KR20190008809A - Image decoding method and apparatus supporting a plurality of reference pixel layers - Google Patents

Abstract

Disclosed are a method and a device for decoding an image supporting multiple reference pixel layers. The method for decoding an image supporting multiple reference pixel layers comprises the steps of: checking whether multiple reference pixel layers are supported in a bit stream; determining a reference pixel layer to be used for a current block by referring to syntax information included in the bit stream when the multiple reference pixel layers are supported; configuring a reference pixel by using a pixel included in the determined reference pixel layer; and performing intra-prediction on the current block by using the reference pixel. Therefore, the image encoding/decoding efficiency can be improved.

Description

TECHNICAL FIELD [0001] The present invention relates to an image decoding method and apparatus for supporting a plurality of reference pixel layers,

The present invention relates to a video decoding method and apparatus supporting a plurality of reference pixel layers, and more particularly, to a video decoding method and apparatus for supporting a plurality of reference pixel layers by setting a plurality of reference pixel layers according to a pixel distance adjacent to a current block, And a method for performing intra prediction using a reference pixel included in a reference pixel hierarchy capable of generating an optimal prediction block.

Recently, demand for multimedia data such as video is rapidly increasing on the Internet. However, the bandwidth of the channel is rapidly increasing, and it is necessary to efficiently compress the amount of multimedia data. ISO / ISE Moving Picture Experts Group (MPEG) and ITU-T Video Coding Experts Group (VCEG) are studying video compression standards through cooperative research.

On the other hand, the intra-frame prediction according to the existing image coding / decoding method constitutes a reference pixel by using the pixels closest to the current block, and it is not preferable to form the reference pixel as the nearest pixel depending on the type of the image .

Accordingly, there is a need for a method of improving intra-picture prediction efficiency by configuring reference pixels differently from conventional ones.

In order to solve the above problems, an object of the present invention is to provide a video decoding method supporting a plurality of reference pixel layers.

It is another object of the present invention to provide an image decoding apparatus supporting a plurality of reference pixel layers.

According to an aspect of the present invention, there is provided an image decoding method supporting a plurality of reference pixel layers.

The video decoding method for supporting a plurality of reference pixel layers includes the steps of: checking whether or not a plurality of reference pixel layers are supported in a bitstream; referring to syntax information included in the bitstream, Determining a reference pixel hierarchy to be used for a current block, constructing a reference pixel using pixels belonging to the determined reference pixel hierarchy, and performing intra prediction on the current block using the constructed reference pixel .

The method may further include confirming whether or not the adaptive reference pixel filtering method is supported in the bitstream, after confirming whether the plurality of reference pixel layers are supported.

If the plurality of reference pixel layers are not supported after the step of checking whether the plurality of reference pixel layers are supported, the step of configuring reference pixels using the predetermined reference pixel layer may be included.

When the image decoding method and apparatus supporting a plurality of reference pixel layers according to the present invention as described above are used, intra prediction accuracy can be increased because a plurality of reference pixels are used.

In addition, according to the present invention, since adaptive reference pixel filtering is supported, optimum reference pixel filtering can be performed according to characteristics of an image.

In addition, there is an advantage that the compression efficiency due to the image portion / decoding can be increased.

1 is a conceptual diagram of an image encoding and decoding system according to an embodiment of the present invention.
2 is a block diagram of an image encoding apparatus according to an embodiment of the present invention.
3 is a block diagram of an image decoding apparatus according to an embodiment of the present invention.
4 is an exemplary diagram illustrating an intra prediction mode according to an embodiment of the present invention.
5 is a first exemplary view of a reference pixel configuration used in intra-frame prediction according to an embodiment of the present invention.
6A to 6C are second exemplary views of a reference pixel structure according to an embodiment of the present invention.
7 is a third exemplary view of a reference pixel structure according to an embodiment of the present invention.
8 is a fourth exemplary view of a reference pixel structure according to an embodiment of the present invention.
Figs. 9A and 9B are diagrams for explaining a method of filling a reference pixel at a preset position in an unusable reference candidate block. Fig.
FIGS. 10A to 10C are views illustrating a method of performing interpolation based on a fractional pixel unit for reference pixels constructed according to an embodiment of the present invention.
11A and 11B are first illustrations for explaining an adaptive reference pixel filtering method according to an embodiment of the present invention.
12 is a second exemplary diagram for explaining an adaptive reference pixel filtering method according to an embodiment of the present invention.
13A to 13B are views illustrating an example of using one reference pixel layer in reference pixel filtering according to an embodiment of the present invention.
FIG. 14 is an exemplary diagram illustrating the use of a plurality of reference pixel layers in reference pixel filtering according to an exemplary embodiment of the present invention.
FIG. 15 is a block diagram for explaining a sub-decoding method for an intra-picture prediction mode according to an embodiment of the present invention.
16 is a first exemplary diagram for explaining a bit stream configuration for intra-picture prediction according to the reference pixel configuration.
17 is a second exemplary diagram for explaining the bit stream structure for intra-picture prediction according to the reference pixel configuration.
18 is a third exemplary diagram for explaining a bit stream configuration for intra-picture prediction according to the reference pixel configuration.
FIG. 19 is a flowchart illustrating a video decoding method supporting a plurality of reference pixel layers according to an exemplary embodiment of the present invention. Referring to FIG.

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

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

It is to be understood that when an element is referred to as being "connected" or "connected" to another element, it may be directly connected or connected to the other element, . On the other hand, when an element is referred to as being "directly connected" or "directly connected" to another element, it should be understood that there are no other elements in between.

The terminology used in this application is used only to describe a specific embodiment and is not intended to limit the invention. The singular expressions include plural expressions unless the context clearly dictates otherwise. In the present application, the terms "comprises" or "having" and the like are used to specify that there is a feature, a number, a step, an operation, an element, a component or a combination thereof described in the specification, But do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, or combinations thereof.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Terms such as those defined in commonly used dictionaries are to be interpreted as having a meaning consistent with the contextual meaning of the related art and are to be interpreted as either ideal or overly formal in the sense of the present application Do not.

In general, an image may be composed of a series of still images. The still images may be classified into a group of pictures (GOP), and each still image is referred to as a picture or a frame can do. As a higher concept, a unit such as a GOP and a sequence may exist, and each picture may be divided into predetermined areas such as slices, tiles, blocks, and the like. In addition, a unit of an I picture, a P picture, a B picture, and the like may be included in one GOP. The I picture may be a picture to be encoded / decoded by itself without using a reference picture, and the P picture and the B picture may be subjected to a process such as motion estimation (Motion estimation) and motion compensation (motion compensation) And may be a picture to be encoded / decoded. In general, an I picture and a P picture can be used as a reference picture in the case of a P picture, and a reference picture can be used as an I picture and a P picture in the case of a B picture, but this definition can also be changed by setting of encoding / decoding .

Here, a picture referred to in encoding / decoding is referred to as a reference picture, and a block or pixel to be referred to is referred to as a reference block and a reference pixel. The reference data may be not only the pixel values of the spatial domain but also the coefficient values of the frequency domain and various encoding / decoding information generated and determined during the encoding / decoding process.

The minimum unit of image can be a pixel, and the number of bits used to represent one pixel is called a bit depth. In general, the bit depth can be 8 bits and can support different bit depths depending on the encoding setting. The bit depth may be supported by at least one bit depth depending on the color space. Also, it may be configured as at least one color space according to the color format of the image. One or more pictures having a predetermined size or one or more pictures having different sizes according to a color format. For example, in the case of YCbCr 4: 2: 0, it may be composed of one luminance component (Y in this example) and two chrominance components (Cb / Cr in this example) The composition ratio may have a width of 1: 2. As another example, in the case of 4: 4: 4, it may have the same composition ratio in the horizontal and vertical directions. If it is composed of more than one color space as in the above example, the picture can perform the division into each color space.

In the present invention, some color spaces (Y in this example) of some color formats (YCbCr in this example) will be described, and the same color space (Cb, Cr in this example) Similar applications (settings dependent on a specific color space) can be made. However, it may also be possible to place a partial difference (an independent setting for a specific color space) in each color space. That is, the setting depending on each color space has a setting proportional to or dependent on the composition ratio of each component (for example, determined by 4: 2: 0, 4: 2: 2, 4: 4: 4, And the setting independent of each color space can be regarded as having a setting of only the corresponding color space regardless of the constituent ratio of each element or independently. In the present invention, depending on the subdecoder, the subdecoder may have an independent setting for some of the configurations or may have a dependent setting.

The setup information or syntax elements required in the image coding process can be determined at a unit level such as a video, a sequence, a picture, a slice, a tile, and a block. The VPS, the sequence parameter set (SPS) Set, Slice Header, Tile Header, Block Header, etc., and transmitted to the decoder. In the decoder, the setting information transmitted from the encoder is parsed by parsing at the same level unit, It can be used for decryption process. In addition, related information can be transmitted and parsed in the form of SEI (Supplement Enhancement Information) or Metadata in a bit stream. Each parameter set has a unique ID value, and in the lower parameter set, it can have an ID value of an upper parameter set to be referred to. For example, information of an upper parameter set having a matching ID value among one or more higher parameter sets in the lower parameter set may be referred to. In the case where any one of the examples of various units mentioned above includes one or more other units, the corresponding unit may be referred to as an upper unit and the included unit may be referred to as a lower unit.

In the case of the setting information generated in the unit, the setting information may include contents of independent setting for each unit, or contents related to setting depending on the previous, the next, or the upper unit. Here, it can be understood that the dependent setting indicates the setting information of the corresponding unit with flag information (for example, 1 if the flag is 1, not followed by 0) to follow the setting of the previous unit and then the higher unit. The setting information in the present invention will be described with reference to an example of an independent setting, but an example in which addition or substitution is made to the contents of a relation that relies on setting information of a previous unit, a subsequent unit, or a higher unit of the current unit .

Hereinafter, preferred embodiments according to the present invention will be described in detail with reference to the accompanying drawings.

1 is a conceptual diagram of an image encoding and decoding system according to an embodiment of the present invention.

1, the image encoding apparatus 105 and the decoding apparatus 100 may be implemented as a personal computer (PC), a notebook computer, a personal digital assistant (PDA), a portable multimedia player (PMP) Player, a PlayStation Portable (PSP), a wireless communication terminal, a smart phone, a TV, a server terminal such as an application server and a service server, A communication device such as a communication modem for performing communication with a wired / wireless communication network, a memory (memories 120 and 125) for storing various programs for inter or intra prediction for encoding or decoding an image and memories (memories 120 and 125) And a processor (processor, 110, 115) for controlling the processor. The video encoded by the video encoding apparatus 105 can be transmitted through a wired or wireless communication network such as the Internet, a short-range wireless communication network, a wireless network, a WiBro network, or a mobile communication network in real time or non- And then transmitted to the image decoding apparatus 100 through various communication interfaces such as a serial bus (USB: Universal Serial Bus), etc., decoded by the image decoding apparatus 100, and restored and reproduced as an image. In addition, the image encoded by the image encoding apparatus 105 as a bit stream can be transferred from the image encoding apparatus 105 to the image decoding apparatus 100 via a computer-readable recording medium.

