KR102472462B1 - Method and apparatus for adaptive encoding and decoding based on image complexity - Google Patents

Abstract

A method and apparatus for adaptive encoding and decoding based on image complexity are disclosed. The encoding device and the decoding device determine the type of the target unit based on the image complexity of the target unit. The encoding device and the decoding device perform inter prediction on the target unit according to the type determined for the target unit. Types of target units include static units and dynamic units. According to the type of the target unit, a maximum depth of segmentation of the target unit is determined, and a search range for the target unit is determined.

Description

Method and apparatus for adaptive encoding and decoding based on image complexity {METHOD AND APPARATUS FOR ADAPTIVE ENCODING AND DECODING BASED ON IMAGE COMPLEXITY}

The following embodiments relate to an image decoding method, a decoding apparatus, an encoding method, and an encoding apparatus, and more particularly, to a method and apparatus for adaptively performing encoding and decoding based on complexity of an image.

Through the continuous development of the information communication industry, broadcasting services having high definition (HD) resolution have been spread worldwide. Through this proliferation, many users have become accustomed to high-resolution and high-definition images and/or videos.

In order to satisfy users' demand for high image quality, many organizations are accelerating the development of next-generation video devices. Users' interest in Ultra High Definition (UHD) TV, which has four times higher resolution than FHD TV, as well as High Definition TV (HDTV) and Full HD (FHD) TV. has increased, and according to this increase in interest, an image encoding/decoding technology for an image having a higher resolution and quality is required.

An image encoding/decoding device and method for encoding/decoding high-resolution and high-quality images, such as inter prediction technology, intra prediction technology, entropy encoding technology, etc. can be used. The inter-prediction technique may be a technique of predicting a value of a pixel included in a current picture using a temporally previous picture and/or a temporally subsequent picture. Intra-prediction technology may be a technology of predicting a value of a pixel included in a current picture by using pixel information in the current picture. The entropy coding technique may be a technique of allocating a short code to a symbol with a high frequency of occurrence and a long code to a symbol with a low frequency of occurrence.

In video encoding and decoding, prediction may mean generating a prediction signal similar to an original signal. Prediction can be largely classified into prediction referring to a spatially reconstructed image, prediction referring to a temporally reconstructed image, and prediction of other symbols. In other words, temporal reference may mean referring to a temporally reconstructed image, and spatial reference may mean referring to a spatially reconstructed image.

The current block may be a block currently being encoded or decoded. The current block may be named a target block or target unit. In encoding, a current block may be named an encoding target block or an encoding target unit. In decoding, a current block may be named a decoding object block or a decoding object unit.

Inter prediction may be a technique of predicting a current block using temporal and spatial references. Intra prediction may be a technique of predicting a current block using only spatial reference.

In general, for inter prediction of blocks of multiple images, the same inter prediction is used. For example, the same inter prediction may be applied without considering the image characteristics of the image including the current block. When the same inter prediction is always used, the complexity of an encoding device may increase and encoding efficiency may decrease. In particular, in prediction of a coding unit including a static region, when inter prediction is performed on more subdivided blocks than necessary, the amount of motion information to be transmitted from the encoding device to the decoding device may increase. , encoding efficiency may decrease due to an increase in the amount of motion information.

An embodiment may provide a method and apparatus for improving encoding efficiency through a technique of performing adaptive encoding and decoding based on characteristics of an image.

An embodiment may provide a method and apparatus for reducing the complexity of an encoding device through a technique for performing adaptive encoding and decoding based on characteristics of an image.

An embodiment may provide a method and apparatus for limiting the number of times a coding unit classified as a static region is divided into subunits based on a quadtree.

An embodiment may provide a method and apparatus for encoding a coding unit as a larger-sized unit by limiting the number of times a coding unit classified as a static region is divided into sub-units.

An embodiment may provide a method and apparatus for reducing the complexity of an encoding device by encoding a coding unit classified as a static region as a larger unit.

An embodiment may provide a method and apparatus for reducing the amount of motion information transmitted from an encoding device to a decoding device by encoding a coding unit classified as a static region as a larger unit.

An embodiment may provide a method and apparatus for reducing bit precision and search range of a motion vector under the assumption that correlation between a static unit and an adjacent block is high.

An embodiment may provide a method and apparatus for improving encoding efficiency and reducing the complexity of an encoding device by reducing bit precision and a search region of a motion vector.

In one aspect, determining a type of a target unit based on an image complexity of the target unit; and performing inter prediction on the target unit according to the determined type.

A method and apparatus for improving coding efficiency through a technique for performing adaptive encoding and decoding based on the characteristics of an image are provided.

A method and apparatus for reducing the complexity of an encoding device through a technique of performing adaptive encoding and decoding based on characteristics of an image are provided.

A method and apparatus for limiting the number of times a coding unit classified as a static region is divided into subunits based on a quadtree are provided.

Provided is a method and apparatus for encoding a coding unit as a larger unit by limiting the number of times a coding unit classified as a static region is divided into sub-units.

A method and apparatus for reducing the complexity of an encoding device by encoding a coding unit classified as a static region as a larger unit are provided.

A method and apparatus for reducing the amount of motion information transmitted from an encoding apparatus to a decoding apparatus by encoding a coding unit classified as a static region as a larger unit are provided.

Provided is a method and apparatus for reducing bit precision and search range of a motion vector under the assumption that correlation between a static unit and an adjacent block is high.

A method and apparatus for improving encoding efficiency and reducing the complexity of an encoding device by reducing the bit precision and search range of motion vectors are provided.

1 is a block diagram showing a configuration according to an embodiment of an encoding device to which the present invention is applied.
2 is a block diagram showing a configuration according to an embodiment of a decoding device to which the present invention is applied.
3 is a diagram schematically illustrating a division structure of an image when encoding and decoding an image.
4A to 7H are diagrams illustrating a form of a prediction unit (PU) that may be included in a coding unit (CU).
5 is a diagram illustrating a form of a transform unit (TU) that may be included in a coding unit (CU).
6 is a diagram for explaining an embodiment of an intra prediction process.
7 is a diagram for explaining an embodiment of an inter prediction process.
8 is a flowchart of an inter prediction method according to an embodiment.
9 illustrates differential images of a current picture and a reference picture according to an example.
10 illustrates type flags of a target unit and reconstructed neighboring units according to an example.
11 is a structural diagram of an electronic device implementing an encoding device and/or a decoding device according to an embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS For detailed descriptions of exemplary embodiments described below, reference is made to the accompanying drawings, which illustrate specific embodiments by way of example. These embodiments are described in sufficient detail to enable those skilled in the art to practice the embodiments. It should be understood that the various embodiments are different, but need not be mutually exclusive. For example, specific shapes, structures, and characteristics described herein may be implemented in one embodiment in another embodiment without departing from the spirit and scope of the invention. Additionally, it should be understood that the location or arrangement of individual components within each disclosed embodiment may be changed without departing from the spirit and scope of the embodiment. Accordingly, the detailed description set forth below is not to be taken in a limiting sense, and the scope of the exemplary embodiments, if properly described, is limited only by the appended claims, along with all equivalents as claimed by those claims.

Like reference numbers in the drawings indicate the same or similar function throughout the various aspects. The shapes and sizes of elements in the drawings may be exaggerated for clarity.

