WO2017048008A1

WO2017048008A1 - Inter-prediction method and apparatus in video coding system

Info

Publication number: WO2017048008A1
Application number: PCT/KR2016/010240
Authority: WO
Inventors: 유선미
Original assignee: 엘지전자 주식회사
Priority date: 2015-09-17
Filing date: 2016-09-12
Publication date: 2017-03-23

Abstract

An inter-prediction method performed by a decoding apparatus according to the present invention comprises the steps of: deriving a motion information candidate list of a current block on the basis of neighboring blocks of the current block; selecting a specific candidate on the basis of the comparison of the candidates in the motion information candidate list; deriving a motion vector of the current block on the basis of the specific candidate; and generating a prediction sample of the current block on the basis of the motion vector of the current block. The present invention is capable of reducing the data amount of the prediction mode information indicating an inter-prediction mode, and reducing the process of searching for a motion vector of the current block by selecting motion vector candidates of the current block, thereby improving coding efficiency.

Description

Inter prediction method and apparatus in image coding system

The present invention relates to image coding technology, and more particularly, to an inter prediction method and apparatus 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 object of the present invention is to provide a method and apparatus for improving the efficiency of inter prediction.

Another technical problem of the present invention is to provide an efficient motion vector derivation method and apparatus based on the modified inter prediction mode.

Another technical problem of the present invention is to provide a matching method and apparatus for deriving a more accurate motion vector among motion vector candidates.

Another technical problem of the present invention is to provide a method and apparatus for selecting a motion vector candidate derived based on a neighboring block to derive a more accurate motion vector while reducing computational complexity.

According to an embodiment of the present invention, there is provided an image decoding method performed by a decoding apparatus. The method may include deriving a motion information candidate list of the current block based on neighboring blocks of the current block, selecting a specific candidate based on a comparison of candidates in the motion information candidate list, and based on the specific candidate. Deriving a motion vector of the current block, and generating a predictive sample of the current block based on the motion vector of the current block.

According to another embodiment of the present invention, a decoding apparatus for performing inter prediction is provided. The decoding apparatus derives a motion information candidate list of the current block based on neighboring blocks of the current block, selects a specific candidate based on a comparison of candidates in the motion information candidate list, and based on the specific candidate And a prediction unit for deriving a motion vector of the block and generating a prediction sample of the current block based on the motion vector of the current block.

According to another embodiment of the present invention, a video encoding method performed by an encoding apparatus is provided. The method may include deriving a motion information candidate list of the current block based on neighboring blocks of the current block, selecting a specific candidate based on a comparison of candidates in the motion information candidate list, and based on the specific candidate. Deriving a motion vector of the current block, generating a prediction sample of the current block based on the motion vector of the current block, and encoding and outputting prediction mode information indicating the inter prediction mode. It is characterized by.

According to another embodiment of the present invention, a video encoding apparatus is provided. The encoding apparatus derives a motion information candidate list of the current block based on neighboring blocks of the current block, selects a specific candidate based on a comparison of candidates in the motion information candidate list, and based on the specific candidate A prediction unit for deriving a motion vector of the block, generating a prediction sample of the current block based on the motion vector of the current block, and an entropy encoding unit for encoding and outputting prediction mode information indicating the inter prediction mode. It is characterized by.

According to the present invention, the data amount of prediction mode information indicating the inter prediction mode can be reduced, thereby improving the overall coding efficiency.

According to the present invention, the process of searching for the motion vector of the current block by selecting the motion vector candidate of the current block can be reduced, thereby reducing the computational complexity and improving the overall coding efficiency.

1 is a block diagram schematically illustrating a video encoding apparatus according to an embodiment of the present invention.

2 is a block diagram schematically illustrating a video decoding apparatus according to an embodiment of the present invention.

3 exemplarily shows an encoding method of a current block to which a modified inter prediction mode is applied.

4 exemplarily illustrates a decoding method of a current block to which a modified inter prediction mode is applied.

5 illustrates an example of comparing a motion vector through a bilateral matching method.

6 illustrates an example of comparing a motion vector through a template matching method.

7 illustrates an example of a method of deriving motion vector candidates.

8 illustrates an example of a method of deriving a motion vector of a current block based on motion information of a neighboring block.

9 illustrates an example of a method of deriving motion vector candidates.

10 illustrates an example of a method of deriving a motion vector of a current block based on motion information of a neighboring block.

11 illustrates an example of a method of deriving motion vector candidates.

12 illustrates an example of a method of deriving a motion vector of a current block based on motion information of a neighboring block.

13 schematically illustrates a video encoding method by an encoding device according to the present invention.

14 schematically illustrates a video decoding method by a decoding apparatus according to the present invention.

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. In this specification, terms such as "comprise" or "have" are intended to indicate that there is a feature, number, step, action, component, part, or combination thereof described on the specification, and one or more other features. It is to be understood that the present invention does not exclude the possibility of the presence or the addition of numbers, steps, operations, components, components, or a combination thereof.

On the other hand, each of the components in the drawings described in the present invention are shown independently for the convenience of description of the different characteristic functions in the video encoding apparatus / decoding apparatus, each component is a separate hardware or separate software It does not mean that it is implemented. 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 present invention without departing from the spirit of the present invention.

Hereinafter, with reference to the accompanying drawings, it will be described in detail an embodiment of the present invention.

Referring to FIG. 1, the encoding apparatus 100 may include a picture divider 105, a predictor 110, a transformer 115, a quantizer 120, a reordering unit 125, an entropy encoding unit 130, An inverse quantization unit 135, an inverse transform unit 140, a filter unit 145, and a memory 150 are provided.

The picture dividing unit 105 may divide the input picture into at least one processing unit block. In this case, the block as the processing unit may be a prediction unit (PU), a transform unit (TU), or a coding unit (CU). A picture may be composed of a plurality of coding tree units (CTUs), and each CTU may be split into CUs in a quad-tree structure. A CU may be divided into quad tree structures with CUs of a lower depth. PU and TU may be obtained from a CU. For example, a PU may be partitioned from a CU into a symmetrical or asymmetrical square structure. The TU may also be divided into quad tree structures from the CU.

The predictor 110 includes an inter predictor for performing inter prediction and an intra predictor for performing intra prediction, as described below. The prediction unit 110 performs prediction on the processing unit of the picture in the picture division unit 105 to generate a prediction block including a prediction sample (or a prediction sample array). The processing unit of the picture in the prediction unit 110 may be a CU, a TU, or a PU. In addition, the prediction unit 110 may determine whether the prediction performed on the processing unit is inter prediction or intra prediction, and determine specific contents (eg, prediction mode, etc.) of each prediction method. In this case, the processing unit in which the prediction is performed and the processing unit in which the details of the prediction method and the prediction method are determined may be different. For example, the method of prediction and the prediction mode may be determined in units of PUs, and the prediction may be performed in units of TUs.

Through inter prediction, a prediction block may be generated by performing prediction based on information of at least one picture of a previous picture and / or a subsequent picture of the current picture. In addition, through intra prediction, a prediction block may be generated by performing prediction based on pixel information in a current picture.

As a method of inter prediction, a skip mode, a merge mode, an advanced motion vector prediction (AMVP), and the like can be used. In inter prediction, a reference picture may be selected for a PU and a reference block corresponding to the PU may be selected. The reference block may be selected in units of integer pixels (or samples) or fractional pixels (or samples). Subsequently, a predictive block is generated in which a residual signal with the PU is minimized and the size of the motion vector is also minimized.

The prediction block may be generated in integer pixel units, or may be generated in sub-pixel units such as 1/2 pixel unit or 1/4 pixel unit. In this case, the motion vector may also be expressed in units of integer pixels or less.

Information such as an index of a reference picture selected through inter prediction, a motion vector difference (MDV), a motion vector predictor (MVP), a residual signal, and the like may be entropy encoded and transmitted to a decoding apparatus. . When the skip mode is applied, the residual may be used as the reconstructed block, and thus the residual may not be generated, transformed, quantized, or transmitted.

When performing intra prediction, a prediction mode may be determined in units of PUs, and prediction may be performed in units of PUs. In addition, a prediction mode may be determined in units of PUs, and intra prediction may be performed in units of TUs.

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).

In intra prediction, a prediction block may be generated after applying a filter to a reference sample. In this case, whether to apply the filter to the reference sample may be determined according to the intra prediction mode and / or the size of the current block.

The residual value (the residual block or the residual signal) between the generated prediction block and the original block is input to the converter 115. In addition, the prediction mode information, the motion vector information, etc. used for the prediction are encoded by the entropy encoding unit 130 together with the residual value and transmitted to the decoding apparatus.

The transform unit 115 performs transform on the residual block in units of transform blocks and generates transform coefficients.

The transform block is a rectangular block of samples to which the same transform is applied. The transform block can be a transform unit (TU) and can have a quad tree structure.

The transformer 115 may perform the transformation according to the prediction mode applied to the residual block and the size of the block.

For example, if intra prediction is applied to a residual block and the block is a 4x4 residual array, the residual block is transformed using a discrete sine transform (DST), otherwise the residual block is transformed into a DCT (Discrete). Can be transformed using Cosine Transform.

The transform unit 115 may generate a transform block of transform coefficients by the transform.