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

2, the image encoding apparatus 20 according to the present embodiment includes a predictor 200, a subtractor 205, a transformer 210, a quantizer 215, an inverse quantizer 220, An inverse transform unit 225, an adder 230, a filter unit 235, an encoding picture buffer 240, and an entropy encoding unit 245.

The prediction unit 200 may include an intra prediction unit for performing intra prediction and an inter prediction unit for performing inter prediction. Intra prediction can generate a prediction block by performing spatial prediction using pixels of adjacent blocks of the current block. In inter-prediction, motion compensation is performed by searching an area that is most matched with the current block from the reference image A prediction block can be generated. (Intra prediction) mode, a motion vector, a motion vector, and the like) for the corresponding unit (coding unit or prediction unit) Video, etc.). At this time, the processing unit to be predicted, the prediction method, and the processing unit in which the concrete contents are determined can be determined according to the subdecryption setting. For example, the prediction method, the prediction mode, and the like are determined as a prediction unit, and the prediction can be performed in units of conversion.

Subtraction unit 205 subtracts the prediction block from the current block to generate a residual block. That is, the subtractor 205 calculates the difference between the pixel value of each pixel of the current block to be encoded and the predicted pixel value of each pixel of the predictive block generated through the predictor to generate a residual block, which is a residual signal of a block form .

The transform unit 210 transforms the residual block into a frequency domain and transforms each pixel value of the residual block into a frequency coefficient. Here, the transforming unit 210 transforms the transformed transformed transformed data into transformed transformed transform coefficients based on Hadamard Transform, DCT Based Transform, DST Based Transform, and KLT Based Transform Transform) can be transformed into a frequency domain by using various transformation techniques for transforming an image signal of a spatial axis into a frequency domain. The residual signal transformed into the frequency domain is a frequency coefficient. The transform can be transformed by a one-dimensional transform matrix. Each transformation matrix can be adaptively used in horizontal and vertical units. For example, in the case of intra prediction, if the prediction mode is horizontal, a DCT-based transformation matrix may be used in the vertical direction and a DST-based transformation matrix may be used in the horizontal direction. In the case of vertical, a DCT-based transformation matrix may be used in the horizontal direction and a DST-based transformation matrix may be used in the vertical direction.

The quantization unit 215 quantizes the residual block having the frequency coefficients converted into the frequency domain by the transform unit 210. Here, the quantization unit 215 may quantize the transformed residual block using Dead Zone Uniform Threshold Quantization, a Quantization Weighted Matrix, or an improved quantization technique. It can be set to one or more quantization schemes as candidates and can be determined by encoding mode, prediction mode information, and the like.

The entropy encoding unit 245 scans the generated quantization frequency coefficient sequence according to various scanning methods to generate a quantization coefficient sequence, and outputs the quantization coefficient sequence using an entropy encoding technique or the like. The scan pattern can be set to one of various patterns such as zigzag, diagonal, and raster. Also, it is possible to generate encoded data including encoded information transmitted from each component and output the generated encoded data as a bit stream.

The inverse quantization unit 220 inversely quantizes the residual block quantized by the quantization unit 215. That is, the dequantizer 220 dequantizes the quantized frequency coefficient sequence to generate a residual block having a frequency coefficient.

The inverse transform unit 225 inversely transforms the inversely quantized residual block by the inverse quantization unit 220. That is, the inverse transform unit 225 inversely transforms the frequency coefficients of the inversely quantized residual block to generate a residual block having a pixel value, that is, a reconstructed residual block. Here, the inverse transform unit 225 may perform the inverse transform using the inverse transform used in the transform unit 210.

The adder 230 restores the current block by adding the predicted block predicted by the predictor 200 and the residual block reconstructed by the inverse transform unit 225. [ The reconstructed current block is stored in the encoding picture buffer 240 as a reference picture (or a reference block), and can be used as a reference picture when coding a next block or another block or another picture in the current block.

The filter unit 235 may include one or more post-processing filter processes such as a deblocking filter, a sample adaptive offset (SAO), and an adaptive loop filter (ALF). The deblocking filter can remove block distortion occurring at the boundary between the blocks in the reconstructed picture. The ALF can perform filtering based on a comparison between the reconstructed image and the original image after the block is filtered through the deblocking filter. The SAO can recover the offset difference from the original image on a pixel-by-pixel basis with respect to the residual block to which the deblocking filter is applied. Such a post-processing filter may be applied to the restored picture or block.

The encoded picture buffer 240 may store a restored block or picture through the filter unit 235. [ The reconstruction block or picture stored in the encoding picture buffer 240 may be provided to the prediction unit 200 that performs intra-picture prediction or inter-picture prediction.

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

3, the image decoding apparatus 30 includes an entropy decoding unit 305, a predicting unit 310, an inverse quantization unit 315, an inverse transform unit 320, an adder / subtracter 325, a filter 330, And a decoded picture buffer 335, as shown in Fig.

In addition, the prediction unit 310 may include an intra prediction module and an inter prediction module.

First, when an image bitstream transmitted from the image encoding apparatus 20 is received, the image bitstream can be transmitted to the entropy decoding unit 305.

The entropy decoding unit 305 may decode the decoded data including the quantized coefficients and the decoded information to be transmitted to the constituent units by decoding the bit stream.

The prediction unit 310 may generate a prediction block based on the data transmitted from the entropy decoding unit 305. [ At this time, based on the reference image stored in the decoded picture buffer 335, a reference picture list using a default construction technique may be constructed.

The inverse quantization unit 315 is provided as a bitstream and can dequantize the quantized transform coefficients decoded by the entropy decoding unit 305. [

The inverse transform unit 320 may apply inverse DCT, inverse integer transform, or similar inverse transformation techniques to the transform coefficients to generate residual blocks.

The inverse quantization unit 315 and the inverse transformation unit 320 inversely perform the processes performed by the transform unit 210 and the quantization unit 215 of the image encoding apparatus 20 described above and may be implemented in various ways have. For example, the same process and inverse transformation that are shared with the transform unit 210 and the quantization unit 215 may be used, and information on the transform and quantization process (for example, transform size, transform Shape, quantization type, etc.), the transformation and quantization processes can be performed inversely.

The residual block subjected to the inverse quantization and inverse transform process may be added to the prediction block derived by the prediction unit 310 to generate a reconstructed image block. This addition may be performed by the adder / subtracter 325.

The filter 330 may apply a deblocking filter to the reconstructed image block to remove a blocking phenomenon if necessary, and may further add other loop filters to improve the video quality before and after the decoding process. It can also be used.

The reconstructed and filtered image block may be stored in the decoded picture buffer 335.

Although not shown in the figure, the image decoding apparatus 30 may further include a division unit, wherein the division unit may include a picture division unit and a block division unit. The division is the same as or equivalent to that of the image encoding apparatus according to FIG. 2, and can be easily understood by a person skilled in the art, so a detailed description will be omitted.

On the other hand, it can be divided into coding units (or blocks) of various sizes through the block dividing unit. At this time, the encoding unit may be composed of a plurality of encoding blocks (for example, one luminance encoding block, two color difference encoding blocks, etc.) according to the color format. For ease of explanation, one color component unit is assumed. The encoding block may have variable sizes such as MxM (e.g., M is 4, 8, 16, 32, 64, 128, etc.). Alternatively, according to a partitioning scheme (for example, tree-based partitioning, quadtree partitioning <Quad Tree. QT>, binary tree <Binary Tree. BT>, and a ternary tree <Ternary Tree. MxN (e.g., M and N may be variable sizes such as 4, 8, 16, 32, 64, 128, etc.). At this time, the encoded block may be a unit that is a basis for intra-picture prediction, inter-picture prediction, conversion, quantization, entropy coding, and the like.

In the present invention, although it is described under the assumption that a plurality of sub-blocks (symmetries) having the same size and shape are obtained according to the division method, asymmetric sub-blocks (for example, in the case of a binary tree, > 1: 3 or 3: 1, or the aspect ratio <the same as horizontal> is 1: 3 or 3: 1. In the case of a ternary tree, the horizontal ratio < 1 < / RTI >: 1 < RTI ID = 0.0 > and the like).

The division of an encoding block (MxN) may have a recursive tree-based structure. At this time, whether or not to divide can be indicated through the division flag. For example, when the division flag of the coding block having the division depth k is 0, the coding block is encoded in the coding block having the division depth k. If the division flag of the coding block having the division depth k is 1 The coding of the coded block may be performed by four sub-coded blocks (quad tree partition) or two sub-coded blocks (binary tree partition) or three sub-coded blocks (turntree partition) with a division depth k + Lt; / RTI &gt;

The sub-encoding block may be divided into a sub-encoding block (k + 2) through the process of setting the encoding block (k + 1) ) Can be supported.

For binary tree partitioning, split flags and split direction flags (horizontal or vertical) can be supported. If the binary tree partition supports one or more partition ratios (e.g., additional partition ratios other than 1: 1 in the horizontal or vertical ratios, i.e., support for asymmetric partitioning) A ratio of one of the ratio candidates <1: 1, 1: 2, 2: 1, 1: 3, 3: 1>) may be supported, or other types of flags (eg, There is no additional information as to the partition, and if 0, additional information on the ratio asymmetric partition is required) can be supported.

In the case of a ternary division, a split flag and a split direction flag can be supported. Additional partition information such as the binary tree may be needed if the ternary partition supports one or more partition ratios.

The above example is partition information that is generated when only one tree partition is valid, and in the case where a plurality of tree partition is effective, partition information can be configured as follows.

For example, in a case where a plurality of tree partitioning is supported, partition information corresponding to a line-up order may be configured first if there is a predetermined partitioning priority. If the division flag corresponding to the preceding rank is true (division is performed), additional division information of the division method may be continued. If the division flag is false (division execution x), division information of the division method Flag, split direction flag, etc.).

Alternatively, in the case where a plurality of tree segmentation is supported, selection information on the partitioning scheme may be additionally generated, and may be configured with partitioning information according to the selected partitioning scheme.

In the case of the partial flags, the flag may be omitted depending on the preceding or previous division result.

The block division starts from the maximum encoding block and can proceed to the minimum encoding block. Alternatively, it may start at the minimum division depth (0) and proceed to the maximum division depth. That is, the partitioning can be performed recursively until the block size reaches the minimum coding block size or the division depth reaches the maximum division depth. At this time, in accordance with the sub / decoding setting (for example, image <slice, tile> type <I / P / B>, coding mode <Intra / Inter>, color difference component <Y / Cb / Cr> The size of the minimum coding block, and the maximum division depth can be adaptively set.