When a component is referred to as being “connected” or “connected” to another component, the two components may be directly connected or connected to each other, but It will be understood that other components may exist in the middle of the two components. In addition, the description of "including" a specific configuration in the exemplary embodiments does not exclude configurations other than the specific configuration above, and additional configurations are the implementation of the exemplary embodiments or the technical idea of the exemplary embodiments. This means that it can be included in the scope.

Terms such as first and second may be used to describe various elements, but the above elements should not be limited by the above terms. The above terms are used to distinguish and refer to one component from another. For example, without departing from the scope of rights, a first element may be termed a second element, and similarly, a second element may also be termed a first element.

In addition, the components appearing in the embodiments are shown independently to represent different characteristic functions, and each component does not mean that each component consists of only a separate hardware or one software unit. That is, each component is listed as each component for convenience of description. For example, at least two of the components may be combined into one component. Also, one component may be divided into a plurality of components. An integrated embodiment and a separate embodiment of each of these components are also included in the scope of rights unless departing from the essence.

In addition, some of the components may not be essential components for performing essential functions, but may be optional components for improving performance. Embodiments may be implemented by including only components essential to implement the essence of the embodiment, and structures excluding optional components, such as components used only for performance improvement, are also included in the scope of rights.

Hereinafter, the embodiments will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily practice the embodiments. In describing the embodiments, if it is determined that a detailed description of a related known configuration or function may obscure the gist of the present specification, the detailed description will be omitted.

Hereinafter, an image may mean one picture constituting a video, and may also indicate the video itself. For example, "encoding and/or decoding an image" may mean "encoding and/or decoding a video", and may mean "encoding and/or decoding one of images constituting a video". may be

First, terms used in the embodiments will be described.

Unit: A “unit” may represent a unit of encoding and decoding of an image. The semantics of unit and block may be the same. Also, the terms “unit” and “block” may be used interchangeably.

A unit (or block) can be an MxN array of samples. M and N may each be a positive integer. A unit may often mean a two-dimensional array of samples. A sample can be a pixel or a pixel value.

In encoding and decoding of an image, a unit may be a region created by dividing one image. One image may be divided into a plurality of units. In encoding and decoding of an image, a predefined process for a unit may be performed according to the type of unit. Depending on the function, the unit type may be classified into a macro unit, a coding unit (CU), a prediction unit (PU), and a transform unit (TU). One unit can be further divided into sub-units having a smaller size relative to the unit.

Block division information may include information about the depth of a unit. Depth information may indicate the number and/or degree of division of a unit.

One unit may be hierarchically divided into a plurality of sub-units while having depth information based on a tree structure. In other words, a unit and a sub-unit generated by division of the unit may correspond to a node and a child node of the node, respectively. Each divided sub-unit may have depth information. Since the depth information of a unit indicates the number and/or degree of division of the unit, the division information of the sub-unit may include information about the size of the sub-unit.

In the tree structure, the highest node may correspond to the first undivided unit. The highest node may be referred to as a root node. Also, the highest node may have the smallest depth value. In this case, the highest node may have a depth of level 0.

A node with a depth of level 1 may represent a unit created as the original unit is split once. A node with a depth of level 2 may represent a unit created as the original unit is split twice.

A node with a depth of level n may represent a unit created as the original unit is split n times.

A leaf node may be the lowest node and may be a node that cannot be further divided. The depth of a leaf node may be the maximum level. For example, the predefined value of the maximum level may be 3.

Transform Unit: The transform unit may be a basic unit in residual signal encoding and/or residual signal decoding, such as transform, inverse transform, quantization, inverse quantization, transform coefficient encoding, and transform coefficient decoding. . One transform unit may be divided into multiple transform units having smaller sizes.

Prediction Unit: A prediction unit may be a basic unit in performing prediction or compensation. A prediction unit may be divided into multiple partitions. A number of partitions may also be a basic unit in performing prediction or compensation. A partition generated by division of a prediction unit may also be a prediction unit.

Reconstructed Neighbor Unit: A reconstructed neighbor unit may be a unit that has already been encoded or decoded and reconstructed around a unit to be coded or a unit to be decoded. The reconstructed neighboring unit may be a spatial neighboring unit or a temporal neighboring unit of the target unit.

Prediction unit partition: A prediction unit partition may mean a form in which a prediction unit is divided.

Parameter Set: A parameter set may correspond to header information among structures in a bitstream. For example, the parameter set may include a sequence parameter set, a picture parameter set, an adaptation parameter set, and the like.

Rate distortion optimization: An encoding device may use rate distortion optimization to provide high encoding efficiency by using a combination of coding unit size, prediction mode, prediction unit size, motion information, and conversion unit size. can

The rate distortion optimization method may calculate a rate distortion cost of each combination in order to select an optimal combination among the above combinations. The rate distortion cost can be calculated using Equation 1 below. In general, a combination that minimizes the rate distortion cost can be selected as an optimal combination in the rate distortion optimization method.

D can represent distortion. D may be a mean square error of difference values between original transform coefficients and reconstructed transform coefficients within a transform block.

R can represent a rate. R may represent a bit rate using related context information.

λ may represent a Lagrangian multiplier. R may include not only encoding parameter information such as a prediction mode, motion information, and a coded block flag, but also bits generated by encoding transform coefficients.

The encoding device performs processes such as inter prediction and/or intra prediction, transformation, quantization, entropy encoding, inverse quantization, and inverse transformation to calculate accurate D and R. These processes can greatly increase complexity in the encoding device. have.

Reference picture: A reference picture may be an image used for inter prediction or motion compensation. A reference picture may be a picture including a reference unit referred to by a target unit for inter prediction or motion compensation. Meanings of a picture and a video may be the same. Also, the terms “picture” and “image” may be used interchangeably.

Reference picture list: The reference picture list may be a list including reference pictures used for inter prediction or motion compensation. Types of reference picture lists may include List Combined (LC), List 0 (L0), and List 1 (List 1; L1).

Motion Vector (MV): A motion vector may be a two-dimensional vector used in inter prediction. For example, MV can be expressed as (mv _x , mv _y ). mv _x may represent a horizontal component, and mv _y may represent a vertical component.

MV may represent an offset between a target picture and a reference picture.

Search range: The search range may be a two-dimensional area where MVs are searched during inter prediction. For example, the size of the search area may be MxN. M and N may each be a positive integer.

1 is a block diagram showing a configuration according to an embodiment of an encoding device to which the present invention is applied.

The encoding device 100 may be a video encoding device or an image encoding device. A video may include one or more images. The encoding device 110 may sequentially encode one or more images of a video according to time.

Referring to FIG. 1, an encoding apparatus 100 includes an inter prediction unit 110, an intra prediction unit 120, a switch 115, a subtractor 125, a transform unit 130, a quantization unit 140, and entropy encoding. It may include a unit 150, an inverse quantization unit 160, an inverse transform unit 170, an adder 175, a filter unit 180, and a reference picture buffer 190.

The encoding apparatus 100 may perform encoding on an input image in an intra mode and/or an inter mode. The input image may be referred to as a current image that is a current encoding target.

Also, the encoding device 100 may generate a bitstream including encoding information through encoding of an input image and output the generated bitstream.

When intra mode is used, switch 115 can be switched to intra. When the inter mode is used, the switch 115 can be switched to inter.

The encoding apparatus 100 may generate a prediction block for an input block of an input image. Also, the encoding apparatus 100 may encode a residual between the input block and the prediction block after the prediction block is generated. An input block may be referred to as a current block that is a target of current encoding.

