KR20140089488A - Method and apparatus for encoding video, and method and apparatus for decoding video - Google Patents

Abstract

Disclosed is a method and apparatus for encoding an image, filtering the neighboring pixels used for intra prediction of a current block to be encoded and performing intra-prediction using the filtered neighboring pixels, and a decoding method and apparatus therefor. Based on the size of the chrominance component block and the intra prediction mode to be applied, surrounding pixels used as reference pixels among the circular peripheral pixels and the filtered peripheral pixels can be determined.

Description

TECHNICAL FIELD The present invention relates to a video encoding method and apparatus, a decoding method,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video encoding method and apparatus for enhancing compression efficiency by performing intraprediction using filtered neighboring pixels, and a decoding method and apparatus therefor.

In an image compression method such as MPEG-1, MPEG-2, MPEG-4, and H.264 / MPEG-4 Advanced Video Coding (AVC), one picture is divided into macroblocks to encode an image. Then, each macroblock is encoded in all coding modes available for inter prediction and intra prediction, and then an encoding mode is selected according to the bit rate required for encoding the macroblock and the degree of distortion between the original macroblock and the decoded macroblock. And the macro block is encoded.

Background of the Invention [0002] As the development and dissemination of hardware capable of playing back and storing high-resolution or high-definition video content increases the need for video codecs to effectively encode or decode high-definition or high-definition video content. According to the existing video codec, video is encoded according to a limited prediction mode based on a macroblock of a predetermined size.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and it is an object of the present invention to determine whether to filter neighboring pixels used as reference pixels in intra prediction of a chrominance component block independently of a luminance component block.

According to an aspect of the present invention, there is provided a video decoding method including: obtaining size information and intraprediction mode information of a current block of a chrominance component from a bitstream; And determines surrounding pixels used for intra prediction of the current block among the filtered neighboring pixels obtained by filtering the reconstructed neighboring pixels and the reconstructed neighboring pixels of the current block based on the size information and the intra prediction mode information step; And performing intra prediction on the current block according to the intra prediction mode information using the determined neighboring pixels.

A video decoding apparatus according to an exemplary embodiment includes a neighboring pixel filtering unit that filters neighboring pixels previously reconstructed from a current block of a chrominance component to generate filtered neighboring pixels; Obtaining the size information and the intra-prediction mode information of the current block of the chrominance component from the bitstream, filtering the reconstructed neighboring pixels and the reconstructed neighboring pixels of the current block based on the size information and the intra- A reference pixel determination unit for determining a neighboring pixel used for intra prediction of the current block among the filtered neighboring pixels; And an intra prediction unit performing intra prediction on the current block according to the intra prediction mode information using the determined neighboring pixels.

According to an embodiment of the present invention, there is provided a video encoding method comprising: filtering surrounding pixels of a current block of a chrominance component to be encoded to obtain filtered neighboring pixels; Determining neighboring pixels to be used for intraprediction of the current block among the filtered neighboring pixels and original neighboring pixels based on the size of the current block and an intra prediction mode to be performed; And performing intra prediction on the current block using the determined neighboring pixels.

According to embodiments of the present invention, the use of the filtered neighboring pixels in the intra-prediction of the chrominance component block is caused more than in the intra-prediction of the luminance component block, thereby improving the prediction efficiency in intra-prediction of the chrominance component .

1 shows a block diagram of a video coding apparatus based on a coding unit of a tree structure according to an embodiment of the present invention.
2 shows a block diagram of a video decoding apparatus based on a coding unit of a tree structure according to an embodiment of the present invention.
FIG. 3 illustrates a concept of an encoding unit according to an embodiment of the present invention.
4 is a block diagram of an image encoding unit based on an encoding unit according to an embodiment of the present invention.
5 is a block diagram of an image decoding unit based on an encoding unit according to an embodiment of the present invention.
FIG. 6 illustrates a depth-based encoding unit and a partition according to an exemplary embodiment of the present invention.
FIG. 7 shows a relationship between an encoding unit and a conversion unit according to an embodiment of the present invention.
FIG. 8 illustrates depth-specific encoding information, in accordance with an embodiment of the present invention.
FIG. 9 shows a depth encoding unit according to an embodiment of the present invention.
FIGS. 10, 11 and 12 show the relationship between an encoding unit, a prediction unit, and a conversion unit according to an embodiment of the present invention.
Fig. 13 shows the relationship between the encoding unit, the prediction unit and the conversion unit according to the encoding mode information in Table 1. Fig.
14 is a block diagram showing a configuration of an intra prediction apparatus 1400 according to an embodiment of the present invention.
FIG. 15 illustrates intra prediction modes according to an embodiment.
FIG. 16 specifically shows the prediction angle of the intra-prediction mode having the direction shown in FIG.
FIG. 17 is a reference diagram for explaining a case where an intra prediction mode value is obtained through linear interpolation for an intra prediction mode having index # 30 in FIG. 15 according to an embodiment.
18 is a diagram illustrating neighboring pixels used in a current block and an intra prediction according to an embodiment of the present invention.
19 is a reference diagram for explaining a process of filtering surrounding pixels according to an embodiment of the present invention.
Figure 20 shows the surrounding pixels to be filtered.
21 is a flowchart of a video encoding method according to an embodiment.
22 is a flowchart of a video decoding method according to an embodiment.

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

1 shows a block diagram of a video encoding apparatus according to an embodiment of the present invention.

The video encoding apparatus 100 according to an exemplary embodiment includes a maximum encoding unit division unit 110, an encoding unit determination unit 120, and an output unit 130.

The maximum coding unit division unit 110 may divide a current picture based on a maximum coding unit which is a coding unit of a maximum size for a current picture of an image. If the current picture is larger than the maximum encoding unit, the image data of the current picture may be divided into at least one maximum encoding unit. The maximum encoding unit according to an exemplary embodiment may be a data unit of square of size 32x32, 64x64, 128x128, 256x256, etc., and a power of 2 square data unit of horizontal and vertical size greater than 8. The image data may be output to the encoding unit determination unit 120 for each of the at least one maximum encoding unit.

An encoding unit according to an embodiment may be characterized by a maximum size and a depth. The depth indicates the number of times the coding unit is spatially divided from the maximum coding unit. As the depth increases, the depth coding unit can be divided from the maximum coding unit to the minimum coding unit. The depth of the maximum encoding unit is the highest depth and the minimum encoding unit can be defined as the least significant encoding unit. As the depth of the maximum encoding unit increases, the size of the depth-dependent encoding unit decreases, so that the encoding unit of the higher depth may include a plurality of lower-depth encoding units.

As described above, according to the maximum size of an encoding unit, the image data of the current picture is divided into a maximum encoding unit, and each maximum encoding unit may include encoding units divided by depth. Since the maximum encoding unit according to an embodiment is divided by depth, image data of a spatial domain included in the maximum encoding unit can be hierarchically classified according to depth.

The maximum depth for limiting the total number of times the height and width of the maximum encoding unit can be hierarchically divided and the maximum size of the encoding unit may be preset.

The encoding unit determination unit 120 encodes at least one divided area in which the area of the maximum encoding unit is divided for each depth, and determines the depth at which the final encoding result is output for each of at least one of the divided areas. That is, the coding unit determination unit 120 selects the depth at which the smallest coding error occurs, and determines the coding depth as the coding depth by coding the image data in units of coding per depth for each maximum coding unit of the current picture. The determined coding depth and the image data of each coding unit are output to the output unit 130.

The image data in the maximum encoding unit is encoded based on the depth encoding unit according to at least one depth below the maximum depth, and the encoding results based on the respective depth encoding units are compared. As a result of the comparison of the encoding error of the depth-dependent encoding unit, the depth with the smallest encoding error can be selected. At least one coding depth may be determined for each maximum coding unit.

As the depth of the maximum encoding unit increases, the encoding unit is hierarchically divided and divided, and the number of encoding units increases. In addition, even if encoding units of the same depth included in one maximum encoding unit, the encoding error of each data is measured and it is determined whether or not the encoding unit is divided into lower depths. Therefore, even if the data included in one maximum coding unit has a different coding error according to the position, the coding depth can be determined depending on the position. Accordingly, one or more coding depths may be set for one maximum coding unit, and data of the maximum coding unit may be divided according to one or more coding depth encoding units.

Therefore, the encoding unit determiner 120 according to the embodiment can determine encoding units according to the tree structure included in the current maximum encoding unit. The 'encoding units according to the tree structure' according to an exemplary embodiment includes encoding units of depth determined by the encoding depth, among all depth encoding units included in the current maximum encoding unit. The coding unit of coding depth can be hierarchically determined in depth in the same coding area within the maximum coding unit, and independently determined in other areas. Similarly, the coding depth for the current area can be determined independently of the coding depth for the other area.

The maximum depth according to one embodiment is an index related to the number of divisions from the maximum encoding unit to the minimum encoding unit. The first maximum depth according to an exemplary embodiment may indicate the total number of division from the maximum encoding unit to the minimum encoding unit. The second maximum depth according to an exemplary embodiment may represent the total number of depth levels from the maximum encoding unit to the minimum encoding unit. For example, when the depth of the maximum encoding unit is 0, the depth of the encoding unit in which the maximum encoding unit is divided once may be set to 1, and the depth of the encoding unit that is divided twice may be set to 2. In this case, if the coding unit divided four times from the maximum coding unit is the minimum coding unit, since the depth levels of depth 0, 1, 2, 3 and 4 exist, the first maximum depth is set to 4 and the second maximum depth is set to 5 .

