Image encoding / decoding method and device for signaling information related to the sub-image and image header, and method for transmitting bitstream

Abstract

A method and device for encoding / decoding images are provided for signaling information related to a sub-image and an image header, as well as a method for transmitting a bitstream. The image decoding method, according to this disclosure, comprises the following steps: acquiring a first indicator that signals whether information related to a sub-image is present in the bitstream; acquiring a second indicator that signals whether information related to the image header is present in the segment header; and decoding the bitstream based on the first and second indicators. If the first indicator signals that information related to the sub-image is present in the bitstream, the second indicator may have a value that indicates that information related to the image header is not present in the segment header.

Description

Image encoding / decoding method and device for signaling information related to the sub-image and image header, and method for transmitting bitstream Technical field The present description relates to a method and / or image encoding / decoding apparatus and, more particularly, to a method and / or image encoding and decoding apparatus for signaling information about a sub-image and an image header, and to a method for transmitting a bit stream generated by the image encoding method / apparatus of the present description. Background of the technique Recently, the demand for high-resolution, high-quality images, such as high-definition (HD) and ultra-high-definition (UHD) images, has been increasing across various fields. As the resolution and quality of image data improve, the amount of transmitted information, or bits, increases relative to existing image data. This increase in the amount of transmitted information, or bits, leads to an increase in both transmission and storage costs. Therefore, there is a need for highly efficient image compression technology to effectively transmit, store, and reproduce information in high-resolution, high-quality images. A description of image headers and slice headers in the draft for a VVC standard is provided by J. Samuelsson et al. in "AHG9: Picture Header in Slice Header," JVET-Q0775, 17th JVET meeting, January 2020, ISO / IEC JTC1 / SC29 / WG11 and ITU-T SG.16, pp. 1–5. Description Technical problem One object of the present description is to provide a method and apparatus for encoding / decoding images with improved encoding / decoding efficiency. Another object of the present description is to provide a method and apparatus for encoding / decoding images to improve encoding / decoding efficiency by efficiently signaling information about a sub-image and an image header. Another object of the present description is to provide a method of transmitting a bit stream generated by an image encoding method or apparatus according to the present description. Another object of the present description is to provide a recording medium that stores a bit stream generated by an image encoding method or apparatus according to the present description. Another object of the present description is to provide a recording medium that stores a received bit stream, decoded and used to reconstruct an image by means of an image decoding apparatus according to the present description. The technical problems solved by the present description are not limited to the above technical problems and other technical problems not described in this document will become evident to persons skilled in the art from the following description. Technical solution The invention is defined in the appended claims. Advantageous effects According to the present description, it is possible to provide a method and apparatus for encoding / decoding images with improved encoding / decoding efficiency. Furthermore, according to the present description, it is possible to provide a method and apparatus for encoding / decoding images to improve encoding / decoding efficiency by efficiently signaling information about a sub-image and an image header. Furthermore, according to the present description, it is possible to provide a method for transmitting a bit stream generated by an image encoding method or apparatus according to the present description. Furthermore, according to the present description, it is possible to provide a recording medium that stores a bit stream generated by an image encoding method or device according to the present description. Furthermore, according to the present description, it is possible to provide a recording medium that stores a received bit stream, decoded and used to reconstruct an image by means of an image decoding apparatus according to the present description. Those experienced in the technique will appreciate that the effects that can be achieved through the present description are not limited to what has been particularly described above in this memorandum, and other advantages of the present description will be more clearly understood from the detailed description. Brief description of the drawings FIG.1 is a view that schematically shows a video coding system, to which an embodiment of the present description is applicable; FIG. 2 is a schematic view showing an image coding apparatus to which an embodiment of the present description is applicable; FIG. 3 is a view that schematically shows an image decoding apparatus, to which an embodiment of the present description is applicable; FIG.4 is a view showing a partitioning structure of an image according to one realization; FIG. 5 is a view showing an implementation of a type of partitioning of a block according to a multi-type tree structure; FIG.6 is a view showing a block division information signaling mechanism in a quaternary tree with a tree structure of multiple nested types according to the present description; FIG.7 is a view showing an embodiment in which a CTU is divided into multiple CUs; FIG. 8 is a flowchart illustrating a method of encoding an image using a segment / tile by means of an image encoding apparatus according to an embodiment of the present description; FIG. 9 is a flowchart illustrating a method of decoding an image using a segment / mosaic by means of an image decoding apparatus according to an embodiment of the present description; FIG.10 is a view showing an example of the present description of a signage and syntax element in an image header; FIG. 11 is a view showing a syntactic structure of a segment header according to one realization of the present description; FIG.12 is a flowchart illustrating a method of parsing and decoding the segment header of FIG.11; FIG. 13 is a flowchart illustrating a method of encoding the segment header of FIG. 11; FIG. 14 is a view showing the syntactic structure of a segment header according to another realization of the present description; FIG.15 is a flowchart illustrating a method of parsing and decoding the segment header of FIG.14; FIG. 16 is a flowchart illustrating a method of encoding the segment header of FIG. 14; FIG. 17 is a view showing the syntactic structure of a segment header according to another realization of the present description; FIG.18 is a flowchart illustrating a method of parsing and decoding the segment header of FIG.17; FIG. 19 is a flowchart illustrating a method of encoding the segment header of FIG. 17; and FIG.20 is a view showing a continuous content transmission system, to which an implementation of the present description is applicable. Mode for the invention Hereafter, the embodiments described herein will be detailed with reference to the accompanying drawings to facilitate their implementation by persons skilled in the art. However, this description can be implemented in various ways and is not limited to the embodiments described herein. In writing this description, if it is determined that a detailed description of a related known function or construction would make the scope of this description unnecessarily ambiguous, that detailed description shall be omitted. On drawings, parts not related to the description in this description shall be omitted, and similar reference numbers shall be attached to similar parts. In this description, when a component is "connected," "coupled," or "linked" to another component, it may include not only a direct connection relationship but also an indirect connection relationship where an intermediate component is present. Furthermore, when a component "includes" or "has" other components, it means that other components may be included, rather than excluding other components unless otherwise stated. In this description, the terms first, second, etc., may be used only to distinguish one component from other components and do not limit the order or importance of the components unless otherwise stated. Therefore, within the scope of this description, a first component in one embodiment may be called a second component in another embodiment, and similarly, a second component in one embodiment may be called a first component in another embodiment. The distinction between components in this description is intended to clearly describe each characteristic and does not imply that the components are necessarily separate. That is, multiple components may be integrated and implemented in a single hardware or software unit, or a single component may be distributed and implemented across multiple hardware or software units.Therefore, even if not otherwise stated, embodiments in which the components are integrated or the component is distributed are also included within the scope of this description. In this description, the components described in various embodiments do not necessarily mean essential components, and some components may be optional. Therefore, an embodiment consisting of a subset of components described in one embodiment is also included within the scope of this description. Furthermore, embodiments that include components other than those described in the various embodiments are also included within the scope of this description. This description refers to the encoding and decoding of an image, and the terms used in this description may have a general meaning commonly used in the technical field to which this description belongs, unless otherwise defined in this description. In this description, an "image" generally refers to a unit that represents an image at a specific point in time, and a segment / tile is an encoding unit that constitutes a part of an image. An image may be composed of one or more segments / tiles. Furthermore, a segment / tile may include one or more encoding tree units (CTUs). In this description, a "pixel" or a "pel" may mean a smaller unit that constitutes an image. Additionally, "sample" may be used as a term corresponding to a pixel. A sample may generally represent a pixel or a pixel value, and may represent only a pixel / pixel value of a luma component or only a pixel / pixel value of a chroma component. In this description, a "unit" may represent a basic image processing unit. The unit may include at least one sample from a specific image region and information related to that region. The unit may be used interchangeably with terms such as, for example, "sample array," "block," or "area" in some cases. In a general case, an MxN block may include samples (or sample arrays) or a set (or array) of transform coefficients with M columns and N rows. In this description, "current block" may mean one of the following: "current encoding block," "current encoding unit," "encoding target block," "decoding target block," or "processing target block." When prediction is performed, "current block" may mean "current prediction block" or "prediction target block." When transform (inverse transform) / quantization (dequantization) is performed, "current block" may mean "current transform block" or "transform target block." When filtering is performed, "current block" may mean "filtering target block." Furthermore, in this description, a "current block" may mean "a luma block of a current block" unless explicitly stated as a chroma block. The "chroma block of the current block" may be expressed by including an explicit description of a chroma block, such as "chroma block" or "current chroma block." In this description, the terms " / " and "," should be interpreted as meaning "and / or". For example, the expressions "A / B" and "A, B" can mean "A and / or B". Furthermore, "A / B / C" and "A / B / C" can mean "at least one of A, B and / or C". In this description, the term "or" should be interpreted as meaning "and / or". For example, the expression "A or B" may include 1) only "A", 2) only "B", and / or 3) both "A" and "B". In other words, in this description, the term "or" should be interpreted as meaning "in addition to or alternatively". Overview of the video encoding system FIG.1 is a view showing a video encoding system according to the present description. The video coding system according to a given implementation may include an encoding device 10 and a decoding device 20. The encoding device 10 may deliver encoded video and / or image information or data to the decoding device 20 in the form of a file or continuous transmission through a digital storage medium or network. The encoding apparatus 10, according to one embodiment, may include a video source generator 11, an encoding unit 12, and a transmitter 13. The decoding apparatus 20, according to one embodiment, may include a receiver 21, a decoding unit 22, and a renderer 23. The encoding unit 12 may be referred to as a video / image encoding unit, and the decoding unit 22 may be referred to as a video / image decoding unit. The transmitter 13 may be included in the encoding unit 12. The receiver 21 may be included in the decoding unit 22. The renderer 23 may include a display, and the display may be configured as a separate device or an external component. The video source generator 11 can acquire video / images through a video / image capture, synthesis, or generation process. The video source generator 11 can include a video / image capture device and / or a video / image generation device. The video / image capture device can include, for example, one or more cameras, video / image files containing previously captured video / images, and similar items. The video / image generation device can include, for example, computers, tablets, and smartphones, and can generate video / images electronically. For example, a virtual video / image can be generated using a computer or similar device. In this case, the video / image capture process can be replaced by a related data generation process. The encoding unit 12 can encode an input video / image. The encoding unit 12 can perform a series of procedures, such