METHOD AND APPARATUS FOR GENERATING / RECEIVING MEDIA FILE BASED ON EOS SAMPLE GROUP AND METHOD FOR TRANSMITTING MEDIA FILE - Patent application

Abstract

A method and apparatus for generating / receiving a media file based on an EOS sample group, and a method for transmitting a media file are provided. The media file receiving method according to the present disclosure includes the steps of obtaining one or more tracks and sample groups from a media file, and recovering an access unit based on samples in the tracks and the sample groups, where the sample groups include a first sample group including end of sequence (EOS) information of video data to which the access unit belongs, and the first sample group includes one or more EOS NAL units and a first syntax element related to the number of the EOS NAL units.

Description

[Technical field]

[0001] The present disclosure relates to a method and apparatus for generating / receiving a media file based on an EOS sample group, and more particularly to a method and apparatus for generating / receiving a media file based on an EOS sample group including a plurality of EOS NAL units, and a method for transmitting a media file generated by the media file generation method / apparatus of the present disclosure. [Background technology]

[0002] Recently, there has been an increasing demand for high-resolution, high-quality images, such as 360-degree images. As image resolution and quality increase, file size and frame rate increase, which inevitably leads to an increase in storage and transmission costs. In addition, as mobile devices such as smartphones and tablet PCs become more popular, there has been a sharp increase in demand for communication network-based multimedia services. However, there is a problem in that hardware and network resources for multimedia services are limited.

[0003] This calls for highly efficient image compression and file processing techniques to more effectively store and transmit image data. Summary of the Invention [Problem to be solved by the invention]

[0004] The present disclosure aims to provide a method and apparatus for generating / receiving media files based on EOS sample groups.

[0005] Another object of the present disclosure is to provide a method and apparatus for generating / receiving a media file based on an EOS sample group including multiple EOS NAL units.

[0006] Another object of the present disclosure is to provide a method and apparatus for generating / receiving a media file based on an EOS sample group that includes information about the number of EOS NAL units.

[0007] Another object of the present disclosure is to provide a method and apparatus for generating / receiving a media file based on EOS sample groups that supports elementary streams with multiple layers.

[0008] Another object of the present disclosure is to provide a method for transmitting a media file generated by the media file generation method or device according to the present disclosure.

[0009] Another object of the present disclosure is to provide a recording medium storing a media file generated by the media file generating method or device according to the present disclosure.

[0010] Another object of the present disclosure is to provide a recording medium storing a media file that is received by a media file receiving device according to the present disclosure and is used to restore an image.

[0011] The technical problems to be solved by the present disclosure are not limited to the above-mentioned technical problems, and other technical problems not described above will be clearly understood by a person having ordinary skill in the art to which the present disclosure pertains from the following description. [Means for solving the problem]

[0012] A media file receiving method according to one aspect of the present disclosure includes steps of obtaining one or more tracks and sample groups from a media file, and reconstructing an access unit based on samples in the tracks and the sample groups, wherein the sample groups include a first sample group including EOS (end of sequence) information of video data to which the access unit belongs, and the first sample group includes one or more EOS NAL units and a first syntax element related to the number of the EOS NAL units.

[0013] A media file receiving device according to another aspect of the present disclosure includes a memory and at least one processor, the at least one processor obtaining one or more tracks and sample groups from a media file and reconstructing an access unit based on samples in the tracks and the sample groups, the sample groups including a first sample group including EOS (end of sequence) information for video data to which the access unit belongs, the first sample group including one or more EOS NAL units and a first syntax element related to the number of the EOS NAL units.

[0014] A media file generating method according to another aspect of the present disclosure includes the steps of encoding video data including an access unit, generating a first sample group including EOS (end of sequence) information of the encoded video data, and generating a media file based on the encoded video data and the first sample group, wherein the first sample group may include one or more EOS NAL units and a first syntax element related to a number of the EOS NAL units.

[0015] A media file generation device according to another aspect of the present disclosure includes a memory and at least one processor, wherein the at least one processor encodes video data including access units, generates a first sample group including EOS (End of Sequence) information for the encoded video data, and generates a media file based on the encoded video data and the first sample group, the first sample group including one or more EOS NAL units and a first syntax element related to a number of the EOS NAL units.

[0016] A media file transmission method according to another aspect of the present disclosure can transmit a media file generated by the media file generation method or apparatus of the present disclosure.

[0017] A computer-readable recording medium according to another aspect of the present disclosure can store a media file generated by the media file generation method or apparatus of the present disclosure.

[0018] The features described above in the brief summary of the present disclosure are merely exemplary embodiments of the detailed description of the present disclosure that follows and are not intended to limit the scope of the present disclosure. Effect of the Invention

[0019] According to the present disclosure, a method and apparatus for generating / receiving media files based on EOS sample groups can be provided.

[0020] In addition, according to the present disclosure, a method and apparatus for generating / receiving a media file based on an EOS sample group including multiple EOS NAL units can be provided.

[0021] In addition, according to the present disclosure, a method and apparatus for generating / receiving a media file based on an EOS sample group including information regarding the number of EOS NAL units can be provided.

[0022] In addition, the present disclosure provides a method and apparatus for generating / receiving a media file based on an EOS sample group that supports elementary streams having multiple layers.

[0023] Also provided is a method for transmitting a media file generated by a media file generation method or apparatus according to the present disclosure.

[0024] According to the present disclosure, a recording medium storing a media file generated by the media file generating method or device according to the present disclosure may be provided.

[0025] Furthermore, according to the present disclosure, a recording medium can be provided that stores a media file that is received by a media file receiving device according to the present disclosure and is used to restore an image.

[0026] The effects obtained by the present disclosure are not limited to the effects described above, and other effects not described above will be clearly understood by those having ordinary skill in the art to which the present disclosure pertains from the following description. [Brief description of the drawings]

[0027] [Figure 1] FIG. 1 is a schematic diagram illustrating a media file transmission and reception system according to an embodiment of the present disclosure.

[0028] [Diagram 2] 1 is a flow chart illustrating a method for transmitting a media file.

[0029] [Diagram 3] 1 is a flow chart illustrating a method for receiving a media file.

[0030] [Figure 4] FIG. 1 is a diagram illustrating an image encoding device according to an embodiment of the present disclosure.

[0031] [Diagram 5] FIG. 1 is a diagram illustrating an image decoding device according to an embodiment of the present disclosure.

[0032] [Figure 6] FIG. 2 shows an example of a hierarchical structure for coded images / video.

[0033] [Figure 7] FIG. 2 illustrates an example of a media file structure.

[0034] [Figure 8] FIG. 8 is a diagram showing an example of the trak box structure of FIG.

[0035] [Figure 9] FIG. 2 is a diagram showing an example of an image signal structure.

[0036] [Figure 10] A diagram showing the syntax structure of an EOS sample group entry.

[0037] [Figure 11] FIG. 1 shows an example of a truck carrying a multilayer.

[0038] [Figure 12] A diagram showing the syntax structure of an EOS sample group entry according to one embodiment of the present disclosure.

[0039] [Figure 13] A diagram showing the syntax structure of an EOS sample group entry according to another embodiment of the present disclosure.

[0040] [Figure 14] A diagram showing the syntax structure of a sample group entry of an EOS according to another embodiment of the present disclosure.

[0041] [Figure 15] 1 is a flowchart illustrating a method for receiving a media file according to an embodiment of the present disclosure.

[0042] [Figure 16] 1 is a flowchart illustrating a method for generating a media file according to one embodiment of the present disclosure.

[0043] [Figure 17] FIG. 1 illustrates a content streaming system to which an embodiment of the present disclosure can be applied. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0044] The present disclosure will be described in detail below with reference to the accompanying drawings so that those skilled in the art can easily implement the present disclosure. However, the present disclosure may be embodied in various different forms and is not limited to the embodiments described herein.

[0045] In describing the embodiments of the present disclosure, if it is determined that a specific description of a known configuration or function may make the gist of the present disclosure unclear, the detailed description thereof will be omitted. In addition, in the drawings, parts that are not related to the description of the present disclosure are omitted, and similar parts are denoted by similar reference numerals.

[0046] In the present disclosure, when a certain component is "connected," "coupled," or "connected" to another component, this includes not only a direct connection relationship, but also an indirect connection relationship in which another component exists between them. Furthermore, when a certain component is described as "including" or "having" another component, this does not mean that the other component is excluded, but that the other component can be further included, unless otherwise specified.

[0047] In this disclosure, terms such as "first" and "second" are used only for the purpose of distinguishing one component from another component, and do not limit the order or importance of the components unless otherwise specified. Therefore, within the scope of this disclosure, 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.

[0048] In this disclosure, components that are distinguished from one another are used to clearly describe the characteristics of each component, and do not necessarily mean that the components are separate. In other words, multiple components may be integrated and configured as a single hardware or software unit, or one component may be distributed and configured as multiple hardware or software units. Thus, even if not otherwise stated, such integrated or distributed embodiments are also included in the scope of the present disclosure.

[0049] In the present disclosure, the components described in the various embodiments are not necessarily essential components, and some may be optional components. Therefore, an embodiment consisting of a subset of the components described in one embodiment is also included in the scope of the present disclosure. In addition, an embodiment including other components in addition to the components described in the various embodiments is also included in the scope of the present disclosure.

[0050] The present disclosure relates to image encoding and decoding, and terms used in this disclosure may have ordinary meanings in the technical field to which the present disclosure belongs, unless they are newly defined in this disclosure.

[0051] In this disclosure, a "picture" generally means a unit indicating any one image in a particular time period, a slice / tile is a coding unit constituting a part of a picture, and one picture may be composed of one or more slices / tiles. Also, a slice / tile may include one or more coding tree units (CTUs).

[0052] In this disclosure, a "pixel" or a "pel" may refer to the smallest unit constituting one picture (or image). A term corresponding to a pixel may be a "sample." A sample may generally indicate a pixel or a pixel value, may indicate only a pixel / pixel value of a luma component, or may indicate only a pixel / pixel value of a chroma component.

[0053] In this disclosure, a "unit" may refer to a basic unit of image processing. A unit may include at least one of a specific region of a picture and information related to the region. A unit may be used interchangeably with terms such as "sample array," "block," or "area," depending on the case. In a general case, an M×N block may include a set (or array) of samples (or sample arrays) or transform coefficients consisting of M columns and N rows.

[0054] In the present disclosure, a "current block" may refer to any one of a "current coding block," a "current coding unit," a "block to be coded," a "block to be decoded," or a "block to be processed." If prediction is performed, a "current block" may refer to a "current predicted block" or a "block to be predicted." If transformation (inverse transformation) / quantization (inverse quantization) is performed, a "current block" may refer to a "current transformed block" or a "block to be transformed." If filtering is performed, a "current block" may refer to a "block to be filtered."

[0055] Furthermore, in this disclosure, unless there is an explicit reference to a chroma block, a "current block" may refer to a block including both a luma component block and a chroma component block, or a "luma block of the current block." The luma component block of the current block may be expressed by explicitly including the reference to a luma component block, such as a "luma block" or a "current luma block." Furthermore, the chroma component block of the current block may be expressed by explicitly including the reference to a chroma component block, such as a "chroma block" or a "current chroma block."

[0056] In the present disclosure, " / " and "," can be interpreted as "and / or." For example, "A / B" and "A, B" can be interpreted as "A and / or B." Also, "A / B / C" and "A, B, C" can mean "at least one of A, B, and / or C."

[0057] In this disclosure, "or" can be interpreted as "and / or." For example, "A or B" can mean 1) only "A," 2) only "B," or 3) "A and B." Alternatively, in this disclosure, "or" can mean "additionally or alternatively."

[0058] Overview of the media file transmission and reception system

[0059] FIG. 1 is a schematic diagram of a media file transmission and reception system according to an embodiment of the present disclosure.

[0060] 1, a media file transmission and reception system 1 may include a transmission device A and a reception device B. According to an embodiment, the media file transmission and reception system 1 may support seamless media content playback by supporting adaptive streaming based on MPEG-DASH (Dynamic Adaptive Streaming over HTTP).

[0061] The sending device A may include a video source 10 , an encoding unit 20 , an encapsulation unit 30 , a transmission processing unit 40 and a sending unit 45 .

[0062] The video source 10 may generate or acquire media data, such as videos or images, etc. To this end, the video source 10 may include a video / image capture device and / or a video / image generation device, or may be coupled to an external device to receive the media data.

[0063] The encoder 20 may encode media data input from the video source 10. The encoder 20 may perform a series of procedures such as prediction, conversion, and quantization based on a video codec standard, for example, the Versatile Video Coding (VVC) standard, for compression and encoding efficiency. The encoder 20 may output the encoded media data in a bitstream format.

