KR20190067732A - Method and apparatus for encoding and decoding using selective information sharing over channels - Google Patents

Abstract

A video decoding method, a video decoding apparatus, a video encoding method, and a video encoding apparatus are disclosed. Coding determination information of a representative channel of a target block is shared as coding determination information of a target channel of the target block, and decoding of the target block is performed by using the coding determination information of the target channel. As the coding determination information of the representative channel is shared with other channels, the same coding determination information can be prevented from being repeatedly signaled. The efficiency of encoding and decoding on the target block or the like can be improved through the prevention.

Description

[0001] METHOD AND APPARATUS FOR ENCODING AND DECODING USING SELECTIVE INFORMATION SHARING OVER CHANNELS [

The following embodiments are directed to a video decoding method, a decoding apparatus, a coding method, and an encoding apparatus, and more particularly, to a video decoding method, a decoding apparatus, a coding method, and an encoding apparatus using selective information sharing among channels.

With the continuous development of the information and telecommunication industry, broadcasting service with HD (High Definition) resolution spread worldwide. With this proliferation, many users become accustomed to high resolution and high quality images and / or video.

In order to meet the users' demand for high image quality, many organizations are spurring development on next generation image devices. In addition to High Definition TV (HDTV) and Full HD (FHD) TVs, users' interest in ultra high definition (UHD) TVs with more than four times the resolution of FHD TVs As the interest increases, there is a need for image encoding / decoding techniques for images with higher resolution and image quality.

An apparatus and method for encoding / decoding an image includes an inter prediction technique, an intra prediction technique, and an entropy coding technique to perform encoding / decoding on high resolution and high image quality images Can be used. The inter prediction technique may be a technique of predicting a value of a pixel included in a target picture temporally using a previous picture and / or a temporally subsequent picture. The intra prediction technique may be a technique of predicting a value of a pixel included in a target picture by using information of a pixel in the target picture. The entropy coding technique may be a technique of allocating a short code to a symbol having a high appearance frequency and allocating a long code to a symbol having a low appearance frequency.

The demand for high quality images that can provide high resolution, wider color space and superior image quality, such as UHD images in recent years, is increasing in various applications. The higher the resolution and quality of the image, the greater the amount of image data required to provide the image, relative to the amount of the existing image data. In accordance with the increase in the amount of the image data, various kinds of broadcasting media such as a wired / wireless broadband line, a satellite, a terrestrial wave, an internet protocol (IP) network, a wireless network, a cable, In a case where the data is stored using various storage media such as a CD, a DVD, a USB, and an HD-DVD, transmission costs and storage costs are increased do.

As high resolution and high quality images are used, high-efficiency image encoding / decoding techniques are required to solve these problems that are inevitably further intensified with respect to image data and to provide images with higher resolution and higher image quality do.

One embodiment can provide an encoding apparatus, an encoding method, a decoding apparatus, and a decoding method using selective information sharing between channels.

Sharing coding determination information of a representative channel of a target block as coding determination information of a target channel of the target block; And decoding the target block using the coding decision information of the target channel.

The decoding method may further include receiving a bitstream including information on the target block.

The information on the target block may include coding determination information of the representative channel.

The information on the target block may not include the coding determination information of the target channel.

The coding determination information of the representative channel may be conversion skip information indicating whether to skip the conversion.

The coding decision information of the representative channel may indicate which transform is to be used for the transform block of the channel.

The coding determination information of the representative channel may be intra-coding determination information of the representative channel.

The representative channel and the target channel may be channels in the YCbCr color space.

The representative channel may be a luma channel.

The target channel may be a chroma channel.

The representative channel may be a color channel having the highest correlation with the luma signal.

The representative channel may be determined by an index indicating a selected representative channel in the bitstream.

The sharing may be performed when the video properties of the plurality of channels of the target block are similar to each other.

If the intra prediction mode for the chroma channel of the target block is the direct mode, it can be determined that the video properties of the plurality of channels are similar to each other.

The sharing may be performed when inter-channel prediction is used.

Whether or not the inter-channel prediction is used can be derived based on the information obtained from the bit stream.

The sharing may be performed when inter-channel prediction is used.

Whether or not the inter-channel prediction is used may be determined based on an intra prediction mode of the target block.

The interchannel prediction may be used if the intra prediction mode for the target block is one of an INTRA_CCLM mode, an INTRA_MMLM mode, and an INTRA_MFLM mode.

The sharing may be determined based on the size of the target block.

Coding determination information of the representative channel among the plurality of channels of the target block may be used for all of the plurality of channels.

Determining, at the other side, coding determination information of a representative channel of a target block; And performing coding of the target block using coding determination information of the representative channel, wherein the coding determination information of the representative channel is shared with other channels of the target block.

The encoding method includes generating a bitstream including information on the target block

As shown in FIG.

The information on the target block may include coding determination information of the representative channel.

The information on the target block may not include the coding determination information of the other channel.

The representative channel and the target channel may be channels in the YCbCr color space.

The representative channel may be a luma channel.

The target channel may be a chroma channel.

A computer-readable recording medium storing a bitstream for decoding an image, the bitstream including information on a target block, and the information on the target block includes information on a target block And the coding decision information of the representative channel is used as the coding decision information of the target channel of the target block and the coding decision information of the target channel is shared using the coding decision information of the target channel, There is provided a computer-readable recording medium on which decoding of a block is performed.

An encoding apparatus, an encoding method, a decoding apparatus, and a decoding method using selective information sharing among channels are provided.

1 is a block diagram illustrating a configuration of an encoding apparatus to which the present invention is applied.
2 is a block diagram illustrating a configuration of a decoding apparatus to which the present invention is applied.
3 is a diagram schematically showing a division structure of an image when coding and decoding an image.
Fig. 4 is a diagram showing a form of a prediction unit (PU) that a coding unit (CU) can include.
5 is a diagram showing a form of a conversion unit (TU) which can be included in a coding unit (CU).
Figure 6 shows the partitioning of a block according to an example.
7 is a diagram for explaining an embodiment of an intra prediction process.
8 is a view for explaining the positions of reference samples used in the intra prediction process.
9 is a diagram for explaining an embodiment of the inter prediction process.
Figure 10 shows spatial candidates according to an example.
FIG. 11 shows an order of addition of motion information of a spatial candidate to a merge list according to an example.
FIG. 12 illustrates a process of transforming and quantizing according to an example.
13 illustrates diagonal scanning according to an example.
14 shows horizontal scanning according to an example.
15 shows vertical scanning according to an example.
16 is a structural diagram of an encoding apparatus according to an embodiment.
17 is a structural diagram of a decoding apparatus according to an embodiment.
18 is a flowchart of a decoding method of coding determination information according to an embodiment.
19 is a flowchart of a decoding method for determining whether to omit conversion according to an embodiment.
20 is a flowchart of a decoding method for determining whether to omit conversion with reference to an intra mode according to an embodiment.
21 is a flow diagram of a method for sharing transformation selection information in accordance with one embodiment.
22 illustrates a single triblock division structure according to an example.
FIG. 23 shows a dual tree block division structure according to an example.
FIG. 24 illustrates a manner of specifying a corresponding block based on a position within a corresponding region according to an example.
FIG. 25 illustrates a method of specifying a corresponding block based on an area within a corresponding area according to an example.
Figure 26 shows another way of specifying the corresponding block based on the area within the corresponding area according to an example.
FIG. 27 shows a manner of specifying a corresponding block based on the shape of the block within the corresponding area according to an example.
Figure 28 shows another way of specifying the corresponding block based on the shape of the block within the corresponding area according to an example.
FIG. 29 shows a manner of specifying the corresponding block based on the aspect ratio of the block within the corresponding area according to an example.
Figure 30 shows another way of specifying the corresponding block based on the aspect ratio of the block within the corresponding area according to an example.
Figure 31 shows another way of specifying the corresponding block based on the coding nature of the block within the corresponding area according to an example.
32 is a flowchart of an encoding method according to an embodiment.
33 is a flowchart of a decoding method according to an embodiment.

While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will herein be described in detail. It should be understood, however, that the invention is not intended to be limited to the particular embodiments, but includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention.

The following detailed description of exemplary embodiments refers to the accompanying drawings, which illustrate, 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 features, structures, and characteristics described herein may be implemented in other embodiments without departing from the spirit and scope of the invention in connection with one embodiment. It is also to be understood that the location or arrangement of the individual components within each disclosed embodiment may be varied without departing from the spirit and scope of the embodiments. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the exemplary embodiments is to be limited only by the appended claims, along with the full scope of equivalents to which such claims are entitled, if properly explained.

In the drawings, like reference numerals refer to the same or similar functions throughout the several views. The shape and size of the elements in the figures may be exaggerated for clarity.

The terms first, second, etc. in the present invention 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 a second component, and similarly, the second component may also be referred to as a first component. And / or < / RTI > includes any combination of a plurality of related listed items or any of a plurality of related listed items.

When it is mentioned that a component is "connected" or "connected" to another component, the two components may be directly connected or connected to each other, It is to be understood that other components may be present in the middle of the components. When a component is referred to as being "directly connected" or "directly connected" to another component, it should be understood that no other component is present in the middle of the two components.

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 composed of separate hardware or one software constituent unit. That is, each component is listed as a separate component for convenience of explanation. At least two components of each component are combined to form one component, or one component is divided into a plurality of components, And the integrated embodiments and the separate embodiments of each of these components are also included in the scope of the present invention unless they depart from the essence of the present invention.

Also, in the exemplary embodiments, the description of "comprising" a specific configuration does not exclude a configuration other than the specific configuration, and the additional configuration is not limited to the implementation of the exemplary embodiments or the technical idea of the exemplary embodiments. Range. ≪ / RTI >

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The singular expressions include plural expressions unless the context clearly dictates otherwise. In the present invention, the term "comprises" or "having ", etc. is intended to specify that there is a feature, number, step, operation, element, But do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, or combinations thereof. In other words, the description of "including" a specific configuration in the present invention does not exclude a configuration other than the configuration, and it is also possible that additional configurations can be included in the scope of the present invention or the scope of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily carry out the embodiments. In the following description of the embodiments, detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present disclosure rather unclear. The same reference numerals are used for the same constituent elements in the drawings, and redundant description of the same constituent elements is omitted.

Hereinafter, an image may denote a picture constituting a video, or may represent a video itself. For example, "encoding and / or decoding of an image" may mean "encoding and / or decoding of video ", which means" encoding and / or decoding of one of the images constituting a video " It is possible.

Hereinafter, the terms "video" and "motion picture" may be used interchangeably and may be used interchangeably.

Hereinafter, the target image may be a coding target image to be coded and / or a decoding target image to be decoded. The target image may be an input image input to the encoding device or an input image input to the decoding device.

In the following, the terms "image", "picture", "frame" and "screen" may be used interchangeably and may be used interchangeably.

Hereinafter, the target block may be a current block to be coded and / or a current block to be decoded. Also, the target block may be the current block that is the current encoding and / or decoding target. For example, the terms "object block" and "current block" may be used interchangeably and may be used interchangeably.

In the following, the terms "block" and "unit" may be used interchangeably and may be used interchangeably. Or "block" may represent a particular unit.

In the following, the terms " region "and" segment "

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

In embodiments, each of the specified information, data, flags and elements, attributes, etc. may have a value. The value "0" of information, data, flags and element, attribute, etc. may represent a logical false or a first predefined value. That is to say, the values "0 ", False, Logical False, and First Default values can be used interchangeably. The value "1" of information, data, flags and elements, attributes, etc. may represent a logical true or a second predefined value. That is to say, the values "1 ", " true ", " logical "

When a variable such as i or j is used to represent a row, column or index, the value of i may be an integer greater than or equal to 0 and may be an integer greater than or equal to one. In other words, in the embodiments, rows, columns, indexes, etc. may be counted from 0 and counted from 1.

Hereinafter, terms used in the embodiments will be described.

Encoder: An apparatus that performs encoding.

Decoder: A device that performs decoding.

Unit: A unit may represent a unit of encoding and decoding of an image. The terms "unit" and "block" may be used interchangeably and may be used interchangeably.

- The unit may be an MxN array of samples. M and N may be positive integers, respectively. A unit can often refer to an array of two-dimensional samples.

- In coding and decoding of an image, a unit may be an area generated by the division of one image. That is to say, a unit may be a specified area in one image. One image may be divided into a plurality of units. Alternatively, a unit may mean the divided portion when one image is divided into subdivided portions and when encoding or decoding is performed on the subdivided portions.

- In the encoding and decoding of images, predetermined processing on the unit may be performed depending on the type of unit.

- Depending on the function, the type of unit may be a Macro Unit, a Coding Unit (CU), a Prediction Unit (PU), a Residual Unit and a Transform Unit (TU) . ≪ / RTI > Alternatively, depending on the function, the unit may include a block, a macroblock, a Coding Tree Unit, a Coding Tree Block, a Coding Unit, a Coding Block, A prediction unit, a prediction block, a residual unit, a residual block, a transform unit, and a transform block.

- A unit may refer to information comprising a luma component block and its corresponding chroma component block, and a syntax element for each block, to distinguish it from a block.

- The size and shape of the unit may vary. In addition, the unit may have various sizes and shapes. In particular, the shape of the unit may include not only squares but also geometric figures that can be expressed in two dimensions, such as rectangles, trapezoids, triangles, and pentagons.

Also, the unit information may include at least one of a unit type, a unit size, a unit depth, a unit encoding order, and a unit decoding order. For example, the type of unit may refer to one of CU, PU, residual unit, and TU.

- one unit may be further subdivided into smaller units with a smaller size than the unit.

Depth: Depth can mean the degree of division of a unit. Unit depth can also indicate the level at which a unit is present when the unit is represented in a tree structure.

- The unit partition information may include a depth for the depth of the unit. The depth may indicate the number and / or the number of times the unit is divided.

In the tree structure, the depth of the root node is the shallowest and the depth of the leaf node is the deepest.

- A unit may be hierarchically divided into a plurality of subunits with depth information based on a tree structure. That is to say, the unit and the lower unit generated by the division of the unit can correspond to the node and the child node of the node, respectively. Each divided subunit may have a depth. Since the depth indicates the number and / or degree of division of the unit, the division information of the lower unit may include information on the size of the lower unit.

- In a tree structure, the top node may correspond to the first unit that has not been partitioned. The superordinate node may be referred to as a root node. Also, the uppermost node may have a minimum depth value. At this time, the uppermost node can have a level 0 depth.

- A node with a depth of level 1 can represent a unit created as the first unit is once partitioned. A node with a depth of level 2 may represent a unit created as the first unit is divided twice.

- A node with a depth of level n can represent a unit created as the first unit is divided n times.

The leaf node may be the lowest node, and may be a node that can not be further divided. The depth of the leaf node may be the maximum level. For example, the default value of the maximum level may be three.

- QT depth can indicate depth for quad split. The BT depth can represent the depth for binary segmentation. The TT depth can represent the depth for the ternary splitting.

Sample: A sample can be a base unit that makes up a block. The samples can be represented as values from 0 to 2 ^Bd- 1, depending on the bit depth (Bd).

The sample may be a pixel or a pixel value.

- In the following, the terms "pixel", "pixel" and "sample" may be used interchangeably and may be used interchangeably.

Coding Tree Unit (CTU): A CTU can consist of one luma component (Y) coding tree block and two chroma component (Cb, Cr) coding tree blocks related to the luma component coding tree block have. The CTU may also include the above blocks and the syntax elements for each block of the above blocks.

- Each coding tree unit may be configured as a quad tree (QT), a binary tree (BT), and a ternary tree (TT) to construct a lower unit such as a coding unit, May be divided using one or more division methods. In addition, each coding tree unit may be partitioned using a MultiType Tree (MTT) using one or more partitioning schemes.

- The CTU can be used as a term to refer to a pixel block, which is a processing unit in the process of decoding and encoding an image, as in the segmentation of an input image.

Coding Tree Block (CTB): A coding tree block can be used as a term for designating any one of a Y coding tree block, a Cb coding tree block, and a Cr coding tree block.

Neighbor block: A neighboring block may mean a block adjacent to a target block. A neighboring block may mean a restored neighboring block.

- In the following, the terms "peripheral block" and "adjacent block" may be used interchangeably and may be used interchangeably.

Spatial neighbor block: A spatial neighbor block may be a block spatially adjacent to a target block. The neighboring block may include a spatial neighboring block.

The target block and the spatial neighboring block may be included in the target picture.

A spatial neighboring block may refer to a block that is bounded to a target block or a block located within a predetermined distance from a target block.

- A spatial neighboring block may mean a block adjacent to the vertex of the target block. Here, a block adjacent to a vertex of a target block may be a block vertically adjacent to a neighboring block horizontally adjacent to the target block or a block horizontally adjacent to a neighboring block vertically adjacent to the target block.

Temporal neighbor block: The temporal neighbor block may be temporally adjacent to the target block. The neighboring blocks may include temporal neighboring blocks.

The temporal neighboring block may include a co-located block (col block).

The call block may be a block in a co-located picture (col picture). The position of the call block in the call picture may correspond to the position in the target picture of the target block. Alternatively, the position of the call block in the call picture may be the same as the position in the target picture of the target block. The call picture may be a picture included in the reference picture list.

The temporal neighboring block may be a block temporally adjacent to the spatial neighboring block of the target block.

Prediction unit: It can mean a base unit for prediction such as inter prediction, intra prediction, inter-compensation, intra compensation, and motion compensation.

- one prediction unit may be divided into a plurality of partitions or lower prediction units having a smaller size. The plurality of partitions may also be a base unit in performing prediction or compensation. The partition generated by the division of the prediction unit may also be a prediction unit.

Prediction unit partition: Prediction unit may mean a partitioned form.

Reconstructed neighboring unit: The reconstructed neighboring unit may be a unit that has already been decoded and reconstructed around the target unit.

The reconstructed neighboring unit may be a spatial adjacent unit or a temporal adjacent unit for the target unit.

The reconstructed spatial surrounding unit may be a unit in the target picture and a unit already reconstructed through coding and / or decoding.

- the reconstructed temporal neighboring unit may be a unit in the reference image and a unit already reconstructed through coding and / or decoding. The position in the reference picture of the reconstructed temporal neighboring unit may be the same as the position in the target picture of the target unit or may correspond to the position in the target picture of the target unit.

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

In addition, the parameter set may include slice header information and tile header information.

Rate-distortion optimization: An encoding apparatus uses rate-distortion optimization to provide a high coding efficiency using a combination of a coding unit size, a prediction mode, a prediction unit size, motion information, Distortion optimization can be used.

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

[Equation 1]

- D can indicate distortion. D may be the mean square error of the difference values between the original transform coefficients and the reconstructed transform coefficients in the transform unit.

- R can represent the rate. R can represent the bit rate using related context information.

- [lambda] can represent a Lagrangian multiplier. R may include coding parameter information such as a prediction mode, motion information, and coded block flag, as well as bits generated by coding the transform coefficients.

- The encoder may perform inter prediction and / or intra prediction, conversion, quantization, entropy coding, inverse quantization, inverse transform, etc. to calculate the correct D and R. These processes can greatly increase the complexity in the encoding apparatus.

Bitstream: A bitstream may be a bit string containing encoded image information.

Parameter set: A parameter set may correspond to header information among structures in a bitstream.

The parameter set may comprise at least one of a video parameter set, a sequence parameter set, a picture parameter set and an adaptation parameter set. The parameter set may also include information of a slice header and information of a tile header.

Parsing: Parsing may entropy-decode the bitstream to determine the value of a syntax element. Or, parsing may mean entropy decoding itself.

Symbol: may include at least one of a syntax element, a coding parameter, and a transform coefficient of a coding target unit and / or a target unit to be decoded. In addition, the symbol may mean a target of entropy encoding or a result of entropy decoding.

Reference picture: A reference picture may refer to an image that a unit refers to for inter prediction or motion compensation. Alternatively, the reference picture may be an image including a reference unit referred to by the target unit for inter prediction or motion compensation.

Hereinafter, the terms "reference picture" and "reference picture" may be used interchangeably and may be used interchangeably.

Reference picture list: A reference picture list may be a list including one or more reference pictures used for inter-prediction or motion compensation.

The types of the reference picture list include a list combination (LC), a list 0 (L0), a list 1 (L1), a list 2 (L2), and a list 3 ) And the like.

- One or more reference picture lists may be used for inter prediction.

Inter Prediction Indicator: An inter prediction indicator may indicate the direction of inter prediction for a target unit. The inter prediction may be one of a unidirectional prediction and a bidirectional prediction. Alternatively, the inter prediction indicator may indicate the number of reference images used when generating the prediction unit of the target unit. Alternatively, the inter prediction indicator may mean the number of prediction blocks used for inter prediction or motion compensation for the target unit.

Reference picture index: The reference picture index may be an index indicating a specific reference picture in the reference picture list.

Motion Vector (MV): A motion vector may be a two-dimensional vector used in inter prediction or motion compensation. A motion vector may mean an offset between a target image and a reference image.

- For example, MV can be expressed in the form (mv _x , mv _y ). mv _x may represent a horizontal component, and mv _y may represent a vertical component.

Search range: The search area may be a two-dimensional area where an MV search is performed during inter prediction. For example, the size of the search area may be MxN. M and N may be positive integers, respectively.

Motion vector candidate: A motion vector candidate may mean a motion vector of a block, which is a prediction candidate or a prediction candidate, when a motion vector is predicted.

- The motion vector candidate may be included in the motion vector candidate list.

Motion Vector Candidate List: A motion vector candidate list may refer to a list constructed using one or more motion vector candidates.

Motion vector candidate index: The motion vector candidate index may indicate an indicator indicating a motion vector candidate in a motion vector candidate list. Alternatively, the motion vector candidate index may be an index of a motion vector predictor.

Motion information: Motion information includes motion picture information, reference picture list information, reference pictures, motion vector candidates, motion vector candidate indexes, merge candidates, and merge indices, as well as motion vectors, reference picture indexes and inter prediction indicators Quot; and " information "

Merge candidate list: A merge candidate list can mean a list constructed using merge candidates.

Merge candidate: A merge candidate can mean a spatial merge candidate, a temporal merge candidate, a combined merge candidate, a combined bi-prediction merge candidate, and a zero merge candidate. The merge candidate may include motion type information such as prediction type information, a reference picture index for each list, and a motion vector.

The merge index: The merge index may be an indicator that indicates the merge candidate in the merge candidate list.

The merge index may indicate a reconstructed unit spatially adjacent to the target unit and a reconstructed unit that derives the merge candidate out of the reconstructed units temporally adjacent to the target unit.

The merge index may indicate at least one of the motion information of the merge candidate.

Transform unit: The transform unit can be a base unit in residual signal coding and / or residual signal decoding such as transform, inverse transform, quantization, inverse quantization, transform coefficient coding and transform coefficient decoding. One conversion unit can be divided into a plurality of conversion units of a smaller size.

Scaling: Scaling can refer to the process of multiplying the transform coefficient level by an argument.

As a result of scaling to the transform coefficient level, a transform coefficient can be generated. Scaling may also be referred to as dequantization.

Quantization Parameter (QP): The quantization parameter may refer to a value used when generating a transform coefficient level for a transform coefficient in quantization. Alternatively, the quantization parameter may mean a value used when generating the transform coefficient by scaling the transform coefficient level in the inverse quantization. Alternatively, the quantization parameter may be a value mapped to a quantization step size.

Delta quantization parameter: A delta quantization parameter means a predicted quantization parameter and a differential value of the quantization parameter of the target unit.

Scan: A scan may mean a method of arranging the order of coefficients within a unit, block, or matrix. For example, arranging a two-dimensional array in a one-dimensional array form can be referred to as a scan. Alternatively, arranging the one-dimensional arrays in the form of a two-dimensional array may be referred to as a scan or an inverse scan.

Transform coefficient: The transform coefficient may be a coefficient value generated as a result of performing the transform in the encoding apparatus. Alternatively, the transform coefficient may be a coefficient value generated by performing at least one of entropy decoding and inverse quantization in the decoding apparatus.

The quantized level or quantized transform coefficient level generated by applying the quantization to the transform coefficients or residual signals may also be included in the meaning of the transform coefficients.

Quantized level: A quantized level may mean a value generated by performing a quantization on a transform coefficient or a residual signal in an encoding apparatus. Alternatively, the quantized level may be a value to be subjected to inverse quantization in performing inverse quantization in the decoding apparatus.

- The quantized transform coefficient levels resulting from the transform and quantization can also be included in the meaning of the quantized levels.

