WO2014107073A1 - Method and apparatus for encoding video, and method and apparatus for decoding said video - Google Patents

Abstract

Disclosed are a method and apparatus for encoding a video, which filter neighboring pixels used in the intra prediction of the encoded current block, and perform intra prediction using the filtered neighboring pixels. Also disclosed are a method and apparatus for decoding said video. The neighboring pixel to be used as a reference pixel from the original neighboring pixel and the filtered neighboring pixel can be determined based on the size of the chrominance component block and the intra prediction mode that is to be applied.

Description

Video encoding method and apparatus, decoding method and apparatus thereof

The present invention relates to a video encoding method and apparatus for improving compression efficiency by performing intra prediction using filtered neighboring pixels, and a decoding method and apparatus thereof.

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

With the development and dissemination of hardware capable of playing and storing high resolution or high definition video content, there is an increasing need for a video codec for efficiently encoding or decoding high resolution 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.

The technical problem to be solved by the present invention is to determine whether to filter the neighboring pixels used as reference pixels in the intra prediction of the chrominance component block independently of the luminance component block.

Based on the size of the chrominance component block and the intra prediction mode, it is determined whether to use the filtered neighboring pixels in the intra prediction of the chrominance component block.

According to the embodiments of the present invention, the filtered neighboring pixels are more frequently used for intra prediction of the chrominance component block than the intra prediction of the luminance component block, thereby improving the prediction efficiency for intra prediction of the chrominance component block. You can.

1 is a block diagram of a video encoding apparatus based on coding units having a tree structure, according to an embodiment of the present invention.

2 is a block diagram of a video decoding apparatus based on coding units having a tree structure, according to an embodiment of the present invention.

3 illustrates a concept of coding units, according to an embodiment of the present invention.

4 is a block diagram of an image encoder based on coding units, according to an embodiment of the present invention.

5 is a block diagram of an image decoder based on coding units, according to an embodiment of the present invention.

6 is a diagram of deeper coding units according to depths, and partitions, according to an embodiment of the present invention.

7 illustrates a relationship between coding units and transformation units, according to an embodiment of the present invention.

8 illustrates encoding information according to depths, according to an embodiment of the present invention.

9 is a diagram of deeper coding units according to depths, according to an embodiment of the present invention.

10, 11, and 12 illustrate a relationship between a coding unit, a prediction unit, and a transformation unit, according to an embodiment of the present invention.

FIG. 13 illustrates a relationship between a coding unit, a prediction unit, and a transformation unit, according to encoding mode information of Table 1. FIG.

14 is a block diagram illustrating a configuration of an intra prediction apparatus 1400 according to an embodiment of the present invention.

15 illustrates intra prediction modes according to an embodiment.

16 illustrates the prediction angle of the intra prediction mode having the directionality of FIG. 15 in detail.

FIG. 17 is a diagram for describing a case of obtaining an intra prediction mode value through linear interpolation for an intra prediction mode having index 30 of FIG. 15, according to an embodiment.

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

19 is a reference diagram for explaining a filtering process of neighboring pixels according to an exemplary embodiment of the present invention.

20 shows the peripheral pixels being 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.

According to an embodiment, a video decoding method includes: obtaining size information and intra prediction mode information of a current block of a color difference component from a bitstream; Determining a neighboring pixel used for intra prediction of the current block among the reconstructed neighboring pixels of the current block and the filtered neighboring pixels filtering the reconstructed neighboring pixel 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 by using the determined neighboring pixel.

In accordance with another aspect of the present invention, a video decoding apparatus includes: a neighboring pixel filter configured to generate filtered neighboring pixels by filtering previously restored neighboring pixels of a current block of a chrominance component; Obtaining size information and intra prediction mode information of the current block of the chrominance component from the bitstream, and 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. A reference pixel determiner configured to determine a neighboring pixel used for intra prediction of the current block among the filtered neighboring pixels; And an intra prediction performing unit configured to perform intra prediction on the current block according to the intra prediction mode information by using the determined neighboring pixel.

According to an embodiment, a video encoding method may include: filtering neighboring pixels of a current block of a color difference component to be encoded to obtain filtered neighboring pixels; Determining neighboring pixels to be used for intra prediction of the current block among the filtered neighboring pixels and the original neighboring pixels based on the size of the current block and the intra prediction mode to be performed; And performing intra prediction on the current block by using the determined neighboring pixels.

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

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

The video encoding apparatus 100 according to an embodiment includes a maximum coding unit splitter 110, a coding unit determiner 120, and an outputter 130.

The maximum coding unit splitter 110 may partition the current picture based on the maximum coding unit that is a coding unit of the maximum size for the current picture of the image. If the current picture is larger than the maximum coding unit, image data of the current picture may be split into at least one maximum coding unit. The maximum coding unit according to an embodiment may be a data unit having a size of 32x32, 64x64, 128x128, 256x256, or the like, and may be a square data unit having a power of 2 of 2 greater than 8 in width and length. The image data may be output to the coding unit determiner 120 for at least one maximum coding unit.

The coding unit according to an embodiment may be characterized by a maximum size and depth. The depth indicates the number of times the coding unit is spatially divided from the maximum coding unit, and as the depth increases, the coding unit for each depth may be split from the maximum coding unit to the minimum coding unit. The depth of the largest coding unit is the highest depth and the minimum coding unit may be defined as the lowest coding unit. As the maximum coding unit decreases as the depth increases, the size of the coding unit for each depth decreases, and thus, the coding unit of the higher depth may include coding units of a plurality of lower depths.

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

The maximum depth and the maximum size of the coding unit that limit the total number of times of hierarchically dividing the height and the width of the maximum coding unit may be preset.

The coding unit determiner 120 encodes at least one divided region obtained by dividing the region of the largest coding unit for each depth, and determines a depth at which the final encoding result is output for each of the at least one divided region. That is, the coding unit determiner 120 encodes the image data in coding units according to depths for each maximum coding unit of the current picture, and selects a depth at which the smallest coding error occurs to determine the coding depth. The determined coded depth and the image data for each maximum coding unit are output to the outputter 130.

Image data in the largest coding unit is encoded based on coding units according to depths according to at least one depth less than or equal to the maximum depth, and encoding results based on the coding units for each depth are compared. As a result of comparing the encoding error of the coding units according to depths, a depth having the smallest encoding error may be selected. At least one coding depth may be determined for each maximum coding unit.

As the depth of the maximum coding unit increases, the coding unit is divided into hierarchically and the number of coding units increases. In addition, even in the case of coding units having the same depth included in one largest coding unit, a coding error of each data is measured, and whether or not division into a lower depth is determined. Therefore, even in the data included in one largest coding unit, since the encoding error for each depth is different according to the position, the coding depth may be differently determined according to 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 partitioned according to coding units of one or more coding depths.

Accordingly, the coding unit determiner 120 according to an embodiment may determine coding units having a tree structure included in the current maximum coding unit. The coding units having a tree structure according to an embodiment include coding units having a depth determined as a coding depth among all deeper coding units included in the maximum coding unit. The coding unit of the coding depth may be hierarchically determined according to the depth in the same region within the maximum coding unit, and may be independently determined for the other regions. Similarly, the coded depth for the current region may be determined independently of the coded depth for the other region.

The maximum depth according to an embodiment is an index related to the number of divisions from the maximum coding unit to the minimum coding unit. The first maximum depth according to an embodiment may represent the total number of divisions from the maximum coding unit to the minimum coding unit. The second maximum depth according to an embodiment may represent the total number of depth levels from the maximum coding unit to the minimum coding unit. For example, when the depth of the largest coding unit is 0, the depth of the coding unit obtained by dividing the largest coding unit once may be set to 1, and the depth of the coding unit 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 depth levels of 0, 1, 2, 3, and 4 exist, the first maximum depth is set to 4 and the second maximum depth is set to 5. Can be.

Predictive coding and frequency transform of the largest coding unit may be performed. Similarly, the prediction encoding and the frequency transformation are performed based on depth-wise coding units for each maximum coding unit and for each depth below the maximum depth.