The quantization unit 120 may generate quantized transform coefficients by quantizing the residual values transformed by the transform unit 115, that is, the transform coefficients. The value calculated by the quantization unit 120 is provided to the inverse quantization unit 135 and the reordering unit 125.

The reordering unit 125 rearranges the quantized transform coefficients provided from the quantization unit 120. By rearranging the quantized transform coefficients, the encoding efficiency of the entropy encoding unit 130 may be increased.

The reordering unit 125 may rearrange the quantized transform coefficients in the form of a 2D block into a 1D vector form through a coefficient scanning method.

The entropy encoding unit 130 entropy-codes a symbol according to a probability distribution based on the quantized transform values rearranged by the reordering unit 125 or the encoding parameter value calculated in the coding process, thereby performing a bitstream. You can output The entropy encoding method receives a symbol having various values and expresses it as a decodable column while removing statistical redundancy.

Here, the symbol means a syntax element, a coding parameter, a value of a residual signal, etc., to be encoded / decoded. An encoding parameter is a parameter necessary for encoding and decoding, and may include information that may be inferred in the encoding or decoding process as well as information encoded by an encoding device and transmitted to the decoding device, such as a syntax element. It means the information you need when you do. The encoding parameter may be, for example, a value such as an intra / inter prediction mode, a moving / motion vector, a reference image index, a coding block pattern, a residual signal presence, a transform coefficient, a quantized transform coefficient, a quantization parameter, a block size, block partitioning information, or the like. May include statistics. In addition, the residual signal may mean a difference between the original signal and the prediction signal, and a signal in which the difference between the original signal and the prediction signal is transformed or a signal in which the difference between the original signal and the prediction signal is converted and quantized It may mean. The residual signal may be referred to as a residual block in the block unit, and the residual sample in the sample unit.

When entropy encoding is applied, a small number of bits are allocated to a symbol having a high probability of occurrence and a large number of bits are allocated to a symbol having a low probability of occurrence, thereby representing the size of the bit string for the symbols to be encoded. Can be reduced. Therefore, the compression performance of video encoding can be increased through entropy encoding.

Encoding methods such as exponential golomb, context-adaptive variable length coding (CAVLC), and context-adaptive binary arithmetic coding (CABAC) may be used for entropy encoding. For example, the entropy encoding unit 130 may store a table for performing entropy encoding, such as a variable length coding (VLC) table, and the entropy encoding unit 130 may store the variable length coding. Entropy encoding can be performed using the (VLC) table. In addition, the entropy encoding unit 130 derives the binarization method of the target symbol and the probability model of the target symbol / bin, and then uses the derived binarization method or the probability model to entropy. You can also perform encoding.

In addition, if necessary, the entropy encoding unit 130 may apply a constant change to a parameter set or syntax to be transmitted.

The inverse quantizer 135 inversely quantizes the quantized values (quantized transform coefficients) in the quantizer 120, and the inverse transformer 140 inversely transforms the inverse quantized values in the inverse quantizer 135.

The residual value (or the residual sample or the residual sample array) generated by the inverse quantizer 135 and the inverse transform unit 140 and the prediction block predicted by the predictor 110 are added together to reconstruct the sample (or the reconstructed sample array). A reconstructed block including a may be generated.

In FIG. 1, it is described that a reconstructed block is generated by adding a residual block and a prediction block through an adder. In this case, the adder may be viewed as a separate unit (restore block generation unit) for generating a reconstruction block.

The filter unit 145 may apply a deblocking filter, an adaptive loop filter (ALF), and a sample adaptive offset (SAO) to the reconstructed picture.

The deblocking filter may remove distortion generated at the boundary between blocks in the reconstructed picture. The adaptive loop filter (ALF) may perform filtering based on a value obtained by comparing the reconstructed image with the original image after the block is filtered through the deblocking filter. ALF may be performed only when high efficiency is applied. The SAO restores the offset difference from the original image on a pixel-by-pixel basis for the residual block to which the deblocking filter is applied, and is applied in the form of a band offset and an edge offset.

Meanwhile, the filter unit 145 may not apply filtering to the reconstructed block used for inter prediction.

The memory 150 may store the reconstructed block or the picture calculated by the filter unit 145. The reconstructed block or picture stored in the memory 150 may be provided to the predictor 110 that performs inter prediction.

2 is a block diagram schematically illustrating a video decoding apparatus according to an embodiment of the present invention. Referring to FIG. 2, the video decoding apparatus 200 includes an entropy decoding unit 210, a reordering unit 215, an inverse quantization unit 220, an inverse transform unit 225, a prediction unit 230, and a filter unit 235. Memory 240 may be included.

When an image bitstream is input in the video encoding apparatus, the input bitstream may be decoded according to a procedure in which image information is processed in the video encoding apparatus.

The entropy decoding unit 210 may entropy decode the input bitstream according to a probability distribution to generate symbols including symbols in the form of quantized coefficients. The entropy decoding method is a method of generating each symbol by receiving a binary string. The entropy decoding method is similar to the entropy encoding method described above.

For example, when variable length coding (VLC, hereinafter called 'VLC') is used to perform entropy encoding in the video encoding apparatus, the entropy decoding unit 210 also uses the VLC. Entropy decoding may be performed by implementing the same VLC table as the table. In addition, when CABAC is used to perform entropy encoding in the video encoding apparatus, the entropy decoding unit 210 may correspondingly perform entropy decoding using CABAC.

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 may be determined using the context model, the probability of occurrence of a bin may be predicted according to the determined context model, and arithmetic decoding of the bin may be performed to generate a symbol corresponding to the value of each syntax element. have. 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 / bean after determining the context model.

Information for generating the prediction block among the information decoded by the entropy decoding unit 210 is provided to the predictor 230, and a residual value where entropy decoding is performed by the entropy decoding unit 210, that is, a quantized transform coefficient It may be input to the reordering unit 215.

The reordering unit 215 may reorder the information of the bitstream entropy decoded by the entropy decoding unit 210, that is, the quantized transform coefficients, based on the reordering method in the encoding apparatus.

The reordering unit 215 may reorder the coefficients expressed in the form of a one-dimensional vector by restoring the coefficients in the form of a two-dimensional block. The reordering unit 215 scans the coefficients based on the prediction mode applied to the current block (transform block) and the size of the transform block to generate an array of coefficients (quantized transform coefficients) in the form of a two-dimensional block. Can be.

The inverse quantization unit 220 may perform inverse quantization based on the quantization parameter provided by the encoding apparatus and the coefficient values of the rearranged block.

The inverse transform unit 225 may perform inverse DCT and / or inverse DST on the DCT and the DST performed by the transform unit of the encoding apparatus with respect to the quantization result performed by the video encoding apparatus.

The inverse transformation may be performed based on a transmission unit determined by the encoding apparatus or a division unit of an image. The DCT and / or DST in the encoding unit of the encoding apparatus may be selectively performed according to a plurality of pieces of information, such as a prediction method, a size and a prediction direction of the current block, and the inverse transform unit 225 of the decoding apparatus is configured in the transformation unit of the encoding apparatus. Inverse transformation may be performed based on the performed transformation information.

The prediction unit 230 may include prediction samples (or prediction sample arrays) based on prediction block generation related information provided by the entropy decoding unit 210 and previously decoded block and / or picture information provided by the memory 240. A prediction block can be generated.

When the prediction mode for the current PU is an intra prediction mode, intra prediction for generating a prediction block based on pixel information in the current picture may be performed.

When the prediction mode for the current PU is an inter prediction mode, inter prediction on the current PU may be performed based on information included in at least one of a previous picture or a subsequent picture of the current picture. In this case, motion information required for inter prediction of the current PU provided by the video encoding apparatus, for example, a motion vector, a reference picture index, and the like, may be derived by checking a skip flag, a merge flag, and the like received from the encoding apparatus.

In inter prediction on a current picture, a prediction block may be generated such that a residual signal with a current block is minimized and a motion vector size is also minimized.

Meanwhile, the motion information derivation scheme may vary depending on the prediction mode of the current block. Prediction modes applied for inter prediction may include an advanced motion vector prediction (AMVP) mode, a merge mode, and the like.

For example, when the merge mode is applied, the encoding apparatus and the decoding apparatus may generate a merge candidate list by using the motion vector of the reconstructed spatial neighboring block and / or the motion vector corresponding to the 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 encoding apparatus may transmit, to the decoding apparatus, 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 decoding apparatus may derive the motion vector of the current block by using the merge index.

As another example, when the Advanced Motion Vector Prediction (AMVP) mode is applied, the encoding device and the decoding device use a motion vector corresponding to a motion vector of a reconstructed spatial neighboring block and / or a Col block, which is a temporal neighboring block, and a motion vector. A predictor candidate list may be generated. 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 encoding apparatus may transmit the predicted motion vector index indicating the optimal motion vector selected from the motion vector candidates included in the list to the decoding apparatus. In this case, the decoding apparatus may select the predicted motion vector of the current block among the motion vector candidates included in the motion information candidate list using the motion vector index.

The encoding apparatus may obtain a motion vector difference MVD between the motion vector MV of the current block and the motion vector predictor MVP, and may encode the same and transmit the encoded motion vector to the decoding device. That is, MVD may be obtained by subtracting MVP from MV of the current block. In this case, the decoding apparatus may decode the received motion vector difference and derive the motion vector of the current block through the addition of the decoded motion vector difference and the motion vector predictor.

