KR20160040977A - Transform skip signaling method and apparatus for video coding - Google Patents

Abstract

According to the present invention, when a size of a current coding unit can have a transform block capable of transform skip, a method for decoding an image comprises the following steps of: parsing a representative flag by information with regard to the coding unit wherein the representative flag represents first information which indicates whether to skip transform of a transform block divided from the coding unit; determining whether to parse the first information based on the representative flag; inferring the first information based on the representative flag when parsing the first information is not needed and parsing the first information when parsing the first information is needed; and performing or skipping transform with regard to the transform block in accordance with the first information.

Description

TECHNICAL FIELD [0001] The present invention relates to a method and apparatus for indicating whether or not a conversion for image compression is omitted.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video encoding and decoding process, and more particularly, to a video encoding / decoding method and apparatus for indicating whether or not a conversion is omitted.

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 encoding or decoding of the image, a conversion omission mode may be applied to omit the conversion process when encoding or decoding the residual signal for the image signal or image. Currently, the translation skip mode can be applied to a 4x4 size transform block (TB) in which a nonzero coefficient exists (i.e., a coded block flag (CBF) is 1). In addition, the flag (transform_skip_flag) information indicating whether the conversion skip mode is applied is signaled for each conversion block.

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 into information on the coding unit; determining whether to parse the first information based on the representative flag; and if the parsing of the first information is not necessary, Parsing the first information if parsing of the first information is required; and performing or omitting a transformation on the transform block according to the first information do.

The representative flag may represent that conversion skip is not applied to the conversion block.

If the representative flag is 1, it is inferred that the first information is not applied to the conversion block, and if the representative flag is 0, the first information is discriminated through parsing, and in accordance with the discriminated first information, It is possible to determine whether or not to omit conversion. In a further simpler alternative realization example, if the representative flag is 0, it may be determined that the first information is not parsed in the first information and that the translation skip is applied to the translation block

According to another aspect of the present invention, there is provided a method of coding an image, the method comprising the steps of: determining whether conversion skip is applied to a conversion block divided from a coding unit to be coded; Comprising the steps of: coding a representative flag representative of a representative flag, 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 do.

The representative flag may represent that conversion skip is not applied to the conversion block.

The representative flag is coded as 1 if the conversion skip is not applied to the conversion block divided from the coding unit and the representative flag can be coded as 0 if the conversion skip is applied to the conversion block divided from the coding unit . In this case, it is possible to further code the first information indicating the case where the conversion skip is applied and the case where the conversion skip is not applied.

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 illustrating 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 conversion block in a coding unit represented by a representative flag according to an embodiment of the present invention.
4 is a diagram for explaining a conversion block in a coding unit represented by a representative flag according to another embodiment of the present invention.
5 is a flowchart illustrating an image decoding method using a representative flag representative of whether or not to omit conversion according to an embodiment of the present invention.
FIG. 6 is a flowchart illustrating a video decoding method using a representative flag representing whether or not to omit conversion according to another embodiment of the present invention.
7 is a flowchart illustrating a process of inferring division information indicating whether or not a conversion unit is divided with reference to a representative flag according to an embodiment of the present invention.
8 is a diagram for explaining IBC prediction according to an embodiment of the present invention.
9 is a flowchart illustrating a method of encoding an image using a representative flag representative of whether or not to omit conversion 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 performance improvement, Are also included in the scope of the present invention.

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

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.

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 transform unit 230, the prediction unit 240, the filter unit 260, and the like directly related to the decoding of the image are distinguished from other components 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 of a 4x4 transform block having a CBF (coded block flag) a flag (transform_skip_flag) indicating whether or not the transform is skipped can be individually signaled to the transform block TB.

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 may be embodied as one or more than one (e.g., one or more) instructions contained within a predetermined unit (which may be a coding unit (CU) according to one embodiment and another embodiment may be a prediction unit The present invention proposes a method of signaling information to be displayed on a representative basis of whether or not conversion of conversion units is omitted and signaling to the decoding apparatus so as to reduce the bit amount for signaling the conversion omission and ultimately increase the image coding efficiency do.

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 is to be applied and a 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 it is divided is indicated by quad tree information having a coding unit root. 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.

In the case of 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 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. Exceptionally, however, if an 8x8 coding unit is divided into quad trees once and the transform unit has a size of 4x4, both the luma and chroma transform blocks 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.

Hereinafter, the present invention provides a method of signaling and decoding a representative flag (e.g., transform_skip_all_zeros_in_cu_flag), which is information representative of whether or not the conversion blocks included in the coding unit are omitted.