Since the number of coding units for each depth increases each time the maximum coding unit is divided for each depth, encoding including prediction coding and frequency transformation should be performed on all the coding units for each depth generated as the depth deepens. For convenience of explanation, the prediction encoding and the frequency transformation will be described based on the coding unit of the current depth among at least one maximum coding unit.

The video encoding apparatus 100 according to an embodiment may variously select a size or shape of a data unit for encoding image data. The encoding of the image data is performed through prediction encoding, frequency conversion, entropy encoding, and the like. The same data unit may be used in every step, or the data unit may be changed in steps.

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

For prediction encoding of the largest coding unit, prediction encoding may be performed based on a coding unit of a coding depth, that is, a more strange undivided coding unit, according to an embodiment. Hereinafter, a more strange undivided coding unit that is the basis of prediction coding is referred to as a 'prediction unit'. The partition in which the prediction unit is divided may include a data unit in which at least one of the prediction unit and the height and the width of the prediction unit are divided.

For example, when a coding unit having a size of 2Nx2N (where N is a positive integer) is no longer split, it becomes a prediction unit of size 2Nx2N, and the size of a partition may be 2Nx2N, 2NxN, Nx2N, NxN, or the like. According to an embodiment, the partition type includes not only symmetric partitions in which the height or width of the prediction unit is divided by a symmetrical ratio, but also partitions divided in an asymmetrical ratio, such as 1: n or n: 1, by a geometric form It may optionally include partitioned partitions, arbitrary types of 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, the intra mode and the inter mode may be performed on partitions having sizes of 2N × 2N, 2N × N, N × 2N, and N × N. In addition, the skip mode may be performed only for partitions having a size of 2N × 2N. The encoding may be performed independently for each prediction unit within the coding unit to select a prediction mode having the smallest encoding error.

Also, the video encoding apparatus 100 according to an embodiment may perform frequency conversion of image data of a coding unit based on not only a coding unit for encoding image data, but also a data unit different from the coding 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, the data unit for frequency conversion may include a data unit for an intra mode and a data unit for an inter mode.

Hereinafter, the data unit on which the frequency conversion is based may be referred to as a 'conversion unit'. In a manner similar to the coding unit, while the transform unit in the coding unit is recursively divided into smaller transform units, the residual data of the coding unit may be partitioned according to the transform unit having a tree structure according to the transform depth.

For a transform unit according to an embodiment, a transform depth indicating a number of divisions between the height and the width of the coding unit divided to the transform unit may be set. For example, if the size of the transform unit of the current coding unit of size 2Nx2N is 2Nx2N, the transform depth is 0, the transform depth 1 if the size of the transform unit is NxN, and the transform depth 2 if the size of the transform unit is N / 2xN / 2. Can be. That is, the transformation unit having a tree structure may also be set for the transformation unit according to the transformation depth.

The encoded information for each coded depth requires not only the coded depth but also prediction related information and frequency transform related information. Accordingly, the coding unit determiner 120 may determine not only a coding depth that generates a minimum coding error, but also a partition type obtained by dividing a prediction unit into partitions, a prediction mode for each prediction unit, and a size of a transformation unit for frequency transformation. .

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. 3 to 12.

The coding unit determiner 120 may measure a coding error of coding units according to depths using a Lagrangian Multiplier-based rate-distortion optimization technique.

The output unit 130 outputs the image data of the maximum coding unit encoded based on the at least one coded depth determined by the coding unit determiner 120 and the information about the encoding modes according to depths in the form of a bit stream.

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

The information about the encoding modes according to depths may include encoding depth information, partition type information of a prediction unit, prediction mode information, size information of a transformation unit, and the like.

The coded depth information may be defined using depth-specific segmentation information indicating whether to encode to a coding unit of a lower depth without encoding to the current depth. If the current depth of the current coding unit is a coding depth, since the current coding unit is encoded in a coding unit of the current depth, split information of the current depth may be defined so that it is no longer divided into lower depths. On the contrary, if the current depth of the current coding unit is not the coding depth, encoding should be attempted using the coding unit of the lower depth, and thus split information of the current depth may be defined to be divided into coding units of the lower depth.

If the current depth is not the coded depth, encoding is performed on the coding unit divided into the coding units of the lower depth. Since at least one coding unit of a lower depth exists in the coding unit of the current depth, encoding may be repeatedly performed for each coding unit of each lower depth, and recursive coding may be performed for each coding unit of the same depth.

Since coding units having a tree structure are determined in one largest coding unit and information about at least one coding mode should be determined for each coding unit of a coding depth, information about at least one coding mode may be determined for one maximum coding unit. Can be. In addition, since the data of the largest coding unit is divided hierarchically according to the depth, the coding depth may be different for each location, and thus information about the coded depth and the coding mode may be set for the data.

Accordingly, the output unit 130 according to an embodiment may allocate encoding information about a corresponding coding depth and an encoding mode to at least one of a coding unit, a prediction unit, and a minimum unit included in the maximum coding unit. .

According to an embodiment, a minimum unit is a square data unit having a minimum coding unit, which is a lowest coding depth, divided into four pieces, and has a maximum size that may be included in all coding units, prediction units, and transformation units included in the maximum coding unit. It may be a square data unit.

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

According to an embodiment of the simplest form of the video encoding apparatus 100, a coding unit according to depths is a coding unit having a size in which a height and a width of a coding unit of one layer higher depth are divided by half. That is, if the size of the coding unit of the current depth is 2Nx2N, the size of the coding unit of the lower depth is NxN. In addition, the current coding unit having a size of 2N × 2N may include up to four lower depth coding units having a size of N × N.

Therefore, the video encoding apparatus 100 according to an embodiment determines a coding unit having an optimal shape and size for each maximum coding unit based on the size and the maximum depth of the maximum coding unit determined in consideration of characteristics of the current picture. In this case, coding units having a tree structure may be configured. In addition, since each of the maximum coding units may be encoded in various prediction modes, frequency transform schemes, or the like, an optimal coding mode may be determined in consideration of image characteristics of coding units having various image sizes.

Therefore, if an image having a very high resolution or a very large data amount is encoded in an existing macroblock unit, the number of macroblocks per picture is excessively increased. Accordingly, since the compressed information generated for each macroblock increases, the transmission burden of the compressed information increases, and the data compression efficiency tends to decrease. Therefore, the video encoding apparatus according to an embodiment may adjust the coding unit in consideration of the image characteristics while increasing the maximum size of the coding unit in consideration of the size of the image, thereby increasing image compression efficiency.

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

The video decoding apparatus 200 according to an embodiment includes a receiver 210, an image data and encoding information extractor 220, and an image data decoder 230. Definitions of various terms such as coding units, depths, prediction units, transformation units, and information about various encoding modes for various processings of the video decoding apparatus 200 according to an embodiment may include the video encoding apparatus 100 of FIG. 1 and the video encoding apparatus 100. Same as described above with reference.

The receiver 205 receives and parses a bitstream of an encoded video. The image data and encoding information extractor 220 extracts image data encoded for each coding unit from the parsed bitstream according to coding units having a tree structure for each maximum coding unit, and outputs the encoded image data to the image data decoder 230. The image data and encoding information extractor 220 may extract information about a maximum size of a coding unit of the current picture from a header for the current picture.

Also, the image data and encoding information extractor 220 extracts information about a coded depth and an encoding mode for the coding units having a tree structure for each maximum coding unit, from the parsed bitstream. The extracted information about the coded depth and the coding mode is output to the image data decoder 230. That is, the image data of the bit string may be divided into maximum coding units so that the image data decoder 230 may decode the image data for each maximum coding unit.

The information about the coded depth and the encoding mode for each largest coding unit may be set with respect to one or more coded depth information, and the information about the coding mode according to the coded depths may include partition type information, prediction mode information, and transformation unit of the corresponding coding unit. May include size information and the like. In addition, split information for each depth may be extracted as the coded depth information.

The information about the coded depth and the encoding mode according to the maximum coding units extracted by the image data and the encoding information extractor 220 may be encoded according to the depth according to the maximum coding unit, as in the video encoding apparatus 100 according to an embodiment. Information about a coded depth and an encoding mode determined to repeatedly perform encoding for each unit to generate a minimum encoding error. Therefore, the video decoding apparatus 200 may reconstruct an image by decoding data according to an encoding method that generates a minimum encoding error.

