KR20220061085A - Method and apparatus for encoding/decoding a video signal - Google Patents

Abstract

A video signal encoding method according to the present invention may comprise: encoding a partial block flag indicating whether at least one non-zero coefficient exists in a current partial block; encoding the absolute value of the coefficient of the current partial block; and encoding the sign of the coefficient of the current partial block. The compression efficiency of a video can be improved.

Description

Video signal encoding/decoding method and apparatus

The present invention relates to a method and apparatus for encoding/decoding a video signal.

Recently, the demand for multimedia data such as moving pictures is rapidly increasing on the Internet. However, it is difficult to keep up with the rapidly increasing amount of multimedia data at the rate of development of the bandwidth of the channel.

A main object of the present invention is to improve image compression efficiency by efficiently encoding/decoding coefficients in partial blocks.

A video signal encoding method and apparatus according to the present invention comprises encoding a partial block flag indicating whether at least one non-zero coefficient exists in a current partial block, encoding an absolute value of a coefficient of the current partial block, and The sign of the coefficient of the current partial block may be encoded.

In the method and apparatus for encoding an image signal according to the present invention, a current partial block is included in a transform block, and the transform block may include one or more partial blocks.

In the video signal encoding method and apparatus according to the present invention, information indicating at least one of a size and a shape of the current partial block may be encoded.

In the video signal encoding method and apparatus according to the present invention, the encoded information includes a merge flag indicating whether blocks are merged, a split flag indicating whether blocks are split, or split index information specifying a split type of the transform block. may include at least one of

In the video signal encoding method and apparatus according to the present invention, at least one of the size and shape of the current partial block may be determined based on the position of the first non-zero coefficient in the encoding order of the transform block.

In the video signal encoding method and apparatus according to the present invention, at least one of a size or a shape of the current partial block may be determined in consideration of properties of a DC component and/or an AC component in a frequency domain.

In the method and apparatus for encoding an image signal according to the present invention, at least one of a size and a shape of the current partial block may be determined based on at least one of a quantization parameter (QP) and a block size.

A video signal decoding method and apparatus according to the present invention decodes a partial block flag indicating whether at least one non-zero coefficient exists in a current partial block, and decodes an absolute value of the coefficient of the current partial block, The sign of the coefficient of the current partial block may be decoded.

In the method and apparatus for decoding an image signal according to the present invention, a current partial block is included in a transform block, and the transform block may include one or more partial blocks.

In the method and apparatus for decoding an image signal according to the present invention, at least one of a size and a shape of the current partial block may be determined based on encoded information.

In the video signal decoding method and apparatus according to the present invention, the encoded information includes a merge flag indicating whether blocks are merged, a split flag indicating whether blocks are split, or split index information specifying a split type of the transform block. may include at least one of

In the method and apparatus for decoding an image signal according to the present invention, at least one of the size and shape of the current partial block may be determined based on the position of the first non-zero coefficient in the encoding order of the transform block.

In the method and apparatus for decoding an image signal according to the present invention, at least one of a size or a shape of the current partial block may be determined in consideration of properties of a DC component and/or an AC component in a frequency domain.

In the method and apparatus for decoding an image signal according to the present invention, at least one of a size and a shape of the current partial block may be determined based on at least one of a quantization parameter (QP) and a block size.

According to the present invention, image compression efficiency can be improved by efficiently encoding/decoding coefficients of a transform block.

1 is a block diagram illustrating an image encoding apparatus according to an embodiment of the present invention.
2 is a block diagram illustrating an image decoding apparatus according to an embodiment of the present invention.
3 illustrates a method of encoding coefficients of a transform block according to an embodiment to which the present invention is applied.
4 illustrates a method of encoding a maximum value of a coefficient of a partial block according to an embodiment to which the present invention is applied.
5 illustrates a method of encoding a first threshold value flag for a partial block according to an embodiment to which the present invention is applied.
6 illustrates a method of decoding coefficients of a transform block according to an embodiment to which the present invention is applied.
7 illustrates a method of decoding a maximum value of a coefficient of a partial block according to an embodiment to which the present invention is applied.
8 is a diagram illustrating a method of decoding a first threshold value flag for a partial block according to an embodiment to which the present invention is applied.
9 is a diagram illustrating a method of deriving a first/second threshold value flag for a current partial block according to an embodiment to which the present invention is applied.
10 illustrates a method of determining the size/shape of a partial block based on a merge flag as an embodiment to which the present invention is applied.
11 illustrates a method of determining the size/shape of a partial block based on a division flag as an embodiment to which the present invention is applied.
12 illustrates a method for determining the size/shape of a partial block based on partition index information as an embodiment to which the present invention is applied.
13 is a diagram illustrating a method of dividing a transform block based on a position of a non-zero coefficient according to an embodiment to which the present invention is applied.
14 illustrates a method of selectively dividing a partial region of a transform block according to an embodiment to which the present invention is applied.
15 is a diagram illustrating a method of dividing a transform block based on a property of a DC/AC component in a frequency domain as an embodiment to which the present invention is applied.

Since the present invention can have various changes and can have various embodiments, specific embodiments are illustrated in the drawings and described in detail in the detailed description. However, this is not intended to limit the present invention to specific embodiments, and it should be understood to include all modifications, equivalents and substitutes included in the spirit and scope of the present invention. In describing each figure, like reference numerals have been used for like elements.

Terms such as first, second, etc. may be used to describe various elements, but the elements should not be limited by the terms. The above terms are used only for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, a first component may be referred to as a second component, and similarly, a second component may also be referred to as a first component. and/or includes a combination of a plurality of related listed items or any of a plurality of related listed items.

When a component is referred to as being “connected” or “connected” to another component, it is understood that the other component may be directly connected or connected to the other component, but other components may exist in between. it should be On the other hand, when it is mentioned that a certain element is "directly connected" or "directly connected" to another element, it should be understood that no other element is present in the middle.

The terms used in the present application are only used to describe specific embodiments, and are not intended to limit the present invention. The singular expression includes the plural expression unless the context clearly dictates otherwise. In the present application, terms such as “comprise” or “have” are intended to designate that a feature, number, step, operation, component, part, or combination thereof described in the specification exists, but one or more other features It should be understood that this does not preclude the existence or addition of numbers, steps, operations, components, parts, or combinations thereof.

Hereinafter, preferred embodiments of the present invention will be described in more detail with reference to the accompanying drawings. Hereinafter, the same reference numerals are used for the same components in the drawings, and repeated descriptions of the same components are omitted.

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

Referring to FIG. 1 , the image encoding apparatus 100 includes a picture division unit 110 , prediction units 120 and 125 , a transform unit 130 , a quantization unit 135 , a rearrangement unit 160 , and an entropy encoding unit ( 165 ), an inverse quantization unit 140 , an inverse transform unit 145 , a filter unit 150 , and a memory 155 .

Each of the constituent units shown in FIG. 1 is independently illustrated to represent different characteristic functions in the image encoding apparatus, and does not mean that each constituent unit is composed of separate hardware or one software constituent unit. That is, each component is listed as each component for convenience of description, and at least two components of each component are combined to form one component, or one component can be divided into a plurality of components to perform a function, and each of these components Integrated embodiments and separate embodiments of the components are also included in the scope of the present invention without departing from the essence of the present invention.

In addition, some of the components are not essential components for performing essential functions in the present invention, but may be optional components for merely improving performance. The present invention can be implemented by including only essential components to implement the essence of the present invention, except for components used for performance improvement, and a structure including only essential components excluding optional components used for performance improvement Also included in the scope of the present invention.

The picture divider 110 may divide the input picture into at least one block. In this case, a block may mean a coding unit (CU), a prediction unit (PU), or a transformation unit (TU). The division may be performed based on at least one of a quadtree and a binary tree. The quad tree divides the upper block into lower blocks whose width and height are half that of the upper block. Binary tree is a method of dividing the upper block into lower blocks whose either width or height is half that of the upper block. Through the binary tree-based partitioning described above, a block may have a non-square shape as well as a square shape.

Hereinafter, in an embodiment of the present invention, a coding unit may be used as a unit for performing encoding or may be used as a meaning for a unit for performing decoding.

The prediction units 120 and 125 may include an inter prediction unit 120 performing inter prediction and an intra prediction unit 125 performing intra prediction. Whether to use inter prediction or to perform intra prediction for a prediction unit may be determined, and specific information (eg, intra prediction mode, motion vector, reference picture, etc.) according to each prediction method may be determined. In this case, a processing unit in which prediction is performed and a processing unit in which a prediction method and specific content are determined may be different. For example, a prediction method and a prediction mode may be determined in a prediction unit, and prediction may be performed in a transformation unit.

A residual value (residual block) between the generated prediction block and the original block may be input to the transform unit 130 . Also, prediction mode information, motion vector information, etc. used for prediction may be encoded by the entropy encoder 165 together with a residual value and transmitted to a decoder. When a specific encoding mode is used, the original block may be encoded and transmitted to the decoder without generating the prediction block through the predictors 120 and 125 .

The inter prediction unit 120 may predict a prediction unit based on information on at least one of a picture before or after the current picture, and in some cases, prediction based on information of a partial region in the current picture that has been encoded Units can also be predicted. The inter prediction unit 120 may include a reference picture interpolator, a motion prediction unit, and a motion compensator.

The reference picture interpolator may receive reference picture information from the memory 155 and generate pixel information of integer pixels or less in the reference picture. In the case of luminance pixels, a DCT-based 8-tap interpolation filter in which filter coefficients are different to generate pixel information of integer pixels or less in units of 1/4 pixels may be used. In the case of the color difference signal, a DCT-based 4-tap interpolation filter in which filter coefficients are different to generate pixel information of integer pixels or less in units of 1/8 pixels may be used.

The motion prediction unit may perform motion prediction based on the reference picture interpolated by the reference picture interpolator. As a method for calculating the motion vector, various methods such as Full search-based Block Matching Algorithm (FBMA), Three Step Search (TSS), and New Three-Step Search Algorithm (NTS) may be used. The motion vector may have a motion vector value of 1/2 or 1/4 pixel unit based on the interpolated pixel. The motion prediction unit may predict the current prediction unit by using a different motion prediction method. As the motion prediction method, various methods such as a skip method, a merge method, and an AMVP (Advanced Motion Vector Prediction) method may be used.