At this time, the conversion blocks in the coding unit, which the representative flag represents, depending on whether or not considering the conversion depth (TU depth) of the conversion blocks included in the coding unit, can be divided into two as follows.

In the first case, the representative flag may represent only the transform blocks of the maximum transform depth (MaxTrafoDepth) that the current coding unit is reachable. In other words, the representative flag represents a minimum-size conversion block that can be divided in the current coding unit.

Here, in the expression of maximum conversion 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. If the depth is 1, it means that the coding unit is divided into quad-trees by 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".

In the second case, the representative flag may represent all transform blocks (of a size that can be omitted) in the current coding unit.

3 is a diagram for explaining a conversion block in a coding unit represented by a representative flag according to an embodiment of the present invention.

The embodiment of FIG. 3 shows a case where the representative flag represents conversion blocks having the maximum conversion depth in the current coding unit.

For example, if it is assumed that the conversion omission is applied to the conversion block from 4x4 to 16x16 size, in the case of the 16x16 size coding unit, the representative flag is signaled on behalf of the conversion block included in the 4x4 conversion unit divided into the maximum depth . In Fig. 3, the blocks shown in gray represent conversion units including conversion blocks represented by representative flags.

That is, the encoding apparatus can determine the representative flag value for the transform blocks divided by the maximum depth in the coding unit, and can signal the value to the decoding apparatus. The decoding device may then receive and parse the representative flag value and determine whether to apply a translation omission to the translation blocks of maximum depth in the current coding unit based on the parsed representative flag value.

4 is a diagram for explaining a conversion block in a coding unit represented by a representative flag according to another embodiment of the present invention.

The embodiment of FIG. 4 shows a case in which the representative flag represents all the transform blocks of a size that can be converted within the current coding unit.

For example, in the case of a 16x16 coding unit, it can be divided into 16x16, 8x8, and 4x4 conversion units. Assuming that the conversion skip is applied to the conversion blocks from 4x4 to 16x16, the conversion skip can be applied to all conversion units having 16x16, 8x8, and 4x4 sizes. The blocks shown in gray in Fig. 4 represent conversion units including conversion blocks to which representative flags are applied.

That is, the encoding apparatus can determine a representative flag value for all conversion blocks of a size that can be skipped in the coding unit, and signal the value to the decoding apparatus. The decoding apparatus can then receive and parse the representative flag value and determine whether to apply a translation omission for all transform blocks of a size that is capable of omitting the transformation within the current coding unit based on the parsed representative flag value.

5 is a flowchart illustrating an image decoding method using a representative flag representative of whether or not to omit conversion according to an embodiment of the present invention. The method of FIG. 5 can be performed by the image decoding apparatus of FIG. 2 described above.

Referring to FIG. 5, a representative flag (for example, transform_skip_all_zeros_in_cu_flag) representative of whether or not the conversion is omitted for the conversion block to which the conversion is omitted according to the present embodiment and a process of converting the image performed according to the representative flag will be described below.

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 (S510).

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. If 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, so that the parsing itself of the representative flag representing the omission of conversion is not necessary .

In step S510, it is determined whether the size of the current coding unit satisfies a size condition to which such a conversion skip can be applied, i.e., a conversion block requiring parsing of a flag (transform_skip_flag) indicating whether or not the conversion block is skipped is present in the current coding unit And whether or not it is possible. 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.

<Table 1>

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.

<Table 2>

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.

Information (transform_skip_group_signalling_enabled_flag) indicating whether or not to use the function of the representative flag according to the embodiment of the present invention as shown in Table 1 and Table 2 can be transmitted through a predetermined parameter set.

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, sps_range_extensions (sequence parameter set range extensions), sps_scc_extensions (sequence parameter set screen content coding extensions), pps_range_extensions (picture parameter set range extensions), or pps_range_extensions (picture parameter set screen content coding extensions).

If the transform_skip_group_signalling_enabled_flag is 1, it indicates that the function representing the translation omission 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.

When the function representing transform skip (transform_skip_group_signalling_enabled_flag = 1) is used, a representative flag according to an embodiment of the present invention can be signaled as shown in Table 3 below.

<Table 3>

Referring to Table 3, when the representative flag parsing condition in step S510 is satisfied, the following can be obtained.