Since the encoded information about the coded depth and the encoding mode according to an embodiment may be allocated to a predetermined data unit among the corresponding coding unit, the prediction unit, and the minimum unit, the image data and the encoding information extractor 220 may determine the predetermined data. Information about a coded depth and an encoding mode may be extracted for each unit. If the information about the coded depth and the coding mode of the maximum coding unit is recorded for each of the predetermined data units, the predetermined data units having the information about the same coded depth and the coding mode are inferred as data units included in the same maximum coding unit. Can be.

The image data decoder 230 reconstructs the current picture by decoding image data of each maximum coding unit based on the information about the coded depth and the encoding mode for each maximum coding unit. That is, the image data decoder 230 may decode the encoded image data based on the read partition type, the prediction mode, and the transformation unit for each coding unit among the coding units having the tree structure included in the maximum coding unit. Can be. The decoding process may include a prediction process including intra prediction and motion compensation, and a frequency inverse transform process.

The image data decoder 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 the prediction unit of the coding unit for each coding depth. .

In addition, the image data decoder 230 may perform frequency inverse transformation according to each transformation unit for each coding unit based on size information of the transformation unit of the coding unit for each coding depth, for a frequency inverse transformation for each maximum coding unit. have.

The image data decoder 230 may determine the coded depth of the current maximum coding unit by using the split information for each depth. If the split information indicates that the split information is no longer split at the current depth, the current depth is the coded depth. Therefore, the image data decoder 230 may decode the coding unit of the current depth using the partition type, the prediction mode, and the transformation unit size information of the prediction unit with respect to the image data of the current maximum coding unit.

In other words, by observing the encoding information set for a predetermined data unit among the coding unit, the prediction unit, and the minimum unit, the data units having the encoding information including the same split information are gathered, and the image data decoder 230 It may be regarded as one data unit to be decoded in the same encoding mode.

According to an embodiment, the video decoding apparatus 200 may obtain information about a coding unit that generates a minimum coding error by recursively encoding each maximum coding unit in an encoding process, and use the same to decode the current picture. have. That is, decoding of encoded image data of coding units having a tree structure determined as an optimal coding unit for each maximum coding unit can be performed.

Therefore, even if a high resolution image or an excessively large amount of data is used, the image data can be efficiently used according to the coding unit size and the encoding mode that are adaptively determined according to the characteristics of the image by using the information about the optimum encoding mode transmitted from the encoding end. Can be decoded and restored.

Hereinafter, a method of determining coding units, a prediction unit, and a transformation unit according to a tree structure according to an embodiment of the present invention will be described with reference to FIGS. 3 to 13.

3 illustrates a concept of hierarchical coding units.

As an example of a coding unit, a size of a coding unit may be expressed by a width x height, and may include 32x32, 16x16, and 8x8 from a coding unit having a size of 64x64. Coding units of size 64x64 may be partitioned into partitions of size 64x64, 64x32, 32x64, and 32x32, coding units of size 32x32 are partitions of size 32x32, 32x16, 16x32, and 16x16, and coding units of size 16x16 are 16x16. Coding units of size 8x8 may be divided into partitions of size 8x8, 8x4, 4x8, and 4x4, into partitions of 16x8, 8x16, and 8x8.

As for the video data 310, the resolution is set to 1920x1080, the maximum size of the coding unit is 64, and the maximum depth is 2. For the video data 320, the resolution is set to 1920x1080, the maximum size of the coding unit is 64, and the maximum depth is 3. As for the video data 330, the resolution is set to 352x288, the maximum size of the coding unit is 16, and the maximum depth is 1. The maximum depth illustrated in FIG. 3 represents the total number of divisions from the maximum coding unit to the minimum coding unit.

When the resolution is high or the amount of data is large, it is preferable that the maximum size of the coding size is relatively large not only to improve the coding efficiency but also to accurately shape the image characteristics. Accordingly, the video data 310 or 320 having a higher resolution than the video data 330 may be selected to have a maximum size of 64.

Since the maximum depth of the video data 310 is 2, the coding unit 315 of the video data 310 is divided twice from a maximum coding unit having a long axis size of 64, and the depth is deepened by two layers, so that the long axis size is 32, 16. Up to coding units may be included. On the other hand, since the maximum depth of the video data 330 is 1, the coding unit 335 of the video data 330 is divided once from coding units having a long axis size of 16, and the depth is deepened by one layer to increase the long axis size to 8. Up to coding units may be included.

Since the maximum depth of the video data 320 is 3, the coding unit 325 of the video data 320 is divided three times from the largest coding unit having a long axis size of 64, and the depth is three layers deep, so that the long axis size is 32, 16. , Up to 8 coding units may be included. As the depth increases, the expressive power of the detailed information may be improved.

4 is a block diagram of an image encoder based on coding units, according to an embodiment of the present invention.

The image encoder 400 according to an embodiment includes operations performed by the encoding unit determiner 120 of the video encoding apparatus 100 to encode image data. That is, the intra predictor 410 performs intra prediction on the coding unit of the intra mode among the current frame 405, and the motion estimator 420 and the motion compensator 425 are the current frame 405 of the inter mode. And the inter frame estimation and motion compensation using the reference frame 495.

Data output from the intra predictor 410, the motion estimator 420, and the motion compensator 425 is output as a quantized transform coefficient through the frequency converter 430 and the quantizer 440. The quantized transform coefficients are restored to the data of the spatial domain through the inverse quantizer 460 and the frequency inverse transformer 470, and the recovered data of the spatial domain is passed through the deblocking block 480 and the loop filtering unit 490. It is post-processed and output to the reference frame 495. The quantized transform coefficients may be output to the bitstream 455 via the entropy encoder 450.

In order to be applied to the video encoding apparatus 100 according to an embodiment, an intra predictor 410, a motion estimator 420, a motion compensator 425, and a frequency converter that are components of the image encoder 400 may be used. 430, quantization unit 440, entropy encoding unit 450, inverse quantization unit 460, frequency inverse transform unit 470, deblocking unit 480, and loop filtering unit 490 are all the maximum coding units. In each case, an operation based on each coding unit among the coding units having a tree structure should be performed in consideration of the maximum depth.

In particular, the intra predictor 410, the motion estimator 420, and the motion compensator 425 partition each coding unit among coding units having a tree structure in consideration of the maximum size and the maximum depth of the current maximum coding unit. And a prediction mode, and the frequency converter 430 should determine the size of a transform unit in each coding unit among the coding units having a tree structure.

5 is a block diagram of an image decoder based on coding units, according to an embodiment of the present invention.

The bitstream 505 is parsed through the parsing unit 510, and the encoded image data to be decoded and information about encoding necessary for decoding are parsed. The encoded image data is output as inverse quantized data through the entropy decoder 520 and the inverse quantizer 530, and the image data of the spatial domain is restored through the frequency inverse transformer 540.

For the image data of the spatial domain, the intra prediction unit 550 performs intra prediction on the coding unit of the intra mode, and the motion compensator 560 uses the reference frame 585 together to apply the coding unit of the inter mode. Perform motion compensation for the

Data in the spatial domain that has passed through the intra predictor 550 and the motion compensator 560 may be post-processed through the deblocking unit 570 and the loop filtering unit 580 to be output to the reconstructed frame 595. In addition, the post-processed data through the deblocking unit 570 and the loop filtering unit 580 may be output as the reference frame 585.

In order to decode the image data in the image data decoder 230 of the video decoding apparatus 200, step-by-step operations after the parser 510 of the image decoder 500 according to an embodiment may be performed.

In order to be applied to the video decoding apparatus 200 according to an exemplary embodiment, a parser 510, an entropy decoder 520, an inverse quantizer 530, and a frequency inverse transform unit which are components of the image decoder 500 may be used. 540, the intra predictor 550, the motion compensator 560, the deblocking unit 570, and the loop filtering unit 580 all perform operations based on coding units having a tree structure for each largest coding unit. shall.

In particular, the intra predictor 550 and the motion compensator 560 determine partitions and prediction modes for each coding unit having a tree structure, and the frequency inverse transform unit 540 must determine the size of the transform unit for each coding unit. do.