as prediction, transformation, and quantization, for efficient compression and encoding. The encoding unit 12 can output encoded data (encoded video / image information) as a bitstream. Transmitter 13 can transmit the encoded video / image information or data output as a bitstream to receiver 21 of the decoding unit 20 via a digital storage medium or a network, either as a file or a continuous stream. The digital storage medium can include various storage media such as USB, SD, CD, DVD, Blu-ray, HDD, SSD, and similar devices. Transmitter 13 can include a component for generating a multimedia file using a predefined file format and a component for transmission over a broadcast / communication network. Receiver 21 can extract / receive the bitstream from the storage medium or network and transmit the bitstream to the decoding unit 22. The decoding unit 22 can decode the video / image by carrying out a series of procedures such as, for example, dequantization, inverse transform and prediction corresponding to the operation of the encoding unit 12. Renderer 23 can render the decoded video / image. The rendered video / image can then be displayed on the screen. Overview of the image encoding apparatus FIG. 2 is a schematic view showing an image encoding apparatus to which an embodiment of the present description is applicable. As shown in FIG. 2, the image encoding apparatus 100 may include an image partitioner 110, a subtractor 115, a transformer 120, a quantizer 130, a dequantizer 140, an inverse transformer 150, an adder 155, a filter 160, a memory 170, an interpredictor 180, an intrapredictor 185, and an entropy encoder 190. The interpredictor 180 and the intrapredictor 185 may be collectively referred to as the "predictor." The transformer 120, the quantizer 130, the dequantizer 140, and the inverse transformer 150 may be included in a residual processor. The residual processor may further include the subtractor 115. All or at least some of the multiple components that make up the image encoding apparatus 100 can be configured by a hardware component (e.g., an encoder or a processor) in some embodiments. Furthermore, the memory 170 can include a decoded image buffer (DPB) and can be configured using a digital storage medium. The image partitioner 110 can divide an input image (or frame) fed into the image encoding apparatus 100 into one or more processing units. For example, the processing unit can be called an encoding unit (CU). The encoding unit can be obtained by recursively partitioning an encoding tree unit (CTU) or a larger encoding unit (LCU) according to a quaternary tree, binary tree, or ternary tree (QT / BT / TT) structure. For example, an encoding unit can be divided into multiple encoding units of greater depth based on a quaternary tree structure, a binary tree structure, and / or a ternary structure.For partitioning the coding unit, a quaternary tree structure can be applied first, and a binary tree and / or ternary structure can be applied later. The coding procedure described here can be carried out based on the final, undivided coding unit. The largest coding unit can be used as the final coding unit, or the deepest-depth coding unit acquired by partitioning the largest coding unit can be used as the final coding unit. In this case, the coding procedure can include a prediction, transformation, and reconstruction procedure, which will be described later. As another example, the processing unit of the coding procedure can be a prediction unit (PU) or a transformation unit (TU).The prediction unit and the transformation unit can be separated or partitioned from the final encoding unit. The prediction unit can be a sample prediction unit, and the transformation unit can be a unit for deriving a transform coefficient and / or a unit for deriving a residual signal from the transform coefficient. The predictor (either the interpredictor 180 or the intrapredictor 185) can perform the prediction on a block to be processed (the current block) and generate a predicted block that includes prediction samples for the current block. The predictor can determine whether intraprediction or interprediction applies based on the current block or CU. The predictor can generate various information related to the prediction of the current block and transmit this information to the entropy encoder 190. The prediction information can be encoded in the entropy encoder 190 and output as a bitstream. The intrapredictor 185 can predict the current block by referencing samples in the current image. The referenced samples can be located near the current block or can be located further apart, depending on the intraprediction mode and / or technique. Intrapredictor modes can include multiple non-directional and multiple directional modes. The non-directional mode might include, for example, a DC mode and a flat mode. The directional mode might include, for example, 33 or 65 directional prediction modes, depending on the level of detail required for the prediction direction. However, this is merely an example; more or fewer directional prediction modes can be used depending on the environment. The intrapredictor 185 can determine the prediction mode applied to the current block using a prediction mode applied to a neighboring block. The 180 interpredictor can derive a predicted block for the current block based on a reference block (reference sample array) specified by a motion vector in a reference image. In this case, to reduce the amount of motion information transmitted in interprediction mode, the motion information can be predicted in block, subblock, or sample units based on the motion information correlation between the neighboring block and the current block. The motion information can include a motion vector and a reference image index. The motion information can also include interprediction direction information (L0 prediction, L1 prediction, Bi prediction, etc.). In the case of interprediction, the neighboring block can include a spatial neighbor block present in the current image and a temporal neighbor block present in the reference image.The reference image that includes the reference block and the reference image that includes the temporal neighbor block can be the same or different. The temporal neighbor block can be called a co-located reference block, a co-located CU (colCU), and similar terms. The reference image that includes the temporal neighbor block can be called a co-located image (colPic). For example, the 180 interpredictor can configure a list of motion information candidates based on neighboring blocks and generate information indicating which candidate is used to derive a motion vector and / or a reference image index for the current block. Interprediction can be performed based on various prediction modes. For example, in the case of a jump mode and a merge mode, the 180 interpredictor can use motion information from the neighboring block as motion information for the current block.In jump mode, unlike merge mode, the residual signal may not be transmitted. In motion vector prediction (MVP) mode, the neighboring block's motion vector can be used as a motion vector predictor, and the current block's motion vector can be signaled by encoding a motion vector difference and a flag for a motion vector predictor. The motion vector difference can represent a difference between the current block's motion vector and the motion vector predictor. The predictor can generate a prediction signal based on various prediction methods and techniques described below. For example, the predictor can apply not only intraprediction or interprediction, but also simultaneously apply both intraprediction and interprediction to predict the current block. A prediction method that simultaneously applies both intraprediction and interprediction to predict the current block can be called combined inter- and intraprediction (CIIP). Additionally, the predictor can perform intra-block copying (IBC) to predict the current block. Intra-block copying can be used for image / video encoding of game content or similar applications, such as screen content coding (SCC).IBC is a method for predicting a current image using a reference block previously reconstructed within the current image at a predetermined distance from the current block. When IBC is applied, the location of the reference block in the current image can be encoded as a vector (block vector) corresponding to the predetermined distance. IBC essentially performs the prediction within the current image, but it can be implemented similarly to interprediction in that a reference block is derived from within the current image. That is, IBC can use at least one of the interprediction techniques described herein. The prediction signal generated by the predictor can be used to generate a reconstructed signal or a residual signal. Subtractor 115 can generate a residual signal (residual block or residual sample array) by subtracting the prediction signal (predicted block or prediction sample array) emitted from the predictor from the input image signal (original block or original sample array). The generated residual signal can then be transmitted to transformer 120. Transformer 120 can generate transform coefficients by applying a transform technique to the residual signal. For example, the transform technique can include at least one of a discrete cosine transform (DCT), a discrete sine transform (DST), a Karhunen-Loève transform (KLT), a graph-based transform (GBT), or a conditionally nonlinear transform (CNT). In this case, GBT means a transform obtained from a graph when the pixel relationship information is represented by the graph. CNT refers to a transform acquired based on a prediction signal generated using all previously reconstructed pixels.Furthermore, the transformation process can be applied to square pixel blocks that are the same size or it can be applied to blocks that are of a variable size instead of square. The quantizer 130 can quantize the transform coefficients and transmit them to the entropy encoder 190. The entropy encoder 190 can encode the quantized signal (information about the quantized transform coefficients) and output a bit stream. The information about the quantized transform coefficients can be called residual information. The quantizer 130 can rearrange the block-quantized transform coefficients into a one-dimensional vector form based on a coefficient scan order and generate information about the quantized transform coefficients based on the quantized transform coefficients in one-dimensional vector form. The Entropy 190 encoder can perform various encoding methods, such as exponential Golomb, context-adaptive variable-length coding (CAVLC), context-adaptive binary arithmetic coding (CABAC), and similar methods. The Entropy 190 encoder can encode information necessary for video / image reconstruction, other than quantized transform coefficients (e.g., syntactic element values), separately. The encoded information (e.g., encoded video / image information) can be transmitted or stored in Network Abstraction Layer (NAL) units as a bitstream.The video / image information may also include information about various parameter sets, such as an Adaptive Parameter Set (APS), a Picture Parameter Set (PPS), a Sequence Parameter Set (SPS), or a Video Parameter Set (VPS). Furthermore, the video / image information may also include general restriction information. The signaled information, transmitted information, and / or syntactic elements described herein may be encoded using the encoding procedure described above and included in the bitstream. The bitstream may be transmitted over a network or stored on a digital storage medium.The network may include a broadcasting network and / or a communications network, and the digital storage medium may include various storage media such as USB, SD, CD, DVD, Blu-ray, HDD, SSD, and the like. A transmitter (not shown) that transmits a signal emitted from the entropy encoder 190 and / or a storage unit (not shown) that stores the signal may be included as an internal / external element of the image encoding apparatus 100. Alternatively, the transmitter may be provided as the component of the entropy encoder 190. The quantized transform coefficients emitted from quantizer 130 can be used to generate a residual signal. For example, the residual signal (residual block or residual samples) can be reconstructed by applying dequantization and inverse transform to the quantized transform coefficients via dequantizer 140 and inverse transformer 150. Adder 155 adds the reconstructed residual signal to the prediction signal emitted from interpredictor 180 or intrapredictor 185 to generate a reconstructed signal (reconstructed image, reconstructed block, reconstructed sample array). If there is no residual signal for the block to be processed, such as in a case where jump mode is applied, the predicted block can be used as the reconstructed block. Adder 155 can be referred to as a reconstructor or reconstructed block generator. The generated reconstructed signal can be used for intraprediction of the next block to be processed in the current image and can be used for interprediction of a subsequent image through filtering, as described below. Filter 160 can improve subjective / objective image quality by applying filtering to the reconstructed signal.For example, filter 160 can generate a modified reconstructed image by applying various filtering methods to the reconstructed image and store the modified reconstructed image in memory 170, specifically, a DPB of memory 170. The various filtering methods can include, for example, unlock filtering, adaptive sampling, adaptive loop filtering, bilateral filtering, and the like. Filter 160 can generate various filtering-related information and transmit the generated information to the entropy encoder 190 as described later in the description of each filtering method. The filtering-related information can be encoded by the entropy encoder 190 and output as a bitstream. The modified reconstructed image transmitted to memory 170 can be used as the reference image in the interpredictor 180. When interprediction is applied through the image encoding apparatus 100, the prediction mismatch between the image encoding apparatus 100 and the image decoding apparatus can be avoided, and the encoding efficiency can be improved. The DPB of memory 170 can store the modified reconstructed image for use as a reference image in interpredictor 180. Memory 170 can store the motion information of the block from which the motion information in the current image is derived (or encoded) and / or the motion information of blocks in the image that have already been reconstructed. The stored motion information can be transmitted to interpredictor 180 and used as