Image encoding / decoding method and apparatus for transmitting compressed video data

Abstract

An image decoding method according to the present disclosure may comprise the steps of: determining a reference picture; and determining block split information of the current block in the current picture by referring to a reference block in the reference picture.

Description

Video encoding / decoding method and device for transmitting compressed video data

[0001] The present disclosure relates to a video signal processing method and device.

[0002] 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.

[0003] 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.

[0004] 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.

[0005] The present disclosure aims to provide a method for encoding / decoding block division information of a block using information stored in a decoded reference picture, and a device therefor.

[0006] The present disclosure aims to provide a method and a device therefor for setting block segmentation information of a current block included in a current picture to be identical to a reference block included in a reference picture.

[0007] The present disclosure aims to provide a method and a device therefor for encoding / decoding a prediction flag indicating whether block division information is identical to a prediction value instead of encoding / decoding block division information for a current block.

[0008] 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.

[0009] A video decoding method according to the present disclosure may include a step of determining a reference picture; and a step of determining block segmentation information of a current block in a current picture by referring to a reference block in the reference picture.

[0010] In the image decoding method according to the present disclosure, it can be determined whether the block division information of the current block is set to be identical to the block division information of the reference block, depending on the similarity flag for the current block.

[0011] In the video decoding method according to the present disclosure, when the similarity flag indicates that the block division information of the reference block is merged with the current block, the block division information of the current block is determined to be identical to the block division information of the reference block, and when the similarity flag indicates that the block division information of the reference block is not merged with the current block, the block division information of the current block can be explicitly decoded.

[0012] In the image decoding method according to the present disclosure, the similarity flag may be decoded in units of a merge determination area, and the merge determination area may be configured to include at least one coding tree block.

[0013] In the image decoding method according to the present disclosure, the similarity flag is decoded in block units, and the similarity flag can be decoded for the current block only when the reference block is divided into a plurality of blocks.

[0014] In the video decoding method according to the present disclosure, the block division information of the current block is determined based on at least one prediction flag for the block division information decoded from a bitstream, the prediction flag indicating whether the block division information of the current block is identical to a prediction value, and the prediction value may be block division information of the reference block.

[0015] In the video decoding method according to the present disclosure, the block division information includes a block division flag indicating whether a block is divided and a QT (QuadTree) flag indicating whether a QT (QuadTree) is divided, and the prediction flag may include a first prediction flag for the block division flag and a second prediction flag for the QT flag.

[0016] In the video decoding method according to the present disclosure, when the first prediction flag for the block division flag is true and the value of the block division flag is determined to be true, the second prediction flag for the QT flag can be additionally decoded.

[0017] In the video decoding method according to the present disclosure, when the first prediction flag for the block division flag is false and the value of the block division flag is determined to be true, the QT flag can be decoded instead of the second prediction flag.

[0018] In the video decoding method according to the present disclosure, reference picture information for determining a reference picture among a plurality of reference pictures can be explicitly decoded.

[0019] In the image decoding method according to the present disclosure, the reference picture may be a collocated picture.

[0020] In the image decoding method according to the present disclosure, the reference block can be referenced only when the segmentation depth of the current block is less than a threshold value.

[0021] In the image decoding method according to the present disclosure, whether the reference block is referencable is determined based on a result of comparing a difference value between the segmentation depth of the current block and the segmentation depth information of a reference region within the reference picture with a threshold value, and the segmentation depth information may include at least one of a minimum segmentation depth, a maximum segmentation depth, or a depth average value of the reference region.

[0022] A video encoding method according to the present disclosure may include a step of determining a reference picture; and a step of determining block segmentation information of a current block in a current picture by referring to a reference block in the reference picture.

[0023] According to the present disclosure, a computer-readable recording medium having recorded thereon a command for storing / transmitting a bitstream generated by an image encoding method can be provided.

[0024] According to the present disclosure, a computer-readable recording medium having recorded thereon a command for performing an image decoding method or an image encoding method can be provided.

[0025] 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.

[0026] According to the present disclosure, there is an effect of reducing the amount of data to be encoded / decoded by determining block division information of a block using information stored in a previously decoded reference picture.

[0027] According to the present disclosure, there is an effect of reducing the amount of data to be encoded / decoded by setting the block division information of the current block included in the current picture to be the same as the reference block included in the reference picture.

[0028] According to the present disclosure, instead of encoding / decoding block division information for the current block, there is an effect of reducing the amount of data to be encoded / decoded by encoding / decoding a prediction flag indicating whether the block division information is identical to a prediction value.

[0029] 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.

[0030] FIG. 1 is a block diagram illustrating an image encoding device according to an embodiment of the present disclosure.

[0031] FIG. 2 is a block diagram showing an image decoding device according to an embodiment of the present disclosure.

[0032] Figure 3 illustrates an example in which decryption is performed in empty units.

[0033] Figure 4 shows a decryption method based on a general coding engine.

[0034] Figure 5 shows an example in which the variable ivlCurrRange is updated identically to the variable ivlMpsRange.

[0035] Figure 6 is a flowchart showing the renormalization process.

[0036] Figure 7 shows a decryption process based on a bypass coding engine.

[0037] Figure 8 is a schematic diagram of a typical video signal.

[0038] Figures 9 to 12 illustrate a block division method according to the present disclosure.

[0039] Figure 13 is a diagram for explaining an example in which block division information for determining the block division structure of a block is encoded / decoded.

[0040] Figure 14 shows an example where QT_flag is encoded / decoded before split_flag.

[0041] FIG. 15 illustrates an example of determining a block division structure of a block according to one embodiment of the present disclosure.

[0042] Figure 16 illustrates reference areas for each of multiple merge judgment areas within the current picture.

[0043] Figure 17 shows an example in which the block division structure of the merge judgment area is set to be the same as that of the reference area.

[0044] Figure 18 illustrates an example in which whether or not to merge block division information is determined on a block-by-block basis within a merge judgment area.

[0045] Figure 19 shows an example in which encoding / decoding of the similarity flag is omitted.

[0046] Figure 20 shows an example in which prediction flags are encoded / decoded.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] 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.

[0051] 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.

[0052] FIG. 1 is a block diagram illustrating an image encoding device according to an embodiment of the present disclosure.

[0053] 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).

[0054] 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.

[0055] 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.

[0056] 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.

[0057] 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.

[0058] 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.

[0059] 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.

[0060] 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.

[0061] 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).

[0062] 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.

[0063] 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.

