WO2019198984A1

WO2019198984A1 - Image coding method based on linear interpolation intra prediction and device therefor

Info

Publication number: WO2019198984A1
Application number: PCT/KR2019/004049
Authority: WO
Inventors: 최장원; 이령; 허진
Original assignee: 엘지전자 주식회사
Priority date: 2018-04-11
Filing date: 2019-04-05
Publication date: 2019-10-17

Abstract

A method by which a decoding device decodes a picture, according to the present invention, comprises the steps of: acquiring, from a bitstream, image information on a current block; deriving a right-bottom corner reference sample of the current block on the basis of neighboring reference samples of the current block; deriving bottom reference samples and right reference samples of the current block on the basis of the derived right-bottom corner reference sample; deriving prediction samples for the current block on the basis of at least one from among the neighboring reference samples, the bottom reference samples and the right reference samples of the current block; and generating restored samples for the current block on the basis of the prediction samples for the current block.

Description

Image Coding Method and Apparatus Based on Linear Interpolation Intra Prediction

The present invention relates to an image coding technique, and more particularly, to an image coding method and apparatus based on linear interpolation prediction (LIP) in an image coding system.

Recently, the demand for high resolution and high quality images such as high definition (HD) images and ultra high definition (UHD) images is increasing in various fields. The higher the resolution and the higher quality of the image data, the more information or bit rate is transmitted than the existing image data. Therefore, the image data can be transmitted by using a medium such as a conventional wired / wireless broadband line or by using a conventional storage medium. In the case of storage, the transmission cost and the storage cost are increased.

Accordingly, a high efficiency image compression technique is required to effectively transmit, store, and reproduce high resolution, high quality image information.

An object of the present invention is to provide a method and apparatus for improving image coding efficiency.

Another technical problem of the present invention is to provide a method and apparatus for increasing the efficiency of the LIP.

Another technical problem of the present invention is to provide a method and apparatus for increasing the efficiency of LIP based on a plurality of reference sample lines.

Another technical problem of the present invention is to provide a method and apparatus for increasing the efficiency of intra prediction by applying a weight to a reference sample in performing LIP.

According to an embodiment of the present invention, a picture decoding method performed by a decoding apparatus is provided. The method includes acquiring image information of a current block from a bitstream, and a right-bottom corner reference sample of the current block based on neighboring reference samples of the current block. Deriving, deriving lower reference samples and right reference samples of the current block based on the derived lower right corner reference sample, the peripheral reference samples, the lower reference samples, and the Deriving prediction samples for the current block based on at least one of the right reference samples and generating reconstruction samples for the current block based on the prediction samples for the current block. .

According to another embodiment of the present invention, a decoding device for performing picture decoding is provided. The decoding apparatus may include an entropy decoding unit configured to obtain image information of a current block from a bitstream, and a right-bottom corner reference sample of a current block based on neighboring reference samples of the current block. reference sample), derive the lower reference samples and the right reference samples of the current block based on the derived lower right corner reference sample, the peripheral reference samples, the lower reference samples and And a predictor for deriving prediction samples for the current block based on at least one of the right reference samples, and an adder for generating reconstruction samples for the current block based on the prediction samples for the current block. It is done.

According to the present invention, the overall video / video compression efficiency can be improved.

According to the present invention, the efficiency of intra prediction can be improved.

According to the present invention can increase the efficiency of the LIP.

According to the present invention, image coding efficiency may be improved by performing LIP based on a plurality of reference sample lines.

According to the present invention, in performing LIP, weights may be applied to reference samples to increase the efficiency of intra prediction.

1 is a diagram schematically illustrating a configuration of an encoding apparatus according to an embodiment.

2 is a diagram schematically illustrating a configuration of a decoding apparatus according to an embodiment.

3 is a diagram illustrating an example of intra prediction modes.

4 is a diagram illustrating another example of intra prediction modes.

5 is a diagram illustrating an LIP according to an embodiment.

6A and 6B illustrate a LIP according to another exemplary embodiment.

7 is a view for explaining a LIP according to another embodiment.

8 is a flowchart illustrating a method of determining an optimal prediction mode in intra prediction encoding, according to an embodiment.

9A and 9B are diagrams illustrating examples of a plurality of reference sample lines.

FIG. 10 is a diagram illustrating an example of deriving a lower right corner reference sample based on a plurality of reference sample lines for LIP.

11 is a flowchart illustrating an operation of performing LIP based on a plurality of reference sample lines according to an embodiment.

12 illustrates an example of performing a LIP by deriving a single reference sample line based on a plurality of reference sample lines, according to an embodiment.

FIG. 13 is a flowchart illustrating an operation of performing a LIP by deriving a single reference sample line based on a plurality of reference sample lines, according to an embodiment.

14A and 14B are diagrams illustrating an example of performing LIP based on peripheral reference samples located on the left and upper sides of the current block.

15 is a flowchart illustrating a method of operating a decoding apparatus, according to an embodiment.

16 is a block diagram illustrating a configuration of a decoding apparatus according to an embodiment.

As the present invention allows for various changes and numerous embodiments, particular embodiments will be illustrated in the drawings and described in detail in the written description. However, this is not intended to limit the invention to the specific embodiments. The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting of the spirit of the present invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. The terms "comprise" or "having" in this specification are intended to indicate that there is a feature, number, step, operation, component, part, or combination thereof described in the specification, and one or more other features It is to be understood that the numbers, steps, operations, components, parts or figures do not exclude in advance the presence or possibility of adding them.

On the other hand, each configuration in the drawings described in the present invention are shown independently for the convenience of description of the different characteristic functions, it does not mean that each configuration is implemented by separate hardware or separate software. For example, two or more of each configuration may be combined to form one configuration, or one configuration may be divided into a plurality of configurations. Embodiments in which each configuration is integrated and / or separated are also included in the scope of the present invention without departing from the spirit of the present invention.

The following description may be applied in the technical field dealing with video, image or video. For example, the method or embodiment disclosed in the following description may include the Versatile Video Coding (VVC) standard (ITU-T Rec. H.266), the next generation video / image coding standard after VVC, or standards prior to VVC (eg For example, it may be related to the disclosure of the High Efficiency Video Coding (HEVC) standard (ITU-T Rec. H.265, etc.).

Hereinafter, with reference to the accompanying drawings, it will be described in detail a preferred embodiment of the present invention. Hereinafter, the same reference numerals are used for the same components in the drawings, and redundant description of the same components is omitted.

