Image decoding / encoding methods, non-forwardable computer readability, and bitstream transmission methods.

Abstract

This invention relates to a method and apparatus for encoding / decoding video. The method for decoding video performed by the video decoding apparatus under this invention comprises the following steps: receiving a bit stream containing video information; and producing a reconstructed image by reconstructing the current image based on the video information, wherein the video information may include source picture timing information (SPTI) messages relating to the time interval between source images and their corresponding decoded images.

Description

Video encoding / decoding method, device, and recording medium for storing bitstream based on SEI (SUPPLEMENTAL ENHANCEMENT INFORMATION) message

[0001] The present disclosure relates to a video encoding / decoding method, a device, and a recording medium for storing a bitstream, and more particularly, to a video encoding / decoding method and device based on a SEI (Supplemental Enhancement Information) message, and a recording medium for storing a bitstream generated by the video encoding method / device of the present disclosure.

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

[0003] Accordingly, a highly efficient image compression technology is required to effectively transmit, store, and play high-resolution, high-quality image information.

[0004] The present disclosure aims to provide a video encoding / decoding method and device with improved encoding / decoding efficiency.

[0005] In addition, the present disclosure aims to provide a video encoding / decoding method and device that performs an intra prediction mode.

[0006] In addition, the present disclosure aims to provide a video encoding / decoding method and device that performs inter prediction mode.

[0007] In addition, the present disclosure aims to provide a video encoding / decoding method and device based on a SEI (Supplemental Enhancement Information) message.

[0008] In addition, the present disclosure aims to provide a video encoding / decoding method and device including a source picture timing information (SPTI) SEI message in a bitstream.

[0009] In addition, the present disclosure aims to provide a non-transitory computer-readable recording medium that stores a bitstream generated by an image encoding method or device according to the present disclosure.

[0010] In addition, the present disclosure aims to provide a non-transitory computer-readable recording medium that stores a bitstream received and decoded by an image decoding device according to the present disclosure and used for restoring an image.

[0011] In addition, the present disclosure aims to provide a method for transmitting a bitstream generated by an image encoding method or device according to the present disclosure.

[0012] The technical problems to be achieved in the present disclosure are not limited to the technical problems mentioned above, and other technical problems not mentioned can be clearly understood by a person having ordinary skill in the technical field to which the present disclosure belongs from the description below.

[0013] According to one embodiment of the present disclosure, in a video decoding method performed in a video decoding device, the video decoding method includes a step of receiving a bitstream including video information and a step of generating a restored picture by restoring a current picture based on the video information, wherein the video information may include a SPTI (Source Picture Timing Information) SEI message regarding a temporal distance between source pictures related to corresponding decoded pictures.

[0014] According to one embodiment of the present disclosure, the SPTI SEI message may include persistence information indicating whether the SPTI SEI message applies only to the current decoded picture.

[0015] According to one embodiment of the present disclosure, the SPTI SEI message may include at least one of first information indicating a maximum number of temporal sub-layers, second information indicating a scale factor used to determine a temporal interval between source pictures corresponding to decoded pictures, or third information indicating whether the current decoded picture belonging to a temporal sub-layer has been synthesized.

[0016] According to one embodiment of the present disclosure, the first information, the second information, and the third information can be obtained based on the persistence information.

[0017] According to one embodiment of the present disclosure, the first information, the second information and the third information may be obtained based on the persistence information indicating that the SPTI SEI message is not only applicable to the current decoded picture.

[0018] According to one embodiment of the present disclosure, the second information and the third information can be obtained further based on the value of the first information.

[0019] According to one embodiment of the present disclosure, based on the second information not being acquired, the value of the second information can be inferred as 1.

[0020] According to one embodiment of the present disclosure, the source picture spacing may be equal to the elemental source picture spacing, based on the persistence information indicating that the SPTI SEI message applies only to the current decoded picture.

[0021] According to one embodiment of the present disclosure, in a video encoding method performed in a video encoding device, the video encoding method includes a step of generating video information about a current picture and a step of encoding a bitstream including the video information, wherein the video information may include a SPTI (Source Picture Timing Information) SEI message about a temporal distance between source pictures related to corresponding decoded pictures.

[0022] According to one embodiment of the present disclosure, there may be a computer-readable recording medium storing a bitstream generated by an image encoding method.

[0023] According to one embodiment of the present disclosure, a method for transmitting a bitstream generated by a video encoding method includes a step of generating video information about a current picture and a step of encoding a bitstream including the video information, wherein the video information may include a SPTI (Source Picture Timing Information) SEI message about a temporal distance between source pictures related to corresponding decoded pictures.

[0024] According to the present disclosure, a video encoding / decoding method and device with improved encoding / decoding efficiency can be provided.

[0025] Additionally, according to the present disclosure, a video encoding / decoding method and device performing an intra prediction mode can be provided.

