KR20190113611A - Method and apparatus for image encoding/decoding - Google Patents

Abstract

A method for encoding/decoding an image according to the present invention may generate a candidate list for the motion information prediction of a current block, derive a control point vector of the current block based on the candidate list and a candidate index, derive a motion vector of the current block based on the control point vector of the current block, and perform the inter prediction on the current block using the motion vector. It is possible to perform the inter prediction.

Description

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

The present invention relates to a method and apparatus for image encoding / decoding.

Recently, the demand for high resolution and high quality images such as high definition (HD) and ultra high definition (UHD) images is increasing in various applications, and high efficiency image compression technologies are being discussed.

An inter-screen prediction technique for predicting pixel values included in the current picture from a picture before or after the current picture using an image compression technology, an intra-prediction technology for predicting pixel values included in the current picture using pixel information in the current picture, Various techniques exist, such as an entropy encoding technique for allocating a short code to a high frequency of appearance and a long code to a low frequency of appearance, and the image data can be effectively compressed and transmitted or stored.

An object of the present invention is to provide an inter prediction method and apparatus.

An object of the present invention is to provide a motion compensation method and apparatus for each sub block.

It is an object of the present invention to provide a method and apparatus for determining affine candidates.

An image encoding / decoding method and apparatus according to the present invention generate a candidate list for motion information prediction of a current block, derive a control point vector of the current block based on the candidate list and the candidate index, Based on a control point vector, a motion vector of the current block may be derived, and inter prediction may be performed on the current block using the motion vector.

In the video encoding / decoding apparatus according to the present invention, the candidate list may include a plurality of affine candidates.

In the image encoding / decoding apparatus according to the present invention, the affine candidate may include at least one of a spatial candidate, a temporal candidate, or a configured candidate.

In the image encoding / decoding apparatus according to the present invention, the motion vector of the current block may be derived in units of subblocks of the current block.

In the image encoding / decoding apparatus according to the present invention, the spatial candidate may be determined in consideration of whether a boundary of the current block is in contact with a boundary of a coding tree block.

In the image encoding / decoding apparatus according to the present invention, the configured candidate may be determined based on a combination of at least two of control point vectors corresponding to each corner of the current block.

According to the present invention, the encoding / decoding performance of an image may be improved through inter prediction based on an affine model.

According to the present invention, it is possible to improve the accuracy of prediction through inter prediction on a sub-block basis.

According to the present invention, the encoding / decoding efficiency of inter prediction can be improved by determining an effective candidate.

1 is a conceptual diagram of an image encoding and decoding system according to an embodiment of the present invention.
2 is a block diagram of a video encoding apparatus according to an embodiment of the present invention.
3 is a block diagram of an image decoding apparatus according to an embodiment of the present invention.
4 illustrates an inter prediction method according to an embodiment to which the present invention is applied.
5 is a view illustrating a method of deriving an affine candidate from a spatial / temporal neighboring block according to an embodiment to which the present invention is applied.
FIG. 6 illustrates a method of deriving a candidate constructed based on a combination of motion vectors of spatial and temporal neighboring blocks according to an embodiment to which the present invention is applied.

As the present invention allows for various changes and numerous embodiments, particular embodiments will be illustrated in the drawings and described in detail in the written description. However, this is not intended to limit the present invention to specific embodiments, it should be understood to include all modifications, equivalents, and substitutes included in the spirit and scope of the present invention.

Terms such as first, second, A, and B may be used to describe various components, but the components should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, the first component may be referred to as the second component, and similarly, the second component may also be referred to as the first component. The term and / or includes a combination of a plurality of related items or any item of a plurality of related items.

When a component is referred to as being "connected" or "connected" to another component, it may be directly connected to or connected to that other component, but it may be understood that other components may be present in between. Should be. On the other hand, when a component is said to be "directly connected" or "directly connected" to another component, it should be understood that there is no other component in between.

The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting of the present invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In the present invention, the terms "comprise" or "have" are intended to indicate that there is a feature, number, step, operation, component, part, or combination thereof described in the specification, and one or more other features. It is to be understood that the present invention does not exclude the possibility of the presence or the addition of numbers, steps, operations, components, components, or a combination thereof.

Unless defined otherwise, all terms used herein, including technical or scientific terms, mean the same as generally understood by one of ordinary skill in the art. Terms such as those defined in the commonly used dictionaries should be construed in accordance with their meaning in the context of the related art and should not be construed in an ideal or excessively formal sense unless explicitly defined in the present invention.

1 is a conceptual diagram of an image encoding and decoding system according to an embodiment of the present invention.

Referring to FIG. 1, the video encoding apparatus 105 and the decoding apparatus 100 may include a personal computer (PC), a notebook computer, a personal digital assistant (PDA), and a portable multimedia player (PMP). Player), PlayStation Portable (PSP: PlayStation Portable), wireless communication terminal (Wireless Communication Terminal), smart phone (Smart Phone) or a user terminal such as a TV, or a server terminal such as an application server and a service server, etc. A communication device such as a communication modem for communicating with a wired / wireless communication network, a memory (memory, 120, 125) or a program for storing various programs and data for inter or intra prediction for encoding or decoding an image and executing the operation And various devices including processors (processors 110 and 115) for controlling.

In addition, the image encoded in the bitstream by the image encoding apparatus 105 is real-time or non-real-time via the wired or wireless communication network (Network), such as the Internet, local area wireless communication network, wireless LAN network, WiBro network or mobile communication network, or cable or general purpose The image decoding apparatus 100 may be transmitted to the image decoding apparatus 100 through various communication interfaces such as a universal serial bus (USB), and may be decoded by the image decoding apparatus 100 to restore and reproduce the image. Also, an image encoded in the bitstream by the image encoding apparatus 105 may be transferred from the image encoding apparatus 105 to the image decoding apparatus 100 through a computer-readable recording medium.

The above-described image encoding apparatus and the image decoding apparatus may be separate apparatuses, but may be made of one image encoding / decoding apparatus according to implementation. In this case, some components of the image encoding apparatus may be implemented to include at least the same structure or to perform at least the same function as substantially the same technical elements as some components of the image decoding apparatus.

Therefore, in the following detailed description of the technical elements and their operation principle, overlapping description of the corresponding technical elements will be omitted. Also, since the image decoding apparatus corresponds to a computing device applying the image encoding method performed by the image encoding apparatus to the decoding, the following description will focus on the image encoding apparatus.

The computing device may include a memory for storing a program or software module for implementing an image encoding method and / or an image decoding method, and a processor connected to the memory and executing a program. Here, the image encoding apparatus may be referred to as an encoder, and the image decoding apparatus may be referred to as a decoder.

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

Referring to FIG. 2, the image encoding apparatus 20 may include a predictor 200, a subtractor 205, a transformer 210, a quantizer 215, an inverse quantizer 220, an inverse transformer 225, An adder 230, a filter 235, an encoded picture buffer 240, and an entropy encoder 245 may be included.

The prediction unit 200 may be implemented using a prediction module, which is a software module, and generates a prediction block with an intra prediction or inter prediction for a block to be encoded. can do. The prediction unit 200 may generate a prediction block by predicting a current block to be currently encoded in an image. In other words, the prediction unit 200 predicts the pixel value of each pixel of the current block to be encoded in the image according to the intra prediction or the inter prediction. Can generate a prediction block with In addition, the prediction unit 200 may transmit information necessary for generating a prediction block, such as information about a prediction mode such as an intra prediction mode or an inter prediction mode, to the encoder so that the encoder encodes the information about the prediction mode. Can be. In this case, the processing unit for which the prediction is performed, the processing method for which the prediction method and the details are determined may be determined according to the encoding / decoding setting. For example, the prediction method, the prediction mode, etc. may be determined in the prediction unit, and the performance of the prediction may be performed in the transformation unit.