The predictive encoding and frequency conversion of the maximum encoding unit can be performed. Likewise, predictive coding and frequency conversion are performed on the basis of the depth coding unit for each maximum coding unit and for each depth below the maximum depth.

Since the number of coding units per depth is increased every time the maximum coding unit is divided by the depth, the coding including the predictive coding and the frequency conversion should be performed for every depth coding unit as the depth increases. For convenience of explanation, predictive coding and frequency conversion will be described based on a coding unit of current depth among at least one maximum coding unit.

The video encoding apparatus 100 according to an exemplary embodiment may select various sizes or types of data units for encoding image data. To encode the image data, a step such as predictive encoding, frequency conversion, and entropy encoding is performed. The same data unit may be used for all steps, and the data unit may be changed step by step.

For example, the video coding apparatus 100 can select not only a coding unit for coding image data but also a data unit different from the coding unit in order to perform predictive coding of the image data of the coding unit.

For predictive coding of the maximum coding unit, predictive coding may be performed based on a coding unit of coding depth according to an embodiment, i.e., a coding unit which is not further divided. Hereinafter, the more unfragmented encoding units that are the basis of predictive encoding will be referred to as 'prediction units'. The partition in which the prediction unit is divided may include a data unit in which at least one of the height and the width of the prediction unit and the prediction unit is divided.

For example, if the encoding unit of size 2Nx2N (where N is a positive integer) is not further divided, it is a prediction unit of size 2Nx2N, and the size of the partition may be 2Nx2N, 2NxN, Nx2N, NxN, and the like. The partition type according to an embodiment is not limited to symmetric partitions in which the height or width of a prediction unit is divided by a symmetric ratio, but also partitions partitioned asymmetrically, such as 1: n or n: 1, Partitioned partitions, arbitrary type partitions, and the like.

The prediction mode of the prediction unit may be at least one of an intra mode, an inter mode, and a skip mode. For example, intra mode and inter mode can be performed for partitions of 2Nx2N, 2NxN, Nx2N, NxN sizes. In addition, the skip mode can be performed only for a partition of 2Nx2N size. Encoding is performed independently for each prediction unit within an encoding unit, and a prediction mode having the smallest encoding error can be selected.

In addition, the video encoding apparatus 100 according to an exemplary embodiment may perform frequency conversion of image data of an encoding unit based on not only an encoding unit for encoding image data but also a data unit different from the encoding unit.

For frequency conversion of a coding unit, frequency conversion may be performed based on a data unit having a size smaller than or equal to the coding unit. For example, a data unit for frequency conversion may include a data unit for intra mode and a data unit for inter mode.

Hereinafter, the data unit on which the frequency conversion is based may be referred to as a 'conversion unit'. In a similar manner to the encoding unit, the conversion unit in the encoding unit is also recursively divided into smaller-sized conversion units, and the residual data of the encoding unit can be divided according to the conversion unit according to the tree structure according to the conversion depth.

For a conversion unit according to one embodiment, a conversion depth indicating the number of times of division until the conversion unit is divided by the height and width of the encoding unit can be set. For example, if the size of the conversion unit of the current encoding unit of size 2Nx2N is 2Nx2N, the conversion depth is set to 0 if the conversion depth is 0, if the conversion unit size is NxN, and if the conversion unit size is N / 2xN / 2, . That is, a conversion unit according to the tree structure can be set for the conversion unit according to the conversion depth.

The coding information according to the coding depth needs not only the coding depth but also prediction related information and frequency conversion related information. Therefore, the coding unit determination unit 120 can determine not only the coding depth at which the minimum coding error is generated, but also the partition type in which the prediction unit is divided into partitions, the prediction mode for each prediction unit, the size of the conversion unit for frequency conversion, .

A method of determining a coding unit and a partition according to a tree structure of a maximum coding unit according to an embodiment will be described later in detail with reference to FIGS.

The encoding unit determination unit 120 may measure the encoding error of the depth-dependent encoding unit using a Lagrangian Multiplier-based rate-distortion optimization technique.

The output unit 130 outputs, in the form of a bit stream, video data of the maximum encoding unit encoded based on at least one encoding depth determined by the encoding unit determination unit 120 and information on the depth encoding mode.

The encoded image data may be a result of encoding residual data of the image.

The information on the depth-dependent coding mode may include coding depth information, partition type information of a prediction unit, prediction mode information, size information of a conversion unit, and the like.

The coding depth information can be defined using depth division information indicating whether or not coding is performed at the lower depth coding unit without coding at the current depth. If the current depth of the current encoding unit is the encoding depth, the current encoding unit is encoded in the current depth encoding unit, so that the division information of the current depth can be defined so as not to be further divided into lower depths. On the other hand, if the current depth of the current encoding unit is not the encoding depth, the encoding using the lower depth encoding unit should be tried. Therefore, the division information of the current depth may be defined to be divided into the lower depth encoding units.

If the current depth is not the encoding depth, encoding is performed on the encoding unit divided into lower-depth encoding units. Since there are one or more lower-level coding units in the current-depth coding unit, the coding is repeatedly performed for each lower-level coding unit so that recursive coding can be performed for each coding unit of the same depth.

Since the coding units of the tree structure are determined in one maximum coding unit and information on at least one coding mode is determined for each coding unit of coding depth, information on at least one coding mode is determined for one maximum coding unit . Since the data of the maximum encoding unit is hierarchically divided according to the depth and the depth of encoding may be different for each position, information on the encoding depth and the encoding mode may be set for the data.

Accordingly, the output unit 130 according to the embodiment can allocate encoding depths and encoding information for the encoding mode to at least one of the encoding unit, the prediction unit, and the minimum unit included in the maximum encoding unit .

The minimum unit according to an exemplary embodiment is a square data unit having a minimum coding unit size of 4 divided by a minimum coding depth and is a unit of a maximum size that can be included in all coding units, Square data unit.

For example, the encoding information output through the output unit 130 may be classified into encoding information per depth unit and encoding information per prediction unit. The encoding information for each depth coding unit may include prediction mode information and partition size information. The encoding information to be transmitted for each prediction unit includes information about the estimation direction of the inter mode, information about the reference picture index of the inter mode, information on the motion vector, information on the chroma component of the intra mode, information on the interpolation mode of the intra mode And the like. Information on the maximum size of a coding unit defined for each picture, slice or GOP, and information on the maximum depth can be inserted into the header of the bitstream.

According to the simplest embodiment of the video coding apparatus 100, the coding unit for depth is a coding unit which is half the height and width of the coding unit of one layer higher depth. That is, if the size of the current depth encoding unit is 2Nx2N, the size of the lower depth encoding unit is NxN. In addition, the current encoding unit of 2Nx2N size can include a maximum of 4 sub-depth encoding units of NxN size.

Therefore, the video encoding apparatus 100 according to an exemplary embodiment determines an encoding unit of an optimal shape and size for each maximum encoding unit based on the size and the maximum depth of the maximum encoding unit determined in consideration of the characteristics of the current picture To form coding units according to a tree structure. In addition, since each encoding unit can be encoded by various prediction modes, frequency conversion methods, and the like, an optimal encoding mode can be determined in consideration of image characteristics of encoding units of various image sizes.

Therefore, if an image having a very high image resolution or a very large data amount is encoded in units of existing macroblocks, the number of macroblocks per picture becomes excessively large. This increases the amount of compression information generated for each macroblock, so that the burden of transmission of compressed information increases and the data compression efficiency tends to decrease. Therefore, the video encoding apparatus according to an embodiment can increase the maximum size of the encoding unit in consideration of the image size, and adjust the encoding unit in consideration of the image characteristic, so that the image compression efficiency can be increased.

2 shows a block diagram of a video decoding apparatus according to an embodiment of the present invention.

The video decoding apparatus 200 includes a receiving unit 210, an image data and encoding information extracting unit 220, and an image data decoding unit 230. The definition of various terms such as coding unit, depth, prediction unit, conversion unit, and information on various coding modes for various processing of the video decoding apparatus 200 according to an embodiment is the same as that of FIG. 1 and the video coding apparatus 100 Are the same as described above.

The receiving unit 205 receives and parses the bitstream of the encoded video. The image data and encoding information extracting unit 220 extracts image data encoded for each encoding unit according to the encoding units according to the tree structure according to the maximum encoding unit from the parsed bit stream and outputs the extracted image data to the image data decoding unit 230. The image data and encoding information extracting unit 220 can extract information on the maximum size of the encoding unit of the current picture from the header of the current picture.

Also, the image data and encoding information extracting unit 220 extracts information on the encoding depth and the encoding mode for the encoding units according to the tree structure for each maximum encoding unit from the parsed bit stream. The information on the extracted coding depth and coding mode is output to the image data decoding unit 230. That is, the video data of the bit stream can be divided into the maximum encoding units, and the video data decoding unit 230 can decode the video data per maximum encoding unit.

