AU2015203385B2

AU2015203385B2 - Method and apparatus for encoding video and method and apparatus for decoding video by considering skip and split order

Info

Publication number: AU2015203385B2
Application number: AU2015203385A
Authority: AU
Inventors: Min-Su Cheon; Hae-Kyung Jung; Il-Koo Kim; Sun-Il Lee; Jung-Hye Min
Original assignee: Samsung Electronics Co Ltd
Current assignee: Samsung Electronics Co Ltd
Priority date: 2010-01-14
Filing date: 2015-06-19
Publication date: 2016-06-23
Anticipated expiration: 2031-01-13
Also published as: AU2015203386B2; AU2015203387B2; AU2015203383A1; AU2015203383B2; AU2015203385A1; AU2015203387A1; AU2015203386A1

Abstract

Abstract A method of encoding a video includes: determining coding units having a tree structure including coding units of coded depths and determining encoding modes for the coding units of the coded depths by performing encoding based on coding units according to depths, the coding units according to depths obtained by hierarchically splitting the maxinium coding unit as a depth deepens: and outputting information indicating an order of split information and skip mode information which is selectively determined for the coding units according to depths, and information about the encoding modes for the coding units of the coded depths including the split inftonnation and the skip mode information which are arranged according to the order.

Description

Title of Invention: METHOD AND APPARATUS FOR ENCODING VIDEO AND METHOD AND APPARATUS FOR DECODING VIDEO BY CONSIDERING SKIP AND SPLIT

ORDER

[1] The present application is a divisional application from Australian Patent Application No. 2011205940, the entire disclosure of which is incorporated herein by reference.

Technical Field [la] Apparatuses and methods consistent with exemplary embodiments relate to encoding and decoding a video.

Background Art [2] As hardware for reproducing and storing high resolution or high quality video content is being developed and supplied, a need for a video codec for effectively encoding or decoding the high resolution or high quality video content is increasing. In a related art video codec, a video is encoded according to a limited encoding method based on a macroblock having a predetermined size.

Disclosure of Invention Technical Problem [3] Exemplary embodiments provide encoding and decoding of a video by considering a skip and split order of a coding unit according to characteristics of a data unit.

Solution to Problem [4] According to an aspect of an exemplary embodiment, there is provided a method of encoding a video by considering a skip and split order, the method including: splitting a picture into a maximum coding unit including coding units being data units in which the picture is encoded; for the maximum coding unit, determining coding units having a tree structure including coding units of coded depths and determining encoding modes for the coding units of coded depths by performing encoding based on coding units according to depths, the coding units according to depths obtained by hierarchically splitting the maximum coding unit as a depth deepens and the depths being proportional to a number of times the maximum coding unit is split; and outputting information about a maximum coding unit size and, for the maximum coding unit, information indicating an order of split information and skip mode information which is selectively determined for the coding units according to depths, information about the encoding modes for the coding units of the coded depths including the split information and the skip mode information which are arranged according to the order, and encoded video data.

Advantageous Effects of Invention [5] Coding units having the tree .structure are formed by determining coding units having an optimum shape and an optimum .size for each maximum coding unit, based on the size of the maximum coding unit and the maximum depfo determined considering characteristics of the current picture. Also, since encoding may be performed on each maximum coding unit by using any one of various prediction modes and transformations, an optimum encoding mode may 1b« determined considering characteristics of the coding- unit of various image sizes.

[61 An order of skip mode information pd spirt infoimatton are determined by considering a data unit, an encoding mode, or the like. Also, the order of the skipmode information and the split information may be determined by considering a total bit number of the skip mode information and the split information, and a frequency of occurrence of a skip mode in encoding and decoding of video data. Since the order of the skip mode information and the split ihforinatibh :bf Pddijjg .«flits, according to depths may be set, encoded data transmission efficiency may be further improved.

Brief Description of Drawings [7] FIG. 1 is a block diagram of an apparatus for encodinga video, according to an exemplary embodiment; [81 FIG. 2 is a block diagram of an apparatus for decoding a video, accofoing to an exemplary embodiment; [9 j FIG. 3 is a diagram for describi ng a concept of coding units according to an exemplary embodiment; [10] FIG. 4 is a block diagram of an image encoder based on coding units according to an exemplary embodiment; [11] FIG, 5 is a block diagram of'an image decoder based on coding niiits: according to an exemplary embodiment; [12] FIG. 6 is a diagram illustrating deeper coding units according to depths, and a prediction unit according to an exemplary embodiment;.

[13] FIG. 7 is a diagram, for describing a relationship between a coding-unit and transformation units, according to an exemplary embodiment; [14] FIG. 8 is a diagram for describing encoding .Information, of coding units corresponding to a coded depth, according to an exemplary embodiment; [15] FIG, 9 is;a diagram. Of deeper coding units according to; depths, according to an exemplary embodiment; [16] FIGS, 10 through 12 are diagrams for describing a relationship between coding units, prediction units, and transformation units, according to an exemplary embodiment; [17] .FIG, 13 is a diagram for describing a relationship between a coding unit, a prediction unit or a partition, and a transformation unit, according to encoding mode information of Table 1; [18] FIG. 14 is a flowchart illustrating a method of encoding a video, according to an exemplary embodiment; [19] FIG. 15 is a flowchart illustrating a method of decoding a video, according to an exemplary embodiment; [20] FIG. 16 is a block diagram illustrating an apparatus for encoding a video by considering a skip and split order, according to an exemplary embodiment; [21] FIG. 17 is a block diagram illustrating an apparatus for decoding a video by considering a skip and split order, according to an exemplary embodiment; [22] FIG. 18 illustrates coding units according to coded depths in a maximum coding unit, according to an exemplary embodiment; [23] FIGS. 19 through 21 are flowcharts illustrating methods of encoding and decoding skip information and split information, according to various exemplary embodiments; [24] FIG. 22 is a flowchart illustrating a method of encoding a video by considering a skip and split order, according to an exemplary embodiment; and [25] FIG. 23 is a flowchart illustrating a method of decoding a video by considering a skip and split order, according to an exemplary embodiment.

Best Mode for Carrying out the Invention [25a] According a first aspect, the present invention provides a method of decoding a video, the method comprising: receiving a bitstream of encoded video; extracting, from the bitstream, split information of a coding unit in a maximum coding unit of a picture; and when the split information indicates a split for a current depth, splitting a coding unit of the current depth, independently from neighboring coding units, into coding units of a lower depth, and when the split information indicates a non-split for the current depth, determining at least one partition from the coding unit of the current depth and decoding the coding unit of the current depth by performing a prediction based on the at least one partition, wherein, when skip information for the coding unit of the current depth indicates a skip mode, the coding unit of the current depth is decoded by performing a prediction in the skip mode based on a partition having a size equal to a size of the coding unit of the current depth; and when the skip information for the coding unit of the current depth does not indicate the skip mode, the coding unit of the current depth is decoded by performing a prediction in a prediction mode indicated by prediction mode information obtained from the bitstream.

[26] There may be provided a method of encoding a video by considering a skip and split order, the method including: splitting a picture into a maximum coding unit including coding units being data units in which the picture is encoded; for the maximum coding unit, determining coding units having a tree structure including coding units of coded depths and determining encoding modes for the coding units of coded depths by performing encoding based on coding units according to depths, the coding units according to depths obtained by hierarchically splitting the maximum coding unit as a depth deepens and the depths being proportional to a number of times the maximum coding unit is split; and outputting information about a maximum coding unit size and, for the maximum coding unit, information indicating an order of split information and skip mode information which is selectively determined for the coding units according to depths, information about the encoding modes for the coding units of the coded depths including the split information and the skip mode information which are arranged according to the order, and encoded video data.

[27] A coding unit may be characterized by a maximum size and a depth. The depth denotes the number of times a coding unit is hierarchically split, and as the depth deepens, deeper coding units according to depths may be split from a maximum coding unit to a minimum coding unit. A depth of the maximum coding unit may be an uppermost depth, and a depth of the minimum coding unit may be a lowermost depth. Since sizes of coding units according to depths decrease as the depth of the maximum coding uni t deepens, a coding unit of an upper depth may include: a plurality of coding units of lower depths.

[28] According to; a: maximum size of a coding uni t, image data of a current picture may be split into maximum coding units, and each of the maximum coding units may include coding units split according to depths. Since a maximum coding unit is split according to depths, image data: of a; spatial domain included tp the·maximum coding unit may be hierarchically classified according to depths.

[29] A maximum depth and a maximum size of a coding unit, which limit, a total number of times a height and a width of the hiaximum coding unit are hiemrchmaliy split, may be predetermined, [30] The order of the split information and the skip mode information which is selectively determined for the: coding units according to depths may be determined by at least one of an image sequence tti which the coding Units according to depths-belong, a slice, a slice type according to a prediction direction, and a quantization parameter of a data unit.

[31] The order of the split information and the skip mode information which is; selectively determined for the coding units according to depths may be determined by the depths of the coding units in the maximum coding unit.

[321 The order of foe^ spht mformatiofi anti (he skip mode information of the coding units according to depths may be determined in such a manner that if a coding unit is the maximum coding unit, the skip mode information precedes fo© split .information, and if the coding unit, is not the maximum coding unit, the split information precedes the skip mode; information.

[33] There may be provided a method of decoding a video by considering a skip and split order, foe method including: receiving and parsing a bitstream of encoded video data; extraeting. froin the bitstream, information about a maximum size of a coding unit being adata unit in'which a picture isdecoded, information about an order of split information and skip mode information about coding units according to depths, and, according to the order of the split information and foe skip mode information, information about a coded depth and an encoding mode and encoded video data according to a maximum coding unit of foe picture; and based on foe extracted information about the maximum size of foe aiding unit and the information about the coded depth and the encoding mode, decoding the encoded video data of the picture aeemtingfo coding units having a tree structure ineluding coding units of coded depths.

[34] The extraeting may include: if a coding unit is the maximum coding unit, according to the order of foe split .information and the skip mode information, determining whether the maximum coding unit is predicted in a skip mode according: to the skip mode information he tore determin mg whether the maximum coding unit is split according to the split information; it'rhc coding unit is not the maximaitt coding:unit, determining whether the coding unit is split according to the split information before determining whether the coding unit is predicted in a skip mode according to the skip mode information; and extracting the infefmation about (he coded depth and the encoding mode of the coded jfcpth and the encoded video data according to coding units of the coded depth.

[35] In the extracting, if Onepiece of split and skip information obtained by comb in ing the split information and the skip mode information for coding unit according to depths is extracted, the coding units according to depths may be predicted is a skip mode without being split, and if the split ffiformatton Or the skip mode information for the coding extracted, the coding units according to depths may not he split or may not be predicted in a skip mode.

