KR20220082791A - Method and apparatus for derivation of motion prediction information - Google Patents

Abstract

Disclosed are a method and apparatus for deriving motion prediction information and performing encoding and/or decoding on a moving picture using the derived motion prediction information. The encoding apparatus and the decoding apparatus generate a list for inter prediction of a target block. In generating the list, whether or not motion information of a candidate block is added to the list is determined based on information about the target block and motion information. If the motion information passes the motion prediction boundary check, the motion information is added to the list. Through the motion prediction boundary check, motion information useful for prediction of the target block is selectively added to the list.

Description

Method and apparatus for deriving motion prediction information

The following embodiments relate to a video decoding method, a decoding apparatus, an encoding method, and an encoding apparatus. More specifically, motion prediction information is derived, and encoding and/or decoding of a video is performed using the derived motion prediction information. It relates to a method and apparatus for doing so.

With the continuous development of the information and communication industry, a broadcasting service having a high definition (HD) resolution has 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 picture quality, many organizations are spurring the development of next-generation imaging devices. User interest in High Definition TV (HDTV) and Full HD (FHD) TV, as well as Ultra High Definition (UHD) TV, which has a resolution four times higher than that of FHD TV has increased, and with this increase in interest, image encoding/decoding technology for an image having higher resolution and image quality is required.

An apparatus and method for encoding/decoding an image include an inter prediction technology, an intra prediction technology, an entropy encoding technology, etc. to perform encoding/decoding on a high-resolution and high-definition image. 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 later picture. The intra prediction technique may be a technique of predicting the value of a pixel included in the current picture by using information on the pixel in the current picture. The entropy encoding technique may be a technique of allocating a short code to a symbol having a high frequency of occurrence and a technique of assigning a long code to a symbol having a low frequency of occurrence.

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

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

In encoding pictures constituting a video, the picture may be divided into a plurality of parts, and the plurality of parts may be encoded. In this case, in order for the decoding apparatus to decode the divided picture, information related to the partition of the picture may be required.

In order to improve the encoding processing speed, pictures may be encoded in parallel through a parallel encoding method. Also, in order to improve decoding processing speed, pictures may be decoded in parallel through a parallel decoding method.

The parallel coding method includes a picture division coding method. As a picture division coding method, a slice-based picture division coding method and a tile-based picture coding method are provided.

The conventional picture division encoding method does not allow reference between fragments of a divided picture in encoding using intra prediction. On the other hand, the conventional picture division encoding method allows reference between fragments of a divided picture in encoding using inter prediction.

Therefore, when parallel encoding is to be performed in units of picture division using the conventional picture division coding method, synchronization must be performed for every picture. The parallel processing efficiency of the encoding apparatus when synchronization is required for every picture is inevitably lower than the parallel processing efficiency of the encoding apparatus when the synchronization is not required.

An embodiment may provide a method and apparatus for preventing inter-segment reference when encoding or decoding a picture divided into segments.

An embodiment may provide a method and apparatus for performing parallel encoding or parallel decoding on segments by preventing inter-segment reference.

An embodiment may provide a method and apparatus for performing encoding or decoding without referring to another segment when performing inter prediction on a target block in one segment.

An embodiment may provide a method and apparatus for generating a list of motion information so as not to refer to another segment when performing inter prediction on a target block in one segment.

An embodiment may provide a method and apparatus for allowing only a reference to a region corresponding to inter prediction when encoding using inter prediction is performed.

An embodiment may provide a method and an apparatus for not including motion information that causes a target block to make a reference outside the boundary of a region in the list.

In one aspect, a method for generating a list for inter prediction of a target block, the method comprising: determining whether motion information of a candidate block is added to the list; and adding the motion information to the list when it is determined that the motion information is to be added to the list, wherein whether the motion information is added to the list is based on information on the target block and the motion information A method for generating a list determined by

The information on the target block may be a location of the target block.

Whether the motion information is added to the list may be determined based on a motion vector of the motion information.

Whether the motion information is added to the list may be determined based on a position indicated by a motion vector of the motion information applied to the target block.

The position indicated by the motion vector may be a position within a reference picture referenced by the target block.

If the location is within the area, the motion information may be added to the list, and if the location is outside the area, the motion information may not be added to the list.

The region may be a region of a slice including the target block, a region of a tile including the target block, or a region of a motion-constrained tile set including the target block.

If the location does not exceed the boundary, the motion information may be added to the list. If the location is outside the boundary, the motion information may not be added to the list.

The boundary may include a boundary of a picture.

The boundary may include a boundary between slices, a boundary between tiles, or a boundary between motion-restricted tile sets.

The intra prediction mode of the target block may be a merge mode or a skip mode.

The list may be a merge list.

The intra prediction mode of the target block may be an advanced motion vector predictor (AMVP) mode.

The list may be a predictive motion vector candidate list.

The candidate block may include a plurality of spatial candidates and temporal candidates.

If the candidate block is available and the motion information of the candidate block does not overlap with other motion information existing in the list, the motion information of the candidate block may be added to the list.

Even if the candidate block is the first available candidate block, when the information on the target block and the motion information satisfy a specified condition, the motion information of the candidate block may not be added to the list.

In another aspect, in the apparatus for generating a list for inter prediction of a target block, a processing unit that determines whether to add the motion information to the list based on the information on the target block and the motion information of the candidate block ; and a storage unit configured to store the list.

In another aspect, there is provided a method for setting availability of a candidate block for inter prediction of a target block, the method comprising: determining whether the candidate block is available; and setting the availability of the candidate block according to a result of the determination, wherein the availability sets the availability of a candidate block determined based on information on the target block and motion information of an object including the candidate block method is provided.

The object may be a prediction unit (PU).

Whether the candidate block is available may be determined based on a motion vector of the motion information.

Whether the candidate block is available may be determined based on a position indicated by a motion vector of the motion information applied to the target block.

If the location is within the area, the candidate block may be set as available, and if the location is outside the area, the candidate block may be set as unavailable.

A method and apparatus for preventing inter-segment reference when encoding or decoding a picture divided into segments are provided.

A method and apparatus for performing parallel encoding or parallel decoding on segments by preventing inter-segment reference are provided.

A method and apparatus for performing encoding or decoding without referring to another segment when performing inter prediction on a target block in one segment are provided.

A method and apparatus for generating a list of motion information so as not to refer to another segment in performing inter prediction on a target block in one segment are provided.

A method and apparatus are provided that allow only a reference to a region corresponding to inter prediction when encoding using inter prediction is performed.

A method and apparatus are provided that do not include motion information that causes a target block to make a reference outside the boundary of a region in a list.

1 is a block diagram illustrating a configuration of an encoding apparatus to which the present invention is applied according to an embodiment.
2 is a block diagram illustrating a configuration of a decoding apparatus to which the present invention is applied according to an embodiment.
3 is a diagram schematically illustrating a structure of an image segmentation when an image is encoded and decoded.
4 is a diagram illustrating a form of a prediction unit (PU) that a coding unit (CU) may include.
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 describing a location of a reference sample used in an intra prediction process.
8 is a diagram for explaining an embodiment of an inter prediction process.
8 is a diagram for explaining an embodiment of an inter prediction process.
9 shows spatial candidates according to an example.
10 illustrates an order of adding motion information of spatial candidates to a merge list according to an example.
11 illustrates division of a picture using tiles according to an example.
12 illustrates division of a picture using a slice according to an example.
13 illustrates distributed encoding of a temporally-spatially partitioned picture according to an example.
14 illustrates processing of a motion-constrained tile set (MCTS) according to an example.
15 shows a PU adjacent to a boundary of a slice according to an example.
16 shows a merge list according to an example.
17 is a flowchart of an inter prediction method according to an embodiment.
18 is a flowchart of a method of generating a merge list for inter prediction of a target block according to an embodiment.
19 is a flowchart of a method of generating a prediction motion vector candidate list for inter prediction of a target block according to an embodiment.
20 is a flowchart of a method of determining availability of a candidate block for inter prediction of a target block according to an embodiment.
21 shows a merge list to which a motion prediction boundary check is applied according to an example.
22 is a structural diagram of an electronic device implementing an encoding device according to an embodiment.
23 is a structural diagram of an electronic device implementing a decoding device according to an embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS [0010] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS [0010] Reference is made to the accompanying drawings, which illustrate specific embodiments by way of example.

Like reference numerals in the drawings refer to the same or similar functions throughout the various aspects. The shapes and sizes of elements in the drawings may be exaggerated for clearer description.

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 in the above 2 It should be understood that other components may exist in the middle of the components. In addition, the description of "including" a specific configuration in the exemplary embodiments does not exclude components other than the above specific configuration, and the additional configuration is the implementation of the exemplary embodiments or the technical spirit of the exemplary embodiments. It means that it can be included in the scope.

Each component is listed as a respective component for convenience of description. For example, at least two components among the components may be combined into one component. Also, one component may be divided into a plurality of components. Integrated embodiments and separate embodiments of each of these components are also included in the scope of rights without departing from the essence.

Hereinafter, the embodiments will be described in detail with reference to the accompanying drawings in order to enable those of ordinary skill in the art to easily implement 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 thereof will be omitted.

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

Hereinafter, “video” and “motion picture” may be used as the same meaning, and may be used interchangeably.

Hereinafter, the target image may be an encoding target image to be encoded and/or a decoding target image to be decoded. Also, the target image may be an input image input to the encoding apparatus or an input image input to the decoding apparatus.

Hereinafter, the terms “image”, “picture”, “frame” and “screen” may be used interchangeably and may be used interchangeably.

Hereinafter, the target block may be an encoding target block to be encoded and/or a decoding target block to be decoded. Also, the target block may be a current block that is a target of current encoding and/or decoding. In other words, “target block” and “current block” may be used interchangeably and may be used interchangeably.

Hereinafter, "block" and "unit" may be used interchangeably and may be used interchangeably. Or “block” may indicate a specific unit.

Hereinafter, "region" and "segment" may be used interchangeably.

Hereinafter, a specific signal may be a signal representing a specific block. For example, the original signal may be a signal representing the target block. A prediction signal may be a signal indicating a prediction block. The residual signal may be a signal representing a residual block.

In embodiments, each of the specified information, data, flags and elements, attributes, etc. may have a value. A value "0" of information, data, flags and elements, attributes, etc. may represent logical false or a first predefined value. In other words, the value “0”, false, logical false and the first predefined value may be used interchangeably. A value “1” of information, data, flags and elements, attributes, etc. may represent logical true or a second predefined value. In other words, the value “1”, true, logical true and the second predefined value may be used interchangeably.

When a variable such as i or j is used to indicate a row, column, or index, the value of i may be an integer of 0 or more, or an integer of 1 or more. That is, in embodiments, a row, column, index, etc. may be counted from 0, and may be counted from 1.

In the following, terms used in the embodiments are described.

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

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

- The terms "pixel" and "sample" may be used interchangeably and may be used interchangeably.

- In image encoding and decoding, a unit may be an area generated by segmentation of one image. One image may be divided into a plurality of units. In encoding and decoding of an image, a predefined process for the unit may be performed according to the type of the unit. According to the function, the type of the unit may be classified into a macro unit, a coding unit (CU), a prediction unit (PU), a transform unit (TU), and the like. One unit may be further divided into sub-units having a smaller size compared to the unit.

- The unit division information may include information about the depth of the unit. The depth information may indicate the number and/or degree to which a unit is divided.

- 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 the 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 uppermost node may be referred to as a root node. Also, the highest node may have a minimum 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 generated as the original unit is split twice.

- A node having a depth of level n may represent a unit generated as the original unit is divided n times.

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

Transform Unit: A 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 a smaller size.

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

Reconstructed Neighbor Unit: The reconstructed neighboring unit may be a unit that has already been decoded and reconstructed near the target unit. The reconstructed neighboring unit may be a spatial (spatial) neighboring unit or a temporal (temporal) neighboring unit with respect to 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: The encoding apparatus uses a combination of a size of a coding unit, a prediction mode, a size of a prediction unit, motion information, and a size of a transform unit to provide high encoding efficiency. Distortion optimization can be used.

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

[Formula 1]

D may represent distortion. D may be the mean square error of the squares of difference values between the original transform coefficients and the reconstructed transform coefficients within the transform unit.

R may 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 prediction mode, motion information, and a coded block flag, but also bits generated by encoding a transform coefficient.

The encoding apparatus may perform processes such as inter prediction and/or intra prediction, transformation, quantization, entropy encoding, inverse quantization, and inverse transformation in order to accurately calculate D and R. These processes may greatly increase the complexity of the encoding apparatus.

