WO2018026118A1 - Image encoding/decoding method - Google Patents

Abstract

The present invention relates to a method for carrying out motion compensation using motion vector prediction. An image decoding method therefor may comprise the steps of: acquiring a residual signal quantized for the current block; inverse-quantizing the quantized residual signal; and determining a transformation scheme for inverse-transforming the residual signal. The inverse transformation comprises a primary transformation and secondary transformation, and at least one from among a primary transformation scheme and secondary transformation scheme can be derived from a reconstructed block, around the current block, for which decoding is complete.

Description

Image coding / decoding method

The present invention relates to a method and apparatus for encoding / decoding an image, and more particularly, to a method and apparatus for deriving encoding information of a current block by using encoding information of a neighboring block.

Recently, the demand for high resolution and high quality images such as high definition (HD) and ultra high definition (UHD) images is increasing in various applications. As the video data becomes higher resolution and higher quality, the amount of data increases relative to the existing video data. Therefore, when the video data is transmitted or stored using a medium such as a conventional wired / wireless broadband line, The storage cost will increase. In order to solve these problems caused by high resolution and high quality image data, a high efficiency image encoding / decoding technique for an image having a higher resolution and image quality is required.

 An inter-screen prediction technique for predicting pixel values included in the current picture from a picture before or after the current picture using an image compression technology, an intra-picture prediction technology for predicting pixel values included in the current picture using pixel information in the current picture, There are various techniques such as transformation and quantization techniques for compressing the energy of the residual signal, entropy coding technique for assigning short codes to high-frequency values and long codes for low-frequency values. Image data can be effectively compressed and transmitted or stored.

In the conventional motion compensation, only spatial motion vector candidates, temporal motion vector candidates, and zero motion vector candidates are added to the motion vector candidate list, and only unidirectional prediction and bidirectional prediction are used, thereby improving coding efficiency.

An object of the present invention is to provide a method and apparatus for deriving encoding information of a current block from a reconstruction block around a current block.

It is an object of the present invention to provide a method and apparatus for encoding / decoding a difference value between a motion vector difference value around a current block and a motion vector difference value of a current block.

According to an embodiment of the present invention, an image encoding method includes generating a prediction signal for a current block, generating a residual signal for the current block based on the prediction signal, and converting the residual signal. Determining, and quantizing the residual signal. In this case, the transform may include a first-order transform and a second-order transform, and at least one of the first-order transform technique and the second-order transform technique may be derived from a reconstructed block in which encoding around the current block is completed.

An image decoding method according to the present invention may include obtaining a quantized residual signal for a current block, inversely quantizing the quantized residual signal, and determining a conversion technique for inversely transforming the residual signal. Can be. In this case, the inverse transform includes a first-order transform and a second-order transform, and at least one of the first-order transform technique and the second-order transform technique may be derived from a decoded reconstruction block around the current block.

In the image encoding method or the image decoding method, when the current block is encoded by intra prediction, at least one of the first transform method and the second transform method may have a periphery in which the intra prediction mode is the same as the current block. Can be derived from a block.

In the image encoding method or the image decoding method, when the first transform scheme of a neighboring block having the same intra prediction mode as the current block indicates a transform skip, the first transform scheme and the second order for the current block The transformation technique may be determined by the transformation skip.

In the image encoding method or the image decoding method, in the second transform scheme, the first transform scheme may be derived from a neighboring block that is the same as the current block.

In the video encoding method or the video decoding method, when the current block is encoded by inter-screen prediction, at least one of the first transform method and the second transform method may be obtained from a neighboring block whose motion information is the same as that of the current block. Can be induced.

In the video encoding method or the video decoding method, the motion information may include at least one of a motion vector, a reference picture index, or a reference picture direction.

According to the present invention, by providing a method and apparatus for deriving encoding information of a current block from a reconstructed block around a current block, an encoding / decoding efficiency can be improved.

According to the present invention, by providing a method and apparatus for encoding / decoding a difference value between a motion vector difference value around a current block and a motion vector difference value of the current block, an encoding / decoding efficiency can be improved.

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

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

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

FIG. 4 is a diagram illustrating a form of a prediction unit PU that may be included in the coding unit CU.

FIG. 5 is a diagram illustrating a form of a transform unit (TU) that a coding unit CU may include.

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

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

8 is a diagram for describing a transform set according to an intra prediction mode.

9 is a view for explaining the process of the conversion.

10 is a diagram for describing scanning of quantized transform coefficients.

11 is a diagram for explaining block division.

12 is a diagram illustrating a coding / decoding unit according to a partition type of a block.

13 is a flowchart illustrating a process of determining whether to decode information related to binary tree splitting.

14 is a flowchart illustrating a process of determining whether to decode information related to binary tree partitioning.

15 to 17 are diagrams for explaining an example in which binary tree splitting is no longer performed on a block having a predetermined size or less.

18 is a flowchart illustrating a process of determining whether to encode encoding information about a residual signal of a current block from a neighboring block when the current block is encoded by intra prediction.

19 is a flowchart illustrating a process of determining whether to derive encoding information about a residual signal of a current block from a neighboring block when the current block is encoded by inter-screen prediction.

20 is a flowchart illustrating a process of decoding a motion vector of a current block.

21 is a diagram for explaining an example of deriving a spatial motion vector candidate.

22 is a diagram for explaining an example of deriving a temporal motion vector candidate.

FIG. 23 is a diagram for describing a second motion vector difference value. FIG.

As the invention allows for various changes and numerous embodiments, particular embodiments will be illustrated in the drawings and described in detail in the written description. However, this is not intended to limit the present invention to specific embodiments, it should be understood to include all modifications, equivalents, and substitutes included in the spirit and scope of the present invention. Like reference numerals in the drawings refer to the same or similar functions throughout the several aspects. Shape and size of the elements in the drawings may be exaggerated for clarity. DETAILED DESCRIPTION For the following detailed description of exemplary embodiments, reference is made to the accompanying drawings that show, by way of illustration, specific embodiments. These embodiments are described in sufficient detail to enable those skilled in the art to practice the embodiments. It should be understood that the various embodiments are different but need not be mutually exclusive. For example, certain shapes, structures, and characteristics described herein may be embodied in other embodiments without departing from the spirit and scope of the invention with respect to one embodiment. In addition, it is to be understood that the location or arrangement of individual components within each disclosed embodiment may be changed without departing from the spirit and scope of the embodiments. The following detailed description, therefore, is not to be taken in a limiting sense, and the scope of the exemplary embodiments, if properly described, is defined only by the appended claims, along with the full scope of equivalents to which such claims are entitled.

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

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

The components shown in the embodiments of the present invention are shown independently to represent different characteristic functions, and do not mean that each component is made of separate hardware or one software component unit. In other words, each component is included in each component for convenience of description, and at least two of the components may be combined into one component, or one component may be divided into a plurality of components to perform a function. Integrated and separate embodiments of the components are also included within the scope of the present invention without departing from the spirit of the invention.

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

Some components of the present invention are not essential components for performing essential functions in the present invention but may be optional components for improving performance. The present invention can be implemented including only the components essential for implementing the essentials of the present invention except for the components used for improving performance, and the structure including only the essential components except for the optional components used for improving performance. Also included in the scope of the present invention.

EMBODIMENT OF THE INVENTION Hereinafter, embodiment of this invention is described concretely with reference to drawings. In describing the embodiments of the present specification, when it is determined that a detailed description of a related well-known configuration or function may obscure the gist of the present specification, the detailed description is omitted and the same reference numerals are used for the same elements in the drawings. Duplicate descriptions of the same components are omitted.

Also, hereinafter, an image may mean one picture constituting a video and may represent 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 of images constituting the video." It may be. Here, the picture may have the same meaning as the image.

Term description

Encoder: This may mean an apparatus for performing encoding.

Decoder: Refers to an apparatus for performing decoding.

Parsing: This may mean determining a value of a syntax element by entropy decoding or may refer to entropy decoding itself.

Block: An MxN array of samples, where M and N are positive integer values, and a block can often mean a two-dimensional sample array.

Sample: This is a basic unit constituting the block, and can represent values from 0 to 2Bd-1 depending on the bit depth (Bd). In the present invention, the pixel and the pixel may be used as the sample.

Unit: may mean a unit of image encoding and decoding. In encoding and decoding of an image, a unit may be an area generated by division of one image. In addition, a unit may mean a divided unit when a single image is divided into subdivided units to be encoded or decoded. In encoding and decoding of an image, a predetermined process may be performed for each unit. One unit may be further divided into subunits having a smaller size than the unit. Depending on the function, the unit may be a block, a macroblock, a coding tree unit, a coding tree block, a coding unit, a coding block, a prediction. It may mean a unit, a prediction block, a transform unit, a transform block, or the like. In addition, the unit may refer to a luma component block, a chroma component block corresponding thereto, and a syntax element for each block in order to refer to the block separately. The unit may have various sizes and shapes, and in particular, the shape of the unit may include a geometric figure that can be expressed in two dimensions such as a square, a trapezoid, a triangle, a pentagon, as well as a rectangle. In addition, the unit information may include at least one of a type of a unit indicating a coding unit, a prediction unit, a transformation unit, and the like, a size of a unit, a depth of a unit, an encoding and decoding order of the unit, and the like.

Reconstructed Neighbor Unit: A reconstructed neighbor unit may refer to a unit that has already been encoded or decoded in a spatial / temporal manner around the encoding / decoding target unit. In this case, the restored peripheral unit may mean a restored peripheral block.

Neighbor block: A neighbor block may mean a block adjacent to an encoding / decoding target block. The block adjacent to the encoding / decoding object block may mean a block in which a boundary of the encoding / decoding object block abuts. The neighboring block may mean a block located at an adjacent vertex of the encoding / decoding target block. The neighboring block may mean a restored neighboring block.

Unit Depth: It means the degree of unit division. In the tree structure, the root node has the smallest depth, and the leaf node has the deepest depth.

Symbol: This may mean a encoding / decoding target unit syntax element, a coding parameter, a value of a transform coefficient, or the like.

Parameter set: may correspond to header information among structures in the bitstream, and includes a video parameter set, a sequence parameter set, a picture parameter set, and an adaptive parameter set. At least one or more of the adaptation parameter set may be included in the parameter set. In addition, the parameter set may have a meaning including slice header and tile header information.

Bitstream: A bitstream may mean a string of bits including encoded image information.

Prediction Unit: This is a basic unit when performing inter prediction or intra prediction and compensation thereof, and one prediction unit may be divided into a plurality of partitions having a small size. In this case, each of the plurality of partitions becomes a basic unit at the time of performing the prediction and compensation, and the partition in which the prediction unit is divided may also be called a prediction unit. The prediction unit may have various sizes and shapes, and in particular, the shape of the prediction unit may include a geometric figure that can be expressed in two dimensions such as a square, a trapezoid, a triangle, a pentagon, as well as a rectangle.

Prediction Unit Partition: This may mean a form in which a prediction unit is divided.

Reference Picture List: Refers to a list including one or more reference pictures used for inter prediction or motion compensation. The types of reference picture lists may be LC (List Combined), L0 (List 0), L1 (List 1), L2 (List 2), L3 (List 3), and the like. Lists can be used.

Inter Prediction Indicator: It may mean the inter prediction direction (unidirectional prediction, bi-directional prediction, etc.) of the block to be encoded / decoded during inter prediction, and the block to be encoded / decoded will generate the prediction block. This may mean the number of reference pictures used, and may mean the number of prediction blocks used when the encoding / decoding target block performs inter prediction or motion compensation.

Reference Picture Index: A reference picture index may mean an index of a specific reference picture in the reference picture list.

Reference Picture: Refers to an image referred to by a specific unit for inter prediction or motion compensation. The reference picture may also be referred to as a reference picture.

Motion Vector: A two-dimensional vector used for inter prediction or motion compensation, and may mean an offset between an encoding / decoding target image and a reference image. For example, (mvX, mvY) may represent a motion vector, mvX may represent a horizontal component, and mvY may represent a vertical component.

Motion Vector Candidate: When a motion vector is predicted, it may mean a unit which is a prediction candidate or a motion vector of the unit.

Motion Vector Candidate List: A motion vector candidate list may mean a list constructed using motion vector candidates.

Motion Vector Candidate Index: An indicator indicating a motion vector candidate in a motion vector candidate list, and may be referred to as an index of a motion vector predictor.

Motion Information: Information including at least one of a motion vector, a reference picture index, an inter prediction indicator, as well as reference picture list information, a reference picture, a motion vector candidate, and a motion vector candidate index. It may mean.

Merge Candidate List: A merge candidate list may mean a list constructed using merge candidates.

Merge Candidate: may include a spatial merge candidate, a temporal merge candidate, a combined merge candidate, a combined two-prediction merge candidate, a zero merge candidate, and the like. The merge candidate may include prediction type information, each of which is a prediction type information. It may include motion information such as a reference picture index and a motion vector for the list.

Merge Index: Refers to information indicating a merge candidate in the merge candidate list. In addition, the merge index may indicate a block in which a merge candidate is derived among blocks reconstructed adjacent to the current block in a spatial / temporal manner. In addition, the merge index may indicate at least one or more of the motion information that the merge candidate has.

Transform Unit: A transform unit may refer to a basic unit when performing residual signal encoding / decoding such as transform, inverse transform, quantization, inverse quantization, and transform coefficient encoding / decoding. It may be divided into a plurality of transform units having a small size. The transform unit may have various sizes and shapes, and in particular, the shape of the transform unit may include a geometric figure that can be expressed in two dimensions such as a square, a trapezoid, a triangle, a pentagon, as well as a rectangle.