[0026] Additionally, according to the present disclosure, a video encoding / decoding method and device performing inter prediction mode can be provided.

[0027] Additionally, according to the present disclosure, a method and device for encoding / decoding an image based on a SEI (Supplemental Enhancement Information) message can be provided.

[0028] Additionally, according to the present disclosure, a video encoding / decoding method and device including a source picture timing information (SPTI) SEI message in a bitstream can be provided.

[0029] In addition, according to the present disclosure, a non-transitory computer-readable recording medium for storing a bitstream generated by an image encoding method or device according to the present disclosure can be provided.

[0030] In addition, according to the present disclosure, a non-transitory computer-readable recording medium can be provided that stores a bitstream received and decoded by an image decoding device according to the present disclosure and used for restoring an image.

[0031] Additionally, according to the present disclosure, a method for transmitting a bitstream generated by an image encoding method or device according to the present disclosure can be provided.

[0032] The effects that can be obtained from the present disclosure are not limited to the effects mentioned above, and other effects that are not mentioned will be clearly understood by a person having ordinary skill in the art to which the present disclosure pertains from the description below.

[0033] FIG. 1 is a diagram schematically illustrating a video coding system to which an embodiment according to the present disclosure can be applied.

[0034] FIG. 2 is a schematic diagram of an image encoding device to which an embodiment according to the present disclosure can be applied.

[0035] FIG. 3 is a schematic diagram illustrating an image decoding device to which an embodiment according to the present disclosure can be applied.

[0036] FIG. 4 illustrates an example of a coding layer and structure to which an embodiment according to the present disclosure may be applied.

[0037] Figure 5 is a flowchart of an image encoding method according to the present disclosure.

[0038] Figure 6 is a flowchart of an image decoding method according to the present disclosure.

[0039] FIG. 7 is a diagram illustrating an example of a content streaming system to which one embodiment of the present disclosure can be applied.

[0040] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the attached drawings so that those skilled in the art can easily implement the present disclosure. However, the present disclosure may be implemented in various different forms and is not limited to the embodiments described herein.

[0041] In describing embodiments of the present disclosure, detailed descriptions of known configurations or functions will be omitted if they are deemed to obscure the gist of the present disclosure. Furthermore, portions unrelated to the description of the present disclosure in the drawings have been omitted, and similar portions have been designated with similar reference numerals.

[0042] In the present disclosure, when a component is said to be "connected," "coupled," or "connected" to 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 said to "include" or "have" another component, unless otherwise specifically stated, this does not exclude the other component, but rather implies that the other component may be included.

[0043] In this disclosure, terms such as first, second, etc. are used solely to distinguish one component from another, and do not limit the order or importance of components unless specifically stated otherwise. Accordingly, within the scope of this disclosure, a first component in one embodiment may be referred to as a second component in another embodiment, and similarly, a second component in one embodiment may be referred to as a first component in another embodiment.

[0044] In this disclosure, distinct components are used to clearly illustrate their respective characteristics, and do not necessarily imply that the components are separated. That is, multiple components may be integrated into a single hardware or software unit, or a single component may be distributed into multiple hardware or software units. Therefore, even if not specifically mentioned, such integrated or distributed embodiments are also included within the scope of this disclosure.

[0045] In the present disclosure, the components described in various embodiments are not necessarily essential components, and some may be optional components. Therefore, embodiments comprising a subset of the components described in one embodiment are also within the scope of the present disclosure. Furthermore, embodiments including other components in addition to the components described in various embodiments are also within the scope of the present disclosure.

[0046] The present disclosure relates to encoding and decoding of images, and terms used in the present disclosure may have their usual meanings commonly used in the technical field to which the present disclosure belongs, unless newly defined in the present disclosure.

[0047] In the present disclosure, “video” may mean a set of images over time.

[0048] In the present disclosure, a "picture" generally refers to a unit representing one image of a specific time period, and a slice / tile is a coding unit that constitutes a part of a picture, and a single picture may be composed of one or more slices / tiles. In addition, a slice / tile may include one or more coding tree units (CTUs).

[0049] In the present disclosure, "pixel" or "pel" may refer to the smallest unit that constitutes a picture (or image). Additionally, "sample" may be used as a term corresponding to a pixel. A sample may generally represent a pixel or a pixel value, and may represent only a pixel / pixel value of a luma component or only a pixel / pixel value of a chroma component.

[0050] In the present disclosure, a "unit" may represent a basic unit of image processing. A unit may include at least one of a specific region of a picture and information related to the region. In some cases, the term "unit" may be used interchangeably with terms such as "sample array," "block," or "area." In general, an MxN block may include a set (or array) of samples (or sample array) or transform coefficients consisting of M columns and N rows.

