Image encoding / decoding method and recording medium for storing bitstream

Abstract

An image decoding method according to the present invention may comprise the steps of: determining current probability information; decoding a target syntax of a current block on the basis of the probability information; and updating the current probability information. The method for determining the current probability information may differ according to the location of the current block.

Description

Video encoding / decoding method and recording medium for storing bitstream The present disclosure relates to a video signal processing method and device. Recently, the demand for high-resolution, high-quality images, such as HD (High Definition) and UHD (Ultra High Definition) images, is increasing across various application fields. As image data becomes higher in resolution and quality, the relative amount of data increases compared to conventional image data. Therefore, transmitting image data using existing media such as wired and wireless broadband lines or storing it using existing storage media leads to increased transmission and storage costs. To address these issues arising from the increasing resolution and quality of image data, high-efficiency image compression technologies can be utilized. There are various technologies for image compression, such as inter-picture prediction technology that predicts pixel values ​​included in the current picture from pictures before or after the current picture, intra-picture prediction technology that predicts pixel values ​​included in the current picture using pixel information in the current picture, and entropy encoding technology that assigns short codes to values ​​with high frequency of appearance and long codes to values ​​with low frequency of appearance. Using these image compression technologies, image data can be effectively compressed and transmitted or stored. Meanwhile, as demand for high-resolution video grows, so does the demand for stereoscopic video content as a new video service. Discussions are underway on video compression technologies to effectively deliver high-resolution and ultra-high-resolution stereoscopic video content. The present disclosure aims to provide a method for determining probability information for syntax encoding / decoding. Specifically, the present disclosure provides a method for encrypting / decrypting the syntax of a current block using updated probability information of a candidate block instead of updated probability information of a block previously encrypted / decrypted before the current block. Specifically, the present disclosure provides a method for decrypting / encrypting the syntax of a current block by re-updating updated probability information of a block decrypted / encrypted prior to the current block. The technical problems to be achieved in the present disclosure are not limited to the technical problems mentioned above, and other technical problems not mentioned can be clearly understood by a person having ordinary skill in the technical field to which the present disclosure belongs from the description below. A video decoding method according to the present disclosure may include a step of determining current probability information; a step of decoding a target syntax of a current block based on the probability information; and a step of updating the current probability information. Here, the method of determining the current probability information may vary depending on the location of the current block. A video encoding method according to the present disclosure may include a step of determining current probability information; a step of encoding a target syntax of a current block based on the probability information; and a step of updating the current probability information. Here, the method of determining the current probability information may vary depending on the location of the current block. In the image decoding / encoding method according to the present disclosure, if the current block is not the first block in the coding tree unit, the current probability information may be updated probability information of the last decoded / encoded previous block. In the image decoding / encoding method according to the present disclosure, when the current block is the first block in the coding tree unit, the current probability information can be determined by referring to a candidate block. In the image decoding / encoding method according to the present disclosure, the updated probability information of the candidate block can be determined as the current probability information. In the image decoding / encoding method according to the present disclosure, the current probability information can be derived by re-updating the updated probability information of the previous block based on the value of the target syntax of the candidate block. In the image decoding / encoding method according to the present disclosure, the candidate block may be an upper neighboring block or a left neighboring block adjacent to the current block. In the image decoding / encoding method according to the present disclosure, the candidate block may be a neighboring block referenced in deriving prediction information of the current block. In the video decoding / encoding method according to the present disclosure, the candidate block is one of a plurality of candidate blocks, and the candidate block may be selected from among the plurality of candidate blocks based on an index decoded from a bitstream. The features briefly summarized above regarding the present disclosure are merely exemplary aspects of the detailed description of the present disclosure that follows and do not limit the scope of the present disclosure. According to the present disclosure, there is an effect of reducing the capacity of a bitstream by efficiently determining probability information for syntax encoding / decoding. Specifically, according to the present disclosure, the capacity of a bitstream can be reduced by encoding / decoding the syntax of a current block using updated probability information of a candidate block instead of updated probability information of a block encoded / decoded before the current block. Specifically, according to the present disclosure, the capacity of a bitstream can be reduced by re-updating the updated probability information of a block previously encoded / decoded before the current block and encoding / decoding the syntax of the current block. The effects that can be obtained from the present disclosure are not limited to the effects mentioned above, and other effects that are not mentioned will be clearly understood by a person having ordinary skill in the art to which the present disclosure pertains from the description below. FIG. 1 is a block diagram illustrating an image encoding device according to an embodiment of the present disclosure. FIG. 2 is a block diagram showing an image decoding device according to an embodiment of the present disclosure. Figure 3 illustrates an example in which decryption is performed in empty units. Figure 4 shows a decryption method based on a general coding engine. Figure 5 shows the probability of MPS occurrence and the probability of LPS occurrence. Figure 6 shows an example in which the variable ivlCurrRange is updated identically to the variable ivlMpsRange. Figure 7 is a diagram illustrating the probability of MPS occurrence and the probability of LPS occurrence within a given range. Figure 8 is a diagram showing the update pattern of the variable ivlCurrRange. Figure 9 illustrates the order of encoding / decoding between blocks. Figure 10 is an example to explain multiple cases. FIG. 11 illustrates a method for encoding / decoding target syntax according to one embodiment of the present disclosure. The present disclosure may be modified in various ways and encompasses numerous embodiments. Specific embodiments are illustrated in the drawings and described in detail in the detailed description. However, this is not intended to limit the present disclosure to specific embodiments, but rather to encompass all modifications, equivalents, and alternatives falling within the spirit and technical scope of the present disclosure. Throughout the description of each drawing, similar reference numerals have been used to designate similar components. While terms such as "first" and "second" may be used to describe various components, these components should not be limited by these terms. These terms are used solely to distinguish one component from another. For example, without departing from the scope of the present disclosure, a first component could be referred to as a "second component," and similarly, a second component could also be referred to as a "first component." The term "and / or" includes a combination of multiple related items described herein or any of multiple related items described herein. When a component is referred to as being "connected" or "connected" to another component, it should be understood that it may be directly connected or connected to that other component, but that there may be other components intervening. Conversely, when a component is referred to as being "directly connected" or "connected" to another component, it should be understood that there are no other components intervening. The terminology used in this application is only used to describe specific embodiments and is not intended to limit the present disclosure. The singular expression includes the plural expression unless the context clearly indicates otherwise. In this application, it should be understood that the terms "comprise" or "have" indicate the presence of a feature, number, step, operation, component, part, or combination thereof described in the specification, but do not preclude the possibility of the presence or addition of one or more other features, numbers, steps, operations, components, parts, or combinations thereof. Hereinafter, preferred embodiments of the present disclosure will be described in more detail with reference to the attached drawings. Hereinafter, identical components in the drawings will be designated by the same reference numerals, and redundant descriptions of identical components will be omitted. FIG. 1 is a block diagram illustrating an image encoding device according to an embodiment of the present disclosure. Referring to FIG. 1, a video encoding device (100) may include a picture segmentation unit (110), a prediction unit (120, 125), a transformation unit (130), a quantization unit (135), a reordering unit (160), an