[0064] The encapsulation unit 30 may encapsulate the encoded media data and / or media data related metadata. For example, the encapsulation unit 30 may encapsulate the data in a file format such as ISO Base Media File Format (BMFF) or Common Media Application Format (CMAF) or process the data in the form of a segment or the like. The media data encapsulated in a file format (hereinafter referred to as a "media file") may be stored in a storage unit (not shown) according to an embodiment. The media file stored in the storage unit may be read by the transmission processing unit 40 and transmitted to the receiving device B according to an on-demand, non-real time (NRT) or broadband method.

[0065] The transmission processor 40 can process the media file in any transmission method to generate an image signal. The media file transmission method can include a broadcast method and a broadband method.

[0066] According to the broadcast method, the media file may be transmitted using an MPEG Media transport (MMT) protocol or a Real Time Object delivery over Unidirectional Transport (ROUTE) protocol. The MMT protocol may be a transmission protocol that supports media streaming regardless of file format or codec in an IP-based network environment. When the MMT protocol is used, the media file may be processed in units of a Media Processing Unit (MPU) based on the MMT and then transmitted according to the MMT protocol. The ROUTE protocol is an extension of File Delivery over Unidirectional Transport (FLUTE) and may be a transmission protocol that supports real-time transmission of the media file. When the ROUTE protocol is used, the media file may be processed into one or more segments based on MPEG-DASH and then transmitted according to the ROUTE protocol.

[0067] According to the broadband method, media files can be transmitted over a network using HyperText Transfer Protocol (HTTP). Information transmitted over HTTP can include signaling metadata, segment information, and / or Non-Real Time (NRT) service information.

[0068] According to an embodiment, the transmission processing unit 40 may include an MPD generating unit 41 and a segment generating unit 42 to support adaptive media streaming.

[0069] The MPD generating unit 41 can generate a Media Presentation Description (MPD) based on the media file. The MPD is a file including detailed information about a media presentation and can be expressed in XML format. The MPD can provide signaling metadata, for example, an identifier for each segment. In this case, the receiving device B can dynamically obtain the segments based on the MPD.

[0070] The segment generator 42 may generate one or more segments based on a media file. The segments may contain actual media data and may have a file format such as ISO BMFF. The segments may be contained within a representation of an image signal and may be identified based on the MPD as described above.

[0071] Then, the transmission processing unit 40 can generate an image signal according to the MPEG-DASH standard based on the generated MPD and segments.

[0072] The transmitting unit 45 may transmit the generated image signal to the receiving device B. According to an embodiment, the transmitting unit 45 may transmit the image signal to the receiving device B via an IP network based on the MMT standard or the MPEG-DASH standard. According to the MMT standard, the image signal transmitted to the receiving device B may include a Presentation Information document (PI document) including playback information of the media data. According to the MPEG-DASH standard, the image signal transmitted to the receiving device B may include the above-mentioned MPD as playback information of the media data. However, according to an embodiment, the MPD and the segment may be transmitted to the receiving device B separately. For example, a first image signal including an MPD may be generated by the transmitting device A or an external server and transmitted to the receiving device B, and a second image signal including a segment may be generated by the transmitting device A2 and transmitted to the receiving device B.

[0073] 1, the transmission processing unit 40 and the transmission unit 45 are shown as separate elements, but may be integrated and realized as a single element depending on the embodiment. Also, the transmission processing unit 40 may be realized as an external device (e.g., a DASH server) separate from the transmission device A. In this case, the transmission device A may operate as a source device that encodes media data to generate a media file, and the external device may operate as a server device that processes the media data according to any transmission protocol to generate an image signal.

[0074] Next, the receiving device B may include a receiving unit 55, a receiving processing unit 60, a decapsulating unit 70, a decoding unit 80, and a rendering unit 90. According to an embodiment, the receiving device B may be an MPEG-DASH-based client.

[0075] The receiving unit 55 may receive an image signal from the transmitting device A. The image signal according to the MMT standard may include a PI document and a media file. Also, the image signal according to the MPEG-DASH standard may include an MPD and a segment. Depending on the embodiment, the MPD and the segment may be transmitted separately via different image signals.

[0076] The receiving processor 60 can process the received image signal according to a transmission protocol to extract / parse media files.

[0077] According to an embodiment, the receiving processing unit 60 may include an MPD parsing unit 61 and a segment parsing unit 62 to support adaptive media streaming.

[0078] The MPD parsing unit 61 can acquire an MPD from a received image signal, parse the acquired MPD, and generate commands required for acquiring segments. The MPD parsing unit 61 can also acquire playback information for media data, such as color conversion information, based on the parsed MPD.

[0079] The segment parsing unit 62 may obtain segments based on the parsed MPD, and parse the obtained segments to extract media files. Depending on the embodiment, the media files may have a file format such as ISO BMFF or CMAF.

[0080] The decapsulating unit 70 may decapsulate the extracted media file to obtain media data and metadata associated therewith. The obtained metadata may have the form of a box or track in a file format. According to an embodiment, the decapsulating unit 70 may receive metadata required for decapsulation from the MPD parsing unit 61.

[0081] The decoding unit 80 can decode the acquired media data based on a video codec standard, for example, the VVC standard. To this end, the decoding unit 80 can perform a series of procedures such as inverse quantization, inverse transform, and prediction corresponding to the operations of the encoding unit 20.

[0082] The rendering unit 90 can render media data such as a decoded picture or image, and the rendered media data can be played back via a display unit (not shown).

[0083] A method for transmitting and receiving a media file will now be described in detail.

[0084] FIG. 2 is a flow chart illustrating a method for transmitting a media file.

[0085] In one example, each step in Fig. 2 may be performed by the transmitting device A in Fig. 1. Specifically, step S210 may be performed by the encoding unit 20 in Fig. 1. Also, step S220 and step S230 may be performed by the transmission processing unit 40. Also, step S240 may be performed by the transmitting unit 45.

[0086] 2, the transmitting device may encode media data such as video or images (S210). The media data may be captured / generated by the transmitting device or obtained from an external device (e.g., a camera, a video archive, etc.). The media data may be encoded in a bitstream format based on a video codec standard, e.g., the VVC standard.

[0087] The transmitting device may generate an MPD and one or more segments based on the encoded media data (S220). The MPD may include detailed information about the media presentation as described above. The segments may include actual media data. Depending on the embodiment, the media data may be encapsulated in a file format such as ISO BMFF or CMAF and included in the segments.

[0088] The transmitting device may generate an image signal including the generated MPD and the segment (S230). Depending on the embodiment, the image signal may be generated separately for each of the MPD and the segment. For example, the transmitting device may generate a first image signal including the MPD and generate a second image signal including the segment.

[0089] The transmitting device may transmit the generated image signal to the receiving device (S240). According to an embodiment, the transmitting device may transmit the image signal in a broadcast manner. In this case, the MMT protocol or the ROUTE protocol may be used. Alternatively, the transmitting device may transmit the image signal in a broadband manner.

[0090] Meanwhile, in FIG. 2, it is described that the MPD and the image signal including the MPD are generated and transmitted by the transmitting device (steps S220 to S240), but depending on the embodiment, the MPD and the image signal including the MPD may be generated and transmitted by an external server different from the transmitting device.

[0091] FIG. 3 is a flow chart illustrating a method for receiving a media file.

[0092] In one example, each step in Fig. 3 may be performed by the receiving device B in Fig. 1. Specifically, step S310 may be performed by the receiving unit 55. Also, step S320 may be performed by the receiving processing unit 60. Also, step S330 may be performed by the decoding unit 80.

[0093] Referring to Fig. 3, the receiving device may receive an image signal from the transmitting device (S310). The image signal according to the MPEG-DASH standard may include an MPD and a segment. According to an embodiment, the MPD and the segment may be received separately through different image signals. For example, a first image signal including the MPD may be received from the transmitting device of Fig. 1 or an external server, and a second image signal including the segment may be received from the transmitting device of Fig. 1.

[0094] The receiving device may extract the MPD and segments from the received image signal, and parse the extracted MPD and segments (S320). Specifically, the receiving device may parse the MPD to generate commands required for acquiring the segments. The receiving device may then acquire the segments based on the parsed MPD, and parse the acquired segments to acquire the media data. Depending on the embodiment, the receiving device may perform decapsulation on the media data in a file format to acquire the media data from the segments.

[0095] The receiving device can decode the captured media data, such as video or images (S330). To decode the media data, the receiving device can perform a series of procedures, such as inverse quantization, inverse transform, and prediction. The receiving device can then render the decoded media data and play the media data through a display.

[0096] The image encoding / decoding device will now be described in detail.

[0097] Overview of the image encoding device

[0098] 4 is a diagram illustrating an image encoding device according to an embodiment of the present disclosure. The image encoding device 400 in FIG. 4 may correspond to the encoding unit 20 of the transmission device A described above with reference to FIG.

[0099] 4, the image encoding device 400 may include an image division unit 410, a subtraction unit 415, a transformation unit 420, a quantization unit 430, an inverse quantization unit 440, an inverse transformation unit 450, an addition unit 455, a filtering unit 460, a memory 470, an inter prediction unit 480, an intra prediction unit 485, and an entropy encoding unit 490. The inter prediction unit 480 and the intra prediction unit 485 may be collectively referred to as a "prediction unit." The transformation unit 420, the quantization unit 430, the inverse quantization unit 440, and the inverse transformation unit 450 may be included in a residual processing unit. The residual processing unit may further include a subtraction unit 415.

[0100] All or at least some of the components constituting the image encoding device 400 may be realized by a single hardware component (e.g., an encoder or a processor) depending on the embodiment. Also, the memory 470 may include a decoded picture buffer (DPB) and may be realized by a digital storage medium.

[0101] The image division unit 410 may divide an input image (or picture, frame) input to the image encoding device 400 into one or more processing units. As an example, the processing units may be called coding units (CUs). The coding units may be obtained by recursively dividing a coding tree unit (CTU) or a largest coding unit (LCU) according to a QT / BT / TT (Quad-tree / Binary-tree / Ternal-tree) structure. For example, one coding unit may be divided into a plurality of coding units of a deeper depth based on a quad-tree structure, a binary-tree structure, and / or a ternary-tree structure. For dividing the coding units, a quad-tree structure may be applied first, and a binary-tree structure and / or a ternary-tree structure may be applied later. A coding procedure according to the present disclosure may be performed based on a final coding unit that is not further divided. The maximum coding unit may be used as the final coding unit, and a lower depth coding unit obtained by dividing the maximum coding unit may be used as the final coding unit. Here, the coding procedure may include procedures such as prediction, transformation, and / or restoration, which will be described later. As another example, a processing unit of the coding procedure may be a prediction unit (PU) or a transform unit (TU). The prediction unit and the transform unit may be divided or partitioned from the final coding unit, respectively. The prediction unit may be a unit of sample prediction, and the transform unit may be a unit that derives transform coefficients and / or a unit that derives a residual signal from the transform coefficients.

[0102] The prediction unit (inter prediction unit 480 or intra prediction unit 485) may perform prediction on a block to be processed (current block) and generate a predicted block including prediction samples for the current block. The prediction unit may determine whether intra prediction or inter prediction is applied to the current block or CU unit. The prediction unit may generate various information related to prediction of the current block and transmit it to the entropy coding unit 490. The prediction information may be coded by the entropy coding unit 490 and output in a bitstream format.

[0103] The intra prediction unit 485 may predict the current block by referring to samples in the current picture. The referenced samples may be located in the neighborhood of the current block or may be located away from the current block according to an intra prediction mode and / or an intra prediction technique. The intra prediction modes may include a plurality of non-directional modes and a plurality of directional modes. The non-directional modes may include, for example, a DC mode and a planar mode. The directional modes may include, for example, 33 directional prediction modes or 65 directional prediction modes depending on the fineness of the prediction direction. However, this is merely an example, and more or less directional prediction modes may be used depending on the setting. The intra prediction unit 485 may also determine a prediction mode to be applied to the current block using prediction modes applied to neighboring blocks.

[0104] The inter prediction unit 480 may derive a predicted block for the current block based on a reference block (reference sample array) identified by a motion vector on a reference picture. In this case, in order to reduce the amount of motion information transmitted in the inter prediction mode, the motion information may be predicted in blocks, sub-blocks, or sample units based on the correlation of motion information between a neighboring block and the current block. The motion information may include a motion vector and a reference picture index. The motion information may further include inter prediction direction (L0 prediction, L1 prediction, Bi prediction, etc.) information. In the case of inter prediction, the neighboring block may include a spatial neighboring block present in the current picture and a temporal neighboring block present in the reference picture. The reference picture including the reference block and the reference picture including the temporal neighboring block may be the same or different from each other. The temporal neighboring block may be called a collocated reference block, a collocated CU (colCU), or the like. The reference picture including the temporal neighboring block may be called a collocated picture (colPic). For example, the inter prediction unit 480 may generate information indicating which candidate is used to derive a motion vector and / or a reference picture index of the current block by forming a motion information candidate list based on neighboring blocks. Inter prediction may be performed based on various prediction modes, and for example, in the case of skip mode and merge mode, the inter prediction unit 480 may use motion information of neighboring blocks as motion information of the current block. In the case of skip mode, unlike the merge mode, a residual signal may not be transmitted.In the case of a motion vector prediction (MVP) mode, the motion vector of the current block can be signaled by using the motion vector of a neighboring block as a motion vector predictor and encoding a motion vector difference and an indicator for the motion vector predictor. The motion vector difference can mean the difference between the motion vector of the current block and the motion vector predictor.

