KR102365937B1 - Method and apparatus for encoding/decoding a video signal - Google Patents

Abstract

A video signal decoding method according to the present invention includes decoding information indicating whether a current block is encoded using a multi-intra prediction mode, and when it is determined that the current block is encoded in a multi-intra prediction mode, the current block partitioning into a plurality of partial blocks, and obtaining an intra prediction mode of each of the plurality of partial blocks.

Description

Video signal encoding/decoding method and apparatus

The present invention relates to a method and apparatus for encoding/decoding a video signal.

Recently, the demand for multimedia data such as moving pictures is rapidly increasing on the Internet. However, it is difficult to keep up with the rapidly increasing amount of multimedia data at the rate of development of the bandwidth of the channel.

A main object of the present invention is to improve image compression efficiency by using a multiple intra prediction mode in encoding/decoding an image.

A main object of the present invention is to improve image compression efficiency by efficiently encoding/decoding multiple intra prediction modes of an encoding/decoding target block in encoding/decoding an image.

A video signal decoding method and apparatus according to the present invention decodes information indicating whether a current block is encoded using a multi-intra-prediction mode, and when it is determined that the current block is encoded in a multi-intra-prediction mode, the current A block may be divided into a plurality of partial blocks, and an intra prediction mode of each of the plurality of partial blocks may be obtained.

In an image signal decoding method and apparatus according to the present invention, when the current block is divided into a plurality of partial blocks, an inflection point is determined among pixels surrounding the current block, and slope information is obtained based on the plurality of pixels surrounding the inflection point. obtained, and based on the inflection point and the slope information, it is possible to determine a division form of the current block.

In the video signal decoding method and apparatus according to the present invention, the inflection point is determined based on an inflection value of each of the neighboring pixels, and the inflection value is based on a difference value between neighboring pixels adjacent to the neighboring pixel can be created by

A video signal decoding method and apparatus according to the present invention, when obtaining the intra prediction mode of each of the plurality of partial blocks, obtains a first intra prediction mode of a first partial block, and obtains the first intra prediction mode and the second intra prediction mode A difference value between second intra prediction modes of partial blocks may be decoded, and the second intra prediction mode may be obtained based on the difference value.

In the method and apparatus for decoding an image signal according to the present invention, the intra prediction mode of each of the plurality of partial blocks may have different values.

A video signal encoding method and apparatus according to the present invention determines whether a current block is encoded in a multi-intra-prediction mode, and receives information indicating whether the current block uses a multi-intra-prediction mode based on a result of the determination encoding, and when the current block is set to use a multiple intra prediction mode, the current block may be divided into a plurality of partial blocks, and an intra prediction mode of each of the plurality of partial blocks may be determined.

An image signal encoding method and apparatus according to the present invention, when dividing the current block into a plurality of partial blocks, determine an inflection point among pixels surrounding the current block, and obtain gradient information based on the plurality of pixels around the inflection point obtained, and based on the inflection point and the slope information, it is possible to determine a division form of the current block.

In the video signal encoding method and apparatus according to the present invention, the inflection point is determined based on an inflection value of each of the neighboring pixels, and the inflection value is based on a difference value between neighboring pixels adjacent to the neighboring pixel. can be created by

In a video signal encoding method and apparatus according to the present invention, a first intra prediction mode of a first partial block among the plurality of partial blocks is determined, and a second intra prediction mode of a first partial block of the plurality of partial blocks is determined. and a difference value between the first intra prediction mode and the second intra prediction mode may be encoded.

In the video signal encoding method and apparatus according to the present invention, the intra prediction mode of each of the plurality of partial blocks may have different values.

According to the present invention, image compression efficiency can be improved by using the multiple intra prediction mode.

According to the present invention, image compression efficiency can be improved by efficiently encoding/decoding multiple intra prediction modes of an encoding/decoding target block.

1 is a block diagram illustrating an image encoding apparatus according to an embodiment of the present invention.
2 is a block diagram illustrating an image decoding apparatus according to an embodiment of the present invention.
3 is a diagram for explaining an intra prediction method using a DC mode.
4 is a diagram for explaining an intra prediction method using a planar mode.
5 is a diagram for explaining an intra prediction method using a directional prediction mode.
6 is a flowchart illustrating a process of determining whether to use a multi-intra prediction mode in an encoding process.
7 is a diagram for explaining an example of searching for an inflection point.
8 is a diagram illustrating a division shape according to the shape of a current block.
9 is a diagram for explaining an example of calculating inclination information of neighboring pixels.
10 is a diagram illustrating an example in which an overlapping area is generated according to a division form of a current block.
11 is a flowchart illustrating a process of encoding an intra prediction mode of a partial block.
12 is a flowchart illustrating a method of encoding an intra prediction mode using an MPM candidate.
13 is a diagram illustrating determining an MPM candidate of a current block.
14 is a flowchart illustrating a method of decoding an intra prediction mode of a current block.
15 is a flowchart illustrating a process of decoding an intra prediction mode of a current block using an MPM candidate.

Since the present invention can have various changes and can have various embodiments, specific embodiments are illustrated in the drawings and described in detail in the detailed description. However, this is not intended to limit the present invention to specific embodiments, and it should be understood to include all modifications, equivalents and substitutes included in the spirit and scope of the present invention. In describing each figure, like reference numerals have been used for like elements.

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

When a component is referred to as being “connected” or “connected” to another component, it is understood that the other component may be directly connected or connected to the other component, but other components may exist in between. it should be On the other hand, when it is mentioned that a certain element is "directly connected" or "directly connected" to another element, it should be understood that no other element is present in the middle.

The terms used in the present application are only used to describe specific embodiments, and are not intended to limit the present invention. The singular expression includes the plural expression unless the context clearly dictates otherwise. In the present application, terms such as “comprise” or “have” are intended to designate that a feature, number, step, operation, component, part, or combination thereof described in the specification exists, but one or more other features It should be understood that this does not preclude the existence or addition of numbers, steps, operations, components, parts, or combinations thereof.

Hereinafter, preferred embodiments of the present invention will be described in more detail with reference to the accompanying drawings. Hereinafter, the same reference numerals are used for the same components in the drawings, and repeated descriptions of the same components are omitted.

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

Referring to FIG. 1 , the image encoding apparatus 100 includes a picture division unit 110 , prediction units 120 and 125 , a transform unit 130 , a quantization unit 135 , a rearrangement unit 160 , and an entropy encoding unit ( 165 ), an inverse quantization unit 140 , an inverse transform unit 145 , a filter unit 150 , and a memory 155 .

Each of the constituent units shown in FIG. 1 is independently illustrated to represent different characteristic functions in the image encoding apparatus, and does not mean that each constituent unit is composed of separate hardware or one software constituent unit. That is, each component is listed as each component for convenience of description, and at least two components of each component are combined to form one component, or one component can be divided into a plurality of components to perform a function, and each of these components Integrated embodiments and separate embodiments of the components are also included in the scope of the present invention without departing from the essence of the present invention.

