KR20190054942A - Method and apparatus for quantization - Google Patents

Abstract

A video decoding method, a decoding apparatus, a coding method, and an encoding apparatus are disclosed. For quantization and dequantization, a plurality of quantization methods and a plurality of dequantization methods can be used. The plurality of quantization methods include a variable-rate step quantization method and a fixed-rate step quantization method. The variable-rate step quantization method is a quantization method in which the increase rate of the quantization step is not fixed as the value of the quantization parameter increases by one. The fixed-rate step quantization method is a quantization method in which the rate of increase of the quantization step is fixed as the value of the quantization parameter is incremented by one.

Description

[0001] METHOD AND APPARATUS FOR QUANTIZATION [0002]

The embodiments described below relate to a video decoding method, a decoding apparatus, a coding method, and an encoding apparatus, and a method and apparatus for performing quantization in video coding and decoding.

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.

Various quantization and dequantization methods have been developed to improve the efficiency of image coding / decoding.

The image encoding / decoding technique can determine optimal coding parameters based on the objective image quality. Decision making using such an objective image quality can improve the efficiency of image encoding / decoding. However, decisions using objective quality can produce results that are different from the perceptual quality that the viewer actually feels. In particular, when the bit rate of the compressed data generated by encoding is low, it may not be easy to control the amount of information and perceptual image quality.

One embodiment can provide an encoding apparatus, an encoding method, a decoding apparatus, and a decoding method using scaling of a residual signal.

One embodiment can provide an encoding apparatus, an encoding method, a decoding apparatus, and a decoding method for determining a quantization parameter and a quantization step.

The variable-rate step quantization method according to claim 1, wherein the variable-rate step quantization method comprises: a step of performing a quantization using a quantization method in a side, Which is a quantization method in which the rate of increase of the rate of increase is not fixed.

The rate of increase of the quantization step of the variable-rate step quantization method as the value of the quantization parameter increases by one as the value of the quantization parameter is smaller.

The encoding method may further include selecting the quantization method among a plurality of quantization methods.

The plurality of quantization methods may include a fixed-rate step quantization method and the variable-rate step quantization method.

The fixed-rate step quantization method may be a fixed quantization method in which the rate of increase of the quantization step as the value of the quantization parameter increases by one.

Wherein the rate of increase of the quantization step of the variable-rate step quantization method is smaller than the rate of increase of the quantization step of the fixed-rate step quantization method in an area where the value of the quantization parameter is relatively larger.

The variable-rate step inverse quantization method may further comprise a step of performing inverse quantization using the inverse quantization method in another side, wherein the inverse quantization method is a variable-rate step inverse quantization method, 1 is an inverse quantization method in which the rate of increase of the quantization step is not fixed.

The rate of increase of the quantization step of the variable-rate step dequantization method as the value of the quantization parameter increases by one as the value of the quantization parameter is smaller.

The decoding method may further include selecting the inverse quantization method among the plurality of inverse quantization methods.

The plurality of dequantization methods may include a fixed-rate step dequantization method and the variable-rate step dequantization method.

The fixed-rate step dequantization method may be a dequantization method in which the rate of increase of the quantization step is fixed as the value of the quantization parameter increases by one.

The rate of increase of the quantization step of the variable-rate step dequantization method may be smaller than the rate of increase of the quantization step of the fixed-rate step dequantization method in an area where the value of the quantization parameter is relatively larger.

The quantization parameter of the fixed-rate step dequantization method corresponding to the quantization parameter of the variable-rate step dequantization method may be determined.

A quantization step corresponding to a quantization parameter of the fixed-rate step dequantization method may be used for the dequantization.

Wherein the quantization step of the fixed-rate step dequantization method corresponding to the quantization parameter is determined according to the fixed-rate step dequantization method, and the quantization step ratio is applied to the quantization step of the fixed-rate step dequantization method, The quantization step for the variable-rate step inverse quantization method can be determined.

The quantization step rate may be a ratio between a quantization step of the variable-rate step inverse quantization method and a quantization step of the fixed-rate step inverse quantization method.

The decoding method may further include obtaining a quantization method indicator.

The quantization method indicator may indicate one inverse quantization method used for inverse quantization of a target block among the plurality of inverse quantization methods.

The quantization method indicator may indicate an inverse quantization method applied to a specified unit.

The specified unit may be a video, a sequence, a picture, or a slice.

The quantization method indicator may indicate whether the variable-rate step inverse quantization method is applied to the specified unit.

The decoding method may further include obtaining a quantization parameter using the quantization parameter difference value.

The quantization parameter may be used for the inverse quantization.

The quantization parameter difference value may be a difference between an intermediate value and a value of the quantization parameter.

The intermediate value may be a value in the middle of the range of the quantization parameter of the variable-rate step dequantization method.

The quantization parameter may be applied to a specified unit.

The decoding method may further include obtaining a quantization parameter using the quantization parameter difference value.

The quantization parameter difference value may be a difference between a value of the quantization parameter of the upper unit and a value of the quantization parameter of the lower unit.