[0064] 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 in units of 1 / 2 or 1 / 4 pixels 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.

[0065] 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.

[0066] 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.

[0067] 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.

[0068] 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.

[0069] 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.

[0070] 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.

[0071] 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).

[0072] 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.

[0073] 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.

[0074] 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).

[0075] The rearrangement unit (160) can perform rearrangement of coefficient values ​​for quantized residual values.

[0076] 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.

[0077] 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).

[0078] 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).

[0079] The entropy encoding unit (165) can entropy encode the coefficient values ​​of the encoding unit input from the rearrangement unit (160).

[0080] 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.

[0081] The filter unit (150) may include at least one of a deblocking filter, an offset correction unit, and an ALF (Adaptive Loop Filter).

[0082] 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.

[0083] 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.

[0084] 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.

[0085] 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.

[0086] FIG. 2 is a block diagram showing an image decoding device according to an embodiment of the present disclosure.

[0087] 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).

[0088] 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.

[0089] 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.

[0090] The entropy decoding unit (210) can decode information related to intra-screen prediction and inter-screen prediction performed in the encoding device.

[0091] 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.

[0092] 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.

[0093] 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.

[0094] The prediction unit (230, 235) can generate a prediction block based on prediction block generation related information provided from the entropy decoding unit (210) and previously decoded block or picture information provided from the memory (245).

[0095] 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.

[0096] 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.

[0097] 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.

[0098] 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.

[0099] 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.

[0100] 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.

[0101] 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.

[0102] 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.

[0103] 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.

[0104] 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.

[0105] 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.

[0106] 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.

[0107] Additionally, the encoding parameters for the current block may be commonly applied to multiple color components for the current block. For example, if the encoding mode of the current block is determined, prediction for the Y component block, the Cb component block, and the Cr component block may be performed based on the encoding mode.

[0108] Alternatively, depending on the color component to be encoded / decoded, the current block may mean a Y component block, a Cb component block, or a Cr component block.

[0109] Furthermore, we will refer to the picture that contains the current block as the current picture.

[0110] When generating a bitstream, the encoder can binarize the syntaxes. Binarization of the syntaxes can be based on CABAC (Context-based Arithmetic Binary Coding). At this time, encoding / decoding of the bitstream can be performed in units of bins. Specifically, the encoder performs encoding in units of bins to output bits, and the decoder receives bits and outputs bins through CABAC.

[0111] 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.

[0112] 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.

[0113] Meanwhile, encoding / decoding for bins can be performed based on a general coding engine or through a bypass coding engine.

[0114] Figure 3 illustrates an example in which decryption is performed in empty units.

[0115] 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.

[0116] 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.

[0117] 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.

[0118] 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.

[0119] To encode / decode bins using CABAC, initialization of the probability and coding engines can be performed.

[0120] 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.

[0121] 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.

[0122]

[0123]

[0124]

[0125]

[0126]

[0127]

[0128]

[0129] The two probability state indices are values ​​that represent the probability that the value of the bin is 1 (i.e., the probability of occurrence of 1). That is, the larger the value of the probability state indices, the greater the probability that the value of the bin is 1.

[0130] 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.

[0131] 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.

[0132] 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).

[0133] Figure 4 shows a decryption method based on a general coding engine.

[0134] 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 the same level, 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.

[0135] 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.

[0136] 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.

[0137]

[0138] 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.

[0139] 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.

[0140] The variable ivlLpsRange represents the range of LPS. The variable ivlLpsRange can be derived by the following mathematical expressions 9 and 10.

[0141]

[0142]

[0143] The range of MPS, ivlMpsRange, can be derived by differentiating the variable ivlLpsRange from the variable ivlCurrRange.

[0144] 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 mathematical expression 11.

[0145]

[0146] 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%.

[0147] 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.

[0148] Figure 5 shows an example in which the variable ivlCurrRange is updated identically to the variable ivlMpsRange.

[0149] Then, compare the sizes of the variables ivlOffset and ivlCurrRange.

[0150] 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).

[0151] 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).

[0152] 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.

[0153] Similarly, if the variable ivlOffset falls within the LPS interval, the value of the variable ivlOffset can also be updated.

[0154] 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.

[0155] 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.

[0156] Meanwhile, the first shifting index shift0 and the second shifting variable shift1 can be derived as in the following mathematical expressions 12 and 13.

[0157]

[0158]

[0159] 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.

[0160] 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.

[0161]

[0162]

[0163] After the probability update is performed, a renormalization process can be performed.

[0164] Figure 6 is a flowchart showing the renormalization process.

[0165] As in the example shown in Figure 6, 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.

[0166] Otherwise, updates to the variables ivlCurrRange and ivlOffset may be performed. In Figure 6, read_bits(1) indicates that one bit is read from the bitstream and output.

[0167] Figure 7 shows a decryption process based on a bypass coding engine.

[0168] As in the example illustrated in Fig. 7, 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.

[0169] 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.

[0170] When a bypass coding engine is used, the number of bins and the number of bits appear to be the same.

[0171] 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.

[0172] Figure 8 is a schematic diagram of a typical video signal.

[0173] As in the example shown in Figure 8, a video can be defined as a set of Group of Pictures (GOPs).

[0174] A GOP can be set as a random access unit. Alternatively, intra-picture insertion within a GOP can prevent restoration errors within the GOP from propagating to the next GOP.

[0175] A GOP can represent a set of pictures.

[0176] A single picture can be divided into multiple regions. For example, a single picture can be divided into multiple sub-pictures, multiple slices, or multiple tiles.

[0177] The subpicture structure can be useful for viewport-based 360-degree VR video streaming. When a single picture is divided into multiple subpictures, the bitstream can be extracted and merged on a subpicture basis. Accordingly, the decoder can decode only the bitstreams of the subpictures required for rendering. A subpicture can be configured to include one or more slices.

[0178] If a picture is divided into multiple slides, data can be encapsulated into packets and signaled on a slice-by-slice basis.

[0179] When a single picture is divided into multiple tiles, encoding / decoding can be performed in parallel between the tiles.

[0180] In an encoder, the current picture can be divided into multiple reference blocks. Here, the reference blocks may be called Coding Tree Units (CTUs) or Coding Tree Blocks (CTBs). A CTU or CTB may be a coding block with the largest size.

[0181] Each of the above-described subpictures, slices and tiles may be a set of reference blocks.