In addition, some of the components are not essential components for performing essential functions in the present invention, but may be optional components for merely improving performance. The present invention can be implemented by including only essential components to implement the essence of the present invention, except for components used for performance improvement, and a structure including only essential components excluding optional components used for performance improvement Also included in the scope of the present invention.

The picture divider 110 may divide the input picture into at least one block. In this case, a block may mean a coding unit (CU), a prediction unit (PU), or a transformation unit (TU). The division may be performed based on at least one of a quadtree and a binary tree. The quad tree divides the upper block into lower blocks whose width and height are half that of the upper block. Binary tree is a method of dividing the upper block into lower blocks whose either width or height is half that of the upper block. Through the binary tree-based partitioning described above, a block may have a non-square shape as well as a square shape.

Hereinafter, in an embodiment of the present invention, a coding unit may be used as a unit for performing encoding or may be used as a meaning for a unit for performing decoding.

The prediction units 120 and 125 may include an inter prediction unit 120 performing inter prediction and an intra prediction unit 125 performing intra prediction. Whether to use inter prediction or to perform intra prediction for a prediction unit may be determined, and specific information (eg, intra prediction mode, motion vector, reference picture, etc.) according to each prediction method may be determined. In this case, a processing unit in which prediction is performed and a processing unit in which a prediction method and specific content are determined may be different. For example, a prediction method and a prediction mode may be determined in a prediction unit, and prediction may be performed in a transformation unit.

The encoding apparatus may determine the optimal prediction mode for the coding block by using various techniques, such as rate-distortion optimization (RDO) on the residual block obtained by subtracting the original block and the prediction block. As an example, RDO may be determined by Equation 1 below.

In Equation 1, D denotes degradation due to quantization, R denotes a rate of a compressed stream, and J denotes RD cost. In addition, Φ denotes a coding mode, and λ denotes a Lagrangian multiplier. λ may be used as a scale correction coefficient for matching the unit between the amount of error and the amount of bits. During the encoding process, the encoding apparatus may determine a mode having the minimum RD cost value as the optimal mode for the encoding block. In this case, the RD-cost value is calculated by considering the bit rate and the error simultaneously.

Among intra prediction modes, a DC mode, which is a non-directional prediction mode (or a non-angle prediction mode), uses an average value of neighboring pixels of the current block. 3 is a diagram for explaining an intra prediction method using a DC mode.

After filling the prediction block with the average value of neighboring pixels, filtering may be performed on pixels located at the boundary of the prediction block. For example, weighted sum filtering with neighboring reference pixels may be applied to pixels located at the left or upper boundary of the prediction block. As an example, Equation 2 is a diagram illustrating an example of generating a prediction pixel through a DC mode for each zone. In Equation 1 below, regions R1, R2, and R3 are regions located at the outermost (ie, boundary) of the prediction block, and weighted sum filtering may be applied to pixels included in the region.

In Equation 2, Wid denotes the horizontal length of the prediction block, and Hei denotes the vertical length of the prediction block. x and y mean the coordinate positions of each prediction pixel when the upper leftmost point of the prediction block is set to (0,0). R stands for surrounding pixels. For example, when the s pixel shown in FIG. 3 is defined as R[-1][-1], the pixels a to i are represented by R[0][-1] to R[8][-1]. Pixels j to r can be expressed as R[-1][0] to R[-1][8]. In the example shown in FIG. 3 , the predicted pixel value Pred is obtained according to the weighted sum filtering method as in Equation 2 for each region R1 to R4.

Among the non-directional modes, the planar mode is a method of generating prediction pixels of the current block by linearly interpolating pixels surrounding the current block according to distances. As an example, FIG. 4 is a diagram for explaining an intra prediction method using a planar mode.

For example, it is assumed that Pred shown in FIG. 4 is to be predicted in an 8x8 coding block. In this case, the e-pixel above Pred and the r pixel at the bottom left of Pred are copied to the bottom of Pred, and the vertical prediction value can be obtained by linear interpolation according to the distance in the vertical direction. Also, by copying the n-pixels on the left of Pred and i-pixels on the upper right of Pred to the far right of Pred, the horizontal prediction value can be obtained by linear interpolation according to the distance in the horizontal direction. Thereafter, the average value of the horizontal and vertical predicted values may be determined as the value of Pred. Equation 3 is a formula for calculating the predicted value Pred under the planner mode.

In Equation 3, Wid denotes the horizontal length of the prediction block, and Hei denotes the vertical length of the prediction block. x and y mean the coordinate positions of each prediction pixel when the upper leftmost point of the prediction block is set as (0, 0). R stands for surrounding pixels. For example, when the s pixel shown in FIG. 4 is defined as R[-1][-1], the pixels a to i are represented by R[0][-1] to R[8][-1]. Pixels j to r can be expressed as R[-1][0] to R[-1][8].

5 is a diagram for explaining an intra prediction method using a directional prediction mode.

The directional prediction mode (or angle prediction mode) is a method of generating at least one or more pixels located in any one of N predetermined directions among neighboring pixels of the current block as prediction samples.

The directional prediction mode may include a horizontal mode and a vertical mode. Here, the horizontal mode means modes having a greater horizontal direction than the angle prediction mode oriented at 45 degrees to the upper left, and the vertical mode means modes having a greater vertical direction than the angle prediction mode oriented to the upper left at 45 degrees. A directional prediction mode having a prediction direction directed in a 45 degree direction to the upper left may be treated as a horizontal mode or a vertical mode. In Fig. 5, a landscape mode and a portrait mode are shown.

Referring to FIG. 5 , there are also directions that do not match the integer pixel portion in each direction. In this case, various interpolation methods such as a linear interpolation method, DCT-IF method, and cubic convolution interpolation method according to the distance between neighboring pixels and pixels After interpolation using , the pixel value may be put into a pixel position corresponding to the direction of the prediction block.

A residual value (residual block or transform block) between the generated prediction block and the original block may be input to the transform unit 130 . The residual block is the smallest unit for transform and quantization processes. The coding block partitioning method may also be applied to the transform block. As an example, the transform block may be divided into 4 or 2 partial blocks.

Prediction mode information, motion vector information, etc. used for prediction may be encoded in the entropy encoder 165 together with a residual value and transmitted to a decoder. When a specific encoding mode is used, the original block may be encoded and transmitted to the decoder without generating the prediction block through the predictors 120 and 125 .

The inter prediction unit 120 may predict a prediction unit based on information on at least one of a picture before or after the current picture, and in some cases, prediction based on information of a partial region in the current picture that has been encoded Units can also be predicted. The inter prediction unit 120 may include a reference picture interpolator, a motion prediction unit, and a motion compensator.

The reference picture interpolator may receive reference picture information from the memory 155 and generate pixel information of integer pixels or less in the reference picture. In the case of luminance pixels, a DCT-based 8-tap interpolation filter in which filter coefficients are different to generate pixel information of integer pixels or less in units of 1/4 pixels may be used. In the case of the color difference signal, a DCT-based 4-tap interpolation filter in which filter coefficients are different to generate pixel information of integer pixels or less in units of 1/8 pixels may be used.

