KR20150092063A - Method and apparatus for decoding video - Google Patents

Abstract

Disclosed are a method and an apparatus for encoding a video, and decoding method and apparatus thereof. The method for encoding a video comprises the steps of: generating a first predictive encoding unit for encoded current encoding unit; generating a second predictive encoding unit by changing pixel value of each pixel of the first predictive encoding unit by selectively using each pixel forming the first predictive encoding unit and at least one surrounding pixel upon whether the current encoding unit includes an area out of a boundary of the current picture or not.

Description

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

The present invention relates to a method and an apparatus for encoding an image that improve the compression efficiency of an image through post-processing according to the position of predicted image data, and a decoding method and apparatus therefor.

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

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

SUMMARY OF THE INVENTION The present invention is directed to a method and an apparatus for encoding an image for improving compression efficiency of an image by generating a new prediction block by modifying pixel values of pixels in a prediction block through post- An apparatus, a decoding method and an apparatus therefor.

According to an embodiment of the present invention, there is provided an image decoding method, comprising: obtaining a first predicted value of the current block using neighboring pixels of a current block; And for a boundary pixel located on a predetermined boundary among pixels located in the current block, using the obtained first predicted value and at least one surrounding pixel located in the same row or the same column as the boundary pixel, And obtaining a predicted value.

An apparatus for decoding an image according to an embodiment of the present invention includes an entropy decoder for obtaining prediction mode information of a current block from a bitstream; And using the obtained first predictive value and at least one neighboring pixel located in the same row or the same column as the boundary pixel for a boundary pixel located on a predetermined boundary among the pixels positioned in the current block according to the prediction mode And a predictor for obtaining a second predicted value of the boundary pixel.

1 is a block diagram of an image encoding apparatus according to an embodiment of the present invention.
2 is a block diagram of an image decoding apparatus according to an embodiment of the present invention.
FIG. 3 illustrates a hierarchical encoding unit according to an embodiment of the present invention.
4 is a block diagram of an image encoding unit based on an encoding unit according to an embodiment of the present invention.
5 is a block diagram of an image decoding unit based on an encoding unit according to an embodiment of the present invention.
FIG. 6 illustrates a depth-based coding unit and a prediction unit according to an embodiment of the present invention.
FIG. 7 shows a relationship between an encoding unit and a conversion unit according to an embodiment of the present invention.
FIG. 8 illustrates depth-specific encoding information, in accordance with an embodiment of the present invention.
FIG. 9 shows a depth encoding unit according to an embodiment of the present invention.
FIGS. 10A and 10B show a relationship between an encoding unit, a prediction unit, and a frequency conversion unit according to an embodiment of the present invention.
FIG. 11 shows encoding information for each encoding unit according to an embodiment of the present invention.
12 is a block diagram showing a configuration of an intra prediction apparatus 1200 according to an embodiment of the present invention.
13 shows the number of intra prediction modes according to the size of an encoding unit according to an embodiment of the present invention.
14A to 14C are views for explaining an example of an intra prediction mode applied to a coding unit of a predetermined size according to an embodiment of the present invention.
15 is a view for explaining another example of an intra prediction mode applied to a coding unit of a predetermined size according to an embodiment of the present invention.
16 is a reference diagram for explaining intra prediction modes having various directions according to an embodiment of the present invention.
17 is a reference diagram for explaining a bilinear mode according to an embodiment of the present invention.
18 is a reference diagram for explaining a post-processing operation of a first predictive-encoding unit according to an embodiment of the present invention.
19 is a reference diagram for explaining the operation of the post-processing unit 1220 according to an embodiment of the present invention.
20 is a reference diagram for explaining peripheral pixels used in the post-processing unit 1220 according to an embodiment of the present invention.
FIG. 21 is a flowchart illustrating an image encoding method according to an embodiment of the present invention.
22 is a reference diagram for explaining an indexing process for post-processing of an encoding unit according to an embodiment of the present invention.
23 is a reference diagram for explaining an indexing process for post-processing of an encoding unit according to another embodiment of the present invention.
24 is a flowchart illustrating a video decoding method according to an embodiment of the present invention.

Hereinafter, an image encoding apparatus, an image decoding apparatus, an image encoding method, and an image decoding method according to preferred embodiments of the present invention will be described with reference to the accompanying drawings.

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

1, an image encoding apparatus 100 according to an exemplary embodiment of the present invention includes a maximum encoding unit division unit 110, an encoding depth determination unit 120, an image data encoding unit 130, (140).

The maximum coding unit division unit 110 divides the current picture or the current slice based on the maximum coding unit which is the coding unit of the maximum size. The current picture or current slice is divided into at least one maximum encoding unit. The divided image data may be output to the coding depth determination unit 120 for each of at least one maximum coding unit.

According to an embodiment of the present invention, an encoding unit can be expressed using a maximum encoding unit and a depth. The maximum coding unit indicates the largest coding unit among the coding units of the current picture, and the depth indicates the size of the sub-coding unit in which the coding unit is hierarchically reduced. As the depth increases, the encoding unit can be reduced from the maximum encoding unit to the minimum encoding unit, the depth of the maximum encoding unit can be defined as the minimum depth, and the depth of the minimum encoding unit can be defined as the maximum depth. As the depth of the maximum encoding unit increases, the size of the depth-dependent encoding unit decreases. Therefore, the sub-encoding unit of k depth may include a plurality of sub-encoding units having a depth of k + 1 or more.

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

The maximum depth for limiting the total number of times the height and width of the current encoding unit are hierarchically reduced from the maximum encoding unit to the highest encoding unit and the maximum size of the encoding unit may be preset. The maximum encoding unit and the maximum depth may be set in units of pictures or slices. That is, each picture or slice may have a different maximum coding unit and maximum depth, and the minimum coding unit size included in the maximum image coding unit may be variably set according to the maximum depth. By setting the maximum coding unit and the maximum depth for each picture or slice in this manner, it is possible to improve the compression ratio by coding the image of the flat area using a larger maximum coding unit, and the image with a large complexity can be encoded The compression efficiency of the image can be improved by using the unit.

The encoding depth determination unit 120 determines a maximum depth that is different for each maximum encoding unit. The maximum depth may be determined based on the Rate-Distortion Cost calculation. The determined maximum depth is output to the encoding information encoding unit 140, and the image data for each maximum encoding unit is output to the image data encoding unit 130.

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

As the depth of the maximum coding unit increases, the coding unit is hierarchically divided and reduced, and the number of coding units increases. In addition, even if encoding units of the same depth included in one maximum encoding unit, the encoding error of each data is measured and it is determined whether or not the encoding units are reduced to a higher depth. Therefore, even if the data included in one maximum coding unit has a different coding error according to the position, the coding depth can be determined depending on the position. In other words, the maximum encoding unit may be divided into sub-encoding units of different sizes according to different depths. One or more encoding depths may be set for one maximum encoding unit, and data of the maximum encoding unit may be set to one or more encoding depths As shown in FIG.

Further, the sub-encoding units of different sizes included in the maximum encoding unit can be predicted or frequency-converted based on the processing units of different sizes. In other words, the image encoding apparatus 100 can perform a plurality of processing steps for image encoding based on various sizes and processing units of various types. In order to encode video data, processing steps such as prediction, frequency conversion, and entropy encoding are performed. Processing units of the same size may be used in all stages, and processing units of different sizes may be used in each step.

For example, in order to predict a coding unit, the image coding apparatus 100 may select a coding unit and a different processing unit. For example, when the size of the encoding unit is 2Nx2N (where N is a positive integer), the processing unit for prediction may be 2Nx2N, 2NxN, Nx2N, NxN, and the like. In other words, motion prediction may be performed based on a processing unit of a type that halves at least one of a height or a width of an encoding unit. Hereinafter, a data unit serving as a basis of prediction is referred to as a 'prediction unit'.

The prediction mode may be at least one of an intra mode, an inter mode, and a skip mode, and the specific prediction mode may be performed only for a prediction unit of a specific size or type. For example, the intra mode can be performed only for a 2Nx2N, NxN sized prediction unit, which is a square. In addition, the skip mode can be performed only for a prediction unit of 2Nx2N size. If there are a plurality of prediction units in an encoding unit, a prediction mode having the smallest coding error can be selected by performing prediction for each prediction unit.