Scaling: This may mean a process of multiplying a transform coefficient level by a factor and generating a transform coefficient as a result. Scaling can also be called dequantization.

Quantization Parameter: A quantization parameter may mean a value used when scaling transform coefficient levels in quantization and inverse quantization. In this case, the quantization parameter may be a value mapped to a quantization step size.

Residual Quantization Parameter: A quantization parameter may mean a differential value between the predicted quantization parameter and the quantization parameter of the encoding / decoding target unit.

Scan: Refers to a method of arranging the order of coefficients in a block or matrix. For example, aligning a two-dimensional array into a one-dimensional array is called a scan, and a one-dimensional array into a two-dimensional array. Sorting can also be called scan or inverse scan.

Transform Coefficient: A coefficient value generated after performing a transform, and in the present invention, a quantized transform coefficient level in which quantization is applied to the transform coefficient may also be included in the meaning of the transform coefficient.

Non-zero Transform Coefficient: A non-zero transform coefficient may mean a transform coefficient whose magnitude is not zero or a transform coefficient level whose magnitude is not zero.

Quantization Matrix: A matrix used in a quantization or inverse quantization process to improve the subjective or objective image quality of an image. The quantization matrix may also be called a scaling list.

Quantization Matrix Coefficient: It may mean each element in the quantization matrix. Quantization matrix coefficients may also be referred to as matrix coefficients.

Default Matrix: A predetermined matrix may mean a predetermined quantization matrix defined in the encoder and the decoder.

Non-default Matrix: A non-default matrix, which is not defined in advance in the encoder and the decoder, may mean a quantization matrix transmitted / received by a user.

Coding Tree Unit: A coding component may be composed of two color difference component (Cb, Cr) coding tree blocks associated with one luminance component (Y) coding tree block. Each coding tree unit may be split using one or more partitioning methods such as a quad tree and a binary tree to form sub-units such as a coding unit, a prediction unit, and a transform unit. As a segmentation of an input image, it may be used as a term for referring to a pixel block that becomes a processing unit in an image decoding / encoding process.

Coding Tree Block: A term used to refer to any one of a Y coded tree block, a Cb coded tree block, and a Cr coded tree block.

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

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

Referring to FIG. 1, the encoding apparatus 100 may include a motion predictor 111, a motion compensator 112, an intra predictor 120, a switch 115, a subtractor 125, a transformer 130, and quantization. The unit 140 may include an entropy encoder 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 input image in an intra mode and / or an inter mode. In addition, the encoding apparatus 100 may generate a bitstream through encoding of an input image, and may output the generated bitstream. When the intra mode is used as the prediction mode, the switch 115 may be switched to intra, and when the inter mode is used as the prediction mode, the switch 115 may be switched to inter. In this case, the intra mode may mean an intra prediction mode, and the inter mode may mean an inter prediction mode. The encoding apparatus 100 may generate a prediction block for the input block of the input image. In addition, after the prediction block is generated, the encoding apparatus 100 may encode a residual between the input block and the prediction block. The input image may be referred to as a current image that is a target of current encoding. The input block may be referred to as a current block or an encoding target block that is a target of the current encoding.

When the prediction mode is the intra mode, the intra prediction unit 120 may use the pixel value of a block that is already encoded around the current block as a reference pixel. The intra predictor 120 may perform spatial prediction using the reference pixel, and generate prediction samples for the input block through spatial prediction. Intra prediction may refer to intra prediction.

When the prediction mode is the inter mode, the motion predictor 111 may search an area that best matches the input block from the reference image in the motion prediction process, and derive a motion vector using the searched area. . The reference picture may be stored in the reference picture buffer 190.

The motion compensator 112 may generate a prediction block by performing motion compensation using a motion vector. Here, the motion vector may be a two-dimensional vector used for inter prediction. In addition, the motion vector may indicate an offset between the current picture and the reference picture. Here, inter prediction may mean inter prediction.

The motion predictor 111 and the motion compensator 112 may generate a prediction block by applying an interpolation filter to a part of a reference image when the motion vector does not have an integer value. . In order to perform inter prediction or motion compensation, a motion prediction and motion compensation method of a prediction unit included in a coding unit based on a coding unit may be skip mode, merge mode, or AMVP mode. ), It may be determined which method is the current picture reference mode, and inter prediction or motion compensation may be performed according to each mode. Here, the current picture reference mode may mean a prediction mode using a pre-restored region in the current picture to which the encoding target block belongs. A motion vector for the current picture reference mode may be defined to specify the pre-restored region. Whether the encoding target block is encoded in the current picture reference mode may be encoded using the reference image index of the encoding target block.

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

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

Quantized transform coefficient levels may be generated by applying quantization to the transform coefficients. In the following embodiments, the quantized transform coefficient level may also be referred to as transform coefficient.

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

The entropy encoder 150 may generate a bitstream by performing entropy encoding according to probability distribution on values calculated by the quantizer 140 or coding parameter values calculated in the encoding process. And output a bitstream. The entropy encoder 150 may perform entropy encoding on information for decoding an image in addition to information on pixels of an image. For example, the information for decoding the image may include a syntax element.

When entropy encoding is applied, a small number of bits are assigned to a symbol having a high probability of occurrence and a large number of bits are assigned to a symbol having a low probability of occurrence, thereby representing bits for encoding symbols. The size of the heat can be reduced. Therefore, compression performance of image encoding may be increased through entropy encoding. The entropy encoder 150 may use an encoding method such as exponential Golomb, context-adaptive variable length coding (CAVLC), or context-adaptive binary arithmetic coding (CABAC) for entropy encoding. For example, the entropy encoder 150 may perform entropy coding using a variable length coding (VLC) table. Also, the entropy encoder 150 derives a binarization method of a target symbol and a probability model of a target symbol / bin, and then performs arithmetic coding using the derived binarization method or a probability model. You may.

The entropy encoder 150 may change a two-dimensional block shape coefficient into a one-dimensional vector form through a transform coefficient scanning method to encode a transform coefficient level. For example, upright scanning can be used to scan the coefficients of a block to change it into a one-dimensional vector. Depending on the size of the transform unit and the intra prediction mode, a vertical scan that scans two-dimensional block shape coefficients in a column direction instead of an upright scan and a horizontal scan that scans two-dimensional block shape coefficients in a row direction may be used. That is, according to the size of the conversion unit and the intra prediction mode, it is possible to determine which scan method among upright scan, vertical scan and horizontal scan is used.

The coding parameter may include information derived from an encoding or decoding process as well as information encoded by an encoder and transmitted to a decoder, such as a syntax element, and may mean information required when encoding or decoding an image. have. For example, block size, block depth, block splitting information, unit size, unit depth, unit splitting information, quadtree split flag, binary tree split flag, binary tree split direction, intra prediction mode, Intra prediction direction, reference sample filtering method, prediction block boundary filtering method, filter tab, filter coefficient, inter prediction mode, motion information, motion vector, reference image index, inter prediction direction, inter prediction indicator, reference image list , Motion vector predictor, motion vector candidate list, motion merge mode, motion merge candidate, motion merge candidate list, skip mode, interpolation filter type, motion vector size, motion vector representation accuracy , Transform type, transform size, additional (secondary) transform availability information, residual signal presence information, coded block pattern, Coded Block Flag, Quantization Parameter, Quantization Matrix, In-loop Filter Information, In-loop Filter Applicability Information, In-loop Filter Coefficient, Binarization / Debinarization Method, Context Model, Context Bean, Bypass Bean, Transform Coefficient, transform coefficient level, transform coefficient level scanning method, image display / output order, slice identification information, slice type, slice partition information, tile identification information, tile type, tile partition information, picture type, bit depth, luminance signal or color difference At least one or more values or a combined form of the information about the signal may be included in the encoding parameter.

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

When the encoding apparatus 100 performs encoding through inter prediction, the encoded current image may be used as a reference image with respect to other image (s) to be processed later. Therefore, the encoding apparatus 100 may decode the encoded current image again and store the decoded image as a reference image. Inverse quantization and inverse transform on the encoded current image may be processed for decoding.

The quantized coefficients may be dequantized in inverse quantization unit 160. The inverse transform unit 170 may perform an inverse transform. The inverse quantized and inverse transformed coefficients may be summed with the prediction block via the adder 175. A reconstructed block may be generated by adding the inverse quantized and inverse transformed coefficients and the prediction block.

The recovery 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 the reconstructed block or the reconstructed image. Can be. The filter unit 180 may be referred to as an in-loop filter.

The deblocking filter may remove block distortion generated at boundaries between blocks. In order to determine whether to perform the deblocking filter, it may be determined whether to apply the deblocking filter to the current block based on the pixels included in the several columns or rows included in the block. When the deblocking filter is applied to the block, a strong filter or a weak filter may be applied according to the required deblocking filtering strength. In addition, in applying the deblocking filter, horizontal filtering and vertical filtering may be performed in parallel when vertical filtering and horizontal filtering are performed.

The sample adaptive offset may add an appropriate offset value to the pixel value to compensate for the encoding error. The sample adaptive offset may correct the offset with the original image on a pixel basis for the deblocked image. In order to perform offset correction on a specific picture, the pixels included in the image are divided into a predetermined number of areas, and then, the area to be offset is determined and the offset is applied to the corresponding area or the offset considering the edge information of each pixel. You can use this method.

The adaptive loop filter may perform filtering based on a comparison value between the reconstructed image and the original image. After dividing the pixels included in the image into a predetermined group, one filter to be applied to the group may be determined and filtering may be performed for each group. For information related to whether to apply the adaptive loop filter, a luminance signal may be transmitted for each coding unit (CU), and the shape and filter coefficient of the adaptive loop filter to be applied according to each block may vary. In addition, an adaptive loop filter of the same type (fixed form) may be applied regardless of the characteristics of the block to be applied.

The reconstructed block that has passed through the filter unit 180 may be stored in the reference picture buffer 190.

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

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

Referring to FIG. 2, the decoding apparatus 200 may include an entropy decoder 210, an inverse quantizer 220, an inverse transform unit 230, an intra predictor 240, a motion compensator 250, and an adder 255. The filter unit 260 may include a reference picture buffer 270.

The decoding apparatus 200 may receive a bitstream output from the encoding apparatus 100. The decoding apparatus 200 may decode the bitstream in an intra mode or an inter mode. In addition, the decoding apparatus 200 may generate a reconstructed image through decoding and output the reconstructed image.

When the prediction mode used for decoding is an intra mode, the switch may be switched to intra. When the prediction mode used for decoding is an inter mode, the switch may be switched to inter.

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 reconstruction block that is a decoding target block by adding the reconstructed residual block and the prediction block. The decoding target block may be referred to as a current block.

The entropy decoder 210 may generate symbols by performing entropy decoding according to a probability distribution of the bitstream. The generated symbols may include symbols in the form of quantized transform coefficient levels. Here, the entropy decoding method may be similar to the entropy encoding method described above. For example, the entropy decoding method may be an inverse process of the above-described entropy encoding method.

In order to decode the transform coefficient level, the entropy decoder 210 may change the one-dimensional vector form coefficient into a two-dimensional block form through a transform coefficient scanning method. For example, upright scanning can be used to scan the coefficients of a block to change it into a two-dimensional block shape. Depending on the size of the conversion unit and the intra prediction mode, vertical scan or horizontal scan may be used instead of upright scan. That is, according to the size of the conversion unit and the intra prediction mode, it is possible to determine which scan method among upright scan, vertical scan and horizontal scan is used.

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

When the intra mode is used, the intra predictor 240 may generate a prediction block by performing spatial prediction using pixel values of blocks that are already decoded around the decoding target block.

When the inter mode is used, the motion compensator 250 may generate a predictive block by performing motion compensation using a reference vector stored in the motion vector and the reference picture buffer 270. When the value of the motion vector does not have an integer value, the motion compensator 250 may generate a prediction block by applying an interpolation filter to a portion of the reference image. In order to perform motion compensation, a motion compensation method of a prediction unit included in a coding unit is selected from among skip mode, merge mode, AMVP mode, and current picture reference mode. It may be determined whether or not it is a method, and motion compensation may be performed according to each mode. Here, the current picture reference mode may mean a prediction mode using a pre-restored region in the current picture to which the decoding target block belongs. A motion vector for the current picture reference mode may be used to specify the pre-restored region. A flag or index indicating whether the decoding object block is a block encoded in the current picture reference mode may be signaled or inferred through a reference picture index of the decoding object block. In the current picture reference mode, the current picture may exist at a fixed position (eg, the position at which the reference image index is 0 or the last position) in the reference image list for the decoding object block. Alternatively, the reference picture index may be variably positioned in the reference picture list, and a separate reference picture index indicating the location of the current picture may be signaled for this purpose.

The reconstructed residual block and the prediction block may be added through the adder 255. As the reconstructed residual block and the prediction block are added, the generated block may pass through the filter unit 260. The filter unit 260 may apply at least one or more of a deblocking filter, a sample adaptive offset, and an adaptive loop filter to the reconstructed block or the reconstructed image. The filter unit 260 may output the reconstructed image. The reconstructed picture may be stored in the reference picture buffer 270 and used for inter prediction.

3 is a diagram schematically illustrating a division structure of an image when encoding and decoding an image. 3 schematically shows an embodiment in which one unit is divided into a plurality of sub-units.

