KR20230005506A - Video Encoding And Decoding Method Using Transform Coefficients Sign Bit Hiding - Google Patents

Abstract

The present disclosure provides a video decoding method which is capable of increasing the efficiency in encoding a video by reducing code information about codes of conversion factors. The method comprises the steps of: obtaining conversion factor magnitude information about the magnitude of predetermined conversion factors among conversion factors of a current block; obtaining a code bit hiding flag indicating whether code bit hiding of the predetermined conversion factors of the current block is performed; determining a code of the predetermined conversion factors without obtaining conversion factor code information for codes of the predetermined conversion factors when the code bit hiding flag indicates that the code bit hiding of the predetermined conversion factors is performed; and determining the predetermined conversion factors according to the magnitude of the predetermined conversion factors according to the conversion factors magnitude information and the determined code of the predetermined conversion factors.

Description

Video Encoding and Decoding Method Using Transform Coefficients Sign Bit Hiding {Video Encoding And Decoding Method Using Transform Coefficients Sign Bit Hiding}

The present invention relates to a video encoding and decoding method, and more particularly, to a video encoding and decoding method using transform coefficient code bit hiding.

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 at which the bandwidth of a channel develops. In order to solve this problem, an international standardization organization, ITU-T's Video Coding Expert Group (VCEG) and ISO/IEC's Moving Picture Expert Group (MPEG), are continuously researching a more advanced video compression standard through joint research.

Video coding is largely composed of intra-prediction, inter-prediction, transform, quantization, entropy coding, and in-loop filter. Transformation and quantization may be performed on a residual block of each block determined by block division of the image. Further, transform coefficient information may be generated for a transform coefficient block determined according to transform and quantization.

Video encoding efficiency can be increased by reducing the size of transform coefficient information using a distribution of transform coefficient values, redundancy among transform coefficients, and the like.

As the resolution of an image increases, the size of encoded image data is rapidly increasing. Therefore, video encoding efficiency can be increased by reducing the code information about the sign of the transform coefficient.

In the present disclosure, obtaining transform coefficient size information on the size of predetermined transform coefficients among transform coefficients of a current block, and a code indicating whether code bit hiding of the predetermined transform coefficients of the current block is performed. Acquiring a bit hiding flag, when the sign bit hiding flag indicates that sign bit hiding of the predetermined transform coefficients is performed, without acquiring transform coefficient sign information for the signs of the predetermined transform coefficients There is provided a video decoding method including the step of determining the sign of , and the step of determining the predetermined transform coefficient according to the size of predetermined transform coefficients according to the transform coefficient size information and the determined sign of the predetermined transform coefficients. .

In an embodiment, the determining of the signs of the predetermined transform coefficients may include determining a code bit cost for each of code combinations for the predetermined transform coefficients, and an optimal code according to the sign bit cost. The method may include determining a combination, and determining a sign of the predetermined transform coefficient according to the optimal code combination.

In an embodiment, the determining of the code bit cost for each of the code combinations for the predetermined transform coefficients may include determining a residual block of the current block according to the code combination; The method may include determining a reconstruction block of the current block, and determining a code bit cost of the code combination based on the reconstruction block and adjacent blocks of the current block.

In an embodiment, the determining of the residual block of the current block according to the code combination may include determining the residual block of the current block according to the code combination according to fast inverse transform.

In an embodiment, the step of determining the code bit cost of the code combination based on the reconstruction block and an adjacent block of the current block may include samples of the reconstruction block adjacent to a left boundary of the current block and the current block. The code bit cost of the code combination can be determined according to the similarity between the samples of the left adjacent block of and the similarity between the samples of the reconstruction block adjacent to the upper boundary of the current block and the samples of the upper adjacent block of the current block. there is.

In an embodiment, the determining of the code bit cost of the code combination based on the reconstructed block and adjacent blocks of the current block may include at least one of a size of the current block, a prediction mode, a transform mode, and a quantization parameter. According to , the code bit cost of the code combination may be determined.

In an embodiment, the step of determining the optimal code combination according to the code bit cost may be characterized in that a code combination having the lowest code bit cost is determined as the optimal code combination.

In an embodiment, the obtaining of the code bit hiding flag may include a code bit indicating whether code bit hiding is allowed for one of a coding tree block, a slice, a tile, a picture, a sequence, and a video of the current block. Acquiring a hiding permission flag, and acquiring the sign bit hiding flag when the sign bit hiding permission flag indicates whether the sign bit hiding is allowed.

In an embodiment, the predetermined transform coefficient may be determined by at least one of a scan order of the current block, a threshold value of the size of the transform coefficient, and a position of the transform coefficient.

In an embodiment, the predetermined number of transform coefficients may be 3 or more.

In the present disclosure, the step of determining transform coefficients of a current block, the step of encoding transform coefficient size information about the magnitudes of predetermined transform coefficients among the transform coefficients of the current block, and the sign of the predetermined transform coefficients A video encoding method is provided that includes determining whether bit hiding is performed, and encoding a sign bit hiding flag indicating whether or not the sign bit information of the predetermined transform coefficients is omitted.

In an embodiment, the determining whether code bit hiding is performed for the signs of the predetermined transform coefficients may include determining a code bit cost for each of code combinations applicable to the predetermined transform coefficients. , determining an optimal code combination among code combinations applicable to the predetermined transform coefficients according to the code bit cost, and performing code bit hiding of the predetermined transform coefficients according to the optimal code combination. It may include the step of determining whether or not.

In an embodiment, the determining of the code bit cost for each of the code combinations for the predetermined transform coefficients may include determining a residual block of the current block according to the code combination; The method may include determining a reconstruction block of the current block, and determining a code bit cost of the code combination based on the reconstruction block and adjacent blocks of the current block.

In an embodiment, the determining of the residual block of the current block according to the code combination may include determining the residual block of the current block according to the code combination according to fast inverse transform.

In an embodiment, the step of determining the code bit cost of the code combination based on the reconstruction block and an adjacent block of the current block may include samples of the reconstruction block adjacent to a left boundary of the current block and the current block. Depending on the similarity between the samples of the left adjacent block of and the similarity between the samples of the reconstruction block adjacent to the upper boundary of the current block and the samples of the upper adjacent block of the current block, the code bit cost of the code combination is determined that can be characterized.

In an embodiment, the determining of the code bit cost of the code combination based on the reconstructed block and adjacent blocks of the current block may include at least one of a size of the current block, a prediction mode, a transform mode, and a quantization parameter. According to , the code bit cost of the code combination may be determined.

In an embodiment, the step of determining whether the code bit hiding of the predetermined transform coefficients is performed according to the optimal code combination may include the optimal code among code combinations applicable to the predetermined transform coefficients. Depending on whether the combination matches the code combination applied to the predetermined transform coefficients, it can be determined whether or not sign bit hiding of the predetermined transform coefficients is performed.