Information on the coding depth and coding mode per coding unit can be set for one or more coding depth information, and the information on the coding mode for each coding depth is divided into partition type information of the coding unit, prediction mode information, The size information of the image data, and the like. In addition, as the encoding depth information, depth-based segmentation information may be extracted.

The encoding depth and encoding mode information extracted by the image data and encoding information extracting unit 220 may be encoded in the encoding unit such as the video encoding apparatus 100 according to one embodiment, And information on the coding depth and coding mode determined to repeatedly perform coding for each unit to generate the minimum coding error. Therefore, the video decoding apparatus 200 can decode the data according to the coding scheme that generates the minimum coding error to recover the video.

The encoding information for the encoding depth and the encoding mode according to the embodiment may be allocated for a predetermined data unit among the encoding unit, the prediction unit and the minimum unit. Therefore, the image data and the encoding information extracting unit 220 may extract predetermined data Information on the coding depth and coding mode can be extracted for each unit. If information on the coding depth and the coding mode of the corresponding maximum coding unit is recorded for each predetermined data unit, the predetermined data units having the same coding depth and information on the coding mode are referred to as data units included in the same maximum coding unit .

The image data decoding unit 230 decodes the image data of each maximum encoding unit based on the information on the encoding depth and the encoding mode for each maximum encoding unit to reconstruct the current picture. That is, the image data decoding unit 230 decodes the image data encoded based on the read partition type, the prediction mode, and the conversion unit for each coding unit among the coding units according to the tree structure included in the maximum coding unit . The decoding process may include a prediction process including intra prediction and motion compensation, and an inverse frequency conversion process.

The image data decoding unit 230 may perform intra prediction or motion compensation according to each partition and prediction mode for each coding unit based on partition type information and prediction mode information of a prediction unit of each coding depth .

In addition, the image data decoding unit 230 may perform inverse frequency conversion according to each conversion unit for each encoding unit based on the size information of the conversion unit of each encoding depth-based encoding unit for frequency inverse conversion per maximum encoding unit have.

The image data decoding unit 230 can determine the coding depth of the current maximum coding unit using the division information by depth. If the division information indicates that it is no longer divided at the current depth, then the current depth is the depth of the encoding. Therefore, the image data decoding unit 230 can decode the current depth encoding unit for the image data of the current maximum encoding unit using the partition type, the prediction mode, and the conversion unit size information of the prediction unit.

In other words, the encoding information set for the predetermined unit of data among the encoding unit, the prediction unit and the minimum unit is observed, and the data units holding the encoding information including the same division information are collected, and the image data decoding unit 230 It can be regarded as one data unit to be decoded in the same encoding mode.

The video decoding apparatus 200 according to an exemplary embodiment recursively performs encoding for each maximum encoding unit in the encoding process to obtain information on an encoding unit that has generated the minimum encoding error and can use the encoded information for decoding the current picture have. That is, it is possible to decode the encoded image data of the encoding units according to the tree structure determined as the optimal encoding unit for each maximum encoding unit.

Accordingly, even if an image with a high resolution or an excessively large amount of data is used, the information on the optimal encoding mode transmitted from the encoding end is used, and the image data is efficiently encoded according to the encoding unit size and encoding mode, Can be decoded and restored.

Hereinafter, a method of determining encoding units, prediction units, and conversion units according to a tree structure according to an embodiment of the present invention will be described with reference to FIG. 3 to FIG.

FIG. 3 shows the concept of a hierarchical coding unit.

An example of an encoding unit is that the size of an encoding unit is represented by a width x height, and may include 32x32, 16x16, and 8x8 from an encoding unit having a size of 64x64. The encoding unit of size 64x64 can be divided into the partitions of size 64x64, 64x32, 32x64, 32x32, and the encoding unit of size 32x32 is the partitions of size 32x32, 32x16, 16x32, 16x16 and the encoding unit of size 16x16 is the size of 16x16 , 16x8, 8x16, and 8x8, and a size 8x8 encoding unit can be divided into partitions of size 8x8, 8x4, 4x8, and 4x4.

With respect to the video data 310, the resolution is set to 1920 x 1080, the maximum size of the encoding unit is set to 64, and the maximum depth is set to 2. For the video data 320, the resolution is set to 1920 x 1080, the maximum size of the encoding unit is set to 64, and the maximum depth is set to 3. With respect to the video data 330, the resolution is set to 352 x 288, the maximum size of the encoding unit is set to 16, and the maximum depth is set to 1. The maximum depth shown in FIG. 3 represents the total number of divisions from the maximum encoding unit to the minimum encoding unit.

It is preferable that the maximum size of the coding size is relatively large in order to improve the coding efficiency as well as to accurately characterize the image characteristics when the resolution or the data amount is large. Therefore, the maximum size of the video data 310 and 320 having the higher resolution than the video data 330 can be selected to be 64. FIG.

Since the maximum depth of the video data 310 is 2, the encoding unit 315 of the video data 310 is divided into two from the maximum encoding unit having the major axis size of 64, and the depths are deepened by two layers, Encoding units. On the other hand, since the maximum depth of the video data 330 is 1, the encoding unit 335 of the video data 330 divides the encoding unit 335 having a long axis size of 16 by one time, Encoding units.

Since the maximum depth of the video data 320 is 3, the encoding unit 325 of the video data 320 divides the encoding unit 325 from the maximum encoding unit having the major axis size of 64 to 3 times, , 8 encoding units can be included. The deeper the depth, the better the ability to express detail.

4 is a block diagram of an image encoding unit based on an encoding unit according to an embodiment of the present invention.

The image encoding unit 400 according to an exemplary embodiment includes operations to encode image data in the encoding unit determination unit 120 of the video encoding device 100. [ That is, the intraprediction unit 410 performs intraprediction on the intra-mode encoding unit of the current frame 405, and the motion estimation unit 420 and the motion compensation unit 425 perform intraprediction on the current frame 405 of the inter- And a reference frame 495. The inter-frame estimation and the motion compensation are performed using the reference frame and the reference frame.

The data output from the intraprediction unit 410, the motion estimation unit 420 and the motion compensation unit 425 is output as a quantized transform coefficient through the frequency transform unit 430 and the quantization unit 440. The quantized transform coefficients are reconstructed into spatial domain data through the inverse quantization unit 460 and the frequency inverse transform unit 470 and the data of the reconstructed spatial domain is passed through the deblocking unit 480 and the loop filtering unit 490 Processed and output to the reference frame 495. [ The quantized transform coefficient may be output to the bitstream 455 via the entropy encoding unit 450.

The motion estimation unit 420, the motion compensation unit 425, and the frequency transformation unit 420, which are components of the image encoding unit 400, are applied to the video encoding apparatus 100 according to an embodiment of the present invention. The quantization unit 440, the entropy encoding unit 450, the inverse quantization unit 460, the frequency inverse transform unit 470, the deblocking unit 480, and the loop filtering unit 490, It is necessary to perform operations based on each encoding unit among the encoding units according to the tree structure in consideration of the maximum depth for each frame.

In particular, the intra prediction unit 410, the motion estimation unit 420, and the motion compensation unit 425 compute the maximum size and the maximum depth of the current maximum encoding unit, And the prediction mode, and the frequency transforming unit 430 determines the size of the transform unit in each encoding unit among the encoding units according to the tree structure.

5 is a block diagram of an image decoding unit based on an encoding unit according to an embodiment of the present invention.

The bitstream 505 passes through the parsing unit 510 and the encoded image data to be decoded and the encoding-related information necessary for decoding are parsed. The encoded image data is output as inverse quantized data through the entropy decoding unit 520 and the inverse quantization unit 530, and the image data in the spatial domain is restored through the frequency inverse transform unit 540.

The intra-prediction unit 550 performs intraprediction on the intra-mode encoding unit for the video data in the spatial domain, and the motion compensating unit 560 performs intra-prediction on the intra-mode encoding unit using the reference frame 585 And performs motion compensation for the motion compensation.

The data in the spatial domain that has passed through the intra prediction unit 550 and the motion compensation unit 560 may be post-processed through the deblocking unit 570 and the loop filtering unit 580 and output to the reconstruction frame 595. Further, the post-processed data via deblocking unit 570 and loop filtering unit 580 may be output as reference frame 585.

In order to decode the image data in the image data decoding unit 230 of the video decoding apparatus 200, operations after the parsing unit 510 of the image decoding unit 500 according to the embodiment may be performed.

The entropy decoding unit 520, the inverse quantization unit 530, and the frequency inverse transforming unit 520, which are components of the video decoding unit 500, to be applied to the video decoding apparatus 200 according to an embodiment of the present invention, The intra prediction unit 550, the motion compensation unit 560, the deblocking unit 570 and the loop filtering unit 580 perform operations on the basis of the encoding units according to the tree structure for each maximum encoding unit shall.

In particular, the intraprediction unit 550 and the motion compensation unit 560 determine a partition and a prediction mode for each coding unit according to the tree structure, and the frequency inverse transform unit 540 determines the size of the conversion unit for each coding unit do.

FIG. 6 illustrates a depth-based encoding unit and a partition according to an exemplary embodiment of the present invention.

The video encoding apparatus 100 and the video decoding apparatus 200 according to an exemplary embodiment use a hierarchical encoding unit to consider an image characteristic. The maximum height, width, and maximum depth of the encoding unit may be adaptively determined according to the characteristics of the image, or may be variously set according to the demand of the user. The size of each coding unit may be determined according to the maximum size of a predetermined coding unit.