Non-zero transform coefficient: A non-zero transform coefficient may mean a transform coefficient having a value other than zero or a transform coefficient level having a non-zero value. Alternatively, the 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 quantization matrix may mean a matrix used in a quantization process or a dequantization process to improve the subjective or objective image quality of an image. The quantization matrix may also be referred to as a scaling list.

Quantization matrix coefficient: The quantization matrix coefficient may refer to each element in the quantization matrix. The quantization matrix coefficient may also be referred to as a matrix coefficient.

Default matrix: The base matrix may be a predefined quantization matrix in the encoder and decoder.

Non-default matrix: The non-default matrix may be a non-default quantization matrix in the encoder and decoder. The non-default matrix may be signaled from the encoder to the decoder.

Most Probable Mode (MPM): The MPM may indicate an intra prediction mode that is likely to be used for intra prediction of a target block.

The encoding device and the decoding device may determine one or more MPMs based on coding parameters related to the object block and attributes of the object related to the object block.

The encoder and decoder may determine one or more MPMs based on the intra prediction mode of the reference block. The reference block may be plural. The plurality of reference blocks may include a spatial neighboring block to the left of the target block and a spatial neighboring block to the top of the target block. That is to say, one or more different MPMs may be determined depending on which intra prediction modes are used for the reference blocks.

One or more MPMs may be determined in the same manner in the encoder and decoder. That is to say, the encoder and decoder can share an MPM list that includes the same one or more MPMs.

MPM list: The MPM list may be a list containing one or more MPMs. The number of one or more MPMs in the MPM list may be predetermined.

MPM indicator: The MPM indicator can indicate the MPM used for intraprediction of the target block of one or more MPMs in the MPM list. For example, the MPM indicator may be an index to the MPM list.

Since the MPM list is determined in the same manner in the encoder and the decoder, the MPM list itself may not need to be transmitted from the encoder to the decoder.

The MPM indicator may be signaled from the encoder to the decoder. As the MPM indicator is signaled, the decoding device may determine the MPM to be used for intra prediction of the target block among the MPMs in the MPM list.

MPM Utilization Indicator: The MPM Utilization Indicator can indicate whether the MPM use mode is to be used for prediction of the target block. The MPM usage mode may be a mode for determining an MPM to be used for intra prediction on a target block using the MPM list.

The MPM usage indicator may be signaled from the encoding device to the decryption device.

Signaling: Signaling may indicate that information is sent from the encoding device to the decoding device. Alternatively, signaling may mean including information in a bitstream or recording medium. The information signaled by the encoding apparatus may be used by the decoding apparatus.

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

The encoding apparatus 100 may be an encoder, 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.

1, an encoding apparatus 100 includes an inter prediction unit 110, an intra prediction unit 120, a switch 115, a subtractor 125, a transform unit 130, a quantization unit 140, An inverse quantization unit 160, an inverse transform unit 170, an adder 175, a filter unit 180, and a reference picture buffer 190.

The encoding apparatus 100 may perform encoding of a target image using an intra mode and / or an inter mode.

In addition, the encoding apparatus 100 can generate a bitstream including encoding information through encoding of a target image, and output the generated bitstream. The generated bit stream can be stored in a computer-readable recording medium and can be streamed through a wired / wireless transmission medium.

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

The encoding apparatus 100 may generate a prediction block for the target block. Also, after the prediction block is generated, the encoding device 100 can code the residual of the target block and the prediction block.

When the prediction mode is the intra mode, the intra prediction unit 120 can use the pixels of the already coded / decoded block around the target block as a reference sample. The intra prediction unit 120 can perform spatial prediction of a target block using a reference sample and generate prediction samples of a target block through spatial prediction.

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

When the prediction mode is the inter mode, the motion predicting unit can search for the best matched region from the reference block in the motion estimation process, derive the motion vector for the target block and the searched region using the searched region, can do.

The reference picture may be stored in the reference picture buffer 190 and may be stored in the reference picture buffer 190 when the coding and / or decoding of the reference picture has been processed.

The motion compensation unit may generate a prediction block for a target block by performing motion compensation using a motion vector. Here, the motion vector may be a two-dimensional vector used for inter prediction. The motion vector may also indicate an offset between the target image and the reference image.

The motion prediction unit and the motion compensation unit can generate a prediction block by applying an interpolation filter to a part of the reference image when the motion vector has a non-integer value. In order to perform inter prediction or motion compensation, a method of motion prediction and motion compensation of a PU included in a CU based on a CU is called a skip mode, a merge mode, an advanced motion vector prediction (AMVP) mode and a current picture reference mode, and inter prediction or motion compensation may be performed according to each mode.

The subtracter 125 may generate a residual block which is a difference between the target block and the prediction block. The residual block may be referred to as a residual signal.

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, quantizing, or transforming and quantizing the difference between the original signal and the prediction signal. The residual block may be a residual signal for a block unit.

The transforming unit 130 may perform a transform on the residual block to generate a transform coefficient, and output the generated transform coefficient. Here, the transform coefficient may be a coefficient value generated by performing a transform on the residual block.

The conversion unit 130 may use one of a plurality of predetermined conversion methods for performing the conversion.

The predetermined plurality of conversion methods may include Discrete Cosine Transform (DCT), Discrete Sine Transform (DST), and Karhunen-Loeve Transform (KLT) have.

The transform method used for transforming the residual block may be determined according to at least one of the coding parameters for the object block and / or the surrounding block. For example, the transformation method may be determined based on at least one of an inter prediction mode for the PU, an intra prediction mode for the PU, a size of the TU, and a type of the TU. Alternatively, conversion information indicating the conversion method may be signaled from the encoding device 100 to the decryption device 200. [

When the transform skip mode is applied, the transforming unit 130 may omit the transform for the residual block.

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

The quantization unit 140 may generate a quantized transform coefficient level or a quantized level by quantizing the transform coefficient in accordance with the quantization parameter. The quantization unit 140 may output the generated quantized transform coefficient level or the generated quantized level. At this time, the quantization unit 140 can quantize the transform coefficient using the quantization matrix.

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

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

When entropy coding is applied, a small number of bits can be assigned to a symbol having a high probability of occurrence, and a large number of bits can be assigned to a symbol having a low probability of occurrence. As the symbol is represented through this allocation, the size of the bit string for the symbols to be encoded can be reduced. Therefore, the compression performance of the image encoding can be improved through the entropy encoding.

In addition, the entropy encoding unit 150 may use an exponential golomb, a context-adaptive variable length coding (CAVLC), and a context-adaptive binary arithmetic coding Arithmetic Coding (CABAC), and the like can be used. For example, the entropy encoding unit 150 may perform entropy encoding using a Variable Length Coding / Code (VLC) table. For example, the entropy encoding unit 150 may derive a binarization method for a target symbol. In addition, the entropy encoding unit 150 may derive a probability model of a target symbol / bin. The entropy encoding unit 150 may perform arithmetic encoding using the derived binarization method, the probability model, and the context model.

The entropy encoding unit 150 may change coefficients of a form of a two-dimensional block into a form of a one-dimensional vector through a transform coefficient scanning method to encode the quantized transform coefficient levels.

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

Coding parameters may include not only information (or flags, indexes, etc.) encoded in a coding apparatus such as syntax elements and signaled from a coding apparatus to a decoding apparatus, but also information derived from a coding process or a decoding process have. In addition, the coding parameters may include information required in coding or decoding an image. For example, the unit / block size, the unit / block depth, the unit / block division information, the unit / block division structure, the information indicating whether the unit / block is divided into quad tree form, Information indicating whether or not the unit / block is divided into a tree form, a division direction (horizontal direction or vertical direction) of a binary tree, a division type (a symmetric division or an asymmetric division) Information indicating whether or not the unit / block is divided into a complex tree form, a compound tree form (information on whether the unit / block is divided into a complex tree form) (Intra-prediction or inter-prediction), intraprediction mode / direction, reference sample filtering method A predictive block filtering method, a predictive block boundary filtering method, a filter tap of filtering, a filter coefficient of filtering, an inter prediction mode, a motion information, a motion vector, a reference picture index, an inter prediction direction, Information indicating whether or not to use the merge mode, information indicating whether a merge candidate, a merge candidate list, a skip mode are used, a type of an interpolation filter, a motion vector prediction candidate, a motion vector candidate list, The filter tap of the interpolation filter, the filter coefficient of the interpolation filter, the size of the motion vector, the accuracy of the motion vector representation, the type of transformation, the size of the transformation, information indicating whether primary transformation is used, Information, primary conversion selection information (or primary conversion index), secondary conversion selection information (or secondary conversion index), residual signal Information indicating whether or not the intra-loop filter is applied, information indicating the presence or absence of the intra-loop filter, a coded block pattern, a coded block flag, a quantization parameter, a quantization matrix, A filter tap of an intra-loop, a shape / form of an intra-loop filter, information indicating whether a deblocking filter is applied, a deblocking filter coefficient, a deblocking filter tap, An adaptive sample offset value, an adaptive sample offset type, an adaptive sample offset type, an adaptive sample offset value, an adaptive sample offset value, an adaptive sample offset value, loop filter), adaptive loop-in filter coefficients, adaptive loop-in filter taps, adaptive loop-in-filter shape / form, binarization / inverse binarization method, contextual model, context A method of determining a model, a method of updating a context model, whether to perform a regular mode, whether to perform a bypass mode, a context bin, a bypass bin, a conversion coefficient, a conversion coefficient level, At least one value, a combined form, or a combination of at least one of information on the slice identification information, slice type, slice division information, tile identification information, tile type, tile division information, picture type, bit depth, Statistics may be included in the coding parameters. The prediction scheme may represent one of an intra prediction mode and an inter prediction mode.

The primary transformation selection information may represent a primary transformation applied to the target block.

The secondary transformation selection information may represent a quadratic transformation applied to the target block.

The residual signal may represent a difference between the original signal and the prediction signal. Alternatively, the residual signal may be a signal generated by transforming the difference between the original signal and the prediction signal. Alternatively, the residual signal may be a signal generated by converting and quantizing the difference between the original signal and the prediction signal. The residual block may be a residual signal for the block.

Signaling a flag or an index may be performed by encoding the entropy-encoded flag or the entropy-encoded index generated by performing entropy encoding on a flag or an index in a bitstream in the encoding apparatus 100 And the decryption apparatus 200 may mean to obtain a flag or an index by performing entropy decoding on an entropy-encoded flag extracted from the bitstream or an entropy-encoded index .

Since encoding is performed through inter-prediction by the encoding apparatus 100, the encoded target image can be used as a reference image for another image (s) to be processed later. Accordingly, the encoding apparatus 100 can reconstruct or decode the encoded target image again, and store the reconstructed or decoded image as a reference image in the reference picture buffer 190. [ The inverse quantization and inverse transform of the encoded object image for decoding can be processed.

The quantized level may be inversely quantized in the inverse quantization unit 160 and may be inversely transformed in the inverse transformation unit 170. [ The dequantized and / or inverse transformed coefficients may be combined with the prediction block via an adder 175. A reconstructed block may be generated by summing the dequantized and / or inverse transformed coefficients and the prediction block. Here, the dequantized and / or inverse transformed coefficient may mean a coefficient on which at least one of dequantization and inverse-transformation is performed, and may mean a reconstructed residual block.

The reconstructed block may pass through filter portion 180. The filter unit 180 includes at least one of a deblocking filter, a sample adaptive offset (SAO), an adaptive loop filter (ALF), and a non-local filter (NLF) One or more can be applied to reconstructed blocks or reconstructed pictures. The filter unit 180 may be referred to as an in-loop filter.

The deblocking filter can remove block distortion occurring at the boundary between the blocks. To determine whether to apply a deblocking filter, it may be determined whether to apply a deblocking filter to a target block based on the number of columns or pixels (or pixels) included in the block.

When a deblocking filter is applied to a target block, the applied filter may differ depending on the strength of the required deblocking filtering. In other words, a filter determined according to the strength of deblocking filtering among different filters can be applied to the target block. When a deblocking filter is applied to a target block, one of a strong filter and a weak filter may be applied to the target block according to the strength of the required deblocking filtering.

Further, when vertical filtering and horizontal filtering are performed on a target block, horizontal filtering and vertical filtering can be processed in parallel.

SAO may add an appropriate offset to the pixel value of the pixel to compensate for coding errors. SAO can perform correction using an offset with respect to a difference between an original image and an image to which deblocking is applied, in units of pixels, for an image to which deblocking is applied. In order to perform offset correction on an image, a method of dividing pixels included in an image into a predetermined number of regions, determining an area to be offset of the divided areas, and applying an offset to the determined area may be used And a method of applying an offset in consideration of edge information of each pixel of the image may be used.

ALF can perform filtering based on the comparison of the reconstructed image and the original image. After dividing the pixels included in the image into predetermined groups, a filter to be applied to each divided group can be determined, and different filtering can be performed for each group. For a luma signal, information related to whether or not to apply an adaptive loop filter may be signaled per CU. The shape and filter coefficients of the ALF to be applied to each block may be different for each block. Alternatively, regardless of the characteristics of the block, a fixed form of ALF may be applied to the block.

The non-local filter can perform filtering based on reconstructed blocks similar to the target block. In the reconstructed image, a region similar to the target block can be selected, and the filtering of the target block can be performed using the statistical properties of the selected similar regions. Information related to whether or not to apply a non-local filter may be signaled to the CU. In addition, the shapes of the non-local filters to be applied to the blocks and the filter coefficients may differ from each other depending on the blocks.

The reconstructed block or reconstructed image through the filter unit 180 may be stored in the reference picture buffer 190. [ The reconstructed block through the filter unit 180 may be part of the reference picture. That is to say, the reference picture may be a reconstructed picture composed of reconstructed blocks via the filter unit 180. [ The stored reference picture can then be used for inter prediction.

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

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

2, the decoding apparatus 200 includes an entropy decoding unit 210, an inverse quantization unit 220, an inverse transform unit 230, an intra prediction unit 240, an inter prediction unit 250, a switch 245, An adder 255, a filter unit 260, and a reference picture buffer 270.

The decoding apparatus 200 can receive the bit stream output from the encoding apparatus 100. [ The decoding apparatus 200 can receive a bitstream stored in a computer-readable recording medium and can receive a bitstream streamed through a wired / wireless transmission medium.

The decoding apparatus 200 may perform decoding of an intra mode and / or an inter mode with respect to a bit stream. In addition, the decoding apparatus 200 can generate a reconstructed image or a decoded image through decoding, and output the reconstructed image or the decoded image.

For example, the switch to the intra mode or the inter mode according to the prediction mode used for decoding may be performed by the switch 245. When the prediction mode used for decoding is the intra mode, the switch 245 can be switched to intra. When the prediction mode used for decoding is the inter mode, the switch 245 can be switched to the inter.

The decoding apparatus 200 can obtain a reconstructed residual block by decoding the input bitstream, and can generate a prediction block. Once the reconstructed residual block and the prediction block are obtained, the decoding apparatus 200 can generate the reconstructed block to be decoded by adding the reconstructed residual block and the prediction block.

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

The entropy decoding unit 210 may change the coefficient of the one-dimensional vector form into a two-dimensional block form through a transform coefficient scanning method to decode the quantized transform coefficient levels.

For example, the coefficients may be changed to a two-dimensional block form by scanning the coefficients of the block using the upper-right diagonal scan. Alternatively, depending on the size of the block and / or the intra prediction mode, it may be determined which of the upper right diagonal scan, the vertical scan and the horizontal scan will be used.

The quantized coefficients may be inversely quantized in the inverse quantization unit 220. The inverse quantization unit 220 may generate inverse quantized coefficients by performing inverse quantization on the quantized coefficients. Also, the inverse quantized coefficient may be inversely transformed by the inverse transform unit 230. The inverse transform unit 230 may generate the reconstructed residual block by performing an inverse transform on the inversely quantized coefficient. As a result of the inverse quantization and inverse transform performed on the quantized coefficients, the reconstructed residual block can be generated. In this case, the inverse quantization unit 220 may apply the quantization matrix to the quantized coefficients in generating the reconstructed residual block.

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

The inter prediction unit 250 may include a motion compensation unit. Alternatively, the inter prediction unit 250 may be named as a motion compensation unit.

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

If the motion vector has a non-integer value, the motion compensation unit can apply an interpolation filter to a part of the reference image and generate a prediction block using the reference image to which the interpolation filter is applied. The motion compensation unit may determine which of the skip mode, the merge mode, the AMVP mode, and the current picture reference mode is used for the PU included in the CU based on the CU to perform motion compensation, To perform motion compensation.

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

The reconstructed block may pass through filter portion 260. The filter unit 260 may apply at least one of the deblocking filter, SAO, ALF, and non-local filter to the reconstructed block or the reconstructed image. The reconstructed image may be a picture including a reconstructed block.

The reconstructed image through the filter unit 260 can be output by the encoding apparatus 100 and can be used by the encoding apparatus 100. [

The reconstructed image through the filter unit 260 can be stored in the reference picture buffer 270 as a reference picture. The reconstructed block through the filter unit 260 may be part of the reference picture. That is to say, the reference picture may be an image composed of reconstructed blocks through the filter unit 260. The stored reference picture may then be used for inter prediction.

3 is a diagram schematically showing a division structure of an image when coding and decoding an image.

3 schematically shows an example in which one unit is divided into a plurality of lower units.

To efficiently divide an image, a coding unit (CU) can be used in coding and decoding. A unit may be a term collectively referred to as 1) a block containing image samples and 2) a syntax element. For example, "division of a unit" may mean "division of a block corresponding to a unit ".

CU can be used as a base unit of image encoding / decoding. Also, the CU can be used as a unit to which one of the intra mode and the inter mode is applied in image encoding / decoding. That is to say, in the image coding / decoding, it is possible to determine which of intra mode and inter mode is applied to each CU.

The CU may also be a base unit for prediction, transform, quantization, inverse transform, dequantization, and encoding / decoding of transform coefficients.

Referring to FIG. 3, an image 300 may be sequentially divided into units of a Largest Coding Unit (LCU). For each LCU, a partition structure can be determined. Here, the LCU can be used in the same sense as a coding tree unit (CTU).

The division of a unit may mean division of a block corresponding to the unit. The block partitioning information may include depth information about the depth of the unit. The depth information may indicate the number and / or the number of times the unit is divided. One unit may be hierarchically subdivided with depth information based on a tree structure. Each divided subunit may have depth information. The depth information may be information indicating the size of the CU. Depth information can be stored for each CU.

Each CU can have depth information. If the CU is partitioned, the CUs generated by partitioning may have an increased depth by one in the depth of the partitioned CU.

The divided structure may mean a distribution of CUs for efficiently encoding an image in the LCU 310. [ This distribution can be determined depending on whether or not to divide one CU into a plurality of CUs. The number of divided CUs may be two or more positive integers including 2, 4, 8, and 16, and so on. The horizontal size and the vertical size of the CU generated by the division may be smaller than the horizontal size and the vertical size of the CU before division according to the number of CUs generated by the division.

The divided CUs can be recursively divided into a plurality of CUs in the same manner. By recursive partitioning, the size of at least one of the horizontal and vertical sizes of the partitioned CUs can be reduced compared to at least one of the horizontal and vertical sizes of the CUs before partitioning.

The partitioning of the CU can be done recursively up to a predetermined depth or a predetermined size. For example, the depth of the CU may have a value from 0 to 3. The size of the CU may range from 64x64 to 8x8 depending on the depth of the CU.

For example, the depth of the LCU may be zero, and the depth of the Smallest Coding Unit (SCU) may be a predetermined maximum depth. Here, the LCU may be a CU having a maximum coding unit size as described above, and the SCU may be a CU having a minimum coding unit size.

The partitioning may be started from the LCU 310 and the depth of the CU may increase by one each time the horizontal and / or vertical size of the CU is reduced by partitioning.

For example, for each depth, the unpartitioned CU may have a size of 2Nx2N. Also, in the case of a CU to be divided, a CU having a size of 2Nx2N can be divided into four CUs having an NxN size. The size of N can be reduced by half each time the depth is increased by one.

Referring to FIG. 3, a LCU having a depth of 0 may be 64x64 pixels or 64x64 block. 0 may be the minimum depth. An SCU with a depth of 3 may be 8x8 pixels or 8x8 block. 3 may be the maximum depth. At this time, the CU of the 64x64 block, which is the LCU, can be represented by the depth 0. The CU of a 32x32 block can be represented by a depth of one. The CU of a 16x16 block can be represented by a depth of two. The CU of an 8x8 block that is an SCU can be represented by a depth of 3.

Information on whether or not the CU is divided can be expressed through the partition information of the CU. The division information may be 1-bit information. All CUs except SCU can contain partition information. For example, the value of the partition information of the unpartitioned CU may be 0, and the value of the partition information of the partitioned CU may be 1.

For example, when one CU is divided into four CUs, the horizontal size and the vertical size of each CU of the four CUs generated by the division are respectively half of the horizontal size and half of the vertical size of the CU before division . When a 32x32 CU is divided into 4 CUs, the sizes of the 4 divided CUs may be 16x16. When one CU is divided into four CUs, it can be said that the CU is divided into quad-tree form.

For example, when one CU is divided into two CUs, the horizontal size or the vertical size of each CU of the two CUs generated by the division is respectively one half of the horizontal size of the CU before the division, . When a 32x32 CU is vertically divided into two CUs, the sizes of the two divided CUs may be 16x32. When a 32x32 CU is divided horizontally into two CUs, the sizes of the two CUs may be 32x16. When one CU is divided into two CUs, it can be said that the CU is divided into a binary-tree form.

In the LCU 310 of FIG. 3, both a quad-tree type partition and a binary-tree type partition are applied.

In the encoding apparatus 100, a 64.times.64 size Coding Tree Unit (CTU) can be divided into a smaller number of CUs by a recursive quad-crree structure. One CU may be divided into four CUs having the same sizes. CUs can be recursively partitioned, and each CU can have a quadtree structure.

Through recursive partitioning for CU, an optimal partitioning method that yields the lowest rate-distortion ratio can be selected.

Fig. 4 is a diagram showing a form of a prediction unit (PU) that a coding unit (CU) can include.

A CU that is not further divided among the CUs divided from the LCU may be divided into one or more Prediction Units (PUs).

The PU can be a base unit for prediction. The PU may be coded and decoded in either a skip mode, an inter mode, or an intra mode. The PU can be divided into various forms according to each mode. For example, the target block described above with reference to FIG. 1 and the target block described above with reference to FIG. 2 may be a PU.

The CU may not be divided into PUs. If the CU is not partitioned into PUs, the size of the CU and the size of the PU may be the same.

In the skip mode, there may be no division in the CU. In the skip mode, the 2Nx2N mode 410 having the same sizes of PU and CU without division can be supported.

In inter mode, eight subdivided forms within the CU can be supported. For example, in the inter mode, 2Nx2N mode 410, 2NxN mode 415, Nx2N mode 420, NxN mode 425, 2NxnU mode 430, 2NxnD mode 435, nLx2N mode 440, Mode 445 may be supported.

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

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

In the NxN mode 425, the PU of the size NxN can be encoded.

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

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

The mode in which the PU is encoded by the 2Nx2N mode 410 and the NxN mode 425 can be determined by the rate-distortion cost.

The encoding apparatus 100 can perform the encoding operation on the 2Nx2N size PU. Here, the encoding operation may be to encode the PU in each of a plurality of intra prediction modes that the encoding apparatus 100 can use. The optimal intra prediction mode for the 2Nx2N size PU can be derived through the encoding operation. The optimal intra prediction mode may be an intra prediction mode in which a minimum rate-distortion cost is incurred for encoding 2Nx2N sized PUs among a plurality of intra prediction modes available for use by the encoding apparatus 100. [

Also, the encoding apparatus 100 can sequentially perform encoding operations on each PU of PUs divided into NxN. Here, the encoding operation may be to encode the PU in each of a plurality of intra prediction modes that the encoding apparatus 100 can use. An optimal intra prediction mode for an NxN size PU can be derived through an encoding operation. The optimal intra prediction mode may be an intra prediction mode in which a minimum rate-distortion cost is incurred for encoding of NxN-sized PUs among a plurality of intra prediction modes available for use by the encoding apparatus 100. [

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

One CU may be divided into one or more PUs, and a PU may be divided into a plurality of PUs.

For example, when one PU is divided into four PUs, the horizontal size and the vertical size of each PU of the four PUs generated by the division are respectively one half of the horizontal size of the PU before division and one half of the vertical size . When a 32x32 PU is divided into 4 PUs, the sizes of the 4 divided PUs may be 16x16. When one PU is divided into four PUs, it can be said that the PU is divided into quad-tree form.