In an embodiment, the video encoding method encodes a code bit hiding permission flag indicating whether code bit hiding is allowed for one of a coding tree block, a slice, a tile, a picture, a sequence, and a video of the current block. The step of determining whether sign bit hiding of the predetermined transform coefficients is performed, and the step of encoding a sign bit hiding flag indicating whether or not the sign bit information of the predetermined transform coefficients is omitted , It may be characterized in that it is performed when the sign bit hiding permission flag indicates that sign bit hiding is allowed.

In an embodiment, the predetermined transform coefficient may be determined by at least one of a scan order of the current block, a threshold value of the size of the transform coefficient, and a position of the transform coefficient.

In an embodiment, the predetermined number of transform coefficients may be 3 or more.

In the present disclosure, a computer-readable recording medium storing a bitstream generated by the above video encoding method is provided.

Sign information of the transform coefficient may be omitted by the process of hiding the sign bit of the transform coefficient according to the present invention. Therefore, the amount of information generated by encoding the transform coefficient can be reduced. Therefore, the generation and dissemination of high-definition video can be facilitated by improving the video encoding efficiency.

1 is a block diagram illustrating an image encoding apparatus according to an embodiment of the present invention.
2 is a block diagram illustrating a video decoding apparatus according to an embodiment of the present invention.
3 shows an image encoding method of encoding a transform coefficient block by hiding code bits.
4 shows an example of a transform coefficient block and a code combination of transform coefficients of the transform coefficient block.
5 illustrates a high-speed inverse transform according to the floating-point DCT2 method.
6 illustrates a residual block determination method according to fast inverse transform according to the floating-point type DCT2 method.
7 illustrates an example of a transform coefficient block and a high-speed inverse transform according to an integer-type DCT2 method.
8 to 10 describe a method for determining residual blocks of each of a plurality of blocks constituting a transform coefficient block.
11 illustrates one embodiment for determining the sign bit cost.
12 describes a video decoding method using code bit hiding.
13 describes a video encoding method using sign bit hiding.

Since the present invention can make various changes and have various embodiments, specific embodiments will be 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 should be understood to include all modifications, equivalents, and substitutes included in the spirit and scope of the present invention. Like reference numbers in the drawings indicate the same or similar function throughout the various aspects. The shapes and sizes of elements in the drawings may be exaggerated for clarity. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS For detailed descriptions of exemplary embodiments described below, reference is made to the accompanying drawings, which illustrate specific embodiments by way of example. These embodiments are described in sufficient detail to enable those skilled in the art to practice the embodiments. It should be understood that the various embodiments are different, but need not be mutually exclusive. For example, specific shapes, structures, and characteristics described herein may be implemented in one embodiment in another embodiment without departing from the spirit and scope of the invention. Additionally, it should be understood that the location or arrangement of individual components within each disclosed embodiment may be changed without departing from the spirit and scope of the embodiment. Accordingly, the detailed description set forth below is not to be taken in a limiting sense, and the scope of the exemplary embodiments, if properly described, is limited only by the appended claims, along with all equivalents as claimed by those claims.

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

When a component of the present invention is referred to as “connected” or “connected” to another component, it may be directly connected or connected to the other component, but there may be other components in the middle. It should be understood that it may be On the other hand, when an element is referred to as “directly connected” or “directly connected” to another element, it should be understood that no other element exists in the middle.

Components appearing in the embodiments of the present invention are shown independently to represent different characteristic functions, and do not mean that each component is composed of separate hardware or a single software component. That is, each component is listed and included as each component for convenience of explanation, and at least two components of each component can be combined to form a single component, or one component can be divided into a plurality of components to perform a function, and each of these components can be divided into a plurality of components. Integrated embodiments and separated embodiments of components are also included in the scope of the present invention as long as they do not depart from the essence of the present invention.

Terms used in the present invention are only used to describe specific embodiments, and are not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly dictates otherwise. In the present invention, terms such as "comprise" or "having" are intended to designate that there is a feature, number, step, operation, component, part, or combination thereof described in the specification, but one or more other features It should be understood that the presence or addition of numbers, steps, operations, components, parts, or combinations thereof is not precluded. That is, the description of "including" a specific configuration in the present invention does not exclude configurations other than the corresponding configuration, and means that additional configurations may be included in the practice of the present invention or the scope of the technical spirit of the present invention.

Some of the components of the present invention are not essential components that perform essential functions in the present invention, but may be optional components for improving performance. The present invention can be implemented by including only components essential to implement the essence of the present invention, excluding 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.

EMBODIMENT OF THE INVENTION Hereinafter, embodiment of this invention is described concretely with reference to drawings. In describing the embodiments of this specification, if it is determined that a detailed description of a related known configuration or function may obscure the gist of the present specification, the detailed description will be omitted, and the same reference numerals will be used for the same components in the drawings. and duplicate 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 , an 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, an entropy encoding unit ( 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 shown independently to represent different characteristic functions in the video encoding device, and does not mean that each component is made of separate hardware or a single software component. That is, each component is listed and included as each component for convenience of explanation, and at least two components of each component can be 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 can be divided into a plurality of components. Integrated embodiments and separated embodiments of components are also included in the scope of the present invention as long as they do not depart from the essence of the present invention.

In addition, some of the components may be optional components for improving performance rather than essential components that perform essential functions in the present invention. The present invention can be implemented by including only components essential to implement the essence of the present invention, excluding 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 division unit 110 may divide an input picture into at least one processing unit. In this case, the processing unit may be a prediction unit (PU), a transform unit (TU), or a coding unit (CU). The picture division unit 110 divides one picture into a plurality of combinations of coding units, prediction units, and transformation units, and combines one coding unit, prediction unit, and transformation unit according to a predetermined criterion (eg, a cost function). You can encode a picture by selecting .

For example, one picture may be divided into a plurality of coding units. In order to divide coding units in a picture, a recursive tree structure such as a quad tree structure can be used. Coding that is divided into different coding units with one image or largest coding unit as the root A unit may be divided with as many child nodes as the number of divided coding units. A coding unit that is not further divided according to a certain limit becomes a leaf node. That is, when it is assumed that only square division is possible for one coding unit, one coding unit can be divided into up to four different coding units.

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

The prediction unit may be divided into at least one square or rectangular shape having the same size within one coding unit, and one of the prediction units divided within one coding unit predicts another prediction unit. It may be divided to have a shape and/or size different from the unit.

When generating a prediction unit for performing intra prediction based on a coding unit, if the coding unit is not a minimum coding unit, intra prediction may be performed without dividing into a plurality of prediction units NxN.