In the present specification, a video may mean a series of images over time. A picture generally refers to a unit representing one image in a specific time zone, and a slice is a unit constituting a part of a picture in coding. One picture may be composed of a plurality of slices, and if necessary, the picture and the slice may be mixed with each other. Also, in some cases, an "image" may mean a concept including a still image and a video, which is a set of a series of still images over time. In addition, “video” does not necessarily mean a set of a series of still images over time, and in some embodiments, may be interpreted as a concept in which still images are included in video.

A pixel or a pel may refer to a minimum unit constituting one picture (or image). Also, 'sample' may be used as a term corresponding to a pixel. A sample may generally represent a pixel or a value of a pixel, and may only represent pixel / pixel values of the luma component, or only pixel / pixel values of the chroma component.

A unit represents the basic unit of image processing. The unit may include at least one of a specific region of the picture and information related to the region. The unit may be used interchangeably with terms such as block or area in some cases. In a general case, an M × N block may represent a set of samples or transform coefficients composed of M columns and N rows.

1 is a diagram schematically illustrating a configuration of a video encoding apparatus to which the present invention may be applied. Hereinafter, the encoding / decoding device may include a video encoding / decoding device and / or an image encoding / decoding device, and the video encoding / decoding device is used as a concept including the image encoding / decoding device, or the image encoding / decoding device is It may be used in a concept including a video encoding / decoding device.

Referring to FIG. 1, the (video) encoding apparatus 100 may include a picture partitioning module 105, a prediction module 110, a residual processing module 120, and an entropy encoding unit ( The entropy encoding module 130 may include an adder 140, a filtering module 150, and a memory 160. The residual processor 120 may include a substractor 121, a transform module 122, a quantization module 123, a rearrangement module 124, and a dequantization module 125. ) And an inverse transform module 126.

The picture divider 105 may divide the input picture into at least one processing unit.

As an example, the processing unit may be called a coding unit (CU). In this case, the coding unit may be recursively split from the largest coding unit (LCU) according to a quad-tree binary-tree (QTBT) structure. For example, one coding unit may be divided into a plurality of coding units of a deeper depth based on a quad tree structure, a binary tree structure, and / or a ternary tree structure. In this case, for example, the quad tree structure may be applied first, and the binary tree structure and the ternary tree structure may be applied later. Alternatively, the binary tree structure / tunary tree structure may be applied first. The coding procedure according to the present invention may be performed based on the final coding unit that is no longer split. In this case, the maximum coding unit may be used as the final coding unit immediately based on coding efficiency according to the image characteristic, or if necessary, the coding unit is recursively divided into coding units of lower depths and optimized. A coding unit of size may be used as the final coding unit. Here, the coding procedure may include a procedure of prediction, transform, and reconstruction, which will be described later.

As another example, the processing unit may include a coding unit (CU) prediction unit (PU) or a transform unit (TU). The coding unit may be split from the largest coding unit (LCU) into coding units of deeper depths along the quad tree structure. In this case, the maximum coding unit may be used as the final coding unit immediately based on coding efficiency according to the image characteristic, or if necessary, the coding unit is recursively divided into coding units of lower depths and optimized. A coding unit of size may be used as the final coding unit. If a smallest coding unit (SCU) is set, the coding unit may not be split into smaller coding units than the minimum coding unit. Here, the final coding unit refers to a coding unit that is the basis of partitioning or partitioning into a prediction unit or a transform unit. The prediction unit is a unit partitioning from the coding unit and may be a unit of sample prediction. In this case, the prediction unit may be divided into sub blocks. The transform unit may be divided along the quad tree structure from the coding unit, and may be a unit for deriving a transform coefficient and / or a unit for deriving a residual signal from the transform coefficient. Hereinafter, a coding unit may be called a coding block (CB), a prediction unit is a prediction block (PB), and a transform unit may be called a transform block (TB). A prediction block or prediction unit may mean a specific area in the form of a block within a picture, and may include an array of prediction samples. In addition, a transform block or a transform unit may mean a specific area in a block form within a picture, and may include an array of transform coefficients or residual samples.

The prediction unit 110 performs prediction on a block to be processed (hereinafter, may mean a current block or a residual block), and generates a predicted block including prediction samples for the current block. can do. The unit of prediction performed by the prediction unit 110 may be a coding block, a transform block, or a prediction block.

The prediction unit 110 may determine whether intra prediction or inter prediction is applied to the current block. As an example, the prediction unit 110 may determine whether intra prediction or inter prediction is applied on a CU basis.

In the case of intra prediction, the prediction unit 110 may derive a prediction sample for the current block based on reference samples outside the current block in the picture to which the current block belongs (hereinafter, referred to as the current picture). In this case, the prediction unit 110 may (i) derive the prediction sample based on the average or interpolation of neighboring reference samples of the current block, and (ii) the neighbor reference of the current block. The prediction sample may be derived based on a reference sample present in a specific (prediction) direction with respect to the prediction sample among the samples. In case of (i), it may be called non-directional mode or non-angle mode, and in case of (ii), it may be called directional mode or angular mode. In intra prediction, the prediction mode may have, for example, 33 directional prediction modes and at least two non-directional modes. The non-directional mode may include a DC prediction mode and a planner mode (Planar mode). The prediction unit 110 may determine the prediction mode applied to the current block by using the prediction mode applied to the neighboring block.

In the case of inter prediction, the prediction unit 110 may derive the prediction sample for the current block based on the sample specified by the motion vector on the reference picture. The prediction unit 110 may apply one of a skip mode, a merge mode, and a motion vector prediction (MVP) mode to derive a prediction sample for the current block. In the skip mode and the merge mode, the prediction unit 110 may use the motion information of the neighboring block as the motion information of the current block. In the skip mode, unlike the merge mode, the difference (residual) between the prediction sample and the original sample is not transmitted. In the MVP mode, the motion vector of the current block may be derived using the motion vector of the neighboring block as a motion vector predictor.

In the case of inter prediction, the neighboring block may include a spatial neighboring block existing in the current picture and a temporal neighboring block present in the reference picture. A reference picture including the temporal neighboring block may be called a collocated picture (colPic). The motion information may include a motion vector and a reference picture index. Information such as prediction mode information and motion information may be encoded (entropy) and output in the form of a bitstream.

When the motion information of the temporal neighboring block is used in the skip mode and the merge mode, the highest picture on the reference picture list may be used as the reference picture. Reference pictures included in a reference picture list may be sorted based on a difference in a picture order count (POC) between a current picture and a corresponding reference picture. The POC corresponds to the display order of the pictures and may be distinguished from the coding order.

The subtraction unit 121 generates a residual sample which is a difference between the original sample and the prediction sample. When the skip mode is applied, residual samples may not be generated as described above.