[0105] The prediction unit may generate a prediction signal based on various prediction methods and / or prediction techniques, which will be described later. For example, the prediction unit may apply intra prediction or inter prediction for prediction of the current block, and may simultaneously apply intra prediction and inter prediction. A prediction method that simultaneously applies intra prediction and inter prediction for prediction of the current block may be called combined inter and intra prediction (CIIP). The prediction unit may also perform intra block copy (IBC) for prediction of the current block. Intra block copy can be used for content image / video coding such as games, for example, as in screen content coding (SCC). IBC is a method of predicting a current block using an already restored reference block in a current picture that is located a predetermined distance away from the current block. When IBC is applied, the position of the reference block in the current picture may be coded as a vector (block vector) corresponding to the predetermined distance. IBC is basically performed in the current picture, but may be performed similarly to inter prediction in that a reference block is derived in the current picture. That is, the IBC may use at least one of the inter prediction techniques described in this disclosure.

[0106] The prediction signal generated by the prediction unit may be used to generate a restored signal or a residual signal. The subtraction unit 415 may subtract the prediction signal (predicted block, prediction sample array) output from the prediction unit from the input image signal (original block, original sample array) to generate a residual signal (residual block, residual sample array). The generated residual signal may be transmitted to the conversion unit 420.

[0107] The transform unit 420 may generate transform coefficients by applying a transform technique to the residual signal. For example, the transform technique may include at least one of a discrete cosine transform (DCT), a discrete sine transform (DST), a Karhunen-Loeve transform (KLT), a graph-based transform (GBT), or a conditionally non-linear transform (CNT). Here, the GBT refers to a transform obtained from a graph when the relationship information between pixels is expressed as a graph. The CNT refers to a transform obtained based on a predicted signal generated using all previously reconstructed pixels. The transform process may be applied to pixel blocks having the same square size, or may be applied to non-square, variable-sized blocks.

[0108] The quantization unit 430 may quantize the transform coefficients and transmit the quantized transform coefficients to the entropy coding unit 490. The entropy coding unit 490 may code the quantized signal (information on the quantized transform coefficients) and output the quantized transform coefficients in a bitstream format. The information on the quantized transform coefficients may be called residual information. The quantization unit 430 may rearrange the quantized transform coefficients in a block format into a one-dimensional vector format based on a coefficient scan order, and may generate information on the quantized transform coefficients based on the quantized transform coefficients in the one-dimensional vector format.

[0109] The entropy coding unit 490 may perform various coding methods, such as exponential Golomb, context-adaptive variable length coding (CAVLC), and context-adaptive binary arithmetic coding (CABAC). The entropy coding unit 190 may also code information required for video / image restoration (e.g., values ​​of syntax elements, etc.) together or separately in addition to the quantized transform coefficients. The coded information (e.g., coded video / image information) may be transmitted or stored in a network abstraction layer (NAL) unit in a bitstream format. The video / image information may further include information on various parameter sets, such as an adaptation parameter set (APS), a picture parameter set (PPS), a sequence parameter set (SPS), or a video parameter set (VPS). The video / image information may further include general constraint information. The signaling information, transmitted information and / or syntax elements referred to in this disclosure may be encoded through the above-mentioned encoding procedures and included in the bitstream.

[0110] The bitstream may be transmitted via a network or may be stored in a digital storage medium. Here, the network may include a broadcasting network and / or a communication network, and the digital storage medium may include various storage media such as a USB, SD, CD, DVD, Blu-ray, HDD, SSD, etc. A transmitting unit (not shown) for transmitting the signal output from the entropy encoding unit 190 and / or a storing unit (not shown) for storing the signal may be provided as an internal / external element of the image encoding device 100, or the transmitting unit may be provided as a component of the entropy encoding unit 490.

[0111] The quantized transform coefficients output from the quantizer 430 can be used to generate a residual signal. For example, the quantized transform coefficients can be inverse quantized and inverse transformed via the inverse quantizer 440 and the inverse transformer 450 to reconstruct a residual signal (residual block or residual sample).

[0112] The adder 455 may generate a reconstructed signal (reconstructed picture, reconstructed block, reconstructed sample array) by adding the reconstructed residual signal to a prediction signal output from the inter prediction unit 480 or the intra prediction unit 485. When there is no residual for the current block to be processed, such as when a skip mode is applied, the predicted block may be used as a reconstructed block. The adder 455 may be referred to as a reconstruction unit or a reconstructed block generator. The generated reconstructed signal may be used for intra prediction of the next current block to be processed in the current picture, and may also be used for inter prediction of the next picture after filtering as described below.

[0113] Meanwhile, luma mapping with chroma scaling (LMCS) can be applied during picture encoding and / or restoration.

[0114] The filtering unit 460 may apply filtering to the reconstructed signal to improve subjective / objective image quality. For example, the filtering unit 460 may apply various filtering methods to the reconstructed picture to generate a modified reconstructed picture, and may store the modified reconstructed picture in the memory 470, specifically, in the DPB of the memory 470. The various filtering methods may include, for example, deblocking filtering, sample adaptive offset, an adaptive loop filter, a bilateral filter, and the like. The filtering unit 460 may generate various information related to filtering, as will be described later in the description of each filtering method, and transmit the information to the entropy coding unit 490. The information related to filtering may be coded by the entropy coding unit 490 and output in a bitstream format.

[0115] The modified reconstructed picture transmitted to the memory 470 may be used as a reference picture in the inter prediction unit 480. When inter prediction is applied through this, the image encoding device 400 may avoid a prediction mismatch between the image encoding device 400 and the image decoding device, and may also improve encoding efficiency.

[0116] The DPB in the memory 470 may store modified reconstructed pictures to be used as reference pictures in the inter prediction unit 480. The memory 470 may store motion information of blocks from which motion information in the current picture is derived (or coded) and / or motion information of already reconstructed intra-picture blocks. The stored motion information may be transmitted to the inter prediction unit 480 to be used as motion information of spatial surrounding blocks or motion information of temporal surrounding blocks. The memory 470 may store reconstructed samples of reconstructed blocks in the current picture and transmit them to the intra prediction unit 485.

[0117] Overview of the image decoding device

[0118] 5 is a diagram illustrating an image decoding device according to an embodiment of the present disclosure. The image decoding device 500 in FIG. 5 may correspond to the decoding unit 80 of the receiving device A described above with reference to FIG.

[0119] 5, the image decoding apparatus 500 may include an entropy decoding unit 510, an inverse quantization unit 520, an inverse transform unit 530, an adder 535, a filtering unit 540, a memory 550, an inter prediction unit 560, and an intra prediction unit 565. The inter prediction unit 560 and the intra prediction unit 565 may be collectively referred to as a "prediction unit." The inverse quantization unit 520 and the inverse transform unit 530 may be included in a residual processing unit.

[0120] All or at least some of the components constituting the image decoding device 500 can be realized by one hardware component (e.g., a decoder or a processor) depending on the embodiment. Also, the memory 550 can include a DPB and can be realized by a digital storage medium.

[0121] The image decoding device 500, which receives a bitstream including video / image information, can reconstruct an image by executing a process corresponding to the process performed by the image encoding device 400 of FIG. 4. For example, the image decoding device 500 can perform decoding using a processing unit applied in the image encoding device. Thus, the processing unit for decoding can be, for example, a coding unit. The coding unit can be obtained by dividing a coding tree unit or a maximum coding unit. Then, the reconstructed image signal decoded and output by the image decoding device 500 can be reproduced by a reproduction device (not shown).

[0122] The image decoding apparatus 500 may receive a signal generated by the image encoding apparatus of FIG. 4 in a bitstream format. The received signal may be decoded via an entropy decoding unit 510. For example, the entropy decoding unit 510 may derive information (e.g., video / image information) required for image reconstruction (or picture reconstruction) by parsing the bitstream. The video / image information may further include information on various parameter sets such as an adaptation parameter set (APS), a picture parameter set (PPS), a sequence parameter set (SPS), or a video parameter set (VPS). In addition, the video / image information may further include general constraint information. The image decoding apparatus may further use information on the parameter set and / or the general constraint information to decode an image. The signaling information, received information, and / or syntax elements referred to in the present disclosure may be obtained from the bitstream by being decoded via the decoding procedure. For example, the entropy decoding unit 510 may decode information in a bitstream based on a coding method such as exponential Golomb coding, CAVLC, or CABAC, and output values ​​of syntax elements required for image restoration and quantized values ​​of transform coefficients related to the residual. More specifically, the CABAC entropy decoding method may receive bins corresponding to each syntax element from the bitstream, determine a context model using syntax element information to be decoded and decoded information of neighboring blocks and a block to be decoded, or information of a symbol / bin decoded in a previous step, predict the occurrence probability of the bin based on the determined context model, and perform arithmetic decoding of the bin to generate a symbol corresponding to the value of each syntax element. In this case, the CABAC entropy decoding method may update the context model using information of the decoded symbol / bin for the context model of the next symbol / bin after determining the context model.Among the information decoded by the entropy decoding unit 510, information regarding prediction is provided to a prediction unit (inter prediction unit 560 and intra prediction unit 565), and the residual value entropy decoded by the entropy decoding unit 510, i.e., the quantized transform coefficients and related parameter information, can be input to the inverse quantization unit 520. In addition, among the information decoded by the entropy decoding unit 510, information regarding filtering can be provided to the filtering unit 540. Meanwhile, a receiving unit (not shown) for receiving a signal output from the image encoding device can be further provided as an internal / external element of the image decoding device 500, or the receiving unit can be provided as a component of the entropy decoding unit 510.

[0123] Meanwhile, the image decoding apparatus according to the present disclosure may be called a video / image / picture decoding apparatus. The image decoding apparatus may include an information decoder (video / image / picture information decoder) and / or a sample decoder (video / image / picture sample decoder). The information decoder may include an entropy decoding unit 510, and the sample decoder may include at least one of an inverse quantization unit 520, an inverse transform unit 530, an adder 535, a filtering unit 540, a memory 550, an inter prediction unit 560, and an intra prediction unit 565.

[0124] The inverse quantization unit 520 may inverse quantize the quantized transform coefficients to output transform coefficients. The inverse quantization unit 520 may rearrange the quantized transform coefficients in a two-dimensional block format. In this case, the rearrangement may be performed based on a coefficient scan order performed in the image encoding device. The inverse quantization unit 520 may perform inverse quantization on the quantized transform coefficients using a quantization parameter (e.g., quantization step size information) to obtain transform coefficients.

[0125] The inverse transform unit 530 can inversely transform the transform coefficients to obtain a residual signal (residual block, residual sample array).

[0126] The prediction unit may perform prediction on a current block and generate a predicted block including a prediction sample for the current block. The prediction unit may determine whether intra prediction or inter prediction is applied to the current block based on the prediction information output from the entropy decoding unit 510, and may determine a specific intra / inter prediction mode (prediction technique).

[0127] The prediction unit can generate a prediction signal based on various prediction methods (techniques) described below, as has been described in the description of the prediction unit of the image encoding device 400.

[0128] The intra prediction unit 565 may predict the current block by referring to samples in the current picture. The description of the intra prediction unit 485 may be similarly applied to the intra prediction unit 565.

[0129] The inter prediction unit 560 may derive a predicted block for the current block based on a reference block (reference sample array) identified by a motion vector on a reference picture. In this case, in order to reduce the amount of motion information transmitted in the inter prediction mode, the motion information may be predicted in blocks, sub-blocks, or sample units based on correlation of motion information between neighboring blocks and the current block. The motion information may include a motion vector and a reference picture index. The motion information may further include inter prediction direction (L0 prediction, L1 prediction, Bi prediction, etc.) information. In the case of inter prediction, the neighboring blocks may include spatial neighboring blocks present in the current picture and temporal neighboring blocks present in the reference picture. For example, the inter prediction unit 560 may configure a motion information candidate list based on the neighboring blocks and derive a motion vector and / or a reference picture index for the current block based on the received candidate selection information. Inter prediction may be performed based on various prediction modes (techniques), and the prediction information may include information indicating a mode (technique) of inter prediction for the current block.

