KR102635240B1 - Method and apparatus for encoding/decoding an image - Google Patents

Abstract

The video encoding/decoding method and device according to the present invention selects at least one reference pixel line from a plurality of reference pixel lines, and based on at least one pixel value included in the selected at least one reference pixel line, A predicted value of one pixel in the current block may be derived, and filtering may be performed on one or more pixels in the prediction block based on at least one reference pixel in the plurality of reference pixel lines.

Description

Video encoding/decoding method and device {METHOD AND APPARATUS FOR ENCODING/DECODING AN IMAGE}

The present invention relates to a method and device for encoding/decoding video signals, and more specifically, to a method and device for encoding/decoding video signals using improved intra-prediction.

Recently, demand for multimedia data such as video is rapidly increasing on the Internet. However, the speed at which channel bandwidth develops is difficult to keep up with the rapidly increasing amount of multimedia data. To solve this problem, ITU-T's VCEG (Video Coding Expert Group), an international standardization organization, and ISO/IEC's MPEG (Moving Picture Expert Group) are continuously researching improved video compression standards through joint research.

Video compression largely consists of intra-screen prediction, inter-screen prediction, transformation, quantization, entropy coding, and in-loop filter. Among these, intra-screen prediction refers to a technology that generates a prediction block for the current block using restored pixels existing around the current block.

Conventional intra-screen prediction generates pixels at fractional positions through an interpolation process using reference pixels at integer positions, and generates a prediction block using the pixels at fractional positions thus generated. At this time, the error between the original pixel value and the predicted value is affected depending on which integer position reference pixels are used and which interpolation method is applied.

The main purpose of the present invention is to improve the efficiency of intra prediction by performing intra prediction using a plurality of reference pixel lines when encoding/decoding an image.

The main purpose of the present invention is to improve the efficiency of intra prediction by deriving an intra prediction block using an interpolation method selected from a plurality of interpolation methods when encoding/decoding an image.

The main purpose of the present invention is to provide a filtering method that can reduce discontinuity between an intra prediction block and a surrounding area when intra prediction is performed using a plurality of reference pixel lines when encoding/decoding an image.

The method and device for decoding an image according to the present invention include selecting at least one reference pixel line from among a plurality of reference pixel lines, and decoding the current image based on at least one pixel value included in the selected at least one reference pixel line. The predicted value of one pixel within a block can be derived.

The method and device for decoding an image according to the present invention obtains reference pixel line index information from an input bitstream and, based on the reference pixel line index information, selects the at least one reference pixel line from among the plurality of reference pixel lines. You can choose.

*The video decoding method and device according to the present invention can select at least one reference pixel line for each pixel in the current block based on the position of each pixel in the current block.

The video decoding method and device according to the present invention select one of a plurality of interpolation methods, and perform interpolation using the selected interpolation method and at least one pixel included in the selected at least one reference pixel line. The above predicted value can be obtained by performing: The selected interpolation method may be selected based on index information indicating one of a plurality of interpolation methods.

The method and device for decoding an image according to the present invention can obtain a prediction block of the current block by deriving predicted values of all pixels of the current block, and filter the prediction block.

The video decoding method and device according to the present invention can filter a predetermined area of the current block according to the size of the current block or the intra prediction mode of the current block.

The method and device for encoding an image according to the present invention include selecting at least one reference pixel line from a plurality of reference pixel lines, and encoding the current image based on at least one pixel value included in the selected at least one reference pixel line. The predicted value of one pixel within a block can be obtained.

*The video encoding method and device according to the present invention can encode reference pixel line index information indicating the selected at least one reference pixel line, and include the encoded reference pixel line index information in a bitstream.

The video encoding method and device according to the present invention can select at least one reference pixel line for each pixel in the current block based on the position of each pixel in the current block.

The video encoding method and device according to the present invention can select at least one reference pixel line for each pixel in the current block based on the intra prediction mode of the current block.

The video encoding method and device according to the present invention select one of a plurality of interpolation methods and perform interpolation using the selected interpolation method and at least one pixel included in the selected at least one reference pixel line. The above predicted value can be obtained by performing:

The video encoding method and device according to the present invention, Index information representing one of the plurality of interpolation methods can be encoded and included in the bitstream.

The video encoding method and device according to the present invention can obtain a prediction block of the current block by deriving the prediction values of all pixels of the current block, and then filter the prediction block.

The video encoding method and device according to the present invention can filter a predetermined area of the current block according to the size of the current block or the intra prediction mode of the current block.

According to the present invention, by applying a more effective intra prediction technology, the compression efficiency of the video and the quality of the reproduced video can be improved. In addition, the image quality of the reproduced image can be improved by applying a filtering method that can reduce discontinuity between the intra prediction block and the surrounding area according to the present invention.

Figure 1 is a block diagram showing a video encoding device according to an embodiment of the present invention.
Figure 2 is a diagram for explaining an example of an intra prediction mode.
Figure 3 is a diagram for explaining the planar mode.
Figure 4 is a diagram for explaining DC mode.
Figure 5 is a diagram for explaining an example of generating a prediction block.
Figure 6 is a block diagram showing an image decoding device according to an embodiment of the present invention.
FIGS. 7A and 7B are diagrams for explaining a method of deriving predicted pixels within a screen using interpolation.
Figure 8 is a diagram for explaining an interpolation method or an implicit method of selecting interpolation coefficients.
Figure 9 is a flowchart explaining the process of selecting an intra-prediction mode by a video encoding device.
FIG. 10 is a flowchart illustrating a process in which one of a plurality of interpolation methods is selected by a video encoding device.
Figure 11 is a flowchart explaining the process of encoding interpolation method index information by a video encoding device.
Figure 12 is a flowchart explaining the process of decoding interpolation method index information by a video decoding device.
FIG. 13 is a diagram illustrating the derivation of a prediction pixel within a screen using a plurality of reference pixel lines, according to an embodiment of the present invention.
Figure 14 is a flowchart for explaining the process of deriving the predicted pixel value within the screen, according to an embodiment of the present invention.
FIG. 15 is a flowchart illustrating a process for adaptively determining a reference pixel line to be used for intra prediction for each prediction block.
Figure 16 is a flowchart showing a process in which reference pixel line index information is encoded by an image encoding device.
Figure 17 is a flowchart showing the process of decoding reference pixel line index information by an image decoding device.
18 and 19 are diagrams for explaining a method of determining a reference pixel line without transmitting a reference pixel line index.
Figure 20 is a diagram for explaining smoothing between a prediction block and a reference pixel line.
Figure 21 shows a case where a common reference pixel line is used for all transform blocks within the current block.
Figures 22a to 22d show a case where a reference pixel line is selected for each transform block and used for intra prediction.

