WO2019235819A1 - Method and apparatus for processing video signal - Google Patents

Abstract

A method for processing a video signal according to an embodiment of the present invention may comprise the steps of: identifying a motion model that has been applied for prediction of a current block intended to be processed, among a previously defined plurality of motion models; determining a motion vector for at least one control point of the current block on the basis of the motion model; determining a motion vector for each sub block of the current block by using the motion vector for the at least one control point; and performing prediction of the current block on the basis of the motion vector for the each sub block, wherein the number of control points of the current block may be determined by the motion model.

Description

Method and apparatus for processing video signal

The present invention relates to a method and apparatus for processing a video signal, and more particularly, to a method and apparatus for processing a video signal using prediction based on a motion model.

Compression coding refers to a series of signal processing techniques for transmitting digitized information through a communication line or for storing in a form suitable for a storage medium. Media such as an image, an image, an audio, and the like may be a target of compression encoding. In particular, a technique of performing compression encoding on an image is called video image compression.

Next-generation video content will be characterized by high spatial resolution, high frame rate and high dimensionality of scene representation. Processing such content would result in a tremendous increase in terms of memory storage, memory access rate, and processing power.

Accordingly, there is a need to design coding tools for more efficiently processing next generation video content.

In inter prediction techniques for performing prediction on a current picture with reference to other pictures, a method and apparatus for representing not only simple motion but also complex or atypical motion are required.

Accordingly, embodiments of the present invention provide a video signal processing apparatus and method for effectively expressing various motions in inter-screen prediction.

In addition, embodiments of the present invention to provide a video signal processing apparatus and method that can reduce the amount of computation while effectively representing a variety of motion.

In addition, embodiments of the present invention to provide a video signal processing apparatus and method that can reduce the data throughput while effectively representing a variety of motion.

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

In accordance with another aspect of the present invention, there is provided a video signal processing method comprising: checking, among a plurality of predefined motion models, a motion model applied for prediction of a current block to be processed, and based on the current model. Determining a motion vector for at least one control point of the block; determining a motion vector for each subblock of the current block using the motion vector for the at least one control point; And predicting the current block based on the motion vector for the current block. The number of control points of the current block may be determined by the motion model.

According to an embodiment of the present disclosure, the checking of the motion model applied for the prediction of the current block may include checking whether a specific motion model is applied to a slice including the current block, and checking the slice in the slice. When a specific motion model is applied, the method may include checking whether the specific motion model is applied to the current block.

According to an embodiment of the present invention, the checking of the motion model applied for the prediction of the current block may include: checking the number of samples included in the current block or the size of the current block. Determining whether the number of samples or the size of the current block is within a threshold range defined in a specific motion model, and the number of samples or the size of the current block is in a threshold range of the specific motion model If included in, may include determining whether the specific motion model is applied.

According to an embodiment of the present invention, the checking of the motion model applied for the prediction of the current block may include checking a motion model applied to a neighboring block adjacent to the current block, and checking a motion model applied to the neighboring block. Identifying the number of corresponding parameters, identifying motion model candidates applicable to the current block among the plurality of motion models based on the number of parameters, and applying the current block among the motion model candidates. And identifying the motion model.

According to an embodiment of the present invention, identifying the motion model applied for the prediction of the current block includes: determining a set of motion model candidates applied to the current block among predefined sets of motion model candidates And identifying an index indicating a motion model applied to the current block among the motion model candidates, and identifying a motion model corresponding to the index among the motion model candidates.

According to an embodiment of the present disclosure, the determining of the motion vector for at least one control point of the current block may include: a motion corresponding to a difference value between the motion vector of the neighboring block adjacent to the current block and the motion vector of the current block; Motion vector difference (MVD) or control point motion vector difference value corresponding to the difference value of the motion vector for the control point of the neighboring block and the control vector of the current block corresponding to the control point of the neighboring block The method may include determining a control point motion vector difference (CPMVD).

According to an embodiment of the present invention, the predefined plurality of motion models may include a translation mode, a scaling mode, a rotation mode, and a simplified affine mode. mode, affine mode, or bilinear interpolation mode.

According to an embodiment of the present invention, the determining of the motion vector for at least one control point of the current block may include: parsing one MVD when the translation mode is applied to the current block. Determining a motion vector, and when the scaling mode is applied to the current block, determining a motion vector for two control points by parsing the x component of CPMVD for a first control point and CPMVD for a second control point; Determining the motion vector for the two control points by parsing the y component of the CPMVD for the first control point and the CPMVD for the second control point when the rotation mode is applied to the current block, and the simplified affine mode. Is applied to the current block, the motion for the two control points by parsing the CPMVD for the first control point and the CPMVD for the second control point. Determining a vector, and when the affine mode is applied to the current block, parsing the CPMVD for the first control point, the CPMVD for the second control point, and the CPMVD for the third control point, by motion vector for the three control points. Determining CPMVD for a first control point, CPMVD for a second control point, CPMVD for a third control point, and CPMVD for a fourth control point when the bilinear interpolation mode is applied to the current block. Determining a motion vector for the four control points.

The video signal processing apparatus according to the embodiment of the present invention may include a memory for storing the video signal, and a decoder functionally coupled to the memory. The decoder identifies, among a plurality of predefined motion models, a motion model applied for prediction of a current block to be processed, and obtains a motion vector for at least one control point of the current block based on the motion model. Determine, determine a motion vector for each subblock of the current block using the motion vector for the at least one control point, and perform prediction of the current block based on the motion vector for each subblock Can be.

According to an embodiment of the present invention, the decoder checks whether a specific motion model is applied to a slice including the current block, and when the specific motion model is applied to the slice, the specific motion model to the current block. It may be set to check whether this has been applied.

According to an embodiment of the present invention, the decoder checks the number of samples included in the current block or the size of the current block, and the number of the samples or the size of the current block is determined by a threshold defined in a specific motion model. If the number of the samples or the size of the current block is included in the threshold range of the specific motion model, it may be set to determine whether the specific motion model is applied.

According to an embodiment of the present invention, the decoder identifies a motion model applied to a neighboring block adjacent to the current block, checks the number of parameters corresponding to the motion model applied to the neighboring block, and based on the number of parameters. Thus, the motion model candidates applicable to the current block among the plurality of motion models may be identified, and the motion model applied to the current block among the motion model candidates may be set.

According to an embodiment of the present invention, the decoder determines a set of motion model candidates applied to the current block among predefined sets of motion model candidates, and determines a motion model applied to the current block among the motion model candidates. It may be set to identify an index indicating and indicate a motion model corresponding to the index among the motion model candidates.

According to an embodiment of the present invention, the decoder may include a motion vector difference (MVD) or a motion vector corresponding to a difference value between a motion vector of a neighboring block adjacent to the current block and a motion vector of the current block. The control point motion vector difference (CPMVD) corresponding to the difference value of the motion vector for the control point of the block and the motion vector for the control point of the current block corresponding to the control point of the neighboring block may be set. Can be.

According to an embodiment of the present invention, the predefined plurality of motion models may include a translation mode, a scaling mode, a rotation mode, and a simplified affine mode. mode, affine mode, or bilinear interpolation mode. The decoder may determine one motion vector by parsing one MVD when the translation mode is applied to the current block, and a first control point when the scaling mode is applied to the current block. Determine the motion vector for the two control points by parsing the C component of the CPMVD and the CPMVD for the second control point, and if the rotation mode is applied to the current block, for the CPMVD and the second control point for the first control point Determine the motion vector for the two control points by parsing the y component of CPMVD, and if the simplified affine mode is applied to the current block, parse the CPMVD for the first control point and the CPMVD for the second control point by Determine a motion vector for a control point, and if the affine mode is applied to the current block, the CPMVD for the first control point, Determine the motion vector for the three control points by parsing one CPMVD, and the CPMVD for the third control point, and if the bilinear interpolation mode is applied to the current block, CPMVD for the first control point, CPMVD for the second control point , CPMVD for the third control point, and CPMVD for the fourth control point, may be set to determine the motion vectors for the four control points.

According to an exemplary embodiment of the present invention, more various motions can be effectively expressed by determining a motion vector for at least one control point of the current block variably according to the motion model applied to the current block to be predicted.

In addition, according to an embodiment of the present invention, by setting the conditions for identifying the motion model in consideration of the characteristics of the current block or neighboring blocks, it is possible to effectively reduce the amount of computation while expressing various motions.

In addition, according to an embodiment of the present invention, by setting a set of motion model candidates and using an index to indicate a motion model to be applied to the current block, data throughput can be reduced while effectively representing various motions.

The effects obtainable in the present invention are not limited to the above-mentioned effects, and other effects not mentioned will be clearly understood by those skilled in the art from the following description. .

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, included as part of the detailed description in order to provide a thorough understanding of the present invention, provide embodiments of the present invention and together with the description, describe the technical features of the present invention.

1 shows an example of a functional configuration of an encoder as an example of a video signal processing apparatus according to an embodiment of the present invention.

2 shows an example of a functional configuration of a decoder as another example of a video signal processing apparatus according to an embodiment of the present invention.

3 illustrates an example of a multitype tree structure according to an embodiment of the present invention.

4 illustrates an example of a signaling mechanism of partition partitioning information of a quadtree with nested multi-type tree structure with a multitype tree according to an embodiment of the present invention.

FIG. 5 illustrates an example of a method of dividing a coding tree unit (CTU) into multiple CUs based on a quadtree and a quadtree and nested multi-type tree structure according to an embodiment of the present invention. .

6 shows an example of a method of limiting ternary-tree splitting according to an embodiment of the present invention.

7 illustrates examples of redundant partition patterns that may occur in binary tree partitioning and ternary tree partitioning according to an embodiment of the present invention.

8 illustrates an example of an operation flowchart for encoding an image in a video signal processing method according to an embodiment of the present invention.

9 illustrates an example of a functional configuration of an inter predictor of an encoder in a video signal processing apparatus according to an embodiment of the present invention.

10 illustrates an example of an operation flowchart for image decoding in a video signal processing method according to an embodiment of the present invention.

11 illustrates an example of a functional configuration of an inter predictor of a decoder in a video signal processing apparatus according to an embodiment of the present invention.

12 shows an example of motion models according to an embodiment of the invention.

13 illustrates an example of a control point motion vector for affine motion prediction according to an embodiment of the present invention.

14 shows an example of a motion vector for each subblock of a block to which affine motion prediction is applied according to an embodiment of the present invention.

FIG. 15 illustrates an example of neighboring blocks used for prediction of a current block in an affine inter mode according to an embodiment of the present invention.

FIG. 16 shows an example of a main block used for prediction of a current block in an affiliate merge mode according to an embodiment of the present invention.

17 illustrates an example of a block in which affine motion prediction is performed using a neighboring block to which affine motion prediction is applied according to an embodiment of the present invention.

18 shows an example of an operation flowchart for affine motion prediction according to an embodiment of the present invention.

19 shows an example of a translation motion model according to an embodiment of the invention.

20 shows an example of a scaling motion model according to an embodiment of the invention.

21 shows an example of a rotation motion model according to an embodiment of the present invention.

22 shows an example of an operation flowchart for prediction using a motion model according to an embodiment of the present invention.

23 illustrates an example of an operation flowchart for identifying a motion model in units of slices and blocks in prediction using a motion model according to an embodiment of the present invention.

24 illustrates an example of an operation flowchart for checking a motion model in consideration of a sample number of a current block or a size of the current block in prediction using a motion model according to an embodiment of the present invention.

25 illustrates an example of an operation flowchart for identifying a motion model using neighboring blocks in prediction using the motion model according to an embodiment of the present invention.

FIG. 26 shows an example of an operation flowchart for identifying a motion model corresponding to an index among a set of motion model candidates in prediction using a motion model according to an embodiment of the present invention.

27 shows an example of a video coding system as an embodiment to which the present invention is applied.

28 shows an example of a video streaming system as an embodiment to which the present invention is applied.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. The detailed description, which will be given below with reference to the accompanying drawings, is intended to explain exemplary embodiments of the present invention and is not intended to represent the only embodiments in which the present invention may be practiced. The following detailed description includes specific details in order to provide a thorough understanding of the present invention. However, one of ordinary skill in the art appreciates that the present invention may be practiced without these specific details.

In some instances, well-known structures and devices may be omitted or shown in block diagram form centering on the core functions of the structures and devices in order to avoid obscuring the concepts of the present invention.

In addition, the terminology used in the present invention was selected as a general term widely used as possible now, in a specific case will be described using terms arbitrarily selected by the applicant. In such a case, since the meaning is clearly described in the detailed description of the part, it should not be interpreted simply by the name of the term used in the description of the present invention, and it should be understood that the meaning of the term should be understood and interpreted. .

