor 407, 408. ) May be included.

When the image bitstream generated by the image encoding apparatus 100 is input to the image decoding apparatus 200, the input bitstream may be decoded according to a process opposite to that performed by the image encoding apparatus 100. .

The entropy decoder 401 may perform entropy decoding in a procedure opposite to that of the entropy encoding unit 407 of the image encoding apparatus 100. For example, various methods such as Exponential Golomb, Context-Adaptive Variable Length Coding (CAVLC), and Context-Adaptive Binary Arithmetic Coding (CABAC) may be applied to the method performed by the image encoder. The entropy decoder 401 may decode the syntax elements described above, that is, Last_sig, Coded_sub_blk_flag, Sig_coeff_flag, Abs_greater1_flag, Abs_greater2_flag, Sign_flag, and remaining_coeff. The entropy decoder 401 may decode information related to intra prediction and inter prediction performed by the image encoding apparatus 100.

The inverse quantization unit 402 generates a transform block by performing inverse quantization on the quantized transform block. It operates substantially the same as the inverse quantizer 108 of FIG.

The inverse transform unit 403 performs inverse transform on the transform block to generate a residual block. In this case, the conversion method may be determined based on information on a prediction method (inter prediction or intra prediction), the size and / or shape of a block, an intra prediction mode, and the like. The inverse transform unit 403 operates substantially the same as the inverse transform unit 109 of FIG. 1.

The adder 404 generates a reconstructed block by adding the prediction block generated by the intra prediction unit 407 or the inter prediction unit 408 and the residual block generated by the inverse transform unit 403. The adder 404 operates substantially the same as the adder 110 of FIG. 1.

The filter unit 405 reduces various kinds of noise generated in the restored blocks.

The filter unit 405 may include a deblocking filter, an offset correction unit, and an ALF.

When the deblocking filter is applied and information about whether the deblocking filter is applied to the corresponding block or picture, the image encoding apparatus 100 may receive information about whether a strong filter or a weak filter is applied. In the deblocking filter of the image decoding apparatus 400, the deblocking filter related information provided by the image encoding apparatus 100 may be provided, and the image decoding apparatus 400 may perform deblocking filtering on the corresponding block.

The offset correction unit may perform offset correction on the reconstructed image based on the type of offset correction and offset value information applied to the image during encoding.

The ALF may be applied to a coding unit based on ALF application information, ALF coefficient information, and the like provided from the image encoding apparatus 100. Such ALF information may be provided included in a specific parameter set. The filter unit 205 operates substantially the same as the filter unit 111 of FIG. 1.

The memory 406 stores the reconstruction block generated by the adder 404. It operates substantially the same as the memory 112 of FIG.

5 is an exemplary diagram illustrating a configuration of a prediction unit of an image decoding device.

The intra prediction unit 501 generates a reference pixel, and the intra prediction mode determiner 502 may determine the intra prediction mode based on the signaled information. A prediction block is generated based on the generated reference pixel and the intra prediction mode. The image decoding apparatus does not perform the prediction mode determination process performed by the image encoding apparatus.

The inter prediction unit 503 does not only perform the process of determining the optimal prediction mode of FIG. 2, but decodes the prediction mode based on the signaled information, and generates a prediction block based on the signal encoding apparatus. Is substantially the same as the inter prediction unit.

FIG. 6 is a diagram for describing an embodiment of decoding encoding information by a video decoding apparatus. FIG.

