KR20140067996A - Method and apparatus for image encoding, and method and apparatus for image decoding - Google Patents

Abstract

Disclosed are a method and an apparatus to encode an image and a method and an apparatus to decode the image. The method to encode an image comprises: splitting a current picture into maximum coding units; determining a split structure of the maximum coding units and a prediction mode and reduction of each split coding unit by encoding image data of the maximum coding units based on the depths of the coding units; setting reduction information and skip mode information about each of the coding units and the reduction information containing whether a coding unit of a lower depth, whereby each of the coding units is included, is split or not; and encoding the reduction information and skip mode information set according to each coding unit.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image encoding method and apparatus,

The present invention relates to encoding and decoding of images.

There are intra prediction and inter prediction methods for predictive coding of an image. Intra prediction is a prediction method based on the correlation of adjacent pixels within a single frame. Inter prediction is a method of predicting an area similar to data to be encoded from adjacent frames through motion prediction and compensation.

Generally, a motion vector of a certain block has a close correlation with a motion vector of an adjacent block. Therefore, the amount of bits generated at the time of encoding can be reduced by predicting the motion vector of the current block from the adjacent block and encoding only the difference motion vector between the motion vector of the current block and the predicted motion vector.

The skip mode is a mode in which a motion vector of a macroblock is the same as a predicted motion vector predicted using a motion vector of a neighboring block, and is selected when the prediction error is sufficiently small. When the skip mode is selected as the prediction mode of the macroblock, the encoder transmits only the skip mode information and does not transmit the residual data. The decoder can recover the macroblock by performing motion compensation using the predicted motion vector predicted from the neighboring block for the macroblock coded in the skip mode.

Disclosure of Invention Technical Problem [8] The present invention provides a method and apparatus for encoding and decoding image data, which is based on hierarchical encoding units of various sizes, and efficiently transmits skip mode information of each encoding unit .

According to an aspect of the present invention, there is provided an image encoding method including: dividing a current picture into at least one maximum encoding unit which is a maximum-size encoding unit; Determining a division mode of the maximum coding unit and a prediction mode of each of the divided coding units by encoding the image data of the maximum coding unit on the basis of the depth coding unit that is hierarchically reduced as the depth increases; Setting shrink information including whether or not a lower-depth encoding unit including the encoding unit is divided for each encoding unit; Setting skip information indicating whether the determined prediction mode is a skip mode for each coding unit; And encoding the reduced information and skip information set for each encoding unit.

According to another aspect of the present invention, there is provided an image encoding method including: dividing a current picture into at least one maximum encoding unit which is a maximum-size encoding unit; Determining a division mode of the maximum coding unit and a prediction mode of each of the divided coding units by encoding the image data of the maximum coding unit on the basis of the depth coding unit that is hierarchically reduced as the depth increases; Setting skip information including whether the prediction mode of the lower depth including the coding unit and the coding unit is a skip mode for each coding unit; Setting shrink information including whether or not a lower-depth encoding unit including the encoding unit is divided for each encoding unit; And encoding the reduced information and skip information set for each encoding unit.

The image decoding method according to an embodiment of the present invention is a method for decoding a current decoded image data from image data encoded for each maximum encoding unit, which is a maximum-size encoding unit, based on a depth- Extracting reduced information including whether or not the decoding unit of the lower depth including the division is included; Extracting skip information indicating whether the prediction mode of the current decoding unit is a skip mode from the image data; Determining a division type of a maximum decoding unit including the current decoding unit according to the reduction information; And determining whether the prediction mode of the current decoding unit is a skip mode according to the skip information.

The image decoding method according to another exemplary embodiment of the present invention is a method for decoding a current decoded image data from image data encoded for each maximum encoding unit, which is a maximum-size encoding unit, based on a depth- And extracting skip information indicating whether a prediction mode of a lower-resolution decoding unit including the current decoding unit is a skip mode; Extracting reduced information including whether to divide a decoding unit of a lower depth including the current decoding unit; Determining whether a prediction mode of a decoding unit of the current decoding unit and the lower decoding unit is a skip mode according to the extracted skip information; And determining a division type of the maximum decoding unit including the current decoding unit according to the reduction information.