The motion prediction unit may perform motion prediction based on the reference picture interpolated by the reference picture interpolator. As a method for calculating the motion vector, various methods such as Full search-based Block Matching Algorithm (FBMA), Three Step Search (TSS), and New Three-Step Search Algorithm (NTS) may be used. The motion vector may have a motion vector value of 1/2 or 1/4 pixel unit based on the interpolated pixel. The motion prediction unit may predict the current prediction unit by using a different motion prediction method. As the motion prediction method, various methods such as a skip method, a merge method, and an AMVP (Advanced Motion Vector Prediction) method may be used.

The encoding apparatus may generate motion information of the current block based on motion estimation or motion information of a neighboring block. Here, the motion information may include at least one of a motion vector, a reference image index, and a prediction direction.

The intra prediction unit 125 may generate a prediction unit based on reference pixel information around the current block, which is pixel information in the current picture. When the neighboring block of the current prediction unit is a block on which inter prediction is performed, and thus the reference pixel is a pixel on which inter prediction is performed, the reference pixel included in the block on which the inter prediction is performed is a reference pixel of the block on which the intra prediction is performed. information can be used instead. That is, when the reference pixel is not available, the unavailable reference pixel information may be replaced with at least one reference pixel among the available reference pixels.

In intra prediction, the prediction mode may have a directional prediction mode in which reference pixel information is used according to a prediction direction and a non-directional mode in which directional information is not used when prediction is performed. A mode for predicting luminance information and a mode for predicting chrominance information may be different, and intra prediction mode information used for predicting luminance information or predicted luminance signal information may be utilized to predict chrominance information.

The intra prediction method may generate a prediction block after applying an adaptive intra smoothing (AIS) filter to a reference pixel according to a prediction mode. The type of AIS filter applied to the reference pixel may be different. In order to perform the intra prediction method, the intra prediction mode of the current prediction unit may be predicted from the intra prediction mode of the prediction unit existing around the current prediction unit. When the prediction mode of the current prediction unit is predicted using mode information predicted from the neighboring prediction unit, if the intra prediction mode of the current prediction unit and the neighboring prediction unit are the same, the current prediction unit and the neighboring prediction unit are used using predetermined flag information It is possible to transmit information indicating that the prediction modes of , and if the prediction modes of the current prediction unit and the neighboring prediction units are different from each other, entropy encoding may be performed to encode the prediction mode information of the current block.

In addition, a residual block including residual information that is a difference value from the original block of the prediction unit and the prediction unit in which prediction is performed based on the prediction unit generated by the prediction units 120 and 125 may be generated. The generated residual block may be input to the transform unit 130 .

The transform unit 130 transforms the residual signal into the frequency domain to generate a residual block (or transform block) having transform coefficients. Here, in order to transform the residual signal into the frequency domain, various transform techniques such as a discrete cosine transform (DCT)-based transform, a discrete sine transform (DST), and a Karhunen Loeve transform (KLT) may be used. . In order to conveniently use the transformation method, matrix operation is performed using a basis vector. In this case, various transformation techniques may be mixed and used during matrix operation according to which prediction mode the prediction block is encoded. For example, in intra prediction, a discrete cosine transform may be used in a horizontal direction and a discrete sine transform may be used in a vertical direction depending on the prediction mode.

The quantization unit 135 may quantize values transformed in the frequency domain by the transform unit 130 . That is, the quantization unit 135 may generate a quantized transform block having the quantized transform coefficient by quantizing the transform coefficients of the transform block generated by the transform unit 130 . Here, the quantization technique may include Dead Zone Uniform Threshold Quantization (DZUTQ) or Quantization Weighted Matrix. An improved quantization technique that improves these quantization techniques may be used. The quantization coefficient may vary according to blocks or the importance of an image. The value calculated by the quantization unit 135 may be provided to the inverse quantization unit 140 and the rearrangement unit 160 .

The transform unit 130 and/or the quantizer 135 may be selectively included in the image encoding apparatus 100 . That is, the image encoding apparatus 100 may encode the residual block by performing at least one of transform or quantization on the residual data of the residual block, or skipping both transform and quantization. Even if either transform or quantization is not performed in the image encoding apparatus 100, or neither transform nor quantization is performed, a block entering the input of the entropy encoder 165 is generally referred to as a transform block (or quantized transform block). refers to

The rearrangement unit 160 may rearrange the coefficient values on the quantized residual values.

The rearrangement unit 160 may change the two-dimensional block form coefficient into a one-dimensional vector form through a coefficient scanning method. For example, the reordering unit 160 may scan from DC coefficients to coefficients in a high frequency region using a predetermined scan type, and may change it into a one-dimensional vector form.

The entropy encoding unit 165 may perform entropy encoding based on the values calculated by the reordering unit 160 . For entropy encoding, various encoding methods such as Exponential Golomb, Context-Adaptive Variable Length Coding (CAVLC), and Context-Adaptive Binary Arithmetic Coding (CABAC) may be used.

The entropy encoder 165 receives the residual value coefficient information, block type information, prediction mode information, division unit information, prediction unit information and transmission unit information, motion of the coding unit from the reordering unit 160 and the prediction units 120 and 125 . Various information such as vector information, reference frame information, interpolation information of a block, and filtering information may be encoded. In the entropy encoding unit 165, coefficients of the transform block are encoded in units of subblocks within the transform block, and various kinds of flags indicating non-zero coefficients, coefficients having an absolute value greater than 1 or 2, and signs of coefficients are encoded. can be Coefficients that are not encoded using only the flag may be encoded using an absolute value of a difference between a coefficient encoded through the flag and a coefficient of an actual transform block.

The entropy encoder 165 may entropy-encode the coefficient values of the coding units input from the reordering unit 160 .

The inverse quantizer 140 and the inverse transform unit 145 inversely quantize the values quantized by the quantizer 135 and inversely transform the values transformed by the transform unit 130 .

Meanwhile, the inverse quantization unit 140 and the inverse transform unit 145 may perform inverse quantization and inverse transformation by inversely using the quantization method and the transformation method used by the quantization unit 135 and the transform unit 130 . In addition, when the transform unit 130 and the quantizer 135 perform only quantization and no transform, only inverse quantization and no inverse transform may be performed. If neither transform nor quantization is performed, the inverse quantization unit 140 and the inverse transform unit 145 may not perform both inverse transform and inverse quantization or may be omitted from being included in the image encoding apparatus 100 .

The residual values generated by the inverse quantizer 140 and the inverse transform unit 145 are combined with the prediction units predicted through the motion estimation unit, the motion compensator, and the intra prediction unit included in the prediction units 120 and 125 and restored. You can create a Reconstructed Block.

The filter unit 150 may include at least one of a deblocking filter, an offset correcting unit, and an adaptive loop filter (ALF).