Since the present invention can make various changes and have various embodiments, specific embodiments will be 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 should be understood to include all changes, equivalents, and substitutes included in the spirit and technical scope of the present invention. While describing each drawing, similar reference numerals are used for similar components.

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

When a component is said to be "connected" or "connected" to another component, it is understood that it may be directly connected to or connected to the other component, but that other components may exist in between. It should be. On the other hand, when it is mentioned that a component is “directly connected” or “directly connected” to another component, it should be understood that there are no other components in between.

The terms used in this application are only used to describe specific embodiments and are not intended to limit the invention. Singular expressions include plural expressions unless the context clearly dictates otherwise. In this application, terms such as “comprise” or “have” are intended to designate the presence of features, numbers, steps, operations, components, parts, or combinations thereof described in the specification, but are not intended to indicate the presence of one or more other features. It should be understood that this does not exclude in advance the possibility of the existence or addition of elements, numbers, steps, operations, components, parts, or combinations thereof.

Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings. Hereinafter, the same reference numerals will be used for the same components in the drawings, and duplicate descriptions of the same components will be omitted.

Figure 1 is a block diagram showing a video encoding device according to an embodiment of the present invention.

Referring to FIG. 1, the image encoding device 100 includes an image segmentation unit 101, an intra-screen prediction unit 102, an inter-screen prediction unit 103, a subtraction unit 104, a transformation unit 105, and a quantization unit. (106), it may include an entropy encoding unit 107, an inverse quantization unit 108, an inverse transform unit 109, a multiplication unit 110, a filter unit 111, and a memory 112.

Each component shown in FIG. 1 is shown independently to represent different characteristic functions in the video encoding device, and does not mean that each component is comprised of separate hardware or a single software component. That is, each component is listed and included as a separate component for convenience of explanation, and at least two of each component can be 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 can be divided into a plurality of components. Integrated embodiments and separate embodiments of the constituent parts are also included in the scope of the present invention as long as they do not deviate from the essence of the present invention.

Additionally, some components may not be essential components that perform essential functions in the present invention, but may simply be optional components to improve performance. The present invention can be implemented by including only essential components for implementing the essence of the present invention excluding components used only to improve performance, and a structure including only essential components excluding optional components used only to improve performance. is also included in the scope of rights of the present invention.

The image segmentation unit 100 may divide the input image into at least one block. At this time, the input image may have various shapes and sizes, such as pictures, slices, tiles, and segments. A block may refer to a coding unit (CU), prediction unit (PU), or transformation unit (TU). The division may be performed based on at least one of a quadtree or binary tree. The quad tree is a method of dividing a parent block into four child blocks whose width and height are half that of the parent block. A binary tree is a method of dividing a parent block into child blocks whose width or height is half that of the parent block. Through the above-described binary tree-based division, blocks can have a non-square shape as well as a square shape.

Hereinafter, in the embodiments of the present invention, the coding unit may be used to mean a unit that performs encoding, or may be used to mean a unit that performs decoding.

The prediction units 102 and 103 may include an inter prediction unit 103 that performs inter prediction and an intra prediction unit 102 that performs intra prediction. It is possible to determine whether to use inter prediction or intra prediction for a prediction unit, and determine specific information (eg, intra prediction mode, motion vector, reference picture, etc.) according to each prediction method. At this time, the processing unit in which the prediction is performed and the processing unit in which the prediction method and specific contents are determined may be different. For example, the prediction method and prediction mode are determined in prediction units, and prediction may be performed in transformation units.

The residual value (residual block) between the generated prediction block and the original block may be input to the conversion unit 105. Additionally, prediction mode information, motion vector information, etc. used for prediction may be encoded in the entropy encoder 107 together with the residual value and transmitted to the decoder. When using a specific encoding mode, it is possible to encode the original block as is and transmit it to the decoder without generating a prediction block through the prediction units 102 and 103.

The intra-screen prediction unit 102 may generate a prediction block based on reference pixel information around the current block, which is pixel information in the current picture. If the prediction mode of the neighboring block of the current block to which intra prediction is to be performed is inter prediction, the reference pixel included in the neighboring block to which inter prediction has been applied may be replaced with a reference pixel in another neighboring block to which intra prediction has been applied. That is, when the reference pixel is not available, the unavailable reference pixel information can be used by replacing at least one reference pixel among the available reference pixels.

In intra prediction, the prediction mode can include a directional prediction mode that uses reference pixel information according to the prediction direction and a non-directional mode that does not use directional information when performing prediction. The mode for predicting luminance information and the mode for predicting chrominance information may be different, and intra prediction mode information used to predict luminance information or predicted luminance signal information may be used to predict chrominance information.

The intra-screen prediction unit 102 may include an Adaptive Intra Smoothing (AIS) filter, a reference pixel interpolation unit, and a DC filter. The AIS filter is a filter that performs filtering on the reference pixels of the current block, and can adaptively determine whether to apply the filter depending on the prediction mode of the current prediction unit. If the prediction mode of the current block is a mode that does not perform AIS filtering, the AIS filter may not be applied.

If the intra prediction mode of the prediction unit is a prediction unit that performs intra prediction based on the pixel value by interpolating the reference pixel, the reference pixel interpolation unit of the intra-screen prediction unit 102 interpolates the reference pixel to obtain the reference pixel at the fractional position. can be created. If 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 can generate a prediction block through filtering when the prediction mode of the current block is DC mode.

A residual block containing residual information, which is a difference value between the prediction unit generated in the prediction units 102 and 103 and the original block of the prediction unit, may be generated. The generated residual block may be input to the conversion unit 130 and converted.

Figure 2 is a diagram for explaining an example of an intra prediction mode. The intra prediction mode shown in Figure 2 has a total of 35 modes. Mode 0 represents planar mode, mode 1 represents DC mode, and modes 2 to 34 represent angular mode.

Figure 3 is a diagram for explaining the planar mode. To generate the predicted value of the first pixel P1 in the current block, the restored pixel located at the same position on the Y-axis and the restored pixel T located in the upper right corner of the current block are linearly interpolated as shown. Similarly, to generate the predicted value of the second pixel P2, the restored pixel located at the same position on the The average value of the two prediction pixels P1 and P2 becomes the final prediction pixel. In planar mode, the prediction block of the current block is generated by deriving prediction pixels in the same manner as above.

