KR20190140422A - A method and an apparatus for encoding/decoding a residual block based on quantization parameter - Google Patents

Abstract

The present invention relates to a method for encoding/decoding a residual block based on a quantization parameter and an apparatus thereof. The method for encoding/decoding a residual coefficient based on a quantization parameter comprises the following steps of: deriving a residual coefficient of a residual block from a btstream; calculating a quantization parameter for the residual block; using the quantization parameter to perform inverse quantization on the residual coefficient; and performing inverse transform on the inverse quantized residual coefficient to restore a residual sample of the residual block. Therefore, the efficiency of encoding/decoding the residual block can be increased.

Description

Residual block coding / decoding method based on quantization parameter {A METHOD AND AN APPARATUS FOR ENCODING / DECODING A RESIDUAL BLOCK BASED ON QUANTIZATION PARAMETER}

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

The demand for high resolution, high quality images is increasing in various applications. As the video data becomes higher resolution and higher quality, the amount of data increases relative to the existing video data. Therefore, when the video data is transmitted or stored using a medium such as a conventional wired / wireless broadband line, The storage cost will increase. High efficiency image compression techniques can be used to solve these problems caused by high resolution and high quality image data.

The present invention seeks to improve the encoding / decoding efficiency of the residual block.

The present invention aims to improve encoding / decoding efficiency through adaptive block division.

A video encoding / decoding method and apparatus according to the present invention derives a residual coefficient of a residual block from a bitstream, calculates a quantization parameter for the residual block, and uses the calculated quantization parameter for the residual coefficient. Inverse quantization may be performed, and an inverse transform may be performed on the inverse quantized residual coefficient to restore a residual sample of the residual block.

In the video encoding / decoding method and apparatus according to the present invention, the quantization parameter may be derived based on at least one of a quantization parameter prediction value or a quantization parameter difference value.

In the video encoding / decoding method and apparatus according to the present invention, the quantization parameter prediction value may be derived based on quantization parameters of one or more neighboring blocks.

In the video encoding / decoding method and apparatus according to the present invention, the neighboring block may be a block spatially and / or temporally adjacent to the residual block.

In the video encoding / decoding method and apparatus according to the present invention, the quantization parameter difference value may be determined based on a size of a block that allows signaling of the quantization parameter difference value.

The video encoding / decoding method and apparatus according to the present invention may correct the derived quantization parameter based on a predetermined quantization parameter offset.

In the video encoding / decoding method and apparatus according to the present invention, the residual block may be divided into variable sizes / forms based on at least one of a quad tree, a binary tree, or a triple tree.

According to the present invention, the encoding / decoding efficiency of the residual block can be improved based on at least one of a predetermined quantization parameter prediction value, a quantization parameter difference value, or a quantization parameter offset.

In addition, according to the present invention, encoding / decoding efficiency can be improved through block division of a tree structure.

1 is a schematic block diagram of an encoding apparatus according to an embodiment of the present invention.
2 is a schematic block diagram of a decoding apparatus according to an embodiment of the present invention.
3 illustrates a block division type according to an embodiment to which the present invention is applied.
4 illustrates a tree structure based block partitioning method according to an embodiment to which the present invention is applied.
FIG. 5 illustrates a method for restoring a residual sample as an embodiment to which the present invention is applied.
6 illustrates a method of deriving a quantization parameter prediction value QPpred according to an embodiment to which the present invention is applied.
FIG. 7 illustrates a method of deriving a quantization parameter prediction value about a color difference component of a block T according to an embodiment to which the present invention is applied.
8 illustrates a method of deriving a quantization parameter based on a signaling unit of a quantization parameter difference value (deltaQP) according to an embodiment to which the present invention is applied.
9 illustrates an inverse transformation process of a residual coefficient as an embodiment to which the present invention is applied.

As the invention allows for various changes and numerous embodiments, particular embodiments will be illustrated in the drawings and described in detail in the written description. However, this is not intended to limit the present invention to specific embodiments, it should be understood to include all modifications, equivalents, and substitutes included in the spirit and scope of the present invention. In describing the drawings, similar reference numerals are used for similar elements.

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

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

The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting of the present invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this application, the terms "comprise" or "have" are intended to indicate that there is a feature, number, step, operation, component, part, or combination thereof described in the specification, and one or more other features. It is to be understood that the present invention does not exclude the possibility of the presence or the addition of numbers, steps, operations, components, components, or a combination thereof.

Hereinafter, with reference to the accompanying drawings, it will be described in detail a preferred embodiment of the present invention. Hereinafter, the same reference numerals are used for the same components in the drawings, and duplicate descriptions of the same components are omitted.

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

Referring to FIG. 1, the encoding apparatus 100 may include a picture splitter 110, a predictor 120 and 125, a transformer 130, a quantizer 135, a reorderer 160, and an entropy encoder 165. ), An inverse quantization unit 140, an inverse transform unit 145, a filter unit 150, and a memory 155.

Each component shown in FIG. 1 is independently shown to represent different characteristic functions in the image encoding apparatus, and may mean that each component is made of separate hardware. However, each component is included in each component unit for convenience of description, at least two components of each of the components are combined to form a single component, or one component is divided into a plurality of components to perform a function, The integrated and separated embodiments of each of these components are also included in the scope of the present invention without departing from the spirit of the present invention.

In addition, some of the components may not be essential components for performing essential functions in the present invention, but may be optional components for improving performance. The present invention can be implemented including only the components essential for implementing the essentials of the present invention except for the components used for improving performance, and the structure including only the essential components except for the optional components used for improving performance. Also included in the scope of the present invention.

The picture dividing unit 110 may divide the input picture into at least one block. In this case, the 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, a binary tree, and a triple tree. Quad tree is a method of dividing an upper block into lower blocks having a width and a height of half of the upper block. The binary tree divides the upper block into lower blocks, which are half of the upper block in either width or height. In the binary tree, the upper block is half-height through the above-described binary tree-based partitioning, so that the block may have a square as well as a non-square shape.