For example, when one PU is divided into two PUs, the horizontal size or the vertical size of each PU of the two PUs generated by the division is a half of the horizontal size or half of the vertical size of the PU before the division, . When a PU of 32x32 size is vertically divided into two PUs, the sizes of the two divided PUs may be 16x32. When a 32x32 size PU is divided horizontally into two PUs, the sizes of the two divided PUs may be 32x16. When one PU is divided into two PUs, it can be said that the PU is divided into a binary-tree form.

5 is a diagram showing a form of a conversion unit (TU) which can be included in a coding unit (CU).

A Transform Unit (TU) can be a basic unit used for transform, quantization, inverse transform, inverse quantization, entropy coding, and entropy decoding processes in a CU.

The TU may have a square shape or a rectangular shape. The form of the TU may be determined depending on the size and / or shape of the CU.

Of the CUs segmented from the LCU, the CUs that are no longer divided into CUs may be divided into one or more TUs. At this time, 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 quad-tree structure. Through partitioning, one CU 510 can be composed of TUs of various sizes.

If a CU is divided more than once, the CU can be considered to be recursively partitioned. Through partitioning, one CU can be composed of TUs with various sizes.

Alternatively, one CU may be divided into one or more TUs based on the number of vertical and / or horizontal lines dividing the CU.

The CU may be divided into symmetric TUs and may be divided into asymmetric TUs. For division into asymmetric TUs, information about the size and / or type of the TU may be signaled from the encoding device 100 to the decoding device 200. Alternatively, the size and / or shape of the TU may be derived from information about the size and / or shape of the CU.

The CU may not be divided into TUs. If the CU is not divided into TUs, the size of the CU and the size of the TU may be the same.

One CU may be divided into one or more TUs, and a TU may be divided into a plurality of TUs.

For example, when one TU is divided into four TUs, the horizontal size and the vertical size of each TU of the four TUs generated by the division are respectively one half of the horizontal size of the TU before the division and one half of the vertical size . When a 32x32 TU is divided into 4 TUs, the sizes of the 4 TUs divided may be 16x16. When one TU is divided into four TUs, it can be said that TU is divided into quad-tree form.

For example, if one TU is divided into two TUs, the horizontal size or vertical size of each TU of the two TUs generated by the partition may be half of the horizontal size of the TU before the partition, . When a 32x32 TU is vertically divided into two TUs, the sizes of the two divided TUs may be 16x32. When a 32x32 TU is divided horizontally into two TUs, the sizes of the two TUs divided may be 32x16. When one TU is divided into two TUs, it can be said that the TU is divided into a binary-tree form.

The CU may be divided in a manner other than that shown in Fig.

For example, one CU may be divided into three CUs. The horizontal size or the vertical size of the three divided CUs may be 1/4, 1/2 and 1/4 of the horizontal size or vertical size of the CU before division, respectively.

For example, if a CU with a size of 32x32 is vertically divided into three CUs, the sizes of the three divided CUs may be 8x32, 16x32, and 8x32, respectively. Thus, when one CU is divided into three CUs, it can be seen that the CU is divided into the form of a triad tree.

One of the partitioning of the illustrated quad tree type, the partitioning of the binary tree type and the partitioning of the triple tree can be applied for partitioning of the CU, and a plurality of partitioning schemes may be combined for partitioning the CU . In this case, a case where a plurality of division methods are used in combination is referred to as a division of the form of a composite tree.

Figure 6 shows the partitioning of a block according to an example.

During the encoding and / or decoding of the image, the target block may be divided as shown in FIG.

To divide the target block, an indicator indicating the division information may be signaled from the coding apparatus 100 to the decoding apparatus 200. [ The partition information may be information indicating how the target block is divided.

(Hereinafter referred to as "quadtree_flag"), a binary tree flag (hereinafter referred to as "binarytree_flag"), a quad-binary flag (hereinafter referred to as "QB_flag" Quot;) and a binary type flag (hereinafter referred to as "Btype_flag").

The split_flag may be a flag indicating whether or not the block is divided. For example, the value 1 of split_flag may indicate that the block is partitioned. A value of 0 in split_flag may indicate that the block is not partitioned.

QB_flag may be a flag indicating whether the block is divided into a quad tree form or a binary tree form. For example, a value of 0 in QB_flag may indicate that the block is partitioned into a quadtree form. A value of 1 in QB_flag may indicate that the block is partitioned into a binary tree. Alternatively, a value of 0 in QB_flag may indicate that the block is partitioned into a binary tree form. A value of 1 in QB_flag may indicate that the block is partitioned into a quadtree form.

The quadtree_flag may be a flag indicating whether the block is divided into a quad tree form. For example, a value of 1 in quadtree_flag may indicate that the block is partitioned into a quadtree form. A value of 0 in the quadtree_flag may indicate that the block is not partitioned into quadtrees.

The binarytree_flag may be a flag indicating whether the block is divided into a binary tree form. For example, a value of 1 in the binarytree_flag may indicate that the block is partitioned into a binary tree. A value of binarytree_flag of 0 may indicate that the block is not partitioned into a binary tree.

Btype_flag may be a flag indicating whether the block is divided into a vertical division or a horizontal division when the block is divided into a binary tree form. For example, a value of 0 for Btype_flag may indicate that the block is divided horizontally. A value of 1 for Btype_flag may indicate that the block is vertically partitioned. Alternatively, a value of 0 for Btype_flag may indicate that the block is vertically split. A value of 1 for Btype_flag may indicate that the block is split horizontally.

For example, the partition information for the block of FIG. 6 can be derived by signaling at least one of quadtree_flag, binarytree_flag, and Btype_flag as shown in Table 1 below.

[Table 1]

For example, the partition information for the block of FIG. 6 can be derived by signaling at least one of split_flag, QB_flag, and Btype_flag as shown in Table 2 below.

[Table 2]

The partitioning method may be limited to a quadtree only according to the size and / or type of the block, or may be limited to a binary tree only. When this restriction is applied, the split_flag may be a flag indicating whether to split into a quadtree form or a flag indicating whether to divide it into a binary tree form. The size and shape of the block may be derived according to the depth information of the block, and the depth information may be signaled from the encoding device 100 to the decoding device 200.

If the size of the block falls within a specified range, only a quadtree-type partition may be possible. For example, the specified range may be defined by at least one of a maximum block size and a minimum block size that can be partitioned only in the form of a quadtree.

The information indicating the maximum block size and / or the minimum block size that can be divided only in the quadtree form can be signaled from the encoding apparatus 100 to the decoding apparatus 200 through the bit stream. In addition, such information may be signaled for at least one of a video, a sequence, a picture, and a slice (or segment).

Alternatively, the maximum block size and / or minimum block size may be a fixed size predefined in the encoding device 100 and the decoding device 200. For example, if the block size is greater than or equal to 64x64, and less than or equal to 256x256, only a quadtree-type partition may be possible. In this case, the split_flag may be a flag indicating whether the split_flag is divided into a quadtree form.

If the size of the block falls within a specified range, only a binary tree-like partition may be possible. Here, for example, the specified range may be defined by at least one of a maximum block size and a minimum block size that can be partitioned only in a binary tree form.

Information indicating the maximum block size and / or minimum block size that can be divided only in the binary tree form can be signaled from the encoding apparatus 100 to the decoding apparatus 200 through the bit stream. This information may also be signaled for at least one of a sequence, a picture, and a slice (or segment).

Alternatively, the maximum block size and / or minimum block size may be a fixed size predefined in the encoding device 100 and the decoding device 200. For example, if the block size is greater than or equal to 8x8 and less than or equal to 16x16, then only a binary tree-like partition may be possible. In this case, the split_flag may be a flag indicating whether the split tree is divided into a binary tree form.

The partitioning of the block can be limited by the previous partitioning. For example, when a block is divided into a binary tree form to generate a plurality of divided blocks, each divided block can be further divided into a binary tree form only.

If the horizontal or vertical size of the partitioned block corresponds to a size that can no longer be partitioned, the aforementioned indicator may not be signaled.

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

The arrows from the center to the outline of the graph of FIG. 7 may indicate the prediction directions of the intra-prediction modes. In addition, the number indicated close to the arrow may represent an example of the mode value assigned to the prediction direction of the intra-prediction mode or the intra-prediction mode.

Intra coding and / or decoding may be performed using reference samples of the units around the target block. The surrounding block may be the reconstructed block around. For example, intra-coding and / or decoding may be performed using values or coding parameters of reference samples included in the reconstructed neighboring blocks.

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

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

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

Alternatively, the prediction block may be a block in the form of a square having a size of 2x2, 4x4, 8x8, 16x16, 32x32, or 64x64, or may be a rectangular block having a size of 2x8, 4x8, 2x16, 4x16, have.

Intra prediction may be performed according to the intra prediction mode for the target block. The number of intra prediction modes that a target block may have may be a predetermined fixed value and may be a value determined differently depending on the property of the prediction block. For example, the attributes of the prediction block may include the size of the prediction block and the type of the prediction block.

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

The intra prediction mode may be a non-directional mode or a directional mode. For example, the intra prediction mode may include two non-directional modes and 33 directional modes as shown in FIG.

The two non-directional modes may include a DC mode and a Planar mode.

The directional modes may be a prediction mode having a specific direction or a specific angle.

The intra prediction mode may be represented by at least one of a mode number, a mode value, and a mode angle. The number of intra prediction modes may be M. M may be at least one. That is to say, the intra prediction mode may be M numbers including the number of non-directional modes and the number of directional modes.

The number of intra prediction modes may be fixed to M, regardless of the size of the block and / or the color component. For example, the number of intra prediction modes can be fixed to either 35 or 67 regardless of the size of the block.

Alternatively, the number of intra prediction modes may differ depending on the size of the block and / or the type of color component.

For example, the larger the block size, the larger the number of intra prediction modes. Alternatively, the larger the block size, the smaller the number of intra prediction modes. If the block size is 4x4 or 8x8, then the number of intra prediction modes may be 67. If the size of the block is 16x16, the number of intra prediction modes may be 35. If the block size is 32x32, the number of intra prediction modes may be 19. If the block size is 64x64, the number of intra prediction modes may be 7.

For example, the number of intra prediction modes may be different depending on whether the color component is a luma signal or a chroma signal. Or the number of intra prediction modes of the luma component block may be greater than the number of intra prediction modes of the chroma component block.

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

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

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

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

The directional mode may include an angular mode. Among the plurality of intra prediction modes, the remaining modes except for the DC mode and the planar mode may be the directional mode.

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

The number of intra prediction modes described above and the mode value of each intra prediction mode may be exemplary only. The number of intra prediction modes described above and the mode value of each intra prediction mode may be differently defined according to the embodiment, implementation and / or necessity.

A step of checking whether samples included in the restored neighboring block can be used as a reference sample of the target block to perform intra prediction on the target block can be performed. A value generated by copying and / or interpolation using at least one sample value of samples included in the reconstructed neighboring block, if there is a sample that is not available as a reference sample of the target block among the samples of the neighboring block It can be replaced with the sample value of the sample which is not available as a reference sample. If the value generated by copying and / or interpolation is replaced with the sample value of the sample, the sample may be used as a reference sample of the target block.

In 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 a target block.

The kind of filter applied to at least one of the reference sample and the prediction sample may be different depending on at least one of an intra prediction mode of a target block, a size of a target block, and a shape of a target block. The type of the filter can be classified according to one or more of the number of filter taps, the value of the filter coefficient, and the filter strength.

When the intra prediction mode is the planar mode, in generating the prediction block of the target block, the upper reference sample of the target sample, the left reference sample of the target sample, and the upper right reference sample of the target block And a weighted sum of the lower left reference samples of the target block may be used to generate a sample value of the prediction target sample.

When the intra prediction mode is the DC mode, in generating the prediction block of the target block, the average value of the upper reference samples and the left reference samples of the target block may be used. Further, filtering may be performed using the values of the reference samples for the specified rows or specified columns in the object block. The specified rows may be one or more top rows adjacent to the reference sample. The specified columns may be one or more left columns adjacent to the reference sample.

When the intra prediction mode is the directional mode, a prediction block can be generated using the upper reference sample, the left reference sample, the upper right reference sample, and / or the lower left reference sample of the target block.

Real-unit interpolation may be performed to generate the prediction samples described above.

The intra prediction mode of the target block can be predicted from the intra prediction mode of the neighboring block of the target block, and the information used for prediction can be entropy encoded / decoded.

For example, if the intraprediction modes of the target block and the neighboring blocks are the same, it can be signaled that the intraprediction modes of the target block and the neighboring block are the same using the predetermined flag.

For example, an indicator indicating an intra prediction mode that is the same as the intra prediction mode of the target block among the intra prediction modes of a plurality of neighboring blocks may be signaled.

If the intra prediction modes of the target block and the neighboring blocks are different from each other, the information of the intra prediction mode of the target block can be encoded and / or decoded using entropy encoding and / or decoding.

8 is a view for explaining the positions of reference samples used in the intra prediction process.

8 shows the location of a reference sample used for intra prediction of a target block. 8, a reconstructed reference sample used for intra prediction of a target block includes lower-left reference samples 831, left reference samples 833, an upper- left corner reference sample 835, top reference samples 837 and top-right reference samples 839, and the like.

For example, the left reference samples 833 may refer to reconstructed reference pixels adjacent to the left of the target block. Top reference samples 837 may refer to a reconstructed reference pixel adjacent the top of the target block. The upper left corner reference sample 835 may refer to a reconstructed reference pixel located at the upper left corner of the object block. In addition, the lower left reference samples 831 may refer to a reference sample located at the lower end of the left sample line among the samples located on the same line as the left sample line composed of the left reference samples 833. Upper right reference samples 839 may refer to reference samples located on the right side of the upper pixel line among samples located on the same line as the upper sample line composed of upper reference samples 837. [

When the size of the target block is NxN, the lower left reference samples 831, the left reference samples 833, the upper reference samples 837, and the upper right reference samples 839 may be N, respectively.

A prediction block can be generated through intraprediction of a target block. The generation of the prediction block may include determining the value of the pixels of the prediction block. The size of the target block and the size of the prediction block may be the same.

The reference sample used for intra prediction of the target block may be changed depending on the intra prediction mode of the target block. The direction of the intra-prediction mode may indicate a dependency between the reference samples and the pixels of the prediction block. For example, the value of the specified reference sample may be used as the value of one or more specified pixels of the prediction block. In this case, the specified reference sample and the specified one or more pixels of the prediction block may be samples and pixels designated by a straight line in the direction of the intra prediction mode. That is to say, the value of the specified reference sample can be copied to the value of the pixel located in the reverse direction of the intra prediction mode. Alternatively, the value of the pixel of the prediction block may be the value of the reference sample located in the direction of the intra-prediction mode with respect to the position of the pixel.

For example, if the intra prediction mode of the target block is a vertical mode with a mode value of 26, upper reference samples 837 may be used for intra prediction. When the intra prediction mode is the vertical mode, the value of the pixel of the prediction block may be the value of the reference sample vertically positioned with respect to the position of the pixel. Thus, top reference samples 837 that are near the top of the target block may be used for intra prediction. In addition, the values of the pixels of a row of the prediction block may be the same as the values of the upper reference samples 837. [

For example, when the intra prediction mode of the target block is a horizontal mode with a mode value of 10, the left reference samples 833 can be used for intra prediction. When the intra prediction mode is the horizontal mode, the value of the pixel of the prediction block may be the value of the reference sample located horizontally on the left side of the pixel. Thus, the left reference samples 833 to the left of the target block may be used for intra prediction. In addition, the values of the pixels in a column of the prediction block may be the same as the values of the left reference samples 833. [

For example, if the mode value of the intra prediction mode of the target block is 18, at least a part of the left reference samples 833, at least a part of the upper left corner reference sample 835 and the upper reference samples 837, Can be used. If the mode value of the intra prediction mode is 18, the value of the pixel of the prediction block may be a value of the reference sample located diagonally to the left of the upper side with respect to the pixel.

Also, if an intra prediction mode with a mode value of 27, 28, 29, 30, 31, 32, 33 or 34 is used, at least some of the upper right reference samples 839 may be used for intra prediction.

Also, when an intra prediction mode having a mode value of 2, 3, 4, 5, 6, 7, 8, or 9 is used, at least a part of the lower left reference samples 831 may be used for intra prediction.

Also, if an intra prediction mode with a mode value of 11 to 25 is used, upper left corner reference sample 835 may be used for intra prediction.

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

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

If the position of the pixel and the position of the reference sample pointed by the direction of the intra prediction mode is not an integer position then an interpolated reference sample may be generated based on the two reference samples closest to the location of the reference sample have. The value of the interpolated reference sample may be used to determine the pixel value of the pixel of the prediction block. That is, when the position of the pixel of the prediction block and the position of the reference sample pointed by the direction of the intra prediction mode indicate between the two reference samples, an interpolated value is generated based on the values of the two samples .

The prediction block generated by the prediction may not be the same as the original target block. That is, there may be a prediction error which is a difference between the target block and the prediction block, and a prediction error may exist between the pixels of the target block and the pixels of the prediction block.

In the following, the terms "difference", "error" and "residual" may be used interchangeably and may be used interchangeably.

For example, in the case of directional intra prediction, the greater the distance between the pixel of the prediction block and the reference sample, the larger the prediction error may occur. Discontinuity may occur between the prediction block generated by the prediction error and the neighboring blocks.

Filtering for the prediction block may be used to reduce the prediction error. The filtering may be adaptively applying a filter to an area of the prediction block that is considered to have a large prediction error. For example, the region considered as having a large prediction error may be the boundary of the prediction block. In addition, depending on the intra-prediction mode, an area regarded as having a large prediction error among the prediction blocks may be different, and the characteristics of the filter may be different.

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

The rectangle shown in FIG. 9 may represent an image (or a picture). In Fig. 9, arrows may indicate the prediction direction. That is, the image can be encoded and / or decoded according to the prediction direction.

Each image can be classified into an I picture (Intra Picture), a P picture (Uni-prediction Picture), and a B picture (Bi-prediction Picture) according to the coding type. Each picture can be coded and / or decoded according to the coding type of each picture.

If the object image to be encoded is an I-picture, the object image can be encoded using data in the image itself without inter-prediction referring to other images. For example, an I-picture can be encoded only by intra prediction.

When the target image is a P picture, the target image can be encoded by inter prediction using only reference pictures existing in a unidirection. Here, the unidirectional may be forward or reverse.

When the target image is a B picture, the target image can be encoded by inter prediction using bi-directional reference pictures or inter prediction using reference pictures existing in one direction of forward and backward directions. Here, both directions may be forward and backward.

P-pictures and B-pictures that are encoded and / or decoded using reference pictures can be regarded as pictures in which inter-prediction is used.

In the following, inter prediction in the inter mode according to the embodiment will be described in detail.

Inter prediction can be performed using motion information.

In inter mode, the encoding apparatus 100 can perform inter prediction and / or motion compensation on a target block. The decoding apparatus 200 may perform inter-prediction and / or motion compensation corresponding to inter-prediction and / or motion compensation in the encoding apparatus 100 with respect to a target block.

The motion information for the target block can be derived during inter-prediction by the encoding apparatus 100 and the decoding apparatus 200, respectively. The motion information may be derived using motion information of the restored neighboring block, motion information of the call block, and / or motion information of a block adjacent to the call block.

For example, the coding apparatus 100 or the decoding apparatus 200 may perform prediction and / or motion compensation by using motion information of a spatial candidate and / or a temporal candidate as motion information of a target block Can be performed. The target block may refer to a PU and / or PU partition.

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

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

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

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

Inter prediction can be performed using a reference picture.

The reference picture may be at least one of a previous picture of a target picture or a subsequent picture of a target picture. The reference picture may refer to an image used for prediction of a target block.

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

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

The motion information may be derived during inter-prediction by the encoding apparatus 100 and the decoding apparatus 200, respectively.

The spatial candidate may be 1) existing in the target picture, 2) already reconstructed through encoding and / or decoding, and 3) adjacent to the target block or a block located at the corner of the target block. Here, a block located at a corner of a target block may be a block vertically adjacent to a neighboring block that is laterally adjacent to the target block, or a block that is laterally adjacent to a neighboring block vertically adjacent to the target block. The "block located at the corner of the target block" may have the same meaning as "the block adjacent to the corner of the target block ". The "block located at the corner of the target block" may be included in the "block adjacent to the target block ".

For example, the spatial candidate may be a reconstructed block located on the left side of the target block, a reconstructed block located on the top of the target block, a reconstructed block located in the lower left corner of the target block, The reconstructed block or the reconstructed block located in the upper left corner of the target block.

Each of the encoding apparatus 100 and the decoding apparatus 200 can identify a block existing in a position spatially corresponding to a target block in a col picture. The position of the target block in the target picture and the position of the identified block in the call picture can correspond to each other.

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

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

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

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

The derivation method of the motion information can be changed according to the inter prediction mode of the target block. For example, there may be an inter-prediction mode applied for inter prediction, such as an Advanced Motion Vector Predictor (AMVP) mode, a merge mode and a skip mode, and a current picture reference mode have. The merge mode may also be referred to as a motion merge mode. Each of the modes will be described in detail below.

1) AMVP mode

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

1-1) Creation of Predicted Motion Vector Candidate List

When the AMVP mode is used as the prediction mode, each of the encoding apparatus 100 and the decoding apparatus 200 can generate a predicted motion vector candidate list using a spatial candidate motion vector, a temporal motion motion vector, and a zero vector have. The predicted motion vector candidate list may include one or more predicted motion vector candidates. At least one of a spatial candidate motion vector, a temporal candidate motion vector, and a zero vector may be determined and used as a predicted motion vector candidate.

Hereinafter, the terms "predicted motion vector (candidate)" and "motion vector (candidate)" may be used interchangeably and may be used interchangeably.

Hereinafter, the terms "predicted motion vector candidate" and "AMVP candidate" can be used interchangeably and can be used interchangeably.

Hereinafter, the terms "predicted motion vector candidate list" and "AMVP candidate list" may be used interchangeably and may be used interchangeably.

Spatial candidates may include reconstructed spatial neighboring blocks. In other words, the motion vector of the reconstructed neighboring block may be referred to as a spatial prediction motion vector candidate.

The temporal candidate may include a call block and a block adjacent to the call block. In other words, a motion vector of a call block or a block adjacent to a call block may be referred to as a temporal prediction motion vector candidate.

The zero vector may be a (0, 0) motion vector.

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

1-2) Retrieving a motion vector using a predicted motion vector candidate list

The encoding apparatus 100 may use the predicted motion vector candidate list to determine a motion vector to be used for encoding the target block within the search range. Also, the encoding apparatus 100 can determine a predicted motion vector candidate to be used as a predicted motion vector of a target block among predicted motion vector candidates of the predicted motion vector candidate list.

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

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

1-3) Transmission of inter prediction information

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

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

Hereinafter, the terms "predicted motion vector index" and "AMVP index" may be used interchangeably and may be used interchangeably.

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

When the mode information indicates that the AMVP mode is used, the decoding apparatus 200 can obtain the predicted motion vector index, the motion vector difference, the reference direction, and the reference picture index from the bitstream through entropy decoding.

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

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

The decoding apparatus 200 can derive a predicted motion vector candidate using the predicted motion vector candidate list and determine the motion information of the target block based on the derived predicted motion vector candidate.

The decoding apparatus 200 can determine a motion vector candidate for a target block from among the predicted motion vector candidates included in the predicted motion vector candidate list using the predicted motion vector index. The decoding apparatus 200 can select a predicted motion vector candidate pointed to by the predicted motion vector index among the predicted motion vector candidates included in the predicted motion vector candidate list as a predicted motion vector of the target block.

The motion vector to be actually used for inter prediction of the target block may not coincide with the predicted motion vector. The MVD may be used to represent the difference between the motion vector to be actually used for inter prediction of the target block and the predicted motion vector. The encoding apparatus 100 can derive a predictive motion vector similar to a motion vector to be actually used for inter prediction of a target block in order to use an MVD as small as possible.

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

The MVD may be transmitted from the encoding apparatus 100 to the decoding apparatus 200 through a bitstream. The decoding apparatus 200 can decode the received MVD. The decoding apparatus 200 can derive a motion vector of a target block by adding the decoded MVD and the predicted motion vector. In other words, the motion vector of the target block derived from the decoding apparatus 200 may be the sum of the entropy-decoded MVD and the motion vector candidate.

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

The reference direction may refer to a reference picture list used for prediction of a target block, but may not indicate that the directions of the reference pictures are limited in a forward direction or a backward direction. That is to say, each of the reference picture list L0 and the reference picture list L1 may include forward and / or backward pictures.