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

The offset correcting unit may correct an offset from the original image in units of pixels with respect to the image on which the deblocking has been performed. In order to perform offset correction on a specific picture, a method of dividing pixels included in an image into a certain number of regions, determining the region to be offset and applying the offset to the region, or taking edge information of each pixel into account can be used to apply

Adaptive loop filtering (ALF) may be performed based on a value obtained by comparing the filtered reconstructed image and the original image. After dividing the pixels included in the image into a predetermined group, one filter to be applied to the corresponding group is determined, and filtering can be performed differentially for each group. As for information related to whether to apply ALF, the luminance signal may be transmitted for each coding unit (CU), and the shape and filter coefficients of the ALF filter to be applied may vary according to each block. In addition, the ALF filter of the same type (fixed type) may be applied regardless of the characteristics of the block to be applied.

The memory 155 may store the reconstructed block or picture calculated through the filter unit 150 , and the stored reconstructed block or picture may be provided to the predictors 120 and 125 when inter prediction is performed.

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

Referring to FIG. 2 , the image decoder 200 includes an entropy decoding unit 210, a reordering unit 215, an inverse quantization unit 220, an inverse transform unit 225, prediction units 230 and 235, and a filter unit ( 240) and a memory 245 may be included.

When an image bitstream is input from an image encoder, the input bitstream may be decoded by a procedure opposite to that of the image encoder.

The entropy decoding unit 210 may perform entropy decoding in a procedure opposite to that performed by the entropy encoding unit of the image encoder. For example, various methods such as Exponential Golomb, Context-Adaptive Variable Length Coding (CAVLC), and Context-Adaptive Binary Arithmetic Coding (CABAC) may be applied corresponding to the method performed by the image encoder. In the entropy decoding unit 210, the coefficients of the transform block are based on various kinds of flags indicating non-zero coefficients, coefficients with absolute values greater than 1 or 2, and signs of coefficients in units of partial blocks within the transform block. can be decrypted as Coefficients that are not expressed only by the flag may be decoded through the sum of the coefficients expressed through the flags and the signaled coefficients.

The entropy decoder 210 may decode information related to intra prediction and inter prediction performed by the encoder.

The reordering unit 215 may perform rearrangement based on a method of rearranging the entropy-decoded bitstream by the entropy decoding unit 210 by the encoder. Coefficients expressed in the form of a one-dimensional vector may be restored and rearranged as coefficients in the form of a two-dimensional block. The reordering unit 215 may receive information related to the coefficient scanning performed by the encoder and perform the rearrangement by performing a reverse scanning method based on the scanning order performed by the corresponding encoder.

The inverse quantization unit 220 may perform inverse quantization based on the quantization parameter provided by the encoder and the reordered coefficient values of the blocks.

The inverse transform unit 225 may perform inverse transform on the inverse quantized transform coefficient using a predetermined transform method. In this case, the transformation method may be determined based on information about a prediction method (inter/intra prediction), a size/shape of a block, an intra prediction mode, and the like.

The prediction units 230 and 235 may generate a prediction block based on the prediction block generation related information provided from the entropy decoding unit 210 and previously decoded block or picture information provided from the memory 245 .

The prediction units 230 and 235 may include a prediction unit determiner, an inter prediction unit, and an intra prediction unit. The prediction unit determiner receives various information such as prediction unit information input from the entropy decoder 210, prediction mode information of the intra prediction method, and motion prediction related information of the inter prediction method, and divides the prediction unit from the current coding unit, and predicts It may be determined whether the unit performs inter prediction or intra prediction. The inter prediction unit 230 uses information required for inter prediction of the current prediction unit provided from the image encoder, and predicts the current based on information included in at least one picture before or after the current picture including the current prediction unit. Inter prediction may be performed on a unit. Alternatively, inter prediction may be performed based on information on a pre-restored partial region in the current picture including the current prediction unit.

In order to perform inter prediction, based on the coding unit, it is determined whether the motion prediction method of the prediction unit included in the corresponding coding unit is a skip mode, a merge mode, or an AMVP mode. can judge

The intra prediction unit 235 may generate a prediction block based on pixel information in the current picture. When the prediction unit is a prediction unit on which intra prediction is performed, intra prediction may be performed based on intra prediction mode information of the prediction unit provided by the image encoder. The intra prediction unit 235 may include an adaptive intra smoothing (AIS) filter, a reference pixel interpolator, and a DC filter. The AIS filter is a part that performs filtering on the reference pixel of the current block, and can be applied by determining whether to apply the filter according to the prediction mode of the current prediction unit. AIS filtering may be performed on the reference pixel of the current block by using the prediction mode and AIS filter information of the prediction unit provided by the image encoder. When the prediction mode of the current block is a mode in which AIS filtering is not performed, the AIS filter may not be applied.

When the prediction mode of the prediction unit is a prediction unit in which intra prediction is performed based on a pixel value obtained by interpolating the reference pixel, the reference pixel interpolator may interpolate the reference pixel to generate a reference pixel of a pixel unit having an integer value or less. When the prediction mode of the current prediction unit is a prediction mode that generates a prediction block without interpolating the reference pixel, the reference pixel may not be interpolated. The DC filter may generate a prediction block through filtering when the prediction mode of the current block is the DC mode.

The reconstructed block or picture may be provided to the filter unit 240 . The filter unit 240 may include a deblocking filter, an offset correcting unit, and an ALF.

Information on whether a deblocking filter is applied to a corresponding block or picture and information on whether a strong filter or a weak filter is applied when the deblocking filter is applied may be provided from the video encoder. The deblocking filter of the image decoder may receive deblocking filter-related information provided from the image encoder, and the image decoder may perform deblocking filtering on the corresponding block.

The offset correction unit may perform offset correction on the reconstructed image based on the type of offset correction applied to the image during encoding and information on the offset value.

ALF may be applied to a coding unit based on information on whether ALF is applied, ALF coefficient information, etc. provided from the encoder. Such ALF information may be provided by being included in a specific parameter set.

The memory 245 may store the reconstructed picture or block to be used as a reference picture or reference block, and may also provide the reconstructed picture to an output unit.

A coding block may be divided into at least one prediction block, and each prediction block may be divided into at least one or more partial blocks (or prediction partial blocks) through an additional division process. In this case, each partial block may be encoded using different intra prediction modes. That is, the coding block or the prediction block may be divided into a plurality of prediction blocks or a plurality of partial blocks using a multiple intra prediction mode (or multiple modes). The prediction block may be divided into a plurality of partial blocks according to a preset pattern. In this case, the segmentation form of the prediction block may be preset and used in an image encoding apparatus and an image decoding apparatus.

Hereinafter, encoding/decoding of multiple intra prediction mode information will be described in detail with reference to the drawings.

6 is a flowchart illustrating a process of determining whether to use a multi-intra prediction mode in an encoding process. In this embodiment, it is assumed that the current block represents a prediction block currently encoded in the intra prediction mode. In some cases, the current block may mean a partial block generated by splitting a coding block, a transform block, or a prediction block.