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

The predictors 120 and 125 may include an inter predictor 120 that performs inter prediction and an intra predictor 125 that performs intra prediction. Whether to use inter prediction or intra prediction on the prediction unit may be determined, and specific information (eg, an intra prediction mode, a motion vector, a reference picture, etc.) according to each prediction method may be determined. In this case, the processing unit in which the prediction is performed may differ from the processing unit in which the prediction method and the details are determined. For example, the method of prediction and the prediction mode may be determined in the prediction unit, and the prediction may be performed in the transform unit. The residual value (residual block) between the generated prediction block and the original block may be input to the transformer 130. In addition, prediction mode information and motion vector information used for prediction may be encoded by the entropy encoder 165 together with the residual value and transmitted to the decoding apparatus. When a specific encoding mode is used, the original block may be encoded as it is and transmitted to the decoder without generating the prediction block through the prediction units 120 and 125.

The inter prediction unit 120 may predict the prediction unit based on the information of at least one of the previous picture or the next picture of the current picture. In some cases, the inter prediction unit 120 may predict the prediction unit based on the information of the partial region in which the current picture is encoded. You can also predict units. The inter predictor 120 may include a reference picture interpolator, a motion predictor, and a motion compensator.

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

The motion predictor may perform motion prediction based on the reference picture interpolated by the reference picture interpolator. As a method for calculating a 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 units based on the interpolated pixels. 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 advanced motion vector prediction (AMVP) method may be used.

The intra predictor 125 may generate a prediction unit based on reference pixel information around the current block, which is pixel information in the current picture. If the neighboring block of the current prediction unit is a block that has performed inter prediction, and the reference pixel is a pixel that has performed inter prediction, the reference pixel of the block that has performed intra prediction around the reference pixel included in the block where the inter prediction has been performed Can be used as a substitute for information. 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, a prediction mode may have a directional prediction mode using reference pixel information according to a prediction direction, and a non-directional mode using no directional information when performing prediction. The mode for predicting the luminance information and the mode for predicting the color difference information may be different, and the intra prediction mode information or the predicted luminance signal information used for predicting the luminance information may be utilized to predict the color difference 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 by using the 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 using the predetermined flag information If the prediction modes of the current prediction unit and the neighboring prediction unit are different, entropy encoding may be performed to encode the prediction mode information of the current block.

Also, a residual block may include a prediction unit performing prediction based on the prediction units generated by the prediction units 120 and 125 and residual information including residual information that is a difference from an original block of the prediction unit. The generated residual block may be input to the transformer 130.

The transformer 130 may convert the residual block including the residual data using a transform type such as DCT, DST, or the like. In this case, the transformation method may be determined based on the intra prediction mode of the prediction unit used to generate the residual block.

The quantization unit 135 may quantize the values converted by the transformer 130 into the frequency domain. The quantization coefficient may change depending on the block or the importance of the image. The value calculated by the quantization unit 135 may be provided to the inverse quantization unit 140 and the reordering unit 160.

The reordering unit 160 may reorder coefficient values with respect to the quantized residual value.

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

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

The entropy encoder 165 receives residual value coefficient information, block type information, prediction mode information, partition unit information, prediction unit information, transmission unit information, and 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 can be encoded.

The entropy encoder 165 may entropy encode a coefficient value of a coding unit input from the reordering unit 160.

The inverse quantizer 140 and the inverse transformer 145 inverse quantize the quantized values in the quantizer 135 and inversely transform the transformed values in the transformer 130. The residual value generated by the inverse quantizer 140 and the inverse transformer 145 is reconstructed by combining the prediction units predicted by the motion estimator, the motion compensator, and the intra predictor included in the predictors 120 and 125. You can create a Reconstructed Block.

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

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

The offset correction unit may correct the offset with respect to the original image on a pixel-by-pixel basis for the deblocking image. In order to perform offset correction for a specific picture, the pixels included in the image are divided into a predetermined number of areas, and then, an area to be offset is determined, an offset is applied to the corresponding area, or offset considering the edge information of each pixel. You can use this method.

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

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

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

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

Each component shown in FIG. 2 is independently illustrated to represent different characteristic functions in the decoding apparatus, and may mean that each component is made of separate hardware. However, each component is included in each component unit for convenience of description, at least two components of each component are combined to form a single component, or one component may be divided into a plurality of components to perform a function. The integrated and separated embodiments of each component are also included in the scope of the present invention without departing from the spirit of the present invention.

The entropy decoder 210 may perform entropy decoding on the input bitstream. For example, for entropy decoding, various methods such as Exponential Golomb, Context-Adaptive Variable Length Coding (CAVLC), and Context-Adaptive Binary Arithmetic Coding (CABAC) may be applied.

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

The reordering unit 215 may reorder the entropy decoded bitstream by the entropy decoding unit 210. Coefficients expressed in the form of a one-dimensional vector may be reconstructed by reconstructing the coefficients in a two-dimensional block form. The reordering unit 215 may receive information related to coefficient scanning performed by the encoding apparatus and perform reordering by performing a reverse scanning method based on the scanning order performed by the encoding apparatus.

The inverse quantization unit 220 may perform inverse quantization based on quantization parameters and coefficient values of the rearranged block.

The inverse transform unit 225 may perform inverse transform on the inverse quantized transform coefficients using a predetermined transform method. In this case, the transformation method may be determined based on information on 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 the prediction block based on the prediction block generation related information provided by the entropy decoder 210 and previously decoded blocks or picture information provided by the memory 245.

The predictors 230 and 235 may include a prediction unit determiner, an inter predictor, and an intra predictor. The prediction unit determiner 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 receives the prediction unit from the current coding unit (CU). The classification unit may determine whether the prediction unit performs inter prediction or intra prediction. The inter prediction unit 230 may use information necessary for inter prediction of the current prediction unit provided by the encoding apparatus and based on information included in at least one of a previous picture or a subsequent picture of the current picture including the current prediction unit. Inter prediction may be performed on the current prediction unit. Alternatively, inter prediction may be performed based on information of some regions pre-restored in the current picture including the current prediction unit.