[0051] In the present disclosure, the "current block" may mean one of the following: a "current coding block," a "current coding unit," a "block to be encoded," a "block to be decoded," or a "block to be processed." When prediction is performed, the "current block" may mean a "current prediction block" or a "block to be predicted." When transformation (inverse transformation) / quantization (inverse quantization) is performed, the "current block" may mean a "current transformation block" or a "block to be transformed." When filtering is performed, the "current block" may mean a "block to be filtered."

[0052] In the present disclosure, a "current block" may mean a block that includes both a luma component block and a chroma component block, or a "luma block of the current block," unless explicitly described as a chroma block. The luma component block of the current block may be explicitly expressed by including an explicit description of the luma component block, such as "luma block" or "current luma block." Additionally, the chroma component block of the current block may be explicitly expressed by including an explicit description of the chroma component block, such as "chroma block" or "current chroma block."

[0053] In this disclosure, " / " and "," can be interpreted as "and / or". For example, "A / B" and "A, B" can be interpreted as "A and / or B". Additionally, "A / B / C" and "A, B, C" can mean "at least one of A, B, and / or C."

[0054] In this 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, "or" in this disclosure may mean "additionally or alternatively."

[0055] In this disclosure, "at least one of A, B, and C" may mean "only A," "only B," "only C," or "any and all combinations of A, B, and C." Additionally, "at least one of A, B, or C" or "at least one of A, B, and / or C" may mean "at least one of A, B, and C."

[0056] The parentheses used in this disclosure may mean "for example." For example, when "prediction (intra-prediction)" is indicated, "intra-prediction" may be suggested as an example of "prediction." In other words, "prediction" in this disclosure is not limited to "intra-prediction," and "intra-prediction" may be suggested as an example of "prediction." Furthermore, even when "prediction (i.e., intra-prediction)" is indicated, "intra-prediction" may be suggested as an example of "prediction."

[0057] Overview of Video Coding Systems

[0058] FIG. 1 is a diagram schematically illustrating a video coding system to which an embodiment according to the present disclosure can be applied.

[0059] A video coding system according to one embodiment may include an encoding device (10) and a decoding device (20). The encoding device (10) may transmit encoded video and / or image information or data to the decoding device (20) in the form of a file or streaming through a digital storage medium or a network.

[0060] An encoding device (10) according to one embodiment may include a video source generation unit (11), an encoding unit (12), and a transmission unit (13). A decoding device (20) according to one embodiment may include a reception unit (21), a decoding unit (22), and a rendering unit (23). The encoding unit (12) may be referred to as a video / image encoding unit, and the decoding unit (22) may be referred to as a video / image decoding unit. The transmission unit (13) may be included in the encoding unit (12). The reception unit (21) may be included in the decoding unit (22). The rendering unit (23) may include a display unit, and the display unit may be configured as a separate device or an external component.

[0061] The video source generation unit (11) can obtain video / images through a process of capturing, synthesizing, or generating video / images. The video source generation unit (11) can include a video / image capture device and / or a video / image generation device. The video / image capture device can include, for example, one or more cameras, a video / image archive including previously captured video / images, etc. The video / image generation device can include, for example, a computer, a tablet, a smartphone, etc., and can (electronically) generate video / images. For example, a virtual video / image can be generated through a computer, etc., in which case the video / image capture process can be replaced with a process of generating related data.

[0062] The encoding unit (12) can encode input video / images. The encoding unit (12) can perform a series of procedures such as prediction, transformation, and quantization to improve compression and encoding efficiency. The encoding unit (12) can output encoded data (encoded video / image information) in the form of a bitstream.

[0063] The transmission unit (13) can obtain encoded video / image information or data output in the form of a bitstream, and transmit it to the reception unit (21) of the decoding device (20) or another external object through a digital storage medium or a network in the form of a file or streaming. The digital storage medium may include various storage media such as USB, SD, CD, DVD, Blu-ray, HDD, SSD, etc. The transmission unit (13) may include an element for generating a media file through a predetermined file format, and may include an element for transmission through a broadcasting / communication network. The transmission unit (13) may be provided as a separate transmission device from the encoding unit (120), and in this case, the transmission device may include at least one processor for obtaining encoded video / image information or data output in the form of a bitstream, and a transmission unit for transmitting it in the form of a file or streaming. The reception unit (21) can extract / receive the bitstream from the storage medium or network and transmit it to the decoding unit (22).

[0064] The decoding unit (22) can decode video / image by performing a series of procedures such as inverse quantization, inverse transformation, and prediction corresponding to the operation of the encoding unit (12).

[0065] The rendering unit (23) can render the decrypted video / image. The rendered video / image can be displayed through the display unit.

[0066] Overview of the video encoding device

[0067] FIG. 2 is a schematic diagram illustrating an image encoding device to which an embodiment according to the present disclosure can be applied.