Figure 4 is a diagram for explaining DC mode. The average of the reconstructed pixels around the current block is calculated, and then the average value is used as the predicted value for all pixels in the current block.

FIG. 5 is a diagram illustrating an example of generating a prediction block using mode 10 (horizontal mode) and mode 26 (vertical mode) of FIG. 2 . When using mode 10, each reference pixel adjacent to the left side of the current block is copied to the right to generate a prediction block of the current block. Likewise, mode 26 generates a prediction block of the current block by copying each reference pixel adjacent to the upper side of the current block in the downward direction.

Referring again to FIG. 1, the inter-screen prediction unit 103 may predict a prediction unit based on information on at least one of the pictures before or after the current picture, and in some cases, the prediction unit 103 may predict a prediction unit after the encoding in the current picture has been completed. The prediction unit can also be predicted based on information in some areas. The inter-screen prediction unit 103 may include a reference picture interpolation unit, a motion prediction unit, and a motion compensation unit.

The reference picture interpolation unit may receive reference picture information from the memory 112 and generate pixel information of an integer number of pixels or less from the reference picture. In the case of luminance pixels, a DCT-based 8-tap interpolation filter with different filter coefficients can be used to generate pixel information of an integer pixel or less in 1/4 pixel units. In the case of color difference signals, a DCT-based 4-tap interpolation filter with different filter coefficients can be used to generate pixel information of an integer pixel or less in 1/8 pixel units.

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

The subtraction unit 104 generates a residual block of the current block by subtracting the block to be currently encoded from the prediction block generated in the intra prediction unit 102 or the inter-screen prediction unit 103.

The transform unit 105 can transform a residual block including residual data using a transform method such as DCT, DST, or KLT (Karhunen Loeve Transform). At this time, the conversion method may be determined based on the intra prediction mode of the prediction unit used to generate the residual block. For example, depending on the intra prediction mode, DCT may be used in the horizontal direction and DST may be used in the vertical direction.

The quantization unit 106 may quantize the values converted to the frequency domain by the conversion unit 105. The quantization coefficient may change depending on the block or the importance of the image. The value calculated by the quantization unit 106 may be provided to the inverse quantization unit 108 and the entropy encoding unit 107.

The transform unit 105 and/or the quantization unit 106 may be optionally included in the image encoding device 100. That is, the image encoding apparatus 100 may perform at least one of transformation or quantization on the residual data of the residual block, or may skip both transformation and quantization to encode the residual block. Even if either transformation or quantization is not performed in the image encoding device 100, or both transformation and quantization are not performed, the block that enters the input of the entropy encoding unit 107 is generally referred to as a transformation block. The entropy encoding unit 107 entropy encodes the input data. Entropy coding can use various coding methods, such as Exponential Golomb, Context-Adaptive Variable Length Coding (CAVLC), and Context-Adaptive Binary Arithmetic Coding (CABAC).

The entropy encoding unit 107 receives coding unit residual value coefficient information, block type information, prediction mode information, division unit information, prediction unit information and transmission unit information, motion vector information, and reference frame information from the prediction units 102 and 103. , various information such as block interpolation information and filtering information can be encoded. In the entropy encoding unit 107, the coefficients of the transform block encode various types of flags indicating coefficients other than 0, coefficients whose absolute value is greater than 1 or 2, and signs of the coefficients, etc., in units of partial blocks within the transform block. It can be. Coefficients that are not encoded using only the flag may be encoded using the absolute value of the difference between the coefficient encoded through the flag and the coefficient of the actual transform block. The inverse quantization unit 108 and the inverse transformation unit 109 inversely quantize the values quantized in the quantization unit 106 and inversely transform the values transformed in the transformation unit 105. The residual value generated in the inverse quantization unit 108 and the inverse transform unit 109 is predicted through the motion estimation unit, motion compensation unit, and intra-screen prediction unit 102 included in the prediction units 102 and 103. It can be combined with a prediction unit to create a reconstructed block. The multiplier 110 multiplies the prediction block generated by the prediction units 102 and 103 and the residual block generated through the inverse transform unit 109 to generate a restored block.

The filter unit 111 may include at least one of a deblocking filter, an offset correction unit, and an adaptive loop filter (ALF).

The deblocking filter can remove block distortion caused by boundaries between blocks in the restored picture. To determine whether to perform deblocking, it is possible to determine whether to apply a deblocking filter to the current block based on the pixels included in several columns or rows included in the block. When applying a deblocking filter to a block, a strong filter or a weak filter can be applied depending on the required deblocking filtering strength. Additionally, when applying a deblocking filter, horizontal filtering and vertical filtering can be processed in parallel when vertical filtering and horizontal filtering are performed.

The offset correction unit may correct the offset of the deblocked image from the original image in pixel units. In order to perform offset correction for a specific picture, the pixels included in the image are divided into a certain number of areas, then the area to perform offset is determined and the offset is applied to that area, or the offset is performed by considering the edge information of each pixel. You can use the method of applying .

Adaptive Loop Filtering (ALF) can be performed based on a comparison between the filtered restored image and the original image. After dividing the pixels included in the image into predetermined groups, filtering can be performed differentially for each group by determining one filter to be applied to that group. Information related to whether to apply ALF may be transmitted for each coding unit (CU), and the shape and filter coefficients of the ALF filter to be applied may vary for each block. Additionally, an ALF filter of the same type (fixed type) may be applied regardless of the characteristics of the block to which it is applied.

The memory 112 may store a reconstructed block or picture calculated through the filter unit 111, and the stored reconstructed block or picture may be provided to the prediction units 102 and 103 when inter prediction is performed.

Figure 6 is a block diagram showing an image decoding device 600 according to an embodiment of the present invention.

Referring to FIG. 6, the image decoding device 600 includes an entropy decoding unit 601, an inverse quantization unit 602, an inverse transform unit 603, a multiplication unit 604, a filter unit 605, a memory 606, and It may include prediction units 607 and 608.

When the video bitstream generated by the video encoding device 100 is input to the video decoding device 600, the input bitstream may be decoded according to a process opposite to the process performed in the video encoding device 100. .

The entropy decoding unit 601 may perform entropy decoding in a procedure opposite to that in which the entropy encoding unit 107 of the video encoding device 100 performs entropy encoding. For example, various methods such as Exponential Golomb, CAVLC (Context-Adaptive Variable Length Coding), and CABAC (Context-Adaptive Binary Arithmetic Coding) can be applied in response to the method performed in the image encoder. In the entropy decoding unit 601, the coefficients of the transform block are based on various types of flags indicating coefficients other than 0, coefficients whose absolute value is greater than 1 or 2, and signs of the coefficients, in units of partial blocks within the transform block. It can be decrypted. Coefficients that are not expressed only by the flag can be decoded through the sum of the coefficients expressed through the flag and the signaled coefficients.