When the prediction mode is the intra mode, the intra predictor 120 may use a pixel value of an already encoded block adjacent to the current block as a reference pixel. The intra predictor 120 may perform spatial prediction on the current block using the reference pixel and generate prediction samples for the current block through the spatial prediction.

The inter prediction unit 110 may include a motion estimation unit and a motion compensation unit.

When the prediction mode is the inter mode, the motion prediction unit may search for an area that best matches the current block from the reference picture in the motion prediction process, and derive a motion vector for the current block and the searched area. The reference picture may be stored in the reference picture buffer 190, and may be stored in the reference picture buffer 190 when encoding and/or decoding of the reference picture is processed.

The motion compensation unit may generate a prediction block by performing motion compensation using a motion vector. Here, the motion vector may be a 2D vector used for inter prediction. Also, the motion vector may indicate an offset between the current image and the reference image.

The subtractor 125 may generate a residual block that is a difference between the input block and the prediction block. A residual block may also be referred to as a residual signal.

The transform unit 130 may generate transform coefficients by performing transform on the residual block, and may output the generated transform coefficients. Here, the transform coefficient may be a coefficient value generated by performing transform on the residual block. When a transform skip mode is applied, the transform unit 130 may skip transform on the residual block.

A quantized transform coefficient level may be generated by applying quantization to the transform coefficient. Hereinafter, in the embodiments, a quantized transform coefficient level may also be referred to as a transform coefficient.

The quantization unit 140 may generate a quantized transform coefficient level by quantizing a transform coefficient according to a quantization parameter. The quantization unit 140 may output the generated quantized transform coefficient level. At this time, the quantization unit 140 may quantize the transform coefficient using a quantization matrix.

The entropy encoding unit 150 may generate a bitstream by performing entropy encoding according to a probability distribution based on the values calculated by the quantization unit 140 and/or encoding parameter values calculated in the encoding process. . The entropy encoding unit 150 may output the generated bitstream.

The entropy encoding unit 150 may perform entropy encoding on information for decoding an image in addition to pixel information of the image. For example, information for decoding an image may include a syntax element and the like.

The encoding parameter may be information required for encoding and/or decoding. The encoding parameter may include information that is encoded by the encoding device and transmitted to the decoding device, and may include information that can be inferred during an encoding or decoding process. For example, as information transmitted to the decoding device, there is a syntax element.

For example, coding parameters include prediction mode, motion vector, reference picture index, coding block pattern, presence or absence of residual signal, transform coefficient, quantized transform coefficient, quantization parameter, block size, block partition It may contain values or statistics such as information. The prediction mode may indicate an intra prediction mode or an inter prediction mode.

The residual signal may mean a difference between the original signal and the predicted signal. Alternatively, the residual signal may be a signal generated by transforming a difference between the original signal and the prediction signal. Alternatively, the residual signal may be a signal generated by transforming and quantizing the difference between the original signal and the predicted signal. A residual block may be a residual signal in units of blocks.

When entropy encoding is applied, a small number of bits may be allocated to a symbol having a high probability of occurrence, and a large number of bits may be allocated to a symbol having a low probability of occurrence. As symbols are represented through such allocation, the size of bitstrings for symbols that are encoding targets can be reduced. Therefore, compression performance of image encoding can be improved through entropy encoding.

In addition, encoding methods such as exponential golomb, context-adaptive variable length coding (CAVLC), and context-adaptive binary arithmetic coding (CABAC) may be used for entropy encoding. . For example, the entropy encoding unit 150 may perform entropy encoding using a variable length coding/code (VLC) table. For example, the entropy encoding unit 150 may derive a binarization method for a target symbol. Also, the entropy encoder 150 may derive a probability model of the target symbol/bin. The entropy encoding unit 150 may perform entropy encoding using the derived binarization method or a probability model.

Since encoding is performed through inter prediction by the encoding apparatus 100, the encoded current image may be used as a reference image for other image(s) to be processed later. Accordingly, the encoding apparatus 100 may decode the encoded current image again and store the decoded image as a reference image. Inverse quantization and inverse transformation of the current image encoded for decoding may be processed.

The quantized coefficient may be inversely quantized in the inverse quantization unit 160. It may be inversely transformed in the inverse transformation unit 170. The inverse quantized and inverse transformed coefficients may be combined with the prediction block through the adder 175. A reconstructed block may be generated by summing the inverse quantized and inverse transformed coefficients and the prediction block.

The reconstruction block may pass through the filter unit 180 . The filter unit 180 may apply at least one of a deblocking filter, a Sample Adaptive Offset (SAO), and an Adaptive Loop Filter (ALF) to a reconstructed block or a reconstructed picture. The filter unit 180 may also be referred to as an adaptive in-loop filter.

The deblocking filter may remove block distortion generated at a boundary between blocks. SAO may add an appropriate offset value to a pixel value to compensate for a coding error. ALF may perform filtering based on a value obtained by comparing the restored image and the original image. A reconstructed block that has passed through the filter unit 180 may be stored in the reference picture buffer 190 .

2 is a block diagram showing a configuration according to an embodiment of a decoding device to which the present invention is applied.

The decoding device 200 may be a video decoding device or an image decoding device.

Referring to FIG. 2 , the decoding apparatus 200 includes an entropy decoding unit 210, an inverse quantization unit 220, an inverse transform unit 230, an intra prediction unit 240, an inter prediction unit 250, and an adder 255. , a filter unit 260 and a reference picture buffer 270.

The decoding device 200 may receive the bitstream output from the encoding device 100. The decoding apparatus 200 may perform intra mode and/or inter mode decoding on a bitstream. Also, the decoding apparatus 200 may generate a restored image through decoding and output the generated restored image.

For example, conversion to an intra mode or an inter mode according to a prediction mode used for decoding may be performed by a switch. When the prediction mode used for decoding is the intra mode, the switch may be switched to the intra mode. When the prediction mode used for decoding is the inter mode, the switch may be switched to inter mode.

The decoding apparatus 200 may obtain a reconstructed residual block from the input bitstream and generate a prediction block. When the reconstructed residual block and the prediction block are obtained, the decoding apparatus 200 may generate a reconstructed block by adding the reconstructed residual block and the prediction block.

The entropy decoding unit 210 may generate symbols by performing entropy decoding on a bitstream based on a probability distribution. The generated symbols may include symbols in the form of quantized coefficients. Here, the entropy decoding method may be similar to the above-described entropy encoding method. For example, the entropy decoding method may be a reverse process of the above-described entropy encoding method.

The quantized coefficient may be inversely quantized in the inverse quantization unit 220 . In addition, the inverse quantized coefficient may be inversely transformed in the inverse transform unit 230 . As a result of inverse quantization and inverse transformation of the quantized coefficients, a reconstructed residual block may be generated. At this time, the inverse quantization unit 220 may apply a quantization matrix to the quantized coefficients.

When the intra mode is used, the intra predictor 240 may generate a prediction block by performing spatial prediction using pixel values of previously encoded blocks adjacent to the current block.

The inter prediction unit 250 may include a motion compensation unit. When the inter mode is used, the motion compensation unit may generate a prediction block by performing motion compensation using a motion vector and a reference image. A reference image may be stored in the reference picture buffer 270 .

The reconstructed residual block and the predicted block may be added through an adder 255. The adder 255 may generate a reconstructed block by adding the reconstructed residual block and the prediction block.