In operation S601, operation information of the SKIP mode is decoded. In step S602 it is determined whether the SKIP mode operation. If the SKIP mode operates in step S602 (Yes), after decoding the MERGE candidate index information for the SKIP mode in step S607, the flowchart ends. If the SKIP mode does not operate in step S602 (No), the prediction mode is decoded in step S603. In step S604, it is determined whether the prediction mode is inter prediction or intra prediction. If the prediction mode is the inter prediction mode in step S604 (Yes), operation information of the MERGE mode is decoded in step S605. In step S606 it is determined whether the MERGE mode operation. If the MERGE mode operates in step S606 (Yes), the flow proceeds to step S607 after decoding the MERGE candidate index information for the MERGE mode, and ends the flowchart. If the MERGE mode does not operate in step S606 (No), the prediction direction is decoded in step S608. The prediction direction may be one of a past direction, a future direction, and a bidirectional direction. In step S609, it is determined whether the prediction direction is a future direction. If the prediction direction is not the future direction in step S609 (Yes), the reference picture index information of the past direction is decoded in step S610. In step S611, MVD (Motion Vector Difference) information in the past direction is decoded. In operation S612, the motion vector predictor (MVP) information of the past direction is decoded. In step S609, if the prediction direction is a future direction or bidirectional (No), and after step S612, it is determined in step S613 whether the prediction direction is the past direction. If the prediction direction is not the past direction in step S613 (Yes), the future direction reference picture index information is decoded in step S614. In step S615, the MVD information of the future direction is decoded. In step S616, after decoding the MVP information of the future direction, the flowchart ends. If the prediction mode is the intra prediction mode at step S604 (No), the MPM mode operation information is decoded at step S617. In operation S618, it is determined whether the MPM mode is operated. If the MPM mode operation is true in step S618 (Yes), index information of the prediction mode in the MPM candidate screen is decoded in step S619. If the MPM mode operation is false at step S618 (No), at step S620, the luma optimal intra prediction mode information of the luma is decoded among the prediction modes other than the prediction mode within the MPM candidate screen. After the steps S619 and S620 are finished, after decoding the optimal intra prediction mode information of Chroma, the flowchart may be terminated.

Example 1

FIG. 7 illustrates an example of intra prediction using a plurality of reference pixel lines.

In the example shown in FIG. 7, the current encoding target block is 4x4 in size, and the intra prediction mode is the right top diagonal direction mode.

8 is a diagram for describing another embodiment of intra prediction using a plurality of reference pixel lines.

9 is an exemplary diagram illustrating an intra prediction unit of an image encoding apparatus using one or more reference pixel lines.

The intra prediction unit of FIG. 9 will be described below with reference to FIGS. 7 and 8. When intra prediction is selected as the prediction mode of the current block, the reference pixel generator 901 generates and filters reference pixels for each reference pixel line. The reference pixel generator 901 may perform the same process as the intra prediction unit 201 of FIG. 2.

Thereafter, the virtual reference pixel generation determiner 902 determines whether the virtual reference pixel line is used and the virtual reference pixel line generation position. The virtual reference pixel line generates a virtual reference pixel line between integer reference pixel lines according to a prediction direction, and uses the same as the reference pixel. The virtual reference pixel lines may generate one or more between integer position reference pixel lines. In this case, the real position may be a position obtained by dividing the distance of two integer position reference pixel lines, or may be a position close to the integer position reference pixel line determined to be optimal. The virtual reference pixel line information may be the same as a preset value in the encoding / decoding apparatus or transmitted in an upper header. The upper header refers to upper header information including block information such as a video parameter stage, a sequence parameter stage, a picture parameter stage, and a slice stage. Alternatively, virtual reference pixel line information that may be generated for each block may be transmitted.

In FIG. 8, reference pixel line information 0 may refer to a first line, reference pixel line information 1 refers to a second line, reference pixel line information 2 refers to a third line, and reference pixel line information 3 refers to a fourth line. A method of generating a virtual reference pixel line will be described as an example of a method of generating 3.5 lines, which are real reference pixel lines, between a third line and a fourth line. As shown in FIG. 8, when the reference pixels pass through the reference pixels E and F, the average value of the E and F pixel values is set to the G pixel values of 3.5 lines.

The reference pixel line combination determination unit 903 selects the reference pixel line combination K. FIG. The reference pixel line combination is a combination of one or more reference pixel line information as one set. In FIG. 7, reference pixel line information 0 refers to a first line, reference pixel line information 1 refers to a second line, reference pixel line information 2 refers to a third line, and reference pixel line information 3 refers to a fourth line. K is an index of a reference pixel line combination, and each index may indicate a combination of one or more reference pixel lines. The information about the K reference pixel line combinations may be set identically in the encoding / decoding apparatus or transmitted in the upper header. Alternatively, reference pixel line information corresponding to the index K may be directly transmitted for each block. For example, if K is 0, the reference pixel line uses only the first line; if K is 1, the reference pixel line uses the first and second lines; if K is 2, the reference pixel line The third line can be made available. The combination indicated by the index K may include not only the reference pixel line but also the virtual reference pixel line.