The inter prediction unit may be classified into a translation motion model and an affine motion model according to a motion prediction method. In the case of the moving motion model, the prediction is performed by considering only the parallel movement. In the case of the out-of-movement model, the prediction can be performed by considering not only the parallel movement but also movements such as rotation, perspective, and zoom in / out. have. Assuming one-way prediction, one motion vector may be required for a motion model, but one or more motion vectors may be required for an out-of-motion motion model. In the case of an out-of-movement motion model, each motion vector may be information applied to a predetermined position of the current block, such as an upper left vertex and an upper right vertex of the current block, and a position of an area to be predicted of the current block through the corresponding motion vector. May be obtained in a pixel unit or a sub block unit. The inter prediction unit may apply some processes to be described later in common according to the motion model, and some processes may be applied separately.

The inter prediction unit may include a reference picture configuration unit, a motion estimation unit, a motion compensator, a motion information determiner, and a motion information encoder. The reference picture configuration unit may include, in the reference picture lists L0 and L1, pictures encoded before or after the current picture. A prediction block may be obtained from a reference picture included in the reference picture list, and the current picture may also be configured as a reference picture and included in at least one of the reference picture lists according to encoding settings.

In the inter prediction unit, the reference picture component may include a reference picture interpolator, and may perform an interpolation process for a fractional pixel according to interpolation precision. For example, an 8-tap DCT based interpolation filter may be applied in the case of luminance components, and a 4-tap DCT based interpolation filter may be applied in the case of chrominance components.

In the inter prediction unit, the motion estimation unit searches a block having a high correlation with the current block through a reference picture, and various methods such as a full search-based block matching algorithm (FBMA) and a three step search (TSS) may be used. The motion compensator means a process of obtaining a prediction block through a motion estimation process.

The motion information determiner may perform a process for selecting the optimal motion information of the current block in the inter prediction unit, and the motion information may be a skip mode, a merge mode, or a competition mode. It may be encoded by a motion information encoding mode. The mode may be configured by combining the supported modes according to the motion model, skip mode (movement), skip mode (movement), merge mode (movement), merge mode (movement), competition mode (movement), Competitive mode (outside the move) may be an example. Some of the modes may be included in the candidate group according to the encoding setting.

In the motion information encoding mode, a prediction value of motion information (motion vector, reference picture, prediction direction, etc.) of the current block may be obtained from at least one candidate block, and optimal candidate selection information is provided when two or more candidate blocks are supported. May occur. In the skip mode (no residual signal) and the merge mode (the residual signal present), the prediction value may be used as the motion information of the current block, and in the contention mode, difference information between the motion information of the current block and the prediction value may be generated. .

The candidate group for the motion information prediction value of the current block may be adaptive and have various configurations according to the motion information encoding mode. The motion information of a block spatially adjacent to the current block (eg, left, top, top left, top right, bottom left block, etc.) may be included in the candidate group, and the motion information of a temporally adjacent block may be included in the candidate group, and the spatial candidate And mixed motion information of temporal candidates may be included in the candidate group.

The temporally adjacent block may include a block in another image corresponding to (or corresponding to) the current block, and mean a block located in a left, right, up, down, top, right, left, bottom, and bottom block with respect to the block. Can be. The mixed motion information may mean information obtained by an average, a median value, etc. through motion information of spatially adjacent blocks and motion information of blocks adjacent in time.

There may be a priority for constructing the motion information prediction value candidate group. The order of inclusion in the prediction value candidate group configuration may be determined according to the priority, and the candidate group configuration may be completed when the number of candidate groups (determined according to the motion information encoding mode) is filled according to the priority. In this case, priority may be determined in order of motion information of spatially adjacent blocks, motion information of temporally adjacent blocks, and mixed motion information of spatial candidates and temporal candidates, but other modifications are also possible.

For example, among spatially adjacent blocks, candidates may be included in the candidate group in the order of left-up-top-right-bottom-left-top block, and candidate blocks in order of right-bottom-middle-right-bottom block among temporally adjacent blocks. It can be included in.

The subtraction unit 205 may generate a residual block by subtracting the prediction block from the current block. In other words, the subtractor 205 calculates a difference between the pixel value of each pixel of the current block to be encoded and the predicted pixel value of each pixel of the prediction block generated through the prediction unit, and is a residual signal in the form of a block. Residual blocks can be created. In addition, the subtraction unit 205 may generate the residual block according to units other than the block unit obtained through the block division unit described below.

The transform unit 210 may convert a signal belonging to a spatial domain into a signal belonging to a frequency domain, and a signal obtained through a transformation process is called a transformed coefficient. For example, a transform block having a transform coefficient may be obtained by transforming the residual block having the residual signal received from the subtractor, but the input signal is determined according to an encoding setting, which is not limited to the residual signal.

The transform unit can transform the residual block using transformation techniques such as a Hadamard transform, a Discrete Sine Transform (DST Based-Transform), or a Discrete Cosine Transform (DCT Based-Transform). The present invention is not limited thereto, and various transformation techniques may be used.

At least one of the transformation schemes may be supported, and at least one detailed transformation scheme may be supported in each transformation scheme. In this case, the detailed changed technique may be a transformation technique in which a part of the basis vector is configured differently in each transformation technique.

For example, in the case of DCT, one or more detailed transformation schemes of DCT-I through DCT-VIII may be supported, and in the case of DST, one or more detailed transformation schemes of DST-I through DST-VIII may be supported. A portion of the detailed transformation scheme may be configured to form a transformation technique candidate group. For example, the transformation may be performed by configuring DCT-II, DCT-VIII, and DST-VII as candidate candidates for transformation techniques.

The conversion can be performed in the horizontal / vertical direction. For example, one-dimensional transform is performed in the horizontal direction using the transform technique of DCT-II, and a total two-dimensional transform is performed by performing one-dimensional transform in the vertical direction using the transform technique of DST-VIII. The pixel value of can be converted into the frequency domain.

The transformation can be performed using one fixed transformation technique, or the transformation can be performed by adaptively selecting the transformation scheme according to the encoding / decoding. In this case, the adaptation method may be selected using an explicit or implicit method. In the explicit case, each transformation technique selection information or transformation technique set selection information applied to the horizontal and vertical directions may occur in a unit such as a block. In an implicit case, encoding settings may be defined according to an image type (I / P / B), a color component, a size, a shape of a block, an intra prediction mode, and a predetermined transformation scheme may be selected.

In addition, it may be possible that the partial transform is omitted depending on the encoding setting. That is, one or more of the horizontal / vertical units may be omitted, either explicitly or implicitly.

In addition, the transformer may transmit information necessary to generate a transform block to the encoder to encode the information, and store the information in the bitstream and transmit the information to the decoder, and the decoder of the decoder parses the information and inversely transforms the information. Can be used for the process.

The quantization unit 215 may quantize the input signal. In this case, the signal obtained through the quantization process is referred to as a quantized coefficient. For example, a quantization block having a quantization coefficient may be obtained by quantizing a residual block having a residual transform coefficient received from a transform unit. The received signal is determined according to an encoding setting, which is not limited to the residual transform coefficient.

The quantization unit may quantize the transformed residual block using a quantization technique such as dead zone uniform threshold quantization, quantization weighted matrix, and the like, but is not limited thereto. Quantization techniques can be used.

The quantization process may be omitted according to the encoding setting. For example, the quantization process may be omitted (including the inverse process) according to the encoding setting (for example, the quantization parameter is 0. That is, the lossless compression environment). As another example, the quantization process may be omitted when the compression performance through quantization is not exhibited according to the characteristics of the image. In this case, the region in which the quantization process is omitted among the quantization blocks M x N may be an entire region or a partial region (M / 2 x N / 2, M x N / 2, M / 2 x N, etc.) and may be quantized. The omission selection information may be determined implicitly or explicitly.