1) The transform_skip_group_signalling_enabled_flag signaled in Table 1 is 1,

2) a flag (transform_skip_enabled_flag) indicating whether or not the application of the conversion omission is possible is 1,

3) If the current coding unit is not lossless encoded (! Cu_transquant_bypass_flag)

4) If the minimum size conversion block that can be partitioned in the current coding unit is less than or equal to the maximum conversion block size to which the translation omission can be applied (if ((log2CbSize - MaxTrafoDepth - (ChromaArrayType% 3 = ) &Lt; = Log2MaxTransformSkipSize).

When the above 1), 2), 3) and 4) are satisfied, the decoding apparatus can determine that the representative flag (transform_skip_all_zeros_in_cu_flag) representing the first information indicating whether or not the conversion is omitted is parsed.

If at least one of the above 1), 2), 3) and 4) is not satisfied (for example, if there is no conversion block in the current coding unit so as to be able to omit conversion, Or the like), the decoding apparatus may determine that the representative flag parsing condition is not satisfied and may not parse the representative flag. In this case, the decoding apparatus regards the value of the representative flag (transform_skip_all_zeros_in_cu_flag) as 0 (S511), and can perform a subsequent decoding process (S515).

If it is determined that the representative flag parsing condition (the condition described with reference to Table 3) is satisfied and the representative flag is to be parsed, the decoding apparatus parses the representative flag representing the first information indicating whether or not the conversion is omitted (S520).

If the value of the parsed representative flag is 1 (S530), the decoding apparatus determines whether the representative flag is a transform block to which the first information to be applied is applied (that is, if the first information is to be applied, ), It is determined whether the parsing omission condition of the first information is satisfied (S540).

In the embodiment of Table 3, the first information parsing skip condition may be whether or not the current transform block to be decoded is the maximum depth transform unit that can be divided in the current coding unit.

If the current transform block to be decoded corresponds to the transform unit of the maximum depth (MaxTrafoDepth), the decoding apparatus can infer the first information to 0 without parsing the first information on the transform block to be decoded (S550) . Here, when the first information has a value of 0, it means that the conversion omission is not applied to the conversion block. That is, it means performing a conversion on the conversion block.

In other words, when the condition of step S540 is satisfied, the decoding apparatus determines that the conversion skip is not applied to the conversion block included in the conversion unit of the maximum depth divided from the coding unit, It can be judged that parsing is not necessary.

When the first information has a value of 0 (when the first information indicates that the conversion omission has not been applied to the conversion block), the decoding device does not apply the conversion omission to the conversion block, And perform a subsequent decoding process (S560).

If the representative flag is 0 in step S530, or if the first information parsing skip condition is not satisfied in step S540, the decoding apparatus parses the first information indicating whether or not the conversion block is skipped individually for the conversion block according to the existing method (S570 ).

That is, if the representative flag is 0, a series of processes for the first information (transform_skip_flag) signaling is performed in a conventional manner, which means that the first information is signaled for each transform block for which the transform_skip_flag signaling is required. Meanwhile, in another simple embodiment, if the representative flag is 0, the decoding apparatus skips the step S570 of parsing the first information on the transform block, and deduces the value of the first information to 1 (i.e., To be implemented).

If the representative flag (transform_skip_all_zeros_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. That is, the decoding apparatus may perform a conversion process or a conversion process and a subsequent decoding process according to whether the conversion is omitted based on the first information (S560, S580).

Table 4 below shows an example of a syntax for signaling first information (transform_skip_flag) indicating whether or not to omit conversion using the representative flag (transform_skip_all_zeros_in_cu_flag) according to an embodiment of the present invention.

<Table 4>

Referring to Table 4, the representative flag (transform_skip_all_zeros_in_cu_flag) may represent the conversion skip flag of the conversion blocks that satisfy the first information parsing skip condition (S540). As described above, the decoding apparatus can determine whether or not the individual conversion skip flag is parsed by judging the first information parsing skip condition when the representative flag is 1.

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

The conditional application of S540 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 smaller than the maximum conversion block size to which the conversion skip is applied, The conversion block having the coefficient information (i.e., CBF = 1)) is the same as that of the existing technology, so redundant description thereof is omitted here.

According to the embodiment of the present invention described above, the representative flag can represent whether or not the conversion block belonging to the conversion unit of the maximum depth that can be divided from the current coding unit is omitted. This has been described with reference to FIG. 3 for the conversion blocks in the coding unit represented by the representative flag.

Further, in the present invention, the representative flag may represent all the conversion units of a certain depth or a size which can omit conversion. This has been described with reference to FIG. 4, in which representative flags are representative of all conversion units of a size capable of omitting conversion. An embodiment in which representative flags represent all the conversion units of a certain depth or a size which can omit conversion will be described with reference to Fig.