First, the encoding apparatus may search for a point (hereinafter, referred to as an 'inflection point') at which a pixel value significantly changes among neighboring pixels adjacent to the current block ( S601 ). The inflection point may mean a point at which a pixel value change between a neighboring pixel and a neighboring pixel adjacent to the neighboring pixel is equal to or greater than a preset threshold, or a point at which a pixel value change between a neighboring pixel and a neighboring pixel neighboring the neighboring pixel is greatest. there is.

7 is a diagram for explaining an example of searching for an inflection point. For convenience of description, it is assumed that the current block is a 4x4 prediction block.

The encoding apparatus may calculate a pixel value change degree (hereinafter, referred to as an 'inflection value') for each of the neighboring pixels adjacent to the current block. The inflection value may be calculated based on a change amount (or a difference value) between a neighboring pixel adjacent to the current block and a neighboring pixel adjacent to the neighboring pixel, or a change amount (or a difference value) between neighboring pixels adjacent to the neighboring pixel.

Here, the neighboring pixels adjacent to the current block include pixels adjacent to the upper boundary of the current block, pixels adjacent to the left boundary of the current block, and pixels adjacent to corners (eg, upper left corner, upper right corner, and lower left corner) of the current block. may include at least one of For example, in the example shown in FIG. 7 , a to k are exemplified as neighboring pixels of the current block.

As another example, the encoding apparatus may configure a pixel adjacent to a corner of the current block among neighboring pixels adjacent to the current block (eg, a pixel adjacent to an upper-left corner of the current block, a pixel adjacent to a lower-left corner of the current block, or an upper-right corner of the current block) The inflection value may be calculated with respect to the remaining neighboring pixels except for at least one of the pixels adjacent to . Alternatively, the encoding apparatus may calculate the inflection value for the remaining neighboring pixels except for the rightmost pixel or the lowest pixel among neighboring pixels adjacent to the current block. For example, in the example shown in FIG. 7 , the encoding apparatus may calculate an inflection value for the remaining pixels excluding pixels f and k among pixels a to k.

The number or range of neighboring pixels may vary according to the size and shape of the current prediction block. Accordingly, according to the size and shape of the current block, the number or range of neighboring pixels for which the inflection value is calculated may also vary.

Equation 4 shows an example of a method for calculating an inflection value.

In Equation 4, the current neighboring pixel represents a neighboring pixel to be calculated inflection value among neighboring pixels adjacent to the current block. The inflection value of the current neighboring pixel may be calculated as a value obtained by taking an absolute value from a difference between neighboring neighboring pixels adjacent to the current neighboring pixel. As an example, the inflection value of the neighboring pixels adjacent to the upper end of the current block (eg, pixels 'b to e' of FIG. 7 ) is a difference between the neighboring pixel adjacent to the left side of the neighboring pixel and the neighboring pixel adjacent to the right side of the neighboring pixel It can be calculated based on the value. The inflection value of the neighboring pixels adjacent to the left side of the current block (eg, pixels 'g to j' in FIG. 7 ) is based on a difference value between the neighboring pixel adjacent to the upper end of the neighboring pixel and the neighboring pixel adjacent to the lower end of the neighboring pixel can be calculated by In addition, the neighboring pixel adjacent to the upper left corner of the current block (eg, pixel 'a' in FIG. 7 ) is to be calculated based on a difference value between the neighboring pixel adjacent to the lower end of the neighboring pixel and the neighboring pixel adjacent to the right of the neighboring pixel. can

As described above, some of the neighboring pixels of the current block (eg, pixels that are not adjacent to the boundary of the current block, f and k among the neighboring pixels) may be excluded from calculation of the inflection value. Inflection values of neighboring pixels of the current block, which are excluded from calculation of inflection values, may be set to a preset value (eg, 0).

When the calculation of the inflection values for the neighboring pixels is completed, the encoding apparatus may select an inflection point based on the calculated inflection values. As an example, the encoding apparatus may set a neighboring pixel having the largest inflection value or a neighboring pixel having the largest inflection value among neighboring pixels having an inflection value equal to or greater than a threshold value as the inflection point. For example, in the example illustrated in FIG. 7 , when the inflection value of the neighboring pixel b is the maximum, the encoding apparatus may set the point 'O' illustrated in FIG. 7 as the inflection point.

When there are a plurality of neighboring pixels having the same maximum inflection value, the encoding device recalculates the inflection value for the plurality of neighboring pixels or selects any one of the plurality of neighboring pixels based on a preset priority It can be selected as an inflection point.

For example, when there are a plurality of neighboring pixels having the same maximum inflection value, the encoding apparatus may recalculate the inflection values of the corresponding inflection points, but may adjust the number or positions of neighboring pixels used when the inflection value is recalculated. For example, when recalculating the inflection value of the neighboring pixel, the encoding apparatus may increase the number of neighboring pixels adjacent to the neighboring pixel by one in both directions (or unidirectional). Accordingly, when the neighboring pixel having the maximum inflection value is the neighboring pixel adjacent to the upper end of the current block, using two neighboring pixels adjacent to the left side of the neighboring pixel and two neighboring pixels adjacent to the right side of the neighboring pixel, Inflection values of neighboring pixels may be recalculated.

As another example, when a plurality of neighboring pixels having the same maximum inflection value exist, the encoding apparatus may select a neighboring pixel close to the pixel at a specific position as the inflection point. For example, the encoding apparatus may give a higher priority to an inflection point closer to the upper left peripheral pixel of the current block.

As another example, when a plurality of neighboring pixels having the same maximum inflection value exist, the encoding apparatus recalculates the inflection values of the corresponding inflection points and determines the inflection point based on the reselected inflection value, even though the inflection value is reselected. , when there are a plurality of neighboring pixels having the maximum inflection value, the inflection point may be selected based on priority.

In the above-described example, it has been described that the inflection point is determined based on the neighboring pixel adjacent to the current block and the neighboring pixels adjacent to the neighboring pixel. Unlike the described example, the inflection point may be determined based on encoding parameters of neighboring blocks adjacent to the current block. Here, the encoding parameters are parameters used to encode neighboring blocks, and may include prediction-related information such as an intra prediction mode and a motion vector. As an example, the inflection point is when the difference in intra prediction modes between neighboring blocks neighboring the current block is equal to or greater than a preset threshold or when the difference in motion vectors between neighboring blocks neighboring the current block is equal to or greater than a preset threshold, etc. Block boundaries can also be set as inflection points. As described above, when the difference in encoding parameters between neighboring blocks is large, it can be predicted that a sudden change occurs at the boundary of the neighboring blocks, so that encoding/decoding efficiency can be improved by using the boundary of the neighboring blocks as an inflection point. The decoding apparatus may also determine the inflection point by using the encoding parameters of the neighboring blocks.

When the inflection point is determined, the encoding apparatus may determine a division form of the current block based on the inflection point ( S602 ).