The encoding apparatus may also transmit a reference picture index or the like indicating the reference picture to the decoding apparatus.

The decoding apparatus may predict the motion vector of the current block using the motion information of the neighboring block, and may derive the motion vector for the current block using the residual received from the encoding apparatus. The decoding apparatus may generate a prediction block for the current block based on the derived motion vector and the reference picture index information received from the encoding apparatus.

As another example, when the merge mode is applied, the encoding apparatus and the decoding apparatus may generate the merge candidate list using the motion information of the reconstructed neighboring block and / or the motion information of the call block. That is, the encoding apparatus and the decoding apparatus may use this as a merge candidate for the current block when there is motion information of the reconstructed neighboring block and / or the call block.

The encoding apparatus may select a merge candidate capable of providing an optimal encoding efficiency among the merge candidates included in the merge candidate list as motion information for the current block. In this case, a merge index indicating the selected merge candidate may be included in the bitstream and transmitted to the decoding apparatus. The decoding apparatus may select one of the merge candidates included in the merge candidate list by using the transmitted merge index, and determine the selected merge candidate as motion information of the current block. Therefore, when the merge mode is applied, motion information corresponding to the reconstructed neighboring block and / or the call block may be used as the motion information of the current block. The decoding apparatus may reconstruct the current block by adding the prediction block and the residual transmitted from the encoding apparatus.

In the above-described AMVP and merge mode, the motion information of the reconstructed neighboring block and / or the motion information of the call block may be used to derive the motion information of the current block.

In the case of a skip mode, which is one of other modes used for inter prediction, information of neighboring blocks may be used in the current block as it is. Therefore, in the skip mode, the encoding apparatus does not transmit syntax information such as residual to the decoding apparatus other than information indicating which block motion information to use as the motion information of the current block.

The encoding apparatus and the decoding apparatus may generate the prediction block of the current block by performing motion compensation on the current block based on the derived motion information. Here, the prediction block may mean a motion compensated block generated as a result of performing motion compensation on the current block. Also, the plurality of motion compensated blocks may constitute one motion compensated image.

The reconstruction block may be generated using the prediction block generated by the predictor 230 and the residual block provided by the inverse transform unit 225. In FIG. 2, it is described that the reconstructed block is generated by combining the prediction block and the residual block in the adder. In this case, the adder may be viewed as a separate unit (restore block generation unit) for generating a reconstruction block. Here, the reconstruction block includes a reconstruction sample (or reconstruction sample array) as described above, the prediction block includes a prediction sample (or a prediction sample array), and the residual block is a residual sample (or a residual sample). Array). Thus, a reconstructed sample (or reconstructed sample array) may be expressed as the sum of the corresponding predictive sample (or predictive sample array) and the residual sample (residual sample array).

The residual is not transmitted for the block to which the skip mode is applied, and the prediction block may be a reconstruction block.

The reconstructed block and / or picture may be provided to the filter unit 235. The filter unit 235 may apply deblocking filtering, sample adaptive offset (SAO), and / or ALF to the reconstructed block and / or picture.

The memory 240 may store the reconstructed picture or block to use as a reference picture or reference block and provide the reconstructed picture to the output unit.

Entropy decoding unit 210, reordering unit 215, inverse quantization unit 220, inverse transform unit 225, predictor 230, filter unit 235, and memory 240 included in the decoding device 200. ) Components directly related to the decoding of an image, for example, an entropy decoding unit 210, a reordering unit 215, an inverse quantization unit 220, an inverse transform unit 225, a prediction unit 230, and a filter unit ( 235) and the like may be distinguished from other components by a decoder or a decoder.

In addition, the decoding apparatus 200 may further include a parsing unit (not shown) for parsing information related to the encoded image included in the bitstream. The parsing unit may include the entropy decoding unit 210 or may be included in the entropy decoding unit 210. Such a parser may also be implemented as one component of the decoder.

As described above, a method of deriving the motion vector of the current block coded in the inter prediction mode is obtained by correctly receiving the motion vector of the neighboring block of the current block and information on the motion vector of the current block. Can be divided into modes. In detail, a method of deriving the motion vector of the current block may include a merge mode and an AMVP mode. However, in the merge mode, information for indicating one of neighbor candidate blocks (ex. Merge index) should be transmitted, and in the AMVP mode, information for indicating one of candidates derived based on neighbor blocks ( ex. MVP flag) and additional MVD (motion vector difference) should still be transmitted.

Accordingly, when the inter prediction mode is performed, a data amount for transmitting side information related to the inter prediction mode is required, and the present invention proposes a modified inter prediction mode that eliminates or minimizes transmission of the side information. Applying the modified inter prediction mode according to the present invention can reduce or eliminate the amount of data for the side information, thereby improving the overall coding efficiency. The present invention provides the modified inter prediction mode for deriving motion vectors of neighboring blocks of the current block and deriving a motion vector of the current block based on a comparison between motion vectors of the neighboring blocks. The modified inter prediction mode may be referred to as a frame rate up-conversion (FRUC) mode. In the modified inter prediction mode, for example, the image may be coded assuming that the object moves at a constant speed in the image, and there is no change in the pixel value (sample value).

3 exemplarily shows an encoding method of a current block to which a modified inter prediction mode is applied. Referring to FIG. 3, motion information of the current block may be derived based on motion information of neighboring blocks of the current block. The motion information may include at least one of a motion vector and a reference picture index. The encoding apparatus may derive the motion information candidate list of the current block based on the neighboring blocks (S300). The motion vector candidate of the neighboring block may be a bi-predicted motion vector candidate or may be a L0 or L1 predicted motion vector candidate. The L0 / or L1 predicted motion vector candidate may also be referred to as a unipredicted motion vector candidate. The bi-predicted motion vector candidate may include a motion vector in the L0 direction and a motion vector in the L1 direction, and the unipredicted motion vector candidate may include only one of the L0 direction motion vector and the L1 direction motion vector. L0 represents a reference picture list L0 (list 0), and L1 represents a reference picture list L1 (list 1). Specifically, when the motion vector information of the neighboring block is bi-predictive motion vector information, the motion vector associated with the L0 reference picture index and the reference picture included in L0, the motion vector associated with the L1 reference picture index and the reference picture included in L1. It may include. Bi-predictive motion vector information of the neighboring block may be derived as a (bipredictive) motion vector candidate of the current block. When the motion vector information of the neighboring block is unipredicted motion vector information, the motion vector may include an L0 reference picture index and a motion vector associated with a reference picture included in L0, or the L1 reference picture index and a reference picture included in L1. It may include an associated motion vector. The short-predicted motion vector information of the neighboring block may be derived as the (unipredictive) motion vector candidate of the current block, or based on the short-predicted motion vector candidate of the neighboring block, It can also be derived.

When the modified inter prediction mode is applied to the current block, motion vectors included in the motion vector candidate may be divided into L0 and L1 directions.

The encoding apparatus may derive an optimal motion vector among the motion vectors by comparing the separated motion vectors through a bilateral matching method (S310), and compare the motion vectors through a template matching method. In operation S320, an optimal motion vector among the motion vectors may be derived. In addition, the encoding apparatus may select a better matching method among the bilateral matching method and the template matching method and derive an optimal motion vector (S330). The motion vector may be derived through one of the above-described methods of deriving the motion vector or a combination of the above methods (S340). In this case, the motion vectors of the sub-blocks in the current block may be more precisely derived by refining the motion vectors (S350). Meanwhile, although both a bilateral matching method and a template matching method are shown in FIG. 3, this is only an example of one of the two matching methods, and in this case, the S330 procedure of selecting one of the S310 and S320 and a better matching method. May be omitted. Meanwhile, the S350 procedure may be omitted in some cases. Meanwhile, the encoding apparatus may generate flag information about the selection of the bilateral matching method or the template matching method, and may encode the flag information and output it in a bitstream form. The decoding apparatus may select a matching method based on the value of the flag information. The bilateral matching method and the template matching method will be described later.

4 exemplarily illustrates a decoding method of a current block to which a modified inter prediction mode is applied. Referring to FIG. 4, a motion vector of the current block may be derived based on motion vectors of neighboring blocks of the current block. The decoding apparatus may derive a motion information candidate list of the current block based on the neighboring blocks (S400). The motion vector candidate of the neighboring block may be a bi-prediction motion vector candidate or a uni-prediction motion vector candidate.

The decoding apparatus may obtain information about a matching method for deriving an optimal motion vector from the encoding apparatus, and may derive an optimal motion vector according to the matching method (S410). The matching method may be the above-described bilateral matching method or template matching method. The decoding apparatus may obtain a flag for selecting the bilateral matching method or template matching method through a bitstream. The flag may also be referred to as a bilateral / template selection flag. The decoding apparatus may select a matching method based on the value of the bilateral / template selection flag. For example, when the value of the bilateral / template selection flag is 1, the bilateral matching method may be performed. When the value of the flag information is 1, the template matching method may be performed. The bilateral matching method and the template matching method will be described later. The decoding apparatus may derive the motion vector of the current block based on the motion vector (S420). In this case, finer motion vectors for each subblock in the current block may be derived by refining the motion vector (S430). Meanwhile, the S430 procedure may be omitted in some cases.