[0068] As illustrated in FIG. 2, the image encoding device (100) may include an image segmentation unit (110), a subtraction unit (115), a transformation unit (120), a quantization unit (130), an inverse quantization unit (140), an inverse transformation unit (150), an addition unit (155), a filtering unit (160), a memory (170), an inter prediction unit (180), an intra prediction unit (185), and an entropy encoding unit (190). The inter prediction unit (180) and the intra prediction unit (185) may be collectively referred to as a “prediction unit.” The transformation unit (120), the quantization unit (130), the inverse quantization unit (140), and the inverse transformation unit (150) may be included in a residual processing unit. The residual processing unit may further include a subtraction unit (115).

[0069] All or at least some of the plurality of components constituting the video encoding device (100) may be implemented as a single hardware component (e.g., the video encoding device (100) or a processor) according to an embodiment. In addition, the memory (170) may include a decoded picture buffer (DPB) and may be implemented by a digital storage medium.

[0070] The image segmentation unit (110) can segment an input image (or picture, frame) input to the image encoding device (100) into one or more processing units. For example, the processing units may be referred to as coding units (CUs). The coding units can be obtained by recursively segmenting a coding tree unit (CTU) or a largest coding unit (LCU) according to a QT / BT / TT (Quad-tree / binary-tree / ternary-tree) structure. For example, one coding unit can be segmented into a plurality of coding units of deeper depth based on a quad-tree structure, a binary-tree structure, and / or a ternary-tree structure. For segmenting the coding unit, the quad-tree structure may be applied first, and the binary-tree structure and / or the ternary-tree structure may be applied later. The coding procedure according to the present disclosure can be performed based on the final coding unit that is no longer segmented. The maximum coding unit can be used directly as the final coding unit, and the coding unit of the lower depth obtained by dividing the maximum coding unit can be used as the final coding unit. Here, the coding procedure may include procedures such as prediction, transformation, and / or restoration described below. As another example, the processing unit of the coding procedure may be 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 prediction unit may be a unit of sample prediction, and the transformation unit may be a unit for deriving a transform coefficient and / or a unit for deriving a residual signal from a transform coefficient.

[0071] The prediction unit (inter-prediction unit (180) or intra-prediction unit (185)) can perform prediction on a block to be processed (current block) and generate a predicted block including prediction samples for the current block. The prediction unit can determine whether intra-prediction or inter-prediction is applied to the current block or CU unit. The prediction unit can generate various information regarding the prediction of the current block and transmit the information to the entropy encoding unit (190). The information regarding the prediction can be encoded by the entropy encoding unit (190) and output in the form of a bitstream.

[0072] The intra prediction unit (185) can predict the current block by referring to samples within the current picture. The referenced samples may be located in the neighborhood of the current block or may be located away from it, depending on the intra prediction mode and / or intra prediction technique. The intra prediction modes may include a plurality of non-directional modes and a plurality of directional modes. The non-directional modes may include, for example, a DC mode and a planar mode. The directional modes may include, for example, 33 directional prediction modes or 65 directional prediction modes, depending on the degree of detail in the prediction direction. However, this is merely an example, and a greater or lesser number of directional prediction modes may be used depending on the settings. The intra prediction unit (185) may also determine the prediction mode applied to the current block by using the prediction mode applied to the neighboring blocks.

[0073] The inter prediction unit (180) 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, in order to reduce the amount of motion information transmitted in the inter prediction mode, the motion information can be predicted in units of blocks, sub-blocks, or samples based on the correlation of the motion information between the neighboring blocks and the current block. The motion information can include a motion vector and a reference picture index. The motion information can further include information on the inter prediction direction (L0 prediction, L1 prediction, Bi prediction, etc.). In the case of inter prediction, the neighboring block can include a spatial neighboring block existing in the current picture and a temporal neighboring block existing in the reference picture. The reference picture including the reference block and the reference picture including the temporal neighboring block may be the same or different from each other. The temporal neighboring block may be called a collocated reference block, a collocated CU (colCU), etc. A reference picture including the above temporal neighboring blocks may be called a collocated picture (colPic). For example, the inter prediction unit (180) may construct a motion information candidate list based on neighboring 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, and for example, in the case of skip mode and merge mode, the inter prediction unit (180) may use the motion information of neighboring blocks as the motion information of the current block. In the case of skip mode, unlike the merge mode, a residual signal may not be transmitted.In the motion vector prediction (MVP) mode, the motion vector of the current block can be signaled by using the motion vector of the surrounding blocks as the motion vector predictor and encoding the motion vector difference and an indicator for the motion vector predictor. The motion vector difference can mean the difference between the motion vector of the current block and the motion vector predictor.