The obtained quantization parameter may be used for the inverse quantization for the subunit.

The quantization parameter difference value may be included in the header of the lower unit.

The upper unit may be a picture, and the lower unit may be a slice.

There is provided a computer-readable recording medium storing a bitstream for decoding an image, the bitstream including information on a target block, information on the target block, and information on the inverse quantization method Wherein the inverse quantization method is a variable-rate step inverse quantization method, and the variable-rate step inverse quantization method performs inverse quantization using a variable-rate step inverse quantization method in which a quantization step increase rate of a quantization step There is provided a computer readable recording medium which is a quantization method.

A coding method, a decoding device, and a decoding method using scaling of a residual signal are provided.

A coding method, a decoding device, and a decoding method for determining a quantization parameter and a quantization step 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.
Figure 18 shows traditional distortion and perceptual distortion according to an example.
FIG. 19 is a graph showing a relationship between a quantization parameter and a quantization step of a fixed-rate step quantization method according to an example.
20 is a graph showing a relationship between a quantization parameter and an SNR of a fixed-rate step quantization method according to an example.
21 is a flow diagram of a quantization method in accordance with an embodiment.
22 is a flowchart of a dequantization method according to an embodiment.
Fig. 23 shows a quantization step according to an example quantization parameter.
24 shows the quantization parameter and the quantization step rate according to an example.
25 shows a table of quantization parameters and quantization steps of a variable-rate step quantization method according to an example.
26 shows the syntax of a set of video parameters according to an example.
27 shows the syntax of a sequence parameter set according to an example.
Figure 28 shows the syntax of a set of picture parameters according to an example.
29 shows the syntax of a slice segment header according to an example.

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 a 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 unit type 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.

- 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 indicate one of CU, PU, remaining 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 may consist of one luminance component (Y) coding tree block and two chrominance component (Cb, Cr) coding tree blocks related to the luminance 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.

- 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. 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 may 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: The 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.

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 neighboring 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) (Intra or inter prediction), intraprediction mode / direction, reference sample filtering method, prediction block filtering method, prediction block boundary filtering method, filtering A filter tap of filtering, an inter prediction mode, motion information, a motion vector, a reference picture index, an inter prediction direction, an inter prediction indicator, Information indicating whether or not to use the merge mode, merge candidate, merge candidate list, information indicating whether or not to use the skip 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 accuracy, the kind of transformation, the size of the transformation, information indicating whether or not the primary transformation is used, A coded block flag, a coded block flag, a quantization parameter, a quantization matrix, and a quantization matrix. Information about the intra-loop filter, information on whether or not to apply the intra-loop filter, coefficients of the intra-loop filter, Filter tap, shape / form of intra-loop filter, information indicating whether a deblocking filter is applied, deblocking filter coefficient, deblocking filter tap, deblocking filter strength, deblocking filter shape / An adaptive sample offset value, an adaptive sample offset type, an adaptive sample offset type, whether to apply an adaptive in-loop filter, an adaptive loop offset, Filter coefficient, adaptive loop-in filter tap, adaptive loop-filter shape / form, binarization / inverse binarization method, context model, context model decision method, context model update method, whether to perform regular mode, bypass Mode, a context bin, a bypass bin, a conversion coefficient, a conversion coefficient level, a conversion coefficient level scanning method, a display / output order of an image, a slice identification information, At least one value, a combined form, or statistics of the type, the slice division information, the tile identification information, the tile type, the tile division information, the picture type, the bit depth, the information on the luminance signal and the information on the color difference signal is included in the coding parameters . The prediction scheme may represent one of an intra prediction mode and an inter prediction mode.

The residual signal may represent the 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 transforming 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 may include at least one of a deblocking filter, a sample adaptive offset (SAO), and an adaptive loop filter (ALF) It can be applied to a picture. 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 the luminance signal, information relating to whether or not to apply an adaptive loop filter can 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 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 prediction block are obtained, the decoding apparatus 200 can generate a 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 performing inverse quantization and inverse transform on the quantized coefficients, reconstructed residual blocks 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, and ALF 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.

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 can be fixed to M irrespective of the size of the block. 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 chrominance 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. 6, 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 can code residual blocks that are the 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 code residual blocks that are the 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 the merge candidate requiring 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 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 motion information items in the list can be specified through indexes on 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. &Quot; 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.

The quantized level can be generated by converting and / or quantizing 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) transformation 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 indicated.

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 in the vertical direction may be predetermined depending on the intra-prediction mode of the target block. 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 object block.

For 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 for each of the 1D directions (i.e., vertical and horizontal directions) as described above.

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) .

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

The primary conversion and the secondary conversion may be applied to at least one of a luminance component and a chrominance 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 the transform to be used for the primary transformation and / or the secondary transformation.

The quantized level can be generated by performing quantization on the result or residual signal generated by performing the primary conversion and / or the secondary conversion.