Hereinafter, a prediction block generation method will be described with reference to FIG. 7. In this example, four reference pixel lines are used by K. In FIG. Four reference pixel lines may be used to obtain pixel values of A, B, C, and D pixels in the prediction block. A line, B line, C line, and D line indicate the prediction directions of A pixel, B pixel, C pixel, and D pixel, respectively. For example, an average of reference pixel values that pass through the A, B, C, and D lines may be used as the prediction value of each pixel. Alternatively, a weight may be applied to each reference pixel line and used as a prediction value of the pixel. The method of applying the weight is as shown in Equation 1, for example.

In Equation 1, P denotes a predicted pixel value to which a weight is applied, and P1 and P2 denote available reference pixels. Α and β are weight information. For example, a higher weight may be applied to a reference pixel line closer to the current block. The weight applied to each reference pixel line may be a predetermined value in the encoding / decoding apparatus or may be transmitted in the same or higher header. Alternatively, weight information applied to each block may be transmitted.

The intra prediction mode determiner 904 performs the same process as the intra prediction mode search unit 202 of FIG. 2. All processes in the intra prediction unit 900 of the image encoding apparatus compare costs using RD-Cost, and then select prediction information of one intra prediction mode, for example, an optimal intra prediction mode.

10 is an exemplary diagram illustrating an intra prediction unit of an image decoding apparatus using one or more reference pixel lines.

When intra prediction is selected as the current prediction mode, the reference pixel generator 1001 may generate and filter the reference pixels. The virtual reference pixel generation determiner 1002 may restore the virtual reference pixel lines transmitted from the encoding apparatus, and the reference pixel line combination determiner 1003 may restore the combination index K. FIG. The intra prediction mode determiner 1004 may reconstruct the intra prediction mode and generate a prediction block using the reconstructed one or more reference pixel lines.

11 is a diagram for describing a method of encoding prediction mode information according to an embodiment of the present invention.

FIG. 11 illustrates the addition of the virtual reference pixel line information encoding S1105 and the reference pixel line combination encoding S1106 in the embodiment described with reference to FIG. 3. The procedure except for S1105 and S1106 is the same as in the embodiment of FIG. 3.

12 is a diagram for describing a method of decoding prediction mode information according to an embodiment of the present invention.

FIG. 12 illustrates the addition of the virtual reference pixel line information decoding S1205 and the reference pixel line combination decoding S1206 in the embodiment described with reference to FIG. 6. The procedure except for S1205 and S1406 is the same as in the embodiment of FIG. 6.

(Example 2)

FIG. 13 is a diagram for describing an intra prediction unit of a video encoding apparatus according to another embodiment. FIG.

When intra prediction is selected as the prediction mode of the current block, a method of generating a prediction block depends on whether the intra prediction mode is transmitted. The intra prediction information may be information indicating whether the intra prediction mode is transmitted from the encoding apparatus to the decoding apparatus.

When the intra prediction mode is transmitted, the mode encoder 1301 is selected, and then the reference pixel generator 1303, the virtual reference pixel generation determiner 1304, the reference pixel line combination determiner 1305, and the screen are displayed. The prediction block may be generated through the prediction mode determiner 1306. Each of the reference pixel generator 1303, the virtual reference pixel generation determiner 1304, the reference pixel line combination determiner 1305, and the intra prediction mode determiner 1306 may be the reference pixel generator 901 of FIG. 9. The virtual reference pixel generation determiner 902, the reference pixel line combination determiner 903, and the intra prediction mode determiner 904 may correspond to each other.

When the intra prediction mode is not transmitted, the decoder-side intra prediction mode derivation (DIMD) encoder 1302 is selected, and then the same process is performed by the encoding apparatus and the decoding apparatus to generate the prediction block.