entropy encoding unit (165), an inverse quantization unit (140), an inverse transformation unit (145), a filter unit (150), and a memory (155). Each component shown in Fig. 1 is independently depicted to represent different characteristic functions in the video encoding device, and does not mean that each component is composed of separate hardware or a single software component. That is, each component is listed and included as a separate component for convenience of explanation, and at least two components among each component may be combined to form a single component, or one component may be divided into multiple components to perform a function, and such integrated and separate embodiments of each component are also included in the scope of the present disclosure as long as they do not deviate from the essence of the present disclosure. Additionally, some components may not be essential components that perform the essential functions of the present disclosure, but may be optional components merely used to enhance performance. The present disclosure may be implemented by including only components essential to implementing the essence of the present disclosure, excluding components used solely for performance enhancement. A structure that includes only essential components, excluding optional components used solely for performance enhancement, is also within the scope of the present disclosure. The picture splitting unit (110) can split the input picture into at least one processing unit. At this time, the processing unit may be a prediction unit (PU), a transform unit (TU), or a coding unit (CU). The picture splitting unit (110) can split one picture into a combination of multiple coding units, prediction units, and transform units, and select one combination of coding units, prediction units, and transform units based on a predetermined criterion (e.g., a cost function) to encode the picture. For example, a picture can be split into multiple coding units. A recursive tree structure such as a quad tree, a ternary tree, or a binary tree can be used to split a coding unit in a picture. A coding unit that is split into other coding units starting from an image or the largest coding unit as the root can be split into as many child nodes as the number of split coding units. A coding unit that cannot be split any further according to a certain restriction becomes a leaf node. For example, assuming that a quad tree split is applied to a coding unit, a coding unit can be split into at most four different coding units. Hereinafter, in the embodiments of the present disclosure, the encoding unit may be used to mean a unit that performs encoding or may be used to mean a unit that performs decoding. A prediction unit may be divided into at least one square or rectangular shape of the same size within a single coding unit, or may be divided such that one prediction unit among the divided prediction units within a single coding unit has a different shape and / or size from another prediction unit. When predicting within a screen, the transformation unit and the prediction unit can be set to be the same. In this case, the encoding unit can be divided into multiple transformation units, and then intra-screen prediction can be performed for each transformation unit. The encoding unit can be divided in the horizontal direction or the vertical direction. The number of transformation units generated by dividing the encoding unit can be 2 or 4, depending on the size of the encoding unit. Alternatively, when the size of the transformation unit is small, multiple transformation units can be set as a single prediction unit. The prediction unit (120, 125) may include an inter-prediction unit (120) that performs inter-prediction and an intra-prediction unit (125) that performs intra-prediction. It may be determined whether to use inter-prediction or intra-prediction for an encoding unit, and specific information (e.g., reference sample line, intra-prediction mode, motion vector, reference picture, etc.) according to each prediction method may be determined. At this time, the processing unit where prediction is performed and the processing unit where the prediction method and specific contents are determined may be different. For example, the prediction method and prediction mode, etc. are determined in the encoding unit, and the prediction may be performed in the prediction unit or the transformation unit. The residual value (residual block) between the generated prediction block and the original block may be input to the transformation unit (130). In addition, the prediction mode information, motion vector information, etc. used for prediction may be encoded together with the residual value in the entropy encoding unit (165) and transmitted to the decoding device. When using a specific encoding mode, it is also possible to encode the original block as is and transmit it to the decoding unit without generating a prediction block through the prediction unit (120, 125). The inter-screen prediction unit (120) may predict a prediction unit based on information of at least one picture among the previous or subsequent pictures of the current picture, and in some cases, may predict a prediction unit based on information of a portion of an encoded region within the current picture. The inter-screen prediction unit (120) may include a reference picture interpolation unit, a motion prediction unit, and a motion compensation unit. The reference picture interpolation unit can receive reference picture information from the memory (155) and generate pixel information less than an integer pixel from the reference picture. In the case of luminance pixels, a DCT-based 8-tap interpolation filter with different filter coefficients can be used to generate pixel information less than an integer pixel in units of 1 / 4 pixels. In the case of a chrominance signal, a DCT-based 4-tap interpolation filter with different filter coefficients can be used to generate pixel information less than an integer pixel in units of 1 / 8 pixels. The motion prediction unit can perform motion prediction based on a reference picture interpolated by the reference picture interpolation unit. Various methods can be used to derive a motion vector, such as FBMA (Full search-based Block Matching Algorithm), TSS (Three Step Search), and NTS (New Three-Step Search Algorithm). The motion vector can have a motion vector value of 1 / 2 or 1 / 4 pixel unit based on the interpolated pixel. The motion prediction unit can predict the current prediction unit by using different motion prediction methods. Various methods can be used as motion prediction methods, such as the Skip method, the Merge method, the AMVP (Advanced Motion Vector Prediction) method, and the Intra Block Copy method. The on-screen prediction unit (125) can generate a prediction block based on reference pixel information, which is pixel information within the current picture. The reference pixel information can be derived from one selected from among a plurality of reference pixel lines. The Nth reference pixel line among the plurality of reference pixel lines can include left pixels having an x-axis difference of N from the upper left pixel within the current block and upper pixels having a y-axis difference of N from the upper left pixel. The number of reference pixel lines that the current block can select can be 1, 2, 3, or 4. If the neighboring blocks of the current prediction unit are blocks that have performed inter-screen prediction and the reference pixel is a pixel that has performed inter-screen prediction, the reference pixel included in the block that has performed inter-screen prediction can be replaced with the reference pixel information of the neighboring block that has performed intra-screen prediction. That is, if the reference pixel is unavailable, the unavailable reference pixel information can be replaced with information from at least one of the available reference pixels. In intra-screen prediction, the prediction mode can have a directional prediction mode that uses reference pixel information according to the prediction direction, and a non-directional mode that does not use directional information when performing prediction. The mode for predicting luminance information and the mode for predicting chrominance information can be different, and the intra-screen prediction mode information used to predict luminance information or the predicted luminance signal information can be utilized to predict chrominance information. When performing intra-screen prediction, if the size of the prediction unit and the size of the transformation unit are the same, intra-screen prediction for the prediction unit can be performed based on the pixels on the left side of the prediction unit, the pixels on the upper left side, and the pixels on the upper side. The on-screen prediction method can generate prediction blocks by applying a smoothing filter to reference pixels according to the prediction mode. Depending on the selected reference pixel line, whether or not the smoothing filter is applied can be determined. In order to perform an intra-screen prediction method, the intra-screen prediction mode of the current prediction unit can be predicted from the intra-screen prediction modes of prediction units existing around the current prediction unit. When the prediction mode of the current prediction unit is predicted using mode information predicted from the surrounding prediction units, if the intra-screen prediction modes of the current prediction unit and the surrounding prediction units are the same, information indicating that the prediction modes of the current prediction unit and the surrounding prediction units are the same can be transmitted using predetermined flag information, and if the prediction modes of the current prediction unit and the surrounding prediction units are different, entropy encoding can be performed to encode the prediction mode information of the current block. Additionally, a residual block containing residual value information, which is the difference between the prediction unit that performed the prediction based on the prediction unit generated in the prediction unit (120, 125) and the original block of the prediction unit, can be generated. The generated residual block can be input to the transformation unit (130). In the transformation unit (130), the residual block including the residual value information of the prediction unit generated through the original block and the prediction unit (120, 125) can be transformed using a transformation