[0074] The prediction unit can generate a prediction signal based on various prediction methods and / or prediction techniques described below. For example, the prediction unit can apply intra prediction or inter prediction to predict the current block, and can also apply intra prediction and inter prediction simultaneously. A prediction method that simultaneously applies intra prediction and inter prediction to predict the current block may be called combined inter and intra prediction (CIIP). In addition, the prediction unit may perform intra block copy (IBC) to predict the current block. Intra block copy can be used for content video / movie coding such as games, such as screen content coding (SCC). IBC is a method of predicting the current block using a previously reconstructed reference block within the current picture located at a predetermined distance from the current block. When IBC is applied, the location of the reference block within the current picture can be encoded as a vector (block vector) corresponding to the predetermined distance. IBC basically performs prediction within the current picture, but can be performed similarly to inter prediction in that it derives reference blocks within the current picture. That is, IBC can utilize at least one of the inter prediction techniques described in the present disclosure.

[0075] The prediction signal generated through the prediction unit can be used to generate a restoration signal or a residual signal. The subtraction unit (115) can generate a residual signal (residual block, residual sample array) by subtracting the prediction signal (predicted block, predicted sample array) output from the prediction unit from the input image signal (original block, original sample array). The generated residual signal can be transmitted to the conversion unit (120).

[0076] The transform unit (120) can apply a transform technique to the residual signal to generate transform coefficients. For example, the transform technique can 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 transform obtained from a graph when the relationship information between pixels is expressed as a graph. CNT refers to a transform obtained based on generating a prediction signal using all previously reconstructed pixels. The transform process can be applied to a pixel block having a square equal size, or can be applied to a block of a non-square variable size.

[0077] The quantization unit (130) can quantize the transform coefficients and transmit them to the entropy encoding unit (190). The entropy encoding unit (190) can encode the quantized signal (information about the quantized transform coefficients) and output it as a bitstream. The information about the quantized transform coefficients can be called residual information. The quantization unit (130) can rearrange the quantized transform coefficients in a block form into a one-dimensional vector form based on a coefficient scan order, and can also generate information about the quantized transform coefficients based on the quantized transform coefficients in the one-dimensional vector form.

[0078] The entropy encoding unit (190) can perform various encoding methods, such as, for example, exponential Golomb, context-adaptive variable length coding (CAVLC), and context-adaptive binary arithmetic coding (CABAC). The entropy encoding unit (190) can also encode, together or separately, information necessary for video / image restoration (e.g., values ​​of syntax elements) in addition to quantized transform coefficients. The encoded information (e.g., encoded video / image information) can be transmitted or stored in the form of a bitstream in the form of a network abstraction layer (NAL) unit. The video / image information may further include information on various parameter sets, such as an adaptation parameter set (APS), a picture parameter set (PPS), a sequence parameter set (SPS), or a video parameter set (VPS). In addition, the video / image information may further include general constraint information. The signaling information, transmitted information and / or syntax elements mentioned in the present disclosure may be encoded through the encoding procedure described above and included in the bitstream.

[0079] 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 the signal output from the entropy encoding unit (190) and / or a storage unit (not shown) for storing the signal may be provided as an internal / external element of the video encoding device (100), or the transmission unit may be provided as a component of the entropy encoding unit (190).

[0080] The quantized transform coefficients output from the quantization unit (130) can be used to generate a residual signal. For example, by applying inverse quantization and inverse transformation to the quantized transform coefficients through the inverse quantization unit (140) and inverse transformation unit (150), a residual signal (residual block or residual samples) can be restored.

[0081] The addition unit (155) 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 (180) or the intra prediction unit (185). When there is no residual for the block to be processed, such as when skip mode is applied, the predicted block can be used as the reconstructed block. The addition unit (155) can be called a reconstructor 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 filtering as described below.

[0082] Meanwhile, LMCS (luma mapping with chroma scaling) may be applied during the picture encoding and / or restoration process.

[0083] The filtering unit (160) can improve subjective / objective picture quality by applying filtering to the restoration signal. For example, the filtering unit (160) can apply various filtering methods to the restoration picture to generate a modified restoration picture, and store the modified restoration picture in the memory (170), specifically, in the DPB of the memory (170). The various filtering methods may include, for example, deblocking filtering, sample adaptive offset, adaptive loop filter, bilateral filter, etc. The filtering unit (160) can generate various information regarding filtering and transmit the information to the entropy encoding unit (190), as described later in the description of each filtering method. The information regarding filtering may be encoded by the entropy encoding unit (190) and output in the form of a bitstream.

[0084] The modified restored picture transmitted to the memory (170) can be used as a reference picture in the inter prediction unit (180). Through this, when inter prediction is applied, the image encoding device (100) can avoid prediction mismatch between the image encoding device (100) and the image decoding device, and can also improve encoding efficiency.