Specific terms used in the following description are provided to help the understanding of the present invention, and the use of such specific terms may be changed to other forms without departing from the technical spirit of the present invention. For example, signals, data, samples, pictures, frames, blocks, etc. may be appropriately replaced and interpreted in each coding process.

Hereinafter, in the present specification, the 'processing unit' refers to a unit in which a process of encoding / decoding such as prediction, transformation, and / or quantization is performed. In addition, the processing unit may be interpreted to include a unit for a luma component and a unit for a chroma component. For example, the processing unit may correspond to a block, a coding unit (CU), a prediction unit (PU), or a transform unit (TU).

Further, the processing unit may be interpreted as a unit for the luminance component or a unit for the chrominance component. For example, the processing unit may correspond to a CTB, CB, PU or TB for the luminance component. Alternatively, the processing unit may correspond to a CTB, CB, PU or TB for the chrominance component. In addition, the present invention is not limited thereto, and the processing unit may be interpreted to include a unit for a luminance component and a unit for a color difference component.

In addition, the processing unit is not necessarily limited to square blocks, but may also be configured in a polygonal form having three or more vertices.

In the following specification, a pixel, a pixel, and the like are referred to collectively as samples. In addition, using a sample may mean using a pixel value or a pixel value.

1 shows an example of a functional configuration of an encoder as an example of a video signal processing apparatus according to an embodiment of the present invention.

Referring to FIG. 1, the encoder 10 may include an image divider 110, a subtractor 115, a transform unit 120, a quantizer 130, an inverse quantizer 140, an inverse transform unit 150, and an adder. The unit 155, the filtering unit 160, the memory 170, the inter prediction unit 180, the intra prediction unit 185, and the entropy encoding unit 190 may be configured. The inter predictor 180 and the intra predictor 185 may be collectively referred to as a predictor. In other words, the predictor may include an inter predictor 180 and an intra predictor 185. The transform unit 120, the quantization unit 130, the inverse quantization unit 140, and the inverse transform unit 150 may be included in the residual processing unit. The residual processing unit may further include a subtracting unit 115. As an example, the image divider 110, the subtractor 115, the transformer 120, the quantizer 130, the inverse quantizer 140, the inverse transformer 150, and the adder 155 may be described. The filtering unit 160, the inter prediction unit 180, the intra prediction unit 185, and the entropy encoding unit 190 may be configured by one hardware component (eg, an encoder or a processor). In addition, the memory 170 may include a decoded picture buffer (DPB) 172 or may be configured by a digital storage medium.

The image divider 110 may divide the input image (or picture or frame) input to the encoder 100 into one or more processing units. For example, the processing unit may be called a coding unit (CU). In this case, the coding unit may be recursively divided according to a quad-tree binary-tree (QTBT) structure from a coding tree unit (CTU) or a largest coding unit (LCU). For example, one coding unit may be divided into a plurality of coding units of a deeper depth based on a quad tree structure and / or a binary tree structure. In this case, for example, the quad tree structure may be applied first and the binary tree structure may be applied later. Alternatively, the binary tree structure may be applied first. The coding procedure according to the present invention may be performed based on the final coding unit that is no longer split. In this case, the maximum coding unit may be used as the final coding unit immediately based on coding efficiency according to the image characteristic, or if necessary, the coding unit is recursively divided into coding units of lower depths and optimized. A coding unit of size may be used as the final coding unit. Here, the coding procedure may include a procedure of prediction, transform, and reconstruction, which will be described later. As another example, the processing unit may further include a prediction unit (PU) or a transform unit (TU). In this case, the prediction unit and the transform unit may be partitioned or partitioned from the aforementioned final coding unit, respectively. The prediction unit may be a unit of sample prediction, and the transformation unit may be a unit for deriving a transform coefficient and / or a unit for deriving a residual signal from the transform coefficient.

The unit may be used interchangeably with terms such as block or area in some cases. In a general case, an M × N block may represent a set of samples or transform coefficients composed of M columns and N rows. A sample may generally represent a pixel or a value of a pixel, and may represent only a pixel / pixel value of a luma component or only a pixel / pixel value of a chroma component. A sample may be used as a term corresponding to one picture (or image) for a pixel or a pel.

The encoder 100 subtracts the prediction signal (predicted block, prediction sample array) output from the inter prediction unit 180 or the intra prediction unit 185 from the input image signal (original block, original sample array) and the residual signal. (residual signal, residual block, residual sample array), and the generated residual signal is transmitted to the converter 120. In this case, as shown, a unit that subtracts a prediction signal (prediction block, prediction sample array) from an input image signal (original block, original sample array) in the encoder 100 may be called a subtraction unit 115. The prediction unit may perform a prediction on a block to be processed (hereinafter, referred to as a current block) and generate a predicted block including prediction samples for the current block. The prediction unit may determine whether intra prediction or inter prediction is applied on a current block or CU basis. As described later in the description of each prediction mode, the prediction unit may generate various information related to prediction, such as prediction mode information, and transmit the generated information to the entropy encoding unit 190. The information about the prediction may be encoded in the entropy encoding unit 190 and output in the form of a bitstream.

The intra predictor 185 may predict the current block by referring to the samples in the current picture. The referenced samples may be located in the neighborhood of the current block or may be located apart according to the prediction mode. In intra prediction, prediction modes may include a plurality of non-directional modes and a plurality of directional modes. The non-directional mode may include, for example, a DC mode and a planner mode (Planar mode). The directional mode may include, for example, 33 directional prediction modes or 65 directional prediction modes according to the degree of detail of the prediction direction. However, as an example, more or less directional prediction modes may be used depending on the setting. The intra predictor 185 may determine the prediction mode applied to the current block by using the prediction mode applied to the neighboring block.

The inter prediction unit 180 may derive the predicted block for the current block based on the reference block (reference sample array) specified by the motion vector on the reference picture. In this case, in order to reduce the amount of motion information transmitted in the inter prediction mode, the motion information may be predicted in units of blocks, subblocks, or samples based on the correlation of the motion information between the neighboring block and the current block. The motion information may include a motion vector and a reference picture index. The motion information may further include inter prediction direction (L0 prediction, L1 prediction, Bi prediction, etc.) information. In the case of inter prediction, the neighboring block may include a spatial neighboring block existing in the current picture and a temporal neighboring block present in the reference picture. The reference picture including the reference block and the reference picture including the temporal neighboring block may be the same or different. The temporal neighboring block may be referred to as a collocated reference block, a collocated CU (colCU), and the like, and a reference picture including the temporal neighboring block is called a collocated picture (colPic). It may be. For example, the inter prediction unit 180 constructs a motion information candidate list based on neighboring blocks, and provides information indicating which candidates are used to derive the motion vector and / or reference picture index of the current block. Can be generated. Inter prediction may be performed based on various prediction modes. For example, in the case of a skip mode and a merge mode, the inter prediction unit 180 may determine motion information of a neighboring block. It can be used as motion information. In the skip mode, unlike the merge mode, the residual signal may not be transmitted. In the case of the motion vector prediction (MVP) mode, the motion vector of the neighboring block is used as a motion vector predictor and the motion vector difference (MVD) is signaled to signal the motion block. It can indicate a motion vector. Specific methods and apparatuses of inter prediction are described in detail with reference to FIGS. 8 to 11. The prediction signal generated by the inter predictor 180 or the intra predictor 185 may be used to generate a reconstruction signal or to generate a residual signal.

The transformer 120 may apply transform techniques to the residual signal to generate transform coefficients. For example, the transformation technique may include at least one of a discrete cosine transform (DCT), a discrete sine transform (DST), a Karhunen-Loeve transform (KLT), a graph-based transform (GBT), or a conditionally non-linear transform (CNT). It may include. Here, GBT means a conversion obtained from this graph when the relationship information between pixels is represented by a graph. CNT refers to a transform that is generated based on and generates a prediction signal using all previously reconstructed pixels. In addition, the conversion process may be applied to pixel blocks having the same size as the square, or may be applied to blocks of variable size rather than square.

The quantization unit 130 quantizes the transform coefficients and transmits them to the entropy encoding unit 190. The entropy encoding unit 190 encodes the quantized signal (information about the quantized transform coefficients) and outputs the bitstream. have. The information about the quantized transform coefficients may be referred to as residual information. The quantization unit 130 may rearrange block quantized transform coefficients into a one-dimensional vector form based on various scan orders, and quantize the quantized transform coefficients based on the quantized transform coefficients of the one-dimensional vector form. Information about transform coefficients may be generated. The entropy encoding unit 390 may perform various encoding methods such as, for example, exponential Golomb, context-adaptive variable length coding (CAVLC), and context-adaptive binary arithmetic coding (CABAC). The entropy encoding unit 390 may encode information necessary for video / image reconstruction in addition to the quantized transform coefficients (eg, values of syntax elements) together or separately. The encoded information (eg, encoded video / image information) may be transmitted or stored in units of NALs (network abstraction layer) in the form of a bitstream. The bitstream may be transmitted over a network or may be stored in a digital storage medium. Here, the network may include a broadcasting network and / or a communication network, and the digital storage medium may include a universal serial bus (USB), a secure digital (SD) card, a compact disk (CD), a digital video disk (DVD), a Blu-ray, and an HDD. (hard disk drive), solid state drive (SSD), flash memory, and a variety of storage media may be included. The signal output from the entropy encoding unit 190 may include a communication unit (not shown) and / or a storage unit or memory (not shown) configured as internal / external components of the encoder 100, or the transmission unit may be entropy. It may be a component of the encoding unit 190.

The quantized transform coefficients output from the quantization unit 130 may be used to generate a prediction signal. For example, the quantized transform coefficients may reconstruct the residual signal by applying inverse quantization and inverse transform through the inverse quantization unit 140 and the inverse transform unit 150 in a loop. The adder 155 adds the reconstructed residual signal to the predicted signal output from the inter predictor 180 or the intra predictor 185 so that a reconstructed signal (reconstructed picture, reconstructed block, reconstructed sample array) is added. Can be generated. If there is no residual for the block to be processed, such as when the skip mode is applied, the predicted block may be used as the reconstructed block. The adder 155 may be called a restoration unit or a restoration block generation unit. The generated reconstruction signal may be used for intra prediction of a next processing target block in a current picture, and may be used for inter prediction of a next picture through filtering as described below.

The filtering unit 160 may improve subjective / objective image quality by applying filtering to the reconstruction signal. For example, the filtering unit 160 may generate a modified reconstruction picture by applying various filtering methods to the reconstruction picture, and the modified reconstruction picture may be stored in the memory 170, specifically, of the memory 170. May be stored in the DPB 172. The various filtering methods may include, for example, deblocking filtering, sample adaptive offset (SAO), adaptive loop filter (ALF), bilateral filter, and the like. Can be. The filtering unit 160 may generate various information related to the filtering and transmit the generated information to the entropy encoding unit 190 as described later in the description of each filtering method. The filtering information may be encoded in the entropy encoding unit 190 and output in the form of a bitstream.

The modified reconstructed picture stored in the memory 170 may be used as the reference picture in the inter predictor 180. When the inter prediction is applied through the encoder 100, the encoder 100 may avoid prediction mismatches in the encoder 100 and the decoder 200, and may improve encoding efficiency.

The DPB 174 of the memory 170 may store the modified reconstructed picture for use as a reference picture in the inter predictor 180. The memory 170 may store the motion information of the block from which the motion information in the current picture is derived (or encoded) and / or the motion information of the blocks in the picture that have already been reconstructed. The stored motion information may be transmitted to the inter predictor 180 to be used as motion information of a spatial neighboring block or motion information of a temporal neighboring block. The memory 170 may store reconstructed samples of reconstructed blocks in the current picture, and transfer the reconstructed samples to the intra predictor 185.

2 shows an example of a functional configuration of a decoder as another example of a video signal processing apparatus according to an embodiment of the present invention.

Referring to FIG. 2, the decoder 200 includes an entropy decoder 210, an inverse quantizer 220, an inverse transformer 230, an adder 235, a filter 240, a memory 250, and inter prediction. The unit 260 and the intra predictor 265 may be configured. The inter predictor 260 and the intra predictor 265 may be collectively called a predictor. That is, the predictor may include an inter predictor 280 and an intra predictor 285. The inverse quantization unit 220 and the inverse transform unit 230 may be collectively referred to as a residual processing unit. That is, the residual processor may include an inverse quantization unit 220 and an inverse transform unit 230. The entropy decoder 210, the inverse quantizer 220, the inverse transformer 230, the adder 235, the filter 240, the inter predictor 260, and the intra predictor 265 are described in the embodiment. Can be configured by one hardware component (eg, decoder or processor). The memory 250 may also include a DPB 252 and may be configured by a digital storage medium.