[0130] The adder 535 may generate a reconstructed signal (reconstructed picture, reconstructed block, reconstructed sample array) by adding the acquired residual signal to a prediction signal (predicted block, predicted sample array) output from a prediction unit (including an inter prediction unit 560 and / or an intra prediction unit 565). When there is no residual for a current block, such as when a skip mode is applied, a predicted block can be used as a reconstructed block. The description of the adder 455 may also be applied to the adder 535. The adder 535 may also be referred to as a reconstruction unit or a reconstructed block generator. The generated reconstructed signal may be used for intra prediction of a next current block in a current picture, and may also be used for inter prediction of a next picture via filtering, as described below.

[0131] Meanwhile, LMCS (luma mapping with chroma scaling) can be applied during picture decoding.

[0132] The filtering unit 540 may apply filtering to the reconstructed signal to improve subjective / objective image quality. For example, the filtering unit 540 may apply various filtering methods to the reconstructed picture to generate a modified reconstructed picture, and may store the modified reconstructed picture in the memory 550, specifically, in the DPB of the memory 550. The various filtering methods may include, for example, deblocking filtering, sample adaptive offset, an adaptive loop filter, a bilateral filter, etc.

[0133] The (modified) reconstructed picture stored in the DPB of the memory 550 may be used as a reference picture in the inter prediction unit 560. The memory 550 may store motion information of a block from which motion information in the current picture is derived (or decoded) and / or motion information of a block in an already reconstructed picture. The stored motion information may be transmitted to the inter prediction unit 560 to be used as motion information of a spatial surrounding block or motion information of a temporal surrounding block. The memory 550 may store a reconstructed sample of a reconstructed block in the current picture and transmit it to the intra prediction unit 565.

[0134] In this specification, the embodiments described for the filtering unit 460, inter prediction unit 480 and intra prediction unit 485 of the image encoding device 400 can also be applied in a similar or corresponding manner to the filtering unit 540, inter prediction unit 560 and intra prediction unit 565 of the image decoding device 500, respectively.

[0135] A quantization unit of an encoding device may apply quantization to transform coefficients to derive quantized transform coefficients, and an inverse quantization unit of an encoding device or an inverse quantization unit of a decoding device may apply inverse quantization to the quantized transform coefficients to derive transform coefficients. In video coding, a quantization rate may be changed, and a compression rate may be adjusted using the changed quantization rate. From the viewpoint of implementation, a quantization parameter (QP) may be used instead of the quantization rate being directly used, taking into consideration complexity. For example, a quantization parameter of an integer value from 0 to 63 may be used, and each quantization parameter value may correspond to an actual quantization rate. A quantization parameter QP for a luma component (luma sample) Y and the quantization parameter QP for the chroma components (chroma samples). C can be set to be different from each other.

[0136] In the quantization process, the transform coefficients C are input, and the quantization rate Q step , and a quantized transform coefficient C' can be derived based on this. In this case, the quantization rate can be multiplied by a scale to convert it into an integer format in consideration of calculation complexity, and a shift operation can be performed by a value corresponding to the scale value. A quantization scale can be derived based on the product of the quantization rate and the scale value. That is, the quantization scale can be derived according to QP. The quantization scale can be applied to the transform coefficient C, and a quantized transform coefficient C' can be derived based on this.

[0137] The inverse quantization process is the inverse process of the quantization process, and applies a quantization rate Q stepand based on this, a reconstructed transform coefficient C" can be derived. In this case, a level scale can be derived according to the quantization parameter, and based on this, the level scale can be applied to the quantized transform coefficient C' to derive a reconstructed transform coefficient C". The reconstructed transform coefficient C" may be slightly different from the original transform coefficient C due to loss in the transform and / or quantization process. Therefore, in the encoding device, in the same way as in the decoding device, inverse quantization can be performed.

[0138] Meanwhile, an adaptive frequency weighting quantization technique that adjusts quantization strength according to frequency can be applied. The adaptive frequency weighting quantization technique can correspond to a method of applying quantization strength differently according to frequency. The adaptive frequency weighting quantization can be applied such that the quantization strength for each frequency is different using a predefined quantization scaling matrix. That is, the above-mentioned quantization / dequantization process can be further performed based on the quantization scaling matrix.

[0139] For example, different quantization scaling matrices may be used depending on the size of a current block and / or whether a prediction mode applied to the current block is inter prediction or intra prediction to generate a residual signal of the current block. The quantization scaling matrix may be referred to as a quantization matrix or a scaling matrix. The quantization scaling matrix may be defined in advance. Also, for frequency adaptive scaling, frequency-specific quantization scale information for the quantization scaling matrix may be configured / encoded in an encoding device and signaled to a decoding device. The frequency-specific quantization scale information may be referred to as quantization scaling information. The frequency-specific quantization scale information may include scaling list data (scaling_list_data).

[0140] The quantization scaling matrix can be derived based on the scaling list data. Also, the frequency-specific quantization scale information can include present flag information indicating whether the scaling list data is present. Also, when the scaling list data is signaled at a higher level (e.g., SPS), the frequency-specific quantization scale information can further include information indicating whether the scaling list data is modified at a lower level (e.g., PPS, APS, or slice header).

[0141] FIG. 6 shows an example of a hierarchical structure for coded images / video.

[0142] The coded image / video can be divided into a video coding layer (VCL), which handles the image / video decoding process and itself, a subsystem that transmits and stores the coded information, and a network abstraction layer (NAL), which exists between the VCL and the subsystem and is responsible for network adaptation functions.

[0143] In VCL, it is possible to generate VCL data including compressed image data (slice data), or to generate parameter sets including information such as a Picture Parameter Set (PPS), a Sequence Parameter Set (SPS), and a Video Parameter Set (VPS), or a Supplemental Enhancement Information (SEI) message that is additionally required for image decoding processing.

[0144] In NAL, NAL units can be generated by adding header information (NAL unit header) to RBSP (Raw Byte Sequence Payload) generated in VCL. In this case, RBSP refers to slice data, parameter set, SEI message, etc. generated in VCL. NAL unit header can include NAL unit type information identified by RBSP data included in the corresponding NAL unit.

[0145] As shown in Fig. 6, NAL units can be classified into VCL NAL units and non-VCL NAL units according to the type of RBSP generated in the VCL. The VCL NAL unit can refer to a NAL unit that includes image information (slice data), and the non-VCL NAL unit can refer to a NAL unit that includes information required for decoding an image (parameter set or SEI message).

[0146] The above-mentioned VCL NAL unit and non-VCL NAL unit can be transmitted over a network with header information according to the data standard of the lower system. For example, the NAL unit can be transformed into a data format of a predetermined standard such as H.266 / VVC file format, RTP (Real-time Transport Protocol) or TS (Transport Stream) and transmitted over various networks.

[0147] As described above, the NAL unit type of an NAL unit can be identified according to an RBSP data structure included in the NAL unit, and information on the NAL unit type can be stored and signaled in a NAL unit header. For example, NAL units can be largely classified into VCL NAL unit types and non-VCL NAL unit types depending on whether they include image information (slice data). The VCL NAL unit types can be further subdivided according to the nature / type of the picture included in the VCL NAL unit, and the non-VCL NAL unit types can be further subdivided according to the type of parameter set included in the non-VCL NAL.

[0148] An example of VCL NAL unit types according to picture type is as follows:

[0149] - "IDR_W_RADL", "IDR_N_LP": VCL NAL unit types for IDR (Instantaneous Decoding Refresh) pictures, which are a type of IRAP (Intra Random Access Point) picture;

[0150] An IDR picture may be the first picture in the bitstream in decoding order, or it may be the first picture after the first. A picture with a NAL unit type such as "IDR_W_RADL" may have one or more Random Access Decodable Leading (RADL) pictures associated with it. In contrast, a picture with a NAL unit type such as "IDR_N_LP" does not have any leading pictures associated with it.

[0151] - "CRA_NUT": VCL NAL unit type for a CRA (Clean Random Access) picture, which is a type of IRAP picture;

[0152] A CRA picture may be the first picture in the bitstream in decoding order, or may be any picture after the first. A CRA picture may be associated with a RADL or RASL (Random Access Skipped Leading) picture.

[0153] - "GDR_NUT": VCL NAL unit type for randomly accessible GDR (Gradual Decoding Refresh) pictures;

[0154] - "STSA_NUT": VCL NAL unit type for randomly accessible STSA (Step-wise Temporal Sublayer Access) pictures;

[0155] - "RADL_NUT": VCL NAL unit type for a RADL picture that is a leading picture;

[0156] - "RASL_NUT": VCL NAL unit type for a RASL picture that is a leading picture;

[0157] - "TRAIL_NUT": VCL NAL unit type for trailing pictures;

[0158] A trailing picture may be a non-IRAP picture that follows the IRAP picture or GDR picture associated with the trailing picture in output order, and may follow the IRAP picture associated with the trailing picture in decoding order.

[0159] Next, an example of a non-VCL NAL unit type according to the type of parameter set is as follows:

[0160] - "DCI_NUT": non-VCL NAL unit type including DCI (Decoding Capability Information)

[0161] - "VPS_NUT": non-VCL NAL unit type including VPS (Video Parameter Set)

[0162] - "SPS_NUT": non-VCL NAL unit type including SPS (Sequence Parameter Set)

[0163] - "PPS_NUT": non-VCL NAL unit type including PPS (Picture Parameter Set)

[0164] - "PREFIX_APS_NUT", "SUFFIX_APS_NUT": non-VCL NAL unit types including APS (Adaptation Parameter Set)

[0165] - "PH_NUT": non-VCL NAL unit type including picture header

[0166] The above-mentioned NAL unit types can be identified by certain syntax information (eg, nal_unit_type) included in the NAL unit header.

[0167] Meanwhile, in the present disclosure, the image / video information encoded in a bitstream format may include not only picture partitioning information, intra / inter prediction information, residual information, and / or in-loop filtering information, but also slice header information, picture header information, APS information, PPS information, SPS information, VPS information, and / or DCI. The encoded image / video information may further include general constraint information (GCI) and / or NAL unit header information. According to an embodiment of the present disclosure, the encoded image / video information may be encapsulated in a media file of a predetermined format (e.g., ISO BMFF) and transmitted to a receiving device.

[0168] Media files

[0169] The encoded image information can be configured (or formatted) based on a predefined media file format to generate a media file. As an example, the encoded image information can form a media file (segment) based on one or more NAL unit / sample entries for the encoded image information.

[0170] A media file may include Sample Entry(s) and Track(s). As an example, a media file may include various Records. Each Record may include information related to a media file format or information related to an image. In an example, one or more NAL units may be stored in a configuration record (or decoder configuration record) field in a media file. Also, a media file may include an operating point record and / or an operating point group box. In this disclosure, a decoder configuration record that supports Versatile Video Coding (VVC) may be referred to as a VVC decoder configuration record. Similarly, an operating point record that supports VVC may be referred to as a VVC operating point record.

[0171] The term "sample" as used in a media file format may refer to all data associated with a single time or element of any one of the three sample arrays (Y, Cb, Cr) that represent a picture. When the term "sample" is used in the context of a track (of a media file format), the "sample" may refer to all data associated with a single time of that track, where the time may correspond to a decoding time or a composition time. Also, when the term "sample" is used in the context of a picture (e.g., a luma sample), the "sample" may refer to a single element of any one of the three sample arrays that represent a picture.

[0172] FIG. 7 is a diagram showing an example of a media file structure.

[0173] As described above, a standardized media file format can be defined for storing and transmitting media data such as audio, video, or images. According to an embodiment, a media file can have a file format according to ISO base media file format (ISO BMFF).

[0174] A media file may include one or more boxes. Here, a box may be a data block or object that includes media data or metadata associated with the media data. Within a media file, boxes may form a hierarchical structure. This allows a media file to have a format suitable for storing and / or transmitting a large amount of media data. Furthermore, a media file may have a structure that facilitates access to specific media data.

[0175] Referring to FIG. 7, a media file 700 may include an ftyp box 710, a moov box 720, a moof box 730, and an mdat box 740.

[0176] The ftyp box 710 may include file type, file version and / or compatibility related information within the media file 700. According to an embodiment, the ftyp box 710 may be located at the beginning of the media file 700.

[0177] The moov box 720 may include metadata describing the media data in the media file 700. Depending on the embodiment, the moov box 720 may be present in the top layer of the metadata related boxes. Furthermore, the moov box 720 may include header information of the media file 700. For example, the moov box 720 may include a decoder configuration record as decoder configuration information.

[0178] The moov box 720 is a sub-box that can include an mvhd box 721 , a trak box 722 , and an mvex box 723 .

[0179] The mvhd box 721 may contain presentation related information for the media data in the media file 700 (eg, media creation time, modification time, periodicity, etc.).

[0180] The trak box 722 may contain metadata for a track of media data. For example, the trak box 722 may contain stream-related, presentation-related, and / or access-related information for an audio or video track. There may be multiple trak boxes 722 depending on the number of tracks present in the media file 700. An example of the structure of the trak box 722 will be described below with reference to FIG. 8.