The quantization unit may transmit information necessary for generating a quantization block to the encoding unit and encode the information. The quantization unit stores the information in a bitstream and transmits the information to the decoder, and the decoder of the decoder parses the information and dequantizes it. Can be used for the process.

Although the above example has been described under the assumption that the residual block is transformed and quantized through the transform unit and the quantization unit, the residual block may be transformed from the residual signal to generate a residual block having transform coefficients, and the quantization process may not be performed. Not only may the quantization process be performed without converting the residual signal into transform coefficients, but neither the transformation nor the quantization process may be performed. This may be determined according to the encoder setting.

The inverse quantization unit 220 inverse quantizes the residual block quantized by the quantization unit 215. That is, the inverse quantizer 220 inversely quantizes the quantized frequency coefficient sequence to generate a residual block having the frequency coefficient.

The inverse transform unit 225 inversely transforms the residual block inversely quantized by the inverse quantization unit 220. That is, the inverse transformer 225 inversely transforms frequency coefficients of the inversely quantized residual block to generate a residual block having a pixel value, that is, a reconstructed residual block. Here, the inverse transform unit 225 may perform inverse transform by using the transformed method used in the transform unit 210 as the inverse.

The adder 230 reconstructs the current block by adding the prediction block predicted by the predictor 200 and the residual block reconstructed by the inverse transform unit 225. The reconstructed current block may be stored as a reference picture (or a reference block) in the coded picture buffer 240 and may be used as a reference picture when encoding the next block of the current block, another block in the future, or another picture.

The filter unit 235 may include one or more post-processing filter processes such as a deblocking filter, a sample adaptive offset (SAO), an adaptive loop filter (ALF), and the like. The deblocking filter may remove block distortion generated at the boundary between blocks in the reconstructed picture. The ALF may perform filtering based on a value obtained by comparing the reconstructed image with the original image after the block is filtered through the deblocking filter. The SAO may restore the offset difference from the original image on a pixel basis with respect to the residual block to which the deblocking filter is applied. Such a post-processing filter may be applied to the reconstructed picture or block.

The encoded picture buffer 240 may store a block or a picture reconstructed by the filter unit 235. The reconstructed block or picture stored in the encoded picture buffer 240 may be provided to the prediction unit 200 that performs intra prediction or inter prediction.

The entropy encoder 245 scans the generated quantization frequency coefficient sequence according to various scan methods to generate a quantization coefficient sequence, and outputs the encoded quantization coefficient sequence by encoding it using an entropy encoding technique. The scan pattern may be set to one of various patterns such as zigzag, diagonal lines, and rasters. In addition, encoded data including encoded information transmitted from each component may be generated and output as a bitstream.

3 is a block diagram of an image decoding apparatus according to an embodiment of the present invention.

Referring to FIG. 3, the image decoding apparatus 30 includes an entropy decoder 305, a predictor 310, an inverse quantizer 315, an inverse transformer 320, an adder and subtractor 325, a filter 330, and the like. The decoded picture buffer 335 may be configured.

In addition, the prediction unit 310 may be configured to include an intra prediction module and an inter prediction module.

First, when an image bitstream transmitted from the image encoding apparatus 20 is received, the image bitstream may be transferred to the entropy decoder 305.

The entropy decoder 305 may decode the bitstream to decode the decoded data including the quantized coefficients and the decoded information transmitted to each component.

The prediction unit 310 may generate a prediction block based on the data transferred from the entropy decoding unit 305. In this case, the reference picture list using a default construction technique may be constructed based on the reference picture stored in the decoded picture buffer 335.

The inter prediction unit may include a reference picture component unit, a motion compensator, and a motion information decoder, and some of the processes may be performed in the same process as the encoder, and some may be reversed.

The inverse quantizer 315 may inverse quantize the quantized transform coefficients provided in the bitstream and decoded by the entropy decoder 305.

The inverse transform unit 320 may generate a residual block by applying inverse transform techniques of inverse DCT, inverse integer transform, or the like to a transform coefficient.

In this case, the inverse quantization unit 315 and the inverse transform unit 320 perform the processes performed by the transform unit 210 and the quantization unit 215 of the image encoding apparatus 20 described above, and may be implemented in various ways. have. For example, the same process and inverse transform shared with the transform unit 210 and the quantization unit 215 may be used, and information about the transform and quantization process from the image encoding apparatus 20 (for example, transform size and transform). Shape, quantization type, etc.) may be used to reverse the transform and quantization processes.

The residual block that has undergone inverse quantization and inverse transformation may be added to the prediction block derived by the prediction unit 310 to generate an image block reconstructed. This addition can be made by the adder and subtractor 325.

The filter 330 may apply a deblocking filter to the reconstructed image block to remove blocking if necessary, and further add other loop filters to improve video quality before and after the decoding process. Can also be used.

The reconstructed and filtered image block may be stored in the decoded picture buffer 335.

Although not shown in the figure, the picture encoding / decoding apparatus may further include a picture divider and a block divider.

The picture splitter may divide (or partition) a picture into at least one processing unit such as a color space (eg, YCbCr, RGB, XYZ, etc.), a tile, a slice, a basic coding unit (or a maximum coding unit), or the like. The block splitter may divide the basic coding unit into at least one processing unit (for example, encoding, prediction, transform, quantization, entropy, in-loop filter unit, etc.).

The basic coding unit may be obtained by dividing a picture at regular intervals in a horizontal direction and a vertical direction. Based on this, division of tiles, slices, etc. may be performed, but is not limited thereto. The division unit such as the tile and the slice may be configured as an integer multiple of the basic coding block, but an exceptional case may occur in the division unit located at the image boundary. To this end, adjustment of the basic coding block size may occur.

For example, a picture may be divided into basic coding units and then divided into the units, or a picture may be divided into basic units and then divided into basic coding units. In the present invention, a description will be given on the assumption that the division and division order of each unit is the former, but the present invention is not limited thereto. In the latter case, the size of the basic coding unit may be changed to an adaptive case according to the division unit (tile, etc.). That is, it means that the basic coding block having a different size for each division unit can be supported.

In the present invention, a case of dividing a picture into basic coding units as a default setting will be described below. The default setting may mean that the picture is not divided into tiles or slices or the picture is one tile or one slice. However, as described above, when each division unit (tile, slice, etc.) is first partitioned and then divided into basic coding units based on the obtained unit (that is, each division unit is not an integer multiple of the basic coding unit, etc.). It should be understood that various embodiments may be applied in the same or modified form.

In the case of the slice unit, a slice may be composed of a bundle of at least one consecutive block according to a scan pattern, and in the case of a tile, the slice may be composed of a rectangular bundle of spatially adjacent blocks, and other additional division units are supported. And can be constructed by definition accordingly. The slice and the tile may be divided units supported for the purpose of parallel processing, and for this purpose, references between the divided units may be limited (that is, cannot be referred to).

A slice may generate split information of each unit as information about a start position of consecutive blocks, and in the case of a tile, generate slice information about horizontal and vertical split lines or tile position information (for example, upper left corner). , Upper right, lower left, and lower right positions).

In this case, the slice and the tile may be divided into a plurality of units according to the encoding / decoding.

For example, some units <A> may be units containing setting information that affects the encoding / decoding process (ie, including tile headers or slice headers), and some units <B> do not include setting information. May be a unit. Alternatively, some units <A> may be units that cannot refer to other units in the encoding / decoding process, and some units <B> may be units that may be referred to. In addition, some units <A> may be in a vertical relationship including other units <B> or some units <A> may be in a relationship equivalent to other units <B>.

Here, A and B may be slices and tiles (or tiles and slices). Alternatively, A and B may be composed of one of slices or tiles. For example, A may be a slice / tile <type 1> and B may be configured as a slice / tile <type 2>.

Here, Type 1 and Type 2 may each be one slice or tile. Alternatively, type 1 may be a plurality of slices or tiles (including type 2) (slice set or tile set), and type 2 may be one slice or tile.