[0182] Meanwhile, the size of the reference block may be predefined in the encoder and decoder. Alternatively, information related to the size of the reference block may be encoded and signaled to the decoder. The information may be encoded / decoded via an upper header. For example, the information may be encoded / decoded via a sequence parameter set or a picture header.

[0183] The reference block may be further divided into multiple blocks (i.e., multiple coding blocks) based on a tree structure partitioning. Here, the tree structure partitioning may include at least one of a quad tree partitioning, a binary tree partitioning, or a ternary tree partitioning.

[0184] As the reference block is divided, when the block to be encoded / decoded (i.e., the leaf node block) is finally determined, the encoder can encode the samples within the block through processes such as prediction, transformation, quantization, and entropy encoding. In addition, the decoder can reconstruct the samples within the block through processes such as entropy decoding, inverse quantization, inverse transformation, and prediction.

[0185] Figures 9 to 11 illustrate a block division method according to the present disclosure.

[0186] In the embodiments described below, a 'block' may represent any one of a coding block, a prediction block, or a transformation block as a target of encoding / decoding.

[0187] A single block can be divided into multiple blocks of various sizes and shapes through a tree structure. These divided blocks can then be further divided into multiple blocks of various sizes and shapes. This recursive division of a block can be defined as "tree-structure-based" division.

[0188] The above tree structure-based segmentation can be performed based on predetermined segmentation information. Here, the segmentation information may be encoded by an encoding device and transmitted through a bitstream, or may be derived from an encoding / decoding device. The segmentation information may include information indicating whether a block is to be segmented (hereinafter referred to as a segmentation flag). If the segmentation flag indicates segmentation of a block, the block is segmented and the encoding order is followed by moving to the next block. Here, the next block refers to the block to be encoded first among the segmented blocks. If the segmentation flag indicates that the block is not to be segmented, after encoding the encoding information of the block, the segmentation process is terminated or moving to the next block depending on whether a next block exists.

[0189] Partition information may include information about tree partitioning. Below, the tree partitioning method used for block partitioning is described.

[0190] The BT (Binary Tree) partitioning method divides a block into two. The blocks created through this partitioning can have the same size. Figure 9 illustrates an example of BT partitioning a block using the BT flag.

[0191] The BT flag can be used to determine whether a block should be split. For example, if the BT flag is 0, BT splitting is terminated. On the other hand, if the BT flag is 1, the block can be split into two blocks using the Dir flag, which indicates the splitting direction.

[0192] Additionally, the segmented blocks can be expressed as depth information. Figure 10 shows an example of depth information.

[0193] FIG. 10 (a) is an example showing the process of dividing a block (400) through BT segmentation and the value of depth information (depth). Each time a block is segmented, the value of depth information can increase by 1. When a block of depth N is segmented into blocks of depth (N+1), the block of depth N is called the parent block of the blocks of depth (N+1). Conversely, the block of depth (N+1) is called the child block of the block of depth N. This can be applied equally to the tree structure described below. FIG. 10 (b) shows the final segmented shape when the block (400) is segmented as in (a) using BT.

[0194] The TT (Ternary-tree) partitioning method divides a block into three parts. The child blocks can have a ratio of 1:2:1. Figure 11 illustrates an example of TT partitioning a block using the TT flag.

[0195] The TT flag can be used to determine whether a block is to be split. For example, if the TT flag is 0, TT splitting is terminated. On the other hand, if the TT flag is 1, the block can be split into three horizontally or vertically using the Dir flag.

[0196] The QT (quad-tree) partitioning method divides a block into four blocks. The four child blocks can have the same size. Figure 12 illustrates an example of QT partitioning a block using the QT flag.

[0197] The QT flag can be used to determine whether a block is to be split. For example, if the QT flag is 0, QT splitting is terminated. On the other hand, if the QT flag is 1, the block can be split into four parts.

[0198] Figure 13 is a diagram for explaining an example in which block division information for determining the block division structure of a block is encoded / decoded.

[0199] Referring to FIG. 13, the block splitting information may include at least one of information indicating whether a block is split (e.g., split_flag), information indicating whether a block is QT split (e.g., QT_flag), information indicating a splitting direction of a block (e.g., DIR_flag), or information indicating whether a block is BT / TT split (e.g., BT_flag). In the embodiment described below, the block splitting information may refer to one of the above-listed information, two or more of the above-listed information, or all of the above-listed information. Whether the block splitting information indicates a single information element or multiple information elements will be clearly understood by those skilled in the art depending on the context.

[0200] The syntax split_flag indicates whether a block is split. For example, a value of 0 for the syntax split_flag indicates that the block is not split. Conversely, a value of 1 for the syntax split_flag indicates that the block is split.

[0201] If the value of the syntax split_flag is 1, the QT_flag indicating whether QT splitting is performed can be additionally encoded / decoded. For example, if the syntax QT_flag is 1, it indicates that QT splitting is performed. If QT splitting is performed, each block generated by QT splitting can be recursively split. That is, split_flag can be encoded / decoded for each block generated by QT splitting.

[0202] A syntax QT_flag of 0 indicates that QT segmentation is not performed. In this case, the DIR_flag indicating the direction of BT or TT segmentation may be further encoded / decoded. For example, a syntax DIR_flag of 1 indicates that the block is segmented horizontally, and a syntax DIR_flag of 0 indicates that the block is segmented vertically.

[0203] Afterwards, BT_flag can be additionally encoded / decoded. Syntax BT_flag can indicate whether the block is BT split or TT split. For example, syntax BT_flag being 1 indicates that BT splitting is applied to the block. Syntax BT_flag being 0 indicates that TT splitting is applied to the block. Each of the blocks generated by BT or TT splitting can be recursively split. That is, split_flag can be encoded / decoded for each of the blocks generated by BT splitting or TT splitting.

[0204] In Fig. 13, the encoding / decoding order of block splitting information is described as being split_flag, QT_flag, DIR_flag, and BT_flag. Unlike what is shown in Fig. 13, QT_flag may be encoded / decoded before split_flag.

[0205] Figure 14 shows an example where QT_flag is encoded / decoded before split_flag.

[0206] A syntax QT_flag of 1 indicates that QT splitting is applied to the block. If syntax QT_flag is 0, syntax split_flag may be additionally encoded / decoded. The syntax split_flag may indicate whether BT or TT splitting is applied to the block.

[0207] For example, if the syntax split_flag is 1, the DIR_flag and BT_flag may be additionally encoded / decoded to apply BT or TT splitting to the block. On the other hand, if the syntax split_flag is 0, the block may not be split any further.