Also, the image encoding apparatus 100 can frequency-convert image data based on a processing unit having a different size from the encoding unit. The frequency conversion may be performed based on a data unit having a size smaller than or equal to the encoding unit for frequency conversion of the encoding unit. Hereinafter, a processing unit serving as a basis of frequency conversion is referred to as a 'conversion unit'.

The coding depth determiner 120 measures the coding error of each depth coding unit using a Lagrangian Multiplier based Rate-Distortion Optimization technique and calculates the maximum coding unit having the optimal coding error Can be determined. In other words, the coding depth determiner 120 can determine which type of the maximum coding unit is divided into a plurality of sub-coding units, wherein the plurality of sub-coding units have different sizes depending on the depth.

The image data encoding unit 130 encodes the image data of the maximum encoding unit based on at least one encoding depth determined by the encoding depth determination unit 120 and outputs the bit stream. Since the encoding depth determination unit 120 has already performed the encoding process for measuring the minimum encoding error, the encoded data stream may be output using the encoding process.

The encoding information encoding unit 140 encodes information on the depth encoding mode for each maximum encoding unit based on at least one encoding depth determined by the encoding depth determining unit 120 and outputs a bit stream. The information on the depth-dependent coding mode may include coding depth information, division type information of a prediction unit of a coding unit of coding depth, prediction mode information per prediction unit, size information of a conversion unit, and the like.

The encoding depth information may be defined using depth reduction information indicating whether or not encoding is performed in a high-depth encoding unit without encoding at the current depth. If the current depth of the current encoding unit is the encoding depth, the current encoding unit is encoded in the current depth encoding unit, so that the reduction information of the current depth can be defined not to be further reduced to the higher depth. Conversely, if the current depth of the current encoding unit is not the encoding depth, encoding using the higher-depth encoding unit should be attempted, so that the current depth reduction information can be defined to be reduced to higher-depth encoding units.

If the current depth is not the depth of the encoding, encoding is performed for the lower-depth encoding unit. Since at least one coding unit of higher depth is present in the coding unit of the current depth, the coding is repeatedly performed for each coding unit of the higher depth so that recursive coding can be performed for each coding unit of the same depth.

At least one coding depth is determined in one maximum coding unit and at least one coding mode information is determined for each coding depth so that information on at least one coding mode can be determined for one maximum coding unit. In addition, since the data of the maximum encoding unit is hierarchically divided according to the depth and the depth of encoding may be different for each position, information on the encoding depth and the encoding mode can be set for the data.

Therefore, the encoding information encoding unit 140 according to the embodiment can set the encoding information for each minimum encoding unit included in the maximum encoding unit. That is, the coding unit of the coding depth includes at least one minimum coding unit that holds the same coding information. By using this, if the neighboring minimum encoding units have the same depth encoding information, it can be the minimum encoding unit included in the same maximum encoding unit.

According to the simplest embodiment of the image encoding apparatus 100, the depth-of-coded unit is a unit of a size which is halved in height and width of a single-layer low-depth encoding unit. That is, if the size of the encoding unit of the current depth (k) is 2Nx2N, the size of the encoding unit of the higher depth (k + 1) is NxN. Therefore, the current coding unit of 2Nx2N size can include up to 4 upper depth coding units of NxN size.

Therefore, the image decoding apparatus 100 according to an exemplary embodiment can determine an optimum shape division type for each maximum encoding unit based on the size and the maximum depth of the maximum encoding unit determined in consideration of the characteristics of the current picture. In addition, since each encoding unit can be encoded by various prediction modes, frequency conversion methods, and the like, an optimal encoding mode can be determined in consideration of image characteristics of encoding units of various image sizes.

If an image having a very high image resolution or a very large data amount is encoded in units of a conventional 16x16 macroblock, the number of macroblocks per picture becomes excessively large. This increases the amount of compression information generated for each macroblock, so that the burden of transmission of compressed information increases and the data compression efficiency tends to decrease. Therefore, the image encoding apparatus according to the embodiment of the present invention can increase the maximum size of the encoding unit in consideration of the image size, and adjust the encoding unit in consideration of the image characteristic, so that the image compression efficiency can be increased .

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

2, an image decoding apparatus 200 according to an exemplary embodiment of the present invention includes an image data obtaining unit 210, an encoding information extracting unit 220, and an image data decoding unit 230.

The image-related data acquisition unit 210 parses the bit string received by the image decoding apparatus 200, acquires image data for each maximum encoding unit, and outputs the image data to the image data decoding unit 230. The image-related data obtaining unit 210 may extract information on the maximum encoding unit of the current picture or slice from the header of the current picture or slice. The image decoding apparatus 200 according to an embodiment of the present invention decodes image data in units of a maximum encoding unit.

The encoding information extracting unit 220 parses the bit stream received by the video decoding apparatus 200 and extracts information on the encoding depth and the encoding mode for each maximum encoding unit from the header of the current picture. The information on the extracted coding depth and coding mode is output to the image data decoding unit 230.

Information on the coding depth and the coding mode per coding unit may be set for one or more coding depth information, and the information on the coding mode according to the coding depth includes information on division type information, prediction mode information, Size information of the conversion unit, and the like. In addition, reduction information for each depth may be extracted as the encoding depth information.

The information on the division type of the maximum encoding unit may include information on sub-encoding units of different sizes according to the depth included in the maximum encoding unit, the information on the encoding mode may include information on a prediction unit for each sub- Information on the prediction mode, information on the conversion unit, and the like.

The image data decoding unit 230 decodes the image data of each maximum encoding unit based on the information extracted by the encoding information extracting unit to restore the current picture. The image data decoding unit 230 can decode the sub-encoding unit included in the maximum encoding unit based on the information on the division type of the maximum encoding unit. The decoding process may include a motion prediction process including intra prediction and motion compensation, and an inverse frequency conversion process.

The image data decoding unit 230 decodes the image data of each maximum encoding unit based on the information on the encoding depth and the encoding mode for each maximum encoding unit to reconstruct the current picture. The image data decoding unit 230 can decode the image data for each coding unit of at least one coding depth based on the coding depth information for each coding unit. The decoding process may include a prediction process including intra prediction and motion compensation and an inverse process.

The image data decoding unit 230 performs intra prediction or motion prediction in each prediction unit and prediction mode for each coding unit on the basis of the division type information and the prediction mode information of the prediction unit of the coding unit for each coding depth, Compensation can be performed. In addition, the image data decoding unit 230 may perform inverse conversion on each conversion unit for each encoding unit, based on the size information of the conversion unit of the encoding unit by encoding depth, for inverse conversion for each maximum encoding unit.

The image data decoding unit 230 can determine the coding depth of the current maximum encoding unit using the depth-dependent reduction information. If the reduced information indicates that the current depth is to be decoded, the current depth is the depth of the encoding. Accordingly, the image data decoding unit 230 can decode the current depth encoding unit for the current image data of the maximum encoding unit using the division type, the prediction mode, and the conversion unit size information of the prediction unit. That is, it is possible to observe the coding information set for the minimum coding unit, and collect the minimum coding units holding the coding information including the same reduction information, and decode them into one data unit.

The image decoding apparatus 200 according to an exemplary embodiment recursively performs encoding for each maximum encoding unit in the encoding process to obtain information on the encoding unit that has generated the minimum encoding error and can use it for decoding the current picture have. That is, it is possible to decode video data in the optimal encoding unit for each maximum encoding unit. Accordingly, even if an image with a high resolution or an excessively large amount of data is used, the information on the optimal encoding mode transmitted from the encoding end is used, and the image data is efficiently encoded according to the encoding unit size and encoding mode, Can be decoded and restored.

FIG. 3 illustrates a hierarchical encoding unit according to an embodiment of the present invention.

Referring to FIG. 3, the hierarchical coding unit according to the present invention may include 32x32, 16x16, 8x8, and 4x4 from a coding unit having a width x height of 64x64. In addition to the square-shaped encoding units, there may be encoding units whose width x height is 64x32, 32x64, 32x16, 16x32, 16x8, 8x16, 8x4, 4x8.

3, the resolution is set to 1920 x 1080, the size of the maximum encoding unit is set to 64, and the maximum depth is set to 2 for the video data 310. For the video data 320, the resolution is set to 1920 x 1080, the maximum size of the encoding unit is set to 64, and the maximum depth is set to 4. [ For the video data 330, the resolution is set to 352 x 288, the maximum size of the encoding unit is set to 16, and the maximum depth is set to 2.

