Video decoding method, video encoding method, computer-readable storage medium, and data transmission method for video

Abstract

This video decoding method performed by a decoding device, according to the present disclosure, comprises the steps of: acquiring a quality metric (QM) supplemental enhancement information (SEI) message included in at least one picture unit; and acquiring quality index information on the basis of the QM SEI message, wherein a first QM SEI message including at least one piece of average quality index information is included in the first picture unit in a CLVS.

Description

Video decoding method, video encoding method, computer-readable storage medium and method for transmitting data for video

[0001] The present disclosure relates to a method for decoding / encoding image information, a computer-readable storage medium for storing image information, and a method for transmitting image information.

[0002] Recently, the demand for high-resolution, high-quality video, such as HD (High Definition) and UHD (Ultra High Definition), has been increasing across various fields. As video data becomes higher in resolution and quality, the relative amount of information or bits transmitted increases compared to conventional video data. This increase in the amount of transmitted information or bits leads to higher transmission and storage costs.

[0003] Accordingly, high-efficiency video compression technology is required to effectively transmit, store, and play back high-resolution, high-quality video information.

[0004] The present disclosure aims to improve the reliability of a coding system including an encoding device and a decoding device.

[0005] The present disclosure aims to improve the coding efficiency of a coding system including an encoding device and a decoding device.

[0006] The present disclosure aims to improve the data transmission efficiency of a coding system including an encoding device and a decoding device.

[0007] The technical problems to be solved in this disclosure are not limited to those mentioned above, and other technical problems not mentioned will be clearly understood by those skilled in the art to which this disclosure belongs from the description below.

[0008] According to one aspect of the present disclosure, an image decoding method comprises the steps of acquiring a quality metric (QM) supplemental enhancement information (SEI) message included in at least one picture unit, and acquiring quality metric information based on the QM SEI message, wherein the first QM SEI message including at least one average quality metric information is included in the first picture unit in the CLVS.

[0009] According to one aspect of the present disclosure, a decoding device for decoding image information acquires a quality metric (QM) supplemental enhancement information (SEI) message included in at least one picture unit, acquires quality metric information based on the QM SEI message, and is characterized in that a first QM SEI message including at least one average quality metric information is included in the first picture unit in the CLVS.

[0010] In a method or apparatus for decoding the above image information, based on the existence of a second QM SEI message that includes at least one average quality indicator information and is not included in the first picture unit in the CLVS, the first QM SEI message is included in the first picture unit in the CLVS.

[0011] In a method or device for decoding the above image information, the value of the at least one average quality indicator information included in the first QM SEI message may be characterized as being the same as the value of the average quality indicator information included in the second QM SEI message.

[0012] In a method or device for decoding the above image information, a second QM SEI message exists that is not included in the first picture unit in the CLVS, and based on the fact that the second QM SEI message is not included in the PON (processing order nesting) SEI message, the first QM SEI message may be characterized as not being included in the PON SEI message.

[0013] In a method or device for decoding the above image information, a third QM SEI message exists that is not included in the first picture unit in the CLVS, and based on the fact that the third QM SEI message is included in a PON (processing order nesting) SEI message, the first QM SEI message may be characterized as being included in a PON SEI message having the same target identifier information as the PON SEI message.

[0014] According to one aspect of the present disclosure, an image encoding method comprises the steps of: generating at least one Quality Metic (QM) supplemental enhancement information (SEI) message included in at least one picture unit based on quality indicator information; and encoding image information including the at least one QM SEI message, wherein the first QM SEI message including at least one average quality indicator information is included in the first picture unit in the CLVS.

[0015] According to one aspect of the present disclosure, an apparatus for encoding image information generates at least one Quality Metic (QM) SEI (supplemental enhancement information) message included in at least one picture unit based on quality indicator information, encodes image information including the at least one QM SEI message, and is characterized in that the first QM SEI message including at least one average quality indicator information is included in the first picture unit in the CLVS.

[0016] In a method or device for encoding the above image information, based on the existence of a second QM SEI message that includes at least one average quality indicator information and is not included in the first picture unit in the CLVS, the first QM SEI message may be characterized as being included in the first picture unit in the CLVS.

[0017] In a method or device for encoding the above image information, the value of the at least one average quality indicator information included in the first QM SEI message may be characterized as being the same as the value of the average quality indicator information included in the second QM SEI message.

[0018] In a method or device for encoding the above image information, a second QM SEI message exists that is not included in the first picture unit in the CLVS, and based on the fact that the second QM SEI message is not included in the PON (processing order nesting) SEI message, the first QM SEI message may be characterized as not being included in the PON SEI message.

[0019] In a method or device for encoding the above image information, a third QM SEI message exists that is not included in the first picture unit in the CLVS, and based on the fact that the third QM SEI message is included in a PON (processing order nesting) SEI message, the first QM SEI message may be characterized as being included in a PON SEI message having the same target identifier information as the PON SEI message.

[0020] According to one aspect of the present disclosure, a bitstream generated by an image encoding method is stored in a computer-readable storage medium. At least one Quality Metic (QM) supplemental enhancement information (SEI) message included in at least one picture unit is generated based on quality indicator information, and a bitstream generated based on image information including the at least one QM SEI message is stored in a computer-readable storage medium, and a first QM SEI message including at least one average quality indicator information is included in the first picture unit in the CLVS.

[0021] According to one aspect of the present disclosure, a method for transmitting data for an image comprises the steps of acquiring image information, wherein the image information includes at least one Quality Metic (QM) SEI (supplemental enhancement information) message included in at least one picture unit, and transmitting the data including the image information, wherein the first QM SEI message including at least one average quality indicator information is included in the first picture unit in the CLVS.

[0022] The features briefly summarized above regarding the present disclosure are merely exemplary aspects of the detailed description of the present disclosure that follows and do not limit the scope of the present disclosure.

[0023] According to the present disclosure, the reliability of a coding system including an encoding device and a decoding device can be improved.

[0024] According to the present disclosure, the coding efficiency of a coding system including an encoding device and a decoding device can be improved.

[0025] According to the present disclosure, the data transmission efficiency of a coding system including an encoding device and a decoding device can be improved.

[0026] The effects obtainable from the present disclosure are not limited to those mentioned above, and other unmentioned effects will be clearly understood by those skilled in the art to which the present disclosure belongs from the description below.

[0027] FIG. 1 is a schematic diagram illustrating a video coding system to which an embodiment according to the present disclosure can be applied.

[0028] FIG. 2 is a schematic diagram showing an encoding device to which an embodiment according to the present disclosure can be applied.

[0029] FIG. 3 is a schematic diagram showing a decoding device to which an embodiment according to the present disclosure can be applied.

[0030] Figure 4 illustrates an exemplary hierarchical structure for a coded video / image.

[0031] FIG. 5 is a diagram illustrating a method for decoding image information according to one embodiment of the present disclosure.

[0032] FIG. 6 is a diagram illustrating a method for encoding image information according to one embodiment of the present disclosure.

[0033] FIG. 7 is a drawing illustrating an exemplary content streaming system to which an embodiment according to the present disclosure can be applied.

[0034] Hereinafter, embodiments of the present disclosure are described in detail with reference to the attached drawings so that those skilled in the art can easily implement them. However, the present disclosure may be embodied in various different forms and is not limited to the embodiments described herein.

[0035] In describing the embodiments of the present disclosure, detailed descriptions of known configurations or functions are omitted if it is determined that such descriptions could obscure the essence of the present disclosure. Additionally, parts of the drawings unrelated to the description of the present disclosure have been omitted, and similar parts are denoted by similar reference numerals.

[0036] In the present disclosure, when a component is described as being "connected," "combined," or "joined" with another component, this may include not only a direct connection but also an indirect connection in which another component exists in between. Furthermore, when a component is described as "comprising" or "having" another component, this means that, unless specifically stated otherwise, it does not exclude the other component but may include an additional component.

[0037] In the present disclosure, terms such as first, second, etc. are used solely for the purpose of distinguishing one component from another and do not limit the order or importance of the components unless specifically stated otherwise. Accordingly, within the scope of the present disclosure, a first component in one embodiment may be referred to as a second component in another embodiment, and likewise, a second component in one embodiment may be referred to as a first component in another embodiment.

[0038] In this disclosure, distinct components are intended to clearly describe their respective features and do not imply that the components are separate. That is, multiple components may be integrated to form a single hardware or software unit, or a single component may be distributed to form multiple hardware or software units. Accordingly, such integrated or distributed embodiments are included within the scope of this disclosure, unless otherwise noted.

[0039] In the present disclosure, the components described in various embodiments do not necessarily mean essential components, and some may be optional components. Accordingly, embodiments consisting of a subset of the components described in one embodiment are also included within the scope of the present disclosure. Furthermore, embodiments including additional components in addition to the components described in various embodiments are also included within the scope of the present disclosure.

[0040] The present disclosure relates to the encoding and decoding of images. For example, the methods and embodiments disclosed in this document may be applied to methods disclosed in the VVC (versatile video coding) standard, EVC (essential video coding) standard, AV1 (AOMedia Video 1) standard, AVS2 (2nd generation of audio video coding standard) or next-generation video / image coding standards (e.g., H.267 or H.268).

[0041] The present disclosure presents various embodiments relating to video / image coding, and unless otherwise stated, said embodiments may be performed in combination with one another.

[0042] Unless newly defined in this disclosure, the terms used herein may have the ordinary meanings commonly used in the technical field to which this disclosure belongs.

[0043] In this disclosure, "video" may refer to a set of images over time. In this disclosure, "picture" generally refers to a unit representing a single image at a specific time, and a slice / tile is a unit that constitutes a part of a picture in coding. A slice / tile may include one or more coding tree units (CTUs). A picture may be composed of one or more slices / tiles. A picture may be composed of one or more tile groups. A tile group may include one or more tiles. A brick may represent a rectangular area of ​​rows of CTUs within a tile in a picture. In this document, tile groups and slices may be used interchangeably. For example, in this document, a tile group / tile group header may be referred to as a slice / slice header.

[0044] In the present disclosure, "pixel" or "pel" may refer to the smallest unit constituting a picture (or image). Additionally, "sample" may be used as a term corresponding to pixel. A sample may generally represent a pixel or a pixel value, may represent only the pixel / pixel value of the luminance component, or may represent only the pixel / pixel value of the chroma component.

[0045] In this disclosure, "unit" may represent a basic unit of image processing. A unit may include at least one of a specific area of ​​a picture and information related to that area. A unit may include one luminance block and two chroma (e.g., cb, cr) blocks. Depending on the case, the term "unit" may be used interchangeably with terms such as "block" or "area." In general, an MxN block may include samples (or sample arrays) or a set (or array) of transform coefficients consisting of M columns and N rows.

[0046] In the present disclosure, "current block" may mean one of "current coding block," "current coding unit," "block to be encoded," "block to be decoded," or "block to be processed." When prediction is performed, "current block" may mean "current prediction block" or "block to be predicted." When transformation (inverse transformation) / quantization (inverse quantization) is performed, "current block" may mean "current transformation block" or "block to be transformed." When filtering is performed, "current block" may mean "block to be filtered."

[0047] In the present disclosure, "current block" may mean a block comprising both a luminous component block and a chroma component block, or "luma block of the current block," unless explicitly stated as a chroma block. The luminous component block of the current block may be expressed by including an explicit description of a luminous component block, such as "luma block" or "current luminous block." Additionally, the chroma component block of the current block may be expressed by including an explicit description of a chroma component block, such as "chroma block" or "current chroma block."

[0048] In the present disclosure, " / " and "," may be interpreted as "and / or." For example, "A / B" and "A, B" may be interpreted as "A and / or B." Additionally, "A / B / C" and "A, B, C" may mean "at least one of A, B and / or C."

[0049] In the present disclosure, "or" may be interpreted as "and / or". For example, "A or B" may mean 1) "A" only, 2) "B" only, or 3) "A and B". Alternatively, in the present disclosure, "or" may mean "additionally or alternatively".

[0050] FIG. 1 is a schematic diagram illustrating a video / image coding system to which an embodiment according to the present disclosure can be applied.

[0051] Referring to FIG. 1, a video / image coding system may include a first device (source device) and a second device (receiving device). The source device may transmit encoded video / image or data in the form of a file or streaming to the receiving device via a digital storage medium or a network.

[0052] The source device may include a video source, an encoding device, and a transmission unit. The receiving device may include a receiver, a decoding device, and a renderer. The encoding device may be called a video / image encoding device, and the decoding device may be called a video / image decoding device. The transmitter may be included in the encoding device. The receiver may be included in the decoding device. The renderer may include a display unit, and the display unit may be composed of a separate device or an external component.

[0053] A video source may acquire video / images through processes such as video / image capture, synthesis, or generation. The video source may include a video / image capture device and / or a video / image generation device. The video / image capture device may include, for example, one or more cameras, a video / image archive containing previously captured video / images, etc. The video / image generation device may include, for example, a computer, a tablet, and a smartphone, etc., and may generate video / images (electronically). For example, virtual video / images may be generated through a computer, etc., in which case the video / image capture process may be replaced by a process in which related data is generated.

[0054] The encoding device can encode input video / images. The encoding device can perform a series of procedures, such as prediction, transformation, and quantization, for compression and coding efficiency. The encoded data (encoded video / image information) can be output in the form of a bitstream.

[0055] The transmission unit can transmit encoded video / image information or data output in the form of a bitstream to the receiving unit of a receiving device in the form of a file or streaming via a digital storage medium or a network. The digital storage medium may include various storage media such as USB, SD, CD, DVD, Blu-ray, HDD, and SSD. The transmission unit may include elements for creating a media file through a predetermined file format and elements for transmission via a broadcasting / communication network. The receiving unit can receive / extract the bitstream and transmit it to a decoding device.

[0056] The decoding device can decode video / images by performing a series of procedures such as inverse quantization, inverse transform, and prediction corresponding to the operation of the encoding device.

[0057] The renderer can render the decoded video / image. The rendered video / image can be displayed through the display unit.

[0058] FIG. 2 is a schematic diagram illustrating an encoding device to which an embodiment according to the present disclosure can be applied.

[0059] Referring to FIG. 2, the encoding device (200) may be configured to include an image partitioner (210), a predictor (220), a residual processor (230), an entropy encoder (240), an adder (250), a filter (260), and a memory (270). The predictor (220) may include an inter-predictor (221) and an intra-predictor (222). The residual processor (230) may include a transformer (232), a quantizer (233), a dequantizer (234), and an inverse transformer (235). The residual processor (230) may further include a subtractor (231). The addition unit (250) may be referred to as a reconstructor or a reconstructed block generator. The above-described image segmentation unit (210), prediction unit (220), residual processing unit (230), entropy encoding unit (240), addition unit (250), and filtering unit (260) may be configured by one or more hardware components (e.g., an encoder chipset or processor) according to the embodiment. Additionally, the memory (270) may include a DPB (Decoded Picture Buffer) and may be configured by a digital storage medium. The hardware component may further include the memory (270) as an internal / external component.

[0060] The image segmentation unit (210) can divide an input image (or picture, frame) input to an encoding device (200) into one or more processing units. For example, the processing unit may be called a coding unit (CU). A coding unit may be recursively divided into a coding tree unit (CTU) or a largest coding unit (LCU) according to a QTBTTT (Quad-tree binary-tree ternary-tree) structure. For example, a single coding unit may be divided into multiple coding units of a deeper depth based on a quad-tree structure, a binary-tree structure, and / or a ternary-tree structure. For example, a quad-tree structure may be applied first, and a binary-tree structure and / or a ternary-tree structure may be applied later. Alternatively, a binary-tree structure may be applied first. A coding procedure according to the present disclosure may be performed based on the final coding unit that is no longer divided. In this case, based on coding efficiency according to image characteristics, the maximum coding unit may be used directly as the final coding unit, or, if necessary, the maximum coding unit may be recursively divided into lower-depth coding units so that a coding unit of the optimal size is used as the final coding unit. Here, the coding procedure may include procedures such as prediction, transformation, and restoration described later. As another example, the processing unit may further include a prediction unit (PU) or a transformation unit (TU). The prediction unit and the transformation unit may each be divided or partitioned from the final coding unit.The above prediction unit may be a unit of sample prediction, and the above transformation unit may be a unit that derives transformation coefficients and / or a unit that derives a residual signal from transformation coefficients.

[0061] The term "unit" may be used interchangeably with terms such as "block" or "area" depending on the context. In general, an MxN block may represent a set of samples or transform coefficients consisting of M columns and N rows. A sample can generally represent a pixel or a pixel value, and may represent only the pixel / pixel value of the luminance component or only the pixel / pixel value of the chroma component. A sample may be used to refer to a single picture (or image) as a term corresponding to a pixel or pel.

[0062] The encoding device (200) can generate a residual signal (residual block, residual sample array) by subtracting a prediction signal (predicted block, prediction sample array) output from an inter prediction unit (221) or an intra prediction unit (222) from an input image signal (original block, original sample array), and the generated residual signal is transmitted to a conversion unit (232). In this case, as illustrated, the unit that subtracts the prediction signal (predicted block, prediction sample array) from the input image signal (original block, original sample array) within the encoding device (200) may be called a subtraction unit (231). The prediction unit (220) can perform a prediction for a block to be processed (hereinafter, current block) and generate a predicted block (predicted block) containing prediction samples for said current block. The prediction unit (220) can determine whether intra prediction is applied or inter prediction is applied in units of the current block or CU. The prediction unit (220) can generate various information regarding prediction, such as prediction mode information, as described below in the description of each prediction mode, and transmit it to the entropy encoding unit (240). The information regarding prediction can be encoded in the entropy encoding unit (240) and output in the form of a bitstream.

[0063] The intra prediction unit (222) can predict the current block by referring to samples within the current picture. The referenced samples may be located near the current block or away from it, depending on the prediction mode. In intra prediction, the 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 degree of fineness of the prediction direction. However, this is merely an example, and depending on the settings, more or fewer directional prediction modes may be used. The intra prediction unit (222) may also determine the prediction mode applied to the current block by using the prediction mode applied to the surrounding blocks.