The prediction units 120 and 125 may include the inter prediction unit 120 performing inter prediction and the intra prediction unit 125 performing intra prediction. It is possible to determine whether to use inter prediction or intra prediction for a prediction unit, and determine specific information (eg, intra prediction mode, motion vector, reference picture, etc.) according to each prediction method. In this case, a processing unit in which prediction is performed and a processing unit in which a prediction method and specific details 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 . In addition, prediction mode information and motion vector information used for prediction may be encoded in the entropy encoder 165 together with residual values and transmitted to the decoder. When a specific encoding mode is used, it is also possible to encode an original block as it is and transmit it to a decoder without generating a prediction block through the prediction units 120 and 125 .

The inter-prediction unit 120 may predict a prediction unit based on information on at least one picture among pictures before or after the current picture, and in some cases, prediction based on information on a partially coded region within the current picture. Units can also be predicted. The inter prediction unit 120 may include a reference picture interpolation unit, a motion prediction unit, and a motion compensation unit.

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 with different filter coefficients may be used to generate pixel information of an integer pixel or less in units of 1/4 pixels. In the case of a color difference signal, a DCT-based 4-tap interpolation filter with 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 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 in units of 1/2 or 1/4 pixels based on interpolated pixels. The motion prediction unit may predict the current prediction unit by using a different motion prediction method. Various methods such as a skip method, a merge method, an advanced motion vector prediction (AMVP) method, and an intra block copy method may be used as motion prediction methods.

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. If a block adjacent to the current prediction unit is a block on which inter prediction is performed, and the reference pixel is a pixel on which inter prediction is performed, the reference pixel of the block on which intra prediction is performed surrounding the reference pixel included in the block on which inter prediction is performed information can be used instead. That is, when a reference pixel is unavailable, information on the unavailable reference pixel may be replaced with at least one reference pixel among available reference pixels.

In intra prediction, a prediction mode may include a directional prediction mode in which reference pixel information is used according to a prediction direction and a non-directional prediction mode in which directional information is not used during prediction. The number of directional prediction modes may be equal to or greater than 33 defined in the HEVC standard, and may be extended to a number within the range of 60 to 70, for example. A mode for predicting luminance information and a mode for predicting chrominance information may be different, and intra prediction mode information or predicted luminance signal information used to predict luminance information may be used to predict chrominance information.

When intra prediction is performed, if the size of the prediction unit and the size of the transformation unit are the same, intra prediction of the prediction unit is based on the pixel on the left, the top left, and the top of the prediction unit. can be performed. However, when performing intra prediction, when the size of a prediction unit and the size of a transformation unit are different, intra prediction may be performed using a reference pixel based on the transformation unit. In addition, intra prediction using N×N splitting may be used only for the smallest coding unit.

In the intra prediction method, a prediction block may be generated 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 modes of prediction units existing around the current prediction unit. When predicting the prediction mode of the current prediction unit 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 are identical, the current prediction unit and the neighboring prediction unit use predetermined flag information It is possible to transmit information that the prediction modes of are the same, and 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.

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

In the transform unit 130, the residual block including the original block and the residual information of the prediction unit generated through the prediction units 120 and 125 is converted into DCT (Discrete Cosine Transform), DST (Discrete Sine Transform), KLT and It can be converted using the same conversion method. Whether to apply DCT, DST, or KLT to transform the residual block may be determined based on intra prediction mode information of a prediction unit used to generate the residual block.

The quantization unit 135 may quantize the values converted to the frequency domain by the transform unit 130 . A quantization coefficient may change according to a block or an 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 rearrangement unit 160 may rearrange the coefficient values of the quantized residual values.

The reordering unit 160 may change a 2D block-type coefficient into a 1-D vector form through a coefficient scanning method. For example, the reordering unit 160 may scan DC coefficients to high-frequency coefficients using a zig-zag scan method and change them into a one-dimensional vector form. Depending on the size of the transform unit and the intra prediction mode, instead of zig-zag scan, a vertical scan for scanning 2D block-type coefficients in a column direction and a horizontal scan for scanning 2-dimensional block-type coefficients in a row direction may be used. That is, it is possible to determine which scan method among zig-zag scan, vertical scan, and horizontal scan is used according to the size of the transform unit and the intra prediction mode.

The entropy encoding unit 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 encoding unit 165 receives residual value coefficient information and block type information of a coding unit from the reordering unit 160 and the prediction units 120 and 125, prediction mode information, division unit information, prediction unit information and transmission unit information, motion Various information such as vector information, reference frame information, block interpolation information, and filtering information can be encoded.

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

The inverse quantization unit 140 and the inverse transform unit 145 inversely quantize the values quantized by the quantization unit 135 and inverse transform the values transformed by the transform unit 130 . The residual generated by the inverse quantization unit 140 and the inverse transform unit 145 is combined with the prediction unit predicted through the motion estimation unit, the motion compensation unit, 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 correction unit, and an adaptive loop filter (ALF).

The deblocking filter may remove block distortion caused by a boundary between blocks in a 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 may be applied according to the required deblocking filtering strength. In addition, in applying the deblocking filter, when vertical filtering and horizontal filtering are performed, horizontal filtering and vertical filtering may be processed in parallel.

The offset correction unit may correct an offset of the deblocked image from the original image in units of pixels. In order to perform offset correction for a specific picture, after dividing the pixels included in the image into a certain number of areas, determining the area to be offset and applying the offset to the area, or offset by considering the edge information of each pixel method can be used.

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 predetermined groups, filtering may be performed differentially for each group by determining one filter to be applied to the corresponding group. Information related to whether or not to apply ALF may be transmitted for each coding unit (CU) of a luminance signal, and the shape and filter coefficients of an ALF filter to be applied may vary according to each block. In addition, the ALF filter of the same form (fixed form) may be applied regardless of the characteristics of the block to be applied.

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

2 is a block diagram illustrating a video 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 rearrangement unit 215, an inverse quantization unit 220, an inverse transform unit 225, a prediction unit 230 and 235, a filter unit ( 240), memory 245 may be included.

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

The entropy decoding unit 210 may perform entropy decoding by a procedure opposite to that performed by the entropy encoding unit of the image encoder. For example, various methods such as exponential Golomb, CAVLC (Context-Adaptive Variable Length Coding), and CABAC (Context-Adaptive Binary Arithmetic Coding) may be applied corresponding to the method performed by the image encoder.

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

The rearrangement unit 215 may perform rearrangement based on a method in which the encoding unit rearranges the entropy-decoded bitstream in the entropy decoding unit 210 . Coefficients expressed in the form of one-dimensional vectors may be reconstructed into coefficients in the form of two-dimensional blocks and rearranged. The rearrangement unit 215 may perform rearrangement through a method of receiving information related to the coefficient scanning performed by the encoder and performing reverse scanning 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 rearranged coefficient value of the block.

