KR101707164B1 - Video encoding and decoding method and apparatus using the same - Google Patents

Abstract

A method for decoding an image according to the present invention is a method for decoding a video, comprising the steps of: if a size of a current coding unit can include a conversion block capable of omitting conversion, Parsing the flag into information about the coding unit; Determining whether the first information is parsed based on the representative flag; If the parsing of the first information is not necessary, inferring the first information based on the representative flag and parsing the first information when parsing of the first information is necessary; And performing a transform on the transform block according to the first information.

Description

TECHNICAL FIELD [0001] The present invention relates to a video encoding / decoding method, and a video encoding /

The present invention relates to an image coding and decoding process, and more particularly, to a method and apparatus for adding / decoding an image to generate a prediction block using a current picture.

Recently, broadcasting service having high definition (HD) resolution has been expanded not only in domestic but also in the world, so that many users are accustomed to high definition and high definition video, and accordingly, many organizations are spurring development for next generation video equipment. In addition, with the increase of interest in UHD (Ultra High Definition) having resolution more than 4 times of HDTV in addition to HDTV, a compression technique for a higher resolution and a higher image quality is required.

An inter prediction technique for predicting a pixel value included in a current picture from temporally preceding and / or following pictures for image compression, an intra-picture prediction technique for predicting pixel values included in a current picture using pixel information in the current picture, An intra-picture prediction technique for predicting a short code, an entropy coding technique for assigning a short code to a symbol having a high appearance frequency and allocating a long code to a symbol having a low appearance frequency, or the like.

On the other hand, in the video decoding, a conversion omission mode may be applied to omit the conversion process in decoding the residual signal to the image. At present, the conversion skip mode can be applied to all 4x4 size transform blocks (TB) having a coded block flag (CBF) of 1. The flag (transform_skip_flag) information indicating whether or not the skip conversion mode is applied, .

The present invention provides a video encoding / decoding method and a device using the same that reduce a bit amount for signaling a conversion omission and increase a video encoding efficiency.

 In the present invention, similar patterns occur repeatedly in the screen, and when there is a frequent occurrence of a residual signal containing a large amount of high frequency, there is a possibility that the conversion skip mode is applied or not commonly applied to the conversion blocks within a predetermined unit. In this case, there is provided an image encoding / decoding method and an apparatus using the image encoding / decoding method capable of increasing a coding efficiency by signaling a flag representing whether or not the conversion is omitted.

In the method of decoding an image according to an embodiment of the present invention, when the size of the current coding unit can include a conversion block capable of omitting conversion, the first information indicating whether to omit conversion of the conversion block divided from the coding unit Parsing the representative flag representative of the coding unit into information on the coding unit; Determining whether the first information is parsed based on the representative flag; If the parsing of the first information is not necessary, inferring the first information based on the representative flag and parsing the first information when parsing of the first information is necessary; And performing or omitting a transformation on the transform block according to the first information.

Wherein the step of determining whether to parse the first information includes determining whether the representative flag is 1 and the conversion block is included in the conversion unit of the maximum depth divided from the coding unit, It is determined that parsing of the first information is unnecessary, and it is possible to deduce that the first information is omitting conversion to the conversion block.

Wherein the step of determining whether to parse the first information includes determining that parsing of the first information is not necessary when the representative flag is 1 and the size of the transform block is equal to or smaller than a maximum transform block size to which the transformation skip is applied And omitting the conversion of the first information into the conversion block.

Determining whether to parse second information indicating whether or not the conversion unit is divided based on the representative flag; If the parsing of the second information is not necessary, inferring the second information based on the representative flag, and receiving and parsing the second information when parsing of the second information is necessary; And perform the division on the conversion unit according to the second information.

Wherein it is determined that parsing of the second information is unnecessary if the representative flag is 1 and the conversion depth for the conversion unit is 0, It can be deduced that the conversion unit is divided.

Wherein the step of determining whether to parse the second information includes the step of determining whether the size of all the transform blocks included in the transform unit having the representative flag of 1, the transform depth for the transform unit being 0, It is determined that the parsing of the second information is not necessary and the second information can be inferred to be that the conversion unit is divided when the skip is larger than the maximum conversion block size to which the skip is applied.

The representative flag may be received corresponding to the prediction mode applied to the coding unit.

The representative flag may be signaled if the prediction mode of the coding unit is an intra block copy prediction mode in which motion prediction is performed in the current picture and an area similar to the current block is set as a prediction value for the current block.

Further receiving flag information indicating whether to use the representative flag to infer whether or not to omit conversion, and the flag information may be signaled in a sequence parameter set or a picture parameter set.

According to another aspect of the present invention, there is provided a method of coding an image, the method comprising: determining whether a conversion skip is applied to a conversion block that is divided from a coding unit to be coded; Coding a representative flag representative of first information indicating whether or not to omit conversion in the conversion block, and signaling the representative flag with information on the coding unit; And coding the first information when coding of the first information is required based on the representative flag.

According to an embodiment of the present invention, there is provided an image encoding / decoding method for reducing a bit amount for signaling a conversion omission and increasing image encoding efficiency and an apparatus using the same.

 According to the present invention, when a similar pattern repeatedly occurs in the screen and a residual signal including a large amount of high frequency is frequently generated, there is a possibility that the conversion skip mode is commonly applied or not applied to the conversion blocks within a predetermined unit Therefore, in this case, there is provided an image encoding / decoding method and an apparatus using the image encoding / decoding method capable of increasing the encoding efficiency by signaling a flag representing whether or not to omit the conversion.

Specifically, the effect of the present invention can be remarkably exhibited in the encoding and decoding of an artificial image produced by a computer.

1 is a block diagram showing a configuration of an image encoding apparatus according to an embodiment of the present invention.
2 is a block diagram illustrating a configuration of an image decoding apparatus according to an embodiment of the present invention.
3 is a diagram for explaining a method of decoding an image according to an embodiment of the present invention
4 is a diagram for explaining a block represented by a representative flag according to an embodiment of the present invention.
5 is a view for explaining a process of estimating a division flag with reference to a representative flag according to an embodiment of the present invention.
FIG. 6 is a diagram for explaining a representative flag applying method according to another embodiment of the present invention.
7 is a diagram for explaining a block represented by a representative flag according to another embodiment of the present invention.
8 is a view for explaining a process of estimating a segmentation flag with reference to a representative flag according to another embodiment of the present invention.
9 is a diagram for explaining an IBC prediction according to the present invention.
10 is a view for explaining a method of encoding an image according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the following description of the embodiments of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present disclosure rather unclear.

It is to be understood that when an element is referred to as being "connected" or "connected" to another element, it may be directly connected or connected to the other element, . In addition, the description of "including" a specific configuration in the present invention does not exclude a configuration other than the configuration, and means that additional configurations can be included in the practice of the present invention or the technical scope of the present invention.

The terms first, second, etc. may be used to describe various components, but the components should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, the first component may be referred to as a second component, and similarly, the second component may also be referred to as a first component.

In addition, the components shown in the embodiments of the present invention are shown independently to represent different characteristic functions, which does not mean that each component is composed of separate hardware or software constituent units. That is, each constituent unit is included in each constituent unit for convenience of explanation, and at least two constituent units of the constituent units may be combined to form one constituent unit, or one constituent unit may be divided into a plurality of constituent units to perform a function. The integrated embodiments and separate embodiments of the components are also included within the scope of the present invention, unless they depart from the essence of the present invention.