6 is a diagram of deeper coding units according to depths, and partitions, according to an embodiment of the present invention.

The video encoding apparatus 100 according to an embodiment and the video decoding apparatus 200 according to an embodiment use hierarchical coding units to consider image characteristics. The maximum height, width, and maximum depth of the coding unit may be adaptively determined according to the characteristics of the image, and may be variously set according to a user's request. According to the maximum size of the preset coding unit, the size of the coding unit for each depth may be determined.

The hierarchical structure 600 of a coding unit according to an embodiment illustrates a case in which a maximum height and a width of a coding unit are 64 and a maximum depth is three. Since the depth deepens along the vertical axis of the hierarchical structure 600 of the coding unit according to an embodiment, the height and the width of the coding unit for each depth are divided. In addition, a prediction unit and a partition on which the prediction encoding of each depth-based coding unit is shown along the horizontal axis of the hierarchical structure 600 of the coding unit are illustrated.

That is, the coding unit 610 has a depth of 0 as the largest coding unit of the hierarchical structure 600 of the coding unit, and the size, ie, the height and width, of the coding unit is 64x64. A depth deeper along a vertical axis, a coding unit 620 of depth 1 having a size of 32x32, a coding unit 630 of depth 2 having a size of 16x16, and a coding unit 640 of depth 3 having a size of 8x8. A coding unit 640 of depth 3 having a size of 8 × 8 is a minimum coding unit.

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

Similarly, the prediction unit of the coding unit 620 having a size of 32x32 having a depth of 1 includes a partition 620 of size 32x32, partitions 622 of size 32x16 and a partition of size 16x32 included in the coding unit 620 of size 32x32. 624, partitions 626 of size 16x16.

Similarly, the prediction unit of the coding unit 630 of size 16x16 having a depth of 2 includes a partition 630 of size 16x16, partitions 632 of size 16x8, and a partition of size 8x16 included in the coding unit 630 of size 16x16. 634, partitions 636 of size 8x8.

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

The coding unit determiner 120 of the video encoding apparatus 100 according to an exemplary embodiment may determine a coding depth of the maximum coding unit 610. The coding unit of each depth included in the maximum coding unit 610. Encoding must be performed every time.

The number of deeper coding units according to depths for including data having the same range and size increases as the depth increases. For example, four coding units of depth 2 are required for data included in one coding unit of depth 1. Therefore, in order to compare the encoding results of the same data for each depth, each of the coding units having one depth 1 and four coding units having four depths 2 should be encoded.

For each depth coding, encoding may be performed for each prediction unit of a coding unit according to depths along a horizontal axis of the hierarchical structure 600 of the coding unit, and a representative coding error, which is the smallest coding error at a corresponding depth, may be selected. . In addition, a depth deeper along the vertical axis of the hierarchical structure 600 of the coding unit, the encoding may be performed for each depth, and the minimum coding error may be searched by comparing the representative coding error for each depth. The depth and the partition in which the minimum coding error occurs in the maximum coding unit 610 may be selected as the coding depth and the partition type of the maximum coding unit 610.

7 illustrates a relationship between coding units and transformation units, according to an embodiment of the present invention.

The video encoding apparatus 100 according to an embodiment or the video decoding apparatus 200 according to an embodiment encodes or decodes an image in coding units having a size smaller than or equal to the maximum coding unit for each maximum coding unit. The size of a transform unit for frequency transformation during the encoding process may be selected based on a data unit that is not larger than each coding unit.

For example, in the video encoding apparatus 100 or the video decoding apparatus 200 according to the embodiment, when the current coding unit 710 is 64x64 size, the 32x32 size conversion unit 720 is Frequency conversion can be performed using the above.

In addition, the data of the 64x64 coding unit 710 is encoded by performing frequency transformation on the 32x32, 16x16, 8x8, and 4x4 transform units having a size of 64x64 or less, and the transform unit having the least error with the original is obtained. Can be selected.

8 illustrates encoding information according to depths, according to an embodiment of the present invention.

The output unit 130 of the video encoding apparatus 100 according to an exemplary embodiment is information about an encoding mode, and information about a partition type 800 and information 810 about a prediction mode for each coding unit of each coded depth. The information 820 about the size of the transformation unit may be encoded and transmitted.

The information about the partition type 800 is a data unit for predictive encoding of the current coding unit and indicates information about a partition type in which the prediction unit of the current coding unit is divided. For example, the current coding 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. It can be divided and used. In this case, the information 800 about the partition type of the current coding unit represents 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. It is set to.

Information 810 relating to the prediction mode indicates the prediction mode of each partition. For example, through the information 810 about the prediction mode, whether the partition indicated by the information 800 about the partition type is performed in one of the intra mode 812, the inter mode 814, and the skip mode 816 is performed. Whether or not can be set.

In addition, the information about the transform unit size 820 indicates whether to transform the current coding unit based on the transform unit. For example, the transform unit may be one of a first intra transform unit size 822, a second intra transform unit size 824, a first inter transform unit size 826, and a second intra transform unit size 828. have.

The image data and encoding information extractor 210 of the video decoding apparatus 200 according to an embodiment may include information about a partition type 800, information 810 about a prediction mode, and transformation for each depth-based coding unit. Information 820 about the unit size may be extracted and used for decoding.

9 is a diagram of deeper coding units according to depths, according to an embodiment of the present invention.

Segmentation information may be used to indicate a change in depth. The split information indicates whether a coding unit of a current depth is split into coding units of a lower depth.

The prediction unit 910 for predictive encoding of the coding unit 900 having depth 0 and 2N_0x2N_0 size includes a partition type 912 having a size of 2N_0x2N_0, a partition type 914 having a size of 2N_0xN_0, a partition type 916 having a size of N_0x2N_0, and a N_0xN_0 It may include a partition type 918 of size. Although only partitions 912, 914, 916, and 918 in which the prediction unit is divided by a symmetrical ratio are illustrated, as described above, the partition type is not limited thereto, and asymmetric partitions, arbitrary partitions, geometric partitions, and the like. It may include.

For each partition type, prediction coding must be performed repeatedly for one 2N_0x2N_0 partition, two 2N_0xN_0 partitions, two N_0x2N_0 partitions, and four N_0xN_0 partitions. For partitions having a size 2N_0x2N_0, a size N_0x2N_0, a size 2N_0xN_0, and a size N_0xN_0, prediction encoding may be performed in an intra mode and an inter mode. The skip mode may be performed only for prediction encoding on partitions having a size of 2N_0x2N_0.

If the encoding error by one of the partition types 912, 914, and 916 of sizes 2N_0x2N_0, 2N_0xN_0, and N_0x2N_0 is the smallest, it is no longer necessary to divide it into lower depths.

If the encoding error of the partition type 918 having the size N_0xN_0 is the smallest, the depth 0 is changed to 1 and split (920), and the encoding is repeatedly performed on the depth 2 and the coding units 930 of the partition type having the size N_0xN_0. We can search for the minimum coding error.

The prediction unit 940 for predictive encoding of the coding unit 930 having a depth of 1 and a size of 2N_1x2N_1 (= N_0xN_0) includes a partition type 942 having a size of 2N_1x2N_1, a partition type 944 having a size of 2N_1xN_1, and a partition type having a size of N_1x2N_1. 946, a partition type 948 of size N_1 × N_1 may be included.

In addition, if the encoding error due to the partition type 948 having the size N_1xN_1 is the smallest, the depth 1 is changed to the depth 2 and divided (950), and repeatedly for the depth 2 and the coding units 960 of the size N_2xN_2. The encoding may be performed to search for a minimum encoding error.

When the maximum depth is d, the split information for each depth may be set until the depth d-1, and the split information may be set up to the depth d-2. That is, when encoding is performed from the depth d-2 to the depth d-1 to the depth d-1, the prediction encoding of the coding unit 980 of the depth d-1 and the size 2N_ (d-1) x2N_ (d-1) The prediction unit for 990 is a partition type 992 of size 2N_ (d-1) x2N_ (d-1), partition type 994 of size 2N_ (d-1) xN_ (d-1), size A partition type 996 of N_ (d-1) x2N_ (d-1) and a partition type 998 of size N_ (d-1) xN_ (d-1) may be included.