For example, when the maximum coded block is 128 x 128, quad tree partitioning can be performed in the range of 32 x 32 to 128 x 128, the binary tree partitioning can be performed in the range of 16 x 16 to 64 x 64, And the ternary division can be performed in the range of 8 x 8 to 32 x 32 and the maximum division depth of 3. Alternatively, the quadtree partitioning may be performed in the range of 8 x 8 to 128 x 128, and the binary tree and the turntree partitioning may be performed in the range of 4 x 4 to 128 x 128 and the maximum division depth of 3. In the former case, it may be an I picture type (for example, a slice), and in the latter case, a P or B picture type.

As described in the above example, the division setting such as the size of the maximum coding block, the size of the minimum coding block, the maximum division depth, and the like can be shared or individually supported according to the division method and the above setting / decoding setting.

If a plurality of partitioning schemes are supported, the partitioning is performed within the block support range of each partitioning scheme, and if the block support ranges of each partitioning scheme overlap, the priority of the partitioning scheme may exist. For example, a quadtree partition may precede a binary tree partition.

Or, the partition selection information to be executed when the partition support range overlaps can be generated. For example, selection information about the partitioning scheme performed during the binary tree and the ternary tree partitioning may occur.

Also, if a plurality of division methods are supported, it may be determined whether or not to perform a following division according to the result of the preceding division. For example, if the result of the preceding partition (quad tree in this example) indicates that the partition is to be performed, then the subsequent partition (in this example, the binary tree or the tertiary tree) The block is set again as an encoding block so that the segmentation can be performed.

Alternatively, if the result of the preceding segmentation indicates that the segmentation is not performed, the segmentation may be performed according to the result of the succeeding segmentation. At this time, when the result of the succeeding division (the binary tree or the turntree tree in this example) indicates that the division is performed, the divided sub-coded blocks are set as encoding blocks again to perform division, and the result of the following division If it indicates that no partitioning is performed, no further partitioning is performed. At this time, when the division result of the succeeding division indicates that division is performed and the divided sub-encoding block is set again as the encoding block, when a plurality of division methods are supported (for example, Case), the preceding partition can not be performed but only the subsequent partition can be supported. That is, when a plurality of division methods are supported, if the result of the preceding division shows that the division is not performed, it means that the preceding division is no longer performed.

For example, if the quad tree partitioning and the binary tree partitioning are possible, the M × N encoded block can check the quad tree division flag first. If the division flag is 1, (M >> 1) × (N >> 1 ) Size sub-encoding block, and the sub-encoding block is set as an encoding block again to perform the segmentation (quad-tree segmentation or binary tree segmentation). If the division flag is 0, the binary tree division flag can be confirmed. If the flag is 1, the sub-encoding block is divided into two sub-coded blocks of size (M >> 1) × N or M × (N >> 1) Is performed and the sub-encoding block is set as an encoding block again to perform segmentation (binary tree segmentation). If the division flag is 0, the dividing process is terminated and the coding process proceeds.

Although a case where a plurality of division methods are performed through the above example has been described, the present invention is not limited thereto, and various combinations of supporting methods can be possible. For example, a quadtree / binary tree / a ternary tree / a quadtree + a binary tree / a quadtree + a binary tree + a ternary tree may be used. At this time, information on whether or not the additional division method is supported may be implicitly determined or may be explicitly included in units of a sequence, a picture, a sub-picture, a slice, and a tile.

In the above example, the information related to the division such as the size information of the encoding block, the support range of the encoding block, and the maximum division depth may be included in the unit of the sequence, picture, sub picture, slice, tile or the like or implicitly determined. In summary, the range of allowable blocks can be determined by the size of the maximum coded block, the range of supported blocks, the maximum division depth, and the like.

The coding block obtained by performing the division through the above process can be set to the maximum size of intra-picture prediction or inter-picture prediction. That is, the coded block after the block division may be the start size of the division of the prediction block for intra-picture prediction or inter-picture prediction. For example, if the coding block is 2M x 2N, the prediction block may have a size of 2M x 2N, M x N that is equal to or smaller than the prediction block. Alternatively, it may have a size of 2Mx2N, 2MxN, Mx2N, and MxN. Alternatively, it may have the same size as the encoding block and have a size of 2M x 2N. In this case, the fact that the encoding block and the prediction block have the same size may mean that the prediction is performed with the size acquired through the division of the encoding block without performing the division of the prediction block. That is, the partition information for the prediction block is not generated. Such a setting may be applied to a transform block, and the transform may be performed on a divided block basis.

Various configurations may be possible according to the following sub-decode settings. For example, at least one prediction block and at least one transform block may be obtained based on an encoding block (after the encoding block is determined). Alternatively, one prediction block having the same size as the encoding block can be obtained, and at least one transform block can be obtained based on the encoding block. Alternatively, one prediction block and one transform block having the same size as the encoding block can be obtained. In the above example, when at least one block is acquired, partition information of each block can be generated (generated), and when one block is acquired, partition information of each block does not occur.

The square or rectangular block of various sizes obtained according to the above result may be a block used for intra prediction or inter prediction, and may be a block used for transforming and quantizing residual components. Lt; / RTI &gt;

4 is an exemplary diagram illustrating an intra prediction mode according to an embodiment of the present invention.

Referring to FIG. 4, 35 prediction modes can be identified, and 35 prediction modes can be classified into 33 directional modes and 2 non-directional modes (DC, Planar). At this time, the directional mode can be identified by a slope (for example, dy / dx) or angle information. The above example may mean a prediction mode candidate group for a luminance component or a chrominance component. Alternatively, the chrominance components may be supported in some prediction modes (e.g., DC, Planar, vertical, horizontal, diagonal mode, etc.). In addition, when the prediction mode of the luminance component is determined, the mode may be included in the prediction mode of the chrominance component, or a mode derived from the chrominance component may be included in the prediction mode.

In addition, the restoration block of another color space, which has been subdivided and decoded using the correlation between the color spaces, can be used for prediction of the current block and can include a prediction mode supporting the same. For example, in the case of a chrominance component, a reconstructed block of the luminance component corresponding to the current block can be generated as a prediction block of the current block.

The prediction mode candidate group can be determined adaptively according to the subdecryption setting. The number of candidate groups can be increased for the purpose of increasing the accuracy of the prediction and the number of candidate groups can be reduced for the purpose of reducing the bit amount according to the prediction mode.

For example, A candidate group (67, 65 directional mode and 2 non-directional mode), B candidate group (35. 33 directional mode and 2 non-directional mode), C candidate group (19, 17 directional mode And two non-directional modes) can be used. If there is no special description in the present invention, it is assumed that intra prediction is performed with one predetermined prediction mode candidate group (A candidate group).

5 is a first exemplary view of a reference pixel configuration used in intra-frame prediction according to an embodiment of the present invention.

The intra-frame prediction method in the image encoding according to an embodiment of the present invention includes a reference pixel forming step, a prediction block generating step using one or more prediction modes with reference to a reference pixel configured, a step of determining an optimal prediction mode, And encoding the mode. In addition, the image encoding apparatus may be configured to include a reference pixel forming step, a prediction block generating step, a prediction mode determining step, a reference pixel forming unit for implementing the prediction mode encoding step, a prediction block generating unit, a prediction mode determining unit, can do. Some of the above-described processes may be omitted or other processes may be added, and the order may be changed in a different order than the above-described order.

Meanwhile, in the intra-frame prediction method according to an embodiment of the present invention, the intra-frame prediction method includes constructing a reference pixel, and estimating a prediction of a current block according to a prediction mode obtained through a syntax element received by the image encoding apparatus Blocks can be created.

The size and type (M x N) of the current block in which the intra prediction is performed can be obtained from the block dividing unit and can have a size of 4 x 4 to 256 x 256. Intra prediction may be performed in units of prediction blocks, but may be performed in units of encoding blocks (or coding units), conversion blocks (or conversion units), etc., depending on the setting of the block division unit. After confirming the block information, the reference pixel composing unit can construct a reference pixel used for predicting the current block. In this case, the reference pixels may be managed through a temporary memory (e.g., array <Array>, primary array, secondary array, etc.), generated and removed for each intra-picture prediction process of the block, May be determined according to the configuration of the pixel.

The reference pixel may be a pixel belonging to an adjacent block (may be referred to as a reference block) positioned at the left, upper, left, upper right, and lower left of the current block, but the present invention is not limited thereto. It can also be used for prediction. Here, adjacent blocks located in the left, upper, upper, right, and lower left positions may be blocks selected depending on whether raster or Z scan is performed, and if the scan order is different, For example, a pixel belonging to the right, lower, left, right, lower, right, lower, left,

In addition, the reference block may be a block corresponding to the current block in a color space different from the color space to which the current block belongs. Here, when the Y / Cb / Cr format is taken as an example, the color space may mean one of Y, Cb and Cr. The block corresponding to the current block may have the same positional coordinates as the current block or may have a positional coordinate corresponding to the current block according to the color component composition ratio.

For convenience of explanation, it is assumed that reference blocks according to the predetermined positions (left, upper, left, upper right, lower left) are composed of one block. However, have.

In summary, the adjacent region of the current block may be the position of the reference pixel for intra-picture prediction of the current block, and the region corresponding to the current block of another color space may be considered as the position of the reference pixel according to the prediction mode have. In addition to the above example, the position of a reference pixel defined according to a prediction mode, a method, and the like can be determined. For example, when a prediction block is generated through a block matching method or the like, the reference pixel position may be determined based on a search range (for example, a search range in a sub-decoded area or a partially decoded area before the current block of the current image, An area included in the left or upper side or the upper left corner, the upper right corner, etc. of the current block) may be considered as the position of the reference pixel.

Referring to FIG. 5, the reference pixels used for the intra-frame prediction of the current block (size of M × N) are the left, upper, left, upper right, and lower left adjacent pixels (Ref_L, Ref_T, Ref_TL, Ref_TR, Ref_BL). In this case, in FIG. 5, what is expressed in the form of P (x, y) may mean pixel coordinates.

Meanwhile, the pixel adjacent to the current block can be classified into at least one reference pixel layer, and the pixel closest to the current block is ref_0 {pixels having a pixel value difference of 1 from the boundary pixel of the current block. p (-1, -1) to p (-1, -1) to p (-1, (2, -2), p (-2, -1) to p (-2, 2N)} ref_1, the next adjacent pixel {the boundary of the current block The difference between pixel and pixel value 3. p (-3, -3) ~ p (2M + 1, -3), p (-3, -2) ~ p (-3,2N + 1)} is divided by ref_2 . That is, the reference pixel can be classified into a plurality of reference pixel layers according to the pixel distance adjacent to the boundary pixel of the current block.