In addition, some of the components are not essential components to perform essential functions in the present invention, but may be optional components only to improve performance. The present invention can be implemented only with components essential for realizing the essence of the present invention, except for the components used for the performance improvement, and can be implemented by only including the essential components except the optional components used for performance improvement Are also included in the scope of the present invention.

1 is a block diagram showing a configuration of an image encoding apparatus according to an embodiment of the present invention. A scalable video encoding / decoding method or apparatus may be implemented by a general image encoding / decoding method or apparatus extension that does not provide scalability, and the block diagram of FIG. 1 is a scalable 1 shows an embodiment of a video encoding apparatus that can be a basis of a video encoding apparatus.

1, the image encoding apparatus 100 includes a prediction unit 110, a subtractor 125, a transform unit 130, a quantization unit 140, an entropy encoding unit 150, an inverse quantization unit 160, An inverse transform unit 170, an adder 175, a filter unit 180, and a reference image buffer 190.

The image encoding apparatus 100 may encode an input image in an intra mode or an inter mode and output a bit stream. Intra prediction is intra prediction, and inter prediction is inter prediction. In the intra mode, the switch (not shown) is switched to intra, and in the inter mode, the switch is switched to the inter-switch. The image encoding apparatus 100 may generate a prediction block for an input block of the input image, and may then code the difference between the input block and the prediction block.

The prediction unit may include an intra prediction unit for performing intra prediction, a motion prediction unit and a motion compensation unit for performing inter prediction, and an IBC prediction unit for performing intra-block copy (IBC) prediction. have. Also, the video encoding apparatus may include a switch (not shown), and the switch may be switched between the inter prediction unit, the intra prediction unit, and the IBC prediction unit.

In the intra mode, the intraprediction unit may generate a prediction block by performing spatial prediction using the pixel value of the already coded block around the current block.

In the inter mode, the motion predicting unit can find a motion vector by searching an area of the reference image stored in the reference image buffer 190 that is best matched with the input block. The motion compensation unit may generate a prediction block by performing motion compensation using a motion vector and a reference image stored in the reference image buffer 190.

The IBC predicting unit may perform motion prediction, i.e., search, in the current picture to determine an area similar to the current block, and obtain a predicted value and a block vector for the current block. The prediction by the IBC predictor is described in detail below.

The subtractor 125 may generate a residual block by a difference between the input block and the generated prediction block. The transforming unit 130 may perform a transform on the residual block to output a transform coefficient. The transforming unit 130 may be configured to omit a transform for some residual blocks. In this case, the output of the transforming unit 130 is referred to as a transform coefficient for the sake of convenience. The quantization unit 140 may quantize the input transform coefficient according to the quantization parameter to output a quantized coefficient.

The entropy encoding unit 150 entropy-codes a symbol according to a probability distribution based on the values calculated by the quantization unit 140 or the encoding parameter value calculated in the encoding process to obtain a bit stream Can be output. The entropy coding method is a method of receiving symbols having various values and expressing them as decodable binary numbers while eliminating statistical redundancy.

Here, the symbol means a syntax element to be encoded / decoded, a coding parameter, a value of a residual signal, and the like. The encoding parameter is a parameter necessary for encoding and decoding. The encoding parameter may include information that can be inferred in an encoding or decoding process, as well as information encoded and encoded in a encoding device such as a syntax element, and may be encoded or decoded It means the information that is needed when doing. The coding parameters include, for example, intra / inter prediction mode, motion / motion vector, reference picture index, coding block pattern, residual signal presence, transform coefficients, quantized transform coefficients, quantization parameters, And the like. In addition, the residual signal may mean a difference between the original signal and the prediction signal, or a signal in which the difference between the original signal and the prediction signal is transformed or a difference between the original signal and the prediction signal is transformed and the quantized signal Or a difference signal between the original signal and the prediction signal or a signal in which the difference signal between the original signal and the prediction signal is quantized. The residual signal can be regarded as a residual block in block units.

When entropy coding is applied, a small number of bits are allocated to a symbol having a high probability of occurrence, and a large number of bits are allocated to a symbol having a low probability of occurrence, so that the size of a bit string for the symbols to be coded Can be reduced. Therefore, the compression performance of the image encoding can be enhanced through the entropy encoding.

For entropy encoding, an encoding method such as exponential golomb, context-adaptive variable length coding (CAVLC), and context-adaptive binary arithmetic coding (CABAC) may be used. For example, a table for performing entropy encoding such as a variable length coding / code (VLC) table may be stored in the entropy encoding unit 150, and the entropy encoding unit 150 may store the stored variable length encoding (VLC) table for performing entropy encoding. Further, the entropy encoding unit 150 derives a binarization method of a target symbol and a probability model of a target symbol / bin, and then performs entropy encoding using the derived binarization method or probability model You may.

The quantized coefficients can be inversely quantized in the inverse quantization unit 160 and inversely transformed in the inverse transformation unit 170. For some blocks, the inverse transform unit 170 may be configured to omit the inverse transform, and in this case also, the output of the inverse transform unit 170 is referred to as an inverse transformed coefficient for convenience. The inverse quantized and inverse transformed coefficients can be added to the prediction block through the adder 175 and a reconstruction block can be generated.

The restoration block passes through the filter unit 180 and the filter unit 180 applies at least one of a deblocking filter, a sample adaptive offset (SAO), and an adaptive loop filter (ALF) can do. The restoration block having passed through the filter unit 180 may be stored in the reference image buffer 190.

2 is a block diagram illustrating a configuration of an image decoding apparatus according to an embodiment of the present invention. As described above with reference to FIG. 1, the scalable video encoding / decoding method or apparatus may be implemented by expanding a general image encoding / decoding method or apparatus that does not provide scalability, and the block diagram of FIG. 2 illustrates scalable video decoding / 1 shows an embodiment of an image decoding apparatus which can be the basis of the apparatus.

2, the image decoding apparatus 200 includes an entropy decoding unit 210, an inverse quantization unit 220, an inverse transform unit 230, a prediction unit 240, a filter unit 260, 270).

The video decoding apparatus 200 receives the bit stream output from the encoding apparatus and decodes the video stream into an intra mode, an inter mode, or an IBC mode, and outputs a reconstructed video, that is, a reconstructed video.

The video decoding apparatus 200 may generate a reconstructed block, i.e., a reconstructed block, by obtaining a reconstructed residual block from the input bitstream, generating a predicted block, and adding the reconstructed residual block to the predicted block.

The entropy decoding unit 210 may entropy-decode the input bitstream according to a probability distribution to generate symbols including a symbol of a quantized coefficient type. The entropy decoding method is a method of generating each symbol by receiving a binary sequence. The entropy decoding method is similar to the entropy encoding method described above.

The quantized coefficients are inversely quantized in the inverse quantization unit 220 and inversely transformed in the inverse transformation unit 230. As a result that the quantized coefficients are inversely quantized / inverse transformed, reconstructed residual blocks can be generated. For some blocks, the inverse transform unit 230 may be configured to omit the inverse transform. Also, the inverse quantization unit 220 may be configured to omit some blocks.

The prediction unit 240 includes an intra prediction unit for performing intra prediction, a motion prediction unit and a motion compensation unit for performing inter prediction, an IBC prediction unit for performing intra-block copy (IBC) prediction, As shown in FIG.