Among the partition types, one partition 2N_ (d-1) x2N_ (d-1), two partitions 2N_ (d-1) xN_ (d-1), two sizes N_ (d-1) x2N_ Prediction encoding is repeatedly performed for each partition of (d-1) and four partitions of size N_ (d-1) xN_ (d-1), so that a partition type having a minimum encoding error may be searched. .

Even if the encoding error of the partition type 998 of size N_ (d-1) xN_ (d-1) is the smallest, the maximum depth is d, so the coding unit CU_ (d-1) of the depth d-1 is no longer The encoding depth of the current maximum coding unit 900 may be determined as the depth d-1, and the partition type may be determined as N_ (d-1) xN_ (d-1) without going through a division process into lower depths. In addition, since the maximum depth is d, split information is not set for the coding unit 952 having the depth d-1.

The data unit 999 may be referred to as a 'minimum unit' for the current maximum coding unit. According to an embodiment, the minimum unit may be a square data unit having a size obtained by dividing the minimum coding unit, which is the lowest coding depth, into four divisions. Through this iterative encoding process, the video encoding apparatus 100 compares the encoding errors for each depth of the coding unit 900, selects a depth at which the smallest encoding error occurs, and determines a coding depth. The partition type and the prediction mode may be set to the encoding mode of the coded depth.

In this way, the depth with the smallest error can be determined by comparing the minimum coding errors for all depths of depths 0, 1, ..., d-1, d, and can be determined as the coding depth. The coded depth, the partition type of the prediction unit, and the prediction mode may be encoded and transmitted as information about an encoding mode. In addition, since the coding unit must be split from the depth 0 to the coded depth, only the split information of the coded depth is set to '0', and the split information for each depth except the coded depth should be set to '1'.

The image data and encoding information extractor 220 of the video decoding apparatus 200 according to an embodiment may extract information about a coding depth and a prediction unit for the coding unit 900 and use the same to decode the coding unit 912. Can be. The video decoding apparatus 200 according to an embodiment may identify a depth having split information of '0' as a coding depth using split information for each depth, and may use the decoding depth by using information about an encoding mode for a corresponding depth. have.

10, 11, and 12 illustrate a relationship between a coding unit, a prediction unit, and a frequency transformation unit, according to an embodiment of the present invention.

The coding units 1010 are coding units according to coding depths determined by the video encoding apparatus 100 according to an embodiment with respect to the maximum coding unit. The prediction unit 1060 is partitions of prediction units of each coding depth of each coding depth among the coding units 1010, and the transformation unit 1070 is transformation units of each coding depth for each coding depth.

If the depth-based coding units 1010 have a depth of 0, the coding units 1012 and 1054 have a depth of 1, and the coding units 1014, 1016, 1018, 1028, 1050, and 1052 have depths. 2, coding units 1020, 1022, 1024, 1026, 1030, 1032, and 1048 have a depth of three, and coding units 1040, 1042, 1044, and 1046 have a depth of four.

Some of the partitions 1014, 1016, 1022, 1032, 1048, 1050, 1052, and 1054 of the prediction units 1060 are obtained by splitting coding units. That is, partitions 1014, 1022, 1050, and 1054 are partition types of 2NxN, partitions 1016, 1048, and 1052 are partition types of Nx2N, and partitions 1032 are partition types of NxN. Prediction units and partitions of the coding units 1010 according to depths are smaller than or equal to each coding unit.

The image data of the part 1052 of the transformation units 1070 may be frequency transformed or inversely transformed in a data unit having a smaller size than the coding unit. In addition, the transformation units 1014, 1016, 1022, 1032, 1048, 1050, 1052, and 1054 are data units having different sizes or shapes when compared to corresponding prediction units and partitions among the prediction units 1060. That is, the video encoding apparatus 100 according to an embodiment and the video decoding apparatus 200 according to the embodiment may be an intra prediction / motion estimation / motion compensation operation and a frequency transform / inverse transform operation for the same coding unit. Each can be performed based on separate data units.

Accordingly, encoding is performed recursively for each coding unit having a hierarchical structure for each largest coding unit, and thus, an optimal coding unit is determined. Accordingly, coding units having a recursive tree structure may be configured. Partition information, partition type information, prediction mode information, and transformation unit size information about a unit may be included. Table 1 below shows an example that can be set in the video encoding apparatus 100 and the video decoding apparatus 200 according to an embodiment.

Table 1

Segmentation information 0 (coding for coding units of size 2Nx2N of current depth d)					Split information 1
Prediction mode	Partition type		Transformation unit size		Iterative coding for each coding unit of lower depth d + 1
Intra interskip (2Nx2N only)	Symmetric Partition Type	Asymmetric Partition Type	Conversion unit split information 0	Conversion unit split information 1
	2Nx2N2NxNNx2NNxN	2NxnU2NxnDnLx2NnRx2N	2Nx2N	NxN (symmetric partition type) N / 2xN / 2 (asymmetric partition type)

The output unit 130 of the video encoding apparatus 100 according to an embodiment outputs encoding information about coding units having a tree structure, and the encoding information extraction unit of the video decoding apparatus 200 according to an embodiment ( 220 may extract encoding information about coding units having a tree structure from the received bitstream.

The split information indicates whether the current coding unit is split into coding units of a lower depth. If the split information of the current depth d is 0, partition type information, prediction mode, and transform unit size information are defined for the coded depth because the depth in which the current coding unit is no longer divided into the lower coding units is a coded depth. Can be. If it is to be further split by the split information, encoding should be performed independently for each coding unit of the divided four lower depths.

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 the symmetric partition types 2Nx2N, 2NxN, Nx2N and NxN, in which the height or width of the prediction unit is divided by the symmetrical ratio, and the asymmetric partition types 2NxnU, 2NxnD, nLx2N, nRx2N, which are divided by the asymmetrical ratio. Can be. The asymmetric partition types 2NxnU and 2NxnD are divided into heights 1: 3 and 3: 1, respectively, and the asymmetric partition types nLx2N and nRx2N are divided into 1: 3 and 3: 1 widths, respectively.

The conversion unit size may be set to two kinds of sizes in the intra mode and two kinds of sizes in the inter mode. That is, if the transformation unit split information is 0, the size of the transformation unit is set to the size 2Nx2N of the current coding unit. If the transform unit split information is 1, a transform unit having a size obtained by dividing the current coding unit may be set. In addition, if the partition type for the current coding unit having a size of 2Nx2N is a symmetric partition type, the size of the transform unit may be set to NxN, and if the asymmetric partition type is N / 2xN / 2.

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

Therefore, if the encoding information held by each adjacent data unit is checked, it may be determined whether the adjacent data units are included in the coding unit having the same coding depth. In addition, since the coding unit of the corresponding coding depth may be identified by using the encoding information held by the data unit, the distribution of the coded depths within the maximum coding unit may be inferred.

Therefore, in this case, when the current coding unit is predicted with reference to the neighboring data unit, the encoding information of the data unit in the depth-specific coding unit adjacent to the current coding unit may be directly referred to and used.

In another embodiment, when the prediction coding is performed by referring to the neighboring coding unit, the data adjacent to the current coding unit in the coding unit according to depths is encoded by using the encoding information of the adjacent coding units according to depths. The neighboring coding unit may be referred to by searching.

FIG. 13 illustrates a relationship between a coding unit, a prediction unit, and a transformation unit, according to encoding mode information of Table 1. FIG.

The maximum coding unit 1300 includes coding units 1302, 1304, 1306, 1312, 1314, 1316, and 1318 of a coded depth. Since one coding unit 1318 is a coding unit of a coded depth, split information may be set to zero. The partition type information of the coding unit 1318 having a size of 2Nx2N is partition type 2Nx2N 1322, 2NxN 1324, Nx2N 1326, NxN 1328, 2NxnU 1332, 2NxnD 1334, nLx2N (1336). And nRx2N 1338.