According to an aspect of the present invention, there is provided an image encoding apparatus including: a maximum encoding unit division unit for dividing a current picture into at least one maximum encoding unit, which is a maximum-size encoding unit; A coding depth determination unit for determining a division mode of the maximum coding unit and a prediction mode of each divided coding unit by encoding image data of the maximum coding unit on the basis of the depth coding unit as the depth increases, ; Setting skip information indicating whether skip mode is determined for each of the encoding units and skip information indicating whether skip mode is determined for each of the encoding units; And an encoded information encoding unit for encoding the information and skip information.

According to another aspect of the present invention, there is provided an image encoding apparatus including: a maximum encoding unit division unit for dividing a current picture into at least one maximum encoding unit, which is a maximum size encoding unit; A coding depth determination unit for determining a division mode of the maximum coding unit and a prediction mode of each divided coding unit by coding the image data of the maximum coding unit on the basis of the depth- ; Wherein the coding unit includes skip information including whether the prediction mode of the lower depth including the coding unit and the coding unit is a skip mode for each coding unit, And a coding information coding unit for coding the set down information and the skip information for each coding unit.

The image decoding apparatus according to an embodiment of the present invention decodes a current decoding unit to be decoded from image data encoded per a maximum encoding unit, which is a maximum-size encoding unit, based on a depth- And a skip information indicating whether the prediction mode of the current decoding unit is a skip mode or not; And a decoding unit that determines a division type of the maximum decoding unit including the current decoding unit according to the reduction information and determines whether the prediction mode of the current decoding unit is a skip mode according to the skip information, do.

The apparatus for decoding an image according to another embodiment of the present invention decodes a current decoded image unit from decoded image data of each maximum encoding unit, which is a maximum-size encoding unit, based on a depth- And skip information indicating whether a prediction mode of a decoding unit of a lower depth including the current decoding unit is a skip mode and a decoding process of extracting reduced information including whether to divide a decoding unit of a lower depth including the current decoding unit An information extracting unit; And determining whether the prediction mode of the decoding unit of the current decoding unit and the lower depth decoding unit is a skip mode according to the extracted skip information, and determining a division type of the maximum decoding unit including the current decoding unit according to the reduction information And a decoding unit for deciding the decoding result.

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 an example of a division type of the maximum encoding unit determined based on the depth encoding unit according to an embodiment of the present invention.
13 is a diagram for explaining reduction information that the encoding unit 1220 in the depth 2 of FIG. 12 has.
FIG. 14 is a diagram for explaining reduction information possessed by the encoding unit 1230 in the depth 3 of FIG.
FIG. 15 is a diagram illustrating an example of a processing procedure of an encoding unit according to an embodiment of the present invention.
16 is a flowchart illustrating an image encoding method according to an embodiment of the present invention.
17 is a flowchart illustrating an image encoding method according to another embodiment of the present invention.
18 is a flowchart illustrating a video decoding method according to an embodiment of the present invention.
FIG. 19 is a flowchart illustrating a process of dividing a maximum-size decoding unit according to an image decoding method according to an embodiment of the present invention and decoding skip information.
20 is a flowchart illustrating a video decoding method according to another embodiment of the present invention.
FIG. 21 is a flowchart illustrating a process of dividing a maximum-size decoding unit and decoding skip information according to the image decoding method according to another 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 the 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.

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. 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 embodiment of the present invention encodes the 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.

Hereinafter, according to an embodiment of the present invention, a split flag indicating division type information of a maximum encoding unit encoded based on a depth encoding unit and a prediction mode of each encoding unit included in the maximum encoding unit are divided into a skip mode A method of hierarchically encoding skip information indicating whether or not skip information is present 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.