When a bitstream including video / image information is input, the decoder 200 may reconstruct an image corresponding to a process in which the video / image information is processed by the encoder 100 of FIG. 1. For example, the decoder 200 may perform decoding using a processing unit applied in the encoder 100. Thus the processing unit of decoding may be a coding unit, for example, which may be split along a quad tree structure and / or a binary tree structure from a coding tree unit or a maximum coding unit. The reconstructed video signal decoded and output through the decoder 200 may be reproduced through the reproducing apparatus.

The decoder 200 may receive a signal output from the encoder 100 of FIG. 1 in the form of a bitstream, and the received signal may be decoded through the entropy decoding unit 210. For example, the entropy decoding unit 210 may parse the bitstream to derive information (eg, video / image information) necessary for image reconstruction (or picture reconstruction). For example, the entropy decoding unit 210 decodes the information in the bitstream based on a coding method such as exponential Golomb coding, CAVLC, or CABAC, and converts a value of a syntax element required for image reconstruction, and a transform coefficient of a residual. You can output quantized values. 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. By using this method, a context model may be determined, and arithmetic decoding of bins may be performed by predicting a probability of occurrence of a bin according to the determined context model to generate a symbol corresponding to a 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. The information related to the prediction among the information decoded by the entropy decoding unit 210 is provided to a predictor (inter predictor 260 or intra predictor 265), and the entropy decoding performed by the entropy decoder 210 is performed. Dual values, that is, quantized transform coefficients and related parameter information, may be input to the inverse quantizer 220. In addition, information on filtering among information decoded by the entropy decoding unit 210 may be provided to the filtering unit 240. Meanwhile, a receiver (not shown) that receives a signal output from the encoder 100 may be further configured as an internal / external element of the decoder 200, or the receiver may be a component of the entropy decoding unit 210. .

The inverse quantization unit 220 may output the transform coefficients by inverse quantization of the quantized transform coefficients. The inverse quantization unit 220 may rearrange the quantized transform coefficients in the form of a two-dimensional block. In this case, the reordering may be performed based on the scan order performed by the encoder 100. The inverse quantization unit 220 may perform inverse quantization on quantized transform coefficients by using a quantization parameter (eg, quantization step size information), and may obtain transform coefficients.

The inverse transform unit 430 may obtain a residual signal (residual block, residual sample array) by inversely transforming the transform coefficients.

The prediction unit may perform prediction on the current block and generate a predicted block including prediction samples for the current block. The prediction unit may determine whether intra prediction or inter prediction is applied to the current block based on the information about the prediction output from the entropy decoding unit 210, and may determine a specific intra / inter prediction mode.

The intra predictor 265 may predict the current block by referring to samples in the current picture. The referenced samples may be located in the neighborhood of the current block or may be located apart according to the prediction mode. In intra prediction, prediction modes may include a plurality of non-directional modes and a plurality of directional modes. The intra predictor 265 may determine the prediction mode applied to the current block by using the prediction mode applied to the neighboring block.

The inter prediction unit 260 may derive the predicted block for the current block based on the reference block (reference sample array) specified by the motion vector on the reference picture. In this case, in order to reduce the amount of motion information transmitted in the inter prediction mode, the motion information may be predicted in units of blocks, subblocks, or samples based on the correlation of the motion information between the neighboring block and the current block. The motion information may include a motion vector and a reference picture index. The motion information may further include inter prediction direction (L0 prediction, L1 prediction, Bi prediction, etc.) information. In the case of inter prediction, the neighboring block may include a spatial neighboring block existing in the current picture and a temporal neighboring block present in the reference picture. For example, the inter prediction unit 260 may construct a motion information candidate list based on neighboring blocks and derive a motion vector and / or a reference picture index of the current block based on the received candidate selection information. Inter prediction may be performed based on various prediction modes, and the information about the prediction may include information indicating a mode of inter prediction for the current block.

The adder 235 adds the obtained residual signal to the predictive signal (predicted block, predictive sample array) output from the inter predictor 260 or the intra predictor 265 to restore the reconstructed signal (reconstructed picture, reconstructed block). , Restore sample array). If there is no residual for the block to be processed, such as when the skip mode is applied, the predicted block may be used as the reconstructed block.

The adder 235 may be called a restoration unit or a restoration block generation unit. The generated reconstruction signal may be used for intra prediction of a next processing target block in a current picture, and may be used for inter prediction of a next picture through filtering as described below.

The filtering unit 240 may improve subjective / objective image quality by applying filtering to the reconstruction signal. For example, the filtering unit 240 may generate a modified reconstructed picture by applying various filtering methods to the reconstructed picture, and the modified reconstruction picture may be stored in the memory 250, specifically, of the memory 250. Pass to DPB 252. The various filtering methods may include, for example, deblocking filtering, a sample adaptive offset, an adaptive loop filter, a bilateral filter, and the like.

The (modified) reconstructed picture stored in the DPB of the memory 250 may be used as the reference picture in the inter predictor 260. The memory 250 may store the motion information of the block from which the motion information in the current picture is derived (or decoded) and / or the motion information of the blocks in the picture that have already been reconstructed. The stored motion information may be transmitted to the inter prediction unit 260 to use the motion information of the spatial neighboring block or the motion information of the temporal neighboring block. The memory 250 may store reconstructed samples of reconstructed blocks in the current picture, and transfer the reconstructed samples to the intra predictor 265.

In the present specification, the embodiments described by the filtering unit 160, the inter prediction unit 180, and the intra prediction unit 185 of the encoder 100 are respectively the filtering unit 240 and the inter prediction unit of the decoder 200. 260 and the intra prediction unit 265 may be applied to the same or corresponding.

Block Partitioning

The video / image coding method according to this document may be performed based on various detailed techniques, and each detailed technique will be described as follows. Techniques described below include prediction, residual processing ((inverse) transformation, (inverse) quantization, etc.), syntax element coding, filtering, partitioning / division, etc. in the encoding / decoding procedures of the video / image described above and / or described below. It will be apparent to those skilled in the art that they may be involved in the relevant procedure of.

The block partitioning procedure according to this document is performed by the image partition unit 110 of the above-described encoder 100, and the partitioning related information is processed (encoded) by the entropy encoding unit 190 to the decoder 200 in the form of a bitstream. Can be delivered. The entropy decoding unit 210 of the decoder 200 derives a block partitioning structure of a current picture based on the partitioning related information obtained from the bitstream, and based on this, a series of procedures (eg, prediction, Residual processing, block reconstruction, in-loop filtering, etc.) may be performed.

Partitioning of picture into CTUs

Each picture of the video signal may be divided into a sequence of coding tree units (CTUs). The CTU may correspond to a coding tree block (CTB). Alternatively, the CTU may include a coding tree block of luma samples and two coding tree blocks of corresponding chroma samples. In other words, for a picture that includes three sample arrays, the CTU may include an N × N block of luma samples and two corresponding blocks of chroma samples.

The maximum allowable size of the CTU for coding and prediction may be different from the maximum allowable size of the CTU for transform. For example, the maximum allowable size of the luma block in the CTU may be 128x128.

Partitioning of the CTUs using a tree structure

The CTU may be divided into CUs based on a quad-tree (QT) structure. The quadtree structure may be referred to as a quaternary tree structure. This is to reflect various local characteristics. Meanwhile, in the present document, the CTU may be divided based on a multitype tree structure partition including a binary tree (BT) and a ternary tree (TT) as well as a quad tree. Hereinafter, the QTBT structure may include a quadtree and binary tree based partition structure, and the QTBTTT may include a quadtree, binary tree, and ternary tree based partition structure. Alternatively, the QTBT structure may include a quadtree, binary tree and ternary tree based partitioning structure. In a coding tree structure, a CU may have a square or rectangular shape. The CTU may first be divided into quadtree structures. After that, the leaf nodes of the quadtree structure may be further divided by the multitype tree structure.

3 illustrates an example of a multitype tree structure according to an embodiment of the present invention.

In one embodiment of the present invention, the multitype tree structure may include four partition types as shown in FIG. The four split types include vertical binary splitting (SPLIT_BT_VER), horizontal binary splitting (SPLIT_BT_HOR), vertical ternary splitting (SPLIT_TT_VER), and horizontal ternary splitting (SPLIT_TT_HOR). ) May be included. Leaf nodes of the multitype tree structure may be referred to as CUs. These CUs can be used for prediction and transform procedures. In general, CU, PU, and TU may have the same block size in this document. However, when the maximum supported transform length is smaller than the width or height of the color component of the CU, the CU and the TU may have different block sizes.

4 illustrates an example of a signaling mechanism of partition partitioning information of a quadtree with nested multi-type tree structure with a multitype tree according to an embodiment of the present invention.

Here, the CTU is treated as the root of the quadtree, and is partitioned for the first time into a quadtree structure. Each quadtree leaf node may then be further partitioned into a multitype tree structure. In the multitype tree structure, a first flag (ex. Mtt_split_cu_flag) is signaled to indicate whether the node is additionally partitioned. If the node is additionally partitioned, a second flag (ex. Mtt_split_cu_verticla_flag) may be signaled to indicate the splitting direction. Thereafter, a third flag (ex. Mtt_split_cu_binary_flag) may be signaled to indicate whether the partition type is binary partition or ternary partition. For example, based on the mtt_split_cu_vertical_flag and the mtt_split_cu_binary_flag, a multi-type tree splitting mode (MttSplitMode) of a CU may be derived as shown in Table 1 below.

MttSplitMode mtt_split_cu_vertical_flag mtt_split_cu_binary_flag SPLIT_TT_HOR 0 0 SPLIT_BT_HOR 0 One SPLIT_TT_VER One 0 SPLIT_BT_VER One One

FIG. 5 illustrates an example of a method of dividing a coding tree unit (CTU) into multiple CUs based on a quadtree and a quadtree and nested multi-type tree structure according to an embodiment of the present invention. .

Here, bold block edges represent quadtree partitioning and the remaining edges represent multitype tree partitioning. Quadtree partitions involving a multitype tree can provide a content-adapted coding tree structure. The CU may correspond to a coding block (CB). Alternatively, the CU may include a coding block of luma samples and two coding blocks of corresponding chroma samples. The size of a CU may be as large as CTU, or may be cut by 4 × 4 in luma sample units. For example, in the 4: 2: 0 color format (or chroma format), the maximum chroma CB size may be 64x64 and the minimum chroma CB size may be 2x2.

For example, in this document, the maximum allowable luma TB size may be 64x64 and the maximum allowable chroma TB size may be 32x32. If the width or height of the CB divided according to the tree structure is larger than the maximum transform width or height, the CB may be automatically (or implicitly) split until the TB size limit in the horizontal and vertical directions is satisfied.

Meanwhile, for a quadtree coding tree scheme involving a multitype tree, the following parameters may be defined and identified as SPS syntax elements.

CTU size: the root node size of a quaternary tree

MinQTSize: the minimum allowed quaternary tree leaf node size

MaxBtSize: the maximum allowed binary tree root node size

MaxTtSize: the maximum allowed ternary tree root node size

MaxMttDepth: the maximum allowed hierarchy depth of multi-type tree splitting from a quadtree leaf

MinBtSize: the minimum allowed binary tree leaf node size

MinTtSize: the minimum allowed ternary tree leaf node size

As an example of a quadtree coding tree structure involving a multitype tree, the CTU size may be set to 64x64 blocks of 128x128 luma samples and two corresponding chroma samples (in 4: 2: 0 chroma format). In this case, MinOTSize can be set to 16x16, MaxBtSize to 128x128, MaxTtSzie to 64x64, MinBtSize and MinTtSize (for both width and height) to 4x4, and MaxMttDepth to 4. Quarttree partitioning may be applied to the CTU to generate quadtree leaf nodes. The quadtree leaf node may be called a leaf QT node. Quadtree leaf nodes may have a 128x128 size (i.e. the CTU size) from a 16x16 size (i.e. the MinOTSize). If the leaf QT node is 128x128, it may not be additionally divided into a binary tree / a ternary tree. This is because in this case, even if split, it exceeds MaxBtsize and MaxTtszie (i.e. 64x64). In other cases, leaf QT nodes may be further partitioned into a multitype tree. Therefore, the leaf QT node is the root node for the multitype tree, and the leaf QT node may have a multitype tree depth (mttDepth) 0 value. If the multitype tree depth reaches MaxMttdepth (ex. 4), further splitting may not be considered further. If the width of the multitype tree node is equal to MinBtSize and less than or equal to 2xMinTtSize, then no further horizontal split may be considered. If the height of the multitype tree node is equal to MinBtSize and less than or equal to 2xMinTtSize, no further vertical split may be considered.