In the intra mode, the intraprediction unit may generate a prediction block by performing spatial prediction using the pixel value of the already coded block around the current block. In the inter mode, the motion compensation unit may generate a prediction block by performing motion compensation using a motion vector and a reference image stored in the reference image buffer 270. [

In case of IBC prediction, the IBC predictor can perform a motion prediction, i.e., a search, in the current picture to determine an area similar to the current block to obtain a predicted value and a block vector for the current block. The prediction by the IBC predictor is described in detail below.

The restored residual block and the prediction block are added through the adder 255, and the added block is passed through the filter unit 260. The filter unit 260 may apply at least one of a deblocking filter, SAO, and ALF to a restoration block or a restored picture. The filter unit 260 outputs a reconstructed image, that is, a reconstructed image. The restored image is stored in the reference image buffer 270 and can be used for inter-view prediction.

The entropy decoding unit 210, the inverse quantization unit 220, the inverse transform unit 230, the predictor 240, the filter unit 260, and the reference image buffer 270 included in the image decoding apparatus 200 The entropy decoding unit 210, the inverse quantization unit 220, the inverse transformation unit 230, the prediction unit 240, the filter unit 260, and the like, which are directly related to the decoding of the image, And can be expressed as a decoding unit or a decoding unit.

In addition, the video decoding apparatus 200 may further include a parsing unit (not shown) for parsing information related to the encoded video included in the bitstream. The parsing unit may include an entropy decoding unit 210 or may be included in the entropy decoding unit 210. Such a parsing unit may also be implemented as one component of the decoding unit.

On the other hand, in the conventional image coding method, a transform skip is applied to a block including a large number of high-frequency components to omit the conversion.

For example, when a value for a transform_skip_enabled_flag signaled at an upper end such as a picture parameter set is 1 and a value for CBF (codedblockflag) is 1 at the time of adding / decoding a residual signal, all 4x4- , TB) can be individually signaled with a flag (transform_skip_flag) indicating whether to omit conversion.

Or the value of the transform_skip_enabled_flag is 1 and the size of the current transform block is larger than the maximum block size defined by the information (for example, log2_max_transform_skip_block_size_minus2) indicating the maximum size of the transform block to which the transformation skip signaled in the picture parameter set can be applied A flag (transform_skip_flag) indicating whether or not the conversion is omitted can be individually signaled for all conversion blocks having a CBF of 1 or less.

In the case of this conversion omission signaling method, since the flag (transform_skip_flag) indicating the conversion omission is separately signaled to all conversion blocks which can be converted to CBF 1, the bit amount may increase.

Accordingly, the present invention sets information for representing whether to omit conversion of one or a plurality of conversion units included in a predetermined unit (in one embodiment, a coding unit (CU)), The present invention aims at reducing the amount of bits for signaling the omission of the conversion and ultimately increasing the image coding efficiency.

Particularly, in the case of an image in which a similar pattern is repeatedly generated in the screen or a residual signal including a large amount of high frequency is frequently generated, all conversion blocks belonging to a predetermined unit are highly likely to be converted or omitted. The encoding efficiency can be increased by signaling a flag representative of whether or not the predetermined unit of conversion is omitted, instead of signaling a flag indicating whether or not to omit conversion for each individual conversion block.

For example, in the case of an artificial image created by a computer, a repetitive similar pattern may occur or a high frequency may be included, so that the effect of the present invention can be enhanced.

In the description of the present invention, a predetermined unit is specifically described using terms of a coding unit for convenience, but the predetermined unit of the present invention is not necessarily limited to a coding unit. Meanwhile, a coding unit, a coding block (CB) used in the present invention will be described as follows.

A coding unit is composed of one coding block or a plurality of coding blocks and syntax element information used by them. In the case of a color image, since there are generally three components, one coding unit has one coding block for each component, and a total of three coding blocks (for example, an image having three components and being independently encoded for each component (For example, in the case of a monochrome image, or even if a color image is independently encoded for each component).

In addition, a transform block (TB) to which a transform is applied or to which a transform omission is applied, and a transform unit transform unit (TU) which is a unit of the dividing will be described as follows.

A transform unit (TU) according to the present invention is a unit that can be divided from a coding unit. One coding unit may be divided into one or a plurality of conversion units for transcoding, specifically how the being divided is indicated by the quad tree information with root as the coding unit. This is called splitting (split information or split_transform_flag information). The conversion unit is composed of one conversion block or a plurality of conversion blocks and syntax element information used by them. The conversion unit may have a collective concept of transform blocks constituting each color component (for example, Y, Cb, Cr), and the number of conversion blocks of one conversion unit may be determined according to the color format can be different

The conversion block corresponds to a basic unit for performing conversion and quantization.

For a color image with three components, if the color format is 4: 2: 0 or 4: 4: 4, then one conversion unit will have three conversion blocks (one is the conversion block for the luma component, And two are transform blocks for the chroma component). On the other hand, in the case of the 4: 2: 2 color format, five conversion blocks (one is a conversion block for a luma component and the remaining four are conversion blocks for a chroma component) If they are independently encoded, they can have one transform block.

On the other hand, when the color format is 4: 4: 4, the conversion blocks belonging to one conversion unit may all have the same size.

If the color format is 4: 2: 0, the size of the luma conversion block is equal to the size of the conversion unit, but the size of the chroma conversion block may be smaller than the conversion unit. That is, the size of the transform block may vary depending on the luma and chroma, even if the transform block belongs to the same transform unit. However, exceptionally, if the 8x8 coding unit is divided into a quad tree once and the transform unit has a size of 4x4, both the luma and the chroma transform block can have the same size of 4x4. This is because transform blocks that are too small (for example, smaller than 4x4) have little utility in terms of increasing complexity in real applications.

3 is a diagram for explaining a method of decoding an image according to an embodiment of the present invention. Referring to FIG. 3, a representative flag (transform_skip_all_ones_in_cu_flag) representing whether or not the conversion block is omitted for the conversion block to which the conversion is omitted according to the present embodiment, and a conversion process of the image performed according to the representative flag will be described.

First, in order to determine whether the representative flag is to be parsed for the current coding unit (CU), the decoding apparatus determines whether the representative flag parsing condition is satisfied (S310).

In the process of encoding and decoding an image, a size of a conversion block to which the conversion skip can be applied is predetermined and signaled. For example, the size of the transform block to which the transform omission can be applied is limited to 4X4, or the size of the maximum transform block to which the transform omission can be applied can be determined. Therefore, when the size of the conversion block in the current coding unit does not correspond to the size to which the conversion omission can be applied, the conversion omission itself does not occur originally. Therefore, parsing itself of the representative flag do.

In this step S310, a transform block that requires parsing of a flag (transform_skip_flag) indicating whether the size of the current coding unit satisfies a size condition to which such a conversion skip can be applied, i.e., whether or not a conversion block is skipped, And whether or not it can exist in the unit. A flag indicating whether or not to omit conversion may be represented by a translation omission flag (transform_skip_flag) or first information for convenience of explanation.

According to an embodiment of the present invention, it is possible to further receive flag information indicating whether or not the function of determining whether to omit conversion using the representative flag is used before parsing the representative flag. Flag information indicating whether or not to use the function representing the omission of conversion using the representative flag can be signaled as shown in Table 1 below, and the decoding apparatus can receive it.