FIG. 6 is a flowchart illustrating a video decoding method using a representative flag representing whether or not to omit conversion according to another embodiment of the present invention. The method of FIG. 6 can be performed by the image decoding apparatus of FIG. 2 described above.

Referring to FIG. 6, the decoding apparatus determines whether a representative flag parsing condition is satisfied in order to determine whether to parse a representative flag with respect to the current coding unit (CU) (S610).

At this time, the representative flag according to this embodiment can be signaled as shown in Table 3 above. Therefore, when the representative flag parsing condition satisfies the same condition as described with reference to Table 3, the decoding apparatus parses the representative flag (S620). The representative flag parsing condition has been described with reference to Table 3, and a description thereof will be omitted here.

If the representative flag parsing condition is not satisfied, the decoding apparatus does not parse the representative flag and regards the representative flag value as 0 (S611), and performs the subsequent decoding process (S615).

If the representative flag parsed satisfying the representative flag parsing condition is 1 (S630), the decoding apparatus does not parse the first information indicating whether or not the conversion block included in the conversion unit to be divided from the coding unit is to be parsed, It is possible to deduce the first information for 0 (S650).

On the other hand, if the parsed representative flag is 0, the decoding apparatus parses the first information on the transform block (S670), skips the conversion according to the value of the parsed first information (if the first information is 1) (When the first information is 0). On the other hand, in another simple embodiment, if the parsed representative flag is 0, the decoding apparatus skips step S670 of parsing the first information on the transform block, and deduces the value of the first information to 1 (i.e., So that the conversion can be omitted).

That is, when the representative flag of the encoding block included in the coding unit is not larger than the size of the maximum conversion block to which the conversion skip can be applied and the representative flag has a value of 1, It is determined that parsing is not necessary, and the first information can be deduced to be zero.

According to the present embodiment, it is possible to represent the conversion omission flag of the conversion blocks satisfying the condition (the encoded conversion block having the block size capable of omitting conversion) in which the conversion in the coding unit being decoded can be omitted have.

Table 5 shows an example of a syntax for signaling first information (transform_skip_flag) indicating whether or not to omit conversion using a representative flag (transform_skip_all_zeros_in_cu_flag) according to another embodiment of the present invention.

<Table 5>

Referring to Table 5, if the representative flag (transform_skip_all_zeros_in_cu_flag) is 1, the first information can be set to 0 without being parsed (transform_skip_flag [x0] [y0] [cIdx] = 0).

That is, in accordance with the present embodiment, the decoding apparatus may not parse the conversion omission flag individually for the conversion blocks in the coding unit when the representative flag is 1.

If the first information is deduced to be 0, the decoding apparatus can perform the conversion and perform the subsequent decoding process without applying the conversion omission to the conversion block in which it is determined by the first information whether or not to omit conversion (S660 ).

If the representative flag is 0 in step S630, the decoding apparatus parses the first information indicating whether or not the conversion block is skipped 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_zeros_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. That is, the decoding apparatus can perform a conversion process or a conversion process and a subsequent decoding process according to whether or not the conversion is omitted based on the first information (S660, S680).

In the present invention, as described above, it is possible to represent whether or not the conversion flag of the conversion block in which the representative flag is divided from the coding unit is omitted. In the present invention, in the embodiment using the representative flag representing the first information of the maximum conversion depth described above with reference to FIG. 5, it is possible to determine whether or not the conversion unit is divided. This will be described with reference to FIG.

7 is a flowchart illustrating a process of inferring division information indicating whether or not a conversion unit is divided with reference to a representative flag according to an embodiment of the present invention. The method of FIG. 7 can be performed by the image decoding apparatus of FIG. 2 described above.

Since steps S710 and S730 of FIG. 7 are similar to steps S510 and S530 of FIG. 5, duplicate descriptions are 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 (S740).

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 (S750).

That is, when the step S740 is satisfied, the decoding apparatus needs 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 It can be judged to be absent.

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.

The following Table 6 shows an example of a syntax for signaling the second information (split_transform_flag) indicating whether or not the conversion unit using the representative flag (transform_skip_all_zeros_in_cu_flag) according to the embodiment of the present invention is divided.

<Table 6>

Referring to Table 6, if the representative flag (transform_skip_all_zeros_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 deduced to be 1, the decoding apparatus performs division on the conversion unit (S760) and may perform subsequent decoding (S780).