The intra prediction unit 125 may generate a prediction unit based on reference pixel information around the current block, which is pixel information in the current picture. When the neighboring block of the current prediction unit is a block on which inter prediction is performed, and thus the reference pixel is a pixel on which inter prediction is performed, the reference pixel included in the block on which the inter prediction is performed is a reference pixel of the block on which the intra prediction is performed. information can be used instead. That is, when the reference pixel is not available, the unavailable reference pixel information may be replaced with at least one reference pixel among the available reference pixels.

In intra prediction, the prediction mode may have a directional prediction mode in which reference pixel information is used according to a prediction direction and a non-directional mode in which directional information is not used when prediction is performed. A mode for predicting luminance information and a mode for predicting chrominance information may be different, and intra prediction mode information used for predicting luminance information or predicted luminance signal information may be utilized to predict chrominance information.

The intra prediction method may generate a prediction block after applying an adaptive intra smoothing (AIS) filter to a reference pixel according to a prediction mode. The type of AIS filter applied to the reference pixel may be different. In order to perform the intra prediction method, the intra prediction mode of the current prediction unit may be predicted from the intra prediction mode of the prediction unit existing around the current prediction unit. When the prediction mode of the current prediction unit is predicted using mode information predicted from the neighboring prediction unit, if the intra prediction mode of the current prediction unit and the neighboring prediction unit is the same, the current prediction unit and the neighboring prediction unit are used using predetermined flag information It is possible to transmit information indicating that the prediction modes of , and if the prediction modes of the current prediction unit and the neighboring prediction units are different from each other, entropy encoding may be performed to encode the prediction mode information of the current block.

In addition, a residual block including residual information that is a difference value from the original block of the prediction unit and the prediction unit in which prediction is performed based on the prediction unit generated by the prediction units 120 and 125 may be generated. The generated residual block may be input to the transform unit 130 .

The transform unit 130 may transform the residual block including the residual data using a transform method such as DCT, DST, or Karhunen Loeve Transform (KLT). In this case, the transform method may be determined based on the intra prediction mode of the prediction unit used to generate the residual block. For example, according to the intra prediction mode, DCT may be used in a horizontal direction and DST may be used in a vertical direction.

The quantization unit 135 may quantize values transformed in the frequency domain by the transform unit 130 . The quantization coefficient may vary according to blocks or the importance of an image. The value calculated by the quantization unit 135 may be provided to the inverse quantization unit 140 and the rearrangement unit 160 .

The transform unit 130 and/or the quantizer 135 may be selectively included in the image encoding apparatus 100 . That is, the image encoding apparatus 100 may encode the residual block by performing at least one of transform or quantization on the residual data of the residual block, or skipping both transform and quantization. Even if either transform or quantization is not performed in the image encoding apparatus 100 or neither transform nor quantization is performed, a block entering the input of the entropy encoder 165 is generally referred to as a transform block.

The rearrangement unit 160 may rearrange the coefficient values on the quantized residual values.

The rearrangement unit 160 may change the two-dimensional block form coefficient into a one-dimensional vector form through a coefficient scanning method. For example, the reordering unit 160 may scan from DC coefficients to coefficients in a high frequency region using a predetermined scan type, and may change it into a one-dimensional vector form.

The entropy encoding unit 165 may perform entropy encoding based on the values calculated by the reordering unit 160 . For entropy encoding, various encoding methods such as Exponential Golomb, Context-Adaptive Variable Length Coding (CAVLC), and Context-Adaptive Binary Arithmetic Coding (CABAC) may be used.

The entropy encoder 165 receives the residual value coefficient information, block type information, prediction mode information, division unit information, prediction unit information and transmission unit information, motion of the coding unit from the reordering unit 160 and the prediction units 120 and 125 . Various information such as vector information, reference frame information, interpolation information of a block, and filtering information may be encoded. In the entropy encoding unit 165, coefficients of the transform block are encoded in units of subblocks within the transform block, and various kinds of flags indicating non-zero coefficients, coefficients having an absolute value greater than 1 or 2, and signs of coefficients are encoded. can be Coefficients that are not encoded using only the flag may be encoded using an absolute value of a difference between a coefficient encoded through the flag and a coefficient of an actual transform block. A method of encoding the coefficients of the transform block will be described in detail with reference to FIG. 3 .

The entropy encoder 165 may entropy-encode the coefficient values of the coding units input from the reordering unit 160 .

The inverse quantizer 140 and the inverse transform unit 145 inversely quantize the values quantized by the quantizer 135 and inversely transform the values transformed by the transform unit 130 . The residual values generated by the inverse quantizer 140 and the inverse transform unit 145 are combined with the prediction units predicted through the motion estimation unit, the motion compensator, and the intra prediction unit included in the prediction units 120 and 125 and restored. You can create a Reconstructed Block.

The filter unit 150 may include at least one of a deblocking filter, an offset correcting unit, and an adaptive loop filter (ALF).

The deblocking filter may remove block distortion caused by the boundary between blocks in the reconstructed picture. In order to determine whether to perform deblocking, it may be determined whether to apply the deblocking filter to the current block based on pixels included in several columns or rows included in the block. When a deblocking filter is applied to a block, a strong filter or a weak filter can be applied according to the required deblocking filtering strength. In addition, in applying the deblocking filter, horizontal filtering and vertical filtering may be concurrently processed when vertical filtering and horizontal filtering are performed.

The offset correcting unit may correct an offset from the original image in units of pixels with respect to the image on which the deblocking has been performed. In order to perform offset correction on a specific picture, a method of dividing pixels included in an image into a certain number of regions, determining the region to be offset and applying the offset to the region, or taking edge information of each pixel into account can be used to apply

Adaptive loop filtering (ALF) may be performed based on a value obtained by comparing the filtered reconstructed image and the original image. After dividing the pixels included in the image into a predetermined group, one filter to be applied to the corresponding group is determined, and filtering can be performed differentially for each group. As for information related to whether to apply ALF, the luminance signal may be transmitted for each coding unit (CU), and the shape and filter coefficients of the ALF filter to be applied may vary according to each block. In addition, the ALF filter of the same type (fixed type) may be applied regardless of the characteristics of the block to be applied.

The memory 155 may store the reconstructed block or picture calculated through the filter unit 150 , and the stored reconstructed block or picture may be provided to the predictors 120 and 125 when inter prediction is performed.

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

Referring to FIG. 2 , the image decoder 200 includes an entropy decoding unit 210, a reordering unit 215, an inverse quantization unit 220, an inverse transform unit 225, prediction units 230 and 235, and a filter unit ( 240) and a memory 245 may be included.

When an image bitstream is input from an image encoder, the input bitstream may be decoded by a procedure opposite to that of the image encoder.

The entropy decoding unit 210 may perform entropy decoding in a procedure opposite to that performed by the entropy encoding unit of the image encoder. For example, various methods such as Exponential Golomb, Context-Adaptive Variable Length Coding (CAVLC), and Context-Adaptive Binary Arithmetic Coding (CABAC) may be applied corresponding to the method performed by the image encoder. In the entropy decoding unit 210, the coefficients of the transform block are based on various kinds of flags indicating non-zero coefficients, coefficients with absolute values greater than 1 or 2, and signs of coefficients in units of partial blocks within the transform block. can be decrypted as Coefficients that are not expressed only by the flag may be decoded through the sum of the coefficients expressed through the flags and the signaled coefficients. A method of decoding the coefficients of the transform block will be described in detail with reference to FIG. 6 .

The entropy decoder 210 may decode information related to intra prediction and inter prediction performed by the encoder.

The reordering unit 215 may perform rearrangement based on a method of rearranging the entropy-decoded bitstream by the entropy decoding unit 210 by the encoder. Coefficients expressed in the form of a one-dimensional vector may be restored and rearranged as coefficients in the form of a two-dimensional block. The reordering unit 215 may receive information related to the coefficient scanning performed by the encoder and perform the rearrangement by performing a reverse scanning method based on the scanning order performed by the corresponding encoder.

The inverse quantization unit 220 may perform inverse quantization based on the quantization parameter provided by the encoder and the reordered coefficient values of the blocks.

The inverse transform unit 225 may perform inverse transform on the inverse quantized transform coefficient using a predetermined transform method. In this case, the transformation method may be determined based on information about a prediction method (inter/intra prediction), a size/shape of a block, an intra prediction mode, and the like.

The prediction units 230 and 235 may generate a prediction block based on the prediction block generation related information provided from the entropy decoding unit 210 and previously decoded block or picture information provided from the memory 245 .

The prediction units 230 and 235 may include a prediction unit determiner, an inter prediction unit, and an intra prediction unit. The prediction unit determining unit receives various information such as prediction unit information input from the entropy decoder 210, prediction mode information of the intra prediction method, and motion prediction related information of the inter prediction method, and divides the prediction unit from the current coding unit, and predicts It may be determined whether the unit performs inter prediction or intra prediction. The inter prediction unit 230 uses information required for inter prediction of the current prediction unit provided from the image encoder, and predicts the current based on information included in at least one picture before or after the current picture including the current prediction unit. Inter prediction may be performed on a unit. Alternatively, inter prediction may be performed based on information on a pre-restored partial region in the current picture including the current prediction unit.

In order to perform inter prediction, based on the coding unit, it is determined whether the motion prediction method of the prediction unit included in the corresponding coding unit is a skip mode, a merge mode, or an AMVP mode. can judge

The intra prediction unit 235 may generate a prediction block based on pixel information in the current picture. When the prediction unit is a prediction unit on which intra prediction is performed, intra prediction may be performed based on intra prediction mode information of the prediction unit provided by the image encoder. The intra prediction unit 235 may include an adaptive intra smoothing (AIS) filter, a reference pixel interpolator, and a DC filter. The AIS filter is a part that performs filtering on the reference pixel of the current block, and can be applied by determining whether to apply the filter according to the prediction mode of the current prediction unit. AIS filtering may be performed on the reference pixel of the current block by using the prediction mode and AIS filter information of the prediction unit provided by the image encoder. When the prediction mode of the current block is a mode in which AIS filtering is not performed, the AIS filter may not be applied.