In addition, when the conversion skip function itself is not used, the function of signaling on behalf of the conversion skip information becomes unnecessary. Therefore, in association with the transform_skip_enabled_flag information, which is flag information indicating whether or not to use the conversion skip function by using the representative flag , The flag information indicating whether to use the function representing the omission of the conversion using the representative flag can be signaled as shown in Table 2 below and the decoding device receives it.

In the embodiment according to Table 2, when the transform_skip_enabled_flag is 0, the transform_skip_group_signalling_enabled_flag is not signaled. In this case, the decoding apparatus deduces this value to be zero.

Flag information (transform_skip_group_signalling_enabled_flag) indicating whether or not the function of the present invention described in Table 1 and Table 2 is used can be transmitted using a predetermined parameter set ().

More specifically, it can be signaled through an extension level of a sequence parameter set or a picture parameter set, which is a higher level. For example, it may be signaled through sps_range_extension (sequence parameter set range extension), sps_scc_extension (sequence parameter set screen content coding extension), pps_range_extension (picture parameter set range extension), or pps_range_extension (picture parameter set screen content coding extension).

The operation of the transform_skip_group_signalling_enabled_flag information of the present invention disclosed in Tables 1 and 2 is as follows.

If the transform_skip_group_signalling_enabled_flag is 1, it indicates that the function representing the skip transformation is used, so that the representative flag can be signaled at the coding unit level. If transform_skip_group_signalling_enabled_flag is 0, it indicates that the function representing the translation omission is not used, or may be used in a different meaning previously set by the encoding apparatus and the decoding apparatus.

If the function of signaling on the basis of the conversion skip information is not used, the transform_skip_group_signalling_enabled_flag may not be signaled.

The representative flag according to the present invention can be signaled as shown in Table 3.

The case where the representative flag parsing condition in step S310 is satisfied with reference to Table 3 includes the following. The transform_skip_group_signalling_enabled_flag signaled in Table 1 is 1, the flag (transform_skip_enabled_flag) indicating whether or not the application of the transform omission is possible is 1, the current coding unit is not lossless coded (! Cu_transquant_bypass_flag) If the size conversion block is less than or equal to the maximum conversion block size to which the translation skip can be applied (if ((log2CbSize? MaxTrafoDepth? (ChromaArrayType% 3 == 0? 0: 1)) <= Log2MaxTransformSkipSize) It can be determined that the representative flag (transform_skip_all_ones_in_cu_flag) representing the first information to be instructed is parsed.

Here, the minimum-size conversion block that can be divided in the current coding unit includes that the conversion unit is divided into a maximum depth (MaxTrafoDepth). Also, in the expression of maximum depth, depth can mean the following. If the depth is zero, it may mean that the current coding unit is not further divided for conversion. Also, a depth of 1 may mean that the coding unit is divided into quad trees one step for conversion. At this time, if the specific transform block constituting the transform unit after the division becomes smaller than the minimum transform block size predetermined by the encoder, the transform block may not be further divided. Also, whenever the depth is increased by 1, it can be further divided into quad trees under the condition that it does not become smaller than the minimum conversion block size as described above. Further, in the description of the present invention, the depth means that the coding unit is divided for conversion, and therefore, unless otherwise specified, the term depth is used in the same meaning as the term "transform depth".

 When the representative flag parsing condition described with reference to Table 3 is satisfied, a representative flag representative of the first information indicating whether or not the conversion is omitted may be parsed (S320).

On the other hand, when the above condition is not satisfied (for example, when there is no conversion block in the current coding unit so that conversion can be omitted, or when the representative flag of the present invention is not used) It can be determined that the parsing condition is not satisfied. If the representative flag parsing condition is not satisfied and parsing is not performed, the value of the representative flag (transform_skip_all_ones_in_cu_flag) is regarded as 0 (S311) and subsequent decoding is performed (S315).

In a realization example in which flag information (transform_skip_group_signalling_enabled_flag) indicating whether or not the function of the present invention is used is signaled as described in Table 2 above, the first two conditions of the condition statement described in connection with Table 3, that is, transform_skip_group_signalling_enabled_flag is 1, Two conditions in which a flag (transform_skip_enabled_flag) indicating whether or not the application of omission can be applied are bundled in an AND condition of 1 can be substantially replaced by transform_skip_group_signalling_enabled_flag. This is because the value of transform_skip_group_signalling_enabled_flag becomes 1 as shown in Table 2 because the transform_skip_enabled_flag value is 1 only.

In Table 3, ChromaArrayType refers to the color format of the image to be decoded. ChromaArrayType can have a value of 1, 2, 3, meaning that the color format is 4: 2: 0, 4: 2: 2, 4: 4: 4. In addition, when a given image is a monochrome image or when decoding in a 4: 4: 4 color image, each color channel is separately encoded without interdependence between the color channels (i.e., information is not used in decoding on a different color channel) (Or decoded), ChromaArrayType has a value of zero. On the other hand, the expression (ChromaArrayType% 3 = = 0? 0: 1) in Table 2 means that the value is 0 when the ChromaArrayType is 0 or 3 and 1 when the ChromaArrayType is 0 or 3.

For example, if the size of the coding unit is NxN, and the minimum size of the transform block size that can be divided by the coding unit is (N / 4) x (N / 4) and the size of the maximum transform block, . &Lt; / RTI &gt; In this case, if the size of the coding unit is 64x64 (i.e., N = 64), the minimum size of the conversion block size that the coding unit can have is 16x16. Therefore, there can not be a conversion block capable of omitting conversion in a 64x64 size coding unit. Therefore, since the representative flag parsing condition in step S310 is not satisfied, parsing of the representative flag (transform_skip_all_ones_in_cu_flag) representing the first information indicating whether or not the conversion is omitted is not performed.

According to the embodiment of the present invention described with reference to Table 3, the representative flag (transform_skip_all_ones_in_cu_flag) may represent the first information of the transform block. That is, according to the representative flag parsing condition of S310 described with reference to Table 3, the representative flag (transform_skip_all_ones_in_cu_flag) of the present invention is a flag indicating whether or not the transformed skip_all_ones_in_cu_flag is equal to or smaller than the maximum transform block size, Lt; RTI ID = 0.0 &gt; 1 &lt; / RTI &gt;

According to another embodiment of the present invention, the representative flag (transform_skip_all_ones_in_cu_flag) may be configured to represent only the first information of the luma conversion block. That is, the representative flag may represent first information indicating whether to omit conversion of the luma conversion block in the coding unit (i.e., the first information of the chroma conversion block is not represented). At this time, the representative flag from the encoding apparatus to the decoding apparatus can be signaled as shown in Table 4. [

Referring to Table 4, when the transform_skip_group_signalling_enabled_flag signaled in Table 1 or Table 2 is 1, the flag (transform_skip_enabled_flag) indicating whether or not the application of the translation omission is possible is 1, the current coding unit is not lossless encoded (! Cu_transquant_bypass_flag) (If ((log2CbSize? MaxTrafoDepth) < = Log2MaxTransformSkipSize) &lt; / RTI &gt; if the size of the minimum size luma conversion block that can be divided in the current coding unit is smaller than or equal to the maximum conversion block size It can be determined that the representative flag (transform_skip_all_ones_in_cu_flag) representing the first information of the luma conversion block among the first information to be parsed is not satisfied. On the other hand, when all the above conditions are not satisfied, If the representative flag is not parsed, the representative flag transf orm_skip_all_ones_in_cu_flag) is assumed to be 0 (S311), and subsequent decoding is performed (S315).