The transform unit 122 generates transform coefficients by transforming the residual sample in units of transform blocks. The transform unit 122 may perform the transform according to the size of the transform block and the prediction mode applied to the coding block or the prediction block that spatially overlaps the transform block. For example, if intra prediction is applied to the coding block or the prediction block that overlaps the transform block, and the transform block is a 4 × 4 residual array, the residual sample is configured to perform a discrete sine transform (DST) transform kernel. The residual sample may be transformed using a discrete cosine transform (DCT) transform kernel.

The quantization unit 123 may quantize the transform coefficients to generate quantized transform coefficients.

The reordering unit 124 rearranges the quantized transform coefficients. The reordering unit 124 may reorder the quantized transform coefficients in the form of a block into a one-dimensional vector form through a coefficient scanning method. Although the reordering unit 124 has been described in a separate configuration, the reordering unit 124 may be part of the quantization unit 123.

The entropy encoding unit 130 may perform entropy encoding on the quantized transform coefficients. Entropy encoding may include, for example, encoding methods such as exponential Golomb, context-adaptive variable length coding (CAVLC), context-adaptive binary arithmetic coding (CABAC), and the like. The entropy encoding unit 130 may encode information necessary for video reconstruction other than the quantized transform coefficients (for example, a value of a syntax element) together or separately according to entropy encoding or a predetermined method. The encoded information may be transmitted or stored in units of network abstraction layer (NAL) units in the form of bitstreams. The bitstream may be transmitted over a network or may be stored in a digital storage medium. The network may include a broadcasting network and / or a communication network, and the digital storage medium may include various storage media such as USB, SD, CD, DVD, Blu-ray, HDD, SSD, and the like.

The inverse quantization unit 125 inverse quantizes the quantized values (quantized transform coefficients) in the quantization unit 123, and the inverse transformer 126 inverse transforms the inverse quantized values in the inverse quantization unit 125 to obtain a residual sample. Create

The adder 140 reconstructs the picture by combining the residual sample and the predictive sample. The residual sample and the predictive sample may be added in units of blocks to generate a reconstructed block. Although the adder 140 has been described in a separate configuration, the adder 140 may be part of the predictor 110. The adder 140 may also be called a reconstruction module or a restore block generator.

The filter unit 150 may apply a deblocking filter and / or a sample adaptive offset to the reconstructed picture. Through deblocking filtering and / or sample adaptive offset, the artifacts of the block boundaries in the reconstructed picture or the distortion in the quantization process can be corrected. The sample adaptive offset may be applied on a sample basis and may be applied after the process of deblocking filtering is completed. The filter unit 150 may apply an adaptive loop filter (ALF) to the reconstructed picture. ALF may be applied to the reconstructed picture after the deblocking filter and / or sample adaptive offset is applied.

The memory 160 may store reconstructed pictures (decoded pictures) or information necessary for encoding / decoding. Here, the reconstructed picture may be a reconstructed picture after the filtering process is completed by the filter unit 150. The stored reconstructed picture may be used as a reference picture for (inter) prediction of another picture. For example, the memory 160 may store (reference) pictures used for inter prediction. In this case, pictures used for inter prediction may be designated by a reference picture set or a reference picture list.

FIG. 2 is a diagram schematically illustrating a configuration of a video / video decoding apparatus to which the present invention can be applied. Hereinafter, the video decoding apparatus may include an image decoding apparatus.

Referring to FIG. 2, the (video) decoding apparatus 200 may include an entropy decoding module 210, a residual processing module 220, a prediction module 230, and an adder. , 240, a filtering module 250, and a memory 260. The residual processor 220 may include a rearrangement module 221, a dequantization module 222, and an inverse transform module 223. In addition, although not shown, the video decoding apparatus 200 may include a receiver that receives a bitstream including video information. The receiver may be configured as a separate module or may be included in the entropy decoding unit 210.

When the bitstream including the video / image information is input, the (video) decoding apparatus 200 may restore the video / image / picture in response to a process in which the video / image information is processed in the (video) encoding apparatus. .

For example, the video decoding apparatus 200 may perform video decoding using a processing unit applied in the video encoding apparatus. Thus, the processing unit block of video decoding may be, for example, a coding unit, and in another example, a coding unit, a prediction unit, or a transform unit. The coding unit may be split along the quad tree structure, binary tree structure and / or ternary tree structure from the largest coding unit.

The prediction unit and the transform unit may be further used in some cases, in which case the prediction block is a block derived or partitioned from the coding unit and may be a unit of sample prediction. At this point, the prediction unit may be divided into subblocks. The transform unit may be divided along the quad tree structure from the coding unit, and may be a unit for deriving a transform coefficient or a unit for deriving a residual signal from the transform coefficient.

The entropy decoding unit 210 may parse the bitstream and output information necessary for video reconstruction or picture reconstruction. For example, the entropy decoding unit 210 decodes information in a bitstream based on a coding method such as exponential Golomb coding, CAVLC, or CABAC, quantized values of syntax elements necessary for video reconstruction, and residual coefficients. Can be output.

More specifically, the CABAC entropy decoding method receives a bin corresponding to each syntax element in a bitstream, and decodes syntax element information and decoding information of neighboring and decoding target blocks or information of symbols / bins decoded in a previous step. The context model is determined using the context model, the probability of occurrence of a bin is predicted according to the determined context model, and arithmetic decoding of the bin is performed to generate a symbol corresponding to the value of each syntax element. can do. In this case, the CABAC entropy decoding method may update the context model by using the information of the decoded symbol / bin for the context model of the next symbol / bin after determining the context model.

The information related to the prediction among the information decoded by the entropy decoding unit 210 is provided to the prediction unit 230, and the residual value on which the entropy decoding has been performed by the entropy decoding unit 210, that is, the quantized transform coefficient, is used as a reordering unit ( 221 may be input.

The reordering unit 221 may rearrange the quantized transform coefficients in a two-dimensional block form. The reordering unit 221 may perform reordering in response to coefficient scanning performed by the encoding apparatus. Here, the rearrangement unit 221 has been described in a separate configuration, but the rearrangement unit 221 may be part of the inverse quantization unit 222.

The inverse quantization unit 222 may dequantize the quantized transform coefficients based on the (inverse) quantization parameter and output the transform coefficients. In this case, information for deriving a quantization parameter may be signaled from the encoding apparatus.

The inverse transform unit 223 may inversely transform transform coefficients to derive residual samples.

The prediction unit 230 may perform prediction on the current block and generate a predicted block including prediction samples for the current block. The unit of prediction performed by the prediction unit 230 may be a coding block, a transform block, or a prediction block.