It is desirable that the maximum size of the encoding size is relatively large in order to accurately reflect not only the compression ratio but also the image characteristic when the resolution is high or the data amount is large. Therefore, the maximum size of the video data 310 and 320 having the higher resolution than the video data 330 can be selected to be 64. FIG.

The maximum depth indicates the total number of layers in the hierarchical encoding unit. Accordingly, since the maximum depth of the video data 310 is 2, the encoding unit 315 of the video data 310 is encoded in units of 32, 16, Units. On the other hand, since the maximum depth of the video data 330 is 2, the encoding unit 335 of the video data 330 has the depth of two layers increased from the encoding units having the major axis size of 16, Units.

Since the maximum depth of the video data 320 is 4, the encoding unit 325 of the video data 320 has a depth of four layers with a major axis size of 32, 16, 8, 4 Encoding unit. As the depth increases, the image is encoded based on a smaller sub-encoding unit, which makes it suitable for encoding an image including a more detailed scene.

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

4, the intra-prediction unit 410 performs intra-prediction on a prediction unit of an intra mode in the current frame 405, and the motion estimation unit 420 and the motion compensation unit 425 perform intra- Inter prediction and motion compensation are performed using the current frame 405 and the reference frame 495 with respect to the unit.

The residual values are generated based on the prediction unit output from the intra prediction unit 410, the motion estimation unit 420 and the motion compensation unit 425, and the generated residual values are input to the frequency conversion unit 430 and the quantization unit 420. [ (440) and output as quantized transform coefficients. In particular, as described later with reference to FIG. 12, the intra-prediction unit 410 according to an exemplary embodiment of the present invention predicts each pixel as a neighboring pixel according to whether an intra- And performs post-processing on the encoding units not belonging to the picture boundary. Residual values, which are difference values between the post-processed encoding unit and the original encoding unit, may be outputted as the transform coefficients quantized through the frequency transforming unit 430 and the quantizing unit 440.

The quantized transform coefficients are restored to a residual value through the inverse quantization unit 460 and the frequency inverse transform unit 470. The restored residual values are passed through the deblocking unit 480 and the loop filtering unit 490, And output to the reference frame 495. [ The quantized transform coefficient may be output to the bitstream 455 via the entropy encoding unit 450.

In order to perform encoding according to the image encoding method according to an embodiment of the present invention, an intra prediction unit 410, a motion estimation unit 420, a motion compensation unit 425, The inverse quantization unit 460, the inverse quantization unit 470, the deblocking unit 480 and the loop filtering unit 490 of the quantization unit 430, the quantization unit 440, the entropy coding unit 450, the inverse quantization unit 460, , Sub-encoding units according to depth, prediction units, and conversion units. In particular, the intra prediction unit 410, the motion estimation unit 420, and the motion compensation unit 425 determine the prediction unit and the prediction mode in the coding unit in consideration of the maximum size and depth of the coding unit, and the frequency conversion unit 430 ) Should consider the size of the conversion unit considering the maximum size and depth of the encoding unit.

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

Referring to FIG. 5, the bitstream 505 is parsed by the parser 510, and the encoded image data to be decoded and the encoding information necessary for decoding are parsed. The encoded image data is output as inverse-quantized data through the entropy decoding unit 520 and the inverse quantization unit 530, and is restored to the residual values through the frequency inverse transform unit 540. [ The residual values are added to the intraprediction result of the intraprediction unit 550 or the motion compensation result of the motion compensation unit 560, and restored for each encoding unit. In particular, the intra-prediction unit 550 according to the present invention selectively performs post-processing on a predictive encoding unit generated as an intra-prediction result, depending on whether the current decoding unit includes an area out of a boundary of a picture. The reconstructed coding unit is used for predicting the next coding unit or the next picture through the deblocking unit 570 and the loop filtering unit 580.

A parsing unit 510, an entropy decoding unit 520, an inverse quantization unit 530, an inverse frequency transforming unit (hereinafter referred to as an inverse quantization unit) 530, The intra prediction unit 550, the motion compensation unit 560, the deblocking unit 570 and the loop filtering unit 580 are all based on the maximum encoding unit, the depth-dependent sub-encoding unit, the prediction unit, And processes the image decoding processes. In particular, the intra prediction unit 550 and the motion compensation unit 560 determine a prediction unit and a prediction mode in an encoding unit in consideration of the maximum size and depth of an encoding unit, and the frequency inverse transform unit 540 transforms the maximum size And the depth of the conversion unit.

FIG. 6 illustrates a depth-based coding unit and a prediction unit according to an embodiment of the present invention.

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

The hierarchical structure 600 of the encoding unit according to an embodiment of the present invention shows a case where the maximum height and width of the encoding unit is 64 and the maximum depth is 4. Since the depth increases along the vertical axis of the hierarchical structure 600 of the coding unit according to the embodiment, the height and width of the coding unit for each depth are reduced. In addition, along the horizontal axis of the hierarchical structure 600 of the coding unit, a prediction unit which is a partial data unit which is a prediction base of each coding unit of depth is shown.

The maximum coding unit 610 is the largest coding unit among the hierarchical structures 600 of the coding units and has a depth of 0, and the size of the coding units, i.e., the height and the width, is 64x64. The depth of the image is increased along the vertical axis, and a depth 1 encoding unit 620 having a size of 32x32, a depth 2 encoding unit 630 having a size 16x16, a depth encoding unit 640 having a depth 8x8, a depth 4x4 having a size 4x4 There is an encoding unit 650. An encoding unit 650 of depth 4 of size 4x4 is the minimum encoding unit.

Referring also to FIG. 6, partial data units are shown along the horizontal axis for each depth, as a prediction unit of an encoding unit. That is, the prediction unit of the maximum encoding unit 610 having a depth 0 size of 64x64 is a partial data unit 610 of size 64x64, partial data units 612 of size 64x32 included in the encoding unit 610 of size 64x64, Partial data units 614 of size 32x64, and partial data units 616 of size 32x32.

The prediction unit of the 32x32 coding unit 620 having the depth 1 is the partial data unit 620 of the size 32x32 included in the coding unit 620 of the size 32x32, the partial data units 622 of the size 32x16, Partial data units 624 of size 16x16, and partial data units 626 of size 16x16.

The prediction unit of the 16x16 coding unit 630 of depth 2 is a partial data unit 630 of size 16x16, partial data units 632 of size 16x8, a size of 8x16 16x16 included in the coding unit 630 of size 16x16, Partial data units 634 of size 8x8, and partial data units 636 of size 8x8.

The prediction unit of the encoding unit 640 having the depth 3 of 8x8 is a partial data unit 640 of the size 8x8, partial data units 642 of the size 8x4, a size 4x8 of the size 8x8 included in the encoding unit 640 of the size 8x8, Partial data units 644 of size 4x4, and partial data units 646 of size 4x4.

Finally, a coding unit 650 of size 4x4 is a minimum coding unit and a coding unit of the highest depth, and the prediction unit is a data unit 650 of size 4x4.

In order to determine the depth of encoding of the maximum encoding unit 610, the encoding depth determining unit 120 of the image encoding apparatus according to an exemplary embodiment may perform encoding for each depth unit included in the maximum encoding unit 610 Should be performed.

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

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

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

The image encoding apparatus 100 and the image decoding apparatus 200 according to an embodiment of the present invention divide and encode or decode an image with a coding unit smaller than or equal to the maximum encoding unit for each maximum encoding unit. The size of the conversion unit for frequency conversion during encoding can be selected based on data units that are not larger than the respective encoding units. For example, when the current encoding unit 710 is 64x64, the frequency conversion can be performed using the 32x32 conversion unit 720. [ In addition, the data of the encoding unit 710 of 64x64 size is encoded by performing the frequency conversion with the conversion units of 32x32, 16x16, 8x8, and 4x4 size of 64x64 or smaller, respectively, and then the conversion unit having the smallest error with the original Can be selected.

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

The encoding information encoding unit of the image encoding apparatus 100 according to an exemplary embodiment of the present invention includes information on the encoding mode and information on the division type 800 and information on the prediction mode 810 ), And information 820 on the conversion unit size may be encoded and transmitted.