Whether the motion prediction method of the prediction unit included in the coding unit is skip mode, merge mode, or AMVP mode based on the coding unit to perform inter prediction. Can be determined.

The intra predictor 235 may generate a prediction block based on pixel information in the current picture. When the prediction unit is a prediction unit that has performed intra prediction, intra prediction may be performed based on intra prediction mode information of the prediction unit provided by the encoding apparatus. The intra predictor 235 may include an adaptive intra smoothing (AIS) filter, a reference pixel interpolator, and a DC filter. The AIS filter is a part of filtering the reference pixel of the current block and determines 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 of the prediction unit and the AIS filter information provided by the encoding apparatus. If the prediction mode of the current block is a mode that does not perform AIS filtering, the AIS filter may not be applied.

When the prediction mode of the prediction unit is a prediction unit that performs intra prediction based on a pixel value interpolating the reference pixel, the reference pixel interpolator may generate a reference pixel having an integer value or less by interpolating the reference pixel. When the prediction mode of the current prediction unit is a prediction mode for generating a prediction block without interpolating the reference pixel, the reference pixel may not be interpolated. The DC filter may generate the 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 correction unit, and an ALF.

Information about whether a deblocking filter is applied to the corresponding block or picture and when the deblocking filter is applied to the block or picture may be provided from the encoding apparatus as to whether a strong filter or a weak filter is applied. The deblocking filter of the decoding apparatus may receive the deblocking filter related information provided by the encoding apparatus, and perform the deblocking filtering on the corresponding block in the decoding apparatus.

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

The ALF may be applied to a coding unit based on ALF application information, ALF coefficient information, and the like provided from the encoder. Such ALF information may be provided included in a specific parameter set.

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

3 illustrates a block division type according to an embodiment to which the present invention is applied.

One block (hereinafter, referred to as a first block) may be divided into a plurality of sub blocks (hereinafter, referred to as a second block) by at least one of a vertical line and a horizontal line. The vertical line and the horizontal line may be one, two or more. Here, the first block may be a coding block (CU) that is a basic unit of image encoding / decoding, a prediction block (PU) that is a basic unit of prediction encoding / decoding, or a transform block (TU) that is a basic unit of transform encoding / decoding. have. The first block may be a square block or a non-square block.

The division of the first block may be performed based on a quad tree, a binary tree, a triple tree, and the like, and will be described in detail with reference to FIG. 3.

3 (a) illustrates quad tree division (QT). QT is a division type that divides the first block into four second blocks. For example, when the first block of 2N × 2N is divided into QTs, the first block may be divided into four second blocks having an N × N size. The QT may be limited to be applied only to square blocks, but may also be applied to non-square blocks.

FIG. 3B illustrates partitioning of a horizontal binary tree (hereinafter referred to as Horizontal BT). Horizontal BT is a division type in which the first block is divided into two second blocks by one horizontal line. The dividing may be performed symmetrically or asymmetrically. For example, when the first block of 2N × 2N is divided into Horizontal BT, the first block may be divided into two second blocks having a height ratio of (a: b). Here, a and b may be the same value, and a may be larger or smaller than b.

3 (c) illustrates splitting of a vertical binary tree (hereinafter referred to as vertical BT). Vertical BT is a division type in which the first block is divided into two second blocks by one vertical line. The dividing may be performed symmetrically or asymmetrically. For example, when the first block of 2N × 2N is divided into Vertical BTs, the first block may be divided into two second blocks having a width ratio of (a: b). Here, a and b may be the same value, and a may be larger or smaller than b.

3 (d) illustrates the division of a horizontal triple tree (hereinafter referred to as a horizontal TT). Horizontal TT is a division type in which the first block is divided into three second blocks by two horizontal lines. For example, when the first block of 2N × 2N is divided into Horizontal TT, the first block may be divided into three second blocks having a height ratio of (a: b: c). Here, a, b, and c may be the same value. Alternatively, a and c may be the same and b may be larger or smaller than a.

3 (e) illustrates splitting of a vertical triple tree (hereinafter referred to as vertical TT). Vertical TT is a split type in which the first block is divided into three second blocks by two vertical lines. For example, when the first block of 2N × 2N is divided into Vertical TT, the first block may be divided into three second blocks having a width ratio of (a: b: c). Here, a, b, and c may be the same value, or may be different values. Alternatively, a and c may be the same and b may be larger or smaller than a. Alternatively, a and b may be the same and c may be larger or smaller than a. Alternatively, b and c are the same, and a may be greater or less than b.

The above-described partitioning may be performed based on the partitioning information signaled from the encoding apparatus. The split information may include at least one of split type information, split direction information, or split ratio information.

The partition type information may specify any one of the partition types that are pre-defined in the encoding / decoding device. The pre-defined split type may include at least one of QT, Horizontal BT, Vertical BT, Horizontal TT, Vertical TT, or No split mode. Alternatively, the partition type information may mean information on whether QT, BT or TT is applied, which may be encoded in the form of a flag or an index. In the case of BT or TT, the split direction information may indicate whether the split direction information is split in the horizontal direction or in the vertical direction. The split ratio information may indicate a ratio of a width and / or a height of a second block in case of BT or TT.

FIG. 4 illustrates a tree structure based block partitioning method according to an embodiment to which the present invention is applied.

It is assumed that the block 400 illustrated in FIG. 4 is a square block (hereinafter, referred to as a first block) having a size of 8N × 8N and having a division depth of k. When the partition information of the first block indicates the QT division, the first block may be divided into four sub blocks (hereinafter, referred to as a second block). The second block may be 4N × 4N in size and have a split depth of (k + 1).