[0181] The mvex box 723 may include information regarding whether one or more movie fragments exist in the media file 700. A movie fragment may be a portion of media data obtained by dividing the media data in the media file 700. A movie fragment may include one or more coded pictures. For example, a movie fragment may include one or more picture groups GOPs, each of which may include multiple coded frames or pictures. The movie fragments may be stored in the mdat boxes 740-1 to 740-N (where N is an integer equal to or greater than 1), respectively.

[0182] The moof boxes 730-1 to 730-N (where N is an integer equal to or greater than 1) may contain metadata for movie fragments, i.e., mdat boxes 740-1 to 740-N. Depending on the embodiment, the moof boxes 730-1 to 730-N may be present in the top layer of the metadata-related boxes of the movie fragment.

[0183] The mdat boxes 740-1 to 740-N may contain actual media data. There may be a plurality of mdat boxes 740-1 to 740-N depending on the number of movie fragments present in the media file 700. Each of the mdat boxes 740-1 to 740-N may contain one or more audio or video samples. In one example, a sample may refer to an Access Unit (AC). When the decoder setting record is stored in the sample entry, the decoder setting record may include not only the parameter set but also the size of a length field for indicating the length of the Network Abstraction Layer (NAL) unit to which each sample belongs.

[0184] According to an embodiment, the media file 700 may be processed and stored and / or transmitted in segments. The segments may include an initialization segment I_seg and a media segment M_seg.

[0185] The initialization segment I_seg may be a data unit in the form of an object including initialization information for accessing a representation. The initialization segment I_seg may include the ftyp box 710 and / or the moov box 720 described above.

[0186] The media segment M_seg may be an object-type data unit including media data divided in time for streaming services. The media segment M_seg may include the above-mentioned moof boxes 730-1 to 730-N and mdat boxes 740-1 to 740-N. Although not shown in FIG. 7, the media segment M_seg may further include a styp box including segment type related information and a sidx box including identification information of sub-segments included in the media file 700 (however, optional).

[0187] FIG. 8 is a diagram showing an example of the trak box structure of FIG.

[0188] Referring to FIG. 8, a trak box 800 may include a tkhd box 810, a tref box 820, and an mdia box 830.

[0189] The tkhd box 810 is a track header box and can contain header information of the track indicated by the track box 800 (hereinafter referred to as the "track in question"), such as the creation / modification time of the track and a track identifier.

[0190] The tref box 820 is a track reference box and may contain reference information for the track, for example track identifiers of other tracks to which the track refers.

[0191] The mdia box 830 may include information and objects describing the media data in the track. According to an embodiment, the mdia box 830 may include a minf box 840 that provides information about the media data. The minf box 840 may also include a stbl box 850 that includes metadata for a sample that includes the media data.

[0192] The stbl box 850 is a sample table box that can include position information, time information, etc. of a sample in a track. Based on the information provided by the stbl box 850, a reader can determine the sample type, the sample size and offset in the container, etc., and position the samples in the correct time order.

[0193] The stbl box 850 may include one or more sample entry boxes 851, 852. The sample entry boxes 851, 852 may provide various parameters for a particular sample. For example, a sample entry box for a video sample may include a width, height, resolution, and / or frame count of the video sample. Also, a sample entry box for an audio sample may include a channel count, channel layout, and / or sampling rate of the audio sample. Depending on the embodiment, the sample entry boxes 851, 852 may be included in a sample description box (not shown) in the stbl box 850. The sample description box may provide detailed information about the coding type applied to the sample and any initialization information required for the coding type.

[0194] The stbl box 850 may also include one or more sample to group boxes 853 , 854 and one or more sample group description boxes 855 , 856 .

[0195] The sample to group boxes 853 and 854 may indicate a sample group to which a sample belongs. For example, the sample to group boxes 853 and 854 may include a grouping type syntax element (e.g., grouping_type) indicating the type of the sample group. Also, the sample to group boxes 853 and 854 may include one or more sample group entries. The sample group entry may include a sample count syntax element (e.g., sample_count) and a group description index syntax element (e.g., group_description_index). Here, the sample count syntax element may indicate the number of consecutive samples to which the corresponding group description index is applied. The sample group may include a stream access point (SAP) sample group, a random access recovery point (RANP) sample group, etc., the specific contents of which will be described later.

[0196] The sample group description boxes 855, 856 may provide a description of the sample group. For example, the sample group description boxes 855, 856 may include a grouping type syntax element (e.g., grouping_type). The sample group description boxes 855, 856 may correspond to sample to group boxes 853, 854 having the same grouping type syntax element value. The sample group description boxes 855, 856 may also include one or more sample group description entries. The sample group description entries may include a "spor" sample group description entry, a "minp" sample group description entry, a "roll" sample group description entry, etc.

[0197] As described above with reference to Figures 7 and 8, media data can be encapsulated in a media file according to a file format such as ISO BMFF, and the media file can be transmitted to a receiving device via an image signal according to the MMT standard or the MPEG-DASH standard.

[0198] FIG. 9 is a diagram showing an example of an image signal structure.

[0199] Referring to FIG. 9, the image signal is in accordance with the MPEG-DASH standard and may include an MPD 910 and multiple representations 920-1 to 920-N.

[0200] The MPD 910 is a file containing detailed information about a media presentation and can be expressed in XML format. The MPD 910 can include information about multiple representations 920-1 to 920-N (e.g., bit rate, image resolution, frame rate, etc. of streaming content) and URLs of HTTP resources (e.g., initialization segments and media segments).

[0201] Each of the representations 920-1 to 920-N (where N is an integer greater than 1) may be divided into a number of segments S-1 to SK (where K is an integer greater than 1). Here, the number of segments S-1 to SK may correspond to the initialization segment and the media segment described above with reference to FIG. 7. The K-th segment SK may indicate the last movie fragment in each of the representations 920-1 to 920-N. Depending on the embodiment, the number of segments S-1 to SK included in each of the representations 920-1 to 920-N (i.e., the value of K) may be different from each other.

[0202] Each segment S-1 to SK may contain actual media data, for example one or more video or image samples. The characteristics of the video or image samples contained within each segment S-1 to SK may be described by the MPD 910.

[0203] Each of the segments S-1 to SK has a unique Uniform Resource Locator (URL) and can therefore be accessed and restored independently.

[0204] Meanwhile, to store VVC content, three types of elementary streams can be defined as follows:

[0205] -video elementary stream: A video elementary stream contains VCL NAL units but does not contain parameter sets, DCI or OPI NAL units. In this case, parameter sets, DCI or OPI NAL units can be stored in one or more sample entries. A video elementary stream can contain non-VCL NAL units except parameter sets, DCI NAL units and OPI NAL units.

[0206] -video and parameter set elementary stream: A video and parameter set elementary stream contains VCL NAL units and may contain parameter set, DCI or OPI NAL units and may have parameter set, DCI or OPI NAL units stored in one or more sample entries.

[0207] -non-VCL elementary stream: A non-VCL elementary stream contains only non-VCL NAL units that are synchronized with the elementary streams carried in the video track.

[0208] The VVC file format also defines different types of tracks:

[0209] - VVC Track: A VVC track can indicate a VVC bitstream by including samples and NAL units in sample entries, possibly by referencing VVC tracks that include other sublayers of the VVC bitstream, and possibly by referencing VVC subpicture tracks. If a VVC track references a VVC subpicture track, the VVC track may be called a VVC base track.

[0210] -VVC non-VCL track: ALF (Adaptive Loop Filter), LMCS (Luma Mapping with Chroma Scaling), or APSs (Adaptive Parameter Sets) carrying scaling list parameters, and other non-VCL NAL units are stored in tracks distinct from tracks containing VCL NAL units and can be transmitted via the tracks. The VVC non-VCL track can refer to the tracks. The VVC non-VCL track does not include parameter sets, DCI, or OPI NAL units in the sample entries.

[0211] - VVC sub-picture track: A VVC sub-picture track may contain a sequence of one or more VVC sub-pictures or a sequence of one or more complete slices forming a rectangular region. Also, a sample of a VVC sub-picture track may contain one or more complete sub-pictures that are contiguous in decoding order, or one or more complete slices that are contiguous in decoding order and form a rectangular region. The VVC sub-pictures or slices included in each sample of a VVC sub-picture track may be contiguous in decoding order.

[0212] Meanwhile, VVC non-VCL tracks and VVC sub-picture tracks can enable optimal delivery of VVC video in streaming applications. Each of the tracks can be carried in a unique DASH representation. Also, for decoding and rendering a subset of the tracks, DASH representations including a subset of VVC sub-picture tracks and DASH representations including non-VCL tracks can be requested by a client on a segment-by-segment basis. In this manner, redundant transmission of APS and other non-VCL NAL units can be avoided.

[0213] Overview of Data Sharing and VVC Bitstream Recovery

[0214] The output of this process is a VVC bitstream, which is sometimes referred to as the output bitstream.

[0215] A file reader can perform this process if one or more of the following conditions are true:

[0216] i) if a VVC bitstream entity group (e.g., "vvcb") is present in a file and a file reader processes a VVC bitstream represented by said entity group to generate an output bitstream;

[0217] ii) if an operation point entity group (e.g., "opeg") is present in the file and the file reader generates an output bitstream using any operation points described by the entity group;

[0218] iii) If a file reader extracts a subset of layers or sublayers of a VVC track that has plt_present_flag equal to 1 to generate an output bitstream,

[0219] iv) If the file reader processes VVC-based tracks,

[0220] v) When a file reader processes a VVC track that is associated with a VVC non-VCL track.

[0221] This process can be comprised of the following steps:

[0222] (Step1):

[0223] If any of the above conditions i) to ii) is true, the operation point is determined at the start of the VVC bitstream and can be determined again for an IRAP or GDR access unit.

[0224] 1) The method for determining the operating point may differ from that specified in standard documents, e.g. ISO / IEC 14496-15.

[0225] 2) When a file reader selects an operation point for the first time, or selects an operation point different from one previously selected, the file reader must indicate to the VVC decoder by including the output layer set index and the highest TemporalID value of the selected operation point in the OPI NAL unit inserted into the output bitstream (the first NAL unit following the AU delimiter NAL unit, if present, in the first access unit where the operation point is used), or by other means.

[0226] In one example, it is possible to down-switch and up-switch layers and sub-layers in access units AUs that do not start a CVS, as long as the layer and sub-layer set being decoded is within the latest operation point indicated to the decoder via an OPI NAL unit or other means. In this case, layer up-switching may occur at an IRAP, GDR or STSA picture unit with a TemporalId such as 0. Also, sub-layer up-switching may occur at an STSA picture unit.

[0227] 3) The subsequent steps can be applied to the sequence of access units in decoding order from the access unit for which the operation point has been determined to the end of the bitstream or to the access unit for which the next operation point has been determined.

[0228] (Step2):

[0229] If a VVC bitstream is represented by multiple VVC tracks, the file parser can identify the tracks required for a selected operation point as follows.

[0230] i) if an operation point from the 'opeg' entity group contains the selected operation point, select the track that belongs to the operation point indicated by said 'opeg' entity group;

[0231] ii) If the 'opeg' entity group is not present (i.e., if the 'vopi' sample group is present), then the VVC track is determined from the 'vvcb' entity group which represents the VVC bitstream. The first entity_id in the 'vvcb' entity group identifies the track which contains the 'vopi' sample group. The mapping of operation points to layers and sublayers is terminated from the 'vopi' sample group. The set of tracks which contain the layers and sublayers of the selected operation point and are therefore needed to decode the selected operation point is terminated from the 'linf' sample group present in the VVC track of the VVC bitstream.

[0232] Since a particular layer or sub-layer can be represented by more than one track, when identifying the tracks required for an operation point, a selection may need to be made from among the set of tracks that carry all of the particular layer or sub-layers.

[0233] (Step3):

[0234] The access units for the output bitstream can be restored in sample decoding time order within the VVC track required for the selected operation point (if condition i, ii, or iii above is true), or within the VVC base track (if condition iv above is true), or within the VVC track (if condition v above is true).

[0235] 4) If multiple tracks contain data for an access unit, the alignment of each sample within a track can be based on sample decoding time.

[0236] 5) By repeatedly invoking the implicit reconstruction process, a sequence of access units can be reconstructed from each sample in the required track.

[0237] 6) The reconstructed access units may be arranged in the output bitstream in ascending decoding time order.

[0238] (Step4):

[0239] A file reader MUST include an EOS NAL unit in each layer of an applied operation point in the output bitstream if all of the following conditions are true:

[0240] - selection of an operating point different from the previously selected one follows in the sequence of access units,

[0241] If the sequence of access units does not end with an EOS NAL unit or an EOB NAL unit in each layer of the applied operation point

[0242] When a VVC bitstream is represented by multiple VVC tracks, the decoding times of the samples must be correctly set as specified in standard documents, e.g. ISO / IEC 23090-3 (VVC standard), such that when the tracks are combined into a single bitstream that is aligned with increasing decoding times, the order of the access units is aligned.