When partition type information is set to one of symmetric partition types 2Nx2N (1322), 2NxN (1324), Nx2N (1326), and NxN (1328), the conversion unit of size 2Nx2N when the conversion unit partition information (TU size flag) is 0 1134 is set, and if the transform unit split information is 1, a transform unit 1344 of size NxN may 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 conversion unit partition information (TU size flag) is 0, a conversion unit of size 2Nx2N ( 1352 is set, and if the transform unit split information is 1, a transform unit 1354 of size N / 2 × N / 2 may be set.

Hereinafter, intra prediction performed by the intra predictor 410 of the image encoding apparatus 400 and the intra predictor 550 of the image decoding apparatus 500 of FIG. 5 according to an embodiment of the present invention. It demonstrates concretely. As described above, intra prediction may be performed in a prediction unit included in a coding unit or a partition unit obtained by dividing the prediction unit. In the following description, a block may refer to a prediction unit included in a coding unit obtained by dividing a maximum coding unit or a partition obtained by dividing a prediction unit.

14 is a block diagram illustrating a configuration of an intra prediction apparatus 1400 according to an embodiment of the present invention. The intra prediction apparatus 1400 of FIG. 14 may be applied to the intra prediction unit 410 of the image encoding apparatus 400 of FIG. 4 and the intra prediction unit 550 of the image decoding apparatus 500 of FIG. 5.

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 determiner 1420, and an intra prediction performing unit 1430.

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

The reference pixel determiner 1420 is configured to filter the current pixels among the filtered neighboring pixels of the restored neighboring pixels and the restored neighboring pixels 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. The neighboring pixels used for intra prediction of the block are determined.

According to one embodiment, a YCbCr (or YUV) color format composed of luminance and chrominance components is used. The reason for using a color format consisting of luminance and chrominance components is to use the fact that the human eye is more sensitive to luminance components than chrominance components. will be. As a color format of a video according to an embodiment, a 4: 4: 4 color format, a 4: 2: 2 color format, and a 4: 2: 0 color format may be used according to the resolution of the video of the luminance component and the video of the chrominance component. Can be. 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 determiner 1420 filters the reconstructed neighboring pixels and the reconstructed neighboring pixels of the luminance component block at least once based on the size of the luminance component block and the intra prediction mode to be applied to the block of the luminance component. The neighboring pixels to be used for intra prediction among the neighboring pixels are determined. As shown in FIG. 15 to be described below, it is assumed that 35 intra prediction modes are available for a block of luminance components. When the index of the currently applied intra prediction mode among the 35 intra prediction modes is called prediction_mode, the reference pixel determiner reconstructs the neighboring pixels reconstructed based on the size of the block of the luminance component and the intra prediction mode as shown in the following pseudo code. The neighboring pixels to be used for the intra prediction of the luminance component block among the neighboring pixels from which the filtered neighboring pixels are filtered may 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 = {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 to be described later. For example, when the intra prediction mode index is 0, it is a planar mode, when 1, DC mode, and when 10, Horizontal mode, 26 indicates a vertical mode. When the pseudo code is analyzed, 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) and the difference between the index of the index of the current intra prediction mode and the vertical mode (prediction_mode-vertical_mode) According to a result of obtaining a smaller value Diff of the absolute value of and comparing the Diff with a predetermined threshold Thres_val determined based on the size of the luminance component block, when the Diff is larger than the threshold, the filtered neighboring pixel is converted into the luminance component block. It is used as a reference pixel for intra prediction of, and when the Diff is less than or equal to the threshold, the original peripheral pixel is used as the reference pixel. The reference pixel determiner 1420 may determine to use only the original peripheral pixel as the reference pixel in the case of a specific intra prediction mode, for example, the DC mode.

Peripheral pixels used as reference pixels in the intra prediction of the luminance component block according to the size of the luminance component according to the above pseudo code and the type of the intra prediction mode may be determined based on Table 2 below. In Table 2, the reference index of the prediction mode using the original neighboring pixel is 0, and the reference index of the prediction mode using the first filtered neighboring pixel is 1. That is, in the case of the reference index having a value of 0, a circle surrounding pixel is used for the corresponding luminance component block, and in the case of a reference index having a value of 1, the case of using a filtered peripheral pixel for the corresponding luminance component block is shown. . For example, when performing intra prediction with a prediction mode index of 2 for a 32x32 luminance block in Table 2, since the reference index has a value of 1, intra prediction with a prediction mode index of 2 for a 32x32 luminance block is performed. In this case, the filtered neighboring pixel is used as the reference pixel instead of the original peripheral pixel.

TABLE 2

Prediction mode index	Block size				Prediction mode index	Block size
	4x4	8x8	16 x 16	32 x 32		4x4	8x8	16 x 16	32 x 32
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 or not to use the filtered peripheral pixels according to various block sizes and intra prediction modes may be set in other ways.

If the reference pixel determiner 1420 determines a peripheral pixel to be used for intra prediction of the luminance component block among the original surrounding pixels and the filtered surrounding pixels, the intra prediction performing unit 1430 performs intra prediction using the determined surrounding pixels. To generate a predicted value of the luminance component block.

In addition, the reference pixel determiner 1420 filters the reconstructed neighboring pixels and the reconstructed neighboring pixels of the chrominance component block based on the size of the chrominance component block and the intra prediction mode to be applied, on the block of the chrominance component. The neighboring pixels to be used for intra prediction among the filtered neighboring pixels may be determined. The reference pixel determiner 1420 may filter the original peripheral pixels and the filtered peripheral pixels of the chrominance component block based on whether the filtered neighboring pixel determined at the time of intra prediction of the block of the luminance component corresponding to the block of the chrominance component. A reference pixel used in intra prediction of the chrominance component block may be determined. However, although the luminance component and the chrominance component have a close correlation with each other, in the case of the chrominance component image, since the noise component may have more noise components than the luminance component image, it is appropriate to apply the filtering method of the filtered peripheral pixels of the luminance component to the chrominance component as it is. Not. Accordingly, the reference pixel determiner 1420 according to an exemplary embodiment independently of the luminance component, based on the size of the chrominance component block and the intra prediction mode to be applied to the block of the chrominance component, the reconstructed neighboring pixels of the chrominance component block And neighboring pixels to be used for intra prediction among the filtered neighboring pixels obtained by filtering the reconstructed neighboring pixels at least once. Since the chrominance component image is more likely to generate noise than the luminance component image, it is preferable that the number of cases where intra prediction is performed using the filtered neighboring pixels is larger than the luminance component. That is, if the original peripheral pixel is used in the luminance component block having the same size and to which the same intra prediction mode is applied, the filtered peripheral pixel may be set to be used for the intra prediction for the color difference component block.

 As shown in FIG. 15 to be described below, it is assumed that 36 intra prediction modes are available for a block of chrominance components. When the intra prediction mode index indicating the 36 intra prediction modes is called prediction_mode, the reference pixel determiner determines the reconstructed neighboring pixels and the reconstructed neighboring pixels based on the size of the block of the chrominance component and the intra prediction mode as shown in the following pseudo code. The neighboring pixels to be used for intra prediction of the color difference component block among the filtered neighboring pixels may 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}

}

When the pseudo code is analyzed, the threshold (Thres_val) has a smaller value than that of the luminance component. Therefore, in the case of the chrominance component, the filtered neighboring pixel is used as a reference pixel for intra prediction.

The peripheral pixels used as reference pixels in the intra prediction of the color difference component block according to the size of the color difference component block and the type of the intra prediction mode according to the above pseudo code may be determined based on Table 3 below. In Table 3, the reference index of the prediction mode using the original neighboring pixel is 0, and the reference index of the prediction mode using the first filtered neighboring pixel is 1. That is, in the case of the reference index having a value of 0, a circle surrounding pixel is used for the corresponding chrominance component block, and in the case of a reference index having a value of 1, the case of using a filtered peripheral pixel for the corresponding color difference component block is shown. .

TABLE 3

Prediction mode index	Block size				Prediction mode index	Block size
	4x4	8x8	16 x 16	32 x 32		4x4	8x8	16 x 16	32 x 32
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 the color difference component increases when the reference index is 1, that is, when intra prediction is performed using the filtered neighboring pixels.