When the prediction mode of the prediction unit is a prediction unit in which intra prediction is performed based on a pixel value obtained by interpolating the reference pixel, the reference pixel interpolator may interpolate the reference pixel to generate a reference pixel of a pixel unit having an integer value or less. When the prediction mode of the current prediction unit is a prediction mode that generates a prediction block without interpolating the reference pixel, the reference pixel may not be interpolated. The DC filter may generate a prediction block through filtering when the prediction mode of the current block is the DC mode.

The reconstructed block or picture may be provided to the filter unit 240 . The filter unit 240 may include a deblocking filter, an offset correcting unit, and an ALF.

Information on whether a deblocking filter is applied to a corresponding block or picture and information on whether a strong filter or a weak filter is applied when the deblocking filter is applied may be provided from the video encoder. The deblocking filter of the image decoder may receive deblocking filter-related information provided from the image encoder, and the image decoder may perform deblocking filtering on the corresponding block.

The offset correction unit may perform offset correction on the reconstructed image based on the type of offset correction applied to the image during encoding and information on the offset value.

ALF may be applied to a coding unit based on information on whether ALF is applied, ALF coefficient information, etc. provided from the encoder. Such ALF information may be provided by being included in a specific parameter set.

The memory 245 may store the reconstructed picture or block to be used as a reference picture or reference block, and may also provide the reconstructed picture to an output unit.

3 illustrates a method of encoding coefficients of a transform block according to an embodiment to which the present invention is applied.

In an image encoding apparatus, coefficients of a transform block may be encoded in units of predetermined blocks (hereinafter, referred to as partial blocks). A transform block may consist of one or more partial blocks. The partial block may be a block of size NxM. Here, N and M are natural numbers, and N and M may be the same as or different from each other. That is, the partial block may be a square or non-square block. The size/shape of the partial block may be a fixed one (eg, 4x4) pre-promised to the image encoding apparatus, or may be variably determined according to the size/shape of the transform block. Alternatively, the image encoding apparatus may determine an optimal size/shape of a partial block in consideration of encoding efficiency and encode it. Information on the size/shape of the encoded partial block may be signaled at at least one of a sequence, a picture, a slice, and a block level.

In the image encoding apparatus, an order of encoding partial blocks belonging to a transform block may be determined according to a predetermined scan type (hereinafter, referred to as a first scan type). Also, the order of encoding coefficients belonging to partial blocks may be determined according to a predetermined scan type (hereinafter, referred to as a second scan type). The first scan type and the second scan type may be the same or different. As the first/second scan type, a diagonal scan, a vertical scan, a horizontal scan, etc. may be used. However, the present invention is not limited thereto, and one or more scan types having a predetermined angle may be further added. The first/second scan type includes coding block related information (eg, maximum/minimum size, partitioning technique, etc.), size/shape of transform block, size/shape of partial block, prediction mode, intra prediction related information ( For example, it may be determined based on at least one of an intra prediction mode value, directionality, angle, etc.) or inter prediction related information.

The image encoding apparatus may encode position information of the first non-zero coefficient (hereinafter, referred to as a non-zero coefficient) in the above-described encoding order in the transform block. Encoding may be sequentially performed from the partial block including the first non-zero coefficient. Hereinafter, a process of encoding coefficients of partial blocks will be described with reference to FIG. 3 .

A partial block flag related to the current partial block may be encoded ( S300 ). The partial block flag may be encoded in units of partial blocks. The partial block flag may indicate whether at least one non-zero coefficient exists in the current partial block. For example, when the partial block flag is a first value, the current partial block indicates that at least one non-zero coefficient exists, and when the partial block flag is a second value, all coefficients of the current partial block are 0 can indicate that

A partial block coefficient flag related to the current partial block may be encoded ( S310 ). The partial block coefficient flag may be coded in units of coefficients. The partial block coefficient flag may indicate whether a coefficient is a non-zero coefficient. For example, when the coefficient is a non-zero coefficient, the partial block coefficient flag may be encoded as a first value, and when the coefficient is 0, the partial block coefficient flag may be encoded as a second value. The partial block coefficient flag may be selectively coded according to the partial block flag. For example, only when at least one non-zero coefficient exists in the current partial block (ie, when the partial block flag is the first value), encoding may be performed for each coefficient of the partial block.

A flag (hereinafter, referred to as a first flag) indicating whether the absolute value of the coefficient is greater than 1 may be encoded (S320). The first flag may be selectively coded according to a value of the partial block coefficient flag. For example, when the coefficient is a non-zero coefficient (that is, when the partial block coefficient flag is a first value), it is possible to determine whether the absolute value of the coefficient is greater than 1 to encode the first flag. . When the absolute value of the coefficient is greater than 1, the first flag may be encoded as a first value, and when the absolute value of the coefficient is not greater than 1, the first flag may be encoded as a second value.

A flag (hereinafter, referred to as a second flag) indicating whether the absolute value of the coefficient is greater than 2 may be encoded ( S330 ). The second flag may be selectively encoded according to a value of the first flag. For example, when the coefficient is greater than 1 (ie, when the first flag is the first value), it is checked whether the absolute value of the coefficient is greater than 2, and the second flag may be encoded. When the absolute value of the coefficient is greater than 2, the second flag may be encoded as a first value, and when the absolute value of the coefficient is not greater than 2, the second flag may be encoded as a second value.

The number of at least one of the aforementioned first flag or second flag may be a minimum of 1 and a maximum of (N*M). Alternatively, at least one of the first flag and the second flag may be a fixed number (eg, one, two, or more) pre-promised to the video encoding apparatus. The number of first/second flags is determined by the bit depth of the input image, the range of original pixel values in an arbitrary region within the image (dynamic range), the block size/depth, the segmentation technique (e.g., quad tree, binary tree), and the conversion technique. (e.g., DCT, DST), whether transform is skipped, a quantization parameter, and a prediction mode (e.g., intra/inter mode) may be different. In addition to the first/second flag, an nth flag indicating whether the absolute value of the coefficient is greater than n may be additionally encoded. Here, n may mean a natural number greater than 2. The number of n-th flags may be one, two, or more, and may be determined in the same/similar manner to the above-described first/second flags.

In the current partial block, the remaining coefficients that are not coded based on the first/second flag may be coded ( S340 ). Here, the encoding may be a process of encoding the coefficient value itself. The remaining coefficient may be greater than or equal to two. The residual coefficient may be encoded based on at least one of a partial block coefficient flag, a first flag, and a second flag for the residual coefficient. For example, the residual coefficient may be coded as a value obtained by subtracting (partial block coefficient flag + first flag + second flag) from an absolute value of the residual coefficient.

Signs for coefficients of partial blocks may be encoded ( S350 ). The code may be encoded in the form of a flag in units of coefficients. The code may be selectively encoded according to the value of the partial block coefficient flag described above. For example, the code may be coded only when the coefficient is a non-zero coefficient (ie, when the partial block coefficient flag is a first value).

As described above, each absolute value of the coefficients of the partial blocks may be encoded through at least one of partial block coefficient flag encoding, first flag encoding, second flag encoding, and remaining coefficient encoding.

Meanwhile, the above-described coefficient encoding of the partial block may further involve a process of specifying a range of coefficient values belonging to the partial block. Through the above process, it may also be checked whether at least one non-zero coefficient exists in the partial block. The above process may be implemented through at least one of (A) encoding a maximum value, (B) encoding a first threshold value flag, and (C) encoding a second threshold value flag, which will be described later. The process may be implemented by being included in any one of steps S300 to S350 described above, or may be implemented in a form replaced with at least one of steps S300 to S350. Hereinafter, a process of specifying a range of coefficient values belonging to a partial block will be described in detail with reference to FIGS. 4 to 5 .

4 is a diagram illustrating a method of encoding a maximum value of a coefficient of a partial block according to an embodiment to which the present invention is applied.

Referring to FIG. 4 , the maximum value among absolute values of the coefficients of the current partial block may be encoded ( S400 ). From the maximum value, a range of coefficient values belonging to the current partial block may be inferred. For example, when the maximum value is m, the coefficient of the current partial block may be in the range of 0 to m. The maximum value may be selectively coded according to the value of the aforementioned partial block flag. For example, the encoding may be performed only when the current partial block includes at least one non-zero coefficient (ie, when the partial block flag is the first value). When all coefficients of the current partial block are 0 (ie, the partial block flag is the second value), the maximum value may be derived to 0.

Also, based on the maximum value, it may be determined whether at least one non-zero coefficient is included in the current partial block. For example, when the maximum value is greater than 0, the current partial block includes at least one non-zero coefficient, and when the maximum value is 0, all coefficients of the current partial block may be 0. Accordingly, the encoding of the maximum value may be performed in place of encoding of the partial block flag of S300.

5 illustrates a method of encoding a first threshold value flag for a partial block according to an embodiment to which the present invention is applied.

The first threshold value flag of the present invention may indicate whether all coefficients of a partial block are less than a predetermined threshold value. The number of the threshold values may be N (N>=1), and in this case, the range of the threshold values is {T ₀ , T ₁ , T ₂ , . . . ,T _N-1 }. Here, the 0th threshold value T ₀ is the minimum value, and the (N-1)th threshold value T _N-1 is the maximum value, respectively, {T ₀ , T ₁ , T ₂ , ... ,T _N-1 } may be in which the threshold values are arranged in ascending order. The number of the threshold values may be preset in the image encoding apparatus. The image encoding apparatus may determine the number of optimal threshold values in consideration of encoding efficiency and encode them.

The threshold value may be obtained by setting the minimum value to 1 and increasing the minimum value by n (n>=1). The threshold value may be pre-set in the image encoding apparatus. The image encoding apparatus may determine an optimal threshold value in consideration of encoding efficiency, and may encode it.

The range of the threshold value may be determined differently according to the quantization parameter QP. The QP may be set in at least one level of a sequence, a picture, a slice, and a transform block.