Here, the reference pixel layer can be set differently for adjacent neighboring blocks. For example, when using the current block as the reference block and the neighboring block as the reference block, the reference pixel according to the ref_0 layer is used. When the neighboring block is used as the reference block, the reference pixel according to the ref_1 layer can be used have.

In general, the reference pixel set referred to when intra prediction is performed belongs to neighboring blocks adjacent to the current block and the lower left, left, upper left, upper right, and ref_0 layers (pixels nearest to the boundary pixel) And are assumed to be such pixels unless otherwise described below. However, only the pixels belonging to some blocks among the above-mentioned neighboring blocks may be used as a reference pixel set, or pixels belonging to two or more layers may be used as a reference pixel set. Here, the reference pixel set or hierarchy may be determined implicitly (preset in the subdecoder / decoder) or explicitly determined (information that can be determined from the encoder).

Here, it is assumed that a maximum of three reference pixel layers are supported. However, the number of reference pixel layers can be more than three, and the number of reference pixel sets according to the number of reference pixel layers and the positions of referenceable neighboring blocks I / P / B < / RTI > At this time, the image may be set differently according to a picture, a slice, a tile, etc., a color component, and the related information may be included in a unit of a sequence, a picture, a slice, or a tile.

In the present invention, a case where a low index (incremented from 0 to 1) is allocated from the reference pixel layer closest to the current block is presupposed, but the present invention is not limited thereto. Further, the reference-pixel-configuration-related information to be described later can be generated under the above-mentioned index setting (binarization in which a short bit is assigned to a small index when one of a plurality of reference pixel sets is selected).

In addition, when two or more reference pixel layers are supported, a weighted average or the like can be applied to each reference pixel included in two or more reference pixel layers.

For example, a prediction block can be generated using reference pixels obtained by summing weights of ref_0 and ref_1 layers of FIG. At this time, the pixel to which the weight sum is applied in each reference pixel layer may be a pixel unit as well as an integer unit pixel according to a prediction mode (for example, prediction mode directionality). (For example, 7: 1, 3: 1, 1: 1, 2: 1, , 2: 1, 1: 1, and so on) to obtain one prediction block. In this case, the weighting value may have a higher weight value as the prediction block according to the reference pixel layer adjacent to the current block.

Assuming that information is explicitly generated in relation to the reference pixel structure, the instruction information (adaptive_intra_ref_sample_enabled_flag in this example) allowing an adaptive reference pixel configuration may occur in units of video, sequence, picture, slice, tile, .

The adaptive reference pixel configuration information (adaptive_intra_ref_sample_flag in this example) may be generated in units of pictures, slices, tiles, blocks, etc., if the instruction information indicates that the adaptive reference pixel configuration is acceptable (adaptive_intra_ref_sample_enabled_flag = 1 in this example) have.

If the configuration information indicates an adaptive reference pixel configuration (adaptive_intra_ref_sample_flag = 1 in this example), the reference pixel organization related information (e.g., selection information on the reference pixel hierarchy and the aggregation, such as intra_ref_idx in this example) Slices, tiles, blocks, and the like.

At this time, if the adaptive reference pixel configuration is not allowed or the adaptive reference pixel configuration is not used, the reference pixel may be configured according to a predetermined setting. (Ref_0 and ref_1, for example, are selected as the reference pixel layer, and ref_0 and ref_1 are weighted through ref_0 and ref_1, respectively). However, the present invention is not limited to this, A case where a predictive pixel value is generated by a method such as summing, that is, an implied case) may be possible.

In addition, the reference pixel organization related information (e.g., reference pixel hierarchy or selection information for the aggregate) may be configured (for example, ref_1, ref_2, ref_3, etc.), but it is not so limited.

Some examples of the reference pixel configuration have been described with reference to the above example, which may be combined with various sub-decode information to determine intra-picture prediction settings. In this case, the sub-decoded information includes at least one of a video type, a color component, a size and a type of a current block, a prediction mode (a type of a prediction mode (directionality and non-directionality), a direction of a prediction mode (vertical, horizontal, diagonal 1, diagonal 2, } Or the like, and an intra-picture prediction setting (reference pixel configuration in this example) can be determined according to the sub-decoding information of the neighboring block and the combination of the sub-decoding information of the current block and the neighboring block.

6A to 6C are second exemplary views of a reference pixel structure according to an embodiment of the present invention.

Referring to FIG. 6A, it can be seen that the reference pixel is composed only of ref_0 reference pixel layer in FIG. (reference pixel generation, reference pixel filtering, and reference pixel generation) after a reference pixel is constructed using pixels belonging to a neighboring block (for example, lower left, left, upper left, Reference pixel interpolation, prediction block generation, post-processing filtering, etc. Some intra-picture prediction processes can be adaptively performed depending on the reference pixel configuration). In this example, there is shown an example in which intra prediction is performed using a non-directional mode without setting information for the reference pixel hierarchy when one preset reference pixel hierarchy is used.

Referring to FIG. 6B, it can be confirmed that reference pixels are formed by using all of the two supported reference pixel layers. That is, the intra prediction can be performed after using the pixels belonging to the hierarchy ref_0 and the hierarchy ref_1 (or by using the weighted average value of the pixels belonging to the two hierarchies) reference pixels. In this example, the setting information for the reference pixel hierarchy is not generated, but a certain directional prediction mode (right upper to left lower direction or the opposite direction in the drawing) And the prediction is performed.

Referring to FIG. 6C, it can be confirmed that a reference pixel is constructed using only one reference pixel layer out of three supported reference pixel layers. In this example, there are a plurality of reference pixel hierarchy candidates, setting information for the reference pixel hierarchy to be used among them is generated, and an example in which the in-screen side is performed using some directional prediction mode (upper left to lower right in the drawing) .

7 is a third exemplary view of a reference pixel structure according to an embodiment of the present invention.

7 is a block having a size of 64 × 64 or more, a drawing symbol b is a block having a size of 16 × 16 or more and less than 64 × 64, and a drawing symbol c is a block having a size of less than 16 × 16.

If the block according to the drawing symbol a is a current block to be subjected to in-picture prediction, intra-picture prediction can be performed using the nearest neighbor reference pixel ref_0.

In addition, if the block according to the drawing symbol b is a current block to be subjected to in-frame prediction, intra prediction can be performed using two supportable reference pixel layers ref_0 and ref_1.

In addition, if the block according to the drawing symbol c is the current block to be subjected to in-frame prediction, intra prediction can be performed using three supportable reference pixel layers ref_0, ref_1, ref_2.

Referring to the explanations with reference to the drawing symbols a to c, it is possible to determine the number of supportable reference pixel layers differently according to the size of a current block to be subjected to intra prediction. In FIG. 7, the larger the size of the current block, the higher the probability that the size of the neighboring block is small. This may be a result of division due to other image characteristics. Therefore, It is assumed that as the size of the block increases, the number of supported reference pixel layers decreases. However, other variants including the opposite case are also possible.

8 is a fourth exemplary view of a reference pixel structure according to an embodiment of the present invention.

Referring to FIG. 8, it can be seen that the current block performing the intra prediction is of a rectangular shape. If the current block is rectangular and the horizontal and vertical are asymmetric, the number of support of the reference pixel layer adjacent to the horizontal side boundary having a long length in the current block is set to be large and the support of the reference pixel layer adjacent to the vertical boundary surface having a short length in the current block You can set a small number. In the figure, it is confirmed that the reference pixel layer adjacent to the horizontal boundary surface of the current block is set to two, and the reference pixel layer adjacent to the vertical boundary surface of the current block is set to one. This is because the accuracy of the prediction can be reduced because the pixels adjacent to the short side of the current block in the short side are often far away from the pixels included in the current block (because of a long length). Therefore, although the number of support of the reference pixel hierarchy adjacent to the side of the longitudinally shortened side is set small, the opposite case may be possible.

In addition, the reference pixel layer to be used for prediction can be determined differently depending on the type of the intra prediction mode or the neighboring block neighboring the current block. For example, in a directional mode using a pixel belonging to a block adjacent to the upper and upper ends of the current block as reference pixels, two or more reference pixel layers are used, and a pixel belonging to a block adjacent to the left end and the lower left end of the current block is referred to The directional mode used as a pixel may use only the nearest reference pixel layer.

On the other hand, if the prediction blocks generated through the reference pixel layers in the plurality of reference pixel layers are the same or similar to each other, generating the setting information of the reference pixel layer may be a result of additionally generating unnecessary data.

For example, if the distribution characteristics of the pixels constituting each reference pixel hierarchy are similar or identical to each other, a similar or identical prediction block can be generated regardless of which reference pixel hierarchy is used. Therefore, it is necessary to generate data for selecting a reference pixel hierarchy There is no. At this time, the distribution characteristic of the pixels constituting the reference pixel layer can be determined by comparing the average or variance of the pixels with a predetermined threshold value.

That is, if the reference pixel layers are the same or similar based on the finally determined intra-picture prediction mode, the reference pixel layer can be selected by a predetermined method (for example, selecting the nearest reference pixel layer).

At this time, the decoder may receive intra-picture prediction information (or intra-picture prediction mode information) from the encoding apparatus and determine whether to receive information for selecting a reference pixel hierarchy based on the received information.

Although reference pixels are formed using a plurality of reference pixel layers through the various examples, the present invention is not limited thereto, and various modifications may be possible and may be combined with other additional configurations.

The reference pixel forming unit of the intra prediction may include a reference pixel generating unit, a reference pixel interpolating unit, a reference pixel filter unit, and the like, and may include all or a part of the above configuration. Herein, a block including pixels which can be reference pixels may be referred to as a reference candidate block. Also, the reference candidate block may be a neighboring block that is generally adjacent to the current block.

It is possible to determine whether a pixel belonging to the reference candidate block can be used as a reference pixel according to the reference pixel availability (Availability) set for the reference candidate block in the reference pixel block.

The usability of the reference pixel can be determined to be unusable when at least one of the following conditions is satisfied. For example, when the reference candidate block is located outside the picture boundary, it does not belong to the same division unit (for example, slice, tile, etc.) as the current block, and the sub- It is determined that the pixels belonging to the corresponding reference candidate block can not be referred to. At this time, if all of the above conditions are not satisfied, it can be judged that it is usable.

Further, the use of the reference pixels can be restricted by the setting of the subdivision / decryption. For example, when a flag (for example, constrained_intra_pred_flag) that restricts a reference to a reference candidate block is activated, the pixel belonging to the reference candidate block can be restricted so that it can not be used as a reference pixel. The flag may be applied to a case where the reference candidate block is a reconstructed block referring to an image temporally different from the current picture in order to perform robust addition / decryption due to various external factors including a communication environment.