[0064] The inter prediction unit (221) can derive a predicted block for the current block based on a reference block (reference sample array) specified by a motion vector on a reference picture. At this time, to reduce the amount of motion information transmitted in the inter prediction mode, motion information can be predicted in blocks, sub-blocks, or samples based on the 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 information on the inter prediction direction (L0 prediction, L1 prediction, Bi prediction, etc.). In the case of inter prediction, neighboring blocks may include spatial neighboring blocks existing within the current picture and temporal neighboring blocks existing in the reference picture. The reference picture containing the reference blocks and the reference picture containing the temporal neighboring blocks may be the same or different from each other. The temporal neighboring blocks may be referred to by names such as collocated reference block, collocated CU (colCU), etc. A reference picture containing the aforementioned temporal surrounding blocks may be called a collocated picture (colPic). For example, the inter prediction unit (221) may construct a list of motion information candidates based on surrounding blocks and generate information indicating which candidate is used to derive the motion vector and / or reference picture index of the current block. Inter prediction may be performed based on various prediction modes, for example, in the case of skip mode and merge mode, the inter prediction unit (221) may use the motion information of surrounding blocks as motion information of the current block. In the case of skip mode, unlike merge mode, a residual signal may not be transmitted.In the motion vector prediction (MVP) mode, the motion vector of surrounding blocks is used as a motion vector predictor, and the motion vector of the current block can be indicated by signaling the motion vector difference.

[0065] The prediction unit (220) may generate a prediction signal based on various prediction methods and / or prediction techniques described below. For example, the prediction unit (220) may apply intra prediction or inter prediction for the prediction of the current block, as well as apply intra prediction and inter prediction simultaneously. A prediction method that applies intra prediction and inter prediction simultaneously for the prediction of the current block may be called combined inter and intra prediction (CIIP). Additionally, the prediction unit (220) may be based on an intra block copy (IBC) prediction mode or a palette mode for the prediction of the block. The IBC prediction mode or palette mode may be used for content video / video coding, such as in games, for example, screen content coding (SCC). IBC basically performs prediction within the current picture, but it may be performed similarly to inter prediction in that it derives a reference block within the current picture. That is, IBC may use at least one of the inter prediction techniques described in this document. Palette mode can be viewed as an example of intra-coding or intra-prediction. When palette mode is applied, sample values ​​within a picture can be signaled based on information regarding palette tables and palette indices.

[0066] The prediction signal generated through the prediction unit (220) can be used to generate a restoration signal or to generate a residual signal. The subtraction unit (231) can generate a residual signal (residual signal, residual block, residual sample array) by subtracting the prediction signal (predicted block, prediction sample array) output from the prediction unit (220) from the input image signal (original block, original sample array). The generated residual signal can be transmitted to the conversion unit (232).

[0067] The transformation unit (232) can generate transform coefficients by applying a transformation technique to a residual signal. For example, the transformation 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, GBT refers to a transformation obtained from a graph when the relationship information between pixels is represented as a graph. CNT refers to a transformation obtained based on a prediction signal generated using all previously reconstructed pixels. The transformation process may be applied to a block of pixels of the same size in a square, or to a block of variable size that is not square.

[0068] The quantization unit (233) can quantize the transformation coefficients and transmit them to the entropy encoding unit (240). The entropy encoding unit (240) can encode the quantized signal (information regarding the quantized transformation coefficients) and output it as a bitstream. The information regarding the quantized transformation coefficients may be called residual information. The quantization unit (233) can rearrange the block-shaped quantized transformation coefficients into a one-dimensional vector form based on the coefficient scan order, and can also generate information regarding the quantized transformation coefficients based on the one-dimensional vector-shaped quantized transformation coefficients.

[0069] The entropy encoding unit (240) can perform various encoding methods such as, for example, exponential Golomb, CAVLC (context-adaptive variable length coding), CABAC (context-adaptive binary arithmetic coding), etc. The entropy encoding unit (190) may encode information required for video / image restoration (e.g., values ​​of syntax elements) together or separately, in addition to quantized transform coefficients. The encoded information (e.g., encoded video / image information) may be transmitted or stored in the form of a bitstream in units of NAL (network abstraction layer) units. The video / image information may further include information regarding 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). Additionally, the video / image information may further include general constraint information. The signaling information, transmitted information, and / or syntax elements mentioned in the present disclosure may be included in the video / image information. The video / image information may be encoded through the encoding procedure described above and included in the bitstream.

[0070] The above bitstream may be transmitted via a network or 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 USB, SD, CD, DVD, Blu-ray, HDD, SSD, etc. A transmission unit (not shown) for transmitting a signal output from the entropy encoding unit (240) and / or a storage unit (not shown) for storing it may be provided as an internal / external element of the encoding device (200), or the transmission unit may be provided as a component of the entropy encoding unit (240).

[0071] The quantized transformation coefficients output from the quantization unit (233) can be used to generate a residual signal. For example, a residual signal (residual block or residual samples) can be restored by applying inverse quantization and inverse transformation to the quantized transformation coefficients through the inverse quantization unit (234) and the inverse transformation unit (235).

[0072] Meanwhile, LMCS (luma mapping with chroma scaling) may be applied during the picture encoding and / or restoration process.

[0073] The adder (250) can generate a reconstructed signal (reconstructed picture, reconstructed block, reconstructed sample array) by adding the reconstructed residual signal to the prediction signal output from the inter prediction unit (221) or the intra prediction unit (222). In cases where there is no residual for the block to be processed, such as when a skip mode is applied, the predicted block can be used as the reconstructed block. The adder (250) may be called a reconstructed unit or a reconstructed block generation unit. The generated reconstructed signal can be used for intra prediction of the next block to be processed within the current picture, and can also be used for inter prediction of the next picture after undergoing filtering as described below.

[0074] The filtering unit (260) can improve subjective / objective image quality by applying filtering to the restored signal. For example, the filtering unit (260) can generate a modified restored picture by applying various filtering methods to the restored picture, and can store the modified restored picture in memory (270), specifically in the DPB of memory (170). The various filtering methods may include, for example, deblocking filtering, sample adaptive offset, adaptive loop filter, bilateral filter, etc. The filtering unit (260) can generate various information regarding filtering and transmit it to the entropy encoding unit (240), as described below in the description of each filtering method. The information regarding filtering can be encoded in the entropy encoding unit (240) and output in the form of a bitstream.

[0075] The modified restored picture transmitted to the memory (270) can be used as a reference picture in the inter-prediction unit (221). Through this, the encoding device (200) can avoid prediction mismatches between the encoding device (200) and the decoding device when inter-prediction is applied, and can also improve encoding efficiency.

[0076] The DPB in memory (270) can store a modified restored picture to be used as a reference picture in the inter prediction unit (221). Memory (270) can store motion information of blocks from which motion information is derived (or encoded) in the current picture and / or motion information of blocks in the picture that have already been restored. The stored motion information can be transmitted to the inter prediction unit (221) to be used as motion information of spatially surrounding blocks or motion information of temporally surrounding blocks. Memory (270) can store restoration samples of restored blocks in the current picture and transmit them to the intra prediction unit (222).

[0077] FIG. 3 is a schematic diagram illustrating a decoding device to which an embodiment according to the present disclosure can be applied.

[0078] As illustrated in FIG. 3, the decoding device (300) may be configured to include an entropy decoder (310), a residual processor (320), a predictor (330), an adder (340), a filter (350), and a memory (360). The predictor (330) may include an inter-predictor (332) and an intra-predictor (331). The residual processor (320) may include a dequantizer (321) and an inverse transformer (321). The aforementioned entropy decoding unit (310), residual processing unit (320), prediction unit (330), addition unit (340), and filtering unit (350) may be configured by a single hardware component (e.g., a decoder chipset or a processor) according to an embodiment. Additionally, the memory (360) may include a decoded picture buffer (DPB) and may be configured by a digital storage medium. The hardware component may further include the memory (360) as an internal / external component.

[0079] When a bitstream containing video / image information is input, the decoding device (300) can restore the image by performing a process corresponding to the process performed by the encoding device (200) of FIG. 2. For example, the decoding device (300) can perform decoding using a processing unit applied in the encoding device (200). Thus, the processing unit for decoding may be, for example, a coding unit. The coding unit may be a coding tree unit, or a maximum coding unit may be obtained by dividing it according to a quad tree structure, a binary tree structure, and / or a binary tree structure. And, the restored image signal decoded and output through the decoding device (300) can be played back through a playback device (not shown).

[0080] The decoding device (300) can receive a signal output from the encoding device (200) of FIG. 2 in the form of a bitstream. The received signal can be decoded through an entropy decoding unit (310). For example, the entropy decoding unit (310) can parse the bitstream to derive information necessary for image restoration (or picture restoration) (e.g., video / image information). The video / image information may further include information regarding 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). Additionally, the video / image information may further include general constraint information. The decoding device (300) can decode the picture based on the information regarding the parameter sets and / or the general constraint information. The signaling / received information and / or syntax elements described below can be obtained from the bitstream by decoding through the decoding procedure. For example, the entropy decoding unit (310) can decode information within the bitstream based on coding methods such as exponential coding, CAVLC, or CABAC, and output values ​​of syntax elements required for image restoration and quantized values ​​of transformation coefficients regarding residuals. More specifically, the CABAC entropy decoding method can receive bins corresponding to each syntax element in the bitstream, determine a context model using information on the syntax element to be decoded and decoding information of surrounding and decoding target blocks or information on symbols / bins decoded in the previous step, predict the probability of occurrence of the bin according to the determined context model, and perform arithmetic decoding of the bin to generate a symbol corresponding to the value of each syntax element.At this time, the CABAC entropy decoding method can update the context model using the decoded symbol / bin information for the context model of the next symbol / bin after determining the context model. Among the information decoded in the entropy decoding unit (310), information regarding prediction is provided to the prediction unit (330), and residual values ​​for which entropy decoding was performed in the entropy decoding unit (310), i.e., quantized transformation coefficients and related parameter information, can be input to the residual processing unit (320). The residual processing unit (320) can derive residual signals (residual blocks, residual samples, residual sample array). Additionally, among the information decoded in the entropy decoding unit (310), information regarding filtering can be provided to the filtering unit (350). Meanwhile, a receiving unit (not shown) that receives a signal output from an encoding device may be further configured as an internal / external element of the decoding device (300), or the receiving unit may be a component of the entropy decoding unit (310). Meanwhile, the decoding device according to the present document may be called a video / image / picture decoding device, and the decoding device may be divided into an information decoder (video / image / picture information decoder) and a sample decoder (video / image / picture sample decoder). The information decoder may include the entropy decoding unit (310), and the sample decoder may include at least one of the inverse quantization unit (321), inverse transform unit (322), adder (340), filtering unit (350), memory (360), inter prediction unit (332), and intra prediction unit (331).

[0081] In the inverse quantization unit (321), the quantized transformation coefficients can be inversely quantized to output transformation coefficients. The inverse quantization unit (321) can rearrange the quantized transformation coefficients into a two-dimensional block form. In this case, the rearrangement can be performed based on the coefficient scan order performed in the encoding device (200). The inverse quantization unit (321) can perform inverse quantization on the quantized transformation coefficients using quantization parameters (e.g., quantization step size information) and obtain transformation coefficients.

[0082] In the inverse conversion unit (322), the conversion coefficients can be inversely converted to obtain a residual signal (residual block, residual sample array).

[0083] The prediction unit (330) can generate a prediction signal based on various prediction methods described below. For example, the prediction unit may apply intra prediction or inter prediction for a single block, and may also apply intra prediction and inter prediction simultaneously. This may be called combined inter and intra prediction (CIIP). Additionally, the prediction unit may be based on an intra block copy (IBC) prediction mode or a palette mode for predicting a block. The IBC prediction mode or palette mode may be used for content video / video coding, such as in games, for example, screen content coding (SCC). IBC basically performs prediction within the current picture, but it can be performed similarly to inter prediction in that it derives a reference block within the current picture. That is, IBC may use at least one of the inter prediction techniques described in this document. The palette mode can be viewed as an example of intra coding or intra prediction. When the palette mode is applied, information regarding the palette table and palette index can be included in the above video / image information and signaled.

[0084] The intra prediction unit (331) can predict the current block by referring to samples within the current picture. The description of the intra prediction unit (222) may be applied equally to the intra prediction unit (331). The referenced samples may be located in the neighborhood of the current block or located away from it, depending on the prediction mode. In intra prediction, the prediction modes may include a plurality of non-directional modes and a plurality of directional modes. The intra prediction unit (331) may determine the prediction mode applied to the current block by using the prediction mode applied to the neighboring blocks.

[0085] The inter prediction unit (332) can derive a predicted block for the current block based on a reference block (reference sample array) specified by a motion vector on a reference picture. At this time, to reduce the amount of motion information transmitted in the inter prediction mode, motion information can be predicted in blocks, sub-blocks, or samples based on the 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 information on the inter prediction direction (L0 prediction, L1 prediction, Bi prediction, etc.). In the case of inter prediction, neighboring blocks may include spatial neighboring blocks existing within the current picture and temporal neighboring blocks existing in the reference picture. For example, the inter prediction unit (332) may construct a motion information candidate list based on the neighboring blocks and derive the motion vector and / or reference picture index of the current block based on the received candidate selection information. Inter-prediction can be performed based on various prediction modes (techniques), and information regarding the prediction may include information indicating the mode (technique) of inter-prediction for the current block.

[0086] The adder (340) can generate a restoration signal (restored picture, restored block, restored sample array) by adding the acquired residual signal to the prediction signal (predicted block, predicted sample array) output from the prediction unit (330) (including the inter prediction unit (332) and / or intra prediction unit (331)). In cases where there is no residual for the block to be processed, such as when a skip mode is applied, the predicted block can be used as the restoration block. The description of the adder (250) can be applied equally to the adder (340). The adder (340) may be called a restoration unit or a restoration block generation unit. The generated restoration signal can be used for intra prediction of the next block to be processed within the current picture, and can also be used for inter prediction of the next picture after undergoing filtering as described below.

[0087] Meanwhile, LMCS (luma mapping with chroma scaling) may be applied during the picture decoding process.

[0088] The filtering unit (350) can improve subjective / objective image quality by applying filtering to the restored signal. For example, the filtering unit (350) can generate a modified restored picture by applying various filtering methods to the restored picture, and can store the modified restored picture in memory (360), specifically in the DPB of memory (360). The various filtering methods may include, for example, deblocking filtering, sample adaptive offset, adaptive loop filter, bilateral filter, etc.

[0089] The (modified) restored picture stored in the DPB of the memory (360) can be used as a reference picture in the inter-prediction unit (332). The memory (360) can store motion information of blocks from which motion information within the current picture has been derived (or decoded) and / or motion information of blocks within the picture that have already been restored. The stored motion information can be transmitted to the inter-prediction unit (332) to be used as motion information of spatially surrounding blocks or motion information of temporally surrounding blocks. The memory (360) can store restoration samples of blocks restored within the current picture and transmit them to the intra-prediction unit (331).

[0090] In this specification, the embodiments described in the filtering unit (260), inter prediction unit (221), and intra prediction unit (222) of the encoding device (200) may be applied to the filtering unit (350), inter prediction unit (332), and intra prediction unit (331) of the decoding device (300) in the same or corresponding manner.

[0091] Figure 4 illustrates an exemplary hierarchical structure for a coded video / image.

[0092] Referring to Figure 4, the coded image is divided into a VCL (video coding layer) that handles the decoding processing of the image and the image itself, a subsystem that transmits and stores the encoded information, and a NAL (network abstraction layer) that exists between the VCL and the subsystem and is responsible for network adaptation functions.

[0093] In VCL, VCL data containing compressed image data (slice data) can be generated, or parameter sets containing information such as Picture Parameter Set (PPS), Sequence Parameter Set (SPS), and Video Parameter Set (VPS), or SEI (Supplemental Enhancement Information) messages that are additionally required in the decoding process of the image can be generated.

[0094] In NAL, a NAL unit can be created by adding header information (NAL unit header) to the Raw Byte Sequence Payload (RBSP) generated in VCL. In this case, the RBSP refers to slice data, parameter sets, SEI messages, etc. generated in VCL. The NAL unit header may include NAL unit type information specified according to the RBSP data included in the NAL unit.

[0095] As shown in FIG. 4, NAL units can be classified into VCL NAL units and Non-VCL NAL units depending on the RBSP generated in VCL. A VCL NAL unit may refer to a NAL unit containing information about an image (slice data), and a Non-VCL NAL unit may refer to a NAL unit containing information necessary to decode an image (parameter set or SEI message).

[0096] The aforementioned VCL NAL unit and Non-VCL NAL unit can be transmitted over a network by attaching header information according to the data specifications of the underlying system. For example, the NAL unit can be transformed into a data format of a specified specification, such as H.266 / VVC file format, RTP (Real-time Transport Protocol), TS (Transport Stream), etc., and transmitted over various networks.

[0097] As described above, the NAL unit type can be determined according to the RBSP data structure included in the NAL unit, and information about this NAL unit type can be stored in the NAL unit header and signaled.

[0098] For example, NAL units can be broadly classified into VCL NAL unit types and Non-VCL NAL unit types depending on whether they contain information about the image (slice data). VCL NAL unit types can be classified according to the properties and types of the picture included in the VCL NAL unit, while Non-VCL NAL unit types can be classified according to the types of parameter sets.

[0099] The following is an example of a NAL unit type specified according to the type of parameter set included in the Non-VCL NAL unit type.

[0100] - APS (Adaptation Parameter Set) NAL unit: Type for the NAL unit containing the APS

[0101] - DPS (Decoding Parameter Set) NAL unit: Type for the NAL unit containing the DPS

[0102] - VPS (Video Parameter Set) NAL unit: Type for the NAL unit containing the VPS

[0103] - SPS (Sequence Parameter Set) NAL unit: Type for the NAL unit containing the SPS

[0104] - PPS(Picture Parameter Set) NAL unit: Type for the NAL unit containing the PPS

[0105] The above-described NAL unit types have syntax information for the NAL unit type, and said syntax information can be stored in the NAL unit header and signaled. For example, said syntax information may be nal_unit_type, and NAL unit types may be specified by the nal_unit_type value.

[0106] The slice header (slice header syntax) may include information / parameters that can be commonly applied to the slice. The APS (APS syntax) or PPS (PPS syntax) may include information / parameters that can be commonly applied to one or more slices or pictures. The SPS (SPS syntax) may include information / parameters that can be commonly applied to one or more sequences. The VPS (VPS syntax) may include information / parameters that can be commonly applied to multiple layers. The DPS (DPS syntax) may include information / parameters that can be commonly applied to the entire video. The DPS may include information / parameters related to the concatenation of the CVS (coded video sequence). In this document, the term High level syntax (HLS) may include at least one of the above APS syntax, PPS syntax, SPS syntax, VPS syntax, DPS syntax, and slice header syntax.

[0107] In the present disclosure, image / video information encoded from an encoding device to a decoding device and signaled in the form of a bitstream includes not only information related to partitioning within a picture, intra / inter prediction information, residual information, in-loop filtering information, etc., but may also include information included in the slice header, information included in the APS, information included in the PPS, information included in the SPS, and / or information included in the VPS.

[0108] In the present disclosure, the following descriptors may define the parsing process for each syntax element.