As a method of searching for an optimal motion vector, for example, a bilateral matching method and / or a template matching method may be used.

5 illustrates an example of comparing a motion vector through a bilateral matching method. When the modified inter prediction mode is applied to the current block, motion vectors included in information about motion vectors of the neighboring blocks may be divided into L0 and L1 directions. The divided motion vectors are sequentially selected one by one, and then interpolated around a picture to which the current block belongs to correspond to the motion vectors in a direction different from the direction associated with the motion vectors among the L0 and L1 directions. Motion vectors can be derived. For example, when the motion vector candidate of the current block is a motion vector in the L0 direction, the motion vector candidate may be scaled in the L1 direction based on a temporal distance between the motion vector and the picture to which the current block belongs. A motion vector in the L1 direction corresponding to the motion vector can be derived. The reference picture including the reference region indicated by the motion vector in the L1 direction includes a difference value from the reference region indicated by the motion vector in the L0 direction among the reference pictures included in the L1, that is, a reference region having the smallest residual. Can be derived as a reference picture. If the motion vector candidate of the current block is a motion vector in the L1 direction, the motion vector candidate may be scaled in the L0 direction based on a temporal distance between the motion vector and the picture to which the current block belongs, and the motion vector A motion vector in the L0 direction corresponding to may be derived. The reference picture including the reference region indicated by the motion vector in the L0 direction includes a difference value from the reference region indicated by the motion vector in the L1 direction among the reference pictures included in the L0, that is, the reference region having the smallest residual. Can be derived as a reference picture.

Next, a motion vector having the smallest difference between the reference region indicated by the motion vector and the reference region indicated by the motion vector corresponding to the motion vector among the motion vectors included in the motion vector candidate of the current block may be derived as the optimal motion vector. Can be. That is, a difference value between samples according to a phase of a reference region indicated by the motion vector and a reference region indicated by the motion vector corresponding to the motion vector, that is, residual can be derived, and the residual is minimal. The motion vector may be derived as an optimal motion vector of the current block.

6 illustrates an example of comparing a motion vector through a template matching method. Referring to FIG. 6, one of a motion vector candidate of the motion vector candidate of the current block may be selected to compare neighboring samples of the reference region indicated by the motion vector with neighboring samples of the current block. When the modified inter prediction mode is applied to the current block, motion vectors included in information about motion vectors of the neighboring blocks may be divided into L0 and L1 directions. The divided motion vectors may be sequentially selected to derive a reference region indicated by the selected motion vector. The value of the neighboring samples 600 of the reference region may be compared with the value of the neighboring samples 610 of the current block. The difference (or residual) of the neighboring samples 600 of the reference region (reference block) and the neighboring samples 610 of the current block may be derived and compared, and the reference region for the case where the difference is minimum is compared. The pointing motion vector can be derived as an optimal motion vector for the current block.

According to the above-described method, the decoding apparatus may not receive from the encoding apparatus what motion vector is used as the motion vector of the current block. Therefore, in order to derive the optimal motion vector described above, the decoding apparatus may need to find the optimal motion vector in the same manner as the encoding apparatus. When the optimal motion vector is found in the same manner as the encoding apparatus, the sophisticated motion can be found and predicted without any additional signaling. However, it is necessary to search for all possible motion vector candidates, which can significantly increase the computational complexity of the decoding apparatus. Accordingly, the present invention additionally provides a method for efficiently reducing motion vector candidates to be considered.

7 illustrates an example of a method of deriving motion vector candidates. Referring to FIG. 7, the decoding apparatus may select an optimal motion vector of the current block by using motion information of neighboring blocks of the current block. The decoding apparatus may derive a preliminary motion information candidate list including bipredicted motion vector candidates based on the neighboring block (S700). The decoding apparatus may derive one of the motion vectors included in the candidate list as the first anchor vector (S710). The first anchor vector may be an L0 direction motion vector or an L1 direction motion vector. After deriving the first anchor vector, the decoding apparatus may derive a second anchor vector by linearly interpolating the first anchor vector in another direction (S720). That is, the second anchor vector may be derived by scaling the first anchor vector in a direction different from the direction associated with the first anchor vector among the L0 direction and the L1 direction. For example, when the first anchor vector is an L0 direction motion vector, the first anchor vector may be scaled in the L1 direction to be derived as a second anchor vector that is an L1 direction motion vector. The reference picture including the reference region indicated by the second anchor vector includes a reference value that includes a difference value from the reference region indicated by the first anchor vector among the reference pictures included in the L1, that is, a reference region having the smallest residual. It can be derived as a picture. Meanwhile, when the first anchor vector is an L1 direction motion vector, the first anchor vector may be scaled in the L0 direction to be derived as a second anchor vector that is an L0 direction motion vector. The reference picture including the reference region indicated by the second anchor vector includes a reference value having a difference value from the reference region indicated by the first anchor vector among the reference pictures included in the L0, that is, a reference region having the smallest residual. It can be derived as a picture.

After deriving the second anchor vector, the decoding apparatus performs motion vectors in a direction different from the first anchor vector among the motion vectors included in the preliminary motion information candidate list, that is, the motion in the same direction as the second anchor vector. Vectors may be compared with the second anchor vector, and a difference value between the value of the second anchor vector and the values of the motion vectors in the same direction may be derived (S730). For example, when the first anchor vector is an L0 direction motion vector, L1 direction motion vectors may be derived, and a difference value between the value of each motion vector and the value of the second anchor vector may be derived. Meanwhile, when the first anchor vector is an L0 direction motion vector, L1 direction motion vectors may be derived, and a difference value between the value of each motion vector and the value of the second anchor vector may be derived.

When deriving difference values between the second anchor vector and the motion vectors, the decoding apparatus derives a motion information candidate list of the current block including motion vectors having difference values equal to or less than a predetermined threshold value among the difference values. It may be (S740). The decoding apparatus may search for an optimal motion vector by deriving motion vectors of some of the motion vector information of the neighboring block through the above-described method.

In the above-described method, the optimal motion vector may be searched after selecting the motion vectors satisfying a predetermined condition instead of finding the optimal motion vector from all motion vectors of the neighboring blocks. Therefore, the above-described method can reduce the process of searching for the optimal motion vector.

8 illustrates an example of a method of deriving a motion vector of a current block based on motion information of a neighboring block. Referring to FIG. 8, an optimal motion vector of the current block may be selected by using motion information of neighboring blocks of the current block. The decoding apparatus may derive a preliminary motion information candidate list including bipredicted motion vector candidates based on the neighboring block (S800). The decoding apparatus may derive one of the motion vectors included in the candidate list as the first anchor vector (S810). The first anchor vector may be an L0 direction motion vector or an L1 direction motion vector. After deriving the first anchor vector, the decoding apparatus may linearly interpolate the first anchor vector in another direction to derive a second anchor vector (S820). That is, the second anchor vector may be derived by scaling the first anchor vector in a direction different from the direction associated with the first anchor vector among the L0 direction and the L1 direction. For example, when the first anchor vector is an L0 direction motion vector, the first anchor vector may be scaled in the L1 direction to be derived as a second anchor vector that is an L1 direction motion vector. The reference picture including the reference region indicated by the second anchor vector includes a reference value that includes a difference value from the reference region indicated by the first anchor vector among the reference pictures included in the L1, that is, a reference region having the smallest residual. It can be derived as a picture. Meanwhile, when the first anchor vector is an L1 direction motion vector, the first anchor vector may be scaled in the L0 direction to be derived as a second anchor vector that is an L0 direction motion vector. The reference picture including the reference region indicated by the second anchor vector includes a reference value having a difference value from the reference region indicated by the first anchor vector among the reference pictures included in the L0, that is, a reference region having the smallest residual. It can be derived as a picture.

After deriving the second anchor vector, the decoding apparatus performs motion vectors in a direction different from the first anchor vector among the motion vectors included in the preliminary motion information candidate list, that is, the motion in the same direction as the second anchor vector. Vectors may be compared with the second anchor vector, and a difference value between the value of the second anchor vector and the values of the motion vectors in the same direction may be derived (S830). For example, when the first anchor vector is an L0 direction motion vector, L1 direction motion vectors may be derived, and a difference value between the value of each motion vector and the value of the second anchor vector may be derived. Meanwhile, when the first anchor vector is an L0 direction motion vector, L1 direction motion vectors may be derived, and a difference value between the value of each motion vector and the value of the second anchor vector may be derived.

When the difference values between the second anchor vector and the motion vectors are derived, the decoding apparatus may derive a motion vector having the minimum difference value among the difference values as the motion vector of the current block (S840). A motion vector having the minimum difference value may be derived as an optimal motion vector.

In the case of using the above-described method, instead of finding an optimal motion vector from all motion vectors of the neighboring blocks, a motion vector satisfying a predetermined condition may be derived as an optimal motion vector. Therefore, the above-described method can reduce the process of searching for the optimal motion vector.