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 for 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. For the result generated by performing the inverse quantization, a second-order inverse transform can be performed depending on whether or not the second-order inverse transform is performed. In addition, for the result generated by performing the second-order inverse transform, the first-order inverse transform can be performed depending on whether or not the first-order inverse transform is performed. The restored 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. [

Quantization method and apparatus for perceptual image quality enhancement

Figure 18 shows traditional distortion and perceptual distortion according to an example.

In Fig. 18, the relationship between the bit rate and distortion of the video is shown.

As shown in Fig. 18, traditional distortion is represented as a curve. On the other hand, perceptual distortion is expressed in the form of stairs.

Perceptual distortion can be a distortion that video feels about the video in which the viewer is actually decoded and output.

For traditional distortion, statistically lossy regions and statistically lossless regions are shown.

For perceptual distortion, a perceptually lossy region and a perceptually lossless region are shown.

According to the perceptual distortion graph, the viewer can suddenly recognize a large distortion at a bit rate a. On the other hand, the viewer may not be aware that the degree of distortion varies between a point where the bit rate is a and a point where the bit rate is b. Therefore, it is advantageous in terms of the perceptual image quality to finely adjust the bit rate in the regions a to b and to perform encoding of the bit rate a if possible.

Furthermore, for video with a particularly low bit rate, fine adjustment to perceptual image quality may be required, depending on the principle of this perceptual distortion.

FIG. 19 is a graph showing a relationship between a quantization parameter and a quantization step of a fixed-rate step quantization method according to an example.

In the following embodiments, a plurality of quantization methods are described.

The plurality of quantization methods may include 1) a fixed-rate step quantization method and 2) a variable-rate step quantization method.

The fixed-rate step quantization method may be a fixed quantization method in which the rate of increase of the quantization step as the value of the quantization parameter increases by one. For example, the fixed step quantization method may be a quantization method in which the quantization step increases by about 12% each time the value of the quantization parameter increases by one.

For example, as shown in FIG. 19, when the fixed-rate step quantization method is used, when the quantization parameter is increased by 6, the quantization step can be doubled.

When the fixed-rate step quantization method is used, the amount of increase in the quantization step in the region where the value of the quantization parameter is relatively smaller may be smaller.

Hereinafter, the terms "increment of quantization step" and "increment of quantization step" can be used interchangeably and can be used interchangeably.

The region where the value of the quantization parameter is relatively smaller may generally be a high-quality region with a high bit rate. Therefore, when the fixed-rate step quantization method is used, a change in the perceptual image quality according to the change of the value of the quantization parameter in the range of high bit rate can be less. In addition, since there is less change in the perceptual image quality, it is easy to finely control the image quality, but the change in the image quality may be insignificant.

In addition, when the fixed-rate step quantization method is used, an increase amount of the quantization step in an area where the value of the quantization parameter is relatively larger may be larger.

The region where the value of the quantization parameter is relatively larger may generally be a low-bit-rate region with a low bit rate. Therefore, when the fixed-rate step quantization method is used, the change in the perceptual image quality according to the change of the value of the quantization parameter in the range of low bit rate may be larger. Also, since the perceptual image quality change is larger, it may be difficult to finely control the image quality.

The variable-rate step quantization method may be a quantization method in which the rate of increase of the quantization step as the value of the quantization parameter increases by one is not fixed. Alternatively, the variable-rate step quantization method may be a quantization method in which the rate of increase of the quantization step as the value of the quantization parameter increases by one, according to the value of the quantization parameter.

The perceptual image quality can be easily controlled in all the bit rate regions when the variable-rate step quantization method is used, because the rate of increase of the quantization step as the value of the quantization parameter increases by 1 according to the value of the quantization parameter. From this viewpoint, the variable-rate step quantization method can be regarded as a quantization method for perceptual image quality.

For example, the smaller the value of the quantization parameter, the larger the rate of increase of the quantization step of the variable-rate step quantization method as the value of the quantization parameter increases by one.

For example, in a region where the value of the quantization parameter is relatively small, the rate of increase of the quantization step of the variable-rate step quantization method may be larger than the rate of increase of the quantization step of the fixed-rate step quantization method.

For example, in an area where the value of the quantization parameter is relatively large, the rate of increase of the quantization step of the variable-rate step quantization method may be smaller than the rate of increase of the quantization step of the fixed-rate step quantization method.

20 is a graph showing a relationship between a quantization parameter and an SNR of a fixed-rate step quantization method according to an example.

FIG. 20 shows that the quantization parameter and the signal-to-noise ratio (SNR) of the fixed-rate step quantization method have a linear relationship. This relationship makes it possible to control the linearity, and the SNR can be easily controlled.

Hereinafter, the description of the quantization method can be applied to the inverse quantization method. Quantization and inverse quantization can be understood to correspond to each other as processes performed respectively in the encoding apparatus 100 and the decoding apparatus 200 for encoding and decoding a target block. For example, the plurality of dequantization methods may include a fixed-rate step dequantization method and a variable-rate step dequantization method. The description of the variable-rate step quantization method can also be applied to the variable-rate step inverse quantization method. The description of the fixed-rate step quantization method can also be applied to the fixed-rate step inverse quantization method.