The reference direction being uni-directional may mean that one reference picture list is used. The bi-directional reference direction may mean that two reference picture lists are used. That is to say, the reference direction may indicate that only the reference picture list L0 is used, only the reference picture list L1 is used, and one of the two reference picture lists.

The reference picture index may indicate a reference picture used for prediction of a target block among reference pictures of the reference picture list. The reference picture index can be entropy-encoded by the encoding apparatus 100. [ The entropy encoded reference picture index may be signaled from the encoding apparatus 100 to the decoding apparatus 200 through the bit stream.

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

The motion vector of the target block can be derived by the predicted motion vector index, the MVD, the reference direction, and the reference picture index.

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

The amount of bits to be transmitted from the encoding apparatus 100 to the decoding apparatus 200 can be reduced by encoding the predicted motion vector index and the MVD without encoding the motion vector of the target block and the encoding efficiency can be improved.

Motion information of the reconstructed neighboring blocks may be used for the target block. In the specific inter prediction mode, the encoding apparatus 100 may not separately encode the motion information on the target block. The motion information of the target block is not coded and other information capable of deriving the motion information of the target block through motion information of the reconstructed neighboring block can be encoded instead. As other information is encoded in place, the amount of bits to be transmitted to the decoding apparatus 200 can be reduced, and the coding efficiency can be improved.

For example, a skip mode and / or a merge mode may be an inter prediction mode in which motion information of the target block is not directly encoded. At this time, the encoding apparatus 100 and the decoding apparatus 200 may use an identifier and / or index indicating which one of the reconstructed neighboring units is used as motion information of the target unit.

2) Mersey mode

As a method for deriving motion information of a target block, there is a merge. A merge may mean a merging of movements for a plurality of blocks. Merging may mean applying motion information of one block to another block as well. In other words, the merge mode may mean a mode in which motion information of a target block is derived from motion information of a neighboring block.

When the merge mode is used, the encoding apparatus 100 can predict motion information of a target block using motion information of a spatial candidate and / or motion information of a temporal candidate. The spatial candidate may include reconstructed spatial neighboring blocks spatially adjacent to the object block. The spatial neighboring block may include a left adjacent block and an upper adjacent block. The temporal candidate may include a call block. The terms "spatial candidate" and "spatial merge candidate" can be used interchangeably and can be used interchangeably. The terms "temporal candidate" and "temporal merge candidate" can be used interchangeably and can be used interchangeably.

The encoding apparatus 100 can obtain a prediction block through prediction. The encoding apparatus 100 can encode a residual block that is a difference between the target block and the prediction block.

2-1) Creating a merge candidate list

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

The merge candidate list may include merge candidates. The merge candidate may be motion information. That is to say, the merge candidate list may be a list in which motion information is stored.

The merge candidates may be motion information such as temporal candidates and / or spatial candidates. In addition, the merge candidate list may include a new merge candidate generated by a combination of merge candidates already present in the merge candidate list. That is, the merge candidate list may include new motion information generated by a combination of motion information already present in the merge candidate list.

The merge candidates may be specified modes for deriving inter prediction information. The merge candidate may be information indicating a specified mode for deriving inter prediction information. The inter prediction information of the target block may be derived according to the specified mode indicated by the merge candidate. At this time, the specified mode may include a process of deriving a series of inter prediction information. This specified mode may be an inter prediction information induction mode or a motion information induction mode.

The inter prediction information of the target block may be derived according to the mode indicated by the merge candidate selected by the merge index among the merge candidates in the merge candidate list.

For example, the motion information derivation modes in the merge candidate list may be at least one of 1) a motion information derivation mode in sub-block units, and 2) an affine motion information derivation mode.

Also, the merge candidate list may include motion information of a zero vector. Zero vectors may also be called zero-merge candidates.

In other words, the motion information in the merge candidate list includes: 1) motion information of a spatial candidate, 2) motion information of a temporal candidate, 3) motion information generated by a combination of motion information existing in an already existing candidate list, 4) Lt; / RTI >

The motion information may include 1) a motion vector, 2) a reference picture index, and 3) a reference direction. The reference direction may be referred to as an inter prediction indicator. The reference direction may be unidirectional or bidirectional. The unidirectional reference direction may represent L0 prediction or L1 prediction.

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

The number of merge candidates in the merge candidate list can be predetermined. The encoding apparatus 100 and the decrypting apparatus 200 may add a merge candidate to the merge candidate list according to the predefined manner and the predefined rank so that the merge candidate list has a predetermined number of merge candidates. The merge candidate list of the encoding apparatus 100 and the merge candidate list of the decryption apparatus 200 may be the same through the predetermined scheme and the default rank.

The merge can be applied in CU units or PU units. When the merging is performed in units of CU or PU, the encoding apparatus 100 may transmit the bitstream including the predetermined information to the decoding apparatus 200. [ For example, the predefined information may include: 1) information indicating whether to perform a merge by block partitions, 2) a block to be merged with any block among the blocks that are spatial candidates and / or temporal candidates for the target block And information about whether or not it is possible.

2-2) Search of motion vectors using merge candidate list

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

Further, the encoding apparatus 100 can determine whether to use the merge mode in encoding the target block.

2-3) Transmission of inter prediction information

The encoding apparatus 100 can generate a bitstream including inter prediction information required for inter prediction. The encoding apparatus 100 may generate entropy-encoded inter prediction information by performing entropy encoding on the inter prediction information, and may transmit the bit stream including the entropy-encoded inter prediction information to the decoding apparatus 200. Through the bitstream, entropy-encoded inter prediction information can be signaled from the encoding apparatus 100 to the decoding apparatus 200. [

The decoding apparatus 200 may perform inter prediction on a target block using inter prediction information of a bit stream.

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

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

The decoding apparatus 200 can obtain a merge index from the bit stream only when the mode information indicates that the merge mode is used.

The mode information may be a merge flag. The unit of mode information may be a block. The information about the block may include mode information, and the mode information may indicate whether the merge mode is applied to the block.

The merge index may indicate a merge candidate used for predicting a target block among merge candidates included in the merge candidate list. Alternatively, the merge index may indicate which of the neighboring blocks spatially or temporally adjacent to the target block is merged with.

The encoding apparatus 100 can select the merge candidate having the highest encoding capability among the merge candidates included in the merge candidate list and set the merge index value to point to the selected merge candidate.

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

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

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

3) Skip Mode

The skip mode may be a mode in which motion information of a spatial candidate or motion information of a temporal candidate is directly applied to a target block. The skip mode may be a mode in which the residual signal is not used. That is to say, when the skip mode is used, the reconstructed block may be a prediction block.

The difference between the merge mode and the skip mode may be the transmission or use of the residual signal. That is to say, the skip mode may be similar to the merge mode, except that the residual signal is not transmitted or used.

When the skip mode is used, the encoding apparatus 100 transmits information indicating which of the blocks, which are spatial candidates or temporal candidates, is to be used as motion information of the target block, to the decoding apparatus 200 through the bit stream Lt; / RTI > The encoding apparatus 100 may generate entropy-encoded information by performing entropy encoding on the information, and may signal entropy-encoded information to the decoding apparatus 200 through the bitstream.

In addition, when the skip mode is used, the encoding apparatus 100 may not transmit other syntax element information such as MVD to the decryption apparatus 200. [ For example, when used in the skip mode, the encoding apparatus 100 may not signal a syntax element related to at least one of the MVC, the coded block flag, and the transform coefficient level to the decoding apparatus 200. [

3-1) Preparation of merge candidate list

Skipped mode You can also use the merge candidate list. That is to say, the merge candidate list can be used in both merge mode and skip mode. In this regard, the merge candidate list may be named a "skip candidate list" or a "merge / skip candidate list ".

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

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

3-2) Search of motion vectors using merge candidate list

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

Further, the encoding apparatus 100 can determine whether to use the skip mode in encoding the target block.

3-3) Transmission of inter prediction information

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

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

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

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

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

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

3-4) Inter prediction of skip mode using inter prediction information

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

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

4) Current picture reference mode

The current picture reference mode may mean a prediction mode using the preexisting reconstructed region in the target picture to which the target block belongs.

A motion vector may be used to specify the periodically reconstructed region. Whether or not the target block is coded in the current picture reference mode can be determined using the reference picture index of the target block.

A flag or an index indicating whether the target block is a block coded in the current picture reference mode may be signaled from the coding apparatus 100 to the decoding apparatus 200. [ Alternatively, whether the target block is a block coded in the current picture reference mode may be inferred through the reference picture index of the target block.

When the target block is coded in the current picture reference mode, the target picture may be in a fixed position or an arbitrary position in the reference picture list for the target block.

For example, the fixed position may be the position where the value of the reference picture index is 0 or the last position.

When the target picture exists at any position in the reference picture list, a separate reference picture index indicating this arbitrary position may be signaled from the coding apparatus 100 to the decoding apparatus 200. [

In the above-described AMVP mode, merge mode, and skip mode, motion information to be used for prediction of a target block among the motion information in the list can be specified through the index for the list.

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

Accordingly, the above-described lists (i.e., the predicted motion vector candidate list and the merge candidate list) may have to be derived in the same manner based on the same data in the encoding apparatus 100 and the decrypting apparatus 200. [ Here, the same data may include reconstructed pictures and reconstructed blocks. Also, in order to specify an element by index, the order of the elements in the list may have to be constant.

Figure 10 shows spatial candidates according to an example.

In Figure 10, the location of spatial candidates is shown.

A large block in the middle can represent a target block. The five small blocks may represent spatial candidates.

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

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

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

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

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

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

Determining Availability of Spatial and Temporal Candidates

In order to include motion information of a spatial candidate or motion information of a temporal candidate, it is necessary to determine whether motion information of a spatial candidate or motion information of a temporal candidate is available.

Hereinafter, the candidate block may include spatial candidates and temporal candidates.

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

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

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

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

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

FIG. 11 shows an order of addition of motion information of a spatial candidate to a merge list according to an example.

As shown in FIG. 11, in order to add motion information of spatial candidates to the merge list, the order of A ₁ , B ₁ , B ₀ , A _0, and B ₂ may be used. That is, the motion information of available spatial candidates can be added to the merged list in the order of A ₁ , B ₁ , B ₀ , A _0, and B ₂ .

How to derive a merge list in merge mode and skip mode

As described above, the maximum number of merge candidates in the merge list can be set. The set maximum number is denoted by N. The set number can be transferred from the encoding apparatus 100 to the decoding apparatus 200. [ The slice header of the slice may contain N. [ That is, the maximum number of merge candidates of the merge list for the target block of the slice can be set by the slice header. For example, basically the value of N may be 5.

The motion information (i.e., merge candidate) may be added to the merge list in the following order of steps 1) to 4) below.

Step 1) Available spatial candidates among the spatial candidates can be added to the merged list. The motion information of the available spatial candidates may be added to the merge list in the order shown in FIG. At this time, if the motion information of the available spatial candidate overlaps with other motion information already existing in the merge list, the motion information may not be added to the merge list. Checking whether or not to overlap with other motion information present in the list can be outlined as "redundancy check ".

The motion information to be added may be a maximum of N pieces.

Step 2) If the number of motion information in the merge list is smaller than N and temporal candidates are available, motion information of temporal candidates may be added to the merge list. At this time, if the available temporal candidate motion information overlaps with other motion information already existing in the merge list, the motion information may not be added to the merge list.

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

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

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

Within the merge list, the L0 motion information may be one or more. Also, within the merge list, the L1 motion information may be one or more.

The combined motion information may be one or more. In generating the combined motion information, it is possible to determine which L0 motion information and which L1 motion information to use among one or more L0 motion information and one or more L1 motion information. The one or more combined motion information may be generated in a predetermined order by combined bidirectional prediction using a pair of different motion information in the merge list. One of the pairs of different motion information may be the L0 motion information and the other may be the L1 motion information.

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

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

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

The zero vector motion information may be motion information whose motion vector is a zero vector.

The zero vector motion information may be one or more. The reference picture indexes of one or more zero vector motion information may be different from each other. For example, the value of the reference picture index of the first zero vector motion information may be zero. The value of the reference picture index of the second zero vector motion information may be one.

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

The reference direction of the zero vector motion information may be bi-directional. The two motion vectors may all be zero vectors. The number of zero vector motion information may be the smaller of the number of reference pictures in the reference picture list L0 and the number of reference pictures in the reference picture list L1. Alternatively, when the number of reference pictures in the reference picture list L0 is different from the number of reference pictures in the reference picture list L1, a unidirectional reference direction can be used for a reference picture index that can be applied to only one reference picture list.

The coding apparatus 100 and / or the decoding apparatus 200 can sequentially add the zero vector motion information to the merged list while changing the reference picture index.

If the zero vector motion information overlaps with other motion information already present in the merge list, the zero vector motion information may not be added to the merge list.

The order of the above-described steps 1) to 4) is merely exemplary, and the order between the steps may be mutually exclusive. In addition, some of the steps may be omitted depending on the predefined conditions.

A method of deriving a predicted motion vector candidate list in AMVP mode

The maximum number of predicted motion vector candidates in the predicted motion vector candidate list can be predetermined. The default maximum number is denoted by N. For example, the default maximum number may be two.

The motion information (i.e., the predicted motion vector candidate) may be added to the predicted motion vector candidate list in the order of the following steps 1) to 3).

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

The first spatial candidate may be one of A ₀ , A ₁ , scaled A _0, and scaled A ₁ . The second spatial candidate may be one of B ₀ , B ₁ , B ₂ , Scaled B ₀ , Scaled B _1, and Scaled B ₂ .

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

The motion information to be added may be a maximum of N pieces.

Step 2) If the number of pieces of motion information in the predicted motion vector candidate list is smaller than N and temporal candidates are available, temporal motion information may be added to the predicted motion vector candidate list. In this case, if the motion information of the available temporal candidate overlaps with other motion information already present in the predicted motion vector candidate list, the motion information may not be added to the predicted motion vector candidate list.

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

The zero vector motion information may be one or more. The reference picture indexes of one or more zero vector motion information may be different from each other.

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

The zero vector motion information may not be added to the predicted motion vector candidate list if the zero vector motion information overlaps with other motion information already present in the predicted motion vector candidate list.

The description of the zero vector motion information described above for the merge list can also be applied to zero vector motion information. Duplicate descriptions are omitted.

The order of the steps 1) to 3) described above is merely exemplary, and the order between the steps may be mutually exclusive. In addition, some of the steps may be omitted depending on the predefined conditions.

FIG. 12 illustrates a process of transform and quantization according to an example.

A quantized level may be generated by performing a conversion and / or quantization process on the residual signal as shown in FIG.

The residual signal can be generated as a difference between the original block and the prediction block. Here, the prediction block may be a block generated by intra prediction or inter prediction.

The residual signal can be transformed into the frequency domain through a transform process that is part of the quantization process.

The transformation kernel used for the transformation may include various DCT kernels and Discrete Sine Transform (DST) kernels such as Discrete Cosine Transform (DCT) type 2 (DCT-II) .

These transform kernels may perform a separable transform or a two-dimensional (2D) non-separable transform on the residual signal. The detachable transform may be a transform that performs a one-dimensional (1D) transform on the residual signal in each of the horizontal and vertical directions.

The DCT type and DST type adaptively used for 1D conversion may include DCT-V, DCT-VIII, DST-I and DST-VII in addition to DCT-II as shown in Table 3 below.

[Table 3]

As indicated in Table 3, a transform set may be used to derive the DCT type or DST type to be used for the transform. Each transform set may include a plurality of transform candidates. Each conversion candidate may be a DCT type or a DST type.

Table 4 below shows an example of a transform set applied in the horizontal direction according to the intra prediction mode.

[Table 4]

In Table 4, the number of the conversion set applied to the horizontal direction of the residual signal in accordance with the intra prediction mode of the target block is shown.

Table 5 below shows an example of a transform set applied in the vertical direction according to the intra prediction mode.

[Table 5]

As illustrated in Tables 4 and 5, the transform sets applied in the horizontal direction and the vertical direction according to the intra-prediction mode of the target block can be predetermined in advance. The encoding apparatus 100 can perform the transform and inverse transform on the residual signal using the transform included in the transform set corresponding to the intra prediction mode of the object block. In addition, the decoding apparatus 200 can perform inverse transform on the residual signal using the transform included in the transform set corresponding to the intra-prediction mode of the target block.

In such transforms and inversions, the transform set applied to the residual signal may be determined as illustrated in Tables 3, 4 and 5 and may not be signaled. The conversion instruction information can be signaled from the encoding apparatus 100 to the decoding apparatus 200. [ The conversion instruction information may be information indicating which conversion candidate is used among a plurality of conversion candidates included in the conversion set applied to the residual signal.

The method of using various transformations as described above can be applied to the residual signal generated by intra prediction or inter prediction.

The transform may include at least one of a primary transform and a secondary transform. A transform coefficient may be generated by performing a first transform on the residual signal and a second transform coefficient may be generated by performing a second transform on the transform coefficient.

The primary transformation can be named primary. Also, the first order transformation can be named as Adaptive Multiple Transform (AMT). AMT may mean that different transforms are applied to each of the 1D directions (i.e., vertical and / or horizontal directions) or selected directions as described above.

The AMT may also be called Multiple Transform Selection (MTS) or Extended Multiple Transform (EMT).

The quadratic transformation may be a transform to improve the energy concentration of the transform coefficients generated by the primary transform. The quadratic transformation can be a separable transformation or a non-separable transformation like the primary transformation. The non-separable transform may be a non-separable secondary transform (NSST).

The primary transformation may be performed using at least one of a plurality of predetermined transformation methods. For example, a plurality of predetermined conversion methods may be implemented using discrete cosine transform (DCT), discrete sine transform (DST), and Karhunen-Loeve Transform (KLT) .

Also, the first order transform may be a transform of various types depending on the kernel function defining the DCT or DST.

For example, the first order transform includes transforms such as DCT-2, DCT-5, DCT-7, DST-7, DST-1, DST-8 and DCT-8 according to the transform kernel shown in Table 6 below. can do. In Table 6, various transformation types and transformation kernel functions for Multiple Transform Selection (MTS) are illustrated.

The MTS may mean that a combination of one or more DCT and / or DST transform kernels is selected for conversion to the horizontal and / or vertical direction of the residual signal.

[Table 6]

In Table 6, i and j may be an integer value of 0 or more and N-1 or less.

A secondary transform may be performed on the transform coefficients generated by performing the primary transform.

The primary transform and / or the quadratic transform may be applied to one or more signal components of a luma component and a chroma component. The application of the primary transformation and / or the secondary transformation may be determined according to at least one of coding parameters for a target block and / or a neighboring block. For example, the application of the primary transformation and / or the secondary transformation may be determined by the size and / or shape of the target block.

The transform method (s) applied to the primary transform and / or the quadratic transform may be determined according to at least one of the coding parameters for the object block and / or the surrounding block. The determined transform method may indicate that the first transform and / or the second transform are not used.

Or conversion information indicating the conversion method may be signaled from the encoding device 100 to the decryption device 200. [ For example, the transformation information may include an index of transformations to be used for the primary transformation and / or the secondary transformation.

The quantized transform coefficients (i.e., quantized levels) can be generated by performing quantization on the result or residual signal generated by performing the primary transform and / or the quadratic transform.

13 illustrates diagonal scanning according to an example.

14 shows horizontal scanning according to an example.

15 shows vertical scanning according to an example.

The quantized transform coefficients may be scanned according to at least one of an intraprediction mode, a block size, and a block type according to at least one of (up-right) diagonal scanning, vertical scanning and horizontal scanning. The block may be a conversion unit.

Each scanning can start at a specified starting point and end at a specified ending point.

For example, the quantized transform coefficients can be changed to a one-dimensional vector form by scanning the coefficients of the block using the diagonal scanning of FIG. Alternatively, horizontal scanning of FIG. 14 or vertical scanning of FIG. 15 may be used instead of diagonal scanning depending on the block size and / or intra prediction mode.

Vertical scanning may be a two dimensional block form factor scan in the column direction. The horizontal scanning may be to scan the two-dimensional block form factor in the row direction.

That is to say, depending on the size of the block and / or the inter prediction mode, it can be determined which one of diagonal scanning, vertical scanning and horizontal scanning is to be used.

As shown in Figs. 13, 14, and 15, the quantized transform coefficients may be scanned along the diagonal direction, the horizontal direction, or the vertical direction.

The quantized transform coefficients may be expressed in block form. A block may include a plurality of sub-blocks. Each sub-block may be defined according to a minimum block size or a minimum block type.

In scanning, the scanning order according to the type or direction of scanning may be first applied to the sub-blocks. In addition, the scanning order according to the scanning direction may be applied to the quantized transform coefficients in the sub-block.

For example, as shown in FIGS. 13, 14, and 15, when the size of the target block is 8x8, the transform coefficients quantized by the first transform, the second transform, and the quantization on the residual signal of the target block Lt; / RTI > Thereafter, one of the three scanning sequences may be applied to four 4x4 subblocks, and the quantized transform coefficients may be scanned for each 4x4 subblock according to the scanning order.

The scanned quantized transform coefficients may be entropy encoded and the bitstream may comprise entropy encoded quantized transform coefficients.

The decoding apparatus 200 can generate quantized transform coefficients through entropy decoding on the bit stream. The quantized transform coefficients may be arranged in a two-dimensional block form through inverse scanning. At this time, as a method of inverse scanning, at least one of top-right diagonal scanning, vertical scanning, and horizontal scanning may be performed.

The inverse quantization can be performed on the quantized transform coefficients. Depending on whether or not the second-order inverse transform is performed, the second-order inverse transform can be performed on the result generated by performing the inverse quantization. Also, depending on whether or not the first-order inverse transform is performed, the first-order inverse transform can be performed on the result generated by performing the second-order inverse transform. The reconstructed residual signal can be generated by performing the first-order inverse transform on the result generated by performing the second-order inverse transform.

16 is a structural diagram of an encoding apparatus according to an embodiment.

The encoding apparatus 1600 may correspond to the encoding apparatus 100 described above.

The encoding device 1600 includes a processing unit 1610, a memory 1630, a user interface (UI) input device 1650, a UI output device 1660, and a storage unit 1630, which communicate with each other via a bus 1690. [ 1640 < / RTI > The encoding apparatus 1600 may further include a communication unit 1620 connected to the network 1699.

The processing unit 1610 may be a semiconductor device that executes processing instructions stored in a central processing unit (CPU), memory 1630, or storage 1640. The processing unit 1610 may be at least one hardware processor.

The processing unit 1610 can generate and process signals, data, or information that are input to the encoding apparatus 1600, output from the encoding apparatus 1600, used in the encoding apparatus 1600, Compare, and judge related to data or information. In other words, in the embodiment, the generation and processing of data or information and the inspection, comparison and judgment relating to data or information can be performed by the processing unit 1610.

The processing unit 1610 includes an inter prediction unit 110, an intra prediction unit 120, a switch 115, a subtractor 125, a transform unit 130, a quantization unit 140, an entropy coding unit 150, An inverse transform unit 170, an adder 175, a filter unit 180, and a reference picture buffer 190, as shown in FIG.

The inter prediction unit 110, the intra prediction unit 120, the switch 115, the subtractor 125, the transform unit 130, the quantization unit 140, the entropy coding unit 150, the inverse quantization unit 160, At least some of the inverse transform unit 170, the adder 175, the filter unit 180, and the reference picture buffer 190 may be program modules and may communicate with an external device or system. The program modules may be included in the encoding device 1600 in the form of an operating system, application program modules, and other program modules.

The program modules may be physically stored on various known storage devices. At least some of these program modules may also be stored in a remote storage device capable of communicating with the encoding device 1600. [

Program modules may be implemented as a set of routines, subroutines, programs, objects, components, and data that perform functions or operations in accordance with one embodiment, implement an abstract data type according to one embodiment, Data structures, and the like, but are not limited thereto.

Program modules may be comprised of instructions or code that are executed by at least one processor of the encoding device 1600. [

The processing unit 1610 includes an inter prediction unit 110, an intra prediction unit 120, a switch 115, a subtractor 125, a transform unit 130, a quantization unit 140, an entropy coding unit 150, The adder 175, the filter unit 180, and the reference picture buffer 190, as shown in FIG.

The storage may represent memory 1630 and / or storage 1640. Memory 1630 and storage 1640 can be various types of volatile or non-volatile storage media. For example, memory 1630 may include at least one of ROM (R) 1631 and RAM (RAM) 1632.

The storage unit may store data or information used for the operation of the encoding apparatus 1600. In the embodiment, the data or information possessed by the encoding apparatus 1600 can be stored in the storage unit.