[0109] - ae(v) is a context-adaptive arithmetic entropy-coded syntax element.

[0110] - b(8) is a byte with an arbitrary bit string pattern of length 8 bits. The parsing process of this descriptor is defined by the return value of the function read_bits(8).

[0111] - f(n) is an n-bit fixed-pattern bit string where the left bits are written first. The parsing process of this descriptor is defined by the return value of the function read_bits(n).

[0112] - i(n) is a signed integer using n bits, where n is denoted as "v" in the syntax table, the number of bits varies depending on the values ​​of other syntax elements. The parsing process of this descriptor is defined by interpreting the return value of the function read_bits(n) into a two's complement integer representation where the most significant bit is written first.

[0113] - se(v) is a 0th-order Exp-Golomb encoded signed integer syntax element, written starting from the left bit. The parsing process of this descriptor is defined with order k set to 0.

[0114] - st(v) is a null-terminated string encoded in UCS (Universal Coded Character Set) transmission format 8 (UTF-8) characters as defined in ISO / IEC 10646. The parsing process is defined as follows.

[0115] st(v) starts at a byte-aligned position within the bitstream and reads and returns a sequence of consecutive bytes from the bitstream, starting from the current position and excluding the next byte-aligned byte with a value of 0x00. The bitstream pointer then advances by (stringLength + 1) * 8 bit positions, where stringLength is equal to the number of returned bytes.

[0116] For reference, the st(v) syntax descriptor is used in this disclosure only when the current position in the bitstream is a byte-aligned position.

[0117] - tu(v) is a truncated unary encoding scheme that uses up to the number of bits defined by the maximum value (maxVal), and maxVal is defined in the semantics of the corresponding syntax element.

[0118] - u(n) is an unsigned integer using n bits. If n is marked as "v" in the syntax table, the number of bits varies depending on the values ​​of other syntax elements. The parsing process of this descriptor is defined by interpreting the return value of the function read_bits(n) as a binary representation of an unsigned integer where the most significant bit is written first.

[0119] - ue(v) is a 0th-order Exp-Golomb encoded unsigned integer syntax element, written starting from the left bit. The parsing process of this descriptor is defined with order k set to 0.

[0120] The SEI message related to the present disclosure will be described below.

[0121] Table 1 shows an example of SEI message syntax for SEI processing order according to one embodiment.

[0122] [Table 1]

[0123]

[0124] An example of the semantics of an SEI message in an SEI processing sequence according to one embodiment is described.

[0125] SEI Processing Order (SPO) SEI messages convey information indicating the preferred processing order determined by the encoder (i.e., content producer) for a group of SEI messages that may exist within the Encoding Layer Video Sequence (CLVS).

[0126] The use of this SEI message requires the following definition.

[0127] - Two lists of payload type values, SeiProcessingOrderSeiList and SpoProcessSeiList.

[0128] The semantics of SPO SEI messages utilize the concept of types of SEI messages. SEI messages with different payloadType values ​​are considered to be of different types of SEI messages. Additionally, different SEI messages that have the same payloadType value but are distinguished by the syntax elements within the SEI payload are considered to be of different types of SEI messages. This distinction based on the syntax elements within the SEI payload must be performed by comparing values ​​transmitted using po_sei_prefix_data_bit[i][j] syntax elements (if present) or values ​​transmitted as SEI messages within a processing order nesting SEI message (if present). For example, Neural Network Post-Filter Feature (NNPFC) SEI messages can be distinguished by having different nnpfc_id values.

[0129] When the i-th SEI message seiA in any SPO SEI message has both po_sei_wrapping_flag[i] and po_sei_prefix_flag[i] set to 0, there must not be another SEI message seiB in the same SPO SEI message or in another SPO SEI message in the current CLVS such that all of the following are true.

[0130] - The value of po_sei_payload_type[i] in seiB is the same as the value in seiA.

[0131] - The value of po_sei_wrapping_flag[i] of seiB is 0.

[0132] - The value of po_sei_prefix_flag[i] of seiB is 1.

[0133] When an SPO SEI message with a specific po_id value exists in any picture unit of the CLVS, that SPO SEI message with the specific po_id value must exist in the first picture unit of the CLVS in decoding order. The number of SEI messages and the payload type codes of the SEI messages indicated within each SPO SEI message with the same po_id value persist in decoding order from the current picture unit to the end of the CLVS in output order.

[0134] An SPO SEI message may carry one or more SEI prefix indications for a specific payloadType. When present, each SEI prefix indication is a bit sequence following the SEI payload syntax of the corresponding payloadType value, and includes multiple complete syntax elements starting from the first syntax element of the SEI payload. These SEI prefix indications must provide sufficient information to determine a specific processing order for SEI message types that have the same payloadType value but different preferred processing orders.

[0135] po_id includes an identification number for identifying SPO SEI messages.

[0136] A processing chain consists of a list of SEI message types identified by the SPO SEI message, according to the preferred processing order indicated in the SPO SEI message. When multiple processing chains are directed by SPO SEI messages for the same access unit, the decoder must operate only one of the directed processing chains.

[0137] Each SEI message type within the processing chain indicated by the SPO SEI message is identified by the syntax elements po_sei_payload_type[i], po_sei_wrapping_flag[i], po_sei_processing_order[i], and, if present, po_num_bits_in_prefix_indication_minus1[i] and po_prefix_data_bit[i][j].

[0138] SEI message types do not need to belong to any processing chain and can belong to any number of processing chains identified by SPO SEI messages having different po_id values.

[0139] Each SEI message of the SEI message type identified within the SPO SEI message has the same persistence scope as when the corresponding SEI message is transmitted outside the SPO SEI message and is not identified within the SPO SEI message.

[0140] For reference, if an SEI message specifies a process and is not associated with a processing chain specified by any SPO SEI message, it is implicitly a processing chain in itself. Some standards, such as Rec. ITU-T H.266 | ISO / IEC 23090-3, specify an implicit processing chain where another NNPF follows a super-resolution NNPF. Implicitly specified processing chains are treated like processing chains specified by SPO SEI messages when selecting the SEI messages to apply.

[0141] po_for_human_viewing_idc identical to 3 indicates that the intended optimal use of the video resulting from the processing chain specified by this SPO SEI message includes human viewing. po_for_human_viewing_idc identical to 2 indicates that the video resulting from the processing chain specified by this SPO SEI message is suitable but not specifically optimized for human viewing. po_for_human_viewing_idc identical to 1 indicates that the video resulting from the processing chain specified by this SPO SEI message is unsuitable for human viewing. po_for_human_viewing_idc identical to 0 indicates that it is impossible to know whether the video resulting from the processing chain specified by this SPO SEI message is suitable for human viewing.

[0142] po_for_machine_analysis_idc identical to 3 indicates that the intended optimal use of the video resulting from the processing chain specified by this SPO SEI message includes machine analysis. po_for_machine_analysis_idc identical to 2 indicates that the video resulting from the processing chain specified by this SPO SEI message is suitable but not specifically optimized for machine analysis. po_for_machine_analysis_idc identical to 1 indicates that the video resulting from the processing chain specified by this SPO SEI message is unsuitable for machine analysis. po_for_machine_analysis_idc identical to 0 indicates that it is impossible to know whether the video resulting from the processing chain specified by this SPO SEI message is suitable for machine analysis.

[0143] The requirement for bitstream conformance is that the values ​​of po_for_human_viewing_idc and po_for_machine_analysis_idc must not both be equal to 1.

[0144] For reference, the values ​​of po_for_human_viewing_idc and po_for_machine_analysis_idc are valid for the output of the processing chain.

[0145] po_reserved_zero_4bits must be 0. Values ​​greater than 0 for po_reserved_zero_4bits are reserved for future use and must not exist within a bitstream suitable for this version of the Specification. Decoders suitable for this version of the Specification must allow any value of po_reserved_zero_4bits within the range of 0 to 15 (inclusive).

[0146] The value of po_num_sei_messages_minus2 plus 2 represents the number of SEI message types that indicate the preferred order of processing within the SPO SEI message. The variable PoNumProcStgs is set to equal po_num_sei_messages_minus2 + 2.

[0147] po_breadth_first_flag equal to 1 specifies that breadth-first handling of the processing chain should be applied to determine the pictures used to interpret the semantics of SEI messages applied as part of the processing chain specified by this SPO SEI message. po_breadth_first_flag equal to 0 specifies that breadth-first handling of the processing chain or depth-first handling of the processing chain should be applied to determine the pictures used to interpret the semantics of SEI messages applied as part of the processing chain specified by this SPO SEI message.

[0148] For reference, when po_breadth_first_flag is equal to 0, the processing chain can be executed on the picture without processing any SEI messages applied to subsequent picture units in output order.

[0149] po_sei_wrapping_flag[i], identical to 1, specifies that the SEI message applied as the i-th SEI message type within the processing chain specified in this SPO SEI message (if any) is a SEI message included in a PON SEI message where all of the following conditions are true.

[0150] - pon_target_po_id[j] with any value j is equal to po_id.

[0151] - Within the processing order nesting SEI message, there exists a k-th loop entry where the payload type of the k-th nested SEI message is equal to po_sei_payload_type[i] and pon_processing_order[k] is equal to po_sei_processing_order[i].

[0152] po_sei_wrapping_flag[i], which is equal to 0, specifies that the SEI message applied as the i-th SEI message type within the processing chain specified in this SPO SEI message (if any) is not included in the PON SEI message and is a SEI message for which all of the following conditions are true.

[0153] - The payload type of the corresponding SEI message is the same as po_sei_payload_type[i].

[0154] - When po_sei_prefix_flag[i] is equal to 0 or po_sei_prefix_flag[i] is equal to 1, the payload of the corresponding SEI message starts with the values ​​of po_sei_prefix_data_bit[i][j].

[0155] For reference, po_sei_wrapping_flag[i], which is equal to 1, enables SEI messages to be passed within processing order nesting SEI messages to prevent such SEI messages from being misinterpreted by decoders that do not process SPO SEI messages. Therefore, po_sei_wrapping_flag[i], which is equal to 1, is intended to be used in cases where unintended results may be produced by such decoders when po_sei_wrapping_flag[i] is 0.

[0156] po_sei_importance_flag[i] influences the derivation of PoSeiList, which is a list of SEI messages that the decoding system must process for a specific picture picA, as specified below.

[0157] po_sei_processing_degree_flag[i] affects the derivation of PoSeiList as specified below.

[0158] A processing chain may contain zero or more sub-chains. A sub-chain contains SEI message types such that all of these SEI message types must be processed by the decoding system, or if the decoding system cannot interpret or does not support one or more of these SEI message types, then no SEI message types in that sub-chain should be processed. The SEI message types belonging to a sub-chain are determined by the values ​​of po_importance_flag[i] and po_processing_degree_flag[i] as specified below.

[0159] Table 2 specifies the interpretation of po_importance_flag[i] and po_processing_degree_flag[i].

[0160] [Table 2]

[0161]

[0162] po_sei_payload_type[i] specifies the payload type value of the i-th type SEI message.

[0163] For reference, the NNPFC SEI message type has a po_sei_payload_type[i] value that is the same as the payload type value of the NNPFC SEI message. Examples of reasons for including the NNPFC SEI message type in the SPO SEI message include the following.

[0164] - The NNPFC SEI message type includes an SEI prefix containing the nnpfc_purpose syntax element, which provides a hint to the decoding system about what kind of processing is included in each NNPF within the processing chain.

[0165] - NNPF must be called only as part of the processing chain, so that the NNPFC SEI message type is associated with po_sei_wrapping_flag[i] which is the same as 1, and each NNPFC SEI message(s) is included in the PON SEI message(s).

[0166] When po_sei_payload_type[i] represents an NNPFC SEI message for a specific NNPF, the same SPO SEI message must contain po_sei_payload_type[j] representing each NNPFA SEI message for the same NNPF for j greater than i.

[0167] po_sei_prefix_flag[i] equal to 1 indicates that the syntax elements po_num_bits_in_prefix_indication_minus1[i] and some po_sei_prefix_data_bit[i][j] exist. po_sei_prefix_flag[i] equal to 0 indicates that these syntax elements do not exist.

[0168] For each i in the range from 0 to po_num_sei_messages_minus2 + 1 (inclusive), the value of po_sei_payload_type[i] must be equal to the value in SeiProcessingOrderSeiList.

[0169] When po_sei_payload_type[i] is equal to any value in SpoProcessSeiList, the SEI message of the i-th type represents a process.

[0170] spoPropertySeiList is configured to consist of payload type values ​​included in SeiProcessingOrderSeiList, excluding payload type values ​​included in SpoProcessSeiList. When po_sei_payload_type[i] is equal to any value in spoPropertySeiList, the SEI message of the i-th type represents a property.

[0171] po_sei_processing_order[i] represents the preferred order of processing for the i-th type of SEI message, for which information on the preferred processing order in SPO SEI messages is provided. For any two distinct integer values ​​of m and n, if po_sei_processing_order[m] is less than po_sei_processing_order[n], it indicates that the type of SEI message associated with index m must be processed before the type of SEI message associated with index n; if po_sei_processing_order[m] is equal to po_sei_processing_order[n], it indicates that there is no preferred order of processing between the types of SEI messages associated with indices m and n (for example, they may represent different attributes applicable at the corresponding stage, or one may represent an attribute and the other a process).

[0172] For i greater than 0, po_sei_processing_order[i] must be greater than or equal to po_sei_processing_order[i - 1].

[0173] seiMsgA is defined as the SEI message that is applied as the i-th SEI message type in the processing chain specified in this SPO SEI message, persists for a specific picture picA, and is associated with po_sei_processing_order[i], such as poValA.

[0174] seiMsgSet is defined as a set of SEI messages consisting of each SEI message for which all of the following conditions are true.

[0175] - The corresponding SEI message is applied as the k-th SEI message type having an arbitrary value k smaller than i in the processing chain specified in this SPO SEI message.

[0176] - The corresponding SEI message persists for picA.

[0177] - po_sei_processing_order[k] is smaller than poValA.

[0178] - The payload type of the corresponding SEI message is among the values ​​included in SpoProcessSeiList.

[0179] The pictures to which the semantics of seiMsgA apply are specified as follows.

[0180] - If seiMsgSet is not empty, the semantics of seiMsgA apply to all pictures generated by the process implied by the SEI message having the largest value of po_sei_processing_order[k] among the SEI messages in seiMsgSet.

[0181] - Otherwise, the semantics of seiMsgA apply to picA.

[0182] For reference, when an NNPF process outputs one or more NNPF-generated pictures, the semantics of the SEI message following the NNPF in the processing order apply to all of these NNPF-generated pictures.

[0183] po_num_bits_in_prefix_indication_minus1[i] and po_sei_prefix_data_bit[i][j] have the same semantics as the num_bits_in_prefix_indication_minus1[i] and sei_prefix_data_bit[i][j] syntax elements of the SEI prefix indication SEI message, with prefix_sei_payload_type replaced by po_sei_payload_type[i] if present.

[0184] When there is one or more SPO SEI messages with a specific po_id value within CLVS, the values ​​of po_for_human_viewing_idc, po_for_machine_analysis_idc, po_num_sei_messages_minus2, and po_breadth_first_flag, and the values ​​of po_sei_wrapping_flag[i], po_sei_importance_flag[i], po_sei_processing_degree_flag[i], po_sei_payload_type[i], po_sei_prefix_flag[i], and po_sei_processing_order[i] for each value i must be equal to the values ​​in other SPO SEI messages within CLVS that have the same po_id value.

[0185] po_byte_alignment_bit_equal_to_one must be equal to 1.

[0186] The list PoProcStgIdx, representing the processing step indices of SEI message types within the processing chain, and the list PoSeiTypeIdx, representing the SEI message type indices of the processing steps within the processing chain, are derived as follows.

[0187] - For each SEI message type in the processing chain, with j initially set to 0, the following is applied in the non-decreasing order of the corresponding po_sei_processing_order[i] values.

[0188] [Formula 1]

[0189]

[0190] Here, PoProcStgIdx[i] represents the processing stage index of the i-th SEI message type within the processing chain, and PoSeiTypeIdx[j] represents the SEI message type index of the j-th processing stage within the processing chain.

[0191] For j in the range from 0 to PoNumProcStgs - 1 (inclusive), the list poSubChainIdx[j], which specifies the sub-chain index of the j-th processing stage of the processing chain, is derived as follows.

[0192] [Equation 2]

[0193]

[0194] For a picture, the list PoSeiList representing the list of SEI messages that can be applied to the picture, the list PoSeiTypeList representing the SEI message type indices of the SEI messages that can be applied to the picture, and the variable PoNumSeiMsgs representing the number of SEI messages that can be applied to the picture are derived as follows.

[0195] - PoSeiList is initially empty, and seiListIdx and PoNumSeiMsgs are both initially set to 0.

[0196] - Unless terminated earlier as specified below, for all j values ​​in the range from 0 to PoNumProcStgs - 1 (inclusive), the following applies in increasing order of j.

[0197] - When the SEI message seiA associated with the PoSeiTypeIdx[j]-th SEI message type persists on picA, the following applies.

[0198] - If all of the following conditions are true, seiA is added to the end of PoSeiList, PoSeiTypeList[seiListIdx] is set to equal PoSeiTypeIdx[j], PoNumSeiMsgs is set to equal PoNumSeiMsgs + 1, and seiListIdx is set to equal seiListIdx + 1.

[0199] - The decoding system can interpret and support the functionality indicated by seiA.

[0200] - One of the following conditions is true.

[0201] - poSubChainIdx[j] is equal to 0.

[0202] - For all k values ​​where poSubChainIdx[k] is equal to poSubChainIdx[j] and po_sei_importance_flag[PoSeiTypeIdx[k]] is equal to 1 or po_sei_processing_degree_flag[PoSeiTypeIdx[k]] is equal to 1, the decoding system can interpret and support the functionality indicated by all SEI message types.

[0203] - Otherwise, if po_sei_importance_flag[PoSeiTypeIdx[j]] is equal to 1 and po_sei_processing_degree_flag[PoSeiTypeIdx[j]] is equal to 1, the processing chain specified by this SPO SEI message should not be performed for picA, PoSeiList is set to empty, PoNumSeiMsgs is set to 0, and the derivation of PoSeiList, PoSeiTypeList, and PoNumSeiMsgs is terminated.

[0204] po_complexity_info_present_flag equal to 1 specifies that there are one or more syntax elements indicating the complexity of invoking NNPFs within the processing chain identified by the SEI processing order SEI message. po_complexity_info_present_flag equal to 0 specifies that there are no syntax elements indicating the complexity of invoking NNPFs within the processing chain identified by the SEI processing order SEI message.