In order to efficiently divide an image, a coding unit (CU) may be used in encoding and decoding. Here, the coding unit may mean a coding unit. A unit may be a term that collectively refers to a block including 1) a syntax element and 2) image samples. For example, "division of a unit" may mean "division of a block corresponding to a unit". The block division information may include information about a depth of a unit. The depth information may indicate the number and / or degree of division of the unit.

Referring to FIG. 3, the image 300 is sequentially divided into units of a largest coding unit (LCU), and a split structure is determined by units of an LCU. Here, the LCU may be used as the same meaning as a coding tree unit (CTU). One unit may be hierarchically divided with depth information based on a tree structure. Each divided subunit may have depth information. Since the depth information indicates the number and / or degree of division of the unit, the depth information may include information about the size of the sub-unit.

The partition structure may mean a distribution of a coding unit (CU) in the LCU 310. The CU may be a unit for efficiently encoding an image. This distribution may be determined according to whether to divide one CU into a plurality of CUs (two or more positive integers including 2, 4, 8, 16, etc.). The horizontal and vertical sizes of the CUs created by splitting are either half of the horizontal and vertical sizes of the CU before splitting, or smaller than the horizontal and vertical sizes of the CU before splitting, depending on the number of splits. Can have The partitioned CU may be recursively divided into a plurality of CUs having reduced horizontal and vertical sizes in the same manner.

At this time, partitioning of the CU may be performed recursively up to a predetermined depth. The depth information may be information indicating the size of a CU and may be stored for each CU. For example, the depth of the LCU may be 0, and the depth of the smallest coding unit (SCU) may be a predefined maximum depth. Here, the LCU may be a coding unit having a maximum coding unit size as described above, and the SCU may be a coding unit having a minimum coding unit size.

The division starts from the LCU 310, and the depth of the CU increases by one each time the division reduces the horizontal and vertical sizes of the CU. For each depth, the CU that is not divided may have a size of 2N × 2N. In the case of a partitioned CU, a 2N × 2N sized CU may be divided into a plurality of CUs having an N × N size. The magnitude of N decreases in half for every 1 increase in depth.

For example, when one coding unit is divided into four coding units, the horizontal and vertical sizes of the divided four coding units may each have a size of half compared to the horizontal and vertical sizes of the coding unit before being split. have. For example, when a 32x32 sized coding unit is divided into four coding units, the four divided coding units may each have a size of 16x16. When one coding unit is divided into four coding units, it may be said that the coding unit is divided into quad-tree shapes.

For example, when one coding unit is divided into two coding units, the horizontal or vertical size of the divided two coding units may have a half size compared to the horizontal or vertical size of the coding unit before splitting. . As an example, when a 32x32 coding unit is vertically divided into two coding units, the two split coding units may have a size of 16x32. For example, when a 32x32 size coding unit is horizontally divided into two coding units, the two divided coding units may each have a size of 32x16. When one coding unit is divided into two coding units, it may be said that the coding unit is divided into a binary-tree.

Referring to FIG. 3, an LCU having a depth of 0 may be 64 × 64 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 represented by a depth of zero. A CU of 32x32 pixels may be represented by depth one. A CU of 16 × 16 pixels may be represented by depth two. A CU of 8x8 pixels, which is an SCU, may be represented by depth 3.

In addition, information on whether the CU is split may be expressed through split information of the CU. The split information may be 1 bit of information. All CUs except the SCU may include partition information. For example, if the value of the partition information is 0, the CU may not be split. If the value of the partition information is 1, the CU may be split.

FIG. 4 is a diagram illustrating a form of a prediction unit PU that may be included in the coding unit CU.

A CU that is no longer split among CUs partitioned from the LCU may be divided into one or more prediction units (PUs). This process may also be called division.

The PU may be a basic unit for prediction. The PU may be encoded and decoded in any one of a skip mode, an inter screen mode, and an intra screen mode. The PU may be divided into various forms according to modes.

Also, the coding unit may not be divided into prediction units, and the coding unit and the prediction unit may have the same size.

As shown in FIG. 4, in the skip mode, there may be no partition in the CU. In the skip mode, the 2N × 2N mode 410 having the same size as the CU without splitting may be supported.

In the inter-screen mode, eight divided forms in the CU can be supported. For example, in the inter-screen mode, 2Nx2N mode 410, 2NxN mode 415, Nx2N mode 420, NxN mode 425, 2NxnU mode 430, 2NxnD mode 435, nLx2N mode 440, and nRx2N mode 445 may be supported. In the in-screen mode, 2Nx2N mode 410 and NxN mode 425 may be supported.

One coding unit may be split into one or more prediction units, and one prediction unit may also be split into one or more prediction units.

For example, when one prediction unit is divided into four prediction units, the horizontal and vertical sizes of the divided four prediction units may each have a size of half compared to the horizontal and vertical sizes of the prediction unit before splitting. have. For example, when a 32x32 size prediction unit is split into four prediction units, the four divided prediction units may each have a size of 16x16. When one prediction unit is divided into four prediction units, it may be said that the prediction unit is divided into quad-trees.

For example, when one prediction unit is divided into two prediction units, the horizontal or vertical size of the divided two prediction units may have a half size compared to the horizontal or vertical size of the prediction unit before splitting. . For example, when a 32x32 size prediction unit is vertically divided into two prediction units, the two divided prediction units may each have a size of 16x32. For example, when a 32x32 size prediction unit is horizontally divided into two prediction units, the two divided prediction units may each have a size of 32x16. When one prediction unit is divided into two prediction units, it may be said that the prediction unit is divided into a binary-tree.

FIG. 5 is a diagram illustrating a form of a transform unit (TU) that a coding unit CU may include.

A transform unit (TU) may be a basic unit used for a process of transform, quantization, inverse transform, and inverse quantization in a CU. The TU may have a shape such as a square shape or a rectangle. The TU may be determined dependent on the size and / or shape of the CU.

Of the CUs partitioned from the 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 the quadtree structure. If a CU is split more than once, it can be said to be split recursively. Through division, one CU 510 may be configured with TUs of various sizes. Or, it may be divided into one or more TUs based on the number of vertical lines and / or horizontal lines dividing the CU. The CU may be divided into symmetrical TUs and may be divided into asymmetrical TUs. Information about the size / shape of the TU may be signaled for division into an asymmetric TU and may be derived from information about the size / shape of the CU.

Also, the coding unit may not be divided into a transform unit, and the coding unit and the transform unit may have the same size.

One coding unit may be split into one or more transform units, and one transform unit may also be split into one or more transform units.

For example, when one transform unit is divided into four transform units, the horizontal and vertical sizes of the divided four transform units may each have a size of half compared to the horizontal and vertical sizes of the transform unit before splitting. have. For example, when a 32x32 transform unit is divided into four transform units, the divided four transform units may have a size of 16x16. When one transform unit is divided into four transform units, it may be said that the transform unit is divided into quad-trees.

For example, when one transform unit is divided into two transform units, the horizontal or vertical size of the divided two transform units may be half the size of the transform unit before the split. . For example, when a 32x32 transform unit is vertically divided into two transform units, the two divided transform units may have a size of 16x32. For example, when a 32x32 transform unit is horizontally divided into two transform units, the divided two transform units may each have a size of 32x16. When one transform unit is divided into two transform units, the transform unit may be said to be divided into a binary-tree.

When performing the transformation, the residual block may be transformed using at least one of a plurality of pre-defined transformation methods. For example, Discrete Cosine Transform (DCT), Discrete Sine Transform (DST), or KLT may be used as a plurality of pre-defined transformation methods. Which transformation method is applied to transform the residual block may be determined using at least one of inter prediction mode information of the prediction unit, intra prediction mode information, and size / shape of the transform block, and in some cases, indicates a transformation method. The information may be signaled.

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

The intra prediction mode may be a non-directional mode or a directional mode. The non-directional mode may be a DC mode or a planar mode, and the directional mode may be a prediction mode having a specific direction or angle, and the number may be one or more M. The directional mode may be expressed by at least one of a mode number, a mode value, a mode number, and a mode angle.

The number of intra prediction modes may be one or more N including the non-directional and directional modes.

The number of intra prediction modes may vary depending on the size of the block. For example, the size of a block may be 67 pieces in case of 4x4 or 8x8, 35 pieces in case of 16x16, 19 pieces in case of 32x32, and 7 pieces in case of 64x64.

The number of intra prediction modes may be fixed to N regardless of the size of the block. For example, it may be fixed to at least one of 35 or 67 regardless of the size of the block.

The number of intra prediction modes may vary depending on the type of color component. For example, the number of prediction modes may vary depending on whether the color component is a luma signal or a chroma signal.

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

In order to encode / decode the current block by intra prediction, a step of checking whether samples included in neighboring reconstructed blocks are available as reference samples of the encoding / decoding target block may be performed. If there are samples that are not available as reference samples of the block to be encoded / decoded, at least one or more of the samples included in the neighboring reconstructed blocks are used to copy and / or sample values to samples that are not available as reference samples. Interpolation may be used as a reference sample of a block to be encoded / decoded.

During intra prediction, a filter may be applied to at least one of a reference sample or a prediction sample based on at least one of an intra prediction mode and a size of an encoding / decoding target block. In this case, the encoding / decoding target block may mean a current block and may mean at least one of a coding block, a prediction block, and a transform block. The type of filter applied to the reference sample or the prediction sample may be different according to at least one or more of the intra prediction mode or the size / shape of the current block. The type of filter may vary depending on at least one of the number of filter taps, a filter coefficient value, or a filter strength.

In the intra prediction mode, the non-directional planar mode generates a predicted block of a target encoding / decoding block. The upper right reference sample of the current block may be generated as a weighted sum of the lower left reference samples of the current block.

Among the intra prediction modes, the non-directional DC mode may be generated as an average value of upper reference samples of the current block and left reference samples of the current block when generating the prediction block of the target coding / decoding block. In addition, one or more upper rows and one or more left columns adjacent to the reference sample in the encoding / decoding block may be filtered using reference sample values.

In the directional modes of the intra prediction modes, the prediction block may be generated by using the upper right and / or lower left reference samples, and the directional modes may have different directions. Real interpolation may be performed to generate predictive sample values.

In order to perform the intra prediction method, the intra prediction mode of the current prediction block may be predicted from the intra prediction mode of the prediction block existing around the current prediction block. In case of predicting the intra prediction mode of the current prediction block by using the mode information predicted from the intra prediction mode, if the intra prediction modes of the current prediction block and the neighboring prediction block are the same, the current prediction is performed by using predetermined flag information. Information that the intra prediction modes of the block and the neighboring prediction block are the same may be transmitted. If the intra prediction modes of the current prediction block and the neighboring prediction block are different, entropy encoding is performed to perform the intra prediction mode of the encoding / decoding target block. Information can be encoded.

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

The rectangle illustrated in FIG. 7 may represent an image (or a picture). In addition, arrows in FIG. 7 may indicate prediction directions. 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 (U-predictive Picture), a B picture (Bi-predictive Picture), and the like. Each picture may be encoded and decoded according to an encoding type of each picture.

When the image to be encoded is an I picture, the image may be encoded in the picture with respect to the image itself without inter prediction. When the image to be encoded is a P picture, the image may be encoded through inter prediction or motion compensation using the reference image only in the forward direction. If the image to be encoded is a B picture, it may be encoded through inter prediction or motion compensation using reference pictures in both forward and reverse directions, and inter prediction or motion using the reference picture in one of the forward and reverse directions. Can be coded through compensation. In this case, when the inter prediction mode is used, the encoder may perform inter prediction or motion compensation, and the decoder may perform motion compensation corresponding thereto. The pictures of the P picture and the B picture that are encoded and / or decoded using the reference picture may be regarded as a picture using inter prediction.

Hereinafter, inter prediction according to an embodiment will be described in detail.

Inter prediction or motion compensation may be performed using a reference picture and motion information. In addition, inter prediction may use the skip mode described above.

The reference picture may be at least one of a previous picture of the current picture or a subsequent picture of the current picture. In this case, the inter prediction may perform prediction on a block of the current picture based on the reference picture. Here, the reference picture may mean an image used for prediction of the block. In this case, an area in the reference picture may be specified by using a reference picture index (refIdx) indicating a reference picture, a motion vector to be described later, and the like.

The inter prediction may select a reference picture corresponding to the current block within the reference picture and the reference picture, and generate a prediction block for the current block using the selected reference block. The current block may be a block targeted for current encoding or decoding among blocks of the current picture.

The motion information may be derived during inter prediction by each of the encoding apparatus 100 and the decoding apparatus 200. In addition, the derived motion information may be used to perform inter prediction. In this case, the encoding apparatus 100 and the decoding apparatus 200 use encoding information and / or decoding efficiency by using motion information of a reconstructed neighboring block and / or motion information of a collocated block (col block). Can improve. The call block may be a block corresponding to a spatial position of a block to be encoded / decoded in a collocated picture (col picture). The reconstructed neighboring block may be a block within the current picture and may be a block that is already reconstructed through encoding and / or decoding. The reconstruction block may be a neighboring block adjacent to the encoding / decoding object block and / or a block located at an outer corner of the encoding / decoding object block. Here, the block located at the outer corner of the encoding / decoding target block is a block vertically adjacent to a neighboring block horizontally adjacent to the encoding / decoding target block or a block horizontally adjacent to a neighboring block vertically adjacent to the encoding / decoding target block. Can be.