[0208] Information indicating in which order the block division information is encoded / decoded among FIGS. 13 and 14 may be encoded and signaled. The information may be encoded and signaled in units of reference blocks.

[0209] Meanwhile, the probability information buffers (i.e., pStateIdx0 and pStateIdx1) for the encoding / decoding method according to Fig. 13 and the encoding / decoding method according to Fig. 14 may exist separately. For example, different probability information buffers may be used when split_flag is encoded / decoded according to the method of Fig. 13 and when split_flag is encoded / decoded according to the method of Fig. 14.

[0210] That is, even if the syntax is the same, different probability information buffers may be used depending on the encoding / decoding order of the block division information.

[0211] In the above example, it is assumed that the block division structure is determined based on the block division information for the block. However, if the division structure of the blocks in the current picture is similar to the division structure of the blocks in the reference picture, the amount of data to be encoded / decoded can be reduced by referring to the block division structure / block division information of the reference picture.

[0212] Accordingly, the present disclosure proposes a method for determining a block division structure / block division information of a block belonging to a current picture by referring to a block division structure / block division information stored in a reference picture.

[0213] FIG. 15 illustrates an example of determining a block division structure of a block according to one embodiment of the present disclosure.

[0214] Referring to FIG. 15, a reference picture to be referenced to determine the block division structure / block division information of a block can be determined (S1510).

[0215] Information indicating which of a plurality of reference pictures has been referenced may be encoded and signaled. The information may include at least one of information indicating the direction to which the reference picture belongs (i.e., the L0 direction, the L1 direction, or an index indicating one of the plurality of reference pictures).

[0216] Alternatively, reference pictures can be selected according to predefined rules. For example, the first reference picture in a list of reference pictures can be fixedly selected.

[0217] Alternatively, a collocated picture may be selected as a reference picture. Meanwhile, information indicating a collocated picture among multiple reference pictures may be encoded and signaled.

[0218] When a reference picture is determined, it is possible to determine whether to determine the block division structure / block division information of the current block in the current picture by referring to the block division structure / block division information of the reference block in the reference picture (S1520).

[0219] If it is determined that the current block refers to a reference block, the block division structure / block division information of the current block can be determined by referring to the block division structure / block division information of the reference block (S1530).

[0220] According to one embodiment of the present disclosure, when it is determined to refer to a reference block, a similarity flag may be encoded / decoded, and depending on the similarity flag, it may be determined whether to set the block division structure / block division information of the current block to be the same as the block division structure / block division information of the reference block.

[0221] Alternatively, according to one embodiment of the present disclosure, the block division information prediction flag of the current block can be encoded / decoded by referring to the block division structure / block division information of the reference block.

[0222] If it is determined that the current block does not refer to a reference block, block splitting information for the current block can be explicitly encoded / decoded (S1540). Here, the block splitting information can include at least one of split_flag indicating whether the block is split, QT_flag indicating whether QT splitting is performed, DIR_flag indicating the splitting direction, or BT_flag indicating whether BT / TT splitting is performed.

[0223] Hereinafter, a method for determining a block division structure / block division information of a current block according to the present disclosure will be described in detail.

[0224] Example 1) Merging of block division structure / block division information

[0225] When dividing a block, the current picture can be divided into multiple merge judgment regions, and then a reference region can be set for each divided region. The reference region may be included in a reference picture whose encoding / decoding was completed prior to the current picture.

[0226] For example, an area having the same location and size as the current merge judgment area within the reference picture can be set as the reference area of ​​the current merge judgment area.

[0227] If the textures between the current region and the reference region are similar, the block division information for the current merge determination region can be encoded / decoded by referring to the block division information of the reference region.

[0228] Figure 16 illustrates reference areas for each of multiple merge judgment areas within the current picture.

[0229] In the example illustrated in FIG. 16, one merge judgment region is illustrated as including two reference blocks. Unlike the illustrated example, one merge judgment region may be composed of one reference block or may include more than two reference blocks.

[0230] The reference region is defined as an area of ​​the same size that exists at the same location as the current merge decision region within the reference picture. The size of each merge decision region within the current picture can be expressed as the number of reference blocks. For example, the horizontal length of the merge decision region can be expressed as the number of reference block columns included in the region, and the vertical length of the merge decision region can be expressed as the number of reference block rows included in the region.

[0231] The size of the merge judgment area may be predefined in the encoder and decoder.

[0232] Alternatively, information related to the configuration of the merge decision area may be encoded and signaled via an upper header. The information related to the configuration of the merge decision area may include at least one of the number of reference blocks included in the merge decision area, the width of the merge decision area, or the height of the merge decision area.

[0233] Alternatively, each of the encoder and decoder can determine the configuration of the merge judgment area according to preset rules.

[0234] Alternatively, the merge decision area may be determined based on the segmentation structure of the current picture. For example, if the current picture is segmented into multiple areas for parallel processing, each area may be set as a merge decision area. Here, the area for parallel processing may be a tile, slice, or sub-picture. In other words, a single merge decision area may be a tile, slice, or sub-picture.

[0235] As another example, the size of the merge judgment region can be set to a size smaller than that of the reference block. For example, if the reference block is QT-segmented, each block generated by the QT segmentation can be set as a merge judgment region.

[0236] For convenience of explanation, in the embodiments described below, it is assumed that each of the merge judgment areas includes one reference block. That is, in the embodiments described below, the merge judgment area may represent a reference block.

[0237] Information indicating which of multiple reference pictures is referenced may be encoded and signaled. The information may be encoded and signaled for each merge decision area within the current picture. In other words, the reference pictures referenced for each merge decision area may be different.

[0238] As another example, a reference region may be set for only one of the multiple reference pictures available in the current picture. That is, all merge decision regions may be set to reference the same reference picture. In this case, information indicating one of the multiple reference pictures may be encoded and signaled through the picture header.

[0239] As another example, information indicating reference pictures can be encoded and signaled on a slice, tile, or subpicture basis.

[0240] Alternatively, reference pictures can be selected according to predefined rules. For example, the first reference picture in a list of reference pictures can be fixedly selected.

[0241] Alternatively, a collocated picture may be selected as a reference picture. Meanwhile, information indicating a collocated picture among multiple reference pictures may be encoded and signaled.

[0242] Information indicating the similarity between the merge decision region within the current picture and the reference region within the reference picture can be encoded and signaled. The information indicating the similarity can be a 1-bit flag. The flag can be referred to as a similarity flag or a merge flag.