[0205] po_parameter_type_idc equal to 0 indicates that NNPFs within the processing chain identified by the SEI processing order SEI message use only integer parameters. po_parameter_type_flag equal to 1 indicates that NNPFs within the processing chain identified by the SEI processing order SEI message may use floating-point or integer parameters. po_parameter_type_idc equal to 2 indicates that NNPFs within the processing chain identified by the SEI processing order SEI message use only binary parameters. po_parameter_type_idc equal to 3 is reserved for future use by ITU-T | ISO / IEC and must not exist in a bitstream conforming to the present disclosure. Decoders suitable for the present disclosure must ignore SPO SEI messages having po_parameter_type_idc identical to 3.

[0206] po_log2_parameter_bit_length_minus3, which is equivalent to 0, 1, 2, and 3, indicates that the NNPFs within the processing chain identified by the SEI processing order SEI message do not use parameters with bit lengths greater than 8, 16, 32, and 64, respectively. When po_parameter_type_idc exists and po_log2_parameter_bit_length_minus3 does not exist, the NNPFs within the processing chain identified by the SEI processing order SEI message do not use parameters with a bit length greater than 1.

[0207] po_num_parameters_idc represents the maximum number of parameters required by NNPFs within the processing chain identified by the SEI processing order SEI message, in powers of 2048. po_num_parameters_idc equal to 0 indicates that the maximum number of parameters required by NNPFs within the processing chain identified by the SEI processing order SEI message is unknown. The value of po_num_parameters_idc must be within the range of 0 to 52 (inclusive). Po_num_parameters_idc values ​​greater than 52 are reserved for future use by ITU-T | ISO / IEC and must not exist in bitstreams conforming to this edition of this document. Decoders conforming to this edition of this document must ignore SPO SEI messages having po_num_parameters_idc greater than 52.

[0208] If the value of po_num_parameters_idc is greater than 0, the variable maxNumParameters is derived as follows.

[0209] [Equation 3]

[0210]

[0211] The requirement of bitstream conformance is that the number of parameters must be less than or equal to maxNumParameters.

[0212] A po_num_kmac_operations_idc greater than 0 indicates that the maximum number of multiply-accumulate operations per sample of NNPFs within the processing chain, identified by the SEI processing order SEI message, is less than or equal to po_num_kmac_operations_idc * 1000. A po_num_kmac_operations_idc equal to 0 indicates that the maximum number of multiply-accumulate operations of NNPFs within the processing chain, identified by the SEI processing order SEI message, is unknown. The value of po_num_kmac_operations_idc ranges from 0 to 2 32 - It must be within the range of up to (inclusive) 2.

[0213] po_total_kilobyte_size greater than 0 indicates the total size in kilobytes required to store uncompressed parameters for NNPFs within the processing chain identified by the SEI processing sequence SEI message. The total size in bits is greater than or equal to the sum of the bits used to store each parameter. po_total_kilobyte_size is the total size in bits divided by 8000 and rounded up. po_total_kilobyte_size equal to 0 indicates that the total size required to store parameters for NNPFs within the processing chain identified by the SEI processing sequence SEI message is unknown. The value of po_total_kilobyte_size ranges from 0 to 2 32 - It must be within the range of up to (inclusive) 2.

[0214] Table 3 shows an example of a processing order nesting SEI message syntax according to one embodiment.

[0215] [Table 3]

[0216]

[0217] An example of the semantics of a processing sequence nesting SEI message according to one embodiment is described.

[0218] A processing order nesting (PON) SEI message includes one or more SEI messages that must be applied only as part of the processing chain identified by the associated SEI processing order SEI message and must not be applied in a manner that contradicts the processing chain identified by the associated SEI processing order SEI message.

[0219] The use of this SEI message requires the following definition.

[0220] - Syntax structure of the container for SEI messages, sei_pon_nested_message()

[0221] SEI messages included in a PON SEI message are referred to as PON-nested SEI messages.

[0222] For reference, an encoder may contain multiple PON SEI messages within the same access unit. For example, the first PON SEI message within the access unit may contain a PON nested SEI message applicable to multiple processing chains, and one or more other PON SEI messages within the same access unit may contain PON nested SEI messages applicable to only a single processing chain.

[0223] It is a requirement of bitstream conformance that the semantics and effects of an SEI message other than a PON-nested SEI message must not depend on any PON-nested SEI message. The consequences of this constraint include the following specific constraints, where an associated SEI message is considered to be an SEI message that influences the semantics or effects of a specific SEI message.

[0224] - When there exists a neural-network post-filter characteristics SEI message with a specific value of nnpfc_id and this is a PON-nested SEI message, all associated neural-network post-filter activation (NNPFA) SEI messages with nnpfa_target_id equal to that specific nnpfc_id value must also be PON-nested SEI messages.

[0225] - When there exists a Neural Network Post-Filter Activation (NNPFA) SEI message with nnpfa_target_id of a specific value and this is not a PON-nested SEI message, the picture (if any) that has an NNPFA SEI message with the same value as the next picture in output order within the same Encoding Layer Video Sequence (CLVS) must not have an associated NNPFA SEI message that is a PON-nested SEI message.

[0226] - When there is a film grain characteristics SEI message with fg_characteristics_persistence_flag equal to 1 and this is not a PON-nested SEI message, there must not be any associated film grain characteristics SEI message that is a PON-nested SEI message within the same CLVS.

[0227] - When there exists a frame packing arrangement SEI message with fp_arrangement_persistence_flag equal to 1 and it is not a PON nested SEI message, there must not be an associated frame packing arrangement SEI message within the same CLVS that is a PON nested SEI message with fp_arrangement_cancel_flag equal to 1 or fp_arrangement_id of the same value.

[0228] - When a content color volume SEI message with ccv_persistence_flag equal to 1 exists and it is not a PON-nested SEI message, there must not be an associated frame packing arrangement SEI message that is a PON-nested SEI message within the same CLVS.

[0229] - When there is an equirectangular projection SEI message with erp_persistence_flag equal to 1 and it is not a PON-nested SEI message, there must not be any associated equirectangular projection SEI message that is a PON-nested SEI message within the same CLVS.

[0230] - When a region-wise packing SEI message with rwp_persistence_flag equal to 1 exists and is not a PON-nested SEI message, there must not be any associated region-wise packing SEI message that is a PON-nested SEI message within the same CLVS.

[0231] - When there is a sample aspect ratio SEI message with sari_persistence_flag equal to 1 and it is not a PON-nested SEI message, there must not be any associated sample aspect ratio SEI message that is a PON-nested SEI message within the same CLVS.

[0232] - When an annotated regions SEI message exists that is not a PON-nested SEI message, there must not be any associated annotated regions SEI message that is a PON-nested SEI message within the same CLVS.

[0233] - When an alpha channel information SEI message exists that is not a PON-nested SEI message, there must not be any associated alpha channel information SEI message that is a PON-nested SEI message within the same CLVS.

[0234] - When a display orientation SEI message exists that is not a PON nested SEI message, there must not be any associated display orientation SEI message that is a PON nested SEI message within the same CLVS.

[0235] - When there is a color transform indication SEI message with colour_transform_persistence_flag equal to 1 and it is not a PON nested SEI message, there must not be an associated color transform indication SEI message within the same CLVS that is a PON nested SEI message with colour_transform_cancel_flag equal to 1 or a colour_transform_id of the same value.

[0236] pon_num_po_ids_minus1 plus 1 specifies the number of SEI processing order SEI messages associated with this PON SEI message.

[0237] pon_target_po_id[i] represents the po_id of the i-th SEI processing sequence SEI message associated with this PON SEI message.

[0238] pon_num_seis_minus1 plus 1 specifies the number of PON nested SEI messages included in this PON SEI message.

[0239] pon_processing_order[i] specifies the position of the i-th PON-nested SEI message within the processing order defined by the associated SEI processing order SEI message. When i is greater than 0, pon_processing_order[i] must be greater than or equal to pon_processing_order[i - 1].

[0240] The associated SEI processing sequence SEI message for the i-th PON nested SEI message is an SEI processing sequence SEI message having entry k for which all of the following conditions are true.

[0241] - po_sei_processing_order[k] is equal to pon_processing_order[i].

[0242] - po_sei_payload_type[k] is equal to the payload type value of the i-th PON-nested SEI message.

[0243] - When po_sei_prefix_flag[k] is equal to 1, po_sei_prefix_data_bit[k][j] for j in the range from 0 to po_num_bits_in_prefix_indication_minus1[k] (inclusive) contains the same content as the initial po_num_bits_in_prefix_indication_minus1[k] plus 1 bits of the SEI message payload of the i-th PON-nested SEI message.

[0244] The i-th PON nested SEI message can have any number of associated SEI processing sequence SEI messages in the range from 0 to pon_num_po_ids_minus1 + 1 (inclusive).

[0245] When the i-th PON-nested SEI message has an associated SEI processing sequence SEI message, the i-th PON-nested SEI message must be applied as the k-th loop entry of the associated SEI processing sequence SEI message.

[0246] The semantics of the i-th PON-nested SEI message applied as the k-th loop entry of an associated SEI processing sequence SEI message having a specific po_id value are applied without considering any of the PON-nested SEI messages that are not associated with any SEI processing sequence SEI message having that specific po_id value.

[0247] For each SEI processing sequence SEI message in which po_id is equal to pon_target_po_id[m] for any m value in the range from 0 to pon_num_po_ids_minus1 (inclusive) existing in CLVS, there must be at least one value n in the range from 0 to pon_num_seis_minus1 (inclusive) such that the SEI processing sequence SEI message becomes the associated SEI processing sequence SEI message for the nth PON nested SEI message.

[0248] The processing of the processing chain is explained.

[0249] Processing chains are alternatives to each other. That is, the decoding system may select at most one processing chain to be applied at a time.

[0250] The implicit NNPF cascading case is defined as the case where two neural-network post-filters (NNPFs) are both activated for a picture by NNPFA SEI messages that are not included in the PON SEI messages, one of the two NNPFs designated as nnpfA has the same nnpfc_purpose as 4, the other designated as nnpfB has multiple input pictures, and the NNPFC SEI messages of the two NNPFs are not included in the PON SEI messages. In this case, the two NNPFs are implicitly considered to belong to a single processing chain, and the processing chain contains only these two NNPFs.

[0251] For reference, the implicit NNPF chaining case can be applied when cropped decoded pictures have different spatial resolutions, which can occur, for example, when sps_ref_pic_resampling_enabled_flag is equal to 1 within a bitstream compliant with Rec. ITU-T H.266 | ISO / IEC 23090-3. In one example, the cropped decoded pictures have two spatial resolutions, and the first NNPF in the processing chain for the implicit NNPF chaining case is optionally enabled so that the low-resolution cropped decoded pictures are upsampled to the resolution of the high-resolution cropped decoded pictures. Consequently, the input pictures for the second NNPF in the processing chain have the same spatial resolution.

[0252] Except for implicit NNPF cascading cases, each processing chain containing multiple SEI message types is indicated by an SPO SEI message having a specific value of po_id. Except for implicit NNPF cascading cases, when a bitstream is not contained in PON SEI messages and has a specific payload type and that payload type contains one or more SEI messages existing in SpoProcessSeiList, the SEI message type for that payload type is within its own processing chain. This case is referred to as the implicit single-processing-stage case.

[0253] In the case of an implicit NNPF chain, po_breadth_first_flag is inferred to be equal to 0 or 1, PoNumProcStgs is set to 2, PoNumSeiMsgs is set to 2, and the following applies.

[0254] 1) SEI message types with indices 0 and 1 correspond to nnpfA and nnpfB, respectively.

[0255] 2) If both NNPFs have the same nnpfc_purpose as 4 and have multiple input pictures, one of them is selected to be applied first, and for the one selected to be applied first, PoProcStgIdx[i] is set to 0 and for the other, PoProcStgIdx[i] is set to 1.

[0256] 3) Otherwise, PoProcStgIdx[0] is set to 0 and PoProcStgIdx[1] is set to 1.

[0257] In the case of an implicit single processing step, po_breadth_first_flag is inferred to be equal to 0 or 1, PoNumProcStgs is set to 1, PoNumSeiMsgs is set to 1, PoProcStgIdx[0] is set to 0, and PoSeiList[0] is set to be a single SEI message.

[0258] The PoSeiList for the corresponding picture of picA or the associated inserted picture of picA is derived identically to the PoSeiList derived for picA.

[0259] The decoding system can select and apply the processing chain as follows.

[0260] 1) The bitstream is decoded, a processing chain is selected, and the following is applied.

[0261] - The list PoCdoPicList is configured to be a list of cropped decoded pictures in output order generated as a result of decoding the bitstream.

[0262] - The list PoDecPicList is configured to be a list of decoded pictures in output order generated as a result of decoding the bitstream.

[0263] 2) For each decoded picture picA in the output order, the following applies.

[0264] a. When an implicit NNPF chain case is selected, the following applies to picA.

[0265] - PoNumSeiMsgs is initially set to 0 for picA.

[0266] When the NNPFA SEI message corresponding to PoProcStgIdx[i], which is equal to 0, enables NNPF for picA, PoSeiList[PoNumSeiMsgs++] is set to be equal to that NNPFA SEI message.

[0267] When the NNPFA SEI message corresponding to PoProcStgIdx[i], which is the same as 1, enables NNPF for picA, PoSeiList[PoNumSeiMsgs++] is set to be the same as the corresponding NNPFA SEI message.

[0268] b. If PoSeiTypeList[0] does not correspond to an FGC SEI message, the pictures in PoCdoPicList corresponding to picA are added to the list CandInputPicList[i] for all i values ​​in the range from 0 to PoSeiTypeList[0] (inclusive).

[0269] c. Otherwise, the picture in PoDecPicList corresponding to picA is added to the list CandInputPicList[i] for all i values ​​in the range from 0 to PoSeiTypeList[0] (inclusive).

[0270] d. Pictures in PoCdoPicList corresponding to picA are added to the list CandInputPicList[i] for all i values ​​in the range from PoSeiTypeList[0] + 1 to PoNumProcStgs (inclusive).

[0271] For reference, the list CandInputPicList[i] for i in the range from 1 to (inclusive) PoNumProcStgs can be updated during the next step. After step 4 below, the list CandInputPicList[PoNumProcStgs] stores the final output of the selected processing chain.

[0272] 3) If the selected processing chain is indicated by the SPO SEI message and the po_breadth_first_flag in the SPO SEI message is equal to 1, the breadth-first handling of the processing chain is called. Otherwise, the depth-first handling of the processing chain or the breadth-first handling of the processing chain is called, and regardless of whether the depth-first handling of the processing chain or the breadth-first handling of the processing chain is called, the resulting CandInputPicList[PoNumProcStgs] must be identical, which is a requirement of bitstream conformance.

[0273] 4) The list PoOutputPicList is set to be identical to CandInputPicList[PoNumProcStgs].

[0274] For reference, the pictures in PoOutputPicList are in increasing output order, and there are no two pictures in PoOutputPicList with the same output order.

[0275] For each processing stage with a processing stage index i in the range from 0 to PoNumProcStgs - 1 (inclusive), the following applies.

[0276] - For any specific pair of pictures inputPicA and inputPicB that are consecutive in output order within CandInputPicList[i], which is a list of candidate input pictures for the corresponding processing step, when applying a process implied by a specific SEI message of the processing step, if one or more intermediate pictures intermediatePicSetA between inputPicA and inputPicB in output order are added to CandInputPicList[i + 1], then the application of the process implied by that specific SEI message when a picture other than currPicA was the current picture, or the application of the process implied by another SEI message of the same processing step when any picture (including currPicA) was the current picture, shall not output any picture between inputPicA and inputPicB in output order.

[0277] For reference, the intention of the constraints expressed above is to prevent the generation of output pictures between any specific consecutive pair of input pictures more than once within the processing step.

[0278] Breadth-first handling of a processing chain is explained.

[0279] For each SEI message type with SEI message type index i of the selected processing chain, the following is applied in increasing order of the corresponding processing step index PoProcStgIdx[i] values.

[0280] - For each picture picA in the output order within CandInputPicList[PoProcStgIdx[i]], if a SEI message associated with the i-th SEI message type exists in picA's PoSeiList, the following applies.

[0281] - When the i-th SEI message type does not correspond to PoSeiList[0], the following is applied for the interpretation of the SEI message.

[0282] - Interface variables for the purpose of interpreting SEI messages are derived from picA.

[0283] - The semantics of the SEI message, or the semantics of the NNPFC SEI message associated with the SEI message if the SEI message is an NNPFA SEI message, are applied to the pictures in CandInputPicList[PoProcStgIdx[i]].

[0284] - When the SEI payloadType value of the i-th SEI message type exists in SpoProcessSeiList, the process implied by the SEI message is executed, and each list CandInputPicList[PoProcStgIdx[i] + j] for j in the range from 1 to PoNumProcStgs - PoProcStgIdx[i] (inclusive) is updated by replacing the pictures with the corresponding processed pictures (if any) resulting from the process, and inserting other pictures (if any) resulting from the process into CandInputPicList[PoProcStgIdx[i] + j] so as to maintain the output order. If the SEI message is an FGC SEI message and is PoSeiList[0], while replacing the picture in CandInputPicList[PoProcStgIdx[i] + j] with the corresponding processed picture, the corresponding processed picture is cropped in the same way as generating a cropped decoded output picture from the corresponding decoded picture, and that cropped picture is used for replacement.

[0285] Depth-first handling of a processing chain is explained.

[0286] For each picture picA in CandInputPicList[0], the following is applied repeatedly in output order.

[0287] - For each SEI message with SEI message index seiIdx in picA's PoSeiList, the following applies in increasing order of the list indices for PoSeiList.

[0288] - When the i-th SEI message type does not correspond to PoSeiList[0], the following is applied for the interpretation of the SEI message.

[0289] Interface variables for the purpose of interpreting SEI messages are derived from the pictures in CandInputPicList[PoProcStgIdx[PoSeiTypeList[seiIdx]]].

[0290] - The semantics of the SEI message, or the semantics of the NNPFC SEI message associated with the SEI message if the SEI message is an NNPFA SEI message, apply to the pictures within CandInputPicList[PoProcStgIdx[PoSeiTypeList[seiIdx]]].