For example, when the QP is greater than a predetermined QP threshold, it may be predicted that the distribution of zero coefficients in the transform block will increase. In this case, the range of the threshold value may be determined as {3}, or the first/second threshold value flag encoding process may be omitted, and the coefficients of the partial blocks may be encoded through the above-described steps S300 to S350.

On the other hand, when the QP is smaller than a predetermined QP threshold, it can be predicted that the distribution of non-zero coefficients in the transform block increases. In this case, the range of the threshold value may be determined as {3, 5} or {5, 3}.

That is, the threshold value range when the QP is small may have a different number and/or size (eg, maximum value) of threshold values from the threshold value range when the QP is large. The number of the QP thresholds may be one, two, or more. The QP threshold may be pre-set in the video encoding apparatus. For example, the QP threshold may correspond to a median value of a range of QPs available in the video encoding apparatus. Alternatively, the image encoding apparatus may determine an optimal QP threshold in consideration of encoding efficiency and encode it.

Alternatively, the range of the threshold value may be determined differently according to the size/type of the block. Here, the block may mean a coding block, a prediction block, a transform block, or a partial block. The size may be expressed by at least one of a block width, a height, a sum of the width and height, or a number of coefficients.

For example, if the size of the block is smaller than the predetermined threshold size, the threshold range is determined as {3}, or the first/second threshold value flag encoding process is omitted, and steps S300 to S350 described above are performed. Through this, the coefficients of the partial blocks can be coded. On the other hand, when the size of the block is larger than the predetermined threshold size, the range of the threshold value may be determined as {3, 5} or {5, 3}.

That is, the threshold value range when the block size is small may have a different number and/or size (eg, maximum value) of threshold values from the threshold value range when the block size is large. The number of the threshold sizes may be one, two, or more. The threshold size may be preset in the image encoding apparatus. For example, the threshold size is expressed by axb, where a and b are 2, 4, 8, 16, 32, 64 or more, and a and b may be the same or different. Alternatively, the image encoding apparatus may determine an optimal threshold size in consideration of encoding efficiency and encode it.

Alternatively, the range of the threshold value may be determined differently according to a range of pixel values. The pixel value range may be expressed as a maximum value and/or a minimum value of pixels belonging to a predetermined region. In this case, the predetermined region may mean at least one of a sequence, a picture, a slice, and a block.

For example, when the difference between the maximum value and the minimum value of the pixel value range is smaller than a predetermined threshold difference value, the threshold value range is determined as {3}, or the first/second threshold value flag encoding process is omitted And, it is possible to encode the coefficients of the partial blocks through the above-described steps S300 to S350. On the other hand, when the difference is greater than a predetermined threshold difference value, the range of the threshold value may be determined as {3, 5} or {5, 3}.

That is, the threshold value range when the difference is small may have a different number and/or size (eg, maximum value) of threshold values from the threshold value range when the difference is large. The number of the threshold difference values may be one, two, or more. The threshold difference value may be preset in the image encoding apparatus. Alternatively, the image encoding apparatus may determine an optimal threshold difference value in consideration of encoding efficiency and encode it.

Referring to FIG. 5 , it may be determined whether absolute values of all coefficients in the current partial block are smaller than a current threshold value ( S500 ).

If the absolute values of all coefficients are not smaller than the current threshold value, the first threshold value flag may be encoded as “false” (S510). In this case, the current threshold value (i-th threshold value) is updated to the next threshold value ((i+1)-th threshold value) (S520), and based on the updated current threshold value, the above-described step S500 is performed. can Alternatively, when the absolute values of all coefficients are not smaller than the current threshold value, the first threshold value flag encoding process in step S510 may be omitted and the current threshold value may be updated to the next threshold value.

When the current threshold value reaches the maximum value of the threshold value or when the number of the threshold values is one, the current threshold value may be updated by adding a predetermined constant to the current threshold value. The predetermined constant may be an integer greater than or equal to 1. In this case, the update may be repeatedly performed until the first threshold value flag is encoded as “true”. Based on the updated current threshold value, the above-described step S500 may be performed. Alternatively, when the current threshold value reaches the maximum value of the threshold value or when the number of the threshold values is one, the update process may be terminated.

If the absolute values of all coefficients are smaller than the current threshold value, the first threshold value flag may be coded as “true” (S530).

As described above, when the first threshold value flag for the i-th threshold is “true”, this may indicate that the absolute values of all coefficients in the partial block are less than the i-th threshold. On the other hand, when the first threshold value flag for the i-th threshold value is “false”, this may indicate that the absolute values of all coefficients in the partial block are greater than or equal to the i-th threshold value. Based on the "true" first threshold value flag, a range of coefficient values belonging to a partial block may be specified. That is, when the first threshold value flag for the i-th threshold value is “true”, coefficients belonging to the partial block may be in the range of 0 to (i-th threshold value-1).

According to the encoded first threshold value flag, at least one of the above-described steps S300 to S350 may be omitted.

For example, when the range of the threshold value is {3, 5}, at least one of the first threshold value flag for the threshold value “3” or the first threshold value flag for the threshold value “5” may be encoded. . When the first threshold value flag for the threshold value “3” is “true”, the absolute values of all coefficients in the partial block may be in the range of 0 to 2. In this case, the coefficients of the partial blocks are encoded by performing the remaining steps except for at least one of the above-described steps S330 and S340, or the coefficients of the partial blocks are encoded by performing the remaining steps except for at least one of the steps S300, S330, and S340. may be

When the first threshold value flag for the threshold value “3” is “false”, the first threshold value flag for the threshold value “5” may be encoded. When the first threshold flag for the threshold value “5” is “false”, at least one of absolute values of coefficients in the partial block may be greater than or equal to 5. In this case, the coefficients of the partial blocks may be encoded by performing the same steps S300 to S350 as described above, or the remaining steps except for the step S300 may be performed to encode the coefficients of the partial blocks.

On the other hand, when the first threshold value flag for the threshold value “5” is “true”, absolute values of all coefficients in the partial block may be in the range of 0 to 4. In this case, the coefficients of the partial blocks may be encoded by performing the same steps S300 to S350 as described above, or the remaining steps except for the step S300 may be performed to encode the coefficients of the partial blocks.

Meanwhile, the first threshold value flag of the current partial block may be derived based on the first threshold value flag of another partial block. In this case, the first threshold flag encoding process may be omitted, which will be described with reference to FIG. 11 .

6 illustrates a method of decoding coefficients of a transform block according to an embodiment to which the present invention is applied.

In the image decoding apparatus, coefficients of the transform block may be decoded in units of predetermined blocks (hereinafter, referred to as partial blocks). A transform block may consist of one or more partial blocks. The partial block may be a block of size NxM. Here, N and M are natural numbers, and N and M may be the same as or different from each other. That is, the partial block may be a square or non-square block. The size/shape of the partial block may be a fixed one (eg, 4x4) pre-promised to the image decoding apparatus, may be variably determined according to the size/shape of the transform block, and the size of the signaled partial block / It may be variably determined based on information about the shape. Information on the size/shape of the partial block may be signaled at at least one of a sequence, a picture, a slice, and a block level.

In the image decoding apparatus, an order of decoding the partial blocks included in the transform block may be determined according to a predetermined scan type (hereinafter, referred to as a first scan type). Also, the decoding order of coefficients belonging to partial blocks may be determined according to a predetermined scan type (hereinafter, referred to as a second scan type). The first scan type and the second scan type may be the same or different. As the first/second scan type, a diagonal scan, a vertical scan, a horizontal scan, etc. may be used. However, the present invention is not limited thereto, and one or more scan types having a predetermined angle may be further added. The first/second scan type includes coding block related information (eg, maximum/minimum size, partitioning technique, etc.), size/shape of transform block, size/shape of partial block, prediction mode, intra prediction related information ( For example, it may be determined based on at least one of an intra prediction mode value, directionality, angle, etc.) or inter prediction related information.

The image decoding apparatus may decode position information of a partial block including a first non-zero coefficient (hereinafter, referred to as a non-zero coefficient) in the above-described decoding order in the transform block. Decoding may be sequentially performed from the partial blocks according to the location information. Hereinafter, a process of decoding the coefficients of a partial block will be described with reference to FIG. 6 .

A partial block flag related to the current partial block may be decoded (S600). The partial block flag may be decoded in units of partial blocks. The partial block flag may indicate whether at least one non-zero coefficient exists in the current partial block. For example, when the partial block flag is a first value, the current partial block indicates that at least one non-zero coefficient exists, and when the partial block flag is a second value, all coefficients of the current partial block are 0 can indicate that

A partial block coefficient flag for the current partial block may be decoded (S610). The partial block coefficient flag may be decoded in units of coefficients. The partial block coefficient flag may indicate whether a coefficient is a non-zero coefficient. For example, when the partial block coefficient flag has a first value, it may indicate that the coefficient is a non-zero coefficient, and when the partial block coefficient flag has a second value, it may indicate that the coefficient is 0. The partial block coefficient flag may be selectively decoded according to the partial block flag. For example, only when at least one non-zero coefficient exists in the current partial block (ie, when the partial block flag is the first value), decoding may be performed for each coefficient of the partial block.

A flag (hereinafter, referred to as a first flag) indicating whether the absolute value of the coefficient is greater than 1 may be decoded (S620). The first flag may be selectively decoded according to a value of the partial block coefficient flag. For example, when the coefficient is a non-zero coefficient (ie, when the partial block coefficient flag has a first value), it is possible to determine whether the absolute value of the coefficient is greater than 1 by decoding the first flag. When the first flag is the first value, the absolute value of the coefficient is greater than 1, and when the first flag is the second value, the absolute value of the coefficient is 1.

A flag (hereinafter, referred to as a second flag) indicating whether the absolute value of the coefficient is greater than 2 may be decoded (S630). The second flag may be selectively decoded according to a value of the first flag. For example, when the coefficient is greater than 1 (ie, when the first flag is the first value), it is possible to determine whether the absolute value of the coefficient is greater than 2 by decoding the second flag. When the second flag is the first value, the absolute value of the coefficient is greater than 2, and when the second flag is the second value, the absolute value of the coefficient is 2.