The hierarchical structure 600 of the encoding unit according to an embodiment shows a case where the maximum height and width of the encoding unit is 64 and the maximum depth is 3. Since the depth is deeper along the vertical axis of the hierarchical structure 600 of the encoding unit according to the embodiment, the height and width of the encoding unit for each depth are divided. In addition, along the horizontal axis of the hierarchical structure 600 of encoding units, prediction units and partitions serving as the basis of predictive encoding of each depth-dependent encoding unit are shown.

That is, the coding unit 610 is the largest coding unit among the hierarchical structures 600 of the coding units and has a depth of 0, and the size of the coding units, that is, the height and the width, is 64x64. An encoding unit 620 having a depth 1 along a vertical axis, a depth 1 encoding unit 620 having a size 32x32, a depth 2 encoding unit 630 having a size 16x16, and a depth encoding unit 640 having a depth 8x8. The encoding unit 640 of depth 3 of size 8x8 is the minimum encoding unit.

Prediction units and partitions of coding units are arranged along the horizontal axis for each depth. That is, if the encoding unit 610 having a depth 0 size of 64x64 is a prediction unit, the prediction unit is a partition 610 having a size of 64x64, a partition 612 having a size 64x32, 32x64 partitions 614, and size 32x32 partitions 616. [

Likewise, the prediction unit of the 32x32 coding unit 620 having the depth 1 is the partition 620 of the size 32x32, the partitions 622 of the size 32x16, the partition 622 of the size 16x32 included in the coding unit 620 of the size 32x32, And a partition 626 of size 16x16.

Likewise, the prediction unit of the 16x16 encoding unit 630 of depth 2 is divided into a partition 630 of size 16x16, partitions 632 of size 16x8, partitions 632 of size 8x16 included in the encoding unit 630 of size 16x16, (634), and partitions (636) of size 8x8.

Finally, the prediction unit of the 8x8 encoding unit 640 of depth 3 is divided into a partition 640 having a size of 8x8, a partition 642 having a size of 8x4, and a partition having a size of 4x8 included in the encoding unit 640 of size 8x8. Partitions 644, and partitions 646 of size 4x4.

The encoding unit determination unit 120 of the video encoding apparatus 100 according to an exemplary embodiment of the present invention determines encoding depths of encoding units of the respective depths included in the maximum encoding unit 610 Encoding is performed.

The number of coding units per depth to include data of the same range and size increases as the depth of the coding unit increases. For example, for data containing one coding unit at depth 1, four coding units at depth 2 are required. Therefore, in order to compare the encoding results of the same data by depth, they should be encoded using a single depth 1 encoding unit and four depth 2 encoding units, respectively.

For each depth-of-field coding, encoding is performed for each prediction unit of the depth-dependent coding unit along the horizontal axis of the hierarchical structure 600 of the coding unit, and a representative coding error, which is the smallest coding error at the corresponding depth, is selected . In addition, depths are deepened along the vertical axis of the hierarchical structure 600 of encoding units, and the minimum encoding errors can be retrieved by comparing the representative encoding errors per depth by performing encoding for each depth. The depth and partition at which the minimum coding error occurs among the maximum coding units 610 can be selected as the coding depth and the partition type of the maximum coding unit 610. [

FIG. 7 shows a relationship between an encoding unit and a conversion unit according to an embodiment of the present invention.

The video coding apparatus 100 or the video decoding apparatus 200 according to an embodiment encodes or decodes an image in units of coding units smaller than or equal to the maximum coding unit for each maximum coding unit. The size of the conversion unit for frequency conversion during encoding can be selected based on data units that are not larger than the respective encoding units.

For example, in the video encoding apparatus 100 or the video encoding apparatus 200 according to an embodiment, when the current encoding unit 710 is 64x64 size, the 32x32 conversion unit 720 The frequency conversion can be performed.

In addition, the data of the encoding unit 710 of 64x64 size is encoded by performing the frequency conversion with the conversion units of 32x32, 16x16, 8x8, and 4x4 size of 64x64 or smaller, respectively, and then the conversion unit having the smallest error with the original Can be selected.

FIG. 8 illustrates depth-specific encoding information, in accordance with an embodiment of the present invention.

The output unit 130 of the video encoding apparatus 100 according to one embodiment includes information on the encoding mode, information 800 relating to the partition type, information 810 relating to the prediction mode for each encoding unit of each encoding depth, , And information 820 on the conversion unit size may be encoded and transmitted.

The partition type information 800 represents information on the type of partition in which the prediction unit of the current encoding unit is divided, as a data unit for predictive encoding of the current encoding unit. For example, the current encoding unit CU_0 of size 2Nx2N may be any one of a partition 802 of size 2Nx2N, a partition 804 of size 2NxN, a partition 806 of size Nx2N, and a partition 808 of size NxN And can be divided and used. In this case, the information 800 regarding the partition type of the current encoding unit indicates one of a partition 802 of size 2Nx2N, a partition 804 of size 2NxN, a partition 806 of size Nx2N, and a partition 808 of size NxN .

The prediction mode information 810 indicates a prediction mode of each partition. For example, it is determined whether the partition indicated by the information 800 relating to the partition type is predictive-encoded in one of the intra mode 812, the inter mode 814, and the skip mode 816 through the prediction mode information 810 Can be set.

In addition, the information 820 on the conversion unit size indicates whether to perform frequency conversion on the basis of which conversion unit the current encoding unit is performed. For example, the conversion unit may be one of a first intra-conversion unit size 822, a second intra-conversion unit size 824, a first inter-conversion unit size 826, have.

The video data and encoding information extracting unit 210 of the video decoding apparatus 200 according to one embodiment is configured to extract the information 800 about the partition type, the information 810 about the prediction mode, Information 820 on the unit size can be extracted and used for decoding.

FIG. 9 shows a depth encoding unit according to an embodiment of the present invention.

Partition information may be used to indicate changes in depth. The division information indicates whether the current-depth encoding unit is divided into lower-depth encoding units.

The prediction unit 910 for predicting the coding unit 900 having the depth 0 and 2N_0x2N_0 size includes a partition type 912 of 2N_0x2N_0 size, a partition type 914 of 2N_0xN_0 size, a partition type 916 of N_0x2N_0 size, N_0xN_0 Size partition type 918. < RTI ID = 0.0 > Only the partitions 912, 914, 916, and 918 in which the prediction unit is divided at the symmetric ratio are exemplified, but the partition type is not limited to the above, and may be an asymmetric partition, an arbitrary type partition, . ≪ / RTI >

For each partition type, predictive encoding should be repeatedly performed for each partition of size 2N_0x2N_0, two 2N_0xN_0 partitions, two N_0x2N_0 partitions, and four N_0xN_0 partitions. For a partition of size 2N_0x2N_0, size N_0x2N_0, size 2N_0xN_0 and size N_0xN_0, predictive coding can be performed in intra mode and inter mode. The skip mode can be performed only on the partition of size 2N_0x2N_0 with predictive coding.

If the encoding error caused by one of the partition types 912, 914, and 916 of the sizes 2N_0x2N_0, 2N_0xN_0 and N_0x2N_0 is the smallest, there is no need to further divide into lower depths.

If the coding error by the partition type 918 of the size N_0xN_0 is the smallest, the depth 0 is changed to 1 and divided (920), and the coding unit 930 of the partition type of the depth 2 and the size N_0xN_0 is repeatedly encoded The minimum coding error can be retrieved.

A prediction unit 940 for predicting the coding unit 930 of the depth 1 and the size 2N_1x2N_1 (= N_0xN_0) includes a partition type 942 of size 2N_1x2N_1, a partition type 944 of size 2N_1xN_1, a partition type 942 of size N_1x2N_1 (946), and a partition type 948 of size N_1xN_1.

If the encoding error by the partition type 948 having the size N_1xN_1 size is the smallest, the depth 1 is changed to the depth 2 and divided (950), and repeatedly performed on the encoding units 960 of the depth 2 and the size N_2xN_2 Encoding can be performed to search for the minimum coding error.

If the maximum depth is d, depth division information is set up to depth d-1, and division information can be set up to depth d-2. That is, when the encoding is performed from the depth d-2 to the depth d-1, the prediction encoding of the encoding unit 980 of the depth d-1 and the size 2N_ (d-1) x2N_ (d- The prediction unit 990 for the size 2N_ (d-1) x2N_ (d-1) includes a partition type 992 of size 2N_ A partition type 998 of N_ (d-1) x2N_ (d-1), and a partition type 998 of size N_ (d-1) xN_ (d-1).

(D-1) x2N_ (d-1), two size 2N_ (d-1) xN_ (d-1) partitions, and two sizes N_ (d-1) and the partition of four sizes N_ (d-1) xN_ (d-1), the partition type in which the minimum coding error occurs can be retrieved .

Even if the coding error by the partition type 998 of the size N_ (d-1) xN_ (d-1) is the smallest, since the maximum depth is d, the coding unit CU_ (d-1) of the depth d- The coding depth for the current maximum coding unit 900 is determined as the depth d-1, and the partition type can be determined as N_ (d-1) xN_ (d-1). Also, since the maximum depth is d, the division information is not set for the encoding unit 952 of the depth d-1.