The reconstruction block may pass through the filter unit 260 . The filter unit 260 may apply at least one of a deblocking filter, SAO, and ALF to a reconstructed block or a reconstructed picture. The filter unit 260 may output a reconstructed image. The reconstructed image may be stored in the reference picture buffer 270 and used for inter prediction.

3 is a diagram schematically illustrating a division structure of an image when encoding and decoding an image.

In order to efficiently segment an image, a coding unit (CU) may be used in encoding and decoding. A unit may be a term that collectively refers to 1) a block including video samples and 2) a syntax element. For example, “division of a unit” may mean “division of a block corresponding to a unit”.

Referring to FIG. 3 , an image 300 may be sequentially divided into units of a largest coding unit (LCU), and a division structure of the image 300 may be determined according to the LCU. Here, LCU may be used as the same meaning as Coding Tree Unit (CTU).

The division structure may refer to a distribution of Coding Units (CUs) in the LCU 310 to efficiently encode an image. This distribution may be determined according to whether one CU is divided into 4 CUs. The horizontal size and vertical size of the CU generated by division may be half of the horizontal size and half of the vertical size of the CU before division, respectively. The divided CU may be recursively divided into four CUs whose horizontal and vertical sizes are reduced by half in the same way.

In this case, the division of the CU may be recursively performed up to a predefined depth. Depth information may be information indicating the size of a CU. Depth information may be stored for each CU. For example, the depth of the LCU may be 0, and the depth of the smallest coding unit (SCU) may be a predefined maximum depth. Here, the LCU may be a CU having the largest coding unit size as described above, and the SCU may be a CU having the smallest coding unit size.

The division may start from the LCU 310, and the depth of the CU may increase by 1 whenever the horizontal and vertical sizes of the CU are reduced by half by division. For each depth, a CU that is not split may have a size of 2Nx2N. In addition, in the case of a CU to be divided, a CU of 2Nx2N size may be divided into 4 CUs having a size of NxN. The size of N can be halved every time the depth increases by 1.

Referring to FIG. 3 , an LCU having a depth of 0 may be 64×64 pixels. 0 may be the minimum depth. A SCU with a depth of 3 may be 8x8 pixels. 3 may be the maximum depth. In this case, a CU of 64x64 pixels, which is an LCU, may be expressed as a depth of 0. A CU of 32x32 pixels can be represented with a depth of 1. A CU of 16x16 pixels can be represented with a depth of 2. A CU of 8x8 pixels, which is an SCU, can be represented with a depth of 3.

Also, information on whether the CU is split may be expressed through split information of the CU. The division information may be 1 bit of information. All CUs except for the SCU may include partition information. For example, when the CU is not split, the value of the split information of the CU may be 0, and when the CU is split, the value of the split information of the CU may be 1.

4A to 4H are diagrams illustrating a form of a prediction unit (PU) that may be included in a coding unit (CU).

Among the CUs divided from the LCU, a CU that is not further divided may be divided into one or more prediction units (PUs). This division may also be referred to as a partition.

A PU may be a basic unit for prediction. A PU may be coded and decoded in any one of skip mode, inter mode, and intra mode. A PU may be divided into various types according to each mode.

As shown in FIG. 4A , in skip mode, there may not be a split within a CU. In the skip mode, a 2Nx2N mode 410 in which sizes of PU and CU are the same may be supported without division.

In inter mode, 8 divided types can be supported within the CU. For example, in inter mode, 2Nx2N mode 410, 2NxN mode 415, Nx2N mode 420, NxN mode 425, 2NxnU mode 430, 2NxnD mode 435, nLx2N mode 440 and nRx2N Mode 445 may be supported.

In intra mode, 2Nx2N mode 410 and NxN mode 425 may be supported.

5 is a diagram illustrating a form of a transform unit (TU) that may be included in a coding unit (CU).

A transform unit (TU) may be a basic unit used for transform, quantization, inverse transform, and inverse quantization processes within a CU. A TU may have a square shape or a rectangular shape.

Among the CUs split from the LCU, a CU that is no longer split into CUs may be split into one or more TUs. In this case, the division structure of the TU may be a quadtree structure. For example, as shown in FIG. 5 , one CU 510 may be divided one or more times according to a quadtree structure. Through division, one CU 510 may be composed of TUs of various sizes.

6 is a diagram for explaining an embodiment of an intra prediction process.

The number of intra prediction modes may be fixed to 35 regardless of the size of a prediction unit.

The prediction mode may include 2 non-directional modes and 33 directional modes as shown in FIG. 6 . The two non-directional modes may include DC mode and Planar mode.

The number of prediction modes may be different according to the type of color component. For example, the number of prediction modes may be different depending on whether the color component is a luma signal or a chroma signal.

A PU may have a square shape, with a size of NxN or a size of 2Nx2N. The size of NxN may include 4x4, 8x8, 16x16, 32x32, and 64x64. A unit of PU may be the size of at least one of CU, PU, and TU.

Intra encoding and/or decoding may be performed using sample values or encoding parameters included in neighboring reconstructed units.

7 is a diagram for explaining an embodiment of an inter prediction process.

The rectangle shown in FIG. 7 may represent an image (or picture). Also, arrows in FIG. 7 may indicate prediction directions. That is, an image may be encoded and/or decoded according to a prediction direction.

Each image (or picture) may be classified into an I picture (Intra Picture), a P picture (Uniprediction Picture), and a B picture (Biprediction Picture) according to an encoding type. Each picture may be coded according to the coding type of each picture.

When an image to be encoded is an I picture, the image itself may be encoded without inter prediction. When an image to be coded is a P picture, the image may be coded through inter prediction using a reference picture only in the forward direction. When an image to be encoded is a B picture, it can be coded through inter prediction using reference pictures in both forward and backward directions, and can be coded through inter prediction using reference pictures in one of the forward and backward directions.

A P picture and a B picture to be encoded and/or decoded using a reference picture may be regarded as an image using inter prediction.

Below, inter prediction in inter mode according to an embodiment is described in detail.

In the inter mode, the encoding apparatus 100 and the decoding apparatus 200 may perform prediction and/or motion compensation on the encoding target unit and the decoding target unit. For example, the encoding apparatus 100 or the decoding apparatus 200 may perform prediction and/or motion compensation by using reconstructed motion information of neighboring units as motion information of the encoding target unit or decoding target unit. Here, the encoding target unit or the decoding target unit may mean a prediction unit and/or a prediction unit partition.

Inter prediction may be performed using a reference picture and motion information. Also, inter prediction may use the aforementioned skip mode.

A reference picture may be at least one of a picture before the current picture or a picture after the current picture. In this case, inter prediction may perform prediction on a block of the current picture based on the reference picture. Here, the reference picture may mean an image used for prediction of a block.

In this case, the region within the reference picture may be specified by using a reference picture index (refIdx) indicating the reference picture and a motion vector to be described later.

Inter prediction may select a reference picture and a reference block corresponding to a current block within the reference picture, and generate a prediction block for the current block using the selected reference block. The current block may be a block currently being encoded or decoded among blocks of the current picture.

Motion information may be derived during inter prediction by each of the encoding apparatus 100 and the decoding apparatus 200 . Also, the derived motion information may be used to perform inter prediction.