The prediction unit 230 may determine whether to apply intra prediction or inter prediction based on the information about the prediction. In this case, a unit for determining which of intra prediction and inter prediction is to be applied and a unit for generating a prediction sample may be different. In addition, the unit for generating a prediction sample in inter prediction and intra prediction may also be different. For example, whether to apply inter prediction or intra prediction may be determined in units of CUs. In addition, for example, in inter prediction, a prediction mode may be determined and a prediction sample may be generated in PU units, and in intra prediction, a prediction mode may be determined in PU units and a prediction sample may be generated in TU units.

In the case of intra prediction, the prediction unit 230 may derive the prediction sample for the current block based on the neighbor reference samples in the current picture. The prediction unit 230 may derive the prediction sample for the current block by applying the directional mode or the non-directional mode based on the neighbor reference samples of the current block. In this case, the prediction mode to be applied to the current block may be determined using the intra prediction mode of the neighboring block.

In the case of inter prediction, the prediction unit 230 may derive the prediction sample for the current block based on the sample specified on the reference picture by the motion vector on the reference picture. The prediction unit 230 may apply any one of a skip mode, a merge mode, and an MVP mode to derive a prediction sample for the current block. In this case, motion information required for inter prediction of the current block provided by the video encoding apparatus, for example, information about a motion vector, a reference picture index, and the like may be obtained or derived based on the prediction information.

In the skip mode and the merge mode, the motion information of the neighboring block may be used as the motion information of the current block. In this case, the neighboring block may include a spatial neighboring block and a temporal neighboring block.

The prediction unit 230 may construct a merge candidate list using motion information of available neighboring blocks, and may use information indicated by the merge index on the merge candidate list as a motion vector of the current block. The merge index may be signaled from the encoding device. The motion information may include a motion vector and a reference picture. When the motion information of the temporal neighboring block is used in the skip mode and the merge mode, the highest picture on the reference picture list may be used as the reference picture.

In the skip mode, unlike the merge mode, the difference (residual) between the prediction sample and the original sample is not transmitted.

In the MVP mode, the motion vector of the current block may be derived using the motion vector of the neighboring block as a motion vector predictor. In this case, the neighboring block may include a spatial neighboring block and a temporal neighboring block.

For example, when the merge mode is applied, a merge candidate list may be generated by using a motion vector of a reconstructed spatial neighboring block and / or a motion vector corresponding to a Col block, which is a temporal neighboring block. In the merge mode, the motion vector of the candidate block selected from the merge candidate list is used as the motion vector of the current block. The information about the prediction may include a merge index indicating a candidate block having an optimal motion vector selected from candidate blocks included in the merge candidate list. In this case, the prediction unit 230 may derive the motion vector of the current block by using the merge index.

As another example, when the Motion Vector Prediction (MVP) mode is applied, a motion vector predictor candidate list may be generated using a motion vector of a reconstructed spatial neighboring block and / or a motion vector corresponding to a Col block which is a temporal neighboring block. Can be. That is, the motion vector of the reconstructed spatial neighboring block and / or the Col vector, which is a temporal neighboring block, may be used as a motion vector candidate. The prediction information may include a prediction motion vector index indicating an optimal motion vector selected from the motion vector candidates included in the list. In this case, the prediction unit 230 may select the predicted motion vector of the current block from the motion vector candidates included in the motion vector candidate list using the motion vector index. The prediction unit of the encoding apparatus may obtain a motion vector difference (MVD) between the motion vector of the current block and the motion vector predictor, and may encode the output vector in a bitstream form. That is, MVD may be obtained by subtracting the motion vector predictor from the motion vector of the current block. In this case, the prediction unit 230 may obtain a motion vector difference included in the information about the prediction, and derive the motion vector of the current block by adding the motion vector difference and the motion vector predictor. The prediction unit may also obtain or derive a reference picture index or the like indicating a reference picture from the information about the prediction.

The adder 240 may reconstruct the current block or the current picture by adding the residual sample and the predictive sample. The adder 240 may reconstruct the current picture by adding the residual sample and the predictive sample in block units. Since the residual is not transmitted when the skip mode is applied, the prediction sample may be a reconstruction sample. Although the adder 240 has been described in a separate configuration, the adder 240 may be part of the predictor 230. The adder 240 may also be called a reconstruction module or a reconstruction block generator.

The filter unit 250 may apply the deblocking filtering sample adaptive offset, and / or ALF to the reconstructed picture. In this case, the sample adaptive offset may be applied in units of samples and may be applied after deblocking filtering. ALF may be applied after deblocking filtering and / or sample adaptive offset.

The memory 260 may store reconstructed pictures (decoded pictures) or information necessary for decoding. Here, the reconstructed picture may be a reconstructed picture after the filtering process is completed by the filter unit 250. For example, the memory 260 may store pictures used for inter prediction. In this case, pictures used for inter prediction may be designated by a reference picture set or a reference picture list. The reconstructed picture can be used as a reference picture for another picture. In addition, the memory 260 may output the reconstructed picture in an output order.

Meanwhile, as described above, prediction is performed in order to increase compression efficiency in performing video coding. Through this, a predicted block including prediction samples of the current block, which is a coding target block, may be generated. Wherein the predicted block comprises prediction samples in the spatial domain (or pixel domain). The predicted block is derived identically in the encoding apparatus and the decoding apparatus, and the encoding apparatus decodes information (residual information) about the residual between the original block and the predicted block, not the original sample value itself of the original block. Signaling to an apparatus may increase image coding efficiency. The decoding apparatus may derive a residual block including residual samples based on the residual information, generate the reconstructed block including reconstructed samples by adding the residual block and the predicted block, and generate reconstructed blocks. A reconstructed picture may be generated.

The residual information may be generated through a transform and quantization procedure. For example, the encoding apparatus derives a residual block between the original block and the predicted block, and performs transform procedure on residual samples (residual sample array) included in the residual block to derive transform coefficients. The quantized transform coefficients may be derived by performing a quantization procedure on the transform coefficients to signal related residual information to the decoding device (via a bitstream). Here, the residual information may include information such as value information of the quantized transform coefficients, position information, a transform scheme, a transform kernel, and a quantization parameter. The decoding apparatus may perform an inverse quantization / inverse transformation procedure and derive residual samples (or residual blocks) based on the residual information. The decoding apparatus may generate a reconstructed picture based on the predicted block and the residual block. The encoding apparatus may then dequantize / inverse transform the quantized transform coefficients for reference for inter prediction of the picture to derive a residual block, and generate a reconstructed picture based thereon.

3 is a diagram illustrating an example of intra prediction modes.

Referring to FIG. 3, in an embodiment, a prediction block of a current block may be generated by using 33 directional prediction methods, two non-directional prediction methods, and a total of 35 prediction methods for intra prediction. In this case, a prediction sample is generated using neighboring reference samples (upper reference samples and left reference samples) to predict the current block, and then the prediction sample generated according to the prediction direction is copied. Intra-prediction simply copies the prediction sample, so the error tends to increase as the distance between the prediction sample and the reference sample increases.