[361 There may be provided anapparatus for encoding a video by considering a skip and split order, the apparatus including: a maximum coding unit splitter which splits a picture into a maximum coding; unit, including;coding units being data units in which the picture is encoded; a coding unhand encoding mode determiner which, for the maximum coding unit, determines eoding units having a tree structure including coding units of coded depths and determines encoding modes lor the coding units of the coded depths by performing encoding based on the coding units according to depths, the coding units according to depths obtained by hierarchically splitting the maximum coding unitvak a depths deepens; and an output unit which outputs information about a maximum coding unit size and, for the:maximum coding unit, information indicating an order of split information and skip mode information which is selectively determined for: the coding Units according to depths, information about; the encoding modes of the coding units of the coded depths including the split information and the skip mode information which are artanged : according; to the order, and encoded video data, [371 There may be: provided an apparatus for decoding: a video: by considering: a skip and split order, the apparatus including: a receiver which receives and.parses a bitstream of encoded video data: a data extractor which 'extracts, from the bitstream,: information, about a maximum size of a coding unit being a data unit in which a picture, is decoded, information about aft Order of split information and skip mode information of coding units according to depfos, and, according to the order of the split information and the skip mode mforrmttfon, Information abouta coded depth and an encodingmode according to amax&mim.eodiftg' unit of the :|deture; and a decoder which, based on the information about the maximum size of the Coding unit and the information about the coded depth and the encoding mode, decodes the encoded video data of the pic ture according to coding units having a tree structure including coding units of coded depths, 1381 There may be provided a computer-readable recording medium having embodied thefoxm a program for executing the encoding method. Also, according to an aspect of another exemplary embodiment, there is provided a computer-readable recording medium having embodied thereon a program for executing the decoding method.

Made for the Invention [39] An apparatus for encod i ng a video, an apparatus for decoding a video, a method of encoding a video, and a method of decoding a video according to exemplary embodiments will be explained with reference to FIGS. 1 through 23. Encodingand decoding of a video based on a spatially hierarchieal ihita unit accprdmgfo one or more exemplary embodiments will he explained with reference to MGS. 1 through 15, and encoding and decoding of a video consideri ng an order of skip and split according to one or more exemplary embodiments will be explained with reference to MGS. 16 through 23, [40] Exemplary embodiments will now be described more hilly with reference to the accompanying drawings.

[4 t J Hereinafter, a 'coding unit' is an encoding-data unit in which the image data is encoded at an encoder side, for example an encoding apparatus including a processor and ail encoder, and an encoded data: unit in which the encoded image data is decoded at adecoder side;,:: for example a decoding apparatus including:: a processor and a decoder, according to the exemplary embodiments·, [42] Hereinafter, an 'image' may denote a still image for a video or a moving image, that is, the video itself, [43] Ah apparatus for encoding a Video, an apparatus for decoding a video, a method of encoding a video:, and a method of decoding a video according to exemplary embodiments will be explained with reference to FIGS. 1 through 15.

[44] FIG. I is a block diagram of an apparatus 100 for encoding a video, according to an exemplary embodiment, [45] The apparatus 100 includes a maximum coding unit splitter: 110, a coding unit.: determiner 120, and an output Unit 130, [46] The. maxi mum coding unit splitter 110 may split a current picture based on a maximum coding unit for the current picture of an image, If the current picture is larger than the maximum, coding unit] image data of the current picture may be split into the at least erne maximum coding unit. The maximum coding unit according to an exemplary embodiment may be a data unit having a size of 32x32, 64x154, 128x128, 256x256, etc., wherein a.'.shape, of the: data unit is a .square having a width: and length in squares of 2, The image data may be output to the coding unit detenninef 120 accoMing to the at least one maximum coding unit, [47] A coding unit according to an exemplary embodiment may be characterized, by a maximum size and; a depth. The depth denotes a number of times the coding unit in spatially split from the maximum coding unit, and as the depth deepens or increases,; deeper codi ng units according to depths may be spl it from the maximum coding unit to a minimum coding unit, A depth of the maximum coding unit is an uppermost depth and adepth of the minimum coding unit is a lowermost depth. Since a size of a. coding unit corresponding to each depth decreases as the depth of the maximum coding unit deepens, a coding unit corresponding to art upper depth may include a plurality of coding units corresponding to lower depths.

[48] As described above, the image data of the current picture is split into the maximum coding units according to a maximum size of the coding unit, and each of the maximum coding units may include deeper coding units that are split accopling to depths. Since the maximum coding unit according to an exemplary emhedhmentis split according to depth s, the image data of a spatial domain included in the maximum coding: unit may be hierarchically classified according to depths.

[49] A: niaximum depth and a maximum size of a coding unit, which limit the total number of times a height and a width of the maximum coding unit are hierarchically split may be predetermined.

[50] The coding unit de terminer 120 encodes at least one split region Obtained by splitting a region of the maximum coding umt according to depths, and determines a depth to output a finally encoded image data according to the at least one split region,. In other words, the coding unit determiner 120 determines a coded depth by encoding the image data in the deeper coding units according to depths, according to the maximum coding unit, of the current picture, and selecting a depth having the least encoding error. Thus, the encoded image data of the coding unit corresponding to the determined coded depth are finally output. Also, the coding units conesponding to the coded depth may be regarded as encoded coding units, [51] The determined coded depth, and the encoded image data according to the determined coded depth are output to the ou tput unit 130.

[52] The image data in the maximum: coding unit % encoded based on the: deeper coding uni ts: corresponding to at least one depth equal to or below the maximum depth, and results of encoding the image data are compared based on each of the deeper coding units, A depth having the least encoding error may be selected after comparing encoding errors .of the deeper coding units. At least one coded depth may he selected for each maximum coding unit, 153 j 1'he size of the maximum coding unit is split as a coding unit is hierarchically split according to depths,: and as: the number of coding units Increases. Also, even if coding unity corresponding to same depth in one; maximum, coding unit, each of the coding units corresponding to the same depth may be spht to aiower depth by measuring an encoding en'or of the image data, of the each coding unit, Separately. Accordingly, even When; image data is included in one maximum coding unit, the image data is split to regionsmceording to the depths, the encoding errors may differ according to regions in the one maximum coding unite, and thus the coded depths may differ according to regions in the image data. Thus, one or more coded depths may be determined in one maximum coding unit, and the image data of the maximum coding urnt may be divided according to:coding units of at least one coded depth, [54] Accordingly, the coding unit determiner 120 may determine coding units having a tree Structure included in the maximum coding unit. The 'coding rants haying a tree structure’ according to an exemplary embodiment include coding units corresponding to a depth determined to be: the coded depth, from among all deepercoding units included in the maximum coding unit. A coding unit of a coded depth may be hierarchically determined according to depths in the same region of the maximum coding unit, and may be independently determined in different regions. Similarly, a coded depth in a;emnent region may be independently determined from a coded depth in another region, [5:5] Λ maximum depth according to an exemplary embodiment is an index related to the number of splitting limes from a maximum coding unit to a minimum coding unit. A first maximum depth according to an exemplary embodiment may denote the total number of splitting times from tire maximum coding unit to the minimum coding unit, A second maximum depth according to an exemplary embodiment may denote the total number of depth levels from the maximum coding unit to the mi nimum coding unit. For example, when a depth of the maximum coding unit is 0, a depth of a coding unit, in which (he maximum coding unit is split once, may be set to 1, and a depth of a coding unit, in which the maximum coding:unit is split twice, may be set to 2. Here, if the minimum coding unit is a coding unitin which the maximum coding unit is split lour times, 5 depth levels of depths 0, 1, 2, 3 and 4 exist, and thus the first maximum depth may be set to 4, find the second maximum depth may be set to 5.

[56] Prediction encoding and transformation may be performed according to the maximum- coding unit The prediction encoding and the transformation are also performed based on the deeper coding units according to a depth equal to or depths less than the maximum depth, according to the maximum coding unit. Transformation may; be performed according to method of orthogonal transforation or integer transformation.

[57] Since the number of deeper coding units increases whenever the maximum coding unit is splif according to depths, encoding inetodtng the prediction encoding and tire transformation is performed on ail of the deeper coding units generated as the depth deepens. For convenience: of description, the prediction encoding and the transformation will now described based on a Coding unit of a current depth, in a maximum coding:unit.

[58] The apparatus 100 may variably select a size or shape of a data unit for encoding the image data. In order to encode the image data, operations, such as prediction encoding, transformation, and entropy encoding, are performed^ and at this time, the same data unit may be used for all operations or different data units may be usedforeach operation, [ 59] For example,.the apparatus 100 may select not only a coding unit for-encoding the image data, but also a data unit different from the coding unit so as to perform the prediction encoding on the image data in the coding unit.

[60] In order to perform prediction encoding in the maximum coding unit, the prediction encoding may be performed based on a cod ingun it corresponding to a coded depth;: i.e., based on a coding unit that is no longer split to coding units corresponding to a lower depth. Hereinafter, the coding unit that is no longer split and becomes a basis unit for prediction encoding will now be referred to as a 'prediction unit’. Λ partition obtained by splitting the prediction unit may include a data unit obtained by splitting at least oiie of a height and a width of the prediction unit [61] For example, when a coding unit of 2Nx2N (where N is a positive integer) is no longer split and becomes a prediction unit of 2Nx2N, and. a size of a partition may; be 2Nx21s[,.2NxN, Nx2N* or NxN, Examples of a partition type include symmetrical partitions that are obtained by symmetrically splitting a height or width of the prediction unit, partitions Obtained by asymmetrically splitting the height or width: of the prediction unit,, such as If nor η; 1, partitions that are obtained by geometrically splitting the predictionunit, and partitions having arbitrary shapes.

[62] A prediction mode Of the prediction unit may beat least One of an infra mode, a inter mode, and a skip mode, For example, the intfa mode Or the inter mode may be performed on the partition of 2I%2N, 2NxN, Nx2N, or hixN, .Also; the skip mode may be pertbrmed only on the: partition of 2Nx2N, The encoding is independently performed on one: prediction unit in a coding unit, thereby selecting a prediction mode having a: least, encoding error, [63] The apparatus 100 may also perform 'the transformation on the image data in a coding unit based not only on the coding unit for encoding the image data, but also based on a data unit that is: different from the coding unit, [64] in order to perform the transformation in the coding unit, the transformation may be performed based on a data unit having a me smaller titan or equal to the coding unit. For example, the data Unit for the; transformation may include a data unit for an infra mode and a data unit ft» an inter mode.

[65] A data, uni t used as a base Of the transformation will now be referred to as a 'transformation unit’. A transformation depth indicating the number of splitting times to reach the transformation unit by splitting the height and width of the coding unit may also be set in the transformation unit. For example, in a current coding unit of 2Nx2N, a transformation depth may be 0 when the size of a translormation uni t is also 2Nx2N, may be 1 when each of the height and width of the euiTent coding unit is split into two equal parts, totally split into 4s transformation units, and the size of the transformation unit is thus NxN, and may be 2 when each of the height and width of the current coding unit is split into four equal parts, totally split into 4- transformation units and the size of the transformation unit is thus N/2x.N/2, For example, the transformation unit may be set according to a hierarchical tree structure, in which a transformation unit of an upper transformation depth is split into four transformation units of a lower transformation depth aeeoiding to the hferarehical characteristics of a transformation depth.

[66] Similarly to the coding unit, the transformation unit in the coding unit may be recursively split into smaller sized regions, ^;tihat.the.::fraB$f#featidn. unit may be determined independently in units of regions. Thus, residual data in. the coding unit may be divided according to the transforinadon havfog the tree structure according to transformation depths.

[67] Encoding information according to ceding units corresponding to a coded depth requires not only information about the coded depth.butaiso information related to prediction encoding and transformation. Accordingly, tile coding unit determiner 120 not only determines a coded depth having a least encoding error, but also determines a partition type in a: prediction unit, a prediction mode according to prediction units, and a size: Of a transformation: unit for transformation.