Also, the reference pixel determiner 1420 may determine neighboring pixels filtered two or more times as reference pixels to be used in intra prediction based on the size of the color difference component block and the intra prediction mode. Such two or more filtered peripheral pixels may be set to apply only to a color difference component block of a predetermined size or more, for example, 16 × 16 or more.

In detail, the reference pixel determiner 1420 filters and reconstructs the neighboring pixels reconstructed and the reconstructed neighboring pixels based on the size of the block of the chrominance component and the intra prediction mode as shown in the following pseudo code. The neighboring pixels to be used for intra prediction of the color difference component block among the neighboring pixels obtained by filtering the extracted neighboring pixels twice may 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

2, // 8x8 block

1, // 16x16 block

0 // 32x32 block}

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

use twice filtered reference pixel

}

Analyzing the pseudo code, if it is determined to use the filtered neighboring pixel for a predetermined size, for example, 16x16 or more color difference component block, it may be set to use the filtered neighboring pixel twice as a reference pixel in intra prediction. have. Peripheral 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 above pseudo code and the type of the intra prediction mode may be determined based on Table 4 below. In Table 4, the reference index of the prediction mode using the original neighboring pixel is 0, the reference index of the prediction mode using the first filtered neighboring pixel is 1, and the reference index of the prediction mode using the second filtered neighboring pixel is 2. It is defined as. That is, in the case of a reference index having a value of 0, a circle surrounding pixel is used for the corresponding chrominance component block, and in the case of a reference index having a value of 1, the surrounding pixel filtered once for the corresponding chrominance component block is used. In the case of the reference index having a value of 2, the neighboring pixel filtered twice for the corresponding color difference component block is used.

Table 4

Prediction mode index	Block size				Prediction mode index	Block size
	4x4	8x8	16 x 16	32 x 32		4x4	8x8	16 x 16	32 x 32
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 above, when it is determined to use the filtered neighboring pixel for the color difference component block having a size of 16 × 16 or more, the filtered neighboring pixel twice is used as the reference pixel.

As described above, according to embodiments of the present invention, the use of the filtered neighboring pixels in the intra prediction of the chrominance component block occurs more than in the intra prediction of the luminance component block, thereby predicting the intra prediction of the chrominance component. The efficiency can be improved.

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

15 illustrates intra prediction modes according to an embodiment.

Referring to FIG. 15, according to an embodiment, a greater number of intra prediction modes may be used than an intra prediction mode used in conventional H.264 / AVC. According to an embodiment, a total of 35 intra prediction modes may be used for a block of luminance components. 15 illustrates a prediction mode index allocated according to an intra prediction mode. The intra prediction mode 0 is a planar mode, the intra prediction mode 1 is a DC mode, and the intra prediction modes 2 to 34 are intra prediction modes having directionalities as illustrated in FIG. 15. In addition to the 35 intra prediction modes, an Intra_FromLuma mode using the intra prediction mode of the luminance component may be added to the block of the chrominance component. The prediction mode index of the Intra_FromLuma mode is assigned a value of 36.

In planner mode, the linear interpolation of the upper right peripheral pixel of the current block and the left peripheral pixel of the same row as the current pixel of the current block, and the average value of the linear interpolation of the upper left peripheral pixel and the upper peripheral pixel of the same column as the current pixel Intra prediction mode for predicting each pixel of the current block by using. The DC mode is an intra prediction mode using an average value of neighboring pixels of the current block as a prediction value.

The 33 directional intra prediction modes 2 to 34 are intra prediction modes that generate prediction values by copying peripheral pixels determined by using the directional lines as shown in FIG. 15.

16 illustrates the prediction angle of the intra prediction mode having the directionality of FIG. 15 in detail. Each arrow in FIG. 16 represents a point matched according to the intra prediction mode having the directionality of FIG. 15.

When the line having the direction according to the intra prediction mode is exactly matched to the neighboring pixel with respect to the intra predicted pixel in the current block, the corresponding neighboring pixel may be used as the reference pixel. However, lines with directivity according to the intra prediction mode may pass between neighboring pixels. In this case, a predictive value is generated through linear interpolation according to the position of the pixel.

FIG. 17 is a diagram for describing a case of obtaining an intra prediction mode value through linear interpolation with respect to 30 intra prediction modes of FIG. 15, according to an embodiment.

Referring to FIG. 17, an x mark is a point at which a line having directionality according to the intra prediction mode 30 of FIG. 15 is matched based on the pixel P00 1730 in the current block. As such, when a line having a direction according to the intra prediction mode points between the neighboring pixels AR1 1710 and AR2 1720, the following equation; A prediction value P00 of the current pixel may be obtained using a weighted average value of the surrounding pixels AR1 1710 and AR2 1720 such as P00 = (19 * AR1 + 13 * AR2) >> 5. The weights 19 and 13, which are multiplied by the neighbor pixels AR1 1710 and AR2 1720, are mapped to the point x and the mapped point when a line having a direction according to the intra prediction mode is mapped to the neighbor pixels based on the current pixel P00. Indicating the distance between pixels, such weights may be tabulated and stored in advance.

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

Referring to FIG. 18, the filtering unit 1410 selects a predetermined number of upper peripheral pixels and left peripheral pixels according to the size of the current block 1800 that is intra predicted. If the size of the current block 1800 is nTbs * nTbs (nTbs is an integer), the filtering unit 1410 selects 2nTbs peripheral pixels as shown by reference numeral 1810. The filtering unit 1410 generates a filtered neighboring pixel by applying a predetermined filter to 2nTbs neighboring pixels. The number of upper and left peripheral pixels 1810 filtered by the filtering unit 1410 is not limited thereto and may be changed in consideration of the directionality of the intra prediction mode applied to the current block.

19 is a reference diagram for describing a filtering process of neighboring pixels according to an exemplary embodiment of the present invention, and FIG. 20 illustrates neighboring pixels to be filtered.

Referring to FIG. 19, when 2nTbs circle peripheral pixels adjacent to the upper and left sides of a current block of size nTbs * nTbs are ContextOrg [n] (n is an integer from 0 to 2nTbs-1), the filtering unit 1410 The circular peripheral pixels are filtered by calculating a weighted average value between the circular peripheral pixels to generate a first filtered peripheral pixel ContextFiltered1 [n]. For example, the filtering unit 1410 generates a first filtered peripheral pixel by applying a 3-tap filter to the circular peripheral pixels ContextOrg [n] as shown in Equation 1 below.

Equation 1

Referring to Equation 1, the filtering unit 1410 includes two neighboring pixels ContextOrg [n-1] and ContextOrg [n + 1] adjacent to the neighboring pixel ContextOrg [n] that is currently filtered among the surrounding pixels. Generate a first filtered peripheral pixel by calculating a weighted average of. For example, referring to FIG. 20, the filtered pixel value of the pixel value p (-1, -1) located at (-1, -1) on the upper left side of the current block is called pF (-1, -1). PF (-1, -1) uses peripheral pixel values p (-1,0) at position (-1,0) and peripheral pixel values p (0, -1) at position (0, -1). By the following equation; pF (-1, -1) = (p (-1,0) + 2 * p (-1, -1) + p (0, -1)) / 4 Among the surrounding pixels, the unfiltered original peripheral pixels p (-1, 2nTbs-1) and the upper right peripheral pixel p (2nTbs-1, -1) are used as the filtered values. Can be.

Similarly, the filtering unit 1410 may generate a second filtered surrounding pixel ContextFiltered2 [n] by recalculating a weighted average value between the first filtered surrounding pixels ContextFiltered1 [n]. For example, the filtering unit 1210 generates a second filtered peripheral pixel by applying a 3-tap filter to the first filtered peripheral pixels ContextFiltered1 [n] as shown in Equation 2 below.

Equation 2

Referring to Equation 2, the filtering unit 1410 may include the neighboring pixels ContextFiltered1 [n-1] and ContextFiltered1 [n + 1] adjacent to the neighboring pixels ContextFiltered1 [n] currently filtered among the first filtered neighboring pixels. Calculates a weighted average of) to produce a second filtered peripheral pixel. The filtering process for the surrounding 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 operation 2110, the filtering unit 1410 filters neighboring pixels of a current block of a color difference component to be encoded to obtain filtered neighboring pixels.