At this time, the encoding apparatus 100 and the decoding apparatus 200 use the motion information of the reconstructed neighboring block and/or the motion information of the collocated block (col block) to achieve encoding efficiency and/or decoding efficiency. can improve A collocated block may be a block corresponding to a current block in a previously reconstructed collocated picture (col picture).

The reconstructed neighboring block may be a block in the current picture and may be a block already reconstructed through encoding and/or decoding. The reconstruction block may be a neighboring block adjacent to the current block and/or a block located at an outer corner of the current block. Here, the block located at the outer corner of the current block may be a block vertically adjacent to a neighboring block horizontally adjacent to the current block or a block horizontally adjacent to a neighboring block vertically adjacent to the current block.

For example, a restored peripheral unit may be a unit located at the left side of the target unit, a unit located at the top of the target unit, a unit located at the lower left corner of the target unit, a unit located at the upper right corner of the target unit, or a unit located at the upper left corner of the target unit. It may be a unit located in a corner.

Each of the encoding apparatus 100 and the decoding apparatus 200 may determine a block spatially located at a position corresponding to the current block in the collocated picture, and may determine a predefined relative position with respect to the determined block. The predefined relative position may be a position inside and/or outside a block spatially existing at a position corresponding to the current block. Also, each of the encoding apparatus 100 and the decoding apparatus 200 may derive a collocated block based on the determined relative position. Here, the collocated picture may be one picture among at least one reference picture included in the reference picture list.

A block in the reference picture may exist at a position spatially corresponding to the position of the current block in the reconstructed reference picture. In other words, the position of the current block in the current picture and the position of the block in the reference picture may correspond to each other. Hereinafter, motion information of a block included in a reference picture may be referred to as temporal motion information.

A method of deriving motion information may change according to a prediction mode of a current block. For example, as a prediction mode applied for inter prediction, there may be an Advanced Motion Vector Predictor (AMVP) and merge.

For example, when AMVP is applied as a prediction mode, each of the encoding apparatus 100 and the decoding apparatus 200 uses a motion vector of a reconstructed neighboring block and/or a motion vector of a collocated block to predict motion vector candidates. You can create a list. A motion vector of a reconstructed neighboring block and/or a motion vector of a collocated block may be used as a predicted motion vector candidate.

A bitstream generated by the encoding apparatus 100 may include a predictive motion vector index. The predicted motion vector index may indicate an optimal predicted motion vector selected from motion vector predicted candidates included in the predicted motion vector candidate list. The predictive motion vector index may be transmitted from the encoding apparatus 100 to the decoding apparatus 200 through a bitstream.

The decoding apparatus 200 may use the predictive motion vector index to select a predictive motion vector of the current block from among the predictive motion vector candidates included in the predictive motion vector candidate list.

The encoding apparatus 100 may calculate a motion vector difference (MVD) between the motion vector of the current block and the predicted motion vector, and may encode the MVD. A bitstream may include an encoded MVD. The MVD may be transmitted from the encoding device 100 to the decoding device 200 through a bitstream. At this time, the decoding apparatus 200 may decode the received MVD. The decoding apparatus 200 may derive a motion vector of the current block through the sum of the decoded MVD and the predicted motion vector.

A bitstream may include a reference picture index indicating a reference picture. The reference picture index may be transmitted from the encoding apparatus 100 to the decoding apparatus 200 through a bitstream. The decoding apparatus 200 may predict a motion vector of the current block using motion information of neighboring blocks, and may derive a motion vector of the current block using the predicted motion vector and the motion vector difference. The decoding apparatus 200 may generate a prediction block for the current block based on the derived motion vector and reference picture index information.

Since motion information of neighboring units reconstructed for the encoding target unit and the decoding target unit can be used, the encoding apparatus 100 may not separately encode motion information for the target unit in a specific inter prediction mode. If the motion information of the target unit is not encoded, the amount of bits transmitted to the decoding apparatus 200 may be reduced and encoding efficiency may be improved. For example, as an inter prediction mode in which motion information of the target unit is not coded, there may be a skip mode and/or a merge mode. In this case, the encoding apparatus 100 and the decoding apparatus 200 may use an identifier and/or an index indicating which of the reconstructed neighboring units' motion information is used as the motion information of the target unit.

Another example of a motion information derivation method is merge. Merge may refer to merging of motions of a plurality of blocks. Merge may mean applying motion information of one block to another block as well. When merge is applied, each of the encoding device 100 and the decoding device 200 may generate a merge candidate list using motion information of a reconstructed neighboring block and/or motion information of a collocated block. have. The motion information may include at least one of 1) a motion vector, 2) an index for a reference picture, and 3) a prediction direction. The prediction direction can be unidirectional or bidirectional.

In this case, merge may be applied in units of CUs or units of PUs. When merging is performed in units of CUs or PUs, the encoding apparatus 100 may transmit predefined information to the decoding apparatus 200 through a bitstream. A bitstream may include predefined information. The predefined information may include 1) information indicating whether merging is to be performed for each block partition, and 2) information about which block to perform merging with among neighboring blocks adjacent to the current block. For example, neighboring blocks of the current block may include a left neighboring block of the current block, an upper neighboring block of the current block, and a temporal neighboring block of the current block.

The merge candidate list may indicate a list in which motion information is stored. Also, the merge candidate list may be generated before merging is performed. Motion information stored in the merge candidate list may be 1) motion information of neighboring blocks adjacent to the current block or 2) motion information of a collocated block corresponding to the current block in the reference image. Also, the motion information stored in the merge candidate list may be new motion information generated by a combination of motion information already existing in the merge candidate list.

The skip mode may be a mode in which information of neighboring blocks is applied to the current block as it is. A skip mode may be one of modes used for inter prediction. When the skip mode is used, the encoding apparatus 100 may transmit only information on which block's motion information is to be used as the current block's motion information to the decoding apparatus 200 through a bitstream. The encoding device 100 may not transmit other information to the decoding device 200. For example, the other information may be syntax information. Syntax information may include motion vector difference information.

8 is a flowchart of an inter prediction method according to an embodiment.

Hereinafter, a method of performing inter prediction on a target unit in an image encoding process will be described as an example. For example, the target unit may be a CU.

In step 810, the inter predictor 110 may determine the type of the target unit based on the image complexity of the target unit.

Here, the type of target unit may include a static region and a dynamic region, and the target unit may be classified into one of a static region and a dynamic region.

Image complexity may be determined based on comparison between the target unit and the corresponding unit. In other words, a result of a predefined operation on a value representing a target unit and a value representing a corresponding unit may be used as the image complexity. Here, the value representing the target unit may be the LCU of the target unit, and the value representing the corresponding unit may be the LCU of the corresponding unit.

The image complexity may be determined based on a sum of absolute difference (SAD) between the LCU of the target unit and the LCU of the corresponding unit. For example, the image complexity may be the SAD of the LCU of the target unit and the LCU of the corresponding unit, and may be a value generated based on the SAD of the LCU of the target unit and the LCU of the corresponding unit.

Alternatively, the image complexity may be determined based on a sum of squared error (SSE) of the LCU of the target unit and the LCU of the corresponding unit. For example, the image complexity may be the SSE of the LCU of the target unit and the LCU of the corresponding unit, and may be a value generated based on the SSE of the LCU of the target unit and the LCU of the corresponding unit.

The corresponding unit may be a unit corresponding to the target unit. For example, the corresponding unit may be a call unit corresponding to a target unit in a reference picture. A position of the target unit in the current picture and a position of the corresponding unit in the reference picture may correspond to each other.