6 shows an example of a method of limiting ternary-tree splitting according to an embodiment of the present invention.

Referring to FIG. 6, the ternary tree (TT) partitioning may be limited in certain cases to allow for 64x64 luma blocks and 32x32 chroma pipeline designs in the hardware decoder. For example, when the width or height of the luma coding block is larger than a predetermined value (eg, 32 and 64), the ternary tree (TT) splitting may be limited as shown in FIG. 6.

In this document, the coding tree scheme may support that the luma and chroma blocks have separate block tree structures. For P and B slices, luma and chroma CTBs in one CTU may be limited to have the same coding tree structure. However, for I slices, luma and chroma blocks may have a separate block tree structure from each other. If an individual block tree mode is applied, the luma CTB may be split into CUs based on a particular coding tree structure, and the chroma CTB may be split into chroma CUs based on another coding tree structure. This may mean that a CU in an I slice may consist of a coding block of a luma component or coding blocks of two chroma components, and a CU of a P or B slice may be composed of blocks of three color components.

In the above-described "CTU partitioning using a tree structure", a quadtree coding tree structure involving a multitype tree has been described, but a structure in which a CU is divided is not limited thereto. For example, the BT structure and the TT structure may be interpreted as a concept included in a multiple partitioning tree (MPT) structure, and the CU may be interpreted to be divided through the QT structure and the MPT structure. In one example where a CU is split through a QT structure and an MPT structure, a syntax element (eg, MPT_split_type) that contains information about how many blocks the leaf node of the QT structure is divided into and the leaf node of the QT structure are vertical The partition structure may be determined by signaling a syntax element (eg, MPT_split_mode) including information about which direction is divided into and horizontally.

In another example, the CU may be partitioned in a different way than the QT structure, BT structure or TT structure. That is, according to the QT structure, the CU of the lower depth is divided into 1/4 size of the CU of the upper depth, or the CU of the lower depth is divided into 1/2 size of the CU of the upper depth according to the BT structure, or according to the TT structure. Unlike the CU of the lower depth is divided into 1/4 or 1/2 size of the CU of the upper depth, the CU of the lower depth is sometimes 1/5, 1/3, 3/8, 3 of the CU of the upper depth. It can be divided into / 5, 2/3 or 5/8 size, the way in which the CU is divided is not limited to this.

On the other hand, the quadtree coded block structure with the multi-type tree described above can provide a very flexible block partitioning structure. Because of the partition types supported in a multitype tree, different partition patterns can sometimes lead to potentially identical coding block structure results. By limiting the occurrence of such redundant partition patterns, the data amount of partitioning information can be reduced. It demonstrates with reference to the following drawings.

7 illustrates examples of redundant partition patterns that may occur in binary tree partitioning and ternary tree partitioning according to an embodiment of the present invention.

As shown in FIG. 7, two levels of consecutive binary splits in one direction have the same coding block structure as the binary split for the center partition after the ternary split. . In this case, the binary tree split in the given direction for the center partition of the ternary tree split may be limited. This restriction can be applied to the CUs of all pictures. If this particular partitioning is restricted, the signaling of the corresponding syntax elements can be modified to reflect this limited case, thereby reducing the number of bits signaled for partitioning. For example, as shown in FIG. 7, when the binary tree split for the center partition of the CU is restricted, the mtt_split_cu_binary_flag syntax element indicating whether the split is a binary split or a tenary split is not signaled, and its value is Can be inferred by the decoder to zero.

Prediction

The decoded portion of the current picture or other pictures in which the current processing unit is included may be used to reconstruct the current processing unit in which decoding is performed.

Intra picture or I picture (slice) using only the current picture for reconstruction, i.e. performing only intra-picture prediction, and picture (slice) using up to one motion vector and reference index to predict each unit A picture (slice) using a picture or P picture (slice), up to two motion vectors, and a reference index may be referred to as a bi-predictive picture or a B picture (slice).

Intra prediction means a prediction method that derives the current processing block from data elements (eg, sample values, etc.) of the same decoded picture (or slice). That is, a method of predicting pixel values of the current processing block by referring to reconstructed regions in the current picture.

Hereinafter, the inter prediction will be described in more detail.

Inter prediction (or inter screen prediction)

Inter prediction means a prediction method of deriving a current processing block based on data elements (eg, sample values or motion vectors) of a picture other than the current picture. That is, a method of predicting pixel values of the current processing block by referring to reconstructed regions in other reconstructed pictures other than the current picture.

Inter prediction (or inter picture prediction) is a technique for removing redundancy existing between pictures, and is mostly performed through motion estimation and motion compensation.

The present invention describes the detailed description of the above-described inter prediction method. The decoder may be represented by the inter prediction-based video / video decoding method of FIG. 10 described later and the inter prediction unit in the decoder 200 of FIG. 11. In addition, the encoder may be represented by the inter prediction based video / video encoding method of FIG. 8 and the inter prediction unit within the encoder 100 of FIG. 9. In addition, the data encoded by FIGS. 10 and 11 may be stored in the form of a bitstream.

The prediction unit of the encoder 100 / decoder 200 may derive the prediction sample by performing inter prediction on a block basis. Inter prediction may represent prediction derived in a manner dependent on data elements (eg, sample values, motion information, etc.) of the picture (s) other than the current picture. When inter prediction is applied to the current block, a predicted block (prediction sample array) for the current block is derived based on a reference block (reference sample array) specified by a motion vector on the reference picture indicated by the reference picture index. Can be.

In this case, in order to reduce the amount of motion information transmitted in the inter prediction mode, the motion information of the current block may be predicted in units of blocks, subblocks, or samples based on the correlation of the motion information between the neighboring block and the current block. The motion information may include a motion vector and a reference picture index. The motion information may further include inter prediction type (L0 prediction, L1 prediction, Bi prediction, etc.) information.

When inter prediction is applied, the neighboring block may include a spatial neighboring block existing in the current picture and a temporal neighboring block present in the reference picture. The reference picture including the reference block and the reference picture including the temporal neighboring block may be the same or different. The temporal neighboring block may be referred to as a collocated reference block, a collocated CU (colCU), and the like, and a reference picture including the temporal neighboring block is called a collocated picture (colPic). It may be. For example, a motion information candidate list (or inheritance candidate list) may be constructed based on neighboring blocks of the current block, and which candidate is selected (used) to derive the motion vector and / or reference picture index of the current block. A flag or index information indicating whether or not) may be signaled.

Inter prediction may be performed based on various prediction modes. For example, in case of a skip mode and a merge mode, motion information of a current block may be the same as motion information of a selected neighboring block. In the skip mode, unlike the merge mode, the residual signal may not be transmitted. In the case of a motion vector prediction (MVP) mode, the motion vector of the selected neighboring block is used as a motion vector predictor, and a motion vector difference value may be signaled. In this case, the sum of the motion vector predictor and the motion vector difference may be used to derive the motion vector of the current block.

8 and 9 illustrate an inter prediction based video / image encoding method and an inter prediction unit in the encoder 100 according to an embodiment of the present invention.

8 and 9, operation S810 may be performed by the inter predictor 180 of the encoder 100, and operation S820 may be performed by the residual processor of the encoder 100. In detail, step S820 may be performed by the subtracting unit 115 of the encoder 100. In operation S830, the prediction information may be derived by the inter prediction unit 180 and encoded by the entropy encoding unit 190. In operation S830, the residual information may be derived by the residual processing unit and encoded by the entropy encoding unit 190. The residual information is information about the residual samples. The residual information may include information about quantized transform coefficients for the residual samples.

As described above, the residual samples may be transformed into transform coefficients through the transform unit 120 of the encoder 100, and the transform coefficients may be derived as transform coefficients quantized through the quantization unit 130. Information about the quantized transform coefficients may be encoded by the entropy encoding unit 190 through a residual coding procedure.

The encoder 100 performs inter prediction on the current block (S810). The encoder 100 may derive inter prediction mode and motion information of the current block and generate prediction samples of the current block. In this case, the inter prediction mode determination, the motion information derivation, and the prediction samples generation procedure may be performed simultaneously, or one procedure may be performed before the other procedure. For example, the inter prediction unit 180 of the encoder 100 may include a prediction mode determination unit 181, a motion information derivation unit 182, and a prediction sample derivation unit 183. The prediction mode determiner 181 may determine the prediction mode for the current block. The motion information derivation unit 182 may derive the motion information of the current block. The predictive sample derivation unit 383 may derive motion samples of the current block.

For example, the inter prediction unit 180 of the encoder 100 searches for a block similar to the current block in a predetermined area (search area) of reference pictures through motion estimation, and compares the current block with the current block. It is possible to derive a reference block whose difference is minimum or below a certain criterion. Based on this, a reference picture index indicating a reference picture in which the reference block is located may be derived, and a motion vector may be derived based on a position difference between the reference block and the current block. The encoder 100 may determine a mode applied to the current block among various prediction modes. The encoder 100 may compare the rate-distortion cost (RD cost) for the various prediction modes and determine the optimal prediction mode for the current block.

For example, when the skip mode or the merge mode is applied to the current block, the encoder 100 constructs a merge candidate list to be described later and differs from the current block among the reference blocks indicated by the merge candidates included in the merge candidate list. Can derive a reference block with a minimum or less than a predetermined criterion. In this case, a merge candidate associated with the derived reference block is selected, and merge index information indicating the selected merge candidate may be generated and signaled to the decoder 200. The motion information of the current block may be derived from the motion information of the selected merge candidate.

As another example, when (A) MVP mode is applied to the current block, the encoder 100 constructs (A) MVP candidate list to be described later, and (A) among the MVP (motion vector predictor) candidates included in the candidate list The motion vector of the selected MVP candidate may be used as the MVP of the current block. In this case, for example, a motion vector indicating a reference block derived by the above-described motion estimation may be used as the motion vector of the current block, and a motion vector having the smallest difference from the motion vector of the current block among MVP candidates. An MVP candidate having may be selected as the MVP candidate. A motion vector difference (MVD), which is a difference obtained by subtracting the MVP from the motion vector of the current block, may be derived. In this case, information about the MVD may be signaled to the decoder 200. In addition, when the (A) MVP mode is applied, the value of the reference picture index may be included in the reference picture index information. Reference picture index information including the reference picture index value may be separately signaled to the decoder 200.

The encoder 100 may derive residual samples based on the prediction samples (S820). The encoder 100 may derive the residual samples through comparison of original samples and prediction samples of the current block. The prediction information is information related to the prediction procedure, and may include, for example, prediction mode information (eg, skip flag, merge flag, or mode index) and information about motion. The information about the motion may include candidate selection information (eg, merge index, mvp flag, or mvp index) that is information for deriving a motion vector. In addition, the information about the motion may include the above-described information about the MVD and / or reference picture index information.

In addition, the information about the motion may include information indicating whether L0 prediction, L1 prediction, or bi prediction is applied. The residual information may include information regarding the residual samples. The residual information may include information about quantized transform coefficients for the residual samples.

The output bitstream may be stored in a (digital) storage medium, transferred directly to the decoder 200, or transferred to the decoder 200 through a network.

Meanwhile, as described above, the encoder 100 may generate a reconstructed picture (including restored samples and a reconstructed block) based on the reference samples and the residual samples. The generation of the reconstructed picture by the encoder 100 is to derive the same prediction result from the encoder 100 as is performed by the decoder 200. Coding efficiency may be increased by generating reconstructed pictures at the encoder 100. Accordingly, the encoder 100 may store a reconstructed picture (or reconstructed samples, a reconstructed block) in a memory and use the reference picture for inter prediction. As described above, an in-loop filtering procedure for the reconstructed picture may be further applied.

10 and 11 are diagrams illustrating an inter prediction based video / image decoding method according to an embodiment of the present invention, and an inter prediction unit 260 in a decoder according to an embodiment of the present invention. 12 and 13, the decoder 200 may perform an operation corresponding to the operation performed by the encoder 100. The decoder 200 may perform prediction on the current block and derive prediction samples based on the received prediction information.

In operation S1010, operation S1030 may be performed by the inter prediction unit 260 of the decoder 200, and the residual information of operation S1040 may be obtained from the bitstream by the entropy decoding unit 210 of the decoder 200. have. The residual processor of the decoder 200 may derive residual samples for the current block based on the residual information. In detail, the inverse quantization unit 220 of the decoder 200 derives the transform coefficients by performing inverse quantization based on the quantized transform coefficients derived based on the residual information, and inverse transform unit of the decoder 200 ( 230 may derive residual samples for the current block by performing an inverse transform on the transform coefficients. The step S1050 may be performed by the adder 235 or the restorer of the decoder 200.