When the DIMD encoder is selected, a method of determining an optimal prediction mode will be described using the example of FIG. 7. In FIG. 7, reference pixel line information 0 refers to a first line, reference pixel line information 1 refers to a second line, reference pixel line information 2 refers to a third line, and reference pixel line information 3 refers to a fourth line. The process of finding the best intra prediction mode using the optimal reference pixel line combination is performed by using the prediction block generated according to each intra prediction mode using the currently selected reference pixel line combination and the previous reference pixel line combination. Two prediction blocks may be performed by selecting intra prediction modes that are most similar to each other by comparing distortion information between prediction blocks generated according to intra prediction modes. The optimal reference pixel line combination selection may be selected in the same manner in the encoding / decoding apparatus among K and K-1, or may be transmitted in an upper header. Alternatively, whether to select a current reference pixel line combination and a previous reference pixel line combination may be transmitted for each block. For example, in FIG. 7, when K is the fourth reference pixel line and K-1 is the third reference pixel line, the prediction block and K-1 generated by each prediction mode in each screen using K are used. By comparing the distortions between the prediction blocks generated for each intra prediction mode, the intra prediction mode having the least distortion may be determined as the optimal intra prediction mode. In this case, SAD, SSE, SATD, etc. may be used to compare the distortion.

FIG. 14 is a diagram for describing an intra prediction unit of an image decoding apparatus according to another exemplary embodiment.

When intra prediction is selected as the current prediction mode, a prediction block generation method varies according to intra prediction information.

When the intra prediction mode is transmitted from the encoding apparatus to the decoding apparatus, the mode decoder 1401 is selected, and then, the reference pixel generator 1403, the virtual reference pixel generation determiner 1404, and the reference pixel line combination determination are performed. The prediction block may be generated through the unit 1405 and the intra prediction mode determiner 1406. Each of the reference pixel generator 1403, the virtual reference pixel generation determiner 1404, the reference pixel line combination determiner 1405, and the intra prediction mode determiner 1406 is a reference pixel generator 1001 of FIG. 10. The virtual reference pixel generation determiner 1002, the reference pixel line combination determiner 1003, and the intra prediction mode determiner 1004 may correspond to each other.

When the intra prediction mode is not transmitted from the encoding apparatus to the decoding apparatus, the DIMD decoder 1402 is selected, and the subsequent process may be the same as the process described with reference to FIG. 13.

15 is a diagram for describing a method of encoding prediction mode information according to an embodiment of the present invention.

FIG. 15 illustrates the addition of DIMD information encoding (S1505), virtual reference pixel line encoding (S1506), and reference pixel line combination encoding (S1507) in the embodiment described with reference to FIG. The procedures other than the above added steps are the same as in the embodiment of FIG. 3.

16 is a diagram for describing a method of decoding prediction mode information according to an embodiment of the present invention.

FIG. 16 adds DIMD information decoding (S1605), virtual reference pixel line decoding (S1606), and reference pixel line combination decoding (S1607) in the embodiment described with reference to FIG. The procedures other than the above added steps are the same as in the embodiment of FIG. 6.

The DIMD information may be information indicating whether to transmit the intra prediction mode to the decoding apparatus or determine whether the optimal prediction mode is determined by performing the same process in the encoding / decoding apparatus.

Example 3

17 is a diagram for describing a method of performing intra prediction according to another embodiment of the present invention.

In FIG. 17, a block to be encoded has a size of 4 × 4, and an intra prediction mode is a right upper direction mode.

18 is a diagram for explaining an intra prediction unit of a video encoding apparatus according to another embodiment.

The intra prediction unit of FIG. 18 may generate a prediction block using a unidirectional or bidirectional prediction mode.

The bidirectional prediction and intra picture prediction mode determiner 1804 of the embodiment of FIG. 18 adds bidirectional prediction to the intra picture prediction mode determiner 904 of the embodiment of FIG. 9, and another configuration of the embodiment of FIG. 18 is illustrated in FIG. 9. Same as the embodiment of.