The four second blocks may be divided again based on any one of QT, BT, TT, or non-divided mode. For example, when the partition information of the second block indicates a binary tree (Horizontal BT) in the horizontal direction, the second block may be divided into two sub-blocks (hereinafter, referred to as a third block) as shown in the second block 410 of FIG. Can be divided into blocks). In this case, the third block may have a size of 4N × 2N and have a division depth of (k + 2).

The third block may also be divided again based on any one of QT, BT, TT, or non-divided mode. For example, when the partition information of the third block indicates a vertical BT in the vertical direction, the third block is divided into two sub-blocks 411 and 412 as shown in FIG. 4. Can be. In this case, the sub blocks 411 and 412 may have a size of 2N × 2N and have a split depth of (k + 3). Alternatively, when the partition information of the third block indicates a binary tree (Horizontal BT) in the horizontal direction, the third block may be divided into two sub blocks 413 and 414 as shown in FIG. 4. have. In this case, the sub blocks 413 and 414 may have a size of 4N × N and have a division depth of (k + 3).

The division may be performed independently or in parallel with neighboring blocks, or may be performed sequentially according to a predetermined priority.

The split information of the current block to be split may be determined based on at least one of split information of the upper block of the current block or split information of the neighboring block. For example, when the second block is divided into Horizontal BT and the upper third block is divided into Vertical BT, the lower third block need not be divided into Vertical BT. When the third block at the bottom is divided into Vertical BT, this is because the same result as the second block is divided into QT. Accordingly, encoding may be omitted in the split information (particularly, split direction information) of the lower third block, and the decoding apparatus may set the lower third block to be split in the horizontal direction.

The upper block may mean a block having a division depth smaller than the division depth of the current block. For example, when the split depth of the current block is (k + 2), the split depth of the higher block may be (k + 1). The neighboring block may be a block adjacent to the top or left side of the current block. The neighboring block may be a block having the same division depth as the current block.

The above-described division may be repeatedly performed up to the minimum unit of encoding / decoding. In the case of splitting to a minimum unit, splitting information for the corresponding block is no longer signaled from the encoding apparatus. The information on the minimum unit may include at least one of the size or shape of the minimum unit. The size of the minimum unit may be expressed as the width, height, minimum or maximum of the width and height, the sum of the width and height, the number of pixels, the division depth, and the like. The information on the minimum unit may be signaled in at least one of a video sequence, a picture, a slice, or a block unit. Alternatively, the information on the minimum unit may be a value pre-committed to the encoding / decoding apparatus. The information on the minimum unit may be signaled for each of CU, PU, and TU. Information on one minimum unit may be equally applied to a CU, a PU, and a TU.

FIG. 5 illustrates a method for restoring a residual sample as an embodiment to which the present invention is applied.

Referring to FIG. 5, a residual coefficient of a residual block may be derived from a bitstream (S500).

The derivation may be performed by decoding at least one of information about the existence of non-zero residual coefficients, an absolute value (abs) or a sign of the encoded residual coefficients.

The derivation may further include setting a residual coefficient of the high frequency region in the residual block to zero. The high frequency region may be defined as an area excluding at least one of n columns or m rows from the top of the residual block. The n and m may be values pre-committed to the encoding / decoding apparatus, or may be variably determined according to the size / shape of the residual block. For example, when the residual block is 64x32, an area excluding 32 columns (here, n = 32, m = 0) from the left side of the residual block may be defined as a high frequency area. When the residual block is 32x64, an area except for 32 rows (where n = 0 and m = 32) from the top of the residual block may be defined as a high frequency area. Alternatively, n and m may be derived based on coded information for specifying a high frequency region.

In addition, the step of setting the residual coefficient to 0 may be selectively performed in consideration of at least one of the size or shape of the residual block. For example, the above process may be applied only when the size of the residual block is greater than or equal to a predetermined threshold. The size of the residual block may be expressed by at least one of the width or height of the residual block. The threshold may mean a minimum size that is allowed to set the residual coefficient to zero. The threshold value may be a value pre-committed to the encoding / decoding apparatus, or may be encoded and signaled by the encoding apparatus. The threshold may be 32, 64, 128, 256 or more.

The step of setting the residual coefficient to 0 may be selectively performed based on flag information. The flag information may indicate whether the residual coefficient of the high frequency region in the residual block is set to zero. The flag information may be derived from the decoding apparatus based on the size / shape of the residual block, or may be encoded and signaled by the encoding apparatus. However, the above process may be limited to be performed only when the residual block is not encoded in the transform skip mode. Therefore, when the residual block is encoded in the transform skip mode, the encoding apparatus may not encode information necessary for setting the residual coefficient to zero.

Referring to FIG. 5, a quantization parameter for the residual block may be calculated (S510).

The quantization parameter may be derived using at least one of a quantization parameter prediction value QPpred or a quantization parameter difference value deltaQP. In other words, the quantization parameter may be set to the quantization parameter prediction value QPpred or derived by adding the quantization parameter difference value deltaQP to the quantization parameter prediction value QPpred.

For example, merge mode, skip mode, no-transform mode, PCM mode, non-zero coefficients are not present (i.e. coded block flag = 0), and the like. Likewise, when inverse quantization is unnecessary for the block, the quantization parameter difference value deltaQP may not be encoded. In this case, the quantization parameter prediction value QPpred may be set as the quantization parameter.

A method of deriving the quantization parameter prediction value QPpred will be described with reference to FIGS. 6 and 7. Meanwhile, the quantization parameter difference value deltaQP may be signaled in a predetermined unit, and a quantization parameter derivation method based on the signaling unit of the quantization parameter difference value deltaQP will be described with reference to FIG. 8.

The calculation of the quantization parameter may further include correcting the previously derived quantization parameter based on a predetermined quantization parameter offset (QPoffset).