The number of at least one of the aforementioned first flag or second flag may be a minimum of 1 and a maximum of (N*M). Alternatively, at least one of the first flag and the second flag may be a fixed number (eg, one, two, or more) that is pre-promised to the image decoding apparatus. The number of the first/second flags is a block size/depth, a partitioning technique (e.g., quad tree, binary tree), a transform technique (e.g., DCT, DST), whether to skip transform, a quantization parameter, and a prediction mode (e.g., intra/ inter mode) and the like. In addition to the first/second flag, an n-th flag indicating whether the absolute value of the coefficient is greater than n may be further decoded. Here, n may mean a natural number greater than 2. The number of n-th flags may be one, two, or more, and may be determined in the same/similar manner to the above-described first/second flags.

In the current partial block, the remaining coefficients that have not been decoded based on the first/second flag may be decoded (S640). Here, the decoding may be a process of decoding the coefficient value itself. The remaining coefficient may be greater than or equal to two. The residual coefficient may be decoded based on at least one of a partial block coefficient flag, a first flag, and a second flag for the residual coefficient. For example, the remaining coefficients may be derived as (partial block coefficient flag + first flag + second flag + signaled coefficient).

Signs of coefficients of partial blocks may be decoded (S650). The code may be decoded in the form of a flag, in units of coefficients. The code may be selectively decoded according to the value of the aforementioned partial block coefficient flag. For example, the code may be decoded only when the coefficient is a non-zero coefficient (ie, when the partial block coefficient flag is a first value).

Meanwhile, the above-described coefficient decoding of the partial block may further involve a process of specifying a range of coefficient values belonging to the partial block. Through the above process, it may also be checked whether at least one non-zero coefficient exists in the partial block. The process may be performed through at least one of (A) decoding of the maximum value, (B) decoding of the first threshold value flag, and (C) decoding of the second threshold value flag, which will be described later. The process may be performed by being included in any one of steps S600 to S650 described above, or may be performed in a form substituted for at least one of steps S600 to S650. Hereinafter, a process of specifying a range of coefficient values belonging to a partial block will be described in detail with reference to FIGS. 7 to 8 .

7 illustrates a method of decoding a maximum value of a coefficient of a partial block according to an embodiment to which the present invention is applied.

Referring to FIG. 7 , information indicating a maximum value among absolute values of coefficients of the current partial block may be decoded ( S700 ). A range of coefficient values belonging to the current partial block may be inferred through the maximum value according to the information. For example, when the maximum value is m, the coefficient of the current partial block may be in the range of 0 to m. The information indicating the maximum value may be selectively decoded according to the value of the aforementioned partial block flag. For example, decoding may be performed only when the current partial block includes at least one non-zero coefficient (ie, when the partial block flag is the first value). When all coefficients of the current partial block are 0 (ie, the partial block flag is the second value), the information indicating the maximum value may be derived as 0.

In addition, it may be determined whether at least one non-zero coefficient is included in the current partial block through the maximum value according to the information. For example, when the maximum value is greater than 0, the current partial block includes at least one non-zero coefficient, and when the maximum value is 0, all coefficients of the current partial block may be 0. Accordingly, the decoding of the maximum value may be performed in place of the decoding of the partial block flag of S600.

8 is a diagram illustrating a method of decoding a first threshold value flag for a partial block according to an embodiment to which the present invention is applied.

The first threshold value flag of the present invention may indicate whether all coefficients of a partial block are less than a predetermined threshold value. The number of the threshold values may be N (N>=1), and in this case, the range of the threshold values is {T ₀ , T ₁ , T ₂ , . . . ,T _N-1 }. Here, the 0th threshold value T ₀ is the minimum value, and the (N-1)th threshold value T _N-1 is the maximum value, respectively, {T ₀ , T ₁ , T ₂ , ... ,T _N-1 } may be in which the threshold values are arranged in ascending order. The number of thresholds may be preset in the image decoding apparatus, or may be determined based on information about the number of signaled thresholds.

The threshold value may be obtained by setting the minimum value to 1 and increasing the minimum value by n (n>=1). The threshold value may be pre-set in the image decoding apparatus, or may be determined based on information about a signaled threshold value.

The range of the threshold value may be determined differently according to the quantization parameter QP. The QP may be set in at least one level of a sequence, a picture, a slice, and a transform block.

For example, when the QP is greater than a predetermined QP threshold, the threshold range is determined as {3}, or the first/second threshold flag decoding process is omitted, and the above-described steps S600 to S650 are performed. Coefficients of partial blocks may be decoded.

On the other hand, when the QP is smaller than a predetermined QP threshold, the range of the threshold may be determined to be {3, 5} or {5, 3}.

That is, the threshold value range when the QP is small may have a different number and/or size (eg, maximum value) of threshold values from the threshold value range when the QP is large. The number of the QP thresholds may be one, two, or more. The QP threshold may be pre-set in the image decoding apparatus. For example, the QP threshold may correspond to a median value of a range of QPs available in the image decoding apparatus. Alternatively, the QP threshold may be determined based on information about the QP threshold signaled by the image encoding apparatus.

Alternatively, the range of the threshold value may be determined differently according to the size/type of the block. Here, the block may mean a coding block, a prediction block, a transform block, or a partial block. The size may be expressed by at least one of a block width, a height, a sum of the width and height, or a number of coefficients.

For example, if the size of the block is smaller than the predetermined threshold size, the threshold range is determined as {3}, or the first/second threshold flag decoding process is omitted, and steps S600 to S650 described above are performed. It is possible to decode the coefficients of the partial blocks through On the other hand, when the size of the block is larger than the predetermined threshold size, the range of the threshold value may be determined as {3, 5} or {5, 3}.

That is, the threshold value range when the block size is small may have a different number and/or size (eg, maximum value) of threshold values from the threshold value range when the block size is large. The number of the threshold sizes may be one, two, or more. The threshold size may be preset in the image decoding apparatus. For example, the threshold size is expressed by axb, where a and b are 2, 4, 8, 16, 32, 64 or more, and a and b may be the same or different. Alternatively, the threshold size may be determined based on information about the threshold size signaled by the image encoding apparatus.

Alternatively, the range of the threshold value may be determined differently according to a range of pixel values. The pixel value range may be expressed as a maximum value and/or a minimum value of pixels belonging to a predetermined region. In this case, the predetermined region may mean at least one of a sequence, a picture, a slice, and a block.

For example, when the difference between the maximum value and the minimum value of the pixel value range is smaller than a predetermined threshold difference value, the threshold value range is determined as {3} or the first/second threshold value flag decoding process is omitted And, the coefficients of the partial blocks may be decoded through the above-described steps S600 to S650. On the other hand, when the difference is greater than a predetermined threshold difference value, the range of the threshold value may be determined as {3, 5} or {5, 3}.

That is, the threshold value range when the difference is small may have a different number and/or size (eg, maximum value) of threshold values from the threshold value range when the difference is large. The number of the threshold difference values may be one, two, or more. The threshold difference value may be preset in the image decoding apparatus, or may be determined based on information about the threshold difference value signaled by the image encoding apparatus.

Referring to FIG. 8 , the first threshold value flag related to the current threshold value may be decoded ( S800 ).

The first threshold value flag may indicate whether absolute values of all coefficients of a partial block are smaller than a current threshold value. For example, when the first threshold value flag is “false”, it may be that absolute values of all coefficients of the partial block are greater than or equal to the current threshold value. On the other hand, when the first threshold value flag is “true”, it may be that the absolute values of all coefficients of the partial block are smaller than the current threshold value.

If the first threshold value flag is “false”, the current threshold value (i-th threshold value) is updated to the next threshold value ((i+1)-th threshold value) (S810), and the updated current threshold value Based on the value, the above-described step S800 may be performed.

When the current threshold value reaches the maximum value of the threshold value or when the number of the threshold values is one, the current threshold value may be updated by adding a predetermined constant to the current threshold value. The predetermined constant may be an integer greater than or equal to 1. In this case, the update may be repeatedly performed until the first threshold value flag that is “true” is decoded. Alternatively, when the current threshold value reaches the maximum value of the threshold value or when the number of the threshold values is one, the update process may be terminated.

As shown in FIG. 8 , when the first threshold value flag is “true”, decoding of the first threshold value flag may not be performed any more.

As described above, when the first threshold value flag for the i-th threshold is “true”, this may indicate that the absolute values of all coefficients in the partial block are less than the i-th threshold. On the other hand, when the first threshold value flag for the i-th threshold value is “false”, this may indicate that the absolute values of all coefficients in the partial block are greater than or equal to the i-th threshold value. Based on the "true" first threshold value flag, a range of coefficient values belonging to a partial block may be specified. That is, when the first threshold value flag for the i-th threshold value is “true”, coefficients belonging to the partial block may be in the range of 0 to (i-th threshold value-1).

According to the decoded first threshold value flag, at least one of the above-described steps S600 to S650 may be omitted.

For example, when the range of the threshold value is {3, 5}, at least one of the first threshold value flag for the threshold value “3” or the first threshold value flag for the threshold value “5” may be decoded . When the first threshold value flag for the threshold value “3” is “true”, the absolute values of all coefficients in the partial block may be in the range of 0 to 2. In this case, the coefficients of the partial blocks are decoded by performing the remaining steps except for at least one of the aforementioned steps S630 and S640, or the coefficients of the partial blocks are decoded by performing the remaining steps except for at least one of the steps S600, S630, and S640. may be

When the first threshold value flag for the threshold value “3” is “false”, the first threshold value flag for the threshold value “5” may be decoded. When the first threshold flag for the threshold value “5” is “false”, at least one of absolute values of coefficients in the partial block may be greater than or equal to 5. In this case, the coefficients of the partial blocks may be decoded by performing the same steps S600 to S650 as described above, or the remaining steps except for the step S600 may be performed to decode the coefficients of the partial blocks.