A prediction block generation method according to the present embodiment will be described with reference to FIG. 17. Unidirectional or bidirectional prediction may be performed according to the intra prediction mode. In the case of unidirectional prediction, a prediction block is generated using reference pixel lines in one direction according to the intra prediction mode. In the case of bidirectional prediction, as illustrated in FIG. 17, a prediction block may be generated using a weighted sum between a reference pixel selected by unidirectional prediction and a reference pixel line opposite to the unidirectional prediction direction. . For example, if the unidirectional is rightward and the first reference pixel line is available, the reference pixel on the first reference pixel line located rightward of the pixel in the current block can be selected. Further, the reference pixel on the first reference pixel line positioned in the lower left direction, which is opposite to the upper right direction, can be selected. The predicted value of the pixel may be derived by weighting the selected reference pixels.

The weights applied to each of the selected reference pixels may be the same or may be different. For example, according to the distance between the prediction pixel to be coded in the current block and the reference pixel, a higher weight may be applied to the reference pixel having a closer distance than the reference pixel having a far distance. Alternatively, in the case of bidirectional prediction, a weight higher than that of the reference pixel in the opposite direction may be applied to the reference pixel of the unidirectional prediction. The weight applied to each reference pixel line may be the same as a preset value in the encoding / decoding apparatus or transmitted in an upper header. Alternatively, the weight value applied to each block may be transmitted and used in the encoding / decoding apparatus.

In the bidirectional prediction, a region without a reconstructed reference pixel may be used as a reference pixel by padding or interpolating surrounding reference pixel values. For example, the H pixel and I pixel values may be padded to be used as reference pixels of an area without a reference pixel, for example, a right area and a bottom area of the current block. In this case, a portion where the right region and the bottom region overlap may be padded with, for example, an average value of the H pixel and the I pixel.

Alternatively, the padding may be padded with an average value or a weighted average value of the H set, an average value or a weighted average value of the I set. For example, the weight applied to the weighted average value may be 1: 2: 1. Alternatively, the padding may be first performed using the weighted average value of the H set and the weighted average value of the I set, and then the padded value may be filtered using the brightness change of the reference pixels of the unidirectional prediction according to the intra prediction mode.

The H set may include H pixels and their adjacent pixels. For example, the H set may include an H pixel and a left adjacent pixel and a right adjacent pixel of the H pixel. Likewise, an I set may include an I pixel and its neighboring pixels. For example, the I set may include an I pixel and an upper adjacent pixel and a lower adjacent pixel of the I pixel.

In the example of FIG. 17, for convenience of description, padding for an area in which no pixel is reconstructed in bidirectional prediction has been described for only one reference pixel line. However, the present invention is not limited thereto, and padding of a region without reconstructed pixels may be performed on some or all of the plurality of reference pixel lines.

The intra prediction unit of the image encoding apparatus of FIG. 18 may compare the RD-Cost cost in each process to determine optimal prediction information.

FIG. 19 is a diagram for explaining an intra prediction unit of a video decoding apparatus according to another exemplary embodiment.

When intra prediction is selected as the current prediction mode, the reference pixel generator 1901 may derive the reference pixel and perform filtering. The virtual reference pixel generation determiner 1902 may determine a virtual reference pixel line based on the information transmitted from the encoding apparatus, and the reference pixel line combination determiner 1901 may determine an optimal reference pixel line combination. The bidirectional prediction and intra prediction mode determiner 1904 may determine the intra prediction mode and generate a prediction block based on the intra prediction mode.

20 is a diagram for describing a method of encoding prediction mode information according to an embodiment of the present invention.

FIG. 20 illustrates the virtual reference pixel line information encoding (S2005), the reference pixel line combination encoding (S2006), and the bidirectional prediction information encoding (S2007) in the embodiment described with reference to FIG. 3. The procedures other than the above added steps are the same as in the embodiment of FIG. 3.

21 is a diagram for describing a method of decoding prediction mode information according to an embodiment of the present invention.