If the representative flag is parsed through step S320 and the value is 1 (S330), the decoding apparatus decodes the representative flag to determine whether the first information represented by the representative flag is to be applied (i.e., , It is determined whether the parsing omission condition of the first information is satisfied (S340). Since there may be conversion blocks (including luma conversion blocks and chroma conversion blocks) of various sizes that can be applied to the conversion omission in the coding unit that performs the current decoding, depending on each realization example, This is because it is possible to represent the first information with respect to the block.

First, the first information parsing omission condition of S340 for the realization example associated with Table 3 may be whether or not the current transform block to be decoded corresponds to a transform unit of the maximum depth (MaxTrafoDepth) at which the coding unit performing the current decoding is divided .

If it is determined in step S340 that the transform block to be decoded corresponds to the transform unit of the maximum depth (MaxTrafoDepth), the decoding apparatus does not parse the first information on the transform block to be decoded and does not parse the first information (S350). &Lt; / RTI &gt;

That is, when the step S340 is satisfied, the decoding apparatus judges that the conversion skip is applied to the conversion block included in the conversion unit of the maximum depth divided from the coding unit, and judges that the parsing of the first information which is the conversion skip flag is not necessary have. Of course, at this time, the size of the conversion block must satisfy the basic condition that is equal to or smaller than the maximum conversion block size that can be omitted. For example, if the size of the maximum conversion block to which the conversion skip can be applied is 4x4, the color format of the encoded image is 4: 2: 0, and the conversion unit of 8x8 size, which is the conversion unit of the maximum depth divided by the coding unit of 32x32 size, Suppose you are decrypting a unit. At this time, the current conversion unit has a 8x8 luma conversion block and a 4x4 chroma conversion block. At this time, since the 8x8 luma conversion block is larger than the maximum conversion block size that can be omitted, there is no need to judge whether or not the conversion is omitted. However, since the chroma conversion block is 4x4 in size, it is necessary to determine whether or not the conversion is omitted, and the first information on these can be inferred through a representative flag (i.e., a value of 1) without parsing.

 Also, the CBF of the current transform block must satisfy the condition of 1. That is, it must be a transform block to be encoded. Since the coded residual signal of CBF 0 is not coded because the coded residual signal of the region included in the corresponding block is regarded as 0, the use of the conversion and translation omission itself is unnecessary and it is not necessary to determine whether or not the conversion is omitted.

Table 5 shows the syntax structure for the conversion skip flag (transform_skip_flag) selectively signaled from the encoding apparatus to the decoding apparatus in the embodiments using the representative flags of the present invention.

According to the embodiment that refers to Table 5, the representative flag may represent the conversion omission flag of the conversion blocks that satisfy the first information parsing omission condition (S340). Therefore, the decoding apparatus can determine whether to parse the individual conversion skip flag by judging the first information parsing skip condition when the representative flag is 1.

The first information parsing omission condition is such that the representative flag transform_skip_all_ones_in_cu_flag is 1 and the conversion block is included in the conversion unit of maximum depth divided from the coding unit (log2TrafoSize == Max (2, log2CbSize? MaxTrafoDepth? (ChromaArrayType% 3 == 0 ? 0: (cIdx? 1: 0)))). If the parse skip condition is satisfied, the first information of the transform block to be currently decoded is not parsed, but may be set to 1 (transform_skip_flag [x0] [y0] [cIdx] = 1).

The conditional application of S340 is basically a block to which the conversion skip function used in the existing technology can be applied (for example, a conversion block to be currently decoded is a conversion block equal to or less than the maximum conversion block size to which the conversion skip is applied, The conversion block having information (i.e., CBF = 1)) is the same as the existing technology, so redundant description thereof is omitted here.

According to this embodiment, the representative flag may represent the omission of conversion of the transform block belonging to the division unit of the maximum depth that can be divided from the current coding unit.

According to the embodiment described with reference to Table 4, that is, according to the embodiment in which the representative flag represents only the first information of the luma conversion block, the syntax structure for the translation omission flag transmitted from the encoding apparatus to the decoding apparatus is shown in Table 6 .

According to the embodiment with reference to Table 6, the representative flag may represent a translation omission flag of luma conversion blocks satisfying the first information parsing omission condition.

The first information parsing omission condition according to Table 6 is that the representative flag transform_skip_all_ones_in_cu_flag is 1, the luma conversion block (cIdx has 0), the conversion block is included in the conversion unit of the maximum depth divided from the coding unit (log2TrafoSize = = Max (2, log2CbSize? MaxTrafoDepth)). If this condition is satisfied, the first information of the luma conversion block currently being decoded is not parsed and may be set to 1, which is a value which means to omit conversion (transform_skip_flag [x0] [y0] [cIdx = 0] = 1) .

Other descriptions of this embodiment are the same as those of the above-mentioned realization example and thus will be omitted.

According to the present embodiment, the representative flag may represent the omission of conversion of the luma conversion block belonging to the maximum depth division unit that can be divided from the current coding unit.

4 is a diagram for explaining a block represented by a representative flag according to an embodiment of the present invention.

Assuming that the conversion skip is applied to a conversion block of the size from 4X4 to 16X16, in the case of a 16X16 coding unit, a representative flag representative of the conversion block included in the 4X4 conversion unit divided into the maximum depth can be signaled.

That is, in FIG. 4, it is assumed that the coding unit of 16X16 is divided into the conversion units having the maximum depth, and the conversion of the encoded conversion block included in the 4X4 conversion unit corresponding to the maximum depth is omitted, Signaling. In Fig. 4, blocks shown in gray represent conversion units including conversion blocks represented by representative flags.

According to the embodiments so far, the representative flag may represent a conversion omission of the conversion block belonging to the division unit of the maximum depth which can be divided from the current coding unit, or a division unit of the maximum depth that can be divided from the current coding unit It can represent the omission of conversion of the luma conversion block to which it belongs. However, according to another embodiment of the present invention, the representative flag may be used to represent omission of conversion of the conversion unit having a certain depth instead of the conversion unit having the maximum depth. This can be easily realized by modifying and implementing step S340 of FIG. This realization example is shown in Fig.

The representative flag according to this embodiment can be signaled as shown in Tables 3 and 4, and when the representative flag is parsed, the decoding apparatus can determine whether or not the first information is parsed based on the representative flag.

If the representative flag is 1 (S630), the decoding apparatus decodes the first information indicating whether or not the conversion block included in the conversion unit to be divided from the coding unit to be divided is parsed without converting the conversion block (or the luma conversion Block) can be estimated as 1 (S650).

If the representative flag is 0, the decoding apparatus parses the first information on the conversion block and skips the conversion according to the parsed value (S660) (if the first information is 1), performs the conversion (S680) If the first information is 0), subsequent decoding is performed.

That is, the decoding apparatus determines that the block of the encoding conversion block (or the luma conversion block in the other realization) included in the coding unit is not larger than the size of the maximum conversion block to which the conversion omission can be applied, It is determined that parsing of the first information for the block is not necessary, and the first information can be deduced to be 1. [

According to the present embodiment, without considering the conversion depth, a conversion block (or a coded conversion block having a block size capable of omitting the conversion) satisfying the condition that the conversion can be omitted in the coding unit being decoded Blocks) can be represented.