On the other hand, for the 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 S730, or if the conversion depth of the conversion unit is not 0 in step S740, the decoding apparatus parses the second information according to the existing method to determine whether the conversion unit is divided (S770).

If the second information is parsed, the transform block may be segmented (S760), and the segmentation may be omitted, so that the decoding device may perform a subsequent decoding process (S780).

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.

On the other hand, in the present invention, the above-described representative flag can 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 if the prediction mode of the coding unit is a predetermined prediction mode that is predetermined.

As another example, the proposed representative flag may be signaled when the prediction mode of the coding unit is intra mode or IBC (Intra Block Copy) 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.

8 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 in the figure, 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 the BV difference (BV difference), similar to the motion vector.

The BV predictor for the current block may be coded in the encoder and signaled to the decoder, and BV of a block previously predicted in IBC mode in a particular area, e.g., the current CTU, may 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 represents 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 based on the prediction mode of the current coding unit, the syntax that the coding apparatus signals to the decoding apparatus at the coding unit level according to the present invention can be expressed as shown in Table 7. [

<Table 7>

Referring to Table 7, when 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 not applied (! Intra_bc_flag [x0] [y0]), the representative flag (transform_skip_all_zeros_in_cu_flag May be received. 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_zeros_in_cu_flag) may be received or parsed.

Table 7 can be applied to the embodiment described with reference to FIG. 5 to FIG. 5, for example, transform_skip_group_signalling_enabled_flag and transform_skip_enabled_flag are 1, not a lossless image coding (! Cu_transquant_bypass_flag), and IBC prediction is not applied (! Intra_bc_flag [x0] [y0 ]). 5, the transform_skip_group_signalling_enabled_flag is not signaled. At this time, in the embodiment in which the decoding apparatus derives this value to 0, the representative flag parsing condition of S510 of FIG. 5 is 1, and the transform_skip_group_signalling_enabled_flag is 1, (! Cu_transquant_bypass_flag), and if IBC prediction is not applied (! Intra_bc_flag [x0] [y0]).

On the other hand, in the present invention, it is possible to signal whether the first information (transform_skip_flag) indicating whether or not the representative flag described above indicates whether or not the conversion is omitted represents the conversion omission or represents that the conversion omission is not applied. In other words, the representative flag may signal whether the transform_skip_flag value is 0, or the transform_skip_flag value is 1.

Table 8 is a syntax showing an example of signaling whether the representative flag according to an embodiment of the present invention represents a shift omission or a shift omission does not apply.

<Table 8>

Referring to Table 8, when it is defined to use the conversion omission signaling method using the representative flag (transform_skip_group_signalling_enabled_flag = 1), information indicating whether the representative flag represents conversion omission or not is not applied transform_skip_group_represented_value) may be signaled.

For example, if the value of the transform_skip_group_represented_value is 1, the representative flag may indicate whether the value of the transform_skip_flag is 1 or not. If the value of the transform_skip_group_represented_value is 0, the representative flag may indicate whether the value of the transform_skip_flag is 0 or not.

Here, when the value of transform_skip_group_represented_value is 0, the representative flag may be transform_skip_all_zeros_in_cu_flag as described above. That is, the transform_skip_all_zeros_in_cu_flag can be used for signaling the transform_skip_flag, and the embodiments described with reference to FIGS. 3 to 8 can be applied.

In the following, a method of signaling the representative flag (transform_skip_all_in_cu_flag) when transform_skip_group_represented_value is signaled and deriving the conversion skip information (transform_skip_flag) based on the representative flag will be described.

When the representative flag (transform_skip_group_represented_value) indicating whether the representative flag represents conversion omission or not represents conversion omission is not signaled, a representative flag (transform_skip_all_in_cu_flag) according to an embodiment of the present invention, as shown in the following Table 9, .

<Table 9>

The condition that the representative flag (transform_skip_all_in_cu_flag) of Table 9 is signaled and parsed has been described with reference to Table 3, and therefore, a detailed description thereof will be omitted here.

If the representative flag is signaled based on the prediction mode of the current coding unit, a representative flag (transform_skip_all_in_cu_flag) according to an embodiment of the present invention may be signaled as shown in the following Table 10. [

<Table 10>

The condition that the representative flag (transform_skip_all_in_cu_flag) of Table 10 is signaled and parsed has been described with reference to Table 73, so that detailed description is omitted here.

(Transform_skip_group_represented_value) indicating whether the representative flag represents conversion skip or represents that conversion skip is not applied is signaled, the first information (transform_skip_flag) indicating whether to omit conversion using the representative flag (transform_skip_all_in_cu_flag) 11 and Table 12, respectively.