The data unit 999 may be referred to as the 'minimum unit' for the current maximum encoding unit. The minimum unit according to an exemplary embodiment may be a quadrangle data unit having a minimum coding unit having the lowest coding depth divided into quadrants. Through the iterative coding process, the video coding apparatus 100 according to an embodiment compares the coding errors of the coding units 900 to determine the coding depth, selects the depth at which the smallest coding error occurs, determines the coding depth, The corresponding partition type and the prediction mode can be set to the coding mode of the coding depth.

In this way, the minimum coding error of each of the depths 0, 1, ..., d-1, and d is compared and the depth with the smallest error is selected to be determined as the coding depth. The coding depth, and the partition type and prediction mode of the prediction unit can be encoded and transmitted as information on the encoding mode. In addition, since the coding unit must be divided from the depth 0 to the coding depth, only the division information of the coding depth is set to '0', and the division information by depth is set to '1' except for the coding depth.

The video data and encoding information extracting unit 220 of the video decoding apparatus 200 according to an exemplary embodiment extracts information on the encoding depth and the prediction unit for the encoding unit 900 and uses the information to extract the encoding unit 912 . The video decoding apparatus 200 according to an exemplary embodiment of the present invention uses division information by depth to grasp the depth with the division information of '0' as a coding depth and can use it for decoding using information on the coding mode for the corresponding depth have.

FIGS. 10, 11 and 12 show the relationship between an encoding unit, a prediction unit, and a frequency conversion unit according to an embodiment of the present invention.

The coding unit 1010 is coding units for coding depth determined by the video coding apparatus 100 according to the embodiment with respect to the maximum coding unit. The prediction unit 1060 is a partition of prediction units of each coding depth unit in the coding unit 1010, and the conversion unit 1070 is a conversion unit of each coding depth unit.

When the depth of the maximum encoding unit is 0, the depth of the encoding units 1012 and 1054 is 1 and the depth of the encoding units 1014, 1016, 1018, 1028, 1050, The coding units 1020, 1022, 1024, 1026, 1030, 1032 and 1048 have a depth of 3 and the coding units 1040, 1042, 1044 and 1046 have a depth of 4.

Some partitions 1014, 1016, 1022, 1032, 1048, 1050, 1052, and 1054 among the prediction units 1060 are in the form of a segment of a coding unit. That is, the partitions 1014, 1022, 1050 and 1054 are 2NxN partition types, the partitions 1016, 1048 and 1052 are Nx2N partition type, and the partition 1032 is NxN partition type. The prediction units and the partitions of the depth-dependent coding units 1010 are smaller than or equal to the respective coding units.

The image data of a part 1052 of the conversion units 1070 is subjected to frequency conversion or frequency inverse conversion in units of data smaller in size than the encoding unit. The conversion units 1014, 1016, 1022, 1032, 1048, 1050, 1052, and 1054 are data units of different sizes or types when compared with the prediction units and the partitions of the prediction units 1060. That is, the video encoding apparatus 100 according to the embodiment and the video decoding apparatus 200 according to an embodiment can perform the intra prediction / motion estimation / motion compensation operation for the same encoding unit and the frequency conversion / , Each based on a separate data unit.

Accordingly, the encoding unit is recursively performed for each encoding unit of the hierarchical structure for each maximum encoding unit, and the optimal encoding unit is determined, so that encoding units according to the recursive tree structure can be configured. Division type information, unit type information, prediction mode information, and conversion unit size information. Table 1 below shows an example that can be set in the video encoding apparatus 100 according to the embodiment and the video decoding apparatus 200 according to an embodiment.

Partition information 0 (encoding for the encoding unit of size 2Nx2N of current depth d) Partition information 1 Prediction mode Partition type Conversion unit size For each sub-depth d + 1 encoding units, Intra
Inter

Skip (2Nx2N only) Symmetrical partition type Asymmetric partition type Conversion unit partition information 0 Conversion unit
Partition information 1 2Nx2N
2NxN
Nx2N
NxN 2NxnU
2NxnD
nLx2N
nRx2N 2Nx2N NxN
(Symmetrical partition type)

N / 2xN / 2
(Asymmetric partition type)

The output unit 130 of the video encoding apparatus 100 according to an exemplary embodiment outputs encoding information for encoding units according to the tree structure and outputs the encoding information to the encoding information extracting unit 220 can extract the encoding information for the encoding units according to the tree structure from the received bitstream.

The division information indicates whether the current encoding unit is divided into low-depth encoding units. If the division information of the current depth d is 0, since the depth at which the current encoding unit is not further divided into the current encoding unit is the encoding depth, the partition type information, prediction mode, and conversion unit size information are defined . When it is necessary to further divide by one division according to the division information, encoding should be performed independently for each of four divided sub-depth coding units.

The prediction mode may be represented by one of an intra mode, an inter mode, and a skip mode. Intra mode and inter mode can be defined in all partition types, and skip mode can be defined only in partition type 2Nx2N.

The partition type information indicates symmetrical partition types 2Nx2N, 2NxN, Nx2N and NxN in which the height or width of the predicted unit is divided into symmetric proportions and asymmetric partition types 2NxnU, 2NxnD, nLx2N, and nRx2N divided by the asymmetric ratio . Asymmetric partition types 2NxnU and 2NxnD are respectively divided into heights 1: 3 and 3: 1, and asymmetric partition types nLx2N and nRx2N are respectively divided into widths of 1: 3 and 3: 1.

The conversion unit size can be set to two kinds of sizes in the intra mode and two kinds of sizes in the inter mode. That is, if the conversion unit division information is 0, the size of the conversion unit is set to the size 2Nx2N of the current encoding unit. If the conversion unit division information is 1, a conversion unit of the size where the current encoding unit is divided can be set. Also, if the partition type for the current encoding unit of size 2Nx2N is a symmetric partition type, the size of the conversion unit may be set to NxN, or N / 2xN / 2 if it is an asymmetric partition type.

The encoding information of the encoding units according to the tree structure according to an exemplary embodiment may be allocated to at least one of encoding units, prediction units, and minimum unit units of the encoding depth. The coding unit of the coding depth may include one or more prediction units and minimum units having the same coding information.

Therefore, if encoding information held in adjacent data units is checked, it can be confirmed whether or not the encoded information is included in the encoding unit of the same encoding depth. In addition, since the encoding unit of the encoding depth can be identified by using the encoding information held by the data unit, the distribution of encoding depths within the maximum encoding unit can be inferred.

Therefore, in this case, when the current encoding unit is predicted with reference to the neighboring data unit, the encoding information of the data unit in the depth encoding unit adjacent to the current encoding unit can be directly referenced and used.

In another embodiment, when predictive encoding is performed with reference to a current encoding unit with reference to a surrounding encoding unit, data adjacent to the current encoding unit in the depth encoding unit is encoded using the encoding information of adjacent encoding units The surrounding encoding unit may be referred to by being searched.

Fig. 13 shows the relationship between the encoding unit, the prediction unit and the conversion unit according to the encoding mode information in Table 1. Fig.

The maximum coding unit 1300 includes coding units 1302, 1304, 1306, 1312, 1314, 1316, and 1318 of the coding depth. Since one of the encoding units 1318 is a coding unit of the encoding depth, the division information may be set to zero. The partition type information of the encoding unit 1318 of the size 2Nx2N is the partition type information of the partition type 2Nx2N 1322, 2NxN 1324, Nx2N 1326, NxN 1328, 2NxnU 1332, 2NxnD 1334, nLx2N 1336, And < RTI ID = 0.0 > nRx2N 1338 < / RTI >

If the partition type information is set to one of the symmetric partition types 2Nx2N 1322, 2NxN 1324, Nx2N 1326 and NxN 1328, if the TU size flag is 0, the conversion unit of size 2Nx2N (1342) is set, and if the conversion unit division information is 1, a conversion unit 1344 of size NxN can be set.

When the partition type information is set to one of the asymmetric partition types 2NxnU 1332, 2NxnD 1334, nLx2N 1336 and nRx2N 1338, if the TU size flag is 0, the conversion unit of size 2Nx2N 1352) is set, and if the conversion unit division information is 1, a conversion unit 1354 of size N / 2xN / 2 can be set.

The intraprediction unit 410 of the image encoding apparatus 400 and the intraprediction unit 550 of the image decoding apparatus 500 of FIG. 5 according to an embodiment of the present invention This will be described in detail. As described above, intraprediction can be performed on a partition unit in which a prediction unit included in an encoding unit or a prediction unit is divided. In the following description, a block may indicate a partition in which a prediction unit included in an encoding unit obtained by dividing a maximum encoding unit or a prediction unit is divided.

14 is a block diagram showing a configuration of an intra prediction apparatus 1400 according to an embodiment of the present invention. The intra prediction apparatus 1400 of FIG. 14 can be applied to the intra prediction unit 410 of the image coding apparatus 400 of FIG. 4 and the intra prediction unit 550 of the image decoding apparatus 500 of FIG.

Referring to FIG. 14, an intra prediction apparatus 1400 according to an embodiment of the present invention includes a filtering unit 1410, a reference pixel determination unit 1420, and an intra prediction unit 1430.