21 is a view illustrating the addition of virtual reference pixel line information decoding (S2105), reference pixel line combination decoding (S2106), and bidirectional prediction information decoding (S2107) in the embodiment described with reference to FIG. The procedures other than the above added steps are the same as in the embodiment of FIG. 6.

The various embodiments of the present disclosure are not an exhaustive list of all possible combinations, but are intended to describe representative aspects of the present disclosure, and the details described in the various embodiments may be applied independently or in combination of two or more.

In addition, various embodiments of the present disclosure may be implemented by hardware, firmware, software, a combination thereof, or the like. For hardware implementations, one or more Application Specific Integrated Circuits (ASICs), Digital Signal Processors (DSPs), Digital Signal Processing Devices (DSPDs), Programmable Logic Devices (PLDs), Field Programmable Gate Arrays (FPGAs), General Purpose It may be implemented by a general processor, a controller, a microcontroller, a microprocessor, and the like.

It is intended that the scope of the disclosure include software or machine-executable instructions (eg, an operating system, an application, firmware, a program, etc.) to cause an operation in accordance with various embodiments of the method to be executed on an apparatus or a computer, and such software or Instructions, and the like, including non-transitory computer-readable media that are stored and executable on a device or computer.

Claims (17)

Restoring reference pixel line information;
Selecting at least one reference pixel line among a plurality of reference pixel lines based on the reference pixel line information; And
And generating a prediction block for the current block by performing intra prediction on the current block based on the selected reference pixel line. The method of claim 1,
And the reference pixel line information is decoded in units of blocks. The method of claim 1,
The prediction block is generated by performing a weighted summation between an upper reference pixel of the current block and a left reference pixel of the current block. The method of claim 3,
And the upper reference pixel and the left reference pixel are selected based on a prediction direction of the current block. The method of claim 3,
The upper reference pixel and the left reference pixel are on a first reference pixel line adjacent to the current block,
And the upper reference pixel and the left reference pixel are selected based on the coordinates of the current pixel in the current block. The method of claim 5,
When the coordinate of the upper left pixel in the current block is (0, 0) and the coordinate of the current pixel is (x, y),
The coordinates of the upper reference pixel are (x + y + 1, -1),
And a coordinate of the left reference pixel is (-1, x + y + 1). The method of claim 3,
The weight used for the weighted sum is determined based on a distance from a current pixel in the current block to the upper reference pixel and the left reference pixel. The method of claim 7, wherein
And a larger weight is applied to a reference pixel having a shorter distance from the current pixel among the upper reference pixel and the left reference pixel. Selecting at least one reference pixel line among the plurality of reference pixel lines;
Generating a prediction block for the current block by performing intra prediction on the current block based on the selected reference pixel line; And
And encoding reference pixel line information about the selected reference pixel line. The method of claim 9,
And the reference pixel line information is encoded in block units. The method of claim 9,
The prediction block is generated by performing a weighted summation between an upper reference pixel of the current block and a left reference pixel of the current block. The method of claim 11,
And the upper reference pixel and the left reference pixel are selected based on a prediction direction of the current block. The method of claim 11,
The upper reference pixel and the left reference pixel are on a first reference pixel line adjacent to the current block,
And the upper reference pixel and the left reference pixel are selected based on the coordinates of the current pixel in the current block. The method of claim 13,
When the coordinate of the upper left pixel in the current block is (0, 0) and the coordinate of the current pixel is (x, y),
The coordinates of the upper reference pixel are (x + y + 1, -1),
And a coordinate of the left reference pixel is (-1, x + y + 1). The method of claim 11,
The weighting value used for the weighted sum is determined based on a distance from a current pixel in the current block to the upper reference pixel and the left reference pixel. The method of claim 15,
And a larger weight is applied to a reference pixel having a shorter distance from the current pixel among the upper reference pixel and the left reference pixel. A computer-readable recording medium including a bitstream received by a video decoding apparatus and decoded to be used to restore an image.
The bitstream includes reference pixel line information,
The reference pixel line information is recovered and used to select at least one reference pixel line among a plurality of reference pixel lines,
And wherein the selected reference pixel line is used to generate a predictive block for the current block by performing in-picture prediction for the current block.

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