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

Encoding device 1600 can be implemented in a computer system that includes a recording medium that can be read by a computer.

The recording medium may store at least one module required for the encoding apparatus 1600 to operate. The memory 1630 may store at least one module, and at least one module may be configured to be executed by the processing unit 1610.

The function related to the communication of data or information of the encoding apparatus 1600 may be performed through the communication unit 1620. [

For example, the communication unit 1620 can transmit the bit stream to the decoding apparatus 1700 to be described later.

17 is a structural diagram of a decoding apparatus according to an embodiment.

The decoding apparatus 1700 may correspond to the decoding apparatus 200 described above.

The decryption apparatus 1700 includes a processing unit 1710, a memory 1730, a user interface (UI) input device 1750, a UI output device 1760, and a storage 1760, which communicate with each other via a bus 1790. [ Lt; RTI ID = 0.0 > 1740 < / RTI > In addition, the decryption apparatus 1700 may further include a communication unit 1720 connected to the network 1799.

The processing unit 1710 may be a semiconductor device that executes processing instructions stored in a central processing unit (CPU), memory 1730, or storage 1740. The processing unit 1710 may be at least one hardware processor.

The processing unit 1710 may perform generation and processing of signals, data, or information to be input to the decoding apparatus 1700, output from the decoding apparatus 1700, or used in the decoding apparatus 1700, Compare, and judge related to data or information. In other words, in the embodiment, the generation and processing of data or information and the inspection, comparison and judgment relating to the data or information can be performed by the processing unit 1710.

The processing unit 1710 includes an entropy decoding unit 210, an inverse quantization unit 220, an inverse transform unit 230, an intra prediction unit 240, an inter prediction unit 250, a switch 245, an adder 255, A reference picture buffer 260, and a reference picture buffer 270.

An entropy decoding unit 210, an inverse quantization unit 220, an inverse transform unit 230, an intra prediction unit 240, an inter prediction unit 250, a switch 245, an adder 255, a filter unit 260, At least some of the reference picture buffer 270 may be program modules and may communicate with an external device or system. The program modules may be included in the decryption device 1700 in the form of an operating system, an application program module, and other program modules.

The program modules may be physically stored on various known storage devices. At least some of these program modules may also be stored in a remote storage device capable of communicating with the decryption device 1700. [

Program modules may be implemented as a set of routines, subroutines, programs, objects, components, and data that perform functions or operations in accordance with one embodiment, implement an abstract data type according to one embodiment, Data structures, and the like, but are not limited thereto.

The program modules may be comprised of instructions or code that are executed by at least one processor of the decoding apparatus 1700.

The processing unit 1710 includes an entropy decoding unit 210, an inverse quantization unit 220, an inverse transform unit 230, an intra prediction unit 240, an inter prediction unit 250, a switch 245, an adder 255, (260) and the reference picture buffer (270).

The storage may represent memory 1730 and / or storage 1740. Memory 1730 and storage 1740 can be various types of volatile or non-volatile storage media. For example, the memory 1730 may include at least one of a ROM 1731 and a RAM 1732. [

The storage unit may store data or information used for the operation of the decoding apparatus 1700. In the embodiment, the data or information possessed by the decryption apparatus 1700 can be stored in the storage unit.

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

The decryption apparatus 1700 can be implemented in a computer system including a recording medium that can be read by a computer.

The recording medium may store at least one module required for the decryption apparatus 1700 to operate. The memory 1730 may store at least one module, and at least one module may be configured to be executed by the processing unit 1710.

The function related to the communication of data or information of the decryption apparatus 1700 may be performed through the communication unit 1720. [

For example, the communication unit 1720 can receive the bit stream from the encoding device 1600. [

Image processing method using information sharing between channels

The method and apparatus of the embodiments can apply a transcoding technique using prediction and various transforms to a high-resolution image such as 4K or 8K, and can share the determined various coding decision information between channels to encode and / And decodes the compressed bitstream or compressed data for the encoded image by sharing the transmitted coding decision information between the channels.

A plurality of channels may denote a plurality of components representing a block. For example, the plurality of channels may include a color channel, a depth channel, and an alpha channel.

In the following, the meanings of the terms "channel" and "color" may be the same and may be used interchangeably. Alternatively, the color may be one of the channels. The term "channel" may be used interchangeably with one or more of the terms "color "," depth ", and "alpha ".

By using the technique of the embodiment, it is possible to improve the problem of degradation of the compression rate and deterioration of image quality, which occurs when the conventional technique is applied to the encoding and decoding of the image. Particularly, when the conventional technique is applied to an image in which the degree of change of pixel values is spatially concentrated, a problem of compression ratio and deterioration of image quality may occur severely.

For example, as various coding determination information shared among channels for encoding and decoding according to the embodiment, there are the following information. In the names of the following information, the "flag" may be omitted.

1) The conversion skip flag (transform_skip_flag) information can indicate whether or not the selective conversion is omitted. Alternatively, the transform_skip_flag information may indicate one of conversion and conversion skipping.

2) intra smoothing filtering information may indicate whether smoothing filtering is applied to reference pixels used in intra prediction.

3) The Position Dependent intra Prediction Combination (PDPC) flag (PDPC_flag) information is used to determine whether or not the neighboring pixels to which smoothing (i.e., filtering) is applied when a specified intra prediction And surrounding pixels not subjected to smoothing (i.e., filtering) are used together to indicate whether to perform intra prediction.

4) Residual Differential Pulse Coded Modulation (RDPCM) flag (rdpcm_flag) information is further subjected to differential pulse coded modulation (DPCM) with respect to the residual signal obtained by one prediction And perform RDPCM to obtain the residual signal again.

5) The Multiple Transform Selection (MTS) flag (mts_flag) information may indicate whether or not an Extended Multiple Transform (EMT) encoding method is used.

The EMT may be a coding method for selecting and using a transform specified for a transform block that is a target block among a plurality of transforms provided.

The EMT may be referred to as an enhanced multiple transform and may also be referred to as Multiple Transform Selection (MTS).

6) The EMT flag information may indicate whether or not the EMT is used.

7) The MTS index (mts_idx) information may indicate which transform is used in the transverse-direction and longitudinal direction when the MTS is used.

A part of the mts_idx information (e.g., one bit specified in mts_idx) may be information indicating a conversion used in the horizontal direction of the residual signal.

Another part or the remaining part of the mts_idx information (e.g., the other one bit specified in mts_idx) may be information indicating a conversion used in the vertical direction of the residual signal.

For example, the determination of the conversion according to the mts_idx information can be configured as shown in Tables 7 and 8 below.

[Table 7]

[Table 8]

In Table 7, the horizontal direction conversion and the vertical direction conversion used in accordance with the intra prediction mode and the value of the mts_idx information are illustrated.

According to Table 7, when mts_idx information is acquired for inter prediction or inter prediction of a target block, a horizontal direction transformation and a vertical direction transformation to be used for transforming a target block may be determined according to the value of mts_idx information.

For example, when the intra-prediction mode of the target block is 6 and the value of the mts_idx information is 2, DCT-7 can be used for the horizontal conversion and DCT-8 can be used for the vertical direction conversion .

Table 8 shows the modified realization examples of Table 7. < tb > < TABLE > In Table 8, MTS_CU_flag may indicate that flag (mts_flag) information indicating whether the Multiple Transform Selection (MTS) method is used is determined and transmitted in units of CUs. In addition, MTS_Hor_flag and MTS_Ver_flag can indicate the conversion used in the horizontal direction and the vertical direction, respectively. Table 8 can illustrate transformations used in the horizontal and vertical directions by the values of MTS_Hor_flag and MTS_Ver_flag.

Alternatively, the determination of the conversion according to the mts_idx information in Table 7 can be made as shown in Table 9 below.

[Table 9]

Table 9 exemplifies the horizontal conversion type and the vertical conversion type used in the intra prediction and inter prediction according to the value of the mts_idx information.

Each value of the horizontal transform type can represent a specified transform. For example, a horizontal conversion type value of 1 may represent DST-7. A horizontal transform type value of 2 may represent DCT-8.

8) The Non-separable Secondary Transform (NSST) flag (nsst_flag) information is not additionally non-separable for all or some of the transform coefficients obtained by the first- separable) NSST coding method for performing the second conversion.

9) The NSST index (nsst_idx) information may indicate the type of quadratic transformation applied to all or part of the transform coefficients when the NSST coding method is used.

The nsst_idx information may indicate a transformation to be used for the 2D non-separating transformation.

10) The CU skip flag information may indicate whether the transmission of coded data to the CU is omitted.

11) The CU brightness difference compensation flag (CU_lic_flag) information may indicate whether or not compensation for the difference between the brightnesses of the blocks.

12) Overlapped Block Motion Compensation (OBMC) flag (obmc_flag) information may indicate whether to generate a final motion compensation block using a plurality of overlapped motion compensation blocks.

13) The codeAlfCtuEnable flag (codeAlfCtuEnable_flag) information can indicate whether Adaptive Loop Filter (ALF) can be applied to the pixel value of the current CTU.

When the coding determination information is shared between the channels, the compression ratio of the image compression is improved, and at the same time, the image of good quality can be obtained.

In describing the coding decision information shared between the channels according to the embodiment, for the sake of an overall explanation and understanding of the embodiments such as the description of operations, drawings and formulas, the coding decision in which the transform_skip_flag information is shared between channels Can be used as an example of information.

However, the transform_skip_flag information is a specific implementation example, and the coding decision information shared among the channels to which the embodiment is applied may not mean only transform_skip_flag.

Such as 1) rdpcm_flag information, 2) mts_flag information, mts_idx information, nsst_flag information and nsst_idx information, 3) obmc_flag information, and 4) PDPC_flag information required for decryption, It may be understood that one or more of the coding decision information is included in the coding decision information that is shared between the channels.

In describing channels for sharing coding determination information required for decoding according to the embodiment, a YCbCr color space may be used as an example. However, the YCbCr color space is one specific implementation, and embodiments can be applied to various color spaces such as YUV color space, XYZ color space, and RGB color space.

The color index (cIDX) may denote a channel index for indicating one channel of the channels in the color space.

For the YCbCr color space and the YUV color space, cIDX may have values of " 0/1/2 "for the displayed channels in order of color space. The value "a / b / c" indicates that the value of cIDX indicating the first channel is a, the value of cIDX indicating the second channel is b, and the value of cIDX indicating the third channel is c .

Or, for the YCbCr color space and the YUV color space, cIDX may be possible to have values of "0/2/1" for the channels displayed in the order of the color space.

For the RGB color space and the XYZ color space, cIDX may have values of "1/0/2" or "2/0/1" for the channels displayed in the order of the color space.

1) an inter prediction technique for predicting a pixel value of a pixel included in a target picture from a previous picture or a following picture of a current picture; 2) an inter prediction technique for predicting a pixel value of a pixel included in a current picture from a previous picture or a following picture of the current picture; An intra prediction technique for predicting a pixel value of a pixel included in a current target picture by using information of pixels in a current picture, 3) a conversion and quantization technique for compressing energy of a residual signal remaining as a prediction error, and 4) There may be a variety of techniques such as entropy coding techniques and arithmetic coding techniques that assign a short code to a value and assign a long code to a value with a low frequency of occurrence. By using such an image compression technique, image data can be compressed, transmitted and stored effectively.

The compression techniques that can be applied to the encoding of an image can vary widely. Also, depending on the nature of the image to be encoded, a particular compression technique may be more advantageous than other compression techniques. Therefore, the encoding apparatus 1600 can perform the most advantageous compression for the target block by adaptively determining whether to use a plurality of various compression techniques for the target block.

Accordingly, of the various compression techniques that can be selected, the encoding device 1600 can typically perform Rate-Distortion Optimization (RDO) to select the most advantageous compression technique for the target block. It may not be known in advance which coding decision among the various image coding decisions that can be selected for coding the image is most optimal in terms of rate-distortion. Thus, the encoder 1600 can calculate the rate-distortion values for the combinations by performing an encoding (or simplified encoding) on each of the combinations of all available image encoding decisions, and the calculated rate-distortion The image encoding decision with the smallest rate-distortion value among the values can be determined and used as the final image encoding decision for the target block.

Also, the encoding apparatus 1600 can record an encoding decision derived by performing such RDO or derived according to another decision method selected by the encoding apparatus 1600, in the bit stream. The decoding apparatus 1700 reads (i.e., parses) an encoding decision recorded in the bitstream and performs an accurate inverse process corresponding to the encoding according to the encoding decision, thereby accurately performing decoding on the object block .

Here, the information indicating the coding decision can be referred to as coding decision information or coding information required for decoding.

Hereinafter, the meanings of the terms "coding determination information" and "coding information" may be the same and may be used interchangeably.

In general, a plurality of channels (e.g., YUV, YCbCr, RGB, and XYZ) of an image may not always have the same or similar properties. Thus, performing independent coding decisions for each channel of a plurality of channels generally exhibits better performance in terms of improving the compression ratio.

For example, as one of the coding decisions mentioned above, there is transform_skip_flag, which is an encoding decision indicating whether to perform conversion in the target block. That is, for each of the blocks, it may be determined whether or not the transform is omitted, and transform_skip_flag information indicating this determination may be written to the bitstream as coding determination information for each channel of the plurality of channels.

Generally, in the coding of image compression, the conversion to the target block has always been considered to be performed. However, if the spatial variation of the pixel values of the pixels in the target block to be compressed is very large, and particularly when the change of the pixel values is locally very limited, the degree of image energy concentration at low frequencies may not be large And a large number of conversion coefficients for a high frequency region having a relatively large value may occur.

Therefore, when conversion and quantization which reduce the amount of data are applied by applying a quantization or when a signal component of a low frequency is generally maintained and a signal component of a low frequency is removed through transformation and quantization, serious image degradation Lt; / RTI > In particular, such a deterioration in image quality may be greater when the spatial variation of the pixel values of the pixels is very large, or when the variation of the pixel values is concentrated in a locally very limited area.

In order to solve the above-mentioned problem, a method of directly encoding pixel values of pixels in a spatial region without conversion can be used instead of uniformly applying a conversion to a target block. According to this method, it is possible to determine whether to perform the conversion for each transform block. Encoding of the transform block can be performed by performing or omitting the transform according to this determination. The bit stream may be recorded with transform_skip_flag information, which is coding determination information indicating whether or not conversion is omitted.

For example, if the value of the transform_skip_flag information is 1, the conversion may be omitted. If the value of the transform_skip_flag information is 0, the conversion can be performed. The encoding apparatus 1600 can transmit to the decoding apparatus 1700 through the transform_skip_flag information whether or not the conversion of the target block is omitted, and the aforementioned problem can be solved through such transfer.

Also, transform_skip_flag information can be set and transmitted for each of a luma channel (i.e., Y channel) and chroma channels (i.e., Cb channel and Cr channel). The decoding apparatus 1700 may perform decoding on the target block by omitting or performing the conversion on the channel of the target block in accordance with the value of the transform_skip_flag information for each channel read out (that is, parsed) from the bitstream.

However, for all transform blocks, when transform_skip_flag information is transmitted for channels such as Y, Cb and Cr, the overhead due to signaling of transform_skip_flag information may increase, and another problem that the compression ratio of the image is lowered Lt; / RTI >

In order to reduce the problem of the degradation of the compression ratio, flag information indicating whether or not the conversion is omitted can be limitedly transmitted only when the size of the conversion block is smaller than or equal to the specified conversion block size. However, even if this scheme is used, transmitting the flag information indicating whether conversion is omitted for all channels for a conversion block having a size larger than the specified conversion block size may still lower the compression rate of the image . In addition, the degraded compression rate can inevitably degrade the quality of the compressed image.

In order to solve the degradation of the compression rate caused by transmitting the coding determination information selected by the coding apparatus 1600 for all of the channels, in the embodiment, a coding and / or decoding method using information sharing between channels is disclosed .

First, the condition for judging that the video properties of the channels are similar to each other can be defined in advance. When such a condition is satisfied, coding determination information for an image, a block, or the like determined by the coding apparatus 1600 can be transmitted to the decoding apparatus 1700 for one representative channel among a plurality of channels.

All of the remaining channels other than the representative channel among the plurality of channels, or the selected channel among the remaining channels, may share the coding determination information transmitted to the representative channel. The compression rate of the image can be improved through such sharing and use. Therefore, the encoding and / or decoding method and the like of the embodiment can provide excellent encoding efficiency even if the coding determination information is not transmitted to each of a plurality of channels.

At this time, the shared coding determination information includes transform_skip_flag information, intra smoothing filtering information, rdpcm_flag information, mts_flag information, mts_idx information, PDPC_flag information, MTS_CU_flag information, MTS_Hor_flag information, MTS_Ver_flag information, nsst_flag information, nsst_idx information, CU skip flag information , CU_lic_flag information, obmc_flag information, codeAlfCtuEnable flag information, and PDPC_flag information.

Conditions for judging that the video properties of the channels are similar to each other

In order to determine that the video properties of the channels are similar to each other, it can be confirmed whether inter-channel prediction is used for the target block.

That is, whether or not to use a prediction method of acquiring a prediction value of a decoding target channel by applying a model specified for reconstructed information of another channel (for example, a luma channel) for prediction of a decoding target channel of the target block Can be confirmed. For example, the reconstructed information may be the pixel value of the reconstructed pixel or the value of the transform coefficient. The specified model may be a linear model.

The decoding target channel may be a current decoding target channel among the plurality of channels. The encoding target channel may be a current encoding target channel among a plurality of channels. Hereinafter, the to-be-encoded channel and / or the to-be-decoded channel may be outlined as a target channel.

For example, it can be ascertained whether intra prediction for a target block uses an intra prediction mode that derives a prediction value of a target channel using reconstructed information of another channel.

In order to derive the prediction values of the target channel using reconstructed information of other channels, a cross component linear model (CCLM) using one linear model, a multi-mode linear model using a plurality of linear models A MultiMode Linear Model (MMLM) and a MultiFilter Linear Model using a plurality of filters may be used. In CCLM, a component may be replaced by a channel.

The INTRA_CCLM mode may be an intra prediction mode using CCLM. The INTRA_MMLM mode may be an intra prediction mode using MMLM. The INTRA_MFLM mode may be an intra prediction mode using MFLM.

Alternatively, it is determined that the video properties of the channels are similar if the intra prediction mode for the target block (for example, intra_chroma_pred_mode information, which is an intra prediction mode for the chroma channel of the target block) is one of INTRA_CCLM mode, INTRA_MMLM mode, and INTRA_MFLM mode Or the like.

Alternatively, determining that the video properties of the channels are similar can be implemented by checking whether the encoding mode of the target channel of the target block uses the encoding mode of another channel (for example, a luma channel) as it is. For example, determining that the video properties of the channels are similar may be implemented by checking whether the intra prediction mode (for example, intra_chroma_pred_mode information) for the target block is a direct mode (DM). The direct mode may also be referred to as a derived mode. The DM may be a mode indicating that the intraprediction mode of the luma channel is directly used as the intraprediction mode of the chroma channel according to the characteristic that the correlation between the luma channel and the chroma channel may be large.

The characteristics and detailed operation of the DM which is one of the intra prediction modes can be defined in more detail in accordance with Table 10 and Table 11 below.

Table 10 shows a method of setting the IntraPredModeC value for intraprediction on the chroma signal. (when the value of the sps_cclm_enabled_flag information is 0)

Table 11 shows a method of setting the IntraPredModeC value for intraprediction on the chroma signal. (when the value of the sps_cclm_enabled_flag information is 1)

[Table 10]

[Table 11]

Generally, in intra prediction, the pixel value of a reconstructed pixel of one channel (e.g., a luma channel or more typically a representative channel) may be used as a reference to another channel (e.g., a chroma channel, Whether the INTRA_CCLM mode, the INTRA_MMLM mode, or the INTRA_MFLM mode, which is used when calculating the predicted value of the target channel, can be confirmed.

Indicating the case of using the INTRA_CCLM mode, the INTRA_MMLM mode, or the INTRA_MFLM mode can be defined in detail by distinguishing the two types according to the value of the sps_cclm_enabled_flag information as described in Table 10 and Table 11. [

The sps_cclm_enabled_flag information may be information indicating whether it is possible to use INTRA_CCLM mode, INTRA_MMLM mode, and INTRA_MFLM mode. Alternatively, the sps_cclm_enabled_flag information may be information indicating whether INTRA_CCLM mode, INTRA_MMLM mode, and INTRA_MFLM mode are enabled.

When the value of sps_cclm_enabled_flag is 0, INTRA_CCLM mode, INTRA_MMLM mode and INTRA_MFLM mode may not be used, and when the value of sps_cclm_enabled_flag is 1, INTRA_CCLM mode may be used. Alternatively, if the value of sps_cclm_enabled_flag is 1, at least one of INTRA_MMLM mode and INTRA_MFLM mode may be used.

Whether or not the intra prediction mode (for example, intra_chroma_pred_mode information) for the target channel is DM is determined by determining whether or not the intra prediction mode for the chroma channel (i.e., the value of intra_chroma_pred_mode) 11 in step 5). In the description of this operation, Table 10 can be referred to when the value of sps_cclm_enabled_flag is 0, and Table 11 can be referred to when the value of sps_cclm_enabled_flag is 1.

If the value of sps_cclm_enabled_flag is 0 and the value of the intra-prediction mode (for example, intra_chroma_pred_mode) for the target channel is 4, DM is applied. Alternatively, if the value of sps_cclm_enabled_flag is 1 and the value of the intra prediction mode (for example, intra_chroma_pred_mode) for the target channel is 5, the DM is considered to be applied. The IntraPredModeY value indicating the intraprediction mode of the representative channel (e.g., the Luma channel) can be directly used as the IntraPredModeC value for intraprediction of a target channel (for example, a chroma channel) of a target block indicated by DM have.

Here, the intra prediction mode intra_chroma_pred_mode for the chroma signal may be index information indicating which type of intra prediction is used for the chroma signal.

According to the index information, the final value indicating the intra prediction mode actually used for intra prediction for the chroma signal may be the value of IntraPredModeC. That is to say, IntraPredModeC can indicate the intra prediction mode actually used for intra prediction for the chroma signal.

If IntraPredModeY has a value of 0, 50, 18, or 1 when the value of sps_cclm_enabled_flag is 0, DM is applied (that is, intra_chroma_pred_mode has a value of 4), the value of IntraPredModeC is also 0, 50, .

Here, a value of 0 may mean a planner mode (say, planar prediction or planar direction), a value of 1 may mean a DC mode, a value of 18 may mean a horizontal mode, a value of 50 may mean a vertical mode , And the value 66 may mean diagonal mode.

If the value of IntraPredModeY is a value X other than the four values of 0, 50, 18 and 1, then the value of IntraPredModeC can also be X equal to the value of IntraPredModeY.

On the other hand, when the value of IntraPredModeY is 0, 50, 18, or 1 when cclm_enabled_flag is 0, the value of IntraPredModeC can be determined by the value of IntraPredModeY as shown in the first four rows of Table 10.

For example, if the value of IntraPredModeY is 0, 50, 18, or 1, as described in the first row of Table 10, the value of IntraPredModeC may be 66, 0, 0 or 0. If the value of IntraPredModeY is a value other than 0, 50, 18, and 1, the value of IntraPredModeC can be zero.

If the value of IntraPredModeY is 0, 50, 18 or 1 when the value of sps_cclm_enabled_flag is 1, DM is applied (that is, the value of intra_chroma_pred_mode is 5), the value of IntraPredModeC is also 0, Or < / RTI >

Here, a value of 0 may mean a planner mode (say, planar prediction or planar direction), a value of 1 may mean a DC mode, a value of 18 may mean a horizontal mode, a value of 50 may mean a vertical mode , And the value 66 may mean diagonal mode.

If the IntraPredModeY value is a value X other than the four values 0, 50, 18, and 1, then the value of IntraPredModeC may also be X equal to the value of IntraPredModeY.

On the other hand, when the value of IntraPredModeY is 0, 50, 18, or 1 when cclm_enabled_flag is 1, the value of IntraPredModeC can be determined by the value of IntraPredModeY, as shown in the first five rows of Table 11.

For example, if the value of IntraPredModeY is 0, 50, 18, or 1, as described in the first row of Table 11, the value of IntraPredModeC may be 66, 0, 0 or 0. If the value of IntraPredModeY is a value other than 0, 50, 18, and 1, the value of IntraPredModeC can be zero.

In another embodiment, it is determined that the image properties of the channels are similar to each other. That is, only the specified mode restricted by the encoding mode of another channel (for example, the luma channel) as the encoding mode for the target channel of the target block It can be implemented by checking whether or not a mode for instructing to use is used. For example, determining that the video properties of the channels are similar to each other can be implemented by checking whether the intra prediction mode of the target channel is DM.