The division type information 800 indicates information on a type in which the current coding unit is divided as a prediction unit for motion prediction of the current coding unit. For example, the current encoding unit CU_0 of depth 0 and size 2Nx2N includes a prediction unit 802 of size 2Nx2N, a prediction unit 804 of size 2NxN, a prediction unit 806 of size Nx2N, a prediction unit 808 of size NxN ) And can be used as a prediction unit. In this case, information 800 regarding the division type of the current encoding unit includes a prediction unit 802 of size 2Nx2N, a prediction unit 804 of size 2NxN, a prediction unit 806 of size Nx2N, and a prediction unit 808 of size NxN. Lt; / RTI >

The prediction mode information 810 indicates a motion prediction mode of each prediction unit. The prediction unit indicated by the information 800 regarding the division type is predicted to be one of the intra mode 812, the inter mode 814 and the skip mode 816 through the prediction mode information 810 Can be set.

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

The encoding information extracting unit of the image decoding apparatus 200 according to an embodiment of the present invention extracts information on the division type 800, information on the prediction mode 810, Information 820 can be extracted and used for decoding.

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

Reduced information may be used to indicate whether the depth is increased. The reduction information indicates whether or not the current-depth encoding unit is reduced to a higher-depth encoding unit.

A prediction unit 910 for motion prediction of a coding unit of depth 0 and 2N_0x2N_0 size includes a division type 912 of 2N_0x2N_0 size, a division type 914 of 2N_0xN_0 size, a division type 916 of N_0x2N_0 size, a division of N_0xN_0 size Type < / RTI >

For each segmentation type, it is necessary to repeatedly perform motion prediction through a prediction unit of 2N_0xN_0 size, two prediction units of 2N_0xN_0 size, two prediction units of N_0x2N_0 size, and prediction units of four N_0xN_0 sizes. For the prediction unit of size 2N_0xN_0 and size N_0xN_0, motion prediction can be performed in intra mode and inter mode, and motion prediction can be performed only in inter mode as a prediction unit of size N_0x2N_0 and size N_0xN_0. The skip mode can be performed only for the prediction unit of size 2N_0xN_0.

If the coding error by the division type 918 of the size N_0xN_0 is the smallest, the depth 0 is increased to 1 (920), and the coding units 922, 924, 926 and 928 of the division type of the depth 2 and the size N_0xN_0 The minimum coding error can be repeatedly searched for.

Since encoding is repeatedly performed on the encoding units 922, 924, 926, and 928 of the same depth, encoding of only one of the encoding units of depth 1, for example, will be described. A prediction unit 930 for motion prediction of a coding unit of depth 1 and a size 2N_1x2N_1 (= N_0xN_0) includes a division type 932 of size 2N_1x2N_1, a division type 934 of size 2N_1xN_1, a division type 936 of size N_1x2N_1, , And a division type 938 of size N_1xN_1. For each segmentation type, it is necessary to repeatedly perform motion prediction through a prediction unit of a size 2N_1x2N_1, a prediction unit of two sizes 2N_1xN_1, a prediction unit of two sizes N_1x2N_1, and a prediction unit of four sizes N_1xN_1.

If the coding error by the division type 938 of the size N_1xN_1 is the smallest, the coding units 942, 944, 946 and 948 of the depth 2 and the size N_2xN_2 are increased while the depth 1 is increased to the depth 2 (940) The minimum coding error can be repeatedly searched for.

If the maximum depth is d, the depth reduction information can be set until the depth d-1. That is, the prediction unit 950 for motion prediction of the coding unit of the depth d-1 and the size 2N_ (d-1) x2N_ (d-1) A division type 954 of size N_ (d-1) xN_ (d-1), a division type 956 of size N_ 1) xN_ (d-1).

(D-1) x2N_ (d-1), a prediction unit of two sizes 2N_ (d-1) ) x2N_ (d-1), and four sizes N_ (d-1) xN_ (d-1). Since the maximum depth is d, the encoding unit 952 of depth d-1 no longer undergoes the reduction process.

The image encoding apparatus 100 according to an exemplary embodiment of the present invention compares depth-based encoding errors to determine depths for encoding units 912 and selects the depths at which the smallest encoding error occurs. For example, a coding error for a coding unit of depth 0 is determined by performing motion prediction for each of the division types 912, 914, 916, and 918, and a prediction unit in which the smallest coding error occurs is determined. Similarly, a prediction unit having the smallest coding error can be searched for every depth 0, 1, ..., d-1. At the depth d, the coding error can be determined through motion prediction based on the prediction unit 960, which is a coding unit of size 2N_dx2N_d. In this way, the minimum coding errors of the depths 0, 1, ..., d-1, and d are compared with each other, and the depth with the smallest error is selected to be determined as the coding depth. The coding depth and the prediction unit of the corresponding depth can be encoded and transmitted as information on the coding mode. In addition, since the coding unit must be reduced from the depth 0 to the coding depth, only the coding depth reduction information is set to '0', and the reduction information by depth is set to '1' except for the coding depth.

The encoding information extracting unit 220 of the image decoding apparatus 200 according to an embodiment of the present invention extracts information on the encoding depth and the prediction unit for the encoding unit 912 and uses the information on the encoding depth 912 to decode the encoding unit 912 . The video decoding apparatus 200 according to an exemplary embodiment of the present invention uses the reduced information according to the depth to determine the depth with the reduced information of '0' as a coding depth and use the information on the coding mode for the corresponding depth to decode have.

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

The coding unit 1010 is coding units for coding depth determined by the image coding apparatus 100 according to the embodiment with respect to the maximum coding unit 1000. [ The prediction unit 1060 is a prediction unit of each coding depth unit among the coding units 1010 and the conversion unit 1070 is a conversion unit of each coding depth unit.

When the depth of the maximum coding unit 1000 is 0, the coding units 1012 and 1054 have depth 1 and coding units 1014, 1016, 1018, 1028, 1050 and 1052 The depths of the encoding units 1020, 1022, 1024, 1026, 1030, 1032 and 1038 are 3 and the depths of the encoding units 1040, 1042, 1044 and 1046 are 4, respectively.

A portion (1014, 1016, 1022, 1032, 1048, 1050, 1052, 1054) of the prediction units 1060 is a type in which the coding unit is divided. That is, the prediction units 1014, 1022, 1050 and 1054 are divided into 2NxN, the prediction units 1016, 1048 and 1052 are divided into Nx2N, and the prediction unit 1032 is divided into NxN. That is, the prediction unit of the depth-dependent coding units 1010 is smaller than or equal to each coding unit.

Frequency conversion or inverse frequency conversion is performed on the image data of a part (1052, 1054) of the conversion units (1070) in units of data smaller in size than the encoding unit. The conversion units 1014, 1016, 1022, 1032, 1048, 1050, 1052, and 1054 are data units of different sizes or types when compared with the prediction units of the prediction units 1060. That is, the image encoding apparatus 100 and the image decoding apparatus 200 according to an exemplary embodiment of the present invention perform prediction and frequency conversion / inverse transform operations on the same encoding unit, respectively, based on separate data units .

FIG. 11 shows encoding information for each encoding unit according to an embodiment of the present invention.

The encoding information encoding unit 140 of the image encoding apparatus 100 according to an exemplary embodiment of the present invention encodes encoding information of each encoding unit and extracts encoding information of the image encoding apparatus 200 according to an embodiment of the present invention Unit 220 can extract the encoding information for each encoding unit.

The encoding information may include reduction information for a coding unit, division type information, prediction mode information, and conversion unit size information. The encoding information shown in FIG. 11 is only an example that can be set in the image encoding apparatus 100 and the image decoding apparatus 200 according to an embodiment of the present invention, and is not limited to the illustrated ones.

The reduction information may indicate the coding depth of the encoding unit. That is, since the depth that is not further reduced according to the reduction information is the encoding depth, the division type information, the prediction mode, and the conversion unit size information can be defined with respect to the encoding depth. In the case where it is required to be further reduced according to the reduction information, the encoding should be performed independently for each of the reduced four higher-depth encoding units.

As the division type information, the division type of the conversion unit of the coding unit of the coding depth can be represented by 2Nx2N, 2NxN, Nx2N and NxN. The prediction mode may indicate the motion prediction mode as one of an intra mode, an inter mode, and a skip mode. The intra mode can be defined only in the split type 2Nx2N and NxN, and the skip mode can be defined only in the split type 2Nx2N. The conversion unit size can be set to two kinds of sizes in the intra mode and two kinds of sizes in the inter mode.