21 is a flow diagram of a quantization method in accordance with an embodiment.

In step 2110, the quantization unit 140 may select a quantization method.

The quantization unit 140 can select a quantization method to be used for the transform coefficients of the target block among the plurality of quantization methods.

The plurality of quantization methods may include a fixed-rate step quantization method and a variable-rate step quantization method.

The quantization method indicator may indicate a selected one of a plurality of quantization methods.

Hereinafter, the selected quantization method may be a variable-rate step quantization method.

In step 2120, the quantization unit 140 may perform quantization using the selected quantization method.

The quantization unit 140 may generate a quantized transform coefficient level by performing quantization using the quantization method selected for the transform coefficient.

In step 2130, the entropy encoding unit 150 may store information about the quantization.

The entropy encoding unit 150 may generate a bitstream including information on quantization. Alternatively, the entropy encoding unit 150 may include information on quantization in the bitstream generated by the encoding apparatus 100. [

The information on the quantization may include 1) quantization method indicator information, 2) quantization parameter information, and 3) quantized transform coefficient level information.

The quantization method indicator information may indicate a quantization method indicator. The quantization parameter information may indicate a quantization parameter. The quantized transform coefficient level information may indicate a quantized transform coefficient level.

The entropy encoding unit 150 may generate quantization method indicator information by performing entropy encoding on the quantization method indicator. Quantization method indicator information may be generated between step 2110 and step 2120 and stored in a bitstream.

The entropy encoding unit 150 may generate quantization parameter information by performing entropy encoding on the quantization parameter. Quantization parameter information may be generated prior to step 2110, or between steps 2110 and 2120, and stored in the bitstream.

The entropy encoding unit 150 may perform entropy encoding on the quantized transform coefficient levels to generate quantized transform coefficient level information.

22 is a flowchart of a dequantization method according to an embodiment.

The entropy decoding unit 210 may receive the bitstream.

The bitstream may include information about a target block. The information on the target block may include information on the quantization.

As described above with reference to FIG. 21, the information on the quantization may include 1) quantization method indicator information, 2) quantization parameter information, and 3) quantized transform coefficient level information.

The quantization method indicator may be named an inverse quantization method indicator. In addition, the quantization parameter may be named as the inverse quantization parameter.

In step 2210, the entropy decoding unit 210 may obtain a quantization method indicator.

The quantization method indicator may indicate one inverse quantization method used for inverse quantization of a target block among a plurality of inverse quantization methods.

The entropy decoding unit 210 can obtain a quantization method indicator by performing entropy decoding on the quantization method indicator information.

In step 2220, the entropy decoding unit 210 may obtain a quantization parameter.

The quantization parameter may be used for inverse quantization on the target block.

The entropy decoding unit 210 may obtain the quantization parameter by performing entropy decoding on the quantization parameter information. Alternatively, the entropy decoding unit 210 may obtain a quantization parameter using a quantization parameter difference value to be described later.

In step 2230, the inverse quantization unit 220 may select an inverse quantization method.

The inverse quantization unit 220 can select an inverse quantization method indicated by the quantization method indicator among the plurality of inverse quantization methods.

In step 2240, the inverse quantization unit 220 may perform inverse quantization using the selected inverse quantization method.

The inverse quantization unit can perform inverse quantization using information on the target block and an inverse quantization method.

The inverse quantization unit 220 can generate the transform coefficients by performing inverse quantization using the inverse quantization method selected for the quantized transform coefficient level.

Fig. 23 shows a quantization step according to an example quantization parameter.

23 illustrates modeling of the relationship between quantization parameters and quantization steps in a variable-rate step quantization method.

In Fig. 23, the relationship between the quantization parameter and the quantization step of the fixed-rate step quantization method is shown as a graph.

In the graph, the x-axis represents the value of the quantization parameter of the fixed-rate step quantization method. and the y-axis represents the value of the quantization step.

In FIG. 23, the symbols " O " represent the values of the quantization step corresponding to the values of the quantization parameter, with respect to the integer values of the quantization parameter of the fixed-rate step quantization method. In other words, the coordinates of one symbol " O " may be (the value of the quantization parameter of the fixed-rate step quantization method, the value of the quantization step corresponding to the value of the quantization parameter of the fixed-rate step quantization method). The symbols " O " are shown above the integer positions of the x-axis because the value of the quantization parameter of the fixed-rate step quantization method is an integer and the x-axis of the graph represents the value of the quantization parameter of the fixed-rate step quantization method.

In FIG. 23, the symbols " X " represent the values of the quantization step corresponding to the integer values of the quantization parameter of the variable-rate step quantization method. Except that the symbol "X" is placed on the curve constituted by the symbols "O" (for comparison with the fixed-rate step quantization method). In other words, the x-coordinate of the symbol " X " may not represent the value of the quantization parameter of the variable-rate step quantization method. Two adjacent symbols " X " may correspond to integer values of a quantization parameter of a variable-rate step quantization method having a difference of one value.