<Table 11>

Referring to Table 11, when the representative flag transform_skip_all_in_cu_flag is 1 and the conversion block is included in the conversion unit of the maximum depth divided from the coding unit (log2TrafoSize == Max (2, log2CbSize - MaxTrafoDepth- (ChromaArrayType% 3 = 0: (cIdx? 1: 0)))) block, the first information (transform_skip_flag) is not parsed and is set to a value of transform_skip_group_represented_value.

<Table 12>

Referring to Table 12, if the representative flag transform_skip_all_in_cu_flag is 1, the first information (transform_skip_flag) is not parsed and is set to the value of transform_skip_group_represented_value. At this time, the representative flag can be applied in the case of representing all the conversion units of the size which can omit conversion.

Second information (split_transform_flag) indicating whether the conversion unit is divided using the representative flag (transform_skip_all_in_cu_flag) when the representative flag indicates conversion omission or information indicating whether conversion omission is not applied (transform_skip_group_represented_value) Can be signaled as shown in Table 13.

<Table 13>

Referring to Table 13, if the representative flag (transform_skip_all_in_cu_flag) is 1 and the conversion depth is 0 (trafoDepth = 0), the second information (split_transform_flag) can be set to 1 without being parsed.

In the present invention, it is possible to signal whether or not the representative flag described above is signaled with reference to the coding mode of the coding unit. In other words, the present invention can provide information (transform_skip_group_referring_mode_flag) indicating whether the representative flag is signaled with reference to the coding mode of the coding unit.

Table 14 is a syntax showing an example of signaling whether a representative flag according to an embodiment of the present invention is signaled with reference to a coding mode of a coding unit.

<Table 14>

Referring to Table 14, information (transform_skip_group_referring_mode_flag) indicating whether the representative flag is signaled with reference to the coding mode of the coding unit (transform_skip_group_reframe_mode_flag) is defined as the coding And can be signaled from the device.

For example, when the value of the transform_skip_group_referring_mode_flag is 1, the representative flag is signaled only when the coding mode of the coding unit is the predefined prediction mode, and when the coding mode of the coding unit is not the predefined prediction mode, Omit signaling is not used. That is, the representative flag is not parsed for the coding unit in which the predefined prediction mode is not used.

If the value of the transform_skip_group_referring_mode_flag is 0, it is possible to parse the representative flag without referring to the prediction mode of the coding unit when determining whether the representative flag is parsed.

When the transform_skip_group_represented_value is signaled and the transform_skip_group_referring_mode_flag is signaled, the representative flag (transform_skip_all_in_cu_flag) can be signaled as shown in Table 15.

<Table 15>

The transform_skip_group_referring_mode_flag? (Transform_skip_group_represented_value == intra_bc_flag [x0] [y0]): 1 shown in Table 15 has the following meaning.

If transform_skip_group_referring_mode_flag is 0, 1 (true) is returned to the if statement including the above sentence. In other words, when the representative flag is not signaled with reference to the coding mode of the coding unit, the representative flag can be parsed regardless of the prediction mode of the coding unit.

If transform_skip_group_referring_mode_flag is 1, it is determined whether or not (transform_skip_group_represented_value == intra_bc_flag [x0] [y0]). In other words, when the representative flag is signaled with reference to the coding mode of the coding unit, it is possible to determine whether the coding mode of the coding unit is a predefined prediction mode (for example, IBC prediction mode) and to parse the representative flag.

At this time, when the value of the transform_skip_group_represented_value is 1 (that is, when the representative flag represents conversion skip_flag = 1), 1 is returned only when the coding mode of the current coding unit is the IBC prediction mode.

On the other hand, if the value of the transform_skip_group_represented_value is 0 (that is, when the representative flag does not apply the transformation skip (transform_skip_flag = 0)), the process returns 1 only if the coding mode of the current coding unit is not the IBC prediction mode.

In the above description, when the transform_skip_group_represented_value is signaled, the process of signaling the transform_skip_group_referring_mode_flag and parsing the representative flag has been described. Hereinafter, the process of signaling the transform_skip_group_referring_mode_flag and parsing the representative flag when the transform_skip_group_represented_value is not signaled will be described.

Table 16 is a syntax showing an example of signaling whether a representative flag according to an embodiment of the present invention is signaled with reference to a coding mode of a coding unit.