The encoding unit-specific encoding information of the belonging encoding depth may be stored for each minimum encoding unit in the encoding unit. Therefore, if encoding information held in each of the adjacent minimum encoding units is checked, it can be confirmed whether or not the encoding information is included in the encoding unit of the same encoding depth. In addition, since the encoding unit of the encoding depth can be identified by using the encoding information held in the minimum encoding unit, the distribution of encoding depths in the maximum encoding unit can be inferred.

The intraprediction performed by the intraprediction unit 410 of the video encoding apparatus 100 and the intraprediction unit 550 of the video decoding apparatus 200 according to an embodiment of the present invention shown in FIG. This will be described in detail. In the following description, a coding unit is a term referred to in an image coding step, and a coding unit may be defined as a decoding unit in terms of a decoding step of an image. That is, the terms coding unit and decoding unit are different only in terms of the coding and decoding stages of the image, and the coding unit in the coding step may be referred to as a decoding unit in the decoding step. For the sake of uniformity of terms, except for special cases, they shall be uniformly coded in the coding step and the decoding step in the same coding unit.

12 is a block diagram showing a configuration of an intra prediction apparatus 1200 according to an embodiment of the present invention.

12, an intra prediction apparatus 1200 according to an exemplary embodiment of the present invention includes a prediction unit 1210, a determination unit 1215, and a post-processing unit 1220. The prediction unit 1210 performs intraprediction on the current encoding unit by applying intra-prediction modes determined according to the size of the current encoding unit, and outputs a first predictive encoding unit. The determination unit 1215 determines whether the current encoding unit includes an area outside the boundary of the current picture, and generates a predetermined index (MPI_PredMode) according to the determination result.

The index (MPI_PredMode) indicates whether to perform a multi-parameter intra-prediction (MPI) described later. The value of "0" as shown in Table 1 below is used to generate a second predictive- Is not performed, and a value of "1" is set to indicate that the process of generating the second predictive encoding unit should be performed.

MPI_PredMode MPI mode name meaning 0 MPI_Mode0 Do not process MPI One MPI_Mode1 MPI processing

In Table 1, the case where the index (MPI_PredMode) has a value of 0 and 1 is described according to whether post-processing is performed. However, if post processing is not performed and N modes exist as a post- (MPI_PredMode) may have an integer value from 0 to N for distinguishing each post-processing mode.

If the current encoding unit does not include an area outside the picture boundary, that is, if the index (MPI_PredMode) is not 0, the post-processor 1220 performs a first predictive encoding A second predictive encoding unit is output by performing a post-process of changing the pixel value of each pixel of the first predictive encoding unit using surrounding pixels of each pixel constituting the unit.

13 shows the number of intra prediction modes according to the size of an encoding unit according to an embodiment of the present invention.

According to an embodiment of the present invention, the number of intra prediction modes to be applied to a coding unit can be variously set according to the size of a coding unit (decoding unit in the decoding step). For example, referring to FIG. 13, the number of intraprediction modes actually performed for each of 2x2, 4x4, 8x8, 16x16, 32x32, 64x64, and 128x128 encoding units is NxN, 5, 9, 9, 17, 33, 5, and 5 (in the case of Example 2). The reason for differentiating the number of actually performed intraprediction modes according to the size of the encoding unit is that the overhead for encoding the prediction mode information differs depending on the size of the encoding unit. In other words, in the case of a small-sized coding unit, the overhead for transmitting the additional information such as the prediction mode of the small coding unit may increase although the portion occupying the entire image is small. Therefore, when a small coding unit is coded in too many prediction modes, the bit amount increases and the compression efficiency may be lowered. In addition, since a coding unit having a large size, for example, a coding unit having a size of 64x64 or more is generally selected as a coding unit for a flat region of an image, a coding unit having a large size Encoding of an encoding unit into too many prediction modes may also be inefficient in terms of compression efficiency.

Therefore, according to an embodiment of the present invention, the coding unit is composed of N1xN1 (2≤N1≤8, N1 is an integer), N2xN2 (16≤N2≤32, N2 is an integer), N3xN3 (A1 is a positive integer), and the number of intra prediction modes to be performed for each coding unit having a size of N2xN2 is defined as the number of intra prediction modes to be performed for each coding unit having the size N1xN1 A2 (A2 is a positive integer), and the number of intra prediction modes to be performed for each coding unit having a size of N3xN3 is A3 (A3 is a positive integer), the size of each coding unit It is desirable to set the number of intra prediction modes to be performed according to the number of intra prediction modes. That is, when the current picture is categorized into a small-sized coding unit, a medium-sized coding unit, and a large-sized coding unit, the medium-sized coding unit has the largest number of prediction modes, And a coding unit of a large size are set to have a relatively smaller number of prediction modes. However, the present invention is not limited to this, and it may be possible to set a larger number of prediction modes for small and large size coding units. The number of prediction modes according to the size of each coding unit shown in FIG. 13 is only one embodiment, and the number of prediction modes according to the size of each coding unit can be changed.

14A is a diagram for explaining an example of an intra prediction mode applied to a coding unit of a predetermined size according to an embodiment of the present invention.

Referring to FIGS. 13 and 14A, for example, a vertical mode (mode 0), a horizontal mode (mode 1), a DC (direct current) mode (Mode 2), Diagonal Down-Left Mode (Mode 3), Diagonal Down-Right Mode (Mode 4), Vertical-Right Mode (Mode 5) (Mode 6), Vertical-Left (Mode 7), and Horizontal-Up (Mode 8) modes.

14B is a diagram showing the directions of the intra prediction modes of FIG. 14A. The number at the end of the arrow in FIG. 14B indicates the corresponding mode value when the prediction is performed in that direction. Mode 2 is not shown as a directional DC prediction mode.

FIG. 14C is a diagram illustrating an intra prediction method for the encoding unit shown in FIG. 14A.

Referring to FIG. 14C, a predictive encoding unit is generated using A - M, which is the neighboring pixel of the current encoding unit, according to the available intra prediction mode determined by the size of the encoding unit. For example, an operation of predicting a 4x4 current encoding unit according to mode 0, that is, a vertical mode in Fig. 14A will be described. First, the pixel values of the pixels A to D adjacent to the upper side of the current encoding unit of 4 × 4 size are predicted as pixel values of the 4 × 4 current encoding unit. That is, the value of the pixel A is divided into four pixel values included in the first column of the 4x4 current coding unit, the pixel B is divided into four pixel values included in the second column of the 4x4 current coding unit, Is predicted to the four pixel values included in the third column of the 4x4 current encoding unit and the pixel D value is predicted to the four pixel values included in the fourth column of the 4x4 current encoding unit. Next, an error value is calculated by subtracting the 4x4 current encoding unit predicted using the pixels A to D and the actual value of the pixel included in the original 4x4 current encoding unit, and the error value is encoded.

15 is a view for explaining another example of an intra prediction mode applied to a coding unit of a predetermined size according to an embodiment of the present invention.

Referring to FIGS. 13 and 15, for example, in the intra prediction of a 2 × 2 encoding unit, a vertical mode, a horizontal mode, a DC (Direct Current) mode, a plane mode, And a right (Diagonal Down-Right) mode.

On the other hand, as shown in FIG. 13, when a coding unit having a size of 32x32 has 33 intra prediction modes, it is necessary to set the directions of 33 intra prediction modes. In an embodiment of the present invention, in addition to the intraprediction modes as shown in FIGS. 14 and 15, in order to set intra prediction modes in various directions, a method for selecting a neighboring pixel to be used as a reference pixel, The prediction direction is set using the dx and dy parameters. For example, when 33 prediction modes are defined as mode N (N is an integer from 0 to 32), mode 0 is a vertical mode, mode 1 is a horizontal mode, mode 2 is a DC mode, and mode 3 is a plane mode (1, 1), (1,1), (1,2), (2,1), (1, -2), (2) (1, -2), (2, -1), (2, -11), (5, -7) , (1,11), (1,1), (12,3), (1,11), (1,7), (3,10), 7, -6), (7, -4), (11,1), (6,1), (8,3), (5,3), (5,7) 5, -7), (4, 3) by using a (dx, dy) is expressed with a value of can be defined as a prediction mode having a directionality of tan ^-1 (dy / dx).

mode # dx dy mode # dx dy mode 4 One -One mode 18 One -11 mode 5 One One mode 19 One -7 mode 6 One 2 mode 20 3 -10 mode 7 2 One mode 21 5 -6 mode 8 One -2 mode 22 7 -6 mode 9 2 -One mode 23 7 -4 mode 10 2 -11 mode 24 11 One mode 11 5 -7 mode 25 6 One mode 12 10 -7 mode 26 8 3 mode 13 11 3 mode 27 5 3 mode 14 4 3 mode 28 5 7 mode 15 One 11 mode 29 2 7 mode 16 One -One mode 30 5 -7 mode 17 12 -3 mode 31 4 -3 mode 0 is a vertical mode, mode 1 is a horizontal mode, mode 2 is a DC mode, mode 3 is a plane mode, and mode 32 is a bi-linear mode.