Each of the encoding apparatus 100 and the decoding apparatus 200 may determine a block existing at a position corresponding to a block to be encoded / decoded spatially within a call picture, and determines a predetermined relative position based on the determined block. Can be. The predefined relative position may be a position inside and / or outside of a block existing at a position corresponding to a block to be encoded / decoded spatially. In addition, each of the encoding apparatus 100 and the decoding apparatus 200 may derive a call block based on the determined predetermined relative position. Here, the call picture may be one picture among at least one reference picture included in the reference picture list.

The method of deriving the motion information may vary according to the prediction mode of the encoding / decoding target block. For example, as a prediction mode applied for inter prediction, there may be an advanced motion vector prediction (AMVP) and a merge mode. The merge mode may be referred to as a motion merge mode.

For example, when AMVP is applied as the prediction mode, each of the encoding apparatus 100 and the decoding apparatus 200 uses a motion vector of the reconstructed neighboring block and / or a motion vector of the call block. create a motion vector candidate list. The motion vector of the reconstructed neighboring block and / or the motion vector of the call block may be used as a motion vector candidate. Here, the motion vector of the call block may be referred to as a temporal motion vector candidate, and the motion vector of the reconstructed neighboring block may be referred to as a spatial motion vector candidate.

The bitstream generated by the encoding apparatus 100 may include a motion vector candidate index. That is, the encoding apparatus 100 may generate a bitstream by entropy encoding a motion vector candidate index. The motion vector candidate index may indicate an optimal motion vector candidate selected from the motion vector candidates included in the motion vector candidate list. The motion vector candidate index may be transmitted from the encoding apparatus 100 to the decoding apparatus 200 through a bitstream.

The decoding apparatus 200 may entropy decode the motion vector candidate index from the bitstream, and select the motion vector candidate of the decoding target block from the motion vector candidates included in the motion vector candidate list using the entropy decoded motion vector candidate index. .

The encoding apparatus 100 may calculate a motion vector difference (MVD) between the motion vector of the encoding target block and the motion vector candidate, and may entropy encode the MVD. The bitstream may include entropy coded MVD. The MVD may be transmitted from the encoding apparatus 100 to the decoding apparatus 200 through a bitstream. At this time, the decoding apparatus 200 may entropy decode the received MVD from the bitstream. The decoding apparatus 200 may derive the motion vector of the decoding object block through the sum of the decoded MVD and the motion vector candidate.

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

Another example of a method of deriving motion information is a merge mode. The merge mode may mean merging of motions for a plurality of blocks. The merge mode may mean applying motion information of one block to other blocks. When the merge mode is applied, each of the encoding apparatus 100 and the decoding apparatus 200 may generate a merge candidate list using the motion information of the reconstructed neighboring block and / or the motion information of the call block. Can be. The motion information may include at least one of 1) a motion vector, 2) a reference picture index, and 3) an inter prediction prediction indicator. The prediction indicator may be unidirectional (L0 prediction, L1 prediction) or bidirectional.

In this case, the merge mode may be applied in a CU unit or a PU unit. When the merge mode is performed in a CU unit or a PU unit, the encoding apparatus 100 may entropy-code predetermined information to generate a bitstream and then transmit the encoded stream to the decoding apparatus 200. The bitstream may include predefined information. The predefined information includes: 1) a merge flag, which is information indicating whether to perform a merge mode for each block partition, and 2) which one of neighboring blocks adjacent to an encoding target block is merged with. It may include a merge index that is information about the merge. For example, the neighboring blocks of the encoding object block may include a left neighboring block of the encoding object block, an upper neighboring block of the encoding object block, and a temporal neighboring block of the encoding object block.

The merge candidate list may represent a list in which motion information is stored. In addition, the merge candidate list may be generated before the merge mode is performed. The motion information stored in the merge candidate list includes motion information of neighboring blocks adjacent to the encoding / decoding target block, motion information of a block corresponding to the encoding / decoding target block in the reference image, and motion already existing in the merge candidate list. At least one or more of the new motion information and the zero merge candidate generated by the combination of the information. Here, the motion information of the neighboring block adjacent to the encoding / decoding target block is a spatial merge candidate and the motion information of the block corresponding to the encoding / decoding target block in the reference image is a temporal merge candidate. It may be referred to as).

The skip mode may be a mode in which motion information of a neighboring block is applied to an encoding / decoding target block as it is. The skip mode may be one of modes used for inter prediction. When the skip mode is used, the encoding apparatus 100 may entropy-encode information on which block motion information is to be used as the motion information of the encoding target block and transmit the information to the decoding apparatus 200 through the bitstream. The encoding apparatus 100 may not transmit other information to the decoding apparatus 200. For example, the other information may be syntax element information. The syntax element information may include at least one of motion vector difference information, a coding block flag, and a transform coefficient level.

The residual signal generated after intra-picture or inter-screen prediction may be converted into a frequency domain through a conversion process as part of a quantization process. In this case, the first transform to be performed may use various DCT and DST kernels in addition to DCT type 2 (DCT-II), and these transform kernels perform a 1D transform on a horizontal and / or vertical direction with respect to a residual signal. The transformation may be performed by a separate transform, each performed, or the transformation may be performed by a 2D non-separable transform.

For example, the DCT and DST types used for the conversion may be adaptively used for 1D conversion of DCT-V, DCT-VIII, DST-I, and DST-VII in addition to DCT-II as shown in the following table. As in the examples of Tables 1 to 2, a transform set may be configured to derive the DCT or DST type used for the transform.

Conversion set	conversion
0	DST_VII, DCT-VIII
One	DST-VII, DST-I
2	DST-VII, DCT-V

Conversion set	conversion
0	DST_VII, DCT-VIII, DST-I
One	DST-VII, DST-I, DCT-VIII
2	DST-VII, DCT-V, DST-I

For example, after defining different transform sets in the horizontal or vertical direction according to the intra prediction mode as shown in FIG. 8, the intra / prediction mode of the current encoding / decoding target block in the sub / decoder and the Transforms and / or inverse transforms may be performed using the transforms included in the corresponding transform set. In this case, the transform set may not be entropy encoded / decoded but may be defined according to the same rules in the sub / decoder. In this case, entropy encoding / decoding indicating which transform is used among transforms belonging to the corresponding transform set may be performed. For example, if the block size is 64x64 or less, three transform sets are constructed according to the intra prediction mode as shown in the example of Figure 2, and each of the three transforms is used as a horizontal transform and a vertical transform. After combining a total of nine multi-transformation methods, encoding efficiency can be improved by encoding / decoding a residual signal using an optimal transform method. In this case, truncated Unary binarization may be used to entropy encode / decode information on which of three transforms belonging to one transform set. In this case, information indicating which transform among transforms belonging to a transform set is used for at least one of a vertical transform and a horizontal transform may be entropy encoded / decoded.

After the above-described first transform is completed, the encoder may perform a secondary transform in order to increase energy concentration of transformed coefficients as shown in the example of FIG. 9. Secondary transformations may also perform discrete transformations that perform one-dimensional transformations respectively in the horizontal and / or vertical directions, or may perform two-dimensional non-separated transformations, and used transformation information may be transmitted or present and surrounding. It may be implicitly derived from the encoder / decoder according to the encoding information. For example, a transform set for a secondary transform may be defined, such as a primary transform, and the transform set may be defined according to the same rules in the encoder / decoder rather than entropy encoding / decoding. In this case, information indicating which transform is used among the transforms belonging to the corresponding transform set may be transmitted, and may be applied to at least one or more of the residual signal through intra prediction or inter prediction.

At least one of the number or type of transform candidates is different for each transform set, and at least one of the number or type of transform candidates is the position, size, partition type, prediction mode (intra / inter mode) of a block (CU, PU, TU, etc.). ) Or directionality / non-direction of the intra prediction mode.

In the decoder, the second inverse transform may be performed according to whether the second inverse transform is performed, and the first inverse transform may be performed according to whether the first inverse transform is performed on the result of the second inverse transform.

The above-described first-order transform and second-order transform may be applied to at least one or more signal components of luminance / chromatic components or according to an arbitrary coding block size / shape, and may be used or used in any coding block. An index indicating a / second order transform may be entropy encoded / decoded or implicitly derived from the encoder / decoder according to at least one of current / peripheral encoded information.

The residual signal generated after intra-picture or inter-screen prediction is subjected to entropy encoding after the first and / or second-order transform is completed, and then subjected to quantization, where the quantized transform coefficient is shown in FIG. Likewise, the image may be scanned in a diagonal, vertical, or horizontal direction based on at least one of an intra prediction mode or a minimum block size / shape.

In addition, the entropy decoded quantized transform coefficients may be inverse scanned and arranged in a block form, and at least one of inverse quantization or inverse transform may be performed on the block. In this case, at least one of a diagonal scan, a horizontal scan, and a vertical scan may be performed as a reverse scanning method.

For example, when the size of the current coding block is 8x8, the residual signal for the 8x8 block is three scanning order methods illustrated in FIG. 10 for each of 4 4x4 subblocks after the first order, second order transform, and quantization. Entropy encoding may be performed while scanning the quantized transform coefficients according to at least one of the following. It is also possible to entropy decode while inversely scanning the quantized transform coefficients. The inverse scanned quantized transform coefficients become transform coefficients after inverse quantization, and at least one of a second order inverse transform or a first order inverse transform may be performed to generate a reconstructed residual signal.

In the video encoding process, one block may be split as shown in FIG. 11 and an indicator corresponding to the split information may be signaled. In this case, the split information may be at least one of a split flag (split_flag), a quad / binary tree flag (QB_flag), a quadtree split flag (quadtree_flag), a binary tree split flag (binarytree_flag), and a binary tree split type flag (Btype_flag). have. Here, split_flag is a flag indicating whether a block is divided, QB_flag is a flag indicating whether a block is divided into quadtrees or binary trees, quadtree_flag is a flag indicating whether a block is divided into quadtrees, binarytree_flag may be a flag indicating whether a block is divided into a binary tree form, and Btype_flag may be a flag indicating a vertical or horizontal division when the block is divided into a binary tree form.

If the division flag is 1, the division flag may be 0, indicating that the partition is not divided. In the case of the quad / binary tree flag, 0 may indicate quadtree division, and 1, binary tree division. This may indicate quadtree splitting. In the case of the binary tree partition type flag, 0 indicates horizontal division, 1 indicates vertical division, and 0 indicates vertical division, and 1 indicates horizontal division.

For example, the split information of FIG. 11 may be derived by signaling at least one of quadtree_flag, binarytree_flag, and Btype_flag as shown in Table 3 below.

quadtree_flag	One	0					One	0					0		0		0		0								0
binarytree_flag			One		0	0			One		0	0		0		0		0		One		One		0	0	0		0
Btype_flag				One						0											0		One

For example, the split information of FIG. 11 may be derived by signaling at least one of split_flag, QB_flag, and Btype_flag as shown in Table 2 below.

split_flag	One		One			0	0	One		One			0	0	0	0	0	One			One		0	0	0	0
QB_flag		0		One					0		One								One
Btype_flag					One							0								0		One

The splitting method may be split only into quadtrees or only binary trees depending on the size / shape of the block. In this case, the split_flag may mean a flag indicating whether quadtree or binary tree is split. The size / shape of the block may be derived according to the depth information of the block, and the depth information may be signaled.

When the size of the block falls within a predetermined range, the block may be divided into quadtrees only. Here, the predetermined range may be defined as at least one of the maximum block size or the minimum block size that can be divided only by the quadtree. Information indicating the size of the maximum / minimum block for which the quadtree type division is allowed may be signaled through a bitstream, and the corresponding information may be signaled in units of at least one of a sequence, a picture parameter, or a slice (segment). have. Alternatively, the size of the maximum / minimum block may be a fixed size preset in the encoder / decoder. For example, when the size of the block corresponds to 256x256 to 64x64, the block may be divided into quadtrees only. In this case, the split_flag may be a flag indicating whether the quadtree is split.

When the size of the block falls within a predetermined range, it may be possible to divide only into a binary tree. Here, the predetermined range may be defined as at least one of the maximum block size or the minimum block size that can be divided only by the binary tree. The information indicating the size of the maximum / minimum block that allows the division of the binary tree type may be signaled through a bitstream, and the corresponding information may be signaled in units of at least one of a sequence, a picture parameter, or a slice (segment). have. Alternatively, the size of the maximum / minimum block may be a fixed size preset in the encoder / decoder. For example, when the size of the block corresponds to 16x16 to 8x8, it may be possible to divide only into a binary tree. In this case, the split_flag may be a flag indicating whether a binary tree is split.

After the one block is partitioned into a binary tree, when the partitioned block is further partitioned, it may be partitioned only into a binary tree.

When the horizontal or vertical size of the divided block is a size that can no longer be divided, the one or more indicators may not be signaled.

In addition to the binary tree splitting under the quadtree, after the binary tree splitting, the quadtree based splitting may be possible.

When a block is split based on a quadtree and / or a binary tree, a block corresponding to a leaf node according to the final splitting result of the block may be set as one coding / decoding unit. That is, when a block having an arbitrary size or any shape is no longer divided, encoding / decoding may be performed for the block. For example, prediction (eg, inter-picture prediction or intra-picture prediction) and transformation for blocks having arbitrary sizes and shapes corresponding to binary leaf nodes generated by quadtree and / or binary tree splitting. The encoding / decoding process may be performed.