method such as DCT (Discrete Cosine Transform), DST (Discrete Sine Transform), or KLT. Whether to apply DCT, DST, or KLT to transform the residual block can be determined based on at least one of the size of the transformation unit, the shape of the transformation unit, the prediction mode of the prediction unit, or the prediction mode information within the screen of the prediction unit. Meanwhile, the transformation can be performed by separating the horizontal direction and the vertical direction. After performing transformations in the horizontal and vertical directions, a secondary transformation can be performed. The secondary transformation may be in a form in which the horizontal and vertical directions are not separated. The secondary transformation can be performed on the transformation coefficients obtained by the primary transformation to generate final transformation coefficients. Meanwhile, the number of final transformation coefficients output by the secondary transformation may be smaller than the number of transformation coefficients input for the secondary transformation. Specifically, the secondary transformation can be performed using a reduced transformation matrix having different numbers of columns and rows. The quantization unit (135) can quantize values ​​converted to the frequency domain by the transformation unit (130). The quantization coefficients can vary depending on the block or the importance of the image. The values ​​produced by the quantization unit (135) can be provided to the dequantization unit (140) and the reordering unit (160). The rearrangement unit (160) can perform rearrangement of coefficient values ​​for quantized residual values. The reordering unit (160) can change a two-dimensional block-shaped coefficient into a one-dimensional vector form through a coefficient scanning method. For example, the reordering unit (160) can change the two-dimensional block-shaped coefficient into a one-dimensional vector form by scanning from the DC coefficient to the coefficient of the high-frequency region using a zig-zag scan method. Depending on the size of the conversion unit and the intra-screen prediction mode, a vertical scan that scans the two-dimensional block-shaped coefficient in the column direction, a horizontal scan that scans the two-dimensional block-shaped coefficient in the row direction, or a diagonal scan that scans the two-dimensional block-shaped coefficient in the diagonal direction may be used instead of the zig-zag scan. That is, depending on the size of the conversion unit and the intra-screen prediction mode, it is possible to determine which scan method among the zig-zag scan, the vertical scan, the horizontal scan, or the diagonal scan is to be used. The entropy encoding unit (165) can perform entropy encoding based on the values ​​produced by the rearrangement unit (160). Entropy encoding can 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) can encode various information such as residual value coefficient information of the encoding unit, block type information, prediction mode information, division unit information, prediction unit information, transmission unit information, motion vector information, reference frame information, block interpolation information, and filtering information from the rearrangement unit (160) and the prediction unit (120, 125). The entropy encoding unit (165) can entropy encode the coefficient values ​​of the encoding unit input from the rearrangement unit (160). The inverse quantization unit (140) and the inverse transformation unit (145) inversely quantize the values ​​quantized in the quantization unit (135) and inversely transform the values ​​transformed in the transformation unit (130). The residual values ​​generated in the inverse quantization unit (140) and the inverse transformation unit (145) can be combined with the predicted prediction units predicted through the motion estimation unit, motion compensation unit, and intra-screen prediction unit included in the prediction unit (120, 125) to generate a reconstructed block. The filter unit (150) may include at least one of a deblocking filter, an offset correction unit, and an ALF (Adaptive Loop Filter). A deblocking filter can remove block distortion caused by boundaries between blocks in a reconstructed picture. To determine whether to perform deblocking, a deblocking filter can be applied to the current block based on the pixels contained in several columns or rows within the block. When applying a deblocking filter to a block, a strong filter or a weak filter can be applied depending on the required deblocking filtering strength. Furthermore, when applying a deblocking filter, horizontal and vertical filtering can be processed in parallel when performing vertical and horizontal filtering. The offset correction unit can correct the offset from the original image on a pixel-by-pixel basis for an image that has undergone deblocking. To perform offset correction for a specific picture, the pixels contained in the image can be divided into a certain number of regions, the regions to be offset can be determined, and the offset can be applied to those regions. Alternatively, the offset can be applied by considering the edge information of each pixel. Adaptive Loop Filtering (ALF) can be performed based on the comparison of the filtered restored image with the original image. After dividing the pixels included in the image into predetermined groups, a filter to be applied to each group can be determined, and filtering can be performed differentially for each group. Information regarding whether to apply ALF can be transmitted by luminance signal for each coding unit (CU), and the shape and filter coefficients of the ALF filter to be applied can vary depending on each block. Furthermore, an ALF filter of the same form (fixed form) can be applied regardless of the characteristics of the target block. The memory (155) can store a restoration block or picture produced through the filter unit (150), and the stored restoration block or picture can be provided to the prediction unit (120, 125) when performing inter-screen prediction. FIG. 2 is a block diagram showing an image decoding device according to an embodiment of the present disclosure. Referring to FIG. 2, the image decoding device (200) may include an entropy decoding unit (210), a rearrangement unit (215), an inverse quantization unit (220), an inverse transformation unit (225), a prediction unit (230, 235), a filter unit (240), and a memory (245). When a video bitstream is input to a video encoding device, the input bitstream can be decoded in the opposite procedure to that of the video encoding device. The entropy decoding unit (210) can perform entropy decoding in a procedure opposite to that of the entropy encoding unit of the video encoding device. For example, various methods such as Exponential Golomb, Context-Adaptive Variable Length Coding (CAVLC), and Context-Adaptive Binary Arithmetic Coding (CABAC) can be applied in response to the method performed in the video encoding device. The entropy decoding unit (210) can decode information related to intra-screen prediction and inter-screen prediction performed in the encoding device. The reordering unit (215) can perform reordering based on the method in which the bitstream entropy-decoded by the entropy decoding unit (210) is reordered by the encoding unit. The coefficients expressed in the form of a one-dimensional vector can be reordered by restoring them back to coefficients in the form of a two-dimensional block. The reordering unit (215) can perform reordering by receiving information related to the coefficient scanning performed by the encoding unit and performing reverse scanning based on the scanning order performed by the corresponding encoding unit. The dequantization unit (220) can perform dequantization based on the quantization parameters provided from the encoding device and the coefficient values ​​of the rearranged block. The inverse transform unit (225) can perform an inverse transform of the transform performed by the transform unit on the quantization result performed by the image encoding device. That is, at least one of an inverse transform of a secondary transform (secondary inverse transform) or an inverse transform for DCT, DST, and KLT (i.e., first inverse transform) can be performed. The inverse transform can be performed based on a transmission unit determined by the image encoding device. The inverse transform unit (225) of the image decoding device can determine a transform matrix for the second inverse transform or a transform technique (e.g., DCT, DST, KLT) for the first inverse transform according to a plurality of pieces of information such as a prediction method, the size and shape of the current block, the prediction mode, and the prediction direction within the screen. Alternatively, information for determining the transform matrix or the transform technique may be explicitly encoded and signaled. The prediction unit (230, 235) can generate a prediction block based on the prediction block generation related information provided by the entropy decoding unit (210) and the previously decoded block or picture information provided by the memory (245). As described above, when performing intra-screen prediction in the same manner as the operation in the video encoding device, if the size of the prediction unit and the size of the transformation unit are the same, intra-screen prediction for the prediction unit is performed based on the pixels on the left side of the prediction unit, the pixels on the upper left side, and the pixels on the upper side. However, when performing intra-screen prediction, if the size of the prediction unit and the size of the transformation unit are different, intra-screen prediction can be performed using reference pixels based on the transformation unit. In addition, intra-screen prediction using NxN division only for the minimum coding unit can be used. The prediction unit (230, 235) may include a prediction unit determination unit, an inter-screen prediction unit, and an intra-screen prediction unit. The prediction unit determination unit may receive various information such as prediction unit information input from the entropy decoding unit (210), prediction mode information of an intra-screen prediction method, and motion prediction-related information of an inter-screen prediction method, and may distinguish a prediction unit from a current encoding unit and determine whether the prediction unit performs inter-screen prediction or intra-screen