The quantization parameter offset QPoffset may be a fixed value pre-committed to the encoding / decoding apparatus, or may be encoded and signaled by the encoding apparatus. The quantization parameter offset QPoffset may be signaled at at least one level of a video sequence, a picture, a slice, a tile, or a block unit. The unit in which the quantization parameter offset is signaled may be larger than the unit in which the quantization parameter difference value is signaled. The value and number of the quantization parameter offsets QPoffset may be adaptively determined according to the block size / shape, the number of divisions, the prediction mode, the intra prediction mode, the component type (e.g., luminance, color difference), and the like.

The number of quantization parameter offsets may be one, two, three, or more. For example, the quantization parameter offset may be defined at at least one of a picture level, slice level, or block level. The quantization parameter offset may be defined for each of the intra mode and the inter mode, and may be defined for each of the luminance component and the chrominance component. Alternatively, a separate offset for the LM mode among the intra prediction modes may be defined. Here, the LM mode may mean a mode in which the color difference block is predicted using the prediction / reconstruction samples of the luminance block.

Referring to FIG. 5, inverse quantization may be performed on the residual coefficient using the calculated quantization parameter (S520).

Specifically, the inverse quantization may be performed based on at least one of the quantization parameter or a predetermined level scale value. The level scale value may be a value pre-committed to the encoding / decoding apparatus, or may be encoded and signaled by the encoding apparatus. The level scale value may be composed of k integer values in a one-dimensional array. For example, the level scale value may be defined as {40, 45, 51, 57, 64, 72}. However, this does not limit the number of level scale values and integer values. That is, the level scale values may be defined as other values, and the number of level scale values may be defined as four, five, seven, eight, or more.

Meanwhile, a predetermined quantization weight m may be further applied to the result of inverse quantization, and this process will be referred to as scaling.

The quantization weight may be derived as a fixed value pre-committed to the encoding / decoding apparatus (method A). In this case, the quantization weight may be one same value regardless of the position of the residual coefficient in the residual block. Alternatively, the quantization weight may be derived based on table information pre-defined in the encoding / decoding apparatus (B method). The table information may define a quantization weight according to at least one of a position of a residual coefficient, a block size, a component type, or a prediction mode. Alternatively, the encoding apparatus may determine the quantization weight for each position of the residual coefficient and encode the same. The decoding apparatus may decode the information about the encoded quantization weight to derive the quantization weight (C method). In this case, the encoding apparatus may encode only a difference between the quantization weight of the previous position and the quantization weight of the current position. The decoding apparatus may derive the quantization weight of the current position by using the decoded quantization weight of the previous position and the encoded information.

The quantization weight of the residual block may be derived by selecting any one of methods A to C described above. The selection may be performed based on at least one of the size / shape of the residual block, partition type, prediction mode, component type, transform type, or predetermined flag information. The flag information may include a flag indicating whether quantization weight is applied, a flag indicating whether to skip transform, and the like.

In the above-described method A to C, the quantization weight of the scaling list may be determined for each of the luminance block and the chrominance block. For example, scaling lists for each of the luminance block and the chrominance block may be signaled. Alternatively, the scaling list of the chrominance block may be determined with reference to the scaling list of the luminance block.

Referring to FIG. 5, a residual sample may be restored by performing inverse transform on an inverse quantized residual coefficient (S530).

The inverse transform is performed based on a predetermined transform type, and the transform type of the residual block may be determined based on a transform candidate set. The transform candidate set may include n transform types. For example, the transform candidate set may include at least one of DCT-II, DCT-V, DCT-VIII, DST-I, or DST-VII.

In the encoding / decoding apparatus, m transform candidate sets may be defined. M may be 1, 2, 3 or more. The number and / or types of transform types belonging to any one of the m transform candidate sets (hereinafter, referred to as a first transform candidate set) may be different from the other (hereinafter, referred to as a second transform candidate set). For example, the first transform candidate set may consist of p transform types, and the second transform candidate set may consist of q transform types smaller than p. Alternatively, even when the first and second transform candidate sets are configured with the same number of transform types, at least one transform type belonging to the first transform candidate set may be different from the transform type belonging to the second transform candidate set.

Any one of the m transform candidate sets may be selectively used.

The selection of the transform candidate set may be performed based on the size of the residual block. For example, if the size of the residual block is less than or equal to the threshold, a first transform candidate set consisting of p transform types is selected, otherwise a second transform candidate set composed of q transform types is selected. Can be. The threshold may be 32, 64, 128, 256 or more, and p may be greater than q.

Alternatively, the selection of the transform candidate set may be performed based on information signaled from the encoding apparatus. The information may specify any one of m transform candidate sets. The information may be signaled at at least one level of a picture, slice, or block.

If the selected transform candidate type includes a plurality of transform types, the encoding apparatus may encode information specifying any one of the plurality of transform types. The decoding apparatus may determine the transform type of the residual block by decoding the encoded information.

 Meanwhile, the inverse transformation may be selectively performed based on a predetermined flag. Here, the flag may indicate whether an inverse transform is skipped with respect to the residual block. For example, when the flag is 1, inverse transform may not be performed on the residual block, and when the flag is 0, inverse transform may be performed on the residual block. Therefore, the transform type of the residual block may be derived only when the flag is zero. Alternatively, the inverse transform may be selectively performed based on the property of the residual block. The decoding apparatus may determine whether the inverse transform is skipped based on the attribute of the residual block. The attribute may mean a size / shape of a residual block, a partition type, a prediction mode, a component type, other residual coefficient related encoding parameters, and the like.

In addition to the inverse transform (hereinafter, referred to as a first inverse transform), an additional inverse transform (hereinafter, referred to as a second inverse transform) may be further performed, which will be described with reference to FIG. 9.

6 illustrates a method of deriving a quantization parameter prediction value QPpred according to an embodiment to which the present invention is applied.

Referring to FIG. 6, the quantization parameter prediction value QPpred for the block T may be derived based on the quantization parameter of the neighboring block. The block T is an NxM size block and may be square or non-square.