Here, if the flag for limiting the reference is disabled (for example, the constrained_intra_pred_flag = 0 in the I picture type or the P or B picture type), the pixel of the reference candidate block can be used as the reference pixel. In addition, depending on whether the reference candidate block is coded by intra-picture prediction or inter-picture prediction when the flag for limiting the reference is activated (for example, constrained_intra_pred_flag = 1 in the P or B picture type) Whether or not reference is possible can be determined. That is, if the reference candidate block is coded by intra prediction, the reference candidate block can be referred to regardless of whether the flag is activated or not, and if the reference candidate block is coded by inter prediction , And the referential candidate block can be referenced according to whether the flag is activated or not.

Also, a restoration block having a position corresponding to the current block in another color space may be a reference candidate block. At this time, whether or not the reference candidate block can be referred to can be determined according to the coding mode of the reference candidate block. For example, if the current block belongs to a certain chrominance component (Cb, Cr), it is determined whether or not the current block has a position corresponding to the current block in the luminance component (Y) Whether or not reference is possible can be determined. This may be an example corresponding to the case where the encoding mode is independently determined according to the color space.

The flag to limit the reference may be a setting applied in some video types (e.g., P or B slice / tile type, etc.).

It is possible to classify all of the reference candidate blocks as usable, partially usable, and all useless as a reference candidate block through the usability of reference pixels. It is possible to fill or generate reference pixels of unusable candidate block positions in all cases except when all of them are usable.

If a reference candidate block is available, a pixel at a predetermined position of the block (or a pixel adjacent to the current block) can be stored in the reference pixel memory of the current block. At this time, the pixel data of the corresponding block position may be copied as it is or may be stored in the reference pixel memory through a process such as reference pixel filtering.

If the reference candidate block is unavailable, the pixel obtained through the reference pixel generation process can be included in the reference pixel memory of the current block.

In summary, a reference pixel can be constructed when the reference pixel candidate block is usable, and an entropy pixel can be generated when the reference pixel candidate block is unusable.

A method of filling a reference pixel at a predetermined position in an unusable reference candidate block is as follows. First, a reference pixel can be generated using an arbitrary pixel value. Here, the arbitrary pixel value is a specific pixel value belonging to a pixel value range, and may be a minimum value, a maximum value, or a median value of a pixel value used in a pixel value adjusting process based on bit depth or a pixel value adjusting process based on pixel value range information of an image , And may be a value derived from the values. Here, generating a reference pixel with an arbitrary pixel value may be applied when all the reference candidate blocks are unusable.

Next, a reference pixel can be generated by using pixels belonging to a block adjacent to the unusable reference candidate block. Specifically, the pixels belonging to the adjacent block can be extrapolated, interpolated, or copied to a predetermined position in the unusable reference candidate block and filled in. At this time, the direction of performing the copying or extrapolation may be clockwise or counterclockwise, and may be determined according to the sub / decryption setting. For example, the reference pixel generation direction in the block may follow a predetermined one direction or may be adaptively determined according to the position of the unusable block.

Figs. 9A and 9B are diagrams for explaining a method of filling a reference pixel at a preset position in an unusable reference candidate block. Fig.

Referring to FIG. 9A, a method of filling pixels belonging to an unusable reference candidate block among reference pixels composed of one reference pixel layer can be confirmed. Referring to FIG. 9A, when a neighboring block adjacent to the current block is an unusable reference candidate block, a reference pixel (denoted by < 1 >) belonging to a neighboring block adjacent to the upper right of the current block is referred to as a reference pixel belonging to a neighboring block adjacent to the upper end of the current block Can be generated by extrapolating in clockwise or linear extrapolation.

In FIG. 9A, when a neighboring block adjacent to the left of the current block is a unusable reference candidate block, a reference pixel (denoted by < 2 >) belonging to a neighboring block adjacent to the left is a neighboring block (Corresponding to a possible block) in a counterclockwise direction. At this time, if extrapolated or linearly extrapolated in the clockwise direction, reference pixels belonging to neighboring blocks adjacent to the lower left end of the current block can be used.

Further, in FIG. 9A, a part of reference pixels belonging to neighboring blocks on the upper side of the current block (denoted by < 3 >) can be generated by interpolating or linearly interpolating reference pixels usable on both sides. That is, a case where not all of the reference pixels belonging to the neighboring block but some of the reference pixels can not be used can also be set. In this case, unusable reference pixels can be used to fill unusable reference pixels.

Referring to FIG. 9B, a method of filling a reference pixel which can not be used when some reference pixels are unavailable among reference pixels composed of a plurality of reference pixel layers can be confirmed. Referring to FIG. 9B, when neighboring blocks adjacent to the upper right corner of the current block are reference blocks that can not be used, pixels (denoted by < 1 >) belonging to the three reference pixel hierarchies belonging to the neighboring block, May be generated clockwise using pixels belonging to adjacent neighboring blocks (corresponding to usable blocks).

If the neighboring block adjacent to the left of the current block is a useless candidate block and the neighboring block adjacent to the upper left and lower left of the current block is a usable candidate block, Direction, the counterclockwise direction, or both directions to generate reference pixels of unusable reference candidate blocks.

At this time, the unusable reference pixels of each reference pixel hierarchy can be generated using the pixels of the same reference pixel hierarchy, but the use of pixels of the same reference pixel hierarchy is not excluded. For example, referring to FIG. 9B, reference pixels (denoted by < 3 >) along three reference pixel layers belonging to neighboring blocks adjacent to the upper end of the current block are assumed as unusable reference pixels. At this time, the pixels belonging to the reference pixel hierarchy ref_0 and the reference pixel hierarchy ref_0 closest to the current block can be generated using the usable reference pixels belonging to the same reference pixel hierarchy. In addition, the pixels belonging to the reference pixel hierarchy ref_1 separated by a distance of one pixel from the current block use pixels belonging to the same reference pixel hierarchy ref_1 as well as pixels belonging to the other reference pixel hierarchy ref_0 and ref_2 Lt; / RTI &gt; At this time, reference pixels usable on both sides can be filled with unusable reference pixels by a method such as quadratic linear interpolation.

The above example shows an example in which a reference pixel is generated when some reference candidate blocks are not available when a plurality of reference pixel layers are configured as reference pixels. Alternatively, in a setting that does not allow an adaptive reference pixel configuration according to a sub / decode setting (e.g., when at least one reference candidate block is unavailable or all reference candidate blocks are unavailable) adaptive_intra_ref_sample_flag = 0) may be possible. That is, the reference pixel can be configured according to a predetermined setting without any additional occurring information.

The reference pixel interpolator can generate the reference pixel in the decimal unit through the linear interpolation of the reference pixel. In the present invention, it is assumed that the process is a partial process of the reference pixel forming unit, but it may be included in the prediction block generating unit and can be understood as a process performed before generating the prediction block.

Although it is assumed that the process is different from the reference pixel filter unit described later, it can be integrated into one process. This may be a case in which a case of generating a distortion in a reference pixel due to an increase in the number of filtering applied to the reference pixel when a plurality of filtering is applied through the reference pixel interpolator and the reference pixel filter unit.

The reference pixel interpolation process may be performed in a certain prediction mode (for example, a horizontal mode, a vertical mode, a partial diagonal mode, a diagonal down left mode, a diagonal down left mode, (A mode in which interpolation is not required in decimal units at the time of generating a prediction block), and other prediction modes (a mode in which a decimal unit interpolation is required at the time of generating a prediction block).

The interpolation precision (for example, pixel units of 1, 1/2, 1/4, 1/8, 1/16, 1/32, 1/64, etc.) can be determined according to the prediction mode have. For example, in the case of a prediction mode having a 45-degree angle, an interpolation process is not required, and in the case of a prediction mode having an angle of 22.5 degrees or 67.5 degrees, a half-pixel interpolation is required. As described above, at least one interpolation accuracy and maximum interpolation precision can be determined according to the prediction mode.

(For example, a 4-tap cubic filter, a 4-tap Gaussian filter, a 6-tap linear interpolation filter, or a 4-tap linear interpolation filter) -tap winner filter, 8-tap Kalman filter, etc.) can be used according to the setting of the sub / decoder. At this time, the interpolation filter can be divided into the difference of the number of filter tap (i.e., the number of pixels to which filtering is applied) and the filter coefficient.

The interpolation may be performed step by step in a low precision to a high precision order (e.g., 1/2 -> 1/4 - 1/8), and may be performed collectively. In the former case, interpolation is performed based on a pixel in an integer unit and a pixel in a decimal unit (a pixel interpolated in advance with a precision lower than a pixel to be interpolated). In the latter case, It may mean performing interpolation.

When using one of a plurality of filter candidate groups, the filter selection information can be explicitly generated or implicitly defined, and the sub-decode setting (e.g., interpolation precision, block size, shape, prediction mode, etc.) . &Lt; / RTI &gt; In this case, explicitly generated units are video, sequence, picture, slice, tile, block, and the like.

For example, in the case of having 1/4 or more interpolation accuracy (1/2, 1/4), an 8-tap Kalman filter is applied to reference pixels in integer units, and an interpolation precision / 8, 1/16), a 4-tap Gaussian filter is applied to the reference pixels in the integer unit and the interpolated reference pixels in units of 1/4 or more, and interpolation precision of 1/16 or less / 64), a 2-tap linear filter can be applied to an integer reference pixel and an interpolated reference pixel of 1/16 or more units.

Alternatively, an 8-tap Kalman filter is applied to 64 × 64 or more blocks, a 6-tap Wiener filter is applied to 64 × 64 or more blocks of 16 × 16 or more, and 4- tap Gaussian filter can be applied.

Alternatively, a 4-tap Gaussian filter may be applied for a prediction mode with a 22.5 degree angular difference based on a vertical or horizontal mode and a 4-tap Gaussian filter for a prediction mode with a 22.5 degree angular difference or more.

In addition, a plurality of candidate filter groups may be composed of a 4-tap cubic filter, a 6-tap winner filter, and an 8-tap Kalman filter for some subdivisions / decode settings, a 2-tap linear filter, tap Wiener filter.

FIGS. 10A to 10C are views illustrating a method of performing interpolation based on a fractional pixel unit for reference pixels constructed according to an embodiment of the present invention.

Referring to FIG. 10A, a method of interpolating a pixel of a decimal unit when one reference pixel layer ref_i is supported as a reference pixel can be confirmed. Specifically, interpolation can be performed by applying filtering (denoted by int_func_1D as a filtering function) to pixels adjacent to the interpolation target pixel (denoted by x) (assuming that a filter is applied to an integer unit pixel in this example). Here, since one reference pixel layer is used as a reference pixel, interpolation can be performed using adjacent pixels belonging to the same reference pixel hierarchy as the pixel x to be interpolated.