Interchannel prediction using associations between channels

The inter-channel prediction may be a technique of using pixel values of pixels of other channels, instead of using intra-prediction or inter-prediction, in predicting pixel values of pixels of a target channel.

In encoding a target block, the performance of such an inter-channel prediction is better than other predictions, which means that there is a considerable similarity between the pixel values of the pixels of the channels of the target block.

 Therefore, in this case, when the value of the coding decision information of the representative channel is determined, the determined value of the coding decision information of the representative channel is used in the same manner for the coding decision information of the other channel or by the value of the coding decision information of the representative channel It may be advantageous to use the indicated specified value for the coding decision information of the other channel.

For example, when the value of the transform_skip_flag information of the representative channel is 0 indicating that the conversion is not omitted, the probability that the value of the transform_skip_flag information is determined to be 0 can be high in other channels as well.

Therefore, for an image or block in which inter-channel prediction is effective, there may be a case in which transform_skip_flag information need not be specified for each of a plurality of channels. This is because the likelihood that the transform_skip_flag information of the channels is the same may be high because the similarity between the channels is high.

Despite the presence of such an image feature, the compression rate and the image quality of the image may be degraded if transform_skip_flag information is transmitted to the channels of the image, respectively.

This principle can also be applied to other coding determination information such as mts_flag information, mts_idx information, nsst_flag information, nsst_idx information, intra smoothing filtering information, PDPC_flag information, and rdpcm_flag information. The probability of being the same as the value of the coding decision information for the first time may be high.

Therefore, it can be determined whether or not the interchannel prediction using the correlation between the channels is determined as the encoding mode of the target block through the condition for judging that the video properties of the channels described above are similar to each other.

For example, determining whether the interchannel prediction is determined to be the coding mode of the target block is based on whether a color-component linear prediction mode (CCLM), which means inter-channel prediction, is applied to the target block Whether the image properties of the channels are similar to each other or not. It can be confirmed whether the prediction mode for the target block is one of INTRA_CCLM mode, INTRA_MMLM mode and INTRA_MFLM mode in order to judge whether CCLM is applied to the target block.

For example, it is determined whether the interchannel prediction is determined as the encoding mode of the target block by determining whether the intra mode of the representative channel (for example, the luma channel) is different from the channel (for example, the chroma channels Cb and Cr) As shown in FIG. Alternatively, determining whether the interchannel prediction is determined as the encoding mode of the target block may be to determine whether the specified intra mode indicated by the intra mode of the representative channel is used in another channel. Alternatively, determining whether the interchannel prediction is determined as the encoding mode of the target block may be to determine whether the specified intra mode induced by the intra mode of the representative channel is used for another channel.

For example, the determination as to whether or not the interchannel prediction is determined as the encoding mode of the target block may be made based on a specific encoding mode (for example, interchannel sharing mode ≪ / RTI > is used.

For example, determining whether the interchannel prediction is determined as the encoding mode of the target block may be to determine whether the intraprediction mode of the chroma channel is DM.

The DM may be a mode indicating that the intraprediction mode of the chroma channel is used intact as the intraprediction mode of the luma channel, depending on the characteristic that the correlation between the luma channel and the chroma channel may be large. Therefore, when the intraprediction mode for the chroma channel of the target block is DM, it can be determined that the condition that the video properties of the channels are similar to each other is satisfied.

In addition to the conditions described in the above examples, it can be determined whether the interchannel prediction is determined to be the encoding mode of the target block based on the size of the block.

For example, the larger the block size, the higher the probability that a pixel having a heterogeneous property exists in the block. Thus, the similarity between the channels of the block having a large size may be smaller than the similarity between the channels of the block having the small size. Also, if the size of the block is too small, the similarity between the channels of the block may not be stable.

For example, sharing of information between channels may be performed only for blocks having the following sizes of specified sizes. The specified size may be 64x64, 32x32 or 16x16. In the case where the size of the block is smaller than or equal to the specified size, the sharing of information between the channels enables the condition that the image properties of the channels are determined to be similar to each other more satisfactorily.

Alternatively, sharing of information between channels may be performed only for blocks having a size larger than a specified size. The specified size can be 4x4. By allowing information to be shared between the channels when the size of the block is larger than the specified size, the condition that the video properties of the channels are determined to be similar to each other can be satisfactorily satisfied.

Alternatively, sharing of information between channels may be performed only if the size of the block is greater than a specified first size (e.g., 4x4) and less than or equal to a specified second size (e.g., 32x32 or 64x64) have. The condition that the image properties of the channels are determined to be similar to each other can be satisfied more satisfactorily by sharing the information between the channels only when the size of the block is within the specified range.

In the embodiment, a method and apparatus for encoding a target block through sharing of information between channels are described, and the following functions can be provided.

- Coding decision information of one channel of the target block from the compressed bitstream can be parsed and decryption of all channels of the target block or selected channels of the target block can be performed using the coding determination information of one channel .

- The bitstream may be configured such that the coding determination information is transmitted only to the representative channel of the target block or the selected channel.

Whether to omit the conversion for one channel can be determined and whether or not the determined conversion for the other channels can be applied.

- transform_skip_flag information can be parsed for one channel of the transform block from the compressed bit stream. The parsed transform_skip_flag information can be used to determine whether to omit the transform for one channel or a plurality of channels of the transform block.

- Transform_skip_flag information can be signaled for one channel of the transform block. The transform_skip_flag information for one channel can be used in another channel.

- Coding decision information can be efficiently signaled using the sharing of information between channels. This efficient signaling can improve the coding efficiency and the subjective image quality.

Particularly, when the spatial variation of the pixel values of the block is very large or very sharp, even if the transformation is applied to the target block, the degree of image energy converging to low frequency may not be large. In addition, when a process of transforming and quantizing is applied to such a block, the signal component of the low frequency is generally maintained and the signal component of the high frequency is removed, or a severe image quality may be degraded when strong quantization is applied to the block . In the embodiment, it can be economically indicated whether or not block conversion is omitted without a large overhead according to the judgment of the encoding apparatus 1600 for such a block. Such an economical instruction can improve the compression ratio of the image and minimize the deterioration of image quality.

When an inter-channel prediction technique using association between channels is used, a plurality of coding determination information for a plurality of channels may not be respectively used. In an embodiment, coding determination information may be transmitted for one channel, and coding determination information transmitted for one channel may be shared and used for all or a selected one of the remaining channels. This sharing can solve the problem of the degradation of the compression ratio and the degradation of the image quality.

Determination of representative channels according to color space

There are YCbCr and YUV, which are used for encoding and decoding a general image, as color spaces for encoding and decoding images, and RGB, XYZ, and YCoCg in addition to them. When one of the various color spaces is a target color space used for encoding and decoding an image, one of the channels of the target color space may be determined as a representative channel of the target color space.

In one embodiment, a color channel having the highest correlation with the luma signal among the channels may be determined as the representative channel. For example, in the RGB color space, the G channel may have the highest correlation to the luma signal, so that the G channel may be selected as the representative channel. In the XYZ color space, the Y channel can have the highest correlation to the luma signal, so that the Y channel can be selected as the representative channel. In the YCoCg color space, the Y channel can be selected as the representative channel since it can have the highest correlation to the luma signal.

Channels in the color space may be represented as index values such as "0/1/2 ". SelectedCIDX may be the index of the selected color. Alternatively, SelectedCIDX may be an index value representing the selected representative channel. The representative channel may be determined by an index SelectedCIDX indicating a selected representative channel among information on a target block in the bitstream.

For example, the value of SelectedCIDX in the YCbCr color space may be zero indicating the Y channel.

For example, in a YCbCr color space, a Cb channel can be determined as a representative channel. When the Cb channel is determined as the representative channel, the value of SelectedCIDX may be 1 indicating the Cb channel.

For example, in the YUV color space, a U-channel can be determined as a representative channel. If the U channel is determined as the representative channel, the value of SelectedCIDX may be one indicating the U channel.

For sharing coding determination information between channels, a specified channel of color space may be selected as a representative channel. Coding and decoding information of the representative channel in the encoding and decoding of the image may be shared in one or more remaining channels.

For example, the encoding apparatus 1600 can signal only decoding information of the representative channel to the decoding apparatus 1700 through the bit stream. Alternatively, the decoding apparatus 1700 may derive coding determination information of a representative channel using a bitstream. The coding decision information of at least some of the remaining channels may not be signaled separately. The decoding apparatus 1700 may derive coding determination information of at least a part of the remaining channels using the coding determination information of the representative channel. That is to say, the coding decision information of the representative channel can be shared for at least some of the remaining channels.

For example, if the Y channel with the highest correlation to the luma signal in the YCbCr color space is selected as the representative channel, then the association (i.e., Y) and chroma channel (i.e., Cb and / or Cr) correlation may exist. Therefore, when predictions for image compression are performed, instead of applying independent predictions to the three channels of the color space, coding determination information for a luma channel, which is a representative channel, is used as coding determination information for one or more chroma blocks Can be implicitly shared. The one or more chroma blocks may comprise one or more of a Cb block and a Cr block.

For example, when a Cb channel is selected as a representative channel in the YCbCr color space, there may be a correlation between the Cb signal and the Cr signal constituting the chroma channels. Therefore, when predictions for image compression are performed, independent predictions are applied to two chroma channels, respectively. Instead, coding determination information for a Cb channel, which is a representative channel, is shared implicitly as coding determination information for a Cr block. .

Coding decision information shared between channels

Coding decision information that can be shared between the channels may be information encoded in the encoding apparatus 1600 such as a syntax element and signaled to the decoding apparatus 1700 as information in the bitstream. For example, the coding determination information may include flags, indexes, and the like. In addition, the coding determination information may include information that is derived in the course of encoding and / or decoding. In addition, the coding decision information may mean information required for encoding and / or decoding an image.

For example, the coding determination information includes a unit / block size, a unit / block depth, a unit / block division information, a unit / block division structure, a division flag indicating whether a unit / block is divided into a quad tree form (Division in the horizontal direction or the vertical direction), division type in the form of binary tree (symmetric division or asymmetric division), unit / block (Symmetrical division or asymmetric division) of the triangle tree type, a division tree structure in which the unit / block is formed as a composite tree form , Information indicating whether or not to be divided into a composite tree, a combination and direction of a composite tree type (horizontal direction or vertical direction, etc.), a prediction method A motion vector, a motion vector, a reference picture index, a motion vector, a motion vector, a motion vector, and a reference picture index, A merge candidate list, a skip image, an inter prediction direction, an inter prediction instruction, a reference picture list, a reference image, a motion vector predictor, a motion vector prediction candidate, a motion vector candidate list, Mode, the type of the interpolation filter, the filter tap of the interpolation filter, the filter coefficient of the interpolation filter, the size of the motion vector, the accuracy of the motion vector expression, the kind of transformation, the size of the transformation, Information indicating whether or not additional (secondary) conversion is used, information indicating whether primary conversion selection information (or primary conversion index A coded block pattern, a coded block flag, a quantization parameter, a quantization matrix, and a quantization matrix. Information about the intra-loop filter, information about whether the intra-loop filter is applied, coefficients of the intra-loop filter, filter tap of the intra-loop, shape / form of the intra- Information indicating whether or not to apply a filter, information indicating whether to apply a filter, deblocking filter coefficient, deblocking filter tap, deblocking filter strength, deblocking filter shape / shape, information indicating whether to apply an adaptive sample offset, Adaptive loop-filter coefficients, adaptive loop-in-filter tap, adaptive loop-in filter, adaptive loop-filter coefficients, Filter shape / form, binarization / inverse binarization method, context model, context model determination method, context model update method, whether to perform regular mode, bypass mode, context bean, bypass bean, A slice type information, a slice division information, a tile identification information, a tile type, a tile division information, a picture type, a bit depth, information on a luma signal, At least one of information on a chroma signal, transform_skip_flag information, primary conversion selection information, secondary conversion selection information, reference sample filtering information, PDPC_flag information, rdpcm_flag information, EMT flag information, mts_flag information, mts_idx information, nsst_flag information, and nsst_idx information Or a combination thereof.

Of the coding decision information that can be shared between the channels, the first order transformation selection information may be obtained by using a combination of at least one DCT transform kernel and / or a DST transform kernel for the horizontal and / Conversion information required for performing the conversion process. For example, the primary conversion selection information may be information for using the MTS in the primary conversion. The primary conversion selection information may include mts_flag information and mts_idx information.

The primary transformation selection information applied to the target block may be explicitly signaled or may be implicitly generated in the encoder 1600 and the decoder 1700 using the coding decision information of the target block and the coding decision information of the neighboring block Respectively.

After the primary conversion is completed in the encoding apparatus 1600, the secondary conversion may be performed to increase the energy concentration of the conversion coefficients.

The secondary transformation selection information applied to the target block may be explicitly signaled or may be implicitly applied to the coding apparatus 1600 and the decoding apparatus 1700 using the coding determination information of the target block and the coding determination information of the neighboring block Respectively. The decoding apparatus 1700 can perform the second-order inverse transformation according to whether or not the second-order inverse transformation is performed, and can perform the first-order inverse transformation on the result of performing the second-order inverse transformation according to whether the first inverse transformation is performed.

The encoder 1600 can generate rdpcm_flag information for the target block and write the rdpcm_flag information in the bitstream. The decoding apparatus 1700 can obtain the rdpcm_flag information through the bit stream and perform or not perform the RDPCM according to the instruction of the rdpcm_flag information.

18 is a flowchart of a decoding method of coding determination information according to an embodiment.

When a specific channel on the color space is selected as a representative channel for sharing information among a plurality of channels according to embodiments, the coding determination information of the representative channel of the target block includes at least one of the plurality of channels The remaining channels can be shared.

For example, when intraprediction is performed on a target block in the YCbCr color space, instead of transmitting intra-coding determination information independently for each of the three channels of the color space, the Y channel is set as a representative channel, The intra coding determination information of the channel can be shared and used in decoding of channels other than the representative channel (i.e., the Cb channel and / or the Cr channel). Alternatively, after the Cb channel is assumed to be the representative channel in the YCbCr color space, the intra coding determination information of the representative channel may be implicitly used in decoding the Cr channel, which is a channel other than the representative channel.

For example, the intra-coding decision information of the representative channels that can be shared in the remaining channels may be used for intra-prediction mode, intra-prediction direction, prediction block boundary filtering method, filter tap for prediction block boundary filtering, Mts_idx information, PDPC_flag information, rdpcm_flag information, EMT flag information, nsst_flag information, nsst_idx information, intra smoothing filtering information, skip (skip) information, ) Flag information, CU_lic flag information, obmc_flag information, codeAlfCtuEnable_ flag information, and PDPC_flag information.

If interchannel predictions are selected among various techniques including angular prediction, DC prediction and planar prediction for chroma signal prediction, or interchannel prediction is advantageous, the characteristics of the luma signal (i.e., Y) That is, Cb and / or Cr).

In this case, if the channel of the Y signal block is a representative channel, the coding determination information determined in the process of encoding and / or decoding the representative channel may be similarly applied to the chroma block. With this application, the bit amount for transmitting the coding decision information can be reduced. Therefore, through inter-channel prediction, coding and decoding can be performed so that one piece of coding decision information is used for a plurality of channels.

For example, after the coding determination information for the luma channel is determined, the determined coding determination information may be shared in the remaining channels, and the coding may be performed through the shared coding determination information. Or without sharing between the channels, the coding decision information can be applied independently to the three channels, and the three channels can be independently encoded and / or decoded. The encoding apparatus 1600 can determine a method in which coding decision information is shared between channels and an advantageous method in terms of rate-distortion of channels in which channels are independently encoded as a coding method. According to this determination, the encoding apparatus 1600 can explicitly write information about whether or not the coding decision information between the channels is shared in the bitstream, and this information is transmitted to the decoding apparatus 1700 through the bitstream .

For example, if the coding condition specified in the coding and / or decoding process is satisfied, information on whether or not the coding decision information is shared between the channels may not be explicitly signaled, and the coding decision information of the representative channel may be Can be shared on the remaining channels.

For example, the specified encoding condition may be using Cross Component Prediction, DM or CCLM.

For example, when predicting the remaining chroma signals (that is, the Cb signal and / or the Cr signal) using at least one of the original signal of the encoded or decoded luma signal, the reconstructed signal, the residual signal and the prediction signal , Sharing of coding decision information between channels can be applied.

For example, when the luma signal is predicted using at least one of the original signal of the encoded or decoded chroma signal, the reconstructed signal, the residual signal, and the prediction signal, the sharing of the coding decision information between the channels can be applied .

For example, when the Cr signal is predicted using at least one of the original signal, the reconstructed signal, the residual signal, and the prediction signal of the Cb signal in which coding or decoding has been completed, the sharing of coding determination information between channels can be applied .

For example, when the Cb signal is predicted using at least one of the original signal of the encoded or decoded Cr signal, the reconstructed signal, the residual signal, and the prediction signal, the sharing of the coding decision information between the channels can be applied .

In the YCbCr color space, when the luma channel is set as the representative channel, instead of signaling the coding decision information for the remaining channels outside the luma channel, the coding decision information can be signaled only for the luma signal, The coding decision information may not be transmitted separately. This selective transmission can improve the compression rate.

In addition, the coding decision information is transmitted only for the Cb signal, and the coding decision information transmitted is shared for the Cr signal, so that the compression ratio can be improved. Alternatively, the coding decision information is transmitted only for the Cr signal, and the coding decision information transmitted is shared for the Cb signal, so that the compression ratio can be improved.

In step 1810, the communication unit 1720 can receive the bit stream. The bitstream may include coding determination information.

In step 1820, the processing unit 1710 may determine whether to use sharing of coding determination information for the target channel of the target block.

If the coding decision information is not shared, step 1830 may be performed.

If the coding decision information is shared, step 1840 may be performed.

In step 1830, the processing unit 1710 may obtain the coding determination information of the target channel from the bitstream. The processing unit 1710 can parse and read the coding determination information of the target channel from the bitstream.

In step 1840, the processing unit 1710 can set the coding determination information of the representative channel to be used as the coding determination information of the target channel.

Steps 1820, 1830, and 1840 may be represented as code 1 below.

[Code 1]

if ((cIdx! = 0) && "Interchannel prediction is used")

    Coding decision information [cIdx] = Coding decision information [0]

else

    PARSE coding decision information [cIdx] from compressed bitstream

cIdx can indicate the target channel of the target block. For example, when the number of channels of the object image is 3, cIdx may be one of the predetermined specified values and may be a value of one of {0, 1, 2}.

In an embodiment, the cIdx of the representative channel may be assumed to be zero.

"cIdx! = 0" may indicate that the target channel is not a representative channel (e.g., a luma channel). That is to say, a value of cIdx of 0 indicates that the target channel is a representative channel.

That is to say, at step 1820, the processing unit 1710 can determine to use sharing of coding decision information for the target channel if the target channel is not a representative channel and inter-channel prediction is used for the target block. The processing unit 1710 can determine that the target channel is a representative channel or not to use the sharing of coding determination information for the target channel if inter-channel prediction is not used for the target block.

Whether interchannel prediction is used in the target block may be derived either 1) based on information obtained from the bitstream and 2) implicitly derived depending on whether the specified condition is satisfied.

As described above, whether or not interchannel prediction is used can be determined based on the intra prediction mode of the target block. It may be determined whether inter-channel prediction is used based on whether the intra-prediction mode for the target block is one of INTRA_CCLM mode, INTRA_MMLM mode, and INTRA_MFLM mode. For example, the processing unit 1710 can determine that inter-channel prediction is used when the intra-prediction mode for the target block is one of INTRA_CCLM mode, INTRA_MMLM mode, and INTRA_MFLM mode.

As described above, it can be determined whether inter-channel prediction is used based on whether or not the intra-prediction mode for the chroma channel of the object block has a specified value. For example, the processing unit 1710 may determine that inter-channel prediction is used if the intra-prediction mode for the chroma channel of the object block has a specified value.

The intra prediction mode for the chroma channel of the target block may be indicated by intra_chroma_pred_mode information.

As described above, it can be determined whether inter-channel prediction is used based on whether the intra-prediction mode of the target channel is DM. For example, the processing unit 1710 can determine that inter-channel prediction is used if the intra-prediction mode of the target channel is DM.

In step 1830, the processing unit 1710 may obtain coding determination information for a block of the channel indicated by cIdx from the bitstream.

The processing unit 1710 can parse and read the coding determination information for the block of the channel indicated by cIdx from the bitstream.

In step 1840, the processing unit 1710 may share coding determination information of the representative channel as coding determination information for a block of a channel indicated by cIdx. In other words, the processing unit 1710 can set the coding determination information of the representative channel to the coding determination information for the block of the channel indicated by cIdx.

According to one embodiment, an operation corresponding to a condition or action may be added before the step 1820, or between the steps 1820 and 1840.

According to one embodiment, coding determination information may be transmitted for the Cb signal, and coding determination information of the Cb signal may be shared for the Cr signal without transmission of the coding determination information. In this case, the code 1 described above can be modified as shown in the following code 2.

[Code 2]

if ((cIdx! = 1) && "Interchannel prediction is used")

    Coding decision information [cIdx] = Coding decision information [0]

else

    PARSE coding decision information [cIdx] from compressed bitstream

19 is a flowchart of a decoding method for determining whether to omit conversion according to an embodiment.

The encoding device 1600 can determine whether to perform a conversion (e.g., a primary conversion and / or a secondary conversion) according to the size of the target block.

The target block may be a transform block.

log2TrafoSize can represent the size of the target block.

For example, if the size of the target block is less than or equal to the threshold value indicating the boundary value of the block size, the encoding device 1600 can omit conversion of the target block.

Log2MaxTransformSkipSize can represent a threshold value indicating the threshold value of the block size.

When the conversion of the target block is omitted, the encoding device 1600 can set the value of the transform_skip_flag information to 1 without performing conversion. The transform_skip_flag information can be transmitted to the decoding apparatus 1700 through the bit stream.

Also, when the conversion of the target block is performed, the encoding device 1600 may perform the conversion and set the value of the transform_skip_flag information to 0. [ The transform_skip_flag information can be transmitted to the decoding apparatus 1700 through the bit stream.

At this time, the transform_skip_flag information can be separately transmitted to the channels constituting the color space of the image.

The decoding apparatus 1700 can obtain the value of the transform_skip_flag information from the bit stream. In other words, the decoding apparatus 1700 can parse and read transform_skip_flag information from the bit stream.

At this time, the decoding apparatus 1700 can obtain the value of the transform_skip_flag information from the bit stream only when the size of the block is less than or equal to a threshold value indicating the boundary value of the block size.

Also, the decoding apparatus 1700 can obtain transform_skip_flag information for a plurality of channels of an image.

The acquisition of the transform_skip_flag information can be expressed as the following code 3.

[Code 3]

If (log2TrafoSize <= Log2MaxTransformSkipSize)

    transform_skip_flag [x0] [y0] [cIdx]

and x0 and y0 may represent spatial coordinates indicating the position of the target block.

cIdx can indicate the target channel of the target block information.

When there are three channels of image, cIdx may have one of the values of {0,1,2} predefined. The value of the representative channel may be zero.

Code 3 can be modified as in Code 4 below.

[Code 4]

If ((log2TbWidth <= Log2MaxTransformSkipSize_W) && (log2TbHeight <= Log2MaxTransformSkipSize_H))

    transform_skip_flag [x0] [y0] [cIdx]

log2TbWidth may be a value according to Equation 11 below. The width may be the width of the target block (i.e., the width).

[Equation 11]

log2TbWidth = log ₂ width

log2TbHeight may be a value according to Equation 12 below. The height may be the height of the target block (i.e., the height).

[Equation 12]

log2TbHeight = log ₂ height

The predetermined thresholds Log2MaxTransformSkipSize_W and Log2MaxTransformSkipSize_H may be the same or different from each other. For example, the value of Log2MaxTransformSkipSize_W can be 2, and the value of Log2MaxTransformSkipSize_H can be 2.

Code 3 may be modified as in Code 5 below.

[Code 5]

If ((log2TbWidth <= 2) && (log2TbHeight <= 2))

    transform_skip_flag [x0] [y0] [cIdx]

As described above, instead of the transform_skip_flag information being signaled separately for a plurality of channels, the transform_skip_flag information may be signaled only for luma (Y) signals and the transform_skip_flag information may not be signaled separately for the remaining chroma channels. Alternatively, the transform_skip_flag information is signaled only for the Cb signal, the transform_skip_flag information for the Cr signal is not separately transmitted, and the transform_skip_flag information transmitted for the Cb signal is also shared for the Cr signal.