[0085] The DPB in the memory (170) can store a modified reconstructed picture to be used as a reference picture in the inter prediction unit (180). The memory (170) can store motion information of a block from which motion information in the current picture is derived (or encoded) and / or motion information of blocks in a picture that has already been reconstructed. The stored motion information can be transferred to the inter prediction unit (180) to be used as motion information of a spatial neighboring block or motion information of a temporal neighboring block. The memory (170) can store reconstructed samples of reconstructed blocks in the current picture and transfer them to the intra prediction unit (185).

[0086] Video Decryption Device Overview

[0087] FIG. 3 is a schematic diagram illustrating an image decoding device to which an embodiment according to the present disclosure can be applied.

[0088] As illustrated in FIG. 3, the image decoding device (200) may be configured to include an entropy decoding unit (210), an inverse quantization unit (220), an inverse transformation unit (230), an addition unit (235), a filtering unit (240), a memory (250), an inter prediction unit (260), and an intra prediction unit (265). The inter prediction unit (260) and the intra prediction unit (265) may be collectively referred to as a “prediction unit.” The inverse quantization unit (220) and the inverse transformation unit (230) may be included in a residual processing unit.

[0089] All or at least some of the plurality of components constituting the image decoding device (200) may be implemented as a single hardware component (e.g., the image decoding device (200) or a processor) according to an embodiment. In addition, the memory (170) may include a DPB and may be implemented by a digital storage medium.

[0090] The image decoding device (200) that receives a bitstream including video / image information can restore the image by performing a process corresponding to the process performed in the image encoding device (100) of FIG. 2. For example, the image decoding device (200) can perform decoding using a processing unit applied in the image encoding device (100). Therefore, the processing unit for decoding can be, for example, a coding unit. The coding unit can be a coding tree unit or can be obtained by dividing a maximum coding unit. In addition, the restored image signal decoded and output by the image decoding device (200) can be reproduced through a reproduction device (not shown).

[0091] The video decoding device (200) can receive a signal output from the video encoding device (100) of FIG. 2 in the form of a bitstream. The received signal can be decoded through the entropy decoding unit (210). For example, the entropy decoding unit (210) can parse the bitstream to derive information (e.g., video / image information) necessary for image restoration (or picture restoration). The video / image information may further include information on various parameter sets, such as an adaptation parameter set (APS), a picture parameter set (PPS), a sequence parameter set (SPS), or a video parameter set (VPS). In addition, the video / image information may further include general constraint information. The video decoding device (200) can additionally use the information on the parameter set and / or the general constraint information to decode the image. The signaling information, received information, and / or syntax elements mentioned in the present disclosure can be obtained from the bitstream by being decoded through the decoding procedure. For example, the entropy decoding unit (210) can decode information in the bitstream based on a coding method such as exponential Golomb coding, CAVLC, or CABAC, and output the values ​​of syntax elements required for image restoration and the quantized values ​​of transform coefficients for residuals. More specifically, the CABAC entropy decoding method receives a bin corresponding to each syntax element in the bitstream, determines a context model using information of the syntax element to be decoded and the decoding information of the surrounding block and the decoding target block or the information of the symbol / bin decoded in the previous step, and predicts the occurrence probability of the bin according to the determined context model to 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 information of the decoded symbol / bin for the context model of the next symbol / bin after determining the context model. Information regarding prediction among the information decoded by the entropy decoding unit (210) is provided to the prediction unit (inter prediction unit (260) and intra prediction unit (265)), and the residual value on which entropy decoding is performed by the entropy decoding unit (210), i.e., quantized transform coefficients and related parameter information, can be input to the inverse quantization unit (220). In addition, information regarding filtering among the information decoded by the entropy decoding unit (210) can be provided to the filtering unit (240). Meanwhile, a receiving unit (not shown) that receives a signal output from an image encoding device (100) may be additionally provided as an internal / external element of an image decoding device (200), or the receiving unit may be provided as a component of an entropy decoding unit (210).

[0092] Meanwhile, the video decoding device (200) according to the present disclosure may be referred to as a video / video / picture decoding device. The video decoding device (200) may include an information decoder (video / video / picture information decoder) and / or a sample decoder (video / video / picture sample decoder). The information decoder may include an entropy decoding unit (210), and the sample decoder may include at least one of an inverse quantization unit (220), an inverse transformation unit (230), an addition unit (235), a filtering unit (240), a memory (250), an inter prediction unit (260), and an intra prediction unit (265).

[0093] The inverse quantization unit (220) can inverse quantize the quantized transform coefficients and output the transform coefficients. The inverse quantization unit (220) can rearrange the quantized transform coefficients into a two-dimensional block form. In this case, the rearrangement can be performed based on the coefficient scanning order performed in the image encoding device (100). The inverse quantization unit (220) can perform inverse quantization on the quantized transform coefficients using quantization parameters (e.g., quantization step size information) and obtain transform coefficients.

[0094] In the inverse transform unit (230), the transform coefficients can be inversely transformed to obtain a residual signal (residual block, residual sample array).