In detail, the decoder 200 may determine a prediction mode for the current block based on the prediction information received from the encoder 100 (S1010). The prediction mode determiner 261 of the decoder 200 may determine which inter prediction mode is applied to the current block based on the prediction mode information included in the prediction information.

For example, the prediction mode determiner 261 may determine whether the merge mode or the (A) MVP mode is applied to the current block based on the merge flag. In addition, the prediction mode determiner 261 may select one of various inter prediction mode candidates based on a mode index. Inter prediction mode candidates may include a skip mode, a merge mode and / or (A) MVP mode, or may include various inter prediction modes (eg, affine merge mode, affine MVP mode) to be described later. .

The motion information derivation unit 262 of the decoder 200 may derive the motion information of the current block based on the inter prediction mode determined by the prediction mode determiner 261 (S1220). For example, when the skip mode or the merge mode is applied to the current block, the motion information derivation unit 262 configures a merge candidate list to be described later, and selects one of the merge candidates included in the merge candidate list. Can be. The motion information derivation unit 262 may select a merge candidate based on the selection information (eg, merge index). The motion information of the current block may be derived from the motion information of the selected merge candidate. In other words, the motion information of the selected merge candidate may be used as the motion information of the current block.

As another example, when (A) MVP mode is applied to the current block, the motion information derivation unit 262 configures (A) MVP candidate list to be described later, and (A) MVP (motion vector) included in the MVP candidate list. predictor) The motion vector of the selected MVP candidate among the candidates may be used as the MVP of the current block. The motion information derivation unit 262 may select a motion vector of the MVP candidate based on the above-described selection information (eg, mvp flag or mvp index). In this case, the MVD of the current block can be derived from the information about the MVD. In addition, the motion vector of the current block may be derived based on the MVP and the MVD of the current block. In addition, the reference picture index of the current block may be derived based on the reference picture index information. The picture indicated by the reference picture index in the reference picture list for the current block may be derived as the reference picture referenced for inter prediction of the current block.

Meanwhile, motion information of the current block may be derived without constructing a candidate list. When motion information of the current block is derived without constructing a candidate list, motion information of the current block may be derived according to a procedure disclosed in the prediction mode. If the motion information of the current block is derived without the candidate list construction, the candidate list construction may be omitted.

The prediction sample derivator 263 may generate prediction samples for the current block based on the motion information of the current block (S1030). The prediction sample derivation unit 263 may derive the reference picture based on the reference picture index of the current block and derive the prediction samples of the current block by using the samples of the reference block indicated on the reference picture by the motion vector of the current block. Can be. In addition, the prediction sample derivator 263 may perform prediction sample filtering on all or part of the prediction samples of the current block.

In other words, the inter prediction unit 260 of the decoder 200 may include a prediction mode determination unit 261, a motion information derivation unit 262, and a prediction sample derivation unit 263. The decoder 200 determines a prediction mode for the current block based on the prediction mode information received by the prediction mode determiner 261, and based on the information about the motion information received by the motion information derivation unit 262. The motion information (motion vector and / or reference picture index, etc.) of the current block may be derived, and the prediction sample derivation unit 263 may derive the prediction samples of the current block. For convenience of description, the operations of the inter prediction unit 260, the prediction mode determination unit 261, or the prediction sample derivation unit 263 are collectively referred to as the operation of the decoder 200.

The decoder 200 may generate residual samples for the current block based on the received residual information (S1040). The decoder 200 may generate reconstructed samples for the current block based on the predicted samples and the residual samples, and generate a reconstructed picture from the generated reconstructed samples (S1050). Thereafter, an in-loop filtering procedure for the reconstructed picture may be further applied.

As described above, the inter prediction procedure may include an inter prediction mode determination step, motion information derivation step according to the determined prediction mode, and prediction execution (prediction sample generation) step based on the derived motion information.

12 shows an example of motion models according to an embodiment of the invention.

Coding standard techniques, including high efficiency video coding (HEVC), use a motion vector to represent the motion of a coding block. Although the method of using one motion vector per block may represent the optimal motion in units of blocks, it may not be the optimal motion of each pixel. Therefore, if the optimal motion vector can be determined in the pixel unit, the coding efficiency can be increased. Thus, an embodiment of the present invention describes a motion prediction method for encoding or decoding a video signal using a multi motion model. In particular, two to four motion vectors may be used to represent a motion vector in each pixel unit or subblock unit of a block, and a prediction technique using the plurality of motion vectors is referred to as affine motion prediction. Can be.

The motion model according to the embodiment of the present invention may represent a motion model as shown in FIG. 12. In the following description, an affine motion prediction method will be described centering on six examples of motion models.

13 illustrates an example of a control point motion vector for affine motion prediction according to an embodiment of the present invention.

As shown in FIG. 13, affine motion prediction may determine a motion vector of a pixel position included in a block by using two control point motion vectors (CPMV) pairs v ₀ and v ₁ . In this case, the set of motion vectors may be called an affine motion vector field (MVF), and may be determined by Equation 1 below.

v _x (x, y) is the x-axis element of the motion vector in the subblock (x, y) of the current block 1300, and v _y (x, y) is the subblock (x, y) of the current block 1300. Is the y-axis element of the motion vector, w is the width of the current block 1300, v _0x is the x-axis element of the first control point motion vector CPMV0 of the top-left of the current block 1300. , v _0y the y-axis elements of the first control point motion vector (CPMV0) the upper left of the current block 1300, v _1x is the second control point motion vector (CPMV1 the upper right side (top-right) of the current block 1300 X-axis element, v _1y may represent the y-axis element of the second control point motion vector (CPMV1) of the top-right of the current block (1300).

14 shows an example of a motion vector for each subblock of a block to which affine motion prediction is applied according to an embodiment of the present invention.

In the encoding or decoding process, the affine motion vector field (MVF) may be determined in a pixel unit or a block unit. When the affine motion vector field is determined in pixel units, a motion vector may be obtained based on each pixel value, and in the case of a block unit, a motion vector of a corresponding block may be obtained based on a center pixel value of a block. In this document, it is assumed that the affine motion vector field MVF is determined in 4 * 4 block units as shown in FIG. 14. However, this is for convenience of description and the embodiments of the present invention are not limited. FIG. 14 shows an example in which a coding block is composed of 16 * 16 samples and an affine motion vector field (MVF) is determined in units of 4 * 4 blocks.

FIG. 15 illustrates an example of neighboring blocks used for prediction of a current block in an affine inter mode according to an embodiment of the present invention.

The affine motion prediction may include an affine merge mode or an AF_MERGE and an affine inter mode or AF_INTER. In affine inter mode AF_INTER, two control point motion vector predictions (CPMVPs) and CPMVs are determined, and a control point motion vector difference (CPMVD) corresponding to the difference is determined by the encoder ( 100 may be transmitted to the decoder 200. In detail, the encoding process of the affine inter mode AF_INTER may be as follows.

Step-1: Determine Two CPMVP Pair Candidates

Step-1.1: Determining Up to 12 CPMVP Candidate Combinations (See Equation 2)

In Equation 2, v ₀ is the motion vector CPMV0 at the upper left control point 1510 of the current block 1500, and v ₁ is the motion vector at the upper right control point 1511 of the current block 1500. CPMV1), v ₂ is the motion vector CPMV2 at the lower left control point 1512 of the current block 1500, and v _A is the neighboring block A adjacent to the upper left side of the upper left control point 1510 of the current block 1500. The motion vector of 1520, v _B is the motion vector of neighboring block B 1522 adjacent to the upper left control point 1510 of the current block 1500, v _C is the upper left control point 1510 of the current block 1500 The motion vector of the neighboring block C 1524 adjacent to the left side, v _D is the motion vector of the neighboring block D 1526 adjacent to the upper right control point 1511 of the current block 1500, v _E is the current block ( 1500) of the motion vectors of the neighboring block E (1528) adjacent to the upper right of the upper right side of the control point (1511), v _F is the peripheral block adjacent to the left side of the left lower side of the control point (1512) of a current block (1500) F (1530) The motion vector, v _G represents a motion vector of the neighboring block G (1532) adjacent to the left side of the left lower side of the control point (1512) of a current block (1500).

Step-1.2: Sort the Difference Value (DV) among the CPMVP Candidate Combinations by Using the Top 2 Candidates (see Equation 3)

v _0x is the x-axis element of the motion vector V0 or CPMV0 of the upper left control point 1510 of the current block 1500, v _1x is the motion vector V1 or CPMV1 of the right upper control point 1511 of the current block 1500. ) of the x-axis Element, v _2x is the current block 1500 in the lower left side of the control point 1512 of the motion vector (V2 or CPMV2) of the x-axis Element, v _0y the upper left control point 1510 of the current block 1500 of The y-axis element of the motion vector V0 or CPMV0, v _1y is the y-axis element of the motion vector V1 or CPMV1 of the upper right control point 1511 of the current block 1500, and v _2y is the lower left of the current block 1500. The y-axis element of the motion vector V2 or CPMV2 of the side control point 1512, w denotes a width of the current block 1500, and h denotes a height of the current block 1500.

Step-2: Use AMVP candidate list when control point motion vector predictor (CPMVP) pair candidate is less than 2

Step-3: Determine the control point motion vector predictor (CPMVP) for each of the two candidates and compare the RD cost to optimally select a candidate with a small value and CPMV

Step-4: Send the index and control point motion vector difference (CPMVD) corresponding to the best candidate

FIG. 16 shows an example of a main block used for prediction of a current block in an affiliate merge mode according to an embodiment of the present invention.

In the affinity merge (AF_MERGE) mode, the encoder 100 may perform encoding as follows.

Step-1: Blocks neighboring blocks A through E (1610, 1620, 1630, 1640, 1650) of the current coding block 1600 in alphabetical order, and are first encoded in the affine prediction mode based on the scanning order. Is determined as a candidate block of affine merge (AF_MERGE)

Step-2: Determine the affine motion model using the determined control point motion vector (CPMV) of the candidate block

Step-3: The control point motion vector CPMV of the current block 1600 is determined according to the affine motion model of the candidate block, and the MVF of the current block 1600 is determined.

17 illustrates an example of a block in which affine motion prediction is performed using a neighboring block to which affine motion prediction is applied according to an embodiment of the present invention.

For example, when block A 1720 is encoded in an affine mode as shown in FIG. 17, after determining block A 1720 as a candidate block, control point motion vectors (CPMVs) of block A 1720 are determined. After deriving an affine motion model using v ₂ and v ₃ , a control point motion vector (CPMV) v ₀ and v ₁ of the current block 1700 may be determined. Based on the control point motion vector (CPMV) of the current block 1700, the affinity motion vector field (MVF) of the current block 1700 is determined, and encoding may be performed.

18 shows an example of an operation flowchart for affine motion prediction according to an embodiment of the present invention. The affine motion prediction illustrated in FIG. 18 is an example of performing the prediction operation S1030 of FIG. 10. Each operation illustrated in FIG. 20 may be performed by the decoder 200.

In operation S1810, the decoder 200 may obtain affine motion information of a current block to be decoded. More specifically, when the decoder 200 determines that the current block to be decoded is a block encoded by affine motion prediction, the decoder 200 may obtain affine motion information necessary for affine motion prediction. For example, the affine motion information may be encoded by an affine motion prediction type (eg, affine merge or affine MVP), information about an affine motion model, information about a neighboring block, and a neighboring block encoded by affine motion prediction. It may include at least one of information on whether or not (eg, an affinity flag), a motion vector of a neighboring block, an affine motion vector of a neighboring block, and information about a reference frame (eg, an index of a reference frame).

In operation S1820, the decoder 200 may perform motion prediction on the current block based on the affine motion information obtained in operation S1810. More specifically, the decoder 200 may perform affine motion prediction by generating an inherited candidate candidate list from the affine motion information of the neighboring block and then selecting an optimal affine motion from the inherited candidate candidate list. . The optimal affine motion to be selected may be indicated by the index generated by the encoder 100. In addition, the decoder 200 may determine an optimal prediction motion vector by selecting an optimal affine motion and considering a prediction direction or a motion vector difference value MVD generated by the encoder. The decoder 200 may then reconstruct the predictive samples from the determined optimal predictive motion information.

19 shows an example of a translation motion model according to an embodiment of the invention.

The translation motion mode is a motion mode for representing a motion in which the position of an object (or block) moves without substantially changing the size or shape of the object. According to the translation motion mode, the motion of the current block may be represented by one motion vector. In addition, it can be seen that the current block includes one control point. In the translation mode, the motion vector of the current block may be expressed as Equation 4 below.