[0243] For example, the Sum of Absolute Difference (SAD) between the merge decision region in the current picture and the reference region in the reference picture is calculated, and the calculated SAD is compared with a threshold value. If the SAD is less than the threshold value, the merge decision region in the current picture and the reference region in the reference picture are determined to be similar to each other, and the information is encoded as 1 (True). On the other hand, if the SAD is greater than or equal to the threshold value, the merge decision region in the current picture and the reference region in the reference picture are determined to be dissimilar to each other, and the information is encoded as 0 (False).

[0244] Meanwhile, a value of the similarity flag of 1 may be defined as indicating that the merge judgment region and the reference region are mutually dissimilar, and a value of the similarity flag of 0 may be defined as indicating that the merge judgment region and the reference region are mutually similar.

[0245] As another example, after determining a block division structure for a merge decision region within the current picture, a similarity flag value may be set based on whether the determined block division structure is identical to / similar to the block division structure of a reference region within a reference picture. In other words, the similarity flag may indicate whether the block division structure / block division information for the merge decision region is merged with the reference region.

[0246] Similarity flags can be encoded and signaled per merge decision region unit.

[0247] If the merge decision area within the current picture and the reference area within the reference picture are similar, i.e., if the value of the similarity flag is 1, the block division information of the merge decision area can be merged with the block division information of the reference area. That is, the division structure of the merge decision area can be set to be the same as the block division structure of the reference area.

[0248] Figure 17 shows an example in which the block division structure of the merge judgment area is set to be the same as that of the reference area.

[0249] In the example illustrated in Fig. 17, if the similarity flag for the merge decision area A in the current picture indicates that it is similar to the reference area a in the reference picture, the segmentation structure of the merge decision area A can be set to be the same as the segmentation structure of the reference area a.

[0250] Accordingly, for blocks belonging to the merge decision area A, explicit encoding / decoding of block splitting information, such as split_flag, QT_flag, DIR_flag, and BT_flag, may be omitted. That is, the block splitting information of blocks belonging to the merge decision area A may be implicitly determined to be the same as that of the reference area.

[0251] On the other hand, if the similarity flag for the merge decision area A in the current picture indicates that it is not similar to the reference area a in the reference picture, block segmentation information can be explicitly encoded / decoded for blocks belonging to the merge decision area A.

[0252] If the similarity flag indicates that the merge decision region and the reference region are similar to each other, only the block division information / block division structure of the reference region up to a certain level of division depth may be applied to the merge decision region. Here, the division depth level to be merged may be predefined in the encoder and decoder. Alternatively, information indicating the division depth level to be merged may be explicitly encoded and signaled.

[0253] For example, if it is decided to merge block division information / block division structure up to the kth division depth, block division information / block division structure up to the kth division depth within the reference area may be applied to the merge decision area. For a block having the kth division depth within the merge decision area, block division information may be explicitly encoded and signaled, and based on the block division information, it may be determined whether to further divide the block having the kth division depth.

[0254] Here, the k-th split depth may indicate the split depth according to the QT split. Alternatively, the k-th split depth may indicate the sum of the split depth according to the QT split and the split depth according to the MTT split. The MTT split represents the BT split and the TT split.

[0255] As another example, only the QT division structure / QT division information among the block division structures of the reference area may be applied to the merge decision area. That is, the QT division structure of the merge decision area is set identically to the QT division structure of the reference area, while the BT / TT division structure of the merge decision area can be set independently from the BT / TT division structure of the reference area.

[0256] In the above example, it is exemplified that the block division structure / block division information is merged by unit of the merge determination area. As another example, a similarity flag indicating whether the block division structure / block division information of a block within the merge determination area is set identically to a reference block belonging to the reference area may be encoded and signaled.

[0257] Meanwhile, the block-level similarity flag can be encoded and signaled when the similarity flag for the merge decision region indicates that the merge decision region and the reference region are similar to each other.

[0258] Figure 18 illustrates an example in which whether or not to merge block division information is determined on a block-by-block basis within a merge judgment area.

[0259] In the example illustrated in FIG. 18, a similarity flag indicating whether the block division structure / block division information of the current block B is identical to that of the reference block b may be encoded / decoded. If the flag indicates that the block division structure / block division information of the current block B is identical to that of the reference block b, the block division structure of the current block B is set to be identical to that of the reference block b, and encoding / decoding of the block division information may be omitted for the current block B.

[0260] On the other hand, if the similarity flag indicates that the block partition structure / block partition information of the current block B is not identical to that of the reference block b, the block partition information for the current block B may be explicitly encoded and signaled.

[0261] Meanwhile, if the reference area or reference block is not split, encoding / decoding of the similarity flag can be omitted.

[0262] Figure 19 shows an example in which encoding / decoding of the similarity flag is omitted.

[0263] In the example illustrated in Fig. 19, the reference block b, which is in the same position as the current block B, is shown as not being split. Accordingly, the similarity flag may not be encoded / decoded for the current block B.

[0264] That is, as in the example illustrated in Fig. 18, if the reference block b has a structure divided into multiple blocks, the similarity flag can be encoded / decoded for the current block B. On the other hand, as in the example illustrated in Fig. 19, if the reference block b is a leaf node block, the similarity flag can not be encoded / decoded for the current block B.

[0265] If encoding / decoding of the similarity flag is omitted, its value can be inferred as 0 (False). That is, if the reference block is not split, the block split structure / block split information of the current block may not be merged with the reference block. In this case, whether the current block B is split or not can be determined based on the block split information that is explicitly encoded / decoded, for example, split_flag.

[0266] Alternatively, the split depth of the reference block may be compared with that of the current block to determine whether to encode / decode the similarity flag for the current block. For example, the similarity flag may be encoded / decoded for the current block only if the split depth of the reference block is the same as that of the current block.

[0267] In the above example, after encoding / decoding the similarity flag for the merge decision area, it is illustrated that the similarity flag is additionally encoded / decoded for the block belonging to the merge decision area.

[0268] As another example, similarity flags may be encoded / decoded on a block-by-block basis without setting a merge decision region or encoding / decoding similarity flags for the merge decision region. In this case, whether to encode / decode a similarity flag for the current block may be determined based on at least one of whether a reference block within a reference picture is split or the split depth of the reference block.

[0269] Meanwhile, merging of block division structure / block division information may be performed only for the current division depth of the current block.