The entropy decoder 601 can decode information related to intra-prediction and inter-prediction performed in the encoder. The inverse quantization unit 602 generates a transform block by performing inverse quantization on the quantized transform block. It operates substantially the same as the inverse quantization unit 108 of FIG. 1.

The inverse transform unit 603 generates a residual block by performing inverse transform on the transform block. At this time, the transformation method may be determined based on information about the prediction method (inter or intra prediction), size and/or shape of the block, intra prediction mode, etc. It operates substantially the same as the inverse conversion unit 109 of FIG. 1.

The multiplication unit 604 generates a restored block by multiplying the prediction block generated by the intra-prediction unit 607 or the inter-screen prediction unit 608 and the residual block generated through the inverse transform unit 603. It operates substantially the same as the multiplier 110 of FIG. 1.

The filter unit 605 reduces various types of noise occurring in restored blocks.

The filter unit 605 may include a deblocking filter, an offset correction unit, and an ALF.

Information on whether a deblocking filter has been applied to the corresponding block or picture can be provided from the video encoding device 100, and when a deblocking filter has been applied, information on whether a strong filter or a weak filter has been applied. In the deblocking filter of the video decoding device 600, information related to the deblocking filter provided by the video encoding device 100 is provided, and the video decoding device 600 can 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 offset value information.

ALF may be applied to the coding unit based on ALF application availability information, ALF coefficient information, etc. provided from the video encoding device 100. This ALF information may be included and provided in a specific parameter set. The filter unit 605 operates substantially the same as the filter unit 111 of FIG. 1.

The memory 606 stores the restored block generated by the multiplication unit 604. It operates substantially the same as the memory 112 of FIG. 1.

The prediction units 607 and 608 may generate a prediction block based on prediction block generation-related information provided by the entropy decoding unit 601 and previously decoded block or picture information provided by the memory 606.

The prediction units 607 and 608 may include an intra-screen prediction unit 607 and an inter-screen prediction unit 608. Although not shown separately, the prediction units 607 and 608 may further include a prediction unit determination unit. The prediction unit discriminator receives various information such as prediction unit information input from the entropy decoder 601, prediction mode information of the intra prediction method, and motion prediction-related information of the inter prediction method, distinguishes the prediction unit from the current coding unit, and makes predictions. It is possible to determine whether a unit performs inter-prediction or intra-prediction. The inter-prediction unit 608 uses the information required for inter prediction of the current prediction unit provided by the video encoding device 100 to predict information included in at least one of the pictures before or after the current picture including the current prediction unit. Based on , inter prediction for the current prediction unit can be performed. Alternatively, inter prediction may be performed based on information on a pre-restored partial region within the current picture including the current prediction unit.

To perform inter-screen prediction, based on the coding unit, whether the motion prediction method of the prediction unit included in the coding unit is Skip Mode, Merge Mode, or AMVP Mode. can be judged.

The intra-screen prediction unit 607 generates a prediction block using previously restored pixels located around the block to be currently encoded.

The intra-screen prediction unit 607 may include an Adaptive Intra Smoothing (AIS) filter, a reference pixel interpolation unit, and a DC filter. The AIS filter is a filter that performs filtering on the reference pixels of the current block, and can adaptively determine whether to apply the filter depending on the prediction mode of the current prediction unit. AIS filtering can be performed on the reference pixel of the current block using the prediction mode and AIS filter information of the prediction unit provided by the image encoding device 100. If the prediction mode of the current block is a mode that does not perform AIS filtering, the AIS filter may not be applied.

If the prediction mode of the prediction unit is a prediction unit that performs intra prediction based on the pixel value by interpolating the reference pixel, the reference pixel interpolation unit of the intra-screen prediction unit 607 interpolates the reference pixel to obtain the reference pixel at the fractional position. can be created. The generated reference pixel at the fractional position can be used as a predicted pixel for the pixel in the current block. If 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 can generate a prediction block through filtering when the prediction mode of the current block is DC mode.

The intra-screen prediction unit 607 operates substantially the same as the intra-screen prediction unit 102 of FIG. 1 .

The inter prediction unit 608 generates an inter prediction block using the reference picture and motion information stored in the memory 606. The inter-screen prediction unit 608 operates substantially the same as the inter-screen prediction unit 103 of FIG. 1 .

The present invention particularly relates to intra prediction, and various embodiments of the present invention will be described in more detail below with reference to the drawings.

< Interpolation for intra-screen prediction>

FIGS. 7A and 7B are diagrams for explaining a method of deriving predicted pixels within a screen using interpolation. Assuming that the prediction angle of mode m, which is one of the intra-prediction modes in FIG. 2, is the same as that in FIG. 7A, when intra-prediction is performed using mode m, the reference pixel X to be used for prediction is at an integer pixel position. does not exist. Therefore, interpolation is performed using reference pixels A and B that exist at integer pixel positions to the left and right of the reference pixel The generated reference pixel

Figure 7b is a diagram for explaining the relationship between pixels X, A, and B. Referring to Figure 7b, the distance between pixels X and A is S1, and the distance between pixels B and X is S2. Depending on the ratio of distances S1 and S2, pixel X can be derived using various interpolation methods. At this time, various interpolation methods such as linear interpolation, cubic convolution interpolation, and B-spline interpolation can be applied.

There are various methods for allowing the image decoding device 100 to know which interpolation method among a plurality of available interpolation methods has been applied or which set of interpolation coefficients has been used. The first method is a method in which the image encoding device 100 transmits index information indicating which interpolation method among a plurality of available interpolation methods has been applied to the image decoding device 600. At this time, the video encoding device 100 can also set index information indicating the interpolation method on a block basis or through a higher-level header. Here, setting through the upper header means setting using headers larger than the block unit, such as slice segment header, picture parameter set, and sequence parameter set. it means. Index information indicating the interpolation method included in the upper header may be encoded by the video encoding device 100 and transmitted to the video decoding device 600.

In another method, the encoding device 100 and the decoding device 600 store a plurality of preset interpolation coefficient sets in the same manner, and interpolation coefficient index information indicating which set was selected and used for encoding is stored in block units or blocks. It can be notified to the decoding device 600 through the upper header.

In another method, instead of the video encoding device 100 transmitting index information indicating the above-described interpolation method or interpolation coefficient index information indicating which interpolation coefficient set is used to the video decoding device 600, The video encoding device 100 and the video decoding device 600 can derive interpolation coefficients in the same implicit manner.