Referring to FIG. 10B, a method of acquiring interpolation pixels of a decimal unit in a case where two or more reference pixel layers ref_i, ref_j, and ref_k are supported as reference pixels can be confirmed. In FIG. 10B, when performing the reference pixel interpolation process in the reference pixel layer ref_j, it is possible to interpolate the interpolation target pixel in the fractional unit by further using another reference pixel layer ref_k, ref_i. Specifically, the pixel (x _k , x) of the interpolation object pixel (position of x _j ) and the pixel (x _k , x) of the position belonging to another reference pixel hierarchy and corresponding to the interpolation object pixel s _i) of the adjacent pixels for each of (a _k ~ h _k, a _j ~ h _j, a _i ~ h _i) the filter (s interpolation process. int_func_1D function) first interpolation pixel is obtained, and the obtained (x _k , by performing an additional filter (which may be applicable instead of the interpolation process, [1, 2, 1] / 4, [1, 6,1] / 8, the weighted average or the like, such as filter) for x _j, x _i) Finally, the final interpolation pixel (x) in the reference pixel hierarchy ref_j can be obtained. In this example, it is assumed that the pixel (x _k , x _i ) of another reference pixel layer corresponding to the pixel to be interpolated is a decimal unit pixel that can be obtained through an interpolation process.

In the above example, the first interpolation pixel is obtained through filtering at each reference pixel layer, and the final interpolation pixel is obtained by performing additional filtering on the first interpolation pixels. However, _k to h _k , a _j to h _j , and a _i to h _i may be filtered to obtain the final interpolation pixel at a time.

Among the three reference pixel layers supported in FIG. 10B, a layer used as an actual reference pixel may be ref_j. In other words, the interpolation of one reference pixel hierarchy constituted of reference pixels is included in the candidate group (for example, not being composed of reference pixels means that pixels of the reference pixel hierarchy are not used for prediction, May refer to the corresponding pixels for interpolation and may be included in the case of being used precisely).

Referring to FIG. 10C, an example in which two supported reference pixel layers are used as reference pixels. ( _I , _j , e _i , e _j in this example) as the input pixels and performing filtering on the adjacent pixels in each of the supported reference pixel layers, The final interpolation pixel x can be obtained. However, as shown in FIG. 10B, it is also possible to obtain a first interpolation pixel at each reference pixel layer and perform additional filtering on the first interpolation pixel to obtain the final interpolation pixel (x).

The above example is not limited to the reference pixel interpolation process but can be understood as a process that is combined with another process of intra-picture prediction (for example, a reference pixel filter process, a prediction block generation process, etc.).

11A and 11B are first illustrations for explaining an adaptive reference pixel filtering method according to an embodiment of the present invention.

The reference pixel filter unit generally includes a low-pass filter. For example, smoothing using a 3-tap or 5-tap filter such as [1, 2, 1] / 4, [2, 3, 6, 3, 2] / 16, (E.g., a high-pass filter, etc.) may be used depending on the purpose of the filter application (e.g., sharpening, etc.). In the present invention, filtering for the purpose of smoothing is performed to reduce deterioration occurring in the sub-decoding process.

The reference pixel filtering can be performed according to the subdecryption setting. However, since applying the filtering presence / absence collectively does not reflect the partial characteristics of the image, filtering based on the partial characteristics of the image may be advantageous for improving the coding performance. Here, the characteristics of the image include not only the image type, the color component, the quantization parameter, the addition / decryption information of the current block (for example, the size, type, division information, and prediction mode of the current block) And a combination of the current block and the sub-block information of the neighboring block. Further, it can be determined according to the reference pixel distribution characteristics (for example, dispersion, standard deviation, flat area, discontinuous area, etc. of the reference pixel area).

11A, if it belongs to the classification (category 0) according to some partial / decode settings (for example, block size range A, prediction mode B, color component C, etc.) (Category 1) according to the decoding setting (for example, the prediction mode A of the current block, the prediction mode B of the predetermined neighboring block, and the like), filtering can be applied.

Referring to FIG. 11B, if the block belongs to a classification (category 0) according to some partial / decode settings (for example, a size A of the current block, a size B of a neighboring block, a prediction mode C of the current block, (Category 1) according to some partial / decryption settings (for example, the size A of the current block, the type B of the current block, the size C of the neighboring block, etc.), filtering is performed using the filter A (Category 2) according to some partial / decryption settings (for example, the parent block A of the current block, the parent block B of the neighboring block, etc.), filtering can be performed using the filter b.

Therefore, it is possible to determine whether or not the filtering is applied, the type of the filter, whether or not the filter information is encoded (explicit / implicit), the number of times of filtering, and the like depending on the size of the current block and the neighboring block, the prediction mode, The number of taps of the filter, the filter coefficient, and the like. At this time, it is also possible to apply the same filter several times or apply different filters to the filter more than once.

In the above example, reference pixel filtering may be preset according to the characteristics of the image. That is, the filter-related information may be implicitly determined. However, if the determination of the characteristics of the image as described above is not appropriate, the coding efficiency may be adversely affected. Therefore, it is necessary to consider a part thereof.

For the purpose of preventing the above case, the reference pixel filtering can be explicitly set. For example, information about whether filtering is applied may occur. At this time, if there is one filter, no filter selection information is generated, and if there are a plurality of filter candidate groups, filter selection information may be generated.

Although the implicit and explicit settings have been described with reference to the reference pixel filtering in the above example, a mixed case may be possible, which is determined in some cases by an explicit setting and in some cases by an implicit setting. Implicitly, the implication here is that the decoder can derive information related to the reference pixel filter (eg, filtering applicability information, filter type information).

12 is a second exemplary diagram for explaining an adaptive reference pixel filtering method according to an embodiment of the present invention.

Referring to FIG. 12, categories can be classified according to the characteristics of images identified through the sub-decryption information, and reference pixel filtering can be adaptively performed according to the classified categories.

For example, if classification is classified as category 0, filtering is not applied. If classification is classified as category 1, filtering A is applied. In the case of categories 0 and 1, it may be an example of implicit reference pixel filtering.

In addition, in the case of category 2 classification, no filtering is applied or filtering A can be applied. Information generated at this time may be information on whether or not filtering is applied, and filter selection information does not occur.

In the case of classification into Category 3, filtering A may be applied or filtering B may be applied. The information generated at this time may be filter selection information, and filtering application may be performed unconditionally. That is, in the case of classifying into category 3, it can be understood that the filtering must be performed but the filtering type must be selected.

In addition, in the case of classification into Category 4, filtering may not be applied, filtering A may be applied, or filtering B may be applied. Information generated at this time may be information on whether to apply filtering and filter selection information.

In summary, explicit or implicit processing can be determined depending on the category, and when proceeding with explicit processing, each reference pixel filter related candidate group setting can be adaptively configured.

The following examples may be considered with respect to the above category.

First, in the case of a block having a size of 64 × 64 or more, one of <filtering off>, <filtering on + filter A>, <filtering on + filter B>, <filtering on + filter C> It can be determined implicitly. In this case, when the reference pixel distribution characteristic is considered, the candidate to be added may be < Filtering on + Filter C >. That is, the filter A and the filter B may be applied or the filter C may be applied in a situation where the filter is on.

In the case of a block having a size of 64 × 64 or less and 16 × 16 or more, one of <filtering off>, <filtering on + filter A>, and <filtering on + filter B> may be implicitly determined according to the prediction mode of the current block have.

In the case of a block having a size smaller than 16 × 16, one of <filtering off>, <filtering on + filter A>, and <filtering on + filter B> is selected according to the prediction mode of the current block. In this case, some prediction modes are implicitly determined as &quot; filtering off &quot;, and one of <filtering off> and <filtering on + filter A> is explicitly selected in some prediction modes, off &gt;, &lt; filtering + filter B &gt; can be explicitly selected.

As an example of the explicit processing for the plurality of reference pixel filter related information, when the reference pixels obtained according to each filtering (including the filtering off situation in this example) are the same or similar, the reference pixel filter information (for example, Reference pixel filtering permission information, reference pixel filter information, etc.) may be the result of generating unnecessary duplicate information. For example, if the reference pixel distribution characteristics obtained according to each filtering (for example, the characteristics obtained by comparing the values obtained through the mean, variance, etc. of each reference pixel with the threshold < Threshold & The reference pixel filter related information may be omitted. If the reference pixel filter related information is omitted, filtering can be applied by a predetermined method (for example, filtering off). The decoder may determine whether to receive the reference pixel filter related information by receiving the intra prediction information, and determine whether to receive the reference pixel filter related information based on the determination.

Assuming that information is explicitly generated in relation to reference pixel filtering, the instruction information (adaptive_ref_filter_enabled_flag in this example) that allows adaptive reference pixel filtering may occur in units of video, sequence, picture, slice, tile, .

If the instruction information means that adaptive reference pixel filtering is allowed (adaptive_ref_filter_enabled_flag = 1 in this example), adaptive reference pixel filtering allowance information (adaptive_ref_filter_flag in this example) is generated in units of pictures, slices, tiles, .

If the permissible information indicates adaptive reference pixel filtering (adaptive_ref_filter_flag = 1 in this example), the reference pixel filtering related information (ref_filter_idx in this example, for example, reference pixel filter selection information) is a picture, a slice, Block or the like.

At this time, when the adaptive reference pixel filtering is not allowed or the adaptive reference pixel filtering is not applied, the reference pixel is set to a predetermined setting (whether or not the filtering is applied in advance, the type of the filter, etc., Lt; / RTI &gt; is determined).

13A to 13B are views illustrating an example of using one reference pixel layer in reference pixel filtering according to an embodiment of the present invention.

13A, filtering (referred to as smt_func_1 function) is performed on the pixels a, b, c, e, f and g adjacent to the target pixel d and the target pixel d among the pixels belonging to the reference pixel layer ref_i, And the interpolation is performed.

13A may generally be an example in which one filtering is applied, but it may also be possible if a plurality of filtering is applied. For example, the secondary filtering may be applied to the reference pixels (a *, b *, c *, d *, etc. in this example) obtained by applying the first-order filtering.

13B, a pixel e * that is filtered (referred to as an smt_func_2 function) through a linear interpolation proportional to a distance (for example, a distance z to a) with respect to pixels located on both sides with respect to a target pixel e, Can be obtained. In this case, the pixels located at both sides of the current block include the upper block, left block, upper block + upper right block, left block + left lower block, upper left block + upper block + upper right block, upper left block + A block located at both end points of adjacent pixels in a block including a + upper block + a lower left block + an upper right block. 13B may be reference pixel filtering performed according to reference pixel distribution characteristics.

13A to 13B show the case of using pixels of the same reference pixel hierarchy as the reference pixel to be filtered for reference pixel filtering. At this time, the types of filters used for reference pixel filtering may or may not be the same depending on the reference pixel hierarchy.

When a plurality of reference pixel layers are used, it may be possible to use not only pixels of the same reference pixel layer but also pixels of the same reference pixel layer for filtering reference pixels in some reference pixel layers.

FIG. 14 is an exemplary diagram illustrating the use of a plurality of reference pixel layers in reference pixel filtering according to an exemplary embodiment of the present invention.