prediction. The inter-screen prediction unit (230) may perform inter-screen prediction on the current prediction unit 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, using information necessary for inter-screen prediction of the current prediction unit provided from the video encoding device. Alternatively, inter-screen prediction may be performed based on information on a pre-restored portion of the current picture including the current prediction unit. In order to perform inter-screen prediction, it is possible to determine whether the motion prediction method of the prediction unit included in the encoding unit is Skip Mode, Merge Mode, AMVP Mode, or Intra-screen Block Copy Mode based on the encoding unit. The intra-screen prediction unit (235) can generate a prediction block based on pixel information within the current picture. If the prediction unit is a prediction unit that has performed intra-screen prediction, intra-screen prediction can be performed based on intra-screen prediction mode information of the prediction unit provided by the video encoding device. The intra-screen prediction unit (235) can include an AIS (Adaptive Intra Smoothing) filter, a reference pixel interpolation unit, and a DC filter. The AIS filter is a part that performs filtering on the reference pixels of the current block, and can determine and apply whether to apply the filter according to the prediction mode of the current prediction unit. AIS filtering can be performed on the reference pixels of the current block using the prediction mode and AIS filter information of the prediction unit provided by the video encoding device. If the prediction mode of the current block is a mode that does not perform AIS filtering, the AIS filter may not be applied. The reference pixel interpolation unit can generate a reference pixel of a pixel unit less than an integer value by interpolating the reference pixel when the prediction mode of the prediction unit is a prediction unit that performs intra-screen prediction based on the pixel value interpolated from the reference pixel. If the prediction mode of the current prediction unit is a prediction mode that generates a prediction block without interpolating the reference pixel, the reference pixel may not be interpolated. The DC filter can generate a prediction block through filtering when the prediction mode of the current block is the DC mode. The restored block or picture may be provided to a filter unit (240). The filter unit (240) may include a deblocking filter, an offset correction unit, and an ALF. Information regarding whether a deblocking filter has been applied to a corresponding block or picture may be received from a video encoding device, and if a deblocking filter has been applied, information regarding whether a strong or weak filter has been applied. The deblocking filter of the video decoding device may receive information related to the deblocking filter provided by the video encoding device, and the video decoding device may perform deblocking filtering on the corresponding block. The offset correction unit can perform offset correction on the restored image based on the type of offset correction applied to the image during encoding and offset value information. ALF can be applied to an encoding unit based on information such as whether ALF is applied and ALF coefficient information provided from an encoding device. This ALF information can be provided by being included in a specific parameter set. The memory (245) can store a restored picture or block so that it can be used as a reference picture or reference block, and can also provide the restored picture to an output unit. As described above, in the following embodiments of the present disclosure, for convenience of explanation, the term coding unit is used as an encoding unit, but it may also be a unit that performs not only encoding but also decoding. In addition, the current block represents a block to be encoded / decoded, and may represent a coding tree block (or coding tree unit), an encoding block (or encoding unit), a transform block (or transform unit), a prediction block (or prediction unit), or a block to which an in-loop filter is applied, depending on the encoding / decoding step. In this specification, a 'unit' represents a basic unit for performing a specific encoding / decoding process, and a 'block' may represent a pixel array of a predetermined size. Unless otherwise distinguished, 'block' and 'unit' may be used with the same meaning. For example, in the embodiment described below, an encoding block (coding block) and an encoding unit (coding unit) may be understood to have the same meaning. Furthermore, we will refer to the picture that contains the current block as the current picture. When generating a bitstream, the encoder may perform binarization based on CABAC (Context-based Arithmetic Binary Coding). At this time, encoding / decoding of the bitstream may be performed in bin units. Specifically, the encoder performs encoding in bin units to output bits, and the decoder receives bits and outputs bins through CABAC. Meanwhile, a set of bins can be named an empty string. For example, if the value of the syntax merge_idx is 4, the value of the syntax merge_idx can be binarized to 1110. In this case, 1 and 0 each represent a bin, and 1110 represents an empty string. That is, the syntax merge_idx with a value of 4 can be represented as an empty string composed of 4 bins. Each of the bins constituting the empty string can be identified by a bin index. Specifically, the indices can be sequentially assigned from the left to the right of the empty string. For example, if the empty string is 1110, the value of the bin assigned to index 0 can be 1, the value of the bin assigned to index 1 can be 1, the value of the bin assigned to index 2 can be 1, and the value of the bin assigned to index 3 can be 0. Meanwhile, encoding / decoding for bins can be performed based on a general coding engine or through a bypass coding engine. Figure 3 illustrates an example in which decryption is performed in empty units. As shown in the example, depending on the value of the variable bypassFlag, it can be determined whether the decoding of the bin is performed through the general coding engine or the bypass coding engine. Here, the general coding engine may indicate a coding method using contextual information, and the bypass coding engine may indicate a coding method that does not use contextual information. The variable bypassFlag is an internal variable defined in the encoder and decoder, which indicates whether the bin to be encoded / decoded is encoded through the bypass coding engine. Meanwhile, whether to use the bypass coding engine can be determined for each syntax element or each bin of the syntax element. For example, when encoding / decoding residual coefficients, the value of the variable bypassFlag can be determined based on whether the number of bins encoded through probability encoding reaches a threshold (e.g., CCB (Context Coded Bin)). Alternatively, the value of the variable bypassFlag can be determined depending on the type of the syntax element. Depending on the variable bypassFlag, the bin can be encoded / decoded using either a general coding engine or a bypass coding engine. Below, the bin encoding / decoding method will be described in detail. To encode / decode bins using CABAC, initialization of the probability and coding engines can be performed. The initial probability can be determined based on the slice type and / or the empty index. Accordingly, the initial probability value (initValue) can vary for each empty index. The initial probability value can be expressed in 6 bits. Once the initial probability value (initValue) is determined, two probability state indices can be derived using the initial probability value. Equations 1 to 7 illustrate the process of deriving the first probability state index pStateIdx0 and the second probability state index pStateIdx1 using the initial probability value initValue. The two probability state indices are values ​​that represent the probability that the value of the bin is 1 (i.e., the probability of 1 occurring). That is, the larger the value of the probability state indices, the greater the probability that the value of the bin is 1. The first probability state index and the second probability state index have different speeds at which probabilities are updated. For example, when bins with a value of 1 are continuously input, the first probability state index pStateIdx0 is updated to increase rapidly compared to the second probability state index pStateIdx1. In other words, the second probability state index pStateIdx1 is updated to increase relatively more gradually compared to the first probability state index pStateIdx0. Finally, the probability of occurrence of 1 is determined by taking the average of the first probability state index pStateIdx0 and the second probability state index pStateIdx1. Meanwhile, referring to mathematical expressions 6 and 7, there is a 4-bit length difference between the first probability state index pStateIdx0 and the second probability state index pStateIdx1. Accordingly, when calculating the average between the first probability state index pStateIdx0 and the second probability state index pStateIdx1, the precision of the two variables can be adjusted to the same extent. For example, after performing an operation of shifting the first probability state index pStateIdx0 to the left by 4, the average between the shifted first probability state index and the second probability state index pStateIdx1 can be obtained. The coding engine can operate based on the variables ivlCurrRange and ivlOffset. The ivlCurrRange variable can be initialized to a predefined value (e.g., 510). Conversely, the ivlOffset variable can be initialized based on information parsed from the bitstream (e.g., 9-bit information). Figure 4 shows a decryption method based on a general coding engine. To decrypt a single bin, a probability can be set. To this end, a variable pState representing a probability state can be derived. The variable pState can be derived by averaging the first probability state index pStateIdx0 and the second probability state index pStateIdx1. Furthermore, in order to adjust the precision of the two probability state indices to be the same, the first probability state index pStateIdx0 can be shifted to the left by 4, and then the variable pState can be derived. Meanwhile, the variable pState can be a positive integer represented by 15 bits. The value with the highest probability