Specifically, the image encoding device 100 and the image decoding device 600 may derive interpolation coefficients through the same method using already restored pixels. For example, R reference pixels (i.e., pixels that have already been restored) are enlarged or reduced by a factor of R x K (K is an arbitrary real number) using an interpolation filter. Afterwards, the original R reference pixels are restored through the inverse process using the same interpolation filter. The optimal interpolation filter can be determined depending on the difference between the values of the restored R reference pixels and the values of the original reference pixels.

FIG. 8 is a diagram for explaining another method in which the video encoding apparatus 100 or the video decoding apparatus 600 selects an interpolation method and/or interpolation coefficients in an implicit manner. Referring to FIG. 8 , the 4x4 block containing the pixel P corresponds to the current block to be decoded through intra prediction. A plurality of reference pixel lines composed of previously restored pixels located around the current block are used to determine an interpolation method or interpolation coefficient. As shown in FIG. 8, each reference pixel line may include a predetermined number of pixels in one horizontal line and a predetermined number of pixels in one vertical line. Alternatively, the reference pixel line may be composed of a predetermined number of pixels in a horizontal line, or may be composed of a predetermined number of pixels in a vertical line.

Referring again to FIG. 8, pixels in reference pixel line 0 are predicted using pixels in reference pixel line 1. At this time, N directional modes identical to the intra prediction mode of the current block are used for prediction. For example, the reference pixel can be induced. At this time, specific interpolation methods and interpolation coefficients are used.

In this way, after generating predicted values of pixels in reference pixel line 0, a difference value between each predicted value and each original pixel value is calculated, and then the difference values are summed. The above process is repeated using the interpolation methods and interpolation coefficients available in the video encoding device 100 or the video decoding device 600, and the interpolation method and/or interpolation coefficients when the sum of each difference value becomes minimum are finally calculated. Select .

The above-described interpolation may be performed by a reference pixel interpolation unit included in each of the intra-prediction unit 102 of the video encoding apparatus 100 and the intra-prediction unit 607 of the video decoding apparatus 600.

FIG. 9 is a flow chart to explain the process of selecting the optimal intra-screen prediction mode by the video encoding device 100. At this time, it is assumed that the interpolation method is set on a block basis or upper header, etc.

9, the variable m representing the prediction mode number within the screen is initialized to 0, and the variable m to store the optimal cost value is initialized to COST_BEST = MAX_VALUE (S901). Here, MAX_VALUE is the maximum value that can be stored in the COST_BEST variable, and is a very large value that cannot actually be output when calculating cost. The total number of preset prediction modes within the screen is set to variable M (S901). BEST_INTRA_MODE, which indicates the optimal intra-screen prediction mode for the current block, is initialized to 0 (S901).

Then, according to the intra-screen prediction mode m, find the interpolation position corresponding to each pixel position in the prediction block, generate an interpolation value using a preset interpolation method or one of a number of interpolation methods set in the upper header, and then block the prediction block. is created (S902). And COST_m, the cost value corresponding to m, is calculated using the generated prediction block (S903). Here, COST_m can be calculated using the number of bits required to encode the mode within the screen and the difference between the prediction block and the current block. If COST_m is less than or equal to COST_BEST (S904), m is stored in BEST_INTRA_MODE, a variable that stores the optimal intra-screen prediction mode, cost_m is stored in the COST_BEST variable, and m is increased by 1 (S905). If COST_m is greater than COST_BEST, only m is increased by 1 (S906). Finally, if m reaches the maximum number of prediction modes in the screen, it terminates. Otherwise, it returns to S902 and repeats. Here, if the interpolation method is a preset method in the video encoding device 100 or the video decoding device 600, set S1 and S2 using the method of FIGS. 7 and 8, and use the preset interpolation method to obtain pixel creates . A prediction block is generated for all pixels in a prediction block using the same method. Alternatively, if multiple interpolation methods are used, the contents of step S902 may be changed.

Additionally, multiple interpolation methods can be adaptively applied to each prediction block. At this time, the contents of step S902 among the steps shown in FIG. 9 are changed.

FIG. 10 is a flowchart illustrating a process in which one of a plurality of interpolation methods is selected by the video encoding device 100.

Referring to FIG. 10, the video encoding device 100 initializes the variable i representing the interpolation method index to 0 and initializes it to COST_BEST_i = MAX_VALUE, which is a variable to store the optimal cost value. Here, MAX_VALUE is the maximum value that can be stored in the COST_BEST_i variable, and is a very large value that cannot actually be output when calculating cost. The variable i is set to the total number of preset, available interpolation methods. BEST_INTERPOLATION, a variable that stores the optimal interpolation method used in the current block, is initialized to 0 (S1001). Afterwards, an interpolation value corresponding to each pixel position of the prediction block is generated according to the interpolation method index i, and then a prediction block is generated (S1002). Then, COST_i, the cost value corresponding to i, is calculated using the generated prediction block (S1003). Here, COST_i is calculated using the number of bits required to encode the interpolation method index and the difference between the prediction block and the current block. If COST_i is less than or equal to COST_BEST_i (S1004), i is stored in BEST_INTERPOLATION, a variable that stores the optimal interpolation method, cost_i is stored in the COST_BEST_i variable, and i is increased by 1 (S1005). If COST_i is greater than COST_BEST_i, only i is increased by 1 (S1006). Finally, if i has reached the maximum number of available interpolation methods, it terminates. Otherwise, it returns to S1002 and repeats. When this method is used, COST_m is calculated by adding the number of bits encoding the interpolation method index to the number of bits of the intra prediction mode encoded in step S903 shown in FIG. 9.

FIG. 11 is a flowchart explaining the process of encoding interpolation method index information when multiple interpolation methods are adaptively applied to each prediction block by the video encoding apparatus 100. First, whether the intra-screen prediction mode is predicted for each prediction block is encoded (S1101). After that, it is determined whether prediction has been made (S1102), and if prediction has been made, an index indicating which candidate was selected from the prediction candidates of the intra-screen prediction mode generated from the surrounding blocks is encoded (S1103). Otherwise, the prediction candidates of the intra-screen prediction mode generated from the surrounding blocks are excluded, the remaining modes are rearranged, and the currently selected intra-screen prediction mode is binarized and encoded (S1104). Afterwards, the used interpolation method index is encoded (S1105) and the process ends.