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

Referring to FIGS. 1 and 16, in step 1610, the maximum coding unit division unit 110 divides the current picture into at least one maximum coding unit which is a coding unit of the maximum size.

In step 1620, the encoding depth determination unit 120 encodes the image data of the maximum encoding unit based on the depth-dependent encoding units that are hierarchically reduced as the depth increases, Lt; / RTI > As described above, the coding depth determiner 120 encodes the image data in units of depth coding for each maximum coding unit of the current picture, selects a depth at which the smallest coding error occurs, and determines the selected depth as the coding depth. Specifically, the coding depth determiner 120 encodes the video data in the maximum coding unit based on the depth coding units according to at least one depth below the maximum depth, and compares the coding results based on the coding units for each depth And selects the depth with the smallest coding error as a comparison result. Also, the coding depth determiner 120 measures coding errors for each data and determines whether to reduce the coding depth to a higher depth, even if the coding units are of the same depth included in one maximum coding unit.

In step 1630, the encoding information encoding unit 140 sets the reduction information including whether or not the lower-depth encoding unit including each encoding unit is divided for each encoding unit. The process of setting the reduction information will be described later with reference to FIG. 12 to FIG.

In step 1640, the encoding information encoding unit 140 sets skip information indicating whether the prediction mode determined for each encoding unit is the skip mode. In step 1650, the reduction information and skip information set for each encoding unit are encoded.

12 is an example of a division type of the maximum encoding unit determined based on the depth encoding unit according to an embodiment of the present invention.

In FIG. 12, it is assumed that the largest block denoted by reference numeral 1200 is a maximum encoding unit, and the maximum encoding unit 1200 has a maximum depth 3. That is, assuming that the size of the maximum encoding unit 1200 is 2Nx2N, the maximum encoding unit 1200 is an encoding unit 1210 of NxN depth 1, a depth 2 of (N / 2) x (N / 2) May be segmented using coding units 1220 of depth 3 with coding unit 1220 and (N / 4) x (N / 4) size. In order to transmit the division type of the maximum encoding unit 1200 as shown in FIG. 12, according to an embodiment of the present invention, the encoding information encoding unit 140 encodes the sub-depth And sets reduction information including whether or not the encoding unit is divided. For example, the coding unit 1210 having the depth 1 of NxN size has 1-bit reduction information indicating whether the maximum coding unit 1200 of the depth 0, which is the lower coding unit, is divided. When each bit of the reduction information has a value of "1 ", the encoding unit of the corresponding depth is divided. If each bit of the reduction information has a value of" 0 & , The coding unit 1210 of depth 1 has reduction information having a value of "1 " in order to have a division form as shown in Fig.

13 is a diagram for explaining reduction information that the encoding unit 1220 in the depth 2 of FIG. 12 has. Reference numeral 1320 in Fig. 13 corresponds to the coding unit 1220 in the depth 2 shown in Fig.

13, the encoding information encoding unit 140 encodes the encoding unit 1310 having the depth 1 and the encoding unit 1320 having the depth 2 including the encoding unit 1320 having the depth 2 as the reduction information of the encoding unit 1320 having the depth 2, 2-bit reduction information indicating whether or not the coding unit 1300 is divided is set. When each bit of the reduction information has a value of "1 ", the encoding unit of the corresponding depth is divided. If each bit of the reduction information has a value of" 0 & The encoding unit 1320 of depth 2 can be generated only when both the encoding unit 1310 of depth 1 and the maximum encoding unit 1300 of depth 0 are generated. Quot; 11 ".

FIG. 14 is a diagram for explaining reduction information possessed by the encoding unit 1230 in the depth 3 of FIG. 14. Reference numeral 1430 in FIG. 14 corresponds to the encoding unit 1230 in the depth 3 shown in FIG.