Reference picture: The reference picture may be an image used for inter prediction or motion compensation. The reference picture may be a picture including the reference unit referenced by the target unit for inter prediction or motion compensation.

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

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

- MV may indicate an offset between the target picture and the reference picture.

Search range: The search range may be a two-dimensional area in which an MV is 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 illustrating a configuration of an encoding apparatus to which the present invention is applied according to an embodiment.

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

Referring to FIG. 1 , the 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 decoding. It may include a unit 150 , an inverse quantizer 160 , an inverse transform unit 170 , an adder 175 , a filter unit 180 , and a reference picture buffer 190 .

The encoding apparatus 100 may encode the target image using the intra mode and the inter mode.

Also, the encoding apparatus 100 may generate a bitstream including encoding information through encoding of the target image, and may output the generated bitstream.

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

The encoding apparatus 100 may generate a prediction block for the target block. Also, after the prediction block is generated, the encoding apparatus 100 may encode a residual between the target block and the prediction block.

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

The inter prediction unit 110 may include a motion prediction unit and a motion compensator.

When the prediction mode is the inter mode, the motion predictor may search for a region that best matches the target block from the reference image in the motion prediction process, and may derive a motion vector for the target block and the searched region. 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 compensator may generate a prediction block for the target block by performing motion compensation using a motion vector. Here, the motion vector may be a two-dimensional vector used for inter prediction. Also, the motion vector may indicate an offset between the target image and the reference image.

The subtractor 125 may generate a residual block that is a difference between the target block and the prediction block.

The transform unit 130 may generate a transform coefficient by performing a transform on the residual block, and may output the generated transform coefficient. 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 embodiments, a quantized transform coefficient level may also be referred to as a transform coefficient.

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

The entropy decoding 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 during the encoding process. . The entropy decoding unit 150 may output the generated bitstream.

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

The encoding parameter may be information required for encoding and/or decoding. The encoding parameter may include information encoded by the encoding apparatus 100 and transmitted from the encoding apparatus 100 to the decoding apparatus, and may include information that can be inferred during encoding or decoding. For example, as information transmitted to the decoding apparatus, there is a syntax element.

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

The residual signal may represent 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 predicted signal. Alternatively, the residual signal may be a signal generated by transforming and quantizing a difference between the original signal and the predicted signal.

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 a symbol is expressed through this allocation, the size of a bitstring for symbols to be encoded may be reduced. Accordingly, compression performance of image encoding may be improved through entropy encoding.

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

Since encoding through inter prediction is performed by the encoding apparatus 100 , the target 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 target image again and store the decoded image as a reference image in the reference picture buffer 190 . Inverse quantization and inverse transformation of the encoded target image for decoding may be processed.

The quantized coefficient may be inversely quantized by the inverse quantization unit 160 and may be inversely transformed by the inverse transform unit 170 . The inverse quantized and inverse transformed coefficients may be summed 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 reconstructed 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. have. The filter unit 180 may be referred to as an adaptive in-loop filter.

The deblocking filter may remove block distortion occurring at the boundary between blocks. The SAO may add an appropriate offset value to the pixel value to compensate for the coding error. The ALF may perform filtering based on a value obtained by comparing the reconstructed image and the original image. The reconstructed block passing through the filter unit 180 may be stored in the reference picture buffer 190 . The reconstructed block passing through the filter unit 180 may be a part of the reference picture. In other words, the reference picture may be a picture composed of reconstructed blocks that have passed through the filter unit 180 . The stored reference picture may be used for inter prediction later.

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

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

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 may be included.

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

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

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

When the intra mode is used, the intra prediction unit 240 may generate a prediction block by performing spatial prediction using pixel values of an already decoded block around the target block.

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

The reconstructed residual block and the prediction 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 reconstructed block may pass through the filter unit 260 . The filter unit 260 may apply at least one of the deblocking filter, SAO, and ALF to the reconstructed block or the reconstructed picture. The reconstructed block passing through the filter unit 260 may be stored in the reference picture buffer 270 . The reconstructed block passing through the filter unit 280 may be a part of the reference picture. The reconstructed block passing through the filter unit 280 may be a part of the reference picture. That is, the reference picture may be a picture composed of blocks reconstructed through the filter unit 280 . The stored reference picture may be used for inter prediction later.

3 is a diagram schematically illustrating a structure of an image segmentation when an image is encoded and decoded.

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 image 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 in units of a Largest Coding Unit (LCU), and the division structure of the image 300 may be determined according to the LCU. Here, LCU may be used in the same meaning as a Coding Tree Unit (CTU).

The division structure may mean a distribution of coding units (CUs) for efficiently encoding an image in the LCU 310 . This distribution may be determined according to whether one CU is divided into four 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 size and vertical size are reduced by half in the same manner.

In this case, the division of the CU may be performed recursively to a predefined depth. The 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 a 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 whenever the horizontal size and the vertical size of the CU are halved by the division, the depth of the CU may increase by one. For each depth, an undivided CU may have a size of 2Nx2N. In addition, in the case of a divided CU, a CU having a size of 2Nx2N may be divided into four CUs having a size of NxN. The size of N can be halved for each increase in depth by 1.

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

Also, information on whether a CU is split may be expressed through split information of the CU. The division information may be 1-bit 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.

4 is a diagram illustrating a form of a prediction unit (PU) that a coding unit (CU) may include.

A CU that is no longer split among CUs split from an LCU may be split into one or more prediction units (PUs).

A PU may be a basic unit for prediction. The PU may be encoded and decoded in any one of a skip mode, an inter mode, and an intra mode. The PU may be divided into various forms according to each mode. For example, the target block described above with reference to FIG. 1 and the target block described above with reference to FIG. 2 may be a PU.

In skip mode, there may not be a split in a CU. In the skip mode, the 2Nx2N mode 410 in which PU and CU sizes are the same without division may be supported.

In the inter mode, 8 types of divided types within a CU may be supported. For example, in the 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 Mode 445 may be supported.

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

In the 2Nx2N mode 410, a PU having a size of 2Nx2N may be encoded. A PU having a size of 2Nx2N may mean a PU having the same size as that of a CU. For example, a PU having a size of 2Nx2N may have a size of 64x64, 32x32, 16x16, or 8x8.

In the NxN mode 425 , a PU having a size of NxN may be encoded.

For example, in intra prediction, when the size of a PU is 8x8, four divided PUs may be coded. The size of the divided PU may be 4x4.

When a PU is encoded by an intra mode, the PU may be encoded using one intra prediction mode among a plurality of intra prediction modes. For example, a High Efficiency Video Coding (HEVC) technique may provide 35 intra prediction modes, and a PU may be encoded in one intra prediction mode among 35 intra prediction modes.

Which mode of the 2Nx2N mode 410 and the NxN mode 425 the PU is coded by may be determined by rate-distortion cost.

The encoding apparatus 100 may perform an encoding operation on a PU having a size of 2Nx2N. Here, the encoding operation may be encoding the PU using each of a plurality of intra prediction modes that the encoding apparatus 100 can use. An optimal intra prediction mode for a PU having a size of 2Nx2N may be derived through an encoding operation. The optimal intra prediction mode may be an intra prediction mode that generates a minimum rate-distortion cost for encoding a PU having a size of 2Nx2N among a plurality of intra prediction modes that can be used by the encoding apparatus 100 .

Also, the encoding apparatus 100 may sequentially perform an encoding operation on each PU of the PUs divided into NxN. Here, the encoding operation may be encoding the PU using each of a plurality of intra prediction modes that the encoding apparatus 100 can use. An optimal intra prediction mode for an NxN-sized PU may be derived through an encoding operation. The optimal intra-prediction mode may be an intra-prediction mode that generates a minimum rate-distortion cost for encoding an NxN-sized PU among a plurality of intra prediction modes that can be used by the encoding apparatus 100 .

The encoding apparatus 100 may determine which of the 2Nx2N PU and the NxN PUs to be encoded based on a comparison of the rate-distortion cost of the 2Nx2N PU and the rate-distortion costs of the NxN PUs.

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, inverse quantization, entropy encoding, and entropy decoding processes within a CU. A TU may have a square shape or a rectangular shape.

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

In the encoding apparatus 100, a 64x64 coding tree unit (CTU) may be divided into a plurality of smaller CUs by a recursive quad-tree structure. One CU may be divided into 4 CUs having the same sizes. CUs may be recursively partitioned, and each CU may have a quad tree structure.

A CU may have depth. When a CU is split, CUs generated by splitting may have a depth increased by 1 from the depth of the split CU.

For example, the depth of the CU may have a value of 0 to 3. The size of the CU may range from 64x64 to 8x8 according to the depth of the CU.

Through recursive segmentation for CUs, an optimal segmentation method that produces the minimum rate-distortion ratio can be selected.

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

Arrows outward from the center of the graph of FIG. 6 may indicate prediction directions of intra prediction modes. Also, a number indicated adjacent to the arrow may indicate an example of an intra prediction mode or a mode value assigned to a prediction direction of the intra prediction mode.

Intra encoding and/or decoding may be performed using reference samples of units adjacent to the target block. The neighboring blocks may be neighboring reconstructed blocks. For example, intra encoding and/or decoding may be performed using a value of a reference sample included in a neighboring reconstructed block or an encoding parameter.

The encoding apparatus 100 and/or the decoding apparatus 200 may generate a prediction block by performing intra prediction on the target block based on information on samples in the target image. When performing intra prediction, the encoding apparatus 100 and/or the decoding apparatus 200 may generate a prediction block for the target block by performing intra prediction based on information on samples in the target image. When performing intra prediction, the encoding apparatus 100 and/or the decoding apparatus 200 may perform directional prediction and/or non-directional prediction based on at least one reconstructed reference sample.

The prediction block may mean a block generated as a result of performing intra prediction. The prediction block may correspond to at least one of a CU, a PU, and a TU.

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

Alternatively, the prediction block may be a square-shaped block having a size such as 2x2, 4x4, 16x16, 32x32 or 64x64, or a rectangular block having a size such as 2x8, 4x8, 2x16, 4x16 and 8x16.

Intra prediction may be performed according to an intra prediction mode for the target block. The number of intra prediction modes that the target block may have may be a predefined fixed value, or may be a value determined differently according to the properties of the prediction block. For example, the properties of the prediction block may include the size of the prediction block and the type of the prediction block.

For example, the number of intra prediction modes may be fixed to 35 regardless of the size of the prediction block. Or, for example, the number of intra prediction modes may be 3, 5, 9, 17, 34, 35, or 36.

The intra prediction mode may include two non-directional modes and 33 directional modes as shown in FIG. 6 . The two non-directional modes may include a DC mode and a planar mode.

For example, in the case of a vertical mode having a mode value of 26, prediction may be performed in a vertical direction based on a pixel value of a reference sample. For example, in the case of a horizontal mode having a mode value of 10, prediction may be performed in a horizontal direction based on a pixel value of a reference sample.

Even in a directional mode other than the above-described mode, the encoding apparatus 100 and the decoding apparatus 200 may perform intra prediction on a target unit by using a reference sample according to an angle corresponding to the directional mode.

The intra prediction mode located to the right of the vertical mode may be referred to as a vertical-right mode. The intra prediction mode located at the bottom of the horizontal mode may be called a horizontal-below mode. For example, in FIG. 6 , intra prediction modes whose mode value is one of 27, 28, 29, 30, 31, 32, 33, and 34 may be vertical right modes 613 . Intra prediction modes in which the mode value is one of 2, 3, 4, 5, 6, 7, 8, and 9 may be horizontal bottom modes 616 .

The non-directional mode may include a DC mode and a planar mode. For example, the mode value of the DC mode may be 1. The mode value of the planner mode may be 0.

The directional mode may include an angular mode. Modes other than the DC mode and the planar mode among the plurality of intra prediction modes may be a directional mode.

In the DC mode, a prediction block may be generated based on an average of pixel values of a plurality of reference samples. For example, a value of a pixel of the prediction block may be determined based on an average of pixel values of a plurality of reference samples.

The number of intra prediction modes and the mode value of each intra prediction mode described above may be merely exemplary. The number of the above-described intra prediction modes and a mode value of each intra prediction mode may be defined differently according to an embodiment, implementation, and/or need.

The number of intra prediction modes may be different depending on 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.

7 is a diagram for describing a location of a reference sample used in an intra prediction process.