The inverse transform unit 225 may perform inverse transforms, that is, inverse DCT, inverse DST, and inverse KLT, on the transforms performed by the transform unit, that is, DCT, DST, and KLT, on the quantization result performed by the video encoder. Inverse transformation may be performed based on the transmission unit determined by the video encoder. The inverse transform unit 225 of the video decoder may selectively perform transformation techniques (eg, DCT, DST, KLT) according to a plurality of pieces of information such as a prediction method, a size of a current block, and a prediction direction.

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

As described above, when intra prediction is performed in the same way as the operation in the video encoder, when the size of the prediction unit and the size of the transformation unit are the same, the pixel existing on the left, the pixel existing on the upper left, and the pixel existing on the upper side of the prediction unit are the same. Intra prediction is performed on a prediction unit based on a pixel to perform intra prediction, but when performing intra prediction, when the size of the prediction unit and the size of the transformation unit are different, intra prediction is performed using a reference pixel based on the transformation unit. can In addition, intra prediction using N×N splitting may be used only for the smallest coding unit.

The prediction units 230 and 235 may include a prediction unit determining unit, an inter prediction unit, and an intra prediction unit. The prediction unit determination unit receives various information such as prediction unit information input from the entropy decoding unit 210, prediction mode information of the intra prediction method, and motion prediction related information of the inter prediction method, classifies the prediction unit from the current coding unit, and predicts It is possible to determine whether a unit performs inter prediction or intra prediction. The inter-prediction unit 230 uses information necessary for inter-prediction of the current prediction unit provided from the video encoder to make current prediction based on information included in at least one picture among pictures before or after the current picture including the current picture. Inter prediction can be performed on units. Alternatively, inter prediction may be performed based on information of a pre-reconstructed partial region in the current picture including the current prediction unit.

In order to perform inter prediction, the motion prediction method of the prediction unit included in the corresponding coding unit based on the coding unit is skip mode, merge mode, AMVP mode, and intra block copy mode. You can judge which way it is.

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 that has undergone intra prediction, intra prediction may be performed based on intra prediction mode information of the prediction unit provided by the video encoder. 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 that performs filtering on reference pixels 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 reference pixels of the current block using the prediction mode of the prediction unit and AIS filter information provided by the image encoder. When the prediction mode of the current block is a mode in which AIS filtering is not performed, 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 obtained by interpolating the reference pixel, the reference pixel interpolator may interpolate the reference pixel to generate a reference pixel of the pixel unit having an integer value or less. When the prediction mode of the current prediction unit is a prediction mode for generating a prediction block without interpolating reference pixels, the reference pixels 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 correction unit, and an ALF.

Information on whether a deblocking filter is applied to a corresponding block or picture and, when a deblocking filter is applied, information on whether a strong filter or a weak filter is applied may be provided from the video coder. The deblocking filter of the video decoder receives information related to the deblocking filter provided by the video encoder, and the video 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 and offset value information of the offset correction applied to the image during encoding.

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

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

As described above, in the following embodiments of the present invention, for convenience of explanation, a coding unit is used as a coding unit, but it may be a unit that performs not only encoding but also decoding.

3 illustrates an image encoding method of encoding a transform coefficient block generated by transforming and quantizing a residual block through sign bit hiding.

In step 302, a transform coefficient block is generated by performing transform and quantization on the residual block. The transform coefficient block may be generated by inverse quantizing a residual block on which transform and quantization have been performed.

After generating the transform coefficient block in step 304, encoding of some sign information of transform coefficients of the transform coefficient block is omitted according to the hiding of the sign bit.

Sign bit hiding may be performed in the transform coefficient block. Coefficients to which sign bit hiding is applied in the transform coefficient block may be arbitrarily limited to N. Said N is an integer of 2 or more.

Signs of transform coefficients obtained in the encoding process may be transmitted through a sign bit hiding flag (1 bit). In the decoding process, it may be determined whether sign bit hiding is applied through the sign bit hiding flag.

The sign bit hiding flag may be determined in units of transform coefficient blocks. Alternatively, the code bit hiding flag may be determined in units of a coding block, a coding tree block, a slice, a tile, a picture, a Coded Video Sequence (CVS), or an entire video, which are higher units than the transform coefficient block.

According to an embodiment, inverse quantization may be performed using a look-up table. Then, by reflecting the sign bit hiding process in the lookup table, the sign bit hiding process in step 304 can be merged into transform coefficient block generation according to the lookup table in step 302.

The lookup table may be determined according to a quantization parameter used to generate a transform coefficient block among a plurality of lookup tables. Alternatively, one lookup table may be selected from among a plurality of lookup tables according to not only the quantization parameter but also other encoding parameters.

When the lookup table is used, the amount of calculation required to generate the transform coefficient block can be reduced. However, a lot of memory capacity may be required to store a plurality of lookup tables.

According to an embodiment, in step 304, whether to hide the sign bit may be determined. In an encoding stage, a reconstructed image generated by decoding data encoded according to an encoding tool is compared with an original image in order to verify an encoding rate of an image according to a specific encoding tool. According to the comparison result, when the difference between the reconstructed image and the original image is small, an encoding tool may be adopted. Conversely, if the difference between the restored image and the original image is large, the encoding tool is not adopted.

Specifically, a difference between a reconstructed image and an original image according to a code combination of a plurality of transform coefficients may be compared to determine an optimal code combination of transform coefficients. In addition, code bit hiding is performed by comparing the difference between the reconstructed image and the original image when code bit hiding is performed according to the code combination of the optimal transform coefficients and the difference between the reconstructed image and the original image when the code bit hiding is not performed. whether can be determined.

The difference between the reconstructed image and the original image may be normalized with a sign bit cost. The code bit cost may be determined according to similarity between reconstructed samples of a transform coefficient block according to a combination of signs of transform coefficients and adjacent samples adjacent to the transform coefficient block.

A method of determining the code bit cost may be determined differently depending on the picture type. For example, a method for determining code bit cost when the picture type is I type (only intra prediction is allowed) and a method for determining code bit cost when the picture type is P type or B type (intra prediction and inter prediction are allowed) can be different

Also, a method for determining the code bit cost may be determined differently according to a conversion method. For example, a method for determining a code bit cost may be different depending on whether a transform method applied to a transform coefficient block is DCT transform or DST transform. Alternatively, a method for determining a code bit cost may be different depending on whether a secondary transform is applied to a transform coefficient block. Alternatively, a method for determining a code bit cost may be different according to a transform method applied to the vertical transform and the horizontal transform of the transform coefficient block. Alternatively, the method for determining the code bit cost may be different according to the size of the transform coefficient block.