[0291] - When the SEI payloadType value of the SEI message exists in SpoProcessSeiList, the process implied by the SEI message is repeatedly invoked in output order for each picture in CandInputPicList[PoProcStgIdx[PoSeiTypeList[seiIdx]]] that is either the picture corresponding to picA or an associated inserted picture of picA. After each call to the process, each list CandInputPicList[PoProcStgIdx[PoSeiTypeList[seiIdx]] + j] for j in the range from 1 to PoNumProcStgs - PoProcStgIdx[PoSeiTypeList[seiIdx]] (inclusive) is updated by replacing the pictures with the corresponding processed pictures (if any) resulting from the process, and inserting other pictures (if any) resulting from the process into CandInputPicList[PoProcStgIdx[PoSeiTypeList[seiIdx]] + j] so as to maintain the output order. If the SEI message is an FGC SEI message and is PoSeiList[0], while replacing the picture in CandInputPicList[PoSeiTypeList[seiIdx]] + j] with the corresponding processed picture, the corresponding processed picture is cropped in the same way as generating the decoded output picture by first cropping it from the corresponding decoded picture, and that cropped picture is used for replacement.

[0292] Table 4 shows an example of a Quality Metric SEI message syntax according to one embodiment.

[0293] [Table 4]

[0294]

[0295] The following shows examples of Quality Indicator (QM) SEI message syntax elements.

[0296] An example of the semantics of a quality indicator SEI message according to one embodiment is described.

[0297] The quality metrics SEI message signals quality metric values ​​representing any one of the following.

[0298] - Single picture quality.

[0299] - Average quality of all pictures corresponding to CLVS.

[0300] Quality gain of a single picture. This is the difference in quality of a single picture relative to the quality of a gain reference picture.

[0301] - Average quality gain of all pictures corresponding to CLVS.

[0302] The use of this SEI message requires the definition of the following variables.

[0303] - Chroma format indicator denoted as ChromaFormatIdc.

[0304] - Number of pictures NumPics.

[0305] - A list of picture widths and heights in units of luma samples. Here, denoted as PicWidth[i] and PicHeight[i] respectively, where i is in the range from 0 to NumPics - 1 (inclusive).

[0306] - A list of pictures TestPicList[i]. Here, i is in the range from 0 to NumPics - 1 (inclusive).

[0307] - When any qm_gain_flag[i] is equal to 1, GainRefPicList[i] is a list of gain-referenced pictures for i in the range from 0 to NumPics - 1 (inclusive).

[0308] The variables SubWidthC and SubHeightC are derived from ChromaFormatIdc.

[0309] TestPicList[i][cIdx] and ReferencePicList[i][cIdx] represent the cIdx-th sample array of the i-th picture in TestPicList and ReferencePicList, respectively.

[0310] TestPicList[i][cIdx][x][y] and ReferencePicList[i][cIdx][x][y] represent the sample at position (x, y) within the cIdx-th sample array of the i-th picture in TestPicList and ReferencePicList, respectively. Here, x is in the range from 0 to ( ( cIdx = = 0 ) ? PicWidth[i] : PicWidth[i] / SubWidthC ) - 1 (inclusive), and y is in the range from 0 to ( ( cIdx = = 0 ) ? PicHeight[i] : PicHeight[i] / SubHeightC ) - 1 (inclusive).

[0311] currPicIdx is set to a value where the output time of TestPicList[currPicIdx] is equal to the output time of the current picture.

[0312] qm_metric_definitions_present_flag, which is equivalent to 1, indicates that information defining quality metrics exists. qm_metric_definitions_present_flag, which is equivalent to 0, indicates that information defining quality metrics does not exist.

[0313] When this SEI message is the first quality metric SEI message in CLVS in decoding order, qm_metric_definitions_present_flag must be equal to 1.

[0314] Otherwise (if this SEI message is not the first quality indicator SEI message in CLVS in the decoding order), at least one of the following two conditions must be satisfied, which is a requirement for bitstream conformance.

[0315] - qm_metric_definitions_present_flag will be equal to 0

[0316] - If the values ​​of the syntax elements qm_metric_type[i], qm_three_component_flag[i], qm_gain_flag[i], qm_gain_reference_flag[i], qm_metric_increasing_flag[i], qm_full_reference_flag[i], qm_value_len_minus1_in_bytes[i], qm_metric_description_present_flag[i], and qm_metric_description[i] exist, they must be equal to the respective syntax elements of the first quality metric SEI message in CLVS.

[0317] A qm_clvs_values_present_flag equal to 1 indicates that qm_clvs_metric_value[i][c] syntax elements exist. A qm_clvs_values_present_flag equal to 0 indicates that qm_clvs_metric_value[i][c] syntax elements do not exist.

[0318] A qm_pic_values_present_flag equal to 1 indicates that qm_pic_metric_value[i][c] syntax elements exist. A qm_pic_values_present_flag equal to 0 indicates that qm_pic_metric_value[i][c] syntax elements do not exist.

[0319] The value obtained by adding 1 to qm_num_metrics_minus1 specifies the number of signaling quality metric items.

[0320] A qm_gain_enabled_flag equal to 1 indicates that the qm_gain_flag[i] syntax element exists. A qm_gain_enabled_flag equal to 0 indicates that the qm_gain_flag[i] syntax element does not exist.

[0321] If qm_gain_flag[i] and qm_gain_reference_flag[i] exist, they represent the interpretation of the values ​​of the syntax elements qm_clvs_metric_value[i][c] and qm_pic_metric_value[i][c]. If qm_gain_flag[i] and qm_gain_reference_flag[i] do not exist, their values ​​are inferred to be equal to 0.

[0322] qm_metric_type[i] specifies the quality metric type of the i-th item as specified in Table 2 below. The value of qm_metric_type[i] must be in the range of 0 to 8 (inclusive) or 128 to 255 (inclusive) within the bitstream suitable for the present disclosure. Values ​​in the range of 9 to 127 (inclusive) for qm_metric_type[i] are reserved for future use and must not exist in the bitstream suitable for the present disclosure.

[0323] If the value of qm_metric_type[i] is in the range from 9 to 127, a decoder suitable for the present disclosure must ignore all syntax elements for the i-th item in this syntax structure.

[0324] If the value of qm_metric_type[i] is in the range of 128 to 255, the quality metric type is unspecified or specified by other means not specified in this disclosure.

[0325] Table 5 below defines the interpretation for qm_metric_type[i].

[0326] [Table 5]

[0327]

[0328] qm_three_component_flag[i] equal to 1 indicates that there will be three component values ​​for the i-th indicator. qm_three_component_flag[i] equal to 0 indicates that there will be a single value for the i-th indicator. It is a requirement of bitstream conformance that qm_three_component_flag[i] must be equal to 0 when ChromaFormatIdc is equal to 0.

[0329] qm_metric_increasing_flag[i] equal to 1 means that a higher value of the i-th metric indicates an improvement in quality. qm_metric_increasing_flag[i] equal to 0 means that a lower value of the i-th metric indicates an improvement in quality. When not present, the value of qm_metric_increasing_flag[i] is inferred to be equal to IncreasingFlag[qm_metric_type[i]] in Table 2.

[0330] qm_full_reference_flag[i], which is equal to 1, indicates that the quality metric is a full reference quality metric calculated by comparing the pictures in TestPicList with their respective quality reference pictures. qm_full_reference_flag[i], which is equal to 0, indicates that the quality metric may or may not include comparing the pictures in TestPicList with their respective quality reference pictures. When not present, the value of qm_full_reference_flag[i] is inferred to be equal to FullReferenceFlag[qm_metric_type[i]] in Table 2.

[0331] The value obtained by adding 1 to qm_value_len_minus1_in_bytes[i] represents the length in bytes of the syntax element qm_pic_metric_value[i][c]. If the value does not exist, the value of qm_value_len_minus1_in_bytes[i] is inferred to be equal to NumBytes[qm_metric_type[i]] - 1.

[0332] qm_metric_description_present_flag[i] equal to 1 indicates that qm_metric_description[i] exists. qm_metric_description_present_flag[i] equal to 0 indicates that qm_metric_description[i] does not exist.

[0333] qm_bit_equal_to_zero must be equal to 0.

[0334] qm_metric_description[i] represents the text description for the i-th quality metric. The length of the syntax element must be less than or equal to 4097 bytes, excluding the null-terminated byte.

[0335] qm_clvs_metric_value[i][c] specifies the mean value of the i-th quality metric for the c-th component of CLVS. The length of the corresponding syntax element is 8 * (qm_value_len_minus1_in_bytes[i] + 1) bits.

[0336] qm_pic_metric_value[i][c] specifies the value of the i-th quality metric for the c-th component of the current picture. The length of the corresponding syntax element is 8 * (qm_value_len_minus1_in_bytes[i] + 1) bits.

[0337] The meaning of the quality metric value is determined by the values ​​of qm_metric_type[i], qm_gain_flag[i], and qm_gain_reference_flag[i].

[0338] When qm_pic_values_present_flag is equal to 1, qm_pic_metric_value[i][c] represents the picture metric value picMetricValue[i][c] of type qm_metric_type[i] described in Table 2 above, and the following applies.

[0339] - When qm_gain_flag[i] is equal to 0, qm_pic_metric_value[i][c] has a value derived by the process specified in this disclosure, with testPic, picWidth, and picHeight assigned to TestPicList[currPicIdx], PicWidth[currPicIdx], and PicHeight[currPicIdx], respectively.

[0340] - Otherwise (if qm_gain_flag[i] is equal to 1), the following applies.

[0341] - picMetricValueTest[i][c] is set to be equal to picMetricValue[i][c] derived by the process specified in this disclosure, with testPic, picWidth, and picHeight assigned to TestPicList[currPicIdx], PicWidth[currPicIdx], and PicHeight[currPicIdx], respectively.

[0342] - picMetricValueGainRef[i][c] is set to be equal to picMetricValue[i][c] derived by the process specified in this disclosure, with testPic, picWidth, and picHeight assigned to become GainRefPicList[currPicIdx], PicWidth[currPicIdx], and PicHeight[currPicIdx], respectively.

[0343] - qm_pic_metric_value[i][c] has the value of picMetricValueTest[i][c] - picMetricValueGainRef[i][c].

[0344] When qm_clvs_values_present_flag is equal to 1, qm_clvs_metric_value[i][c] represents listPicMetricValue[j][i][c], which is the mean value of picture metric values ​​calculated for all pictures in TestPicList of type qm_metric_type[i] as described in Table 2 above. Here, each listPicMetricValue[j][i][c] is derived as follows for each value of j in the range from 0 to NumPics - 1 (inclusive).

[0345] - When qm_gain_flag[i] is equal to 0, listPicMetricValue[j][i][c] is equal to picMetricValue[i][c] derived according to the process specified in this disclosure, with testPic, picWidth, and picHeight assigned to TestPicList[j], PicWidth[j], and PicHeight[j], respectively.

[0346] - Otherwise (qm_gain_flag[i] is equal to 1), the following applies.

[0347] - listPicMetricValueTest[j][i][c] is set to be equal to picMetricValue[i][c] derived by the process specified in this disclosure, with testPic, picWidth, and picHeight assigned to TestPicList[currPicIdx], PicWidth[currPicIdx], and PicHeight[currPicIdx], respectively.

[0348] - picMetricValueGainRef[j][i][c] is set to be equal to picMetricValue[i][c] derived by the process specified in this disclosure, with testPic, picWidth, and picHeight assigned to become GainRefPicList[currPicIdx], PicWidth[currPicIdx], and PicHeight[currPicIdx], respectively.

[0349] - qm_pic_metric_value[j][i][c] has the value of picMetricValueTest[j][i][c] - picMetricValueGainRef[j][i][c].

[0350] The derivation process of picMetricValue[i][c] is explained.

[0351] The inputs for this process are the tested picture testPic, the picture width picWidth in luma samples, and the picture height picHeight in luma samples.

[0352] The quality reference picture, referencePic, is given as input to the encoding system and is called the original picture, having an output time equal to the output time of testPic.

[0353] testPic[cIdx] and referencePic[cIdx] represent the cIdx-th sample array of testPic and referencePic, respectively.

[0354] testPic[cIdx][x][y] and referencePic[cIdx][x][y] represent samples at position (x, y) within the cIdx-th sample array of testPic and referencePic, respectively.

[0355] The picture quality metric picMetricValue[i][c] is derived as follows.

[0356] - When qm_metric_type[i] is equal to 0,

[0357] - listPicMetricValueTest[j][i][c] is set to be equal to picMetricValue[i][c] derived by the process specified in this disclosure, with testPic, picWidth, and picHeight assigned to TestPicList[currPicIdx], PicWidth[currPicIdx], and PicHeight[currPicIdx], respectively.

[0358] - picMetricValueGainRef[j][i][c] is set to be equal to picMetricValue[i][c] derived by the process specified in this disclosure, with testPic, picWidth, and picHeight assigned to become GainRefPicList[currPicIdx], PicWidth[currPicIdx], and PicHeight[currPicIdx], respectively.

[0359] - When qm_metric_increasing_flag[i] is equal to 1, a higher value of picMetricValue[i][c] indicates that testPic is of better quality than a picture with a lower picMetricValue[i][c] value.

[0360] - When qm_full_reference_flag[i] is equal to 1, picMetricValue[i][c] represents the quality metric value calculated from the comparison between testPic and referencePic.

[0361] - qm_metric_description[i] provides a text description of the quality metric displayed by picMetricValue[i][c].

[0362] - Further interpretation of picMetricValue[i][c] is determined by external means not specified in this specification.

[0363] - When qm_metric_type[i] is equal to 1,

[0364] - picMetricValue[i][0] is set to the same as the PSNR value calculated using Section 9.4.2 and Section D.2 of ISO / IEC 23001-11 [2] for the lumina components of testPic and referencePic with bit depth OrigBitDepth, width picWidth, and height picHeight.

[0365] - When qm_three_component_flag[i] is equal to 1, - picMetricValue[i][1] and picMetricValue[i][2] are set to have the bit depth OrigBitDepth, width picWidth / SubWidthC, and height picHeight / SubHeightC, and are equal to the PSNR values ​​calculated for the Cb and Cr components of testPic and referencePic, respectively, using sections 9.4.2 and D.2 of ISO / IEC 23001-11 [2].

[0366] - When qm_metric_type[i] is equal to 2,

[0367] - picMetricValue[i][0] is set to be equal to the value of the variable psnrYUV calculated as follows.

[0368] - The variable psnrY is set to the same as the PSNR value calculated using Section 9.4.2 and Section D.2 of ISO / IEC 23001-11 [2] for the luminance components of testPic and referencePic with bit depth OrigBitDepth, width picWidth, and height picHeight.

[0369] - Variables psnrU and psnrV are set to have bit depth OrigBitDepth, width picWidth / SubWidthC, and height picHeight / SubHeightC, and are equal to the PSNR values ​​calculated using sections 9.4.2 and D.2 of ISO / IEC 23001-11 [2] for the Cb and Cr components of testPic and referencePic, respectively.

[0370] [Equation 4]

[0371]

[0372] - When qm_metric_type[i] is equal to 3,

[0373] - picMetricValue[i][0] is set to the same as the SSIM value calculated from Section 9.4.2 and Section D.5 of ISO / IEC 23001-11 [2] for the luminance components of testPic and referencePic, with bit depth OrigBitDepth, width picWidth, and height picHeight.

[0374] - When qm_three_component_flag[i] is equal to 1,

[0375] - picMetricValue[i][1] and picMetricValue[i][2] have bit depth OrigBitDepth, width picWidth / SubWidthC, and height picHeight / SubHeightC, and are set to be equal to the SSIM values ​​calculated from Section 9.4.2 and Section D.5 of ISO / IEC 23001-11 [2] for the Cb and Cr components of testPic and referencePic, respectively.

[0376] - When qm_metric_type[i] is equal to 4,

[0377] - picMetricValue[i][0] is set to the same as the MS-SSIM value calculated from Section 4.3.3 of ISO / IEC 23001-10 [1] for the luminance components of testPic and referencePic with the bit depth OrigBitDepth.

[0378] - When qm_three_component_flag[i] is equal to 1,

[0379] - picMetricValue[i][1] and picMetricValue[i][2] have a bit depth of OrigBitDepth and are set to be equal to the MS-SSIM values ​​calculated from Section 4.3.3 of ISO / IEC 23001-10 [1] for the Cb and Cr components of testPic and referencePic, respectively.

[0380] - When qm_metric_type[i] is equal to 5,

[0381] - picMetricValue[i][0] is set to the same as the MOS value specified in Section 4.3.6 of ISO / IEC 23001-10 [1].

[0382] - When qm_metric_type[i] is equal to 6,

[0383] - picMetricValue[i][0] is set to the same as the wPSNR value calculated from Section 9.4.2 and Section D.3 of ISO / IEC 23001-11 [2] for the luminance components of testPic and referencePic, with bit depth OrigBitDepth, width picWidth, and height picHeight.

[0384] - When qm_three_component_flag[i] is equal to 1,

[0385] - picMetricValue[i][1] and picMetricValue[i][2] have bit depth OrigBitDepth, width picWidth / SubWidthC, and height picHeight / SubHeightC, and are set to be equal to the wPSNR values ​​calculated from Section 9.4.2 and Section D.3 of ISO / IEC 23001-11 [2] for the Cb and Cr components of testPic and referencePic, respectively.

[0386] - When qm_metric_type[i] is equal to 7,

[0387] - picMetricValue[i][0] is set to the same WS-PSNR value calculated from Section 9.4.2 and Section D.4 of ISO / IEC 23001-11 [2] for the luminance components of testPic and referencePic with bit depth OrigBitDepth, width picWidth, and height picHeight.

[0388] - When qm_three_component_flag[i] is equal to 1,

[0389] - picMetricValue[i][1] and picMetricValue[i][2] have bit depth OrigBitDepth, width picWidth / SubWidthC, and height picHeight / SubHeightC, and are set to be equal to the WS-PSNR values ​​calculated from Section 9.4.2 and Section D.4 of ISO / IEC 23001-11 [2] for the Cb and Cr components of testPic and referencePic, respectively.

[0390] The following describes the case where qm_metric_type[i] is 8.

[0391] - When qm_metric_type[i] is equal to 8,

[0392] - picMetricValue[i][0] is set to the value of lumaMse derived as follows, which is interpreted as a floating-point value.

[0393] [Formula 5]

[0394]

[0395] If qm_three_component_flag[i] is equal to 1, picMetricValue[i][1] and picMetricValue[i][2] are set to the values ​​of CbMse and CrMse, respectively derived as follows, which are interpreted as floating-point values.

[0396] [Equation 6]

[0397]

[0398] - When qm_metric_type[i] is equal to 9,

[0399] - picMetricValue[i][0] is set to equal the VMAF calculated from Section 4.3.3 of ISO / IEC 23001-10 [1] for the luminance components of testPic and referencePic with the bit depth OrigBitDepth. VMAF is a full reference metric that uses machine learning to fuse scores from multiple elementary quality metrics to generate a quality score for the video. This metric is trained to simulate a quality evaluation obtained as a result of a subjective test. The range of values ​​obtained from the standard (HD) VMAF model is [0,..100].