On the other hand, when the first threshold value flag for the threshold value “5” is “true”, absolute values of all coefficients in the partial block may be in the range of 0 to 4. In this case, the coefficients of the partial blocks may be decoded by performing the same steps S600 to S650 as described above, or the remaining steps except for the step S600 may be performed to decode the coefficients of the partial blocks.

Meanwhile, the first threshold value flag of the current partial block may be derived based on the first threshold value flag of another partial block. In this case, the first threshold flag decoding process may be omitted, which will be described with reference to FIG. 9 .

9 is a diagram illustrating a method of deriving a first/second threshold value flag for a current partial block according to an embodiment to which the present invention is applied.

In this embodiment, the transform block 900 is 8x8, the partial block is 4x4, the block including the first non-zero coefficient is 920, and the partial block of the transform block is 940, 920, 930, 910 according to the scan type. It is assumed that encoding/decoding is performed in order.

In the current partial block, a first threshold value flag related to a specific threshold value may be derived based on the first threshold value flag of the previous partial block. For example, based on the first threshold value flag that is “false” in the previous partial block, the first threshold value flag of the current partial block may be derived as “false”. Here, it is assumed that {3, 5, 7} is used as the range of the threshold value.

In detail, since the encoding/decoding order of the first partial block 940 in the encoding/decoding order precedes the position of the partial block 920 to which the first non-zero coefficient belongs, the first threshold value flag may not be encoded/decoded. In the second partial block 920 in the encoding/decoding order, since the first threshold value flag for the threshold value “3” is “true”, only the first threshold value flag for the threshold value “3” can be encoded/decoded. . In the third partial block 930 in the encoding/decoding order, since the first threshold value flag for the threshold value “3” is “false” and the first threshold value flag for the threshold value “5” is “true”, the threshold The first threshold value flags for values “3” and “5” may be encoded/decoded, respectively. In the last partial block 910 in the encoding/decoding order, the first threshold value flag for the threshold value “3” is “false”, and the first threshold value flag for the threshold value “5” is “false”. At this time, since the first threshold value flag for the threshold value “3” in the previous partial block 930 is “false”, the current partial block 910 predicts that at least one absolute value of a coefficient equal to or greater than 3 exists, and the threshold value “3” The first threshold flag for ? may be derived as “false”.

In the current partial block, a first threshold value flag related to a specific threshold value may be derived based on the first threshold value flag of the previous partial block. For example, based on the first threshold value flag that is “false” in the previous partial block, the first threshold value flag of the current partial block may be derived as “false”.

Hereinafter, a method of determining a partial block of a transform block will be described in detail with reference to FIGS. 10 to 15 .

The image encoding apparatus may determine a partial block having a predetermined size/shape constituting the transform block, and may encode information about the size/shape of the partial block. The image decoding apparatus may determine the size/shape of the partial block based on the encoded information (first method). Alternatively, the size/shape of a partial block may be determined through a rule pre-promised to the image encoding/decoding apparatus (second method). Information indicating which method of the first method and the second method determines the size/shape of a partial block may be signaled in at least one layer of a video, a sequence, a picture, a slice, or a block. The block may mean a coding block, a prediction block, or a transform block.

The size of the partial block in the transform block may be equal to or smaller than the size of the transform block. The shape of the transform block/partial block may be square or non-square. The shape of the transform block may be the same as or different from that of the partial block.

Information about the shape of the transform block may be encoded. In this case, the information may include at least one of information on whether to use only a square, a non-square, or both a square and a non-square in the form of a transform block. The information may be signaled in at least one layer of a video, a sequence, a picture, a slice, or a block. The block may mean a coding block, a prediction block, or a transform block. Information about the size of the transform block may be encoded. In this case, the information may include at least one of a minimum size, a maximum size, a division depth, and a maximum/minimum value regarding the division depth. The information may be signaled in at least one layer of a video, a sequence, a picture, a slice, or a block.

Information about the shape of the partial block may be encoded. In this case, the information may include at least one of information on whether to use only a square, a non-square, or both a square and a non-square in the form of a partial block. The information may be signaled in at least one layer of a video, a sequence, a picture, a slice, or a block. The block may mean a coding block, a prediction block, or a transform block. Information about the size of a partial block may be encoded. In this case, the information may include at least one of a minimum size, a maximum size, a division depth, and a maximum/minimum value regarding the division depth. The information may be signaled in at least one layer of a video, a sequence, a picture, a slice, or a block.

10 illustrates a method of determining the size/shape of a partial block based on a merge flag as an embodiment to which the present invention is applied.

From a partial block of the minimum size to a partial block of the maximum size, the image encoding apparatus may determine which type of merge is the most optimal through RDO.

Referring to FIG. 10 , an RD-cost value for the transformation block 1001 including the plurality of partial blocks 1-16 may be calculated. The partial block may be a partial block having a pre-promised minimum size to the image encoding apparatus. The transform block 1002 is a case in which four partial blocks 13 - 16 of the transform block 1001 are merged into one partial block, and an RD-cost value for the transform block 1002 can be calculated. The transformation block 1003 is a case in which four partial blocks 9-12 of the transformation block 1001 are merged into one partial block, and an RD-cost value for the transformation block 1003 can be calculated. . The transform block 1004 is a case in which four partial blocks 5-8 of the transform block 1001 are merged into one partial block, and an RD-cost value for the transform block 1004 can be calculated. .

The image encoding apparatus may calculate the RD-cost value while merging the partial blocks in the transform block up to the partial blocks of the maximum size using a quad tree method. An optimal merging may be determined based on the RD-cost value, and a merging flag indicating the optimal merging may be encoded. The image decoding apparatus may determine the size/shape of a partial block in the transform block based on the encoded merge flag.

For example, the transform block 1004 is the optimal merging, the minimum size of the partial block is equal to the size of the partial block "1" of the transform block 1004, and the maximum size of the partial block is the transform block 1004 ) is assumed to be the same as the partial block "5". In this case, the image encoding apparatus may encode a merge flag (“false”) indicating that the transform block 1001 is not an optimal merge. Then, the four partial blocks 10-13 of the transform block 1004 encode a merge flag (“false”) indicating that the unmerged state is optimal, and the four partial blocks 6 - 6 of the transform block 1004 are encoded. 9) may encode a merge flag (“false”) indicating that the unmerged state is optimal. Then, a merge flag (“True”) indicating that the state in which the four partial blocks 6-9 in the transform block 1001 are merged into one partial block is optimal is encoded, and the four partial blocks 6-9 of the transform block 1004 are encoded. A merge flag (“false”) indicating that the partial blocks 1 - 4 are not merged is optimal. That is, the image encoding apparatus may generate the bitstream "00010" through the encoding, and the image decoding apparatus may decode the bitstream to determine the merge type of the transform block 1004 .

10 does not limit the merging order of partial blocks, and merging in another order is also possible. The above-described merging may be performed within a range of a block size/shape pre-promised to the image encoding/decoding apparatus. The shape of the merged partial block may be a square or a non-square shape. The shape of the merged partial block may be determined based on an encoding order or a scanning order of the partial blocks.

For example, when the encoding order of the partial blocks in the transform block is in the diagonal direction, square merging may be used. Alternatively, when the encoding order of partial blocks in the transform block is in the vertical direction, vertical non-square merging may be used. Alternatively, when the encoding order of the partial blocks in the transform block is in the horizontal direction, a long horizontal non-square merge may be used.

11 illustrates a method of determining the size/shape of a partial block based on a division flag as an embodiment to which the present invention is applied.

The apparatus for encoding an image may determine what type of split the transform block is most optimal through RDO from a partial block of the maximum size to a partial block of the minimum size.

Referring to FIG. 11 , an RD-cost value for the transform block 1101 including one partial block 1 may be calculated. The partial block 1 may be a partial block of a maximum size pre-promised to the image encoding apparatus. The transform block 1002 is a case in which a partial block of the maximum size is divided into four partial blocks 1-4, and an RD-cost value for the transform block 1002 may be calculated. The transformation block 1103 is a case in which the partial block “1” of the transformation block 1102 is divided into four partial blocks 1-4, and an RD-cost value for the transformation block 1103 can be calculated. there is. The transformation block 1104 is a case where the partial block “1” of the transformation block 1103 is again divided into four partial blocks 1-4, and the RD-cost value for the transformation block 1104 is calculated. can

The image encoding apparatus may calculate the RD-cost value while dividing the partial blocks in the transform block up to the partial blocks of the minimum size using a quad tree method. An optimal partition may be determined based on the RD-cost value, and a partition flag indicating the optimal partition may be encoded. The image decoding apparatus may determine the size/shape of a partial block in the transform block based on the coded split flag.

For example, the transform block 1103 is an optimal partition, the minimum size of the partial block is equal to the size of the partial block "1" of the transform block 1103, and the maximum size of the partial block is the transform block 1103 is assumed to be the same as In this case, the image encoding apparatus may encode a split flag (“true”) indicating that the transform block 1101 is not optimal split. Then, in the transform block 1102 , a split flag (“true”) indicating that the partial block '1' is optimal to be divided into 4 partial blocks may be encoded. In the transform block 1102, a split flag (“false”) indicating that it is optimal not to split the remaining subblocks 2-4 into 4 subblocks may be encoded. That is, the image encoding apparatus may generate "11000" of the bitstream through the encoding, and the image decoding apparatus may decode the bitstream to determine the division type of the transform block 1103 .

11 does not limit the division order of the partial blocks, and it is possible to divide the partial blocks in another order. The above-described division may be performed within a range of a block size/shape pre-promised to the image encoding/decoding apparatus. The shape of the divided partial blocks may be a square or a non-square shape. The shape of the divided partial block may be determined based on an encoding order or a scan order of the partial block.

For example, when the encoding order of the partial blocks in the transform block is in the diagonal direction, square division may be used. Alternatively, when the encoding order of the partial blocks in the transform block is in the vertical direction, vertical non-square division may be used. Alternatively, when the encoding order of the partial blocks in the transform block is in the horizontal direction, a horizontally long non-square division may be used.

12 illustrates a method for determining the size/shape of a partial block based on partition index information as an embodiment to which the present invention is applied.