[68] Coding units according to a tree structure in a maximum coding unit and a method of determining a partition,, according to exemplary embodiments , will be described tin detail later with reference to FIGS. 3 through 12.

[69] The coding unit determiner 120 may measure an encoding error of deeper coding units: according to depths by using; Rate-Distortion Optimization based on. Lagrangian multipliers, [70] The output unit 130 outputs the image: data of the m axi mum coding unit, which is encoded based on the, at,least one codeddepth determined by the; coding unit determiner 120, and information about the encoding mode according to the coded depth, in bitstreams.

[711 The encoded image data may be obtained by encoding residual data of an image, [72] The information about the encoding mode according to coded depth may include information about the coded depth, about the partition type in the prediction unit, die prediction mode, and the size of the transformation unit.

[73] The information about the coded depth may be defined by using split information according to depths, which indicates whether encoding is performed on coding units of a lower depth instead of a current depth. If the current depth of the current coding unit is the coded depth:*. image data in the current coding unit is encoded and output, and thus the split information may be defined not to spli t the current coding unit to a lower depth. Alternatively, if the current depth of the current taxiing unit is not the coded depth,, the encoding is performed on the coding unit of the lower depth, and thus the split information may be defined to split the current coding unit to obtain the coding units of the lower depth. £74] If the current depth is not the coded depth, encoding is performed on the coding unit that is split into the coding unit of the lower depth. Since at least one coding unit of the lower depth exists in one coding unit of the current depth, the encoding is repeatedly performed on each coding unit of the lower depth, and thus the .encoding may be recursively: performed-for the coding units having tire same depth.

[75] Since the coding units having a tree sttTietufe are determined for one maximum coding unit, and information about at least One encoding-mode is determined for a coding unit, of a coded depth, information about at least one encoding mode may be de* termined for one maximum coding unit,- Also, a coded depth of the image data of the maximum coding unit may be different, according to locations since the image data is hierarchically split according to depths,· and thus information about the coded depth and the encoding mode may be set lor· the image data.

[76] Accordingly, the output unit 130 may assign, encoding information about a corresponding coded depth and an encoding mode to at least one of the coding unit, the prediction unit, and a minimum unit included 'in the maximum coding unit.

[77] The minimum unit according to an exemplary embodiment is a rectangular data unit obtained by splitting the minimum coding unit constituting the lowermost: depth by 4. Alternatively, the minimum unit may be a maximum rectangular data unit that may be |ηρ1ΐφ4·'ίΛ.'Λ.οί the coding units, prediction units, partition units, and transformation units included in the maximum coding unit.

[78] For example, the encoding infbmiation output through the output unit 130 may be classified into encoding infbnnation according to coding units, and encoding: in-fdtmaiion according to prediction units. The encoding information aceording to the coding: units may include the information about the prediction mode and about the size of the partitions. The encoding information according to the prediction units may include information about an estimated direction of an inter mode, about a reference image index of the inter mode, about a motion Sector, about a chroma component of an intra mode, and about an interpolation method of the inha mode. Also, information about a maximum size of the coding unit defined according to pictures,, slices, or GOPs, and information about a maximum depth may be inserted into SP$ (Sequence Parameter Set) or a header of a bitstream.

[79] in the apparatus lOQ, the deeper coding unit may be a coding unit obtained by dividing a height or width of a coding unit of an upper depth by two. In other words, when the size of the coding unit of the current depth is 2Nx2N, the size of the coding unit of the lower depth is -NxN. Also, the coding unit of the current depth having the size Of 2NX2bi may include maximum 4 of the coding unit of the lower depth.

[ 80] Accordingly, the apparatus 100 may form the coding units having the tree structure by determining coding units having an optimum shape and an optimum size for each maximum coding unit, based on the size of the maximum, coding unit and the maximum depth determined considering characteristics: of die current picture. Also, since encoding may he performed on each maximum coding unit by using any one of various prediction modes and transformations, an optimum encoding mode may be determined considering characteristics of the .coding unit of various image sizes, [81] Thus, if an image, having high resolution :or large data amount is encoded in a conventional macrrihlock, it number of macroblrfcks per picture excessively increases. Accordingly, a number of pieces of compressed information generated for each macroblock increases, and thus it; is: difficult to transmit the compressed information and:data compression efficiency decreases. However, by using the apparatus ΓΟΟ, image:compression efficiency may be increased since :a coding unit is adjusted while considering characteristics of an image while increasing a maximum size of a coding unit while considering a size of the image, [ 82] FIG. 2 is a block diagram of an apparatus 200 for decoding a-video, accordingto an exemplary embodiment.

[83] The apparatus 200 includes a receiver 210, an image data and encoding inftirmation extractor 220·, and an image data decoder 230. Defi nitions of various terms, such as a Coding unit, a depth, a prediction unit, a tfansfOiTnation unit, and information about various encoding modes, for various operations of the apparatus 200 are identical to those described with reference to.FIG. 1 and the apparatus 100.

[84] The receiver 210 receives and parses a bitstream of an encoded video, The image data and encoding information extractor 220 extracts encoded image data for each coding unit from the parsed bitstream, wherein the coding uni^Mve-a.--ttee.stractuti& according to eachand outputs the extractedimage data to the image data decoder 230. The image data and encoding .information extractor 220 may extract information about a maximum size of a coding unit of a current picture, from a header about the current picture or SPS.

[85] Also, the image data and encoding information extractor 220 extracts information about a coded depth a encoding mode for the coding units having a tree structure according to each maximumcoding unit, from the paired bitstream. The extracted information about th^ coded depth and the encoding mode is output to the image data decoder 230. In other words, the image data in a bit stream is split into the maximum coding unit so that the image data decoder 230 decodes the image data tor each maximum coding unit [86] The information about the coded depth and the encoding mode according to the maximum coding unit m<^ be set for information about at least one coding unit corresponding to the codeddepth, and information about an encoding mode may include information about a pafotfon type of a corresponding coding unit, corresponding to the coded depth, about a predimipn mode, and a size of a transformation unit. Also, Splitting informatiop according to depths may be extracted as the information about the coded depth, [87] The information about the coded depth and the encoding mode according to each maximum coding unit extracted by the image data and encoding information extractor 220 is deformation about a coded depth and an encoding mode determined to generate a .minimum encoding error when an encoder, such astbeapparatus 100, repeatedly performs encoding; for each deeper coding unit according to depths according to each maximum coding1 unit. Accordingly, the apparatus 200 may restore an image by decoding the image data iaecording to a coded depth and an encoding mode that generates the minimum encoding error.

[88] Since encoding information about the coded depth and the encoding mode may be assigned to a predetermined data unit from among acorresponding coding unit, a prediction unit, and a minimum unit, the image data and encrxlinginf ormatkm extractor 220 may extract the information about the coded depth and the encoding mode itocording to the predetermined data units. Thepredelermined data units to which the same information about the coded depth and the encoding mode is assigned may be inferred to be the data units included in the same maximum coding unit.

[89] The image data decoder 230 restores the currant picture by decoding the image dam in each maximum coding unit based on the information about the coded depth and the encoding mode according to the maximum coding units. In other words, the image data decoder 230 may decode the encoded image data based on the extracted information about the partition type, the prediction mode, and the transformation unit for each coding: unit from among the coding; units having the tree structure included· in each maximum coding trait. A decoding process may include a prediction including intra prediction and motion compensation, and a inverse transformation, inverse transformation m ay be performed aecordi ng to method of inverse orthogonal txansfdrmation or inverse integer transformation.

[90 i The image data decoder 230 may perform intra prediction or motion compensation accoiding to a partition and a prediction mode of each coding unit, based on the information about the partition type and the prediction mode of die prediction unit of the coding unit according to coded depths, [91] Also, the image data decoder 230 may perform inverse transformation according to each transformation unit in the coding unit, based on the information about the size of the transformation unit of the coding unit according to coded depths, so as to perform the inverse transformation according to maximum coding units.

[92] The image dfea decoder 230 may determine at least one coded depth of a current maximum coding unit by using split information acedtding to depths. If the split in-formation indicates that image data.is.hp lh' the current depth, the current depth is a coded depth. Accordingly, the image data decoder 230 may decode encoded data of at least one coding unit corresponding to thereach coded depth in; fee current maximum coding unit by using the information about fee partition type of fee prediction unit, the prediction mode , and the; size of fee transformation unit for each codihg unit eorrespohding to fee coded depth, and output fee image data of the current maximum coding: unit.

[93] li other words; data units containing fee encoding information including fee same split information may be gathered by observing the encoding information set psigned for the predetermined data unit from among fee coding unit, fee prediction unit, and the minimum unit* and fee gathered data un its may be: considered to be one data unit to be decoded by the image data decoder 230 in the same encoding mode, [94] The apparatus 200 may obtain information about at least one coding unit feat generates the minimum encoding error when encoding is recursively performed: for each, maximum coding; unit, and may use fee information to decode fee: current picture. In Other words, the coding units havingthe tree struct lire determined to be the Optimum coding units in each maximum coding unit may be decoded. Also, fee: maximum size of coding unit is detennined considerihg resolution and a amount of image data, [95] Accordingly, even if image data has high resold Dion and a large amount of data, fee image data may be efficiently decoded and restored by using a size of a coding umt and an encoding mode, which are adaptively determined according to characteristics of fee image data, by using information about an optimum encoding mode received from an encoder.

[96] A method of determining coding units having a tree structure, aprediction unit* and a transforma ton unit, according to an exemplary embodiment, will now be described with reference to FIGS. 3 through 13.

[97] FIG·. 3 is a diagram for describing a concept of coding units according to an exemplary embodimen t, [98] A size; of a coding unit may be expressed in width x height, and may be 64x64, 32x32,16x16, and 8x8. A coding nipt of 64x64 niay be split into paitititJns pf 64x64, 64x32,32x64, or 32x32, and a coding unit of 32x32 may be split into panitions of 32x32,32x16, 16x32, or 16x16, 'a-coding unit of 16x16 may be split into partitions of 16x1.6, 16x8, 8x16, or 8x8, and a coding unit of 8x8 may be split into partitions of 8x8, 8x4, 4x8,: or 4x4.

[99 j in video data 3 30, a resolution is 1920x1080, a maximum size of a coding unit is 64, and a maximum depth is 2. lit video data 320, a resolution is 1920x1080, a maximum size of a coding unit is 64, and a maximum depth is 3, In video data 330, a resolution is 362x288, a maximum size of a coding unit is 16, and a maximum depth is 1. The maximum depth shown in FIG, 3 denotes a total number of splits from a maximum coding unit Up a minimum decoding unit .

[1001 If a resolution is high or a data amount is large, a maximum size of a coding unit may be large so as to not only increase encoding efficiency but also to accurately reflect characteristics of an image. Accordingly, the maximum size of the coding unit of the video data 310 and 320 having the higher resolution than the video data 330 may be 64, [ 101 ] Since the maximum depth of the video data· 310 is 2, coding units 315 of the video data 310 may include a maximum coding unit haying a long axis size of 64, and coding units having long axis sizes of 32 and 16 Since depths are deepened to two layers by splitting the maximum coding unit twice. Meanwhile., since the maximum depth of the video data 330 is 1, coding units 335 of the video data 330 may include a maximum coding unit having a long axis size of 3 6, and coding units having a.long?axis size of 8 since depths are deepened to one layer by splitting the maximum-coding unit once, [1..02 ] Since the maximum depth: of the video data 320 is 3, coding uni ts 325 Of the video data 320 may include a maximum coding unit having a long axissize of 64, and coding units having long axis sizes of 32, 16, and flip depths, 3 layers by splitting the maximum coding unit three times. As a depth deepens:, detailed Information may be precisely expressed.