the motion information of the spatially neighboring block or the motion information of the temporally neighboring block. Memory 170 can store reconstructed samples of reconstructed blocks in the current image and can transfer the reconstructed samples to intrapredictor 185. Overview of the image decoding apparatus FIG. 3 is a view that schematically shows an image decoding apparatus, to which an embodiment of the present description is applicable. As shown in FIG. 3, the image decoding apparatus 200 may include an entropy decoder 210, a dequantizer 220, an inverting transformer 230, a summing amplifier 235, a filter 240, a memory 250, an interpredictor 260, and an intrapredictor 265. The interpredictor 260 and the intrapredictor 265 may be collectively referred to as the "predictor." The dequantizer 220 and the inverting transformer 230 may be incorporated into a residual processor. All or at least some of the multiple components that make up the image decoding apparatus 200 can be configured by means of a hardware component (e.g., a decoder or a processor) according to a specific embodiment. Furthermore, the memory 250 can include a decoded image buffer (DPB) or can be configured by means of a digital storage medium. The image decoding apparatus 200, having received a bitstream containing video / image information, can reconstruct an image by performing a process corresponding to that carried out by the image encoding apparatus 100 in FIG. 2. For example, the image decoding apparatus 200 can perform the decoding using a processing unit applied within the image encoding apparatus. Therefore, the decoding processing unit can be an encoding unit, for instance. The encoding unit can be obtained by partitioning an encoding tree unit or a larger encoding unit. The reconstructed image signal, decoded and output by the image decoding apparatus 200, can be reproduced by a playback apparatus (not shown). The image decoding unit 200 can receive a signal emitted from the image encoding unit of FIG. 2 in the form of a bitstream. The received signal can be decoded by the entropy decoder 210. For example, the entropy decoder 210 can analyze the bitstream to obtain information (e.g., video / image information) necessary for image reconstruction. The video / image information can also include information about various parameter sets, such as an adaptation parameter set (APS), an image parameter set (PPS), a sequence parameter set (SPS), or a video parameter set (VPS). Furthermore, the video / image information can also include general constraint information.The image decoding device can further decode the image based on parameter set information and / or general constraint information. The signaled / received information and / or syntactic elements described herein can be decoded through the decoding procedure and obtained from the bitstream. For example, the entropy decoder 210 decodes the information in the bitstream based on an encoding method such as exponential Golomb coding, CAVLC, or CABAC, and outputs values ​​of syntactic elements required for image reconstruction and quantized values ​​of transform coefficients for residuals.More specifically, the CABAC entropy decoding method can receive a bin corresponding to each syntactic element in the bitstream, determine a context model using information from the target syntactic element, decode information from a neighboring block and a target decoding block or information from a symbol / bin decoded in a previous stage, and perform arithmetic decoding on the bin by predicting a probability of occurrence of a bin according to the determined context model, and generate a symbol corresponding to the value of each syntactic element. In this case, the CABAC entropy decoding method can update the context model using information from the decoded symbol / bin for a subsequent symbol / bin after determining the context model.Information related to the prediction between the information decoded by the entropy decoder 210 can be provided to the predictor (the interpredictor 260 and the intrapredictor 265), and the residual value at which the entropy decoding was carried out in the entropy decoder 210, i.e., the quantized transform coefficients and related parameter information, can be fed into the dequantizer 220. In addition, information about the filtering between the information decoded by the entropy decoder 210 can be provided to the filter 240. Meanwhile, a receiver (not shown) for receiving a signal emitted from the image encoding apparatus can be further configured as an internal / external element of the image decoding apparatus 200, or the receiver can be a component of the entropy decoder 210. Meanwhile, the image decoding apparatus as described herein may be called a video / image decoding apparatus. The image decoding apparatus may be classified into an information decoder (video / image information decoder) and a sample decoder (video / image sample decoder). The information decoder may include the entropy decoder 210. The sample decoder may include at least one of the dequantizer 220, the inverse transformer 230, the adder 235, the filter 240, the memory 250, the interpredictor 160, or the intrapredictor 265. The dequantizer 220 can dequantize quantized transform coefficients and output the transform coefficients. The dequantizer 220 can rearrange the quantized transform coefficients into a two-dimensional block. In this case, the rearrangement can be based on the coefficient scan order performed in the image encoding apparatus. The dequantizer 220 can perform dequantization on the quantized transform coefficients using a quantization parameter (e.g., quantization stage size information) and obtain the transform coefficients. The inverse 230 transformer can inversely transform the transform coefficients to obtain a residual signal (residual block, residual sample array). The predictor can perform the prediction on the current block and generate a predicted block that includes prediction samples for the current block. The predictor can determine whether intraprediction or interprediction is applied to the current block based on the prediction information emitted from the entropy decoder 210 and can determine a specific intraprediction / interprediction mode (prediction technique). It is the same as described in the image coding apparatus 100 predictor that the predictor can generate the prediction signal based on various prediction methods (techniques) that will be described later. Intrapredictor 265 can predict the current block by referencing the samples in the current image. The description of intrapredictor 185 also applies to intrapredictor 265. The 260 interpredictor can derive a predicted block for the current block based on a reference block (reference sample array) specified by a motion vector in a reference image. In this case, to reduce the amount of motion information transmitted in interprediction mode, the motion information can be predicted in block, subblock, or sample units based on the motion information correlation between the neighboring block and the current block. The motion information can include a motion vector and a reference image index. The motion information can also include interprediction direction information (L0 prediction, L1 prediction, Bi prediction, etc.). In the case of interprediction, the neighboring block can include a spatial neighbor block present in the current image and a temporal neighbor block present in the reference image.For example, the 260 interpredictor can configure a list of motion information candidates based on neighboring blocks and derive a motion vector of the current block and / or a reference image index based on the received candidate selection information. Interprediction can be performed using various prediction modes, and the prediction information can include details indicating the interprediction mode for the current block. Adder 235 can generate a reconstructed signal (reconstructed image, reconstructed block, reconstructed sample array) by adding the resulting residual signal to the prediction signal (predicted block, predicted sample array) emitted from the predictor (including interpredictor 260 and / or intrapredictor 265). If there is no residual for the block to be processed, such as when the skip mode is applied, the predicted block can be used as the reconstructed block. The description of adder 155 is equally applicable to adder 235. Adder 235 can be referred to as a reconstructor or a reconstructed block generator. The generated reconstructed signal can be used for the intraprediction of the next block to be processed in the current image and can be used for the interprediction of the next image through filtering as described below. Filter 240 can improve subjective / objective image quality by applying filtering to the reconstructed signal. For example, Filter 240 can generate a modified reconstructed image by applying various filtering methods to the reconstructed image and storing the modified reconstructed image in memory 250, specifically, a DPB of memory 250. The various filtering methods can include, for example, unlock filtering, adaptive sampling, adaptive loop filtering, bilateral filtering, and similar methods. The reconstructed (modified) image stored in the DPB of memory 250 can be used as a reference image in interpredictor 260. Memory 250 can store the motion information of the block from which the motion information in the current image is derived (or decoded) and / or the motion information of blocks in the image that have already been reconstructed. The stored motion information can be transmitted to interpredictor 260 for use as the motion information of the spatially neighboring block or the motion information of the temporally neighboring block. Memory 250 can store reconstructed samples of reconstructed blocks in the current image and transfer the reconstructed samples to intrapredictor 265. In the present description, the realizations described in filter 160, interpredictor 180 and intrapredictor 185 of image encoding apparatus 100 may be applied equally or correspondingly to filter 240, interpredictor 260 and intrapredictor 265 of image decoding apparatus 200. Image partitioning overview The video / image coding method described herein can be implemented based on an image partitioning structure as follows. Specifically, the prediction, residual processing (inverse transform, dequantization, etc.), syntactic element encoding, and filtering procedures, which will be described later, can be implemented based on a CTU, CU (and / or TU, PU) derived from the image partitioning structure. The image can be partitioned into block units, and the block partitioning procedure can be performed in the image partitioner 110 of the encoding apparatus. The partitioning information can be encoded by the entropy encoder 190 and transmitted to the decoding apparatus as a bitstream.The entropy decoder 210 of the decoding apparatus can derive a block partitioning structure of the current image based on partitioning-related information obtained from the bitstream and, based on this, can carry out a series of procedures (e.g., prediction, residual processing, block / image reconstruction, loop filtering, etc.) for image decoding. Images can be partitioned into a sequence of coding tree units (CTUs). Figure 4 shows an example of an image partitioned into CTUs. A CTU can correspond to a coding tree block (CTB). Alternatively, a CTU can include one luma sample coding tree block and two corresponding chroma sample coding tree blocks. For example, for an image containing three sample arrays, the CTU might include one NxN luma sample block and two corresponding chroma sample blocks. CTU Partition Overview As described above, the coding unit can be acquired by recursively partitioning the coding tree unit (CTU) or the larger coding unit (LCU) according to a quaternary tree / binary tree / ternary tree (QT / BT / TT) structure. For example, the CTU can first be partitioned into quaternary tree structures. Then, the leaf nodes of the quaternary tree structure can be further partitioned using a multi-type tree structure. Partitioning according to a quaternary tree means that a current CU (or CTU) is partitioned into four equal units. Using this partitioning method, the current CU can be divided into four CUs that have the same width and height. When the current CU is no longer partitioned into a quaternary tree structure, it becomes the leaf node of that structure. The CU corresponding to the leaf node of the quaternary tree structure can then be left unpartitioned and used as the final encoding unit described earlier. Alternatively, the CU corresponding to the leaf node of the quaternary tree structure can be further partitioned using a multi-type tree structure. Figure 5 shows an implementation of a block partitioning method based on a multi-type tree structure. Partitioning based on a multi-type tree structure can include two types of splits based on a binary tree structure and two types based on a ternary tree structure. The two types of splits based on the binary tree structure can include vertical binary splitting (SPLIT_BT_VER) and horizontal binary splitting (SPLIT_BT_HOR). Vertical binary splitting (SPLIT_BT_VER) means that the current CU is split into two equal parts in the vertical direction. As shown in Figure 4, vertical binary splitting can generate two CUs that have the same height as the current CU and a width that is half the width of the current CU. Horizontal binary splitting (SPLIT_BT_HOR) means that the current CU is split into two equal parts in the horizontal direction. As shown in Figure 4,5. By horizontal binary division, two CUs can be generated that have a height that is half the height of the current CU and that have the same width as the current CU. Two types of splitting based on the ternary tree structure include vertical ternary splitting (SPLIT_TT_VER) and horizontal ternary splitting (SPLIT_TT_HOR). In vertical ternary splitting (SPLIT_TT_VER), the current CU is split vertically in a 1:2:1 ratio. As shown in FIG. 5, vertical ternary splitting can generate two CUs that have the same height as the current CU and a width that is 1 / 4 the width of the current CU, and one CU that has the same height as the current CU and a width that is half the width of the current CU. In horizontal ternary splitting (SPLIT_TT_HOR), the current CU is split horizontally in a 1:2:1 ratio. As shown in FIG.5. By horizontal ternary division, two CUs can be generated that have a height that is 1 / 4 of the height of the current CU and that have the same width as the current CU, and one CU that has a height that is half the height of the current CU and that has the same width as the current CU. FIG. 6 is a view showing a block division information