In operation 2120, the reference pixel determiner 1420 determines neighboring pixels to be used for intra prediction of the current block among the filtered neighboring pixels and the original neighboring pixels based on the size of the current block and the intra prediction mode to be performed. . As illustrated in Tables 2 to 4, the reference pixel determiner 1420 is based on the size of the chrominance component block and the intra prediction mode to be applied, independently of the process of determining the reference pixel during intra prediction of the luminance component block. The neighboring pixels used in the intra prediction of the color difference component block among the original neighboring pixels or at least one filtered neighboring pixels are determined.

In operation 2130, the intra prediction performing unit 1430 performs intra prediction on the color difference 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 a bitstream of a NAL unit and transmitted to the decoding side, and the decoding side is based on the size information and the intra prediction mode information of the chrominance component block. In the same manner as that of the encoding side, a reference pixel to be used for intra prediction of the color difference component block among the original neighbor pixels and the filtered neighbor pixels is determined.

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

Referring to FIG. 22, when the size information and the intra prediction mode information of the current block of the chrominance component are obtained from the bitstream in step 2210, the reference pixel determiner 1420 may determine the size and the intra prediction mode information in step 2220. The neighboring pixel used for intra prediction of the current block is determined among the restored neighboring pixels of the current block and the filtered neighboring pixels filtered from the restored neighboring pixels. As a result of the determination in step 2220, when the filtered neighboring pixel is used in the intra prediction of the current chrominance component block, the filtering unit 1410 may determine the size and intra prediction mode of the chrominance component block as illustrated in Tables 2 to 4. Based on the filtering of the surrounding pixels once or twice, the filtered neighboring pixels are output.

In operation 2230, the intra prediction execution unit 1430 generates an prediction value by performing intra prediction on the current block according to the intra prediction mode information by using the neighboring pixel determined by the reference pixel determination unit 1420.

The video encoding and decoding method according to the present invention can also be embodied as computer readable codes on a computer readable recording medium. The computer-readable recording medium includes all kinds of recording devices in which data that can be read by a computer system is stored. Examples of computer-readable recording media include ROM, RAM, CD-ROM, magnetic tape, floppy disks, optical data storage devices, and the like. The computer readable recording medium can also be distributed over network coupled computer systems so that the computer readable code is stored and executed in a distributed fashion.

So far I looked at the center of the preferred embodiment for the present invention. Those skilled in the art will understand that the present invention may be implemented in a modified form without departing from the essential characteristics of the present invention. Therefore, the disclosed embodiments should be considered in descriptive sense only and not for purposes of limitation. The scope of the present invention is shown in the claims rather than the foregoing description, and all differences within the scope will be construed as being included in the present invention.

Claims (15)

1. In the video decoding method,

   Obtaining intra prediction mode information and size information of a current block of a chrominance component from the bitstream;

   Determining a neighboring pixel used for intra prediction of the current block among the reconstructed neighboring pixels of the current block and the filtered neighboring pixels filtering the reconstructed neighboring pixel 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 by using the determined neighboring pixel.
2. The method of claim 1,

   The determining of the peripheral pixel

   Intra filtering the neighboring pixels filtered for the current block of the chrominance component according to a determination method independent of a determination method for determining whether to use the filtered neighboring pixels for intra prediction during intra prediction of a block of luminance components constituting the video. A video decoding method comprising determining whether to use for prediction.
3. The method of claim 1,

   The determining of the peripheral pixel

   Based on the size information and the intra prediction mode information, among the reconstructed neighboring pixels of the current block, the neighboring pixels once filtered out of the restored neighboring pixels, and the neighboring pixels filtered twice the restored neighboring pixels; And determine one filtered peripheral pixel group.
4. The method of claim 1,

   The determining of the peripheral pixel

   Determining a smaller value of the difference between the intra prediction mode index of the current block and the horizontal intra prediction mode index and the difference between the intra prediction mode index of the current block and the vertical intra prediction mode index;

   By comparing the determined difference value with a predetermined threshold determined based on the size information, an intra prediction of the current block among the filtered neighboring pixels filtering the restored neighboring pixels of the current block and the restored neighboring pixels. Determining a peripheral pixel to be used.
5. The method of claim 1, wherein the current block is

   A prediction unit included in a coding unit obtained by dividing a current picture or a partition obtained by dividing the prediction unit based on a maximum coding unit that is a coding unit having a maximum size and a depth that is hierarchical split information of the maximum coding unit. Video decoding method.
6. In the video decoding apparatus,

   A peripheral pixel filtering unit for filtering the previously reconstructed peripheral pixels of the current block of the chrominance component to generate filtered peripheral pixels;

   Obtaining size information and intra prediction mode information of the current block of the chrominance component from the bitstream, and 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. A reference pixel determiner configured to determine a neighboring pixel used for intra prediction of the current block among the filtered neighboring pixels; And

   And an intra prediction performing unit configured to perform intra prediction on the current block according to the intra prediction mode information by using the determined neighboring pixel.
7. The method of claim 6,

   The reference pixel determiner

   Intra filtering the neighboring pixels filtered with respect to the current block of the chrominance component according to a determination method independent of a determination method for determining whether to use the filtered neighboring pixels for intra prediction in the intra prediction of the block of the luminance component constituting the video. And a video decoding apparatus for determining whether to use for prediction.
8. The method of claim 6,

   The reference pixel determiner

   Based on the size information and the intra prediction mode information, among the reconstructed neighboring pixels of the current block, the neighboring pixels once filtered out of the restored neighboring pixels, and the neighboring pixels filtered twice the restored neighboring pixels; And determine one filtered peripheral pixel group.
9. The method of claim 6,

   The reference pixel determiner

   The smaller difference value between the intra prediction mode index of the current block and the horizontal intra prediction mode index and the difference between the intra prediction mode index and the vertical intra prediction mode index of the current block is determined, and the determined difference is determined. A periphery used for intra prediction of the current block among the reconstructed neighboring pixels of the current block and the filtered neighboring pixels filtering the reconstructed neighboring pixels by comparing a predetermined threshold determined based on the value and the size information. And a pixel is determined.
10. The method of claim 6, wherein the current block is

    A prediction unit included in a coding unit obtained by dividing a current picture or a partition obtained by dividing the prediction unit based on a maximum coding unit that is a coding unit having a maximum size and a depth that is hierarchical split information of the maximum coding unit. Video decoding device.
11. In the video encoding method,

    Filtering peripheral pixels of the current block of the encoded color difference component to obtain filtered peripheral pixels;

    Determining neighboring pixels to be used for intra prediction of the current block among the filtered neighboring pixels and the original neighboring pixels based on the size of the current block and the intra prediction mode to be performed; And

    And performing intra prediction on the current block by using the determined neighboring pixels.
12. The method of claim 11,

    The determining of the peripheral pixel

    Intra filtering the neighboring pixels filtered with respect to the current block of the chrominance component according to a determination method independent of a determination method for determining whether to use the filtered neighboring pixels for intra prediction in the intra prediction of the block of the luminance component constituting the video. A video encoding method characterized by determining whether to use for prediction.
13. The method of claim 11,

    The determining of the peripheral pixel

    Based on the size information and the intra prediction mode information, among the reconstructed neighboring pixels of the current block, the neighboring pixels once filtered out of the restored neighboring pixels, and the neighboring pixels filtered twice the restored neighboring pixels; And determine one filtered peripheral pixel group.
14. The method of claim 11,

    The determining of the peripheral pixel

    Determining a smaller value of the difference between the intra prediction mode index of the current block and the horizontal intra prediction mode index and the difference between the intra prediction mode index of the current block and the vertical intra prediction mode index;

    By comparing the determined difference value with a predetermined threshold determined based on the size information, an intra prediction of the current block among the filtered neighboring pixels filtering the restored neighboring pixels of the current block and the restored neighboring pixels. Determining a peripheral pixel to be used.
15. The method of claim 11, wherein the current block is

    A prediction unit included in a coding unit obtained by dividing a current picture or a partition obtained by dividing the prediction unit based on a maximum coding unit that is a coding unit having a maximum size and a depth that is hierarchical split information of the maximum coding unit. Video coding method.

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