[0400] - When qm_metric_description_present_flag[i] is equal to 1, qm_metric_description[i] may contain information about the version of the VMAF metric, such as the metric release number and the VMAF model.

[0401] For the purpose of interpreting quality metric SEI messages, the derivation of the variables ChromaFormatIdc, NumPics, TestPicList, PicWidth, PicHeight, and GainRefPicList is specified as follows.

[0402] TestPicList is initially composed of cropped decoded pictures of the current CLVS in output order.

[0403] When a quality indicator SEI message is included as an SEI message type within an SEI processing order SEI message, any quality indicator SEI message associated with that SEI processing order SEI message must be included within a processing order nesting SEI message.

[0404] When a quality indicator SEI message is included as the i-th SEI message type within an SEI processing sequence SEI message, the following applies.

[0405] - It is a bitstream conformance requirement that the SEI message seiB, which implies post-processing to be performed, must exist as the j-th SEI message type within the same SEI processing order SEI message, and that po_sei_processing_order[j] must be equal to po_sei_processing_order[i].

[0406] - The corresponding quality indicator SEI message represents the picture quality resulting from the post-processing implied by seiB.

[0407] - TestPicList is updated as follows for each post-processing step where po_sei_processing_order[j] is less than or equal to po_sei_processing_order[i], in the non-decreasing order of j.

[0408] - When the post-processing step generates a picture picA as a result that has the same output time as any picture picB in TestPicList, picB in TestPicList is replaced with picA.

[0409] - When the post-processing step generates a picture picA as a result that has an output time not equal to the output time of any picture in TestPicList, picA is inserted into TestPicList in such a way that the pictures in TestPicList maintain their output order.

[0410] NumPics is set to be equal to the number of pictures in TestPicList.

[0411] PicWidth[i] and PicHeight[i] are each set to be equal to the width and height of TestPicList[i] in units of luma samples.

[0412] When a quality metric SEI message is included as the k-th SEI message within a processing order nesting SEI message and qm_gain_flag[i] is equal to 1 for any value of i, the following applies.

[0413] - When qm_gain_reference_flag[i] is equal to 0, the i-th metric value in the quality metric SEI message represents the gain of the post-processing step where po_sei_processing_order[j] is equal to pon_processing_order[k] for the picture or pictures used as input to the corresponding post-processing step, and GainRefPicList is set to be equal to TestPicList derived for the processing steps up to that point, excluding the processing step with po_sei_processing_order[j].

[0414] - Otherwise (when qm_gain_reference_flag[i] is equal to 1), the i-th metric value in the quality metric SEI message represents the cumulative gain of all post-processing steps for the clipped decoded picture or pictures for which po_sei_processing_order[j] is less than or equal to pon_processing_order[k], and GainRefPicList consists of the clipped decoded pictures of the current CLVS in output order.

[0415] - Bitstream conformance requirements state that the number of pictures in GainRefPicList must be equal to NumPics, and that the width and height of GainRefPicList[i] in luma samples must be equal to PicWidth[i] and PicHeight[i], respectively.

[0416] The value of ChromaFormatIdc is derived as follows.

[0417] - If a quality metric SEI message is not included in a PON (Processing Order Nesting) SEI message, ChromaFormatIdc is set to be equal to sps_chroma_format_idc.

[0418] - Otherwise (when the quality indicator SEI message is included in the PON SEI message), ChromaFormatIdc is set to a value that matches the chroma format of the pictures in TestPicList, and it is a bitstream conformance requirement that the chroma formats of all pictures in TestPicList and GainRefPicList (if present) must be identical.

[0419] When the quality metric SEI message qmSeiA exists in a picture unit other than the first picture unit of CLVS in the decoding order and at least one value of qm_clvs_metric_value[i][c] exists, the following applies.

[0420] - If qmSeiA is not included in the PON SEI message, each value of qm_clvs_metric_value[i][c] must be equal to the value of qm_clvs_metric_value[i][c] in the quality metric SEI message that exists in the first picture unit of CLVS and is not included in the processing order nesting SEI message.

[0421] - Otherwise (where qmSeiA is included within a PON SEI message containing a specific set of pon_target_po_id[i] values), the following applies.

[0422] - It is a requirement of bitstream conformance that there must be a quality indicator SEI message qmSeiB contained within a processing order nesting SEI message that exists in the first picture unit of CLVS and has the same set of pon_target_po_id[i] values.

[0423] - Each value of qm_clvs_metric_value[i][c] in qmSeiA must be equal to the value of qm_clvs_metric_value[i][c] in qmSeiB.

[0424] Conventional Quality Metric SEI messages include signaling the average quality for CLVS by including the signaling of the syntax elements qm_clvs_values_present_flag and qm_clvs_metric_value[i][c]. These syntax elements are as follows.

[0425] A qm_clvs_values_present_flag equal to 1 indicates that qm_clvs_metric_value[i][c] syntax elements exist. A qm_clvs_values_present_flag equal to 0 indicates that qm_clvs_metric_value[i][c] syntax elements do not exist.

[0426] qm_clvs_metric_value[i][c] specifies the average value of the i-th quality metric for the c-th component of CLVS. The length of the corresponding syntax element is 8 * (qm_value_len_minus1_in_bytes[i] + 1) bits.

[0427] Conventional designs that signal the average quality of CLVS in quality indicator SEI messages have the following problems.

[0428] If the average quality of the CLVS exists in any QM SEI message, it is expected that the first QM SEI message must exist in the first picture unit of the CLVS. However, conventionally, despite the disclosure that the average value of the QM SEI message existing in a picture unit other than the first picture unit of the CLVS must be the same as the average value of the QM SEI message existing in the first picture unit of the CLVS, a constraint is omitted that enforces the necessity of such existence (i.e., that the QM SEI message must exist in the first picture unit of the CLVS).

[0429] In addition, the explanation that the average quality value in a picture unit other than the first picture unit of CLVS must be the same as the value of the QM SEI message in the first picture unit of CLVS is specified only for VVC (i.e., in the sub-semantics item "Use of the quality metric SEI message in VVC"). However, since this must also be applicable and usable in other codecs that can use VSEI, it is desirable to move these semantics elements to the general semantics item of the QM SEI message.

[0430] In one embodiment, the following items may be applied individually or in combination.

[0431] 1. If an average quality value for a CLVS exists in a QM SEI message, the first QM SEI message for that CLVS must exist in the first picture unit of the CLVS, and the average quality value(s) signaled in these two SEIs must be the same.

[0432] 2. The above constraints should be applied to the general semantics of QM SEI messages, so that they are not applied only to specific codecs (e.g., VVC, etc.) but can be applied to all codecs that reference or use VSEI.

[0433] One embodiment relates to Item 1 described above. One embodiment is based on the VSEI specification. An example of the semantics of a quality indicator SEI message according to one embodiment is described. Semantics different from the semantics of the quality indicator SEI message described above are described, and any description of semantics identical to the semantics of the quality indicator SEI message described above is replaced by the description of the semantics of the quality indicator SEI message described above.

[0434] ...

[0435] For the interpretation of Quality Metric SEI messages, the derivation method for the variables ChromaFormatIdc, NumPics, TestPicList, PicWidth, PicHeight, and GainRefPicList is defined as follows.

[0436] If a quality metric SEI message (qmSeiA) exists in a picture unit other than the first picture unit of CLVS in the decoding order, and at least one qm_clvs_metric_value[i][c] value exists, the following applies.

[0437] If qmSeiA is not included in the PON (Processing Order Nesting) SEI message, the following applies.

[0438] - As a bitstream conformity requirement, a quality indicator SEI message (qmSeiB) must exist in the first picture unit of the CLVS and is not included in the PON SEI message.

[0439] - Each qm_clvs_metric_value[i][c] value included in qmSeiA must be identical to the corresponding qm_clvs_metric_value[i][c] value included in qmSeiB.

[0440] Otherwise (if qmSeiA is included in a PON SEI message having a specific set of pon_target_po_id[i] values), the following applies.

[0441] - As a bitstream conformance requirement, there must be a quality indicator SEI message (qmSeiC) contained in a PON SEI message that exists in the first picture unit of CLVS and has the same set of pon_target_po_id[i] values.

[0442] - Each qm_clvs_metric_value[i][c] value included in qmSeiA must be identical to the corresponding qm_clvs_metric_value[i][c] value included in qmSeiC.

[0443] One embodiment relates to items 1 and 2 described above. One embodiment is based on the VSEI specification. An example of the semantics of a quality indicator SEI message according to one embodiment is described. Semantics different from the semantics of the quality indicator SEI message described above are described, and any description of semantics identical to the semantics of the quality indicator SEI message described above is replaced by the description of the semantics of the quality indicator SEI message described above.

[0444] ...

[0445] An example of a Quality Metrics SEI message syntax element is explained.

[0446] Quality Indicator (QM) SEI messages signal a quality indicator value representing one of the following.

[0447] ...

[0448] qm_clvs_metric_value[i][c] specifies the mean value of the i-th quality metric for the c-th component of CLVS. The length of the syntax element is 8 * (qm_value_len_minus1_in_bytes[i] + 1) bits.

[0449] If a quality metric SEI message (qmSeiA) exists in a picture unit other than the first picture unit of CLVS in the decoding order, and at least one qm_clvs_metric_value[i][c] value exists, the following applies.

[0450] - If qmSeiA is not included in the PON (Processing Order Nesting) SEI message, the following applies.

[0451] - As a bitstream conformity requirement, a quality indicator SEI message (qmSeiB) must exist in the first picture unit of the CLVS and is not included in the PON SEI message.

[0452] - Each qm_clvs_metric_value[i][c] value included in qmSeiA must be the same as the qm_clvs_metric_value[i][c] value included in qmSeiB.

[0453] - Otherwise (if qmSeiA is included in a PON SEI message that has a specific set of pon_target_po_id[i] values), the following applies.

[0454] - As a bitstream conformance requirement, there must be a quality indicator SEI message (qmSeiC) contained in a PON SEI message that exists in the first picture unit of CLVS and has the same set of pon_target_po_id[i] values.

[0455] - Each qm_clvs_metric_value[i][c] value included in qmSeiA must be the same as the qm_clvs_metric_value[i][c] value included in qmSeiC.

[0456] ...

[0457] The use of the quality metric SEI message in VVC is explained.

[0458] For the interpretation of quality indicator SEI messages, the derivation method for the variables ChromaFormatIdc, NumPics, TestPicList, PicWidth, PicHeight, and GainRefPicList is defined as follows.

[0459] ...

[0460] The terms or names described below (e.g., names of syntax elements or variables, etc.) are merely examples, and the technical features of the present disclosure are not limited to the terms, etc. described below. For example, the image information described below may include various information according to the embodiments described in the present disclosure and may include information described in at least one of the tables described above.

[0461] The operations described below do not constitute an essential component of one embodiment, and at least some of the operations described below may be omitted. Furthermore, the operations described below do not constitute a sufficient component of one embodiment, and previously described operations may be added. Moreover, unless they contradict previously described operations, the operations described below form one embodiment integrally with previously described operations and do not form a separate embodiment distinct from previously described operations.

[0462] FIG. 5 is a diagram illustrating a method for decoding image information according to one embodiment of the present disclosure.

[0463] The decoding method (S500) may include the operations described below.

[0464] The terms or names described below (e.g., names of syntax elements or variables, etc.) are merely examples, and the technical features of the present disclosure are not limited to the terms or names described below. For example, the image information described below may include various information according to the embodiments described in the present disclosure and may include information described in at least one of the tables described above.

[0465] The operations described below do not constitute an essential component of the decoding method according to one embodiment, and at least some of the operations described below may be omitted. Furthermore, the operations described below do not constitute a sufficient component of the decoding method according to one embodiment, and the previously described operations may be added.

[0466] The operations described below form a single embodiment integrally with the configurations and / or operations described above, unless they conflict with the configurations and / or operations described above, and do not form a separate embodiment distinct from the configurations and / or operations described above.

[0467] The decoding method (S500) can be executed by a decoding device including a memory and a processor electrically connected to the memory, for example, by a processor.

[0468] A decoding device can acquire image information. For example, a processor of a decoding device can acquire image information. The image information may include a picture to be decoded.

[0469] For example, the image information may include additional information related to at least one picture (e.g., analysis information that can be used to calculate quality indicators). Additionally, quality indicator information calculated by an encoding device may be provided for quality evaluation of at least one picture. The encoding device may perform image analysis on the picture and generate statistical values ​​or quality evaluation results necessary for calculating quality indicator information, and provide them to a decoding device. Accordingly, since the decoding device utilizes the quality indicators provided by the encoding device without the need to perform separate quality analysis operations, the amount of computation and power consumption during the decoding process may be reduced.

[0470] The decoding device can acquire a SEI (supplemental enhancement information) message (S510).

[0471] SEI messages can convey specific types of information that assist in processes related to the decoding, display, or other purposes of image information. Here, SEI messages may not be necessary for the decoding process to determine the sample values ​​of the decoded picture.

[0472] For example, SEI messages may include processing order nesting (PON) SEI messages and / or quality metrics (QM) SEI messages.

[0473] A PON SEI message may include at least one PON-nested SEI message in which information regarding the processing order is provided by a SEI processing order (SPO) SEI message.

[0474] The PON SEI message may have various names, such as Processing order nesting SEI message, Processing order nesting related message, Processing order nesting related information, Processing order nesting message, Processing order nesting information, PON SEI message, PON related message, PON related information, PON message, PON information, Nesting SEI message, Nesting related message, Nesting related information, Nesting message, Nesting information, etc., and such names are not limited.

[0475] A PON SEI message can take various forms. For example, a PON SEI message may be a syntax element or a syntax structure containing one or more syntax elements. Additionally, a PON SEI message may be a raw byte sequence payload (RBSP) containing one or more syntax elements or one or more syntax structures. For example, a PON SEI message may be represented as processing_order_nesting( payloadSize ), but is not limited thereto.

[0476] A PON nested SEI message may include target identifier information, PON processing sequence information, and a PON nested SEI message.

[0477] Target identifier information may include the identifier of an SPO SEI message associated with a PON-nested SEI message. A PON-nested SEI message may be associated with multiple SPO SEI messages, and the target identifier information may include multiple target identifiers.

[0478] Target identifier information may take various forms and may be represented by various names. For example, target identifier information may be a syntax element or a syntax structure containing one or more syntax elements. For example, target identifier information that is a syntax element may include an unsigned integer consisting of 8 bits or variable-length bits. Target identifier information that is a syntax element may be represented as pon_target_po_id[i], etc., but is not limited thereto.

[0479] PON processing order information can indicate the processing order for payload types of PON-nested SEI messages. For example, PON processing order information can indicate the position of PON-nested SEI messages within the processing order defined by the associated SPO SEI message.

[0480] PON processing order information may take various forms and may be represented by various names. For example, PON processing order information may be a syntax element or a syntax structure containing one or more syntax elements. For example, PON processing order information that is a syntax element may include an unsigned integer composed of 8 bits or variable-length bits. PON processing order information that is a syntax element may be represented as pon_processing_order[i], etc., but is not limited thereto.

[0481] PON nested SEI messages are SEI messages contained within PON SEI messages, and like general SEI messages, they can convey specific types of information that assist in processes related to the decoding, display, or other purposes of image information. If a specific SEI message is not defined in some of the multiple decoding devices, that specific SEI message may be included in the PON SEI message so that undefined SEI messages are ignored by the decoding devices.

[0482] For example, the decoding device can acquire a QM SEI message contained in at least one picture unit.

[0483] The QM SEI message may include at least one of information regarding the quality of a single picture, information regarding the average quality of all pictures corresponding to the CLVS, information regarding the quality gain of a single picture, and / or information regarding the average quality gain of all pictures corresponding to the CLVS. The information regarding quality may be expressed in various ways, such as quality information, quality indicator information, or quality indicators, and may include subjective or objective indicators regarding the quality of the picture.

[0484] QM SEI messages may have various names, such as quality indicator SEI messages, quality indicator related messages, quality indicator related information, quality indicator messages, QM messages, QM related messages, and QM related information, and such names are not limited.

[0485] QM SEI messages can take various forms. For example, a QM SEI message may be a syntax element or a syntax structure containing one or more syntax elements. Additionally, a QM SEI message may be a raw byte sequence payload (RBSP) containing one or more syntax elements or one or more syntax structures. For example, a QM SEI message may be represented as quality_metric(payloadSize), but is not limited thereto.

[0486] The decoding device can obtain quality indicator information based on the SEI message (S520).

[0487] The decoding device can obtain quality indicator information for the decoded picture based on at least one QM SEI message.

[0488] QM SEI messages may include picture quality indicator existence information, average quality indicator existence information, quality indicator definition information, quality gain information, quality gain reference information, quality indicator type information, quality three-component information, quality indicator increase information, quality overall reference information, quality indicator length information, quality indicator description existence information, quality indicator description information, picture quality indicator information and / or average quality indicator information.

[0489] Picture quality indicator presence information may indicate whether the QM SEI message contains picture quality indicator information for a single picture. For example, picture quality indicator presence information with a value of 1 may indicate that the QM SEI message contains picture quality indicator information for a single picture. Additionally, picture quality indicator presence information with a value of 0 may indicate that the QM SEI message does not contain picture quality indicator information for a single picture. However, this is not limited thereto, and what picture quality indicator presence information with a value of 1 indicates may be different from what picture quality indicator presence information with a value of 0 indicates.

[0490] Picture quality indicator presence information may take various forms and may be expressed by various names. For example, picture quality indicator presence information may be a syntax element or a syntax structure containing one or more syntax elements. For example, picture quality indicator presence information may include a flag consisting of one bit or an indicator consisting of two or more bits or a variable-length bit. For example, picture quality indicator presence information may include qm_pic_values_present_flag or qm_pic_values_present_idc, but is not limited thereto.

[0491] For example, the processor of the decoding device can process QM SEI messages. The processor of the decoding device can obtain quality indicator information for a picture based on information regarding the existence of a picture quality indicator, picture quality indicator information, information regarding the existence of an average quality indicator, and average quality indicator information from the QM SEI message.

[0492] Information on the presence of average quality indicators may indicate whether a QM SEI message contains information on average quality indicators for the pictures included in CLVS. Information on the presence of average quality indicators may take various forms and may be expressed by various names. For example, information on the presence of average quality indicators may be a syntax element or a syntax structure containing one or more syntax elements. For example, information on the presence of average quality indicators that is a syntax element may include, but is not limited to, syntax elements such as qm_clvs_values_present_flag or qm_clvs_values_present_idc.