In Equation 4, mv ₀ may represent a motion vector of the current block, v _x0- may represent an x-axis scalar value of the motion vector, and v _y0 may represent a y-axis scalar value of the motion vector of the current block 1900.

20 shows an example of a scaling motion model according to an embodiment of the invention.

Scaling motion model, as shown in Figure 20, to be described by a motion vector (CPMV0) for a first control point (v _0x, v _0y) and one of the elements of the motion vector (CPMV1) for a second control point (v _1x) Can be. Here, it is assumed that the remaining elements v _1y of the motion vector CPMV1 for the second control point are implicitly the same as the y-axis elements v _0y of the motion vector for the first control point. The motion vector field MVF of the current block according to the scaling motion model may be expressed as in Equation 1 above.

21 shows an example of a rotation motion model according to an embodiment of the present invention.

Rotation motion model, also as shown in 21, is described by the motion vectors (CPMV0) for a first control point (v _0x, v _0y) and a single Element (v _1y) of the motion vector (CPMV1) for a second control point Can be. Here, the remaining elements v _1x of the motion vector CPMV1 with respect to the second control point may be expressed implicitly as shown in Equation 5 below.

In Equation 5, v _1x is the x-axis element of the motion vector (CPMV1) for the second control point of the current block, v _0x is the x-axis element of the motion meter (CPMV0) for the first control point of the current block, v _1y is y-Element, v _0y is y-Element, w is the current block width of the motion vector (CPMV0) for the first control point of the current block of the motion vector (CPMV1) for the second control point of the current block (width) Can be represented.

In addition to the motion models (translation, scaling, rotation) described with reference to FIGS. 19 through 21, various motion models may be used to represent various motions. For example, a motion model according to an embodiment of the present invention may include a simplified affine mode, an affine mode, and a bilinear interpolation mode.

In the simplified affine mode, the motion vector field MVF of the current block may be represented by the motion vector CPMV0 for the first control point and the motion vector CPMV1 for the second control point. In the simplified affine mode, the motion vectors of the subblocks included in the motion vector field (MVF) of the current block may be expressed as in Equation 1. The simplified affine mode may be referred to as a 4-parameter affine motion model.

In the affine mode, the motion vector field (MVF) of the current block is determined by the motion vector (CPMV0) for the first control point, the motion vector (CPMV1) for the second control point, and the motion vector (CPMV2) for the third control point. Can be expressed. In the affine mode, the motion vectors of the subblocks included in the motion vector field (MVF) of the current block may be expressed as in Equation 6 below.

In Equation 6, v _x is the x-axis element of the motion vector in the subblock (x, y) of the current block, and v _y is v _y (x, y) in the subblock (x, y) of the current block. The y-axis element of the motion vector, v _0x is the x-axis element of the first control point motion vector CPMV0 of the top-left of the current block, and v _1x is the second of the top-right of the current block. of the control point motion vector (CPMV1) x-Element, v _2x the current block of the left lower side (bottom-left) the third control point motion vector (CPMV2) of the x-axis Element, v _0y the upper left (top-left of the current block Is the y-axis element of the first control point motion vector (CPMV0), v _1y is the y-axis element of the second control point motion vector (CPMV1) of the top-right of the current block, v _2y is the lower left side of the current block y-axis element of the third control point motion vector (CPMV2) of (bottom-left), w is the width of the current block, h is the height of the current block, x and y are the x-axis of each subblock each of the y-axis positions Can be.

In bilinear interpolation mode, the motion vector field MVF of the current block may be represented by motion vectors for four control points CPMV0, CPMV1, CPMV2, CPMV3. CPMV0 is the motion vector for the upper left control point of the current block, CPMV1 is the motion vector for the upper right control point of the current block, CPMV2 is the motion vector for the lower left control point of the current block, and CPMV3 is the motion for the lower right control point of the current block. Can represent a vector. In the bilinear interpolation mode, the motion vector of each subblock of the current block may be expressed as in Equations 7 to 11 below.

In Equations 7 to 11, mv is a motion vector of each subblock included in the motion vector field (MVF) of the current block, cpmv _k is a motion vector for control point k, and w is a motion vector of the current block. Width, h may represent the height of the current block, x and y may represent the x-axis and y-axis position of each subblock, respectively.

Motion model indices may be parsed to determine whether a motion model was used for inter-frame coding. The number of MVD, CPMV or CPMVD may be determined according to the index of the motion model. For example, for a translation motion model, there is one MVD (or CPMVD), for a four-parameter motion model (or simplified affine motion model), two CPMVs, and for a six-parameter motion In the case of a model (or an affine motion model), three CPMVs may be configured. In addition, an index for identifying each motion model may be used. The index for identifying the motion model may be referred to as a motion model index. For example, a translation model with one MV (or CPMV) if the index is 0, a four-parameter motion model (or a simplified affine motion model) with two CPMVs if the index is 1, 2 may correspond to a 6-parameter motion model (or affine motion model) each having three CPMVs. That is, the number of CPMVs may be determined based on the index of the motion model. For example, the number of CPMVs may be determined by the motion model index + 1 (or other integer).

A process of deriving a motion vector based on a motion model according to an embodiment of the present invention will be described. The following embodiments show an example of a process of deriving a motion vector difference value (MVD) or a control point motion vector difference value (CPMVD) based on an MVP mode (or affine MVP mode), but the present invention is limited to the MVP mode. Rather, it can be used for various predictions, including merge mode (or affine merge mode). The syntax included in Tables 2 to 8 below represents an operation or operation of the encoder 100 or the decoder 200 in a programming language format, and an operator included in each syntax is typically used. It will be easily understood by those skilled in the art.

Example 1 Prediction Using Multiple Motion Models

The motion model according to the embodiment of the present invention is a translation mode, a scaling mode, a rotation mode, a rotation mode, a simplified affine mode, and an affine mode. ), Or bilinear interpolation mode. Motion model based prediction according to the above six motion models may be performed as shown in Table 2.

In Table 2, 'translation_flag' is a flag indicating whether a translation mode is applied, 'MVD' is motion vector difference value (MVD) information, and 'CPMVDk' is motion vector difference of the kth control point. Value (MVD) information, 'scaling_flag' is a flag indicating whether scaling mode is applied, 'rotaion_flag' is a flag indicating whether rotation mode is applied, and 'simplified_affine_flag' is a simplified affine mode (4-parameter affine mode). ) Is a flag indicating whether or not to be applied, 'affine_flag' is a flag indicating whether the affine mode (6-parameter affine mode) is applied, 'bi_interpolation_flag' is a flag indicating whether the bilinear interpolation mode is applied.

Example 2 Checking the Motion Model in Split Level Units

According to an embodiment of the present invention, a slice is a region of a higher level than a block, and according to an embodiment of the present invention, whether a motion model is applied hierarchically at a picture, tile, or tile group level may be performed hierarchically. . Information on whether a specific motion model is applied to the current slice may be included in a picture parameter set (PPS) or a slice header. For example, a translation flag (pps_translation_flag) indicating whether a translation motion model has been applied to that slice, a translation flag (pps_scaling_flag) indicating whether a scaling motion model has been applied to that slice, and rotating to that slice. A rotation flag (pps_rotation_flag) to indicate whether a motion model has been applied, a simplified affine flag (pps_simplified_affine_flag) to indicate whether a simplified affine motion model has been applied to that slice, and affine motion model to that slice An affine flag (pps_affine_flag) and a bilinear interpolation flag (pps_bi_interpolation_flag) may be included in a picture parameter set (PPS) or a slice header. The decoder 200 may check whether each motion model is applied to the corresponding slice by checking the picture parameter set (PPS) or the slice header. Since the translation motion model can always be used, the slice level translation flag can always be set to true (pps_translation_flag = true). If necessary, translation flag verification at the slice level may be omitted.

According to an embodiment of the present invention, if a flag about a slice level motion model is set to true, the flag and motion vector difference (MVD) information or control point motion vector difference for the next level block level motion model is set to true. Value (CPMVD) information may be parsed. For example, when the slice level rotation flag is true (pps_rotation_flag = true), the block level rotation flag may be parsed to determine whether the rotation flag is applied to the current block. If the slice level rotation flag is false (pps_rotation_flag = false), the parsing of the block level rotation flag is not performed, and the determination of whether the rotation flag is applied to the current block is omitted and the rotation mode is not used. You may not.

The motion model based prediction method of the split level unit may be performed as shown in Table 3 below.

In Table 3, 'translation_flag' is a flag indicating whether a translation mode is applied, 'MVD' is motion vector difference value (MVD) information, and 'CPMVDk' is motion vector difference of the kth control point. The value (MVD) information, 'pps_scaling_flag' is a flag indicating whether scaling mode is applied at the slice level to which the current block belongs, 'scaling_flag' is a flag indicating whether scaling mode is applied, and 'pps_rotation_flag' is the slice to which the current block belongs A flag indicating whether the rotation mode has been applied at the level, 'rotaion_flag' is a flag indicating whether the rotation mode has been applied, a 'pps_simplified_affine_flag' is a flag indicating whether the simplified affine mode has been applied at the slice level to which the current block belongs, 'simplified_affine_flag' is the simplified affine mode (4-parameter affine mode) A flag indicating whether or not applied, 'pps_affine_flag' indicates whether or not affine mode is applied at the slice level to which the current block belongs, and 'affine_flag' indicates whether or not affine mode (6-parameter affine mode) is applied. The flag 'bi_interpolation_flag' is a flag indicating whether the bilinear interpolation mode is applied.

Example 3: Confirmation of Motion Model Considering Block Size

Generally, translation motion models are efficient for small blocks, but motion models generated by many control point motion vectors (CPMVs), such as affine or bilinear interpolation, may not be efficient for small blocks. Therefore, according to the block size or the number of samples of the block, the motion model can be used adaptively. Based on this concept, an adaptive motion model selection is proposed. Table 4 shows an example of a syntax table according to the present embodiment.

In Table 4, 'sampleNum' indicates the number of samples included in the current block, 'TH_xxx' indicates a threshold range set for each motion model, and 'translation_flag' indicates whether a translation mode has been applied. Flag, 'MVD' is motion vector difference value (MVD) information, 'CPMVDk' is motion vector difference value (MVD) information of kth control point, 'scaling_flag' is flag indicating whether scaling mode is applied, 'rotaion_flag' is Flag indicating whether rotation mode is applied, 'simplified_affine_flag' is a flag indicating whether simplified affine mode (4-parameter affine mode) is applied, and 'affine_flag' is affine mode (6-parameter affine mode) A flag indicating whether or not is applied, 'bi_interpolation_flag' is a flag indicating whether or not the bilinear interpolation mode is applied.

Example 4 Motion Model Verification Using Peripheral Blocks

A motion model may be selected for encoding or decoding the current block according to the motion model used for encoding the neighboring block.

As an example, the motion model for encoding the current block may be determined according to the number of parameters of the motion model used for the neighboring block. This is because a motion model applied in a neighboring block is likely to be applied to the current block. In other words, it is because of high spatial correlation. In addition, even though high spatial correlation does not necessarily apply the motion model of the neighboring block, it is not necessary to define and use a set of candidates of the motion model to be used in the current block based on the motion model of the neighboring block. It may be more reasonable.

Here, each parameter means a parameter for defining each motion model, and the number of control point motion vectors (CPMVs) used to determine the parameters in the motion models expressed through Tables 2 and 3 are required. It is a multiple of 1/2 of the parameter. The number of parameters required for the representation of each motion model and the number of CPMVs required for it are shown in Table 5 below. Where the decimal representation of 1.5 indicates that the required control point motion vector (CPMV) is the x-component or y-component of one control point motion vector (CPMV) and another control point motion vector (CPMV). it means.

Motion model The number of parameter The number of CPMV Translation 2 One Scaling 3 1.5 Rotation 3 1.5 Simplified affine 4 2 Affine 6 3 Bilinear 8 4

Specifically, the syntax table of the present embodiment may be as shown in Table 6, and checkAvailableMotion () is a function for determining a motion model to be used for the current block. Here, checkAvailableMotion () can be operated by one of the following methods.

Example 4-1: Examining the Maximum Number of Parameters of the Motion Model Used in the Surrounding Block

According to an embodiment of the present invention, the motion model of the current block can be identified by checking the maximum number of parameters of the motion model used in the neighboring block. Here, if the maximum parameter value of the motion model used in the neighboring block is maxNumParam, the motion model candidate that can be used in the current block may be defined as in Equation 12.

In Equation 12, maxNumParam is the maximum parameter value of the motion model used in the neighboring block, N is the number of parameters of the motion model that can be included in the candidate group, N0, N1 are experimentally determined values as integer values, and MIN (A , B) and MAX (A, B) are functions that return the minimum and maximum values of A and B.