8 is a diagram illustrating a division shape according to the shape of a current block.

In the example shown in FIG. 8 , the current block may be divided into two or more partial blocks according to at least one reference line. In this case, a partial block generated by dividing the current block may have a triangular or trapezoidal shape as well as a rectangular shape. Identifier 801 of FIG. 8 exemplifies that 18 dividing lines (or 18 division shapes) may exist when the current block has a square shape, and IDs 802 and 803 of FIG. 8 indicate that the current block has a rectangular shape In this case, it is exemplified that it can have 20 dividing lines (or 20 dividing lines). However, the division form of the current block is not limited to the illustrated example. In addition to those shown, various types of diagonal division or bipartite division may be applied.

The encoding apparatus may select a dividing line having the determined inflection point as a starting point or a dividing line having a starting point closest to the determined inflection point, and divide the current block according to the selected dividing line. For example, when the position of the inflection point does not coincide with the left or upper starting point of the dividing line, the encoding apparatus may change the position of the inflection point to the closest starting point of the dividing line.

Thereafter, the encoding apparatus may calculate gradient information of pixels around the inflection point in order to determine how to divide the current block from the inflection point.

As an example, FIG. 9 is a diagram for explaining an example of calculating inclination information of neighboring pixels. For convenience of description, it is assumed that the size of the current block is 4x4 and the inflection point is b1.

The encoding apparatus may calculate gradient information by using the N pixels selected based on the inflection point. For example, as in the example shown in FIG. 9 , the encoding apparatus may configure a 3x3 block including the inflection point b1, and calculate gradient information based on pixels included in the configured 3x3 block.

When the inflection point of the current block is a neighboring pixel located at the top of the current block, the inflection point may be included in the lowest row of the 3x3 block. On the other hand, when the inflection point of the current block is a neighboring pixel located on the left side of the current block, the inflection point may be included in the rightmost column of the 3x3 block. That is, when the inflection point of the current block is located at the top, the 3x3 block may be configured with pixels surrounding the inflection point and pixels located in the upper direction of the inflection point. On the other hand, when the inflection point of the current block exists on the left, a 3x3 block may be configured with pixels surrounding the inflection point and pixels located in the left direction of the inflection point.

The encoding apparatus may calculate a horizontal gradient and a vertical gradient by using neighboring pixels adjacent to the inflection point, and may calculate gradient information on the current block based on the horizontal gradient and the vertical gradient. As an example, Equation 5 shows a series of processes for calculating slope information.

In Equation 5, f _x (x, y) represents the degree of inclination in the horizontal direction, and f _y (x, y) represents the degree of inclination in the vertical direction. The gradient of the current block may be obtained by taking the arc tangent to a horizontal gradient value with respect to a vertical gradient value. The direction of the outline of the current block can be known through the gradient value of the current block.

In the above-described example, it has been described that the gradient value is calculated based on the neighboring pixels adjacent to the current block and the neighboring pixels adjacent to the neighboring pixels. As another example, the slope of the current block may be determined based on encoding parameters of neighboring blocks adjacent to the current block. As an example, the gradient value may be determined based on intra prediction modes (or intra prediction mode angles) of neighboring blocks around the inflection point or motion vectors of neighboring blocks around the inflection point. When the inflection point is located at the boundary between the neighboring blocks, the encoding apparatus may encode index information indicating which block of the neighboring blocks located at the inflection point will use the encoding parameter to determine the gradient value. Here, the index information may be information indicating any one of the neighboring blocks.

When the gradient of the current block is calculated, the encoding apparatus may determine an optimal partitioning form for the current block in consideration of the position of the inflection point and the degree of inclination. Here, the optimal division form is a dividing line having an inclination angle coincident with the inclination angle of the current block among dividing lines using the inflection point of the current block as a starting point, or a dividing line having an inclination angle most similar to the inclination angle of the current block ( That is, a dividing line having an inclination angle with a minimum difference from the inclination angle of the current block) may be used. In this case, when there are a plurality of division types having a slope angle most similar to the slope angle of the current block, the encoding apparatus may select a division type having a higher priority according to a preset priority.

The encoding apparatus may encode information for determining the division form of the current block, and transmit the encoded information to the decoding apparatus through a bitstream. Information for determining the splitting form of the current block may be encoded in units of prediction blocks or through higher headers. Here, the upper header may mean a coding block layer, a slice layer, a picture layer, a sequence layer, a video layer, and the like.

The information for determining the partition shape of the current block may include at least one of an index for identifying the partition shape of the current block, location of an inflection point, or slope information. For example, the position of the inflection point may be encoded in units of prediction blocks or through higher headers and transmitted to the decoding apparatus.

As another example, the decoding apparatus may determine the splitting form of the current block in the same way as the encoding apparatus. For example, the decoding apparatus derives an inflection point based on the amount of change in pixel values between neighboring blocks, calculates gradient information using N pixels around the induced inflection point, and then selects any one of the preset division patterns. The division type of the current block may be determined.

In this case, the encoding apparatus encodes information on whether to use the multiple intra prediction mode (that is, whether to perform intra prediction by dividing one current block into a plurality of partial blocks), and transmits the encoded information through the bitstream. can be transmitted The decoding apparatus may encode the information and divide the current block into a plurality of partial blocks only when the information indicates that intra prediction is to be performed by dividing the current block into a plurality of partial blocks.

When the partitioning form of the current block is determined, the encoding apparatus may determine an intra prediction mode for each partial block included in the current block ( S603 ). In this case, the encoding apparatus may allocate different intra prediction modes to each partial block.

The encoding apparatus determines the intra prediction mode of each partial block included in the current block based on a Rate Distortion-Cost calculated by performing Rate Distortion Optimization (RDO) for each intra prediction mode on the partial block. can decide As an example, the encoding apparatus may determine the intra prediction mode in which the RD-cost value for each partial block included in the current block is minimized as the intra prediction mode of each partial block.

In performing RDO, the encoding apparatus may calculate the RD-cost value for all available intra prediction modes or calculate the RD-cost value for some intra prediction modes. Some intra prediction modes may be set and used in the same manner in the image encoding apparatus and the image decoding apparatus. Alternatively, some intra prediction modes may include only the intra prediction mode using only reference pixels adjacent to the current block.

As another example, some intra prediction modes may include at least one of an intra prediction mode of a neighboring block adjacent to the current block and a preset additional intra prediction mode. As an example, when the intra prediction mode of the neighboring block is the non-directional mode, RDO is selected by selecting all non-directional modes and some directional prediction modes with high selection frequency (eg, vertical prediction mode, horizontal prediction mode, etc.) as candidates. can be done Alternatively, when the intra-prediction mode of the neighboring block is the directional mode, all non-asymmetric prediction modes and the intra-prediction mode of the neighboring block and the intra-prediction mode having a similar direction to the intra-prediction mode of the neighboring block (eg, the intra-prediction mode of the neighboring block) RDO may be performed by selecting an intra prediction mode (with a difference of equal to or less than a threshold) as a candidate.