[0243] Implicit decompression of VVC bitstreams

[0244] This process can represent access unit reconstruction from time-aligned samples with the current decoding time in the requested VVC track, the associated VVC non-VCL track, and the referenced VVC sub-picture track.

[0245] When recovering a bitstream containing sublayers whose VCL NAL units have a TemporalId greater than 0, all sublayers within the same layer (i.e., sublayers whose VCL NAL units have a smaller TemporalId) may also be included in the bitstream.

[0246] If a sample of the current decode time contains a VCL NAL unit with a TemporalId greater than the largest TemporalId contained in the selected operation point, no access unit can be recovered from the current decode time.

[0247] When recovering an access unit, picture units from samples having the same decoding time (picture units as specified in standard documents, e.g. ISO / IEC 23090-3 (VVC standard)) may be located within said access unit in ascending order of nuh_layer_id value. Depending on a given condition, the following steps may be taken:

[0248] -If a sample of a track containing the first picture unit of a sample is marked as belonging to a sample group "aud" that includes ols_idx and lower_ols_idx_inclusive and corresponds to a target operation point, then an AUD NAL unit in the "aud" sample group can be placed within an access unit as the first NAL unit of the access unit.

[0249] -If a sample in a track is marked as belonging to sample group 'eos' with ols_idx, max_tid, and lower_ols_idx_inclusive corresponding to the target operation point, then the EOS NAL unit in the 'eos' sample group can be placed at the indicated position in the access unit, i.e., next to the eos_position-th NAL unit of the restored access unit excluding the AUD NAL unit if inserted by sample group 'aud'.

[0250] -If samples in a track are marked as belonging to an "eob" sample group with ols_idx, max_tid, and lower_ols_idx_inclusive that correspond to the target operation point, then EOB NAL units in the "eob" sample group can be placed after all other NAL units (including EOS NAL units) in the access unit.

[0251] Only picture units from layers and sublayers within the target operation point can be included in the output bitstream.

[0252] In one example, if an Operating Points Entity Group is not present, there may be layers or sublayers conveyed within a track that are required for reconstruction of the bitstream but that do not belong to the target operation point.

[0253] In one example, a VVC decoder implementation can take as input a bitstream corresponding to a target output layer set index TargetOlsIdx and the highest TemporalId value HighestTid of the target operation point, as defined in a standard document, such as ISO / IEC 23090-3 (VVC Standard): 2021. The file parser must ensure that the file does not contain any other layers and sublayers than those included in the target operation point before sending it to the VVC decoder.

[0254] When recovering an access unit based on the operation point associated with output layer set index i (in a for-loop for num_olss within the 'vopi' sample group), the following applies:

[0255] When recovering an access unit, for each layer in the output layer set with index j in the range from 0 to layer_count[i]-1, if num_ref_sublayers_in_layer_in_ols[i][j] is greater than 0, the VCL NAL unit may belong to a sublayer of a layer with TemporalId less than or equal to Min(num_ref_sublayers_in_layer_in_ols[i][j]-1, max_temporal_id) and, as a result, may be included in the bitstream and the requested track may be selected accordingly, where max_temporal_id may refer to the value of the corresponding syntax element for the operation point.

[0256] -When recovering an access unit, for each layer in the output layer set with index j in the range from 0 to layer_count[i]-1, if num_ref_sublayers_in_layer_in_ols[i][j] is equal to 0, then among all picture units of the reference layer, only IRAP and GDR picture units with ph_recovery_poc_cnt like 0 can be included in the resulting bitstream, and the requested track can be selected accordingly.

[0257] If an access unit of a VVC track contains an unspecified NAL unit type (a NAL unit having a nal_unit_type value in the range of UNSPEC_28 to UNSPEC_31, i.e. a nal_unit_type value in the range of 28 to 31 defined in a standard document, e.g. ISO / IEC 23090-3 (VVC standard)), the unspecified NAL unit type shall be discarded from the final reconstructed bitstream.

[0258] If the VVC track contains a "subp" track reference, each picture unit can be restored as specified in a standard document, e.g., subclause 11.6.3 of ISO / IEC 14496-15. If the VVC track contains a "recr" track reference, each picture unit can be restored as specified in a standard document, e.g., subclause 11.6.6 of ISO / IEC 14496-15. The process specified in the subclause can be repeated for each layer of the target operation point in ascending order of nuh_layer_id.

[0259] The reconstructed access units may be placed in the VVC bitstream in ascending order of decoding time.

[0260] Since a particular layer or sublayer can be represented by more than one track, when figure out the track required for an operating point, a selection must be made from among the set of all tracks that carry that particular layer or sublayer.

[0261] Recovering picture units from samples in a VVC track that references a VVC subpicture track

[0262] The samples of a VVC track can be resolved into picture units according to the following procedure:

[0263] If an AUD NAL unit is present within a sample or within a time-aligned sample of the associated VVC non-VCL track, the AUD NAL unit can be included within a picture unit.

[0264] In one example, if an AUD NAL unit is present in a sample, the AUD NAL unit may be the first NAL unit in the sample.

[0265] - If there is an associated VVC non-VCL track and the picture unit is the first picture unit in an access unit reconstructed from samples, the next NAL unit may be included in said picture unit.

[0266] If there is at least one NAL unit in the time-aligned samples of the associated VVC non-VCL track with a nal_unit_type such as EOS_NUT, EOB_NUT, SUFFIX_APS_NUT, SUFFIX_SEI_NUT, FD_NUT, or RSV_NVCL_27 (NAL units with the above mentioned NAL unit types cannot precede the first VCL NAL unit in a picture unit), then the NAL units in the time-aligned samples of the associated VVC non-VCL track (but not the AUD NAL unit) except for the first of these NAL units; otherwise, all NAL units in the time-aligned samples of the associated VVC non-VCL track.

[0267] -If there is at least one NAL unit in a sample with a nal_unit_type such as EOS_NUT, EOB_NUT, SUFFIX_APS_NUT, SUFFIX_SEI_NUT, FD_NUT, or RSV_NVCL_27 (NAL units with the above mentioned NAL unit types cannot precede the first VCL NAL unit in a picture unit), then the NAL units in the sample except for the first one of these NAL units can be contained in a picture unit. Otherwise, all NAL units in the sample can be contained in a picture unit.

[0268] When a reader selects an operating point, the reader must exclude all OPI NAL units stored in the sample entry and sample from the access units recovered in all steps above.

[0269] In one example, when a multi-track is used to store layers or sub-layers of a VVC bitstream, it is preferable not to include OPI NAL units within the sample entries or samples.

[0270] If a VVC track does not reference a VVC sub-picture track, the sample NAL units in a VVC track can be contained within picture units.

[0271] Otherwise, the following applies:

[0272] Track references can be resolved as specified in standard documents, for example ISO / IEC 14496-15, subclause 11.6.4.

[0273] Also, if necessary, the parameter set can be updated as specified in standard documents, for example sub-clause 11.6.5 of ISO / IEC 14496-15.

[0274] Furthermore, except for all SEI NAL units, including scalable nesting SEI messages with sn_subpic_flag as 1, and all DCI, OPI, VPS, SPS, PPS, AUD, PH, EOS, and EOB NAL units, picture units can be appended by the contents of time-aligned decomposed samples in each referenced VVC subpicture track (in decoding time) in the order of the VVC subpicture track referenced in the "subp" track reference (if num_subpic_ref_idx is 0 within the same group entry of the "spor" sample group entry mapped to this sample) or in the order specified in the "spor" sample group description entry mapped to this sample (if num_subpic_ref_idx is greater than 0 within the same group entry of the "spor" sample group entry mapped to this sample).

[0275] Also, if the referenced VVC subpicture is associated with a VVC non-VCL track, the decomposed samples of the VVC subpicture track may contain the following NAL units: i) NAL units in the time-aligned samples of the associated VVC non-VCL track (but not the AUD NAL unit) except the first of these NAL units, if there is at least one NAL unit in the time-aligned samples of the associated VVC non-VCL track with a nal_unit_type such as EOS_NUT, EOB_NUT, SUFFIX_APS_NUT, SUFFIX_SEI_NUT, FD_NUT, or RSV_NVCL_27 (NAL units with the above mentioned NAL unit types cannot precede the first VCL NAL unit in a picture unit); ii) all NAL units in the time-aligned samples of the associated VVC non-VCL track, otherwise; and iii) NAL units in the samples of the referenced VVC subpicture track. iv) The remaining NAL units within the time-aligned samples of the associated VVC non-VCL track.

[0276] All NAL units within a sample with a nal_unit_type such as EOS_NUT, EOB_NUT, SUFFIX_APS_NUT, SUFFIX_SEI_NUT, FD_NUT, or RSV_NVCL_27 may be contained within a picture unit.

[0277] -If an associated VVC non-VCL track exists and the picture unit is the last picture unit in the access unit recovered from the sample, all NAL units in the time-aligned samples of the associated VVC non-VCL track that have a nal_unit_type such as EOS_NUT, EOB_NUT, SUFFIX_APS_NUT, SUFFIX_SEI_NUT, FD_NUT, or RSV_NVCL_27 can be included in the picture unit.

[0278] - All NAL units and NAL-unit-like structures in the sample with nal_unit_type in the range of UNSPEC_28 to UNSPEC_31 shall be removed from the picture unit.

[0279] The EOS sample group and the EOB sample group are described in detail below.

[0280] EOS Sample Group - Problems with the conventional technology

[0281] The sample group description entry of an end of sequence (EOS) sample group may include an EOS NAL unit. When a sample is mapped to an EOS sample group ("eos"), the EOS NAL unit included in the sample group may indicate that the target operation point should be restored and inserted at the indicated position in the t access unit when it corresponds to the output layer set and the maximum temporal ID indicated in the EOS sample group. Meanwhile, an EOS sample group may also be referred to as an "eos" sample group or "eos", and these terms will be used interchangeably unless otherwise noted below.

[0282] FIG. 10 is a diagram showing the syntax structure of an EOS sample group entry.

[0283] FIG. 11 is a diagram showing an example of a truck carrying a multi-layer.

[0284] First, referring to FIG. 10, an EOS sample entry (EndOfSequenceSampleEntry) may include syntax elements ols_idx, max_tid, lower_ols_idx_inclusive, eos_position, and eosNalUnit.

[0285] The syntax elements ols_idx and max_tid may indicate the operating point to which the EOS sample group applies.

[0286] The syntax element lower_ols_idx_inclusive may indicate whether the EOS sample group applies only to a particular operation point. For example, a second value (e.g., 0) of lower_ols_idx_inclusive may indicate that the EOS sample group applies only to operation points with an output layer set index (OLS index) such as ols_idx. In contrast, a first value (e.g., 1) of lower_ols_idx_inclusive may indicate that the EOS sample group applies to all output layer sets with indexes from 0 to ols_idx.

[0287] The syntax element eos_position may indicate the index of the NAL unit of the reconstructed access unit after which the EOS NAL unit is located in the reconstructed bitstream.

[0288] The syntax element eosNalUnit can contain an EOS NAL unit specified in a standard document, for example ISO / IEC 23090-3 (VVC standard).

[0289] If a VVC elementary stream contains multiple layers, a track can carry multiple layers. In this case, multiple EOS NAL units, one for each layer, need to be inserted into an access unit. For example, as shown in FIG. 11, in track 1 of a multi-layer structure, a video sequence can be generated layer by layer. As a result, two EOS NAL units, one for each layer (layer 0 and layer 1), must be inserted into AU2 as the last access unit to indicate the end of the video sequence.

[0290] However, according to the syntax structure of Fig. 10, one "eos" sample group can only carry one EOS NAL unit. Considering that only one "eos" sample group is mapped to each sample or access unit, this means that only one EOS NAL unit can be inserted into each sample or access unit. Therefore, a problem occurs that the "eos" sample group design of Fig. 10 cannot work for a VVC elementary stream with multiple layers.

[0291] To solve such problems, embodiments of the present disclosure provide a new "eos" sample group design that can carry multiple EOS NAL units.

[0292] The embodiments of the present disclosure may include at least one of the following features. Depending on the embodiment, these features may be implemented individually or in combination of two or more.

[0293] (Configuration 1): It is permissible for an "eos" sample group to carry multiple EOS NAL units.

[0294] (Configuration 2): To support configuration 1, the syntax of the 'eos' sample group can be modified as follows:

[0295] A new syntax element num_eos_nal_unit_minus1 can be signaled to indicate the number of EOS NAL units present in an 'eos' sample group. Then, the number of EOS NAL units in the 'eos' sample group can be num_eos_nal_unit_minus1+1.

[0296] -A for loop for the EOS NAL unit and its insertion position can be added.

[0297] (Configuration 3): When signaling the insertion position of an EOS NAL unit (i.e., eos_position[i]), said insertion position may only consider NAL units within a sample and may not count the NAL unit to be inserted.