[103] FIG. 4 is a block diagram of an image:encoder 400 based on coding units, according to an exemplaiy embodiment.

[104] The image encoder 400 performs operations of the coding unit determiner 120 of the apparatus 100 to encode image data. In other words, an intra predictor 410. performs' intra predicfen on coding units in an intra mode, from among a current frame 405, and a motion estimator 420 and a motion compensator 425 performs inter estimation and motion compensation on coding units in an inter mode from among the current frame 405 by using the current frame 405, Shfoamference frame 495.

[105] Data output from the intra predictor 410, the motion estimator 420, and the motion compensator 425 is output as a quantized trans formation coefficient through a fransfottner 430 and a:;.q$iiidrer'440. The quantized nansformation coefficient is restored as data in a spatial domain through an inverse quantizer 460 and an inverse transformer 470, and the restored data in the spatial domain is output as the reference frame 495 after being post-processed through a deblocking unit 480 and a loop filtering unit 490. The quantized transformation coefficient may be output as a bitstream 455 through an entropy encoder 450.

[106] In order for the image encoder 400 to be applied in the apparatus 100, all elements of the image encoder 400, i.e., the infra predictor 410, the motion estimator 420, the mot ion compensator 425, the transformer 430, the quantizer 440, the entropy encoder 450, the inverse quantizer 460, the inverse transformer 470, the deblocking unit 480, and the loop filtering unit 490 perform operations based on each coding unit from among coding units having a tree structure while considering foe maximum depth of each maximum coding unit [ 107] Specifically, the infra predictor 410, the motion estimator420, and the motion compensator 425 determines partitions and a prediction mode of each; coding unit from among the coding units: having a tree structure while considering the maximum size and the maximum depth of a current maximum coding, unit, and foe transformer 430 determines foe size of the trfosformation unit in. each coding unit from among foe coding units having a tree structure.

[ 108] FIG. 5 is a block diagram of an image.decoder 500 based on coding units, according to an exemplary embodiment.

[109] A parser 510 parses encoded image data to be. decoded and information about encoding required for decoding from a bitstream 505. The encoded image data is output as inverse quantized data through an entropy decoder 520 and an inverse quantizer 530,and the Inverse quantized data is restored to image data in a spatial domain through an inverse transformer 540.

[110] An fotra predictor 550 performs intra prediction on coding:units in an intra mode with respect to foe image data in the spatial domafor and a motion compensator 560 performs motion compensation on coding unite: in an inter mode by using a reference frame 585.

[111] The image data in foe spatial domain, which passed through the intra predictor 550 and the motion compensator :560, may be output as a restored frame:595 after being post-processed through a deblocking unit 570 and a loop filtering unit 580. Also, the image data that is post-processed through the deblocking unit 550 and the loop filtering unit 580 may be output as the reference frame 585.

[ 11.2] In order to decode the image data in the image data decoder 230 of the apparatus 200, the image decoder 500 may perforin operations that are performed after the parse]' 510.

[113] In order for the image decoder500 to be app 1 Fed in the apparatus 200, all elements of the image decoder 500, i.e., die parser 510, the entropy decoder 520, the inverse quandw 530. the inversetransiormer 540., the intra predictor 550, the motion eom-pensator560, the deblocking unit 570. and Lhe kx)p filtering unit 580 perform operations based on coding units having a tree structure for each maximum coding unit.

[114] Specifically, the intra predictor 550 and the motion compensator 560 perform op-emtidna based on partitions aadrrpred&tiOM. ftiihieXct-eaeft of the coding units having a tree structure, and the inverse transformer 540 perfprrn operations based on a size of a transformation unit tor each codittg unit.

[115] FIG, 6 is a diagram illustrating deeper eoding uni ts according to depths, and partitions, according to an exemplary embodiment, [116] The apparatus 100 and the apparatus 200 use hierarchical coding units so as to consider characteristics of an image, A maximum, height, a maximum width, and a maximum depth of coding units may be adapti vely determined aecoitling to the characteristics of the image, or ritay be differently setby a user. Sizes of deeper coding units according to depths maybe determinedaccojfhng to the predetermined maximum size of the coding unit.

[117] hi a hierarchical structure 600of coding units, according to an exemplary embodiment, the maxunpin height andMjifih':pt'|he''co4iflg units are each 64, and the maximum depth: is 4. Since a depth deepens along a vertical axis of the hierarchical structure 600, a height and a width of the deeper coding unit are each split. Also, a prediction uni t and partitions, which are bases for prediction encoding of each deeper coding unit, are shown along a horizontal axis of the hierarchical structure 600, [118] In other words, a coding unit 610 is a maximum coding unit in: the hierarchical stntctiire 600, wherein,a depth is 0 and:assize, i.e,, a height by width,.is 64x64. The depth deepens along the vertical axis:, and, a coding unit 620: having: a .Size of 32x32 arid a depth of 1, a coding unit 630 having::a,:size: of 16x16 and adeptb::qf:2,;:a;coding^ 640 having a size of 8x8 and a depth of 3, and a. coding unit 650 having a size of 4x4 andvadcpthof 4 exist. The coding unit 650 having the size of 4x4 and the depth of 4 is a minimum coding unit.

[ 1 :.19] The prediction unit and the partitions of a coding unit are arranged along the: horizontal axis according to each depth . In other words, if the. coding unit 6.10 having the size of 64x64 and the depth of 0 is a prediction unit, foe prediction unit may be split into partitions include in the coding unit 610, i.e. a partition. 610 having a size of 64x64, partitions 612 having the size of 64x32, partitions 614 having the size of 32x64, or partitions 61.6 haying the size of 32x32.

[120] Similarly, a prediction unit of the coding unit 620 having the size of 32x32 and the depth of 1 may be split into partitions included in the coding unit 620, he,, a partition 620 having a size of 32x32, partitions 622 having a size of 32x16, partitions 624 having a size of 16x32, and partitions 626 haying a size of 16x16.

[121] Similarly, a prediction unit of the coding unit 630 having the size of 16x16 and the depth of 2 may be split into partitions ineluded in the coding unit 630, i.e, a partition: having a size of 16x16 included in the coding unit 630, partitions 632 having a size of 16x8, partitions 634 having a size of 8x16, and partitions 636 having a size of 8x8.

[ 1221 Similarly,, a prediction unit of the coding uni t 640- having: the size of 8x8 and the depth of 3 may he spiit into partitions included in:the coding unit 640, i.e. a partition, having :a size: of 8x8:iheluded in the coding unit: 640:, ,partitions 642 having a size of 8x4, partitions 644 having a size of 4x8, and partitions: 646 having a size of 4x4.

[ 1:23] The coding unit 650 having the size of 4x4 and the depth of 4 is the minimum coding unit and a coding timt of the lowermost depth. A prediction unit of the coding unit 650 ifs only assigned to a partition having a size of 4x4, as: opposed to being partitioned into partitions 652 having a size of 4x2, partitions 654 having a size of 2x4, and partitions 656 having a size of 2x2.

[124] In order to determine the at least one coded depth of the coding units constituting the maximum coding unit 610, die coding unit determiner 120 of the apparatus 100 performs encoding for coding units eoiresponding to each depth included in the maximum coding unit 610.

[125] A number of deeper coding units according to depths including data-in the same range and the same size increases as the depth deepens. For example, four coding units corresponding to a depth of 2 ate required to cover data that is included in one coding unit corresponding toya depth of 1. Accordingly, in older to compare encoding results of the same data according to depths, the coding unitcorresponding to the depth of 1 and four coding units ctfoespanding to the depth of 2 are each encoded.

[126] In order to perform encoding for a current depth from among the depth, a least encoding error may be selected for the current depth by performing encoding for each prediction unit in foe coding units corresponding to the current depth, along the horizontal axis oTjfoeMeraxelucal/Spmcture 600, Alternatively, foe minimum encoding error may be searched fbr by comparing the least encoding errors according to depths, by performing encoding for each depth as the depth deepens along the vertical axis of the hierandiical structure 600, A depth and a partition having the minimum encoding error in the coding unit 610 may be selected as the coded-depth and a partition type of the coding unit 610, [127] FIG. 7 is a diagram for describing a relationship between a coding unit 710 and transformation units 720. aecoiding to an exemplary embodiment.

[128] The apparatus 100 or 200 encodes or decodes an image according to coding units having sizes smaller than or equal to a maximum coding unit for each maximum coding unit Sizes of transformation units for transformation during encoding may be selected based on data units that are not larger than corresponding coding unit.

[129] For example, in the apparatus 100 or 200, if a size of the coding unit 710 is 64x64, transformation may be performed by using the transformation units 720 having a size of 32x32.

[130] Also, data of the coding unit 710 having the size of 64x64 may he encoded by performing the transformation on each of the tousformation units having the size of 32x32, 16x16, 8x8, and 4x4, which am smaller than 64x64, and then a transfomiation unit having the least coding error may be selected.

[131] FIG. 8 is adiagram for describing encoding information of coding units corresponding to a coded depth, according to an exemplary embodiment.

[132] The output unit 130 of the apparatus 100 may encode and transmit information 800 about a partition type, information 810 about a prediction mode, and information 820 about a size of a transformationunit for each coding unit corresponding: to a coded depth, as information about an encoding mode.

[133] The information 800 indicates information about a shape, of a partition obtained by splitting a predipdon unit oia cuirent coding unit, wherein the partition is a data unit for prediction encoding ώόCUirentAdding unit. For example, a current coding unit CU...0 having a size of 2Nx2N may be split info any one of a partition 802 having a size of 2Nx2M, a partition 804 haying; a size of 2NxN, a partition 806 having a size of Nx2N, and a partition 808 having a.size:of NxN. Here, the information 800 about a parti tion type is set to indicate one of the partition 804 having a size of 2NxN, .the partition 806 having a size ofNx2bi,and the partition 808 having a size of NxN

[134] The information 810 indicates a prediction mode of each partition. For example, the information 810 may indicate a mode of prediction encoding; peifortned on: a partition indicated by the information 800, i.e., an intxa mode 812, aft intermdde 814, or a skip mode 816.

[135] The information 820 indicates a transformation unit to be based on when transformation is perforated: on a current coding uniti For example, the nuns formation unit may be a first intra transformation unit 822, a second intra transformation unit 824, a first inter transformation unit; 826, or a second inter transformation unit 828.

[ 136] The image data and .encoding information extractor 220 of the apparatus 200 may extract and use the information 8(M>, 810, and 820 for decoding, [137] FIG, 9 is a diagram of deeper coding units according to depths, according to an exemplar^' embodiment.

[138] Split information may be used to indicate a change of a depth. The spilt infonmatidn indicates whether a coding unit of a current depth is split into coding units of a lower depth.

[139] Λ prediction unit 910 for prediction encoding a coding unit 900 haying a depth of 0 and a size of 2NJ3x2N_0 may include partitions of a partition type 912 having a size of 2N_.0x2N_0, a partition type 914having a size of 2Ν^.0χΗ_;0, a partition type 916 having a size of H_0x2N_0, and a partition type 918 having a size of N_0xN_0. FIG. 9 only illustrates the partition types 912 through 918 which are obtained by symmetrically splitting the prediction unit 910, but a partition type is not limited thereto, arid the partitions ofthe prediction unit. 910 may include asymmetrical partitions, partitions having a pfodeteimined shape, and partitions having a geometrical shape.