An embodiment in which such transform_skip_flag information is shared is described below.

In an embodiment, the decoding apparatus 1700 may obtain transform_skip_flag information from the bitstream. This acquisition can be expressed as code 6 below.

[Code 6]

if (log2TrafoSize <= Log2MaxTransformSkipSize) {

  if ((cIdx! = 0) && "Interchannel prediction is used")

    transform_skip_flag [x0] [y0] [cIdx] = transform_skip_flag [x0] [y0] [0]

  else

    PARSE transform_skip_flag [x0] [y0] [cIdx] from compressed bitstream

} else

  transform_skip_flag [x0] [y0] [cIdx] = 0

x0 and y0 may be space coordinates indicating the position of the target block.

cIdx can indicate the target channel of the target block.

(Log2TbWidth &lt; = Log2MaxTransformSkipSize_W) && (log2TbHeight &lt; = Log2MaxTransformSkipSize_H)) in code 6 and in other codes including the condition "if (log2TrafoSize <= Log2MaxTransformSkipSize) "Or the condition" if ((log2TbWidth <= 2) && (log2TbHeight <= 2)) ".

When there are three channels of image, cIdx may have one of the values of {0,1,2} predefined. The value of the representative channel may be zero. Alternatively, it may be 1 or 2, which is the value of the representative channel.

In step 1910, the communication unit 1720 can receive the bit stream.

In step 1920, the processing unit 1710 can determine whether or not the conversion of the target block is omissible.

If the omission of the transformation is possible, step 1930 may be performed.

If the omission of the conversion is not possible, step 1960 may be performed.

For example, the processing unit 1710 can determine that the conversion can not be omitted if the size of the target block is smaller than or equal to the specified size.

For example, the processing unit 1710 can determine that the conversion can not be omitted if the size of the target block is larger than the specified size.

Here, the specified size may be a boundary value of a block size in which omission of conversion is allowed.

For example, the processing unit 1710 can determine that the conversion is not possible if the condition of code 7 below is satisfied (i.e., the result of the condition of code 7 is true), and the condition of code 7 below Is not satisfied (that is, the result of the condition of the code 7 is false), it can be determined that the conversion can be omitted.

[Code 7]

if (log2TrafoSize <= Log2MaxTransformSkipSize)

In step 1930, the processing unit 1710 may determine whether to use the sharing of transform_skip_flag information for the target channel of the object block.

If the transform_skip_flag information is not shared, step 1940 may be performed.

If the transform_skip_flag information is shared, step 1950 can be performed.

For example, the processing unit 1710 may determine that the transform_skip_flag information is shared if the conditions of code 8 below are met (i.e., the result of the condition of code 8 is true), and the condition of code 8 below is met (That is, the result of the condition of the code 8 is false), it can be determined that the transform_skip_flag information is not shared.

[Code 8]

if ((cIdx! = 0) && (interchannel prediction is used))

In other words, in step 1930, the processing unit 1710 may determine that the target channel is not a representative channel and that transform_skip_flag information is to be shared for the target channel if inter-channel prediction is used for the target block. In addition, the processing unit 1710 can determine that the target channel is a representative channel or not to share transform_skip_flag information if interchannel prediction is not used for the target block.

In step 1940, the processing unit 1710 may obtain transform_skip_flag information of the target channel from the bitstream. The processing unit 1710 can parse and read the transform_skip_flag information of the target channel from the bitstream.

The transform_skip_flag information may be stored in transform_skip_flag [x0] [y0] [cIdx].

In step 1950, the processing unit 1710 can set the transform_skip_flag information of the representative channel to be used as the transform_skip_flag information of the target channel.

The processing unit 1710 can use the transform_skip_flag information of the representative channel as the transform_skip_flag information of the target channel instead of parsing and reading the transform_skip_flag information of the target channel from the bit stream. That is to say, the processing unit 1710 can store the value of transform_skip_flag [x0] [y0] [0] in transform_skip_flag [x0] [y0] [cIdx].

That is to say, the value already stored in transform_skip_flag [x0] [y0] [0] can be used equally in transform_skip_flag [x0] [y0] [cIdx] without parsing and reading the transform_skip_flag information of the target channel from the bitstream .

For example, the transform_skip_flag information signaled for the luma (Y) channel, which is the representative channel, can also be used for the chroma channel (Cb and / or Cr).

According to one embodiment, transform_skip_flag information may be transmitted for the Cb signal, and transform_skip_flag information of the Cb signal may be shared for the Cr signal without transmission of the transform_skip_flag information. In this case, the code 6 described above can be modified as shown in the following code 9.

[Code 9]

if (log2TrafoSize <= Log2MaxTransformSkipSize) {

  if ((cIdx! = 1) && "Interchannel prediction is used")

    transform_skip_flag [x0] [y0] [cIdx] = transform_skip_flag [x0] [y0] [1]

  else

    PARSE transform_skip_flag [x0] [y0] [cIdx] from compressed bitstream

} else

  transform_skip_flag [x0] [y0] [cIdx] = 0

Step 1960 can be performed if the omission of the transform itself is not possible for the target block.

In step 1960, it can be set that the transformation is not omitted for the target block. The value of transform_skip_flag [x0] [y0] [cIdx] may be set to 0 as the omission of conversion is not allowed for the target block.

20 is a flowchart of a decoding method for determining whether to omit conversion with reference to an intra mode according to an embodiment.

There may be significant correlation between the luma channel (i.e., Y) of the image and the chroma channel (i.e., Cb and / or Cr). For example, the luma channel may contain a lot of information about the texture of the image, and the Cb channel and the Cr channel, which are chroma channels, may additionally provide color information to be added to this texture.

Therefore, in performing prediction for compressing and reconstructing an image, instead of performing independent predictions on the three channels of the color space, the Cb block in which predictions are performed from the luma channel signals already obtained through decoding And Cr blocks can be calculated.

The technique of calculating these predicted values may be named as Cross Channel Prediction (CCP) or the above-mentioned CCLM.

The decoding apparatus 1700 can determine whether interchannel prediction is used by checking whether the intra prediction mode for the target block is one of the INTRA_CCLM mode, the INTRA_MMLM mode, and the INTRA_MFLM mode.

Since a significant portion of the texture information of the chroma signal is also included in the luma signal, such interchannel prediction may be effective. Likewise, prediction values for Cr blocks to be predicted can be calculated from Cb channel signals using inter-channel prediction.

In the case where inter-channel prediction is selected among various techniques including angular prediction, DC prediction, and planar prediction for prediction of chroma signal, or inter-channel prediction is advantageous, when the signal characteristic of the channel corresponding to SelectedCIDX is different from the signal Lt; RTI ID = 0.0 &gt; characteristic. &Lt; / RTI &gt;

Therefore, if it is advantageous to omit (or perform) the conversion for the block of the channel corresponding to SelectedCIDX, it may be advantageous to omit (or perform) the same conversion for the remaining channels.

Thus, when interchannel prediction is used, it may not perform parsing of the bitstream for each of the three channels in order to obtain transform_skip_flag information. If the transform_skip_flag information for the representative channel is parsed, the transform_skip_flag information for the other channel may not be parsed separately. The transform_skip_flag information for the representative channel can be shared and used as the transform_skip_flag information for the other channel, and information indicating such sharing can be recorded in the bitstream. For example, for such sharing, the channel corresponding to SelectedCIDX may be used to determine whether to omit conversion.

Alternatively, values of the rate-distortion may be calculated for the case where the same conversion is omitted for three channels and the values of the rate-distortion are calculated for the case where the same conversion is performed for the three channels . The values of the rate-distortion when the transform is omitted and the value of the rate-distortion when the transform is performed can be compared, and according to this comparison, the coding for the channels in a more favorable way, Can be performed.

In the embodiment, instead of the transform_skip_flag information being signaled separately for a plurality of channels, the transform_skip_flag information may be signaled only for the channel corresponding to SelectedCIDX and the transform_skip_flag information may not be separately signaled for the remaining channels.

An embodiment in which such transform_skip_flag information is shared is described below.

In an embodiment, the decoding apparatus 1700 may obtain transform_skip_flag information from the bitstream. This acquisition can be expressed as code 10 below.

[Code 10]

if (log2TrafoSize <= Log2MaxTransformSkipSize) {

  if ((cIdx! = SelectedCIDX) && "Interchannel prediction is used")

    transform_skip_flag [x0] [y0] [cIdx] = transform_skip_flag [x0] [y0] [SelectedCIDX]

  else

    PARSE transform_skip_flag [x0] [y0] [cIdx] from compressed bitstream

} else

  transform_skip_flag [x0] [y0] [cIdx] = 0

x0 and y0 may be space coordinates indicating the position of the target block.

cIdx can indicate the target channel of the target block.

When the number of channels in the image is 3, the value of cIdx in code 10 may be one of {0, 1, 2}. For example, the value of cIdx may be a predefined value in {0, 1, 2}.

In step 2010, the communication unit 1720 can receive the bit stream.

In step 2020, the processing unit 1710 can determine whether or not conversion of the object block is possible.

If the omission of the transformation is possible, step 2030 may be performed.

If the omission of the transformation is not possible, step 2060 may be performed.

For example, the processing unit 1710 can determine that the conversion can not be omitted if the size of the target block is smaller than or equal to the specified size.

For example, the processing unit 1710 can determine that the conversion can not be omitted if the size of the target block is larger than the specified size.

Here, the specified size may be a boundary value of a block size in which omission of conversion is allowed.

For example, the processing unit 1710 can determine that the conversion is not possible if the condition of code 7 below is satisfied (i.e., the result of the condition of code 7 is true), and the condition of code 7 below Is not satisfied (that is, the result of the condition of the code 7 is false), it can be determined that the conversion can be omitted.

[Code 11]

if (log2TrafoSize <= Log2MaxTransformSkipSize)

In step 2030, the processing unit 1710 may determine whether to use the sharing of transform_skip_flag information for the target channel of the object block based on the selected representative channel.

If the transform_skip_flag information is not shared, step 2040 may be performed.

If the transform_skip_flag information is shared, step 2050 may be performed.

For example, the processing unit 1710 may determine that the transform_skip_flag information is shared if the conditions of code 8 below are met (i.e., the result of the condition of code 8 is true), and the condition of code 8 below is met (That is, the result of the condition of the code 8 is false), it can be determined that the transform_skip_flag information is not shared.

[Code 12]

if ((cIdx! = SelectedCIDX) && "Interchannel prediction is used")

In other words, in step 2030, the processing unit 1710 may determine that the target channel is not the selected representative channel indicated by the SelectedCIDX, and that the interchannel prediction is used for the target block to share the transform_skip_flag information for the target channel. In addition, the processing unit 1710 may determine that the target channel is the selected representative channel indicated by SelectedCIDX, or that it will not share the transform_skip_flag information if interchannel prediction is not used for the target block.

In step 2040, the processing unit 1710 may obtain transform_skip_flag information of the target channel from the bitstream. The processing unit 1710 can parse and read the transform_skip_flag information of the target channel from the bitstream.

The transform_skip_flag information may be stored in transform_skip_flag [x0] [y0] [cIdx].

In step 2050, the processing unit 1710 can set the transform_skip_flag information of the selected representative channel indicated by SelectedCIDX to be used as the transform_skip_flag information of the target channel.

The processing unit 1710 can use the transform_skip_flag information of the selected representative channel indicated by SelectedCIDX as the transform_skip_flag information of the target channel instead of parsing and reading the transform_skip_flag information of the target channel from the bit stream. That is to say, the processing unit 1710 can store the value of transform_skip_flag [x0] [y0] [SelectedCIDX] in transform_skip_flag [x0] [y0] [cIdx].

That is to say, the values already stored in the transform_skip_flag [x0] [y0] [SelectedCIDX] can be used for the transform_skip_flag [x0] [y0] [cIdx] without parsing and reading the transform_skip_flag information of the target channel from the bit stream.

In step 2060, it can be set that the transform is not omitted for the target channel of the target block. The value of transform_skip_flag [x0] [y0] [cIdx] may be set to 0 as the omission of conversion is not allowed for the target block.

That is, instead of parsing and reading the transform_skip_flag information indicating whether or not the conversion from the bitstream is omitted, the target channel of the target block indicated by cIdx is replaced with a predetermined value 0 can be set in the transform_skip_flag information.

As described in the above embodiment, the coding decision information of the selected representative channel can be shared with all of the channels other than the selected representative channel.

The above-described embodiment can be partially modified. That is, the coding determination information of the selected representative channel can be shared as the coding determination information of another specified channel. For example, the coding decision information may include transform_skip_flag information.

For example, when the value of SelectedCIDX is 1, the value 1 of cIDX indicates the Cb signal, and the cIDX value 2 indicates the Cr signal, the coding decision information for the Cb signal can be shared as the coding decision information of the Cr signal .

In other words, the coding determination information for the Cb signal can be transmitted from the coding apparatus 1600 to the decoding apparatus 1700, and the coding determination information for the Cr signal can be set using the coding determination information for the Cb signal .

When the coding decision information for the Cb signal is shared as the coding decision information of the Cr signal, the code 10 described above can be transformed as shown in the following code 13.

[Code 13]

if (log2TrafoSize <= Log2MaxTransformSkipSize) {

  if ((cIdx! = 2) or (! "Interchannel prediction is used")) //! Means logical negation.

  PARSE

    transform_skip_flag [x0] [y0] [cIdx] from compressed bitstream // Step 2040:

  Else

    transform_skip_flag [x0] [y0] [cIdx] = transform_skip_flag [x0] [y0] [SelectedCIDX] // step 2050:

} else

  transform_skip_flag [x0] [y0] [cIdx] = 0 // Step 2060:

In step 2030, the processing unit 1710 may determine that the transform_skip_flag information is shared if the conditions of code 8 below are met (i.e., the result of the condition of code 8 is true) Is not satisfied (i.e., the result of the condition of the code 8 is false), it can be determined that the transform_skip_flag information is not shared.

[Code 14]

if ((cIdx! = 2) or (! "Interchannel prediction is used"))

In other words, in step 2030, the processing unit 1710 determines whether 1) the target channel is not the channel on which the coding determination information of the selected representative channel indicated by SelectedCIDX is shared, or 2) if interchannel prediction is not used for the target block, It may decide not to share the transform_skip_flag information for the target channel. Also, the processing unit 1710 can determine that 1) the target channel is the channel in which the coding determination information of the selected representative channel indicated by the SelectedCIDX is shared, and 2) the transform_skip_flag information is shared when the interchannel prediction is used for the target block.

The steps of code 13 may be implemented as other steps where the semantics remain the same. For example, code 13 may be modified as in code 15 below.

[Code 15]

if (log2TrafoSize <= Log2MaxTransformSkipSize) {

  if ((cIdx == 2) && ("Interchannel prediction is used"))

    transform_skip_flag [x0] [y0] [cIdx] = transform_skip_flag [x0] [y0] [SelectedCIDX] // step 2050:

  Else

    PARSE transform_skip_flag [x0] [y0] [cIdx] from compressed bitstream // Step 2040:

} else

  transform_skip_flag [x0] [y0] [cIdx] = 0 // Step 2060:

Sharing of conversion selection information

21 is a flow diagram of a method for sharing transformation selection information in accordance with one embodiment.

In the above-described embodiments, transform_skip_flag information has been described as shared coding determination information. The transform_skip_flag information in the above-described embodiments can be replaced with other coding determination information. In the following, the conversion selection information is described as shared coding determination information.

The conversion selection information may be information indicating which conversion to use for the conversion block of the target channel. The conversion selection information may include the above-mentioned primary conversion selection information and / or secondary conversion selection information.

There may be significant correlation between the luma channel (i.e., Y) of the image and the chroma channel (i.e., Cb and / or Cr). For example, the luma channel may contain a lot of information about the texture of the image, and the Cb channel and the Cr channel, which are chroma channels, may additionally provide color information to be added to this texture.

Therefore, in performing prediction for compressing and reconstructing an image, instead of performing independent predictions on the three channels of the color space, the Cb block in which predictions are performed from the luma channel signals already obtained through decoding And Cr blocks can be calculated. Since a significant amount of the texture information of the chroma signal may be included in the luma signal, such interchannel prediction may be effective.

If interchannel prediction is selected among various techniques including angular prediction, DC prediction, and planar prediction for chroma signal prediction, or channel-to-channel prediction is advantageous, the signal characteristics of the luma channel may be affected by chroma channels / RTI &gt; and / or &lt; RTI ID = 0.0 &gt; Cr). &Lt; / RTI &gt;

Thus, it may be advantageous to use the same transform for a chroma block (i.e., a Cb block and / or a Cr block) if it is advantageous to use a specified transform among a plurality of transforms for a luma block.

That is to say, the same transform can generally be used for luma blocks and chroma blocks. Alternatively, if a transformation specified for a luma block is used, another specific transformation corresponding to the specified transformation used for the luma block may be used for the chroma block.

Thus, when inter-channel prediction is used, instead of being each signaled for the transformations used for the luma channel and the chroma channel (s), the determined transform can be used equally for the three channels if one transform is determined.

Alternatively, if one transform is determined for the luma channel, a transform corresponding to the transform determined for the luma channel may be used for the chroma channel.

Once the transform to be used for the channels is determined in this way, the luma channel and chroma channel (s) can be encoded according to the decision. For this encoding, one transform of a plurality of available transformations can be selected for the luma channel only, and the transform for the chroma channel (s) can be automatically determined as one transform for the luma channel is selected .

Alternatively, encoding may be performed using the same transform for the three channels. Through this encoding, the values of the rate-distortion can be calculated for a plurality of transforms. Thereafter, according to a comparison of the values of the rate-distortion of applicable transforms, the transform with the most favorable rate-distortion value can be selected and the encoding according to the selected transform can be made.

Alternatively, encoding may be performed using a transform set for three channels. The transform set may include transform (s) corresponding to the specified transform used for the luma channel and the specified transform used for the chroma channel (s).

With this encoding, values of rate-distortion can be calculated for a plurality of transform sets. Thereafter, according to a comparison of the rate-distortion values of the applicable transform sets, a transform set with the most favorable rate-distortion value can be selected and the encoding according to the selected transform set can be made.

In an embodiment, instead of the conversion selection information being signaled separately for a plurality of channels, the conversion selection information may be signaled only for luma signals and the conversion selection information may not be signaled separately for the remaining chroma channels.

In an embodiment, the decoding apparatus 1700 may obtain conversion selection information from the bitstream.

In step 2110, the communication unit 1720 can receive the bit stream.

In step 2120, the processing unit 1710 may determine whether to use the sharing of the conversion selection information for the target channel of the target block.

If the transform selection information is not shared, step 2130 may be performed.

If the conversion selection information is shared, step 2140 may be performed.

In step 2130, the processing unit 1710 may obtain conversion selection information of the target channel from the bitstream. The processing unit 1710 can parse and read the conversion selection information of the target channel from the bitstream.

In step 2140, the processing unit 1710 can set the conversion selection information of the representative channel to be used as the conversion selection information of the target channel.

Steps 2120, 2130 and 2140 may be represented as code 16 below.

 [Code 16]

if ((cIdx! = 0) && "Interchannel prediction is used")

  Conversion selection information [x0] [y0] [cIdx] = conversion selection information [x0] [y0] [0]

else

  PARSE conversion selection information [x0] [y0] [cIdx] from compressed bitstream

x0 and y0 may be space coordinates indicating the position of the target block.

cIdx can indicate the target channel of the target block.

When the number of channels in the image is 3, the value of cIdx in code 10 may be one of {0, 1, 2}. For example, the value of cIdx may be a predefined value in {0, 1, 2}.

The cIdx of the representative channel can be assumed to be zero.

"cIdx! = 0" may indicate that the target channel is not a representative channel (e.g., a luma channel). A value of cIdx of 0 indicates that the target channel is a representative channel.

That is to say, at step 2120, the processing unit 1710 can determine to use the sharing of the conversion selection information for the target channel if the target channel is not a representative channel and inter-channel prediction is used for the target block. The processing unit 1710 can determine that the target channel is a representative channel or not to use the sharing of the conversion selection information for the target channel if interchannel prediction is not used for the target block.

In step 2130, the processing unit 1710 may obtain conversion selection information of the target channel from the bitstream. The processing unit 1710 can parse and read the conversion selection information of the target channel from the bitstream.

The conversion selection information may be stored in the conversion selection information [x0] [y0] [cIdx].

In step 2140, the processing unit 1710 can set the conversion selection information of the representative channel to be used as the conversion selection information of the target channel.

The processing unit 1710 can use the conversion selection information of the representative channel as the conversion selection information of the target channel instead of parsing and reading the conversion selection information of the target channel from the bit stream. That is to say, the processing unit 1710 can store the values of the conversion selection information [x0] [y0] [0] in the conversion selection information [x0] [y0] [cIdx].

That is, the values already stored in the conversion selection information [x0] [y0] [0] are converted into the conversion selection information [x0] [y0] [cIdx] without the process of parsing and reading the conversion selection information of the target channel from the bitstream Can be used.

Determining whether to use interchannel prediction

In the above-described embodiment with reference to Figs. 18 to 21, whether interchannel prediction is used or not is exemplified by checking whether the intra prediction mode for the target block is one of INTRA_CCLM mode, INTRA_MMLM mode, and INTRA_MFLM mode. That is, inter-channel prediction can be used when the intra-prediction mode for the target block is one of INTRA_CCLM mode, INTRA_MMLM mode, and INTRA_MFLM mode. Interchannel prediction may not be used unless the intra prediction mode for the target block is INTRA_CCLM mode, INTRA_MMLM mode, and INTRA_MFLM mode.

The determination as to whether or not to use the interchannel prediction described above is an example, and whether or not interchannel prediction is used can also be achieved by one of the following codes 17 to 23. For example, interchannel prediction may be used if the value of the condition of the following code is true, and interchannel prediction may not be used if the value of the condition of the code below is false. intra_chroma_pred_mode may be an intra prediction mode for the chroma channel.

[Code 17]

if (intra_chroma_pred_mode == CCLM mode)

[Code 18]

if (intra_chroma_pred_mode == DM mode)

[Code 19]

if (intra_chroma_pred_mode == INTRA_CCLM mode)

[Code 20]

if (intra_chroma_pred_mode == INTRA_MMLM mode)

[Code 21]

if (intra_chroma_pred_mode == INTRA_MFLM mode)

[Code 22]

if ((intra_chroma_pred_mode == INTRA_CCLM mode) ||

(intra_chroma_pred_mode == INTRA_MMLM mode) ||

(intra_chroma_pred_mode == INTRA_MFLM mode)

[Code 23]

if ((intra_chroma_pred_mode == DM mode) ||

(intra_chroma_pred_mode == INTRA_CCLM mode) ||

(intra_chroma_pred_mode == INTRA_MMLM mode) ||

(intra_chroma_pred_mode == INTRA_MFLM mode)

The CCLM mode, the DM mode, the INTRA_CCLM mode, the INTRA_MMLM mode, and the INTRA_MFLM mode described in codes 17 to 23 can represent one value of intra_chroma_pred_mode shown in the first column of Tables 10 and 11 described above . The explanations described above with reference to Table 10 and Table 11 can be referred to for CCLM mode, DM mode, INTRA_CCLM mode, INTRA_MMLM mode and INTRA_MFLM mode.

In determining whether inter-channel prediction is to be used, the size of the block may be further considered in a scheme according to the following code 17 to code 23.

Whether or not interchannel prediction is used can also be achieved by one of the following codes 24 to 30. For example, interchannel prediction may be used if the value of the condition of the following code is true, and interchannel prediction may not be used if the value of the condition of the code below is false.

[Code 24]

if ((intra_chroma_pred_mode == CCLM mode) && block size condition)

[Code 25]

if ((intra_chroma_pred_mode == DM mode) && block size condition)

[Code 26]

if ((intra_chroma_pred_mode == INTRA_CCLM mode) && block size condition)

[Code 27]

if ((intra_chroma_pred_mode == INTRA_MMLM mode) && block size condition)

[Code 28]

if ((intra_chroma_pred_mode == INTRA_MFLM mode) && block size condition)

[Code 29]

if ((intra_chroma_pred_mode == INTRA_CCLM mode) ||

(intra_chroma_pred_mode == INTRA_MMLM mode) ||

(intra_chroma_pred_mode == INTRA_MFLM mode) && block size condition)

[Code 30]

if ((intra_chroma_pred_mode == DM (direct mode) mode) ||

(intra_chroma_pred_mode == INTRA_CCLM mode) ||

(intra_chroma_pred_mode == INTRA_MMLM mode) ||

(intra_chroma_pred_mode == INTRA_ MFLM mode) && block size condition)

The block size condition indicated in codes 24 to 30 may be replaced by one of codes 31, 32, 33 and 34 below.