7 illustrates a position of a reference sample used for intra prediction of a target block. Referring to FIG. 7 , in a reconstructed reference pixel used for intra prediction of a target block, for example, reference samples include lower-left reference samples 731 and left reference samples 733 . , an above-left corner reference sample 735 , above reference samples 737 , and above-right reference samples 739 , and the like.

For example, the left reference samples 733 may mean a reconstructed reference pixel adjacent to the left side of the object block. The upper reference samples 737 may refer to reconstructed reference pixels adjacent to the upper end of the target block. The upper left corner reference pixel 735 may mean a reconstructed reference pixel located in the upper left corner of the target block. Also, the lower left reference samples 731 may refer to reference samples located at the lower end of the left sample line among samples located on the same line as the left sample line composed of the left reference samples 733 . The upper right reference samples 739 may refer to reference samples located to the right of the upper pixel line among samples located on the same line as the upper sample line composed of the upper reference samples 737 .

When the size of the target block is NxN, there may be N number of lower left reference samples 731 , left reference samples 733 , upper reference samples 737 , and upper right reference samples 739 , respectively.

A prediction block may be generated through intra prediction of the target block. Generation of the prediction block may include determining values of pixels of the prediction block. The size of the target block and the prediction block may be the same.

A reference sample used for intra prediction of the target block may vary according to the intra prediction mode of the target block. The direction of the intra prediction mode may indicate a dependency relationship between reference samples and pixels of a prediction block. For example, the value of the specified reference sample may be used as the value of the specified one or more pixels of the predictive block. In this case, the specified one or more pixels of the specified reference sample and prediction block may be samples and pixels specified by a straight line in the direction of the intra prediction mode. In other words, the value of the specified reference sample may be copied as a value of a pixel located in a direction opposite to the direction of the intra prediction mode. Alternatively, the value of the pixel of the prediction block may be the value of the reference sample located in the direction of the intra prediction mode with respect to the position of the pixel.

For example, when the intra prediction mode of the target block is a vertical mode having a mode value of 26, upper reference samples 737 may be used for intra prediction. When the intra prediction mode is the vertical mode, the value of the pixel of the prediction block may be the value of the reference pixel positioned vertically above the pixel position. Accordingly, upper reference samples 737 adjacent to the top of the target block may be used for intra prediction. Also, the values of pixels in one row of the prediction block may be the same as values of the upper reference samples 737 .

For example, when the intra prediction mode of the target block is a horizontal mode having a mode value of 10, left reference samples 733 may be used for intra prediction. When the intra prediction mode is the horizontal mode, the value of the pixel of the prediction block may be the value of the reference pixel located horizontally to the left of the pixel. Accordingly, left reference samples 733 adjacent to the left of the target block may be used for intra prediction. Also, values of pixels in one column of the prediction block may be the same as values of left reference samples 733 .

For example, when the mode value of the intra prediction mode of the target block is 18, at least some of the left reference samples 733, the upper left corner reference sample 735, and at least some of the upper reference samples 737. can be used When the mode value of the intra prediction mode is 18, the value of the pixel of the prediction block may be the value of the reference pixel located at the upper left diagonally with respect to the pixel.

Also, when an intra prediction mode having a mode value of 27, 28, 29, 30, 31, 32, 33, or 34 is used, at least some of the upper right reference pixels 739 may be used for intra prediction.

Also, when an intra prediction mode having a mode value of 2, 3, 4, 5, 6, 7, 8, or 9 is used, at least some of the lower left reference pixels 739 may be used for intra prediction.

Also, when an intra prediction mode having a mode value of one of 11 to 25 is used, upper left corner reference samples 735 may be used for intra prediction.

The reference sample used to determine the pixel value of one pixel of the prediction block may be one, or may be two or more.

As described above, the pixel value of the pixel of the prediction block may be determined according to the position of the pixel and the position of the reference sample indicated by the direction of the intra prediction mode. When the position of the reference sample pointed to by the position of the pixel and the direction of the intra prediction mode is an integer position, the value of one reference sample pointed to by the integer position may be used to determine the pixel value of the pixel of the prediction block.

When the position of the reference sample indicated by the position of the pixel and the direction of the intra prediction mode is not an integer position, an interpolated reference sample may be generated based on the two reference samples closest to the position of the reference sample. have. The values of the interpolated reference samples may be used to determine the pixel values of the pixels of the prediction block. In other words, when the position of the pixel of the prediction block and the position of the reference sample pointed to by the direction of the intra prediction mode indicate between two reference samples, an interpolated value will be generated based on the values of the two samples. can

A prediction block generated by prediction may not be the same as the original target block. That is, a prediction error that is a difference between the target block and the prediction block may exist, and a prediction error may also exist between a pixel of the target block and a pixel of the prediction block. For example, in the case of directional intra prediction, a larger prediction error may occur as the distance between a pixel of a prediction block and a reference sample is greater. Discontinuity may occur between a prediction block generated by such a prediction error and the like and a neighboring block.

Filtering on the prediction block may be used to reduce the prediction error. Filtering may be adaptively applying a filter to a region considered to have a large prediction error among prediction blocks. For example, a region considered to have a large prediction error may be a boundary of a prediction block. Also, a region considered to have a large prediction error among prediction blocks may be different according to an intra prediction mode, and filter characteristics may be different.

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

The rectangle shown in FIG. 8 may represent an image (or a picture). Also, an arrow in FIG. 8 may indicate a prediction direction. That is, the image may be encoded and/or decoded according to the prediction direction.

Each picture may be classified into an I picture (intra picture), a P picture (uni-prediction picture), and a B picture (bi-prediction picture) according to an encoding type. Each picture may be encoded according to the encoding type of each picture.

When the target image to be encoded is an I picture, the target image may be encoded using data within the image itself without inter prediction referring to another image. For example, an I picture may be coded only with intra prediction.

When the target picture is a P picture, the target picture may be encoded through inter prediction using a reference picture only in a forward direction.

When the target picture is a B picture, the target picture may be encoded through inter prediction using reference pictures in both forward and backward directions or inter prediction using reference pictures in one of the forward and backward directions.

P-pictures and B-pictures that are encoded and/or decoded using a reference picture may be regarded as images for which inter prediction is used.

Hereinafter, inter prediction in inter mode according to an embodiment will be 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 target block.

For example, the encoding apparatus 100 or the decoding apparatus 200 performs prediction and/or motion compensation by using motion information of a spatial candidate and/or a temporal candidate as motion information of a target block. can be done The target block may mean a PU and/or a PU partition.

The spatial candidate may be a reconstructed block spatially adjacent to the target block.

The temporal candidate may be a reconstructed block corresponding to a target block in an already reconstructed collocated picture (col picture).

In inter prediction, the encoding apparatus 100 and the decoding apparatus 200 may improve encoding efficiency and decoding efficiency by using motion information of a spatial candidate and/or a temporal candidate. The motion information of the spatial candidate may be referred to as spatial motion information. The motion information of the temporal candidate may be referred to as temporal motion information.

Hereinafter, motion information of a spatial candidate may be motion information of a PU including a spatial candidate. The motion information of the temporal candidate may be motion information of a PU including the temporal candidate. The motion information of the candidate block may be motion information of the PU including the candidate block.

Inter prediction may be performed using a reference picture.

The reference picture may be at least one of a picture before the target picture or a picture after the target picture. The reference picture may mean an image used for prediction of a target block.

In inter prediction, a region within a reference picture may be specified by using a reference picture index (or refIdx) indicating a reference picture and a motion vector to be described later. Here, the specified region in the reference picture may indicate a reference block.

Inter prediction may select a reference picture and select a reference block corresponding to a target block in the reference picture. In addition, inter prediction may generate a prediction block for the target block by using the selected reference block.

Motion information may be derived during inter prediction by each of the encoding apparatus 100 and the decoding apparatus 200 .

A spatial candidate may be a block that 1) exists in the target picture, 2) has already been reconstructed through encoding and/or decoding, and 3) is adjacent to the target block or located at a corner of the target block. Here, the block located at the corner of the target block may be a block vertically adjacent to a neighboring block horizontally adjacent to the target block or a block horizontally adjacent to a neighboring block vertically adjacent to the target block. “A block located at the corner of the target block” may have the same meaning as “a block adjacent to the corner of the target block”. A “block located at the corner of the target block” may be included in “a block adjacent to the target block”.

For example, the spatial candidate is a reconstructed block located at the left side of the target block, a reconstructed block located at the top of the target block, a reconstructed block located at the lower left corner of the target block, and a reconstructed block located at the upper right corner of the target block Alternatively, it may be a reconstructed block located in the upper left corner of the target block.

Each of the encoding apparatus 100 and the decoding apparatus 200 may identify a block existing at a location spatially corresponding to the target block in the col picture. The location of the target block in the target picture and the location of the identified block in the collocated picture may correspond to each other.

Each of the encoding apparatus 100 and the decoding apparatus 200 may determine a col block existing at a predetermined relative position with respect to the identified block as a temporal candidate. The predefined relative position may be a position inside and/or outside the identified block.

For example, the collocated block may include a first collocated block and a second collocated block. When the coordinates of the identified block are (xP, yP) and the size of the identified block is (nPSW, nPSH), the first collocated block may be a block located at the coordinates (xP + nPSW, yP + nPSH). The second collocated block may be a block located at coordinates (xP + (nPSW >> 1), yP + (nPSH >> 1)). The second collocated block may be selectively used when the first collocated block is unavailable.

The motion vector of the target block may be determined based on the motion vector of the collocated block. Each of the encoding apparatus 100 and the decoding apparatus 200 may scale the motion vector of the collocated block. A scaled motion vector of the collocated block may be used as the motion vector of the target block. Also, the motion vector of the motion information of the temporal candidate stored in the list may be a scaled motion vector.

A ratio of the motion vector of the target block and the motion vector of the collocated block may be the same as the ratio of the first distance and the second distance. The first distance may be a distance between the reference picture and the target picture of the target block. The second distance may be a distance between the reference picture and the collocated picture of the collocated block.

A method of deriving motion information may vary according to the inter prediction mode of the target block. For example, as an inter prediction mode applied for inter prediction, there may be an advanced motion vector predictor (AMVP) mode, a merge mode, and a skip mode. Below, each of the modes is described in detail.

1) AMVP mode

When the AMVP mode is used, the encoding apparatus 100 may search for a similar block in the vicinity of the target block. The encoding apparatus 100 may obtain a prediction block by performing prediction on the target block using the found motion information of a similar block. The encoding apparatus 100 may encode a residual block that is a difference between the target block and the prediction block.

1-1) Creation of a prediction motion vector candidate list

When the AMVP mode is used as the prediction mode, each of the encoding apparatus 100 and the decoding apparatus 200 may generate a prediction motion vector candidate list by using a motion vector of a spatial candidate and/or a motion vector of a temporal candidate. . A motion vector of a spatial candidate and/or a motion vector of a temporal candidate may be used as a prediction motion vector candidate.

The prediction motion vector candidate may be a motion vector predictor for prediction of a motion vector. Also, in the encoding apparatus 100, the prediction motion vector candidate may be an initial motion vector search position.

1-2) Searching for a motion vector using the predicted motion vector candidate list

The encoding apparatus 100 may determine a motion vector to be used for encoding a target block within a search range by using the prediction motion vector candidate list. Also, the encoding apparatus 100 may determine a prediction motion vector candidate to be used as a motion vector prediction for the target block from among motion vector prediction candidates in the prediction motion vector candidate list.

A motion vector to be used for encoding a target block may be a motion vector that can be encoded with a minimum cost.

Also, the encoding apparatus 100 may determine whether to use the AMVP mode in encoding the target block.

1-3) Transmission of inter prediction information

The encoding apparatus 100 may generate a bitstream including inter prediction information required for inter prediction. The decoding apparatus 100 may perform inter prediction on the target block using inter prediction information of the bitstream.

Inter prediction information includes 1) mode information indicating whether AMVP mode is used, 2) prediction motion vector index, 3) motion vector difference (MVD), 4) reference direction, and 5) reference picture index can do.

Also, the inter prediction information may include a residual signal.

The decoding apparatus 200 may obtain the prediction motion vector index, the motion vector difference, the reference direction, and the reference picture index from the bitstream only when the mode information indicates that the AMVP mode is used.

The prediction motion vector index may indicate a prediction motion vector candidate used for prediction of a target block among prediction motion vector candidates included in the prediction motion vector candidate list.