Referring to FIG. 14, filtering can be performed using pixels belonging to the same reference pixel layer in the reference pixel layers ref_k and ref_i, respectively. That is, the filtered pixel d _k * can be obtained by performing filtering (defined by the function smt_func_1D) on the target pixel d _k and its neighboring pixels a _k to g _k in the reference pixel layer ref_k, The filtered pixel d _i * may be obtained by performing filtering (defined by the function smt_func_1D) on the target pixel d _i and its neighboring pixels a _i to g _i in the layer ref_i.

In addition, when reference pixel filtering is performed on the reference pixel layer ref_j, not only the same reference pixel layer ref_j but also pixels belonging to ref_i and ref_k which are spatially adjacent to the reference pixel layer ref_j can be used. In detail, the pixels (c _k , d _k , e _k , c _j , e _j , c _i , d _i and e _i spatially adjacent to the target pixel d _j , Filter (which may be a filter) (defined by smt_func_2D function) to obtain the interpolated pixel d _j *. However, 3 × 3 is not limited to a square shape, 5 × 2 rectangular shape around the target pixel _{(b k, c k, d} k, e k, f k, b j, c j, e j, f j ), 3 × 3 having the mask, such as a diamond shape _{(d k, c j, e} j, d i), 5 × 3 cross form _{(d k, b j, c} j, e j, f j, d i) You can also use filters.

Here, the reference pixel layer is composed of pixels belonging to neighboring blocks adjacent to the current block and close to the boundary of the current block, as shown in FIGS. 5 to 9B and the like. Considering this aspect, the filtering using the pixels at the same reference pixel layer in the reference pixel layer ref_k and the reference pixel layer ref_i can apply the filter of the one-dimensional mask type using the pixels to be interpolated and the pixels that are horizontally or vertically adjacent . However, the interpolation pixel for the reference pixel d _j in the reference pixel hierarchy ref_j can be obtained by applying a two-dimensional mask type filter using all the pixels spatially adjacent in the up / down / left / right direction.

Second reference pixel filtering can be applied to reference pixels to which the first reference pixel filtering is applied in each reference pixel layer. For example, it is possible to perform first-order reference pixel filtering using reference pixels included in each of the reference pixel layers ref_k, ref_j, and ref_i, (ref_k *, ref_j *, ref_i *) can perform reference pixel filtering using reference pixels of other reference pixel layers as well as their reference pixel layers.

The prediction block generator may generate a prediction block according to at least one intra-picture prediction mode (or may be briefly referred to as a prediction mode), and may use the reference pixel based on the prediction mode. At this time, it is possible to generate a prediction block by extrapolating, interpolating, averaging (DC mode), or copying the reference pixel according to the prediction mode. Here, the extrapolation can be applied to the directional mode among the intra prediction modes, and the rest can be applied to the non-directional mode.

On the other hand, when the reference pixels are copied, one reference pixel may be copied to a plurality of pixels in the prediction block to generate one or more prediction pixels, or one or more reference pixels may be copied to generate one or more prediction pixels, The number of copied reference pixels may be equal to or less than the number of copied prediction pixels.

In addition, it is common that one prediction block is generated for each prediction according to one intra-picture prediction mode. However, it is also possible to acquire a plurality of prediction blocks and apply a weighting sum to a plurality of obtained prediction blocks Lt; RTI ID = 0.0 &gt; block &lt; / RTI &gt; Here, the plurality of prediction blocks may refer to prediction blocks obtained according to the reference pixel hierarchy.

In the prediction mode determination unit of the encoding apparatus, a process for selecting an optimal mode among a plurality of prediction mode candidates is performed. Typically, block distortion {for example, Distortion of current block and restoration block. It is possible to determine an optimal mode in terms of encoding cost by using a Sum-of-Absolute Difference (SAD), a Sum of Square Difference (SSD), and a Rate-Distortion The prediction block generated based on the prediction mode determined through the above process can be transmitted to the subtraction unit and the addition unit. (At this time, since the decoding apparatus can acquire information indicating the optimal prediction mode from the coding apparatus, The process of selecting the optimal prediction mode may be omitted.)

The prediction mode encoding unit of the encoding apparatus can encode the optimal intra prediction mode selected through the prediction mode deciding unit. At this time, the index information indicating the optimum prediction mode is directly encoded, or the optimal prediction mode is predicted through a prediction mode obtainable in other neighboring blocks or the like, and the prediction information for the prediction mode (for example, And the difference value between the prediction mode index of the current block). Here, the former case can be applied to a chrominance component, and the latter case to a luminance component.

The prediction value (or prediction information) for the prediction mode can be referred to as MPM (Most Probable Mode) when the optimal prediction mode for the current block is predicted and encoded. In this case, the MPM is a prediction mode having a high possibility of becoming an optimal prediction mode for the current block, and may be a prediction mode (for example, DC, Planar, vertical, horizontal, diagonal mode, Left, upper, upper left, upper right, lower left block, etc.). Here, the diagonal mode means a diagonal up right, a diagonal down right, and a diagonal down left, and may be a mode corresponding to the second, the 18th, and the 34th modes of FIG.

Also, a mode derived from the prediction mode included in the MPM candidate group, which is a set of prediction modes that can be configured by the MPM, can be added to the MPM candidate group. In the case of the directional mode, the MPM candidate group may include a prediction mode in which the index interval with the prediction mode included in the MPM candidate group has a predetermined value. For example, in FIG. 4, if the 10th mode is included in the MPM candidate group, the 9th, 11th, 8th, and 12th modes may be derived.

The MPM candidate group configuration (for example, the number of prediction modes included in the MPM candidate group, the configuration priority) may correspond to a case in which the MPM candidate group is composed of a plurality of modes, A prediction mode candidate group, a video type, a block size, a block type, and the like), and may include at least one mode.

The priority of the prediction mode to be included in the MPM candidate group can be set. The order of the prediction modes to be included in the MPM candidate group can be determined according to the set priorities, and the MPM candidate group configuration can be completed if the predetermined number of prediction modes are filled. Here, the priority order may be set to a mode order derived from a prediction mode of a block spatially adjacent to a current block to be predicted, a preset prediction mode, and a prediction mode included first in the MPM candidate group, but is not limited thereto.

More specifically, in spatially adjacent blocks, priorities can be set in the order of left-upper-lower-right-upper-left block, and in the order of DC-Planar-vertical- And the prediction mode obtained by adding +1, -1, etc. (integer value) in the index value (corresponding to the prediction mode number according to FIG. 4) according to the prediction mode included in the MPM candidate group is set to the MPM candidate group . As an example of such an example, the priority is given in the order of left-top-DC-Planar-left-right-top-left-top (space adjacency block mode) +1 Can be set.

In the above example, the priority order of the MPM candidate group is fixed, but the priority can be adaptively determined according to the block type, size, and the like.

When performing the prediction mode encoding of the current block using the MPM, information (e.g., most_probable_mode_flag) can be generated as to whether the prediction mode matches the MPM.

MPM index information (for example, mpm_idx) may be additionally generated according to the configuration of the MPM when it matches the MPM (for example, most_probable_mode_flag = 1). For example, when the MPM is configured in one prediction mode, additional MPM index information is not generated. In a case where the MPM candidate structure is composed of a plurality of prediction modes, index information corresponding to the prediction mode of the current block can be generated have.

In the case where the MPM does not coincide with the MPM (for example, most_probable_mode_flag = 0), among the supported intra-picture prediction modes, the prediction mode candidates excluding the MPM candidate group (referred to as non-MPM candidate groups) MPM index information (for example, non_mpm_idx), which may be an example corresponding to a case where non-MPMs are composed of one group.

In the case where the non-MPM candidate group is composed of a plurality of groups, information on which group the prediction mode of the current block belongs to can be generated. For example, when non-MPM is composed of groups A and B, and the prediction mode of the current block coincides with the prediction mode of group A (for example, non_mpm_A_flag = 1), the prediction mode of the current block The index information corresponding to the prediction mode of the current block can be generated from the remaining prediction mode candidate group (or B group candidate group) when the corresponding index information does not match (e.g., non_mpm_A_flag = 0) . As in the above example, the non-MPM may be composed of a plurality of groups, and the number of groups may be determined according to the prediction mode candidates. For example, it may be 1 if the number of prediction mode candidates is 35 or less, and 2 or more if the prediction mode candidate is 35 or less.

At this time, the specific A group may be composed of modes that are determined to have a high probability of matching with the prediction mode of the current block next to the MPM candidate group. For example, the prediction modes of the next rank that are not included in the MPM candidate group may be included in the A group, or the directional modes having the constant interval may be included in the A group.

In the case where the non-MPM is composed of a plurality of groups as described above, the mode encoding bit amount may be reduced when the number of prediction modes is large and the prediction mode of the current block does not coincide with the MPM.

When performing the prediction mode encoding (or prediction mode decoding) of the current block using the MPM, the binarization tables applied to each prediction mode candidate group (for example, MPM candidate group, non-MPM candidate group, etc.) , And the binarization method applied to each candidate group can also be applied individually.

In this example, terms such as MPM candidate group, non-MPM candidate group, and the like are a few terms used in the present invention, but are not limited thereto. Specifically, the current intra-frame prediction mode is classified into a plurality of categories, and information on which category belongs is expressed by the mode information in the corresponding category. In other words, terms such as a primary MPM candidate group and a secondary MPM candidate group It may also be possible to use it as a.

FIG. 15 is a block diagram for explaining a sub-decoding method for an intra-picture prediction mode according to an embodiment of the present invention.

Referring to FIG. 15, MPM_flag is first obtained (S10) and it is checked whether MPM_flag matches with the primary MPM (indicated by mpm_flag) (S11). If they match, MPM index information mpm_idx is confirmed )can do. If it does not match the MPM, the rem_mpm_flag is obtained (S13) and it is checked whether it matches the secondary MPM (indicated by rem_mpm_flag) (S14). If they match, the secondary MPM index information (rem_mpm_idx) S16). If it does not coincide with the secondary MPM, the index information (rem_mode_idx) for the candidate group configured in the remaining prediction mode can be checked (S15). In this example, the index information generated according to the coincidence with the secondary MPM is expressed by the same syntax element, but other mode encoding settings (for example, a binarization method or the like) may be applied, May be set differently and processed.

The intra prediction in the image decoding method according to an embodiment of the present invention may be configured as follows. The intra prediction in the prediction unit may include a prediction mode decoding step, a reference pixel construction step, and a prediction block generation step. Also, the image decoding apparatus may include a prediction mode decoding unit, a reference pixel unit, and a prediction block generation unit that implement a prediction mode decoding step, a reference pixel configuration step, and a prediction block generation step. Some of the above-described processes may be omitted or other processes may be added, and the order may be changed in a different order than the above-described order.

The reference pixel constituting unit and the prediction block generating unit of the image decoding apparatus perform the same functions as those of the corresponding components of the image encoding apparatus, and thus a detailed description thereof will be omitted. The prediction mode decoding unit performs the decoding using the method used in the prediction mode encoding unit .