The encoding apparatus may perform intra prediction on the current block by using the selected intra prediction mode. In this case, if the current block is divided into partial blocks by an oblique line, the dividing line does not coincide with the pixel boundary, and overlapping pixels (ie, overlapping regions) may appear between the partial blocks.

As an example, FIG. 10 is a diagram illustrating an example in which an overlapping area is generated according to a division form of a current block.

In the case of blocks corresponding to the identification codes 1001 and 1002 shown in FIG. 10, since the dividing line coincides with the pixel boundary, overlapping regions between partial blocks do not occur. However, in the case of the blocks corresponding to the identification codes 1003 to 1005, there is a portion where the dividing line does not coincide with the pixel boundary (ie, the portion passing through the pixel), so that the overlapping pixels between the partial blocks (ie, the overlapping region) can be seen to exist.

As such, when there is an overlapping region between partial blocks, the prediction value of a pixel included in the overlapping region may be obtained through an average of prediction values generated as a result of intra prediction of partial blocks including the overlapping region or linear interpolation of the predicted values. there is. For example, if it is assumed that the current block is divided into a first partial block and a second partial block, a prediction value of a pixel commonly included in the first partial block and the second partial block is based on the intra prediction mode of the first partial block. It may be determined as an average value between the first prediction value calculated using the , and the second prediction value calculated using the intra prediction mode of the second partial block, or a value obtained by linearly interpolating the first prediction value and the second prediction value.

As another example, the prediction value of the pixel included in the overlapping region may be generated using an intra prediction mode of any one of the partial blocks including the overlapping region. In this case, which block of the partial blocks to use may be determined based on a predetermined priority between partial blocks, a predetermined priority between intra prediction modes, or a position of a pixel included in an overlapping area, and the like. For example, the prediction value of the pixel included in the overlapping region may be generated using a preset priority among intra prediction modes of partial blocks including the overlapping region.

Next, the encoding apparatus for encoding the intra prediction mode for each partial block will be described in detail.

11 is a flowchart illustrating a process of encoding an intra prediction mode of a partial block. For convenience of description, intra prediction modes of partial blocks are divided into a main prediction mode and a sub prediction mode. Here, the main prediction mode may indicate an intra prediction mode of any one of the partial blocks, and the sub prediction mode may indicate the intra prediction mode of the other one of the partial blocks. Alternatively, the main prediction mode and the sub-prediction mode may be determined according to the priority of the intra prediction mode, the size of the partial block, the position of the partial block, the size of the partial block, and the like. The sub-prediction mode may be determined as an intra-prediction mode different from the main prediction mode.

First, the encoding apparatus may encode motion information for multi-intra prediction (S1101). Here, the multi-mode operation information indicates whether it is optimal to use a single intra prediction mode or to use a plurality of intra prediction modes for the current block.

When the multiple intra prediction mode is true ( S1102 ), the encoding apparatus may encode the intra prediction mode determined as the main prediction mode ( S1103 ), and then encode the intra prediction mode determined as the sub prediction mode ( S1104 ). The main prediction mode may be encoded through an encoding process using a Most Probable Mode (MPM) candidate or may be encoded without using an MPM candidate. The sub-prediction mode may be encoded through an encoding process using an MPM candidate or may be encoded without using an MPM candidate.

The encoding apparatus may encode a difference value between the main prediction mode and the sub-prediction mode. As an example, the encoding apparatus may encode the main prediction mode by using the MPM candidate as the main prediction mode, and may encode a difference value between the main prediction mode and the sub-prediction mode. In this case, the decoding apparatus may derive the main prediction mode using the MPM candidate and obtain the sub-prediction mode through a difference value between the main prediction mode and the sub-prediction mode.

When the multiple intra prediction mode is false (S1102), the encoding apparatus may encode a single intra prediction mode for the current block (S1105). As an example, the encoding apparatus may encode the intra prediction mode for the current block by using the MPM candidate.

Based on FIG. 12 , encoding of an intra prediction mode for a current block using an MPM candidate will be described in detail.

12 is a flowchart illustrating a method of encoding an intra prediction mode using an MPM candidate. In this embodiment, the intra prediction mode of the current block may mean any one of a main prediction mode, a sub prediction mode, or a single prediction mode.

Referring to FIG. 12 , first, the encoding apparatus may determine an MPM candidate for the current block ( S1201 ). The encoding apparatus may determine an MPM candidate of the current block based on intra prediction modes of neighboring blocks adjacent to the current block.

As an example, FIG. 13 is a diagram illustrating determining an MPM candidate of a current block. In FIG. 13 , L denotes an intra prediction mode with the highest frequency of use among intra prediction modes of left neighboring blocks adjacent to the left of the current block, and A denotes the frequency of use among intra prediction modes of upper neighboring blocks adjacent to the top of the current block. Indicates the highest intra prediction mode. Alternatively, L may indicate an intra prediction mode of a left neighboring block of a specific position, and A may indicate an intra prediction mode of an upper neighboring block of a specific position.

In FIG. 13 , there are three MPM candidates of the current block, and the three MPM candidates are an intra prediction mode (ie, L-1, L+1) in a direction similar to L, A, and L, and a non-directional mode (Planar, DC). ) and a preset directional mode (vertical mode). However, according to the illustrated example, the present invention is not limited, and the MPM candidate of the current block may be generated by a method different from that illustrated. As an example, the MPM candidates of the current block may include more than three.

If a neighboring block adjacent to the current block is encoded in the multiple intra prediction mode, the MPM candidate of the current block may be determined by considering all the multiple intra prediction modes of the neighboring block, or only one of the multiple intra prediction modes of the neighboring block It may be decided by considering As an example, the MPM candidate of the current block may be determined in consideration of a main prediction mode among multiple intra prediction modes of a neighboring block.

Alternatively, the MPM candidate for the main prediction mode of the current block may be determined using the main prediction mode of the neighboring block, and the MPM candidate for the sub-prediction mode of the current block may be determined using the sub-prediction mode of the neighboring block. .

The encoding apparatus may determine whether an MPM candidate identical to the intra prediction mode of the current block exists, and may encode motion information according to the determination result (S1202). Here, the operation information may be a 1-bit flag (eg, an MPM flag). For example, when the same MPM candidate as the intra prediction mode of the current block exists, the encoding apparatus encodes the MPM flag as 'true', and when the same MPM candidate as the intra prediction mode of the current block does not exist, the encoding apparatus MPM flag can be encoded as 'false'.

When the same MPM candidate as the intra prediction mode of the current block exists (S1203), the encoding apparatus may encode index information specifying the same MPM candidate as the intra prediction mode of the current block (S1204).

When the same MPM candidate as the intra prediction mode of the current block does not exist ( S1203 ), the encoding apparatus may encode a residual mode indicating an optimal intra prediction mode for the current block among residual intra prediction modes except for the MPM candidate. (S1205). Specifically, the encoding apparatus may encode the residual mode by allocating bits as many as the number of residual intra prediction modes obtained by subtracting the number of MPM candidates from among all intra prediction modes (or intra prediction modes usable by the current block).