[0270] As an example, referring to FIG. 18, a reference block b in a reference picture is divided by QT division, and then vertical TT division, vertical BT division, horizontal BT division, and QT division are applied to each of the four sub-blocks generated by QT division.

[0271] At this time, if the similarity flag of the current block B is true, only the QT partition structure of the reference block b can be applied to the current block B. That is, the block partition structure / block partition information of the sub-blocks belonging to the reference block b may not be immediately merged into the current block B.

[0272] Afterwards, the similarity flag can be encoded / decoded again for each of the four sub-blocks generated by QT-splitting the current block. That is, the similarity flag can be encoded / decoded recursively.

[0273] Meanwhile, the similarity flag may be encoded / decoded only when the similarity flag of the parent node block of the current block is true. That is, if the similarity flag of the parent node block of the current block indicates that the block division structure / block division information is not identical to that of the reference block, the similarity flag may not be encoded / decoded for the current block.

[0274] Example 2) Encoding / decoding prediction flags of block segmentation information

[0275] After setting the block division structure / block division information of the reference area of ​​the current block as a predicted value, information indicating whether the block division structure / block division information of the current block matches the predicted value can be encoded / decoded. The above information can be a 1-bit flag, and the flag can be called a "prediction flag."

[0276] That is, instead of directly encoding / decoding block division information for the current block, a prediction flag for the block division information can be encoded / decoded.

[0277] For convenience of explanation, it is assumed that a prediction flag of 1 (True) indicates that the block division structure / block division information of the current block is identical to the predicted value, and a prediction flag of 0 (False) indicates that the block division structure / block division information of the current block is not identical to the predicted value. However, it is also possible that the value of the prediction flag is set in the opposite direction.

[0278] Figure 20 shows an example in which prediction flags are encoded / decoded.

[0279] For convenience of explanation, we assume that the current block will be partitioned by QT partitioning. We also assume that a reference block of the same size as the current block has been partitioned by QT partitioning.

[0280] In the past, split_flag was used to determine whether the current block was split. In contrast, in the present disclosure, instead of directly encoding / decoding split_flag, information indicating whether the split_flag of the current block matches the predicted value can be encoded / decoded.

[0281] That is, after checking whether a reference block of the same size as the current block has been split, whether the reference block has been split can be set as a predicted value for the split_flag of the current block. In the example illustrated in Fig. 20, since a reference block of the same size as the current block has been split, the predicted value for the split_flag of the current block can be set to 1.

[0282] Afterwards, a prediction flag indicating whether the splitting of the current block is identical to the predicted value can be encoded / decoded. In Fig. 20, since it is assumed that the current block is split, the prediction flag for the split_flag of the current block is set to 1 (True) and can be encoded / decoded.

[0283] If the splitting status of the current block is not the same as the predicted value, the predicted flag for split_flag of the current block is set to 0 (False) so that it can be encoded / decoded.

[0284] If the prediction flag for the syntax split_flag is 1, and accordingly, the value of the syntax split_flag is determined to be 1, the prediction flag for the QT_flag of the current block can be encoded / decoded.

[0285] In Fig. 20, since a reference block of the same size as the current block has QT segmentation applied, the predicted value for QT_flag of the current block can be set to 1.

[0286] Afterwards, the prediction flag for QT_flag, which indicates whether the QT segmentation applied to the current block is the same as the predicted value, can be encoded / decoded. In Fig. 20, since it is assumed that QT segmentation is applied to the current block, the prediction flag for QT_flag of the current block is set to 1 (True) and can be encoded / decoded.

[0287] If the application of QT division to the current block is not the same as the predicted value, the predicted flag for QT_flag is set to 0 (False) so that encoding / decoding can be performed.

[0288] Meanwhile, if the current block is QT-split, there is no need to encode / decode information for BT / TT splitting (e.g., DIR_flag indicating the splitting direction and BT_flag indicating whether BT / TT splitting is performed). Accordingly, if the current block is QT-split, the prediction flag for DIR_flag and the prediction flag for BT_flag indicating whether BT / TT splitting is performed are also not encoded / decoded.

[0289] On the other hand, if QT splitting is not applied to the current block, the splitting direction of the reference block can be set to the predicted value for DIR_flag, and the predicted flag for DIR_flag can be encoded / decoded. In addition, whether the reference block is BT / TT split can be set to the predicted value for BT_flag, and the predicted flag for BT_flag can be encoded / decoded.

[0290] Assuming that the block split structure of the current block is determined by referring to the block split information in the order of split_flag, QT_flag, DIR_flag, and BT_flag, as in the example illustrated in Fig. 13, the prediction flag for the current syntax can be encoded / decoded only when the value of the prediction flag for the previous syntax is 1 (True). If the value of the prediction flag for the previous syntax is not 1, the current syntax can be encoded / decoded instead of the prediction flag for the current syntax.

[0291] For example, if the value of the prediction flag for the syntax split_flag is 1, and the value of the syntax split_flag is determined to be 1, the prediction flag for the syntax QT_flag can be encoded / decoded instead of the syntax QT_flag. On the other hand, if the value of the prediction flag for the syntax split_flag is 0, the prediction flag for the QT_flag may not be encoded / decoded. On the other hand, even if the value of the prediction flag for the syntax split_flag is 0, if the value of the syntax split_flag is determined to be 1, QT_flag, DIR_flag and / or BT_flag must be additionally encoded / decoded to determine the block division structure of the current block. At this time, if the value of the prediction flag for the syntax split_flag was 0, instead of encoding / decoding the prediction flag of the syntax QT_flag, the syntax QT_flag itself can be encoded / decoded.

[0292] Similarly, if the value of the prediction flag for syntax QT_flag is 1 and the value of syntax QT_flag is determined to be 0, the prediction flag for syntax DIR_flag can be encoded / decoded instead of syntax DIR_flag. On the other hand, if the value of the prediction flag for syntax split_flag is 0 and the value of QT_flag is determined to be 0, the syntax DIR_flag itself can be encoded / decoded instead of the prediction flag for syntax DIR_flag.

[0293] Meanwhile, whether syntax BT_flag is encoded / decoded depends only on syntax QT_flag, not on syntax DIR_flag. Accordingly, regardless of how the value of syntax DIR _flag is determined, it is possible to determine whether to encode / decode the prediction flag for syntax BT_flag based on whether the prediction flag for syntax DIR_flag is 1 (True). For example, if the prediction flag for syntax DIR_flag is 1, the prediction flag for syntax BT_flag can be encoded / decoded instead of syntax BT_flag. On the other hand, if the prediction flag for syntax DIR_flag is 0, syntax BT_flag itself can be encoded / decoded instead of the prediction flag for syntax BT_flag.