signaling mechanism in a nested quaternary tree with a multi-type tree structure according to the present description. In this case, the current CTU is treated as the root node of the quad tree and is partitioned into a quad tree structure for the first time. Information (e.g., qt_split_flag) is signaled to indicate whether the quad tree split is performed with respect to the current CU (CTU or QT_node of the quad tree). For example, when qt_split_flag has a first value (e.g., "1"), the current CU can be partitioned into a quad tree. Furthermore, when qt_split_flag has a second value (e.g., "0"), the current CU is not split into a quad tree but instead becomes a leaf node (QT_leaf_node) of the quad tree. Each leaf node of the quad tree can then be further partitioned into multi-type tree structures. That is, the leaf node of the quaternary tree can become the (MTT_node) node of the multitype tree. In the multitype tree structure, a first indicator is noted (e.g.The flags `Mtt_split_cu_flag` and `Mtt_split_cu_flag` are used to indicate whether the current node is further partitioned. If the corresponding node is further partitioned (e.g., if the first flag is 1), a second flag (e.g., `Mtt_split_cu_vertical_flag`) can be signaled to indicate the split direction. For example, the split direction might be vertical if the second flag is 1 and horizontal if the second flag is 0. A third flag (e.g., `Mtt_split_cu_binar` and `_flag`) can then be signaled to indicate whether the split type is a binary split type or a ternary split type. For example, the split type might be binary when the third flag is 1 and ternary when the third flag is 0. The multi-type tree node acquired by binary splitting or ternary splitting can then be further partitioned into multi-type tree structures.However, the multi-type tree node may not partition into quaternary tree structures. If the first indicator is 0, the corresponding multi-type tree node is no longer partitioned but becomes the leaf node (MTT_leaf_node) of the multi-type tree. The CU corresponding to the leaf node of the multi-type tree can be used as the final encoding unit described above. Based on mtt_split_cu_vertical_flag and mtt_split_cu_binar and _flag, a multi-type tree split mode (MttSplitMode) can be derived from a CU as shown in Table 1 below. In the following description, the multi-type tree split mode may be referred to as the multi-tree split type or split type. [Table 1] Figure 7 shows an example where a CTU is partitioned into multiple CUs by applying a multitype tree after applying a quaternary tree. In Figure 7, the bold block edges (710) represent the quaternary tree partition, and the remaining edges (720) represent the multitype tree partition. The CU may correspond to an encoding block (CB). In one embodiment, the CU may include a luma sample encoding block and two chroma sample encoding blocks corresponding to the luma samples. A chroma component CB or TB size (sample) can be derived based on a luma component CB or TB size (sample) according to the component ratio based on the image's color format (chroma format, e.g., 4:4:4, 4:2:2, 4:2:0, or similar). For a 4:4:4 color format, the chroma component CB / TB size can be set equal to the luma component CB / TB size. For a 4:2:2 color format, the width of the chroma component CB / TB can be set to half the width of the luma component CB / TB, and the height of the chroma component CB / TB can be set to the height of the luma component CB / TB. In the case of 4:2:0 color format, the width of the chroma component CB / TB can be set to half the width of the luma component CB / TB and the height of the chroma component CB / TB can be set to half the height of the luma component CB / TB. In one embodiment, when the CTU size is 128 based on the luma sample unit, the CU size can range from 128x128 to 4x4, which is the same size as the CTU. In another embodiment, in the case of a 4:2:0 color format (or chroma format), a chroma CB size can range from 64x64 to 2x2. Meanwhile, in one implementation, the CU size and the TU size can be equal. Alternatively, there can be multiple TUs in a CU region. The TU size generally represents a transform block (TB) size of the luma component (sample). The TU size can be derived based on a larger permissible TB size, maxTbSize, which is a default value. For example, when the CU size is larger than maxTbSize, multiple TUs (TBs) with maxTbSize can be derived from the CU, and the transform / inverse transform can be performed in TU (TB) units. For example, the largest permissible luma TB size might be 64x64, and the largest permissible chroma TB size might be 32x32. If the width or height of the CB partitioned according to the tree structure is greater than the width or height of the largest transform, the CB can be automatically (or implicitly) partitioned until the TB size limit is met in the horizontal and vertical directions. Furthermore, for example, when intraprediction is applied, an intraprediction mode / type can be obtained in CU (or CB) units, and a procedure for deriving neighboring reference samples and generating prediction samples can be carried out in TU (or TB) units. In this case, there may be one or multiple TU (or TB) units in a CU (or CB) region, and in this case, the multiple TU or (TB) units may share the same intraprediction mode / type. Meanwhile, for a nested multitype tree quaternary tree encoding tree scheme, the following parameters can be signaled as SPS syntactic elements from the encoding apparatus to the decoding apparatus.For example, at least one of the following is signaled: CTU size, which is a parameter representing the root node size of a quaternary tree; MinQTSize, which is a parameter representing the minimum allowed leaf node size of a quaternary tree; MaxBtSize, which is a parameter representing the maximum allowed root node size of a binary tree; MaxTtSize, which is a parameter representing the maximum allowed root node size of a ternary tree; MaxMttDepth, which is a parameter representing the maximum allowed depth of multi-type tree splitting hierarchy from a leaf node of a quaternary tree; MinBtSize, which is a parameter representing the minimum allowed leaf node size of a binary tree; or MinTtSize, which is a parameter representing the minimum allowed leaf node size of a ternary tree. As a realization of using a 4:2:0 chroma format, the CTU size can be set to 128x128 luma blocks and two 64x64 chroma blocks corresponding to the luma blocks. In this case, MinOTSize can be set to 16x16, MaxBtSize to 128x128, MaxTtSize to 64x64, MinBtSize and MinTtSize to 4x4, and MaxMttDepth to 4. Quaternary tree partitioning can be applied to the CTU to generate quaternary tree leaf nodes. The quaternary tree leaf node can be referred to as a leaf QT node. Leaf nodes in a quaternary tree can range in size from 16x16 (e.g., the MinOTSize) to 128x128 (e.g., the CTU size). If the QT leaf node is 128x128, it may not need to be further partitioned into a binary / ternary tree. This is because, in this case, even if partitioned, it exceeds the MaxBtsize and MaxTtsize (e.g., 64x64).In other cases, leaf QT nodes can be further partitioned into a multitype tree. Therefore, the leaf QT node is the root node for the multitype tree, and the leaf QT node can have a multitype tree depth (mttDepth) of 0. If the multitype tree depth reaches MaxMttdepth (e.g., 4), further partitioning may not be considered. If the width of the multitype tree node is equal to MinBtSize and less than or equal to 2xMinTtSize, then further horizontal partitioning may not be considered. If the height of the multitype tree node is equal to MinBtSize and less than or equal to 2xMinTtSize, further vertical partitioning may not be considered. When partitioning is not considered, the encoding apparatus may omit signaling of partitioning information. In this case, the decoding apparatus may derive partitioning information with a default value. Meanwhile, a CTU can include one luma sample encoding block (hereafter referred to as the "luma block") and two corresponding chroma sample encoding blocks (hereafter referred to as the "chroma blocks"). The encoding tree scheme described above can be applied equally or separately to the luma block and the chroma block of the current CU. Specifically, the luma and chroma blocks in a CTU can be partitioned into the same block tree structure, in which case the tree structure is represented as SINGLE_TREE. Alternatively, the luma and chroma blocks in a CTU can be partitioned into separate block tree structures, in which case the tree structure can be represented as DUAL_TREE.In other words, when the CTU is partitioned into dual trees, the block tree structure for the luma block and the block tree structure for the chroma block can be separate. In this case, the block tree structure for the luma block can be called DUAL_TREE_LUMA, and the block tree structure for the chroma component can be called DUAL_TREE_CHROMA. For segment / tile groups P and B, the luma and chroma blocks in a CTU can simply have the same encoding tree structure. However, for segment / tile groups I, the luma and chroma blocks can have separate block tree structures. If separate block tree structures are applied, the luma CTB can be partitioned into CUs based on one particular encoding tree structure, and the chroma CTB can be partitioned into chroma CUs based on another encoding tree structure.That is, this means that a CU in a segment / mosaic group I, to which the separate block tree structure is applied, can include a luma component encoding block or two chroma component encoding blocks, and a CU of a segment / mosaic group P or B can include three color component blocks (one luma component and two chroma components). Although a quaternary tree encoding tree structure with a nested multitype tree has been described, a structure in which a CU is partitioned is not limited to it. For example, the BT structure and the TT structure can be interpreted as a concept included in a multi-partition tree (MPT) structure, and the CU can be interpreted as partitioned through the QT structure and the MPT structure. In an example where the CU is partitioned through a QT structure and an MPT structure, a syntactic element (e.g., MPT_split_type) that includes information about how many blocks the leaf node of the QT structure is partitioned into and a syntactic element (e.g., MPT_split_mode) that includes information about which of the vertical and horizontal directions the leaf node of the QT structure is partitioned in can be signaled to determine a partitioning structure. In another example, the CU can be partitioned differently than in the QT, BT, or TT structures. That is, unlike the QT structure, where the shallower CU is partitioned into 1 / 4 of the deeper CU, the BT structure into 1 / 2 of the deeper CU, or the TT structure into 1 / 4 or 1 / 2 of the deeper CU, the shallower CU can be divided into 1 / 5, 1 / 3, 3 / 8, 3 / 5, 2 / 3, or 5 / 8 of the deeper CU, and the CU partitioning method is not limited to these. The quaternary tree encoding block structure with the multi-type tree can provide a very flexible block partitioning structure. Due to the partitioning types supported in a multi-type tree, different partitioning patterns can potentially result in the same encoding block structure in some cases. In the encoding and decoding apparatus, limiting the occurrence of such redundant partitioning patterns can reduce the amount of partitioning information data. Image encoding / decoding based on subimages A target encoding image can be partitioned into multi-CTU units, segments, tiles, or bricks, and an image can be partitioned into multi-sub-image units. Within the image, a sub-image can be encoded or decoded independently of whether a previous sub-image is encoded or decoded. For example, different quantization or different resolutions can be applied to multiple sub-images. Furthermore, each sub-image can be processed as a separate image. For example, a target encoding image can be a projected image or an image packaged within an omnidirectional image / video or a 360-degree image / video. In such an embodiment, a portion of an image can be rendered or displayed based on the graphics window of a user terminal (e.g., a head-mounted display). Therefore, to implement low latency among the sub-images that make up an image, at least one sub-image covering the graphics window can be encoded or decoded, preferably or independently of the remaining sub-images. The result of encoding the sub-image can be called a bitstream, substream, or simply bitstream. The decoding apparatus can decode the sub-image from the bitstream, substream, or bitstream. In this case, a high-level syntax (HLS) such as a PPS, SPS, VPS, and / or a decoding parameter set (DPS) can be used to encode / decode the sub-image. In this description, high-level syntax (HLS) may include at least one of the following syntaxes: APS, PPS, SPS, VPS, DPS, or SH. For example, APS (APS syntax) or PPS (PPS syntax) may include information / parameters that can commonly be applied to one or more segments or images. SPS (SPS syntax) may include information / parameters that can commonly be applied to one or more sequences. VPS (VPS syntax) may include information / parameters that can commonly be applied to multiple layers. DPS (DPS syntax) may include information / parameters that can commonly be applied to the overall video. For example, DPS may include information / parameters related to the concatenation of a condensed video sequence (CVS). The subimage can define a rectangular region of the encoded image. The size of the subimage can be set differently within the image. For all images belonging to a sequence, the size and location of a particular separate subimage can be set the same. The separate subimage sequence can be decoded independently. A tile and a segment (and CTB) can be restricted so as not to span a subimage boundary. To this end, the encoding apparatus can perform encoding in such a way that the subimages are decoded independently. Semantic restrictions on the bitstream may be required for this purpose. Furthermore, for each image in a sequence, the arrangement of tiles, segments, and bricks within the subimage can be configured differently. Subimage design aims to abstract or encapsulate an interval smaller than an image level but larger than a group of segments or tiles. Consequently, a VCL NAL unit from a subset of Motion Constraint Tile Sets (MCTS) can be extracted from a VVC bitstream, and processing, such as reorganizing it into another VVC bitstream, can be performed as easily as modification at the VCL level. In this case, MCTS is an encoding technology that allows spatial and temporal independence between tiles. When MCTS is applied, information about tiles not included in the MCTS to which