Since the sub-prediction mode is set to a value different from that of the main prediction mode, the residual mode for the sub-prediction mode may be encoded based on the residual intra prediction mode except for the MPM candidate and the main prediction mode.

Next, a method of decoding the optimal intra prediction mode in the decoding apparatus will be described.

14 is a flowchart illustrating a method of decoding an intra prediction mode of a current block.

Referring to FIG. 14 , first, the decoding apparatus may decode multi-mode operation information from a bitstream (S1401). Here, the multi-mode operation information indicates whether the current block is encoded using the multi-intra prediction mode.

When it is determined that the current block is encoded using the multi-intra prediction mode ( S1402 ), the decoding apparatus may divide the current block into a plurality of partial blocks. Here, the decoding apparatus may divide the current block based on block division pattern information signaled from the encoding apparatus, calculate an inflection point and a slope, and select a division pattern corresponding to the calculated inflection point and slope to divide the current block can also be split.

When the current block is divided into a plurality of partial blocks, the decoding apparatus may decode the main prediction mode for the current block (S1403), and then decode the sub-prediction mode (S1404). As described above in the encoding process, the main prediction mode or the sub-prediction mode may be decoded using the MPM candidate or may be decoded without using the MPM candidate. Alternatively, after decoding the main prediction mode, the sub-prediction mode may be obtained based on a difference value between the main prediction mode and the sub-prediction mode.

When it is determined that the current block is encoded without using the multiple intra prediction mode, the decoding apparatus may decode a single intra prediction mode for the current block ( S1405 ). Here, a single intra prediction mode for the current block may be decoded using an MPM candidate.

15 is a flowchart illustrating a process of decoding an intra prediction mode of a current block using an MPM candidate. In this embodiment, the intra prediction mode of the current block may mean any one of a main prediction mode, a sub prediction mode, or a single prediction mode.

First, the decoding apparatus may determine an MPM candidate for the current block (S1501). Specifically, the decoding apparatus may determine the MPM candidate based on intra prediction modes of neighboring blocks adjacent to the current block. Since the generation of the MPM candidate of the current block has been described in detail with reference to FIG. 13 , a detailed description thereof will be omitted at this stage.

Thereafter, the decoding apparatus may decode information indicating whether an MPM candidate identical to the intra prediction mode of the current block exists ( S1502 ). The information may be a 1-bit flag, but is not limited thereto.

When it is determined that the same MPM candidate as the intra prediction mode of the current block exists (S1503), the decoding apparatus may decode information (eg, MPM index information) specifying the same MPM candidate as the intra prediction mode of the current block. (S1504). In this case, the intra prediction mode of the current block may be determined as the intra prediction mode specified by the MPM index information.

On the other hand, when it is determined that the same MPM candidate as the intra prediction mode of the current block does not exist (S1503), the decoding apparatus decodes residual mode information (S1505), and based on the decoded residual mode information, An intra prediction mode may be determined. Here, the residual mode information may be coded except for the MPM candidate among intra prediction modes available for the current block.

Example methods of the present disclosure are expressed as a series of operations for clarity of description, but this is not intended to limit the order in which the steps are performed, and if necessary, each step may be performed simultaneously or in a different order. In order to implement the method according to the present disclosure, other steps may be included in addition to the illustrated steps, other steps may be excluded from some steps, or additional other steps may be included except some steps.

Various embodiments of the present disclosure do not list all possible combinations, but are intended to describe representative aspects of the present disclosure, and matters described in various embodiments may be applied independently or in combination of two or more.

In addition, various embodiments of the present disclosure may be implemented by hardware, firmware, software, or a combination thereof. For implementation by hardware, one or more Application Specific Integrated Circuits (ASICs), Digital Signal Processors (DSPs), Digital Signal Processing Devices (DSPDs), Programmable Logic Devices (PLDs), Field Programmable Gate Arrays (FPGAs), general purpose It may be implemented by a processor (general processor), a controller, a microcontroller, a microprocessor, and the like.

The scope of the present disclosure includes software or machine-executable instructions (eg, operating system, application, firmware, program, etc.) that cause an operation according to the method of various embodiments to be executed on a device or computer, and such software or and non-transitory computer-readable media in which instructions and the like are stored and executable on a device or computer.

Claims (10)

determining a dividing line for dividing the current block; Here, the dividing line is determined by any one of a plurality of dividing line candidates pre-defined in the image decoding apparatus, and each of the dividing line candidates is distinguished by at least one of a predetermined slope or position;
dividing the current block into two or more partial blocks based on the determined dividing line; and
Using the prediction information for each of the partial blocks, comprising the step of generating a prediction block of the current block,
The prediction information includes first prediction information for predicting a first partial block of the current block and second prediction information for predicting a second partial block of the current block,
The method of claim 1, wherein the first prediction information is determined based on index information signaled through a bitstream, and the second prediction information is determined based on the first prediction information. The method of claim 1,
The shape of at least one of the partial blocks of the current block is a triangle. The method of claim 1,
Further comprising the step of obtaining information for determining the division form of the current block from the bitstream,
The dividing line is determined based on information for determining a division type of the current block. 4. The method of claim 3,
The information for determining the division form of the current block specifies at least one of a slope or a position of the division line. 5. The method of claim 4,
The number of inclinations of the dividing line candidates pre-defined in the image decoding apparatus is 20, the image signal decoding method. The method of claim 1,
The predicted value of the pixel located on the dividing line is determined as an average value of the first predicted value of the first partial block and the second predicted value of the second partial block. delete determining a dividing line for dividing the current block; wherein the dividing line is determined by any one of a plurality of dividing line candidates pre-defined in the image encoding apparatus, and each of the dividing line candidates is distinguished by at least one of a predetermined slope or position;
dividing the current block into two or more partial blocks based on the determined dividing line; and
Using the prediction information for each of the partial blocks, comprising the step of generating a prediction block of the current block,
The prediction information includes first prediction information for predicting a first partial block of the current block and second prediction information for predicting a second partial block of the current block,
Index information for determining the first prediction information is encoded, and the second prediction information is determined based on the first prediction information. A computer-readable recording medium storing a bitstream, comprising:
The bitstream includes a coded residual coefficient of a residual block obtained based on a prediction block of the current block,
The prediction block of the current block is generated using prediction information on each of the partial blocks of the current block,
The partial blocks are blocks in which the current block is divided into two or more parts based on a dividing line,
The dividing line is any one of a plurality of dividing line candidates pre-defined in the video encoding apparatus;
Each of the dividing line candidates is distinguished by at least one of a predetermined slope or position,
The prediction information includes first prediction information for predicting a first partial block of the current block and second prediction information for predicting a second partial block of the current block,
The first prediction information is determined based on index information included in the bitstream, and the second prediction information is determined based on the first prediction information. delete

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