[0294] Alternatively, instead of the prediction flag for DIR_flag, it may be determined whether to encode / decode the prediction flag for syntax BT_flag based on the value of the prediction flag for QT_flag and the value of QT_flag. For example, if the value of the prediction flag for syntax QT_flag is 1 and the value of syntax QT_flag is determined to be 0, the prediction flag for syntax BT_flag may be encoded / decoded instead of syntax BT_flag. On the other hand, if the value of the prediction flag for syntax split_flag is 0 and the value of QT_flag is determined to be 0, the syntax BT_flag itself may be encoded / decoded instead of the prediction flag for syntax BT_flag.

[0295] Alternatively, as in the example illustrated in FIG. 14, if QT_flag is encoded / decoded before split_flag, the prediction flag for QT_flag can be referenced to determine whether to encode / decode the prediction flag for split_flag.

[0296] Similarly, by referring to the prediction flag for split_flag, it can be determined whether to encode / decode the prediction flag for DIR_flag and / or BT_flag.

[0297] When encoding / decoding prediction flags, a buffer for storing accumulated probability information can be set. At this time, the buffer for the prediction flags can exist separately from the buffer for the block segmentation information. That is, pStateIdx0 and pStateIdx1 for the prediction flags can exist separately.

[0298] For example, when encoding split_flag, QT_flag, DIR_flag, and BT_flag using a general coding engine, the initial probability state is defined by initValue defined in Equations 1 and 2. In addition, the probability state can be updated every time the syntax is encoded / decoded.

[0299] Meanwhile, the prediction flag may be encoded / decoded using a probability state buffer that is different (i.e., separate) from the probability state buffers used by the block split information, split_flag, QT_flag, DIR_flag, and BT_flag. That is, the probability state buffer for the prediction flag may have its initial probability state defined by a separate initValue. In addition, the probability state of the corresponding probability state buffer may be updated only when encoding / decoding the prediction flag, and may not be updated when encoding / decoding the block split information (i.e., at least one of split_flag, QT_flag, DIR_flag, and BT_flag).

[0300] Instead of encoding / decoding the block segmentation information as is, a flag indicating whether to encode / decode the prediction flag for the block segmentation information can be encoded and signaled.

[0301] The above flag can be encoded / decoded in units of coding blocks or coding tree blocks.

[0302] Meanwhile, a flag indicating whether encoding / decoding of prediction flags for block segmentation information is permitted may be encoded / decoded through the upper header. For example, the flag may be encoded / decoded on a tile, slice, subpicture, picture, or sequence basis.

[0303] Alternatively, it may be determined whether to encode / decode the prediction flag of the block partition information based on the partition depth of the current block. For example, if the partition depth of the current block is less than a threshold, the prediction flag of the block partition information may be encoded / decoded instead of encoding / decoding the block partition information as is. Conversely, if the partition depth of the current block is equal to or greater than the threshold, the block partition information may be encoded / decoded as is.

[0304] Alternatively, based on the block division structure of the parent node block, it may be determined whether to encode / decode the prediction flag of the block division information. For example, if the current block is generated by QT division, the prediction flag of the block division information may be encoded / decoded instead of encoding / decoding the block division information as is. On the other hand, if the current block is generated by BT division or TT division, the block division information may be encoded / decoded as is.

[0305] Alternatively, depending on the size of the current block, it may be determined whether to encode / decode the prediction flag of the block segmentation information. For example, if the size of the current block is greater than a threshold, the prediction flag of the block segmentation information may be encoded / decoded instead of encoding / decoding the block segmentation information as is. Conversely, if the size of the current block is equal to or less than the threshold, the block segmentation information may be encoded / decoded as is.

[0306] As described through Embodiments 1) and 2), in order to refer to the block division structure / block division information of a reference region or reference block within a reference picture, the block division information of the reference picture must also be stored together. At this time, the block division structure / block division information for all blocks within the reference picture may be stored.

[0307] Alternatively, considering the buffer size, only block division structures / block division information that satisfy predefined conditions within the reference picture may be stored.

[0308] For example, only the block division structure / block division information up to a certain level of division depth within the reference picture may be stored. For example, only the block division structure / block division information of blocks with a division depth of 1 or less may be stored, and the block division structure / block division information of blocks with a division depth greater than 1 may not be stored.

[0309] If the segmentation depth of the current block within the current picture is less than or equal to a specific level of segmentation depth, the block segmentation structure / block segmentation information of the current block can be determined by referring to the block segmentation structure / block segmentation information of the reference block within the reference picture.

[0310] On the other hand, if the segmentation depth of the current block in the current picture is greater than a certain level of segmentation depth, the block segmentation information of the current block can be encoded / decoded as is without referring to the reference block in the reference picture.

[0311] Here, the split depth level to be stored may be predefined in the encoder and decoder. Alternatively, information indicating the split depth level to be stored may be explicitly encoded and signaled.

[0312] Alternatively, only block segmentation information up to QT segmentation within the reference picture may be stored. That is, block segmentation information of blocks that are not segmented or blocks to which QT segmentation is applied may be stored, but block segmentation information of blocks to which BT segmentation or TT segmentation is applied may not be stored.

[0313] Alternatively, only the block division structure / block division information of blocks within the reference picture whose size is greater than the threshold may be stored. That is, the block division structure / block division information of blocks within the reference picture whose size is greater than the threshold may be stored, and the block division structure / block division information of blocks within the reference picture whose size is equal to or smaller than the threshold may be discarded without being stored. Accordingly, the block division structure / block division information of a reference block within the reference picture may be referenced only when the size of the current block is greater than the threshold.

[0314] Segmentation depth information of a reference region within a reference picture can be stored. In this case, by comparing the segmentation depth of the current block with the depth information of the reference region, it can be determined whether to segment the current block or to determine the block segmentation structure / block segmentation information by referring to the reference block. Here, the segmentation depth information can include at least one of a minimum segmentation depth, a maximum segmentation depth, or an average depth value.

[0315] For example, if the difference between the segmentation depth information of the reference area and the segmentation depth of the current block is greater than a preset threshold, the current block can be determined to be segmented.