the current tile belongs cannot be referenced. When the image is partitioned into MCTS and encoded, independent transmission and encoding of the MCTS are possible.Such a sub-image design has the advantage of changing the display orientation in continuous 360° transmission schemes dependent on the mixed resolution graphics window. From now on, an image encoding / decoding method using a segment / mosaic will be described with reference to FIGS.8 and 9. FIG. 8 is a flowchart illustrating a method of encoding an image using a segment / mosaic by means of an image encoding apparatus according to an embodiment of the present description. The image encoding apparatus can derive segment(s) / mosaic(s) in a current image by partitioning the current image (E810). The image encoding apparatus can encode the current image based on the derived segment(s) / mosaic(s) in stage E810 (E820). FIG. 9 is a flowchart illustrating a method of decoding an image using a segment / mosaic by means of an image decoding apparatus according to an embodiment of the present description. The image decoding device can acquire information about a video / image from a bitstream (E910). Furthermore, the image decoding apparatus can derive segment(s) / tile(s) in a current image based on the video / image information acquired in stage E910 (E920). Here, the video / image information may include information about the segment(s) / tile(s). Next, the image decoding apparatus can decode the current image based on the derived segment(s) / mosaic(s) in stage E920 (E930). In Figures 8 and 9, the segment / tile information may include various information and / or syntactic elements described herein. The video / image information may include high-level syntax, and the high-level syntax may include segment and / or tile information. The high-level syntax may include an image header, and the image header information may be included in the segment header described herein. The segment information may include information specifying one or more segments, and the tile information may include information specifying one or more tiles. A segment that includes one or more tiles may be present in the image. High-level syntax signaling (HLS) As described above, high-level syntax can be encoded / signaled for video / image encoding. The signaling and syntactic elements in an image header and a segment header will be described below. Image header and segment header An encoded image can consist of one or multiple segments. The parameters for an encoded image are signaled within an Image Header (PH), and the parameters for a segment are signaled within a Segment Header (SH). The PH is carried in its own type of NAL unit. The SH may be present at the beginning of an NAL unit containing a segment's payload (i.e., segment data). Hereafter, the syntactic element(s) of the PH and SH and the semantics of the syntactic elements will be described with reference to Figure 10 and Figure 11. Figure 10 is a view showing an example of the present description of a signal and a syntactic element in an image header. `picture_header_rbsp()` contains information that is common to all segments of the encoded image associated with the picture header (PH). For example, `picture_header_rbsp()` might include a reference image flag (`non_reference_picture_flag`), GDR image identification information (`gdr_pic_flag`), `no_output_of_prior_pics_flag`, `recover` and `_poc_cnt`, `ph_pic_parameter_set_id`, or similar. Here, `recover` and `_poc_cnt` are flagged in `picture_header_rbsp()` when `gdr_pic_flag` is 1. A first value (e.g., 1) of non_reference_picture_flag specifies that the image associated with the pH is not used as a reference image. A second value (e.g., 0) of non_reference_picture_flag specifies that the image associated with the pH may or may not be used as a reference image. A first value (e.g., 1) of gdr_pic_flag specifies that the image associated with the PH is a GDR image. A second value (e.g., 0) of gdr_pic_flag specifies that the image associated with the PH is not a GDR image. no_output_of_prior_pics_flag affects the output of previously decoded images in the DPB after decoding a Coded Layer Video Sequence (CLVSS) image that is not the first image in the bitstream. `recover` and `_poc_cnt` specify the recovery point of the decoded images in output order. `ph_pic_parameter_set_id` specifies the value of `pps_pic_parameter_set_id` for the image parameter set (PPS) in use. `pps_pic_parameter_set_id` is a value used to identify the PPS that will be referenced in other syntax. The syntactic elements included in the syntactic structure picture_header_rbsp() of FIG. 10 can be included and pointed to in the syntactic structure picture_header_structure(). In this case, the syntactic structure picture_header_structure() can be included and pointed to in the syntactic structure picture_header_rbsp(). FIG. 11 is a view showing a syntactic structure of a segment header according to one implementation of the present description. As shown in FIG. 11, picture_header_in_slice_header_flag, picture_header_structure(), slice_subpic_id, slice_address, num_tiles_in_slice_minus1 or similar can be signaled through a segment header. In the example shown in FIG. 11, `picture_header_in_slice_header_flag` specifies whether an image header syntactic structure is present in a segment header syntactic structure. A first value (e.g., 1 or True) of `picture_header_in_slice_header_flag` specifies that the image header is present in the segment header, and a second value (e.g., 0 or False) of `picture_header_in_slice_header_flag` specifies that the image header is not present in the segment header. `picture_header_structure()` can be acquired based on `picture_header_in_slice_header_flag`. For example, `picture_header_structure()` can be signaled when `picture_header_in_slice_header_flag` has a first value. When `picture_header_in_slice_header_flag` has a second value, `picture_header_structure()` may not be included in the segment header, but may be included and signaled in a separate NAL unit. `slice_subpic_id` can be information about a sub-image identifier to identify a sub-image that includes a current segment. `slice_subpic_id` can be acquired based on `subpics_present_flag`. For example, `slice_subpic_id` can be signaled when `subpics_present_flag` is 1. `subpics_present_flag` can specify whether a sub-image is present in the current image or whether information about a sub-image is present in the bitstream. For example, a first value (e.g., 1 or True) of `subpics_present_flag` can specify that information about a sub-image is present in the bitstream or that one or more sub-images are present in the current image. A second value (e.g., 0 or False) of `subpics_present_flag` can specify that information about a sub-image is not present in the bitstream or that a sub-image is not present in the current image. `slice_address` can specify the address of the current segment within the current image. `slice_address` can be derived based on `rect_slice_flag` and / or `NumTilesInPic`. For example, when `rect_slice_flag` is a first value (e.g., 1 or True) or `NumTilesInPic` is greater than 1, `slice_address` can be signaled in the segment header. At this point, `rect_slice_flag` can be used to indicate whether the segment included in the current image is rectangular. For example, `rect_slice_flag` can be signaled at the image level (PPS or image header). Additionally, `NumTilesInPic` can specify the number of tiles included in the current image. `num_tiles_in_slice_minus1` can specify the number of tiles included in the current slice. `num_tiles_in_slice_minus1` can be inferred based on `rect_slice_flag` and `NumTilesInPic`. For example, when `rect_slice_flag` is a second value (e.g., 0 or False) and `NumTilesInPic` is greater than 1, `num_tiles_in_slice_minus1` can be flagged in the slice header. In the embodiment shown in FIG. 11, the following may be included as a bitstream conformance requirement associated with picture_header_in_slice_header_flag. To satisfy bitstream conformity, the value of picture_header_in_slice_header_flag is required to be the same in all segments of a CLVS. Additionally, when picture_header_in_slice_header_flag is a first value (e.g., 1), to satisfy bitstream conformity, it is required that a NAL unit with a NAL unit type equal to PH_NUT is not present in the CLVS. Additionally, when picture_header_in_slice_header_flag is a second value (e.g., 0), to satisfy bitstream conformity, a NAL unit with a NAL unit type equal to PH_NUT is required to be present in the PU, preceding the first VCL NAL unit of the PU. FIG.12 is a flowchart illustrating a method of parsing and decoding the segment header of FIG.11. First, the picture decoding apparatus can acquire a first indicator (picture_header_in_slice_header_flag) included in the segment header (E1210). The first indicator can specify whether an image header is present in the segment header. Additionally, the first indicator can specify whether the current image includes only one segment. When the first indicator is a first value (e.g., 1 or True) (stage E1220-Yes), the image decoding apparatus can acquire an image header from the segment header (E1230). When the first indicator is a second value (e.g., 0 or False) (stage E1220-No), the image header can be acquired from the image header NAL unit instead of the segment header (not shown). Next, you can determine whether `subpics_present_flag` is a first value (e.g., 1 or True) in step E1240. `subpics_present_flag` can specify whether the current image includes a subimage. Furthermore, `subpics_present_flag` can specify whether information about a subimage is included in the bitstream. `subpics_present_flag` can be signaled at a higher level within a segment. For example, `subpics_present_flag` can be included and signaled within a sequence parameter set. When subpics_present_flag is a first value (e.g., 1 or True) (step E1240-Yes), the image decoding apparatus can acquire slice_subpic_id from the segment header (E1250). When subpics_present_flag is a second value (e.g., 0 or False) (step E1240-No), the image decoding apparatus can skip the parsing of slice_subpic_id from the segment header. Next, in step E1260, it can be determined whether rect_slice_flag is a first value (e.g., 1 or True) and / or NumTilesInPic is greater than 1. rect_slice_flag can be an indicator that shows whether the segment included in the current image is a rectangular segment. For example, rect_slice_flag can be signaled at the image level (PPS or image header). Additionally, NumTilesInPic can specify the number of tiles included in the current image. When rect_slice_flag is a first value (e.g., 1 or True) or NumTilesInPic is greater than 1 (stage E1260-Yes), the image decoding apparatus can acquire slice_address from the segment header (E1270). When rect_slice_flag is a second value (e.g., 0 or False) and NumTilesInPic is not greater than 1 (stage E1260-No), the image decoding apparatus can skip parsing slice_address from the segment header. Next, in step E1280, you can determine if rect_slice_flag is a first value (e.g., 1 or True) and / or if NumTilesInPic is greater than 1. When rect_slice_flag is a first value (e.g., 1 or True) or NumTilesInPic is not greater than 1 (stage E1280-No), the image decoding apparatus can omit (skip) the parsing of num_tiles_in_slice_minus1 from the segment header. When rect_slice_flag is a second value (e.g., 0 or False) and NumTilesInPic is greater than 1 (stage E1280-Yes), the image decoding apparatus can acquire num_tiles_in_slice_minus1 from the segment header (E1290). Next, the image decoding apparatus can decode the segment header by syntactically analyzing subsequent, unshown syntactic elements of the segment header. FIG. 13 is a flowchart illustrating a method of encoding the segment header of FIG. 11. First, the picture encoding device can determine the value of a first flag (picture_header_in_slice_header_flag) and encode the first flag in the segment header (E1310). When the first flag is a first value (e.g., 1 or True) (stage E1320-Yes), the picture encoding device can encode the picture header in the segment header (E1330). When the first flag is a second value (e.g., 0 or False) (stage E1320-No), the picture header is not encoded in the segment header but can be included and signaled in the picture header NAL unit (not shown). Next, in step E1340, it can be determined whether `subpics_present_flag` is a first value (e.g., 1 or True). `subpics_present_flag` can be determined and signaled at a higher segment level. For example, `subpics_present_flag` can be included and signaled in the sequence parameter set. When `subpics_present_flag` is a first value (e.g., 1 or True) (step E1340-Yes), the image encoding apparatus can encode `slice_subpic_id` in the segment header (E1350). When `subpics_present_flag` is a second value (e.g., 0 or False) (step E1340-No), the image encoding apparatus can omit (skip) encoding `slice_subpic_id` in the segment header. Next, in step E1360, you can determine if rect_slice_flag is a first value (e.g., 1 or True) and / or if NumTilesInPic is greater than 1. When rect_slice_flag is a first value (e.g., 1 or True) or when NumTilesInPic is greater than 1 (stage E1360-Yes), the image encoding appliance can encode slice_address in the segment header (E1370). When rect_slice_flag is a second value (e.g., 0 or False) and NumTilesInPic is not greater than 1 (stage E1360-No), the image encoding appliance can skip encoding slice_address in the segment header. Next, in step E1380, you can determine if rect_slice_flag is a first value (e.g., 1 or True) and / or if NumTilesInPic is greater than 1. When rect_slice_flag is a first value (e.g., 1 or True) or when NumTilesInPic is not greater than 1 (stage E1380-No), the image encoding apparatus can omit (skip) the encoding of num_tiles_in_slice_minus1 in the segment header. When rect_slice_flag is a second value (e.g., 0 or False) and NumTilesInPic is greater than 1 (stage E1380-Yes), the image encoding apparatus can encode num_tiles_in_slice_minus1 in the segment header (E1390). Next, the image encoding apparatus can encode the segment header, encoding subsequent syntactic elements, which are not shown, in the segment header. In the example described with reference to FIGS. 12 and 13, some steps can be changed or omitted. For example, the conditions related to the encoding / decoding of slice_address and / or num_tiles_in_slice_minus1 can be changed. A method for improving the realization described with reference to FIGS.11 to 13 will now be described, taking into account the encoding / decoding of an image based on a sub-image. The image encoding device can encode the current image based on a sub-image. Alternatively, the image encoding device can encode at least