[140] Prediction encoding is repeatedly performed on erne partition having a size of 2N_0x2N j0, two petitions having a size of 2N_0xN_0, two partitions haying a size of having a size of N„0xN„.O, turearding to each partition type. The prediction encoding in an intra mode and an inter mode may be performed-on the partitions having the sizes of 2NjOx2N_0, ,2XJkN_0, and M„0xNJ3. The prediction encoding in a skip mode is performed only on the paifition having the size of 2N_0x2NJ).

[ 1411 Errors of encoding including the prediction; encoding in the partition types 912 through 918 are compared, and the least encoding error is determined among the partition types. If an encoding error is smallest in one of the partition type* 912 through 916. the prediction unit 910 may not be split into a lower depth.

[142] If the encoding error is the smallest in the partition type 918, a:depth is changed from 0 to 1 to split the partition type 91.8 in operation 920, and encoding is repeatedly performed on coding units 930 having a depth of 2 and a size of N_0xN_0 to search for a minimum encoding error.

[ 143] A prediction unit 940 for prediction encomng the coding unit 930 having a depth of 1 and a sizeof 2N_lx2N_l (=N_0xN 0) may inchide partitions of a partition type 942 haying a srz» of 2N„lx2N„X, a partition type 944 having a. size of 2N JxN.J, a partition type 946 having a size of 1SU x2N_l, and a partition type 948 having a size of N.lxN.l.

[144] If an encoding error is: the smallest in the partition type 948, a depth is changed from 1 to 2 to split the partition type 948 in operation 950, and encoding is repeatedly performed on coding units 960, which have a depth of 2 and a size of N„2xN„2 to search for a minimum erieoding error. 1145] When a maximum depth is d, split operation according to each depth may he performed up to when a depth becomes d-1, and spit information may be encoded as up to when a depth is one of 0 to d-2. in other words, when encoding is. performed up to when the depth is d-d after a coding trait corresponding to a depth of d-2 is split in operation 970, a prediction unit 990 for prediction encoding a coding unit 980 having a depth of d-1 and a size of 2K,(d-l)x2Nj;d-i) may include partitions of a partition type 992 having a size Of 2Ν Jd-i)x2hL,(d-i% a.partition type 994 haying a size of 2N_(d-l)xN_(d-l ), :a partition. type 996' haying a size of l^(d-l)x2N^(d-i)vand a partition type 998 haying: a.size: of-NjUd )xN..,(d-l), [146] Prediction encoding may be repeatedly performed on. one partition having a .size of 2M_(d-l)x2NJd-l), two partitions having;a size of 2N_(d-.l)xN_(d-1), two partitions haying a size of N_(d-l)x2NiJd- 1.), four partitions having a size of N^(d-l)xNjd-l) from among the partition types 992 through 998 to search for a partition type having a minimum encoding error· [ 1.47] Even when the partition type 998 'has the. minimum encoding error, since a maximum depth is d, a coding unit €.lL(d-1 ) having a depth of d-1 is no longer split to; a lower depth, and a coded depth for the coding units: constituting a current maximum coding: unit 900 Is determined to be d-1 and a partition type of the coding unit 900 may be determined to be N_(d- l)xK_(d-1,). Also, since the maximum depth is d and a minimum coding unit 980 having a lowermost depth of d-1 is no longer split to a lower depth, split information for a coding unit 980 is not set.

[148] A data unit 999 may be a 'minimum u'nit'·nuDi;ifttum coding unit. A minimum unit according to an: exemplary embodiment may be a rectangular data unit obtained by splitting a minimum coding unit 980 by 4, By performing the encoding repeatedly, the apparatus 100 may select a depth having the by comparing encoding errors according to depths of the coding:Utuf'900fo^i^Nrtnine a coded depth, and set a corresponding partition type and a prediction mode as an encoding mode of the coded depth.

[149] As such, , the minimum encoding errors according to depths are compared in all of the depths of 1 through d, and a depth having the least encoding error may be· determined as a. coded depth. The coded depth, the partition type of the prediction unit, and the prediction modemay he encoded and transmitted as information about an encoding mode. Also, since a coding unit is splitfrom a depth of 0 to a coded depth, only split inforiTiiation of the coded depth is set to 0, and split information of depths excluding the coded depth is set to 1, [150] The image data and encoding information extractor 220 of the apparatus 200 may extract and use the information .about'Thecoded depth and the prediction unit of the coding unit 900 to decode the partition 912; The apparatus 200 may determine a depth. in which splttinformation is 0,. as a coded; depth by using split information according to depths, and use information about an encoding mode of the corresponding depth for decoding.

[151]. FIGS. 10 through 12 afe diagrams lor describing a; relationship between coding unitS: 1010, prediction units 1060, and transfk^lEh^^bni^ilO^O, according to an exemplary embodiment.

[I|2] The coding units 1010 are coding units having: a .tree structure:, corresponding to coded depths: dptermined by the apparatus 100. in a maximum coding unit. The prediction units 1060 are partitions of prediction: units: of each of the coding: units 1010 , and the transformation units 1070 are ttansformation units of each: of the coding units 1010.

[153] When a depth of a maximum coding unit is 0 in the eoding units 1010, depths of coding units 1012 and 1054 axe 1, depths Of coding units 1.014,1016, 1018,1028, 1050, and 1052 are 2, depths of coding units: 1020,. 1022,1024, 1026,1030,1032, and 1048 are 3, and depths of coding units 10¾ 1042,1044, and 1046 are 4.

[ 154] In the prediction units 1060, some coding units 1014, 1016,1022, 1032, 1048,1050, 1052, and 1054 are split into partitions for prediction encodingt ifodlhecyyps&i partition types in the coding units 1014,1022, 1050, and 1054 have a size of 2lS[xH, parti tion types in the coding units 1016,1048, and 1052 have a size of Nx2N,: and a partition type of the coding unit 1032 has a size of Nxfi. Prediction units and partitions of the coding umts 1010 are smaller than or eejual to each codingwnit.

[155] Transformation or inverse transformation is performed on image data of the coding unit 1052 in the transformation units 1070 in a data unit that is smaller than the coding unit 1052. Also, the coding units 1014, 1016.1022,1032, 1048, 1050, and 1052m the transformation units 1070 are different from those in the prediction units 1060 in terms of sizes and shapes. In other words, the apparatuses 100 and 200 may perform intra prediction, motion estimation, motion compensation, transformation, and inverse transformation individually on a data unit in the same coding unit.

[156] Accordingly, e,needing is recursi vely performed on each of coding units havi ng a hierarchical structure in each region of a maximum eoding unit to determine an optimum Coding unit, and thus eoding units having a recursive tree structure may be obtained, Imeodxng mformafion may include split informatipn about a coding unit, information about a pardtion type, information about a prediction mode, and information about a size of fi: fransfprmatfon unit. Table 1 shows die encoding information that may be set by the apparatuses 100 and 200.

[157] Table 1 jTable J j f Table]

[ 158] The output unit 130 of the apparatus 100 may output the encoding ju&rmation about the coding;units having a tree structure, and the image data and encoding infoimatidn extractor 220 of the apparatus 200 may extract the encoding information about the coding units haying a tree structure from a received bitstream.

[159] whether a cmrent coding unit is split into coding units of a lower depth. If split information of a current depth d is 0, a depth, In which a current coding unit is no longer split into a lower depth, is a .coded depth, and thus information about a partition type, prediction mode, and a size of a transformation unit may be defined for the coded depth. If the current coding unit is split inloimatiOn, encoding is independently performed mi four split codingunits of a lower depth.

[160] A prediction mode may be one of an intra mode, an inter mode, and a skip mode. The infra mode and the inter mode may be defined in all partition types, and the skip mode is;defined only in a partition type having a size of 2Nx2N.

[161] The information about the partition type may indicate symmetrical partition types having sizes of 2Nx2N, 2NxN; 18x218, and -NxN, which are obtained by symmetrically: splitting a height or a width of a prediction unit, andasymmetrical par tition types having sizes of 2NxnU, SNxnDj nJ2x2Nv and nRx2N, which are obtained by asymmetrically splitting the height of width of the prediction unit. The asymmetrical partition types 'having the sizesof 2NxnU and 2NxnD may be respectively obtained by splitting the height of the prediction .unitin.. 1:3 and 3:1* and the asymmetrical partition types having the sizes of nLx2N and nRxlNmay be respectively obtained by splitting tire width of the prediction unit in 1:3. and 3:1 [,162] The size of the transformation unitmay beiset to be two types lit the intra mode and two types in the inter mode. In other words.,, if split information of die transformation iiiiit is 0, the Size of the ttansfornlatipn Unit may be 2Nx2N, which is the size of the current coding unit, If split: information of the- ttansfprmation unit is 1, the transformation units may be Obtained by splitting the current coding unit. Also,, if a partition type of the ciurent coding: unit having the size of 2Νχ2ΚΓ is-a symmetrical partition, type, a size of a transformation unit may be Nxbl, and if the partition type of the current coding unit is an asymmetrical partition type, the size of the transformation unit may; be :N/2xN/2, [163] The encoding information about Coding units having a tree structure may include at leastOhe of a coding unit corresponding to a coded depth, a prediction unit, and a minimum unit. The coding unit corresponding to the coded depth may include at least one of a predic tion unit and a imnimum unit containing the same; encoding information, [.164] Accordingly, it is determined whether adjacent data units are included in the same coding unit corresponding to the coded depth by comparing encoding information of the adjacent dataunits. Also, a Corresponding coding unit corresponding to a: coded depth is determined by using eneodihg; information of a. data unit, and thus a: distribution of coded depths in. a maJUHMtt coding unit may be determined.

[165] Accordingly, if a current coding unit: is predicted based on encoding .Information of adjacent data units, encoding information of data units in deeper coding units adjacent to the current coding unit may be directly referred to and used, [ 166] Alternati vely, if a current coding unit is predicted, based on encoding information of adjacent data units, data: units adjacent to the current coding unit are searched using encoded information of the data units, and the searched adjacent coding units may be referred for predicting the curiont coding unit, [167] FIG. 13 isa diagram. for describing a relationship between a coding unit, a prediction unit or a partition,.and a transfonttatiOii unit, according to encoding mode information of Table 1, [168] A maxlnmitt coding unit 1300 includes coding units 1302, 1304, 1306,1312,1314, 1316, and 1318 of coded depths. Here, since the coding unit.Til 8 is a coding unit of a coded depth, split information may be set to 0. Information about a partition type of the coding: unit 1318 having a size of 2Nx2N may be,set To,be one of a partition type 1322 havingasize bf 2Nx2N, a partition ty pe 1324 having a, size of 2N'xN, a partition type 1326 having a size of Nx2N, a partition type 1328haying a size of NxN, a paitition type 1332 having a size of 2NxnU, a partition: type 1334 having a size of 2NxnD, a partition type 1336 having a size of hLx2N, and a partition type 1338 haying a size of nRx2N.

[169] When the partition type is set to be symmetrical, i.e. the partition type 1322, 1324, 1326, or 1328, a transformation unit 1342 having a size of 2Νχ2ϊί is set if split information (TU size flag) of a tiansionnation unit is 0, and'1344 having a size of NxN is set if a TIJ size flag is 1.