The neighboring pixel filtering unit 1410 filters neighboring pixels used for intra prediction of the current block to generate filtered neighboring pixels. The neighboring pixel filtering unit 1410 may generate filtered neighboring pixels by applying a predetermined filter to neighboring pixels to calculate a weighted sum between neighboring pixels. The specific peripheral pixel filtering process will be described later.

The reference pixel determination unit 1420 determines a current pixel of the current block based on the color component of the current block, the size of the current block, and the intra-prediction mode information, And determines the surrounding pixels used for intra prediction of the block.

According to one embodiment, a YCbCr (or YUV) color format composed of luminance and chrominance components is used. The reason why the color format composed of the luminance and chrominance components is used is to use a fact that the human eye is sensitive to the luminance components as compared with the chrominance components and allocate a relatively larger bandwidth to the luminance components than to the chrominance components to efficiently encode the video will be. 4: 4: 4 color format, 4: 2: 2 color format and 4: 2: 0 color format may be used depending on the resolution of video of luminance component and video of chrominance component in the color format of video according to an embodiment . The 4: 4: 4 color format is a case where the video of the luminance component and the video of the chrominance component have the same resolution. The 4: 2: 2 color format is a case where the color difference signal has a resolution of 1/2 in either the horizontal or vertical direction of the luminance signal. The 4: 2: 0 color format is a case where the color difference signal has a resolution of 1/2 for both the horizontal and vertical directions of the luminance signal.

The reference pixel determination unit 1420 performs filtering on the reconstructed neighboring pixels of the luminance component block and the reconstructed neighboring pixels at least once based on the size of the luminance component block and the intra prediction mode to be applied, And determines surrounding pixels to be used for intra prediction among the neighboring surrounding pixels. It is assumed that 35 intra prediction modes are available for a block of luminance components, as shown in Fig. 15 to be described later. If the current intra prediction mode index among the 35 intra prediction modes is referred to as prediction_mode, the reference pixel determination unit reconstructs the reconstructed neighboring pixels based on the block size of the luminance component and the intra prediction mode, such as the following pseudo code, The neighboring pixels to be used for intraprediction of the luminance component block among the neighboring pixels that have been filtered through the neighboring pixels.

{

Diff = min (abs (prediction_mode-horizontal_mode), abs (prediction_mode-vertical_mode));

If Diff> Thres_val, then use filtered reference pixel;

else use original reference pixel;

If (prediction_mode) == DC mode) use original reference pixel;

Thres_val = {10, // 4x4 block

7, // 8x8 block

1, // 16x16 block

0 // 32x32 block}

}

The intra prediction mode index is a value assigned to each intra prediction mode as shown in FIG. 15 described later. For example, when the intra prediction mode index is 0, it is a planar mode. When the intra prediction mode index is 1, Horizontal mode, and 26 indicates a vertical mode. The pseudo code is analyzed to find the absolute value of the difference between the index of the current intra prediction mode and the index of the horizontal mode (prediction_mode - horizontal_mode), the difference between the index of the current intra prediction mode and the index of the vertical mode (prediction_mode - vertical_mode) And when the Diff is greater than the threshold value, the filtered neighboring pixels are divided into a luminance component block, a luminance component block, and a luminance component block, in accordance with a result obtained by comparing Diff with a predetermined threshold value Thres_val determined based on the size of the luminance component block. When the Diff is less than or equal to the threshold value, the pixel around the circle is used as a reference pixel. The reference pixel determination unit 1420 may determine that only the original peripheral pixels are used as reference pixels without using the filtered neighboring pixels in the specific intra prediction mode, for example, the DC mode.

Neighboring pixels used as reference pixels at the intra-picture side of the luminance component block may be determined based on the following Table 2 according to the magnitude of the luminance component according to the pseudo code described above and the type of the intra prediction mode. In Table 2, the reference index of the prediction mode using the original surrounding pixels is set to 0, and the reference index of the prediction mode using the first filtered neighboring pixels is set to 1. That is, in the case of a reference index having a value of 0, a circle surrounding pixels is used for the luminance component block, and in the case of a reference index having a value of 1, the filtered neighboring pixels are used for the luminance component block . For example, in Table 2, when intraprediction having a prediction mode index of 2 is performed for a luminance block of 32x32 size, since the reference index has a value of 1, intra prediction with a prediction mode index of 2 for a 32x32 luminance block It indicates that the filtered neighboring pixel is used as a reference pixel instead of the surrounding pixels.

Predictive mode index
Block size Predictive mode index
Block size 4x4 8x8 16x16 32x32 4x4 8x8 16x16 32x32 0 0 One One One 18 0 One One One One 0 0 0 0 19 0 0 One One 2 0 One One One 20 0 0 One One 3 0 0 One One 21 0 0 One One 4 0 0 One One 22 0 0 One One 5 0 0 One One 23 0 0 One One 6 0 0 One One 24 0 0 One One 7 0 0 One One 25 0 0 0 One 8 0 0 One One 26 0 0 0 0 9 0 0 0 One 27 0 0 0 One 10 0 0 0 0 28 0 0 One One 11 0 0 0 One 29 0 0 One One 12 0 0 One One 30 0 0 One One 13 0 0 One One 31 0 0 One One 14 0 0 One One 32 0 0 One One 15 0 0 One One 33 0 0 One One 16 0 0 One One 34 0 One One One 17 0 0 One One

Table 2 is only one example, and whether to use the filtered neighboring pixels according to various block sizes and intra prediction modes can be set in a different manner.

The intra prediction unit 1430 performs intra prediction using the determined neighboring pixels when the neighboring pixels to be used in the intra prediction of the luminance component block among the surrounding pixels and the filtered neighboring pixels are determined in the reference pixel determination unit 1420 Thereby generating a predicted value of the luminance component block.

In addition, the reference pixel determination unit 1420 performs filtering on the reconstructed neighboring pixels and reconstructed neighboring pixels of the chrominance component block at least once based on the size of the chrominance component block and the intra prediction mode to be applied, The neighboring pixels to be used for intra prediction among the one filtered neighboring pixels can be determined. The reference pixel determination unit 1420 determines whether or not the neighboring pixels of the chrominance component block and the filtered neighboring pixels of the chrominance component block based on the use of the filtered neighboring pixels determined at intra prediction of the block of the luminance component corresponding to the block of the chrominance component A reference pixel to be used in intra prediction of a chrominance component block may be determined. However, since the luminance component and the chrominance component are closely related to each other, the chrominance component image may have more noise components than the luminance component image. Therefore, it is preferable to apply the determination method of the filtered peripheral pixels to the chrominance component as they are I do not. Therefore, the reference pixel determiner 1420 according to an embodiment determines, for the block of the chrominance component independently of the luminance component, the reconstructed neighboring pixels of the chrominance component block based on the size of the chrominance component block and the intra- And neighboring pixels to be used for intra prediction among the filtered neighboring pixels obtained by filtering the reconstructed neighboring pixels at least once. In the case of a chrominance component image, noise is more likely to occur than a luminance component image. Therefore, it is preferable that the number of cases in which intraprediction is performed using the filtered neighboring pixels is set to be larger than the luminance component. That is, if circular surrounding pixels are used in a luminance component block having the same size and to which the same intra prediction mode is applied, the filtered neighboring pixels may be set to be used for intra prediction for the chrominance component block.

 It is assumed that 36 intra prediction modes are available for the block of chrominance components, as shown in FIG. 15 to be described later. If the intra-prediction mode index indicating the 36 intra-prediction modes is referred to as prediction_mode, the reference pixel determination unit determines the surrounding pixels restored based on the size of the block of the chrominance component and the intra- The neighboring pixels to be used for intra prediction of the chrominance component block among the filtered neighboring pixels can be determined.

{

Diff = min (abs (prediction_mode-horizontal_mode), abs (prediction_mode-vertical_mode));

If Diff> Thres_val, then use filtered reference pixel;

else use original reference pixel;

If (prediction_mode) == DC mode) use original reference pixel;

Thres_val = {6, // 4x4 block

1, // 8x8 block

0, // 16x16 block

0 // 32x32 block}

}

Since the threshold value (Thres_val) is smaller than that of the luminance component by analyzing the pseudo code, the case where the filtered neighboring pixels are used as the reference pixels in the intra prediction is increased in the case of the chrominance components.

The neighboring pixels used as reference pixels in the intra prediction of the chrominance component block according to the size of the chrominance component block according to the pseudo code and the kind of the intra prediction mode can be determined based on the following Table 3. [ In Table 3, the reference index of the prediction mode using the original surrounding pixels is set to 0, and the reference index of the prediction mode using the first filtered neighboring pixels is set to 1. In other words, in the case of a reference index having a value of 0, a circle surrounding pixels is used for the chrominance component block, and in the case of a reference index having a value of 1, a filtered neighboring pixel is used for the chrominance component block .