one sub-image that makes up the current image and generate a bitstream that includes encoded information from the at least one encoded sub-image. The image decoding device can decode at least one sub-image included in the current image based on the bitstream that includes encoded information from at least one sub-image. As described earlier, `picture_header_in_slice_header_flag` can specify whether an image header is present in the segment header. Additionally, `picture_header_in_slice_header_flag` can be used to specify whether the current image includes only one segment or multiple segments. When the current image includes only one segment, since that segment is the only segment in the current image, some syntactic elements in the segment header have fixed values. In this case, it can be efficient not to flag some of these fixed-valued syntactic elements. The following sections will describe various configurations of the system described herein to achieve efficient signaling. These configurations can be applied to the implementations of this system individually or in combination. Configuration 1 When the current image includes only one segment, the signaling of some syntactic elements in the segment header can be skipped (omitted). The value of the syntactic element whose signaling is omitted can be derived or inferred by the image encoding and / or image decoding apparatus. If the current image includes only one segment, this can be indicated by a predefined indicator. Therefore, when the indicator shows that the current image includes only one segment, some syntactic elements may not be included in the segment header, and their values ​​may need to be inferred or derived. In this case, the indicator can be used as a condition to determine whether certain syntactic elements are included in the segment header. Configuration 2 The indicator described in Configuration 1 could be, for example, picture_header_in_slice_header_flag. Configuration 3 A syntactic element in the segment header, whose signaling can be omitted depending on the value of picture_header_in_slice_header_flag, may include at least one of (a) or (b) below. (a) Syntactic element(s) that specifies the subimage that includes the segment The reason the signaling of syntactic element (a) can be omitted is that, when only one segment is included per image, it is obvious that no sub-image is specified. For example, when `picture_header_in_slice_header_flag` indicates that the current image includes only one segment, since the current image is not encoded / decoded based on the sub-image, the signaling of information in the sub-image can be omitted. (b) syntax element(s) that specifies (n) the segment address The reason the signaling of syntactic element (b) can be omitted is because it is obvious that the segment is the only first segment in the image. For example, when picture_header_in_slice_header_flag indicates that the current image includes only one segment, since the current segment is the only segment in the current image, the direction signaling for the current segment can be omitted. Configuration 4 When each image in the sequence has only one segment, the sub-image is not used. For example, `subpics_present_flag` or `subpic_info_present_flag`, which is a syntactic element for the sub-image, can be limited to a second value (e.g., 0 or False). `subpics_present_flag` or `subpic_info_present_flag` can specify whether a sub-image is present in the current image or whether information about a sub-image is present in the bitstream. `subpics_present_flag` or `subpic_info_present_flag` can be included and flagged in the sequence parameter set, for example. Similarly, when `subpics_present_flag` or `subpic_info_present_flag` is a first value (e.g., 1 or True), a flag indicating whether each image in the sequence includes only one segment, or a flag (e.g., `picture_header_in_slice_header_flag`) indicating whether an image header is present in the segment header, may not indicate that the current image includes only one segment and may not indicate that an image header is present in the segment header. Therefore, for example, when `subpics_present_flag` or `subpic_info_present_flag` is a first value (e.g., 1 or True), `picture_header_in_slice_header_flag` may be limited to having a second value (e.g., 0 or False). Configuration 5 When an image header is not present in the image header NAL unit but is present in the segment header, in a CLVS of a particular layer (layer A), the image headers of all layers that refer to layer A (i.e., layers dependent on layer A) and all layers referred to by layer A may be restricted to being present in the segment header, not in the image header NAL unit. The above restriction is imposed to simplify the detection of image boundaries within an access unit for the case of multilayer bitstreaming. FIG. 14 is a view showing the syntactic structure of a segment header according to another realization of the present description. Since the description of the same syntactic elements and the same signaling conditions are the same in the segment header structure according to the realization of FIG. 14 and the segment header structure according to the realization of FIG. 11, a repeated description will be omitted. According to the implementation in FIG. 14, the condition for signaling slice_subpic_id can be changed. Specifically, the segment header can include slice_subpic_id based on subpics_present_flag and picture_header_in_slice_header_flag. For example, when subpics_present_flag is a first value (e.g., 1 or True) and picture_header_in_slice_header_flag is a second value (e.g., 0 or False), slice_subpic_id can be signaled in the segment header. This is because, as described above, when picture_header_in_slice_header_flag has a first value, the current image includes only one segment, and no sub-image encoding / decoding is performed; therefore, signaling sub-image information is unnecessary. Furthermore, according to the implementation in FIG. 14, the condition for signaling slice_address can be changed. Specifically, the segment header can include slice_address based on rect_slice_flag, NumTilesInPic, and picture_header_in_slice_header_flag. For example, when rect_slice_flag is a first value (e.g., 1 or True) or NumTilesInPic is greater than 1, and picture_header_in_slice_header_flag is a second value (e.g., 0 or False), slice_address can be signaled in the segment header. This is because, as described earlier, when picture_header_in_slice_header_flag has a first value, since the current image includes only one segment, signaling the segment address information is unnecessary. In the implementation of FIG. 14, a bitstream conformance requirement for picture_header_in_slice_header_flag can be improved as follows. First, the value of picture_header_in_slice_header_flag is required to be the same in all slices in the CLVS. Furthermore, when picture_header_in_slice_header_flag is a first value (e.g., 1), a NAL unit with a NAL unit type equal to PH_NUT is not required in the CLVS. This is because the picture header is included and signaled in the segment header, and therefore a separate NAL unit is not needed to transmit the picture header. Furthermore, when picture_header_in_slice_header_flag is a second value (e.g., 0), a NAL unit with a NAL unit type equal to PH_NUT is required in the PU, preceding the first VCL NAL unit in the PU. In other words, the current PU is required to have the PH NAL unit. This is because a separate NAL unit is needed to transmit the picture header. Furthermore, when subpics_present_flag or subpic_info_present_flag is a first value (e.g., 1), picture_header_in_slice_header_flag is not required to be a first value (e.g., 1). In this case, picture_header_in_slice_header_flag can simply have a second value (e.g., 0). In the example in FIG. 14, slice_subpic_id indicates the identifier of the subimage that includes the segment. When slice_subpic_id is present, a SubPicIdx variable is obtained such that SubpicIdList[SubPicIdx] is equal to slice_subpic_id. When slice_subpic_id is not present, a SubPicIdx variable can be obtained and set to 0. In the example in FIG. 14, the length (bit length) of slice_subpic_id can be derived as follows. If sps_subpic_id_signalling_present_flag is equal to 1, the length of slice_subpic_id is calculated to be equal to sps_subpic_id_len_minus1 + 1. In this case, sps_subpic_id_signalling_present_flag can specify whether the sub-image identifier is signaled in the sequence parameter set. sps_subpic_id_len_minus1 is the length information for the sub-image identifier and can be included and signaled in the sequence parameter set. Otherwise (if sps_subpic_id_signalling_present_flag is not 1), if ph_subpic_id_signalling_present_flag is 1, the length of slice_subpic_id can be derived to be equal to ph_subpic_id_len_minus1 + 1. In this case, ph_subpic_id_signalling_present_flag can specify whether the sub-image identifier is signaled in the image header. ph_subpic_id_len_minus1 is the length information of the sub-image identifier and can be included and signaled in the image header. Otherwise (if both sps_subpic_id_signalling_present_flag and ph_subpic_id_signalling_present_flag are not 1), if pps_subpic_id_signalling_present_flag is 1, the length slice_subpic_id can be derived to be equal to pps_subpic_id_len_minus1 + 1. In this case, pps_subpic_id_signalling_present_flag can specify whether the subpicture identifier is flagged in the image parameter set. pps_subpic_id_len_minus1 is the sub-image identifier length information and can be included and signaled in the image parameter set. Otherwise (if all sps_subpic_id_signalling_present_flag, ph_subpic_id_signalling_present_flag, and pps_subpic_id_signalling_present_flag are not 1), the length of slice_subpic_id can be derived to be equal to Ceil(Log2(sps_num_subpics_minus1 + 1)). sps_num_subpics_minus1 is the number of sub-images for each image in the CLVS and can be included and signaled in the sequence parameter set. slice_address specifies the segment address of the current segment. When slice_address is not present, it is inferred that the value of slice_address is equal to 0. picture_header_structure() may include at least one syntactic element included in picture_header_rbsp() described with reference to FIG.10. FIG.15 is a flowchart illustrating a method of parsing and decoding the segment header of FIG.14. Stages E1510 to E1530 in FIG. 15 are the same as stages E1210 to E1230 in FIG. 12, respectively, and therefore a repeated description of them will be omitted. Stages E1540 to E1570 in FIG. 15 may correspond to stages E1240 to E1270 in FIG. 12, respectively. Therefore, a repeated description of the common portions will be omitted. According to the implementation of FIG. 15, in step E1540, it is possible to determine whether subpics_present_flag is a first value (e.g., 1 or True) and whether a first indicator is a second value (e.g., 0 or False). When subpics_present_flag is a first value and the first flag is a second value (step E1540-Yes), the image decoding apparatus can acquire slice_subpic_id from the segment header (E1550). When subpics_present_flag is a second value (e.g., 0 or False) or the first flag is a first value (e.g., 1 or True) (step E1540-No), the image decoding apparatus can omit (skip) parsing slice_subpic_id from the segment header. Next, in step E1560, it can be determined whether rect_slice_flag is a first value (e.g., 1 or True) or whether NumTilesInPic is greater than 1 and whether the first flag is a second value (e.g., 0 or False). When rect_slice_flag is a first value or NumTilesInPic is greater than 1 and the first flag is a second value (step E1560-Yes), the image decoding apparatus can acquire slice_address from the segment header (E1570). When rect_slice_flag is a second value (e.g., 0 or False) and NumTilesInPic is not greater than 1 or the first flag is a first value (e.g., 1 or True) (E1560-No step), the image decoding apparatus can omit (skip) the slice_address parsing of the segment header. Stages E1580 to E1590 in FIG. 15 are the same as stages E1280 to E1290 in FIG. 12, respectively, and therefore a repeated description of them will be omitted. As described with reference to FIG. 12, the image decoding apparatus can decode the segment header by syntactically analyzing subsequent, unshown syntactic elements of the segment header. FIG. 16 is a flowchart illustrating a method of encoding the segment header of FIG. 14. Stages E1610 to E1630 in FIG. 16 are the same as stages E1310 to E1330 in FIG. 13, respectively, and therefore a repeated description of them will be omitted. Stages E1640 to E1670 in FIG. 16 may correspond to stages E1340 to E1370 in FIG. 16, respectively. Therefore, a repeated description of the common portions will be omitted. According to the implementation of FIG. 16, in step E1640, it can be determined whether subpics_present_flag is a first value (e.g., 1 or True) and a first indicator is a second value (e.g., 0 or False). When subpics_present_flag is a first value and the first flag is a second value (stage E1640-Yes), the image encoding apparatus can encode slice_subpic_id in the segment header (E1650). When subpics_present_flag is a second value (e.g., 0 or False) or the first flag is a first value (e.g., 1 or True) (stage E1640-No), the image encoding apparatus can omit (skip) the encoding of slice_subpic_id in the segment header. Next, in step E1660, it can be determined whether rect_slice_flag is a first value (e.g., 1 or True) or whether NumTilesInPic is greater than 1 and a first flag is a second value (e.g., 0 or False). When rect_slice_flag is a first value or NumTilesInPic is greater than 1 and the first flag is a second value (step E1660-Yes), the image encoding apparatus can encode slice_address in the segment header (E1670). When rect_slice_flag is a second value (e.g., 0 or False) and NumTilesInPic is not greater than 1 or the first flag is a first value (e.g., 1 or True) (step E1660-No), the image encoding apparatus can skip encoding slice_address in the segment header. Stages E1680 to E1690 in FIG. 16 are the same as stages E1380 to E1390 in FIG. 13, respectively, and therefore a repeated description of them will be omitted. As described with reference to FIG. 13, the image coding apparatus can encode the segment header, encoding subsequent syntactic elements, which are not shown, in the segment header. In the example described with reference to FIGS. 15 and 16, some steps can be changed or omitted. For example, the conditions related to the encoding / decoding of slice_address and / or num_tiles_in_slice_minus1 can be changed. As a modified example of the implementations described with reference to Figures 14 to 16, the improved restrictions on `picture_header_in_slice_header_flag` are applicable to the