9 illustrates an example of a method of deriving motion vector candidates. Referring to FIG. 9, an optimal motion vector of the current block may be selected by using motion information of neighboring blocks of the current block. The decoding apparatus may derive a preliminary motion information candidate list including bipredicted motion vector candidates based on the neighboring block (S900). Next, a difference value between the absolute value of the L0 direction motion vector and the absolute value of the L1 direction motion vector included in the bi-predicted motion vector candidate may be derived (S910). When a difference value of each bi-predicted motion vector candidate is derived, the decoding apparatus may compare the values of the difference values with a preset threshold, and include motion vectors having a difference value less than or equal to the threshold value of the current block. The motion information candidate list may be derived (S920). In the decoding apparatus, the L0 direction motion vector and the L1 direction motion vector of the motion vector information of the neighboring blocks are not vectors having a size of 0, and the absolute value of the L0 direction motion vector and the L1 direction motion vector are described above. The optimal motion vector may be searched by deriving bi-predicted motion vector candidates whose difference between the absolute values of is less than or equal to the threshold.

10 illustrates an example of a method of deriving a motion vector of a current block based on motion information of a neighboring block. Referring to FIG. 10, an optimal motion vector of the current block may be selected by using motion information of neighboring blocks of the current block. A preliminary motion information candidate list including bipredicted motion vector candidates may be derived based on the neighboring block (S1000). Next, a difference value between the absolute value of the L0 direction motion vector and the absolute value of the L1 direction motion vector included in the bi-predicted motion vector candidate may be derived (S1010). When the difference value of the bi-prediction motion vector candidates is derived, the decoding apparatus may derive the bi-prediction motion vector candidate having the minimum difference value as the optimal motion vector (S1020). The decoding apparatus is a bi-predictive motion in which the L0 direction motion vector and the L1 direction motion vector are not vectors having a magnitude of zero, and the difference value between the absolute value of the L0 direction motion vector and the absolute value of the L1 direction motion vector is minimum. Vector candidates can be derived.

11 illustrates an example of a method of deriving motion vector candidates. Referring to FIG. 11, an optimal motion vector of the current block may be selected by using motion information of neighboring blocks of the current block. The decoding apparatus may derive a preliminary motion information candidate list including unipredicted motion vector candidates based on the neighboring block (S1100). Next, an absolute value of a motion vector included in each of the single predictive motion vector candidates may be compared with a preset threshold value, and the motion of the current block including short predictive motion vector candidates having the absolute value less than or equal to the threshold value may be compared. The information candidate list may be derived (S1110). The motion vector of each of the short prediction motion vector candidates may be a L0 direction motion vector or an L1 direction motion vector. When the modified inter prediction mode is applied, it may be assumed that when the motion prediction is performed, ideally, the motion of the object in the image is constant and the sample value does not change. In this case, it can be said that the vector having small motion is most likely to meet the above condition.

12 illustrates an example of a method of deriving a motion vector of a current block based on motion information of a neighboring block. Referring to FIG. 12, an optimal motion vector of the current block may be selected by using motion information of neighboring blocks of the current block. A preliminary motion information candidate list including unipredicted motion vector candidates may be derived based on the neighboring block (S1200). Next, absolute values of the motion vectors of the single predicted motion vector candidates may be compared, and a motion vector having a minimum absolute value may be derived as a motion vector of the current block (S1210). The motion vector of each of the short prediction motion vector candidates may be a L0 direction motion vector or an L1 direction motion vector. When the modified inter prediction mode is applied, it may be assumed that when the motion prediction is performed, ideally, the motion of the object in the image is constant and the sample value does not change. In this case, it can be said that the vector having small motion is most likely to meet the above condition.

In the above-described embodiments, the methods shown in FIGS. 7 to 10 may be implemented in consideration of only the bi-predicted motion vector candidates of neighboring blocks. In addition to the bi-predicted motion vector candidate, the short predicted motion vector candidate of the neighboring block may be additionally considered. In this case, the single predicted motion vector candidate may be derived and executed in the same form as the bipredicted motion vector candidate. In detail, a motion vector corresponding to the motion vector may be derived by scaling a motion vector included in the single predicted motion vector candidate in a direction different from a direction associated with the motion vector among the L0 direction and the L1 direction. . For example, when the motion vector included in the short-predicted motion vector candidate is an L0 direction motion vector, the L0 direction motion vector may be scaled in the L1 direction to derive an L1 direction motion vector corresponding to the L0 direction motion vector. have. A reference picture including a reference region indicated by the L1 direction motion vector includes a reference value that is a difference value from the reference region indicated by the L0 direction motion vector among the reference pictures included in the L1, that is, a reference region having the smallest residual. It can be derived as a picture. Meanwhile, when the motion vector included in the short-predicted motion vector candidate is an L1 direction motion vector, the L1 direction motion vector may be scaled in the L0 direction to derive an L0 direction motion vector corresponding to the L1 direction motion vector. The reference picture including the reference region indicated by the L0 direction motion vector includes a reference value that is a difference value from the reference region indicated by the L1 direction motion vector among the reference pictures included in the L0, that is, a reference region having the smallest residual. It can be derived as a picture.

In addition, the single-predicted motion vector candidate may be added as a candidate of the motion information candidate list of the current block of the methods shown in FIGS. 7 to 10 without any separate selection process. In addition, the short-predicted motion vector candidates are selected through the methods shown in FIGS. 11 to 12 and the selected short-predicted motion vector candidates are candidates for the motion information candidate list of the current block of the methods shown in FIGS. 7 to 10. You can add

In the above-described embodiments, the methods illustrated in FIGS. 11 to 12 may be implemented in consideration of only a single predictive motion vector candidate of a neighboring block.

In addition, the prediction may be performed in consideration of the bi-predicted motion vector candidate of the neighboring block as well as the single-predicted motion vector candidate. In this case, all of the bi-predicted motion vector candidates may be added as candidates for the motion information candidate list of the current block without a separate selection process. In this case, all the motion vectors included in the bi-predicted motion vector candidate, that is, both the L0 direction motion vector and the L1 direction motion vector may be used in a method for deriving an optimal motion vector.

In addition, the bi-predicted motion vector candidate is selected through the methods shown in FIGS. 7 to 10 described above, and the selected bi-predicted motion vector candidate is selected as a candidate of the motion information candidate list of the current block of the methods shown in FIGS. 11 to 12. You can add

Meanwhile, the encoding apparatus may transmit a flag indicating whether the modified inter prediction mode is applied to the decoding apparatus. The flag may also be referred to as a FRUC flag. The encoding apparatus may transmit information indicating whether the modified prediction mode of the current block is applied through the flag. For example, if the value of the flag is 1, the modified inter prediction mode may be applied to derive an optimal motion vector of the current block. For example, if the value of the FRUC flag is 0, the merge mode or the AMVP mode may be used. Accordingly, the motion vector of the current block can be derived.

13 schematically illustrates a video encoding method by an encoding device according to the present invention. The method disclosed in FIG. 13 may be performed by the encoding apparatus disclosed in FIG. 1. Specifically, for example, S1300 to S1330 of FIG. 13 may be performed by the prediction unit of the encoding apparatus, and S1340 may be performed by the entropy encoding unit of the encoding apparatus.

The encoding apparatus derives the motion information candidate list of the current block based on the neighboring blocks of the current block (S1300). The motion vector candidate of the neighboring block may be a bi-prediction motion vector candidate or a uni-prediction motion vector candidate. The bi-predicted motion vector candidate may include a motion vector in the L0 direction and a motion vector in the L1 direction, and the unipredicted motion vector candidate may include only one of the L0 direction motion vector and the L1 direction motion vector.

The encoding apparatus may derive all motion vector information as a candidate to construct the motion information candidate list. In addition, the encoding apparatus may construct the motion information candidate list by selectively deriving a candidate from the motion vector information of the neighboring block.

For example, the encoding apparatus may derive a first motion information candidate list including bipredicted motion vector candidates based on the neighboring block, and the encoding apparatus may generate a motion vector of one of the first motion information candidate lists first. Can be derived from the anchor vector. The first anchor vector may be an L0 direction motion vector or an L1 direction motion vector. After deriving the first anchor vector, the encoding apparatus may scale the first anchor vector in a direction different from a direction associated with the first anchor vector among the L0 direction and the L1 direction to derive a second anchor vector. Can be. For example, when the first anchor vector is an L0 direction motion vector, the first anchor vector may be scaled in the L1 direction to be derived as a second anchor vector that is an L1 direction motion vector. The reference picture including the reference region indicated by the second anchor vector includes a reference value that includes a difference value from the reference region indicated by the first anchor vector among the reference pictures included in the L1, that is, a reference region having the smallest residual. It can be derived as a picture. Meanwhile, when the first anchor vector is an L1 direction motion vector, the first anchor vector may be scaled in the L0 direction to be derived as a second anchor vector that is an L0 direction motion vector. The reference picture including the reference region indicated by the second anchor vector includes a reference value having a difference value from the reference region indicated by the first anchor vector among the reference pictures included in the L0, that is, a reference region having the smallest residual. It can be derived as a picture.

After deriving the second anchor vector, the encoding apparatus performs the current block based on the motion vector having the same direction as the second anchor vector in the first motion information candidate list and a magnitude difference from the second anchor vector is equal to or less than a preset threshold. The motion information candidate list can be derived. For example, when the second anchor vector is a L0 direction motion vector, the motion information candidate list of the current block based on a motion vector whose magnitude difference from the second anchor vector among the L0 direction motion vectors is equal to or less than a preset threshold. Can be derived. On the other hand, when the second anchor vector is a L1 direction motion vector, a motion information candidate list of the current block is derived based on a motion vector whose magnitude difference from the second anchor vector in the L1 direction is less than or equal to a preset threshold. can do.