Hereinafter, various embodiments of intra-picture prediction according to the reference pixel configuration of the decoding apparatus will be described with reference to FIG. 16 to FIG. At this time, the description of the reference pixel hierarchy support and reference pixel filtering method described above with reference to the drawings should be construed as being equally applicable to the decoding apparatus, and a detailed description is omitted to avoid redundant explanations.

16 is a first exemplary diagram for explaining a bit stream configuration for intra-picture prediction according to the reference pixel configuration.

16, a plurality of reference pixel layers are supported, at least one reference pixel layer among the supported reference pixel layers is used as a reference pixel, a plurality of candidate groups related to reference pixel filtering are supported, It is assumed that one of the filters is selected.

After a plurality of reference pixel layers are constituted by a reference pixel candidate group in the encoder (in the present example, the reference pixel generation process is completed), at least one reference pixel layer is constructed as a reference pixel, and reference pixel filtering and reference pixel interpolation are applied . At this time, a plurality of candidate groups related to reference pixel filtering are supported.

A process for selecting an optimal mode among the prediction mode candidates is performed. When an optimal prediction mode is determined, a prediction block according to the mode is generated and transmitted to a subtractor, and the intra-picture prediction related information is encoded. In this example, it is assumed that the reference pixel layer and the reference pixel filtering are determined implicitly according to the encoding information.

The decoder reconstructs intra prediction information (e.g., a prediction mode), generates a prediction block according to the reconstructed prediction mode, and transmits the prediction block to the subtraction unit. At this time, it is assumed that the reference pixel layer and the reference pixel filtering for the prediction block generation are determined implicitly.

Referring to FIG. 16, a bitstream may be configured with one intra-mode prediction mode (intra_mode) (S20). At this time, the reference pixel layer ref_idx and the reference pixel filtering category ref_filter_idx that are supported (or used) in the current block may be implicitly determined (defined as Category A and B, S21 to S22, respectively) according to the intra prediction mode. However, at this time, the partial / decoded information (for example, a video type, a color component, a block size, a format, and the like) may be additionally considered.

FIG. 17 is a second exemplary diagram for explaining a bit stream configuration for intra-picture prediction according to the reference pixel configuration; FIG.

In the second exemplary embodiment according to FIG. 17, it is assumed that a plurality of reference pixel layers are supported, and one reference pixel layer among a plurality of supported reference pixel layers is used as a reference pixel. It is also assumed that a plurality of candidate groups related to reference pixel filtering are supported and one of these filters is selected. 16 differs from FIG. 16 in that the encoding apparatus explicitly generates information about the selection.

If it is determined that the encoder supports a plurality of reference pixel layers, reference pixel filtering and reference pixel interpolation are applied after configuring one reference pixel layer as a reference pixel. At this time, a plurality of filtering methods related to reference pixel filtering are supported.

When the process of determining the optimal prediction mode for the current block is performed in the encoder, it is further considered to select the optimal reference pixel layer for each prediction mode and to select the optimum reference pixel filtering. The optimal prediction mode for the current block, and the reference pixel layer and the reference pixel filtering are determined, the generated prediction block is transferred to the subtractor, and the intra-picture prediction related information is encoded.

The decoder reconstructs intra prediction information (for example, a prediction mode, a reference pixel hierarchy, reference pixel filtering information, and the like), generates a prediction block using the reconstructed information, and transmits the prediction block to the subtraction unit. At this time, the reference pixel layer and the reference pixel filtering for the prediction block generation are set according to the information determined according to the information transmitted from the encoder.

Referring to FIG. 17, the decoder confirms the optimal prediction mode for the current block through the intra-mode prediction mode information (intra_mode) included in the bitstream (S30), determines whether a plurality of reference pixel layers are supported (multi_ref_flag) (S31). If a plurality of reference pixel layers are supported, the reference pixel layer selection information ref_idx is confirmed (S32), and the reference pixel layer used for intra prediction can be determined. If a plurality of reference pixel layers are not supported, the step S32 of obtaining the reference pixel layer selection information ref_idx may be omitted.

Next, a determination is made as to whether adaptive reference pixel filtering is supported (adap_ref_smooth_flag) (S33). If adaptive reference pixel filtering is supported, a filtering method for a reference pixel is determined through reference pixel filter information (ref_filter_idx) can do.

18 is a third exemplary diagram for explaining the bit stream configuration for intra-picture prediction according to the reference pixel configuration.

In the third example according to FIG. 18, it is assumed that a plurality of reference pixel layers are supported, and one reference pixel layer is used among a plurality of reference pixel layers. It is assumed that a plurality of candidate groups related to reference pixel filtering are supported and one of these filters is selected. The difference from FIG. 17 lies in that selection information is adaptively generated.

Reference pixel filtering and reference pixel interpolation are applied after the reference pixel is constructed by using one reference pixel layer among a plurality of reference pixel layers supported by an encoder. At this time, a plurality of filtering related to reference pixel filtering is supported.

When the process for selecting the optimal mode among the plurality of prediction mode candidates is performed, it is further considered to select the optimal reference pixel layer for each prediction mode and to select the optimum reference pixel filtering. When the optimal prediction mode, the reference pixel layer, and the reference pixel filtering are determined, a prediction block corresponding to the optimal prediction mode is generated and transmitted to the subtractor, and the intra-picture prediction related information is encoded.

At this time, if the redundancy of the generated prediction block is confirmed, and if the prediction block is the same as or similar to the prediction block obtained using another reference pixel hierarchy, the selection information for the optimal reference pixel hierarchy may be omitted and a preset reference pixel hierarchy may be used . At this time, the preset reference pixel layer may be the layer closest to the current block.

For example, it is possible to determine redundancy based on the difference value (distortion value) between the prediction block generated through ref_0 and the prediction block generated through ref_1 in FIG. 6C. If the difference value is smaller than a preset threshold value, it is determined that there is redundancy in the prediction block. Otherwise, it can be determined that there is no redundancy in the prediction block. At this time, the threshold value may be adaptively determined according to a quantization parameter and the like.

Also, if the reference pixel filtering information is the same as or similar to the prediction block obtained by applying the other reference pixel filtering, the reference pixel filtering information may be omitted and preset reference pixel filtering may be applied .

For example, redundancy is determined based on the difference between the prediction block obtained through the filtering A (3-tap filter in this example) and the prediction block obtained through the filtering B (5-tap filter in this example) . At this time, if the difference value is smaller than a preset threshold value, it can be determined that there is redundancy of the prediction block. If there is redundancy of the prediction block, a prediction block can be generated through a preset reference pixel filtering method. Here, the preset reference pixel filtering may be a filtering method with a low number of taps or a low complexity, and may include a case where filtering application is omitted.

The decoder reconstructs intra prediction information (e.g., prediction mode, reference pixel information, reference pixel filtering information, and the like), generates a prediction block corresponding to the prediction block, and transmits the prediction block to the subtraction unit. At this time, the reference pixel layer information and the reference pixel filtering for generating a prediction block are set according to the information determined by the information transmitted from the encoder. However, the decoder can directly check whether the redundancy exists (without passing the syntax element) According to the method.

Referring to FIG. 18, the decoder may first check the intra-mode prediction mode (intra_mode) information of the current block (S40) and confirm whether the plurality of reference pixel layers are supported (multi_ref_flag) (S41). If the plurality of reference pixel layers are supported, the redundancy of the prediction blocks according to the plurality of supported reference pixel layers is checked (indicated by ref_check process, S42). If there is no redundancy in the redundancy check result (redund_ref = 0, S43) , And the optimum reference pixel hierarchy can be determined by referring to the bitstream of the selection information ref_idx for the reference pixel hierarchy (S44).

If adaptive reference pixel filtering is supported (step S45), it is checked whether adaptive reference pixel filtering is supported (adap_ref_smooth_flag), and redundancy of a prediction block according to a plurality of supported reference pixel filtering methods is checked , S46). If there is no redundancy in the prediction block (redund_ref = 0, S47), the optimum reference pixel filtering method can be determined by referring to the bitstream for the selection information ref_filter_idx for the reference pixel filtering method (S48).

At this time, in the drawing, redund_ref is a value indicating a result of redundancy check, and if it is 0, there is no redundancy.

In addition, when there is redundancy in the prediction block, the decoder can perform intra prediction using a reference pixel hierarchy set in advance and a preset reference pixel filtering method.

19 is a flowchart illustrating an image decoding method supporting a plurality of reference pixel layers according to an embodiment of the present invention.

Referring to FIG. 19, an image decoding method supporting a plurality of reference pixel layers includes checking whether a plurality of reference pixel layers are supported in a bitstream (S100), and if a plurality of reference pixel layers are supported, (S110) determining a reference pixel hierarchy to be used in a current block by referring to syntax information included in a stream, constructing a reference pixel using pixels belonging to the determined reference pixel hierarchy (S120) And performing intra-picture prediction on the current block (S130).

Here, after confirming whether the plurality of reference pixel layers are supported (S100), it may further include checking whether the adaptive reference pixel filtering method is supported in the bitstream.

Here, if it is determined that the plurality of reference pixel layers are not supported after step S100, it may include configuring reference pixels using a predetermined reference pixel layer .

The methods according to the present invention can be implemented in the form of program instructions that can be executed through various computer means and recorded on a computer readable medium. The computer readable medium may include program instructions, data files, data structures, and the like, alone or in combination. The program instructions recorded on the computer readable medium may be those specially designed and constructed for the present invention or may be available to those skilled in the computer software.

Examples of computer-readable media include hardware devices that are specially configured to store and execute program instructions, such as ROM, RAM, flash memory, and the like. Examples of program instructions may include machine language code such as those produced by a compiler, as well as high-level language code that may be executed by a computer using an interpreter or the like. The hardware devices described above may be configured to operate with at least one software module to perform the operations of the present invention, and vice versa.

Furthermore, the above-mentioned method or apparatus may be implemented by combining all or a part of the structure or function, or may be implemented separately.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the present invention as defined by the following claims It can be understood that

Claims (3)

A video decoding method supporting a plurality of reference pixel layers,
Determining whether the bitstream supports a plurality of reference pixel layers;
Determining a reference pixel hierarchy to be used in a current block by referring to syntax information included in the bitstream if a plurality of reference pixel hierarchies are supported;
Constructing a reference pixel using pixels belonging to the determined reference pixel hierarchy; And
And performing intra-picture prediction on the current block using the constructed reference picture. In claim 1,
After confirming whether the plurality of reference pixel layers are supported,
Further comprising the step of: determining whether the adaptive reference pixel filtering method is supported in the bitstream. In claim 1,
After confirming whether the plurality of reference pixel layers are supported,
And constructing a reference pixel using a preset reference pixel hierarchy if a plurality of reference pixel layers are not supported.

Images