implementation shown in Figure 11. In this case, at least some of the problems of the conventional methods can be resolved. Specifically, for example, the value of `picture_header_in_slice_header_flag` can be restricted based on information about a sub-image (`subpics_present_flag` or `subpic_info_present_flag`) signaled at a higher level of the segment header. More specifically, when `subpics_present_flag` or `subpic_info_present_flag` is a first value, `picture_header_in_slice_header_flag` can be restricted to having a second value.Therefore, when `subpics_present_flag` (or `subpic_info_present_flag`) is a first value (when information about a sub-image is present in a bitstream or the current image includes a sub-image), `picture_header_in_slice_header_flag` may indicate that an image header is not present in the segment header or that the current image does not include only a segment. In the implementation shown in Figure 14, when `subpics_present_flag` is a first value and `picture_header_in_slice_header_flag` is a second value, `slice_subpic_id` can be acquired from the segment header. However, when `subpics_present_flag` is a first value, since `picture_header_in_slice_header_flag` is limited to having a second value, it may be sufficient to check `subpics_present_flag` as the parsing condition for `slice_subpic_id`.In other words, according to this modified example, in steps E1540 and E1640, a determination as to whether the first flag is a second value can be omitted. According to this modified example, the image encoding device can encode picture_header_in_slice_header_flag, which has a second value, when subpics_present_flag or subpic_info_present_flag is a first value. Furthermore, the image decoding device can acquire picture_header_in_slice_header_flag, which has a second value, when subpics_present_flag or subpic_info_present_flag is a first value. FIG. 17 is a view showing the syntactic structure of a segment header according to another realization of the present description. Since the description of the same syntactic elements and the same signaling conditions are the same in the segment header structure according to the realization of FIG. 17 and the segment header structure according to the realization of FIG. 14, a repeated description will be omitted. According to the implementation in FIG. 17, the condition for signaling `picture_header_in_slice_header_` can be changed. Specifically, the segment header can include `picture_header_in_slice_header_flag` based on `subpics_present_flag`. For example, when `subpics_present_flag` is a first value (e.g., 1 or True), `picture_header_in_slice_header_flag` may not be signaled in the segment header. For example, when `subpics_present_flag` is a second value (e.g., 0 or False), `picture_header_in_slice_header_flag` may be signaled in the segment header. This is because, as described above, when `subpics_present_flag` has a first value, since the current image cannot contain only one segment, `picture_header_in_slice_header_flag` has a fixed value (second value). Therefore, the picture_header_in_slice_header_flag signaling is unnecessary.In this case, an image header that is signaled if picture_header_in_slice_header_flag is a first value may not be signaled through the slice header. Furthermore, according to the implementation in FIG. 17, when subpics_present_flag is a first value, slice_subpic_id can be signaled in the segment header. Henceforth, for the description of slice_address and num_tiles_in_slice_minus1, it is necessary to refer to FIG.14. In the implementation of FIG. 17, a bitstream conformance requirement for picture_header_in_slice_header_flag may be the same as those described with reference to FIG.14. FIG.18 is a flowchart illustrating a method of parsing and decoding the segment header of FIG.17. The method according to FIG. 18 and the method according to FIG. 15 differ in some conditions and order for syntactically analyzing the syntactic element, and the description of the syntactic elements that are commonly described may be the same. According to the implementation in FIG. 18, the image decoding apparatus can determine whether the value of subpics_present_flag is a second value (e.g., 0 or False) at stage E1810. When the value of subpics_present_flag is a first value (e.g., 1 or True) in step E1810, since encoding / decoding is performed on a sub-image basis, the actual image does not include only a segment. Consequently, in this case, the image decoding apparatus may not acquire picture_header_in_slice_header_flag and an image header from the segment header, but may instead acquire slice_subpic_id (E1850). When the value of subpics_present_flag is a second value in stage E1810, the picture decoding apparatus acquires a first flag (picture_header_in_slice_header_flag) from the segment header (E1820). The picture decoding apparatus can determine if the first flag is a first value (E1830) and acquire a picture header from the segment header when the first flag is a first value (E1840). When the first flag is a second value, the picture decoding apparatus does not acquire the picture header from the segment header, and in this case, the picture decoding apparatus can acquire the picture header through a separate NAL unit.When the value of subpics_present_flag is a second value in stage E1810, since encoding / decoding is not performed based on the subimage, the image decoding apparatus may not acquire information about a subimage (slice_subpic_id). Stages E1860 to E1890 in FIG. 18 are the same as stages E1560 to E1590 in FIG. 15, respectively, and therefore a repeated description of them will be omitted. As described with reference to FIG. 12, the image decoding apparatus can decode the segment header by syntactically analyzing subsequent, unshown syntactic elements of the segment header. FIG. 19 is a flowchart illustrating a method of encoding the segment header of FIG. 17. The method according to FIG. 19 and the method according to fig. 16 differ in some conditions and order for encoding the syntactic element, and the description of the syntactic elements that are commonly described may be the same. According to the implementation in FIG. 19, the image encoding apparatus can determine whether the value of subpics_present_flag is a second value (e.g., 0 or False) at step E1910. When the value of subpics_present_flag is a first value (e.g., 1 or True) in step E1910, since encoding / decoding is performed on a sub-image basis, the actual image does not include only a segment. Therefore, in this case, the image encoding apparatus may not encode picture_header_in_slice_header_flag and an image header in the segment header, but may instead encode slice_subpic_id (E1950). When the value of subpics_present_flag is a second value in stage E1910, the picture encoding apparatus can determine the value of a first flag (picture_header_in_slice_header_flag) and encode the first flag in the segment header (E1920). The picture encoding apparatus can determine if the first flag is a first value (E1930) and encode a picture header in the segment header when the first flag is a first value (E1940). When the first flag is a second value, the picture encoding apparatus may not encode the picture header in the segment header, and in this case, the picture encoding apparatus may signal the picture header through a separate NAL unit.When the value of subpics_present_flag is a second value in stage E1910, since encoding / decoding is not performed based on a sub-image, the image encoding apparatus may not encode information about a sub-image (slice_subpic_id) in the segment header. Stages E1960 to E1990 in FIG. 19 are the same as stages E1660 to E1690 in FIG. 16, respectively, and therefore a repeated description of them will be omitted. As described with reference to FIG. 13, the image coding apparatus can encode the segment header, encoding subsequent syntactic elements, which are not shown, in the segment header. In the examples described with reference to FIGS. 18 and 19, some steps may be changed or omitted. For example, the conditions related to the encoding / decoding of slice_address and / or num_tiles_in_slice_minus1 may be changed. According to the implementation of this description, it is possible to more efficiently signal information about whether an image header is present in a segment header and / or information about whether an image includes only one segment. Furthermore, according to the implementation of this description, since the information about whether the image header is present in the segment header is indicated based on whether encoding / decoding is performed based on a sub-image, it is possible to avoid signaling unnecessary information. The names of the syntactic elements described herein may include information about a location where the corresponding syntactic element is signaled. For example, a syntactic element beginning with "sps_" may mean that the corresponding syntactic element is signaled in a sequence parameter set (SPS). Furthermore, syntactic elements beginning with "pps_", "ph_", "sh_", etc., mean that the corresponding syntactic elements are signaled respectively in an image parameter set (PPS), an image header, and a segment header. Although the example methods described above are presented as a series of operations for clarity, the order in which the steps are performed is not intended to be limited, and the steps may be carried out simultaneously or in a different order as needed. To implement the method as described, the steps described may include additional steps, may include the remaining steps except for some of them, or may include other additional steps except for some of them. In this description, the image encoding or image decoding apparatus that performs a predetermined operation (step) may perform a confirmation operation (step) for a condition or situation related to the execution of the corresponding operation (step). For example, if it is described that a predetermined operation is performed when a predetermined condition is met, the image encoding or image decoding apparatus may perform the predetermined operation after determining whether the predetermined condition is met. The various embodiments of this description are not a list of all possible combinations and are intended to describe representative aspects of this description, and the aspects described in the various embodiments may be applied independently or in combination with two or more. Various embodiments of this description can be implemented in hardware, firmware, software, or a combination thereof. If implemented in hardware, this description can be implemented using application-specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DSPDs), programmable logic devices (PLDs), field-programmable gate arrays (FPGAs), general-purpose processors, controllers, microcontrollers, microprocessors, etc. Furthermore, the image decoding apparatus and the image encoding apparatus to which the embodiments of the present description apply may be included in a multimedia broadcasting transmission and reception device, a mobile communication terminal, a home cinema video device, a digital cinema video device, a surveillance camera, a video chat device, a real-time communication device such as video communication, a mobile streaming device, a storage medium, a video camera, a video-on-demand (VoD) service provision device, an over-the-top (OTT) video device, an Internet streaming service provision device, a three-dimensional (3D) video device, a videotelephony video device, a medical video device, and the like.and can be used to process video or data signals. For example, OTT video devices can include a game console, a Blu-ray player, an internet-connected TV, a home theater system, a smartphone, a tablet, a digital video recorder (DVR), or similar devices. FIG.20 is a view showing a continuous content transmission system, to which an implementation of the present description is applicable. As shown in FIG.20, the continuous content transmission system, to which the implementation of the present description applies, may largely include an encoding server, a continuous transmission server, a web server, a media storage device, a user device, and a media input device. The encoding server compresses the content input from multimedia input devices, such as smartphones, cameras, camcorders, etc., into digital data to generate a bitstream and transmits the bitstream to the streaming server. Alternatively, when multimedia input devices such as smartphones, cameras, camcorders, etc., directly generate a bitstream, the encoding server can be bypassed. The bitstream can be generated by an image encoding method or an image encoding device, to which the implementation of this description applies, and the streaming server can temporarily store the bitstream during the transmission or reception process. The streaming server transmits the multimedia data to the user's device based on a user request via the web server, which serves as a means of informing the user about a service. When the user requests a desired service from the web server, the web server can deliver it to a streaming server, and the streaming server can then transmit multimedia data to the user. In this case, the content streaming system may include a separate control server.In this case, the control server serves to control a command / response between devices in the continuous content transmission system. The streaming server can receive content from a media storage device and / or an encoding server. For example, when content is received from the encoding server, it can be received in real time. In this case, to provide uninterrupted streaming, the streaming server may store the bitstream for a predetermined amount of time. Examples of user devices may include a mobile phone, a smartphone, a laptop computer, a digital broadcasting terminal, a personal digital assistant (PDA), a portable media player (PMP), navigation, a slate PC, a tablet PC, ultrabooks, wearable devices (e.g., smartwatches, smart glasses, head-mounted displays), digital TVs, a desktop computer, digital signage, and the like. Each server in the continuous content transmission system can be operated as a distributed server, in which case the data received from each server can be distributed. The scope of the description includes machine-executable software or commands (e.g., an operating system, an application, firmware, a program, etc.) to enable operations according to the methods of various embodiments to be executed on a device or computer, a non-transient computer-readable medium having such software or commands stored therein and executable on the device or computer. Industrial applicability The realizations in this description can be used to encode or decode an image.