[0316] On the other hand, if the difference between the segmentation depth information of the reference region and the segmentation depth of the current block is equal to or less than a preset threshold, information indicating whether to segment the current block may be additionally encoded / decoded. The information may include at least one of a similarity flag, block segmentation information, or a prediction flag of the block segmentation information.

[0317] Meanwhile, Example 1) and Example 2) may be performed alternatively.

[0318] Alternatively, embodiment 2) may be performed dependently on embodiment 1). For example, whether to encode the prediction flag of embodiment 2) may be determined depending on the value of the similarity flag of embodiment 1).

[0319] For example, the prediction flag of the block segmentation information can be encoded / decoded only when the value of the similarity flag is 1 (True). Specifically, when the similarity flag is 1 (True), only the block segmentation structure / block segmentation information of the reference block up to a certain level of segmentation depth or the QT segmentation structure / QT segmentation information of the reference block can be merged into the block in the current picture. For subsequent blocks (i.e., blocks having a segmentation depth greater than a certain level or blocks generated by QT segmentation), the block segmentation information of the reference block in the same position / same size in the reference picture can be set as the prediction value, and then the prediction flag of the block segmentation information can be encoded / decoded.

[0320] Alternatively, the prediction flag of the block segmentation information may be set to be encoded / decoded only when the value of the similarity flag is 0 (False).

[0321] Meanwhile, in embodiments 1) and 2), it was exemplified that the reference block within the reference picture has the same location and the same size as the current block.

[0322] As another example, after setting a global motion vector, it is also possible to set a block located at a position spaced apart by the global motion vector from the position of the current block in the reference picture as a reference block.

[0323] Wide-area motion vectors can be encoded / decoded block-by-block, for example, coding tree block-by-block. Alternatively, wide-area motion vectors can be encoded / decoded tile-by-tile, slice-by-slice, sub-picture, or picture-by-picture.

[0324] Alternatively, a reference block for the current block within the current coding tree block may be determined by referring to the motion vector of a neighboring coding tree block. Here, the neighboring coding tree block may be adjacent to the top or left of the current block. In addition, the motion vector of the neighboring coding tree block may be the motion vector of the last encoded / decoded block within the neighboring coding tree block or the motion vector of a block bordering the bottom or right boundary within the neighboring coding tree block.

[0325] For example, if a neighboring coding tree block is adjacent to the left side of the current coding tree block, the reference block of the current block within the current coding tree block can be determined based on the motion vector of the block adjacent to the right boundary within the neighboring coding tree block.

[0326] Alternatively, if a neighboring coding tree block is adjacent to the top of the current coding tree block, the reference block of the current block within the current coding tree block can be determined based on the motion vector of the block bordering the bottom within the neighboring coding tree block.

[0327] Meanwhile, the above-described embodiments have described that the block division structure / block division information for the recursive block of the coding block is determined by referring to the reference block.

[0328] Additionally, even when dividing a coding block into multiple prediction blocks or multiple transformation blocks, it is also possible to refer to a reference block.

[0329] For example, whether an Intra Sub-Partition (ISP) is applied to the current block or at least one of the ISP splitting directions can be determined by referring to a reference block.

[0330] For example, whether a Sub-Block Transform (SBT) is applied to the current block, whether the current block is split in an asymmetrical shape, or at least one of the splitting directions of the current block can be determined by referring to a reference block.

[0331] Here, the decision by referring to the reference block may be made by using a similarity flag or a prediction flag for each piece of information.

[0332]

[0333] 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.

[0334] 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.

[0335] 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.

[0336] 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.

[0337] 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.

Claims

1. Step of determining a reference picture; and A video decoding method, comprising a step of determining block segmentation information of a current block in a current picture by referring to a reference block in the above reference picture.

2. In paragraph 1, A video decoding method, characterized in that it is determined whether the block division information of the current block is set to be identical to the block division information of the reference block, based on a similarity flag for the current block.

3. In paragraph 2, If the similarity flag indicates that the block division information of the reference block is merged with the current block, the block division information of the current block is determined to be identical to the block division information of the reference block, A video decoding method, characterized in that the block division information of the current block is explicitly decoded when the similarity flag indicates that the block division information of the reference block is not merged with the current block.

4. In paragraph 2, The above similarity flag is decoded in units of merge determination areas, A video decoding method, characterized in that the above merge judgment area is configured to include at least one coding tree block.

5. In paragraph 2, The above similarity flag is decoded in block units, An image decoding method, characterized in that the similarity flag is decoded for the current block only when the reference block is divided into multiple blocks.

6. In paragraph 1, The block division information of the current block is determined based on at least one prediction flag for the block division information decoded from the bitstream, The above prediction flag indicates whether the block division information of the current block is identical to the predicted value, An image decoding method, characterized in that the above predicted value is block division information of the reference block.

7. In paragraph 6, The above block division information includes a block division flag indicating whether the block is divided and a QT flag indicating whether the QT (QuadTree) is divided. A video decoding method, characterized in that the prediction flag includes a first prediction flag for the block division flag and a second prediction flag for the QT flag.

8. In paragraph 7, A video decoding method, characterized in that when the first prediction flag for the block division flag is true and the value of the block division flag is determined to be true, the second prediction flag for the QT flag is additionally decoded.

9. In paragraph 8, A video decoding method, characterized in that when the first prediction flag for the block division flag is false and the value of the block division flag is determined to be true, the QT flag is decoded instead of the second prediction flag.

10. In paragraph 1, A video decoding method, characterized in that reference picture information for determining a reference picture among a plurality of reference pictures is explicitly decoded.

11. In paragraph 1, A video decoding method, characterized in that the above reference picture is a collocated picture.

12. In paragraph 1, An image decoding method, characterized in that the reference block is referenceable only when the segmentation depth of the current block is less than a threshold value.

13. In paragraph 1, Based on the result of comparing the difference between the segmentation depth of the current block and the segmentation depth information of the reference area within the reference picture with a threshold value, it is determined whether the reference block is referable, An image decoding method, characterized in that the above segmentation depth information includes at least one of a minimum segmentation depth, a maximum segmentation depth, or a depth average value of the reference area.

14. Step of determining a reference picture; and A video encoding method, comprising a step of determining block division information of a current block in a current picture by referring to a reference block in the above reference picture.

15. A processor that generates compressed video data; and In a device including a transmitter for transmitting the compressed video data, The process of generating the above compressed video is as follows: a step of determining a reference picture; and A device for transmitting compressed video data, comprising a step of determining block division information of a current block in a current picture by referring to a reference block in the above reference picture.

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