The inter predictor 110 may determine the type of the target unit based on a comparison between the image complexity of the target unit and a predefined threshold value Th. The predefined threshold value Th may be a value optimally determined for determining the type of target unit. For example, the inter predictor 110 may determine the type of the target unit as a dynamic unit when the image complexity or SAD of the target unit is greater than or equal to a predefined threshold value Th. The inter predictor 110 may determine the type of the target unit as a static unit when the image complexity or SAD of the target unit is less than a predefined threshold value Th.

The inter predictor 110 may set the value of the flag “type flag” according to a result of comparison between the image complexity of the target unit and the predefined threshold value Th.

The inter prediction unit 110 sets the "type flag" to "true", "logic 1" or a predefined first value if the image complexity or SAD of the target unit is greater than or equal to a predefined threshold value (Th). can be set The inter predictor 110 sets the "type flag" to "false", "logic 0", or "logic 0" if the image complexity or SAD of the target unit is less than a predefined threshold value Th. It may be set to a predefined second value. For example, the flag "type flag" may indicate the type of the target unit. If the value of “type flag” is a predefined first value, the target unit may be a dynamic unit. If the value of “type flag” is a predefined second value, the target unit may be a static unit.

When the slice type of the slice of the target unit is Bslice, the inter prediction unit 110 may use two reference pictures in determining the type of the target unit. When the slice type of the slice of the target unit is non-slice, the inter predictor 110 may calculate the LCU of the target unit and the first SAD of the LCU of the first corresponding unit of the reference picture 0, and calculate the LCU and reference of the target unit. The second SAD of the LCU of the second corresponding unit of Picture 1 may be calculated. The inter predictor 110 may use the average of the first SAD and the second SAD as the SAD for the target unit.

The type of target unit may be classified into an initial type and a final type. The initial type may be the type of the target unit indicated by the “type flag”. The final type may be a type determined based on a weighted sum of the “type flag” of the target unit and the “type flag” of adjacent units. The adjacent unit may be a unit adjacent to the target unit that has already been encoded or decoded prior to processing on the target unit. Adjacent units may be plural. For example, the plurality of adjacent units may include at least one of a unit that is upper left adjacent to the target unit, a unit that is uppermost adjacent to the target unit, a unit that is upper right adjacent to the target unit, and a unit that is left adjacent to the target unit. .

The inter predictor 110 may determine the final type of the target unit based on image complexities of the target unit and neighboring units. For example, if the weighted sum of the "type flag" of the target unit and the "type flag" of the adjacent unit is greater than or equal to a predefined third value, the inter predictor 110 dynamically determines the final type of the target unit. unit can be determined. For example, the inter prediction unit 110 statically determines the final type of the target unit when the weighted sum of the "type flag" of the target unit and the "type flag" of the adjacent unit is smaller than a predefined fourth value. unit can be determined.

In step 820, the inter prediction unit 110 may perform inter prediction on the target unit according to the determined type.

When the type of the target unit is a dynamic unit, the inter prediction unit 110 may perform prediction on the target unit using conventional inter prediction. Here, the conventional inter prediction may be the inter prediction described above with reference to FIGS. 1 to 7 .

When the type of the target unit is a static unit, the inter predictor 110 may perform prediction on the target unit using simplified inter prediction.

The inter prediction unit 110 may perform prediction on a target unit using different inter predictions for a plurality of types.

Inter predictions that are different from each other are, for example, 1) different from each other in the number of quadtree splits for the target unit, 2) different from each other in the number of reference pictures, or 3) different from each other in the type of inter-prediction direction. can do.

For example, simplified inter prediction may be inter prediction that limits the number of quadtree splits for a target unit. Simplified inter prediction may be prediction in which encoding and/or decoding is performed with a prediction unit having a larger size by limiting the number of quad tree splits for the target unit. The inter predictor 110 may perform segmentation on the target unit by applying a smaller maximum depth to the static unit than to the dynamic unit.

Alternatively, simplified inter prediction may be prediction in which the number of reference pictures of inter prediction is limited. Simplified inter prediction may be prediction that proposes the number of reference pictures for a target unit. The inter prediction unit 110 may perform prediction on a target unit by using fewer reference pictures for a dynamic unit than for a static unit.

Alternatively, simplified inter prediction may be prediction in which the inter prediction direction of inter prediction is limited. Simplified inter prediction may be prediction in which an inter prediction direction for a target unit is restricted. The inter-prediction unit 110 may perform prediction on a target unit in a more limited inter-prediction direction for a static unit than for a dynamic unit.

The inter prediction unit 110 may perform prediction on a target unit using different search ranges for a plurality of types.

For example, simplified inter prediction may be prediction in which a search is performed in a reduced search area. The inter predictor 110 may perform prediction on a target unit in a search area smaller than that of a dynamic unit for a static unit.

The above-described steps 810 and 820 may be performed in combination with operations performed by other components of the encoding device 110 described above with reference to FIG. 1 .

The inter prediction by the aforementioned inter prediction unit 110 may also be performed by the inter prediction unit 250 of the decoding apparatus 200 . The aforementioned steps 810 and 820 may also be performed by the inter prediction unit 250 . In addition, the above-described steps 810 and 820 may be performed in combination with operations performed by other components of the decoding apparatus 200 described above with reference to FIG. 2 .

9 illustrates differential images of a current picture and a reference picture according to an example.

In FIG. 9, a current picture and two reference pictures are shown. The current picture may be a target picture that is currently being encoded or decoded. The current picture may be a picture including the current block.

In FIG. 9 , LCU _CUR may indicate a target unit. LCU _AL , LCU _A , LCU _AR , and LCU _L may represent reconstructed neighboring units of the target unit.

There may be two reference picture lists, L0 and L1, for the current picture. Among the two reference pictures, a first reference picture may be a picture selected in L0, and a second reference picture may be a picture selected in L1.

In FIG. 9 , LCU ^L0 _CUR may indicate a corresponding unit of a first reference picture. LCU ^L0 _AL , LCU ^L0 _A , LCU ^L0 _AR and, LCU ^L0 _L may indicate reconstructed neighboring units of the corresponding unit of the first reference picture. LCU ^L1 _CUR may indicate a corresponding unit of the second reference picture. LCU ^L1 _AL , LCU ^L1A _, LCU ^L1 _AR and, LCU ^L1 _L may indicate reconstructed neighboring units of the corresponding unit of the second reference picture.

In FIG. 9 , two difference images are shown. The left difference image may be a difference image between the reference picture of L0 and the current picture. The difference image on the left may indicate the SAD of the reference picture of L0 and the current picture. The difference image on the right side may be a difference image between the reference picture of L1 and the current picture. The difference image on the right may indicate SAD of the reference picture of L1 and the current picture.

As shown, a current picture may be composed of a plurality of CUs, and encoding or decoding may be performed for each CU according to a raster scan order.

In general, the CU of a difference image may have the following characteristics according to characteristics of an image.

1) When there is a moving object in the CU, mainly the object boundary and edge of the object due to the change in the phase of the object and the change in detailed motion within the object with time difference There may be (relatively larger) difference values in regions. In FIG. 9 , a portion marked with “A” may represent a difference value generated in the object boundary and edge regions of the moving object.