According to an embodiment, sign bit costs for code combinations of transform coefficients are determined according to the method for determining sign bit costs described above. Also, code combinations having the lowest code bit cost are determined as optimal code combinations. If the optimal sign combination matches the actual sign combination of the transform coefficient block, it is determined that sign bit hiding is applied. And when it is determined that the sign bit hiding is applied, the sign bit hiding flag is determined to be 1. Conversely, if the optimal code combination does not match the actual code combination of the transform coefficient block, it is determined that the code bit hiding is not applied. And when it is determined that sign bit hiding is not applied, the sign bit hiding flag is determined to be 0.

Alternatively, when the determined reconstruction block according to the optimal code combination coincides with the determined reconstruction block without applying sign bit hiding, it is determined that sign bit hiding is applied. And when it is determined that the sign bit hiding is applied, the sign bit hiding flag is determined to be 1. Conversely, when the determined reconstruction block according to the optimal code combination does not match the determined reconstruction block without applying the code bit hiding, it is determined that the code bit hiding is not applied. And when it is determined that sign bit hiding is not applied, the sign bit hiding flag is determined to be 0.

The sign bit cost is discussed in detail below.

4 shows an example of a transform coefficient block 400 and a code combination of transform coefficients of the transform coefficient block.

The transform coefficient block 400 includes 3 nonzero transform coefficients and 13 zero transform coefficients. Accordingly, the transform coefficient block 400 requires three sign bits to indicate the signs of the three non-zero transform coefficients. In order to apply sign bit hiding, the sign bit cost of the code combination of transform coefficients can be determined with three issues of the transform coefficient block 400 . In addition, when the optimal code combination having the lowest code bit cost coincides with the code combination of the three non-zero transform coefficients of the transform coefficient block 400, code bit hiding may be applied. Conversely, when the optimal code combination having the lowest code bit cost does not match the sign combination of the three zero transform coefficients of the transform coefficient block 400, the code bit hiding may not be applied.

Since the transform coefficient block 400 includes three non-zero transform coefficients, 2^3 (= 8) code combinations exist in the transform coefficient block 400 according to codes. Specifically, (1,1,1) (1,1,1), (1,1,1), (1,1,1), (1,1,1), (1,1,1), The sign combinations of (1,1,1) and (1,1,1) are present in the transform coefficient block 400. Accordingly, the code bit cost according to each code combination is calculated, and the code combination having the lowest code bit cost is determined as the optimal code combination.

For fast calculation of the code bit cost of each code combination, a fast inverse transform of the transform coefficient block 400 is required. For fast inverse transformation, the transform coefficient block 400 may be represented by a combination of a first block 402, a second block 404, and a third block 406 including only one nonzero transform coefficient. In addition, the inverse transform result of the transform coefficient block 400 can be quickly calculated according to the inverse transform results of the first block 402 , the second block 404 , and the third block 406 .

Hereinafter, a method for determining an optimal code combination according to the floating point DCT2 method in FIGS. 5 and 6 will be described.

5 illustrates fast inverse-transform according to the floating-point DCT2 method.

According to FIG. 5 , the transform coefficient block 400 is equal to the sum of a multiple of 3 of the first block 402 , a multiple of (−5) of the second block 404 , and a multiple of 7 of the third block 406 . For rapid inverse transformation of the transform coefficient block, the result value 512 of the inverse transformation of the first block 402, the result value 514 of the inverse transformation of the second block 404, and the result value of the inverse transformation of the third block 406 ( 516) may be set in advance.

The resulting value 512 may be generated by horizontally transforming the intermediate block 502 generated by vertically transforming the first block 402 . The resulting value 514 may be generated by horizontally transforming the intermediate block 504 generated by vertically transforming the second block 404 . The resulting value 516 may be generated by horizontally transforming the intermediate block 506 generated by vertically transforming the third block 406 .

6 illustrates a residual block determination method according to fast inverse-transform according to the floating-point type DCT2 method.

In order to determine the optimal code combination of the transform coefficients of the transform coefficient block 400, the result values 512, 514, and 514 of the first block 402, the second block 404, and the third block 516) may be used. For example, the residual block for the sign combination of (1,1,1) can be determined by adding a multiple of 3 of the result value 512, a multiple of 5 of the result value 514, and a multiple of 7 of the result value 516. there is. And the residual block for the code combination of (1,1,1) can be determined by adding a multiple of (-3) the result value 512, a multiple of 5 the result value 514, and a multiple of 7 the result value 516. there is. Residual blocks can be determined in the same way for other code combinations.

As described in FIGS. 4 to 6 , a total of 8 residual blocks can be generated by fast inverse transform according to the floating point DCT2 method. Code bit costs for 8 residual blocks may be determined based on information of adjacent blocks adjacent to the transform coefficient block 400 . An optimal code combination is determined based on the residual block having the smallest code bit cost. If the optimal sign combination coincides with the actual sign combination of the transform coefficients as the subject of the transform coefficient block 400, it is determined that sign bit hiding is applied to the transform coefficient block 400. Conversely, if the optimal code combination does not match the actual code combination of the transform coefficients as the topic of the transform coefficient block 400, it is determined that sign bit hiding is not applied to the transform coefficient block 400. When sign bit hiding is not applied, signs of transform coefficients of the transform coefficient block 400 are encoded.

7 illustrates an example of a transform coefficient block 700 and fast inverse-transform according to the integer type DCT2 method.

The transform coefficient block D 700 may be inversely transformed according to the 4x4 integer DCT-II matrix A 710 . Specifically, the inverse transform result of the transform coefficient block D 700 may be determined by Equation A ^T DA.

For fast inverse transformation, the transform coefficient block D 700 can be represented by a combination of a first block 702, a second block 704, and a third block 706 including only one nonzero transform coefficient. In addition, the inverse transform result of the transform coefficient block 700 can be quickly calculated according to the inverse transform results of the first block 702 , the second block 704 , and the third block 706 .

Since the transform coefficient block 700 includes three non-zero transform coefficients, there are 2^3 (= 8) code combinations. Accordingly, the code bit cost according to each code combination is calculated, and the code combination having the lowest code bit cost is determined as the optimal code combination. According to the high-speed inverse transform according to the integer type DCT2 method, the code bit cost of each code combination can be quickly calculated.

8 to 10 show the first residual block 752, the second residual block 754, and the third residual block 756 of the first block 702, the second block 704, and the third block 706. Describe how to determine

The first block 702 may be vertically inverse transformed by A ^T 712 . According to the vertical inverse transform of the first block 702, the first vertical inverse transform block 722 is determined. The size of the transform coefficient of the first vertical inverse transform block 722 may be adjusted by a shift operation. Therefore, according to the shift operation of the first vertical inverse transform block 722, the first intermediate block 732 may be generated. The first intermediate block 732 may be horizontally inversely transformed by A 710 . According to the horizontal inverse transform of the first intermediate block 732, the first horizontal inverse transform block 742 is determined. Similar to the first vertical inverse transform block 722, the size of the transform coefficient of the first horizontal inverse transform block 742 may be adjusted by a shift operation. Therefore, according to the shift operation of the first horizontal inverse transform block 742, the first residual block 752 may be generated.