Referring to FIG. 14, the encoding information encoding unit 140 encodes the encoding unit 1420 of the depth 2 including the encoding unit 1430 of the depth 3 as the reduction information of the encoding unit 1430 of the depth 3, Bit reduction information indicating whether the unit 1410 and the maximum coding unit 1400 are divided. When each bit of the reduction information has a value of "1 ", the encoding unit of the corresponding depth is divided. If each bit of the reduction information has a value of" 0 & , The coding unit 1430 of depth 3 can be generated only when the coding unit 1420 of depth 2, the coding unit 1410 of depth 1 and the maximum coding unit 1400 of depth 0 are all divided, The encoding unit 1430 at depth 3 has 3-bit reduction information of "111 ".

In this way, the coding information coding unit 140 sets the maximum depth d (d is an integer) indicating the number of times the height and width of the current coding unit are hierarchically reduced from the maximum coding unit to the highest coding unit, the depth of the current coding unit (n-1), where n is an integer (0? n? (d-1), and n is an integer), it is possible to determine whether the lower- Each bit of the n-bit reduced information is set to indicate whether or not the lower-depth coding units are divided from the current coding unit from the depth 0 to the depth (n-1). At this time, it is possible to change the order in which the sub-depths are divided in order of MSB (Most Significant Bit) and LSB (Least Significant Bit) among the n-bit reduction information.

If the division of the lower depth including the current coding unit is set for each coding unit as the reduction information, the position to which each coding unit belongs in the maximum coding unit is set to the coding unit and the decoding unit in the same processing order It can be easily determined from the information on whether or not to divide it. For example, as shown in FIG. 15, in an embodiment of the present invention, each coding unit in the maximum coding unit 1500 processes the coding units of the same depth in a zigzag scanning order, and in the same zigzag scanning order It is possible to restore the division form of the largest coding unit determined at the time of coding from the reduction information indicating whether or not the coding units of the lower depths of each coding unit described above are divided. The block processing procedure according to an embodiment of the present invention may be variously set in addition to the illustrated zigzag scanning order. However, in order to determine the division type of the maximum encoding unit at the time of decoding, It is necessary to set the processing order.

The coding information coding unit 140 sets skip information indicating whether the determined prediction mode of each coding unit is the skip mode by allocating 1 bit for each coding unit. For example, if the bit of skip information has a value of "1 ", it indicates that the prediction mode of the encoding unit is a skip mode. If the bit has a value of" 0 & It can be shown that it is predicted. The reason why the skip information is set for each encoding unit can be restored from the motion information of the surrounding encoding unit without a separate prediction process in the skip mode and the encoding unit determined in the skip mode is skipped in decoding So that the compression efficiency and processing performance of the image can be improved.

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

Referring to FIG. 17, in step 1710, the maximum coding unit division unit 110 divides the current picture into at least one maximum coding unit which is the coding unit of the maximum size.

In step 1720, the encoding depth determiner 120 encodes the image data of the maximum encoding unit based on the depth-dependent encoding units that are hierarchically reduced as the depth increases, and outputs the segmentation type of the maximum encoding unit, Lt; / RTI > As described above, the coding depth determiner 120 encodes the image data in units of depth coding for each maximum coding unit of the current picture, selects a depth at which the smallest coding error occurs, and determines the selected depth as the coding depth.

In step 1730, the coding information coding unit 140 sets skip information including whether the prediction mode of each coding unit and lower depth including the coding unit is a skip mode for each coding unit. That is, according to another embodiment of the present invention, the skip information of each coding unit may include not only the current coding unit but also a skip mode of the lower-depth coding unit including the current coding unit. Specifically, the maximum depth indicating the number of times the height and width of the current coding unit are hierarchically reduced from the maximum coding unit to the highest coding unit is d (d is an integer), the depth of the current coding unit is n (0? N? (n-1) and n is an integer), the encoding information encoding unit 140 determines whether the prediction mode of the current encoding unit and the encoding unit of the lower (n-1) depths is a skip mode, As shown in FIG. If n = 1, that is, if the current coding unit is a coding unit having a depth of 1, then the lower-depth coding unit becomes the highest coding unit. In this case, a 1-bit skip indicating whether the prediction mode is a skip mode Information. For example, in FIG. 12, the coding unit 1210 of depth 1 has skip information of 1 bit indicating whether its prediction mode is a skip mode.