As described above, the present invention is described assuming that a picture is composed of one slice or tile. However, when two or more division units occur, the above description may be applied to an embodiment to be described below. In addition, A and B are examples of properties that a division unit may have, and an example in which A and B of each example are mixed is also possible.

Meanwhile, the block divider may be divided into blocks of various sizes. In this case, the block may be composed of one or more blocks according to the color format (for example, one luminance block and two chrominance blocks, etc.), and the size of the block may be determined according to the color format. In the following description, for convenience of description, a block corresponding to one color component (luminance component) will be described.

The following description applies to one color component but differs in proportion to the color format (e.g., in the case of YCbCr 4: 2: 0, the ratio of the width and height of the luminance component and the chrominance component is 2: 1). It should be understood that modifications may be made to the color components. It should also be understood that block partitioning that is dependent on other color components (e.g., depending on the block partitioning result of Y in Cb / Cr) may be possible, but block partitioning independent of each color component may be possible. . In addition, although one common block division setting (which is proportional to the length ratio) can be used, it is also necessary to consider and consider that the individual block division setting is used according to the color component.

The block may have a variable size such as M × N (M and N are integers such as 4, 8, 16, 32, 64, 128, etc.) and may be a unit (coding block) for performing encoding. In detail, the present invention may be a unit that is a basis for prediction, transform, quantization, and entropy encoding, and in the present invention, this is collectively referred to as a block. Herein, the block may be understood as a broad concept including not only a rectangular block but also various types of regions such as a triangle and a circle, and the present invention will be described based on the case of a rectangular shape.

The block divider may be set in relation to each component of the image encoding apparatus and the decoding apparatus, and the size and shape of the block may be determined through this process. In this case, the set block may be defined differently according to the configuration unit, and a prediction block in the prediction unit, a transform block in the transform unit, and a quantization block in the quantization unit may correspond to this. Can be. However, the present invention is not limited thereto, and a block unit according to another component may be further defined. In the present invention, it is assumed that the inputs and outputs are blocks (that is, rectangular shapes) in each component, but some components may be input / output in other forms (eg, squares, triangles, etc.). .

The size and shape of the initial (or starting) block of the block division may be determined from higher units. For example, in the case of a coding block, a basic coding block may be an initial block, and in the case of a prediction block, a coding block may be an initial block. In addition, in the case of a transform block, a coding block or a prediction block may be an initial block, which may be determined according to a sub / decoding setting.

For example, when the encoding mode is intra, the prediction block may be an upper unit of the transform block, and in the inter case, the prediction block may be an independent unit of the transform block. The initial block, which is the start unit of the partition, may be divided into blocks of small size, and when the optimal size and shape according to the partition of the block is determined, the block may be determined as the initial block of the lower unit. The initial block, which is the start unit of the division, may be referred to as the initial block of the upper unit. Here, the upper unit may be a coding block and the lower unit may be a prediction block or a transform block, but is not limited thereto. When the initial block of the lower unit is determined as in the above example, a partitioning process for searching for a block having an optimal size and shape like the upper unit may be performed.

In summary, the block division unit may divide the basic coding unit (or the largest coding unit) into at least one coding unit (or the lower coding unit). In addition, the coding unit may perform division in at least one prediction unit and may perform division in at least one transformation unit. The coding unit may perform splitting into at least one coding block, the coding block may perform splitting into at least one prediction block, and may split into at least one transform block. The prediction unit may perform division into at least one prediction block, and the transform unit may perform division into at least one transform block.

In this case, some blocks may be combined with other blocks to perform one division process. For example, when the coding block and the transform block are combined into one unit, a partitioning process is performed to obtain an optimal block size and shape, which is optimized for the transform block as well as the optimal size and shape of the coding block. Size and shape. Alternatively, the coding block and the transform block may be combined in one unit, the prediction block and the transform block may be combined in one unit, the coding block, the prediction block and the transform block may be combined in one unit, Combination of other blocks may be possible. However, the combination or not is not applied collectively in an image (picture, slice, tile, etc.), but detailed conditions in units of blocks (for example, image type, encoding mode, block size / shape, prediction mode information, etc.). ) May be adaptively determined.

As described above, when a block having an optimal size and shape is found, mode information (for example, split information, etc.) for this may be generated. The mode information may be stored in the bitstream together with information generated by the component to which the block belongs (for example, prediction related information and transform related information) and transmitted to the decoder, and may be parsed in units of the same level by the decoder. Can be used in the video decoding process.

Hereinafter, the division scheme will be described. For convenience of explanation, it is assumed that the initial block is in the form of a square, but the same may be similarly or similarly applied to the case where the initial block is in the form of a rectangle.

Various methods for block partitioning may be supported, but the present invention will be described with emphasis on tree-based partitioning, and at least one tree partitioning may be supported. In this case, a quad tree (Quad Tree. QT), a binary tree (BT), a ternary tree (TT), etc. may be supported. When one tree method is supported, it may be referred to as a single tree split, and when two or more tree methods are supported, a multi-tree method.

In the case of quad-tree splitting, this means that the blocks are divided into two in the horizontal and vertical directions, and in the case of binary tree splitting, the blocks are divided into two in either the horizontal or vertical directions. This means that the system is divided into three directions in either the horizontal or vertical direction.

In the present invention, when the pre-division block is M x N, the quad tree division is divided into four M / 2 x N / 2, and the binary tree division is divided into two M / 2 x N or M x N / 2, In the case of ternary tree partitioning, it is assumed that the partition is divided into M / 4 x N / M / 2 x N / M / 4 x N or M x N / 4 / M x N / 2 / M x N / 4. However, the splitting result is not limited to the above case, and various modification examples may be possible.

One or more of the tree divisions may be supported according to the encoding / decoding setting. For example, it can support quad-tree splitting, or can support quad-tree splitting and binary tree splitting, or it can support quad-tree splitting and ternary tree splitting, or it can support quad-tree splitting and binary tree splitting and ternary tree splitting. Can support

The above example is a case where the basic partitioning scheme is a quad tree and binary tree partitioning and ternary tree partitioning are included in the additional partitioning scheme depending on whether other trees are supported, but various modifications may be possible. In this case, information on whether or not the other tree is supported (bt_enabled_flag, tt_enabled_flag, bt_tt_enabled_flag, etc., may have a value of 0 or 1, 0 is not supported, 1 is supported) or is implicitly determined according to the encoding / decoding setting or sequence, It may be determined explicitly in units of a picture, a slice, a tile, and the like.

The split information may include information on whether to split (tree_part_flag. Or qt_part_flag, bt_part_flag, tt_part_flag, bt_tt_part_flag. The value may be 0 or 1, and 0 may be split and 1 is split). In addition, depending on the partitioning scheme (binary tree, ternary tree), the partition direction (dir_part_flag., Or bt_dir_part_flag, tt_dir_part_flag, bt_tt_dir_part_flag.) May be 0 or 1, and 0 is <horizontal / horizontal>, and 1 is <vertical / Vertical>) may be added, which may be information that may occur when splitting is performed.

When a plurality of tree partitions are supported, various partition information configurations may be possible. The following description assumes an example of how the partition information is configured at one depth level (ie, for the convenience of explanation, although recursive partitioning may be possible because one or more supported partition depths are set to one or more). do.

As an example (1), information on whether to divide is checked. At this time, if the division is not performed, the division ends.

If the split is performed, the selection information on the split type (for example, tree_idx. 0 is QT, 1 is BT, 2 is TT) is checked. At this time, additionally check the split direction information according to the selected split type, and start again from the beginning if additional splitting is possible due to the next step (when the split depth has not reached the maximum, or end splitting if splitting is not possible). Go to)

In one example (2), the information on whether to split some tree methods (QT) is checked and the process proceeds to the next step. In this case, if the split is not performed, information on whether or not the partial tree method BT is split is checked. In this case, if the split is not performed, information on whether or not the partial tree method TT is split is checked. At this time, if the division is not performed, the division ends.