[0298] (Configuration 4): A syntax element eos_position[i] for an insertion position of an EOS NAL unit can be signaled, where the syntax element eos_position[i] can indicate the index of the NAL unit within the sample where the i-th EOS NAL unit is inserted.

[0299] (Configuration 5): Instead of signaling eos_position[i], delta_eos_position[i] may be signaled. In this case, the value of eos_position[i] may be derived based on delta_eos_position[i] as follows:

[0300] If -i is 0, eos_position[i] can be guided to the same value as delta_eos_position[i].

[0301] -Otherwise, eos_position[i] can be induced to the same value as eos_position[i-1] + delta_eos_position[i].

[0302] (Configuration 6): Unlike configuration 3 described above, position information regarding where an EOS NAL unit is placed does not need to be signaled. If samples mapped to an 'eos' sample group are included for the reconstruction of an access unit, the EOS NAL unit in the 'eos' sample group may be inserted at the end of the reconstructed access unit.

[0303] (Configuration 7): Unlike configuration 3 above, position information regarding where the EOS NAL unit is placed does not need to be signaled. If samples mapped to an "eos" sample group are included for the reconstruction of an access unit, the EOS NAL unit in said "eos" sample group can be inserted into the reconstructed access unit after all NAL units from the samples required for the access unit.

[0304] Hereinafter, an embodiment of the present disclosure based on the above-mentioned configuration will be described in detail.

[0305] Example 1

[0306] A first embodiment of the present disclosure can be provided based on the above-described configurations 1 to 4. The realization of the first embodiment can be related to the VVC file format specification.

[0307] According to the first embodiment, unlike the existing EOS sample group, a plurality of EOS NAL units can be carried within one EOS sample group. Hereinafter, with reference to FIG. 10, the description overlapping with the above-mentioned existing EOS sample group will be omitted.

[0308] FIG. 12 is a diagram illustrating a syntax structure of an EOS sample group entry according to one embodiment of the present disclosure.

[0309] Referring to FIG. 12, the EOS sample group entry (EndOfSequenceSampleEntry) may include syntax elements ols_idx, max_tid, lower_ols_idx_inclusive, num_eos_nal_unit_minus1, eos_position[i], and eosNalUnit[i].

[0310] The syntax elements ols_idx and max_tid may indicate the operating point to which the EOS sample group applies.

[0311] The syntax element lower_ols_idx_inclusive may indicate whether the EOS sample group applies only to a particular operation point. For example, a second value (e.g., 0) of lower_ols_idx_inclusive may indicate that the EOS sample group applies only to operation points with an output layer set index (OLS index) such as ols_idx. In contrast, a first value (e.g., 1) of lower_ols_idx_inclusive may indicate that the EOS sample group applies to all output layer sets with indexes from 0 to ols_idx.

[0312] The syntax element num_eos_nal_unit_minus1 may indicate the number of EOS NAL units present in the EOS sample group minus one.

[0313] The syntax element eos_position[i] may indicate the NAL unit index after which the i-th EOS NAL unit is placed in the current sample. Here, the NAL unit index may consider only NAL units natively present in the current sample, excluding other NAL units that may be inserted / placed in the current sample. The 1st NAL unit in the current sample may be regarded as the 0th NAL unit.

[0314] In one example, the current sample may also be mapped to an "aud" sample group and / or an "eob" sample group that induces an AUD NAL unit and / or an EOB NAL unit to be inserted into the sample or the reconstructed access unit, in which case eos_position[i] may be based on the position of the NAL unit before the insertion of the AUD NAL unit and / or the EOB NAL unit.

[0315] The syntax element eosNalUnit[i] may contain the i-th EOS NAL unit in a sample group as specified in a standard document, for example ISO / IEC 23090-3 (the VVC standard).

[0316] Meanwhile, a part of the above-mentioned implicit restoration process of the VVC bitstream can be modified according to the first embodiment as follows.

[0317] When recovering an access unit, picture units from samples having the same decoding time (picture units as specified in standard documents, e.g. ISO / IEC 23090-3 (VVC standard)) may be located within said access unit in ascending order of nuh_layer_id value. Depending on a given condition, the following steps may be taken:

[0318] -If a sample of a track containing the first picture unit of a sample is marked as belonging to a sample group "aud" including ols_idx and lower_ols_idx_inclusive and corresponds to a target operation point, then an AUD NAL unit in the "aud" sample group can be placed within the AU as the first NAL unit of an access unit.

[0319] - If samples in a track are marked as belonging to a sample group 'eos' with ols_idx, max_tid, and lower_ols_idx_inclusive corresponding to the target operation point, then the EOS NAL units in the 'eos' sample group can be arranged in the access unit as follows:

[0320] i) For the first EOS NAL unit, the following applies:

[0321] The first (ie, eos_position[0]+1) NAL unit of the sample is positioned within the reconstructed access unit.

[0322] The EOS NAL unit with index 0 in the "eos" sample group (ie, eosNalUnit[i]) is located within the access unit.

[0323] ii) For the second to last EOS NAL unit (i.e., the EOS NAL units with index i greater than 0), the following applies:

[0324] The next (eos_position[i]-eos_position[i-1])th NAL unit of the sample is positioned within the recovered access unit.

[0325] Locate the EOS NAL unit with index i in the 'eos' sample group (ie, eosNalUnit[i]) within the access unit.

[0326] iii) if there are remaining NAL units of the sample, place said remaining NAL units within the reconstructed access unit.

[0327] -If samples in a track are marked as belonging to an "eob" sample group with ols_idx, max_tid, and lower_ols_idx_inclusive that correspond to the target operation point, then EOB NAL units in the "eob" sample group can be placed after all other NAL units (including EOS NAL units) in an access unit (including EOS NAL units).

[0328] Only picture units from layers and sublayers within the target operation point can be included in the output bitstream.

[0329] As described above, according to the first embodiment, an EOS sample group can include a plurality of EOS NAL units and their number information, which allows an access unit with a multi-layer structure to be correctly restored.

[0330] Example 2

[0331] A second embodiment of the present disclosure can be provided based on all the configurations except for the above-mentioned configuration 4. The implementation of the second embodiment can be related to the first embodiment.

[0332] According to the second embodiment, unlike the existing EOS sample group, a plurality of EOS NAL units can be carried within one EOS sample group. Hereinafter, with reference to FIG. 10, the description overlapping with the above-mentioned existing EOS sample group will be omitted.

[0333] FIG. 13 is a diagram illustrating a syntax structure of an EOS sample group entry according to another embodiment of the present disclosure.

[0334] Referring to FIG. 13, the EOS sample group entry (EndOfSequenceSampleEntry) may include syntax elements ols_idx, max_tid, lower_ols_idx_inclusive, num_eos_nal_unit_minus1, delta_eos_position[i], and eosNalUnit[i].

[0335] The syntax elements ols_idx and max_tid may indicate the operating point to which the EOS sample group applies.

[0336] The syntax element lower_ols_idx_inclusive may indicate whether the EOS sample group applies only to a specific operation point. For example, a second value (e.g., 0) of lower_ols_idx_inclusive may indicate that the EOS sample group applies only to operation points having an output layer set index (OLS index) such as ols_idx. In contrast, a first value (e.g., 1) of lower_ols_idx_inclusive may indicate that the EOS sample group applies to all output layer sets having indexes from 0 to ols_idx.

[0337] The syntax element num_eos_nal_unit_minus1 may indicate the number of EOS NAL units present in the EOS sample group minus one.

[0338] The syntax element delta_eos_position[i] may be used to derive a value of eos_position[i] indicating a NAL unit index after which the i-th EOS NAL unit is placed in the current sample. Here, the NAL unit index may consider only NAL units natively present in the current sample, excluding other NAL units that may be inserted / placed in the current sample. The first NAL unit in the current sample may be regarded as the 0-th NAL unit. eos_position[0] may be set equal to delta_eos_position[0]. For i greater than 0, eos_position[i] may be set equal to eos_position[i-1]+delta_eos_position[i]. Thus, the EOS sample group entry of FIG. 13 may differ from that of FIG. 12, which includes information indicating the insertion position of the EOS NAL unit, in that it includes difference information for deriving the insertion position of the EOS NAL unit.

[0339] Alternatively, in one example, the current sample may be mapped to an 'aud' sample group and / or an 'eob' sample group that induces an AUD NAL unit and / or an EOB NAL unit to be inserted into the sample or the reconstructed access unit, in which case eos_position[i] may be based on the position of the NAL unit before the insertion of the AUD NAL unit and / or the EOB NAL unit.

[0340] The syntax element eosNalUnit[i] may contain the i-th EOS NAL unit in a sample group as specified in a standard document, for example ISO / IEC 23090-3 (the VVC standard).

[0341] As described above, according to the second embodiment, an EOS sample group can include a plurality of EOS NAL units and their number information, which allows an access unit with a multi-layer structure to be correctly restored.

[0342] Example 3

[0343] A third embodiment of the present disclosure can be provided based on the above-mentioned configurations 1, 2, and 6. The implementation of the third embodiment can be related to the VVC file format specification.

[0344] According to the third embodiment, unlike the existing EOS sample group, a single EOS sample group can carry multiple EOS NAL units. Also, information indicating the insertion position of the EOS NAL unit can be excluded from the EOS sample group. Hereinafter, the description of the overlap with the existing EOS sample group described above with reference to FIG. 10 will be omitted.

[0345] FIG. 14 is a diagram illustrating a syntax structure of an EOS sample group entry according to another embodiment of the present disclosure.

[0346] Referring to FIG. 14, the EOS sample group entry (EndOfSequenceSampleEntry) may include syntax elements ols_idx, max_tid, lower_ols_idx_inclusive, num_eos_nal_unit_minus1, and eosNalUnit[i].

[0347] The syntax elements ols_idx and max_tid may indicate the operating point to which the EOS sample group applies.

[0348] The syntax element lower_ols_idx_inclusive may indicate whether the EOS sample group applies only to a particular operation point. For example, a second value (e.g., 0) of lower_ols_idx_inclusive may indicate that the EOS sample group applies only to operation points with an output layer set index (OLS index) such as ols_idx. In contrast, a first value (e.g., 1) of lower_ols_idx_inclusive may indicate that the EOS sample group applies to all output layer sets with indexes from 0 to ols_idx.

[0349] The syntax element num_eos_nal_unit_minus1 plus 1 can indicate the number of EOS NAL units present in the EOS sample group.

[0350] The syntax element eosNalUnit[i] may contain the i-th EOS NAL unit in a sample group as specified in a standard document, for example ISO / IEC 23090-3 (the VVC standard).

[0351] The EOS sample group entry in Figure 14 does not include syntax elements (e.g., eos_position[i], delta_eos_position[i]) related to the insertion position of the EOS NAL unit, unlike the EOS sample group entries in Figures 12 and 13. This allows the bit size of the EOS sample group entry to be further reduced.

[0352] Meanwhile, a part of the above-mentioned implicit restoration process of the VVC bitstream can be modified according to the third embodiment as follows.

[0353] When recovering an access unit, picture units from samples having the same decoding time (such as picture units as specified in standard documents, e.g. ISO / IEC 23090-3 (VVC standard)) may be located within said access unit in ascending order of nuh_layer_id value. Depending on a given condition, the following steps may be taken:

[0354] -If a sample of a track containing the first picture unit of a sample is marked as belonging to a sample group "aud" that includes ols_idx and lower_ols_idx_inclusive and corresponds to a target operation point, then an AUD NAL unit in the "aud" sample group can be placed within the access unit as the first NAL unit of the access unit.

[0355] -If a sample in a track is marked as belonging to a sample group "eos" with ols_idx, max_tid, and lower_ols_idx_inclusive that corresponds to the target operation point, then an EOS NAL unit in the "eos" sample group MAY be placed in the access unit after all NAL units of the access unit except for the EOB NAL unit (if present).

[0356] -If samples in a track are marked as belonging to an "eob" sample group with ols_idx, max_tid, and lower_ols_idx_inclusive that correspond to the target operation point, then EOB NAL units in the "eob" sample group can be placed after all other NAL units (including EOS NAL units) in the access unit.

[0357] As described above, according to the third embodiment, an EOS sample group can include a plurality of EOS NAL units and their number information. Also, information indicating the insertion position of an EOS NAL unit can be excluded from the EOS sample group. This allows the access unit of a multi-layer structure to be correctly restored while saving the number of bits.

[0358] Example 4

[0359] A fourth embodiment of the present disclosure can be provided based on the above-described configurations 1, 2, and 7. The implementation of the fourth embodiment can be related to the VVC file format specification.

[0360] According to the fourth embodiment, unlike the existing EOS sample group, a single EOS sample group can carry multiple EOS NAL units. Also, information indicating the insertion position of the EOS NAL unit can be excluded from the EOS sample group. Hereinafter, the description overlapping with the existing EOS sample group described above with reference to FIG. 10 will be omitted.