of occurrence between 0 and 1 can be set as the Most Probable Symbol (MPS), and the value with the lowest probability of occurrence can be set as the Least Probable Symbol (LPS). Since the value of a bin is either 0 or 1, the sum of the occurrence probability of 0 and the occurrence probability of 1 can be 1.0. Depending on the variable pState, it can be determined whether the value of MPS is 0 or 1. The variable valMps, which indicates whether MPS is 0 or 1, can be derived by the following mathematical expression 8. The variable pState is a positive integer represented by 15 bits. Accordingly, if the value of the variable pState is greater than 16383, valMps can be set to 1. This means that the probability of occurrence of 1 is higher than the probability of occurrence of 0. On the other hand, if the value of variable pState is less than or equal to 16383, variable valMps can be set to 0. This means that the probability of occurrence of 0 is higher than the probability of occurrence of 1. The variable ivlLpsRange represents the range of LPS. The variable ivlLpsRange can be derived by the following mathematical expressions 9 and 10. The range of MPS, ivlMpsRange, can be derived by differentiating the variable ivlLpsRange from the variable ivlCurrRange. As a result, the probability of occurrence of MPS within the ivlCurrRange range is P MPS and the probability of occurrence of LPS P LPS can be defined as in Fig. 13. In the example shown in Fig. 13, the occurrence probability of MPS and the occurrence probability of LPS can be defined as in mathematical expression 11. At this time, the sum of the occurrence probability of MPS and the occurrence probability of LPS can be 1 (i.e., 100%). For example, let's assume that MPS is 1 (i.e., the value of valMPS is 1) and the value of ivlCurrRange is 200. P MPS and P LPS If are 140 and 60 respectively, the probability of occurrence of 1 (i.e., MPS) may be 70%, and the probability of occurrence of 0 (i.e., LPS) may be 30%. Afterwards, the variable ivlOffset is derived from the bitstream, and the variable ivlCurrRange is updated. The variable ivlCurrRange can be updated to a value that is the difference between ivlLpsRange and ivlCurrRange, i.e., the same value as ivlMpsRange. Figure 6 shows an example in which the variable ivlCurrRange is updated identically to the variable ivlMpsRange. Then, compare the sizes of the variables ivlOffset and ivlCurrRange. If the variable ivlOffset is greater than or equal to the variable ivlCurrRange, then ivlOffset can be determined to be within the range of the LPS (i.e., ivlLpsRange). Otherwise, the variable ivlOffset can be determined to be within the range of the MPS (i.e., ivlMpsRange). Based on the above results, if the variable ivlOffset is determined to belong to the LPS interval, the value set to LPS can be output as the bin value (i.e., variable binVal). On the other hand, if ivlOffset belongs to the MPS interval, the value set to MPS can be output as the bin value (i.e., variable binVal). If the variable ivlOffset belongs to the MPS interval, the value of the variable ivlCurrRange remains the same. On the other hand, if the variable ivlOffset belongs to the LPS interval, the variable ivlCurrRange can be updated to the variable ivlLpsRange. Similarly, if the variable ivlOffset falls within the LPS interval, the value of the variable ivlOffset can also be updated. After the bin values ​​are determined, probability updates are performed. Specifically, the first probability state index pStateIdx0 and the second probability state index pStateIdx1, which indicate the probability of occurrence of 1, can be updated at different rates by the decrypted bin values ​​(i.e., binVal) and a variable that controls the update rate. Specifically, the first probability state index pStateIdx0 and the second probability state index pStateIdx1 can be updated at different rates by the first shifting variable shift0 and the second shifting variable shift1 that control the update rate. Meanwhile, the first shifting index shift0 and the second shifting variable shift1 can be derived as in the following mathematical expressions 12 and 13. Meanwhile, the variable shiftIdx may be predefined (i.e., a fixed value) in the encoder and decoder for each syntax element to be encoded / decoded. The first probability state index pStateIdx0 and the second probability state index pStateIdx1 can be updated as in the following mathematical expressions 14 and 15. After the probability update is performed, a renormalization process can be performed. Figure 7 is a flowchart showing the renormalization process. As in the example shown in Figure 7, the variable ivlCurrRange is compared with the predefined constant 256. If the variable ivlCurrRange is greater than or equal to 256, renormalization may not be performed. Otherwise, updates to the variables ivlCurrRange and ivlOffset may be performed. In Figure 7, read_bits(1) indicates that one bit is read from the bitstream and output. Figure 8 shows a decryption process based on a bypass coding engine. As in the example illustrated in Fig. 8, the value of the bin (i.e., binVal) can be determined by determining the values ​​of the variables ivlOffset and ivlCurrRange. If the value of the bin is 1, the variable ivlCurrRange can be updated with a value that is less than the variable ivlOffset. On the other hand, if the value of the bin is 0, the variable ivlCurrRange may not be updated. In the bypass coding engine, probability information is not utilized. That is, when the bypass coding engine is applied, the probability of occurrence of 0 or 1 is not defined, and the bin values ​​can be encoded / decoded. In other words, when the bypass coding engine is used, the probability of occurrence of 0 and the probability of occurrence of 1 can be set to the same value. When a bypass coding engine is used, the number of bins and the number of bits appear to be the same. Based on the above characteristics, the bypass coding engine is used for information for which probability settings are meaningless. Furthermore, the bypass coding engine's primary goal is to improve throughput, i.e., processing rate, rather than improving encoding / decoding efficiency through entropy coding. For each syntax element used by the general coding engine, the values ​​of the probability state indices (i.e., pStateIdx0 and pStateIdx1) and the shifting index (i.e., shiftIdx) can be derived. That is, for each syntax element to be encoded / decoded, the values ​​of the probability state indices and the shifting index can be derived. Meanwhile, whenever a bin constituting a syntax element is encoded / decoded, the probability state indices can be updated and stored. That is, whenever a bin is encoded / decoded, the first probability state index pStateIdx0 and the second probability state index pStateIdx1 are updated, and the variable pState can also be updated by the updated first probability state index pStateIdx0 and the second probability state index pStateIdx1. As the variable pState is updated, the value of the variable valMps is also updated (see Equation 8), and the variable ivlLpsRange can also be updated by the updated variable valMps (see Equation 10). Meanwhile, the variable ivlCurrRange may be shared across all syntax elements. That is, a single variable ivlCurrRange may be used regardless of the number of syntax elements being encoded / decoded. If the above-described method is followed, the update of variables can be performed according to the encoding / decoding order of the blocks. Figure 9 illustrates the order of encoding / decoding between blocks. In the example illustrated in Fig. 9, one picture is illustrated as being composed of four CTUs (i.e., CTU0 to CTU3), and each CTU is divided into multiple blocks (i.e., multiple CUs). When following a raster scan, the encoding / decoding order of each block may be in ascending order of the numbers written on each CU in Fig. 9. Meanwhile, in the embodiments described below, the syntax to be encoded / decoded is referred to as the target syntax. Furthermore, it is assumed that the target syntax is encoded / decoded by a general coding engine, and that the target syntax is a flag indicating the on / off of a specific technology. In general, not only flags, but also syntax elements encoded / decoded by a general coding engine can be set as the target syntax. Additionally, it is assumed that the probability and coding engines are initialized when a picture is first encoded / decoded. That is, the embodiments described below may relate to encoding / decoding the target syntax for each block. For example, the target syntax may be at least one of information for determining a prediction mode to be encoded / decoded at the block level, information for determining prediction information, information about a residual signal, or information about an in-loop filter. For example, embodiments proposed in the present disclosure may be applied to at least one of the syntax elements listed below. pred_mode_flag: Information indicating whether to apply intra-screen prediction mode or inter-screen prediction mode. pred_mode_ibc_flag: Information indicating whether to apply the block copy mode within the screen. pred_mode_plt_flag: Information indicating whether to apply palette mode. intra_bdpcm_flag: Information indicating whether BDPCM is applied. intra_mip_flag: Information indicating whether MIP is applied. intra_ref_idx: Information indicating the reference sample line, MPM_flag: Information indicating whether the on-screen prediction mode of the current block is derived from the MPM list. MPM_idx: Information indicating one of the multiple MPMs included in the MPM list. MPM_remainder: Information indicating the prediction mode within the screen of the current block among the remaining prediction modes within the screen excluding MPMs. merge_flag: Information indicating whether to apply the motion information merge mode. merge_idx: Information indicating one of the motion information merge candidates. mvp_flag: Information indicating one of the motion vector prediction candidates. regular_merge_flag: Information indicating whether to apply regular motion information merge mode. mmvd_merge_flag: Information indicating whether to apply MMVD (Merge mode with MVD). ciip_flag: Information indicating whether to apply CIIP (Combined Intra-Inter Predcition). merge_sublock_flag: Information indicating whether to apply sub-block unit merge mode. inter_affine_flag: Information indicating whether to apply the affine model. affine_type_flag: Information indicating the number of affine