1-4) Inter prediction in AMVP mode using inter prediction information

The decoding apparatus 200 may select a prediction motion vector candidate indicated by a prediction motion vector index from among prediction motion vector candidates included in the prediction motion vector candidate list as the prediction motion vector of the target block.

A motion vector to be actually used for inter prediction of the target block may not match the predicted motion vector. An MVD may be used to indicate a difference between a motion vector to be actually used for inter prediction of a target block and a prediction motion vector. The encoding apparatus 100 may derive a prediction motion vector similar to a motion vector to be actually used for inter prediction of a target block in order to use an MVD of as small a size as possible.

The MVD may be a difference between a motion vector of a target block and a prediction motion vector. The encoding apparatus 100 may calculate the MVD and may encode the MVD.

The MVD may be transmitted from the encoding apparatus 100 to the decoding apparatus 200 through a bitstream. The decoding apparatus 200 may decode the received MVD. The decoding apparatus 200 may derive the motion vector of the target block through the sum of the decoded MVD and the prediction motion vector.

The reference direction may indicate a reference picture list used for prediction of a target block. For example, the reference direction may point to one of the reference picture list L0 and the reference picture list L1.

The reference direction only indicates a reference picture list used for prediction of a target block, and may not indicate that directions of reference pictures are limited to a forward direction or a backward direction. In other words, each of the reference picture list L0 and the reference picture list L1 may include forward and/or backward pictures.

That the reference direction is uni-direction may mean that one reference picture list is used. That the reference direction is bi-direction may mean that two reference picture lists are used. In other words, the reference direction may indicate that only the reference picture list L0 is used, that only the reference picture list L1 is used, and one of two reference picture lists.

The reference picture index may indicate a reference picture used for prediction of a target block among reference pictures of the reference picture list.

When two reference picture lists are used for prediction of the target block. One reference picture index and one motion vector may be used for each reference picture list. Also, when two reference picture lists are used for prediction of the target block, two prediction blocks may be specified for the target block. For example, a (final) prediction block of the target block may be generated through an average or a weighted-sum of two prediction blocks for the target block.

The motion vector of the target block may be specified by the prediction motion vector index, the MVD, the prediction direction, and the reference picture index.

The decoding apparatus 200 may generate a prediction block for the target block based on the derived motion vector and reference picture index information. For example, the prediction block may be a reference block indicated by a derived motion vector in a reference picture indicated by the reference picture index information.

By encoding the prediction motion vector index and the MVD without encoding the motion vector itself of the target block, the amount of bits transmitted from the encoding apparatus 100 to the decoding apparatus 200 may be reduced, and encoding efficiency may be improved.

Motion information of a neighboring block reconstructed with respect to the target block may be used. In a specific inter prediction mode, the encoding apparatus 100 may not separately encode motion information itself for the target block. The motion information of the target block is not coded, but other information capable of deriving the motion information of the target block through the motion information of the reconstructed neighboring block may be coded instead. As other information is encoded instead, 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 the motion information of the target block is not directly encoded, 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.

2) Merge mode

As a method of deriving motion information of a target block, there is a merge. Merge may mean merging motions for a plurality of blocks. Merge may mean applying motion information of one block to another block as well.

When the merge mode is used, the encoding apparatus 100 may perform prediction on motion information of a target block using motion information of a spatial candidate and/or motion information of a temporal candidate. The encoding apparatus 100 may obtain a prediction block through prediction. The encoding apparatus 100 may encode a residual block that is a difference between the target block and the prediction block.

2-1) Preparation of merge candidate list

When the merge mode is used, each of the encoding apparatus 100 and the decoding apparatus 200 may generate a merge candidate list using motion information of a spatial candidate and/or motion information of a temporal candidate. The motion information may include 1) a motion vector, 2) a reference picture index, and 3) a reference direction. The reference direction may be unidirectional or bidirectional.

The merge candidate list may include merge candidates. The merge candidate may be motion information. In other words, the merge candidates may be motion information such as a temporal candidate and/or a spatial candidate. Also, the merge candidate list may include a new merge candidate generated by a combination of merge candidates already existing in the merge candidate list. Also, the merge candidate list may include zero vector motion information.

The merge candidate may include 1) a motion vector, 2) a reference picture index, and 3) a reference direction.

The merge candidate list may be generated before prediction by the merge mode is performed.

The number of merge candidates in the merge candidate list may be predefined. The encoding apparatus 100 and the decoding apparatus 200 may add merge candidates to the merge candidate list according to a predefined method and a predefined order so that the merge candidate list has a predefined number of merge candidates. The merge candidate list of the encoding apparatus 100 and the merge candidate list of the decoding apparatus 200 may become the same through a predefined method and a predefined rank.

Merge may be applied on a CU basis or a PU basis. When the merge is performed in units of CUs or PUs, the encoding apparatus 100 may transmit a bitstream including predefined information to the decoding apparatus 200 . For example, the predefined information includes: 1) information indicating whether to perform the merge for each block partition, 2) which block among blocks that are spatial and/or temporal candidates for the target block to be merged with It may include information about whether

2-2) Search for motion vector using merge candidate list

The encoding apparatus 100 may determine a merge candidate to be used for encoding the target block. For example, the encoding apparatus 100 may perform predictions on a target block using merge candidates in the merge candidate list, and generate residual blocks for the merge candidates. The encoding apparatus 100 may use a merge candidate requiring a minimum cost in prediction and encoding of a residual block for encoding of a target block.

Also, the encoding apparatus 100 may determine whether to use the merge mode in encoding the target block.

2-3) Transmission of inter prediction information

The encoding apparatus 100 may generate a bitstream including inter prediction information required for inter prediction. The decoding apparatus 200 may perform inter prediction on the target block using inter prediction information of the bitstream.

The inter prediction information may include 1) mode information indicating whether a merge mode is used and 2) a merge index.

Also, the inter prediction information may include a residual signal.

The decoding apparatus 200 may obtain the merge index from the bitstream only when the mode information indicates that the merge mode is used.

The merge index may indicate a merge candidate used for prediction of a target block among merge candidates included in the merge candidate list.

2-4) Inter prediction of merge mode using inter prediction information

The decoding apparatus 200 may perform prediction on the target block by using a merge candidate indicated by a merge index among merge candidates included in the merge candidate list.

The motion vector of the target block may be specified by the motion vector of the merge candidate indicated by the merge index, the reference picture index, and the reference direction.

3) Skip mode

The skip mode may be a mode in which motion information of a spatial candidate or motion information of a temporal candidate is directly applied to a target block. Also, the skip mode may be a mode that does not use a residual signal. In other words, when the skip mode is used, the reconstructed block may be a prediction block.

The difference between the merge mode and the skip mode may be whether a residual signal is transmitted or used. In other words, skip mode may be similar to merge mode except that no residual signal is transmitted or used.

When the skip mode is used, the encoding apparatus 100 transmits, through a bitstream, only information on which block of blocks that are spatial or temporal candidates to use as the motion information of the target block to the decoding apparatus 200 through the bitstream. can Also, when the skip mode is used, the encoding apparatus 100 may not transmit other syntax information such as MVD to the decoding apparatus 200 .

3-1) Preparation of merge candidate list

The skip mode may also use the merge candidate list. In other words, the merge candidate list can be used in both the merge mode and the skip mode. In this aspect, the merge candidate list may be referred to as a “skip candidate list” or “merge/skip candidate list”.

Alternatively, the skip mode may use a different candidate list from the merge mode. In this case, in the following description, the merge candidate list and the merge candidate may be replaced with the skip candidate list and the skip candidate, respectively.

The merge candidate list may be generated before prediction by skip mode is performed.

3-2) Search for motion vector using merge candidate list

The encoding apparatus 100 may determine a merge candidate to be used for encoding the target block. For example, the encoding apparatus 100 may perform predictions on the target block using merge candidates in the merge candidate list. The encoding apparatus 100 may use a merge candidate requiring a minimum cost in prediction for encoding the target block.

Also, the encoding apparatus 100 may determine whether to use the skip mode in encoding the target block.

3-3) Transmission of inter prediction information

The encoding apparatus 100 may generate a bitstream including inter prediction information required for inter prediction. The decoding apparatus 200 may perform inter prediction on the target block using inter prediction information of the bitstream.

The inter prediction information may include 1) mode information indicating whether a skip mode is used and 2) a skip index.

The skip index may be the same as the above-described merge index.

When the skip mode is used, the target block may be coded without a residual signal. The inter prediction information may not include a residual signal. Alternatively, the bitstream may not include a residual signal.

The decoding apparatus 200 may obtain the skip index from the bitstream only when the mode information indicates that the skip mode is used. As described above, the merge index and the skip index may be the same. The decoding apparatus 200 may obtain the skip index from the bitstream only when the mode information indicates that the merge mode or the skip mode is used.

The skip index may indicate a merge candidate used for prediction of a target block among merge candidates included in the merge candidate list.

3-4) Skip mode inter prediction using inter prediction information

The decoding apparatus 200 may perform prediction on the target block by using a merge candidate indicated by a skip index among merge candidates included in the merge candidate list.

The motion vector of the target block may be specified by the motion vector of the merge candidate indicated by the skip index, the reference picture index, and the reference direction.

In the aforementioned AMVP mode, merge mode, and skip mode, motion information to be used for prediction of a target block among motion information in a list may be specified through an index to the list.

In order to improve encoding efficiency, the encoding apparatus 100 may signal only the index of the element causing the minimum cost in inter prediction of the target block among elements of the list. The encoding apparatus 100 may encode the index and may signal the encoded index.

Accordingly, the above-described lists (ie, the prediction motion vector candidate list and the merge candidate list) may have to be derived in the same manner based on the same data in the encoding apparatus 100 and the decoding apparatus 200 . Here, the same data may include a reconstructed picture and a reconstructed block. Also, in order to specify an element by index, the order of the elements in the list may have to be constant.

9 shows spatial candidates according to an example.

In Fig. 9, the locations of spatial candidates are shown.

A large block in the middle may represent a target block. Five small blocks may represent spatial candidates.

The coordinates of the target block may be (xP, yP), and the size of the target block may be (nPSW, nPSH).

The spatial candidate A ₀ may be a block adjacent to the lower left corner of the target block. A ₀ may be a block occupying a pixel of coordinates (xP - 1, yP + nPSH + 1).

The spatial candidate A ₁ may be a block adjacent to the left of the target block. A ₁ may be the lowest block among blocks adjacent to the left of the target block. Alternatively, A ₁ may be a block adjacent to the upper end of A ₀ . A ₁ may be a block occupying a pixel of coordinates (xP - 1, yP + nPSH).

The spatial candidate B ₀ may be a block adjacent to the upper right corner of the target block. B ₀ may be a block occupying a pixel of coordinates (xP + nPSW + 1, yP - 1).

The spatial candidate B ₁ may be a block adjacent to the top of the target block. B ₁ may be a rightmost block among blocks adjacent to the top of the target block. Alternatively, B ₁ may be a block adjacent to the left of B ₀ . B ₁ may be a block occupying a pixel of coordinates (xP + nPSW, yP - 1).

The spatial candidate B ₂ may be a block adjacent to the upper left corner of the target block. B ₂ may be a block occupying a pixel of coordinates (xP - 1, yP - 1).

Determination of availability of spatial and temporal candidates

In order to include the motion information of the spatial candidate or the motion information of the temporal candidate in the list, it should be determined whether motion information of the spatial candidate or the motion information of the temporal candidate is available.

Hereinafter, a candidate block may include a spatial candidate and a temporal candidate.

For example, the above determination may be made by sequentially applying the following steps 1) to 4).

Step 1) If the PU including the candidate block is outside the boundary of the picture, the availability of the candidate block may be set to false. "Availability set to false" may have the same meaning as "availability set to unavailable".

Step 2) If the PU including the candidate block is outside the boundary of the slice, the availability of the candidate block may be set to false. If the target block and the candidate block are located in different slices, the availability of the candidate block may be set to false.

Step 3) If the PU including the candidate block is outside the boundary of the tile, the availability of the candidate block may be set to false. If the target block and the candidate block are located in different tiles, the availability of the candidate block may be set to false.

Step 4) If the prediction mode of the PU including the candidate block is the intra prediction mode, the availability of the candidate block may be set to false. If the PU including the candidate block does not use inter prediction, the availability of the candidate block may be set to false.

10 illustrates an order of adding motion information of spatial candidates to a merge list according to an example.

As shown in FIG. 10 , in adding motion information of spatial candidates to the merge list, the order of A ₁ , B ₁ , B ₀ , A ₀ and B ₂ may be used. That is, in the order of A ₁ , B ₁ , B ₀ , A ₀ and B ₂ , motion information of available spatial candidates may be added to the merge list.