12 is a diagram illustrating a coding / decoding unit according to a partition type of a block. In the example shown in FIG. 12, the solid line is for distinguishing blocks generated by quadtree splitting, and the dotted line is for distinguishing blocks generated by binary tree splitting. As in the example shown in FIG. 12, assuming that the structure of the coding block is determined, the last split node may be defined as a binary leaf node through actual and dotted lines. The block corresponding to the binary leaf node may be encoded / decoded in the size or shape of the block corresponding to the leaf node without further splitting according to the prediction subblock or the transform subblock (for example, intra prediction or inter prediction, Primary transform, secondary transform, quantization or entropy encoding / decoding, etc.) may be performed.

For convenience of description, in the following embodiments, the partition type of the block based on the quadtree and / or the binary tree will be defined as a block structure.

In the encoding / decoding process, the block structure for each color component may be the same, and the block structure for each color component may be different. As an example, the block structure may be the same for the luminance and chrominance components or may differ for the luminance and the chrominance components according to an arbitrary encoding parameter condition. Here, the same block structure of the luminance component and the chrominance component may mean that the chrominance component inherits the block structure information determined for the luminance component or the luminance component inherits the block structure determined for the chrominance component. For example, according to a picture or slice type currently encoded / decoded, luminance and color difference signals may have different block structures or have the same block structure in an intra frame or an intra slice. In this case, whether the same or different block structures for luminance and chrominance components constituting an intra picture or an intra picture slice are set equally or differently is determined after obtaining a rate distortion cost function for each block structure. For example, the method may be determined through an encoding process of selecting a block structure having a minimum cost function.

The encoding apparatus may entropy encode information indicating whether to use the same block structure for each color component, and transmit the information to the decoding apparatus. In this case, the information may be a sequence level (eg, Sequence Parameter Set, SPS), picture level (eg, Picture Parameter Set, PPS), slice header, maximum coding unit (LCT or CTU), or coding unit (or encoding). Block).

For example, encoding parameter information indicating whether a block structure for each color component is the same for an intra picture, an intra picture, an inter picture, or an inter picture slice may be transmitted through an SPS or a PPS.

Alternatively, encoding parameter information indicating whether a block structure for each color component is the same for an intra-picture slice or an inter-picture slice may be transmitted through a slice header.

Alternatively, encoding parameter information indicating whether the block structure for each color component is the same for the maximum coding unit or the coding unit may be transmitted in the maximum coding unit or the coding unit.

When the encoding / decoding object block satisfies a predetermined condition, block division may not be allowed for the encoding / decoding object block. Accordingly, encoding / decoding of block division information may be omitted for blocks that satisfy a predetermined condition. Here, the predetermined condition is related to at least one of the size of the block, the shape of the block, or the splitting depth of the block, and indicates the size, shape, or depth of the block in which quadtree and / or binary tree splitting is allowed or not allowed. Can be. The size or shape of the block may be a reference value indicating the size or shape of the block where quadtree and / or binary tree splitting is allowed or disallowed, and the block depth is such that quadtree and / or binary tree splitting is allowed or not allowed. It may represent a threshold of the block depth. The block depth may be a variable that increases by 1 as quadtree and / or binary tree splitting is performed.

The block splitting information may include information indicating whether to split a block (eg, split_flag), information indicating whether to split a quadtree (eg, Quadtree_flag or QB_flag), information indicating whether a binary tree is split (eg, Binarytree_flag or QB_flag) or binary tree splitting. It may include at least one of information (eg, Btype_flag) indicating the type.

For example, if a predetermined condition indicates that a block size is equal to or smaller than a reference value, and the binary tree splitting is not allowed for a block that satisfies the predetermined condition, the information related to the binary tree splitting may be used for a block having a size smaller than or equal to the reference value. For example, encoding / decoding of a quad / binary tree flag (QB_flag), a binary tree split flag (binaraytree_flag), or a binary tree split type flag (Btype_flag) may be omitted. If encoding / decoding for the quad / binary tree flag QB_flag is omitted, the split flag fla_flag may be used for indicating whether a block is quadtree split.

The present invention is not limited to the example described above, and may be configured not to allow quadtree splitting for blocks satisfying a predetermined condition. In this case, encoding / decoding of information related to quadtree splitting (eg, quad / binarytree flag QB_flag or quadtree_flag) may be omitted for a block that satisfies a predetermined condition. If encoding / decoding for the quad / binary tree flag QB_flag is omitted, the split flag flag may be used for indicating whether a block is binary tree split.

As another example, no form of division may be allowed for a block satisfying a predetermined condition. In this case, no segmentation information may be encoded / decoded for a block that satisfies a predetermined condition.

A process of determining whether to skip encoding / decoding of partition information will be described in more detail with reference to the accompanying drawings.

13 is a flowchart illustrating a process of determining whether to decode information related to binary tree splitting. For convenience of description, in the present embodiment, it is assumed that binary tree based partitioning is not allowed for a block satisfying a predetermined condition.

First, information related to a predetermined condition may be obtained (S1301). In this case, the information related to the predetermined condition may include at least one of the size, shape or division depth of the block. The predetermined condition is based on information related to the predetermined condition, whether the size of the block is greater than or equal to the threshold, whether the size of the block is less than or equal to the threshold, whether the type of the block is a preset type, or the depth of the block is greater than or equal to the threshold Or whether the depth of the block is equal to or less than a threshold value.

The information related to the predetermined condition may be predefined in the encoder and the decoder. Here, the information related to the predetermined condition may indicate at least one of the size of the block, the shape of the block, or the depth of the block defining the predetermined condition. For example, the size / shape or split depth of a block from which encoding / decoding of split information is omitted may have a fixed value predefined in the encoder and the decoder. Alternatively, the information related to the predetermined condition may be variably determined by encoding parameters indicating the size / shape of the encoding / decoding target block or the division depth of the block.

As another example, information related to a predetermined condition may be encoded / decoded in units of a sequence level, a picture level, a slice header, or a predetermined coding region. In this case, the predetermined coding region has a size / shape smaller than a picture or slice currently encoded / decoded, and has a size or a random block (eg, a maximum size) included in a maximum coding unit (LCU or CTU) or a maximum coding unit. And a block generated by quadtree dividing the coding unit. The information related to the predetermined condition may be expressed in the form of the maximum size of the block and / or the minimum size of the block, or may be expressed in the form of the maximum depth of the block and / or the minimum size of the block.

The encoder determines a block structure by comparing a rate distortion between a quadtree and binary tree based encoding result and a quadtree based encoding result, and determines a block structure according to the determined block structure. In consideration of the size, shape, or depth of a block in which binary tree splitting is no longer performed, information related to a predetermined condition may be encoded. In addition, the decoder may decode information related to a predetermined condition from which the binary tree split is not allowed from the bitstream, and determine whether the current block satisfies the predetermined condition based on the decoded information.

The decoder may determine whether the current block satisfies a predetermined condition (S1302). As a result of determination, when the current block satisfies a predetermined condition, decoding of information related to binary tree splitting for the current block may be omitted.

On the other hand, if the current block does not satisfy a predetermined condition, information related to binary tree splitting for the current block may be decoded according to whether the current block is quadtree split (S1303). For example, if quadtree splitting is not performed for the current block, information related to binary tree splitting for the current block may be decoded.

That is, by comparing whether the size, shape, or depth of the current block corresponds to the size, shape, or depth of the block according to a predetermined condition, it may be determined whether to block / decode the block partition information for the current block.

As another example, according to an embodiment of the present invention, information indicating whether block division is allowed for a block having any size, any shape, or any depth may be encoded / decoded. Here, the information indicating whether block division is allowed may include information indicating whether a quadtree split exists (eg, NoPresent_Quadtree_flag) or information indicating whether binary tree split exists (eg, NoPresent_Binarytree_flag).

For a block having any size, any shape, or any depth, block splitting may not be allowed, not only for the block but for the lower block, as well. Here, the lower block may include at least one of a block having a smaller size than the block, a block having the same shape as the block, a block having a larger division depth than the block, or a lower node block of the block.

For example, if information indicating whether a binary tree split exists for a block having an arbitrary size / type is signaled and the information indicates that there is no binary tree split, not only the block but also a smaller size / For a block having a form, information related to binary tree splitting (eg, information indicating whether or not a binary tree splitting is performed (eg, quad / binary tree flag QB_flag), binary tree splitting flag binaraytree_flag, or binary tree splitting type flag Btype_flag Coding / decoding of at least one) may be omitted.

Not limited to the example described, it is also possible to signal information indicating whether a quadtree split or binary tree split type flag is present for a block having any size / shape.

Information indicating whether block division is allowed may be transmitted for each predetermined encoding region. In this case, the predetermined coding region has a size / shape smaller than a picture or slice currently encoded / decoded, and has a size or a random block (eg, a maximum size) included in a maximum coding unit (LCU or CTU) or a maximum coding unit. And a block generated by quadtree dividing the coding unit. The encoder determines a block structure by comparing rate distortion between a result of performing quadtree and binary tree-based encoding on a block of arbitrary size / shape and a result of performing quadtree-based encoding. According to the determined block structure, it is possible to determine whether to encode information indicating whether binary tree splitting is allowed.

Information indicating whether block division is allowed may be hierarchically encoded / decoded. For example, when the information signaled for the upper block indicates that block division is allowed, information indicating whether block division is allowed again for the lower block generated by dividing the upper block may be encoded / decoded.

As another example, information about the size, shape, or depth of a block in which information indicating whether block division is allowed may be signaled may be encoded / decoded at a higher level. For example, information about a block size, shape, or depth may be transmitted through at least one of a sequence level, a picture level, or a slice header. In this case, information indicating whether block division is allowed may be signaled only for a block corresponding to a block size, a shape, or a depth signaled through a higher level or higher blocks thereof.

14 is a flowchart illustrating a process of determining whether to decode information related to binary tree partitioning. For convenience of description, in the present embodiment, it is assumed that the information about whether binary tree split is allowed is signaled for the current block only.

First, information indicating whether a binary tree is split for a current block may be decoded (S1401).

When the information indicates that binary tree splitting is not allowed (S1402), decoding of the binary tree splitting information on the current block may be omitted. In addition, the binary tree partitioning information may not be decoded for the lower block generated by the quadtree partitioning of the current block.

On the other hand, when the information indicates that binary tree splitting is allowed (S1402), information related to binary tree splitting may be decoded according to whether the current block is quadtree splitted (S1403). For example, if quadtree splitting is not performed for the current block, information related to binary tree splitting for the current block may be decoded. In addition, even for a lower block generated by quadtree or binary tree splitting, information related to binary tree splitting may be decoded according to whether the lower block is quadtree splitted.

15 to 17 are diagrams for explaining an example in which binary tree splitting is no longer performed on a block having a predetermined size or less.

As in the example shown in FIG. 15, it is assumed that the size / shape of the maximum coding unit is 128x128, and through the rate-distortion optimization performed by the encoding apparatus, only quadtree splitting exists without binary tree splitting in the maximum coding unit. do.

If the information indicating that the binary tree splitting is not performed for a predetermined size block is not encoded / decoded, as in the example shown in FIG. 16, whether binary tree splitting is performed on a block for which no further quadtree splitting is performed. Information should be encoded / decoded.

However, when encoding / decoding information that binary tree splitting is not performed for blocks smaller than 128x128 size, whether or not binary tree splitting is performed for blocks smaller than 128x128 size, as in the example shown in FIG. It is not necessary to encode / decode the information about the information. As a result, the amount of information to be encoded is small, and the encoding / decoding efficiency can be increased.

As described above with reference to FIG. 13, the encoder may encode and transmit information about a size (eg, information indicating 128 × 128), a shape, or a depth of a block in which binary tree splitting is not allowed, to be transmitted to the decoding apparatus. The decoding apparatus may decode information about a size of a block in which binary tree splitting is not performed from the bitstream, and may not further decode information related to binary tree splitting for a block smaller than or equal to the size indicated by the decoded information.

As another example, as described above with reference to FIG. 14, the encoding apparatus may encode and transmit information indicating that binary tree segmentation is not allowed for an arbitrary size block in which binary tree segmentation is not performed. Here, the information may be a 1-bit flag (eg, NoPresent_BinaryTree_flag), but is not limited thereto. In the example shown in FIG. 17, for a 128x128 size block, NoPresent_BinaryTree_flag is signaled as being signaled.

In Figs. 16 and 17, it is shown that the value of the flag is set to 1 when the quadtree or binary tree splitting is performed, otherwise the value of the flag is set to 0, but the reverse setting is also possible.

Embodiments relating to disallowing block division can be applied for the luminance component and the chrominance component. At this time, the information indicating that the block division is not allowed (for example, information indicating the block size, shape or size, or the information indicating whether the block division is allowed, etc., for which the block division is not allowed) is applied to the luminance component and the chrominance component. It may be applied in common or may be signaled separately for the luminance component and the chrominance component. In case of entropy encoding / decoding the information, truncated rice binarization method, K-th order Exp_Golomb binarization method, limited K-th order Exp_Golomb binarization method At least one entropy encoding method may be used, such as a fixed-length binarization method, a unary binarization method, or a truncated unary binarization method. In addition, after binarizing the information, the information may be finally encoded / decoded using CABAC (ae (v)).

Next, the residual signal conversion and scanning for the current block will be described.