If splitting of some tree type (QT) is performed, the process proceeds to the next step. In addition, if the splitting of some tree methods BT is performed, the split direction information is checked and the process proceeds to the next step. In addition, if the split of some tree split schemes (TT) is performed, the split direction information is checked and the process proceeds to the next step.

In one example (3), the information on whether to split for some tree method (QT) is checked. At this time, if the split is not performed, the information on whether or not to split some tree methods (BT and TT) is checked. At this time, if the division is not performed, the division ends.

If splitting of some tree type (QT) is performed, the process proceeds to the next step. In addition, if splitting of some tree methods BT and TT is performed, the split direction information is checked and the process proceeds to the next step.

The above example may be the case where the priority of the tree split exists (examples 2 and 3) or does not exist (example 1), but various modification examples may be possible. In addition, in the above example, the division of the current step is an example for explaining a case that is not related to the division result of the previous step, but it may also be possible to set the division of the current step depending on the division result of the previous step.

For example, in the case of the first to third examples, if the tree-type partitioning (QT) is performed in the previous step and the current step is transferred to the current step, the splitting of the same tree method (QT) may be supported in the current step.

On the other hand, if some tree-type splitting (QT) is not performed in the previous step and another tree-type splitting (BT or TT) is carried out to the current step, except for some tree-type splitting (QT), some tree-type splitting is performed. It may also be possible that the division of (BT and TT) is supported for subsequent steps, including the current step.

In the above case, since the tree configuration supported for block partitioning may be adaptive, the partitioning information configuration described above may also be configured differently. (Examples to be described below are assumed to be examples 3) In other words, if the splitting of some tree methods (QT) is not performed in the previous step, the splitting process may be performed without considering some tree methods (QT) in the present step. Can be. In addition, splitting information (eg, splitting information, splitting direction information, etc.) regarding the related tree method may be configured by removing the splitting information.

The above example is adaptive for the case where block partitioning is allowed (e.g., block size is within the range between the maximum and minimum values, the partitioning depth of each tree method does not reach the maximum depth <allowed depth>, etc.). It is related to the structure of partitioning information, and adapts to the case where the block partitioning is limited (for example, the block size does not exist in the range between the maximum value and the minimum value, the partitioning depth of each tree method reaches the maximum depth, etc.). Partitioning information may be configured.

As already mentioned, tree-based partitioning in the present invention can be performed using a recursive manner. For example, when the partition flag of the coding block having the partition depth k is 0, encoding of the coding block is performed in the coding block having the partition depth k, and when the partition flag of the coding block having the partition depth k is 1, the coding block. The encoding of is performed in N sub-coding blocks having a division depth of k + 1 (wherein N is an integer of 2 or more, such as 2, 3, 4) according to a division scheme.

The sub coded block may be set again to a coded block k + 1 and divided into sub coded blocks k + 2 through the above process. It can be determined according to.

In this case, the bitstream structure for expressing the partition information may be selected from one or more scan methods. For example, the bitstream of the split information may be configured based on the split depth order, or the bitstream of the split information may be configured based on whether the split information is divided.

For example, in the case of the partition depth ordering method, after obtaining partitioning information at the current level of depth based on the first block, the partitioning information is obtained at the next level of depth. A method of preferentially acquiring additional splitting information in the received block, and another additional scanning method may be considered. In the present invention, it is assumed that a bitstream of partitioning information is configured based on partitioning.

As described above, various cases regarding block partitioning have been described, and a fixed or adaptive setting regarding block partitioning may be supported.

In this case, the setting regarding block division may explicitly include related information in units of a sequence, a picture, a slice, a tile, and the like. Alternatively, the block division setting may be implicitly determined according to the sub / decoding setting, wherein the sub / decoding setting includes various sub / decoding elements such as image type (I / P / B), color component, type of division, and depth of division. It may be configured according to one or a combination of two or more.

4 illustrates an inter prediction method according to an embodiment to which the present invention is applied.

Referring to FIG. 4, a candidate list for motion information prediction of the current block may be generated (S400).

The candidate list may include one or more candidates based on affine models (hereinafter, referred to as affine candidates). Affine Candidate may mean a candidate having a control point vector. The control point vector may mean a motion vector of a control point for an affine model and may be defined with respect to a corner position of the block (eg, at least one of a top left, top right, bottom left, or bottom right corner).

An affine candidate may include at least one of a spatial candidate, a temporal candidate, or a configured candidate. Here, the spatial candidate may be derived from a vector of neighboring blocks spatially adjacent to the current block, and the temporal candidate may be derived from a vector of neighboring blocks temporally adjacent to the current block. Here, the neighboring block may mean a block encoded by an affine model. The vector may mean a motion vector or a control point vector.

A method of deriving a spatial / temporal candidate based on a vector of spatial / temporal neighboring blocks will be described in detail with reference to FIG. 5.

Meanwhile, the configured candidate may be derived based on a combination between motion vectors of spatial / temporal neighboring blocks in the current block, which will be described in detail with reference to FIG. 6.

The plurality of affine candidates described above may be arranged in the candidate list based on a predetermined priority. For example, the plurality of affine candidates may be arranged in the candidate list in the order of spatial candidates, temporal candidates, and configured candidates. Alternatively, the plurality of affine candidates may be arranged in the candidate list in the order of temporal candidates, spatial candidates, and configured candidates. However, the present invention is not limited thereto and the temporal candidate may be arranged after the configured candidate. Alternatively, some of the configured candidates may be arranged before the spatial candidates, and others may be arranged after the spatial candidates.

Based on the candidate list and the candidate index, a control point vector of the current block may be derived (S410).

The candidate index may mean an index encoded to derive a control point vector of the current block. The candidate index may specify any one of a plurality of affine candidates belonging to the candidate list. The control point vector of the current block may be derived by using the control point vector of the affine candidate specified by the candidate index.

For example, assume that the type of the affine model of the current block is 4-parameter (ie, the current block is determined to use two control point vectors). In this case, when the candidate candidate specified by the candidate index has three control point vectors, only two control point vectors (eg, a control point vector having Idx = 0, 1) among the three control point vectors are selected, and the current block is selected. Can be set to the control point vector of. Alternatively, three control point vectors of the identified candidates may be set as control point vectors of the current block. In this case, the type of the affine model of the current block may be updated to 6-parameter.

In contrast, it is assumed that the type of the affine model of the current block is 6-parameter (ie, the current block is determined to use three control point vectors). In this case, when the candidate candidate specified by the candidate index has two control point vectors, one additional control point vector is generated, and the two control point vectors and the additional control point vectors of the candidate candidates are the control point vectors of the current block. Can be set. The additional control point vector may be derived based on at least one of two control point vectors of the candidate candidate, the size or position information of the current / peripheral block. Alternatively, two control point vectors of the identified candidates may be set as control point vectors of the current block. In this case, the type of the affine model of the current block may be updated to 4-parameter.

The motion vector of the current block may be derived based on the control point vector of the current block (S420).

The motion vector may be derived in units of subblocks of the current block. Here, the NxM subblock may be in the form of a rectangle (N> M or N <M) or a square (N = M). The N and M values may be 4, 8, 16, 32 or more. The size / shape of the sub block may be a fixed size / shape pre-defined in the decoding apparatus.

Alternatively, the size / shape of the sub block may be variably derived based on the attributes of the above-described block. For example, if the size of the current block is greater than or equal to a predetermined threshold size, the current block is divided into units (eg, 8x8, 16x16) of the first subblock, otherwise, the current block is the second subblock. It may be divided into units (eg, 4x4). Alternatively, the information about the size / shape of the sub block may be encoded and signaled by the encoding apparatus.