As shown in FIG. 23, in the fixed-rate step quantization method, the quantization step can be constantly increased by about 12% as the value of the quantization parameter increases by one. That is to say, the difference between the quantization steps of the adjacent symbols " O " may be about 12%.

As shown in Fig. 23, the interval between symbols " X " may be wider than the interval between symbols " O " in the range where the value of the quantization parameter is relatively smaller. This may mean that the increment of the quantization step of adjacent symbols " X " is greater than the increment of the quantization step of adjacent symbols " O ". In other words, when the value of the quantization parameter is increased by 1 in a range where the value of the quantization parameter is relatively smaller, the amount of increase of the quantization step of the variable-rate step quantization method is smaller than that of the quantization step of the fixed- It can be big.

Also, in the range where the value of the quantization parameter is relatively larger, the interval between symbols " X " may be narrower than the interval between symbols " O ". This may mean that the increment of the quantization step of adjacent symbols " X " is smaller than the increment of the quantization step of adjacent symbols " O ". In other words, when the value of the quantization parameter is increased by 1 in a range where the value of the quantization parameter is relatively larger, the amount of increase of the quantization step of the variable-rate step quantization method is further increased compared with the amount of increase of the quantization step of the fixed- Can be small.

24 shows the quantization parameter and the quantization step rate according to an example.

In the graph of Fig. 24, the x-axis can indicate the value of the quantization parameter. and the y-axis can represent the value of the quantization step ratio. The quantization step rate may be the ratio between the quantization step of the variable-rate step quantization method and the quantization step of the fixed-rate step quantization method.

The quantization step rate may be derived by a function having a gamma function, a calorie function, or a form and / or characteristic similar to these functions.

According to the graph of Fig. 24, the quantization step rate is increased in the range where the value of the quantization parameter is relatively smaller. That is, the quantization step of the variable-rate step quantization method can be increased more rapidly than the quantization step of the fixed-rate step quantization method in the range where the value of the quantization parameter is relatively smaller.

Further, according to the graph of Fig. 24, the quantization step rate decreases in a range where the value of the quantization parameter is relatively larger. That is, the quantization step of the fixed-rate step quantization method can be increased more rapidly than the quantization step of the variable-rate step quantization method in a range where the value of the quantization parameter is relatively larger.

The quantization method according to perceptual image quality can be implemented by defining and / or adjusting the increasing rate of the value of the quantization step as the value of the quantization parameter is increased by 1 as described above. Such definition and / or adjustment may be carried out through the following methods 1) and 2) or the like.

1) A quantization parameter of the fixed-rate step quantization method corresponding to the quantization parameter of the variable-rate step quantization method is determined, and a quantization step corresponding to the determined quantization parameter of the fixed-rate step quantization method may be used for quantization.

2) According to the fixed-rate step quantization method, the quantization step corresponding to the quantization parameter is determined, and the quantization step for the variable-rate step quantization method can be determined by applying the quantization step rate to the determined quantization step. That is, the determined quantization step may be a product of the quantization step and the quantization step ratio of the fixed-rate step quantization method.

One example of a method for determining a quantization parameter of a fixed-rate step quantization method corresponding to a quantization parameter of a variable-rate step quantization method and using a quantization step corresponding to the determined quantization parameter of a fixed-rate step quantization method .

Hereinafter, the quantization parameter of the variable-rate step quantization method is denoted by QP _perceptual , and the quantization parameter of the fixed-rate step quantization method is denoted by QP .

In order to use the variable-rate step quantization method, which is a quantization method according to perceptual image quality, QP _perceptual and QP can be mapped to each other through various methods. In addition, the equation or relation between the QP and the quantization step used in the fixed-rate step quantization method can be defined and used. According to this mapping, and the relationship, the quantization staff corresponding to QP _perceptual and defined and / or can be derived according to QP _perceptual, there is quantization staff corresponding to the _perceptual QP may be used.

Equation 2 below is a gamma function representing the relationship between QP _perceptual and QP according to an example.

[Equation 2]

The QP _perceptual corresponding to the specified QP can be determined according to the relationship indicated by the gamma function of Equation (2).

When QP _perceptual is used for quantization and / or inverse quantization, the value of the QP corresponding to the value of QP _perceptual can be derived via a gamma function such as Equation 2. The gamma function may have gamma function parameters ([alpha], [gamma]). The value of QP corresponding to the value of QP _perceptual can be determined by the gamma function parameters (?,?).

The fixed predetermined values may be used in the encoding apparatus 100 and the decoding apparatus 200 as the gamma function parameters alpha and gamma. In other words, the encoding apparatus 100 and the decoding apparatus 200 may share the same gamma function parameters? And?.

Alternatively, the parameters? And? Of the gamma function can be signaled from the encoder 100 to the decoder 200 through the bitstream.

For example, the information about the quantization described above may include gamma function parameters information. The entropy encoding unit 150 may perform entropy encoding on the gamma function parameters of the gamma function to generate gamma function parameters information. The entropy decoding unit 210 may obtain gamma function parameters by performing entropy decoding on the gamma function parameters information.