In performing encoding / decoding on the residual signal of the current block, at least one or more pieces of encoding information on the residual signal of the current block are encoded / encoded on the residual signal of blocks that have been encoded / decoded around the current block. Can be implicitly derived from the decoder. Here, the encoding information about the residual signal may include information related to the transformation technique of the residual signal (for example, the transformation technique used for the first-order and second-order transformation), the information for scanning the quantized transformation coefficient, and the like. . Here, the quantized transform coefficient may mean that transform (eg, primary transform and secondary transform) and quantization are performed on the residual signal generated after intra prediction.

In detail, when the current block is encoded through intra prediction, encoding information about the current block may be derived from neighboring blocks around the current block based on the intra prediction mode of the current block. On the other hand, when the current block is encoded through inter prediction, encoding information about the current block may be derived from neighboring blocks around the current block based on motion related information of the current block. Hereinafter, referring to FIGS. 18 and 19, when the current block is encoded through intra prediction and when the current block is encoded through inter prediction, encoding information about a residual signal of the current block may be obtained from neighboring blocks. Let's take a closer look at derivation.

18 is a flowchart illustrating a process of determining whether to encode encoding information about a residual signal of a current block from a neighboring block when the current block is encoded by intra prediction.

First, it may be determined whether there is a neighboring block encoded in the same intra prediction mode as the intra prediction mode of the current block (S1801). Here, the neighboring block of the current block may mean a block included in the same picture as the current block (ie, the current picture) and encoded / decoded before the current block. For example, the neighboring block may include a block adjacent to the current block among blocks that are encoded / decoded before the current block. Here, a block adjacent to the current block is a block adjacent to a boundary of the current block (for example, a left boundary or a top boundary) and a block adjacent to a corner of the current block (for example, an upper left corner, an upper right corner, or a lower left corner). It may include at least one.

If there is a neighboring block encoded in the same intra prediction mode as the intra prediction mode of the current block, the encoding information on the residual signal of the neighboring block may be derived as the encoding information of the current block (S1802). In detail, at least one of the first transform, the second transform, or the scanning information of the current block may be derived from a neighboring block having the same intra prediction mode as the current block.

For example, if the intra prediction mode of the current block is the same as the neighboring block of the current block and the neighboring block skips the first transform, the residual signal of the current coding block may also skip the first transform. . When the primary transform of the current block is skipped, the secondary transform of the current block may also be skipped.

Alternatively, when the intra prediction mode of the current block is the same as the neighboring block of the current block, the first transform for the horizontal and vertical directions of the current block is applied to the neighboring block having the same intra prediction mode as the current block. May be set equal to Accordingly, encoding / decoding of encoding information (eg, transformation information (or transformation index) for the horizontal and vertical directions used for the primary transformation) required for the primary transformation of the residual signal of the current block may be omitted.

For example, when the intra prediction mode of the current block is determined as mode 23 and at least one intra prediction mode of at least one neighboring block adjacent to the current block is also determined as mode 23, the intra prediction mode is determined to be 23. The first order transform applied to the residual signal of the neighboring block of No. 23 may be used as the first order transform of the residual signal of the current block. For example, if the residual signal of the neighboring block having the same intra prediction mode as the current block is first transformed by DCT-V in the horizontal direction and DST-VII in the vertical direction, the first transform of the residual signal of the current block is also horizontal. The direction can be carried out by DCT-V and the vertical direction by DST-VII.

As another example, when the intra prediction mode of the current block is the same as the neighboring block of the current block, the secondary transform of the current block may be set equal to the secondary transform applied to the neighboring block having the same intra prediction mode as the current block. Can be. Accordingly, encoding / decoding of encoding information (eg, transform information (or transform index) for the secondary transform) required for secondary transforming the residual signal of the current block may be omitted.

For example, when the intra prediction mode of the current block is determined to be mode 35, and at least one intra prediction mode of at least one neighboring block adjacent to the current block is also determined to be mode 35, the intra prediction mode is determined to be 35. The secondary transform applied to the residual signal of the neighboring block of number 35 may be used as the secondary transform of the residual signal of the current block.

As another example, when the intra prediction mode of the current block is the same as the neighboring block of the current block, the scanning order of the current block may be set to be the same as the scanning order of the neighboring block having the same intra prediction mode as the current block. Accordingly, encoding information (e.g., diagonal, horizontal, or vertical), which is required for scanning quantized transformed coefficients for the residual signal of the current block, means scanning order. Encoding / decoding of at least one scanning order index of the vertical direction may be omitted.

In addition to the above-described example, two or more of the first transform, the second transform, and the scanning order of the neighboring block having the same intra prediction mode as the current block may be derived as encoding information of the current block.

For example, the first and second transforms of the neighboring block having the same intra prediction mode as the current block may be applied to the current block, or the first and second transform orders of the neighboring blocks or the second order and scanning sequences of the neighboring blocks may be applied. Applicable to the current block. Alternatively, it is also possible to apply the first transform, the second transform and the scanning order of the neighboring blocks having the same intra prediction mode as the current block to the current block.

When there are a plurality of neighboring blocks having the same intra prediction mode as the current block around the current block, encoding information of the current block may be derived based on the priority of the neighboring blocks. For example, if the left neighboring block and the top neighboring block of the current block have the same intra prediction mode as the current block, and the priority of the left neighboring block is higher than that of the upper neighboring block, the encoding information of the current block is the left neighboring. It may be derived based on the encoding information of the block.

As another example, when there are a plurality of neighboring blocks having the same intra prediction mode as the current block around the current block, information for identifying a neighboring block used to derive encoding information of the current block may be signaled through a bitstream. have. In this case, encoding information about the residual signal of the current block may be derived from the neighboring block indicated by the information for identifying the neighboring block (for example, the neighboring block index).

If there is no neighboring block having the same intra prediction mode as the current block, entropy encoding / decoding of the encoding information on the residual signal of the current block may be performed (S1803). For example, when there is no neighboring block having the same intra prediction mode as the current block, the transform information (or transform index) for the primary transform of the current block, the transform information (or transform index) for the secondary transform, or At least one of the information (or the scanning index) about the scanning order may be entropy encoded / decoded.

In the above-described embodiment, it has been described that the encoding information for the residual signal of the current block is derived from the neighboring block, provided that the intra prediction mode of the current block and the intra prediction mode of the neighboring block are the same. As another example, it is also possible to derive the second encoding information on the residual signal of the current block from the neighboring block in which the first encoding information on the residual signal is the same as the current block. Here, the first encoding information and the second encoding information may include at least one of information on the first transform, information on the second transform, and a scanning order.

For example, if there is at least one neighboring block using the same primary transform as the primary transform determined for the current block, the secondary transform of the current block is applied to the neighboring block using the same primary transform as the current block. Can be set to transform. In this case, the encoding / decoding of the encoding information necessary to quadratic transform the residual signal for the current block may be omitted. For example, assume that the first-order transform on the residual signal of the current block is determined as DCT-V in the horizontal direction and DST-VII in the vertical direction. If the primary transform of one or more of the neighboring blocks of the current block is determined to be DCT-V in the horizontal direction and DST-VII in the vertical direction, the secondary transform of the neighboring block to which the same primary transform is applied as the current block is applied. It can be applied as a quadratic transformation of a block.

Alternatively, the scanning order of neighboring blocks using the same primary transform as the primary transform of the current block may be applied as the scanning order of the current block. Alternatively, it is also possible to apply the secondary transform and scanning order of the neighboring block using the same primary transform as the primary transform of the current block to the current block.

In the above-described embodiment, it has been described that the at least one of the secondary transform or the scanning order of the current block is derived from the neighboring block using the same primary transform as the current block, but the neighbor using the same secondary transform as the current block has been described. Deriving at least one of the first transform or scanning order of the current block from the block, or deriving at least one of the first or second transform of the current block from a neighboring block using the same scanning order as the current block It is possible.

The second encoding information of the current block may be derived from a neighboring block in which the intra prediction mode and the first encoding information are the same as the current block.

For example, if there is at least one neighboring block using the same intra prediction mode and the primary transform as the intra prediction mode determined for the current block and the primary transform determined for the current block, the secondary transform of the current block is performed. It may be set to a second transform applied to a neighboring block that is the same as the intra prediction mode of the current block and uses the same first transform as the current block. In this case, the encoding / decoding of the encoding information necessary to quadratic transform the residual signal for the current block may be omitted.

Alternatively, the scanning order of neighboring blocks having the same intra prediction mode and the first transform may be applied as the scanning order of the current block. Alternatively, the secondary transform and scanning order of neighboring blocks in which the intra prediction mode and the primary transform are the same as the current block may be applied to the current block.

In the above-described embodiment, it has been described that at least one of the secondary transform or the scanning order of the current block is derived from a neighboring block having the same intra prediction mode as the current block and using the same primary transform as the current block. Not only this, but derive at least one of the first transform or scanning order of the current block from the neighboring block having the same intra prediction mode as the current block and using the same secondary transform as the current block, or the same screen as the current block It is also possible to derive at least one of the first-order transform or the second-order transform of the current block from the neighboring block with the prediction mode and using the same scanning order as the current block.

19 is a flowchart illustrating a process of determining whether to derive encoding information about a residual signal of a current block from a neighboring block when the current block is encoded by inter-screen prediction.

First, it may be determined whether the inter prediction mode of the current block is a merge mode (S1901). When the inter prediction mode of the current block is the merge mode, a neighboring block merged with the current block may be determined in order to derive motion information of the current block (S1902). As an example, the neighboring block merged with the current block may be determined by a merge index indicating a neighboring block to be merged with the current block in the merge candidate list. Here, the neighboring blocks of the current block may include not only neighboring blocks spatially adjacent to the current block, but also neighboring blocks temporally adjacent to the current block.

When the neighboring block merged with the current block is determined, the encoding information of the residual signal of the neighboring block merged with the current block may be derived as the encoding information of the residual signal of the current block (S1903). For example, at least one of the primary transform, the secondary transform, or the scanning order of the current block may be set to be the same as at least one of the primary transform, the secondary transform, or the scanning order of the neighboring block merged with the current block.

When the inter prediction mode of the current block is not the merge mode, it may be determined whether a neighboring block having the same motion information as the motion information of the current block exists among the neighboring blocks of the current block (S1904). Here, the motion information may include at least one of a motion vector, a reference picture index, or a reference picture direction.

When a neighboring block having the same motion information as the motion information of the current block exists, encoding information about the residual signal of the neighboring block having the same motion information as the current block may be derived as encoding information about the residual signal of the current block. (S1905). For example, at least one of the first transform, the second transform, or the scanning order of the current block may include a first transform of a neighboring block in which at least one of a motion vector, a reference picture index, and a reference picture direction of the current block is the same as the current block, It may be set equal to at least one of the quadratic transformation or the scanning order.

If there is no neighboring block having the same motion information as the current block, entropy encoding / decoding of the encoding information on the residual signal of the current block may be performed (S1906). For example, when there is no neighboring block having the same motion information as the current block, the transform information (or transform index) for the primary transform of the current block, the transform information (or transform index) for the secondary transform, or the scanning order At least one of information (or scanning indexes) for the entropy may be encoded / decoded.

In the example illustrated in FIG. 19, it is illustrated that a neighboring block for deriving encoding information about a residual signal of the current block is adaptively determined according to whether an inter prediction mode of the current block is a merge mode. Unlike the example illustrated in FIG. 19, only when the inter prediction mode of the current block is the merge mode, encoding information about the residual signal of the current block may be derived from the neighboring block. Alternatively, the encoding information of the current block may be derived from a neighboring block having the same motion information as the current block, regardless of whether the inter prediction mode of the current block is the merge mode.

In the above-described embodiment, the encoding information for the residual signal of the current block is derived from the neighboring block, provided that the motion information of the current block is identical to the motion information of the neighboring block. As another example, it is also possible to derive the second encoding information for the residual signal of the current block from the neighboring block in which the first encoding information for the motion information and the residual signal are the same as the current block.

After obtaining the motion information of the current block as in the above-described embodiment, it is possible to derive the encoding information of the current block from the neighboring block based on whether the motion information of the current block is the same as the motion information of the neighboring block. In addition, it is also possible to derive encoding information of the current block based on the motion information of the neighboring block without considering the motion information of the current block.

Encoding information such as the above-described primary transform, secondary transform, or scanning order may include information indicating whether a predefined type (eg, a predefined transform type or a predefined scanning type) is used or a predefined type. It may be encoded / decoded based on at least one of information indicating any one of the remaining residual types (eg, residual transform type or residual scanning type).

For example, when a residual signal is generated through intra prediction and / or inter prediction, information indicating whether a predefined transformation type is applied to the residual signal may be encoded. Here, the predefined transformation type may be, but is not limited to, a transformation type (eg, DCT-II) most used to transform the residual signal. The information may be a 1-bit flag (eg, Transform Flag, TM flag). For example, when the TM flag is 0 (or 1), it means that a predefined transformation type is applied to the residual signal, and when the TM flag is 1 (or 0), a transformation predefined in the residual signal is applied. This may mean that a conversion type other than the type is applied. Alternatively, the information may be configured with a flag of two or more bits, and the first bit may be used to indicate whether or not a predefined transform type is used for the first transform, and the second bit may be a predefined transform for the secondary transform. It may indicate whether a type is used.

When the information indicates that a transform type other than the predefined transform type is applied to the residual signal, information for specifying one of the residual transform types may be encoded. Here, the residual transform type may indicate a remaining transform type except for a predefined transform type among transform types applicable to the residual signal. For example, when the predefined transform type is DCT-II, the residual transform type may include at least one of DCT-V, DCT-VIII, DST-I, or DST-VII. The information may be index information TM idx specifying any one of the remaining transform types, and the index information may have any positive integer. For example, TM idx 1 may represent DCT-V, 2 is DCT-VIII, 3 is DST-I, and 4 is DST-VII.