FIG. 12 is a flowchart explaining the process of decoding interpolation method index information by the video decoding device 600. First, whether the intra-screen prediction mode is predicted for each prediction block is decoded (S1201). After that, it is determined whether prediction has been made (S1202), and if prediction has been made, an index indicating which candidate was selected from the prediction candidates of the intra-screen prediction mode generated from the surrounding blocks is decoded (S1203). Otherwise, the currently selected intra-prediction mode is decoded by excluding prediction candidates of the intra-screen prediction mode generated from neighboring blocks and rearranging the remaining modes (S2104). Afterwards, the interpolation method index used in the encoder is decoded (S1205) and the process ends.

<Induction of predicted pixels within the screen using multiple reference pixel lines>

Below, the derivation of an intra-screen prediction pixel using a plurality of reference pixel lines according to another embodiment of the present invention will be described.

FIG. 13 is a diagram illustrating the derivation of a prediction pixel within a screen using a plurality of reference pixel lines, according to an embodiment of the present invention.

In conventional intra prediction, one reference pixel line is used. This is reference pixel line 0 shown in FIG. 13. Reference pixel line 0 is composed of a predetermined number of reference pixels in contact with the top of the current block and a predetermined number of reference pixels in contact with the left side of the current block. The present invention can improve the accuracy of intra prediction by deriving a prediction pixel or prediction block using various reference pixel lines and reference pixels belonging to the reference pixel lines. This embodiment can be equally performed by the intra-screen prediction unit 102 of the video encoding device 100 and the intra-screen prediction unit 607 of the video decoding device 600.

For the following explanation, it is assumed that a total of three reference pixel lines are used. However, any number of N reference pixel lines can be used. Here, the number N of reference pixel lines can be informed to the decoding device 600 in block units or included in the upper header. Alternatively, it is also possible for the encoding device 100 and the decoding device 600 to use N preset reference pixel lines without encoding the number N of the reference pixel lines.

Referring to FIG. 13 , a 4x4 block containing a pixel P corresponds to a current block to be encoded or decoded using intra prediction. Three reference pixel lines 0, 1 and 2 are located around the current block.

When the intra prediction mode of the current block is the m directional mode, prediction pixels that can be used as prediction pixels of the current pixel P using the three reference pixel lines 0, 1, and 2 can be X, Y, and Z. At this time, a prediction block can be generated using each of the three reference pixel lines and the optimal reference pixel line can be determined. The encoding device 100 can encode reference pixel line index information indicating the optimal reference pixel line determined in this way. As for the reference pixel line index, for example, as shown in FIG. 13, a low index number may be assigned to a reference pixel line close to the current block.

Figure 14 is a flowchart for explaining the process of deriving the predicted pixel value within the screen, according to an embodiment of the present invention. Referring to FIG. 14, at least one reference pixel line to be used for intra prediction of the current block is selected from a plurality of reference pixel lines (S1301). The plurality of reference pixel lines exist in the same image as the current block to be decoded using intra prediction. The selected at least one reference pixel line may be indicated by the reference pixel line index described above. As another alternative, at least one reference pixel line to be used for intra prediction of the current block may be selected using a method common to the image encoding apparatus 100 and the image decoding apparatus 600 by an implicit method to be described later. .

Additionally, the selected at least one reference pixel line may be selected for each prediction block. This will be described later with reference to FIG. 15. Alternatively, it may be adaptively selected for each pixel in the prediction block. This will be described later with reference to FIGS. 18 and 19.

The image encoding device 100 or the image decoding device 600 may obtain a predicted value of one pixel in the current block based on at least one pixel value included in the selected at least one reference pixel line (S1303). The video encoding apparatus 100 or the video decoding apparatus 600 may derive a prediction block of the current block by repeating all or part of steps S1301 or S1303.

FIG. 15 is a flowchart illustrating a process for adaptively determining a reference pixel line to be used for intra prediction for each prediction block. At this time, step S902 shown in FIG. 9 may be replaced with the steps shown in FIG. 15.

Referring to FIG. 15, the variable n representing the reference pixel line index is initialized to 0, and the variable to store the optimal cost value is initialized to COST_BEST_n = MAX_VALUE. Here, MAX_VALUE is the maximum value that can be stored in the COST_BEST_n variable, and is a very large value that cannot actually be output when calculating cost. The variable N is set to the total number of preset reference pixel lines. BEST_n, which represents the optimal reference pixel line index for the current block, is initialized to 0 (S1401). Afterwards, the interpolation position corresponding to each pixel position of the prediction block is found according to the reference pixel line index n, and a prediction block is generated (S1402). Then, COST_n, the cost value corresponding to n, is calculated using the generated prediction block (S1403). Here, COST_n is calculated using the number of bits required to encode reference pixel line n and the difference between the prediction block and the current block. If COST_n is less than or equal to COST_BEST_n (S1404), n is stored in BEST_n, a variable that stores the optimal reference pixel line, cost_n is stored in the COST_BEST_n variable, and n is increased by 1 (S1405). If COST_n is greater than COST_BEST_n, only n is increased by 1 (S1406). Finally, if n reaches the maximum number of reference pixel lines, the process ends. Otherwise, returns to S1402 and repeats.

FIG. 16 is a flowchart showing a process in which reference pixel line index information indicating the selected reference pixel line is encoded by the encoding device 100 when a reference pixel line is adaptively selected for each prediction block. First, whether the intra-screen prediction mode is predicted for each prediction block is encoded (S1501). After that, it is determined whether prediction has been made (S1502), and if prediction has been made, an index indicating which candidate was selected from the prediction candidates of the intra-screen prediction mode generated from the surrounding blocks is encoded (S1503). Otherwise, the prediction candidates of the intra-screen prediction mode generated from the surrounding blocks are excluded, the remaining modes are rearranged, and the currently selected intra-screen prediction mode is binarized and encoded (S1504). Afterwards, the used reference pixel line index is encoded (S1505) and the process ends.

FIG. 17 is a flowchart showing a process in which reference pixel line index information indicating the selected reference pixel line is decoded by the decoding device 600 when a reference pixel line is adaptively selected for each prediction block. First, whether the intra-screen prediction mode is predicted for each prediction block is decoded (S1601). After that, it is determined whether prediction has been made (S1602), and if prediction has been made, an index indicating which candidate was selected from the prediction candidates of the intra-screen prediction mode generated from the surrounding blocks is decoded (S1603). Otherwise, the currently selected intra-prediction mode is decoded by excluding prediction candidates of the intra-screen prediction mode generated from neighboring blocks and rearranging the remaining modes (S1604). Afterwards, the used reference pixel line index is decoded (S1605) and the process ends.