As another example, the encoding apparatus may derive a first motion information candidate list based on the neighboring block, and the absolute value and the L1 direction of the L0 direction motion vector of each bi-predicted motion vector candidate included in the first motion information candidate list. The difference between the absolute values of the motion vectors can be derived. The encoding apparatus may derive a motion information candidate list of the current block based on the bi-predicted motion vector candidate having the difference value equal to or less than a preset threshold. In the case of the short predicted motion vector candidate included in the first motion information candidate list, the encoding apparatus is further configured to associate the first motion vector included in the short predicted motion vector candidate with the first motion vector in the L0 direction and the L1 direction. A second motion vector may be derived by scaling in a direction different from a direction, and the single-predicted motion vector candidate is derived as a bi-predicted motion vector candidate including the first motion vector and the second motion vector. One method can be applied. In detail, when the first motion vector is a L0 direction motion vector, a second motion vector that is an L1 direction motion vector may be derived by scaling in the L1 direction. In addition, when the first motion vector is a L1 direction motion vector, a second motion vector that is a L0 direction motion vector may be derived by scaling in the L0 direction. In this case, the reference picture associated with the second motion vector includes the second reference area having a minimum residual between the first reference area indicated by the first motion vector and the second reference area indicated by the second motion vector. It may be a picture to include.

As another example, the encoding apparatus may derive a first motion information candidate list based on the neighboring block, and determine whether an absolute value of a motion vector of each motion vector candidate is less than or equal to a preset threshold in the first motion information candidate list. can do. The encoding apparatus may derive a motion information candidate list of the current block based on the motion vector candidate whose absolute value of the motion vector is less than or equal to the threshold. When the motion vector candidate is a unidirectional motion vector candidate, the motion vector of the short prediction motion vector candidate may be a L0 direction motion vector or an L1 direction motion vector. The encoding apparatus may additionally consider the bi-prediction motion vector candidate. The encoding apparatus may determine each motion vector by dividing the L0 direction motion vector and the L1 direction motion vector included in the bi-predicted motion vector candidate, and include each motion vector as a candidate of the motion information candidate list. .

Meanwhile, when the modified inter prediction mode is applied to the current block, the encoding apparatus may derive the motion information candidate list based on the above-described method, and generate a FRUC flag. When the modified inter prediction mode of the current block is applied, the value of the FRUC flag may appear as 1.

The encoding apparatus selects a specific candidate based on the comparison of the candidates in the motion information candidate list (S1310). For example, the encoding apparatus may compare candidates in the motion information candidate list through a bilateral matching method. The encoding apparatus may divide the motion vectors included in the motion information candidate list into the L0 direction and the L1 direction. The encoding apparatus may sequentially select the divided motion vectors as the first motion vector. The encoding apparatus scales the first motion vector included in the motion information candidate list in a direction different from a direction associated with the first motion vector among the L0 direction and the L1 direction to correspond to the first motion vector. We can derive 2 motion vectors. For example, when the first motion vector is a motion vector in the L0 direction, the first motion vector may be scaled in the L1 direction based on a temporal distance between the current picture and a reference picture associated with the first motion vector. The second motion vector in the L1 direction corresponding to the first motion vector may be derived. The reference picture including the reference region indicated by the second motion vector includes a reference value that is a difference value from the reference region indicated by the first motion vector among the reference pictures included in the L1, that is, a reference region having the smallest residual. It can be derived as a picture. In addition, when the first motion vector is a motion vector in the L1 direction, the first motion vector may be scaled in the L0 direction based on a temporal distance between the current picture and a reference picture associated with the first motion vector. The second motion vector in the L0 direction corresponding to the vector may be derived. The reference picture including the reference region indicated by the second motion vector includes a reference value that is a difference value from the reference region indicated by the first motion vector among the reference pictures included in the L0, that is, a reference region having the smallest residual. It can be derived as a picture.

Next, the encoding apparatus may derive a residual of the reference region indicated by the first motion vector and the reference region indicated by the second motion vector, and encodes the first motion vector and the second motion vector having the minimum residual. You can choose to be a specific candidate. That is, a first motion vector and a second motion vector having a minimum difference value between samples according to a phase of a reference region indicated by the first motion vector and a reference region indicated by the second motion vector are the specific candidates. Can be derived.

As another example, the encoding apparatus may compare candidates in the motion information candidate list through a template matching method. The encoding apparatus may derive the reference block indicated by the motion vector 1 included in the motion information candidate list. The encoding apparatus may derive a difference value between the value of the neighboring sample of the reference block and the value of the neighboring sample of the current block corresponding to the neighboring sample. The encoding apparatus may select the motion vector 1 as the specific candidate when the difference value is the minimum among the difference values of the motion vectors included in the motion information candidate list.

As another example, the encoding apparatus may select a specific candidate based on an anchor vector. In detail, the encoding apparatus may derive one motion vector of the motion information candidate list as a first anchor vector. The first anchor vector may be an L0 direction motion vector or an L1 direction motion vector. After deriving the first anchor vector, the encoding apparatus may scale the first anchor vector in a direction different from a direction associated with the first anchor vector among the L0 direction and the L1 direction to derive a second anchor vector. Can be. For example, when the first anchor vector is an L0 direction motion vector, the first anchor vector may be scaled in the L1 direction to be derived as a second anchor vector that is an L1 direction motion vector. The reference picture including the reference region indicated by the second anchor vector includes a reference value that includes a difference value from the reference region indicated by the first anchor vector among the reference pictures included in the L1, that is, a reference region having the smallest residual. It can be derived as a picture. Meanwhile, when the first anchor vector is an L1 direction motion vector, the first anchor vector may be scaled in the L0 direction to be derived as a second anchor vector that is an L0 direction motion vector. The reference picture including the reference region indicated by the second anchor vector includes a reference value having a difference value from the reference region indicated by the first anchor vector among the reference pictures included in the L0, that is, a reference region having the smallest residual. It can be derived as a picture.

After deriving the second anchor vector, the encoding apparatus may select, as the specific candidate, a motion vector having the same direction as the second anchor vector in the motion information candidate list and having a minimum size difference from the second anchor vector. For example, when the second anchor vector is a L0 direction motion vector, a motion vector having a minimum difference in magnitude from the second anchor vector among the L0 direction motion vectors may be derived as the specific candidate. Meanwhile, when the second anchor vector is an L1 direction motion vector, a motion vector having a minimum size difference from the second anchor vector among the motion vectors in the L1 direction may be derived as the specific candidate.

As another example, the encoding apparatus may select the specific candidate based on a comparison between the absolute value of the absolute value of the L0 direction motion vector and the absolute value of the L1 direction motion vector of each bi-predicted motion vector candidate included in the vector candidate list. . The encoding apparatus may derive a difference value between the absolute value of the L0 direction motion vector and the absolute value of the L1 direction motion vector of each bi-predicted motion vector candidate included in the motion information candidate list. The encoding apparatus may select the bi-predicted motion vector candidate having the minimum difference value as the specific candidate. In the case of the short predicted motion vector candidate included in the motion information candidate list, the encoding apparatus may determine a first motion vector included in the short predicted motion vector candidate and a direction associated with the first motion vector among the L0 direction and the L1 direction. A second motion vector can be derived by scaling in a different direction, and the method described above by deriving the single predicted motion vector candidate as a bi-predicted motion vector candidate including the first motion vector and the second motion vector. Can be applied. In detail, when the first motion vector is a L0 direction motion vector, a second motion vector that is an L1 direction motion vector may be derived by scaling in the L1 direction. In addition, when the first motion vector is a L1 direction motion vector, a second motion vector that is a L0 direction motion vector may be derived by scaling in the L0 direction. In this case, the reference picture associated with the second motion vector includes the second reference area having a minimum residual between the first reference area indicated by the first motion vector and the second reference area indicated by the second motion vector. It may be a picture to include.

As another example, the encoding apparatus may select the specific candidate based on a comparison of magnitudes of absolute values of the motion vectors. The encoding apparatus may compare the magnitude of the absolute value of the motion vector of each motion vector candidate to the motion information candidate list. The encoding apparatus may select a motion vector candidate having a minimum absolute value of the motion vector as a specific candidate. When the motion vector candidate is a unidirectional motion vector candidate, the motion vector of the short prediction motion vector candidate may be a L0 direction motion vector or an L1 direction motion vector. The encoding apparatus may additionally consider the bi-prediction motion vector candidate. The encoding apparatus may determine each motion vector by dividing the L0 direction motion vector and the L1 direction motion vector included in the bi-predicted motion vector candidate, and include each motion vector as a candidate of the motion information candidate list. .

Meanwhile, the encoding apparatus may generate a bilateral / template selection flag indicating information on the selection of the above-described matching method. The value of the bilateral / template selection flag may correspond to the bilateral matching method and the template matching method.

The encoding apparatus derives the motion vector of the current block based on the specific candidate (S1320). The motion vector of the current block may be one of a bi-prediction motion vector and a uni-prediction motion vector.

The encoding apparatus generates a prediction sample of the current block based on the motion vector of the current block (S1330). The encoding apparatus may obtain a predictive sample value on the reference picture indicated by the motion vector, and generate the predictive sample.