The index information may indicate a combination of transform types for the horizontal and vertical directions of the residual signal. That is, the 1D transform type for the horizontal / vertical direction may be determined by one index information. For example, if TM idx is 1 while TM flag is 1, a transform type combination mapped to TM idx 1 may be determined as a transform type for horizontal and vertical directions for the current block. For example, if TM idx indicates DCT-V for the horizontal direction and DCT-VIII for the vertical direction, the DCT-V and DCT-VIII may be determined as the horizontal direction transform type and the vertical direction transform type of the current block, respectively. have.

In determining the encoding parameter of the current block, at least one of information specifying whether a predefined type is used or a residual type may be derived from a neighboring block of the current block. For example, at least one of information (TM flag) indicating whether a predefined transform type of the current block is applied or information (TM idx) for specifying one of a residual transform type may be derived from a neighboring block of the current block. have.

For example, at least one of the TM flag and TM idx of the current block may be derived with the same value as the neighboring block of the current block.

Alternatively, when at least one TM flag of the neighboring blocks of the current block is 1, the TM flag for the current block may be implicitly assumed to be 1 to perform encoding / decoding. In this case, the TM idx for the current block may be explicitly transmitted over the bitstream or may be implicitly derived from neighboring blocks.

For example, from among neighboring blocks used in intra-picture prediction or inter-screen prediction of the current block, any one of information (TM flag) indicating whether a predefined transform type for the current block is applied or a residual transform type At least one of information TM idx for specifying a may be derived.

For example, when the inter prediction mode of the current block is the merge mode, the merge candidate may be newly configured in consideration of at least one of the TM flag and TM idx. The newly configured merge candidate list may include a merge candidate having at least one of a TM flag and a TM idx having a different value. For example, although the first merge candidate and the second merge candidate have the same motion information, the merge candidate list may be configured to have different TM flags and / or TM idx. At least one of the TM flag or TM idx of the current block may be determined to be the same as the merge candidate indicated by the merge index Merge_idx. Accordingly, not only motion information (motion vector, reference picture index, inter prediction prediction direction indicator) of the current block, but also TM flag and / or TM idx may be encoded / decoded based on the merge mode.

In this case, the information indicating that the merge candidate list is newly configured may be explicitly transmitted through the bitstream. The transmitted information may be a 1-bit flag, but is not limited thereto. Alternatively, when the TM flag of at least one or more neighboring blocks of the current block is 1, it may be implicitly recognized that the merge candidate list is newly constructed. Here, the neighboring block may be a block in which the TM flag is first of 1 according to a predetermined neighboring block scan order, or may be a block having a predefined position.

In the above-described embodiment, a method of deriving information (eg, TM flag and / or TM idx) for determining a transform type from neighboring blocks of the current block has been described. The described embodiment may be applied to at least one of determining a transform type for the primary transform of the current block or determining a transform type for the secondary transform. As an example, that is, transformation information (eg, TM flag (1 ^st TM flag) and / or TM idx (1 ^st TM idx)) for the primary transformation or transformation information (eg, TM flag (2nd) for the secondary transformation at least one of the flag TM) or TM idx (idx 2 ^nd TM)) can be derived from a neighboring block to the current block.

In addition, apart from the merge candidate list generated based on the motion information, the merge candidate list may be generated based on the transform information for the current block. For example, the merge candidate list generated based on the motion information of the neighboring block is defined as a 'first merge candidate list', and the merge candidate list generated based on the transform information of the neighboring block is referred to as a 'second merge candidate list'. If defined, the motion information of the current block is derived from the merge candidate specified by the first merge index in the first merge candidate list, while the transform information of the current block is determined by the second merge index in the second merge candidate list. It can be derived from the specified merge candidate.

In addition, information for determining the scanning order of the current block (eg, Scan flag and / or Scan idx) may be derived from neighboring blocks of the current block. Here, the scan flag indicates whether the scanning order of the current block is the same as the predefined scanning order, and Scan idx may be information indicating any one of the remaining scanning orders.

According to another embodiment of the present invention, the same encoding information may be applied to all blocks located in a signaling block in a picture or slice currently encoded / decoded. Here, the signaling block may mean an area having a small size for at least one of horizontal and vertical resolutions of the current picture or the current slice. That is, the signaling block may be defined as a predetermined area having a size smaller than the current picture or the current slice.

Information on the signaling block may be transmitted through at least one of a sequence unit, a picture unit, or a slice header. For example, at least one of the size, shape, or location of the signaling block may be transmitted through at least one of a sequence parameter set, a picture parameter set, or a slice header. Alternatively, the information about the signaling block may be implicitly derived through encoding information of the current block or neighboring blocks adjacent to the current block. The signaling block may have a square or rectangular shape, but is not limited thereto.

Encoding information about the signaling block may be applied to all blocks included in the signaling block. For example, for all blocks included in the signaling block, at least one of a primary transform, a secondary transform, or a scanning order may be set to be the same. Encoding information applied to all blocks included in the signaling block may be transmitted through a bitstream. Alternatively, encoding information of a specific location block in the signaling block may be applied to all blocks included in the signaling block.

In the above-described embodiment, all blocks included in the signaling block have been described as having the same encoding information. As another example, only blocks satisfying a predetermined condition among blocks included in the signaling block may be configured to have the same encoding information. Here, the predetermined condition may be defined by at least one of the size, shape or depth of the block. For example, at least one of a primary transform, a secondary transform, or a scanning order may be set to be the same for blocks that are smaller than or equal to a predetermined size (eg, blocks of 4x4 size or less) among all blocks included in the signaling block.

The above-described embodiments of obtaining encoding information of the current block may be applied to luminance and color difference components. In addition, by using at least one method of the above embodiments, information indicating that at least one of the first transform, the second transform, or the scanning of the residual signal of the current block may be encoded / decoded. In the case of entropy encoding / decoding the information, truncated rice binarization method, K-th order Exp_Golomb binarization method, limited K-th order Exp_Golomb binarization method At least one entropy encoding method may be used, such as a fixed-length binarization method, a unary binarization method, or a truncated unary binarization method. In addition, after binarizing the information, the information may be finally encoded / decoded using CABAC (ae (v)). Alternatively, it may be implicitly derived that encoding information of the current block is determined using at least one of the above embodiments according to the size and shape of the current block.

Next, the encoding / decoding of the motion vector information will be described in detail.

When the current block is encoded by inter-screen prediction, the encoder may transmit a motion vector difference (MVD) indicating a difference between the motion vector of the current block around the current block and the motion vector of the current block, to the decoder. have.

The decoder may derive the motion vector candidate of the current block in which the neighboring coding of the current block is completed and the motion vector candidate of the current block. In detail, the decoder may derive a motion vector candidate from at least one of temporal and / or spatial motion vectors for which decoding is completed for the current block, and then construct a motion vector candidate list (MVP list).

The encoder may transmit information (eg, MVP list index) indicating information about a motion vector prediction value used to derive a motion vector difference value among motion vector candidates included in the motion vector candidate list. Then, the decoding apparatus may determine a motion vector candidate indicated by the MVP list index as a motion vector prediction value, and derive a motion vector for the current block by using the motion vector prediction value and the motion vector difference value.

Based on the above description, a method of encoding / decoding motion vector information of a current block according to the present invention will be described in detail.

20 is a flowchart illustrating a process of decoding a motion vector of a current block.

First, a spatial motion vector candidate for the current block can be derived (S2001). The spatial motion vector of the current block may be derived from a pre-encoded / decoded block included in the same picture as the current block.

21 is a diagram for explaining an example of deriving a spatial motion vector candidate.

As in the example shown in FIG. 21, the block B1 adjacent to the top of the current block X, the block A1 adjacent to the left of the current block, the block B0 adjacent to the upper right corner of the current block, the current block The spatial motion vector of the current block can be derived from the block B2 located at the upper left corner and the block A0 adjacent to the lower left corner of the current block. The spatial motion vector derived from the neighboring block of the current block may be determined as the spatial motion vector candidate of the current block.

In this case, the spatial motion vector candidates may be derived in a predetermined order. For example, the spatial motion vector candidate may determine whether a motion vector exists in each block in the order of A0, A1, B0, B1, and B2. When the motion vector of the neighboring block exists, the motion vector of the neighboring block may be determined as a spatial motion vector candidate.

If the reference image of the neighboring block is different from the reference image of the current block, the movement of the neighboring block is performed using the distance between the current image and the reference image referenced by the neighboring block and the distance between the current image and the reference image referenced by the current block The vector may be scaled with a motion vector, and the scaled motion vector may be determined as a spatial motion vector of the current block.

Next, a temporal motion vector candidate of the current block can be derived (S2002). The temporal motion vector of the current block may be derived from the reconstructed block in the co-located picture.

22 is a diagram for explaining an example of deriving a temporal motion vector candidate.

As in the example shown in FIG. 22, outside of a co-located block C corresponding to a position spatially identical to the current block X in a co-located picture of the current picture. A temporal motion vector candidate of the current block can be derived from a block of H position existing at or a block of C3 position present in the corresponding position block C. The temporal motion vector candidate may be derived sequentially from the block at the H position and the block at the C3 position. For example, when a motion vector can be derived from a block of H position, a temporal motion vector candidate can be derived from a block of H position. On the other hand, if the motion vector cannot be derived from the block at the H position, a temporal motion vector candidate can be derived from the block at the C3 position. If the H position or C3 position block is encoded by intra prediction, the temporal motion vector candidate of the current block cannot be derived.

In addition to the example illustrated in FIG. 22, a co-located picture indicated by the motion information acquired for the current block and a corresponding location block included in the corresponding location image indicated by the motion information and surrounding the corresponding location block From the block, one or more temporal motion vector candidates may be derived for the current block. Here, the motion information may include at least one of a picture index indicating a corresponding location image and a motion vector indicating a corresponding location block in the corresponding location image. The motion information for specifying the location of the corresponding location image and the corresponding location block may be separately signaled with respect to the current block.

Temporal motion vector candidates of the current block may be obtained in units of subblocks smaller in size than the current block. For example, when the size of the current block is 8x8, a temporal motion vector candidate may be obtained in units of subblocks smaller than the size of the current block, such as 2x2, 4x4, 8x4, 4x8, and the like. The shape of the sub block may have a square or rectangular shape. In addition, the size or shape of the sub-block may be a predetermined fixed in the encoder / decoder, or may be determined dependent on the size or shape of the current block.

Thereafter, a motion vector candidate list including at least one of a spatial motion vector candidate and a temporal motion vector candidate may be generated (S2003).

 In this case, the motion vector candidate list may be configured to include at least one temporal motion vector candidate. For example, when the number of motion vector candidates that a motion vector candidate list can include is N (where N is a positive integer greater than 0), at least one motion vector candidate must be included in the motion vector candidate list. A motion vector candidate list can be constructed. If at least N different spatial motion vector candidates can be derived in the process of deriving the spatial motion vector candidates, at least one of the N spatial motion vector candidates is removed from the motion vector candidate list through randomness determination. can do. Accordingly, the temporal motion vector candidate may be included in the motion vector candidate list. Here, any similarity determination may be performed using two or more spatial motion vectors through a maximum, minimum, average, median, or arbitrary sum of weights, even if the spatial motion vectors have different values. Can mean merging them into one. The randomness determination can reduce the number of spatial motion vector candidates.

Alternatively, when N spatial motion vector candidates are included according to a predetermined priority in the motion vector candidate list, at least one or more of the spatial motion vector candidates may be removed from the motion vector candidate list in the reverse order of priority. That is, at least one or more can be removed from the motion vector candidate list, starting with the next-order spatial motion vector candidate. Accordingly, the temporal motion vector candidate may be included in the motion vector candidate list.

Whether to remove the spatial motion vector candidate from the motion vector candidate list described above may be determined depending on whether the temporal motion vector candidate is used. In addition, the number of spatial motion vector candidates removed from the motion vector candidate list may be determined according to the number of temporal motion vector candidates used for the current block or the number of temporal motion vector candidates available for the current block.

Alternatively, the temporal motion vector candidate may be included in the motion vector candidate list by increasing the number of motion vector candidates that may be included in the motion vector candidate list (ie, up to N + 1).

Thereafter, any one of the motion vector candidates included in the motion vector candidate list may be determined as the motion vector prediction value of the current block (S2004). For example, decoding may determine a motion vector prediction value of the current block based on information (eg, MVP list index) specifying one of the motion vector candidates included in the motion vector candidate list.

When the motion vector prediction value of the current block is determined, the motion vector of the current block may be obtained using the motion vector difference value (S2005). The motion vector difference value may indicate a difference between the motion vector of the current block and the motion vector prediction value of the current block. The motion vector difference value for the current block may be entropy encoded / decoded through the bitstream.

According to an embodiment of the present invention, in order to reduce the amount of information on the motion vector difference value, the motion vector difference value of the current block is encoded using the motion vector difference value of the reconstructed blocks encoded by inter-screen prediction around the current block. You may. For example, a second motion vector difference indicating a difference between a motion vector difference value indicating a difference between a motion vector and a motion vector prediction value of the current block and a motion vector difference value of the reconstructed blocks encoded by inter-screen prediction around the current block. The value can be encoded for the current block.