parameters. ref_idx: Information pointing to the index of the reference picture, amvr_flag: Information indicating whether AMVR (Adaptive Motion Vector Resolution) is applied. amvr_precision_idx: Information indicating one of the motion vector resolution candidates. bcw_idx: Information indicating one of the bidirectional prediction weight candidates. coded_block_flag: Information indicating whether residual coefficients exist. cu_sbt_flag: Information indicating whether to apply SBT (Sub-block Transform). lfnst_idx: Information indicating whether LFNST (Low Frequency Non-Separable Transform) is applied and the transformation matrix. mts_idx: Information indicating the conversion type, mvd_greaterN_flag: Information indicating whether the absolute value of the motion vector difference is greater than N (N is a natural number such as 1 or 2). mvd_sign_flag: Information indicating the sign of the motion vector difference value. transform_skip_flag: Information indicating whether to skip transformation / inverse transformation. Even for syntax elements not listed above, if they are encoded / decoded by a general coding engine, the encoding / decoding method according to the embodiments described below may be applied. For the first block, in order to encode / decode the target syntax, the initial values ​​of the first probability state index pStateIdx0 and the second probability state index pStateIdx1 for encode / decode the target syntax can be set. Thereafter, when encoding / decoding the target syntax of the first block, the variable pState for encoding / decoding the target syntax can be derived using the first probability state index pSateIdx0 and the second probability state index pStateIdx1. Using the variable pState, we can derive the variables valMps and ivlLpsRange, and using the variable ivlCurrRange, we can derive the variable binVal. Using the derived variable binVal, we can encode / decode the target syntax. After encoding / decoding the target syntax of the first block, the first probability state index pStateIdx0 and the second probability state index pStateIdx1 can be updated. For example, according to the examples of Equations 14 and 15, the first probability state index pStateIdx0 and the second probability state index pStateIdx1 can be updated. The target syntax for the second block, which is encoded / decoded after the first block, can be encoded / decoded. Meanwhile, the first probability state index pStateIdx0 and the second probability state index pStateIdx1, which are updated after encoding / decoding the target syntax of the first block, can be used to encoding / decoding the target syntax of the second block. After the target syntax of the second block is encoded / decoded, the first probability state index pStateIdx0 and the second probability state index pStateIdx1 can be updated. The updated first probability state index pStateIdx0 and the updated second probability state index pStateIdx1 can be used to encoded / decoded the target syntax for the third block, which is encoded / decoded after the second block. That is, the target syntax of the Nth block can be encoded / decoded based on the first probability state index pStateIdx0 and the second probability state index pStateIdx1, which are updated after the target syntax of the previous block is encoded / decoded. Here, the previous block can mean the (N-1)th block or the block whose target syntax was last encoded / decoded before the current block. As described above, the probability information for encoding / decoding the target syntax can be sequentially updated according to the decoding order of the blocks. Here, the probability information can include at least one of a first probability state index and a second probability state index. Meanwhile, after defining multiple cases, probability information can be individually managed or stored for each case. Then, based on the probability information for the case corresponding to the current block, the target syntax for the current block can be encoded / decoded. Furthermore, after encoding / decoding the target syntax, probability information can be updated only for the case corresponding to the current block. Here, multiple cases can be defined by considering at least one adjacent block adjacent to the current block. Figure 10 is an example to explain multiple cases. Multiple cases can be classified by considering whether the values ​​of the target syntax of each of the adjacent blocks (i.e., the upper reference block and the left reference block) adjacent to the current block are the same. For example, the first case represents a case where the target syntax of each of the top reference block and the left reference block both has a value of true (i.e., 1). For example, the second case represents a case where the target syntax of one of the top reference block and the left reference block has a value of true, while the target syntax of the other has a value of false (i.e., 0). For example, the third case represents a case where the target syntax of each of the upper reference block and the left reference block both has a false value. Probability information can be managed individually for each case. When trying to encode / decode the target syntax for the current block, you can use the probability information for the case that the current block corresponds to. For example, if the target syntax of the upper neighboring block of the current block is true, while the target syntax of the left neighboring block of the current block is false, the target syntax of the current block can be encoded / decoded using the probability information in the second case. Additionally, after encrypting / decrypting the target syntax of the current block, the probability information can be updated only for the cases that the current block corresponds to. For example, if the current block belongs to the second case, the probability information may be updated only for the second case, and the probability information may not be updated for the first and third cases. Meanwhile, the variable shiftIdx can be set differently for each case. Depending on the type of syntax element to be encoded / decoded or the location of the empty space within the syntax element, it may be determined whether to use probability information from a corresponding case among multiple cases or to use single probability information not based on case classification. Meanwhile, instead of using probability information updated according to the decoding order of blocks, syntax elements can also be encoded / decoded by referring to updated probability information at a predefined position encoded / decoded before the current block. For example, when trying to encode / decode the target syntax for the first block (i.e., the current block) in a coding tree unit, instead of referring to the updated probability information of the last block (i.e., the previous block in the decoding order) in the previous coding tree unit, the target syntax of the current block can be encode / decoded by referring to the updated probability information of the block at a predefined position. Here, the block at the predefined location may be a neighboring block adjacent to the current block. For example, in the example illustrated in FIG. 9, when trying to encode / decode the target syntax for block 27, the updated probability information of block 13 adjacent to the top of block 27 or block 21 adjacent to the left of block 27 can be referenced. Alternatively, one of a plurality of candidate blocks corresponding to a plurality of predefined locations may be selected, and updated probability information of the selected candidate block may be referenced. For example, probability information for the target syntax of each of a plurality of candidate blocks can be inserted into a probability information candidate list as probability information candidates. Then, among the plurality of probability information candidates included in the probability information candidate list, a probability information candidate used to encode / decode the target syntax of the current block can be selected. Based on the selected probability information candidate, the target syntax of the current block can be encode / decode. Meanwhile, information indicating one of multiple probability information candidates or multiple candidate blocks may be encoded and signaled. The information may be an index indicating one of the multiple probability information candidates or multiple candidate blocks. The number of probability information candidates that the probability information candidate list can include may be 1, 2, 3, or 4. In addition, the candidate blocks may include at least one of the upper neighboring block, the left neighboring block, or the upper-left neighboring block. Meanwhile, when the number of candidate blocks (or probability information candidates) is 1, the encoding / decoding of information (i.e., the index) indicating one of the multiple candidate blocks may be omitted. For example, if the number of probability information candidates is 2, the probability information candidate list for block 27 may include updated probability information of block 13 adjacent to the top of block 27 and updated probability information of block 21 adjacent to the left of block 27. A block that is not adjacent to the current block can also be set as a candidate block. Meanwhile, if the probability information is updated according to the decryption order, it is sufficient to store only the probability information of the last block to be decrypted / decrypted. For example, when the target syntax of block 27 is decoded / encoded with reference to the probability information of block 26, which is a block decoded / encoded before block 27, the target syntax of block 27 is decoded / encoded with reference to the updated probability information of block 26. After decoding / encoding the target syntax of block 27, the probability information is updated, and the updated probability information can be used to decode / encode the target syntax of the next block, that is, block 28. That is, the probability information of block 26 is used only to decode / encode the target syntax of block 27, and is not used to decode / encode the target syntax of subsequent blocks. Accordingly, probability information updated for each block can be stored using buffers pStateIdx0[idx] and pStateIdx1[idx]. Here, idx represents the index of the block. In Fig. 9, assuming that the number written in each block is the index of the block, idx can have a value from 1 to 37. For example, pStateIdx0