Claims

1. An image decoding method comprising: acquiring a first flag, in a set of sequence parameters, specifying whether information about a sub-image is present in a bitstream; acquiring a second flag, in a segment header, specifying whether image header information is present in the segment header, when the first flag specifies that the sub-image is not present in the bitstream; acquiring an image header structure in the segment header, when the second flag specifies that image header information is present in the segment header; acquiring an identifier of a sub-image that includes a segment related to the segment header when the first flag specifies that information about the sub-image is present in the bitstream; acquiring segment address information, in the segment header,specifying a segment address of the segment included in a current image when the segment is a rectangular segment or the number of tiles included in the current image is greater than 1, and image header information is not present in the segment header; and decoding the bitstream based on the first indicator, the second indicator, and the segment address information, wherein, when the first indicator specifies that sub-image information is present in the bitstream, the second indicator has a fixed value specifying that image header information is not present in the segment header.

2. The image decoding method of claim 1, wherein the second indicator has the same value with respect to all segments in a Coded Layer Video Sequence (CLVS).

3. The image decoding method of claim 1, wherein,1. When the second indicator specifies that the image header information is present in the segment header, a network abstraction layer unit, NAL, for transmitting the image header information is not present in a coded layer video sequence, CLVS.

2. The image decoding method of claim 1, wherein, when the second indicator specifies that the image header information is not present in the segment header, the image header information is acquired from a network abstraction layer unit, NAL, with a NAL unit type equal to PH_NUT.

3. An image encoding method comprising: encoding a first indicator, in a set of sequence parameters, specifying whether information about a sub-image is present in a bitstream; encoding a second indicator, in a segment header,specifying whether image header information is present in the segment header, when the first indicator specifies that the subimage is not present in the bitstream; encoding an image header structure in the segment header, when the second indicator specifies that image header information is present in the segment header; encoding an identifier of a subimage that includes a segment related to the segment header when the first indicator specifies that information about the subimage is present in the bitstream; encoding segment address information, in the segment header, that specifies a segment address of the segment included in a current image when the segment is a rectangular segment or the number of tiles included in the current image is greater than 1,and the image header information is not present in the segment header; and encoding the bitstream based on the first flag, the second flag, and the segment address information, wherein, when the first flag specifies that the sub-image information is present in the bitstream, the second flag has a fixed value specifying that the image header information is not present in the segment header.

6. The image encoding method of claim 5, wherein the second flag has the same value with respect to all segments in a coded layer video sequence, CLVS.

7. The image encoding method of claim 5, wherein, when the second flag specifies that the image header information is not present in the segment header, the image header information is signaled through a network abstraction layer unit, NAL.with a unit type NAL equal to PH_NUT.

8. A method for transmitting a bitstream for an image, the bitstream transmission method comprising: generating the bitstream according to the method of claim 5; and transmitting the bitstream.

9. A non-transient, computer-readable recording medium that stores instructions which, when executed, cause an image encoding apparatus to perform an image encoding method, the image encoding method comprising: encoding a first indicator, in a set of sequence parameters, specifying whether information about a sub-image is present in a bitstream; encoding a second indicator, in a segment header,specifying whether image header information is present in the segment header when the first indicator specifies that the subimage is not present in the bitstream; encoding an image header structure in the segment header when the second indicator specifies that image header information is present in the segment header; encoding an identifier of a subimage that includes a segment related to the segment header when the first indicator specifies that information about the subimage is present in the bitstream; encoding segment address information in the segment header that specifies a segment address of the segment included in a current image when the segment is a rectangular segment or the number of tiles included in the current image is greater than 1.and the image header information is not present in the segment header; and encoding the bitstream based on the first flag, the second flag, and the segment address information, wherein, when the first flag specifies that the sub-image information is present in the bitstream, the second flag has a fixed value specifying that the image header information is not present in the segment header.

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