FIG. 23 is a diagram for describing a second motion vector difference value. FIG.

Assume that the motion vector difference value MVD for the current block 2 is (5, 5). In this case, the second motion vector difference value for the current block may be encoded by using the motion vector difference value of the upper block Block 1 located at the top of the current block.

For example, assuming that the motion vector difference value of the upper block is (5, 5), since the motion vector difference value of the current block is the same as the motion vector difference value of the upper block, the second motion vector difference value of the current block is ( 0, 0). If the second motion vector difference value (0, 0) is encoded instead of the motion vector difference value (5, 5), the amount of information used to encode the motion vector difference value for the current block can be reduced.

Alternatively, when a block having a motion vector difference value equal to the motion vector difference value of the current block exists, instead of transmitting the motion vector difference value of the current block, the motion vector difference value of the current block may be derived from the neighboring block. .

As in the above example, information indicating the position of the neighboring block used to derive the second motion vector candidate of the current block or the position of the neighboring block having the same motion vector difference value as the current block is explicitly transmitted through the bitstream. Can be. For example, information used to derive a second motion vector candidate among neighboring blocks of the current block or identifying a neighboring block having the same motion vector candidate as the current block is transmitted to the decoder through a bitstream. Can be.

As another example, the information indicating the position of the neighboring block used to derive the second motion vector candidate of the current block or the position of the neighboring block having the same motion vector difference value as the current block is implied according to the same process in the encoder / decoder. May be induced. For example, the motion vector difference value of the neighboring block used as the motion vector predictor (MVP) of the current block may be used as the motion vector difference predictor (MVD Predictor) for deriving the second motion vector difference value of the current block. .

When the current block is encoded by bidirectional prediction, information indicating whether motion vector difference values for the reference picture list 0 (List 0) and the reference picture list 1 (List 1) are the same may be encoded. Here, the same motion vector difference values may mean a case in which the signs and magnitudes of the motion vector difference values are the same, or may mean a case in which the signs of the motion vector difference values are different but the same magnitude. When the motion vector difference values for the reference picture list 0 and the reference picture list 1 are the same, encoding / decoding for any one of the motion vector difference values of the reference picture list 0 and the reference picture list 1 may be omitted.

According to another embodiment of the present invention, all blocks located in a signaling block in a picture or slice to be currently encoded / decoded may have one or more identical motion vector prediction values to derive an optimal motion vector difference value (MVD). (MVP). Alternatively, according to another embodiment of the present invention, all blocks located in a signaling block in a picture or slice to be currently encoded / decoded may include one or more identical motion vectors to derive an optimal second motion vector difference value. It may have a differential prediction value (MVD Predictor). In this case, a motion vector prediction value or a motion vector difference prediction value may be transmitted for each signaling block, or a motion vector prediction value or a motion vector difference prediction value may be implicitly derived using encoding information of neighboring blocks around the signaling block. Here, the signaling block may mean an area having a small size for at least one of horizontal and vertical resolutions of the current picture or the current slice. That is, the signaling block may be defined as a predetermined area having a size smaller than the current picture or the current slice.

Information on the signaling block may be transmitted through at least one of a sequence unit, a picture unit, or a slice header. For example, at least one of the size, shape, or location of the signaling block may be transmitted through at least one of a sequence parameter set, a picture parameter set, or a slice header. Alternatively, the information about the signaling block may be implicitly derived through encoding information of the current block or neighboring blocks adjacent to the current block. The signaling block may have a square or rectangular shape, but is not limited thereto.

The inter-screen decoding / decoding process may be performed on each of luminance and chrominance signals. For example, at least one method of acquiring an inter-prediction indicator, generating a motion vector candidate list, deriving a motion vector, and performing a motion compensation may be differently applied to the luminance signal and the chrominance signal during the inter-picture encoding / decoding process.

The inter-decoding / decoding process for the luminance and chrominance signals may be performed in the same manner. For example, at least one of an inter prediction prediction indicator, a motion vector candidate list, a motion vector candidate, a motion vector, and a reference image may be equally applied to the color difference signal in the inter-picture sub / decoding process applied to the luminance signal.

The above methods can be performed in the same way in the encoder and the decoder. For example, at least one or more methods of motion vector candidate list derivation, motion vector candidate derivation, motion vector derivation, and motion compensation may be applied to the encoder and the decoder in the inter-picture encoding / decoding process. In addition, the order of applying the above methods may be different in the encoder and the decoder.

The above embodiments of the present invention may be applied according to the size of at least one of a coding block, a prediction block, a block, and a unit. The size here may be defined as a minimum size and / or a maximum size for the above embodiments to be applied, or may be defined as a fixed size to which the above embodiments are applied. In addition, in the above embodiments, the first embodiment may be applied at the first size, and the second embodiment may be applied at the second size. That is, the embodiments may be applied in combination according to the size. In addition, the above embodiments of the present invention can be applied only when the minimum size or more and the maximum size or less. That is, the above embodiments can be applied only when the block size is included in a certain range.

For example, the above embodiments may be applied only when the size of an encoding / decoding target block is 8x8 or more. For example, the above embodiments may be applied only when the size of the encoding / decoding target block is 16x16 or more. For example, the above embodiments may be applied only when the size of the encoding / decoding target block is 32x32 or more. For example, the above embodiments may be applied only when the size of the encoding / decoding target block is 64x64 or more. For example, the above embodiments may be applied only when the size of the encoding / decoding target block is 128x128 or more. For example, the above embodiments may be applied only when the size of the encoding / decoding target block is 4x4. For example, the above embodiments may be applied only when the size of an encoding / decoding target block is 8x8 or less. For example, the above embodiments may be applied only when the size of an encoding / decoding target block is 16x16 or less. For example, the above embodiments may be applied only when the size of an encoding / decoding target block is 8x8 or more and 16x16 or less. For example, the above embodiments may be applied only when the size of the encoding / decoding target block is 16x16 or more and 64x64 or less.

The above embodiments of the present invention can be applied according to a temporal layer. A separate identifier is signaled to identify the temporal layer to which the embodiments are applicable and the embodiments can be applied to the temporal layer specified by the identifier. The identifier here may be defined as a minimum layer and / or a maximum layer to which the embodiment is applicable, or may be defined as indicating a specific layer to which the embodiment is applied.

For example, the above embodiments may be applied only when the temporal layer of the current image is the lowest layer. For example, the above embodiments may be applied only when the temporal layer identifier of the current image is zero. For example, the above embodiments may be applied only when the temporal layer identifier of the current image is one or more. For example, the above embodiments may be applied only when the temporal layer of the current image is the highest layer.

The reference picture set used in the process of reference picture list construction and reference picture list modification as in the embodiment of the present invention is one of L0, L1, L2, and L3. At least one reference picture list may be used.

According to the embodiment of the present invention, when calculating the boundary strength in the deblocking filter, one or more motion vectors of the encoding / decoding target block may be used. Where N represents a positive integer of 1 or more, and may be 2, 3, 4, or the like.

When predicting motion vectors, the motion vectors are in 16-pel units, 8-pel units, 4-pixel units, integer-pel units, 1/2 -1 / 2-pel units, 1 / 4-pel units, 1 / 8-pixel units 1 / 8-pel, 1 / 16-pixel units The above embodiments of the present invention may also be applied when the device has at least one of 1), 1 / 32-pixel (1 / 32-pel) units, and 1 / 64-pixel (1 / 64-pel) units. In addition, when performing motion vector prediction, a motion vector may be selectively used for each pixel unit.

A slice type to which the above embodiments of the present invention are applied is defined, and the above embodiments of the present invention may be applied according to the corresponding slice type.

For example, when the slice type is Tri-predictive (T) -slice, a prediction block is generated using at least three or more motion vectors, and a weighted sum of at least three or more prediction blocks is calculated to calculate a block to be encoded / decoded. It can be used as the final prediction block of. For example, when the slice type is Q (quad-predictive) -slice, the prediction block is generated using at least four or more motion vectors, and the weighted sum of the at least four or more prediction blocks is calculated to calculate the block to be encoded / decoded. It can be used as the final prediction block of.

The above embodiments of the present invention can be applied not only to inter prediction and motion compensation methods using motion vector prediction, but also to inter prediction and motion compensation methods using skip mode and merge mode.

The shape of the block to which the embodiments of the present invention are applied may have a square shape or a non-square shape.

In the above-described embodiments, the methods are described based on a flowchart as a series of steps or units, but the present invention is not limited to the order of steps, and certain steps may occur in a different order or simultaneously from other steps as described above. Can be. Also, one of ordinary skill in the art appreciates that the steps shown in the flowcharts are not exclusive, that other steps may be included, or that one or more steps in the flowcharts may be deleted without affecting the scope of the present invention. I can understand.

The above-described embodiments include examples of various aspects. While not all possible combinations may be described to represent the various aspects, one of ordinary skill in the art will recognize that other combinations are possible. Accordingly, the invention is intended to embrace all other replacements, modifications and variations that fall within the scope of the following claims.

Embodiments according to the present invention described above may be implemented in the form of program instructions that may be executed by various computer components, and may be 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. Program instructions recorded on the computer-readable recording medium may be those specially designed and configured for the present invention, or may be known and available to those skilled in the computer software arts. Examples of computer-readable recording media include magnetic media such as hard disks, floppy disks and magnetic tape, optical recording media such as CD-ROMs, DVDs, and magneto-optical media such as floptical disks. media), and hardware devices specifically configured to store and execute program instructions, such as ROM, RAM, flash memory, and the like. Examples of program instructions include not only machine code generated by a compiler, but also high-level language code 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 to perform the process according to the invention, and vice versa.

Although the present invention has been described by specific embodiments such as specific components and the like, but the embodiments and the drawings are provided to assist in a more general understanding of the present invention, the present invention is not limited to the above embodiments. For those skilled in the art, various modifications and variations can be made from these descriptions.

Accordingly, the spirit of the present invention should not be limited to the above-described embodiments, and all of the equivalents or equivalents of the claims, as well as the appended claims, fall within the scope of the spirit of the present invention. I will say.

The present invention can be used in an apparatus for encoding / decoding an image.

Claims (14)

1. Generating a prediction signal for the current block;

   Generating a residual signal for the current block based on the prediction signal;

   Determining a conversion technique for transforming the residual signal; And

   Quantizing the residual signal;

   The transform includes a primary transform and a secondary transform, and at least one of the primary transform method and the secondary transform method is derived from a reconstructed block in which encoding around the current block is completed. .
2. According to claim 1,

   The prediction signal is generated through intra prediction.

   At least one of the first order transform method and the second order transform method is characterized in that the intra prediction mode is derived from a neighboring block that is the same as the current block.
3. The method of claim 2,

   In the case where the intra-prediction mode of the neighboring block equal to the current block indicates a transform skip, the first transform method and the second transform method for the current block are determined as transform skip. The video encoding method.
4. According to claim 1,

   At least one of the second order transform technique or the scanning order of the quantized residual signal is characterized in that the first order transform scheme is derived from the same neighboring block as the current block.
5. According to claim 1,

   The prediction signal is generated through inter prediction.

   At least one of the first-order transform technique and the second-order transform technique is characterized in that the motion information is derived from the same neighboring block as the current block.
6. The method of claim 5,

   And the motion information comprises at least one of a motion vector, a reference picture index, or a reference picture direction.
7. Obtaining a quantized residual signal for the current block;

   Dequantizing the quantized residual signal; And

   Determining a transformation technique for inversely transforming the residual signal,

   The inverse transform includes a first-order transform and a second-order transform, and at least one of the first-order transform method and the second-order transform method is derived from a decoded reconstructed block around the current block. .
8. The method of claim 7, wherein

   When the current block is encoded by intra prediction, at least one of the first transform method and the second transform method is characterized in that the intra prediction mode is derived from a neighboring block that is the same as the current block. Way.
9. The method of claim 8,

   In the case where the intra-prediction mode of the neighboring block equal to the current block indicates a transform skip, the first transform method and the second transform method for the current block are determined as transform skip. A video decoding method.
10. The method of claim 7, wherein

    The secondary transform scheme is a video decoding method, characterized in that the primary transform scheme is derived from the same neighboring block as the current block.
11. The method of claim 7, wherein

    And when the current block is encoded by inter prediction, at least one of the first transform method and the second transform method is characterized in that motion information is derived from a neighboring block identical to the current block.
12. The method of claim 11, wherein

    The motion information includes at least one of a motion vector, a reference picture index, and a reference picture direction.
13. Determining a motion vector for the current block;

    Determining a motion vector prediction value for the current block based on at least one of a spatial motion vector candidate or a temporal motion vector candidate of the current block;

    Determining a first motion vector prediction difference value representing a difference value between the motion vector and the motion vector prediction value; And

    And encoding a second motion vector prediction difference value indicating a difference between the first motion vector prediction difference value and a motion vector prediction difference value of a reconstructed block around the current block.
14. Deriving at least one of a spatial motion vector candidate or a temporal motion vector candidate for the current block;

    Generating a motion vector candidate list including at least one of the spatial motion vector candidate or the temporal motion vector candidate;

    Obtaining a motion vector prediction value of the current block by using the motion vector candidate list;

    Obtaining a second motion vector difference value for the current block;

    Obtaining a first motion vector difference value based on a motion vector difference value of the reconstructed block around the current block and the second motion vector difference value; And

    And obtaining a motion vector of the current block based on the first motion vector difference value and the motion vector prediction value.

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