Table 7 shows the syntax structure of the signals transmitted from the encoding apparatus to the decoding apparatus in this realization example.

Referring to Table 7, if the representative flag (transform_skip_all_ones_in_cu_flag) is 1, the first information can be set to 1 without being parsed (transform_skip_flag [x0] [y0] [cIdx] = 1).

That is, in accordance with the present embodiment, the decoding apparatus does not parse the individual conversion skip flags even in the case of the conversion blocks to which the skip conversion can be applied when the representative flag is 1.

FIG. 7 is a diagram for explaining a block represented by a representative flag according to an embodiment of the present invention. As shown, a 16x16 coding unit can be divided into 16x16, 8x8 and 4x4 conversion units. Assuming that the conversion skip is applied to the conversion blocks of size 4X4 to 16X16, the conversion skip may be applied to all conversion units having a size of 16x16, 8x8, and 4x4. The blocks shown in gray in Fig. 7 represent conversion units including conversion blocks to which representative flags are applied. That is, when the representative flag is signaled as 1, the conversion skip can be applied to the coded conversion block included in the conversion unit divided in the 16x16 coding unit.

If a 16x16 coding unit is divided into 8x8 conversion units and not additionally divided, the representative flag can represent all of the conversion omissions of the conversion blocks included in each of the 4 8x8 conversion units.

If the first information is deduced to be 1, the decoding apparatus can perform the subsequent decoding without performing the conversion process for the conversion block for which the conversion is skipped by the first information, i.e., omitting the conversion (S660 ).

If the representative flag is 0 in step S630, the decoding apparatus parses the conversion skip flag individually for the conversion block according to the existing method (S670).

That is, if the representative flag is 0, a series of processes for parsing the transform_skip_flag of each transform block is performed in a conventional manner. That is, the first information is parsed for each transform block for which the transform_skip_flag signaling is required.

If the representative flag (transform_skip_all_ones_in_cu_flag) does not exist, the representative flag can be regarded as 0.

According to the first information, the transform block may be transformed, and the transform may be omitted. A conversion process according to whether or not the conversion is omitted and a subsequent decoding process may be performed (S680, S660).

Another realizing example of the present invention is to provide a luma conversion block which satisfies a condition capable of omitting the conversion in the coding unit being decoded (for example, a coded conversion block having a block size capable of omitting conversion) Can be represented by the conversion skip flag.

Table 8 shows the syntax structure of the signals transmitted from the encoding apparatus to the decoding apparatus in this realization example.

According to Table 8, for a luma conversion block (cIdx has a value of 0) when the representative flag is 1, the decoding device outputs first information indicating whether or not the luma conversion block included in the conversion unit to be divided from the coding unit is omitted, The transform_skip_flag [x0] [y0] [cIdx = 0] = 1) can be inferred as 1 without parsing the first information (S650).

If the representative flag is 0, the decoding apparatus parses the first information on the luma conversion block and skips the conversion according to the parsed value (S660) (if the first information is 1) or performs the conversion (S680) (If the first information is 0), and performs subsequent decoding.

That is, when the representative flag of the encoded luma conversion block included in the coding unit is not larger than the size of the maximum conversion block to which the conversion omission can be applied and the representative flag has a value of 1, It is determined that the parsing of the first information is not necessary, and the first information can be deduced to be 1. Other descriptions of this embodiment are the same as those of the above-mentioned realization example and thus will be omitted.

According to the present embodiment, the representative flag may represent the omission of conversion of the luma conversion block belonging to the maximum depth division unit that can be divided from the current coding unit.

Alternatively, the representative flags may represent the omission of translation of the translation block for an individual channel. In this case, a representative channel may be displayed in the representative flag. For example, when representing a luma block, the representative flag may be signaled as transform_skip_all_ones_in_cu_luma_flag, or signaled as transform_skip_all_ones_in_cu_chroma_flag if it represents a chroma block. Of course, when the color channel is RGB, a representative flag representing all channels may be signaled, and a representative flag representing each color R, G, B may be signaled.

Referring back to FIG. 3, if the first information is found to be 1 in step S350, the decoding apparatus does not perform a conversion process on the corresponding conversion block, that is, skips the conversion and performs subsequent decoding (S360).

If the representative flag is 0 in step S330, or if the first information parsing skip condition of S340 is not satisfied, the decoding apparatus parses the conversion skip flag individually for the conversion block according to the conventional method (S370).

That is, if the representative flag is 0, a series of processes for current transform_skip_flag signaling is performed in a conventional manner, which means that the first information is signaled for each transform block in which the transform_skip_flag signaling is required.

If the representative flag (transform_skip_all_ones_in_cu_flag) does not exist, the representative flag can be regarded as 0.

According to the first information, the transform block may be transformed, and the transform may be omitted. A conversion process according to whether or not the conversion is omitted and a subsequent decoding process may be performed (S360, S380).

Since the conversion is performed in the decoding process, the conversion is an inverse transform, which is an inverse process of the conversion performed by the encoding device. However, since the inverse transform 7 is also a kind of conversion, There will be no confusion in what you do.

5 is a view for explaining a method of decoding an image according to another embodiment of the present invention. Specifically, FIG. 5 is a diagram for explaining a process of inferring a division flag with reference to a representative flag.

Step S510 and step S530 in Fig. 5 are similar to step S310 and step S330 in Fig. 3, so duplicate descriptions will be omitted. That is, the representative flag according to the present embodiment represents the omission of conversion of the conversion block belonging to the division unit of the maximum depth that can be divided from the current coding unit, and whether or not the conversion unit is divided based on such representative flag can be determined .

When the representative flag is parsed, the decoding apparatus can determine whether to parse the second information (split_transform_flag) indicating whether or not the conversion unit is divided based on the representative flag. As a result of the determination, if the parsing of the second information is not necessary, the second information may be inferred based on the representative flag, and the second information may be parsed when parsing of the second information is necessary.

If the representative flag is 1, the decoding apparatus can determine whether the conversion depth for the conversion unit is 0 (S540).

If the conversion depth for the conversion unit is 0, the decoding apparatus can infer the second information to 1 without parsing the second information for the conversion unit having the conversion depth of 0 (S550).

In other words, if the step S540 is satisfied, the decoding apparatus does not need to parse the second information (split_transform_flag indicating whether or not to divide the conversion depth 0? 1) indicating whether or not the conversion unit having the same size as the size of the coding unit is divided .

At this time, the size of the current coding unit must satisfy the condition that the divided conversion unit can be obtained. For example, if the size of the minimum conversion unit is set to 8X8, and the size of the current coding unit is 8X8, then the current coding unit can not have a divided conversion unit, so that it does not need to be determined whether or not to divide.

Table 9 shows a syntax structure in which the coding apparatus signals the second information to the decoding apparatus according to the present embodiment.

Referring to Table 9, if the representative flag (transform_skip_all_ones_in_cu_flag) is 1 and the conversion depth is 0 (trafoDepth = 0), the second information can be set to 1 without being parsed (split_transform_flag [x0] [y0] [trafoDepth] = 1).

If the second information is inferred as 1, the decoding apparatus performs division on the conversion unit (S560) and may perform subsequent decoding (S580).