[170] When the partition type is set to be -asymmetrical,. i.e„ the partition type 1332, 1334, 1336, or 1338, a transformation unit 1352 having a size of 2Nx2N is set if a TU size flag is 0, and a transformation unit 1354 having a size of N/2x.N/2 is set if a TU size flag is 1, [171] Referri tig to FIG. 13, the TU size flag is a flag having a value or 0 or 1, hut the TU size flag is not limited to 1 bit, and a transformation unit may be luerarchically split having a tree Structure while the TU size flag increases from 0.

[172] In this case, the size of a transfonnation unit that has been actually used may be expressed by using a TU size flag of a tiansformafion unit, according to an exemplary embodiment* together with a maximum size and minimum size of the transformation uni t. According to an exemplary, embodiment, the video encoding apparatus 100 is capable of encoding maximum transformation unit size information, minimum trans-foroiation unit size: inforttiation, and a maximum TU size flag. The result of encoding the maximum transfofmatibn unit size information, the minimum transformation unit Size inibrmatioh, and the maximum TU size flag may be inserted into an SPS. According to an exemplary embodiment, the video decoding apparatus 200 may decode video by using the maximum transformation unit size information, the minimum transformation unit size information, and the maximum TUsize flag.

[173] For example* if the size of a current coding unit is 64x64 and a maximum transformation unit size is 32x32, then the size of a transformation unit may be 32x32 when a TU size flag is 0, may be 16x16 when the TU size flag is 1., and may be 8x8 when the TU size flag is 2,.

[174] As another example* if the size of the current coding unit is 32x32 and a minimum transformation unit size is 32x32, then the size of the transformation unit may be 32x32 when the TU size flag is 0. Here, the TU size flag cannot be set to a value other than 0, Since the; size pf the transfonnation unit cannot be less than 32x32.

[175] As anoiher exampie, if the size of the current coding unit is 64x64 and a maximum TU size flag is 1, then the TU size flag may he 0 or :1. Here, the TU size flag cannot be set to a value Other than 0 or 1.

[176] Ihus, if it is defined that the maximum TU size flag is MaxTransformSizeindex', a minimum transformation unit size is ’MluTransftnmSize’, and size is 'RootTuSize' when the TU size flag Is 0, then a cument minimum transfomiatiQn unit size 'CnrrMinTuSize* that embe determined in a current coding unit, may be defined by Equation ί I): [177] CurrMi.ilTa^^:^.m^(MinTi^^BpttSize,. RootTuSize/ (2AMaxTransformSize Index))..........(1) [178] Compared to the current minimum transformation unit size 'CurrMinTuSize’ that can he detemunedin the current coding unit, a transformation unit size RootTuSize’ when the Tit size flag is 0 may denote a maximum transformation unit size that can be selected in the system. In Equation (1), Rm>tTuSi7.e/(2AMaxTransformSiz«fodex)‘ denotes a transformation unit size when the transformation iinit size RootTuSize1, when the TU size flag is 0, is split a number of times corresponding.-to the maximum TU size flag, and ’MnTransformSize’denotes a minimum transformation size. Thus, a smaliermtue from among 'RootTuSize/(2AMaxTransforrnSizeIndex)’ and MihTrans-formSize’ may be the current minimum transformation unit size 'Cun'MinTuSize' that can be determined w the current coding unit, [179] According to an exemplary embodiment, the maximum transformation unit size RootTuSize may vary accoiding to the type of a prediction mode.

[.180] For example, if aeurrent prediction mode is an inter mode, then ’RootTuSize1 may be determined by using Equation (2) below. In Equation,.(2), ’MaxTransforatSize’ denotes a maxiniuih transfbnnation unit size, and ’PUSize’ denotes a cut^nt prsdieto unit size, [1:81] RootTuSize— minfMaxTransformSize, PUSize).........(2) [182] That is, if the current prediction mode is the inter mode, the Uansforaiatiqn unit size 'RootTuSize1 when the TU size flag is 0, may he a smaller value from among the maximum transformation unit size and the current prediction unit size, [183] If a prediction mode of a current partition unit is an infra mode, ’RootTuSize' may be determined by using Equation (3) below. In Equation (3), ’PartitionSize' denotes the size of the current partition unit.

[184] RtxATuSize ~ min(:MaxTran.sforniSize, PartitionSize).......,...(3) [185] That is, if the current prediction mode is the infra' mode, the transformation unit size ’RootTuSize1 when the TU size flag is 0 may be a smaller value from among the maximum transformation unit size and the size of the current partition unit, [ 186( However, the current maximum transformation unit size RootTuSize’ that varies accoiding to the type of a prediction mode rn a partition unit is just an example and is not limited thereto.

[ 187] FIG. 14 is a flowchart illustrating a method of encoding a video, according to an exeniplaty embodiment.

[ 188 j ίη operation 1210, a current picture is split into at least one maximum coding unit. A maximum depth indicating the total number of possible splitting times may be: predetermined. ί 189) In operation 1220, a coded depth to output a final encoding resulthccoidiftg to at least one split region, which is obtained by splitting a region of each maximum coding unit according to depths, is determined by encoding die at least oneyplit region, and a coding unit according to a tree: structure is determined, [19()] The maximum: coding unit is spatially split whenever the depth deepens, and thus is split into coding units of a lower depth. Each coding unit may be split into coding units, of another lower depth by being spatially split independently from adjacent coding units. Encoding is repeatedly performed on each coding;unit according to depths.

[ 191J Also, a transformation unit according to partition, types haying the least, encoding error is determined for each deeper coding uni t. In: order to determine a coded depth having a minimum encoding error in each maximum coding unit, encoding errors may be measured and compared in all deeper coding: units accordingto depths.

[192] In operation 1230, encoded image data constituting the final encoding result according to the coded depth is outputibr each maxmiutn coding unit, with encoding information about the coded depth and an encodingmode, The iniormation about 1he encoding mode may include: information about a coded depth or split information, information about a partition type of a prediction unit, a prediction mode, and a size of a transformation unit. The encoded information about the encoding mode may be transmitted, to a decoder with theencoded image data.

[193] FIG, 15 is a flowchart lUu&hsaijiig $me&od Of decoding a video, according to an exemplary embodiment.

[ 194j hi operation 1310. a bitstream of an encoded video is received and parsed, [195] In operation 1320, encoded image data of a current picture ass igned to a maximum coding unit, and information about a coded depth and an encoding mode according to maximum'coding units are extracted from die parsed bitstream. Hie coded depth of each maximum coding unit is a depth having the least encoding error for the each maximum taxiing unit. coding unit, the image data is encoded based on at least one data unit obtained by hierarchically splitting the each maximum coding unit according to depths. f 196] According to the information about the coded depth and the encoding mode, the maximum coding unit may be split into coding units having a tree structure. Each coding unit of the coding units having the tree structure is determined as a coding unit corresponding to a coded depth, optimally encoded as to output the least encoding error·. Accordingly, encoding and decoding efficiency of an image may be improved by decoding each piece of encoded image data la die coding uni ts after- detennining at least one coded depth according to coding units.

[19Tj in operation 1330, the image data of each maximum coding unit is decoded based on the information about the coded depth and the encoding mode according to the maximum coding, uni ts . The decoded image data may be reproduced by a reproducing apparatus, stmedin a storage medium, or transmitted through a network,, [198] ' Encoding and .decoding of a video considering an order of skip and split :according to exemplary embodiments will now be explained with reference to: FIGS, 16 through 23.

[199] FIG. 16 is a block diagram illustrating an apparatus 14(¾) for encoding a video by considering a skip and split order, according to an exemplary embodiment, [200] .Referring to FIG, 16, the apparatus 1400 includes a maximum, coding unit splitter 1410, a coding unit and encoding mode detenniner 1420, and an output unit 1430.

[201] The apparatus 1400 of FIG, 16 may be an example of the apparatus 100 of FIG. 1, and the maximum coding unit splitter 110, the coding unit deteiminer 120, and the output unit 130 of the apparatus 100 of FIG. 1 may correspond to the maximum coding unit splitter 1410, the crkhiig unit and encoding mode determiner 1420, and the output unit 1430 of FIG, 16, respectively.

[202] The maximum coding unit splitter 1410 splits a picture of an input image into maximum coding units having predetermined sizes, and image data according to the maximum coding units is output to the coding unit and encoding mode determiner 1420.

[203] Th:e coding unit and encoding mode determiner 1420 hierarchically splits legions of each of the maximum, coding units input from the maximum coding unit splitter 141,0 as a depth deepens, and individually performs encoding based on coding units according to depths: corresponding to Split numbers tor every independent region hier-amhieally split. The coding unit and encoding mode determiner 1420 determines an encoding mode and a coded depth to output an encoding result according to each region. The encoding mode may include information about a partition, type, of a.coding unit corresponding to the coded depth, about a prediction mode, and about a size of a transformation unit.

[ 204] In order to determine an encoding mode and a coded depth to output an encoding result for every independent region of a maximum coding; unit, the coding unit and encoding mode determiner 1420 may perform encoding based on coding units aeeoiding to depths,, and may search for a coded depth having a least encoding error in original image data and an encoding mode related to the coded depth. Accordingly, the coding unit and encoding mode determiner 1420 may determine the coding units having the tree structure by determining coding units corresponding to coded depths for each maximum coding unit of the current picture [205] Information about the coded depth and the encoding mode itetemined by the coding unit and encoding mode determiner 1420 and a corresponding encoding result are output to the output unit 1430.

[206] The output unit 1430 outputs information about.a coded depth and an encoding mode according to a maximum coding unit, and encoded video data. An encoding mode includes sMjdifiode infca^ a prediction mode of a coding unit is a skip mode, and split whether the coding unit is split to a lower depth. Since a prediction mode of a coding unit may be determined in a coding unit of a eod^ depth which is not further split, skip mode information may be encoded in the coding unit of the coded depth.

[207] The output unit 1430 may selectively determine an older in which skip mode informationand split information of codi ng uni ts according to depth s are output.

[2()8] The output unit 1430 may output information indicating a selectively determined order in which skip mode information and split information are output. Accordingly, the output unit 1430 may output information about an order in which skip mode information and split information are output, the information about an encoding mode including the skip mode information and the split information which are arranged in the selectively^ternuhed order, and encoded video data.

[209] The order of the slop mode information and the split information which is selectively determined for every coding uni t according to depths may be determined according to at least one: of an image sequence to which a cixling unit con'esponding to each depth belongs, a slice, a slice type according to a quantization parameter (QP) of a data uni t.

[210] Also, the order of the skip mode information and the split information which is se lectively determined lor every'coding anil according to depths may be individually determined according to depths of coding units in a maximum coding unit.

[211] For example, the order of the skip mode information and the split information may be determined in such a manner that the ski p mode information precedes the split information for a maximum coding unit and the .split information precedes die: skip mode information for coding units of lower depths other than the maximum coding unit.

[212] The output unit 1430 may perform encoding by combining the split; information and the skip mode information as one piece of split and skip information. Also, the output unit 1430 may assign different bit numbers to the split and skip information: according to a frequency of occurrence of a combination of the split information: and: the skip mode information, [213] For example, if both split information indicating that a corresponding; coding unit is spli t and skip mode informat ion indicating that a prediction mode, of the. corresponding' coding unit is not a skip mode are encoded, the split and skip ihformatidh may be assigned one bit. Also, in cases other than the ease where both the split information indicating that the corresponding coding unit is split and the skip mode information indicating that the prediction mode of the corresponding coding unit is not the skip mode am encoded, the split and skip information may be assigned two bits and output.