Example 4-2: Examining the Minimum Number of Parameters of the Motion Model Used in the Surrounding Block

According to an embodiment of the present invention, the motion model of the current block can be identified by checking the minimum number of parameters of the motion model used in the neighboring block. Here, if the minimum parameter value of the motion model used in the neighboring block is minNumParam, the motion model candidate that can be used in the current block may be defined as in Equation (13).

In Equation 13, maxNumParam is the maximum parameter value of the motion model used in the neighboring block, N is the number of parameters of the motion model that can be included in the candidate group, N0, N1 are experimentally determined values as integer values, and MIN (A , B) and MAX (A, B) are functions that return the minimum and maximum values of A and B.

In addition to the method of the embodiment 4-1 or the embodiment 4-2, a method of unconditionally considering the translation model may be considered. This is the most commonly used motion model in the case of the translation model, because the adaptive reliability of the motion model may be inferior in coding reliability. An example of the syntax table according to the present embodiment may be as shown in Table 6.

In Table 6, 'translation_flag' is a flag indicating whether a translation mode is applied, 'MVD' is motion vector difference (MVD) information, and 'CPMVDk' is motion vector difference of the kth control point. Value (MVD) information, 'scaling_flag' is a flag indicating whether scaling mode is applied, 'rotaion_flag' is a flag indicating whether rotation mode is applied, and 'simplified_affine_flag' is a simplified affine mode (4-parameter affine mode). ) Is a flag indicating whether or not to be applied, 'affine_flag' is a flag indicating whether the affine mode (6-parameter affine mode) is applied, 'bi_interpolation_flag' is a flag indicating whether the bilinear interpolation mode is applied.

Example 5: Selecting a motion model from a set of case-by-case motion models

According to an embodiment of the present invention, a method of adaptively using a motion model by defining a motion model for each case may be used. This may correspond to, for example, one of the specific embodiments of the method described in the fourth embodiment. Here, the motion model may be defined as shown in Table 7 below. This has the disadvantage of using a limited number of motion models, but by reducing the number of motion model candidates can reduce the number of bits used to represent the motion model, and may also be advantageous in terms of coding complexity.

Case # Motion model candidates Case 1 Translation (2), scaling (3), simplified affine (4) Case 2 Translation (2), rotation (3), simplified affine (4) Case 3 Translation (2), scaling (3), rotation (3), simplified affine (4)

The motion model of one of the candidates may be determined according to a predetermined condition as described above, or may be determined based on signal or flag information signaled. For example, the flag or index information may be referred to as a motion model flag or a motion model index, respectively.

The syntax table for Case 1 may be as shown in Table 8 below. This article describes how to adaptively use scaling and simplified affine. This reduces the coding complexity and reduces the number of bits representing the motion model by one bit. Specifically, it may be applied as in Equation 14 below.

In Equation 14, maxNumParam is the maximum parameter value of the motion model used in the neighboring block, N is the number of parameters of the motion model that can be included in the candidate group, N0, N1 are experimentally determined values as integer values, and MIN (A , B) and MAX (A, B) are functions that return the minimum and maximum values of A and B. In Equation 14, if only neighboring blocks encoded by the translation model exist, only the translation and scaling model are used for encoding. Otherwise, all motion models are used. Means to use for encoding.

The syntax table according to the present embodiment may be expressed as shown in Table 8.

In the case of Table 2 and Case 3 of Table 7, only the motion model used is changed, and the method of Case 1 may be applied in the same or similar manner. In this case, as described above, the number of control point motion vectors (CPMVs) signaled according to the motion model may be changed, and in some cases (eg, when a rotation model is applied), the x component or the y component of the specific control point motion vector may be changed. Can be signaled.

Hereinafter, a method of performing a motion model based prediction on a current block to be decoded based on the decoder 200 will be described. In the following description, embodiments of the present invention are described with reference to the decoder 200, but the scope of the present invention is not limited to the decoder 200, and the same process may be applied to the encoder 100.

22 shows an example of an operation flowchart for prediction using a motion model according to an embodiment of the present invention.

In operation S2210, the decoder 200 may check a motion model of the current block. More specifically, the decoder 200 may identify a motion model applied for prediction of a current block to be processed, from among a plurality of predefined motion models. Here, the motion model may refer to a type in which motions used for inter prediction are classified. According to an embodiment of the present invention, the number of control points for prediction of the current block and the method of calculating the elements of the motion vector for the control points may be defined for each motion model. According to an embodiment of the present invention, the motion model may be defined in advance, for example, a translation mode, a scaling mode, a rotation mode, a simplified affine. Mode, affine mode, or bilinear interpolation mode.

In operation S2220, the decoder 200 may determine a control point motion vector. More specifically, the decoder 200 may determine a motion vector for at least one control point of the current block based on the motion vector determined in step S2210. According to an embodiment of the present invention, the decoder 200 may include a motion vector difference (MVD) or a neighboring block corresponding to a difference value between a motion vector of a neighboring block adjacent to the current block and a motion vector of the current block. The control point motion vector difference (CPMVD) corresponding to the difference value of the motion vector for the control point of the current block and the control point of the current block corresponding to the control point of the neighboring block may be determined.

In addition, the decoder 200 may derive motion vectors for a motion vector or a plurality of control points for deriving a motion vector of subblocks included in the current block, corresponding to the motion model determined in operation S2210. For example, when the translation mode is applied to the current block, the decoder 200 may determine one motion vector by parsing one MVD. When the scaling mode is applied to the current block, the decoder 200 parses the x component of the CPMVD for the first control point (upper left control point) and the CPMVD for the second control point (upper right control point) by motion vector for the two control points. Can be determined. When the rotation mode is applied to the current block, the decoder 200 motions the two control points by parsing the y component of the CPMVD for the first control point (upper left control point) and the CPMVD for the second control point (upper right control point). The vector can be determined. When the simplified affine mode is applied to the current block, the decoder 200 motions the two control points by parsing the CPMVD for the first control point (upper left control point) and the CPMVD for the second control point (upper right control point). The vector can be determined. When the affine mode is applied to the current block, the decoder 200 includes the CPMVD for the first control point (upper left control point), the CPMVD for the second control point (upper right control point), and the third control point (lower left control point). By parsing the CPMVD, the motion vectors for the three control points can be determined. When the bilinear interpolation mode is applied to the current block, the decoder 200 includes the CPMVD for the first control point (upper left control point), the CPMVD for the second control point (upper right control point), and the third control point (lower left control point). The motion vectors for the four control points can be determined by parsing the CPMVD for the fourth control point and the CPMVD for the fourth control point (the lower right control point).

In operation S2230, the decoder 200 may perform prediction on the current block based on the motion vector information. More specifically, the decoder 200 determines a motion vector of each subblock of the motion vector field of the current block by deriving a motion vector for at least one control point of the current block determined in step S2220, and then motions for each subblock unit. Prediction may be performed by referring to another screen using a vector.

23 illustrates an example of an operation flowchart for identifying a motion model in units of slices and blocks in prediction using a motion model according to an embodiment of the present invention. 23 is an example of checking the motion model of the current block of FIG. 22 (S2210).

In operation S2310, the decoder 200 may check a motion model of a slice to which the current block belongs. More specifically, the decoder 200 may determine whether the specific motion model is applied to the current slice with respect to the specific motion model. According to an embodiment of the present invention, a slice is a region of a higher level than a block, and according to an embodiment of the present invention, whether a motion model is applied hierarchically at a picture, tile, or tile group level may be performed hierarchically. . Information on whether a specific motion model is applied to the current slice may be included in a picture parameter set (PPS) or a slice header.

In operation S2320, the decoder 200 may check a motion model of the current block. More specifically, when the decoder 200 confirms that the specific motion model is applied at the slice level including the current block in operation S2310, the decoder 200 may determine whether the specific motion model is applied to the current block. According to an embodiment of the present invention, if a flag about a slice level motion model is set to true, the flag and motion vector difference (MVD) information or control point motion vector difference for the next level block level motion model is set to true. Value (CPMVD) information may be parsed. An example of the syntax table for the flowchart according to FIG. 23 may be configured as shown in Table 2.

24 illustrates an example of an operation flowchart for checking a motion model in consideration of the number of samples of a current block in prediction using a motion model according to an embodiment of the present invention. 24 is an example of checking the motion model of the current block of FIG. 22 (S2210). 24 illustrates an example of a case in which a motion model is adaptively selected for prediction of a block based on the number of samples of the current block.

In operation S2410, the decoder 200 may check the number of samples of the current block or the size of the current block. More specifically, the decoder 200 may check the number of samples included in the current block through information on the size of the current block.

In operation S2420, the decoder 200 may check the threshold range of the motion model. The decoder 200 may determine whether the number of samples included in the current block or the size of the current block is included in a range set in a specific motion model. For example, a lower limit threshold and an upper limit threshold of the number of samples of a block that can be used for each motion model are set, and whether the number of samples of the current block is included in the threshold range of the corresponding motion model can be checked.

In operation S2430, the decoder 200 may check a motion model applied to the current block. The decoder 200 may determine whether a specific motion model is applied to the current block when the number of samples of the current block or the size of the current block identified in step S2410 is included in the threshold range of the specific motion model.

25 illustrates an example of an operation flowchart for identifying a motion model using neighboring blocks in prediction using the motion model according to an embodiment of the present invention. 25 is an example of checking the motion model of the current block of FIG. 22 (S2210). FIG. 25 illustrates an example of a case in which a motion model is adaptively selected for encoding or decoding a current block according to a motion model used for encoding a neighboring block.

In operation S2510, the decoder 200 may check the motion model of the neighboring block. The decoder 200 may identify a motion model applied to at least one neighboring block in which decoding is performed among a plurality of neighboring blocks adjacent to the current block. The neighboring block adjacent to the current block may be a block located on the upper side, upper left side, and left side of the current block.

In operation S2520, the decoder 200 may check the number of parameters of the neighboring block motion model. The decoder 200 may check the number of parameters corresponding to the motion model of the neighboring block identified in operation S2510. Here, the number of parameters is the number of control point motion vector components for motion prediction. For example, when the parameter is three, it may be configured to include the x, y component of one control point motion vector (CPMV) and the x component of the other control point motion vector (CPMV). That is, the number of control point motion vectors CPMV may correspond to 1/2 of the number of parameters. The number of parameters for each motion model and the number of control point motion vectors may be configured as shown in Table 4 above.

In operation S2530, the decoder 200 may check whether each motion model of the current block is available. The decoder 200 may identify a motion model applicable to the current model among the plurality of motion models from the number of parameters of the motion model applied to the neighboring block.

In operation S2540, the decoder 200 may check a motion model of the current block. The decoder 200 determines whether a specific motion model is applicable to the current block from the number of parameters of the motion model applied to the neighboring block, and then checks a flag indicating whether the specific motion model is applied to the current block. You can check whether it is applied. If it is determined that the flag related to the specific motion model is not applied to the current block, the decoder may perform a check procedure on the motion model confirmed to be usable in operation S2530. The syntax table according to the flowchart shown in FIG. 25 may be configured as shown in Table 6.

FIG. 26 shows an example of an operation flowchart for identifying a motion model corresponding to an index among a set of motion model candidates in prediction using a motion model according to an embodiment of the present invention. 26 is an example of checking a motion model of the current block of FIG. 22 (S2210). FIG. 26 shows an example of a case in which a motion model is adaptively selected for encoding or decoding a current block by defining a motion model candidate that can be used for each case.

In operation S2610, the decoder 200 may determine a motion model candidate set of the current block. The decoder 200 may determine a candidate set of the motion model to be used for determining the motion model of the current block, from a table consisting of candidates for the motion model available for each case. The configuration of motion model candidates that can be used for each case may be configured as shown in Table 6 described above.

In operation S2620, the decoder 200 may check an index of the motion model. The decoder 200 may check the index of the motion model by checking a parameter set transmitted from the encoder 100. The index for identifying the motion model may be referred to as a motion model flag or a motion model index.

In operation S2630, the decoder 200 may identify a motion model corresponding to the index. The decoder 200 may identify the motion model to be used for prediction of the current block among the motion model candidate sets determined in step S2610 by referring to the motion model index transmitted from the encoder 100.

27 shows an example of a video coding system as an embodiment to which the present invention is applied.

The video coding system can include a source device and a receiving device. The source device may deliver the encoded video / image information or data to a receiving device through a digital storage medium or network in a file or streaming form.