The encoding apparatus encodes and outputs prediction mode information indicating the inter prediction mode (S1340). The encoding apparatus may entropy-encode the prediction mode information indicating the modified inter prediction mode that derives the motion vector of the current block based on the neighboring blocks of the current block and output the result in a bitstream form. In addition, the encoding apparatus may generate, encode, and output the FRUC flag for determining whether the modified inter prediction mode is applied to the current block, in the form of the bitstream. In addition, the encoding apparatus may generate a bilateral / template selection flag for selecting a matching method for comparing candidates in the motion information candidate list, and may encode and output the bilateral / template selection flag. The prediction mode information, the FRUC flag, and the bilateral / template selection flag may be transmitted to the decoding apparatus in the bitstream form. The bitstream may be transmitted to a decoding apparatus via a network or a storage medium.

Although not shown, the encoding apparatus may encode and output information about the residual sample for the current block. The information about the residual sample may include transform coefficients regarding the residual sample.

14 schematically illustrates a video decoding method by a decoding apparatus according to the present invention. The method disclosed in FIG. 14 may be performed by the decoding apparatus disclosed in FIG. 2. Specifically, for example, S1400 to S1430 of FIG. 14 may be performed by the prediction unit of the decoding apparatus.

The decoding apparatus derives a motion information candidate list of the current block based on the neighboring blocks of the current block (S1400). The motion vector candidate of the neighboring block may be a bi-prediction motion vector candidate or a uni-prediction motion vector candidate. The bi-predicted motion vector candidate may include a motion vector in the L0 direction and a motion vector in the L1 direction, and the unipredicted motion vector candidate may include only one of the L0 direction motion vector and the L1 direction motion vector.

The decoding apparatus may derive all motion vector information as a candidate to construct the motion information candidate list. In addition, the decoding apparatus may construct the motion information candidate list by selectively deriving a candidate from the motion vector information of the neighboring block.

For example, the decoding apparatus may derive a first motion information candidate list including bi-predicted motion vector candidates based on the neighboring block, and the decoding apparatus may determine a first motion vector of one of the first motion information candidate lists. Can be derived from the anchor vector. The first anchor vector may be an L0 direction motion vector or an L1 direction motion vector. After deriving the first anchor vector, the decoding apparatus may scale the first anchor vector in a direction different from a direction associated with the first anchor vector among the L0 direction and the L1 direction to derive a second anchor vector. Can be. For example, when the first anchor vector is an L0 direction motion vector, the first anchor vector may be scaled in the L1 direction to be derived as a second anchor vector that is an L1 direction motion vector. The reference picture including the reference region indicated by the second anchor vector includes a reference value that includes a difference value from the reference region indicated by the first anchor vector among the reference pictures included in the L1, that is, a reference region having the smallest residual. It can be derived as a picture. Meanwhile, when the first anchor vector is an L1 direction motion vector, the first anchor vector may be scaled in the L0 direction to be derived as a second anchor vector that is an L0 direction motion vector. The reference picture including the reference region indicated by the second anchor vector includes a reference value having a difference value from the reference region indicated by the first anchor vector among the reference pictures included in the L0, that is, a reference region having the smallest residual. It can be derived as a picture.

After deriving the second anchor vector, the decoding apparatus determines the current block based on the motion vector having the same direction as the second anchor vector in the first motion information candidate list and having a magnitude difference from the second anchor vector less than or equal to a preset threshold. The motion information candidate list can be derived. For example, when the second anchor vector is a L0 direction motion vector, the motion information candidate list of the current block based on a motion vector whose magnitude difference from the second anchor vector among the L0 direction motion vectors is equal to or less than a preset threshold. Can be derived. On the other hand, when the second anchor vector is a L1 direction motion vector, a motion information candidate list of the current block is derived based on a motion vector whose magnitude difference from the second anchor vector in the L1 direction is less than or equal to a preset threshold. can do.

As another example, the decoding apparatus may derive a first motion information candidate list based on the neighboring block, and the absolute value and the L1 direction of the L0 direction motion vector of each bi-predicted motion vector candidate included in the first motion information candidate list. The difference between the absolute values of the motion vectors can be derived. The decoding apparatus may derive a motion information candidate list of the current block based on the bi-predicted motion vector candidate having the difference value equal to or less than a preset threshold. In the case of the short predicted motion vector candidate included in the first motion information candidate list, the decoding apparatus is further configured to associate the first motion vector included in the short predicted motion vector candidate with the first motion vector in the L0 direction and the L1 direction. A second motion vector may be derived by scaling in a direction different from a direction, and the single-predicted motion vector candidate is derived as a bi-predicted motion vector candidate including the first motion vector and the second motion vector. One method can be applied. In detail, when the first motion vector is a L0 direction motion vector, a second motion vector that is an L1 direction motion vector may be derived by scaling in the L1 direction. In addition, when the first motion vector is a L1 direction motion vector, a second motion vector that is a L0 direction motion vector may be derived by scaling in the L0 direction. In this case, the reference picture associated with the second motion vector includes the second reference area having a minimum residual between the first reference area indicated by the first motion vector and the second reference area indicated by the second motion vector. It may be a picture to include.

As another example, the decoding apparatus may derive a first motion information candidate list based on the neighboring block, and determine whether an absolute value of a motion vector of each motion vector candidate is less than or equal to a preset threshold in the first motion information candidate list. can do. The decoding apparatus may derive a motion information candidate list of the current block based on the motion vector candidate whose absolute value of the motion vector is less than or equal to the threshold. When the motion vector candidate is a unidirectional motion vector candidate, the motion vector of the short prediction motion vector candidate may be a L0 direction motion vector or an L1 direction motion vector. The decoding apparatus may additionally consider and consider a bi-prediction motion vector candidate. The decoding apparatus may determine each motion vector by dividing the L0 direction motion vector and the L1 direction motion vector included in the bi-predicted motion vector candidate, and include each motion vector as a candidate of the motion information candidate list. .

On the other hand, the decoding apparatus may obtain the FRUC flag through the bitstream, and when the value of the FRUC flag is 1, it may determine that the modified inter prediction mode is applied to the current block. When the modified inter prediction mode is applied to the current block, the decoding apparatus may derive the motion information candidate list through the above-described method.

The decoding apparatus selects a specific candidate based on the comparison of the candidates in the motion information candidate list (S1410). For example, the decoding apparatus may compare candidates in the motion information candidate list through a bilateral matching method. The decoding apparatus may divide the motion vectors included in the motion information candidate list into the L0 direction and the L1 direction. The decoding apparatus may sequentially select the divided motion vectors as the first motion vector. The decoding apparatus scales the first motion vector included in the motion information candidate list in a direction different from a direction associated with the first motion vector among the L0 direction and the L1 direction to correspond to the first motion vector. We can derive 2 motion vectors. For example, when the first motion vector is a motion vector in the L0 direction, the first motion vector may be scaled in the L1 direction based on a temporal distance between the current picture and a reference picture associated with the first motion vector. The second motion vector in the L1 direction corresponding to the first motion vector may be derived. The reference picture including the reference region indicated by the second motion vector includes a reference value that is a difference value from the reference region indicated by the first motion vector among the reference pictures included in the L1, that is, a reference region having the smallest residual. It can be derived as a picture. In addition, when the first motion vector is a motion vector in the L1 direction, the first motion vector may be scaled in the L0 direction based on a temporal distance between the current picture and a reference picture associated with the first motion vector. The second motion vector in the L0 direction corresponding to the vector may be derived. The reference picture including the reference region indicated by the second motion vector includes a reference value that is a difference value from the reference region indicated by the first motion vector among the reference pictures included in the L0, that is, a reference region having the smallest residual. It can be derived as a picture.

Next, the decoding apparatus may derive the residuals of the reference region indicated by the first motion vector and the reference region indicated by the second motion vector, and include the first motion vector and the second motion vector having the minimum residual. You can choose to be a specific candidate. That is, a first motion vector and a second motion vector having a minimum difference value between samples according to a phase of a reference region indicated by the first motion vector and a reference region indicated by the second motion vector are the specific candidates. Can be derived.

As another example, the decoding apparatus may compare candidates in the motion information candidate list through a template matching method. The decoding apparatus may derive the reference block indicated by the motion vector 1 included in the motion information candidate list. The decoding apparatus may derive a difference value between the value of the neighboring sample of the reference block and the value of the neighboring sample of the current block corresponding to the neighboring sample. If the difference value is the minimum among the difference values of the motion vectors included in the motion information candidate list, the decoding device may select the motion vector 1 as the specific candidate.

As another example, the decoding apparatus may select a specific candidate based on an anchor vector. In detail, the decoding apparatus may derive one motion vector of the motion information candidate list as a first anchor vector. The first anchor vector may be an L0 direction motion vector or an L1 direction motion vector. After deriving the first anchor vector, the decoding apparatus may scale the first anchor vector in a direction different from a direction associated with the first anchor vector among the L0 direction and the L1 direction to derive a second anchor vector. Can be. For example, when the first anchor vector is an L0 direction motion vector, the first anchor vector may be scaled in the L1 direction to be derived as a second anchor vector that is an L1 direction motion vector. The reference picture including the reference region indicated by the second anchor vector includes a reference value that includes a difference value from the reference region indicated by the first anchor vector among the reference pictures included in the L1, that is, a reference region having the smallest residual. It can be derived as a picture. Meanwhile, when the first anchor vector is an L1 direction motion vector, the first anchor vector may be scaled in the L0 direction to be derived as a second anchor vector that is an L0 direction motion vector. The reference picture including the reference region indicated by the second anchor vector includes a reference value having a difference value from the reference region indicated by the first anchor vector among the reference pictures included in the L0, that is, a reference region having the smallest residual. It can be derived as a picture.