The apparatus for encoding an image may determine the most optimal splitting form of the partial blocks through RDO from when all partial blocks of the transform block are partial blocks of the maximum size to all partial blocks of the minimum size.

Referring to FIG. 12 , the transformation block 1201 is configured with one partial block 1, and in this case, the RD-cost value can be calculated. The partial block 1 may be a partial block of a maximum size pre-promised to the image encoding apparatus. The transform block 1202 is a case in which the transform block 1201 is divided into four partial blocks 1-4, and in this case, an RD-cost value can be calculated. The transform block 1203 is a case in which each partial block of the transform block 1202 is again divided into four partial blocks, and in this case, the RD-cost value can be calculated.

As described above, the RD-cost value may be calculated while dividing the transform block into partial blocks of the same size within the range of the partial blocks of the maximum size and the minimum size. An optimal partition may be determined based on the RD-cost value, and partition index information indicating the optimal partition may be encoded. The image decoding apparatus may determine the size/shape of a partial block in the transform block based on the encoded segmentation index information.

For example, the image encoding apparatus sets “0” as the split index information when the transform block 1201 is the optimal split, and “1” as the split index information when the transform block 1202 is the optimal split. , when the transform block 1203 is an optimal partition, "2" may be encoded as partition index information, respectively. The image decoding apparatus may determine the size/shape of a partial block in the transform block based on the encoded segmentation index information.

13 is a diagram illustrating a method of dividing a transform block based on a position of a non-zero coefficient according to an embodiment to which the present invention is applied.

In the transform block, the size/shape of the partial block may be determined based on the position of the first non-zero coefficient in the encoding/decoding order.

The size/shape of the partial block may be determined by the size/shape of the block including the location of the first non-zero coefficient (hereinafter, referred to as a first reference block). The first reference block may have a minimum size among blocks including the position of the first non-zero coefficient and the position of the lower-right coefficient of the transform block. In this case, the first reference block may belong to a range of a minimum size and a maximum size of a partial block pre-promised to the image encoding/decoding apparatus. The transform block may be divided according to the determined size/shape of the partial block.

For example, if the transform block 1301 is 16x16 and the position of the first non-zero coefficient in the encoding/decoding order is (12,12) based on (0,0) at the upper left of the transform block, the coefficient (12) , 12) may be determined to have a size of 4x4, and as shown in FIG. 13 , the transform block 1301 may be divided into 16 partial blocks having a size of 4x4. Alternatively, if the transform block 1302 is 16x16 and the position of the first non-zero coefficient in the encoding/decoding order is (8,8) with respect to the upper left end (0,0) of the transform block, the corresponding coefficient (8,8) ) may be determined to be 8x8, and the transform block 1302 may be divided into 4 subblocks having a size of 8x8 as shown in FIG. 13 . Alternatively, if the transform block 1303 is 16x16 and the position of the first non-zero coefficient in the encoding/decoding order is (8,0) with respect to the upper left end (0,0) of the transform block, the coefficient (8,0) ) may be determined to be 8×16, and in this case, the transform block 1303 may be divided into two partial blocks having a size of 8×16.

Alternatively, the size/shape of the partial block may be determined as the size/shape of a block that does not include the location of the first non-zero coefficient (hereinafter, a second reference block). The second reference block may have a maximum size among blocks that do not include the position of the first non-zero coefficient and include the position of the lower-right coefficient of the transform block. In this case, the second reference block may belong to a range of a minimum size and a maximum size of a partial block pre-promised to the image encoding/decoding apparatus. The transform block may be divided according to the determined size/shape of the partial block.

For example, if the transform block 1301 is 16x16 and the position of the first non-zero coefficient in the encoding/decoding order is (12,11) with respect to the upper-left (0,0) of the transform block, the corresponding coefficient (12) , 11) may be determined to have a size of 4x4, and in this case, the transform block 1301 may be divided into 16 partial blocks having a size of 4x4. Alternatively, if the transform block 1302 is 16x16 and the position of the first non-zero coefficient in the encoding/decoding order is (7,13) with respect to the upper left end (0,0) of the transform block, the corresponding coefficient (7,13) ) may be determined to be 8x8, and in this case, the transform block 1302 may be divided into 4 partial blocks having a size of 8x8. Alternatively, if the transform block 1303 is 16x16, and the position of the first non-zero coefficient in the encoding/decoding order is (6,14) with respect to the upper left end (0,0) of the transform block, the corresponding coefficient (6,14) ) may be determined to be 8×16, and in this case, the transform block 1303 may be divided into two partial blocks having a size of 8×16.

14 illustrates a method of selectively dividing a partial region of a transform block according to an embodiment to which the present invention is applied.

A region other than a partial region in the transform block may be divided into partial blocks having a predetermined size/shape. Here, the partial region may be specified based on the position (a, b) of the first non-zero coefficient. For example, the partial region may include at least one of a region having an x-coordinate greater than a and a region having a y-coordinate greater than b. Here, the size/shape of the partial block may be determined in the same/similar manner to the at least one embodiment described above, and thus a detailed description thereof will be omitted.

For example, when the transform block 1401 is 16x16 and the position of the first non-zero coefficient in the encoding/decoding order is (11,11) with respect to the upper left end (0,0) of the transform block, (11,11) ) and a region below the y-coordinate of (11,11) are excluded from the partial block setting range and may not be encoded/decoded. In this case, the remaining region of the transform block 1401 may be divided into 4 partial blocks having a size of 6x6.

Alternatively, the remaining region except for a partial region in the transform block may be divided into partial blocks having a predetermined size/shape. Here, the partial region may be specified based on the position (a,b) of the first non-zero coefficient and the maximum coordinate value (c,d) of the transform block. The maximum coordinate value (c, d) may be the position of the lower right coefficient of the transform block. For example, "(c-a)" and "(d-b)", which are differences between the position (a,b) of the first non-zero coefficient and the maximum coordinate value (c,d) of the transform block, may be calculated, respectively. Based on the position of the lower-right coefficient of the transform block, the position (e,f) shifted by the minimum value among the difference values may be determined. In this case, the partial region may include at least one of a region having an x-coordinate greater than e and a region having a y-coordinate greater than f. Here, the size/shape of the partial block may be determined in the same/similar manner to the at least one embodiment described above, and thus a detailed description thereof will be omitted.

For example, if the transform block 1401 is 16x16 and the position of the first non-zero coefficient in the encoding/decoding order is (11,8) with respect to the upper left end (0,0) of the transform block, the x of the corresponding coefficient - "4", which is the difference value between the coordinate "11" and the maximum x-coordinate "15" of the transform block, and " 7" can be obtained. Based on the position of the lower right coefficient of the transform block, a position shifted by "4", which is the minimum value among the difference values, may be determined as (11, 11). In this case, the region to the right of the x-coordinate of (11,11) and the region below the y-coordinate of (11,11) are excluded from the partial block setting range, and encoding/decoding may not be performed. In this case, the remaining region of the transform block 1401 may be divided into 4 partial blocks having a size of 6x6.

Alternatively, the transform block may be divided into a plurality of regions based on a predetermined boundary line. The boundary line may be one, two or more. The boundary line has a slope of a predetermined angle, and the angle may be within a range of 0 degrees to 90 degrees. The boundary line may include the position of the first non-zero coefficient in the encoding/decoding order of the coefficients in the transform block. Specifically, based on the boundary line, the transformation block may be divided into a first region and a second region. In this case, the first area may be divided into partial blocks having a predetermined size/shape, and the second area may not be divided into partial blocks having a predetermined size/shape. That is, the coefficients belonging to the first region may be encoded/decoded based on partial blocks having a predetermined size/shape, and encoding/decoding of the coefficients belonging to the second region may be skipped. The first area may refer to an area located at the upper end, the left side, or the upper left end with respect to the boundary line. In this case, the first area may further include an area of the partial block including the boundary line. The second area may refer to an area located at the lower end, the right side, or the lower right end with respect to the boundary line.

For example, the transform block 1402 is 16x16, the position of the first non-zero coefficient in the encoding/decoding order is (10,6) based on (0,0) at the upper left of the transform block, and the transform block 1402 It is assumed that all subblocks of are pre-divided into 4x4 units. In this case, based on (10,6), the position of the last pixel in the upper right 45 degree direction is (15,1), and the last pixel position in the lower left 45 degree direction is (1,15). Based on the boundary line connecting the two pixel positions, the partial blocks 1-10 of the region located at the upper left are determined to be encoded/decoded partial blocks, and the partial blocks of the region located at the lower right are the portions that are not encoded/decoded. Blocks can be determined. In this case, the shape of the partial block of the region located at the upper left may be determined to be a rectangle and/or a triangle.

For example, the transform block 1403 is 16x16, the position of the first non-zero coefficient in the encoding/decoding order is (8,7) based on (0,0) at the upper left of the transform block, and the transform block 1403 It is assumed that all subblocks of are pre-divided into 4x4 units. In this case, the position of the last pixel in the 45 degree direction from the upper right corner is (15, 0), and the last pixel position in the lower left 45 degree direction is (0,15) based on (8,7). Based on the boundary line connecting the two pixel positions, the partial blocks 1-10 of the region located at the upper left are determined to be encoded/decoded partial blocks, and the partial blocks of the region located at the lower right are the portions that are not encoded/decoded. Blocks can be determined. In this case, in the case of a partial block including the boundary line, only coefficients in the upper left region with respect to the boundary line may be included in the partial block, and coefficients in the lower right region may be excluded from the partial block. The shape of the partial block of the region located at the upper left may be determined to be a rectangle (part blocks 1-5 and 8) and/or a triangle (part blocks 6, 7, 9, and 10).

15 is a diagram illustrating a method of dividing a transform block based on a property of a DC/AC component in a frequency domain as an embodiment to which the present invention is applied.

In the frequency domain, the division form of the transform block may be determined by considering the properties of DC/AC components constituting the transform block. The attribute may mean a component position, distribution, density, or strength, and the attribute may be determined dependently on a transformation method (eg, DCT, DST, etc.) of a transformation block.