[0493] Information regarding the existence of an average quality indicator may include a flag consisting of one bit, or an indicator consisting of two or more bits or a variable-length bit. For example, if the value of the information regarding the existence of an average quality indicator is 1, it may indicate that a syntax element of the average quality indicator information exists. Additionally, if the value of the information regarding the existence of an average quality indicator is 0, it may indicate that a syntax element of the average quality indicator information does not exist. However, this is not limited thereto, and alternatively, specifying that the value of the information regarding the existence of an average quality indicator is 1 may be changed to specifying that the value of the information regarding the existence of an average quality indicator is 0.

[0494] Quality indicator definition information may indicate whether the QM SEI message includes relevant information involved in deriving quality indicators, namely quality gain information, quality gain reference information, quality indicator type information, quality three-component information, quality indicator increase information, quality overall reference information, quality indicator length information, quality indicator description existence information, and / or quality indicator description information. For example, quality indicator definition information with a value of 1 may indicate that the QM SEI message includes relevant information involved in deriving quality indicators. Additionally, quality indicator definition information with a value of 0 may indicate that the QM SEI message does not include relevant information involved in deriving quality indicators. However, this is not limited thereto, and what quality indicator definition information with a value of 1 indicates may be different from what quality indicator definition information with a value of 0 indicates.

[0495] Quality metric definition information may take various forms and may be represented by various names. For example, quality metric definition information may be a syntax element or a syntax structure containing one or more syntax elements. For example, quality metric definition information may include a flag consisting of one bit or an indicator consisting of two or more bits or a variable-length bit. For example, quality metric definition information may include qm_metric_definitions_present_flag or qm_metric_definitions_present_idc, but is not limited thereto.

[0496] Quality gain information may indicate whether picture quality indicator information and / or average quality indicator information represents absolute quality or whether picture quality indicator information and / or average quality indicator information represents relative quality relative to a reference object. For example, quality gain information with a value of 1 may indicate that picture quality indicator information and / or average quality indicator information represents relative quality relative to a reference object. Additionally, quality gain information with a value of 0 may indicate that picture quality indicator information and / or average quality indicator information represents absolute quality. However, this is not limited thereto, and what quality gain information with a value of 1 represents may be different from what quality gain information with a value of 0 represents.

[0497] Quality gain information may take various forms and may be represented by various names. For example, quality gain information may be a syntax element or a syntax structure containing one or more syntax elements. For example, quality gain information may include a flag consisting of one bit or an indicator consisting of two or more bits or a variable-length bit. For example, quality gain information may include qm_gain_flag[i] or qm_gain_idc[i], but is not limited thereto.

[0498] Quality gain reference information can be obtained based on the quality gain information indicating that picture quality indicator information and / or average quality indicator information represents relative quality compared to the reference target.

[0499] Quality gain reference information may indicate whether picture quality indicator information and / or average quality indicator information represents relative quality compared to the input image of the current or previous post-processing step, or whether picture quality indicator information and / or average quality indicator information represents relative quality compared to the initial decoded image to which post-processing is not applied. For example, quality gain reference information with a value of 1 may indicate that picture quality indicator information and / or average quality indicator information represents relative quality compared to the initial decoded image to which post-processing is not applied. Additionally, quality gain reference information with a value of 0 may indicate that picture quality indicator information and / or average quality indicator information represents relative quality compared to the input image of the current or previous post-processing step. However, this is not limited thereto, and what quality gain reference information with a value of 1 represents may be different from what quality gain reference information with a value of 0 represents.

[0500] Quality gain reference information may take various forms and may be represented by various names. For example, quality gain reference information may be a syntax element or a syntax structure containing one or more syntax elements. For example, quality gain reference information may include a flag consisting of one bit or an indicator consisting of two or more bits or a variable-length bit. For example, quality gain reference information may include qm_gain_reference_flag[i] or qm_gain_reference_idc[i], but is not limited thereto.

[0501] Quality indicator type information may indicate what type of measurement method the picture quality indicator information and / or average quality indicator information represents. For example, the quality indicator type information may indicate whether the picture quality indicator information and / or average quality indicator information is a user-defined quality indicator, PSNR (Peak Signal-to-Noise Ratio), PSNR-YUV (PSNR integrating Y, U, and V components), SSIM (Structural Similarity), MS-SSIM (Multi-Scale SSIM), MOS (Mean Opinion Score), wPSNR (Weighted PSNR), WS-PSNR (Weighted Spherical PSNR), MSE (Mean Squared Error), or VMAF (Video Multimethod Assessment Fusion). The quality indicator type information is not limited to the types of quality indicators exemplified above and may indicate any unexemplified quality indicator capable of representing the quality of the image.

[0502] Quality metric type information may take various forms and may be represented by various names. For example, quality metric type information may be a syntax element or a syntax structure containing one or more syntax elements. For example, quality metric type information may include an unsigned integer consisting of 8 bits or variable-length bits. For example, quality metric type information may include, but is not limited to, qm_metric_type[i], qm_metric_type_flag[i], or qm_metric_type_idc[i].

[0503] Quality three-component information may indicate whether quality indicator information includes quality indicator values ​​for three components. For example, quality three-component information with a value of 1 may indicate that the quality indicator information includes quality indicator values ​​for three components. Quality three-component information with a value of 0 may indicate that the quality indicator information includes a single quality indicator value. However, this is not limited thereto, and what quality three-component information with a value of 1 indicates may be different from what quality three-component information with a value of 0 indicates.

[0504] Quality three-component information may take various forms and may be represented by various names. For example, quality three-component information may be a syntax element or a syntax structure containing one or more syntax elements. For example, quality three-component information may include a flag consisting of one bit or an indicator consisting of two or more bits or a variable-length bit. For example, quality three-component information may include qm_three_component_flag[i] or qm_three_component_idc[i], but is not limited thereto.

[0505] Quality indicator increase information can indicate whether the value of high quality indicator information indicates an improvement in quality. For example, quality indicator increase information with a value of 1 may indicate that the value of high quality indicator information indicates an improvement in quality. Quality indicator increase information with a value of 0 may indicate that the value of low quality indicator information indicates an improvement in quality. However, this is not limited to this, and what quality indicator increase information with a value of 1 indicates may be different from what quality indicator increase information with a value of 0 indicates.

[0506] Quality metric increase information may take various forms and may be represented by various names. For example, quality metric increase information may be a syntax element or a syntax structure containing one or more syntax elements. For example, quality metric increase information may include a flag consisting of one bit or an indicator consisting of two or more bits or a variable-length bit. For example, quality metric increase information may include qm_metric_increasing_flag[i] or qm_metric_increasing_idc[i], but is not limited thereto.

[0507] Quality overall reference information may indicate whether quality indicator information is an overall reference quality indicator obtained by comparing each picture in the list with reference pictures. For example, quality overall reference information with a value of 1 may indicate that the quality indicator information is an overall reference quality indicator obtained by comparing each picture in the list with reference pictures. Quality overall reference information with a value of 0 may indicate that it is not determined whether the quality indicator information is an overall reference quality indicator obtained by comparing each picture in the list with reference pictures. However, this is not limited to, and what quality overall reference information with a value of 1 indicates may change from what quality overall reference information with a value of 0 indicates.

[0508] Quality full reference information may take various forms and may be represented by various names. For example, quality full reference information may be a syntax element or a syntax structure containing one or more syntax elements. For example, quality full reference information may include a flag consisting of one bit or an indicator consisting of two or more bits or a variable-length bit. For example, quality full reference information may include qm_full_reference_flag[i] or qm_full_reference_idc[i], but is not limited thereto.

[0509] Quality indicator length information can represent the length of the quality indicator information in bytes.

[0510] Quality indicator length information may take various forms and may be represented by various names. For example, quality indicator length information may be a syntax element or a syntax structure containing one or more syntax elements. For example, quality indicator length information may include an unsigned integer consisting of two bits or variable-length bits. For example, quality total reference information may include qm_value_len_minus1_in_bytes[i], but is not limited thereto.

[0511] Quality indicator description existence information may indicate whether a QM SEI message contains quality indicator description information. For example, quality indicator description existence information with a value of 1 may indicate that the QM SEI message contains quality indicator description information. Additionally, quality indicator description existence information with a value of 0 may indicate that the QM SEI message does not contain quality indicator description information. However, this is not limited thereto, and what quality indicator description existence information with a value of 1 indicates may be different from what quality indicator description existence information with a value of 0 indicates.

[0512] Quality metric description present information may take various forms and may be represented by various names. For example, quality metric description present information may be a syntax element or a syntax structure containing one or more syntax elements. For example, quality metric description present information may include a flag consisting of one bit or an indicator consisting of two or more bits or a variable-length bit. For example, quality metric description present information may include qm_metric_description_present_flag[i] or qm_metric_description_present_idc[i], but is not limited thereto.

[0513] Quality indicator description information can display a text description of the quality indicator information.

[0514] Quality metric description information may take various forms and may be expressed by various names. For example, quality metric description information may be a syntax element or a syntax structure containing one or more syntax elements. For example, quality metric description information may include a text string composed of variable-length bytes. For example, quality metric description information may include qm_metric_description[i], but is not limited thereto.

[0515] Picture quality indicator information can be obtained based on picture quality existence information indicating the existence of picture quality indicator information.

[0516] Picture quality metric information may represent quality metrics for a single picture. For example, picture quality metric information may represent absolute quality based on the value of quality gain information or relative quality relative to a reference object. For example, picture quality metric information may be a user-defined quality metric based on the value of quality metric type information, or PSNR, PSNR-YUV, SSIM, MS-SSIM, MOS, wPSNR, WS-PSNR, MSE, and / or VMAF.

[0517] Picture quality metric information may take various forms and may be represented by various names. For example, picture quality metric information may be a syntax element or a syntax structure containing one or more syntax elements. For example, picture quality metric information may include a flag consisting of one bit, an indicator consisting of two or more bits or a variable-length bit, or an unsigned integer consisting of two or more bits or a variable-length bit. For example, picture quality metric information may include qm_pic_metric_value[i], but is not limited thereto.

[0518] For example, average quality indicator information can be obtained based on the fact that information indicating the existence of average quality indicator information indicates the existence of average quality indicator information. That is, if average quality indicator information exists within the QM SEI message, the decoding device can obtain the average quality indicator information.

[0519] Average quality metric information may represent the average quality metric for the pictures included in CLVS. For example, the average quality metric information may represent the absolute average quality based on the value of the quality gain information, or the relative average quality relative to the reference. For example, the average quality metric information may be a user-defined quality metric based on the value of the quality metric type information, or PSNR, PSNR-YUV, SSIM, MS-SSIM, MOS, wPSNR, WS-PSNR, MSE, or VMAF.

[0520] Average quality metric information may take various forms and may be represented by various names. For example, average quality metric information may be a syntax element or a syntax structure containing one or more syntax elements. For example, average quality metric information may include a flag consisting of one bit, an indicator consisting of two or more bits or a variable-length bit, or an unsigned integer consisting of two or more bits or a variable-length bit. For example, average quality metric information may include qm_clvs_metric_value[i], but is not limited thereto.

[0521] For example, if the average quality metric information is represented as qm_clvs_metric_value[i][c], qm_clvs_metric_value[i][c] may represent the average value of the i-th quality metric for the c-th component of CLVS. Here, index c represents the c-th component of the pictures included in clvs, and index i represents the i-th quality metric entry.

[0522] If average quality indicator information for a CLVS exists in any QM SEI message, it is desirable to include a reference QM SEI message in the first picture unit of the corresponding CLVS. By providing average quality indicator information to be referenced throughout the entire length of the CLVS, this reference QM SEI message enables consistent interpretation of QM SEI messages included in subsequent picture units within the corresponding CLVS.

[0523] For example, a first QM SEI message containing at least one average quality indicator information may be included in the first picture unit of the CLVS. Here, the average quality indicator information included in the first picture unit may be average quality indicator information that serves as a standard for the entire CLVS. For example, the average quality indicator information included in the first QM SEI message may be average quality indicator information for the CLVS.

[0524] For example, based on the existence of a second QM SEI message containing at least one average quality indicator information that is not included in the first picture unit of the CLVS, the first QM SEI message may be included in the first picture unit of the CLVS. This indicates that if a QM SEI message containing average quality indicator information exists in a picture unit other than the first picture unit within the CLVS, the QM SEI message serving as the standard for said average quality indicator information is included in the first picture unit within the CLVS. For instance, the first QM SEI message may be a QM SEI message included in the first picture unit within the CLVS, and the second QM SEI message may be a QM SEI message included in a picture unit other than the first picture unit within the same CLVS.

[0525] For example, the value of at least one average quality indicator information included in the first QM SEI message may be set to be the same as the value of the average quality indicator information included in the second QM SEI message. For example, if the first QM SEI message is included in the first picture unit within the CLVS and the second QM SEI message is included in a picture unit other than the first picture unit within the same CLVS, the average quality indicator information included in the second QM SEI message may be set to be the same as the average quality indicator information of the first QM SEI message.

[0526] For example, the average quality indicator information included in the first QM SEI message can function as reference information for the entire CLVS, and subsequent QM SEI messages within the same CLVS can be configured to have the same average quality indicator information as that reference information. By configuring all QM SEI messages signaled within the same CLVS to reference the same average quality indicator information, the interpretation criteria for the average quality indicator information within the same CLVS can be prevented from being arbitrarily changed. Therefore, even if multiple QM SEI messages exist within the same CLVS, the average quality indicator information can be interpreted according to a consistent standard.

[0527] Meanwhile, the processor of the decoding device can acquire a PON SEI message and acquire PON nested SEI messages based on the PON SEI message. For example, the SEI messages included in the PON SEI message may be PON nested SEI messages.

[0528] A PON-nested SEI message may include target identifier information, and the target identifier information may represent the identifier values ​​of one or more SPO SEI messages associated with the PON SEI message. When a specific PON-nested SEI message is associated with a specific SPO SEI message, the PON-nested SEI message is processed according to the processing order defined in the said SPO SEI message and can be interpreted independently without relying on the semantics of other PON-nested SEI messages that are not associated with the same identifier value.

[0529] For example, there exists a second QM SEI message that is not included in the first picture unit in CLVS, and based on the fact that the second QM SEI message is not included in the PON SEI message, the first QM SEI message may not be included in the PON SEI message.

[0530] This indicates that if a second QM SEI message located at a position other than the first picture unit in the CLVS is not included in the PON SEI message, then a first QM SEI message located at the first picture unit in the CLVS, having the same payload type, is also not included in the PON SEI message. In other words, if a second QM SEI message located at a position other than the first picture unit within the CLVS is not a PON-nested SEI message, then a first QM SEI message located at the first picture unit within the CLVS, having the same payload type, may also not be a PON-nested SEI message.

[0531] Meanwhile, if a QM SEI message is a PON-nested SEI message included in a PON SEI message, the QM SEI message may include specific target identifier information depending on the information contained in the PON-nested SEI message.

[0532] Target identifier information may include the identifier of an SPO SEI message associated with a PON-nested SEI message. A PON-nested SEI message may be associated with multiple SPO SEI messages, and the target identifier information may include multiple target identifiers.

[0533] Target identifier information may take various forms and may be represented by various names. For example, target identifier information may be a syntax element or a syntax structure containing one or more syntax elements. For example, target identifier information that is a syntax element may include an unsigned integer consisting of 8 bits or variable-length bits. Target identifier information that is a syntax element may be represented as pon_target_po_id[i], etc., but is not limited thereto.

[0534] For example, if a third QM SEI message exists that is not included in the first picture unit in the CLVS, and based on the fact that the third QM SEI message is included in a PON SEI message, the first QM SEI message may be included in a PON SEI message having the same target identifier information as the PON SEI message. That is, if the third QM SEI message existing in a picture unit other than the first picture unit in the CLVS is included in a PON SEI message having specific target identifier information, the first QM SEI message existing in the first picture unit of the CLVS may also be included in a PON SEI message having the same target identifier information.

[0535] This indicates that if a third QM SEI message located at a position other than the first picture unit within the CLVS is a PON-nested SEI message having specific target identifier information, a first QM SEI message sharing the same target identifier information is also a PON-nested SEI message corresponding to that target identifier information.

[0536] In this way, the purpose is to ensure that QM SEI messages having the same target identifier information are included in the same PON SEI message, so that these SEI messages are consistently processed and interpreted according to the same SEI processing sequence chain (SPO chain). Furthermore, even if multiple QM SEI messages exist within the CLVS, the decoding device can identify the reference relationships between PON-nested SEI messages based on the target identifier information, thereby maintaining structural consistency during the interpretation of SEI messages.

[0537] Terms such as "first QM SEI message," "second QM SEI message," and "third QM SEI message" used in this disclosure are merely distinguishing indicators for identifying specific messages among a plurality of QM SEI messages that may be included in a CLVS, and are not intended to limit the order, importance, or relative priority of these messages or to restrict them to specific embodiments. For example, "first QM SEI message" refers merely to at least one QM SEI message included in at least one picture unit within a CLVS, and does not imply that the message must be generated or decoded first.

[0538] One example of a Quality Metrics SEI message syntax element can be explained.

[0539] Quality Indicator (QM) SEI messages can signal a quality indicator value representing one of the following.

[0540] Average quality metric information may represent the average quality metric for the pictures included in CLVS. For example, the average quality metric information may represent the absolute average quality based on the value of the quality gain information, or the relative average quality relative to the reference. For example, the average quality metric information may be a user-defined quality metric based on the value of the quality metric type information, or PSNR, PSNR-YUV, SSIM, MS-SSIM, MOS, wPSNR, WS-PSNR, MSE, or VMAF.

[0541] Average quality metric information may take various forms and may be represented by various names. For example, average quality metric information may be a syntax element or a syntax structure containing one or more syntax elements. For example, average quality metric information may include a flag consisting of one bit, an indicator consisting of two or more bits or a variable-length bit, or an unsigned integer consisting of two or more bits or a variable-length bit. For example, average quality metric information may include qm_clvs_metric_value[i], but is not limited thereto.

[0542] For example, when average quality metric information is represented as qm_clvs_metric_value[i][c], qm_clvs_metric_value[i][c] may represent the average value of the i-th quality metric for the c-th component of CLVS. Here, index c represents the c-th component of the pictures included in clvs, and index i represents the i-th quality metric entry. In this case, the length of the syntax element of the average quality metric information may be 8 * (qm_value_len_minus1_in_bytes[i] + 1) bits.

[0543] The syntax elements of the QM SEI message described below, even if they were included in the "Use of the quality metric SEI message in VVC" item in the conventional VVC standard, can be reorganized into the "Quality metric SEI message semantics" item if their function and meaning are not limited to a specific codec. This corresponds to a structural rearrangement intended to generalize the semantics of the QM SEI message and enable it to be commonly referenced in various video coding systems.