<Table 16>

Referring to Table 16, information (transform_skip_group_reference_mode_flag) indicating whether the representative flag is signaled with reference to the coding mode of the coding unit (transform_skip_group_signalling_enabled_flag = 1) is defined by using the conversion skip signaling method using the representative flag And can be signaled from the device.

If the transform_skip_group_referring_mode_flag is signaled, the representative flag can be signaled as shown in Table 17 and Table 18. At this time, the representative flag (transform_skip_all_zeros_in_cu_flag) in Table 17 represents (transform_skip_flag = 0) when the representative flag does not apply the translation omission. The representative flag (transform_skip_all_ones_in_cu_flag) in Table 18 represents the case where the representative flag applies the translation omission (transform_skip_flag = 1).

<Table 17>

Referring to Table 17, the representative flag transform_skip_all_zeros_in_cu_flag can be parsed according to the value of the transform_skip_group_referring_mode_flag by determining whether the coding mode of the coding unit is a predefined prediction mode (for example, IBC prediction mode).

<Table 18>

Referring to Table 18, the representative flag transform_skip_all_ones_in_cu_flag can be parsed according to the value of the transform_skip_group_referring_mode_flag by determining whether the coding mode of the coding unit is a predefined mode (for example, IBC prediction mode).

9 is a flowchart illustrating a method of encoding an image using a representative flag representative of whether or not to omit conversion according to an embodiment of the present invention. The method of FIG. 9 can be performed by the image encoding apparatus of FIG. 1 described above.

The encoding apparatus determines whether or not the conversion skipping is applied to the conversion block that is divided from the coding unit to be coded (S910).

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. 5 and 6, Signaling with information on the coding unit (S920).

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 The representative flag may be coded as 1 if no conversion skip is used in all the conversion blocks that satisfy the conversion condition (i.e., CBF is 1).

Alternatively, when the conversion skip is not used in all the conversion blocks that satisfy the basic condition to which the skip conversion can be applied among the conversion units included in the conversion unit divided from the coding unit, the encoding device can code the representative flag with 1 have.

If the representative flag is 1 (S930), coding of the first information is skipped for the conversion block that satisfies the above conditions, and coding of the first information is performed for the conversion block requiring coding of the first information (S940).

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.

In step S950, the encoding apparatus codes 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.

Steps S940 and S950 may be performed sequentially, but each may be performed in an independent step, 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 (S960).

The conversion performed in the decoding process refers to an inverse transform, which is an inverse process of the conversion performed in the encoding device. However, since the inverse conversion is also a kind of conversion, there is no real confusion in the meaning.

The method according to the present invention may be implemented as a program for execution on a computer and stored in a computer-readable recording medium. Examples of the computer-readable recording medium include a ROM, a RAM, a CD- , A floppy disk, an optical data storage device, and the like, and may also be implemented in the form of a carrier wave (for example, transmission over the Internet).

The computer readable recording medium may be distributed over a networked computer system so that computer readable code can be stored and executed in a distributed manner. And, functional programs, codes and code segments for implementing the above method can be easily inferred by programmers of the technical field to which the present invention belongs.

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 the steps, and some steps may occur in different orders or simultaneously . 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 foregoing description is merely illustrative of the technical idea of the present invention, and various changes and modifications may be made by those skilled in the art without departing from the essential characteristics of the present invention. Therefore, the embodiments disclosed in the present invention are intended to illustrate rather than limit the scope of the present invention, and the scope of the technical idea of the present invention is not limited by these embodiments. The scope of protection of the present invention should be construed according to the claims, and all technical ideas within the scope of the claims should be construed as being included in the scope of the present invention.

Claims (19)