As another example, referring to FIG. 13, the encoded information encoding unit 140 may include 1 bit indicating skip information of the encoding unit 1320 of depth 2 as skip information of the encoding unit 1320 of depth 2, Bit skip information indicating 1 bit skip information of the coding unit 1310 of depth 1 including the unit 1320 is set. 14, the coded information encoding unit 140 skips the skip information of the coding unit 1430 of depth 3 and the skip information of the coding unit 1430 of depth 3 as skip information of the coding unit 1430 of depth 3, And the skip information of the coding unit 1410 of the depth 1 and the skip information of the total of 3 bits of the skip information of the depth 1 coding unit 1410. [

Referring again to FIG. 17, in step 1740, reduction information including whether or not a lower-depth coding unit including each coding unit is divided is set for each coding unit. The step of setting the reduction information according to step 1740 is the same as the embodiment of the present invention described above, and a detailed description thereof will be omitted.

In step 1750, the reduction information and skip information set for each encoding unit are encoded.

18 is a flowchart illustrating a video decoding method according to an embodiment of the present invention. The image decoding method according to an embodiment of the present invention corresponds to decoding of a bit stream encoded according to an embodiment of the present invention shown in FIG.

Referring to FIGS. 2 and 18, in step 1810, the encoding information extracting unit 220 extracts the encoded image per a maximum encoding unit, which is a maximum-size encoding unit, based on depth-dependent encoding units that are hierarchically reduced as the depth increases Extracts from the data the reduction information including whether or not the decoding unit of the lower depth including the current decoding unit to be decoded is divided.

In step 1820, the encoding information extracting unit 220 extracts skip information indicating whether the prediction mode of the current decoding unit is the skip mode, from the image data.

In step 1830, the decoding unit 230 determines the division type of the maximum decoding unit including the current decoding unit according to the reduction information. As described above, since the reduction information includes n-bit reduction information indicating whether or not the decoding unit of the lower depth including the current decoding unit is divided, it is possible to reduce the maximum decoding unit to the depth of the current decoding unit Can be divided up to the encoding unit of FIG.

In step 1840, the decoding unit 230 determines whether the prediction mode of the current decoding unit is the skip mode according to the skip information. If the current decoding unit is predicted as a skip mode, the dividing process is stopped and other information included in the encoding information is decoded.

FIG. 19 is a flowchart illustrating a process of dividing a maximum-size decoding unit according to an image decoding method according to an embodiment of the present invention and decoding skip information.

Referring to FIG. 19, in step 1910, encoding information of the encoding units belonging to the maximum encoding unit is extracted. As described above, the encoding unit includes the reduction information and the skip information.

In step 1920, the reduced information is decoded. In step 1930, in accordance with the reduced information decoded in step 1930, the maximum decoded unit is divided according to the currently set depth to determine whether it is divided up to the depth of the current decoded unit. For example, as described above, if the current decoding unit is a decoding unit of depth 2 having reduced information of "11 ", it should be included in the coding unit obtained by reducing the maximum decoding unit twice.

If it is determined in step 1930 that the maximum decoding unit is not divided up to the depth of the current decoding unit, step 1935 increases the depth by one.

If it is determined in step 1930 that the maximum decoding unit is divided up to the depth of the current decoding unit, skip information is decoded in step 1940. It is determined whether the current decoding mode is a skip mode. If the current decoding mode is a skip mode, it is determined in step 1960 whether the current decoding unit is the last decoding unit and proceeds to decoding in the next maximum decoding unit (step 1970) The index value of the unit is increased by one step so that decoding of the next decoding unit proceeds (step 1980)

As a result of the determination in step 1950, if the prediction mode of the current decoding unit is the skip mode in step 1955, information on image data other than the reduced information and skip information is decoded.