4 is a diagram illustrating another example of intra prediction modes.

Referring to FIG. 4, an intra prediction mode having horizontal directionality and an intra prediction mode having vertical directionality may be distinguished from an intra prediction mode 34 having a left upward diagonal prediction direction. H and V in FIG. 3 mean horizontal directionality and vertical directionality, respectively, and a number of -32 to 32 represents a displacement of 1/32 on a sample grid position. Intra prediction modes 2 to 33 have horizontal orientation, and intra prediction modes 34 to 66 have vertical orientation. Intra prediction mode 18 and intra prediction mode 50 indicate a horizontal intra prediction mode and a vertical intra prediction mode, respectively. Intra prediction mode 2 indicates a left downward diagonal intra prediction mode, The 34th intra prediction mode may be referred to as a left upward diagonal intra prediction mode, and the 66th intra prediction mode may be referred to as a right upward diagonal intra prediction mode.

Linear interpolation prediction (LIP) uses the right and bottom buffers (video encodings are generally encoded by raster scans) to reduce the errors that occur in these intra prediction encodings. Since the right block and the lower block are not yet encoded based on the block to be generated, the right end sample and the bottom sample cannot be used as reference samples), and then the prediction block can be generated by interpolating the existing reference samples. .

5 is a diagram illustrating an LIP according to an embodiment.

In FIG. 5, a linear interpolation prediction (LIP) method of generating a prediction block using a right buffer in intra prediction encoding is shown.

In order to perform linear interpolation prediction, as mentioned above, it is necessary to generate a right sample buffer and a bottom sample buffer. To do this, you can first generate a bottom right sample (BR) using the surrounding reference samples.

6A and 6B illustrate a LIP according to another embodiment.

In order to perform linear interpolation prediction, as mentioned above, the right sample buffer and the bottom sample buffer need to be generated. To do this, we first create a bottom right sample (BR) using the surrounding reference samples. FIG. 6A illustrates a method for generating a right bottom sample using a top right sample and a bottom left sample, and FIG. 6B shows a most top right sample that is two times as long as a block to be currently encoded. ) And most bottom left sample to show how to generate the bottom right sample. An equation for generating the lower right sample using each sample is shown in Equation 1 or Equation 2 below.

[Equation 1]

Lower right sample = (right upper sample + lower left sample + 1) >> 1

[Equation 2]

Lower right sample = (most upper right sample + most lower left sample + 1) >> 1

The actual right bottom sample can be generated using various methods in addition to the two methods mentioned above.

7 is a view for explaining a LIP according to another embodiment.

After the bottom right sample is generated, the bottom samples (bottom buffer) and the right samples (right buffer) are generated using the bottom left and top right samples. . Figure 5 shows how to generate the bottom and right samples. The lower samples are linearly interpolated between the lower left sample and the lower right sample, and the right samples are generated by linear interpolating the upper right sample and the lower right sample. In this case, the method of generating the lower right samples using the lower left sample and the lower right sample and the right upper samples using the right upper sample and the lower right sample may be generated differently by giving various weight values.

After generating the bottom and right samples, linear interpolation prediction is performed using the generated bottom and right samples. Referring back to FIG. 5, a method of generating the current prediction sample C using the linear interpolation intra prediction method is as follows. In FIG. 5, the prediction mode will be described as an example of a vertical sequence having positive directionality.

In the first step, the bottom buffer may be generated by copying the left reference sample (dark gray) into the bottom sample buffer and using the generated bottom samples.

In a second step, a predicted sample value P may be generated (using an existing intra prediction coded prediction sample generation method) by interpolating the A reference sample and the B reference sample of the upper reference buffer using the reconstructed value.

In a third step, a predicted sample value P 'may be generated by using interpolation between the A' reference samples and the B 'reference samples of the newly generated lower reference buffer (using the existing intra prediction coded prediction sample generation method).

In a fourth step, the final prediction value C may be generated based on Equation 3 below by linearly interpolating the generated P and P ′.

[Equation 3]

C = (w _UP * P + w _DOWN * P '+ (w _UP + w _DOWN ) / 2) / (w _UP + w _DOWN )

A prediction value is generated by applying the second to fourth steps to all samples in the block to be currently encoded. The prediction method in the linear interpolation screen can be applied to all directional boards except planar mode and DC mode where no directionality exists.

As shown in FIG. 8, in the intra prediction encoding, the optimal prediction mode determination method first determines a candidate even mode for full rate (DRD) through an approximate mode determination method for the even mode. In this case, the coarse mode determination method determines the cost value based on the difference between the prediction block and the original block and the bits necessary for simply encoding the mode information, and determines the mode having the low cost value as the candidate mode. Next, the full RD can be obtained through the mode decision method for the odd mode of ± 1 in the determined even mode (for example, the number of the odd mode in mode ± 1 is 19 and 21 when the selected even mode is 20). Re-determine the candidate mode for. After determining the candidate mode through coarse mode determination, the most probable mode (MPM) method is used to find a similar mode around the current block and add it to the candidate mode. Finally, from the viewpoint of rate-distortion optimization (RDO), the optimal intra prediction mode is determined through Full RD.

In this embodiment, a method of applying a linear interpolation intra prediction method (LIP) using a plurality of reference sample lines is proposed. As illustrated in FIGS. 9A and 9B, a plurality of reference sample lines may be used at the top and the left of the block to perform intra prediction of the current block. Therefore, the present embodiment proposes a method of selectively determining a reference sample line when using the linear interpolation intra prediction method. When the accuracy of the first reference sample line is low due to the edge and noise of the image, applying the LIP using the second or another reference sample line may have higher prediction accuracy.

In this embodiment, as shown in the example of FIG. 10, a LPS is applied by selectively determining a reference sample line to which prediction is to be applied, and after encoding the information in an encoder, the information may be transmitted to a decoder for use in decoding. Referring to FIG. 10, a second reference sample line among four reference sample lines of the current block may be selected, and LIP may be applied based on the selected second reference sample line.

When using two lines, three lines, and four line-based reference samples, information of a line selected for LIP may transmit information through binarization as shown in Tables 1 to 3 below.

Selected lineSelected line	binarizationbinarization
1^st line1 ^st line	00
2^nd line2 ^nd line	1One

Table 1 shows an example of a method of transmitting reference sample line information for LIP prediction and corresponds to a two-line case.

Selected lineSelected line	binarizationbinarization
1^st line1 ^st line	00
2^nd line2 ^nd line	1010
3^rd line3 ^rd line	1111

Table 2 shows an example of a method of transmitting reference sample line information for LIP prediction and corresponds to a three-line case.