[0544] If a QM SEI message exists in a picture unit other than the first picture unit in the decoding order of CLVS, and at least one average quality metric value exists in said QM SEI message, the following may apply.

[0545] If a first QM SEI message existing in a picture unit other than the first picture unit in CLVS is not included in a PON (Processing Order Nesting) SEI message, as a bitstream conformity requirement, a second QM SEI message existing in the first picture unit of CLVS and not included in a PON SEI message may exist. Additionally, each average quality indicator value included in the first QM SEI message may be set to be equal to the average quality indicator value included in the second QM SEI message.

[0546] In the case where a first QM SEI message existing in a picture unit other than the first picture unit in CLVS is included in a PON SEI message having specific target identifier information, as a bitstream conformity requirement, a third QM SEI message existing in the first picture unit of CLVS and included in a PON SEI message having the same target identifier information may exist. In this case, each average quality indicator value included in the first QM SEI message may be set to be the same as the average quality indicator value included in the third QM SEI message.

[0547] FIG. 6 is a diagram illustrating a method for encoding image information according to one embodiment of the present disclosure.

[0548] The encoding method (S600) may include the operations described below.

[0549] The terms or names described below (e.g., names of syntax elements or variables, etc.) are merely examples, and the technical features of the present disclosure are not limited to the terms or names described below. For example, the image information described below may include various information according to the embodiments described in the present disclosure and may include information described in at least one of the tables described above.

[0550] The operations described below do not constitute an essential component of the decoding method according to one embodiment, and at least some of the operations described below may be omitted. Furthermore, the operations described below do not constitute a sufficient component of the decoding method according to one embodiment, and the previously described operations may be added.

[0551] The sequence of actions illustrated in the drawings regarding the actions described below is merely an example, and the actions described below may be performed in a different order as long as it does not contradict the causal relationship of the actions to be described.

[0552] The operations described below form a single embodiment integrally with the configurations and / or operations described above, unless they conflict with the configurations and / or operations described above, and do not form a separate embodiment distinct from the configurations and / or operations described above.

[0553] The encoding method (S600) can be executed by an encoding device including a memory and a processor electrically connected to the memory, for example, by a processor.

[0554] The encoding device can generate a SEI (supplemental enhancement information) message (S610).

[0555] SEI messages may convey specific types of information that assist in processes related to the decoding, display, or other purposes of image information. Here, SEI messages may not be necessary for the decoding process to determine the sample values ​​of the decoded picture.

[0556] For example, SEI messages may include processing order nesting (PON) SEI messages and / or quality metric (QM) SEI messages.

[0557] The processor of the encoding device may generate a quality indicator for the decoded picture and generate a QM SEI message based on the quality indicator for the decoded picture. The QM SEI message may include at least one of information regarding the quality of a single picture, information regarding the average quality of all pictures corresponding to the CLVS, information regarding the quality gain of a single picture, and / or information regarding the average quality gain of all pictures corresponding to the CLVS. The information regarding quality may be expressed in various ways, such as quality information, quality indicator information, or quality indicator, and may include subjective or objective indicators regarding the quality of the picture.

[0558] The processor can obtain quality metrics for the decoded picture, including values ​​of user-defined metrics, PSNR (Peak Signal-to-Noise Ratio), PSNR-YUV (PSNR with integrated Y, U, and V components), SSIM (Structural Similarity), MS-SSIM (Multi-Scale SSIM), MOS (Mean Opinion Score), wPSNR (Weighted PSNR), WS-PSNR (Weighted Spherical PSNR), MSE (Mean Squared Error), and / or VMAF (Video Multimethod Assessment Fusion).

[0559] The processor can generate quality indicator information (e.g., picture quality indicator information and / or average quality indicator information) based on quality indicators. Here, the picture quality indicator information and / or average quality indicator information correspond to quality indicator information that directly represents the quality indicators for the decoded picture.

[0560] In addition, the processor may generate relevant information involved in deriving quality indicators, namely quality gain information, quality gain reference information, quality indicator type information, quality three-component information, quality indicator increase information, quality overall reference information, quality indicator length information, quality indicator description existence information, and / or quality indicator description information. As such, this information corresponds to relevant information for obtaining quality indicators, in other words, quality indicator related information.

[0561] Depending on the embodiment, quality gain information, quality gain reference information, quality indicator type information, quality three-component information, quality indicator increase information, overall quality reference information, quality indicator length information, quality indicator description existence information and / or quality indicator description information may be included in quality indicator related information. Additionally, depending on the embodiment, quality gain information, quality gain reference information, quality indicator type information, quality three-component information, quality indicator increase information, overall quality reference information, quality indicator length information, quality indicator description existence information and / or quality indicator description information may each correspond to quality indicator related information.

[0562] For example, the encoding device can generate at least one QM (Quality Metic) SEI (supplemental enhancement information) message included in at least one picture unit based on quality metric information. For example, the processor of the encoding device can generate at least one QM SEI message associated with a picture based on quality metric information.

[0563] For example, the processor of the encoding device may generate a QM SEI message based on the acquired quality indicator, including picture quality indicator existence information, average quality indicator existence information, quality indicator definition information, quality gain information, quality gain reference information, quality indicator type information, quality three-component information, quality indicator increase information, quality total reference information, quality indicator length information, quality indicator description existence information, quality indicator description information, picture quality indicator information and / or average quality indicator information.

[0564] The QM SEI message may be the same as the QM SEI message described in FIG. 5. The description of the QM SEI message may be replaced with the description of the QM SEI message described in FIG. 5.

[0565] Average quality metric information may represent the average quality metric for the pictures included in CLVS. For example, the average quality metric information may represent the absolute average quality based on the value of the quality gain information, or the relative average quality relative to the reference. For example, the average quality metric information may be a user-defined quality metric based on the value of the quality metric type information, or PSNR, PSNR-YUV, SSIM, MS-SSIM, MOS, wPSNR, WS-PSNR, MSE, or VMAF.

[0566] Average quality metric information may take various forms and may be represented by various names. For example, average quality metric information may be a syntax element or a syntax structure containing one or more syntax elements. For example, average quality metric information may include a flag consisting of one bit, an indicator consisting of two or more bits or a variable-length bit, or an unsigned integer consisting of two or more bits or a variable-length bit. For example, average quality metric information may include qm_clvs_metric_value[i], but is not limited thereto.

[0567] For example, if the average quality metric information is represented as qm_clvs_metric_value[i][c], qm_clvs_metric_value[i][c] may represent the average value of the i-th quality metric for the c-th component of CLVS. Here, index c represents the c-th component of the pictures included in clvs, and index i represents the i-th quality metric entry.

[0568] If average quality indicator information for a CLVS exists in any QM SEI message, it is desirable to include a reference QM SEI message in the first picture unit of the corresponding CLVS. By providing average quality indicator information to be referenced throughout the entire length of the CLVS, this reference QM SEI message enables consistent interpretation of QM SEI messages included in subsequent picture units within the corresponding CLVS.

[0569] For example, a first QM SEI message containing at least one average quality indicator information may be included in the first picture unit of the CLVS. Here, the average quality indicator information included in the first picture unit may be average quality indicator information that serves as a standard for the entire CLVS. For example, the average quality indicator information included in the first QM SEI message may be average quality indicator information for the CLVS.

[0570] For example, based on the existence of a second QM SEI message containing at least one average quality indicator information that is not included in the first picture unit of the CLVS, the first QM SEI message may be included in the first picture unit of the CLVS. This indicates that if a QM SEI message containing average quality indicator information exists in a picture unit other than the first picture unit within the CLVS, the encoding device may include the QM SEI message serving as the standard for said average quality indicator information in the first picture unit within the CLVS. For example, the first QM SEI message may be a QM SEI message included in the first picture unit within the CLVS, and the second QM SEI message may be a QM SEI message included in a picture unit other than the first picture unit within the same CLVS.

[0571] For example, the value of at least one average quality indicator information included in the first QM SEI message may be set to be the same as the value of the average quality indicator information included in the second QM SEI message. For example, if the first QM SEI message is included in the first picture unit within the CLVS and the second QM SEI message is included in a picture unit other than the first picture unit within the same CLVS, the encoding device may set the average quality indicator information included in the second QM SEI message to be the same as the average quality indicator information of the first QM SEI message.

[0572] For example, the processor of the encoding device may generate a PON SEI message based on a PON nested SEI message. The PON SEI message may include at least one PON nested SEI message in which information regarding the processing order is provided by an SPO SEI message.

[0573] PON nested SEI messages are SEI messages contained within PON SEI messages, and like general SEI messages, they can convey specific types of information that assist in processes related to the decoding, display, or other purposes of image information. If a specific SEI message is not defined in some of the multiple decoding devices, that specific SEI message may be included in the PON SEI message so that undefined SEI messages are ignored by the decoding devices.

[0574] The PON SEI message may be the same as the PON SEI message described in FIG. 5. The description of the PON SEI message may be replaced with the description of the PON SEI message described in FIG. 5.

[0575] For example, there exists a second QM SEI message that is not included in the first picture unit in CLVS, and based on the fact that the second QM SEI message is not included in the PON SEI message, the first QM SEI message may not be included in the PON SEI message.

[0576] This indicates that if a second QM SEI message located at a position other than the first picture unit in the CLVS is not included in the PON SEI message, the encoding device may also not include a first QM SEI message located at the first picture unit in the CLVS, which has the same payload type, in the PON SEI message. In other words, if a second QM SEI message located at a position other than the first picture unit in the CLVS is not a PON-nested SEI message, then a first QM SEI message located at the first picture unit in the CLVS, which has the same payload type, may also not be a PON-nested SEI message.

[0577] Meanwhile, if a QM SEI message is a PON-nested SEI message included in a PON SEI message, the QM SEI message may include specific target identifier information depending on the information contained in the PON-nested SEI message.

[0578] Target identifier information may include the identifier of an SPO SEI message associated with a PON-nested SEI message. A PON-nested SEI message may be associated with multiple SPO SEI messages, and the target identifier information may include multiple target identifiers.

[0579] Target identifier information may take various forms and may be represented by various names. For example, target identifier information may be a syntax element or a syntax structure containing one or more syntax elements. For example, target identifier information that is a syntax element may include an unsigned integer consisting of 8 bits or variable-length bits. Target identifier information that is a syntax element may be represented as pon_target_po_id[i], etc., but is not limited thereto.

[0580] For example, if a third QM SEI message exists that is not included in the first picture unit in the CLVS, and based on the fact that the third QM SEI message is included in the PON SEI message, the first QM SEI message may be included in the PON SEI message having the same target identifier information as the PON SEI message. That is, if the encoding device includes the third QM SEI message existing in a picture unit other than the first picture unit in the CLVS into the PON SEI message having specific target identifier information, the first QM SEI message existing in the first picture unit of the CLVS may also be included in the PON SEI message having the same target identifier information.

[0581] This indicates that if a third QM SEI message located at a position other than the first picture unit within the CLVS is a PON-nested SEI message having specific target identifier information, then a first QM SEI message having the same target identifier information is also a PON-nested SEI message corresponding to that target identifier information.

[0582] In this way, the encoding device can ensure that QM SEI messages having the same target identifier information are included in the same PON SEI message, so that these SEI messages are consistently processed and interpreted according to the same SEI processing sequence chain (SPO chain).

[0583] Terms such as "first QM SEI message," "second QM SEI message," and "third QM SEI message" used in this disclosure are merely distinguishing indicators for identifying specific messages among a plurality of QM SEI messages that may be included in a CLVS, and are not intended to limit the order, importance, or relative priority of these messages or to restrict them to specific embodiments. For example, "first QM SEI message" refers merely to at least one QM SEI message included in at least one picture unit within a CLVS, and does not imply that the message must be generated or decoded first.

[0584] The encoding device can encode video information (S620).

[0585] For example, the processor of the encoding device can encode image information including QM SEI messages and / or PON SEI messages.

[0586] An encoding device can encode an image or image information. Here, the image may include a still image or a video, and the image information may refer to pixel data of the image, object information, additional information (e.g., SEI messages, etc.), or a combination thereof.

[0587] An encoding device can generate a bitstream by performing an encoding process on an input image or image information. At this time, the encoding process may include one or more steps such as prediction, transformation, quantization, and entropy encoding, and the generated bitstream can be used as data for reconstructing the image or image information by a decoding device.

[0588] In addition, the present disclosure may be applied not only to general encoding structures for encoding images or image information, but also to encoding methods of QM SEI messages including quality indicator information and related additional information.

[0589] The encoding device may generate one or more QM SEI messages associated with a specific picture based on information related to image quality, and the generated QM SEI messages may be included in a bitstream so that they can be utilized in the decoding or post-processing process. Here, the QM SEI messages may include not only picture-level quality indicator information but also average quality indicator information in CLVS units.

[0590] Video information encoded according to the encoding method (S600) described above can be output in the form of a bitstream. In other words, the bitstream can be generated based on the video information encoded according to the encoding method (S600) described above.

[0591] A bitstream generated based on video information encoded according to the encoding method (S600) described above can be stored on a computer-readable storage medium.

[0592] A bitstream generated based on video information encoded according to the encoding method (S600) described above can be transmitted through a transmission unit and / or a transmission medium.

[0593] According to one embodiment, image information may include SEI messages. SEI messages may convey specific types of information that assist in processes related to the decoding, display, or other processing purposes of image information. Here, SEI messages may include QM SEI messages and PON SEI messages.

[0594] FIG. 7 is a drawing illustrating an exemplary content streaming system to which an embodiment according to the present disclosure can be applied.

[0595] As illustrated in FIG. 7, a content streaming system to which an embodiment of the present disclosure is applied may largely include an encoding server, a streaming server, a web server, a media storage, a user device, and a multimedia input device.

[0596] The above encoding server compresses content input from multimedia input devices, such as smartphones, cameras, and camcorders, into digital data to generate a bitstream and transmits it to the streaming server. As another example, if multimedia input devices, such as smartphones, cameras, and camcorders, generate the bitstream directly, the encoding server may be omitted.

[0597] The bitstream may be generated by a video encoding method and / or encoding device to which an embodiment of the present disclosure is applied, and the streaming server may temporarily store the bitstream during the process of transmitting or receiving the bitstream.

[0598] The streaming server transmits multimedia data to a user device based on a user request through 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 it to the streaming server, and the streaming server can transmit multimedia data to the user. At this time, the content streaming system may include a separate control server, and in this case, the control server can perform the role of controlling commands and responses between each device within the content streaming system.

[0599] The streaming server can receive content from a media storage and / or an encoding server. For example, when receiving content from the encoding server, the content can be received in real time. In this case, to provide a seamless streaming service, the streaming server can store the bitstream for a certain period of time.

[0600] Examples of the above user devices may include mobile phones, smartphones, laptop computers, digital broadcasting terminals, PDAs (personal digital assistants), PMPs (portable multimedia players), navigation systems, slate PCs, tablet PCs, ultrabooks, wearable devices (e.g., smartwatches, smart glasses, HMDs (head-mounted displays)), digital TVs, desktop computers, digital signage, etc.

[0601] Each server within the above-mentioned content streaming system can be operated as a distributed server, and in this case, data received from each server can be processed in a distributed manner.

[0602] The scope of the present disclosure includes software or machine-executable instructions (e.g., operating system, application, firmware, program, etc.) that enable an operation according to a method of various embodiments to be executed on a device or computer, and a non-transitory computer-readable medium on which such software or instructions, etc. are stored and executable on a device or computer.

[0603] An embodiment according to the present disclosure can be used to encode / decode images.

Claims

1. In a video decoding method performed by a decoding device, A step of acquiring a QM (quality metric) SEI (supplemental enhancement information) message contained in at least one picture unit; and It includes the step of obtaining quality indicator information based on the above QM SEI message, and A video decoding method characterized in that a first QM SEI message containing at least one average quality indicator information is included in the first picture unit in the CLVS.

2. In Paragraph 1, A video decoding method characterized by the existence of a second QM SEI message containing at least one average quality indicator information that is not included in the first picture unit in the above CLVS, wherein the first QM SEI message is included in the first picture unit in the above CLVS.

3. In Paragraph 2, A video decoding method characterized in that the value of at least one average quality indicator information included in the first QM SEI message is the same as the value of the average quality indicator information included in the second QM SEI message.

4. In Paragraph 1, A video decoding method characterized by the existence of a second QM SEI message that is not included in the first picture unit in the above CLVS, and based on the fact that the second QM SEI message is not included in the PON (processing order nesting) SEI message, the first QM SEI message is not included in the PON SEI message.

5. In Paragraph 1, A video decoding method characterized by the existence of a third QM SEI message not included in the first picture unit in the above CLVS, and based on the fact that the third QM SEI message is included in a PON (processing order nesting) SEI message, the first QM SEI message is included in a PON SEI message having the same target identifier information as the PON SEI message.

6. In a video encoding method performed by an encoding device, A step of generating at least one QM (Quality Metic) SEI (supplemental enhancement information) message included in at least one picture unit based on quality indicator information; and The method includes the step of encoding image information including at least one QM SEI message, and A video encoding method characterized in that a first QM SEI message containing at least one average quality indicator information is included in the first picture unit in the CLVS.

7. In Paragraph 6, A video encoding method characterized by the existence of a second QM SEI message containing at least one average quality indicator information that is not included in the first picture unit in the above CLVS, wherein the first QM SEI message is included in the first picture unit in the above CLVS.

8. In Paragraph 7, A video encoding method characterized in that the value of at least one average quality indicator information included in the first QM SEI message is the same as the value of the average quality indicator information included in the second QM SEI message.

9. In Paragraph 6, A video encoding method characterized by the existence of a second QM SEI message that is not included in the first picture unit in the above CLVS, and based on the fact that the second QM SEI message is not included in the PON (processing order nesting) SEI message, the first QM SEI message is not included in the PON SEI message.

10. In Paragraph 6, A video encoding method characterized by the existence of a third QM SEI message not included in the first picture unit in the above CLVS, and based on the fact that the third QM SEI message is included in a PON (processing order nesting) SEI message, the first QM SEI message is included in a PON SEI message having the same target identifier information as the PON SEI message.

11. A computer-readable storage medium for storing a bitstream generated based on the encoding method of paragraph 6.

12. A method for transmitting data regarding an image, wherein the method comprises the step of acquiring image information, wherein the image information includes at least one QM (Quality Metic) SEI (supplemental enhancement information) message included in at least one picture unit; and The method includes the step of transmitting the data including the above image information, A bitstream transmission method characterized in that a first QM SEI message containing at least one average quality indicator information is included in the first picture unit in CLVS.

Images