Of the gamma function parameters, alpha may be a parameter that allows the value of QPs within an arbitrary range to be issued for the input QP _perceptual . alpha can have an integer value or a value scaled to an integer.

Of the parameters of the gamma function _,? May be a parameter that determines the QP corresponding to the input QP _perceptual . gamma can have an integer value or a value scaled to an integer.

In general, the QP may have an integer value in the range of 0 to 51. [ On the other hand, the value of the QP corresponding to the inputted QP _perceptual may be a real value within the range of 0 to 51. [ However, the value of the quantization step actually applied to the scaling of the transform coefficients may be an integer. The value of the quantization step may be a value approximated in the form of an integer through scaling. That is to say, although the value of the QP derived through the above-described method can be expressed as a real number, not an integer, the integer value of the quantization step can be determined in various ways.

For example, the value of the quantization step may be scaled and approximated to an integer value using a relational function between the QP and the quantization step. Alternatively, the value of the quantization step may be determined through a table look-up.

25 shows a table of quantization parameters and quantization steps of a variable-rate step quantization method according to an example.

In Fig. 25, values of a quantization parameter qP and a quantization step q_step used in quantization and inverse quantization using a variable-rate step quantization method are shown.

In Fig. 25, the value of the quantization step q_step for the value of the specified quantization parameter qP has been illustrated. For example, when the value of the quantization parameter is 0, the value of the quantization step may be 40.

QP and q_step shown in FIG. 25 may represent quantization steps corresponding to QP _perceptual and QP _perceptual , respectively. That is to say, the table shown in Fig. 25 can be used for the look-up to determine the value of the above quantization step.

The quantization parameter may be used for each unit for encoding and / or decoding a moving picture. For example, a quantization parameter may be determined for a slice. In the case of the luminance component, the quantization parameter determined for the slice may be SliceQpY. The quantization parameter qP for the target block in the slice can be determined by the quantization parameter determined for the slice.

The values of the quantization step corresponding to the quantization parameter qP can be determined by 1) a table look-up for a table such as that shown in FIG. 25, 2) a relation between the quantization parameters and the quantization step, and 3) .

For example, the value of the quantization step may be derived using a relational function of the quantization parameter and the increasing rate of the value of the quantization step.

For example, the value of the quantization step may be determined with reference to a predetermined value as shown in Fig. 25 through table look-up. The value of the quantization step may be determined through table look-up as shown in Equation 3 below.

[Equation 3]

q_step = q_step_table [qP]

Here, q_step_table can represent a table.

For example, the value of the quantization step may be determined as Equation 4 using a relational expression between the quantization parameter and the quantization step.

[Equation 4]

q_step = q_function (qP, param1, param2, ...)

The input parameters of q_function for determining the value of the quantization step are: 1) the value qP of the quantization parameter of the variable-rate step quantization method; and 2) the value qP of the quantization parameter of the variable-rate step quantization method as the value of the corresponding quantization step May be one or more parameters of the function to be transformed. For example, one or more of the parameters may be α and γ as described above.

As these input parameters are input, q_function can derive the value of the quantization step.

The q_function may be implemented as a fixed-point operation to determine the scaled value of the integer type of the quantization type for the value qP of the input quantization parameter.

The inverse quantization method using the value of the quantization step can be performed as the following Equation (5).

[Equation 5]

dq_transCoeffLevel = TransCoeffLevel * m * q_step

TransCoeffLevel may be one quantized transform coefficient. m may be a scaling factor. q_step may be a quantization step.

Scaling can be performed on the one quantized transform coefficient TransCoeffLevel by the scaling factor m.

The dequantized transform coefficient dq_transCoeffLevel may be a product of a scaled quantized transform coefficient and a quantization step q_step. Alternatively, the dequantized transform coefficient dq_transCoeffLevel may be a quantized transform coefficient TransCoeffLevel, a scaling factor m for the quantized transform coefficient, and a product of the quantization step.

The inverse quantized transform coefficients may be converted or determined to an integer type through an operation considering the data type of each value and the dynamic range of each value according to the implementation of the encoding apparatus 100 and the decoding apparatus 200 have. Here, the values may include TransCoeffLevel, m and q_step described above. The operation may include a clipping operation and a rounding operation.

The above-described dequantization may be performed by the inverse quantization unit 160 of the encoding apparatus 100 and / or the dequantization unit 220 of the decoding apparatus 200. [ Further, the quantization corresponding to the above-described inverse quantization can be performed by the quantization unit 140 of the encoding apparatus 100. [

26 shows the syntax of a set of video parameters according to an example.

27 shows the syntax of a sequence parameter set according to an example.

Figure 28 shows the syntax of a set of picture parameters according to an example.

29 shows the syntax of a slice segment header according to an example.

In performing the inverse quantization, the quantization method to be applied to the unit specified through the high-level syntax may be indicated. Here, the indicated quantization method may be one of a plurality of quantization methods. The higher level syntax may include a quantization method indicator and the quantization method indicator included in the higher level syntax may indicate a quantization method to be applied to the specified unit that is the object of the higher level syntax.