Inter prediction may be performed on the current block by using the derived motion vector (S430).

Specifically, the reference block may be specified using the motion vector of the current block. The reference block may be specified for each sub block of the current block. The reference block of each sub block may belong to one reference picture. That is, a sub block belonging to the current block may share one reference picture. Alternatively, the reference picture index may be independently set for each subblock of the current block.

The specified reference block may be set as a prediction block of the current block. The above-described embodiment may be applied to the same / similarly in the merge mode as well as the general inter mode (e.g., AMVP mode). The above-described embodiment may be performed only when the size of the current block is greater than or equal to a predetermined threshold size. Here, the threshold size may be 8x8, 8x16, 16x8, 16x16 or more.

For the above-described prediction in the sub-block units, a flag indicating the prediction or parameter derivation in the sub-block unit may be signaled. At least one of the above-described S400 to S430 may be performed according to the value of the flag. The flag may be signaled only when it is larger than or equal to the threshold size. The parsing of the flag may be performed based on CABAC, where the probability information (e.g., ctxInc) may be derived based on the value of the flag of the neighboring block. Here, the neighboring block may include at least one of the left or the upper neighboring block of the current block.

5 is a view illustrating a method of deriving an affine candidate from a spatial / temporal neighboring block according to an embodiment to which the present invention is applied.

For convenience of description, a method of deriving affine candidates from spatial neighboring blocks will be described in this embodiment.

Referring to FIG. 5, the width and height of the current block 500 are cbW and cbH, respectively, and the positions of the current block are (xCb and yCb). The width and height of the spatial peripheral block 510 are nbW and nbH, respectively, and the position of the spatial peripheral block is (xNb, yNb). 5 illustrates a block in the upper left of the current block as a spatial neighboring block, but is not limited thereto. That is, the spatial neighboring block may include at least one of a left block, a lower left block, a right upper block, an upper block, or an upper left block of the current block.

The spatial candidate may have n control point vectors (cpMV). Here, the n value may be an integer of 1, 2, 3, or more. The value of n is based on at least one of information on whether the data is decoded in units of sub-blocks, information on whether the block is encoded by the affine model, or information on the type (4-parameter or 6-parameter) of the affine model. Can be determined.

The information may be encoded and signaled by the encoding apparatus. Alternatively, all or part of the information may be derived from the decoding apparatus based on the attribute of the block. Here, the block may mean a current block or may mean a spatial / temporal neighboring block of the current block. The attribute may mean a size, a shape, a position, a split type, an inter mode, a parameter related to a residual coefficient, and the like. The inter mode is a mode predefined in the decoding apparatus and may mean a merge mode, a skip mode, an AMVP mode, an affine model, an intra / inter combination mode, a current picture reference mode, or the like. Alternatively, the n value may be derived from the decoding apparatus based on the attributes of the aforementioned block.

In the present embodiment, the n control point vectors include a first control point vector (cpMV [0]), a second control point vector (cpMV [1]), a third control point vector (cpMV [2]),? It may be represented by the n th control point vector cpMV [n-1]. For example, the first control point vector cpMV [0], the second control point vector cpMV [1], the third control point vector cpMV [2] and the fourth control point vector cpMV [3] It may be a vector corresponding to the positions of the upper left sample, the upper right sample, the lower left sample and the lower right sample, respectively. Here, it is assumed that the spatial candidate has three control point vectors, and the three control point vectors may be any control point vectors selected from the first through n-th control point vectors. However, the present invention is not limited thereto, and the spatial candidate may have two control point vectors, and the two control point vectors may be any control point vectors selected from the first through n-th control point vectors.

Meanwhile, the control point vector of the spatial candidate may be derived differently depending on whether the boundary 520 illustrated in FIG. 5 is a CTU boundary.

1. The boundary of the current block 520 does not touch the CTU boundary

The first control point vector is derived based on at least one of a first control point vector of a spatial neighboring block, a predetermined difference value, position information (xCb, yCb) of the current block, or position information (xNb, yNb) of the spatial neighboring block. Can be.

The number of difference values may be one, two, three, or more. The number of difference values may be variably determined in consideration of the attributes of the above-described block, or may be a fixed value pre-committed to the decoding apparatus. The difference value may be defined as a difference value between any one of the plurality of control point vectors and the other one. For example, the difference value may include a first difference value between the second control point vector and the first control point vector, a second difference value between the third control point vector and the first control point vector, and a second difference between the fourth control point vector and the third control point vector. It may include at least one of a third difference value, or a fourth difference value between the fourth control point vector and the second control point vector.

For example, the first control point vector may be derived as in Equation 1 below.

[Equation 1]

cpMvLX [0] [0] = (mvScaleHor + dHorX * (xCb-xNb) + dHorY * (yCb-yNb))

cpMvLX [0] [1] = (mvScaleVer + dVerX * (xCb-xNb) + dVerY * (yCb-yNb))

In Equation 1, the variables mvScaleHor and mvScaleVer may mean a first control point vector of a spatial neighboring block or a value derived by applying a shift operation by k to the first control point vector. Here, k may be an integer of 1, 2, 3, 4, 5, 6, 7, 8, 9 or more. The variables dHorX and dVerX correspond to the x component and the y component of the first difference value between the second control point vector and the first control point vector, respectively. The variables dHorY and dVerY correspond to the x component and the y component of the second difference value between the third control point vector and the first control point vector, respectively. The aforementioned variable may be derived as in Equation 2 below.

[Equation 2]

mvScaleHor = CpMvLX [xNb] [yNb] [0] [0] << 7

mvScaleVer = CpMvLX [xNb] [yNb] [0] [1] << 7

dHorX = (CpMvLX [xNb + nNbW-1] [yNb] [1] [0]-CpMvLX [xNb] [yNb] [0] [0]) << (7-log2NbW)

dVerX = (CpMvLX [xNb + nNbW-1] [yNb] [1] [1]-CpMvLX [xNb] [yNb] [0] [1]) << (7-log2NbW)

dHorY = (CpMvLX [xNb] [yNb + nNbH-1] [2] [0]-CpMvLX [xNb] [yNb] [2] [0]) << (7-log2NbH)

dVerY = (CpMvLX [xNb] [yNb + nNbH-1] [2] [1]-CpMvLX [xNb] [yNb] [2] [1]) << (7-log2NbH)

The second control point vector may be a first control point vector of a spatial neighboring block, a predetermined difference value, position information (xCb, yCb) of a current block, a block size (width or height), or positional information of a spatial neighboring block (xNb, yNb). It can be derived based on at least one of. Here, the block size may mean the size of the current block and / or spatial neighboring blocks. The difference value is as described in the first control point vector, and a detailed description thereof will be omitted. However, the range and / or number of difference values used in the derivation process of the second control point vector may be different from the first control point vector.

For example, the second control point vector may be derived as in Equation 3 below.

[Equation 3]

cpMvLX [1] [0] = (mvScaleHor + dHorX * (xCb + cbWidth-xNb) + dHorY * (yCb-yNb))

cpMvLX [1] [1] = (mvScaleVer + dVerX * (xCb + cbWidth-xNb) + dVerY * (yCb-yNb))

In Equation 3, the variables mvScaleHor, mvScaleVer, dHorX, dVerX, dHorY, and dVerY are as described in Equation 1, and a detailed description thereof will be omitted.

The third control point vector may be a first control point vector of a spatial neighboring block, a predetermined difference value, position information (xCb, yCb) of the current block, a block size (width or height), or positional information (xNb, yNb) of the spatial neighboring block. It can be derived based on at least one of. Here, the block size may mean the size of the current block and / or spatial neighboring blocks. The difference value is as described in the first control point vector, and a detailed description thereof will be omitted. However, the range and / or number of difference values used in the derivation process of the third control point vector may be different from the first control point vector or the second control point vector.

For example, the third control point vector may be derived as in Equation 4 below.