The last mode 32 may be set to a bilinear mode using bilinear interpolation as described below with reference to FIG.

16 is a reference diagram for explaining intra prediction modes having various directions according to an embodiment of the present invention.

As described above with reference to Table 2, the intra-prediction modes according to an exemplary embodiment of the present invention may have various directions of tan ^-1 (dy / dx) using a plurality of (dx, dy)

Referring to FIG. 16, the angle of tan ^-1 (dy / dx) determined according to the value of each mode (dx, dy) shown in Table 2 centered on the current pixel P to be predicted in the current encoding unit The neighboring pixels A and B located on the extension line 150 having the current pixel P can be used as a predictor of the current pixel P. [ In this case, the neighboring pixels used as the predictor are preferably pixels of the previous coding unit on the upper side and the left side of the current coding unit, which have been previously encoded and restored. Further, a peripheral pixel closer to the extension line 160 can be used as a predictor of the current pixel P when the extension line 160 passes between pixels around an integer position rather than a peripheral pixel at an integer position. As shown in the figure, when two peripheral pixels of the upper side peripheral pixel A and the left side peripheral pixel B that meet the extension line 160 exist, the upper peripheral pixel A and the left peripheral pixel B Is used as the predictor of the current pixel P or when the dx * dy value is positive, the upper neighboring pixel A is used and when the dx * dy value is negative, the neighboring pixel B is used. Can be used.

It is preferable that the intraprediction modes having various directions as shown in Table 2 are set in advance in the encoding and decoding stages so that only the corresponding indexes of the intra prediction modes set for each encoding unit are transmitted.

17 is a reference diagram for explaining a bilinear mode according to an embodiment of the present invention.

Referring to FIG. 17, a bi-linear mode is a mode in which a current pixel P and its neighboring pixel values around a current pixel P to be predicted in a current encoding unit, a current pixel P, And the resultant value is used as a predictor of the current pixel P, as shown in FIG. That is, in the bilinear mode, the pixel A 171, the pixel B 172, the pixel D 176, and the pixel E 177 located at the upper, lower, left, and right boundaries of the current pixel P as a predictor of the current pixel P A geometric average value of the distances to the upper, lower, left, and right boundaries of the current pixel P is used. In this case, since the bilinear mode is also one of the intra prediction modes, the upper and lower neighboring pixels, which have been previously encoded and restored, are used as reference pixels at the time of prediction. Therefore, instead of using the corresponding pixel value in the current encoding unit as the pixel A 161 and the pixel B, the virtual pixel value generated using the upper and left peripheral pixels is used.

Specifically, first, by calculating the average value of the upper leftmost neighboring pixel (RightUpPixel) 174 and the lower leftmost neighboring pixel (LeftDownPixel) 175 adjacent to the current encoding unit as shown in the following equation, And calculates a virtual pixel C (173).

C = 0.5 (LeftDownPixel + RightUpPixel)

The virtual pixel A 171 located at the lowermost boundary line when the current pixel P is extended to the lower end in consideration of the distance W1 to the left boundary of the current pixel P and the distance W2 to the right boundary ) Is calculated according to the following equation.

A = (C * W1 + LeftDownPixel * W2) / (W1 + W2)

Similarly, when the current pixel P is extended to the right in consideration of the distance h1 to the upper boundary of the current pixel P and the distance h2 to the lower boundary, the imaginary pixel B ( 172) is calculated according to the following equation.

B = (C * h1 + RightUpPixel * h2) / (h1 + h2)

When the values of the virtual pixel A 171 on the lower borderline of the current pixel P 170 and the pixel B 172 on the right borderline are determined using the above equations, the average value of A + B + D + And can be used as a predictor of the pixel P (170). Such a bilinear prediction process is applied to all the pixels in the current encoding unit, and a predictive encoding unit of the current encoding unit according to the bilinear prediction mode is generated.

According to an embodiment of the present invention, predictive encoding is performed according to various intra prediction modes set according to the size of an encoding unit, thereby enabling more efficient compression depending on the characteristics of an image.

As described above, the predictive encoding unit output by applying the intra-prediction modes set variously according to the size of the encoding unit from the predictor 1210 of the intra-prediction unit 1200 of FIG. 12 outputs a predetermined directionality Respectively. If the pixels of the current coding unit to be coded have a certain direction, the prediction efficiency may be improved. However, if the pixels of the current coding unit have no directionality, the prediction efficiency may be lowered. Accordingly, the post-processing unit 1220 performs a post-processing operation on the predictive encoding unit generated through the intra-prediction, using the pixels in the predictive encoding unit and at least one neighboring pixel to calculate the pixel value To thereby generate a new predictive encoding unit, thereby improving the prediction efficiency of the image. At this time, the post-processing unit 1220 does not perform post-processing on all of the predictive encoding units, but based on the determination result of the determination unit 1215, the post-processing unit 1220 determines that the current predictive encoding unit does not include an area , That is, if the MPI_PredMode is not 0, post-processing is performed.

22 is a reference diagram for explaining an indexing process for post-processing of an encoding unit according to an embodiment of the present invention.

22, when the current picture 2210 is divided into coding units of a predetermined size and coded, the width 'Frame_width' of the current picture 2210 is not a multiple of the horizontal length of the coding unit, If the height 'Frame_height' of the current picture 2210 is not a multiple of the vertical length of the coding unit, the coding units hatched by the right border and the lower border of the current picture 2210 are overlapped as shown in FIG. The determination unit 1215 determines a coding unit including an out-of-bounds region by setting a predetermined index (MPI_PredMode) indicating whether to perform a post-process to 0, To be skipped.

 The reason why the post-processing is not performed when the current predictive encoding unit includes an area outside the boundary of the picture is that the surrounding pixels of each pixel are used in the post-processing process itself. It is difficult to expect the improvement of the prediction efficiency because not only surrounding pixels but also missing pixels are generated through padding or extrapolation to perform post-processing and new pixels are newly generated and processed Because.

23 is a reference diagram for explaining an indexing process for post-processing of an encoding unit according to another embodiment of the present invention.

23, when the determination unit 1215 determines that the coding unit 2320 is located on the boundary of the picture boundary 2310, the coding unit 2320 is not subjected to post-processing as a whole Instead of setting, it is desirable to divide the coding unit 2320 into coding units of greater depth, and then determine whether each of the divided coding units of the greater depth includes an out-of-bounds region. This segmentation process can be repeated until the encoding units 2324 and 2328 that span the boundary are the minimum encoding units and can not be divided into smaller encoding units, that is, until the maximum depth is obtained. 23, the index (MPI_PredMode) is set to 0 so that post-processing is not performed on the minimum bounding coding units 2324 and 2328, and the minimum coding units 2322 and 2326 in the boundary are set to 0 The index (MPI_PredMode) is set to 1 so that post-processing is performed.

Hereinafter, the post-processing operation of the predictive encoding unit performed by the post-processing unit 1220 of FIG. 12 will be described.

If the current encoding unit does not include a region out of bounds as a result of the determination by the determination unit 1215, the post-processing unit 1220 generates at least one of the pixels constituting the first predictive encoding unit generated by the predictor 1210 The second predictive encoding unit is generated by changing the pixel values of the pixels constituting the first predictive encoding unit through post-processing using the neighboring pixels of the second predictive encoding unit. Here, the prediction unit 1220 generates the first predictive encoding unit by applying the available intra-prediction modes according to the size of the encoding unit, as described above.

18 is a reference diagram for explaining a post-processing operation of a first predictive-encoding unit according to an embodiment of the present invention. In FIG. 18, reference numerals 1810 to 1860 denote, in chronological order, the process of changing pixel values in the first predictive encoding unit processed by the post-processing unit 1220.