Method of derivation of merge list in merge mode and skip mode

As described above, the maximum number of merge candidates in the merge list may be set. The set maximum number is displayed as N. The set number may be transmitted from the encoding apparatus 100 to the decoding apparatus 200 . A slice header of a slice may include N. That is, the maximum number of merge candidates in the merge list for the target block of the slice may be set by the slice header. For example, the value of N may be 5 by default.

Motion information (ie, a merge candidate) may be added to the merge list in the order of steps 1) to 4) below.

Step 1) Available spatial candidates among spatial candidates may be added to the merge list. Motion information of available spatial candidates may be added to the merge list in the order shown in FIG. 10 . In this case, when motion information of an available spatial candidate overlaps with other motion information already present in the merge list, the motion information may not be added to the merge list. Checking whether or not it overlaps with other motion information existing in the list may be abbreviated as "redundancy check".

There may be a maximum of N pieces of added motion information.

Step 2) If the number of motion information in the merge list is smaller than N and a temporal candidate is available, the motion information of the temporal candidate may be added to the merge list. In this case, when motion information of an available temporal candidate overlaps with other motion information already present in the merge list, the motion information may not be added to the merge list.

Step 3) If the number of motion information in the merge list is smaller than N and the type of target slice is “B”, the combined motion information generated by combined bi-prediction is added to the merge list. can

The target slice may be a slice including the target block.

The combined motion information may be a combination of L0 motion information and L1 motion information. The L0 motion information may be motion information referring only to the reference picture list L0. The L1 motion information may be motion information referring only to the reference picture list L1.

In the merge list, there may be one or more L0 motion information. Also, in the merge list, there may be more than one L1 motion information.

The combined motion information may be one or more. In generating the combined motion information, which L0 motion information and which L1 motion information among the one or more L0 motion information and the one or more L1 motion information are to be used may be predefined. One or more combined motion information may be generated in a predefined order by combined bidirectional prediction using different pairs of motion information in the merge list. One of the different pairs of motion information may be L0 motion information and the other may be L1 motion information.

For example, the combined motion information added with the highest priority may be a combination of L0 motion information having a merge index of 0 and L1 motion information having a merge index of 1. If the motion information having the merge index of 0 is not the L0 motion information or the motion information having the merge index of 1 is not the L1 motion information, the combined motion information may not be generated and added. Next added motion information may be a combination of L0 motion information having a merge index of 1 and L1 motion information having a merge index of 0. The following specific combinations may follow other combinations of encoding/decoding fields of moving pictures.

In this case, if the combined motion information overlaps with other motion information already existing in the merge list, the combined motion information may not be added to the merge list.

Step 4) If the number of motion information in the merge list is smaller than N, zero vector motion information may be added to the merge list.

The zero vector motion information may be motion information in which a motion vector is a zero vector.

There may be one or more zero vector motion information. Reference picture indices of one or more pieces of zero vector motion information may be different from each other. For example, the value of the reference picture index of the first zero vector motion information may be 0. The value of the reference picture index of the second zero vector motion information may be 1.

The number of zero vector motion information may be the same as the number of reference pictures in the reference picture list.

The reference direction of the zero vector motion information may be bidirectional. Both motion vectors may be zero vectors. The number of zero vector motion information may be the smaller of the number of reference pictures in the reference picture list L0 and the number of reference pictures in the reference picture list L1. Alternatively, when the number of reference pictures in the reference picture list L0 and the number of reference pictures in the reference picture list L1 are different from each other, a unidirectional reference direction may be used for a reference picture index that can be applied to only one reference picture list.

The encoding apparatus 100 and/or the decoding apparatus 200 may sequentially add zero vector motion information to the merge list while changing the reference picture index.

When the zero motion information overlaps with other motion information already existing in the merge list, the zero motion information may not be added to the merge list.

The order of steps 1) to 4) described above is merely exemplary, and the order between the steps may be interchanged. Also, some of the steps may be omitted according to predefined conditions.

Method of deriving a predictive motion vector candidate list in AMVP mode

The maximum number of prediction motion vector candidates in the prediction motion vector candidate list may be predefined. The predefined maximum number is indicated by N. For example, the predefined maximum number may be two.

The motion information (ie, the prediction motion vector candidate) may be added to the prediction motion vector candidate list in the order of steps 1) to 3) below.

Step 1) Available spatial candidates among spatial candidates may be added to the prediction motion vector candidate list. The spatial candidates may include a first spatial candidate and a second spatial candidate.

The first spatial candidate may be one of A ₀ , A ₁ , scaled A ₀ and scaled A ₁ . The second spatial candidate may be one of B ₀ , B ₁ , B ₂ , scaled B ₀ , scaled B ₁ , and scaled B ₂ .

Motion information of the available spatial candidates may be added to the prediction motion vector candidate list in the order of the first spatial candidate and the second spatial candidate. In this case, if motion information of an available spatial candidate overlaps with other motion information already existing in the prediction motion vector candidate list, the motion information may not be added to the prediction motion vector candidate list. That is, when the value of N is 2, if the motion information of the second spatial candidate is the same as the motion information of the first spatial candidate, the motion information of the second spatial candidate may not be added to the prediction motion vector candidate list.

There may be a maximum of N pieces of added motion information.

Step 2) If the number of motion information in the prediction motion vector candidate list is smaller than N and a temporal candidate is available, the motion information of the temporal candidate may be added to the prediction motion vector candidate list. In this case, when motion information of an available temporal candidate overlaps with other motion information already existing in the prediction motion vector candidate list, the motion information may not be added to the prediction motion vector candidate list.

Step 3) If the number of motion information in the prediction motion vector candidate list is smaller than N, zero motion information may be added to the prediction motion vector candidate list.

There may be one or more zero motion information. Reference picture indices of one or more pieces of zero motion information may be different from each other.

The encoding apparatus 100 and/or the decoding apparatus 200 may sequentially add zero motion information to the prediction motion vector candidate list while changing the reference picture index.

When the zero motion information overlaps with other motion information already existing in the predicted motion vector candidate list, the zero motion information may not be added to the predicted motion vector candidate list.

The description of the zero vector motion information described above with respect to the merge list may also be applied to the zero motion information. A duplicate description is omitted.

The order of steps 1) to 3) described above is merely exemplary, and the order between the steps may be interchanged. Also, some of the steps may be omitted according to predefined conditions.

11 illustrates division of a picture using tiles according to an example.

In Fig. 11, pictures are shown with solid lines, and tiles are shown with dotted lines. As shown, the picture may be divided into a plurality of tiles.

A tile may be one of entities used as a unit of division of a picture. A tile may be a unit of picture division. Alternatively, a tile may be a unit of picture division coding.

Tile-related information may be signaled through the PPS. The PPS may include information on tiles of a picture or information for dividing a picture into a plurality of tiles.

Table 1 below shows an example of the structure of pic_parameter_set_rbsp. The picture division information may be pic_parameter_set_rbsp or may include pic_parameter_set_rbsp.

pic_parameter_set_rbsp may include the following elements.

- tiles_enabled_flag: tiles_enabled_flag may be a tile existence indication flag indicating whether one or more tiles exist in a picture referring to the PPS.

For example, that the value of tiles_enabled_flag is “0” may indicate that a tile does not exist in a picture referring to the PPS. A value of “1” of tiles_enabled_flag may indicate that one or more tiles exist in a picture referring to the PPS.

Values of tile_enabled_flags of all activated PPSs in one Coded Video Sequence (CVS) may be the same.

- num_tile_columns_minus1: num_tile_columns_minus1 may be column tile number information corresponding to the number of tiles in the horizontal direction of the divided picture. For example, a value of “num_tile_columns_minus1 + 1” may indicate the number of tiles in the horizontal direction in the divided picture. Alternatively, a value of “num_tile_columns_minus1 + 1” may indicate the number of tiles in one row.

- num_tile_rows_minus1: num_tile_rows_minus1 may be information on the number of row tiles corresponding to the number of tiles in the vertical direction of the divided picture. For example, a value of “num_tile_rows_minus1 + 1” may indicate the number of tiles in the vertical direction in the divided picture. Alternatively, a value of “num_tile_row_minus1 + 1” may indicate the number of tiles in one column.

- uniform_spacing_flag: uniform_spacing_flag may be an even division indication flag indicating whether a picture is equally divided into tiles in a horizontal direction and a vertical direction. For example, uniform_spacing_flag may be a flag indicating whether sizes of tiles of a picture are all the same. For example, a value of "0" of uniform_spacing_flag may indicate that the picture is not evenly divided in the horizontal direction and/or the vertical direction. A value of uniform_spacing_flag of “1” may indicate that the picture is equally divided in the horizontal direction and the vertical direction. When the value of uniform_spacing_flag is “0”, an element that more specifically defines division, such as column_width_minus1[ i ] and row_height_minus1[ i ], which will be described later, may be additionally required for picture division.

- column_width_minus1[ i ]: column_width_minus1[ i ] may be tile width information corresponding to the width of the tile in the i-th column. i may be an integer greater than or equal to 0 and less than the number n of columns of tiles. For example, "column_width_minus1[ i ] + 1" may indicate the width of a tile in the i+1th column. The area may be expressed in a predefined unit. For example, the unit of the area may be a Coding Tree Block (CTB).

- row_height_minus1[ i ]: row_height_minus1[ i ] may be tile height information corresponding to the height of the tile in the i-th row. i may be an integer greater than or equal to 0 and less than the number n of rows of tiles. For example, "row_height_minus1[i] + 1" may indicate the height of the tile in the i+1th row. The height may be expressed in a predefined unit. For example, the unit of height may be CTB.

In one example, the picture division information may be included in the PPS, and may be transmitted as part of the PPS when the PPS is transmitted. The decoding apparatus may obtain picture division information required for picture division by referring to the PPS for the picture.

In order for the encoding apparatus to signal different picture division information from previously transmitted, the encoding apparatus may first transmit a new PPS including new picture division information and a new PPS ID to the decoding apparatus. Next, the encoding apparatus may transmit the slice header including the PPS ID to the decoding apparatus.

11 illustrates division of a picture using a slice according to an example.

In FIG. 11 , a picture is illustrated by a solid line, a slice is illustrated by a thick dotted line, and a Coding Tree Unit (CTU) is illustrated by a thin dotted line. As shown, a picture may be divided into a plurality of slices. One slice may be sequential one or more CTUs.

A slice may be one of entities used as a unit of division of a picture. A slice may be a unit of picture division. Alternatively, a slice may be a unit of picture division coding.

Slice-related information may be signaled through a slice segment header. The slice segment header may include information on slices.

When a slice is a unit of picture division coding, picture division information may define a start address of each slice of one or more slices.

The unit of the start address of the slice may be a CTU. The picture partition information may define a start CTU address of each slice of one or more slices. A picture division type may be defined by start addresses of slices.

Table 2 below shows an example of the structure of slice_segment_header. The picture segmentation information may be slice_segment_header or may include slice_segment_header.

slice_segment_header may include the following elements.

- first_slice_segment_in_pic_flag: first_slice_segment_in_pic_flag may be a first slice indication flag indicating whether the slice indicated by slice_segment_header is the first slice of the picture.

For example, a value of "0" of first_slice_segment_in_pic_flag may indicate that the slice is not the first slice of the picture. A value of "1" of first_slice_segment_in_pic_flag may indicate that the slice is the first slice of the picture.

- dependent_slice_segment_flag: dependent_slice_segment_flag may be a dependent slice segment indication flag indicating whether the slice indicated by slice_segment_header is a dependent slice.

For example, a value of "0" of dependent_slice_segment_flag may indicate that the slice is not a dependent slice. A value of "1" of dependent_slice_segment_flag may indicate that the slice is a dependent slice.

For example, a slice of a substream of Wavefront Parallel Processing (WPP) may be a dependent slice. Independent corresponding to the dependent slice may exist. When the slice indicated by slice_segment_header is a dependent slice, at least one element of slice_segment_header may not exist. In other words, the value of an element in slice_segment_header may not be defined. For an element for which the value of the dependent slice is not defined, the value of the element of the independent slice corresponding to the dependent slice may be used. That is, a value of a specified element that does not exist in slice_segment_header of a dependent slice may be the same as a value of a specified element of slice_segment_header of an independent slice corresponding to the dependent slice. For example, a dependent slice may inherit values of elements of a corresponding independent slice, and may redefine values of elements of at least some of the independent slices.