2) When the CU exists in a static region, most of the pixel values (or difference values) are values close to 0 because there is no change in the characteristics (eg, complexity) of the image according to the time difference. can have A portion marked “B” in FIG. 9 may represent an area other than the portion marked “A” and may represent a static area.

Based on the above-described general phenomena of images, a target unit may be classified into one of a static unit and a dynamic unit according to characteristics of images in the target unit.

For classification of the target unit, the inter prediction unit 110 may calculate an error value in units of pixels between the target unit of the current picture and the corresponding unit of the reference picture. A corresponding unit may be a collocated block in a reference picture.

The SAD described above with reference to FIG. 8 may be an example of an error value in units of pixels. For example, the error value may be other error values such as a sum of squared error (SSE) in addition to SAD. 8, SAD may be replaced with an example value or SSE.

The inter predictor 110 may calculate the SAD of the target block based on Equation 2 below.

Here, k may indicate a reference picture of L0 or a reference picture of L1. i may represent the x-coordinate of a pixel. j may represent the y-coordinate of a pixel. N may represent the size of the target unit.

Each CU of the current picture may have a 1-bit "type_flag". If the value of the SAD calculated for the CU is greater than or equal to a predefined SAD threshold value (Th _SAD ), the CU may be determined as a dynamic unit. In this case, the value of "type flag" may be set to "true", "logic 1" or a predefined first value. The SAD value calculated for the CU is a predefined SAD threshold value (Th _SAD ), the CU may be determined as a static unit. In this case, the value of "type flag" may be set to "false", "logic 0" or a predefined second value.

10 illustrates type flags of a target unit and reconstructed neighboring units according to an example.

In FIG. 10, TF _CUR may indicate a “type flag” of a target unit. TF _AL may indicate a “type flag” of an adjacent unit adjacent to the upper left of the target unit. TF _A may indicate a “type flag” of an adjacent unit uppermost adjacent to the target unit. TF _AR may indicate a “type flag” of a unit adjacent to the upper right of the target unit. TF _L may indicate a “type flag” of a unit adjacent to the left of the target unit.

In addition to the relatively simple method of determining the type of the target unit described above, the inter predictor 110 may provide a more reliable method of determining the type of the target unit by considering correlation between adjacent units and the target unit.

For example, in a general natural video, when it is assumed that there is no movement of a camera, a static area existing in the background tends to appear over a wide range. Accordingly, in determining the type of the target unit, the type of the target unit may have a high degree of correlation with the previously determined types of neighboring units.

In order to consider this correlation, the inter predictor 110 may calculate a weighted sum "flag_sum" of the "type_flag" of the target unit and the "type_flag" of adjacent units.

The inter prediction unit 110 may calculate the weighted sum of the target unit “flag_sum” based on Equation 3 below.

TF _i may indicate "type_flag" of unit i. i represents CUR representing the target unit, AL representing the above left adjacent unit, A representing the above adjacent unit, AR representing the above right adjacent unit, and representing the left adjacent unit. may be one of L. K may be the number of available adjacent units. w _i may be the weight of unit i.

The weights of the target unit and the neighboring unit may be different predefined values. For example, under the assumption that the correlation between the target unit and the left adjacent unit is the highest, the weight of TF _i may be determined as w _cur =0.5, w _L =0.2, and w _AL =w _A = w _AR =0.1. For example, a unit having a higher correlation with the target unit among neighboring units may have a higher weight.

The inter predictor 110 may determine the final type of the target unit using the weighted sum "flag_sum".

The inter predictor 110 may determine the final type of the target unit based on Equation 4 below.

"type_flag" may indicate the final type of the target unit. Th may be a predefined threshold value.

When the slice type of the slice of the target unit is Bslice, the inter prediction unit 110 may use the left reference picture and the right reference picture in determining the type of the target unit. The inter prediction unit 110 may calculate SAD1 between the LCU of the target unit and the LCU of the corresponding unit of the left reference picture, and calculate SAD2 of the LCU of the target unit and the LCU of the corresponding unit of the right reference picture. The inter predictor 110 may use SAD1 and the average of SAD1 as the SAD for the target unit. The inter predictor 110 may calculate SAD using a 1-bit right arithmetic shift operation as shown in Equation 5 below.

When the SAD is calculated, the inter predictor 110 may determine a TF that is a "type flae" of the target unit based on Equation 6 below.

As described above with reference to FIG. 3, when the conventional inter prediction technique is applied, each CU may be recursively divided to a predefined depth. In this case, the depth information may indicate the size of the CU and may be stored for each CU. For example, the depth of the LCU may be 0, and the depth of the SCU may be a predefined maximum depth. When the CU is a static unit, an image represented by the CU may have a mostly homogeneous area or a gradually changing characteristic. Therefore, CUs that are static units may tend to be encoded as large prediction units. When the conventional inter-prediction technique is used, there is a possibility that a CU is coded into a plurality of prediction blocks subdivided more than necessary.

When a CU is divided more than necessary, encoding efficiency may decrease because motion information must be transmitted for each lower prediction unit. In addition, complexity of the encoding apparatus 100 may increase because recursive division and prediction of the CU must be performed up to the defined maximum depth.

The inter predictor 110 may divide the target unit by applying different maximum depths to a plurality of types according to the type of the target unit. Here, the inter prediction unit 110 may set a maximum depth of a static unit smaller than a maximum depth of a dynamic unit among a plurality of types.

In other words, the inter-prediction unit 110 may reduce information of a predefined maximum depth for segmentation of the static unit so that the static unit is coded only as a prediction unit having a large size. The inter predictor 110 can improve encoding efficiency and reduce the complexity of the encoding apparatus 100 by encoding static units only with large prediction units.

For example, when the maximum depth for recursive segmentation is N, the maximum depth for static units may be NL. Here, N may be an integer of 1 or greater. L may be an integer greater than or equal to 0 and less than or equal to N1. Alternatively, L may have a value between 1 and N.

The inter predictor 110 may adaptively determine the value of L. For example, the inter predictor 110 may determine the value of L based on the value of flag_sum in Equation 3. Under the assumption that the values of all weights w _i are 1, the value of L can be calculated as N(Mflag_sum). In other words, when the value of flag_sum is 5, L=N holds, when the value of flag_sum is 4, L=N1 holds, and when the value of flag_sum is 3, L=N2, etc. may be determined. Here, M may be the number of units used to calculate flag_sum or the number of TF _i . For example, when the adjacent units are a top left adjacent unit, a top adjacent unit, a right adjacent unit, and a left unit, the value of M may be 5.

When the conventional inter-prediction technique is applied, the motion vector value range may be determined by a predefined search range (SR). Also, actual information transmitted from the encoding apparatus 100 to the decoding apparatus 200 may be a motion vector difference (MVD) between the determined MV and an MV of an adjacent block.

In the case of a static unit, since correlation with an adjacent block is high, an MV having a relatively small value tends to be determined. Therefore, by using a SR that is smaller than the defined SR for the static coding unit, the complexity of the encoding apparatus 100 for motion prediction can be reduced and the transmission amount of motion information can be reduced to increase coding efficiency.

For example, when the size of SR predefined for a normal unit or dynamic unit is N, the size of SR for a static unit may be NL. Here, N may be an integer of 2 or greater. N may be an integer greater than or equal to 1 and smaller than N.