Alternatively, the high-level syntax may indicate whether a variable-rate step quantization method is applied to the specified unit. For example, the quantization method indicator included in the high-level syntax may indicate whether the variable-rate step quantization method is applied to the specified unit that is the object of the high-level syntax.

Alternatively, the high-level syntax may indicate a quantization method applied to the specified unit of a plurality of quantization methods for a specified unit.

For example, the specified unit may be a video, a sequence, a picture, or a slice.

For example, a video parameter set may indicate a quantization method to be applied to an object of a video parameter set. The video parameter set may include quantization method indicator information as described above. The quantization method indicator information may indicate a quantization method to be applied to the object of the video parameter set among the plurality of quantization methods. Alternatively, the quantization method indicator information may indicate whether a variable-rate step quantization method is applied to the object of the video parameter set.

As the quantization method indicator information for the video parameter set, vps_perceptual_qp_enabled_flag is illustrated in FIG. The quantization method indicator information may be a flag of 1 bit.

For example, the sequence parameter set may indicate a quantization method to be applied to the object of the sequence parameter set. The sequence parameter set may include the above-described quantization method indicator information. The quantization method indicator information may indicate a quantization method to be applied to a target of a sequence parameter set among a plurality of quantization methods. Alternatively, the quantization method indicator information may indicate whether a variable-rate step quantization method is applied to the object of the sequence parameter set.

As the quantization method indicator information for the sequence parameter set, sps_perceptual_qp_enabled_flag is illustrated in FIG. The quantization method indicator information may be a flag of 1 bit.

For example, a picture parameter set may indicate a quantization method to be applied to a target of a picture parameter set. The picture parameter set may include the quantization method indicator information described above. The quantization method indicator information may indicate a quantization method to be applied to a target of a picture parameter set among a plurality of quantization methods. Alternatively, the quantization method indicator information may indicate whether the variable-rate step quantization method is applied to the object of the picture parameter set.

As the quantization method indicator information for the picture parameter set, pps_perceptual_qp_enabled_flag is illustrated in FIG. The quantization method indicator information may be a flag of 1 bit.

For example, the slice segment header may indicate a quantization method to be applied to the object of the slice segment header. The slice segment header may include the quantization method indicator information described above. The quantization method indicator information may indicate a quantization method to be applied to the object of the slice segment header among the plurality of quantization methods. Alternatively, the quantization method indicator information may indicate whether the variable-rate step quantization method is applied to the object of the picture parameter set.

As the quantization method indicator information for the slice segment header, slice_segment_header_perceptual_qp_enabled_flag is illustrated in FIG. The quantization method indicator information may be a flag of 1 bit.

In performing the inverse quantization, a quantization parameter to be applied to the unit specified through the high-level syntax may be indicated. For example, the high-level syntax may be a video parameter set, a sequence parameter set, a picture parameter set, or a slice segment header.

For example, the video parameter set may include a quantization parameter applied to an object of the video parameter set. The sequence parameter set may include a quantization parameter applied to an object of the sequence parameter set. The picture parameter set may include a quantization parameter applied to the object of the picture parameter set. The slice segment header may include a quantization parameter applied to the object of the slice segment header.

The higher-level syntax may include additional syntax elements for variable-rate step dequantization if the value of the quantization method indicator information is a predefined value (e.g., " 1 "). Additional syntax elements may be used to construct the values used in the variable-rate step quantization method described above. For example, the additional syntax elements may include gamma function parameters ([alpha], [gamma]).

A specified number of bits may be required to indicate the quantization parameters of the variable-rate step quantization method. Instead of directly signaling the value of the quantization parameter to reduce the number of such required bits, alternative information indicating the value of the quantization parameter can be used instead. Such replacement information can be used for a specified unit, and can be included in a high-level syntax applied to the specified unit to be signaled by a specified unit. Alternatively, the information on quantization described above with reference to Figs. 21 and 22 may include such substitution information.

For example, the replacement information for indicating the value of the quantization parameter may be a quantization parameter difference value.

For example, the quantization parameter difference value may be the difference between the intermediate value and the value of the quantization parameter. The intermediate value may be a value in the middle of the range of the quantization parameter of the variable-rate step quantization method.

The quantization unit 140 may generate quantization parameter difference value information by performing entropy encoding on a quantization parameter difference value using a signed exponential Golomb.

Alternatively, the quantization parameter difference value may be a difference between a value of the quantization parameter of the upper unit and a value of the quantization parameter of the lower unit. For example, the upper unit may be a picture, and the lower unit may be a slice. The quantization parameter values of each unit can be signaled through the Signed Exponential Golomb method described above. The quantization parameter obtained using the quantization parameter difference value may be used for quantization on the sub-unit.

The quantization parameter difference value may be included in the header of the lower unit.

For the target picture, the picture quantization parameter difference value information can be signaled. For example, the picture parameter set may include a picture quantization parameter difference value. The picture quantization parameter difference value may be information used to derive the quantization parameter applied to the picture.