[0095] The prediction unit can perform a prediction on the current block and generate a predicted block containing prediction samples for the current block. The prediction unit can determine whether intra-prediction or inter-prediction is applied to the current block based on the prediction information output from the entropy decoding unit (210), and can determine a specific intra / inter-prediction mode (prediction technique).

[0096] The fact that the prediction unit can generate a prediction signal based on various prediction methods (techniques) described below is the same as that mentioned in the description of the prediction unit of the image encoding device (100).

[0097] The intra prediction unit (265) can predict the current block by referring to samples within the current picture. The description of the intra prediction unit (185) can be equally applied to the intra prediction unit (265).

[0098] The inter prediction unit (260) 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, in order to reduce the amount of motion information transmitted in the inter prediction mode, the motion information can be predicted in units of blocks, sub-blocks, or samples based on the correlation of the motion information between the neighboring blocks and the current block. The motion information can include a motion vector and a reference picture index. The motion information can further include information on the inter prediction direction (L0 prediction, L1 prediction, Bi prediction, etc.). In the case of inter prediction, the neighboring blocks can include spatial neighboring blocks existing in the current picture and temporal neighboring blocks existing in the reference picture. For example, the inter prediction unit (260) can 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 the information about the prediction can include information indicating the mode (technique) of inter prediction for the current block.

[0099] The addition unit (235) can generate a restoration signal (restored picture, restoration block, restoration sample array) by adding the acquired residual signal to the prediction signal (predicted block, prediction sample array) output from the prediction unit (including the inter prediction unit (260) and / or the intra prediction unit (265)). When there is no residual for the block to be processed, such as when the skip mode is applied, the predicted block can be used as the restoration block. The description of the addition unit (155) can be equally applied to the addition unit (235). The addition unit (235) can 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 going through filtering as described below.

[0100] The filtering unit (240) can improve subjective / objective image quality by applying filtering to the restored signal. For example, the filtering unit (240) can apply various filtering methods to the restored picture to generate a modified restored picture, and store the modified restored picture in the memory (250), specifically, in the DPB of the memory (250). The various filtering methods can include, for example, deblocking filtering, sample adaptive offset, adaptive loop filter, bilateral filter, etc.

[0101] The (modified) reconstructed picture stored in the DPB of the memory (250) can be used as a reference picture in the inter prediction unit (260). The memory (250) can store motion information of a block from which motion information is derived (or decoded) within the current picture and / or motion information of blocks within a picture that has already been reconstructed. The stored motion information can be transferred to the inter prediction unit (260) to be used as motion information of a spatial neighboring block or motion information of a temporal neighboring block. The memory (250) can store reconstructed samples of reconstructed blocks within the current picture and transfer them to the intra prediction unit (265).

[0102] In this specification, the embodiments described in the filtering unit (160), the inter prediction unit (180), and the intra prediction unit (185) of the image encoding device (100) can be applied to the filtering unit (240), the inter prediction unit (260), and the intra prediction unit (265) of the image decoding device (200) in the same or corresponding manner, respectively.

[0103] Coding hierarchy and structure

[0104] The coded video / image according to this document can be processed according to the coding layers and structures described below, for example.

[0105] Figure 4 is a diagram illustrating a hierarchical structure for a coded image.

[0106] The coded video is divided into the video coding layer (VCL), which handles the decoding process of the video and the video itself, the subsystem that transmits and stores the coded information, and the network abstraction layer (NAL), which exists between the VCL and the subsystem and is responsible for network adaptation functions.

[0107] In VCL, VCL data containing compressed image data (slice data) can be generated, or a parameter set containing information such as a picture parameter set (PPS), a sequence parameter set (SPS), a video parameter set (VPS), etc., or an SEI (Supplemental Enhancement Information) message additionally required for the image decoding process can be generated.

[0108] In NAL, a NAL unit can be created by adding header information (NAL unit header) to an RBSP (Raw Byte Sequence Payload) generated from a VCL. At this time, RBSP refers to slice data, parameter sets, SEI messages, etc. generated from a VCL. The NAL unit header can include NAL unit type information that is specific to the RBSP data included in the NAL unit.

[0109] As illustrated in Fig. 4, NAL units can be divided into VCL NAL units and non-VCL NAL units according to the RBSP generated from the VCL. A VCL NAL unit can refer to a NAL unit that contains information about a video (slice data), and a non-VCL NAL unit can refer to a NAL unit that contains information necessary for decoding a video (parameter set or SEI message).

[0110] The above-described VCL NAL units and non-VCL NAL units can be transmitted over a network by attaching header information according to the data specifications of the lower system. For example, NAL units can be transformed into data formats of a certain standard, such as the H.266 / VVC file format, RTP (Real-time Transport Protocol), TS (Transport Stream), etc., and transmitted over various networks.