[Equation 4]

cpMvLX [2] [0] = (mvScaleHor + dHorX * (xCb-xNb) + dHorY * (yCb + cbHeight-yNb))

cpMvLX [2] [1] = (mvScaleVer + dVerX * (xCb-xNb) + dVerY * (yCb + cbHeight-yNb))

In Equation 4, the variables mvScaleHor, mvScaleVer, dHorX, dVerX, dHorY, and dVerY are as described in Equation 1, and a detailed description thereof will be omitted. Meanwhile, the n th control point vector of the spatial candidate may be derived through the above-described process.

2. The boundary of the current block 520 abuts the CTU boundary

The first control point vector is based on at least one of a motion vector (MV) of a spatial neighboring block, a predetermined difference value, position information (xCb, yCb) of the current block, or position information (xNb, yNb) of the spatial neighboring block. Can be derived.

The motion vector may be a motion vector of a sub block located at the bottom of a spatial neighboring block. The sub block may be located at the leftmost, center, or rightmost side of the plurality of subblocks located at the bottom of the spatial neighboring block. Alternatively, the motion vector may mean an average value, a maximum value, or a minimum value of the motion vector of the subblock.

The number of difference values may be one, two, three, or more. The number of difference values may be variably determined in consideration of the attributes of the above-described block, or may be a fixed value pre-committed to the decoding apparatus. The difference value may be defined as a difference value between any one of a plurality of motion vectors stored in units of sub-blocks in a spatial neighboring block and the other one. For example, the difference value may mean a difference value between a motion vector of a lower right subblock and a motion vector of a lower left subblock of a spatial neighboring block.

 For example, the first control point vector may be derived as in Equation 5 below.

[Equation 5]

cpMvLX [0] [0] = (mvScaleHor + dHorX * (xCb-xNb) + dHorY * (yCb-yNb))

cpMvLX [0] [1] = (mvScaleVer + dVerX * (xCb-xNb) + dVerY * (yCb-yNb))

In Equation 5, the variables mvScaleHor and mvScaleVer may mean values derived by applying a shift operation by k to the motion vector (MV) of the above-described spatial neighboring block or the motion vector. Here, k may be an integer of 1, 2, 3, 4, 5, 6, 7, 8, 9 or more.

The variables dHorX and dVerX correspond to the x component and the y component of the predetermined difference value, respectively. Here, the difference value means a difference value between the motion vector of the lower right subblock and the motion vector of the lower left subblock in the spatial neighboring block. Variables dHorY and dVerY may be derived based on the variables dHorX and dVerX. The aforementioned variable may be derived as in Equation 6 below.

[Equation 6]

mvScaleHor = MvLX [xNb] [yNb + nNbH-1] [0] << 7

mvScaleVer = MvLX [xNb] [yNb + nNbH-1] [1] << 7

dHorX = (MvLX [xNb + nNbW-1] [yNb + nNbH-1] [0]-MvLX [xNb] [yNb + nNbH-1] [0]) << (7-log2NbW)

dVerX = (MvLX [xNb + nNbW-1] [yNb + nNbH-1] [1]-MvLX [xNb] [yNb + nNbH-1] [1]) << (7-log2NbW)

dHorY =-dVerX

dVerY = dHorX

The second control point vector may be a motion vector (MV) of a spatial neighboring block, a predetermined difference value, position information (xCb, yCb) of a current block, a block size (width or height), or positional information of a spatial neighboring block (xNb, yNb). May be derived based on at least one of Here, the block size may mean the size of the current block and / or spatial neighboring blocks. The motion vector and the difference value are as described in the first control point vector, and a detailed description thereof will be omitted. However, the position, range and / or number of motion vectors used in the derivation process of the second control point vector may be different from the first control point vector.

For example, the second control point vector may be derived as in Equation 7 below.

[Equation 7]

cpMvLX [1] [0] = (mvScaleHor + dHorX * (xCb + cbWidth-xNb) + dHorY * (yCb-yNb))

cpMvLX [1] [1] = (mvScaleVer + dVerX * (xCb + cbWidth-xNb) + dVerY * (yCb-yNb))

In Equation 7, variables mvScaleHor, mvScaleVer, dHorX, dVerX, dHorY, and dVerY are as described in Equation 5, and a detailed description thereof will be omitted.

The third control point vector may be a motion vector (MV) of a spatial neighboring block, a predetermined difference value, position information (xCb, yCb) of a current block, a block size (width or height), or positional information of a spatial neighboring block (xNb, yNb). May be derived based on at least one of Here, the block size may mean the size of the current block and / or spatial neighboring blocks. The motion vector and the difference value are as described in the first control point vector, and a detailed description thereof will be omitted. However, the position, range and / or number of motion vectors used in the derivation process of the third control point vector may be different from the first control point vector or the second control point vector.

For example, the third control point vector may be derived as in Equation 8 below.

[Equation 8]

cpMvLX [2] [0] = (mvScaleHor + dHorX * (xCb-xNb) + dHorY * (yCb + cbHeight-yNb))

cpMvLX [2] [1] = (mvScaleVer + dVerX * (xCb-xNb) + dVerY * (yCb + cbHeight-yNb))

In Equation 8, the variables mvScaleHor, mvScaleVer, dHorX, dVerX, dHorY, and dVerY are as described in Equation 5, and a detailed description thereof will be omitted. Meanwhile, the n th control point vector of the spatial candidate may be derived through the above-described process.

The derivation process of the affine candidate described above may be performed for each of the pre-defined spatial peripheral blocks. The pre-defined spatial neighboring block may include at least one of a left block, a lower left block, a right upper block, an upper block, or an upper left block of the current block.

Alternatively, the process of deriving the affine candidate may be performed for each group of the spatial neighboring blocks. Here, the spatial neighboring blocks may be classified into a first group including a left block and a lower left block, and a second group including a right upper block, an upper block, and an upper left block.

For example, one affine candidate may be derived from a spatial neighboring block belonging to the first group. The derivation may be performed until an available affine candidate is found, based on a predetermined priority. The priority may be in the order of the left block-> lower left block, or the reverse order.

Similarly, one affine candidate can be derived from the spatial neighboring blocks belonging to the second group. The derivation may be performed until an available affine candidate is found, based on a predetermined priority. The priority may be in the order of upper right block-> upper block-> upper left block, or vice versa.

The above-described embodiment may be applied to the same / similar to the temporal neighboring block. Here, the temporal neighboring block belongs to a picture different from the current block, but may be a block at the same position as the current block. The block of the same position may be a block including the position of the upper left sample of the current block, the center position, or the position of the sample adjacent to the lower right sample of the current block.

Alternatively, the temporal neighboring block may mean a block of a position shifted by a predetermined shift vector in the block of the same position. Here, the disparity vector may be determined based on the motion vector of any one of the spatial neighboring blocks of the current block described above.

FIG. 6 illustrates a method of deriving a candidate constructed based on a combination of motion vectors of spatial and temporal neighboring blocks according to an embodiment to which the present invention is applied.

The configured candidate of the present invention may be derived based on a combination of at least two of control point vectors (hereinafter referred to as control point vectors cpMVCorner [n]) corresponding to each corner of the current block. Here, n may be 0, 1, 2, 3.

The control point vector may be derived based on a motion vector of a spatial neighboring block and / or a temporal neighboring block. Here, the spatial neighboring block may include a first peripheral block (C, D or E) adjacent to the upper left sample of the current block, a second peripheral block (F or G) adjacent to the upper right sample of the current block, or a lower left sample of the current block. It may include at least one of the adjacent third peripheral block (A or B). The temporal neighboring block is a block belonging to a picture different from the current block and may mean a fourth neighboring block Col adjacent to a lower right sample of the current block.