The neighboring block may be a block spatially / temporally adjacent to the block T and may mean a block pre-decoded before the block T. For example, the peripheral block may include at least one of a left block, an upper block, an upper left block, an upper right block, or a lower left block of the block T. Alternatively, the neighboring block may further include a collocated block corresponding to the block T in time. The call block is a block belonging to a picture different from the block T, and may be defined as a block including at least one position of an upper left corner sample, a lower right corner sample, or a center sample of the block T.

The position of the neighboring block may be a position pre-committed to the encoding / decoding apparatus. For example, the pre-committed position may be a left block and an upper block, or may be a left block, an upper block and an upper left block. However, the present invention is not limited thereto and may further include a lower left block and a right upper block. The location of the neighboring block may be variably determined based on an attribute (e.g., size, shape, division depth, division type, component type, etc.) of the block T or the neighboring block. For example, the neighboring block may be determined as the block having the largest area among the blocks adjacent to the block T, or may be determined to be the block having the longest boundary length. This may be performed for the upper block and the left block of the block T, respectively.

Alternatively, information specifying the position of the neighboring block may be encoded and signaled by an encoding apparatus. The information may be encoded in the form of a flag, an index, or the like. For example, when the information is index 0, the quantization parameter prediction value QPpred of the block T may be derived using the quantization parameter of the left block. When the information is index 1, the quantization parameter prediction value QPpred of the block T may be derived using the quantization parameter of the upper block.

The number of neighboring blocks is n, where n may be 1, 2, 3, 4 or more natural numbers. The number may be a fixed value pre-committed by the encoding / decoding apparatus. Alternatively, the number may be variably determined based on at least one attribute (e.g., size, shape, split depth, split type, component type, etc.) of the block T or neighboring blocks. Alternatively, the maximum number information of neighboring blocks used to derive the quantization parameter prediction value QPpred of the block T may be encoded and signaled by the encoding apparatus. That is, the block T may use neighboring blocks within the number range according to the maximum number information. The maximum number information may be signaled at at least one level of a video sequence, a picture, and other fragment regions (e.g. slice, tile, Coding Tree Block row, block).

As described above, the quantization parameter prediction value QPpred of the block T may be derived using one or more neighboring blocks.

When a plurality of neighboring blocks are used, the quantization parameter predicted value QPpred of the block T may be derived through a calculation process such as an intermediate value, an average value, a minimum value, a maximum value, or a mode value of the quantization parameters of the plurality of neighboring blocks.

Alternatively, the quantization parameter prediction value QPpred of the block T may be derived by subtracting the QP of the upper left block from the sum of the QP of the upper block and the QP of the left block. In this case, when there are a plurality of upper blocks or left blocks, the QP of the upper block or the left block may be determined through a calculation process such as an intermediate value, an average value, a minimum value, a maximum value, or a mode value.

When there is an unavailable block among the neighboring blocks, the quantization parameter predicted value of the block T may be derived using only available neighboring blocks. Alternatively, when the neighboring block is not available, the quantization parameter of the neighboring block may be derived based on the quantization parameter defined in the predetermined fragment area. The fragment area may mean a slice, a tile, a Coding Tree Block row, a block, or the like. The fragment region may mean a region coded / decoded before the block T or a region to which a block T which is currently encoded / decoded belongs belongs. The unavailability may refer to a case in which the neighboring block does not exist physically or may be a case in which reference is impossible due to a rule of an encoding / decoding apparatus. For example, if the block T and the neighboring block belong to different parallel processing regions (e.g. slice, tile, etc.), the block T may not be allowed to refer to the neighboring block.

FIG. 7 illustrates a method of deriving a quantization parameter prediction value about a color difference component of a block T according to an embodiment to which the present invention is applied.

Hereinafter, the luminance component and the chrominance component of the block T will be referred to as the luminance block and the chrominance block, respectively.

In the 4: 2: 0 color format, the chrominance block Tc may correspond to the luminance block TY. The quantization parameter prediction value of the chrominance block may be derived using the quantization parameter of the corresponding luminance block.

However, as shown in FIG. 7, the division structure between the luminance block and the chrominance block may be different. In this case, there may be a plurality of luminance blocks corresponding to the color difference blocks. The quantization parameter predicted value of the chrominance block may be derived using any one of the plurality of luminance blocks. In this case, a luminance block corresponding to the position of the center sample of the chrominance block or the position of the upper left sample may be used. The luminance block with the largest area overlapping with the chrominance block may be used. Alternatively, the quantization parameter prediction value of the chrominance block may be derived through calculation of an average value, a median value, a minimum value, a maximum value, and a mode value of the quantization parameters of the plurality of luminance blocks.

The quantization parameter prediction value of the chrominance block may be derived using the quantization parameter of the neighboring block, which has been described in detail with reference to FIG. 6, and a detailed description thereof will be omitted.

As described above, the quantization parameter predicted value of the chrominance block is derived using both the method of using the quantization parameter of the corresponding luminance block (first method) and the method of using the quantization parameter of the neighboring block of the chrominance block (second method). Can be. Alternatively, the quantization parameter prediction value of the chrominance block may be derived by selecting either the first method or the second method.

The selection may be performed in consideration of whether the luminance block and the chrominance block have the same division structure, the prediction mode of the block T, the intra prediction mode, the color format, or the size / shape. For example, when the block T is encoded in the inter mode, and the division structure of the chrominance block is the same as the division structure of the luminance block, the quantization parameter of the chrominance block may be predicted using the first method. Alternatively, when the division structure of the chrominance block is the same as the division structure of the luminance block, the first method may be used, otherwise the second method may be used. Alternatively, when the intra prediction mode of the block T is the LM mode, the quantization parameter of the chrominance block may be predicted using the first method.

Alternatively, the selection may be performed based on information specifying either the first method or the second method. The information may be encoded and signaled by the encoding apparatus. The information may be signaled at at least one level of a video sequence, a picture, and other fragment regions (e.g. slice, tile, Coding Tree Block row, block).