[0026] and pStateIdx1

[0026] represent the updated first probability state index and the updated second probability state index of block 26, respectively. That is, the probability information of the last encoded / decoded block may be stored in the buffers pStateIdx0[idx] and pStateIdx1[idx]. On the other hand, if you want to refer to the probability information of a candidate block at a predefined location, the probability information of the candidate block at the predefined location must be stored. For example, when encrypting / decrypting the target flag of block 27, if one of the upper neighboring block (i.e., block 13) and the left neighboring block (i.e., block 21) is selected, if one is used, the probability information of the upper neighboring block (i.e., pStateIdx1

[0013] and pStateIdx1

[0013] ) and the probability information of the left neighboring block (i.e., pStateIdx1

[0021] and pStateIdx1

[0021] ) must be stored. To do this, you can set it to store updated probability information for each block. That is, buffers pStateIdx0[idx] and pStateIdx1[idx] can be set for each block, and the updated probability information of the block can be stored in the buffer corresponding to the block. Meanwhile, when updating probability information for the current block, the probability information of the candidate block referenced by the current block can be utilized. For example, when decoding / encrypting the target syntax of block 27, if the probability information of the upper neighboring block (i.e., block 13) is referenced, then after decoding / encrypting the target syntax of block 27, the probability information can be updated using the probability information of block 13. That is, mathematical expressions 14 and 15 can be changed to the following mathematical expressions 16 and 17. In the above mathematical expressions 16 and 17, N represents the index of the current block, and M represents the index of the candidate block referenced by the current block. Meanwhile, if updated probability information is set to be stored for each block, a problem occurs in which the buffer size increases. To solve this problem, the updated probability information of the block previously encrypted / decrypted before the current block can be updated based on the candidate block, and the target syntax for the current block can be encrypted / decrypted based on the updated probability information. For example, when attempting to encode / decode the target syntax for block 27, the updated probability information of block 26, which was encode / decoded before block 27, can be set as the initial probability information. Thereafter, the initial probability information can be updated by referring to the value of the target syntax of the candidate block. For example, if block 27 is set to reference block 13, the initial probability information can be updated based on the value of the target syntax of block 13. Thereafter, the target syntax of block 27 can be encoded / decoded using the updated probability information. Meanwhile, the updating can be performed using Equations 14 and 15 or Equations 16 and 17. Alternatively, each time the subcoding / decoding of a coding tree unit begins, the updated probability information of the last subcoding / decoding block may be re-updated using the neighboring blocks that touch the upper boundary of the coding tree unit. For example, when trying to encode / decode block 27, which is the first block in the coding tree unit, the updated probability information of block 26 can be re-updated using the neighboring blocks, block 16, block 15, block 14, and block 13, which are adjacent to the upper boundary of the coding tree unit to which block 27 belongs. At this time, the updated probability information of block 26 can be sequentially updated by referencing the neighboring blocks adjacent to the upper boundary of the coding tree unit in order from left to right (i.e., block 13, block 14, block 15, and block 16) or in order from right to left (i.e., block 16, block 15, block 14, and block 13). For example, the updated probability information of block 26 can be updated based on the value of the target syntax of block 16, and the updated result can be re-updated based on the value of the target syntax of block 15. In addition, the result updated by block 15 can be re-updated based on the value of the target syntax of block 14, and the result updated by block 14 can be re-updated based on the value of the target syntax of block 13. Based on the probability information obtained through the above repeated update process, the target syntax of block 27 can be encoded / decoded. Meanwhile, the initial probability information can be updated by selecting one of multiple candidate blocks. Alternatively, the initial probability information can be updated using a block at a predefined location. Alternatively, the initial probability information can be updated by sequentially referencing multiple candidate blocks. For example, the updated probability information of block 26 can be set as the initial probability information, and the initial probability information can be updated by referencing the target syntax of the first candidate block. The updated initial probability information is referred to as the intermediate probability information. Thereafter, the intermediate probability information can be updated by referencing the target syntax of the second candidate block. Thereafter, the target syntax of block 27 can be encoded / decoded using the final probability information (i.e., the updated intermediate probability information). For example, one of the first candidate block and the second candidate block may be the upper neighboring block of block 27 (i.e., block 13), and the other may be the left neighboring block of block 27 (i.e., block 21). Meanwhile, prediction information for the current block can be derived by referring to neighboring blocks adjacent to the current block. For example, when intra-screen prediction is applied to the current block, it can be determined whether the intra-screen prediction mode of the current block is encoded / decoded based on the intra-screen prediction mode of a neighboring block. If the intra-screen prediction mode of the current block is the same as the intra-screen prediction mode of one of the plurality of neighboring blocks, information indicating one of the plurality of neighboring blocks can be encoded and signaled. For example, an index (e.g., MPM_idx) indicating one of the plurality of neighboring blocks can be encoded and signaled. Meanwhile, when encoding / decoding the target syntax for the current block, updated probability information for neighboring blocks with the same on-screen prediction mode as the current block can be referenced. In other words, the target syntax for the current block can be encoded / decoded by referencing the updated probability information for the neighboring block indicated by the index. Meanwhile, the target syntax may be encoded / decoded later than the syntax being encoded / decoded for in-screen prediction or the syntax indicating one of multiple neighboring blocks. For example, the target syntax may be information about the residual signal or information about the in-loop filter. In contrast to the above, if there is no neighboring block having the same intra-screen prediction mode as the intra-screen prediction mode of the current block, or if the intra-screen prediction mode of the current block is encoded / decoded without reference to the neighboring block, probability information may be used according to a predefined method. Here, the predefined method may refer to one of the above-described embodiments, such as a method of using updated probability information of the block encoded / decoded most recently in the encoding / decoding order, a method of using updated probability information of a block at a predefined position, a method of using updated probability information of one of a plurality of candidate blocks, or a method of re-updating updated probability information of the block encoded / decoded most recently. Alternatively, when inter-screen prediction is performed on the current block, it may be determined whether the motion information of the current block is encoded / decoded based on the intra-screen prediction mode of a neighboring block. If the motion information of the current block is encoded / decoded based on the motion information of one of the plurality of neighboring blocks, information indicating one of the plurality of neighboring blocks may be encoded and signaled. For example, an index indicating one of the plurality of neighboring blocks may be encoded and signaled. For example, when the motion information merge mode is applied, a merge index (e.g., merge_idx) indicating one of the plurality of motion information merge candidates may be encoded and signaled. Alternatively, when the motion vector prediction mode is applied, an index (e.g., mvp_flag) indicating one of the plurality of motion vector prediction candidates may be encoded and signaled. Meanwhile, when decoding / encoding the target syntax for the current block, the updated probability information of the referenced neighboring block can be referenced to derive the motion information of the current block. In other words, the target syntax of the current block can be decoded / encoded by referencing the updated probability information of the neighboring block indicated by the index. Meanwhile, the target syntax may be encoded / decoded later than the syntax being encoded / decoded for inter-screen prediction or the syntax indicating one of multiple neighboring