- slice_segment_address: slice_segment_address may be start address information indicating the start address of the slice indicated by slice_segment_header. The unit of the start address information may be CTB.

A method of dividing a picture into one or more slices may include the following methods 1) to 3).

Method 1) A first method may be to divide a picture into a maximum size of a bitstream that one slice can include.

Method 2) The second method may be to divide a picture into the maximum number of CTUs that one slice can contain.

Method 3) A third method may be to divide a picture by the maximum number of tiles that one slice can include.

When the encoding apparatus attempts to perform parallel encoding in units of slices, the second method and the third method among the above three methods may be generally used.

In the case of the first scheme, since the size of the bitstream can be known after encoding is completed, it may be difficult to define slices to be processed in parallel before the start of encoding. Accordingly, the picture partitioning method enabling parallel encoding of slice units may be a second method using a unit of the maximum number of CTUs and a third method using a unit of the maximum number of tiles.

When the second method and the third method are used, a size to divide a picture may be predetermined before the pictures are encoded in parallel. Also, slice_segment_address may be calculated according to a predetermined size. When the encoding apparatus uses a slice as a unit of parallel encoding, slice_segment_address does not usually change for every picture, but tends to be repeated according to a certain period and/or a specified rule.

13 illustrates distributed encoding of a temporally-spatially partitioned picture according to an example.

13 shows a configuration in which one picture is divided into four slices. Also, each of the 4 pictures was divided into 4 slices. Each picture may include slice 0, slice 1, slice 2, and slice 3.

That is to say, the video can be partitioned in space and time. Each picture of a video may be divided into a specified number of slices.

A slice of pictures may be processed by an encoding node.

The same slice of pictures may be grouped in units of an intra period. Slices of a picture may be encoded in parallel by a plurality of encoding nodes distributed in a network.

For example, as shown in FIG. 13 , slice 0 of pictures may be processed by encoding node 0, slice 1 may be processed by encoding node 1, and slice 2 may be processed by encoding node 2 and slice 3 may be processed by encoding node 3 .

In parallel encoding, communication efficiency between nodes and parallel encoding efficiency may be improved by not allowing inter-referencing between blocks in different slices.

14 illustrates processing of a motion-constrained tile set (MCTS) according to an example.

The MCTS may be a set of one or more tiles that limits the range of inter prediction to a specified region within a picture.

For example, when a region of interest (ROI) of a picture is set to MCTS, a region outside the boundary of the MCTS in the picture may not be used in inter prediction.

In FIG. 14 , it is shown that inter prediction of picture 2 uses only the region of MCTS of picture 1. In addition, it is shown that the inter prediction of picture 3 uses only the MCTS area of picture 1 and the MCTS area of picture 2 .

15 shows a PU adjacent to a boundary of a slice according to an example.

In Fig. 15, a target picture is shown. The target picture was divided into two slices. A slice boundary between two slices exists in the target picture.

In addition, a target PU that is a target block is adjacent to a boundary of a slice and a boundary of a picture.

If the above-described method of adding motion information of a spatial candidate to a list is used to generate a list, a case in which motion information of the list cannot be used as motion information of a middle target PU may frequently occur. This case will be described in detail below with reference to FIG. 16 .

16 shows a merge list according to an example.

16 may be a merge list generated for the target PU of FIG. 15 .

The merge list of FIG. 16 may be generated by the above-described method for generating a merge list.

The maximum number of motion information in the merge list may be 5.

Each row of the merge list may indicate motion information. For example, the first row 1610 may indicate motion information in which the value of the merge index is 0.

The first column in the merge list may be a merge index. The second column and the third column may indicate a list of reference pictures of motion information. For motion information using the reference picture list L0, a motion vector and reference picture index may be described in the second column. For motion information using the reference picture list L1, a motion vector and a reference picture index may be described in the third column. For motion information using the reference picture list L0 and the reference picture list L1, respectively, a motion vector and a reference picture index may be described in each of the second and third columns.

The indication of “(X, Y), Z” may indicate a motion vector (X, Y) and a reference picture index Z.

For example, "(-1, -2), 0" and "-" of the first row 1610 refer to the first motion information, the motion vector (-1, -2), the reference picture list L0, It is information of picture index 0, and may indicate that the reference picture list L1 is not used. The motion information of the first row 1610 may indicate a picture having index 0 among reference pictures in the reference picture list L0, and may indicate a motion vector moving one space to the left and two spaces upward.

Also, the fourth row 1640 may indicate motion information of bi-directional prediction indicating the reference picture list L0 and the reference picture list L1.

Since the target PU of FIG. 15 is located at the lower right of the slice, when either one of the x value or the y value of the motion vector of the motion information is 1 or more, the position indicated by the motion vector applied to the target PU is the boundary of the picture or the slice can cross boundaries. Accordingly, such motion information cannot be used for the target PU without using an additional adjustment method such as adjustment using MVD.

For example, the motion information of the second row 1620 may be derived from the spatial candidate B ₁ . A motion vector of (-1, 1) for B ₁ may be a valid motion vector that does not deviate from a slice boundary and a picture boundary. However, the motion vector (-1, 1) may be a motion vector that crosses a slice boundary for a target PU. That is, the motion vector (-1, 1) may be a motion vector that cannot be used for the target PU, and the motion information in the second column may be motion information that cannot be used.

For example, the motion vector (1, 0) of the third row 1630 may be derived from the spatial candidate B ₂ . However, the motion vector (1, 0) may be a motion vector that crosses a picture boundary for a target PU.

For example, the motion vector (1, 1) of the fourth row 1640 may be derived from a temporal candidate. However, the motion vector (1, 1) may be a motion vector that crosses a picture boundary for a target PU.

For example, the motion information of the fifth row 1650 may be combined motion information generated by the combined bidirectional prediction of the motion information of the first row 1610 and the motion information of the second row 1620 . However, since the motion information of the second row 1602 cannot be used for the target PU, the motion information of the fifth row 1650 also cannot be generated.

As described above, in some cases, many of the motion information of the merge list may not be used for the target block. In addition, such unusable motion information may prevent other lower-order motion information from being added to the merge list.

In this case, the encoding apparatus 100 cannot use motion information that crosses a slice boundary or a picture boundary among motion information of the merge list. In a specific case, none of the motion information of the merge list may actually be used.

When the encoding apparatus 100 selects an optimal inter prediction mode for a target block, as use of at least some of motion information in the merge list is restricted, encoding efficiency may decrease. Also, some motion information may cause overhead such as MVD.

In the following embodiments, a method of motion prediction boundary checking for improving encoding efficiency while limiting the range of inter prediction is presented.

The process of motion prediction boundary check may be performed when motion information of a candidate block is added to a list or when the availability of a candidate block is determined.

The motion prediction boundary check may be to check whether a position determined using motion information of a candidate block is outside an area or boundary. In other words, the motion prediction boundary check may be to check whether a location referenced by a target block according to a motion vector of motion information exists in a region. That is, in inter prediction, a position referenced by a target block may be limited within a region. Motion information that has passed the motion prediction boundary check may be used for motion prediction of the target block.

The “determined position” may be a position indicated by a motion vector of motion information applied to the target block. Here, the position indicated by the motion vector may be a position in which the motion vector is added to the position of the target block.

According to the motion prediction boundary check, the motion information of the candidate block may be added to the list as a motion information candidate for the target block only when the determined position is within the region (or when the determined position does not deviate from the boundary).

The region may be a region of a slice including the target block, a region of a tile including the target block, or an MCTS region including the target block. In other words, the region may be a unit including a target block among units for dividing a picture.

The boundary may include a boundary of a picture. Also, the boundary may include a boundary between slices, a boundary between tiles, or a boundary between MCTSs. In other words, the boundary may indicate 1) a boundary of a picture and 2) a boundary between a unit including a target block among units dividing a picture and another unit.

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

In operation 1710, the inter prediction unit 250 may confirm that inter prediction is used for prediction of the target block.

For example, if prediction information of the bitstream indicates inter prediction, the inter prediction unit 250 may confirm that inter prediction is used for the target block.

In operation 1720, the inter prediction unit 250 may obtain inter prediction information from the bitstream.

The inter prediction information may include mode information. The mode information may indicate which mode among 1) AMVP mode, 2) merge mode, and 3) skip mode is used for inter prediction of a target block.

The mode information may be plural. For example, the inter prediction information may include skip mode information. The skip mode information may indicate that the skip mode is used for inter prediction of the target block.

Inter prediction information may be different according to mode information.

In operation 1730, the inter prediction unit 250 may generate a list.

The list may be a predictive motion vector candidate list or a merge list.

The list may be a list corresponding to the mode indicated by the inter prediction information. For example, if the inter prediction information indicates to use the AMVP mode, the generated list may be a prediction motion vector candidate list. If the inter prediction information indicates that the merge mode or the skip mode is used, the generated list may be a merge list.

List generation is described in detail below with reference to FIGS. 18 and 19, respectively.

In operation 1740, the inter prediction unit 250 may generate motion information of the target block based on the list and inter prediction information.

In operation 1750 , the inter prediction unit 250 may perform inter prediction on the target block based on motion information of the target block.

At least some of the steps 1710 , 1720 , 1730 , 1740 , and 1750 may also be performed by the inter prediction unit 110 of the encoding apparatus 100 . For example, the operation 1730 of generating the list may be performed in the same manner in the encoding apparatus 100 . In the following descriptions of the steps, the inter prediction unit 250 may be replaced with the inter prediction unit 110 .

Steps 1710 , 1720 , 1730 , 1740 , and 1750 may be combined with operations of other components of the encoding apparatus 100 described with reference to FIG. 1 . Also, steps 1710 , 1720 , 1730 , 1740 , and 1750 may be combined with operations of other components of the decoding apparatus 200 described with reference to FIG. 2 .

18 is a flowchart of a method of generating a merge list for inter prediction of a target block according to an embodiment.

Step 1730 described above with reference to FIG. 17 may include steps 1810 , 1820 , 1830 , 1840 , 1850 , 1860 , 1870 and 1880 to be described below.

In this embodiment, the intra prediction mode of the target block may be a merge mode or a skip mode. The list may be a merge list. The motion information of the candidate block may correspond to the merge candidate.

In operation 1810, the inter prediction unit 230 may determine whether motion information of the spatial candidate is added to the list.

When it is determined that the motion information of the spatial candidate is added to the list, step 1820 may be performed.

When it is determined that the motion information of the spatial candidate is not to be added to the list, operation 1830 may be performed.

In operation 1820, when it is determined to add the motion information of the spatial candidate to the list, the inter prediction unit 230 may add the motion information of the spatial candidate to the list.

Through steps 1810 and 1820 , motion information of a spatial candidate may be added to the list.

In an embodiment, in steps 1810 and 1820, the inter prediction unit 230 may determine whether the motion information of the spatial candidate is added to the list based on the information on the target block and the motion information of the spatial candidate. .

In an embodiment, the information on the target block may be a location of the target block. The inter prediction unit 230 may determine whether to add the motion information of the spatial candidate to the list based on the position of the target block and the motion vector of the spatial candidate.

In an embodiment, the inter prediction unit 230 may determine whether the motion information of the spatial candidate is added to the list based on the motion prediction boundary check for the target block and the spatial candidate.

In an embodiment, the inter prediction unit 230 may determine whether motion information of a spatial candidate is to be added to the list based on a position indicated by a motion vector applied to the target block. Here, the applied motion vector may be a motion vector of motion information of a spatial candidate.

Here, the position indicated by the motion vector may be a position determined by adding the motion vector to the position of the target block.

Also, a position indicated by a motion vector applied to the target block may be a reference position of the target block. Hereinafter, a position indicated by a motion vector applied to the target block will be abbreviated as a reference position of the target block. The reference position may point to a reference block of the target block.

The position or reference position indicated by the motion vector may be a position in the reference picture referenced by the target block.

In an embodiment, if the reference position of the target block is within the region, the inter prediction unit 230 may add motion information of the spatial candidate to the list. The inter prediction unit 230 may not add the motion information of the spatial candidate to the list when the reference position of the target block is out of the region.

The region may be a region of a slice including the target block, a region of a tile including the target block, or an MCTS region including the target block.

In an embodiment, if the reference position of the target block does not deviate from the boundary, the inter prediction unit 230 may add motion information of the spatial candidate to the list. The inter prediction unit 230 may not add the motion information of the spatial candidate to the list when the reference position of the target block is out of the region.