The quantization parameter of the chrominance block may be derived in the same manner as the quantization parameter predicted value of the derived chrominance block, or may be derived by adding a predetermined quantization parameter difference value. In addition, the derived quantization parameter may be corrected using a predetermined quantization parameter offset, as shown in FIG. 5.

For example, in the case of a color difference block encoded in the LM mode, the quantization parameter prediction value may be set as the quantization parameter. In this case, the quantization parameter difference value may not be signaled, or the process of adding the signaled quantization parameter difference value may be omitted. Alternatively, in the case of the color difference block encoded in the LM mode, the quantization parameter may be corrected using one, two or more quantization parameter offsets.

FIG. 8 illustrates a method of deriving a quantization parameter based on a signaling unit of a quantization parameter difference value deltaQP according to an embodiment to which the present invention is applied.

The encoding apparatus may determine a unit of a block for encoding deltaQP and encode information indicating the size of the block. Here, the size may be expressed by at least one of the width or height of the block, the product of the width and height, the sum of the width and height, the minimum value / maximum value of the width and height, and the like. The decoding apparatus may determine the minimum size of a block that allows signaling of deltaQP by decoding the signaled information. The information may be signaled at at least one level of a video sequence, picture, slice or tile. Alternatively, the minimum size may be derived as the minimum size of the transform block or may be defined as a fixed size pre-committed to the encoding / decoding apparatus. For example, the minimum size may be defined as 4x4, 8x4, 4x8, 8x8, and the like. Information indicating the size of the block may be signaled for the luminance component and the chrominance component, respectively. Alternatively, the minimum size for the chrominance block may be derived based on the minimum size for the luminance block. For example, in the case of the 4: 2: 0 color format, the minimum size of the chrominance block may be determined to be half of the minimum size of the luminance block. In the inter mode, the division structure of the chrominance block may be different from that of the luminance block, and the minimum size of the chrominance block may be determined to be half of the luminance block.

Referring to FIG. 8, the quantization parameter of the current block may be derived based on a comparison result between the size of the current block and the minimum size. Here, the current block may mean a block that is no longer divided by a block division type such as QT, BT, or TT.

FIG. 8 (a) shows the case where the size of the current block is 2Mx2N and the minimum size is MxN. As shown in FIG. 8A, when the size of the current block is larger than the minimum size, the quantization parameter of the current block may be derived using deltaQP signaled with QPpred.

The QPpred may be derived based on at least one of the first method or the second method described above. The deltaQP may be signaled in block a, and the remaining blocks b, c and d may share the deltaQP signaled in block a. In this case, the current block has one quantization parameter. Alternatively, the deltaQPs may be signaled for blocks a-d having a minimum size, respectively. In this case, quantization parameters may be derived for blocks a-d belonging to the current block, and blocks a-d may have different quantization parameters.

On the other hand, if the size of the current block and the minimum size is the same, it can of course be derived using the deltaQP signaled with the QPpred.

FIG. 8B illustrates a case where the minimum size is MxN and the current blocks a-d are smaller than the minimum size. As shown in FIG. 8B, when the size of the current block is smaller than the minimum size, the quantization parameter of the current block may be derived using deltaQP signaled with QPpred.

The QPpred may be derived based on at least one of the above-described first or second method based on the current block. For example, QPpred may be derived for blocks a-d, respectively. Alternatively, QPpred may be derived for block a, and the remaining blocks b-d may share QPpred derived in block a. Alternatively, the QPpred may be derived based on at least one of the first method or the second method described above, based on an upper block of the current block. Here, the upper block is a block including the current block, and may be a block having a partition depth smaller than that of the current block. For example, when the division depth of the current block is k, the division depth of the higher block may be (k-1), (k-2), or the like. The upper block may be defined in units of blocks that share the QPpred. The upper block may be set to the same size (MxN) as the minimum size. Alternatively, the encoding apparatus may determine a unit of a block sharing the QPpred, and may encode information specifying the unit of the block. The decoding apparatus may specify the position, size, shape, etc. of the upper block based on the encoded information.

The deltaQP may be signaled in an upper block of the current block. Here, the upper block is a block including the current block, and may mean a block having a partition depth smaller than that of the current block. That is, when the division depth of the current block is k, the division depth of the higher block may be (k-1), (k-2), or the like. Here, it is assumed that the upper block is MxN shown in FIG. 8 (b). Thus, the same one quantization parameter may be derived for block a-d, and different quantization parameters may be derived for each of block a-d. Alternatively, as illustrated in FIG. 8B, when the size of the current block is smaller than the minimum size, the quantization parameter of the current block may be derived using QPpred. In this case, decoding of deltaQP may be omitted. As described above, the QPpred may be derived based on at least one of the first method and the second method based on the current block or the higher block, and a detailed description thereof will be omitted. Similarly, one same quantization parameter may be derived for block a-d belonging to the M × N block, and different quantization parameters may be derived for each block a-d.

Meanwhile, when a specific block is a block adjacent to a boundary of a picture, a slice, or a tile, the block may not satisfy the minimum size. In this case, the quantization parameter of the corresponding block is derived using only Qppred, and decoding for deltaQP may be omitted.

9 illustrates an inverse transformation process of a residual coefficient as an embodiment to which the present invention is applied.

Referring to FIG. 9, a residual sample of a residual block may be restored by performing at least one of a first inverse transform or a second inverse transform on a residual coefficient.

The second inverse transform may be applied to the entire area of the residual block or may be applied to only a partial area of the residual block. The partial region may mean a low frequency region within the residual block. The region to which the second inverse transform is applied may be variably determined in consideration of at least one of the size / shape of the residual block or the size / shape of the transform matrix of the second inverse transform.

For example, if either the width or height of the residual block is equal to or greater than 8, a second inverse transform with an 8x8 transformation matrix may be applied. When the size of the residual block is 8x8, the second inverse transform is applied to the entire area of the residual block, and when the size of the residual block is 16x16, the second inverse transform may be applied only to a part of the residual block. The partial region may refer to an area other than an 8x8 region located at the top left of the residual block, a 16x8 region located at the top of the residual block, an 8x16 region located at the left side of the residual block, or an 8x8 region located at the bottom right of the residual block. .