Selected lineSelected line	Binarization example 1Binarization example 1	Binarization example 2Binarization example 2
1^st line1 ^st line	0000	00
2^nd line2 ^nd line	0101	1010
3^rd line3 ^rd line	1010	110110
4^th line4 ^th line	1111	111111

Table 3 shows an example of a method of transmitting reference sample line information for LIP prediction and corresponds to a four-line case. 11 is a flowchart illustrating an operation of performing LIP based on a plurality of reference sample lines according to an embodiment.

Through the method proposed in this specification, LIP prediction may be performed through the selected prediction sample line, and the block predicted through the LIP prediction is used to obtain a residual image through the difference from the original image in the encoder, or in the decoder. It can be used to obtain a reconstructed image through the sum with the residual signal. 11 shows a flow chart of the method proposed in this patent embodiment.

As shown in FIG. 11, the decoding apparatus according to an embodiment may select a reference sample line for the LIP, and apply the LIP based on the selected reference sample line.

In this embodiment, a method of applying a linear interpolation intra prediction method (LIP) by combining a plurality of reference sample lines is proposed. As illustrated in FIG. 12, after integrating a multi-line reference sample into one line of reference samples, LIP may be applied as in the conventional method. Since the method proposed in this embodiment interpolates a plurality of reference sample values, it is possible to obtain more sophisticated reference sample values than the first line reference samples. Thus, more sophisticated prediction can be performed.

The integration can be performed adaptively to the reference sample line by the following equation.

[Equation 4]

ref_unified = (

x ref_1 +

x ref_2 +

x ref_3 + ...) / (

+

+ ...)

In the above expression, ref_unified means an integrated reference sample, ref_1 means a reference sample value of the first line of the position corresponding to ref_unified, and ref_n means a reference sample value of the nth line of the position corresponding to ref_unified. n can be used variably according to the number of reference sample lines, and the weight applied to each reference sample line (

,

, ...) can be applied as in the following example.

In one example,

= 1,

= 1/2,

= 1/3, ... can be applied. The closer the reference sample line is to the current block, the higher the weight can improve the accuracy of the reference sample.

In another example,

= 1,

= 1, ... can be applied. By giving the same weight to all reference sample lines, a higher accuracy reference sample can be generated in the case where the reference sample is noisy.

The reference sample line integrated through the method proposed in this embodiment is used for the existing LIP prediction, and the block predicted through the LIP prediction is used to obtain the residual image through the difference from the original image in the encoder, or the decoder It can be used to obtain a reconstructed image through the sum with the residual signal in. 13 shows a flowchart of a method proposed in an embodiment of the present specification.

Meanwhile, according to an embodiment, a method of using a linear interpolation intra prediction method (LIP) by generating a reference sample line through a combination of Embodiment 1 and Embodiment 2 described above is proposed. That is, after generating a plurality of reference samples by partially integrating the plurality of reference sample lines, the LIP may be applied using the plurality of reference sample lines. The following example shows the method proposed in this embodiment.

First, there is an example of a 4 reference sample line case. The first and second sample lines / the third and fourth sample lines are combined based on the embodiment according to FIG. 12 to generate two new sample lines, and the first and second sample lines are selected by selecting one line as shown in FIG. 10. Information about the reference sample line may be transmitted to the decoder.

Second, there is an example of a 2 reference sample line case. The first sample line may be used as it is, and the second sample line may be newly created by combining the first sample line with the embodiment of FIG. 12, and then one line may be selected from the two lines as shown in the embodiment of FIG. 10. .

According to an embodiment, a method of performing intra-linear interpolation prediction through each reference sample line and then combining them may be proposed. That is, the prediction is performed like the existing LIP through the first reference sample line with respect to the current coding block, and then the LIP prediction is performed through the second reference sample line. In this case, since the distance between the current block and the reference sample line increases by one pixel, the LIP calculation takes this into account. LIP prediction may be performed as many as the number of sample lines referable to the current coding block, and each calculated LIP prediction block may be combined into one prediction block through linear combination.

According to an embodiment, a method of assigning a higher weight to a reference sample (P of Equation 3) used for the existing intra prediction in the linear interpolation intra prediction (LIP) described above is proposed. That is, when generating the final prediction value C by linearly interpolating P and P 'as shown in Equation 3, the final prediction value is applied by applying different weights to P and P' in addition to the linear interpolation proportional to the existing distance. May be generated as in Equation 5 below.

[Equation 5]

C = (w _UP * w _REF1 * P + w _DOWN * w _REF2 * P '+ (w _UP * w _REF1 + w _DOWN * w _REF2 ) / 2)

/ (w _UP * w _REF1 + w _DOWN * w _REF2 )

That is, by giving w _REF1 and w _REF2 in addition to the linear interpolation weights w _UP and w _DOWN proportional to the distance between the current prediction pixels C, P, and P ', a higher weight can be given to P, which is a pixel used for prediction in the original screen. Can be. Since P, a reconstructed sample of the neighboring block, has a higher accuracy than P 'which is far from the prediction direction in the current screen, a higher weight can be given to P to increase the accuracy of the pixel C generated by the prediction in the linear interpolation screen. . The weights w _REF1 and w _REF2 can be set as in the following example. (w _REF1 , w _REF2 ) = (2, 1), (3, 2), (3, 1), (4, 1), (4, 3) or (8, 1).

Alternatively, higher weighting may be given to P in the same manner as in Equation 6 below.

[Equation 6]

C = ((w _UP + w _REF1 ) * P + (w _DOWN + w _REF2 ) * P '+ (w _UP + w _REF1 + w _DOWN + w _REF2 ) / 2) / (w _UP + w _REF1 + w _DOWN + w _REF2 )

w _REF1 and w _REF2 can be set as described above.

The weight changed by the method proposed in this embodiment is used for LIP prediction, and the block predicted through LIP prediction is used to obtain a residual image by difference from an original image in an encoder, or a residual signal in a decoder. It can be used to obtain the reconstructed image through the sum.

According to an embodiment, a method of assigning a higher weight to a reference sample (P of Equation 3) used for an existing intra prediction during linear interpolation intra prediction (LIP) is proposed. 'Using the new C, P, P as shown in Equation 7 below in addition to the pixel C generated by the LIP Using equation (3) For this purpose, generates, by interpolation with the two final prediction as shown in Equation 8 C _FINAL Can be generated.

[Equation 7]

C '= (w _REF1 * P + w _REF2 * P' + (w _REF1 + w _REF2 ) / 2) / (w _REF1 + w _REF2 )

[Equation 8]

C _FINAL = (w _C * C + w _{C '} * C' + (w _C + w _{C '} ) / 2) / (w _C + w _C' )

In Equation 7, w _REF1 and w _REF2 may be set as in Equation 6.