In the transform block, the region where the AC component is the weakest concentration may be divided into partial blocks having a size larger than that of the remaining regions. For example, in the 16×16 transform block 1501 , the AC component may be mainly located in partial blocks “5” to “13”. In this case, an 8x8 partial block may be allocated only to partial block 13, which is an area in which the AC component is weakly concentrated, and a 4x4 partial block may be allocated to the remaining area.

Alternatively, in the transform block, the region where the AC component is the weakest concentration may be divided into partial blocks having a size smaller than that of the remaining regions. For example, in the transform block 1502 having a size of 16x16, the AC component may be mainly located in partial blocks “2” to “7”. In this case, a partial block having a size of 4x4 may be allocated only to partial blocks "4" to "7", which are regions in which the AC component is the weakest, and a partial block having a size of 8x8 may be allocated to the remaining regions.

Alternatively, within the transform block, a region in which the DC component is most strongly concentrated may be divided into partial blocks having a size smaller than that of the remaining regions. For example, in the 16×16 transform block 1503 , the DC component may be mainly located in partial blocks “1” to “4”. In this case, a partial block having a size of 4x4 may be allocated only to partial blocks “1” to “4”, which are regions having the strongest DC component, and a partial block having a size of 8x8 may be allocated to the remaining regions.

Alternatively, within the transform block, a region in which the DC component is most strongly concentrated may be divided into partial blocks having a size larger than that of the remaining regions. For example, in the transform block 1504 having a size of 16x16, the DC component may be mainly located in the partial block “1” region. In this case, a partial block having a size of 8x8 may be allocated only to partial block "1", which is a region having the strongest DC component, and a partial block having a size of 4x4 may be allocated to the remaining regions.

In the above-described embodiment, the region of the DC/AC component in the transform block is assumed based on the quadrant transform block. However, the present invention is not limited thereto, and the same/similar application may be applied to the case of a transform block divided into N (N ≥ 1) equal parts or 2 to the N power.

According to a quantization parameter (QP) of the transform block, all or a part of partial blocks in the transform block may be selectively encoded/decoded. For example, when the QP of the transform block is greater than a predetermined QP threshold, encoding/decoding may be performed of only a partial region within the transform block. On the other hand, when the QP of the transform block is less than a predetermined QP threshold, all partial blocks in the transform block may be encoded/decoded.

Here, the partial region may be specified by at least one of a predetermined vertical line or a horizontal line. The vertical line may be located at a point a distance to the left from the left boundary of the transform block, and the horizontal line may be located at a point b below the upper boundary of the transform block. A and b are natural numbers, and may be the same as or different from each other. The partial region may be a region located to the left with respect to the vertical line and/or to an upper side with respect to the horizontal line. The positions of the vertical/horizontal lines may be pre-promised to the image encoding/decoding apparatus, or may be variably determined in consideration of the size/shape of the transform block. Alternatively, the image encoding apparatus encodes and signals information specifying the partial region (for example, information specifying the position of the vertical/horizontal line), and the image decoding apparatus performs a partial signal based on the signaled information. You can also specify an area. The boundary of the specified partial region may or may not be in contact with the boundary of the partial block within the transform block.

For example, the partial region may be one partial block of the region in which the DC component is concentrated or N number of partial blocks (N≥1) including adjacent partial blocks. Alternatively, the partial region may be specified by a vertical line passing through a point 1/n of an upper boundary of the transform block and/or a horizontal line passing through a point 1/m of a left boundary of the transform block. n and m are natural numbers, and may be the same as or different from each other.

The number of the QP thresholds may be one, two, or more. The QP threshold may be pre-set in the video encoding apparatus. For example, the QP threshold may correspond to a median value of a range of QPs usable in an image encoding/decoding apparatus. Alternatively, the image encoding apparatus may determine an optimal QP threshold in consideration of encoding efficiency and encode it.

Alternatively, all or part of the partial blocks in the transform block may be selectively encoded/decoded according to the size of the transform block. For example, when the size of the transform block is greater than or equal to a predetermined threshold size, encoding/decoding may be performed only in a partial region within the transform block. On the other hand, when the size of the transform block is smaller than a predetermined threshold size, all partial blocks in the transform block may be encoded/decoded.

Here, the partial region may be specified by at least one of a predetermined vertical line or a horizontal line. The vertical line may be located at a point a distance to the left from the left boundary of the transform block, and the horizontal line may be located at a point b below the upper boundary of the transform block. A and b are natural numbers, and may be the same as or different from each other. The partial region may be a region located to the left with respect to the vertical line and/or to an upper side with respect to the horizontal line. The positions of the vertical/horizontal lines may be pre-promised to the image encoding/decoding apparatus, or may be variably determined in consideration of the size/shape of the transform block. Alternatively, the image encoding apparatus encodes and signals information specifying the partial region (for example, information specifying the position of the vertical/horizontal line), and the image decoding apparatus performs a partial signal based on the signaled information. You can also specify an area. The boundary of the specified partial region may or may not be in contact with the boundary of the partial block within the transform block.

For example, the partial region may be one partial block of the region in which the DC component is concentrated or N number of partial blocks (N≥1) including adjacent partial blocks. Alternatively, the partial region may be specified by a vertical line passing through a point 1/n of an upper boundary of the transform block and/or a horizontal line passing through a point 1/m of a left boundary of the transform block. n and m are natural numbers, and may be the same as or different from each other.

The number of the threshold sizes may be one, two, or more. The threshold size may be preset in the image encoding apparatus. For example, the threshold size is expressed as cxd, where c and d are 2, 4, 8, 16, 32, 64 or more, and c and d may be the same or different. Alternatively, the image encoding apparatus may determine an optimal threshold size in consideration of encoding efficiency and encode it.

Example methods of the present disclosure are expressed as a series of operations for clarity of description, but this is not intended to limit the order in which the steps are performed, and if necessary, each step may be performed simultaneously or in a different order. In order to implement the method according to the present disclosure, other steps may be included in addition to the illustrated steps, steps may be excluded from some steps, and/or other steps may be included except for some steps.

Various embodiments of the present disclosure do not list all possible combinations but are intended to describe representative aspects of the present disclosure, and matters described in various embodiments may be applied independently or in combination of two or more.

In addition, various embodiments of the present disclosure may be implemented by hardware, firmware, software, or a combination thereof. For implementation by hardware, one or more Application Specific Integrated Circuits (ASICs), Digital Signal Processors (DSPs), Digital Signal Processing Devices (DSPDs), Programmable Logic Devices (PLDs), Field Programmable Gate Arrays (FPGAs), general purpose It may be implemented by a processor (general processor), a controller, a microcontroller, a microprocessor, and the like.

The scope of the present disclosure includes software or machine-executable instructions (eg, operating system, application, firmware, program, etc.) that cause an operation according to the method of various embodiments to be executed on a device or computer, and such software or and non-transitory computer-readable media in which instructions and the like are stored and executable on a device or computer.

Claims (4)

decoding coefficients of a transform block from the bitstream; and
Reconstructing the transform block using the decoded coefficients,
Decoding of the coefficients of the transform block is performed only on all or some regions within the transform block according to a result of comparing the size of the transform block with a pre-defined threshold size,
When the size of the transform block is greater than or equal to the threshold size, decoding of the coefficients of the transform block is performed only on a partial region within the transform block,
When the size of the transform block is smaller than the threshold size, decoding of the coefficients of the transform block is performed on the entire area of the transform block,
The partial region is specified by a predetermined vertical line or horizontal line based on information obtained from the bitstream, wherein the information includes information specifying the position of the vertical line or the position of the horizontal line. contains information specifying;
The vertical line is located at a point a distance to the right from the left boundary of the transformation block, and the horizontal line is located at a point that is separated by b from the upper boundary of the transformation block downward,
The partial area is an area located on the left with respect to the vertical line or an area located above with respect to the horizontal line,
The partial area is divided into a plurality of partial blocks,
and the coefficients of the partial region are decoded in units of the partial blocks. The method of claim 1,
The threshold size is an NxM size preset in the image decoding apparatus,
Wherein N and M are integers of 8, 16 or more, respectively, video signal decoding method. generating a transform block including residual data that is a difference between an original block and a prediction block of a current coding block; and
encoding the coefficients of the transform block;
Coding of the coefficients of the transform block is performed only on all or some regions within the transform block according to a result of comparing the size of the transform block with a pre-defined threshold size,
When the size of the transform block is greater than or equal to the threshold size, decoding of the coefficients of the transform block is performed only on a partial region within the transform block,
When the size of the transform block is smaller than the threshold size, decoding of the coefficients of the transform block is performed on the entire area of the transform block,
The partial region is specified by a predetermined vertical line or horizontal line,
The vertical line is located at a point a distance to the right from the left boundary of the transformation block, and the horizontal line is located at a point that is separated by b from the upper boundary of the transformation block downward,
The partial area is an area located on the left with respect to the vertical line or an area located above with respect to the horizontal line,
Information specifying the partial region is encoded,
The information includes information specifying the position of the vertical line or information specifying the position of the horizontal line,
The partial area is divided into a plurality of partial blocks,
and the coefficients of the partial region are encoded in units of the partial blocks. A computer-readable recording medium storing a bitstream, comprising:
The bitstream includes coefficients of a coded transform block,
Decoding of the coefficients of the coded transform block is performed only on all or some regions within the transform block according to a result of comparing the size of the transform block with a pre-defined threshold size,
When the size of the transform block is greater than or equal to the threshold size, decoding of the coefficients of the transform block is performed only on a partial region within the transform block,
When the size of the transform block is smaller than the threshold size, decoding of the coefficients of the transform block is performed on the entire area of the transform block,
The partial region is specified by a predetermined vertical line or horizontal line based on information obtained from the bitstream, wherein the information includes information specifying the position of the vertical line or the position of the horizontal line. contains information specifying;
The vertical line is located at a point a distance to the right from the left boundary of the transformation block, and the horizontal line is located at a point that is separated by b from the upper boundary of the transformation block downward,
The partial area is an area located on the left with respect to the vertical line or an area located above with respect to the horizontal line,
The partial area is divided into a plurality of partial blocks,
and the coefficients of the partial area are decoded in units of the partial blocks.

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