Referring to FIG. 18, the post-processing unit 1220 according to an embodiment of the present invention calculates a weighted average value of pixel values of a pixel to be changed and its neighboring pixels in a first predictive encoding unit, Change the pixel value of each pixel. For example, if f [1] [1] is the pixel value of the pixel 1821 to be changed and f [0] is the pixel value of the pixel 1822 located at the upper side in the first predictive encoding unit 1810, 1], the value obtained by changing the pixel value f [1] [1] of the pixel 1821 is represented as f '[1] [0] 1], f '[1] [1] can be calculated by the following equation (1).

As shown in FIG. 18, the post-processing unit 1220 according to an embodiment of the present invention includes a pixel to be changed from the uppermost left side to the highest-right side with respect to each pixel in the first predictive- The pixel value of each pixel of the first predictive encoding unit is changed by calculating the weighted average value of the pixels located on the left side. However, the post-processing operation of the predictive encoding unit according to the present invention is not limited to the uppermost-to-lowermost direction from the uppermost-left side, but may be performed from the highest-order side to the lowermost- For each pixel of the first predictive encoding unit in the top-most direction. For example, when the pixels of the first predictive encoding unit are changed from the highest to lowest left in the upper left direction as opposed to the processing procedure shown in FIG. 18, the post-processing unit 1220 determines the pixel to be changed and the pixels The pixel value of each pixel of the first predictive encoding unit is changed.

19 and 20 are reference views for explaining the operation of the post-processing unit 1220 according to an embodiment of the present invention. In FIG. 19, reference numeral 1910 denotes a first pixel of the first predictive encoding unit to be changed, and reference numerals 1911 to 1918 denote neighboring pixels located around the first pixel 1910.

Referring to FIG. 19, the post-processing unit 1220 according to an embodiment of the present invention is not limited to neighboring pixels located on the upper and left sides of the first predictive encoding unit as shown in FIG. 18, Processing may be performed on the first pixel 1910 using a predetermined number of peripheral pixels selected from the plurality of peripheral pixels 1918 to 1918. [ That is, referring to FIG. 20, a predetermined number of neighboring pixels among the neighboring pixels P1 to P8 around the first pixel c of the current encoding unit are selected, and the selected neighboring pixels and the first pixel (c) The pixel value of the first pixel c is changed through a predetermined operation using the first pixel c. For example, if the size of the first predictive encoding unit is mxn (m and n are positive integers), i (i is an integer from 0 to m-1) th column to be changed in the first predictive encoding unit, j (j is an integer from 0 to n-1), f [i] [j] is the pixel value of the first pixel 1910 located in the first row of the first pixel 1910 and the neighboring pixels 1911 to 1918 of the first pixel 1910 The post-processing unit 1220 calculates the values of the n (n is 2 or 3) pixels selected for the post-processing of the first pixel 1910 from f1 to fn, respectively, I] [j] to f '[i] [j].

The post-processing unit 1220 generates a second predictive encoding unit by applying the above-described Equation (2) to all the pixels in the first predictive encoding unit 1900, thereby changing the pixel value. In the above equation (2), up to three neighboring pixels are used, but the present invention is not limited thereto. The post-processing unit 1220 may perform post-processing operations using four or more neighboring pixels.

The post-processing unit 1220 according to the second embodiment of the present invention includes a post-processing unit 1220 and a post-processing unit 1220. The post-processing unit 1220 according to the second embodiment of the present invention calculates a pixel value of each pixel in the first predictive- Thereby generating a second prediction block.

For example, the post-processing unit 1220 according to the second embodiment of the present invention uses the neighboring pixels on the upper side and the left side as shown in the following Equation (3) to locate the i-th column and the j- The pixel value f [i] [j] of the pixel is changed to f '[i] [j].

In Equation (3),?,?,? May have any positive integer value, and for example,? = 2,? = 2,? = 1.

The post-processing unit 1220 according to the third embodiment of the present invention changes the pixel value of each pixel of the first predictive-encoding unit through the weighted geometric average value of each pixel to be changed and the surrounding pixels of the first predictive- Thereby generating a second predictive encoding unit.

For example, the post-processing unit 1220 according to the third embodiment of the present invention uses the neighboring pixels on the upper side and the left side as shown in the following Equation (4) The pixel value f [i] [j] of the pixel is changed to f '[i] [j].

In Equation (4),?,?,? May have any positive integer value, and for example,? = 1,? = 1,? = 2. In Equations (2) to (4) described above, a relatively large weight is given to the pixel f [i] [j] to be changed.

As described above, in the first to third embodiments of the present invention, the post-processing unit 1220 is not limited to peripheral pixels on the upper and left sides of a pixel to be changed, but may include surrounding pixels 1911 To perform a post-processing operation using a predetermined number of peripheral pixels selected from among the peripheral pixels.

The post-processing unit 1220 according to the fourth embodiment of the present invention calculates a pixel value of each pixel of the first predictive encoding unit by an average value of a pixel to be changed and a selected one of surrounding pixels of the first predictive- To thereby generate a second predictive encoding unit.

For example, the post-processing unit 1220 according to the fourth exemplary embodiment of the present invention may use the neighboring pixels on the upper side as shown in the following equation (5) to calculate the pixel values of the pixels located in the i- The pixel value f [i] [j] can be changed to f '[i] [j].

Similarly, the post-processing unit 1220 according to the fifth embodiment of the present invention changes the pixel value of each pixel under the first predictive coding unit to an average value of pixels to be changed in the first predictive coding unit and neighboring pixels located in the left side thereof Thereby generating a second predictive encoding unit.

That is, the post-processing unit 1220 according to the fifth embodiment of the present invention calculates the pixel value f [i] [j] of the pixel located in the i-th column and the j-th row of the first predictive- To f '[i] [j].

The post-processing unit 1220 according to the sixth embodiment of the present invention generates a second predictive encoding unit by modifying a pixel value to a median between pixels to be changed in the first predictive encoding unit and surrounding pixels thereof do. 19, the pixel value f [i] [j] of the first pixel 1910 located in the i-th column and the j-th row of the first predictive encoding unit 1900, The pixel values f [i] [j-1] of the third pixel 1911 and the pixel values f [i-1] [j] of the third pixel 1911 satisfy the following size order; Let f [i] [j-1]> f [i-1] [j]> f [i] [j] be assumed. In this case, the post-processing unit 1220 according to the sixth embodiment of the present invention sets the pixel value f [i] [j] of the first pixel 510 to be changed to f [i-1] [j] Change it.

The post-processing unit 1220 according to the seventh through ninth embodiments of the present invention may use the pixel values of adjacent encoding units reconstructed after being encoded before the current encoding unit instead of using surrounding pixels of the changed pixel 2 prediction encoding unit.

19, the post-processing unit 1220 according to the seventh embodiment of the present invention includes a first pixel 1910 located in an i-th column and a j-th row to be changed in a first predictive encoding unit 1900, The pixel value of the first pixel 1910 is calculated as f '[i] [j] by calculating the average value of the pixels 1921 located in the same column as the current pixel and located in the upper adjacent encoding unit of the current encoding unit, Change it.

In Equation (7), f [-1] [j] represents the pixel value of the pixel 1921 located in the same column as the first pixel 1910 and located in the upper adjacent encoding unit of the current encoding unit.

Likewise, the post-processing unit 1220 according to the eighth embodiment of the present invention includes a post-processing unit 1220 in the same row as the first pixel 1910 located in the i-th column and the j-th row to be changed in the first predictive- The pixel value of the first pixel 1910 is changed to f '[i] [j] by calculating an average value of the pixels 1922 located in the left adjacent encoding unit of the current encoding unit as shown in Equation (8).

In Equation (8), f [i] [- 1] represents the pixel value of the pixel 1922 located in the same row as the first pixel 1910 and located in the left adjacent encoding unit of the current encoding unit.

The post-processing unit 1220 according to the ninth embodiment of the present invention includes a first pixel 1910, a first pixel 1910, and a second pixel 1910 located in the i-th column and the j-th row to be changed in the first predictive- A weighted average value of a pixel 1921 located in the upper adjacent encoding unit of the current encoding unit and a pixel 1922 located in the same row and located in the left neighboring encoding unit of the current encoding unit is located in the same column as the following Equation 9 And changes the pixel value of the first pixel 1910 to f '[i] [j].