The inter predictor 110 may adaptively determine the value of L. For example, the inter predictor 110 may determine the value of L based on the value of flag_sum in Equation 3. For example, the inter predictor 110 may set the value of L to increase as the value of flag_sum increases. Under the assumption that the values of all weights w _i are 1, the value of L can be calculated as N(Mflag_sum). In other words, when the value of flag_sum is 5, the value of L= may be 3*N/4. When the value of flag_sum is 4, the value of L may be N/2. When the value of flag_sum is 3 or less, the value of L may be N/4.

11 is a structural diagram of an electronic device implementing an encoding device and/or a decoding device according to an embodiment.

According to an embodiment, the inter prediction unit 110, the intra prediction unit 120, the switch 115, the subtractor 125, the transform unit 130, the quantization unit 140, and the entropy encoding of the encoding apparatus 100 At least some of the unit 150, the inverse quantization unit 160, the inverse transform unit 170, the adder 175, the filter unit 180, and the reference picture buffer 190 may be program modules, and may be external devices or systems. can communicate with Program modules may be included in the encoding device 100 in the form of an operating system, application program modules, and other program modules.

Also, according to an embodiment, the entropy decoding unit 210, the inverse quantization unit 220, the inverse transform unit 230, the intra prediction unit 240, the inter prediction unit 250, and the adder 255 of the decoding apparatus 200 ), the filter unit 260, and at least a part of the reference picture buffer 270 may be program modules, and may communicate with an external device or system. Program modules may be included in the decryption device 200 in the form of an operating system, application program modules, and other program modules.

Program modules may be physically stored on various known storage devices. In addition, at least some of these program modules may be stored in a remote storage device capable of communicating with the encoding device 100 or a remote storage device capable of communicating with the decoding device 200.

Program modules include routines, subroutines, programs, objects, components, and data that perform functions or operations according to an embodiment or implement abstract data types according to an embodiment. A data structure, etc. may be encompassed, but is not limited thereto.

The program modules may include instructions or codes executed by at least one processor of the encoding device 100 or at least one processor of the decoding device 200 .

The encoding device 100 and/or the decoding device 200 may be implemented as the electronic device 1100 shown in FIG. 10 . The electronic device 1100 may be a general-purpose computer system that operates as the encoding device 100 and/or the decoding device 200.

As shown in FIG. 10 , the electronic device 1100 includes at least one processing unit 1110, a memory 1130, and a user interface (UI) input device communicating with each other through a bus 1190. 1150 , a UI output device 1160 and a storage 1140 . In addition, the electronic device 1100 may further include a communication unit 1120 connected to the network 1199 . The processing unit 1110 may be a semiconductor device that executes processing instructions stored in a central processing unit (CPU), memory 1130 or storage 1140 . Memory 1130 and storage 1140 may be various forms of volatile or non-volatile storage media. For example, the memory may include at least one of a ROM (ROM) 1131 and a RAM (RAM) 1132 .

The encoding device 100 and/or the decoding device 200 may be implemented in a computer system including a recording medium readable by a computer.

The recording medium may store at least one module required for the electronic device 1100 to operate as the encoding device 100 and/or the decoding device 200. The memory 1130 may store at least one module and may be configured to be executed by at least one processing unit 1110 .

A function related to communication of data or information of the encoding device 100 and/or the decoding device 200 may be performed through the communication unit 1120 .

In the foregoing embodiments, the methods are described on the basis of a flow chart as a series of steps or units, but the present invention is not limited to the order of steps, and some steps may occur in a different order or concurrently with other steps as described above. can In addition, those skilled in the art will understand that the steps shown in the flow chart are not exclusive, that other steps may be included, or that one or more steps of the flow chart may be deleted without affecting the scope of the present invention. You will understand.

Embodiments according to the present invention described above may be implemented in the form of program instructions that can be executed through various computer components and recorded on a computer-readable recording medium. The computer readable recording medium may include program instructions, data files, data structures, etc. alone or in combination. Program instructions recorded on the computer-readable recording medium may be specially designed and configured for the present invention, or may be known and usable to those skilled in the art of computer software. Examples of computer-readable recording media include magnetic media such as hard disks, floppy disks and magnetic tapes, optical recording media such as CDROMs and DVDs, magnetooptical media such as floptical disks, and ROMs. Hardware devices specially configured to store and execute program instructions, such as RAM, flash memory, and the like. Examples of program instructions include high-level language codes that can be executed by a computer using an interpreter or the like as well as machine language codes such as those produced by a compiler. The hardware device may be configured to act as one or more software modules to perform processing according to the present invention and vice versa.

In the above, the present invention has been described by specific details such as specific components and limited embodiments and drawings, but these are provided to help a more general understanding of the present invention, and the present invention is not limited to the above embodiments. , Those skilled in the art to which the present invention pertains may seek various modifications and variations from these descriptions.

Therefore, the spirit of the present invention should not be limited to the above-described embodiments, and not only the claims described later, but also all modifications equivalent or equivalent to these claims belong to the scope of the spirit of the present invention. will do it

Claims (21)

determining a type of a target unit in inter prediction; and
performing inter prediction on the target unit according to the type;
including,
The inter prediction is performed based on a sum operation of absolute differences based on corresponding units corresponding to the target unit,
The type is designated in response to whether or not a result of the sum operation of the absolute difference is greater than or equal to a threshold value,
The type determines a search region for the target unit and affects segmentation of the target unit. delete delete delete delete determining a type of a target unit in inter prediction; and
performing inter prediction on the target unit according to the type;
including,
The decoding method of claim 1 , wherein the determination of the type is performed based on a sum operation of absolute differences based on a first corresponding unit in a first reference picture and a second corresponding unit in a second reference picture. delete delete delete delete delete delete delete A computer-readable recording medium storing a bitstream for decoding of a target unit,
The bitstream is
Encoded information about the target unit
including,
The decoding of the target unit is performed using the encoded information;
In the decoding, the type of the target unit is determined in inter prediction,
Inter prediction is performed on the target unit according to the type,
The inter prediction is performed based on a sum operation of absolute differences based on corresponding units corresponding to the target unit,
The type is designated in response to whether or not a result of the sum operation of the absolute difference is greater than or equal to a threshold value,
The type determines a search area for the target unit and affects segmentation for the target unit. delete delete delete delete A computer-readable recording medium storing a bitstream for decoding of a target unit,
The bitstream is
Encoded information about the target unit
including,
The decoding of the target unit is performed using the encoded information;
In the decoding, the type of the target unit is determined in inter prediction,
Inter prediction is performed on the target unit according to the type,
Wherein the determination of the type is performed based on a sum operation of absolute differences based on a first corresponding unit in a first reference picture and a second corresponding unit in a second reference picture. generating a bitstream including encoding information through encoding of an input image; and
outputting the bitstream
including,
In performing decoding using inter prediction on a target unit using the bitstream, the inter prediction is performed based on a sum operation of absolute differences based on a corresponding unit corresponding to the target unit, and the type is the The bit, which is specified corresponding to whether a result of a sum operation of absolute differences is greater than or equal to a threshold value, the type determines a search region for the target unit, and the type affects division for the target unit. An encoding method that creates a stream. generating a bitstream including encoding information through encoding of an input image; and
outputting the bitstream
including,
In performing decoding using inter prediction for a target unit using the bitstream, the determination of the type is an absolute difference based on a first corresponding unit in a first reference picture and a second corresponding unit in a second reference picture. An encoding method for generating the bitstream, which is performed based on a sum operation.

Images