In the present exemplary embodiment, a new prediction sample C 'is generated by applying a higher weight to P, which is a reconstructed reference pixel as shown in Equation 7, and then combined with C generated by an existing LIP as shown in Equation 8, thereby providing a LIP screen. Higher weights can be given to the reconstructed reference pixels in the prediction.

The weights w _C and w _{C ′} in Equation 8 are basically set to 1, or may be variously set as follows. (w _C , w _{C '} ) = (3, 1) or (1, 3).

The block predicted by the method proposed in this embodiment may be used to obtain a residual image by difference from an original image in an encoder, or may be used to obtain a reconstructed image by adding a residual signal in a decoder. .

According to an embodiment, a method of adaptively applying weights according to prediction block positions in LIP prediction is proposed.

The lower reference block and the right reference block generated during LIP prediction are adaptively used for the prediction mode in the LIP picture. That is, as shown in FIGS. 14A and 14B, the LIP prediction may be performed by combining the upper reference pixel and the left reference pixel according to the LIP prediction direction and the pixel position in the block, which is higher than using the lower reference pixel and the right reference pixel. Prediction of accuracy can be performed. That is, when performing LIP prediction by combining the upper reference pixel and the left reference pixel, it may not be necessary to apply the weight change proposed in the description of Equations 5 to 8 herein.

According to an embodiment, a method of not applying the proposed weights according to Equations 5 to 8 when LIP prediction is performed by using an upper reference pixel and a left reference pixel during LIP prediction is proposed.

According to an embodiment, a method of applying changed LIP prediction to an encoder and a decoder based on the description of Equations 5 to 8 and the description of FIGS. 14A and 14B is proposed. Description of Equations 5 to 8 and descriptions of FIGS. 14A and 14B The LIP prediction block generated through the proposed weight change may be used as an alternative to the existing intra prediction, in which case additional information for LIP prediction is used. May be unnecessary. Alternatively, the presence or absence of LIP application may be transmitted to the decoder by using a flag for whether LIP is applied. In this case, the encoder may use the RDO to determine whether LIP is applied to the intra prediction.

15 is a flowchart illustrating a method of operating a decoding apparatus according to an embodiment, and FIG. 16 is a block diagram illustrating a configuration of a decoding apparatus according to an embodiment.

Each step disclosed in FIG. 15 may be performed by the decoding apparatus 200 disclosed in FIG. 2. More specifically, S1500 may be performed by the entropy decoding unit 210 shown in FIG. 2, S1510 to S1530 may be performed by the predictor 230 shown in FIG. 2, and S1540 is the addition shown in FIG. 2. It may be performed by the unit 240. In addition, operations according to S1500 to S1540 are based on some of the above descriptions in FIGS. 3 to 14B. Therefore, detailed description overlapping with the above description in FIGS. 2 to 14b will be omitted or simply described.

As shown in FIG. 16, a decoding apparatus according to an embodiment may include an entropy decoding unit 210, a predictor 230, and an adder 240. However, in some cases, all of the components shown in FIG. 16 may not be essential components of the decoding apparatus, and the decoding apparatus may be implemented by more or fewer components than those illustrated in FIG.

In the decoding apparatus according to an embodiment, the entropy decoding unit 210, the prediction unit 230, and the adder 240 are each implemented as separate chips, or at least two or more components are implemented through one chip. May be

The decoding apparatus according to an embodiment may obtain image information about the current block from the bitstream (S1500).

The decoding apparatus according to an embodiment may derive the right-bottom corner reference sample of the current block based on neighboring reference samples of the current block (S1510).

In one embodiment, the peripheral reference samples of the current block may be composed of multiple reference sample lines.

In example embodiments, the image information of the current block includes reference sample line index information for indicating each of the plurality of reference sample lines, and the lower right side of the current block. The corner reference sample may be derived based on the reference sample line indicated by the reference sample line index information.

In one embodiment, the right bottom corner reference sample of the current block includes a top-right sample and a bottom-left of samples included in the reference sample line indicated by the reference sample line index information. Can be derived based on the sample.

In one embodiment, the number of lines of the plurality of reference sample lines is two, three or four, and the reference sample line index information may include a binary code for each of the plurality of reference sample lines. Can be.

In an embodiment, the deriving of the lower right corner reference sample of the current block based on the peripheral reference samples of the current block may include applying a single reference sample to each of the plurality of reference sample lines by applying at least one weight. Deriving a line and deriving the lower right corner reference sample of the current block based on the derived single reference sample line.

In an embodiment, deriving the lower right corner reference sample of the current block based on the peripheral reference samples of the current block may include applying a single excess to each of the plurality of reference sample lines by applying at least one weight. deriving a reference sample line and deriving the lower right corner reference sample of the current block based on the derived single excess reference sample line, wherein the number of lines of the single excess reference sample line The number of lines of the plurality of reference sample lines may be smaller.

The decoding apparatus according to an embodiment may derive the lower reference samples and the right reference samples of the current block based on the derived lower right corner reference sample (S1520).

The decoding apparatus according to an embodiment may derive prediction samples for the current block based on at least one of the peripheral reference samples, the lower reference samples, and the right reference samples of the current block (S1530). .

In one embodiment, a first weight is applied to a first prediction reference sample value derived based on the neighboring reference samples of the current block, and a second prediction reference sample derived based on the lower reference samples of the current block. A second weight is applied to a third predictive reference sample value derived based on a value or the right reference samples, and the deriving of the predictive samples for the current block includes: the first predictive reference to which the first weight is applied. Deriving prediction samples for the current block based on at least one of a sample value, the second prediction reference sample value to which the second weight is applied, and the third prediction reference sample value to which the second weight is applied. Can be.

In one embodiment, the first weight may be greater than the second weight.

In one embodiment, the first weight may be twice the second weight.

In one embodiment, deriving the prediction samples for the current block includes deriving the prediction samples for the current block based on a linear interpolation weight based on the position of the prediction sample for the current block. can do.

In one embodiment, the predicted value of the predictive sample is derived based on Equation 7, wherein C represents the predicted value of the predictive sample, and w _UP and w _DOWN represent the linear interpolation weights, respectively. , w _REF1 And w _REF2 may represent the first weight value and the second weight value, respectively, and P and P ′ may represent the first prediction reference sample value and the second prediction reference sample value, respectively.

In one embodiment, the predicted value of the predictive sample is derived based on Equation 8, wherein C represents the predicted value of the predictive sample, and w _UP and w _DOWN represent the linear interpolation weights, respectively. , w _REF1 And w _REF2 may represent the first weight and the second weight, respectively, and P and P ′ may represent the first prediction reference sample value and the second prediction reference sample value, respectively.