[214] The output unit 1430 may not encode a transformation coefficient and prediction-related information such as a prediction direction and a motion vector, for a coding unit that is predicted in a skip mode. Selectively, the output unit 1430 inay encode motion vector predictor index information about a; prediction unit adjacent to a current coding unit. Also, the output unit 14^''tnay^oq^ut;:ti#mmudon about a maximoum size of the coding units.

[215] P IG. 17 is a block diagram illustrating an apparatus 1500 for decoding a video by considering a skip and split order, according to an exemplary embodiment.

[ 216] Referring to FIG. 17, the apparatus 1500 includes a recei ver 1510, a data extractor 1520, and a decoder 1530. The apparatus 1500 of FIG. 17 may be an example of the apparatus 200 of FIG. 2. The receiver 210, the image data and encoding information extractor 220, and the image data decider[230 of the apparatus 200 of FIG. 2 may coirespond to the receiver 1510, the data extractor 152Q, and the decoder 1530 of the apparatus 1500 of FIG. 17, respectively, [217] The receiver .1510 receives and parses a bitstream of an encoded video.

[218] The data extractor 1520 receives the parsed bitstream.-from the receiver 1510, and extracts encoded video data and information about a coded depth and an encoding: modefor each^nraximum coding unit ffoffl the bitstream Also, the data extractor 1520 may extract infoimation about a naxixnum size df:the<foding units from the bitstream. The data extractor 1520 extracts, ifoni the bitstream, information about an order of skip mode information and split information of coding units according to depths.

[219] The data extractor 1520 may read the skip mode information and the split in-formation from theinfonnation about the encoding mode based on the extracted information about the order of the skip mode information and the split information, and extract the encoded video data in coding units according to depths based on the skip mode information and the split information, [220] The order of the skipmodeinformation andthe split information may be selectively setaeeoiding to at least one of an image sequence to which a coding unit corresponding to each depth belongs, a slice, a slice type according to a prediction direction, and a QP of a data unit. Also, the order of the sMp mode infoimatiott apd' the split information may be selectively set according to depths of coding units according to depths in a maximum coding unit.

[221 ] For ex ample, if a coding unit is a maximum coding uni t, according to the order of tire skip mode information and the split information, whether the coding unit is predicted in a skip mode according to the skip mode information may be determined before determining whether the coding unit is split according to the split information. Alspylf a coding unit is not a maximum coding unit, whether the coding unit is split according to the split information may be detemtined before determining whether the coding; unit is predicted in a skip tnode acco^ to the skip mode infoniiation.

[222] The data extractor 1520 may extract one piece of split and skip infoniiation obtained by combining themode information and the split information for the Coding units according to the depths. Fry ex if one bit of split and skip information is extracted, a correspondingcoding unit may be predicted in a skip mode without being split, and if two bits of split and skip information is read, whether a corresponding coding unit is split may be determined based on the split information and whether the corresponding coding unit is predicted in a skip mode may be determined based on tire skip mode information.

[223] The data extractor 1520 may extract only the split information and the skip mode information for a coding unit that is predicted in a skip mode, and may not extract in· formation for prediction decoding such as a transformation coefficient and prediction-related information such as a prediction direction and a motion vector. Motion vector predictor index information for a coding ufotihat is predicted in a skip mode may be selectively extracted, Aceotxiingly, the decoder 1530 may perform prediction decoding on a current coding unit by borrowing motion information of a prediction unit adjacent to the current Coding unit that is predicted in a skip mode, or inforring motion information of the current coding unit from motion information of the adjacent prediction unit.

[224] The decoder 1530 decodes encoded video data according to a coding unit of at least one coded depth for every maximum coding unit of the encoded video data based on the information about the coded depth and the encoding mode.

[225] Decoded and restored video data may be transmitted to varioas terminals which may reproduce the video data or may be stored in a storage device.

[ 226] The apparatus 1400 of FIG. 16 and the apparatus 1500 of FIG. 17 may determine an order of skip mode information and split information by considering a data unit, an encoding mode, of the like. Also, the orderof the skip mode in formation and the split information may be determined by eonsidefmg a total bit number of the skip mode in formation and the split information, and a frequency of occurrence of a skip mode in encoding and decoding of video data. Since foe order of the skip mode information and the split information of coding units-according to depths may be set, encoded data transmission efficiency may be further improved.

[227] FIG. 18 illustrates codingun its acconling to coded depths in a maximum coding unit, according to an exemplary embodiment.

[22'8’j in order to explain an order in which....the data extractor 1520 reads an encoded bi tstream output from the output uni t 1430 by considering an ..order of skip mode in-fommtion and split information, a maximum coding unit 1(¾¾) is exemplary Illustrated, [229] Coding units included in the maximum coding unit 1600 include the maximum coding unit 1600 having a depth of 0, coding units 1610,1620, 1630, and 1640 haying a depth of 1, and coding units 1622,1624, 1626, and 1628 having a depth of 2, Also, the coding units 1610, 1630, and 1640 having die coded depth of 1 and the coding units 1622,1624,1626, and 1628 having the coded depth of 2 are determined as coded depths of the maximum coding un it 1600, Also, it is assumed that prediction modes of the coding units 161.0,1.630, and 1640 haying the depth of .1 are set to skip modes, and prediction modes of the coding units 1622,1624,1626, and 1628 having the depth of 2 are not set to skip modes.

[230] An example where the data extractor 1520 of the apparatus 1500 reads split, information before reading skip mode information for the maximum coding unit 1600 of a current picture will be first explained. In this example where the split information precedes the skip mode inform if the split infdrmadon is 1, split information of coding uiiits of lower depths i$ recursively read, and if the split information is 0, skip mode information of a coding unit of a corresponding depth is read.

[231 ] Accordingly, ail order in which split information and skip mode information are set or read is as follows, [232] Split information 1 about the maximum coding unit 1600, split infonnation Q: and skip information 1 about the:coding unit 1610 having the depth of 1, split information 0 about the coding unit 1620 haying the ;depth of 1, split information;0 and skip information 0 about the coding unit: 1622 haying the depth:of 2, splfinfermation 0 and the skip infonnation 0 about· the coding unit 1624 haying the depth of 2, split in formation 0 and skip information 0 about the coding unit 1626 haying the depth of 2, split information 0 and skip infonnation 0 about :the. coding unit 1628 haying.the depth of 2, split information 0 and skip information 1 about the coding unit :163()having the depth of 1, and split information (land skip information 1. about tlie coding unit: 1640 having: the depth of 1 may be sequentially read. Accordingly, a total bit: number of the split .information and the skip mode information of the maximum coding Unit 1600 is 16.

[233] Also, another example where the data extractor .1520 of the apparatus 1400 .reads skip mode information of die maximum coding unit 1600 of a current picture earlier than split information will be explained. In this example where the skip mode information precedes the split information, if the skip mode information is 1, split information of coding units having lower depths do not need to be set and if the skip mode information is 0, the split: information is set. Accordingly, ah order in which the split infonnation and the skip mode incarnation are set or read is as follows.

[234] Skip mode information 0 about the maximum coding unit 1600, skip mode information 1 about the coding unit MM having the depth of 1, skip mode information 0 and splif information 1 about the coding unit 1620 having fhedepth of 1, skip mode information 0 and split information 0 about the coding unit 1622 having the depth of:2,.. Skip imode information Oand split information 0 about the coding unit 1624 haying the depth of 2, skip mode information 0 and split information 0 about the coding: unit 1626 having the depth of 2, skip mode information 0 and split information 0 about tire coding unit 1628 having the depth of 2, skip mode information 1 about the coding unit 1630 having the: depth of '1, and skip mode information 1 about the coding unit 1640 having the depth of 1 may be sequentially read. In this case, a total bit number of the split infonnation and the skip mode information about the maximum coding unit 1600 is 14.

[235] FIGS. 19 through 21 are flowcharts illustrating methods of encoding: and decoding skip information and split information, according to various exemplary embodiments.

[236] If the output unit 1430 of the apparatus 1400 outputs an encoded bitstream in such a manner that split information precedes skip mode information according to a split first method, the data extractor 1520 of the apparatus 1500 reads encoded video data according to an order in which the skip mode infonnation and the split information are read.

[237] That is, in operation 1650, according to the split first, method, the data extractor 1520 reads split information about a maximum coding unit having a depth M0 and determines whether the maximum coding unit is split. If it is determined in operation 1650 that the maximum coding unit is not split, the method proceeds to operation 1652. In operation 1652, skip mode information is read and it is determined whether the maximum coding unit is predicted in a skip mode. If it is determined in operation 1.650 that the maximum coding unit i,s split, the method proceeds to operation 1654. In operation 1654, .split information of a coding unit having a depth of 1 is read.

Similarly, in operation 1654, it is determined whether the coding unit having the depth of 1 is split. If itis.dtetenn.ined. i»;.0g£ration 1654 that the coding unit having the depth of 1 is not split according to split information of the coding unit having the depth of 1, the method proceeds to operation 1656. in operation 1656, skip mode information Of the coding unit having the depth of 1 is read. If it is determined in operation 1654 that the coding unit having the depth of 1 is split, the method proceeds to operation 1658,

In operation 1658, split information of a coding unit having a depth of 2 is read atul it is determined whether the coding imit having the depth of 2 is split. If it is determined in operation 1658 that the coding unit having the depth of 2 is not split, the method proceeds to operation 1660. In operation 1660, skip mode infonnation of the coding unit having the depth of 2 is read. If it is determined in operation 1658 that the coding unit having thedepth of2 is split, the method may proceed to a next depth, [238] If the output unit 1430 of the apparatus 1400 outputs an encoded bitstream in such a manner that skip mode information precedes split information according to a skip first method, the data extractor 1520 of the apparatus 1500 reads encoded video data, according to ail order in which tire skip mode information and the split information are read, [239] That is, in operation 1670, according to the skip first method,: the; data extractor 1520 reads skip mode information about a maximum coding unit having a depth of 0. If it is determined from the reading that a prediction mode of the maximum coding unit is a skip mode, the decoder 1530 may decode the maximum coding unit in a skip mode. In operation 1670, if it is determined from the reading that the prediction mode of the maximum coding unh is not a skip mode, the method may proceed to operation 1672, In operation 1672, the data extractor 1520 may read split information of the maximum coding unit having the depth of 0. In operation 1672, if it is determined from the reading that thernaxiinum coding unit is not split, the decoder 1530 may decode the maximum taxiing unit. In operation 1672, if it is determined from the reading that the maximum coding unit is split, the methodproceeds to operation 1674, In operation 1674, the data extractor 1520 may read skip: mode-information of a coding unit having a depth of 1.

[240] Similarly, in operation 1674, according to toe skip mode information of the coding unit having the depth of 1, if it is determined from the;; reading that a prediction mode of the coding unit having toe depth of 1 isvtoSMp mode, the coding unit having the depth of 1 may be decoded in a. Skip mode. If it is determined from toe reading in operation 1674 that a prediction mode of the; coding unit: having the depth;qf l.ispota skip mode, the method proceeds to operation 1676, In operation 1676, split information of the-.coding unit having; the depth of 1. may be read, [.241] If toe output unit 1430 of the apparatus 1400 performs encoding: in such a manner that skip mode information precedes split information for a maxim um coding uni t : and: Split information precedes skip mode information for coding: units other than toe maxim um coding 'unit, the data extractor 1520 of the apparatus 1500 reads: encoded video data according to an order in which the skip mode information and the split Information are read.