Predictive mode index
Block size Predictive mode index
Block size 4x4 8x8 16x16 32x32 4x4 8x8 16x16 32x32 0 0 One One One 18 One One One One One 0 0 0 0 19 One One One One 2 One One One One 20 0 One One One 3 One One One One 21 0 One One One 4 0 One One One 22 0 One One One 5 0 One One One 23 0 One One One 6 0 One One One 24 0 One One One 7 0 One One One 25 0 0 One One 8 0 One One One 26 0 0 0 0 9 0 0 One One 27 0 0 One One 10 0 0 0 0 28 0 One One One 11 0 0 One One 29 0 One One One 12 0 One One One 30 0 One One One 13 0 One One One 31 0 One One One 14 0 One One One 32 0 One One One 15 0 One One One 33 0 One One One 16 0 One One One 34 One One One One 17 One One One One 35 One One One One

Comparing Table 2 and Table 3, the case of performing the intra-prediction using the filtered neighboring pixels is increased when the reference index is 1 in the case of the chrominance component.

In addition, the reference pixel determination unit 1420 can determine the surrounding pixels that are filtered more than twice based on the size of the chrominance component block and the intra-prediction mode as reference pixels to be used in intra prediction. The two or more filtered neighboring pixels may be set to be applied to a chrominance component block of a predetermined size or more, for example, 16x16 or more.

Specifically, the reference pixel determination unit 1420 reconstructs surrounding pixels restored based on the size of the block of the color difference component and the intra-prediction mode, The neighboring pixels to be used for intra prediction of the chrominance component block among neighboring pixels that have been filtered twice.

{

Diff = min (abs (prediction_mode-horizontal_mode), abs (prediction_mode-vertical_mode));

If Diff> Thres_val, then use filtered reference pixel;

else use original reference pixel;

If (prediction_mode) == DC mode) use original reference pixel;

Thres_val = {6, // 4x4 block

2, // 8x8 block

1, // 16x16 block

0 // 32x32 block}

If ((use filtered reference pixel) && (block size> = 16x16))

use twice filtered reference pixel

}

If the pseudo code is determined to use the filtered neighboring pixels for a predetermined size, for example, 16x16 or more chrominance component blocks, the neighboring pixels filtered twice may be set as reference pixels for intraprediction have. The neighboring pixels used as reference pixels in the intra prediction of the chrominance component block according to the size of the chrominance component block according to the pseudo code and the type of the intra prediction mode can be determined based on the following Table 4. [ In Table 4, the reference index of the prediction mode using the original surrounding pixels is 0, the reference index of the prediction mode using the first filtered neighboring pixels is 1, the reference index of the prediction mode using the second filtered neighboring pixels is 2 . That is, in the case of a reference index having a value of 0, a circle surrounding pixels is used for the chrominance component block, and in the case of a reference index having a value of 1, the surrounding pixels filtered once for the chrominance component block are used And in the case of a reference index having a value of 2, neighboring pixels filtered twice for the chrominance component block are used.

Predictive mode index
Block size Predictive mode index
Block size 4x4 8x8 16x16 32x32 4x4 8x8 16x16 32x32 0 0 One 2 2 18 One One 2 2 One 0 0 0 0 19 One One 2 2 2 One One 2 2 20 0 One 2 2 3 One One 2 2 21 0 One 2 2 4 0 One 2 2 22 0 One 2 2 5 0 One 2 2 23 0 One 2 2 6 0 One 2 2 24 0 One 2 2 7 0 One 2 2 25 0 0 2 2 8 0 One 2 2 26 0 0 0 0 9 0 0 2 2 27 0 0 2 2 10 0 0 0 0 28 0 One 2 2 11 0 0 2 2 29 0 One 2 2 12 0 One 2 2 30 0 One 2 2 13 0 One 2 2 31 0 One 2 2 14 0 One 2 2 32 0 One 2 2 15 0 One 2 2 33 0 One 2 2 16 0 One 2 2 34 One One 2 2 17 One One 2 2 35 One One 2 2

As illustrated in Table 4, when it is determined to use the filtered neighboring pixels for the chrominance component block having a size of 16x16 or more, the neighboring pixels twice filtered are used as reference pixels.

As described above, according to the embodiments of the present invention, the use of the filtered neighboring pixels at the intra-prediction of the chrominance component block is caused more than at the intra-prediction of the luminance component block, The efficiency can be improved.

Hereinafter, an intra prediction method according to an embodiment will be described in detail.

FIG. 15 illustrates intra prediction modes according to an embodiment.

Referring to FIG. 15, according to an embodiment, a larger number of intra prediction modes than the intra prediction mode used in conventional H.264 / AVC can be used. According to one embodiment, a total of 35 intra prediction modes may be used for the blocks of luminance components. FIG. 15 shows a prediction mode index allocated according to the intra prediction mode. The 0-th intra-prediction mode is a planar mode, the 1-th intra-prediction mode is a DC mode, and the 2-th to 34-th intra modes are intra-prediction modes having directionality as shown in FIG. For the block of chrominance components, Intra_FromLuma mode using Intra prediction mode of luminance component in addition to 35 intra-prediction modes can be added. The prediction mode index of Intra_FromLuma mode is assigned a value of 36.

The planner mode is a mode in which a value obtained by linearly interpolating the upper left peripheral pixel of the current block and the left peripheral pixel of the same row as the current pixel of the current block and a value obtained by linearly interpolating the upper peripheral pixels of the upper left neighboring pixel and the upper neighboring pixel Prediction mode in which each pixel of the current block is predicted using the prediction mode. The DC mode is an intra prediction mode in which an average value of neighboring pixels of the current block is used as a predicted value.

The intra-prediction mode having 33 directionality from No. 2 to No. 34 is an intra-prediction mode in which predicted values are generated by copying peripheral pixels determined using a directional line as shown in FIG.

FIG. 16 specifically shows the prediction angle of the intra-prediction mode having the direction shown in FIG. 16, each arrow represents a point matched according to the intra-prediction mode having the direction of Fig.

When a line having a direction according to the intra prediction mode is accurately matched to neighboring pixels around a pixel to be intra-predicted in the current block, the matched neighboring pixel can be used as a reference pixel. However, a line having a direction according to the intra-prediction mode may pass between surrounding pixels. In this case, the value of the neighboring pixel is generated by linear interpolation according to the position of the pixel.

FIG. 17 is a reference diagram for explaining a case where an intra prediction mode value is obtained through linear interpolation for the intra-prediction mode # 30 of FIG. 15 according to an embodiment.

Referring to FIG. 17, x is a point at which a line having a direction according to the intra-prediction mode # 30 in FIG. 15 is matched with respect to a pixel P00 (1730) in the current block. Thus, when a line having a direction according to the intra-prediction mode indicates between neighboring pixels AR1 1710 and AR2 1720, The predicted value P00 of the current pixel can be obtained by using the weighted average value of the neighboring pixels AR1 1710 and AR2 1720 as P00 = (19 * AR1 + 13 * AR2) >> 5. The weights 19 and 13 multiplied by the neighboring pixels AR1 1710 and AR2 1720 are calculated by multiplying the mapped point x and the neighboring points x1 and x2 when the line having the directionality according to the intra- And the weight may be tabulated and stored in advance.

18 is a diagram illustrating neighboring pixels used in a current block and an intra prediction according to an embodiment of the present invention.

Referring to FIG. 18, the filtering unit 1410 selects a predetermined number of neighboring pixels on the upper side and neighboring pixels on the left according to the size of the current block 1800 to be intra-predicted. If the size of the current block 1800 is nTbs * nTbs (nTbs is an integer), the filtering unit 1410 selects 2nTbs neighboring pixels as indicated by reference numeral 1810. [ The filtering unit 1410 applies a predetermined filter to 2nTbs neighboring pixels to generate filtered neighboring pixels. The number of upper and left neighboring pixels 1810 filtered by the filtering unit 1410 is not limited to this and may be changed in consideration of the directionality of the intra prediction mode applied to the current block.

FIG. 19 is a reference diagram for explaining a process of filtering surrounding pixels according to an embodiment of the present invention, and FIG. 20 shows surrounding pixels to be filtered.

Referring to FIG. 19, if the neighboring pixels of 2 nTbs adjacent to the upper side and the left side of the current block of nTbs * nTbs size are ContextOrg [n] (n is an integer from 0 to 2 nTbs-1), the filtering unit 1410 And filters the surrounding pixels by calculating the weighted average value between the pixels around the circle to generate the first filtered surrounding pixel ContextFiltered1 [n]. For example, the filtering unit 1410 applies the 3-tap filter to the surrounding pixels ContextOrg [n] as shown in the following Equation 1 to generate the first filtered neighboring pixels.

[Equation 1]

ContextFiltered1 [n] = (ContextOrg [n-1] + 2 * ContextOrg [n] + ContextOrg [n + 1]) / 4

Referring to Equation (1), the filtering unit 1410 generates two neighboring pixels ContextOrg [n-1] and ContextOrg [n + 1] adjacent to the currently filtered neighboring pixels ContextOrg [n] To produce a first filtered surrounding pixel. For example, referring to FIG. 20, a filtered pixel value of a pixel value p (-1, -1) located at (-1, -1) on the upper left of the current block is pF (-1, -1) , PF (-1, -1) is calculated using the surrounding pixel values p (-1,0) and (0, -1) at the (-1,0) ≪ / RTI > p (-1, -1) = (p (-1,0) + 2 * p (-1, -1) + p (0, -1)) / 4. The values of the unrounded pixels around the pixel are used as the filtered values for the surrounding pixels p (-1, 2nTbs-1) on the lower left and the surrounding pixels p (2nTbs-1, -1) .