Next, with reference to FIGS. 18 and 19, a method for adaptively determining a reference pixel line for each pixel position of a prediction block without transmitting a reference pixel line index will be described.

For each pixel in a prediction block, the precision of the position of the prediction pixel obtained through interpolation within each reference pixel line may be different. Therefore, among the prediction pixels obtained through interpolation within each reference pixel line, the prediction pixel closest to the integer pixel position can be selected as the prediction pixel of the current pixel P. At this time, the above process can be applied to N predetermined reference pixel lines.

If there are a plurality of prediction pixels at integer pixel positions, a prediction pixel close to the current block may be selected as the final prediction pixel.

FIG. 19 is a reference diagram for explaining a method of adaptively selecting a reference pixel line without transmitting a reference pixel line index. As shown in FIG. 19, a prediction pixel line can be adaptively selected for each prediction block by prioritizing lines with many prediction pixels at integer positions. Assuming that the precision and frequency of the interpolated pixels used when generating a prediction block using each reference pixel line are the same as in FIG. 19, the line can be selected by weighting according to the precision of each pixel position.

Referring again to FIG. 19, when generating a prediction block using line 1, there are 5 integer position prediction pixels, 3 1/2 position prediction pixels, 4 1/4 position prediction pixels, and 1/4 position prediction pixels. Two 8 position prediction pixels, one 1/16 position prediction pixel, and one 1/32 position prediction pixel were selected. Therefore, the total number of pixels in the prediction block is 16. The case of reference pixel line 2 and reference pixel line 3 can be explained in the same way.

If priority is given only to integer pixel positions, line 1 with the most integer pixel positions may be selected as the reference pixel line. Alternatively, it is also possible to apply weights to each position, calculate the sum of the weights and frequencies, and then select the line with the largest calculated value as the reference pixel line. Alternatively, it is also possible to assign a weight to each line, calculate the sum of the weight and frequency, and then select the line with the largest calculated value as the reference pixel line. Alternatively, it is also possible to apply weight to both each line and position, calculate the sum of the weight and frequency, and then select the line with the largest calculated value as the reference pixel line.

As another example, it is also possible to generate a prediction block using weighted pixels by adding weights to each line. For example, if there are pixel values at the Alternatively, it is also possible to add more weight the closer it is to the integer pixel location and select the weighted sum as the predicted pixel for the P location. Alternatively, in addition to deriving the predicted pixel using a weighted sum, that is, a weighted average, the value of the predicted pixel can also be derived using an arithmetic mean, median, etc.

Alternatively, it can be encoded using a reference pixel line index and used to exclude one of the N lines. For example, if the reference pixel line index is set to 1, N-1 lines excluding line 1 are used. At this time, when interpolating the predicted value using the m mode, higher priority may be given closer to the integer pixel position, or different priorities may be given depending on the precision of the interpolated position. According to this preset arbitrary priority, predicted values can be generated from lines other than line 1 on a per-pixel basis without line distinction.

Alternatively, it is also possible for the encoding device 100 to encode and transmit to the decoding device 600 whether a method of directly encoding the reference pixel line index or a method of not encoding was used in the block unit or upper header. .

<Smoothing between prediction block and reference pixel line>

Hereinafter, smoothing between a prediction block and a reference pixel line will be described as another embodiment of the present invention.

When a prediction block is derived using predetermined pixel(s) in a reference pixel line, a discontinuity may exist between the reference pixel line not used for derivation of the prediction block and the prediction block, or between an area adjacent to the prediction block and the prediction block. . Smoothing can be used to reduce these discontinuities. Smoothing can correspond to a type of low-pass filter.

Smoothing according to an embodiment of the present invention may be performed by the intra-screen prediction unit 102 of the video encoding device 100 and the intra-screen prediction unit 607 of the video decoding device 600, respectively.

Figure 20 is a diagram for explaining smoothing between a prediction block and a reference pixel line.

The intra-screen prediction mode used below will be explained by taking as an example a mode in which intra-screen prediction is performed in the 45-degree up-right direction. Also assume that reference pixel line 1 is selected for intra prediction. In addition, smoothing is explained using pixels A to E as pixels to which smoothing is applied, but the same can be applied to other pixels.

In the example of FIG. 20, since intra-screen prediction was performed in the 45-degree up-right direction, smoothing may be performed in the 45-degree down-left direction, which is the opposite direction of the intra-screen prediction direction. At this time, the area of the prediction block to which smoothing is applied may be determined depending on the size or shape of the prediction block of the current block. In Figure 20, pixels belonging to half of the area of the prediction block are smoothed. In other words, smoothing can be applied only to the darkened left half pixels. Alternatively, a preset area or ratio may be used depending on the size of the prediction block and/or the intra-screen prediction mode. For example, smoothing may be applied to only 1/4 of the prediction block, and other ratios are also possible.

In FIG. 20, since reference pixel line 1 is determined as the reference pixel line for intra prediction, prediction pixel A can be smoothed using equation 1 below using pixel D existing in reference pixel line 1.

In Equation 1 above, A', A, and D are the value of prediction pixel A after smoothing, the value of prediction pixel A before smoothing, and the value of reference pixel D, respectively, and w1 and w2 are the values applied to prediction pixel A, respectively. Weight and reference This is the weight applied to pixel D.

Additionally, the predicted pixel B can be smoothed using the pixel D present in the reference pixel line 1 using an equation similar to Equation 1 above.

At this time, the intensity of smoothing can be adjusted depending on the distance. Since prediction pixel A is further away from pixel D than prediction pixel B, the smoothing is performed more strongly when smoothing prediction pixels A and D than when smoothing prediction pixels B and pixel D. Here, strong smoothing can be performed by smoothing the predicted pixel by placing more weight on pixel D.

Alternatively, separately from the reference pixel line selected for intra prediction, the reference pixel line used for smoothing may be set to a line close to the prediction block. Referring to FIG. 20, although reference pixel line 1 is selected for intra prediction, it is also possible to set the pixel used for smoothing prediction pixels A and B to C instead of D. In this case as well, the strength of smoothing can be selected depending on the distance. For example, when smoothing prediction pixel B using reference pixel C, the same weight is applied to each, and when smoothing prediction pixel A using reference pixel C, smoothing is performed by placing more weight on pixel C. It may be possible.