Similarly, the second block 704 may be vertically inverse transformed by A ^T 712 . According to the vertical inverse transform of the second block 704, the second vertical inverse transform block 724 is determined. The size of the transform coefficient of the second vertical inverse transform block 724 may be adjusted by a shift operation. Accordingly, the second intermediate block 734 may be generated according to the shift operation of the second vertical inverse transform block 724 . The second intermediate block 734 may be horizontally inversely transformed by A 710 . According to the horizontal inverse transform of the second intermediate block 734, the second horizontal inverse transform block 744 is determined. Similar to the second vertical inverse transform block 724, the size of the transform coefficient of the second horizontal inverse transform block 744 may be adjusted by a shift operation. Therefore, according to the shift operation of the second horizontal inverse transform block 744, the second residual block 754 may be generated.

Similarly, the third block 706 may be vertically inverse transformed by A ^T 712 . According to the vertical inverse transform of the third block 706, a third vertical inverse transform block 726 is determined. The size of the transform coefficient of the third vertical inverse transform block 726 may be adjusted by a shift operation. Therefore, according to the shift operation of the third vertical inverse transform block 726, the third intermediate block 736 may be generated. The third intermediate block 736 may be horizontally inverse transformed by A 710 . According to the horizontal inverse transform of the third intermediate block 736, the third horizontal inverse transform block 746 is determined. Similar to the third vertical inverse transform block 726, the size of the transform coefficient of the third horizontal inverse transform block 746 may be adjusted by a shift operation. Therefore, according to the shift operation of the third horizontal inverse transform block 746, the third residual block 756 may be generated.

The first residual block 752, the second residual block 754, and the third residual block 756 may be added according to eight code combinations. Specifically, (1,1,1) (1,1,1), (1,1,1), (1,1,1), (1,1,1), (1,1,1), A code combination of (1,1,1) and (1,1,1) is applied to the sum operation of the first residual block 752, the second residual block 754, and the third residual block 756. can For example, according to the code combination of (1,1,1), the values of the first residual block 752, the second residual block 754, and the third residual block 756 are summed. Then, a code bit cost according to the generated residual block is calculated according to the summed result. For the remaining code combinations, a code bit cost according to a summation result of the first residual block 752, the second residual block 754, and the third residual block 756 is calculated. Finally, whether to apply sign bit hiding is determined according to whether the code combination having the lowest sign bit cost matches the actual code combination of the transform coefficient block.

7 to 10, the first residual block 752, the second residual block 754, and the third residual block ( 756) is determined. That is, the code combination of (1, 1, 1) is the actual code combination of the transform coefficient block 700. Therefore, according to an embodiment, whether to apply the code bit hiding may be determined according to whether the cost of the code bit according to the code combination of (1, 1, 1) is lower than the cost of the code bit according to other code combinations.

11 illustrates one embodiment for determining the sign bit cost.

Residual blocks of transform coefficient blocks determined according to the above-described fast inverse transform or other inverse transform methods are added to the corresponding prediction blocks. A reconstructed block is generated according to the sum of the residual block and the prediction block. A code bit cost may be determined according to continuity between samples adjacent to a left boundary and/or an upper boundary among samples of a reconstruction block corresponding to the transform coefficient block and samples of an adjacent block of the reconstruction block.

One embodiment of a method for determining the sign bit cost is described in Equation 1 below.

[Equation 1]

Based on Equation 1 above, a code bit cost is calculated for each code combination of a transform coefficient block. In addition, whether to apply code bit hiding of the transform coefficient block may be determined by comparing the optimal code combination according to the code bit cost with the actual code combination of the transform coefficient block.

α and β in Equation 1 are arbitrary constants. For example, both α and β may be 1. Alternatively, α and β may be 1 and 2, respectively. α and β may be determined differently depending on the prediction method of the current block. r[x,y] in Equation 1 means a sample value at the (x,y) position of the reconstructed block r. For example, r[1,1] represents a sample value at position (1,1) of reconstruction block r.

11 and Equation 1 above, the sign bit cost is calculated based on samples separated by a distance of 2 samples from the boundary. However, according to embodiments, the sign bit cost may be calculated based on samples separated by a distance of 1 sample. Alternatively, according to an embodiment, the sign bit cost may be calculated based on samples separated by a distance of N samples. Said N is 3 or more.

4 to 10, methods for hiding sign bits of three transform coefficients have been described. However, depending on embodiments, it may be determined whether to hide the sign bits of the two transform coefficients. Alternatively, according to embodiments, it may be determined whether to hide sign bits of four or more transform coefficients.

In the above embodiment, it has been explained that whether to apply code bit hiding of the transform coefficient block is determined according to whether the optimal code combination is the same as the actual code combination. However, according to embodiments, code bit hiding may be applied when a restoration error between the optimal code combination and the actual code combination is small even when the optimal code combination is different from the actual code combination.

According to an embodiment, a method for calculating the code bit cost may be determined differently according to characteristics of the transform coefficient block and the current picture. For example, a method for calculating a code bit cost may be determined according to a prediction mode corresponding to a transform coefficient block. Alternatively, a method for calculating the code bit cost may be determined by considering the prediction mode of the transform coefficient block and the prediction mode of the adjacent block. Alternatively, a method for calculating the code bit cost may be determined according to the picture type of the current picture. Specifically, a method for calculating the code bit cost may be determined according to whether the current picture is an I picture allowing only intra prediction, or a P picture or B picture allowing inter prediction. Alternatively, a method for calculating the sign bit cost may be determined according to a transform scheme applied to the transform coefficient block. Alternatively, a method for calculating a code bit cost may be determined according to a quantization parameter applied to a transform coefficient block. Alternatively, the method of calculating the code bit cost may be determined according to the type of in-loop filter applied to the transform coefficient block.

The position of the transform coefficient to which sign bit hiding is applied can be determined in various ways. For example, sign bit hiding may be applied to consecutive nonzero transform coefficients that are scanned first in the scan order. Alternatively, sign bit hiding may be applied to successive nonzero transform coefficients that are scanned later in the scan order.

Alternatively, sign bit hiding may be applied to nonzero transform coefficients located far from the upper left of the transform coefficient block. Conversely, sign bit hiding may be applied to nonzero transform coefficients located close to the upper left of the transform coefficient block.

Alternatively, sign bit hiding may be applied to a transform coefficient smaller than a predetermined size among transform coefficients of the transform coefficient block. Conversely, sign bit hiding may be applied to a transform coefficient larger than a predetermined size among transform coefficients of the transform coefficient block.