blocks. For example, the target syntax may be information about a motion vector difference, information about a residual signal, or information about an in-loop filter. Unlike the above, if the motion information of the current block is encoded / decoded without reference to neighboring blocks, the probability information can be used according to a predefined method. Here, the predefined method may refer to one of the above-described embodiments, such as a method of using the updated probability information of the block that was encoded / decoded most recently in the encoding / decoding order, a method of using the updated probability information of a block at a predefined location, a method of using the updated probability information of one of a plurality of candidate blocks, or a method of re-updating the updated probability information of the block that was encoded / decoded most recently. Meanwhile, among the multiple probability information determination methods described above, the method that uses the updated probability information of a block that was decoded / encoded before the current block in the order of encoding / decoding to encode / decode the target syntax of the current block is called a conventional method, and the other probability information determination methods are called improved methods. At this time, depending on the location of the current block, a method for deriving probability information for encoding / decoding the target syntax for the current block can be adaptively determined. Here, the location of the current block can refer to the location of the current block within the current picture, slice, tile, or coding tree unit. For example, if the current block is the first block in a coding tree unit, if the current block is adjacent to the upper boundary of the coding tree unit, or if the current block is adjacent to the left boundary of the coding tree unit, the target syntax of the current block can be encoded / decoded using probability information determined based on the improved method. On the other hand, if the above conditions are not met, the target syntax of the current block can be encoded / decoded using probability information determined based on traditional methods. Meanwhile, among the above-described embodiments, re-update can be performed for both the first probability state index pStateIdx0 and the second probability state index pStateIdx1. Alternatively, re-updating may be performed only for one of the first probability state index pStateIdx0 and the second probability state index pStateIdx1. That is, the first probability state index pStateIdx0 (or the second probability state index pStateIdx1) of the block that was sub-encrypted / decrypted before the current block may not be re-updated, but the updated second probability state index pStateIdx1 (or the first probability state index pStateIdx0) of the block that was sub-encrypted / decrypted before the current block may be re-updated. FIG. 11 illustrates a method for encoding / decoding target syntax according to one embodiment of the present disclosure. To encode / decode the target syntax of the current block, probability information can be determined (S1110). The probability information can be determined based on a traditional or improved method. Once the probability information is determined, the target syntax of the current block can be encoded / decoded based on the probability information (S1120). After the target syntax of the current block is encoded / decoded, the probability information can be updated again based on the empty value (binVal) of the target syntax (S1130). Applying the embodiments described above, focusing on the decoding or encoding process, to the encoding or decoding process is within the scope of the present disclosure. Changing the embodiments described above, in a given order, to a different order is also within the scope of the present disclosure. Although the above-described disclosure is described based on a series of steps or a flowchart, this does not limit the chronological order of the invention, and may be performed simultaneously or in a different order as needed. In addition, each component (e.g., unit, module, etc.) constituting the block diagram in the above-described disclosure may be implemented as a hardware device or software, or multiple components may be combined to be implemented as a single hardware device or software. For example, the hardware device may include at least one of a processor for performing calculations, a memory for storing data, a transmitter for transmitting data, and a receiver for receiving data. The above-described disclosure may be implemented in the form of program commands that can be executed by various computer components and recorded on a computer-readable recording medium. The computer-readable recording medium may include program commands, data files, data structures, etc., either singly or in combination. In addition, according to the present disclosure, a computer-readable recording medium can be provided that stores a bitstream generated by the above-described encoding method. The bitstream can be transmitted by an encoding device, and a decoding device can receive the bitstream and decode an image. 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, magneto-optical media such as floptical disks, and hardware devices specifically configured to store and execute program instructions, such as ROMs, RAMs, and flash memories. The hardware devices may be configured to operate as one or more software modules to perform processing according to the present disclosure, and vice versa. The present disclosure may be applied to a computing or electronic device capable of encoding / decoding a video signal.

Claims

1. Step of determining current probability information; A step of decoding the target syntax of the current block based on the above probability information; and Including a step of updating the above current probability information, An image decoding method, characterized in that the method for determining the current probability information is different depending on the location of the current block.

2. In paragraph 1, A video decoding method, characterized in that, if the current block is not the first block in the coding tree unit, the current probability information is updated probability information of the last decoded previous block.

3. In paragraph 2, A video decoding method, characterized in that, when the current block is the first block in the coding tree unit, the current probability information is determined by referring to a candidate block.

4. In paragraph 3, An image decoding method, characterized in that the updated probability information of the candidate block is determined by the current probability information.

5. In paragraph 3, An image decoding method, characterized in that the current probability information is derived by re-updating the updated probability information of the previous block based on the value of the target syntax of the candidate block.

6. In paragraph 3, An image decoding method, characterized in that the candidate block is an upper neighboring block or a left neighboring block adjacent to the current block.

7. In paragraph 3, An image decoding method, characterized in that the candidate block is a neighboring block referenced in deriving prediction information of the current block.

8. In paragraph 3, The above candidate block is one of a plurality of candidate blocks, A video decoding method, characterized in that a candidate block is selected from among the plurality of candidate blocks based on an index decoded from a bitstream.

9. Step of determining current probability information; A step of encoding the target syntax of the current block based on the above probability information; and Including a step of updating the above current probability information, An image encoding method, characterized in that the method of determining the current probability information is different depending on the location of the current block.

10. In paragraph 9, A video encoding method, characterized in that, if the current block is not the first block in the coding tree unit, the current probability information is updated probability information of the last encoded previous block.

11. In paragraph 10, A video encoding method, characterized in that, when the current block is the first block in the coding tree unit, the current probability information is determined by referring to a candidate block.

12. In paragraph 11, An image encoding method, characterized in that the updated probability information of the candidate block is determined by the current probability information.

13. In paragraph 11, A video encoding method, characterized in that the current probability information is derived by re-updating the updated probability information of the previous block based on the value of the target syntax of the candidate block.

14. In paragraph 11, A video encoding method, characterized in that the candidate block is an upper neighboring block or a left neighboring block adjacent to the current block.

15. Step for determining current probability information; A step of encoding the target syntax of the current block based on the above probability information; and Including a step of updating the above current probability information, A computer-readable recording medium recording a bitstream generated by an image encoding method, characterized in that a method of determining the current probability information is different depending on the location of the current block.

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