The first neighboring block may mean a neighboring block at the upper left end D, the upper end E, or the left C of the current block. The motion vector of the neighboring blocks C, D, and E may be determined according to a predetermined priority, and the control point vector may be determined using the motion vectors of the available neighboring blocks. The availability determination may be performed until a neighboring block with available motion vectors is found. Here, the priority may be in the order of D-> E-> C. However, the present invention is not limited thereto and may be in the order of D-> C-> E, C-> D-> E, E-> D-> C.

The second neighboring block may mean a block around the upper end F or the upper right end G of the current block. Similarly, it may be determined whether the motion vectors of the neighboring blocks F and G are available according to a predetermined priority, and the control point vector may be determined using the motion vectors of the available neighboring blocks. The availability determination may be performed until a neighboring block with available motion vectors is found. Here, the priority may be in the order of F-> G or in the order of G-> F.

The third neighboring block may mean a neighboring block on the left side B or the lower left end A of the current block. Similarly, it may be determined whether the motion vector of the neighboring block is available according to a predetermined priority, and the control point vector may be determined using the motion vector of the available neighboring block. The availability determination may be performed until a neighboring block with available motion vectors is found. Here, the priority may be in the order of A-> B, or may be in the order of B-> A.

For example, the first control point vector cpMVCorner [0] may be set as the motion vector of the first neighboring block, and the second control point vector cpMVCorner [1] may be set as the motion vector of the second neighboring block. The third control point vector cpMVCorner [2] may be set as the motion vector of the third neighboring block. The fourth control point vector cpMVCorner [3] may be set as the motion vector of the fourth neighboring block.

Alternatively, any one of the first to fourth control point vectors may be derived based on the other. For example, the second control point vector may be derived by applying a predetermined offset vector to the first control point vector. The offset vector may be a difference vector between the third control point vector and the first control point vector or derived by applying a predetermined scaling factor to the difference vector. The scaling factor may be determined based on at least one of the width or height of the current block and / or neighboring blocks.

K combination candidates ConstK according to the present invention may be determined through a combination of at least two of the above-described first to fourth control point vectors. The K value may be an integer of 1, 2, 3, 4, 5, 6, 7 or more. The K value may be derived based on information signaled by the encoding apparatus, or may be a value pre-committed to the decoding apparatus. The information may include information indicating the maximum number of configured candidates included in the candidate list.

In detail, the first configured candidate Const1 may be derived by combining the first to third control point vectors. For example, the first configured candidate Const1 may have a control point vector as shown in Table 1 below. Meanwhile, as long as the reference picture information of the first neighboring block is the same as the reference picture information of the second and third neighboring blocks, the control point vector may be limited as shown in Table 1 below. Here, the reference picture information may mean a reference picture index indicating the position of the reference picture in the reference picture list or a picture order count (POC) value indicating the output order.

Idx Control point vector 0 cpMvCorner [0] One cpMvCorner [1] 2 cpMvCorner [2]

The second configured candidate Const2 may be derived by combining the first, second and fourth control point vectors. For example, the second configured candidate Const2 may have a control point vector as shown in Table 2 below. Meanwhile, as long as the reference picture information of the first neighboring block is the same as the reference picture information of the second and fourth neighboring blocks, the control point vector may be limited as shown in Table 2. Here, the reference picture information is as described above.

Idx Control point vector 0 cpMvCorner [0] One cpMvCorner [1] 2 cpMvCorner [3] + cpMvCorner [1]-cpMvCorner [0]

The third configured candidate Const3 may be derived by combining the first, third and fourth control point vectors. For example, the third configured candidate Const3 may have a control point vector as shown in Table 3 below. Meanwhile, as long as the reference picture information of the first neighboring block is the same as the reference picture information of the third and fourth neighboring blocks, the control point vector may be limited as shown in Table 2. Here, the reference picture information is as described above.

Idx Control point vector 0 cpMvCorner [0] One cpMvCorner [3] + cpMvCorner [0]-cpMvCorner [2] 2 cpMvCorner [2]

The fourth configured candidate Const4 may be derived by combining the second, third, and fourth control point vectors. For example, the fourth configured candidate Const4 may have a control point vector as shown in Table 4 below. Meanwhile, as long as the reference picture information of the second neighboring block is the same as the reference picture information of the third and fourth neighboring blocks, it may be limited to be configured as shown in Table 4 below. Here, the reference picture information is as described above.

Idx Control point vector 0 cpMvCorner [1] + cpMvCorner [2]-cpMvCorner [3] One cpMvCorner [1] 2 cpMvCorner [2]

The fifth configured candidate Const5 may be derived by combining the first and second control point vectors. For example, the fifth configured candidate Const5 may have a control point vector as shown in Table 5 below. Meanwhile, as long as the reference picture information of the first neighboring block is the same as the reference picture information of the second neighboring block, the control point vector may be limited as shown in Table 5 below. Here, the reference picture information is as described above.

Idx Control point vector One cpMvCorner [0] 2 cpMvCorner [1]

The sixth configured candidate Const6 may be derived by combining the first and third control point vectors. For example, the sixth configured candidate Const6 may have a control point vector as shown in Table 6 below. Meanwhile, as long as the reference picture information of the first neighboring block is the same as the reference picture information of the third neighboring block, the control point vector may be limited as shown in Table 6. Here, the reference picture information is as described above.

Idx Control point vector One cpMvCorner [0] 2 cpMvCorner [1]

In Table 6, cpMvCorner [1] may be a second control point vector derived based on the first and third control point vectors. The second control point vector may be derived based on at least one of the first control point vector, a predetermined difference value, or the size of the current / peripheral block. For example, the second control point vector may be derived as in Equation 9 below.

[Equation 9]

cpMvCorner [1] [0] = (cpMvCorner [0] [0] << 7) + ((cpMvCorner [2] [1]-cpMvCorner [0] [1]) << (7 + Log2 (cbHeight / cbWidth) ))

cpMvCorner [1] [1] = (cpMvCorner [0] [1] << 7) + ((cpMvCorner [2] [0]-cpMvCorner [0] [0]) << (7 + Log2 (cbHeight / cbWidth)))

All of the above-described first to sixth configured candidates may be included in the candidate list, and only some of them may be included in the candidate list.

The methods according to the invention can be implemented in the form of program instructions that can be executed by various computer means and recorded on a computer readable medium. Computer-readable media may include, alone or in combination with the program instructions, data files, data structures, and the like. The program instructions recorded on the computer readable medium may be those specially designed and constructed for the present invention, or may be known and available to those skilled in computer software.

Examples of computer readable media may include hardware devices specifically configured to store and execute program instructions, such as ROM, RAM, flash memory, and the like. Examples of program instructions may include high-level language code that can be executed by a computer using an interpreter, as well as machine code such as produced by a compiler. The hardware device described above may be configured to operate with at least one software module to perform the operations of the present invention, and vice versa.

In addition, the above-described method or apparatus may be implemented by combining all or part of the configuration or function, or may be implemented separately.

Although described above with reference to a preferred embodiment of the present invention, those skilled in the art will be variously modified and changed within the scope of the invention without departing from the spirit and scope of the invention described in the claims below I can understand that you can.

Claims (5)

Generating a candidate list for motion information prediction of the current block; Here, the candidate list includes a plurality of affine candidates,
Deriving a control point vector of the current block based on the candidate list and a candidate index;
Deriving a motion vector of the current block based on the control point vector of the current block; And
And performing inter prediction on the current block by using the motion vector. The method of claim 1,
Wherein the affine candidate comprises at least one of a spatial candidate, a temporal candidate, or a configured candidate. The method of claim 1,
The motion vector of the current block is derived in units of sub-blocks of the current block. The method of claim 2,
The spatial candidate is determined in consideration of whether a boundary of the current block is in contact with a boundary of a coding tree block (CTU boundary). The method of claim 2,
The configured candidate is determined based on a combination of at least two of control point vectors corresponding to each corner of the current block.

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