Similarly, the filtering unit 1410 may generate a second filtered surrounding pixel (Context Filtered2 [n]) by recalculating the weighted average value between the first filtered surrounding pixels (ContextFiltered1 [n]). For example, the filtering unit 1210 applies the 3-tap filter to the first filtered peripheral pixels ContextFiltered1 [n] as shown in the following Equation 2 to generate the second filtered peripheral pixels.

&Quot; (2) "

ContextFiltered2 [n] = (ContextFiltered1 [n-1] + 2 * ContextFiltered1 [n] + ContextFiltered1 [n + 1]) / 4

The filtering unit 1410 filters the neighboring pixels ContextFiltered1 [n-1] and ContextFiltered1 [n + 1] adjacent to the currently filtered neighboring pixels (ContextFiltered1 [n]) among the first filtered neighboring pixels. ≪ / RTI > to produce a second filtered surrounding pixel. The filtering process for the peripheral pixels may be repeated two or more times.

21 is a flowchart of a video encoding method according to an embodiment.

Referring to FIG. 21, in step 2110, the filtering unit 1410 filters neighboring pixels of a current block of a chrominance component to be encoded to obtain filtered neighboring pixels.

In step 2120, the reference pixel determination unit 1420 determines neighboring pixels to be used for intraprediction of the current block among the filtered neighboring pixels and the original neighboring pixels based on the current block size and the intra-prediction mode to be performed . As exemplified in Tables 2 to 4 above, the reference pixel determination unit 1420 determines, based on the size of a chrominance component block and an intra prediction mode to be applied, independent of a process of determining a reference pixel in intra-prediction of a luminance component block To determine the surrounding pixels used in the intra prediction of the chrominance component block among the pixels around the circle or the surrounding pixels filtered at least once.

In step 2130, the intra prediction unit 1430 performs intra prediction on the chrominance block using the determined neighboring pixels. The intra prediction mode information determined for the current chrominance component block and the size information of the current chrominance component block are included in the bitstream of the NAL unit and transmitted to the decoding side. On the decoding side, based on the size information and the intra prediction mode information of the chrominance component block A reference pixel to be used for intraprediction of a chrominance component block among the surrounding pixels and the filtered neighboring pixels is determined in the same manner as in the encoding side.

22 is a flowchart of a video decoding method according to an embodiment.

22, when the size information and intra prediction mode information of the current block of chrominance components are obtained from the bitstream in step 2210, the reference pixel determination unit 1420 determines, based on the size information and the intra prediction mode information, , Peripheral pixels used for intra prediction of the current block among the filtered neighboring pixels obtained by filtering the reconstructed neighboring pixels and the reconstructed neighboring pixels of the current block are determined. As a result of the determination in step 2220, if the filtered neighboring pixels are used in the intra prediction of the current chrominance component block, the filtering unit 1410 calculates the size of the chrominance component block and the intraprediction mode And the surrounding pixels are filtered one or two times to output the filtered peripheral pixels.

In step 2230, the intra prediction unit 1430 performs intra prediction on the current block in accordance with the intra prediction mode information using the neighboring pixels determined in the reference pixel determination unit 1420 to generate a prediction value.

The image coding and decoding method according to the present invention can also be implemented as computer-readable codes on a computer-readable recording medium. A computer-readable recording medium includes all kinds of recording apparatuses in which data that can be read by a computer system is stored. Examples of the computer-readable recording medium include ROM, RAM, CD-ROM, magnetic tape, floppy disk, optical data storage, and the like. The computer readable recording medium may also be distributed over a networked computer system so that computer readable code can be stored and executed in a distributed manner.

The present invention has been described with reference to the preferred embodiments. It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. Therefore, the disclosed embodiments should be considered in an illustrative rather than a restrictive sense. The scope of the present invention is defined by the appended claims rather than by the foregoing description, and all differences within the scope of equivalents thereof should be construed as being included in the present invention.

Claims (15)

A video decoding method comprising:
Obtaining size information and intraprediction mode information of a current block of a chrominance component from a bitstream;
And determines surrounding pixels used for intra prediction of the current block among the filtered neighboring pixels obtained by filtering the reconstructed neighboring pixels and the reconstructed neighboring pixels of the current block based on the size information and the intra prediction mode information step; And
And performing intra prediction on the current block according to the intra prediction mode information using the determined neighboring pixels. The method according to claim 1,
The step of determining the surrounding pixels
The neighboring pixels filtered with respect to the current block of the chrominance component are intra-coded in accordance with a determination scheme that is independent of a determination scheme used to determine whether intra-prediction is performed on neighboring pixels filtered at the time of intraprediction of a block of luminance components constituting the video, Predicted video data to be used for prediction. The method according to claim 1,
The step of determining the surrounding pixels
The reconstructed neighboring pixels of the current block, neighboring pixels of the reconstructed neighboring pixels once, and neighboring pixels of the reconstructed neighboring pixels of the neighboring pixels twice, based on the size information and the intra-prediction mode information, And determining one filtered group of neighboring pixels. The method according to claim 1,
The step of determining the surrounding pixels
Determining a difference between an intra prediction mode index and a horizontal intra prediction mode index of the current block and a difference value between an intra prediction mode index of the current block and a vertical intra prediction mode index;
And comparing the determined difference value with a predetermined threshold value determined based on the size information to perform intra prediction of the current block among the filtered neighboring pixels obtained by filtering the reconstructed neighboring pixels and the reconstructed neighboring pixels of the current block And determining a peripheral pixel to be used. 2. The method of claim 1,
Wherein the partition is a prediction unit or prediction unit included in an encoding unit obtained by dividing a current picture based on a depth of the maximum encoding unit and a depth of the maximum encoding unit. Video decoding method. A video decoding apparatus comprising:
A neighboring pixel filtering unit for filtering neighboring pixels reconstructed before the current block of the chrominance component to generate filtered neighboring pixels;
Obtaining the size information and the intra-prediction mode information of the current block of the chrominance component from the bitstream, filtering the reconstructed neighboring pixels and the reconstructed neighboring pixels of the current block based on the size information and the intra- A reference pixel determination unit for determining a neighboring pixel used for intra prediction of the current block among the filtered neighboring pixels; And
And an intra prediction unit performing intra prediction on the current block according to the intra prediction mode information using the determined neighboring pixels. The method according to claim 6,
The reference pixel determination unit
The neighboring pixels filtered with respect to the current block of the chrominance component are intra-coded in accordance with a determination scheme that is independent of a determination scheme used to determine whether intra-prediction is performed on neighboring pixels filtered at the time of intraprediction of a block of luminance components constituting the video, And determines whether or not to use the prediction for prediction. The method according to claim 6,
The reference pixel determination unit
The reconstructed neighboring pixels of the current block, neighboring pixels of the reconstructed neighboring pixels once, and neighboring pixels of the reconstructed neighboring pixels of the neighboring pixels twice, based on the size information and the intra-prediction mode information, And determines one filtered group of neighboring pixels. The method according to claim 6,
The reference pixel determination unit
A difference value between an intra prediction mode index and a horizontal direction intra prediction mode index of the current block and a difference value between an intra prediction mode index and a vertical direction intra prediction mode index of the current block, And a threshold value determined based on the size information to compare the reconstructed neighboring pixels of the current block and the reconstructed neighboring pixels, And a pixel is determined. 7. The method of claim 6,
Wherein the partition is a prediction unit or prediction unit included in an encoding unit obtained by dividing a current picture based on a depth of the maximum encoding unit and a depth of the maximum encoding unit. Video decoding apparatus. A video encoding method comprising:
Filtering neighboring pixels of a current block of a chrominance component to be encoded to obtain filtered neighboring pixels;
Determining neighboring pixels to be used for intraprediction of the current block among the filtered neighboring pixels and original neighboring pixels based on the size of the current block and an intra prediction mode to be performed; And
And performing intra prediction on the current block using the determined neighboring pixels. 12. The method of claim 11,
The step of determining the surrounding pixels
The neighboring pixels filtered with respect to the current block of the chrominance component are intra-coded in accordance with a determination scheme that is independent of a determination scheme used to determine whether intra-prediction is performed on neighboring pixels filtered at the time of intraprediction of a block of luminance components constituting the video, Predicted video data to be used for prediction. 12. The method of claim 11,
The step of determining the surrounding pixels
The reconstructed neighboring pixels of the current block, neighboring pixels of the reconstructed neighboring pixels once, and neighboring pixels of the reconstructed neighboring pixels of the neighboring pixels twice, based on the size information and the intra-prediction mode information, And determining one filtered neighboring pixel group. 12. The method of claim 11,
The step of determining the surrounding pixels
Determining a difference between an intra prediction mode index and a horizontal intra prediction mode index of the current block and a difference value between an intra prediction mode index of the current block and a vertical intra prediction mode index;
And comparing the determined difference value with a predetermined threshold value determined based on the size information to perform intra prediction of the current block among the filtered neighboring pixels obtained by filtering the reconstructed neighboring pixels and the reconstructed neighboring pixels of the current block And determining a surrounding pixel to be used. 12. The method of claim 11,
Wherein the partition is a prediction unit or prediction unit included in an encoding unit obtained by dividing a current picture based on a depth of the maximum encoding unit and a depth of the maximum encoding unit. / RTI >

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