[Code 31]

((log2TbWidth <= Log2MaxSizeWidth) && (log2TbHeight <= Log2MaxSizeHeight))

[Code 32]

((log2TbWidth> = Log2MinSizeWidth) && (log2TbHeight> = Log2MinSizeHeight))

[Code 33]

((log2TbWidth> Log2MinSizeWidth) && (log2TbHeight <= Log2MaxSizeHeight))

[Code 34]

((log2TbWidth> Log2MinSizeWidth) && (log2TbHeight> Log2MaxSizeHeight))

log2TbWidth and log2TbHeight have been described above with reference to Equation 11 and Equation 12.

Log2MaxSizeWidth, Log2MaxSizeHeight, Log2MinSizeWidth, and Log2MinSizeHeight may be predetermined values. Log2MaxSizeWidth can correspond to the width of the block of maximum size. Log2MaxSizeHeight can correspond to the height of the block with the maximum size. Log2MinSizeWidth can correspond to the width of the minimum size block. Log2MinSizeHeight can correspond to the height of the minimum size block.

For example, the value of Log2MaxSizeWidth may be 16, the value of Log2MaxSizeHeight may be 16, the value of Log2MinSizeWidth may be 4, and the value of Log2MinSizeHeight may be 4.

Alternatively, the value of Log2MaxSizeWidth may be 32, and the value of Log2MaxSizeHeight may be 32.

If DM is used, the intra prediction mode for the chroma signal may not be signaled separately. If DM is used, the intraprediction mode signaled for the luma signal can be used as is for the chroma mode.

Coding and decoding using selective sharing of information between channels under a block partition structure

Generally, when encoding of an image is performed, appropriate encoding schemes may be separately used for a plurality of spatial regions reflecting spatial characteristics in an image. For this encoding, the image can be divided into CUs, and the divided CUs can be respectively encoded.

For this encoding, the same block division structure may be used for the luma channel and the chroma channel.

However, the characteristics of the luma signal and the characteristics of the chroma signal may be different from each other. In consideration of the difference of these characteristics, different block division structures may be used for the luma channel and the chroma channel, respectively, for more effective encoding.

Hereinafter, the same block division structure of an image for a luma signal and a chroma signal (or a plurality of channels) is named as a single tree block division structure or a single tree.

In the following, what is not the same for block segmentation structures for luma signals and chroma signals (or multiple channels) is referred to as a dual tree block division structure or dual tree.

In an embodiment, it can be specified which block of the other channel the target block of the target channel of the luma channel and chroma channel (or a plurality of channels) corresponds to. And blocks of other channels corresponding to the target block of the target channel are designated as corresponding blocks.

In an embodiment, if the luma channel and the chroma channel (or a plurality of channels) have the same block partition structure (i.e., a single tree is applied), the target block of the target channel corresponds to which block of the other channel Can be specified.

In an embodiment, if the luma channel and the chroma channel (or a plurality of channels) each have different block partition structures (i.e., a dual tree is applied), the target block of the target channel Can be specified.

If the luma channel and the chroma channel (or a plurality of channels) each have different block partition structures (i.e., a dual tree is applied), the coding determination information of the corresponding block may be shared with the target block of the target channel have. The encoding efficiency can be improved as the target block is encoded through the sharing of the coding decision information.

The coding determination information of the corresponding block corresponding to the target block of the target channel from the compressed bitstream can be parsed.

The coding determination information of the corresponding block corresponding to the target block of the target channel from the compressed bitstream can be parsed and the target block of the target channel can be decoded using the coding determination information of the corresponding block.

For example, the transform_skip_flag information of the corresponding block corresponding to the target block of the target channel can be parsed, and the transform_skip_flag information of the corresponding block can be used to determine whether or not the conversion of the target block is omitted.

The shared information may refer to coding decision information that is shared between luma blocks and chroma blocks.

If the spatial position of the first block of the first channel and the spatial position of the second block of the second channel correspond to each other when the block division structure of the first channel and the block division structure of the second channel are the same, The blocks may correspond to each other. That is to say, the corresponding blocks of the different channels may be blocks of different channels with corresponding spatial positions. The shared information of the second block corresponding to the first block may be used for coding and / or decoding of the first block.

When the block division structure of the chroma channel and the block division structure of the luma channel are the same, the luma block corresponding to the specific chroma block of the chroma channel may be a luma block of the spatial position corresponding to the spatial position of the specific chroma block. In this case, the shared information of the luma block corresponding to the chroma block may be used for encoding and / or decoding the chroma block.

22 illustrates a single triblock division structure according to an example.

FIG. 23 shows a dual tree block division structure according to an example.

Under a color subsampling scheme of 4: 2: 0, a luma signal region spatially corresponding to a chroma block can occupy an area four times as large as a chroma block. That is to say, the width and height of the luma signal area can be twice the width and height of the chroma block.

As shown in Fig. 22, in the video regions corresponding to each other of the chroma channel and the luma channel, the block division structure of the chroma channel and the block division structure of the luma channel may be equal to each other. That is, a single tree may be used for the chroma channel and the luma channel.

22 and below, the video regions corresponding to each other are indicated as "corresponding regions ".

As shown in FIG. 23, within the corresponding image regions of the chroma channel and the luma channel, the block division structure of the chroma channel and the block division structure of the luma channel may be different from each other. That is to say, a dual tree can be used for the chroma channel and the luma channel.

For example, in FIG. 23, the area of the luma channel corresponding spatially to one chroma block is divided into eight blocks.

A block of luma channels spatially corresponding to a specified chroma block may be specified without ambiguity if the block division structures within the corresponding video regions of the luma channel and the chroma channel are the same.

On the other hand, when the block division structure of the luma channel and the block division structure of the chroma channel are not equal to each other, for a specified chroma block determined by division according to the block division structure of the chroma channel, The luma block may not be explicitly specified within the luma channel. This uncertainty is due to the fact that the block division structure of the chroma channel and the block division structure of the luma channel are not equal to each other, as shown in Fig.

In the embodiment, a method of specifying a luma block corresponding to a chroma block when the block division structure of the luma channel and the block division structure of the chroma channel are not equal to each other will be described.

For example, a plurality of luma blocks corresponding to a chroma block may be specified. Through this specification, the shared information (s) can be obtained from one or more luma blocks corresponding to the chroma block, which is the target block, and the coding and / or decoding of the chroma block is performed using the acquired shared information .

Hereinafter, a method of specifying one or more blocks of a second channel corresponding to a block of the first channel will be described when the block division structure of the first channel is not the same as the block division structure of the second channel. In the following description, the first channel is described as a chroma channel and the second channel is described as a luma channel, but the chroma channel and luma channel are merely exemplary, and each of the first channel and the second channel is different from the above- Channel.

FIG. 24 illustrates a manner of specifying a corresponding block based on a position within a corresponding region according to an example.

The corresponding area representing the luma blocks corresponding to the chroma block may be specified as a rectangular area. The position of the top-leftmost pixel of the rectangular area may be (xCb, yCb). The position of the lowermost-rightmost pixel of the rectangular region may be (xCb + cbWidth - 1, yCb + cbHeight - 1).

(xCb, yCb) may represent the position of the luma pixel corresponding to the position of the leftmost-topmost pixel in the chroma block (i.e., the chroma coding block).

cbWidth and cbHeight may be values indicating the width and height of the target block based on luma pixels, respectively.

In other words, the corresponding area representing the luma blocks corresponding to the chroma block is defined by the position of the top-left pixel as (xCb, yCb), the width as cbWidth, and the height as cbHeight As shown in FIG.

The corresponding regions representing the luma blocks corresponding to the chroma blocks as described above can be applied to the embodiments described with reference to Figs.

The luma blocks corresponding to the chroma block in Fig. 24 may be luma blocks present at predetermined positions within the corresponding region of the luma channel that spatially correspond to the chroma block.

That is to say, luma blocks existing at predetermined locations within the corresponding area of the luma channel corresponding spatially to the chroma block may be specified as one or more luma blocks corresponding to the chroma block. Alternatively, luma blocks occupying predetermined positions within the corresponding region of the luma channel corresponding spatially to the chroma block may be specified as one or more luma blocks corresponding to the chroma block.

For example, the predefined locations may be located in the center (CR) position, upper left (TL), upper right (TR), lower left (BL) and lower right BR).

The CR position may mean (xCb + cbWidth / 2, yCb + cbHeight / 2). The TL position can mean (xCb, yCb). TR can mean (xCb + cbWidth - 1, yCb). The BL position can mean (xCb, yCb + cbHeight - 1). The BR position may mean (xCb + cbWidth - 1, yCb + cbHeight - 1).

In an embodiment, it can be specified which block of the other channel the target block of the target channel corresponds to in a plurality of channels such as a luma channel and a chroma channel. And blocks of other channels corresponding to the target block of the target channel are designated as corresponding blocks.

In one embodiment, within a region of the luma channel that spatially corresponds to the chroma block, a luma block containing luma pixels at a location (xCb + cbWidth / 2, yCb + cbHeight / 2) Corresponding block. Therefore, when the target block is divided into a dual-tree, it is ambiguous whether a target block of a target channel (for example, a chroma channel) among a plurality of channels corresponds to a block of another channel (for example, a luma channel) Can be specified. In an embodiment, in coding and / or decoding a chroma channel, a luma block containing a luma pixel at a location of (xCb + cbWidth / 2, yCb + cbHeight / 2) may be specified as a corresponding block. Information of the specified corresponding block may be used for coding and / or decoding of the target block.

For example, the default locations may be part of the CR location, TL location, TR location, BL location and BR location within the area of the luma channel corresponding spatially to the chroma block.

For example, the luma blocks corresponding to the chroma block may be blocks comprising at least one of the pixels located in the center, upper left, upper right, lower left, or lower right of the region of the luma channel spatially corresponding to the chroma block have.

For example, the luma blocks corresponding to the chroma block may be part of the blocks including at least one of the pixels located in the center, upper left, upper right, lower left, or lower right of the region of the luma channel spatially corresponding to the chroma block .

For example, the luma blocks corresponding to the chroma block include blocks comprising at least one of the pixels located in the center, upper left, upper right, lower left, or lower right of the region of the luma channel spatially corresponding to the chroma block can do.

FIG. 25 illustrates a method of specifying a corresponding block based on an area within a corresponding area according to an example.

Figure 26 shows another way of specifying the corresponding block based on the area within the corresponding area according to an example.

The luma blocks corresponding to the chroma block may be luma blocks having the widest area in the area of the luma channel that spatially corresponds to the chroma block.

Alternatively, the luma blocks corresponding to the chroma block may be a predetermined number of luma blocks having the widest area in the area of the luma channel spatially corresponding to the chroma block.

This specification indicates that the property of the luma block having the widest area in the area of the luma channel corresponding to the chroma block or the predetermined number of luma blocks having the widest area is likely to be similar to the property of the chroma block Can be attributed.

As shown in Fig. 25, the predetermined number may be two. In Fig. 25, two blocks (i.e., block 1 and block 2) having the widest area among eight luma blocks in the area of the luma channel corresponding to the chroma block can be selected.

As shown in Fig. 26, the predetermined number may be three. In Fig. 25, three blocks (i.e., block 1, block 2 and block 3) having the widest area among the eight luma blocks in the area of the luma channel corresponding to the chroma block can be selected.

With this specification, even when the block division structure of the luma channel and the block division structure of the chroma channel are not the same, the encoding efficiency can be improved through the use of the shared information.

FIG. 27 shows a manner of specifying a corresponding block based on the shape of the block within the corresponding area according to an example.

Figure 28 shows another way of specifying the corresponding block based on the shape of the block within the corresponding area according to an example.

The luma blocks corresponding to the chroma block may be luma blocks having the same shape as the shape of the chroma block in the region of the luma channel spatially corresponding to the chroma block.

For example, the shape of the block may include the size of the block.

27 and 28, the block division structure of the CU of the chroma channel and the block division structure of the CU of the luma channel region corresponding to the CU of the chroma channel may not be the same have. In this case also, the area of the luma channel corresponding to the area of the target block in the CU of the chroma channel may exist as one block.

In this case, one luma block in the area of the luma channel corresponding to the chroma block can accurately correspond to the chroma channel. The shared information of the corresponding luma block can be shared as the coding determination information of the chroma block.

FIG. 29 shows a manner of specifying the corresponding block based on the aspect ratio of the block within the corresponding area according to an example.

Figure 30 shows another way of specifying the corresponding block based on the aspect ratio of the block within the corresponding area according to an example.

The luma blocks corresponding to the chroma block may be luma block (s) having the aspect ratio equal to the aspect ratio of the chroma block in the region of the luma channel spatially corresponding to the chroma block.

Alternatively, the luma blocks corresponding to the chroma block may be luma block (s) having an aspect ratio similar to the aspect ratio of the chroma block in the region of the luma channel that spatially corresponds to the chroma block.

For example, luma block 2 may be selected in the area of the luma channel of Fig. 29, and luma block 1 may be selected in the area of the luma channel of Fig.

Here, the aspect ratio of the block may be a ratio between the horizontal length of the block and the vertical length of the block. That is to say, the aspect ratio of the block may be a value obtained by dividing the width of the block by the vertical length.

For example, whether or not the aspect ratios are equal to each other can be judged by the following expression (13).

[Equation 13]

(log ₂ Width _Chroma  - log ₂ Height _Chroma ) == (log ₂ Width _Luma  - log ₂ Height _Luma )

Width _Chroma can be the width of the chroma block. Height _Chroma can be the height of the chroma block.

Width _Luma can be the width of the luma block corresponding to the chroma block. Height _Luma can be the height of the luma block corresponding to the chroma block.

Whether or not the aspect ratios are similar to each other can be judged by the following expression (14).

[Equation 14]

| (Log ₂ Width _Chroma  - log ₂ Height _Chroma ) == (log ₂ Width _Luma  - log ₂ Height _Luma ) | <THD

"| X |" can represent the absolute value of x.

THD may be a threshold. For example, the value of THD may be 2.

 According to Equations 13 and 14, one or more luma blocks having the same aspect ratio as the aspect ratio of the chroma block may be specified as corresponding blocks. Alternatively, one or more luma blocks having an aspect ratio similar to an aspect ratio of a chroma block may be specified as corresponding blocks.

Figure 31 shows another way of specifying the corresponding block based on the coding nature of the block within the corresponding area according to an example.

Even if the block division structure of the chroma channel and the block division structure of the luma channel are independent from each other, among the luma blocks in the area of the luma channel spatially corresponding to the chroma block, the luma blocks having the same coding determination information as the coding determination information of the chroma block The sharing information of the chroma block and the sharing information of the luma block may be the same.

To take advantage of this feature, a luma block having the same value as the value of the chroma block can be specified as the luma block corresponding to the chroma block, with respect to the predetermined coding determination information. Alternatively, for the predetermined coding determination information, a luma block having a value similar to the value of the chroma block may be specified as a luma block corresponding to the chroma block.

For example, the predetermined coding determination information may be whether to use intra prediction, an intra prediction mode, motion prediction information, a motion vector, whether to use the merge mode, derived mode, conversion selection information, and the like.

For example, the intra prediction mode can be used as the predetermined coding determination information. 31, luma block 1, luma block 2 and luma block 3 are shown in the area of the luma channel. Luma block 1, luma block 2, and luma block 3 may be luma blocks having the same (or similar) intra prediction mode as the intra prediction mode of the chroma block. Luma block 1, luma block 2 and luma block 3 may be specified as luma blocks corresponding to the chroma block.

According to the particular schemes described above, the luma block corresponding to the chroma block may be plural. If the shared information of the plurality of luma blocks are all the same, there is no problem in using the shared information for the chroma block. On the other hand, if the shared information of the plurality of luma blocks is not the same, the shared information to be used for coding and / or decoding the chroma block may not be clear.

A plurality of values of the shared information values of the plurality of corresponding blocks may be used as the value of the shared information of the chroma block. This decision method can be named as a multiple base shared information decision method. In this way, shared information can be efficiently shared without further signaling.

For example, when transform_skip_flag information is shared, a value occupying a plurality of values of transform_skip_flag information of a plurality of luma blocks corresponding to a chroma block can be shared as values of transform_skip_flag information of a chroma block. Through this sharing, encoding and / or decoding of chroma blocks can be performed.

For example, shared information may be used only if there is only one luma block corresponding to a chroma block. Within the area of the luma channel that spatially corresponds to the chroma block, the shared information can be used only if there is only one luma block that meets the specific conditions described above. Alternatively, coding determination information may be shared among channels when an area of another channel spatially corresponding to a target block of a target channel is specified as one block.

Referring to FIG. 27, when a luma channel region spatially corresponding to a target block of a chroma channel is divided into only one block, the one block may be a corresponding block of a luma channel. The shared information of this corresponding block may be used for encoding and / or decoding of the chroma block.

If the area of the luma channel corresponding spatially to the target block of the chroma channel is not divided into one block, the coding decision information may not be shared without signaling.

32 is a flowchart of an encoding method according to an embodiment.

The encoding method and the bit stream generating method of the embodiment can be performed by the encoding apparatus 1600. [ The embodiment may be part of a coding method or a video coding method for an object.

In step 3210, the processing unit 1610 may determine the coding determination information of the representative channel of the target block.

In step 3220, the processing unit 1610 can generate information on the target block by performing encoding of the target block using the coding determination information of the representative channel of the target block.

In step 3230, the processing unit 1610 may generate a bitstream that includes information about the object block.

The information on the target block may include coding determination information of the representative channel. In addition, the information on the bitstream and the target block may not include the coding determination information of the target channel.

The embodiment described with reference to Fig. 32 can be combined with the other embodiments described above. Duplicate descriptions are omitted.

33 is a flowchart of a decoding method according to an embodiment.

The decoding method of the embodiment can be performed by the decoding apparatus 1600. [

In step 3310, the communication unit 1710 may receive a bitstream including information on a target block.

The information on the target block may include coding determination information of the representative channel. In addition, the information on the bitstream and the target block may not include the coding determination information of the target channel.

In step 3320, the processing unit 1720 can share the coding determination information of the representative channel of the target block as the coding determination information of the target channel of the target block.

The coding determination information of the representative channel can be shared as the coding determination information of the target channel.

In step 3320, the processing unit 1610 may perform decoding of a target block using the coding determination information of the target channel.

The embodiment described with reference to Fig. 33 can be combined with the other embodiments described above. Duplicate descriptions are omitted.

The embodiments described above can be performed in the same way in the encoding apparatus 1600 and the decoding apparatus 1700. [

The order in which the steps, operations, and procedures of the embodiments are applied may be different from each other in the encoding apparatus 1600 and the decoding apparatus 1700. Alternatively, the order in which the steps, operations, and procedures of the embodiments are applied may be the same in the encoding apparatus 1600 and the decoding apparatus 1700.

Embodiments may be performed for each of a luma signal and a chroma signal. Alternatively, embodiments may be performed identically for a luma signal and a chroma signal.

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

Embodiments may be determined based on the size of at least one of the CU, PU, TU and target block. Here, the size may be defined as a minimum size and / or a maximum size for an embodiment to be applied to an object, or may be defined as a fixed size for an embodiment to be applied to an object.

Further, the first embodiment may be applied to the first size, and the second embodiment may be applied to the second size. That is, the embodiments can be applied in combination according to the size of the object. Embodiments may also be applied only when the size of the object is at least the minimum size and less than the maximum size. That is, the embodiments may be applied only when the size of the object is included in a certain range.

For example, the embodiments can be applied only when the size of the target block is 8x8 or more. For example, the embodiments may be applied only when the size of the target block is 4x4. For example, the embodiments can be applied only when the size of the target block is 16x16 or less. For example, the embodiments can be applied only when the size of the target block is 16x16 or more and 64x64 or less.

The embodiments may be determined depending on the temporal layer. A separate identifier may be signaled to identify the temporal layer to which the embodiments are applied. Embodiments may optionally be applied to the temporal hierarchy specified by the identifier. Here, the identifier may represent the lowest layer and / or the highest layer for which the embodiment is to be applied, and may represent a particular layer to which the embodiment is applied. In addition, the temporal hierarchy to which the embodiment is applied may be predetermined.

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

A slice type to which the embodiments are applied can be defined. Embodiments may be selectively applied depending on the type of slice.

In the above-described embodiments, although the methods are described on the basis of a flowchart as a series of steps or units, the present invention is not limited to the order of the steps, and some steps may occur in different orders or simultaneously . It will also be understood by those skilled in the art that the steps depicted in the flowchart illustrations are not exclusive and that other steps may be included or that one or more steps in the flowchart may be deleted without affecting the scope of the invention You will understand.

The embodiments of the present invention described above can be implemented in the form of program instructions that can be executed through various computer components and recorded on a computer-readable recording medium. The computer-readable recording medium may include program commands, data files, data structures, and the like, alone or in combination. The program instructions recorded on the computer-readable recording medium may be those specially designed and constructed for the present invention or may be those known and used by those skilled in the computer software arts.

The computer-readable recording medium may include information used in embodiments according to the present invention. For example, the computer readable recording medium may comprise a bit stream, and the bit stream may comprise the information described in embodiments according to the present invention.

The computer-readable recording medium may comprise a non-transitory computer-readable medium.

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 and DVDs, 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 machine language code such as those generated by a compiler, as well as 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 for performing the processing according to the present invention, and vice versa.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, but, on the contrary, Those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.

Therefore, the spirit of the present invention should not be construed as being limited to the above-described embodiments, and all of the equivalents or equivalents of the claims, as well as the following claims, I will say.

Claims (20)

Sharing coding determination information of a representative channel of a target block as coding determination information of a target channel of the target block; And
Performing decoding of the target block using coding determination information of the target channel
/ RTI &gt; The method according to claim 1,
Receiving a bitstream including information on the target block
Further comprising:
Wherein the information on the target block includes coding determination information of the representative channel,
Wherein information on the target block does not include coding determination information of the target channel. The method according to claim 1,
Wherein the coding determination information of the representative channel is conversion skip information indicating whether to skip the conversion. The method according to claim 1,
Wherein the coding determination information of the representative channel is conversion selection information indicating which conversion is to be used for the conversion block of the channel. The method according to claim 1,
And the coding determination information of the representative channel is intra-coding determination information of the representative channel. The method according to claim 1,
Wherein the representative channel and the target channel are channels in a YCbCr color space. The method according to claim 1,
Wherein the representative channel is a luma channel,
Wherein the target channel is a chroma channel. The method according to claim 1,
Wherein the representative channel is a color channel having the highest correlation with a luma signal. The method according to claim 1,
Wherein the representative channel is determined by an index representing a selected representative channel in the bitstream. The method according to claim 1,
Wherein the sharing is performed when the video properties of the plurality of channels of the target block are similar to each other. 11. The method of claim 10,
Wherein if the intraprediction mode for the chroma channel of the target block is a direct mode, then the video properties of the plurality of channels are determined to be similar to each other. The method according to claim 1,
The sharing is performed when inter-channel prediction is used,
Wherein whether the inter-channel prediction is used is derived based on information obtained from the bit stream. The method according to claim 1,
The sharing is performed when inter-channel prediction is used,
Wherein whether the inter-channel prediction is used is determined based on an intra prediction mode of the target block. 14. The method of claim 13,
Wherein the interchannel prediction is used when the intra prediction mode for the target block is one of an INTRA_CCLM mode, an INTRA_MMLM mode, and an INTRA_MFLM mode. The method according to claim 1,
And whether or not the sharing is determined based on the size of the target block. The method according to claim 1,
And coding determination information of the representative channel among a plurality of channels of the target block is used for all of the plurality of channels. Determining coding determination information of a representative channel of a target block; And
Performing coding of the target block using coding determination information of the representative channel
Lt; / RTI &gt;
And the coding determination information of the representative channel is shared with other channels of the target block. 18. The method of claim 17,
Generating a bitstream including information on the target block
Further comprising:
Wherein the information on the target block includes coding determination information of the representative channel,
Wherein information on the target block does not include coding determination information of the other channel. 18. The method of claim 17,
Wherein the representative channel and the other channel are channels in a YCbCr color space. A computer-readable recording medium storing a bitstream for decoding an image,
Information about the target block
Lt; / RTI &gt;
The information on the target block includes coding determination information of the representative channel of the target block
Lt; / RTI &gt;
Coding determination information of the representative channel of the target block is used as coding determination information of a target channel of the target block,
Wherein decoding of the target block is performed using coding determination information of the target channel.

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