[242] That is, in operation 1680, according to a skip first method for a maximum coding unit having a depth of 0, the data extractor: 1520 reads skip mode information about the maximum coding unit having the depth of 0, If it is determined from the reading that a prediction mode, of the maximum coding- unit is a skip mode, the decoder 1530 may decode fhe maximum coding unit in a skip mode. In operation 1680, if it is determined from the reading that the prediction mode of the maximum coding unit is not a skip mode, the method proceeds to operation 1682; In operation 1682, the data extractor 1520 may read split information of the maximum coding unit haying thedepth of 0, In. opefatf&d 1682, if it is determined front thh heading that the maximum coding unit is not split, the decoder 1530 may decode: the maximum coding unit. In operation 1682, if it is determined from the feadiflg. maximum coding unit is split, the data extractor 1520 may read split information and Skip mode information of a coding unit having a depth of 1 in opertaionS: 1684.and 1686.

[243] In operation 1684, according to a split: first method for die coding unit having the depth of 1, if it is determined^ from the -i«iuli:pg:'that the coding unit having: the depth of 1 is not split according to split information of the coding unit having the depth of 1, the method proceeds to operation 1686. In operation 1686, skip mode information of the coding unit having the depth Of I is read. In operation 1684. if it is determined from the reading that the coding unit having the depth of 1 is split, the method proceeds to operation i 688, and Split information of adodJ.ng unit, having a depth of 2 may be read. In operation 1688, if the coding unit having the depth of 2 is not split according to the split information of the coding unit having the depth of 2, the method proceeds to operation 1690. In operation 169CH skip mode information of the coding unit having the depth of 2 may be read, and if the coding unit having the depth of 2 is split, the method may proceed to a next depth.

[244] Total bit numbers of skip mode information and split information according to the exemplar embodiments of FIGS. 19 through 21 will be compat*d with one another as follows.

[245] In detail, if a maximum coding unit is encoded in a sMp mode, total bit numberxof skip.mode mfOrmtniou and split information, accoidlng to various exemplary embodiments am as shown in Table 2.

[246] Table! [Table!] [Table]

[ 247] According to a split first method of Table 2, since split information of a maximum coding unit having a depth of 0 is encoded to be O' and ship mode information of the maximum coding nnit having the depth: of 0 is encoded to be ’lithe data extractor 1520 may read two bits of skip mode information and split information i n total. AceoiOing to a skip first method of Table 2, since skip mode information of the maximum coding unit having the depth of 0 is encoded to. be l1, die data extractor 1520 may read one bit of ship mode: information in total. According to a maximum coding unit skip first;method of Table 2, since skip mode information of the maximum coding unit: having.the depth of 0 is encoded to be T, the data extractor 1520 may read only one bit of skip mode i nformation in total.

[248] in detail,. if a coding, unit having a depth of .2 is.encoded in a skip mode, total bit numbers of skip mode information and. split, information according to various exemplary1 embodiments are as shown in Table 3.

[249] Table 3 [Table 3| [Table]

[250] According to a split first method of Table 3, since split information of a maximum coding unit having a depth of 0 is encoded to be T, split information-of a coding unit having a depth of I is encoded to be 'Γ, split information of a coding unit having a depth of 2 is encoded to be Ό1, and skip mode information of the coding uni t having the depth of 2. is encoded to be; '1', the data extractor 1520 may read four bits of skip mode information and split information in total. According to a skip first method of Table: 3, since skip mode information of the maximum coding unit having the depth of 0 is encoded to be '0:', split initiation of the:maximum coding uni t having the depth of 0 is encoded to be T, skip mode infomiation of the coding unit having the depth, of 1 is encoded to be. ’O', split information of the coding unit haying the depth of 1 is encoded to be, ’f, and skip mode information of the coding Unit haying the depth of 2 is encoded to be T, the data extractor .1520 may read five bits of skip mode information and split information in total,: According to a maximum coding unit: skip first method of Table 3, since skip mode information of the maximum coding: unit having the depth of#.is encoded .to be split information of the maximum coding unit having the depth of 0. is encoded to be T, split information of the coding unit:having the depth of 1 is encoded to be T, spilt infiMThation of the codihg unit having the depth of 2 is encoded to be '0', and skip inode ihfoimation of the coding Unit haying the. depth of 2 is encoded to be T, the datadxtraetOr 1520 may read five:bits of skip mode information and split information in total, [251] As described above: with mfetpnce to FIGS. 19 through 21, by changing an order of split information and skip mode yiformatiomafotal bit number of skip mode Information about coding units according to depths may be varied. For example, if a coding unit of an upper depth is predicted and encoded in a skip mode, since split information of a coding uilif of a lower depth does not need to be encoded, if there ate many regions predicted and encoded in a skip mode, it may be advantageous in terms of a bit rate that skip mode information precedes split information. However, mail image with a small number of skip modes, it may be advantageous in terms of a bit rate that split infoimation precedes skip mode information.

[252] Accordingly, a bit rate may be adjusted by adjusting an order of split information and skip mode information according to characteristics of an image, a sequence, a data unit level such as a slice, a QP, and a slice type. Also, like in the example explained with reference to FIG. 21 where a skip first method is selected only for a maximum: coding Unit and a split first method is selected for coding units havingdepths other than the maximum coding unit, an order of split information and skip mode infomiation may be changed according to depths, [253] In the exemplary embodiment described with reference to FIG. 18, skip mode information or split Mbirnation is earlier read in units of pictures. The apparatus; 1400 of FIG. 16 and the apparatus 1500 of FIG, 17 may variably determine an order in which skip mode information and spli t information are output or read according to a data unit, a depth, a QP, and a slice type according to a prediction direction without being limited to the exemplary embodiment of FIG. 18.

[ 254] Also, split information and skip mode information may be combined and used as one piece of split and skip information. The apparatus 1400 of FIG. 1:6 and the apparatus I50G of FIG, 17 may use.split and skip information that Is assigned 1 bit. for a combination of split, information and skip mode information: having a high frequency of occurrence, and .split and skip information that is assigned :2 bits for a combination having a low frequency of occurrence.

[255] If split information precedes skip mode information, Since split information of a coding unit of a lower depth is immediately read, when Split information of a coding; unit, of a current depth is 1, a skip mode of a current coding unit is not read.. Accordingly, three combinations, that is, split information: 1, a combination of split information 0 and skip mode information 0, and a combination of split information 0 and skip mode information 1, may occur. For example, a .frequency of occurrence of the combination of split information 0 and skip mode information 1 is the highest, the combination is assigned .1 bit, and each of the split information 1 and the combination of split information 0 and skip mode information G may be assigned 2 bits.

[256] FIG, 22 is a flowchart illustrating a method of encoding a video by considering a skip and split order, according to an exemplary embodiment.

[257] hi operation 1710, .a-picture.is split into maximum coding units having predetemiined maximum sizes.

[258] In operation 172(¾ for each of coding units having a tree structure, an encoding mode about a coded depth40 output an encoding result, and a coding unit of the coded depth is determined by performing encodi ng based on coding units according to depths, according to regions obtained by MeratfciueaUy splitting the maximum coding unit as a depth deepens.

[259] Ih operation 1730;, information indicating an order of skip mode information and split information which is selectively determined for every coding unit according to depths, information about the encoding mode including the skip mode .information and the split information which are arranged according to the determined order, and encoded video data are output for every maximum coding unit [26Q] Also, one piece of combined split and skip inftemation obtained by combining the split information and the skip Rip# mfoirnation may be set. Also, a bit number of the corresponding split and skip information may he assigned based on a frequency of oc-cuiTence qf a combination of the split information and the skip mtxfe information.

[261] FIG. 23 is; a flowchart illustrating a method of decoding a video by considering a skip and split order, according to an exemplary embodiment.

[262] hi operation 1,810, a bitstream of an encoded video is received and parsed.

[263] In operation 1820, information about an order of skip mode information and split information Of coding units according to depths is and according to the order of'the: skip mod®. information and the split information,; information about a coded depth and an. encoding mode and encoded video data are extracted according to a maximum coding unit from the bitstream.

[264] Also, one piece of combined split and skip infotihation obtained by combining the split information and the skip mode information may be read. The method of decoding the video of FIG. 23 may read a combination of the split information and the skip mode information based on the split and skip information that is discriminatlyely assigned based on a frequency of occurrence of a combination of the split information and the skip mode information, [265] In operation 1830, encoded video data is decoded according to coding units having a tree structure for every maximum coding unit of encoded video data based on the information about the coded depth and the encoding mode.

[266] Exemplary embodiments can be written as computer programs and can be implemented in general-use digital computers that execute the programs using a computer readable recording medium. Examples of the computer readable recording medium inefode magnetic storage media (e.g„ ROM, floppy disks, hard disks, etc.) and optical recording media ie.g.. CD-ROMs, or DVDs). Moreover, one or more units of the apparatus 1400 and the appat-atiis 1500 can include a processor or microprocessor executing a computer program stored in a computer-readable medium, such as the local storage 220 [267] While exernplasry embodiments have been particularly shown and described above, it will be understood by those of ordinaty skill in the art that various ehanges in form and details- may be made therein without departing from the spirit and scope of the inventiye concept as defined by the appended claimSi The exemplaiy embommems should be considered in a descriptive sense only and not for purposes of limitation. Therefore, the scope of the Inventive concept is defined not by the detailed description of exemplary em bodiments but by the appended claims,: and all differences within the scope will be,construed as being included in the present invention, 1:268]

Claims

The claims defining the invention are as follows

1. A method of decoding a video, the method comprising: receiving a bitstream of encoded video; extracting, from the bitstream, split information of a coding unit in a maximum coding unit of a picture; and when the split information indicates a split for a current depth, splitting a coding unit of the current depth, independently from neighboring coding units, into coding units of a lower depth, and when the split information indicates a non-split for the current depth, determining at least one partition from the coding unit of the current depth and decoding the coding unit of the current depth by performing a prediction based on the at least one partition, wherein, when skip information for the coding unit of the current depth indicates a skip mode, the coding unit of the current depth is decoded by performing a prediction in the skip mode based on a partition having a size equal to a size of the coding unit of the current depth; and when the skip information for the coding unit of the current depth does not indicate the skip mode, the coding unit of the current depth is decoded by performing a prediction in a prediction mode indicated by prediction mode information obtained from the bitstream.
2. The method of claim 1, wherein the split information indicates whether a corresponding coding unit is split into coding units of a lower depth.
3. The method of claim 1, wherein, when the skip information for the coding unit of the current depth does not indicate the skip mode, the coding unit of the current depth is decoded by performing a prediction in a prediction mode indicated by prediction mode information, obtained from the bitstream, based on at least one partition having a size equal to or less than the size of the coding unit of the current depth.
4. The method of claim 3, wherein the at least one partition having a size equal to or less than the size of the coding unit of the current depth is obtained from the coding unit of the current depth based on partition type information obtained from the bitstream.
5. The method of claim 4, wherein the partition type information indicates one of a symmetric partition type and an asymmetric partition type.