20 is a flowchart illustrating a video decoding method according to another embodiment of the present invention. The image decoding method according to another embodiment of the present invention corresponds to decoding of a bit stream encoded according to another embodiment of the present invention shown in FIG.

Referring to FIGS. 2 and 20, in step 2010, the encoding information extracting unit 220 extracts the encoded image per a maximum encoding unit, which is a maximum-size encoding unit, based on the depth-dependent encoding units that are hierarchically reduced as the depth increases From the data, skip information indicating whether the prediction mode of the decoding unit of the lower depth including the current decoding unit to be decoded and the current decoding unit is the skip mode is extracted.

In step 2020, the encoding information extracting unit 220 extracts reduction information including whether the decoding unit of the lower depth including the current decoding unit is divided from the image data.

In step 2030, the decoding unit 230 determines whether the prediction mode of the decoding unit of the current decoding unit and the lower decoding unit is the skip mode, according to the extracted skip information. As described above, according to another embodiment of the present invention, when the skip information is decoded prior to decoding the reduced information, the decoding process can be omitted for the decoded unit determined as the skip mode, so that the processing performance of the image can be improved .

In step 2040, the division type of the maximum decoding unit including the current decoding unit is determined according to the reduction information for the decoding unit not determined as the skip mode.

FIG. 21 is a flowchart illustrating a process of dividing a maximum-size decoding unit and decoding skip information according to the image decoding method according to another embodiment of the present invention.

Referring to FIG. 21, in step 2110, encoding information of encoding units belonging to the maximum encoding unit is extracted. As described above, the encoding unit includes the reduction information and the skip information.

In step 2120, skip information is decoded and it is determined whether the prediction mode of the busy decoding unit is the skip mode according to the skip information decoded in step 2130. If the prediction mode of the current decoding unit is the skip mode, it is determined whether the current decoding unit is the last decoding unit (Step 2135). If the current decoding unit is the last decoding unit, the process proceeds to the decoding of the next maximum decoding unit (Step 2140) If not, the decoding unit index is increased by one to allow decoding to be performed for the next decoding unit (step 2145). If the prediction mode of the current decoding unit is not the skip mode, the reduction information of the current decoding unit is decoded in step 2150.

The maximum decoding unit is divided according to the currently set depth according to the reduced information decoded in step 2160, and it is determined whether or not the maximum decoding unit is divided up to the depth of the current decoding unit. For example, if the current decoding unit is a decoding unit of depth 2 having reduced information of "11 ", the maximum decoding unit should be reduced by two.

If it is determined in step 2160 that the maximum decoding unit is not divided up to the depth of the current decoding unit, the depth is increased by one in step 2180. If it is determined in step 2160 that the maximum decoding unit is divided up to the depth of the current decoding unit The decoding of the information related to the video data other than the reduced information and the skip information is started in step 2170.

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 (1)

In the image decoding method,
As the depth of field increases, reduction information indicating whether or not the lower-depth coding unit including the current coding unit to be decoded is divided is extracted from the image data coded using the highest coding unit hierarchically divided into higher-depth coding units Extracting;
Extracting skip information indicating whether the prediction mode of the current encoding unit is a skip mode from the image data;
Determining a division type of a maximum encoding unit including the current encoding unit according to the reduction information; And
And determining whether the prediction mode of the current encoding unit is a skip mode according to the skip information,
Wherein the image is divided into a plurality of maximum encoding units according to information on a size of a maximum encoding unit,
Wherein the maximum encoding unit is hierarchically divided into a plurality of encoding units having a depth according to the reduction information,
The encoding unit of the current depth is one of the square data units divided from the encoding unit of the higher depth,
Wherein the coding unit of the current depth is divided into coding units of lower depth independently of the surrounding coding units when the reduction information indicates that the coding information is divided at the current depth,
Wherein at least one prediction unit is obtained from the coding unit of the lower depth when the reduction information indicates that the reduction information is not divided at the lower depth.

Images