Alternatively, sign bit hiding may be applied to a transform coefficient smaller than a predetermined size among successive transform coefficients scanned first in the scanning order. Conversely, sign bit hiding may be applied to a transform coefficient smaller than a predetermined size among successive transform coefficients scanned later in the scan order.

12 describes a video decoding method using code bit hiding.

In step 1202, transform coefficient size information about the size of predetermined transform coefficients among transform coefficients of the current block is obtained.

According to an embodiment, the predetermined transform coefficient may be determined by at least one of a scan order of a current block, a threshold value of a transform coefficient size, and a position of the transform coefficient. The number of predetermined transform coefficients may be three or more.

In step 1204, a sign bit hiding flag indicating whether sign bit hiding of predetermined transform coefficients of the current block is performed is obtained.

According to an embodiment, a code bit hiding permission flag indicating whether code bit hiding is allowed for one of a coding tree block, a slice, a tile, a picture, a sequence, and a video of a current block may be obtained. And when the sign bit hiding allowed flag indicates whether the sign bit hiding is allowed, the sign bit hiding flag can be obtained.

In step 1206, when the sign bit hiding flag indicates that sign bit hiding of the predetermined transform coefficients is performed, signs of the predetermined transform coefficients are determined without acquiring transform coefficient sign information about the signs of the predetermined transform coefficients.

According to an embodiment, when the sign bit hiding flag indicates that sign bit hiding of predetermined transform coefficients is not performed, transform coefficient sign information about the signs of predetermined transform coefficients is obtained. Signs of predetermined transform coefficients are determined according to the transform coefficient sign information.

According to an embodiment, a code bit cost for each of code combinations of predetermined transform coefficients may be determined. An optimal code combination may be determined according to the code bit cost. In addition, the sign of a predetermined transform coefficient may be determined according to an optimal code combination.

According to an embodiment, in order to determine a code bit cost, a residual block of a current block according to a code combination is determined. Then, a reconstruction block of the current block is determined from the remaining blocks. The code bit cost of the code combination is determined based on the reconstructed block and the adjacent blocks of the current block.

According to an embodiment, a residual block of the current block according to the code combination may be determined according to fast inverse transform.

According to an embodiment, in order to determine the code bit cost of the code combination, similarity between samples of a reconstruction block adjacent to the left boundary of the current block and samples of the left adjacent block of the current block and adjacent to the upper boundary of the current block in order to determine the code bit cost of the code combination. A code bit cost of a code combination may be determined according to a similarity between samples of the reconstruction block and samples of an upper adjacent block of the current block.

According to an embodiment, a code bit cost of a code combination may be determined according to at least one of a size of a current block, a prediction mode, a transform mode, and a quantization parameter.

According to an embodiment, a code combination having the smallest code bit cost is determined as an optimal code combination.

In step 1208, the predetermined transform coefficient is determined according to the magnitudes of predetermined transform coefficients according to the transform coefficient size information and the determined signs of the predetermined transform coefficients.

13 describes a video encoding method using sign bit hiding.

In step 1302, transform coefficients of the current block are determined.

In step 1304, transform coefficient magnitude information about the magnitudes of predetermined transform coefficients among transform coefficients of the current block is encoded.

According to an embodiment, a predetermined transform coefficient may be determined based on at least one of a scan order of a current block, a threshold value of a transform coefficient size, and a position of a transform coefficient. The number of predetermined transform coefficients may be three or more.

In step 1306, it is determined whether sign bit hiding is performed for the sign of certain transform coefficients.

According to an embodiment, a code bit cost for each of code combinations applicable to predetermined transform coefficients may be determined. According to the code bit cost, an optimal code combination among code combinations applicable to predetermined transform coefficients may be determined. Depending on the optimal code combination, it can be determined whether sign bit hiding of certain transform coefficients is performed.

According to an embodiment, a residual block of the current block is determined according to the code combination. A reconstruction block of the current block is determined from the remaining blocks. The code bit cost of the code combination is determined based on the reconstructed block and the adjacent blocks of the current block.

According to an embodiment, a residual block of a current block according to a code combination may be determined according to fast inverse transform.

According to an embodiment, a similarity between samples of a reconstruction block adjacent to a left boundary of the current block and samples of a left adjacent block of the current block and samples of a reconstruction block adjacent to an upper boundary of the current block and an upper adjacent block of the current block Depending on the similarity between the samples of , the sign bit cost of the code combination may be determined.

According to an embodiment, a code bit cost of a code combination may be determined according to at least one of a size of a current block, a prediction mode, a transform mode, and a quantization parameter.

According to an embodiment, whether code bit hiding of predetermined transform coefficients is performed according to whether an optimal code combination among code combinations applicable to predetermined transform coefficients matches the code combination applied to predetermined transform coefficients. whether can be determined.

In step 1308, a sign bit hiding flag indicating whether sign bit information of predetermined transform coefficients is omitted is encoded.

According to an embodiment, a code bit hiding permission flag indicating whether code bit hiding is allowed for one of a coding tree block, a slice, a tile, a picture, a sequence, and a video of a current block may be encoded. And steps 1306 and 1308 can be performed when the sign bit hiding allowed flag indicates that the sign bit hiding is allowed.

According to an embodiment, a bitstream in which video data is encoded is generated according to the video encoding method. The generated bitstream may be transmitted to a video decoder or stored in a computer-readable recording medium. Also, the bitstream transmitted to the video decoder may be decoded according to the video decoding method.

In the foregoing embodiments, the methods are described on the basis of a flow chart as a series of steps or units, but the present invention is not limited to the order of steps, and some steps may occur in a different order or concurrently with other steps as described above. can In addition, those skilled in the art will understand that the steps shown in the flow chart are not exclusive, that other steps may be included, or that one or more steps of the flow chart may be deleted without affecting the scope of the present invention. You will understand.

The foregoing embodiment includes examples of various aspects. It is not possible to describe all possible combinations to represent the various aspects, but those skilled in the art will recognize that other combinations are possible. Accordingly, it is intended that the present invention cover all other substitutions, modifications and variations falling within the scope of the following claims.

Embodiments according to the present invention described above may be implemented in the form of program instructions that can be executed through various computer components and recorded on a computer-readable recording medium. The computer readable recording medium may include program instructions, data files, data structures, etc. alone or in combination. Program instructions recorded on the computer-readable recording medium may be specially designed and configured for the present invention, or may be known and usable to those skilled in the art of computer software. Examples of computer-readable recording media include magnetic media such as hard disks, floppy disks and magnetic tapes, optical recording media such as CD-ROMs and DVDs, and magneto-optical media such as floptical disks. media), and hardware devices specially configured to store and execute program instructions, such as ROM, RAM, flash memory, and the like. Examples of program instructions include high-level language codes that can be executed by a computer using an interpreter or the like as well as machine language codes such as those produced by a compiler. The hardware device may be configured to act as one or more software modules to perform processing according to the present invention and vice versa.