The boundary may include a boundary of a picture. Also, the boundary may include a boundary between slices, a boundary between tiles, or a boundary between MCTSs.

Spatial candidates may be plural. The plurality of spatial candidates may be A ₁ , B ₁ , B ₀ , A ₀ and B ₂ .

If the number of motion information in the list is less than the set maximum number, steps 1810 and 1820 may be sequentially repeated for a plurality of spatial candidates.

In operation 1830, the inter prediction unit 230 may determine whether motion information of the temporal candidate is added to the list.

When it is determined that the motion information of the temporal candidate is added to the list, step 1840 may be performed.

If it is determined that the motion information of the temporal candidate is not to be added to the list, step 1850 may be performed.

In operation 1840, when it is determined to add the motion information of the temporal candidate to the list, the inter prediction unit 230 may add the motion information of the temporal candidate to the list.

Through steps 1830 and 1840, motion information of a temporal candidate may be added to the list.

In an embodiment, in steps 1830 and 1840, the inter prediction unit 230 may determine whether the motion information of the temporal candidate is added to the list based on the information on the target block and the motion information of the temporal candidate. .

Hereinafter, the motion vector of the temporal candidate may be a scaled motion vector.

In an embodiment, the information on the target block may be a location of the target block. The inter prediction unit 230 may determine whether the motion information of the temporal candidate is added to the list based on the position of the target block and the motion vector of the temporal candidate.

In an embodiment, the inter prediction unit 230 may determine whether the motion information of the temporal candidate is to be added to the list based on the motion prediction boundary check for the target block and the temporal candidate.

In an embodiment, the inter prediction unit 230 may determine whether the motion information of the temporal candidate is to be added to the list based on the position indicated by the motion vector applied to the target block. Here, the applied motion vector may be a motion vector of motion information of a temporal candidate.

The position or reference position indicated by the motion vector may be a position in the reference picture referenced by the target block.

In an embodiment, when the reference position of the target block is within the region, the inter prediction unit 230 may add motion information of the temporal candidate to the list. The inter prediction unit 230 may not add the motion information of the temporal candidate to the list when the reference position of the target block is out of the region.

In an embodiment, if the reference position of the target block does not deviate from the boundary, the inter prediction unit 230 may add the motion information of the temporal candidate to the list. The inter prediction unit 230 may not add the motion information of the temporal candidate to the list when the reference position of the target block is out of the region.

The temporal candidate may be the aforementioned first collocated block or the second collocated block. If the first collocated block is available, the temporal candidate may be the first collocated block. When the first collocated block is not available and the second collocated block is available, the temporal candidate may be the second collocated block. That is, the first collocated block may be used preferentially compared to the second collocated block.

If the number of motion information in the list is the same as the set maximum number before step 1830 is performed, steps 1830 , 1840 , 1850 , 1860 , 1870 and 1880 may not be performed, and motion information of a temporal candidate may not be included in the list.

The above-described steps 1810 , 1820 , 1830 and 1840 may be replaced with first and second steps for a plurality of spatial candidates and temporal candidates.

In a first step, the inter prediction unit 230 may determine whether motion information of a candidate block is to be added to the list.

In the second step, when the motion information of the candidate block is determined to be added to the list, the motion information may be added to the list.

The candidate block may include a plurality of spatial candidates and temporal candidates.

The first step and the second step may be sequentially and repeatedly performed for a plurality of spatial candidates and temporal candidates. The first step and the second step may be performed repeatedly until the first step is performed for all the plurality of spatial candidates and the temporal candidates, or the number of motion information in the list reaches a set maximum number.

In an embodiment, the inter prediction unit 230 may determine whether motion information of the candidate block is to be added to the list based on the availability of the candidate block. If the candidate block is not available, the inter prediction unit 230 may not add motion information of the candidate block to the list. The inter prediction unit 230 may add the motion information of the candidate block to the list if the candidate block is available and the motion information of the candidate block does not overlap with other motion information existing in the list.

In one embodiment, the determination of whether a motion vector is out of bounds or a corresponding determination may relate to a determination of availability. For example, even if the motion vector of the candidate block satisfies another condition for availability, the inter prediction unit 230 may determine whether the candidate block is available according to the result of the motion prediction boundary check. The determination of availability is described in detail below with reference to FIG. 20 .

In one embodiment, the determination or a corresponding determination as to whether the motion vector is out of bounds may be separate from the availability determination. For example, the inter prediction unit 230 for the availability of the candidate block may determine whether motion information of the candidate block is added to the list according to the result of the motion prediction boundary check, even if the candidate block is available.

Before the first and second steps are performed for all of the plurality of spatial candidates and the temporal candidates, if the number of motion information in the list reaches the set maximum number, the remaining candidates may not be checked for availability.

In operation 1850, the inter prediction unit 230 may determine whether the combined motion information generated by the combined bidirectional prediction is added to the list of motion information.

If it is determined that the combined motion information is to be added to the list, step 1860 may be performed.

If it is determined that the combined motion information is not to be added to the list, step 1870 may be performed.

In operation 1860 , when it is determined to add the combined motion information to the list, the inter prediction unit 230 may add the combined motion information to the list.

The inter prediction unit 230 1) the number of motion information in the list is less than the set maximum number, 2) the combined motion information can be generated by combined bidirectional prediction using the motion information in the list, and 3) the combination If the combined motion information does not overlap with other motion information in the list, the combined motion information may be added to the list.

In this case, each of the motion information in the list may be motion information that has already passed the motion prediction boundary check. Accordingly, the combined motion information generated by the combined bidirectional prediction using the motion information in the list may pass the motion prediction boundary check. Alternatively, the inter prediction unit 230 may perform a motion prediction boundary check on the combined motion information, and add only the combined motion information that has passed the motion prediction boundary check to the list.

Steps 1850 and 1860 may be performed only when the type of the target slice is “B”.

The combined motion information may be plural.

As described above, according to a predefined order, a plurality of combined motion information may be generated. Steps 1850 and 1860 may be sequentially and repeatedly performed for a plurality of combined motion information. Steps 1850 and 1860 may be repeatedly performed until all possible combined motion information is added to the list or the number of motion information in the list reaches a set maximum number.

In operation 1870, the inter prediction unit 230 may determine whether zero vector motion information is added to the list.

If it is determined that the zero vector motion information is to be added to the list, step 1880 may be performed.

If it is determined that the zero vector motion information is not to be added to the list, the procedure may end.

In operation 1880, when it is determined to add the zero vector motion information to the list, the inter prediction unit 230 may add the zero vector motion information to the list.

The inter prediction unit 230 determines that 1) the number of motion information in the list is less than the set maximum number, 2) zero vector motion information can be generated, and 3) the zero vector motion information does not overlap with other motion information in the list. , zero vector motion information can be added to the list.

There may be a plurality of zero vector motion information.

Steps 1870 and 1880 may be sequentially and repeatedly performed for a plurality of zero vector motion information. Steps 1870 and 1880 may be repeatedly performed until all possible zero vector motion information is added to the list or the number of motion information in the list reaches a set maximum number.

19 is a flowchart of a method of generating a prediction motion vector candidate list for inter prediction of a target block according to an embodiment.

Step 1730 described above with reference to FIG. 17 may include steps 1910 , 1920 , 1930 , 1940 , 1970 and 1980 to be described below.

In this embodiment, the intra prediction mode of the target block may be AMVP mode. The list may be a predictive motion vector candidate list. The motion information of the candidate block may correspond to the prediction motion vector candidate.

Steps 1910 , 1920 , 1930 , 1940 , 1970 and 1980 may correspond to steps 1810 , 1820 , 1830 , 1840 , 1870 and 1880 described above with reference to FIG. 18 , respectively. That is to say, the description of steps 1810 , 1820 , 1830 , 1840 , 1870 and 1880 may also apply to steps 1910 , 1920 , 1930 , 1940 , 1970 and 1980 . Redundant descriptions are omitted, and differences between steps 1810 , 1820 , 1830 , 1840 , 1870 and 1880 and steps 1910 , 1920 , 1930 , 1940 , 1970 and 1980 are described below.

In operation 1910, the inter prediction unit 230 may determine whether motion information of the spatial candidate is added to the list.

When it is determined that the motion information of the spatial candidate is added to the list, step 1920 may be performed.

If it is determined that the motion information of the spatial candidate is not to be added to the list, step 1930 may be performed.

Spatial candidates may be plural. The plurality of spatial candidates may include a first spatial candidate and a second spatial candidate. The first spatial candidate may be one of A ₀ , A ₁ , scaled A ₀ and scaled A ₁ . The second spatial candidate may be one of B ₀ , B ₁ , B ₂ , scaled B ₀ , scaled B ₁ , and scaled B ₂ .

If the number of motion information in the list is less than the set maximum number, steps 1910 and 1920 may be sequentially repeated for a plurality of spatial candidates.

In operation 1930, the inter prediction unit 230 may determine whether motion information of the temporal candidate is to be added to the list.

When it is determined that the motion information of the temporal candidate is added to the list, step 1940 may be performed.

When it is determined that the motion information of the temporal candidate is not to be added to the list, step 1970 may be performed.

In operation 1940, when it is determined to add the motion information of the temporal candidate to the list, the inter prediction unit 230 may add the motion information of the temporal candidate to the list.

Through steps 1930 and 1940, the motion information of the temporal candidate may be added to the list.

If the number of motion information in the list is the same as the set maximum number before step 1930 is performed, steps 1930, 1940, 1970 and 1980 may not be performed, and the motion information of the temporal candidate is included in the list it may not be

For example, if both the first spatial candidate and the second spatial candidate are available and the motion information of the first spatial candidate and the motion information of the second spatial candidate do not overlap, the motion information of the first spatial candidate and the second spatial candidate Both of the motion information of can be added to the list. In this case, when the set maximum number is 2, a temporal candidate may not be derived, and motion information of the temporal candidate may not be added to the list.

The steps 1910 , 1920 , 1930 and 1940 described above may be replaced with first and second steps for a plurality of spatial candidates and temporal candidates.

In a first step, the inter prediction unit 230 may determine whether motion information of a candidate block is to be added to the list.

In the second step, when the motion information of the candidate block is determined to be added to the list, the motion information may be added to the list.

In operation 1970, the inter prediction unit 230 may determine whether zero vector motion information is added to the list.

If it is determined that the zero vector motion information is to be added to the list, step 1980 may be performed.

If it is determined that the zero vector motion information is not to be added to the list, the procedure may end.

In operation 1980, when it is determined to add the zero vector motion information to the list, the inter prediction unit 230 may add the zero vector motion information to the list.

Steps 1970 and 1980 may be sequentially and repeatedly performed for a plurality of zero vector motion information. Steps 1970 and 1980 may be repeatedly performed until all possible zero vector motion information is added to the list or the number of motion information in the list reaches a set maximum number.

20 is a flowchart of a method of determining availability of a candidate block for inter prediction of a target block according to an embodiment.

The candidate block may include the aforementioned spatial candidates and temporal candidates.

In operation 2010, the inter prediction unit 230 may check whether a sample including a candidate block exists within a boundary of a picture.

If the sample including the candidate block exists within the boundary of the picture, step 2020 may be performed.

If the sample including the candidate block does not exist within the boundary of the picture, operation 2060 may be performed.

In operation 2020, the inter prediction unit 230 may check whether an object including a candidate block exists within a boundary of a region.

The object including the candidate block may be a PU. In other words, the subject providing the motion information may be a PU.

The region may be a region of a slice including the target block, a region of a tile including the target block, or an MCTS region including the target block.

If the object including the candidate block exists within the boundary of the region, operation 2030 may be performed.

If the object including the candidate block does not exist within the boundary of the region, operation 2060 may be performed.

The region may be a plurality of regions among a slice region including the target block, a tile region including the target block, or an MCTS region including the target block. In this case, if the object including the candidate block exists within a plurality of boundaries of a plurality of regions, operation 2030 may be performed. When the object including the candidate block does not exist within at least one boundary among the plurality of boundaries of the plurality of regions, operation 2060 may be performed.

In operation 2030, the inter prediction unit 230 may check whether the prediction mode of the object including the candidate block is the inter mode.

When the prediction mode of the object including the candidate block is the inter mode, operation 2040 may be performed.

When the prediction mode of the object including the candidate block is not the inter mode, operation 2060 may be performed.

In operation 2040, the inter prediction unit 230 may determine whether a point indicated by a motion vector of an object including the candidate block exists within the boundary of the region.