The post-processing unit 1220 according to the tenth embodiment of the present invention compares the pixel value f [i] [j] of the first pixel to be changed within the first predictive coding unit 1900 with the following equation We use one to change it to f '[i] [j].

Equation (10) is to change the pixel values in a row unit of the first predictive encoding unit to a gradually increasing value in the downward direction, and Equation (11) Value. Equation (12) is to change each pixel value in a row unit of the first predictive encoding unit to a value that gradually decreases in a downward direction, and Expression (13) To a decreasing value.

라고 할 때, 다음의 수학식 14와 같이 제 1 픽셀의 픽셀값을 f'[i][j]로 변경한다.The post-processing unit 1220 according to the eleventh embodiment of the present invention calculates f [i] [j] as the pixel value of the first pixel located in the i-th column and the j-th row to be changed in the first predictive- F [0] [0] is a pixel value of a pixel located at the upper left of the first predictive encoding unit, f [0] [0] is a pixel value of a pixel located at the j- 0] [j], a pixel value of a pixel located in the i-th row which is the same as the first pixel and located in the leftmost column of the first predictive encoding unit is denoted by f [i]

, The pixel value of the first pixel is changed to f '[i] [j] as shown in the following Equation (14).

Equation (14) is based on a kind of wave equation. In order to smoothing the pixel value inside the first predictive encoding, the pixel value of the best-forward line in the first predictive encoding unit and the pixel value in the left- , And calculates the average value of G [i] [j] and f [i] [j] by changing the pixel value of the pixels of the first predictive coding unit.

As in the first to eleventh embodiments of the present invention, the cost of the bitstream obtained by encoding the second predictive encoding units generated by applying various post-processing modes is compared, and the second predictive encoding unit having the minimum cost is The post-processing mode used to generate is added to the header area of the bitstream. A variable length coding scheme is employed in which a small number of bits are allocated to a frequently used post-processing mode based on distribution of a post-processing mode determined after encoding of a predetermined number of coding units is completed when a post-processing mode is added to a bitstream Different post-processing modes can be distinguished and displayed. For example, when the post-processing mode according to the first embodiment of the present invention is an optimal operation that generates the smallest cost in most coding units, Bits to distinguish the post-processing mode according to the first embodiment from the post-processing modes according to another embodiment.

Meanwhile, when prediction is performed by dividing an encoding unit into smaller sub-encoding units, it is possible to generate a second predictive encoding unit by applying different post-processing modes to each sub-encoding unit, simplify the calculation, To reduce the rate, the same post-processing mode may be applied to the sub-encoding units included in the same encoding unit.

A rate-distortion optimization method may be used as the cost for determining the optimal post-processing mode. Since the encoding method according to an embodiment of the present invention is applied to intra prediction encoding units used as reference data of other encoding units, it is preferable to calculate a cost by assigning a high weight to a distortion value in a rate-distortion optimization method Do. That is, the conventional rate-distortion optimization method calculates the cost based on the distortion value, which is the difference between the encoded image and the original image, and the generated bit rate as shown in Equation (15).

On the other hand, in the encoding method according to an embodiment of the present invention, it is preferable to allocate a higher weight value to the distortion value in comparison with the conventional rate-distortion optimization method as shown in the following Equation 16 to determine the optimal post-processing mode.

FIG. 21 is a flowchart illustrating an image encoding method according to an embodiment of the present invention.

Referring to FIG. 21, in step 2110, a first predictive encoding unit for the current encoding unit to be encoded is generated. Here, the first predictive coding unit is an intra prediction block generated by applying intra prediction modes having various directions according to a general intra prediction method and a coding unit size as described above.

In step 2120, it is determined whether or not the current encoding unit includes an area outside the boundary of the current picture. According to the determination result, a value of "0 " indicates that the process of generating the second predictive encoding unit is not performed through post-processing, and a value of" 1 " A predetermined index (MPI_PredMode) indicative of the index value can be generated.

If it is determined in step 2120 that the current encoding unit does not include an area out of the bounds of the current picture, in step 2130, using each pixel constituting the first predictive encoding unit and at least one neighboring pixel, And generates a second predictive encoding unit by changing the value. As described in the first to eleventh embodiments of the post-processing unit 1220, by applying various post-processing modes to surrounding pixels around the pixel to be changed in the first predictive encoding unit, The second predictive encoding unit can be generated by changing the pixel value of each pixel of the encoding unit. A transform, a quantization, and an entropy encoding process are performed on the residue, which is a difference between the output second predictive encoding unit and the current encoding unit, to generate a bitstream. Processing mode information used for generating the second predictive encoding unit is added to a predetermined area of the generated bitstream so that the second predictive encoding unit for the current decoding unit can be generated in the decoding apparatus.

If it is determined in step 2120 that the current encoding unit includes an area outside the boundary of the current picture, the second predictive encoding unit is not generated in step 2140, and the first predictive encoding unit is output as prediction information of the current encoding unit do. The transform, quantization, and entropy encoding are performed on the residue, which is the difference between the output first predictive encoding unit and the current encoding unit, to generate a bitstream.

24 is a flowchart illustrating a video decoding method according to an embodiment of the present invention.

Referring to FIG. 24, in step 2410, prediction mode information of the current decoding unit to be decoded is extracted from the bitstream received.

In step 2420, a first predictive decoding unit for the current decoding unit is generated according to the extracted prediction mode information.

In step 2430, it is determined whether or not the current decoding unit includes an area outside the boundary of the current picture. According to the determination result, a value of "0 " indicates that the process of generating the second predictive encoding unit is not performed through post-processing, and a value of" 1 " A predetermined index (MPI_PredMode) indicative of the index value can be generated.

If it is determined in step 2430 that the current decoding unit does not include a region out of the boundary of the current picture, in step 2440, using each pixel constituting the first predictive decoding unit and surrounding pixels of each pixel, And generates a second predictive decoding unit by changing the pixel value. As described in the first to eleventh embodiments of the post-processing unit 1220, by applying various post-processing modes to surrounding pixels around the pixel to be changed in the first predictive encoding unit, The second predictive encoding unit can be generated by changing the pixel value of each pixel of the encoding unit.

If it is determined in step 2430 that the current decoding unit includes an area out of the boundary of the current picture, it is determined in step 2450 that the first predictive decoding unit does not perform the post-processing for generating the second predictive decoding unit, Unit prediction information. The output first predictive decoding unit is added to the residual of the current decoding unit extracted from the bitstream, and the current decoding unit is restored.

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

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

Claims (2)

Obtaining prediction mode information of a current block from a bitstream;
Determining neighboring pixels used for intra prediction of the current block using available neighboring pixels of the current block when the prediction mode information indicates that the prediction mode of the current block is an intra prediction mode;
Obtaining a first predicted value of the current block using the neighboring pixels; And
And obtaining a second predicted value of pixels located at an upper boundary and a left boundary of the current block using the obtained first predicted value and at least one neighboring pixel,
An image is divided into a plurality of maximum encoding units based on information on a maximum size of an encoding unit, a maximum encoding unit is hierarchically divided into one or more encoding units having depth according to the division information, Unit is one of the square data units divided from the encoding unit of the higher depth,
If the division information indicates division of the current depth, the current-depth coding unit is divided into coding units of lower depth independently of the surrounding coding units,
Wherein at least one prediction unit is obtained from the coding unit of the current depth when the division information indicates non-division of the current depth, and the current block corresponds to the at least one prediction unit. An entropy decoder for obtaining prediction mode information of a current block from a bitstream; And
Wherein when the prediction mode information indicates that the prediction mode of the current block is an intra prediction mode, neighboring pixels used for intra prediction of the current block are determined using available neighboring pixels of the current block, And a predictor for obtaining a first predicted value of the current block and obtaining a second predicted value of pixels located at an upper boundary and a left boundary of the current block using the obtained first predicted value and at least one neighboring pixel, ,
An image is divided into a plurality of maximum encoding units based on information on a maximum size of an encoding unit, a maximum encoding unit is hierarchically divided into one or more encoding units having depth according to the division information, Unit is one of the square data units divided from the encoding unit of the higher depth,
If the division information indicates division of the current depth, the current-depth coding unit is divided into coding units of lower depth independently of the surrounding coding units,
Wherein at least one prediction unit is obtained from the coding unit of the current depth when the division information indicates non-division of the current depth, and the current block corresponds to the at least one prediction unit.

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