The source device may include a video source, an encoding apparatus, and a transmitter. The receiving device may include a receiver, a decoding apparatus, and a renderer. The encoding device may be called a video / image encoding device, and the decoding device may be called a video / image decoding device. The transmitter may be included in the encoding device. The receiver may be included in the decoding device. The renderer may include a display unit, and the display unit may be configured as a separate device or an external component.

The video source may acquire the video / image through a process of capturing, synthesizing, or generating the video / image. The video source may comprise a video / image capture device and / or a video / image generation device. The video / image capture device may include, for example, one or more cameras, video / image archives including previously captured video / images, and the like. Video / image generation devices may include, for example, computers, tablets and smartphones, and may (electronically) generate video / images. For example, a virtual video / image may be generated through a computer or the like. In this case, the video / image capturing process may be replaced by a process of generating related data.

The encoding device may encode the input video / image. The encoding apparatus may perform a series of procedures such as prediction, transform, and quantization for compression and coding efficiency. The encoded data (encoded video / image information) may be output in the form of a bitstream.

The transmitter may transmit the encoded video / video information or data output in the form of a bitstream to the receiver of the receiving device through a digital storage medium or a network in the form of a file or streaming. The digital storage medium may include various storage media such as USB, SD, CD, DVD, Blu-ray, HDD, SSD, and the like. The transmission unit may include an element for generating a media file through a predetermined file format, and may include an element for transmission through a broadcast / communication network. The receiver may extract the bitstream and transmit the extracted bitstream to the decoding apparatus.

The decoding apparatus may decode the video / image by performing a series of procedures such as inverse quantization, inverse transformation, and prediction corresponding to the operation of the encoding apparatus.

The renderer may render the decoded video / image. The rendered video / image may be displayed through the display unit.

28 shows an example of a video streaming system as an embodiment to which the present invention is applied.

Referring to FIG. 28, a content streaming system to which the present invention is applied may largely include an encoding server, a streaming server, a web server, a media storage, a user device, and a multimedia input device.

The encoding server compresses content input from multimedia input devices such as a smartphone, a camera, a camcorder, etc. into digital data to generate a bitstream and transmit the bitstream to the streaming server. As another example, when multimedia input devices such as smart phones, cameras, camcorders, etc. directly generate a bitstream, the encoding server may be omitted.

The bitstream may be generated by an encoding method or a bitstream generation method to which the present invention is applied, and the streaming server may temporarily store the bitstream in the process of transmitting or receiving the bitstream.

The streaming server transmits the multimedia data to the user device based on the user's request through the web server, and the web server serves as a medium for informing the user of what service. When a user requests a desired service from the web server, the web server delivers it to a streaming server, and the streaming server transmits multimedia data to the user. In this case, the content streaming system may include a separate control server. In this case, the control server plays a role of controlling a command / response between devices in the content streaming system.

The streaming server may receive content from a media store and / or an encoding server. For example, when the content is received from the encoding server, the content may be received in real time. In this case, in order to provide a smooth streaming service, the streaming server may store the bitstream for a predetermined time.

Examples of the user device include a mobile phone, a smart phone, a laptop computer, a digital broadcasting terminal, a personal digital assistant (PDA), a portable multimedia player (PMP), navigation, a slate PC, Tablet PCs, ultrabooks, wearable devices, such as smartwatches, glass glasses, head mounted displays, digital TVs, desktops Computer, digital signage, and the like.

Each server in the content streaming system may operate as a distributed server, and in this case, data received from each server may be distributedly processed.

As described above, the embodiments described herein may be implemented and performed on a processor, microprocessor, controller, or chip. For example, the functional units shown in each drawing may be implemented and performed on a computer, processor, microprocessor, controller, or chip.

In addition, the decoder and encoder to which the present invention is applied include a multimedia broadcasting transmitting and receiving device, a mobile communication terminal, a home cinema video device, a digital cinema video device, a surveillance camera, a video chat device, a real time communication device such as video communication, a mobile streaming device, Storage media, camcorders, video on demand (VoD) service providing devices, OTT video (Over the top video) devices, Internet streaming service providing devices, three-dimensional (3D) video devices, video telephony video devices, and medical video devices. It can be used to process video signals or data signals. For example, the OTT video device may include a game console, a Blu-ray player, an Internet access TV, a home theater system, a smartphone, a tablet PC, a digital video recorder (DVR), and the like.

In addition, the processing method to which the present invention is applied can be produced in the form of a program executed by a computer, and stored in a computer-readable recording medium. Multimedia data having a data structure according to the present invention can also be stored in a computer-readable recording medium. The computer readable recording medium includes all kinds of storage devices and distributed storage devices in which computer readable data is stored. The computer-readable recording medium may be, for example, a Blu-ray disc (BD), a universal serial bus (USB), a ROM, a PROM, an EPROM, an EEPROM, a RAM, a CD-ROM, a magnetic tape, a floppy disk, and an optical disc. It may include a data storage device. The computer-readable recording medium also includes media embodied in the form of a carrier wave (eg, transmission over the Internet). In addition, the bitstream generated by the encoding method may be stored in a computer-readable recording medium or transmitted through a wired or wireless communication network.

In addition, an embodiment of the present invention may be implemented as a computer program product by program code, which may be performed on a computer by an embodiment of the present invention. The program code may be stored on a carrier readable by a computer.

The embodiments described above are the components and features of the present invention are combined in a predetermined form. Each component or feature is to be considered optional unless stated otherwise. Each component or feature may be embodied in a form that is not combined with other components or features. It is also possible to combine some of the components and / or features to form an embodiment of the invention. The order of the operations described in the embodiments of the present invention may be changed. Some components or features of one embodiment may be included in another embodiment or may be replaced with corresponding components or features of another embodiment. It is obvious that the claims may be combined to form an embodiment by combining claims that do not have an explicit citation relationship in the claims or as new claims by post-application correction.

Embodiments according to the present invention may be implemented by various means, for example, hardware, firmware, software, or a combination thereof. In the case of a hardware implementation, an embodiment of the present invention may include one or more application specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DSPDs), programmable logic devices (PLDs), FPGAs ( field programmable gate arrays), processors, controllers, microcontrollers, microprocessors, and the like.

In the case of implementation by firmware or software, an embodiment of the present invention may be implemented in the form of a module, procedure, function, etc. that performs the functions or operations described above. The software code may be stored in memory and driven by the processor. The memory may be located inside or outside the processor, and may exchange data with the processor by various known means.

It will be apparent to those skilled in the art that the present invention may be embodied in other specific forms without departing from the essential features of the present invention. Accordingly, the above detailed description should not be construed as limiting in all aspects and should be considered as illustrative. The scope of the present invention should be determined by reasonable interpretation of the appended claims, and all changes within the equivalent scope of the present invention are included in the scope of the present invention.

As mentioned above, preferred embodiments of the present invention are disclosed for purposes of illustration, and those skilled in the art can improve and change various other embodiments within the spirit and technical scope of the present invention disclosed in the appended claims below. , Replacement or addition would be possible.

Claims (14)

A method for processing a video signal, Identifying a motion model applied for prediction of a current block to be processed, among a plurality of predefined motion models; Determining a motion vector for at least one control point of the current block based on the motion model; And Determining a motion vector for each subblock of the current block using the motion vector for the at least one control point; And Performing prediction of the current block based on the motion vector for each subblock, The number of control points of the current block is determined by the motion model. The method of claim 1, Identifying the motion model applied for the prediction of the current block, Checking whether a specific motion model is applied to a slice including the current block; And If the specific motion model is applied to the slice, determining whether the specific motion model is applied to the current block. The method of claim 1, Identifying the motion model applied for the prediction of the current block, Checking the size of the current block or the number of samples included in the current block; Checking whether the size of the current block or the number of samples falls within a threshold range defined in a specific motion model; And If the size of the current block or the number of samples is included in a threshold range of the specific motion model, determining whether the specific motion model has been applied. The method of claim 1, Identifying the motion model applied for the prediction of the current block, Identifying a motion model applied to a neighboring block adjacent to the current block; Checking the number of parameters corresponding to the motion model applied to the neighboring block; Identifying motion model candidates applicable to the current block among the plurality of motion models based on the number of parameters; And Identifying a motion model applied to the current block among the motion model candidates. The method of claim 1, Identifying the motion model applied for the prediction of the current block, Determining a set of motion model candidates applied to the current block from among a set of predefined motion model candidates; Identifying an index indicating a motion model applied to the current block among the motion model candidates; And Identifying a motion model corresponding to the index among the motion model candidates. The method of claim 1, Determining a motion vector for at least one control point of the current block, The motion vector difference (MVD) corresponding to the difference value between the motion vector of the neighboring block adjacent to the current block and the motion vector of the current block, or the motion vector for the control point of the neighboring block and the neighboring block. And determining a control point motion vector difference (CPMVD) corresponding to the difference value of the motion vector with respect to the control point of the current block corresponding to the control point. The method of claim 6, The plurality of predefined motion models, Translation mode, scaling mode, rotation mode, simplified affine mode, affine mode, or bilinear interpolation mode), Determining a motion vector for at least one control point of the current block, When the translation mode is applied to the current block, determining one motion vector by parsing one MVD; When the scaling mode is applied to the current block, determining the motion vectors for the two control points by parsing the x-axis components of the CPMVD for the first control point and the CPMVD for the second control point; When the rotation mode is applied to the current block, determining the motion vectors for the two control points by parsing the y-axis components of the CPMVD for the first control point and the CPMVD for the second control point; When the simplified affine mode is applied to the current block, determining a motion vector for two control points by parsing the CPMVD for a first control point and the CPMVD for a second control point; Determining the motion vector for the three control points by parsing the CPMVD for the first control point, the CPMVD for the second control point, and the CPMVD for the third control point when the affine mode is applied to the current block; And When the bilinear interpolation mode is applied to the current block, motion for four control points by parsing CPMVD for a first control point, CPMVD for a second control point, CPMVD for a third control point, and CPMVD for a fourth control point Determining a vector. An apparatus for processing a video signal, A memory for storing the video signal; A decoder functionally coupled with the memory, The decoder, From among a plurality of predefined motion models, identify the motion model applied for prediction of the current block to be processed, Determine a motion vector for at least one control point of the current block based on the motion model, Determine a motion vector for each subblock of the current block using the motion vector for the at least one control point, Perform prediction of the current block based on the motion vector for each subblock, The number of control points of the current block is determined by the motion model. The method of claim 8, The decoder, Check whether a specific motion model is applied to the slice including the current block, And when the specific motion model is applied to the slice, determine whether the specific motion model is applied to the current block. The method of claim 8, The decoder, Checking the number of samples included in the current block or the size of the current block, Determine whether the number of samples or the size of the current block falls within a threshold range defined in a specific motion model, And determine whether the specific motion model is applied when the number of samples or the size of the current block falls within a threshold range of the specific motion model. The method of claim 8, The decoder, Identify a motion model applied to a neighboring block adjacent to the current block, Checking the number of parameters corresponding to the motion model applied to the neighboring block, Based on the number of parameters, identifying motion model candidates applicable to the current block among the plurality of motion models, And identify a motion model applied to the current block among the motion model candidates. The method of claim 8, The decoder, Determine a set of motion model candidates applied to the current block among a set of predefined motion model candidates, Identify an index indicating a motion model applied to the current block among the motion model candidates, And identify a motion model corresponding to the index among the motion model candidates. The method of claim 8, The decoder, The motion vector difference (MVD) corresponding to the difference value between the motion vector of the neighboring block adjacent to the current block and the motion vector of the current block, or the motion vector for the control point of the neighboring block and the neighboring block. And determine a control point motion vector difference (CPMVD) corresponding to the difference value of the motion vector for the control point of the current block corresponding to the control point. The method of claim 13, The plurality of predefined motion models, Translation mode, scaling mode, rotation mode, simplified affine mode, affine mode, or bilinear interpolation mode), The decoder, When the translation mode is applied to the current block, one motion vector is determined by parsing one MVD, When the scaling mode is applied to the current block, determine the motion vectors for the two control points by parsing the x-axis components of the CPMVD for the first control point and the CPMVD for the second control point, When the rotation mode is applied to the current block, determine the motion vectors for the two control points by parsing the y-axis components of the CPMVD for the first control point and the CPMVD for the second control point, When the simplified affine mode is applied to the current block, determine the motion vectors for the two control points by parsing the CPMVD for the first control point and the CPMVD for the second control point, When the affine mode is applied to the current block, determining a motion vector for three control points by parsing a CPMVD for a first control point, a CPMVD for a second control point, and a CPMVD for a third control point, When the bilinear interpolation mode is applied to the current block, motion for four control points by parsing CPMVD for a first control point, CPMVD for a second control point, CPMVD for a third control point, and CPMVD for a fourth control point A video signal processing apparatus, configured to determine a vector.

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