On the other hand, for a conversion unit whose conversion depth is not 0, the second information (split_transform_flag indicating the division other than the conversion depth 0? 1) is parsed to determine whether or not the conversion unit is divided as in the conventional method.

If the representative flag is 0 in step S530, or if the conversion depth of the conversion unit is not 0 in step S540, the decoding apparatus parses the second information according to the existing method to determine whether the conversion unit is divided (S570).

If the second information is parsed, the transform block may be segmented (S560), and the segmentation may be omitted, so that the decoding device may perform a subsequent decoding process (S580).

To summarize this embodiment, when the representative flag is 1, since the coding unit can be divided up to the maximum conversion depth, it is inferred that the division unit is divided without signaling the division flag for the conversion unit having the conversion depth of 0.

8 is a view for explaining a process of estimating a segmentation flag with reference to a representative flag according to another embodiment of the present invention.

As shown in FIG. 8, FIG. 8 differs from FIG. 5 in most of the steps, and when the representative flag is 1, only the step S840 of determining the second information to be 1 is different. Duplicate description is omitted.

According to step S840, the decoding apparatus determines whether the size of the conversion unit having the conversion depth of 0, that is, the conversion unit having the same size as the coding unit, is a size to which the conversion omission can not be applied.

As a result of the determination, if the size of the conversion unit is a size to which the conversion skip can not be applied (i.e., the size of all the conversion blocks corresponding to the conversion unit having the conversion depth of 0 is larger than the maximum size of the conversion blocks, The decoding apparatus can infer the second information to 1 (S850) without parsing the second information (split_transform_flag indicating that the conversion depth 0? 1 is divided) to the conversion unit having the conversion depth of 0.

In another realization, in the case where the size of the next conversion unit after the one-step quad-tree division of the conversion unit according to the second information inferred to 1 is a size at which the conversion skip can not be applied, The second information (split_transform_flag) may be further parsed so that the second information is again parsed as one. This additional configuration is limited to a predetermined number of times such as once or twice, or the size of the next conversion unit after the conversion unit is once again subjected to one-stage quad-tree division according to the second information inferred to 1 is applied It can be configured to be repeated until reaching a possible size.

On the other hand, if the conversion depth of the conversion unit is not 0 or if the conversion depth is 0, if the size of the conversion unit is such that the conversion skip can be applied, the second information (split_transform_flag) .

The syntax structure for the second information transmitted from the encoding apparatus to the decryption apparatus according to the present embodiment is shown in Table 10.

Referring to Table 10, when the representative flag transform_skip_all_ones_in_cu_flag is 1 and the size of the conversion unit is a size to which the conversion omission can not be applied (Max (2, log2TrafoSize? (ChromaArrayType% 3 = = 0? 0: 1))> Log2MaxTransformSkipSize ), The second information may be set to 1 without being parsed (split_transform_flag [x0] [y0] [trafoDepth] = 1).

On the other hand, according to another embodiment of the present invention, the representative flag described above may be applied corresponding to the prediction mode applied to the coding unit. That is, it can be determined whether signaling of the representative flag corresponds to the specific prediction mode applied to the coding unit.

For example, the proposed representative flag may be signaled only when the prediction mode of the coding unit is a predetermined prediction mode that is predetermined.

For another example, the proposed representative flag may be signaled if the prediction mode of the coding unit is an intra mode or an IBC prediction mode. In this case, the decoding apparatus can parse the representative flag only when the prediction mode is the intra mode or the IBC prediction mode. Or a prediction mode for the screen content, or if the prediction mode of the coding unit is limited by signaling which defines a particular mode, then a representative flag may only be signaled for that prediction mode.

The IBC prediction is a prediction method that can be used when the same (or similar) region or object exists in the current picture, and the decoding apparatus can generate a prediction value for the current block using the IBC mode.

9 is a diagram for explaining IBC prediction according to an embodiment of the present invention.

In IBC prediction, a specific area in the current picture can be used as a reference block of the current block, and a block vector (hereinafter referred to as &quot; BV &quot; ) Can be used.

In the case of the conventional inter prediction, the reference picture is a previous picture or a subsequent picture different from the current picture. In the case of IBC prediction, the reference picture is a current picture, and the block vector indicates a vector indicating a reference block in the current picture.

As shown, according to an embodiment of the present invention, a region existing in a coding tree unit (CTU) adjacent to a current prediction block in a current picture may be selected as a reference block of a current prediction block.

When carrying out the IBC prediction, the area for the search of the reference block may be limited or set to a specific area. According to one example, the reference block may be limited to being searched in the current CTU to which the current prediction block belongs or in the left CTU adjacent to the current CTU.

Conversely, when performing IBC prediction, it may also be possible to extend an area for the search of a reference block to all areas in the current picture that have been decoded before the current coding unit.

The type of prediction block in which IBC prediction is performed may be 2Nx2N, 2NxN, Nx2N, NxN.

BV can be derived from the BV predictor and BV difference similar to the motion vector.

The BV predictor for the current block can be coded at the encoder and signaled to the decoder, and BV of a block previously predicted in IBC mode within a particular area, e.g., the current CTU, can be used as a predictor, The BV of the predicted block in the IBC mode among adjacent blocks may also be used as a predictor.

At this time, since there is a need to reset or refresh the data in the middle of image processing, the BV predictor for each CTU can be initialized to an initial value such as (-2 * w, 0) or (-w, 0). Here, w may be the width of the current coding unit.

The BV difference value indicates the difference between the BV and BV predictors and can be coded in the encoder as a BVdx, BVdy value and signaled to the decoder.

In the case of the realization example in which the representative flag is signaled only when the above-described IBC prediction mode is applied, the syntax for signaling to the decoding apparatus by the coding apparatus at the coding unit level according to the present invention can be expressed as shown in Table 11. [

Referring to Table 11, at the coding unit level, when the transform_skip_group_signalling_enabled_flag and transform_skip_enabled_flag are 1, not the lossless image coding (! Cu_transquant_bypass_flag), and the IBC prediction is applied (intra_bc_flag [x0] [y0] have. Further, the decoding apparatus can parse the representative flag when such a series of conditions is satisfied.

Of course, the condition ((log2CbSize? MaxTrafoDepth? (ChromaArrayType% 3 = = 0? 0: 1)) == Log2MaxTransformSkipSize) may be satisfied if the current coding unit may include a conversion block smaller than the size of the maximum conversion block to which the conversion skip is applied The representative flag (transform_skip_all_ones_in_cu_flag) may be received or parsed.

Table 11 can be applied to the embodiment described with reference to Figs. 3 to 8 above. For example, the representative flag parsing condition in S310 of FIG. 3 is a case where the transform_skip_group_signalling_enabled_flag and the transform_skip_enabled_flag are 1, not the lossless image coding (! Cu_transquant_bypass_flag), and the IBC prediction is applied (intra_bc_flag [x0] [y0] Can be included. 3, the transform_skip_group_signalling_enabled_flag is not signaled. If the transform_skip_group_signalling_enabled_flag is 1, the representative flag parsing condition of S310 in FIG. 3 is 1, and the transform_skip_group_signalling_enabled_flag is 1, (! Cu_transquant_bypass_flag), and when the IBC prediction is applied (intra_bc_flag [x0] [y0]).

10 is a view for explaining a method of encoding an image according to an embodiment of the present invention.