Although the present invention has been described above with specific details such as specific components and limited embodiments and drawings, these are only provided to help a more general understanding of the present invention, and the present invention is not limited to the above embodiments. , Those skilled in the art to which the present invention pertains may seek various modifications and variations from these descriptions.

Therefore, the spirit of the present invention should not be limited to the above-described embodiments, and not only the claims described later, but also all modifications equivalent or equivalent to these claims belong to the scope of the spirit of the present invention. will do it

Claims (20)

obtaining transform coefficient magnitude information about the magnitudes of predetermined transform coefficients among transform coefficients of a current block; and
obtaining a sign bit hiding flag indicating whether sign bit hiding of the predetermined transform coefficients of the current block is performed;
determining signs of the predetermined transform coefficients without obtaining transform coefficient sign information about the signs of the predetermined transform coefficients when the sign bit hiding flag indicates that sign bit hiding of the predetermined transform coefficients is performed;
and determining the predetermined transform coefficients according to magnitudes of predetermined transform coefficients according to the transform coefficient size information and signs of the determined predetermined transform coefficients.
According to claim 1,
Determining the signs of the predetermined transform coefficients,
determining a code bit cost for each of code combinations for the predetermined transform coefficients;
determining an optimal code combination according to the code bit cost; and
and determining a sign of the predetermined transform coefficient according to the optimal code combination.
According to claim 2,
Determining a code bit cost for each of the code combinations for the predetermined transform coefficients,
determining a residual block of the current block according to a code combination;
determining a reconstruction block of the current block from the residual block; and
and determining a code bit cost of the code combination based on the reconstruction block and an adjacent block of the current block.
According to claim 3,
Determining the residual block of the current block according to the code combination,
A video decoding method characterized in that determining a residual block of the current block according to the code combination according to fast inverse transform.
According to claim 3,
Determining the code bit cost of the code combination based on the restored block and adjacent blocks of the current block,
Similarity between samples of the reconstruction block adjacent to the left boundary of the current block and samples of the left adjacent block of the current block and samples of the reconstruction block adjacent to the upper boundary of the current block and the upper adjacent block of the current block A code bit cost of the code combination is determined according to a similarity between samples of .
According to claim 3,
Determining the code bit cost of the code combination based on the restored block and adjacent blocks of the current block,
A code bit cost of the code combination is determined according to at least one of the size of the current block, a prediction mode, a transform mode, and a quantization parameter.
According to claim 2,
Determining the optimal code combination according to the code bit cost,
A video decoding method characterized in that a code combination having the lowest code bit cost is determined as an optimal code combination.
According to claim 1,
Obtaining the sign bit hiding flag comprises:
obtaining a code bit hiding permission flag indicating whether code bit hiding is allowed for one of the coding tree block, slice, tile, picture, sequence, and video of the current block; and
and acquiring the sign bit hiding flag when the sign bit hiding permission flag indicates whether the sign bit hiding is allowed.
According to claim 1,
The predetermined conversion coefficient is,
and a scan order of the current block, a threshold value of the size of the transform coefficient, and a position of the transform coefficient.
According to claim 1,
The video decoding method, characterized in that the number of the predetermined transform coefficients is 3 or more.
determining transform coefficients of the current block;
encoding transform coefficient magnitude information about the magnitudes of predetermined transform coefficients among transform coefficients of the current block;
determining whether sign bit hiding is performed for the signs of the predetermined transform coefficients; and
and encoding a sign bit hiding flag indicating whether sign bit information of the predetermined transform coefficients is omitted.
According to claim 11,
The step of determining whether sign bit hiding is performed for the signs of the predetermined transform coefficients,
determining a code bit cost for each of code combinations applicable to the predetermined transform coefficients;
determining an optimal code combination among code combinations applicable to the predetermined transform coefficients according to the code bit cost; and
and determining whether code bit hiding of the predetermined transform coefficients is performed according to the optimal code combination.
According to claim 12,
Determining a code bit cost for each of the code combinations for the predetermined transform coefficients,
determining a residual block of the current block according to a code combination;
determining a reconstruction block of the current block from the residual block; and
and determining a code bit cost of the code combination based on the reconstruction block and an adjacent block of the current block.
According to claim 13,
Determining the residual block of the current block according to the code combination,
and determining a residual block of the current block according to the code combination according to fast inverse transform.
According to claim 13,
Determining the code bit cost of the code combination based on the restored block and adjacent blocks of the current block,
Similarity between samples of the reconstruction block adjacent to the left boundary of the current block and samples of the left adjacent block of the current block and samples of the reconstruction block adjacent to the upper boundary of the current block and the upper adjacent block of the current block A code bit cost of the code combination is determined according to a similarity between samples of .
According to claim 13,
Determining the code bit cost of the code combination based on the restored block and adjacent blocks of the current block,
and a code bit cost of the code combination is determined according to at least one of the size of the current block, a prediction mode, a transform mode, and a quantization parameter.
According to claim 12,
The step of determining whether or not the code bit hiding of the predetermined transform coefficients is performed according to the optimal code combination,
Depending on whether or not the optimal code combination among code combinations applicable to the predetermined transform coefficients matches the code combination applied to the predetermined transform coefficients, whether or not the code bit hiding of the predetermined transform coefficients is performed A video encoding method characterized in that it is determined.
According to claim 11,
The video encoding method,
Encoding a code bit hiding permission flag indicating whether code bit hiding is allowed for one of the coding tree block, slice, tile, picture, sequence, and video of the current block,
The step of determining whether sign bit hiding of the predetermined transform coefficients is performed, and the step of encoding a sign bit hiding flag indicating whether sign bit information of the predetermined transform coefficients is omitted, the sign bit hiding allow flag A video encoding method characterized in that it is performed when indicates that sign bit hiding is allowed.
According to claim 11,
The predetermined conversion coefficient is,
determined by at least one of a scan order of the current block, a threshold value of the size of the transform coefficient, and a position of the transform coefficient;
The video encoding method, characterized in that the number of the predetermined transform coefficients is 3 or more.
A computer-readable recording medium storing a bitstream generated by a video encoding method,
The video encoding method,
determining transform coefficients of the current block;
encoding transform coefficient magnitude information about the magnitudes of predetermined transform coefficients among transform coefficients of the current block;
determining whether sign bit hiding is performed for the signs of the predetermined transform coefficients; and
and encoding a sign bit hiding flag indicating whether sign bit information of the predetermined transform coefficients is omitted.

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