After deriving the second anchor vector, the decoding apparatus may select, as the specific candidate, a motion vector having the same direction as that of the second anchor vector in the motion information candidate list and having a minimum size difference from the second anchor vector. For example, when the second anchor vector is a L0 direction motion vector, a motion vector having a minimum difference in magnitude from the second anchor vector among the L0 direction motion vectors may be derived as the specific candidate. Meanwhile, when the second anchor vector is an L1 direction motion vector, a motion vector having a minimum size difference from the second anchor vector among the motion vectors in the L1 direction may be derived as the specific candidate.

As another example, the decoding apparatus may select the specific candidate based on a comparison between the absolute value of the L0 direction motion vector and the absolute value of the L1 direction motion vector of each bi-predicted motion vector candidate included in the vector candidate list. . The decoding apparatus may derive a difference value between the absolute value of the L0 direction motion vector and the absolute value of the L1 direction motion vector of each bi-predicted motion vector candidate included in the motion information candidate list. The decoding apparatus may select the bi-predicted motion vector candidate having the minimum difference value as the specific candidate. In the case of the short predicted motion vector candidate included in the motion information candidate list, the decoding apparatus may determine a first motion vector included in the short predicted motion vector candidate and a direction associated with the first motion vector among the L0 direction and the L1 direction. A second motion vector can be derived by scaling in a different direction, and the method described above by deriving the single predicted motion vector candidate as a bi-predicted motion vector candidate including the first motion vector and the second motion vector. Can be applied. In detail, when the first motion vector is a L0 direction motion vector, a second motion vector that is an L1 direction motion vector may be derived by scaling in the L1 direction. In addition, when the first motion vector is a L1 direction motion vector, a second motion vector that is a L0 direction motion vector may be derived by scaling in the L0 direction. In this case, the reference picture associated with the second motion vector includes the second reference area having a minimum residual between the first reference area indicated by the first motion vector and the second reference area indicated by the second motion vector. It may be a picture to include.

As another example, the decoding apparatus may select the specific candidate based on a comparison of magnitudes of absolute values of the motion vectors. The decoding apparatus may compare the magnitude of the absolute value of the motion vector of each motion vector candidate to the motion information candidate list. The decoding apparatus may select a motion vector candidate having a minimum absolute value of the motion vector as a specific candidate. When the motion vector candidate is a unidirectional motion vector candidate, the motion vector of the short prediction motion vector candidate may be a L0 direction motion vector or an L1 direction motion vector. The decoding apparatus may additionally consider and consider a bi-prediction motion vector candidate. The decoding apparatus may determine each motion vector by dividing the L0 direction motion vector and the L1 direction motion vector included in the bi-predicted motion vector candidate, and include each motion vector as a candidate of the motion information candidate list. .

Meanwhile, the decoding apparatus may acquire a bilateral / template selection flag through a bitstream, and select a matching method for comparing candidates of the motion information candidate list based on the value of the bilateral / template selection flag.

The decoding apparatus derives the motion vector of the current block based on the specific candidate (S1420). The motion vector of the current block may be one of a bi-prediction motion vector and a uni-prediction motion vector.

The decoding apparatus generates a predictive sample of the current block based on the motion vector of the current block (S1430). The decoding apparatus may obtain a predictive sample value on the reference picture indicated by the motion vector, and generate the predictive sample.

The decoding apparatus may generate a reconstructed sample for the current sample based on the prediction value. The decoding apparatus may obtain a residual signal from the bitstream received from the encoding apparatus, and generate a residual sample for the current sample. In this case, the decoding apparatus may generate the reconstructed sample based on the prediction sample and the residual sample. The decoding apparatus may generate a reconstructed picture based on the reconstructed sample.

According to the present invention described above, the data amount of prediction mode information indicating the inter prediction mode can be reduced, thereby improving the overall coding efficiency.

Further, according to the present invention, the process of searching for the motion vector of the current block by selecting the motion vector candidate of the current block can be reduced, thereby reducing the computational complexity and improving the overall coding efficiency.

In the above-described embodiment, the methods are described based on a flowchart as a series of steps or blocks, but the present invention is not limited to the order of steps, and any steps may occur in a different order or simultaneously from other steps as described above. have. In addition, those skilled in the art will appreciate that the steps shown in the flowcharts are not exclusive and that other steps may be included or one or more steps in the flowcharts may be deleted without affecting the scope of the present invention.

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 application-specific integrated circuits (ASICs), 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 inter prediction method performed by the decoding apparatus,

Deriving a motion information candidate list of the current block based on neighboring blocks of the current block;

Selecting a specific candidate based on a comparison of candidates in the motion information candidate list;

Deriving a motion vector of the current block based on the specific candidate; And

Generating a prediction sample of the current block based on the motion vector of the current block.
The method of claim 1,

The motion information candidate list includes a bi-prediction motion vector candidate or a uni-prediction motion vector candidate,

The bi-predicted motion vector candidate includes a motion vector in the L0 direction and a motion vector in the L1 direction, and the unipredicted motion vector candidate includes only one of the L0 direction motion vector and the L1 direction motion vector,

And the L0 direction motion vector indicates a motion vector relating to a reference picture included in the reference picture list L0, and the L1 direction motion vector is a motion vector relating to a reference picture included in the reference picture list L1.
The method of claim 2,

Deriving a motion information candidate list of the current block based on neighboring blocks of the current block,

Deriving a first motion information candidate list based on the neighboring block;

Deriving a motion vector of one of the first motion information candidate lists as a first anchor vector; And

Deriving a second anchor vector by scaling the first anchor vector in a direction different from the direction associated with the first anchor vector among the L0 direction and the L1 direction; And

Deriving a motion information candidate list of the current block based on a motion vector of the first motion information candidate list in the same direction as the second anchor vector and having a magnitude difference from the second anchor vector less than or equal to a preset threshold; The inter prediction method characterized by the above-mentioned.
The method of claim 3,

And the specific candidate is selected as a motion vector having a minimum difference from the second anchor vector in the motion information candidate list.
The method of claim 2,

Deriving a motion information candidate list of the current block based on neighboring blocks of the current block,

Deriving a first motion information candidate list based on the neighboring block;

Deriving a difference value between the absolute value of the L0 direction motion vector and the absolute value of the L1 direction motion vector of each bi-predicted motion vector candidate included in the first motion information candidate list; And

And deriving a motion information candidate list of the current block based on the bi-predicted motion vector candidate having the difference value equal to or less than a preset threshold.
The method of claim 5,

Scaling a first motion vector included in the unipredicted motion vector candidate included in the first motion information candidate list in a direction different from a direction associated with the first motion vector among the L0 direction and the L1 direction to form a second motion vector; Deriving a motion vector; And

Deriving the single predicted motion vector candidate as a bi-predicted motion vector candidate including the first motion vector and the second motion vector,

The reference picture associated with the second motion vector includes a picture including a second reference region having a minimum residual between a first reference region indicated by the first motion vector and a second reference region indicated by the second motion vector. The inter prediction method characterized by the above-mentioned.
The method of claim 5,

Wherein the specific candidate is selected as a bi-predicted motion vector candidate having the minimum difference value.
The method of claim 2,

Deriving a motion information candidate list of the current block based on neighboring blocks of the current block,

Deriving a first motion information candidate list based on the neighboring block;

Determining whether an absolute value of a motion vector of each motion vector candidate included in the first motion information candidate list is less than or equal to a preset threshold; And

And deriving a motion information candidate list of the current block based on a motion vector candidate whose absolute value of the motion vector is less than or equal to the threshold value.
The method of claim 8,

And wherein the specific candidate is selected as a motion vector candidate including a motion vector having a minimum absolute value of the motion vector.
The method of claim 2,

Selecting a specific candidate from the motion information candidate list,

A second motion vector corresponding to the first motion vector by scaling a first motion vector included in the motion information candidate list in a direction different from a direction associated with the first motion vector among the L0 direction and the L1 direction Deriving;

Deriving residuals of the reference region indicated by the first motion vector and the reference region indicated by the second motion vector; And

And selecting the first motion vector and the second motion vector having the smallest residual as the specific candidates.
The method of claim 2,

Selecting a specific candidate from the motion information candidate list,

Deriving a reference block indicated by motion vector 1 included in the motion information candidate list;

Deriving a difference value between a value of a neighboring sample of the reference block and a value of a neighboring sample of the current block corresponding to the neighboring sample; And

And selecting the motion vector 1 as the specific candidate when the difference value is the minimum among the difference values of the motion vectors included in the motion information candidate list.
The method of claim 1,

Receiving a frame rate up-conversion (FRUC) mode flag over the bitstream; And

The method may further include determining whether to apply the FRUC mode to the current block.

And when the value of the FRUC mode flag is 1, it is determined that the FRUC mode is applied to the current block.