First, the encoding apparatus determines whether or not the conversion omission is applied to the conversion block that is divided from the coding unit to be coded (S1010).

As a result of the determination, the representative flag representing the first information indicating whether or not the conversion is omitted is encoded in the conversion block to which the conversion skip is applied while satisfying the predetermined condition described with reference to Figs. 3 and 6, Signaling with information on the coding unit (S1020).

The encoding apparatus is configured so that a basic condition under which conversion skipping can be applied among the conversion blocks corresponding to the conversion unit of the maximum depth divided from the coding unit (i.e., the size of the conversion block is equal to or smaller than the maximum conversion block size to which the conversion skip is applied If the conversion skip is used for all conversion blocks that satisfy the condition that the conversion coefficient should be present (i.e., CBF is 1), the representative flag can be coded as 1. [

Alternatively, in the case where, among the conversion units included in the conversion unit divided from the coding unit, the conversion skip is used for all the conversion blocks satisfying the basic condition to which the skip conversion can be applied, the encoding device can code the representative flag with 1 .

If the representative flag is 1 (S1030), coding of the first information is skipped for the conversion block satisfying the above conditions, and coding of the first information is performed for the conversion block requiring coding of the first information (S1040).

The encoding apparatus may also determine whether to code second information indicating whether or not the conversion unit is divided based on the representative flag.

If the representative flag is 1 and the conversion depth for the conversion unit is 0, it may be determined that coding of the second information is not necessary. If the representative flag is 1, the conversion depth for the conversion unit is 0, Is larger than the maximum transform block size to which the transform omission is applied, it may be determined that coding of the second information is not necessary. In this case, for the conversion unit having the conversion depth of 0, the second information may not be coded.

The encoding apparatus codes the second information indicating whether or not to divide a division unit other than the division unit in which the conversion depth is 0-1, which requires coding of the second information (S1050).

Steps S1040 and S1050 may be performed sequentially, but may be performed independently of each other, and coding for the second information may be performed first. That is, the order of the steps after the representative flag is coded is not limited to that shown in the drawings.

If the representative flag is 0, the first information and the second information are coded according to the existing coding scheme and signaled (S1060).

As described above, according to the present invention, when the size of the current coding unit is such that the conversion skip can occur, the representative flag representing the conversion skip flag is signaled for each coding unit to reduce the bit amount, A method for increasing the coding efficiency and an apparatus using the same are provided.

In the above-described embodiments, the methods are described on the basis of a flowchart as a series of steps or blocks, but the present invention is not limited to the order of steps, and some steps may occur in different orders or in a different order than the steps described above have. It will also be understood by those skilled in the art that the steps depicted in the flowchart illustrations are not exclusive and that other steps may be included or that one or more steps in the flowchart may be deleted without affecting the scope of the invention You will understand.

The above-described embodiments include examples of various aspects. While it is not possible to describe every possible combination for expressing various aspects, one of ordinary skill in the art will recognize that other combinations are possible. Accordingly, it is intended that the invention include all alternatives, modifications and variations that fall within the scope of the following claims.

100: Image encoding device 110:
130: conversion unit 140: quantization unit
150: an entropy encoding unit 160: an inverse quantization unit
170: inverting section 180: filter section

Claims (15)

A method of decoding an image,
Determining whether a size of a transform block in a coding unit being decoded is smaller than or equal to a transform block size to which a transform omission can be applied;
Parsing information indicating whether or not to omit conversion of the conversion block according to the determination, and performing or omitting conversion of the luma conversion blocks of the conversion block; And
Using as a prediction block for a current prediction block a block indicated in a current picture as a vector, the block being a block in the current picture. 2. The method of claim 1, wherein an area existing in a coding tree unit (CTU) adjacent to the current prediction block in the current picture is used as a prediction block of the current prediction block. The method as claimed in claim 1, wherein a current CTU (coding tree unit) to which the current prediction block belongs or a current CTU (coding tree unit) neighboring the current CTU is used as a prediction block of the current prediction block A method of decoding an image. 2. The method of claim 1, wherein an area decoded before the current coding unit in the current picture is used as a prediction block of the current prediction block. The method according to claim 1,
Wherein the vector is derived from a vector predictor and a vector difference value. 6. The method of claim 5,
Wherein the vector difference value indicates a difference between the vector and the vector predictor, and the vector difference value is coded in an encoder and signaled to a decoding apparatus. 2. The method of claim 1, wherein the specific region in the current picture used as the prediction block is indicated by the vector received from the encoder. A method of decoding an image,
Determining whether the size of the transform block is less than or equal to the transform block size to which the transform skip can be applied;
Parsing information indicating whether the conversion block is omitted in accordance with the determination;
Performing or omitting conversion for the transform block according to the information; And
Using as a prediction block for a current prediction block a block indicated in a current picture as a vector, the block being a block in the current picture. 9. The method of claim 8, wherein the specific region in the current picture used as the prediction block is indicated by the vector received from the encoder. A method of decoding an image,
Parsing information indicating whether or not to omit conversion of the transform block being divided from the current coding unit;
Performing or omitting conversion for the transform block according to the information;
Using as a prediction block for a current prediction block a block indicated in a current picture as a vector, the block being a block in the current picture,
Wherein the step of parsing the information indicating whether or not the conversion block is omitted in the step of parsing the information indicating whether or not the conversion block is to be omitted is performed when the flag indicating whether or not the conversion skip is applicable is 1 and the current coding unit is not lossless coded, And parsing the information indicating whether the conversion is omitted if the conversion block size is smaller than or equal to the applicable conversion block size. 11. The method of claim 10, wherein the specific region in the current picture used as the prediction block is indicated by the vector received from the encoder. A method of decoding an image,
Determining whether a size of a transform block in a coding unit being decoded is smaller than or equal to a transform block size to which a transform omission can be applied;
Parsing information indicating whether or not to omit conversion of the conversion block according to the determination, and performing or omitting conversion of the luma conversion blocks of the conversion block; And
And using the specific region in the current picture indicated by the vector received from the encoder as a reference block for the current prediction block. A method of decoding an image,
Determining whether the size of the transform block is less than or equal to the transform block size to which the transform skip can be applied;
Parsing information indicating whether the conversion block is omitted in accordance with the determination;
Performing or omitting conversion for the transform block according to the information; And
And using the specific region in the current picture indicated by the vector received from the encoder as a reference block for the current prediction block. A method of decoding an image,
Parsing information indicating whether or not to omit conversion of the transform block being divided from the current coding unit;
Performing or omitting conversion for the transform block according to the information;
And using a specific area in the current picture indicated by the vector received from the encoder as a reference block for the current prediction block,
Wherein the step of parsing the information indicating whether or not the conversion block is omitted in the step of parsing the information indicating whether or not the conversion block is to be omitted is performed when the flag indicating whether or not the conversion skip is applicable is 1 and the current coding unit is not lossless coded, And parsing the information indicating whether the conversion is omitted if the conversion block size is smaller than or equal to the applicable conversion block size. A method of decoding an image,
Determining whether a size of a transform block in a coding unit being decoded is smaller than or equal to a transform block size to which a transform omission can be applied;
Parsing information indicating whether or not to omit conversion of the conversion block according to the determination, and performing or omitting conversion of the luma conversion blocks of the conversion block; And
And using a particular region in the current picture indicated by the vector received from the encoder as a reference block for the transform block.

Images