[0361] The syntax and semantics of the EOS sample entry (EndOfSequenceSampleEntry) according to the fourth embodiment may be similar to that of the third embodiment described above with reference to FIG.

[0362] Meanwhile, a part of the aforementioned implicit restoration process of the VVC bitstream can be modified according to Example 4. The implicit restoration process modified according to Example 4 can be the same as that of Example 3, except for the insertion position of the EOS NAL unit. The insertion position of the EOS NAL unit according to Example 4 is as follows.

[0363] -If a sample in a track is marked as belonging to a sample group "eos" with ols_idx, max_tid, and lower_ols_idx_inclusive that corresponds to the target operation point, then an EOS NAL unit in the "eos" sample group can be placed in the access unit after all NAL units from the sample except for the EOB NAL unit (if present).

[0364] As described above, according to the fourth embodiment, an EOS sample group can include a plurality of EOS NAL units and their number information. Also, information indicating the insertion position of an EOS NAL unit can be excluded from the EOS sample group. This allows the access unit of a multi-layer structure to be correctly restored while saving the number of bits.

[0365] A method for receiving / generating a media file according to an embodiment of the present disclosure will now be described in detail.

[0366] 15 is a flowchart illustrating a method for receiving a media file according to an embodiment of the present disclosure. Each step of FIG. 15 may be performed by a media file receiving device. In one example, the media file receiving device may correspond to receiving device B of FIG. 1.

[0367] 15, a media file receiving device may obtain one or more tracks and sample groups from a media file received from a media file generating / transmitting device (S1510). In one example, the media file may have a file format such as ISO Base Media File Format (BMFF) or Common Media Application Format (CMAF).

[0368] The media file receiving device can then reconstruct access units based on the samples in the track and the sample groups (S1520).

[0369] The sample groups may include a first sample group that includes end-of-sequence information for video data that includes the access unit.

[0370] The first sample group may include an end of sequence (EOS) NAL unit belonging to the first sample group and a first syntax element related to the number of the EOS NAL units. The first sample group may have the syntax structure described above with reference to Figures 12 to 14. In this case, the EOS NAL unit may correspond to the above-mentioned syntax element eosNalUnit[i]. Also, the first syntax element may correspond to the above-mentioned syntax element num_eos_nal_unit_minus1.

[0371] In one embodiment, the value of the first syntax element plus 1 may indicate the number of EOS NAL units. The first syntax element may have an unsigned integer type (i.e., unsigned int), such that the value of the first syntax element may be equal to or greater than 0, such that the first sample group includes at least one EOS NAL unit.

[0372] In one embodiment, the EOS NAL units can be listed in a loop controlled based on the first syntax element, for example, as shown in Figures 12 to 14, the syntax element eosNalUnit[i] can be obtained from the EOS sample group in the order of NAL unit index i via a for-loop that is repeated num_eos_nal_unit_minus1+1 times.

[0373] In one embodiment, the maximum NAL unit index value that the EOS NAL unit has may be equal to the value of the first syntax element (eg, num_eos_nal_unit_minus1).

[0374] In one embodiment, based on the samples in the track belonging to the first sample group, the EOS NAL unit may be located at a predetermined position within the access unit, where the predetermined position may be determined to be the next position of all NAL units of the sample, except for an end of bitstream (EOB) NAL unit, within the access unit, or the predetermined position may be determined to be the next position of all NAL units of the access unit, except for an end of bitstream (EOB) NAL unit, within the access unit.

[0375] 16 is a flowchart illustrating a media file generation method according to an embodiment of the present disclosure. The steps of FIG. 16 may be performed by a media file generation device. In one example, the media file generation device may correspond to the sending device A of FIG. 1.

[0376] 16, a media file generating apparatus may encode video data including an access unit (S1610). In one example, the video data may be encoded through prediction, transformation, and quantization processes according to a video codec standard, for example, the VVC standard.

[0377] The media file generating apparatus may generate a first sample group including end-of-sequence information of the encoded video data (S1620).

[0378] Then, the media file generating device may generate a media file based on the encoded video data and the first sample group (S1630). In one example, the media file may have a file format such as ISO Base Media File Format (BMFF) or Common Media Application Format (CMAF).

[0379] The first sample group may include an end of sequence (EOS) NAL unit belonging to the first sample group and a first syntax element related to the number of the EOS NAL units. The first sample group may have the syntax structure described above with reference to Figures 12 to 14. In this case, the EOS NAL unit may correspond to the above-mentioned syntax element eosNalUnit[i]. Furthermore, the first syntax element may correspond to the above-mentioned syntax element num_eos_nal_unit_minus1.

[0380] In one embodiment, the value of the first syntax element plus 1 may indicate the number of EOS NAL units. The first syntax element may have an unsigned integer type (i.e., unsigned int), such that the value of the first syntax element may be equal to or greater than 0, such that the first sample group includes at least one EOS NAL unit.

[0381] In one embodiment, the EOS NAL units can be listed in a loop controlled based on the first syntax element, for example, as shown in Figures 12 to 14, the syntax element eosNalUnit[i] can be inserted (or coded) in the EOS sample group in the order of NAL unit index i via a for-loop that is repeated num_eos_nal_unit_minus1+1 times.

[0382] In one embodiment, the maximum NAL unit index value that the EOS NAL unit has may be equal to the value of the first syntax element (eg, num_eos_nal_unit_minus1).

[0383] In one embodiment, based on the samples in the track belonging to the first sample group, the EOS NAL unit may be located at a predetermined position in the access unit, where the predetermined position may be determined to be the next position of all NAL units of the sample except for an end of bitstream (EOB) NAL unit in the access unit, or the predetermined position may be determined to be the next position of all NAL units of the access unit except for an end of bitstream (EOB) NAL unit in the access unit.

[0384] As described above, according to the embodiment of the present disclosure, a new "eos" sample group design that can carry multiple EOS NAL units is provided, which allows the "eos" sample group to operate correctly for VVC elementary streams with multiple layers.

[0385] Although the exemplary method of the present disclosure is expressed as a series of operations for clarity of explanation, this is not intended to limit the order in which the steps are performed, and each step may be performed simultaneously or in a different order, if necessary. To realize the method according to the present disclosure, the steps illustrated may include other steps, some steps may be omitted and the remaining steps may be omitted, or some steps may be omitted and additional steps may be included.

[0386] In the present disclosure, an image encoding device or an image decoding device that performs a predetermined operation (step) can perform the operation (step) to check the execution conditions or circumstances of the operation (step). For example, if it is described that a predetermined operation is performed when a predetermined condition is satisfied, the image encoding device or the image decoding device can perform the predetermined operation after performing an operation to check whether the predetermined condition is satisfied or not.

[0387] The various embodiments of the present disclosure are not intended to enumerate all possible combinations, but are intended to describe representative aspects of the present disclosure, and the matters described in the various embodiments may be applied independently or in combination of two or more.

[0388] Additionally, various embodiments of the present disclosure may be implemented using hardware, firmware, software, or a combination thereof, etc. In the case of a hardware implementation, the implementation may be implemented using one or more Application Specific Integrated Circuits (ASICs), Digital Signal Processors (DSPs), Digital Signal Processing Devices (DSPDs), Programmable Logic Devices (PLDs), Field Programmable Gate Arrays (FPGAs), general processors, controllers, microcontrollers, microprocessors, etc.

[0389] In addition, the media file receiving device and the media file generating device to which the embodiment of the present disclosure is applied may be included in a multimedia broadcast transmitting / receiving device, a mobile communication terminal, a home cinema video device, a digital cinema video device, a surveillance camera, a video conversation device, a real-time communication device such as a video communication, a mobile streaming device, a storage medium, a camcorder, a custom video (VoD) service providing device, an over-the-top video (OTT) device, an internet streaming service providing device, a three-dimensional (3D) video device, an image telephone video device, and a medical video device, and may be used to process a video signal or a data signal. For example, the over-the-top video (OTT) device may include a game console, a Blu-ray player, an internet-connected TV, a home theater system, a smartphone, a tablet PC, a digital video recorder (DVR), and the like.

[0390] FIG. 17 is a diagram illustrating a content streaming system to which an embodiment of the present disclosure can be applied.

[0391] As shown in FIG. 17, a content streaming system to which an embodiment of the present disclosure is applied may broadly include an encoding server, a streaming server, a Web server, a media storage, a user device, and a multimedia input device.

[0392] The encoding server compresses content input from a multimedia input device such as a smartphone, camera, camcorder, etc. into digital data to generate a bitstream and transmits the bitstream to the streaming server. As another example, if a multimedia input device such as a smartphone, camera, video camera, etc. directly generates a bitstream, the encoding server can be omitted.

[0393] The bitstream may be generated by an image encoding method and / or image encoding device to which an embodiment of the present disclosure is applied, and the streaming server may temporarily store the bitstream in the process of transmitting or receiving the bitstream.

[0394] The streaming server transmits multimedia data to a user device based on a user request via a web server, and the web server can act as a medium to inform the user of available services. When a user requests a desired service from the web server, the web server transmits the request to the streaming server, and the streaming server can transmit the multimedia data to the user. At this time, the content streaming system can include a separate control server, and in this case, the control server can control commands / responses between devices in the content streaming system.

[0395] The streaming server may receive the content from a media storage and / or an encoding server. For example, when receiving the content from the encoding server, the content may be received in real time. In this case, the streaming server may store the bitstream for a certain period of time in order to provide a smooth streaming service.

[0396] Examples of the user devices include mobile phones, smart phones, laptop computers, digital broadcasting terminals, personal digital assistants (PDAs), portable multimedia players (PMPs), navigation systems, slate PCs, tablet PCs, ultrabooks, wearable devices such as smartwatches, smart glass, head mounted displays (HMDs), digital TVs, desktop computers, and digital signage.

[0397] Each server in the content streaming system can be operated as a distributed server, in which case data received from each server can be processed in a distributed manner.

[0398] The scope of the present disclosure includes software or machine-executable commands (e.g., operating systems, applications, firmware, programs, etc.) that cause operations according to the methods of the various embodiments to be performed on a device or computer, and non-transitory computer-readable medium on which such software or commands can be stored and executed on a device or computer. [Industrial Applicability]

[0399] Embodiments of the present disclosure can be used to create, send and receive media files.

Claims

1. A method for receiving a media file performed by a media file receiving device, comprising: obtaining one or more tracks and sample groups from a media file; reconstructing an access unit based on the samples in the track and the sample groups; The sample group includes a first sample group including end of sequence (EOS) information of video data to which the access unit belongs, The first sample group includes one or more EOS NAL units and a first syntax element related to a number of the EOS NAL units.

2. The method of claim 1 , wherein a value of the first syntax element plus one indicates a number of the EOS NAL units.

3. The method of claim 1 , wherein the EOS NAL units are listed in a loop controlled based on the first syntax element.

4. The method of claim 1 , wherein a maximum index value of the EOS NAL unit is the same as a value of the first syntax element.

5. The method of claim 1 , wherein the EOS NAL unit is placed at a predetermined location within the access unit based on the samples in the track belonging to the first sample group.

6. The method of claim 5, wherein the predetermined position is a position within the access unit next to all NAL units of the sample except an end of bitstream (EOB) NAL unit.

7. A media file receiving device including a memory and at least one processor, The at least one processor: Retrieving one or more tracks and sample groups from a media file; Reconstructing an access unit based on the samples in the track and the sample groups; The sample group includes a first sample group including end of sequence (EOS) information of video data to which the access unit belongs, The first sample group includes one or more EOS NAL units and a first syntax element related to a number of the EOS NAL units.

8. 1. A method for generating a media file performed by a media file generating device, comprising: encoding video data including access units; generating a first sample group including end of sequence (EOS) information of the encoded video data; generating a media file based on the encoded video data and the first group of samples; The first sample group includes one or more EOS NAL units and a first syntax element related to a number of the EOS NAL units.

9. The method of claim 8 , wherein the value of the first syntax element plus one indicates the number of EOS NAL units.

10. The method of claim 8 , wherein the EOS NAL units are listed in a loop controlled based on the first syntax element.

11. The method of claim 8 , wherein a maximum index value of the EOS NAL unit is the same as a value of the first syntax element.

12. The method of claim 8 , wherein the EOS NAL unit is placed at a predetermined location within the access unit based on the sample of the video data belonging to the first sample group.

13. The method of claim 12, wherein the predetermined position is a position within the access unit next to all NAL units of the sample except an end of bitstream (EOB) NAL unit.

14. A method for transmitting a media file generated by the method of claim 8.

15. 1. A media file generation device including a memory and at least one processor, The at least one processor: encoding video data including access units; generating a first sample group including end of sequence (EOS) information of the encoded video data; generating a media file based on the encoded video data and the first group of samples; The first sample group includes one or more EOS NAL units and a first syntax element related to a number of the EOS NAL units.

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