Also, slice quantization parameter difference value information may be signaled for each slice of one or more slices of the target picture. The slice header of each slice may contain a slice quantization parameter difference value.

The slice quantization parameter difference value may indicate the difference between the value of the quantization parameter applied to the picture and the value of the quantization parameter applied to the 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)

A step of performing quantization using a quantization method
Lt; / RTI >
The quantization method is a variable-rate step quantization method,
Wherein the variable-rate step quantization method is a quantization method in which an increase rate of a quantization step is not fixed as the value of a quantization parameter increases by one. The method according to claim 1,
Wherein the rate of increase of the quantization step of the variable-rate step quantization method as the value of the quantization parameter increases by a smaller value of the quantization parameter is larger. The method according to claim 1,
Selecting the quantization method among the plurality of quantization methods
Further comprising:
Wherein the plurality of quantization methods comprise a fixed-rate step quantization method and the variable-rate step quantization method,
Wherein the fixed-rate step quantization method is a fixed quantization method in which the rate of increase of the quantization step as the value of the quantization parameter is incremented by one. The method of claim 3,
Wherein the rate of increase of the quantization step of the variable-rate step quantization method is smaller than the rate of increase of the quantization step of the fixed-rate step quantization method in an area where the value of the quantization parameter is relatively larger. Performing inverse quantization using the inverse quantization method
Lt; / RTI >
Wherein the inverse quantization method is a variable-rate step inverse quantization method,
Wherein the variable-rate step inverse quantization method is a dequantization method in which an increment rate of a quantization step is not fixed as the value of a quantization parameter increases by one. 6. The method of claim 5,
Wherein the rate of increase of the quantization step of the variable-rate step dequantization method as the value of the quantization parameter increases by a smaller value of the quantization parameter is larger. 6. The method of claim 5,
Selecting the inverse quantization method among the plurality of inverse quantization methods
Further comprising:
Wherein the plurality of dequantization methods include a fixed-rate step dequantization method and the variable-rate step dequantization method,
Wherein the fixed rate step inverse quantization method is a fixed inverse quantization method in which the rate of increase of the quantization step is fixed as the value of the quantization parameter is incremented by one. 8. The method of claim 7,
Wherein the rate of increase of the quantization step of the variable-rate step dequantization method is smaller than the rate of increase of the quantization step of the fixed-rate step dequantization method in an area where the value of the quantization parameter is relatively larger. 8. The method of claim 7,
The quantization parameter of the fixed-rate step dequantization method corresponding to the quantization parameter of the variable-rate step dequantization method is determined,
Wherein a quantization step corresponding to a quantization parameter of the fixed-rate step dequantization method is used for the inverse quantization. 8. The method of claim 7,
Wherein the quantization step of the fixed-rate step dequantization method corresponding to the quantization parameter is determined according to the fixed-rate step dequantization method, and the quantization step ratio is applied to the quantization step of the fixed-rate step dequantization method, The quantization step for the variable-rate step inverse quantization method is determined,
Wherein the quantization step rate is a ratio between a quantization step of the variable-rate step inverse quantization method and a quantization step of the fixed-rate step inverse quantization method. 6. The method of claim 5,
Obtaining a quantization method indicator
Further comprising:
Wherein the quantization method indicator indicates one inverse quantization method used for inverse quantization of a target block among the plurality of inverse quantization methods. 12. The method of claim 11,
Wherein the quantization method indicator indicates a dequantization method applied to a specified unit. 13. The method of claim 12,
Wherein the specified unit is a video, a sequence, a picture, or a slice. 13. The method of claim 12,
Wherein the quantization method indicator indicates whether the variable-rate step inverse quantization method is applied to the specified unit. 6. The method of claim 5,
Obtaining a quantization parameter using the quantization parameter difference value
Further comprising:
Wherein the quantization parameter is used for the inverse quantization,
Wherein the quantization parameter difference value is a difference between an intermediate value and a value of the quantization parameter,
Wherein said intermediate value is a value intermediate the range of quantization parameters of the variable-rate step dequantization method. 6. The method of claim 5,
Wherein the quantization parameter is applied to a specified unit. 6. The method of claim 5,
Obtaining a quantization parameter using the quantization parameter difference value
Further comprising:
Wherein the quantization parameter difference value is a difference between a value of a quantization parameter of an upper unit and a value of a quantization parameter of a lower unit,
Wherein the obtained quantization parameter is used for the inverse quantization for the lower unit. 18. The method of claim 17,
Wherein the quantization parameter difference value is included in the header of the lower unit. 18. The method of claim 17,
Wherein the upper unit is a picture and the lower unit is a slice. A computer-readable recording medium storing a bitstream for decoding an image,
Information about the target block
Lt; / RTI >
Information on the target block and inverse quantization using the inverse quantization method are performed,
Wherein the inverse quantization method is a variable-rate step inverse quantization method,
Wherein the variable-rate step inverse quantization method is an inverse quantization method in which an increase rate of a quantization step is not fixed as the value of a quantization parameter increases by one.

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