A method of decoding an image,
Wherein when the size of the current coding unit can include a conversion block capable of omitting conversion, a representative flag representative of first information indicating whether to omit conversion of a conversion block capable of omitting conversion, which is divided from the coding unit, Parsing the received information into information about the content;
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,
The representative flag represents that the conversion skip is not applied to the conversion block,
And if the representative flag is 1, the first information is inferred that the conversion skip is not applied to the conversion block,
If the representative flag is 0, the first information is inferred to be a translation block omission, or the first information is determined through parsing, and the first information is added to the conversion block in accordance with the parsed first information. Wherein the transform is omitted or the transform is applied. The method according to claim 1,
Further comprising receiving representative value information indicating whether the representative flag represents that the conversion omission is not applied to the conversion block or represents that conversion omission is applied to the conversion block,
If the representative value information is 1, the representative flag represents that the conversion skip is applied to the conversion block,
And if the representative value information is 0, the representative flag represents that conversion omission is not applied to the conversion block. The method according to claim 1,
Wherein the step of determining whether to parse the first information comprises:
When the representative flag is 1 and the conversion block is included in the conversion unit of the maximum depth divided from the coding unit and the size of the conversion block is equal to or less than a maximum conversion block size to which the conversion omission is applied, If parsing is not necessary,
And the first information is inferred to be not applied to the transform block. The method according to claim 1,
Wherein the step of determining whether to parse the first information comprises:
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 the first information is inferred to be not applied to the transform block. The method according to claim 1,
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 parsing the second information when parsing of the second information is necessary;
And performing division on the conversion unit according to the second information. 6. The method of claim 5,
Wherein the step of determining whether to parse the second information comprises:
If the representative flag is 1 and the conversion depth for the conversion unit is 0, it is determined that parsing of the second information is not necessary,
And the second information is inferred to be obtained by dividing the conversion unit. 6. The method of claim 5,
Wherein the step of determining whether to parse the second information comprises:
When the representative flag is 1, the conversion depth for the conversion unit is 0, and the size of all the conversion blocks included in the conversion unit having the conversion depth of 0 is larger than the maximum conversion block size to which the conversion skip is applied, It is determined that parsing of the second information is not necessary,
And the second information is inferred to be obtained by dividing the conversion unit. The method according to claim 1,
Wherein the representative flag is signaled corresponding to a prediction mode applied to the coding unit. 9. The method of claim 8,
Wherein the representative flag is signaled when the prediction mode of the coding unit performs an intra prediction in the current picture and an intra block copy (IBC) prediction mode in which an area similar to the current block is set as a prediction value for the current block A method of decoding an image. 9. The method of claim 8,
Further comprising receiving prediction mode reference information indicating whether the representative flag is signaled in response to a prediction mode applied to the coding unit,
When the prediction mode reference information indicates signaling corresponding to a prediction mode applied to the coding unit, the representative flag is signaled when the prediction mode of the coding unit is a predefined prediction mode,
Wherein if the prediction mode reference information indicates that the signal is not signaled corresponding to the prediction mode applied to the coding unit, whether to parse the reference flag is determined without referring to the prediction mode of the coding unit. Way. The method according to claim 1,
Further receiving flag information indicating whether or not a function of inferring whether or not to omit conversion is used by using the representative flag,
Wherein the flag information is signaled in a sequence parameter set or a picture parameter set. 3. The method of claim 2,
Wherein when the representative value information is received, determining whether to parse the first information comprises:
When the representative flag is 1 and the conversion block is included in the conversion unit of the maximum depth divided from the coding unit and the size of the conversion block is equal to or less than a maximum conversion block size to which the conversion omission is applied, If parsing is not necessary,
And the first information is inferred as the representative value information. 3. The method of claim 2,
Wherein when the representative value information is received, determining whether to parse the first information comprises:
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 the first information is inferred as the representative value information. A method of encoding an image,
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,
The representative flag represents that no conversion omission is applied to the conversion block,
When the conversion skip is not applied to the conversion block divided from the coding unit, the representative flag is coded as 1,
Wherein when the conversion skip is applied to a conversion block that is divided from the coding unit, the representative flag is coded with 0. 15. The method of claim 14,
Wherein the step of coding the representative flag comprises:
When the conversion skip is not applied to all of the conversion blocks included in the conversion unit of the maximum depth divided from the coding unit and having a size equal to or smaller than the maximum conversion block size to which the conversion skip is applied, And the representative flag is coded by 1. 15. The method of claim 14,
Wherein the step of coding the representative flag comprises:
If the conversion skip is not applied to all of the conversion blocks divided from the coding unit and having a size equal to or smaller than the maximum conversion block size to which the conversion skip is applied and in which the residual signal exists, Wherein the image coding method comprises the steps of: 15. The method of claim 14,
Determining whether to code second information indicating whether or not the conversion unit is divided based on the representative flag;
And coding and signaling the second information if coding of the second information is required. 18. The method of claim 17,
Wherein the step of determining whether to code the second information comprises:
Wherein if the representative flag is 1 and the conversion depth for the conversion unit is 0, it is determined that coding of the second information is not necessary. 18. The method of claim 17,
Wherein the step of determining whether to code the second information comprises:
When the representative flag is 1 and the conversion depth for the conversion unit is 0 and the size of all the conversion blocks included in the conversion unit having the conversion depth of 0 is larger than the maximum conversion block size to which the conversion skip is applied, 2 &lt; / RTI &gt; information is not necessary.

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