When performing smoothing, it is also possible to use both directions. For example, assuming that smoothing is performed using reference pixel line 0, when smoothing prediction pixel A, weights may be placed on reference pixels F and C, respectively, to perform smoothing with prediction pixel A. When smoothing prediction pixel B, it is also possible to smooth prediction pixel B by assigning weight to pixels F and C respectively. At this time, since line 1 is selected as the reference pixel line for intra prediction, it is also possible to use pixel G in the up-right direction and pixel C in the down-left direction.

According to one embodiment of the present invention, it is also possible to vary the weight depending on the distance between the reference pixel and the prediction pixel. For example, when smoothing prediction pixel A using reference pixels F and C, the distance between pixels C and A is greater than the distance between pixels F and A, so smoothing may be performed by placing greater weight on pixel C. Alternatively, it is also possible to perform smoothing using an arbitrary line using a preset method. It is also possible to encode the application of this smoothing method on a block-by-block basis, and it is also possible to encode it through the upper header. Alternatively, it is also possible for the encoder and decoder to perform the same operation according to preset conditions without encoding whether or not smoothing is applied. For example, whether to perform smoothing may be determined depending on which angle the intra-screen prediction mode was performed. In this embodiment, for convenience of explanation, it is explained that smoothing is stronger as the distance increases, but the opposite case is also possible depending on the characteristics of the image.

Next, with reference to FIGS. 21 and 22A to 22D, the unit of a block from which a reference pixel line for intra prediction is selected will be described, according to an embodiment of the present invention.

Hereinafter, for convenience of explanation, an example will be given where the current block is 16x16 in size, the current block is divided into four 8x8 transform blocks, and the transform is performed a total of four times in units of 8x8 transform blocks. The current block may be divided into multiple transformation blocks smaller than the size of the current block for transformation. Therefore, when the intra-screen prediction mode is determined in units of the current block, actual prediction can be performed in units of transform blocks by applying the determined intra-prediction mode in units of transform blocks. The advantage of this method is that it can compensate for the fact that the correlation between pixels may decrease as the reference pixel moves away from the current block. Referring to FIG. 21, when intra-prediction is applied on a block basis, the pixels of transform block A are closer to the reference pixels than the pixels of transform block D. Therefore, the pixels in the transform block D may be farther away from the reference pixels, thereby lowering prediction efficiency.

In order to compensate for the above-described shortcomings, only the intra-screen prediction mode can be determined on a block basis, and intra-screen prediction can be performed on a transform block basis.

FIG. 21 illustrates a case where, when intra prediction is performed on a transform block basis, at least one reference pixel line selected for intra prediction of the current block is commonly used for all transform blocks within the current block.

Figures 22A to 22D illustrate a case where at least one reference pixel line is selected for each transform block and used for intra prediction.

Referring to FIG. 22A, when four transform blocks with a size of 8x8 are used and prediction is performed on a transform block basis, the same reference pixel lines as shown in FIG. 21 are used for intra prediction of transform block A.

Referring to FIG. 22B, transform block B can use the reference pixel lines as shown using the restored pixels of transform block A for intra prediction. Likewise, in FIG. 22C, reference pixel lines as shown using pixels of restored transform blocks A and B can be used for intra prediction. Reference pixel lines as shown in FIG. 22D using pixels of restored transform blocks A, B, and C can be used for intra prediction.

As described above, when using a plurality of reference pixel lines, the pixel lines determined on a block basis as shown in FIG. 21 may be directly applied when prediction is performed on a transform block basis in FIGS. 22A to 22D. Alternatively, it is also possible to obtain a new optimal reference pixel line on a conversion block basis. Alternatively, whether to use the optimal reference pixel line obtained on a block-by-block basis for the entire transform block or derive and use a reference pixel line for each transform block can be encoded on a block-by-block basis or through a higher-level header and notified to the decoding device 600. possible.

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

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

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

The scope of the present disclosure is software or machine-executable instructions (e.g., operating system, application, firmware, program, etc.) that cause operations according to the methods of various embodiments to be executed on a device or computer, and such software or It includes non-transitory computer-readable medium in which instructions, etc. are stored and can be executed on a device or computer.

Claims (11)

In the video decoding method,
selecting at least one reference pixel line from a plurality of reference pixel lines, wherein the plurality of reference pixel lines are included in a current picture including a current block;
Deriving an intra prediction mode of the current block;
generating a prediction block of the current block based on the at least one reference pixel line and an intra prediction mode of the current block; and
Comprising: performing filtering on one or more pixels in the prediction block based on at least one reference pixel in the plurality of reference pixel lines,
The one or more pixels are determined based on the size of the prediction block.
Video decoding method.
delete According to paragraph 1,
If the intra prediction mode of the current block is a predetermined angle mode,
The first pixel in the prediction block is filtered based on the first reference pixel included in the at least one reference pixel line.
Video decoding method. According to paragraph 3,
The predetermined angle mode has a 45 degree up-right prediction direction.
Video decoding method. According to paragraph 3,
The first reference pixel is disposed in a direction opposite to the prediction direction of the predetermined angle mode.
Video decoding method. According to paragraph 3,
A reference pixel line including the first reference pixel is disposed adjacent to the prediction block.
Video decoding method. According to paragraph 3,
The first pixel is filtered by applying a first weight to the first reference pixel.
Video decoding method. In clause 7,
The first weight is determined based on the distance between the first pixel and the first reference pixel.
Video decoding method. In clause 7,
The first weight decreases as the distance between the first pixel and the first reference pixel increases.
Video decoding method. In the video encoding method,
selecting at least one reference pixel line from a plurality of reference pixel lines, wherein the plurality of reference pixel lines are included in a current picture including a current block;
Deriving an intra prediction mode of the current block;
generating a prediction block of the current block based on the at least one reference pixel line and an intra prediction mode of the current block;
performing filtering on one or more pixels in the prediction block based on at least one reference pixel in the plurality of reference pixel lines; and
Encoding first information about the intra prediction mode of the current block and second information about the at least one reference pixel line,
The one or more pixels are determined based on the size of the prediction block.
Video encoding method. A non-transitory computer-readable recording medium storing a bitstream generated by an image encoding method, the image encoding method comprising:
selecting at least one reference pixel line from a plurality of reference pixel lines, wherein the plurality of reference pixel lines are included in a current picture including a current block;
Deriving an intra prediction mode of the current block;
generating a prediction block of the current block based on the at least one reference pixel line and an intra prediction mode of the current block;
performing filtering on one or more pixels in the prediction block based on at least one reference pixel in the plurality of reference pixel lines; and
Encoding first information about the intra prediction mode of the current block and second information about the at least one reference pixel line into a bitstream,
The one or more pixels are determined based on the size of the prediction block.
A non-transitory computer-readable recording medium.