Alternatively, when either the width or height of the residual block is 4, a second inverse transform with a 4x4 transformation matrix may be applied. When the size of the residual block is 4x8 or 8x4, the second inverse transform may be applied only to a portion of the residual block (eg, the 4x4 region located at the upper left of the residual block), and the second inverse transform may be applied to two 4x4 regions belonging to the residual block. The second inverse transform may be applied respectively.

The size of the transform matrix of the second inverse transform may be 4x4, 8x8, 16x16, 32x32 or more. The form of the transformation matrix is not limited to a square, and may be implemented as a non-square. However, in order to reduce the complexity of the transformation, the size of the transformation matrix allowed for the second inverse transformation may be limited to NxM or less. N and M may be 4, 8, or 16, respectively, and N and M may be the same or different from each other.

In the second inverse transform process, the transform type of the residual block may be determined through the transform type derivation method described with reference to FIG. 5. Alternatively, the transform type in the second inverse transform may be pre-committed to the encoding / decoding apparatus. For example, as the transform type in the second inverse transform, any one of the five transform types described above may be fixedly used.

The second inverse transform may be selectively performed based on a flag (hereinafter, referred to as a first flag) indicating whether the first inverse transform is skipped in the residual block. That is, according to the first flag, when the first inverse transform is skipped in the residual block, the performance of the second inverse transform may also be skipped.

Alternatively, a flag indicating whether the second inverse transform is skipped (hereinafter, referred to as a second flag) may be separately signaled. When the second flag is 1, the second inverse transform is not performed. When the flag is 0, the second inverse transform may be performed. The first flag and the second flag may be encoded and signaled independently of each other. Alternatively, one of the first flag and the second flag may be signaled depending on the other. For example, only when one of the first flag and the second flag is 1, the other may be signaled. On the contrary, only when one of the first flag and the second flag is 0, the other may be signaled.

The second inverse transform may not be applied when the number of non-zero residual coefficients belonging to the residual block is less than n. Here, n may be a value pre-committed to the encoding / decoding device. For example, n can be a natural number of 1, 2, 3 or 8 or less. Alternatively, n may be variably determined based on the size of the residual block.

Meanwhile, although FIG. 9 illustrates performing the second inverse transform before the first inverse transform, this does not limit the order of performing the inverse transform. That is, the second inverse transform may be performed before the first inverse transform or may be performed after the first inverse transform. When the second inverse transform is performed before the first inverse transform, the scaling illustrated in FIG. 5 may be performed between the inverse quantization and the second inverse transform, or may be performed between the first inverse transform and the second inverse transform. Conversely, when the second inverse transform is performed after the first inverse transform, the scaling described with reference to FIG. 5 may be performed between the inverse quantization and the first inverse transform, or may be performed between the first inverse transform and the second inverse transform.

Exemplary methods of the present disclosure are represented as a series of operations for clarity of description, but are not intended to limit the order in which the steps are performed, and each step may be performed simultaneously or in a different order as necessary. In order to implement the method according to the present disclosure, the illustrated step may further include other steps, may include remaining steps except for some steps, or may include other additional steps except for some steps.

The various embodiments of the present disclosure are not an exhaustive list of all possible combinations and are intended to describe representative aspects of the present disclosure, and the matters described in the 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 hardware implementations, 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 general processor, a controller, a microcontroller, a microprocessor, and the like.

It is intended that the scope of the disclosure include software or machine-executable instructions (eg, an operating system, an application, firmware, a program, etc.), and such software or software to cause an operation in accordance with various embodiments of the method to be executed on an apparatus or a computer. Instructions, and the like, including non-transitory computer-readable media that are stored and executable on a device or computer.

Claims (12)

Deriving a residual coefficient of the residual block from the bitstream;
Calculating a quantization parameter for the residual block;
Performing inverse quantization on the residual coefficient using the calculated quantization parameter; And
Reconstructing residual samples of the residual block by performing inverse transform on the inverse quantized residual coefficients. The method of claim 1,
And the quantization parameter is derived based on at least one of a quantization parameter prediction value or a quantization parameter difference value. The method of claim 2,
Wherein the quantization parameter prediction value is derived based on a quantization parameter of one or more neighboring blocks, wherein the neighboring block is a block spatially or temporally adjacent to the residual block. The method of claim 2,
The quantization parameter difference value is determined based on a size of a block that is allowed to signal the quantization parameter difference value. The method of claim 2,
The calculating may further include correcting the derived quantization parameter based on a predetermined quantization parameter offset. The method of claim 1,
And the residual block is divided into variable sizes / shapes based on at least one of quad tree, binary tree, or triple tree. An entropy decoder for deriving a residual coefficient of the residual block from the bitstream;
An inverse quantization unit configured to calculate a quantization parameter for the residual block and perform inverse quantization on the residual coefficient using the calculated quantization parameter; And
And an inverse transform unit for performing inverse transform on the inverse quantized residual coefficients to reconstruct residual samples of the residual block. The method of claim 7, wherein
And the inverse quantization unit derives the quantization parameter based on at least one of a quantization parameter prediction value or a quantization parameter difference value. The method of claim 8,
The dequantization unit derives the quantization parameter prediction value based on the quantization parameter of one or more neighboring blocks,
And the neighboring block is a block spatially or temporally adjacent to the residual block. The method of claim 8,
And the inverse quantization unit determines the quantization parameter difference value based on a size of a block that allows signaling of the quantization parameter difference value. The method of claim 8,
And the inverse quantization unit corrects the derived quantization parameter based on a predetermined quantization parameter offset. The method of claim 7, wherein
And the residual block is divided into variable sizes / shapes based on at least one of a quad tree, a binary tree, or a triple tree.

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