In an embodiment, a first weight is also applied to a fourth prediction reference sample value derived based on the neighboring reference samples of the current block, and the deriving of the prediction samples for the current block includes: And deriving the prediction samples for the current block based on the first prediction reference sample value to which the second prediction reference sample value is applied and the fourth prediction reference sample value to which the first weight is applied.

The decoding apparatus according to an embodiment may generate reconstruction samples for the current block based on the prediction samples for the current block (S1540).

According to the decoding apparatus and the method of operating the decoding apparatus disclosed in FIGS. 15 and 16, the decoding apparatus obtains image information about a current block from a bitstream (S1500), and neighboring reference samples of the current block. A right-bottom corner reference sample of the current block is derived based on (S1510), and the lower reference samples and the right reference samples of the current block are based on the derived lower right corner reference sample. Deriving (S1520), deriving prediction samples for the current block based on at least one of the peripheral reference samples, the lower reference samples, and the right reference samples of the current block (S1530), and the current block Reconstruction samples for the current block may be generated (S1540) based on the predictive samples for the S block. The decoding apparatus may increase image coding efficiency by performing LIP on the basis of a plurality of reference sample lines, and may increase intra prediction efficiency by applying a weight to a reference sample in performing LIP.

The above-described method according to the present invention may be implemented in software, and the encoding device and / or the decoding device according to the present invention may perform image processing of, for example, a TV, a computer, a smartphone, a set-top box, a display device, and the like. It can be included in the device.

When embodiments of the present invention are implemented in software, the above-described method may be implemented as a module (process, function, etc.) for performing the above-described function. The module may be stored in memory and executed by a processor. The memory may be internal or external to the processor and may be coupled to the processor by various well known means. The processor may include an application-specific integrated circuit (ASIC), other chipsets, logic circuits, and / or data processing devices. The memory may include read-only memory (ROM), random access memory (RAM), flash memory, memory card, storage medium and / or other storage device.

Claims

In the picture decoding method performed by the decoding apparatus,

Obtaining image information on the current block from the bitstream;

Deriving a right-bottom corner reference sample of the current block based on neighboring reference samples of the current block;

Deriving lower reference samples and right reference samples of the current block based on the derived lower right corner reference sample;

Deriving prediction samples for the current block based on at least one of the peripheral reference samples, the lower reference samples and the right reference samples of the current block; And

Generating reconstructed samples for the current block based on the predicted samples for the current block.
The method of claim 1,

And wherein the peripheral reference samples of the current block consist of a plurality of reference sample lines.
The method of claim 2,

The image information of the current block includes reference sample line index information for indicating each of the plurality of reference sample lines.

And the lower right corner reference sample of the current block is derived based on a reference sample line indicated by the reference sample line index information.
The method of claim 3,

The lower right corner reference sample of the current block is derived based on a top-right sample and a bottom-left sample among samples included in the reference sample line indicated by the reference sample line index information. Picture decoding method.
The method of claim 3,

The number of lines of the plurality of reference sample lines is two, three or four,

And the reference sample line index information includes a binary code for each of the plurality of reference sample lines.
The method of claim 2,

Deriving the lower right corner reference sample of the current block based on the peripheral reference samples of the current block,

Deriving a single reference sample line by applying at least one weight to each of the plurality of reference sample lines; And

Deriving the lower right corner reference sample of the current block based on the derived single reference sample line.
The method of claim 2,

Deriving the lower right corner reference sample of the current block based on the peripheral reference samples of the current block,

Deriving a single excess reference sample line by applying at least one weight to each of the plurality of reference sample lines; And

Deriving the lower right corner reference sample of the current block based on the derived single excess reference sample line;

And the number of lines of the single excess reference sample line is less than the number of lines of the plurality of reference sample lines.
The method of claim 1,

A first weight is applied to a first prediction reference sample value derived based on the neighboring reference samples of the current block,

A second weight is applied to a second prediction reference sample value derived based on the lower reference samples of the current block or a third prediction reference sample value derived based on the right reference samples.

Deriving the prediction samples for the current block,

The current block based on at least one of the first prediction reference sample value to which the first weight is applied, the second prediction reference sample value to which the second weight is applied, and the third prediction reference sample value to which the second weight is applied. Deriving predictive samples for the picture decoding method.
The method of claim 8,

And wherein the first weight is greater than the second weight.
The method of claim 9,

And wherein the first weight is twice the second weight.
The method of claim 8,

Deriving the prediction samples for the current block includes deriving the prediction samples for the current block based on a linear interpolation weight based on the position of the prediction sample for the current block. , Picture decoding method.
The method of claim 11,

The prediction value of the prediction sample is derived based on the following equation,

C = (w UP * w REF1 * P + w DOWN * w REF2 * P '+ (w UP * w REF1 + w DOWN * w REF2 ) / 2) / (w UP * w REF1 + w DOWN * w REF2 )

In the above equation, C represents the prediction value of the prediction sample, w UP and w DOWN represent the linear interpolation weight, respectively, w REF1 And w REF2 represents the first weight and the second weight, respectively, and P and P ′ represent the first prediction reference sample value and the second prediction reference sample value, respectively.
The method of claim 11,

The prediction value of the prediction sample is derived based on the following equation,

C = ((w UP + w REF1 ) * P + (w DOWN + w REF2 ) * P '+ (w UP + w REF1 + w DOWN + w REF2 ) / 2) / (w UP + w REF1 + w DOWN + w REF2 )

In the above equation, C represents the prediction value of the prediction sample, w UP and w DOWN represent the linear interpolation weight, respectively, w REF1 And w REF2 represents the first weight and the second weight, respectively, and P and P ′ represent the first prediction reference sample value and the second prediction reference sample value, respectively.
The method of claim 8,

A first weight is also applied to a fourth predictive reference sample value derived based on the neighboring reference samples of the current block,

Deriving the prediction samples for the current block,

And deriving the prediction samples for the current block based on the first prediction reference sample value to which the first weight is applied and the fourth prediction reference sample value to which the first weight is applied. Picture decoding method.
In the decoding apparatus for performing picture decoding,

An entropy decoding unit for obtaining image information on the current block from the bitstream;

A right-bottom corner reference sample of the current block is derived based on neighboring reference samples of the current block, and the current block is based on the derived right-bottom corner reference sample. Deriving the lower reference samples and the right reference samples of and deriving prediction samples for the current block based on at least one of the peripheral reference samples, the lower reference samples and the right reference samples of the current block. Prediction unit; And

And an adder for generating reconstructed samples for the current block based on prediction samples for the current block.