When the point indicated by the motion vector of the object including the candidate block exists within the boundary of the region, operation 2050 may be performed.

When the point indicated by the motion vector of the object including the candidate block does not exist within the boundary of the region, operation 2060 may be performed.

In operation 2050 , the inter prediction unit 230 may set the availability of the candidate block to “true”. In other words, the inter prediction unit 230 may set the candidate block to be available.

In operation 2060 , the inter prediction unit 230 may set the availability of the candidate block to “false”. In other words, the inter prediction unit 230 may set the candidate block to be unavailable.

In other words, in steps 201 , 2020 , 2030 and 2040 , the inter prediction unit 230 may determine whether a candidate block is available, and in steps 2050 and 2060 , the inter prediction unit ( 230) may set the availability of the candidate block according to the result of the determination.

According to operation 2040, the availability of the candidate block may be determined based on information on the target block and motion information on the object including the candidate block.

In an embodiment, the information on the target block may be a location of the target block. The inter prediction unit 230 may determine whether a candidate block is available based on the position of the target block and the motion vector of the object.

In an embodiment, the inter prediction unit 230 may determine whether a candidate block is available based on a motion prediction boundary check for the target block and the object.

In an embodiment, the inter prediction unit 230 may determine whether a candidate block is available based on a position indicated by a motion vector applied to the target block. Here, the applied motion vector may be a motion vector of motion information of an object.

Here, the position indicated by the motion vector may be a position determined by adding the motion vector to the position of the target block.

Also, a position indicated by a motion vector applied to the target block may be a reference position of the target block.

The position or reference position indicated by the motion vector may be a position in the reference picture referenced by the target block.

In an embodiment, the inter prediction unit 230 may determine that the candidate block is available when the reference position of the target block is within the region. The inter prediction unit 230 may determine that the candidate block is not available when the reference position of the target block is out of the region.

The region may be a region of a slice including the target block, a region of a tile including the target block, or an MCTS region including the target block.

In an embodiment, the inter prediction unit 230 may determine that the candidate block is available if the reference position of the target block does not deviate from the boundary. The inter prediction unit 230 may determine that the candidate block is not available when the reference position of the target block is out of the region.

The boundary may include a boundary of a picture. Also, the boundary may include a boundary between slices, a boundary between tiles, or a boundary between MCTSs.

The order of the above-described steps 2010, 2020, 2030, 2040 is merely exemplary, and the order of the above-described steps 2010, 2020, 2030, 2040 may be arbitrarily changed.

21 shows a merge list to which a motion prediction boundary check is applied according to an example.

Referring to the merge list of FIG. 16 , as described above with reference to FIG. 16 , motion information in the second row 1620 , the third row 1630 , and the fourth row 1640 of the merge list passes the motion prediction boundary check. may not be able to Accordingly, the motion information of the second row 1620 , the third row 1630 , and the fourth row 1640 may not be added to the merge list of FIG. 21 .

In addition, the motion information of the fifth row 1650 is combined motion information generated by the combined bidirectional prediction on the motion information of the first row 1610 and the motion information of the second row 1620 , the second row Since the motion information of 1620 does not pass the motion prediction boundary check, the combined motion information of the fifth row 1650 may not be generated.

Accordingly, only motion information corresponding to the first row 1610 may exist in the merge list of FIG. 21 .

Since there is only one motion information added to the merge list among motion information of spatial candidates, motion information of temporal candidates, and combined motion information, zero vector motion information may be added to the merge list.

When the number of reference pictures is 2, zero vector motion information having a reference picture index of 0 and zero vector motion information having a reference picture index of 1 may be added to the merge list.

As illustrated in FIG. 21 , through the above-described embodiments, only motion information that does not cross a boundary among available motion information may be added to the list, and the merge list may include only useful motion information. In other words, while the merge list of FIG. 16 includes only one piece of motion information that can be actually used, all three pieces of motion information of the merge list of FIG. 21 can be effectively used. Accordingly, encoding efficiency may be improved by the merge list of FIG. 21 .

22 is a structural diagram of an electronic device implementing an encoding 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 decoding of the encoding apparatus 100 . At least some of the unit 150 , the inverse quantizer 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 an external device or system. can communicate with The program modules may be included in the encoding apparatus 100 in the form of an operating system, an application program module, and other program modules.

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

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. It may include, but is not limited to, a data structure and the like.

The program modules may include instructions or codes that are executed by at least one processor of the encoding apparatus 100 .

The encoding device 100 may be implemented as the electronic device 2200 illustrated in FIG. 22 . The electronic device 2200 may be a general-purpose computer system operating as the encoding device 100 .

As shown in FIG. 22 , the electronic device 2200 includes a processing unit 2210 , a memory 2230 , a user interface (UI) input device 2250 , and a UI output device that communicate with each other through a bus 2290 . 2260 and storage 2240 . Also, the electronic device 2200 may further include a communication unit 2220 connected to the network 2299 .

The processor 2220 may be a semiconductor device that executes processing instructions stored in a central processing unit (CPU), the memory 2230 , or the storage 2240 . The processing unit 2220 may be at least one hardware processor.

The processing unit 2220 may be input to the electronic device 2200 , output from the electronic device 2200 , or generate and process signals, data, or information of the electronic device 2200 , and may Related inspections, comparisons and judgments may be performed. In other words, in the embodiment, generation and processing of data or information, and inspection, comparison, and judgment related to data or information may be performed by the processing unit 10 .

For example, the processing unit 2220 may perform the steps of FIGS. 17 , 18 , 19 and 20 .

Storage may represent memory 2230 and/or storage 2240 . The memory 2230 and the storage 2240 may be various types of volatile or non-volatile storage media. For example, the memory may include at least one of a ROM 2231 and a RAM 2232 .

The storage unit may store data or information used for an operation of the electronic device 2200 . In an embodiment, data or information possessed by the electronic device 2200 may be stored in the storage unit.

For example, the storage unit may store pictures, blocks, lists, motion information, inter prediction information, and bitstreams.

The electronic device 2200 may be implemented in a computer system including a recording medium that can be read by a computer.

The recording medium may store at least one module required for the electronic device 2200 to operate as the encoding device 100 . The memory 2230 may store at least one module and may be configured to be executed by the processing unit 2210 .

A function related to communication of data or information of the electronic device 2200 may be performed through the communication unit 2220 .

For example, the communication unit 2220 may transmit a bitstream including inter prediction information and the like to the decoding apparatus 200 .

23 is a structural diagram of an electronic device implementing a decoding device according to an embodiment.

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 . , at least some of the filter unit 260 and the reference picture buffer 270 may be program modules, and may communicate with an external device or system. The program modules may be included in the decryption apparatus 200 in the form of an operating system, an application program module, and other program modules.

Program modules may be physically stored on various known storage devices. Also, at least some of these program modules may be stored in a remote storage device capable of communicating with the decryption 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. It may include, but is not limited to, a data structure and the like.

The program modules may include instructions or codes that are executed by at least one processor of the decryption apparatus 200 .

The decryption apparatus 200 may be implemented as the electronic device 2300 illustrated in FIG. 23 . The electronic device 2300 may be a general-purpose computer system operating as the encoding device 100 .

As shown in FIG. 23 , the electronic device 2300 includes a processing unit 2310 , a memory 2330 , a user interface (UI) input device 2350 , and a UI output device that communicate with each other through a bus 2390 . 2360 and storage 2340 . Also, the electronic device 2300 may further include a communication unit 2320 connected to the network 2399 .

The processing unit 2320 may be a semiconductor device that executes processing instructions stored in a central processing unit (CPU), the memory 2330 , or the storage 2340 . The processing unit 2320 may be at least one hardware processor.

The processing unit 2320 may be input to, output from, or output from the electronic device 2300, or generate and process signals, data, or information of the electronic device 2300, and may Related inspections, comparisons and judgments may be performed. In other words, in the embodiment, generation and processing of data or information, and inspection, comparison, and judgment related to data or information may be performed by the processing unit 10 .

For example, the processing unit 2320 may perform the steps of FIGS. 17 , 18 , 19 and 20 .

Storage may represent memory 2330 and/or storage 2340 . The memory 2330 and the storage 2340 may be various types of volatile or non-volatile storage media. For example, the memory may include at least one of a ROM 2331 and a RAM 2332 .

The storage unit may store data or information used for an operation of the electronic device 2300 . In an embodiment, data or information possessed by the electronic device 2300 may be stored in the storage unit.

For example, the storage unit may store pictures, blocks, lists, motion information, inter prediction information, and bitstreams.

The electronic device 2300 may be implemented in a computer system including a recording medium that can be read by a computer.

The recording medium may store at least one module required for the electronic device 2300 to operate as the decryption device 200 . The memory 2330 may store at least one module and may be configured to be executed by the processing unit 2210 .

A function related to communication of data or information of the electronic device 2300 may be performed through the communication unit 2320 .

For example, the communication unit 2320 may receive a bitstream including inter prediction information and the like from the encoding apparatus 100 .

In the above-described embodiments, the methods are described on the basis of a flowchart 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 at the same time as other steps as described above. can In addition, those of ordinary skill in the art will recognize that the steps shown in the flowchart are not exclusive, other steps may be included, or that one or more steps in the flowchart may be deleted without affecting the scope of the present invention. You will understand.

The 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 in a computer-readable recording medium. The computer-readable recording medium may include program instructions, data files, data structures, etc. alone or in combination. The program instructions recorded on the computer-readable recording medium may be specially designed and configured for the present invention, or may be known and available to those skilled in the computer software field. Examples of the computer-readable recording medium include a hard disk, a magnetic medium such as a floppy disk and a magnetic tape, an optical recording medium such as a CD-ROM and DVD, and a magneto-optical medium such as a floppy disk. media), and hardware devices specially configured to store and execute program instructions, such as ROM, RAM, flash memory, and the like. Examples of program instructions include not only machine language codes such as those generated by a compiler, but also high-level language codes that can be executed by a computer using an interpreter or the like. The hardware device may be configured to operate as one or more software modules for carrying out the processing according to the present invention, and vice versa.

In the above, the present invention has been described with specific matters 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. , various modifications and variations can be devised from these descriptions by those of ordinary skill in the art to which the present invention pertains.

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

Claims (19)

generating a merge list for the target block; and
Determining motion information of the target block using the merge list and the merge index
including,
The merge index indicates a merge candidate for inter prediction for the target block among the merge candidates in the merge list,
A decoding method in which it is determined whether or not motion information of the candidate block is added to the merge list based on information on the candidate block. According to claim 1,
Whether the motion information of the candidate block is added to the list is determined by whether the position of the candidate block is within a boundary. 3. The method of claim 2,
If the location is not within the boundary, the availability of the candidate block is set to false. 4. The method of claim 3,
The boundary is a boundary of a region generated by dividing a picture. 3. The method of claim 2,
The position is a decoding method for determining the candidate block. According to claim 1,
wherein the motion information is motion information of a temporal candidate. generating a merge list for the target block; and
generating a merge index indicating a merge candidate corresponding to the motion information of the target block among the merge candidates in the merge list;
including,
An encoding method in which it is determined whether or not motion information of the candidate block is added to the merge list based on information on the candidate block. 8. The method of claim 7,
Whether the motion information of the candidate block is added to the list is determined by whether the position of the candidate block is within a boundary. 9. The method of claim 8,
and the availability of the candidate block is set to false if the location is not within the boundary. 10. The method of claim 9,
The boundary is a boundary of a region generated by dividing a picture. 9. The method of claim 8,
The position is an encoding method for determining the candidate block. 8. The method of claim 7,
wherein the motion information is motion information of a temporal candidate. A recording medium for recording a bitstream generated by the encoding method according to claim 7. A computer-readable recording medium for storing a bitstream, comprising:
The bitstream is
A merge index indicating a merge candidate for inter prediction of a target block among merge candidates in the merge list
including,
The merge list is created,
Motion information of the target block is determined using the merge list and the merge index,
Inter prediction is performed on the target block using motion information of the target block,
A computer-readable recording medium in which it is determined whether or not motion information of the candidate block is added to the merge list based on the information on the candidate block. 15. The method of claim 14,
Whether the motion information of the candidate block is added to the list is determined by whether the position of the candidate block is within a boundary. 16. The method of claim 15,
and the availability of the candidate block is set to false if the location is not within the boundary. 17. The method of claim 16,
The boundary is a boundary of an area created by division for a picture. 16. The method of claim 15,
The location determines the candidate block. 15. The method of claim 14,
wherein the motion information is motion information of a temporal candidate.

Images