[0111] As described above, a NAL unit can be specified as a NAL unit type according to the RBSP data structure included in the NAL unit, and information about the NAL unit type can be stored and signaled in the NAL unit header.

[0112] For example, depending on whether a NAL unit contains information about a picture (slice data), it can be broadly classified into VCL NAL unit types and Non-VCL NAL unit types. The VCL NAL unit type can be classified according to the nature and type of the picture contained in the VCL NAL unit, and the Non-VCL NAL unit type can be classified according to the type of parameter set, etc.

[0113] Below are examples of NAL unit types, specified by the type of parameter set included in the Non-VCL NAL unit type.

[0114] - APS (Adaptation Parameter Set) NAL unit: Type for NAL units containing APS

[0115] - DPS (Decoding Parameter Set) NAL unit: Type for NAL unit containing DPS

[0116] - VPS (Video Parameter Set) NAL unit: Type for NAL unit containing VPS

[0117] - SPS (Sequence Parameter Set) NAL unit: Type for NAL units containing SPS

[0118] - PPS (Picture Parameter Set) NAL unit: Type for NAL units containing PPS

[0119] The above-described NAL unit types have syntax information for the NAL unit type, and the syntax information can be stored and signaled in the NAL unit header. For example, the syntax information can be nal_unit_type, and NAL unit types can be specified by the nal_unit_type value.

[0120] The above slice header (slice header syntax) may include information / parameters that can be commonly applied to the slices. 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 CVS (coded video sequence). In this document, high level syntax (HLS) may include at least one of the APS syntax, PPS syntax, SPS syntax, VPS syntax, DPS syntax, and slice header syntax.

[0121] In the present disclosure, image / video information encoded from an image encoding device (100) to an image decoding device (200) and signaled in the form of a bitstream may include information related to partitioning within a picture, intra / inter prediction information, residual information, in-loop filtering information, etc., and 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.

[0122] SEI messages - Source Picture Timing Information (SPTI)

[0123] The SPTI SEI message indicates the temporal distance between the source picture associated with the decoded output picture prior to encoding. For example, for content captured by a camera, the temporal distance between source pictures could be the difference between the time the image sensor was exposed to generate the source picture associated with the currently decoded picture and the time the image sensor was exposed to generate the source picture associated with the previously decoded picture in the output sequence.

[0124] Table 1 below is an example of the SPTI SEI message syntax structure.

[0125]

[0126] A value of spti_cancel_flag of 1 may indicate that the SPTI SEI message cancels the persistence of the previous SPTI SEI message in the output order applied to the current layer. A value of spti_cancel_flag of 0 may indicate that the source picture timing information is persisted.

[0127] spti_persistence_flag can indicate the persistence of the SPTI SEI message for the current layer. An spti_persistence_flag with a value of 0 can indicate that the SPTI SEI message applies only to the currently decoded picture. An spti_persistence_flag with a value of 1 can indicate that the SPTI SEI message applies not only to the currently decoded picture but also persists for all subsequent pictures of the current layer in output order until one or more of the following conditions (conditions 1 to 3) are true.

[0128] - Condition 1: When a new CLVS of the current layer starts

[0129] - Condition 2: When the bitstream ends

[0130] - Condition 3: If the picture in the current layer within the AU associated with the SPTI SEI message is output after the current picture in the output order.

[0131] spti_source_picture_timing_type may indicate a timing relationship between a source picture and its corresponding decoded output picture as specified in Table 2 below. Here, if (spti_source_picture_timing_type & bitmask) is not 0, the interpretation related to the bitmask value in Table 2 may not be applied to the SPTI SEI message. If the value of spti_source_picture_timing_type is 0, the timing relationship may be specified by the application.

[0132]

[0133] If the value of spti_source_timing_equals_output_timing_flag is 1, it may indicate that the timing of the source picture is the same as the timing of the corresponding decoded output picture. If the value of spti_source_timing_equals_output_timing_flag is 0, it may indicate that the timing of the source picture is not the same as the timing of the corresponding decoded output picture.

[0134] If the value of spti_source_timing_equals_output_timing_flag is 1 and a picture timing SEI message exists for the current picture, the source picture timing can be determined by the information conveyed in the picture timing SEI message.

[0135] spti_time_scale can represent the number of time units that pass in one second. A spti_time_scale with a value of 0 may not exist. For example, a time coordinate system that measures time using a 27 MHz clock may have an spti_time_scale of 27,000,000.

[0136] spti_num_units_in_elemental_source_picture_interval may represent the number of time units of a clock operating at a frequency of spti_time_scale Hz corresponding to the specified elemental source picture interval of consecutive images in output order in the CLVS. spti_max_sublayers_minus_1 plus 1 may represent the maximum number of temporal sublayers that can exist in the CLVS.

[0137] If spti_sublayer_source_picture_interval_scale_factor[i] exists, it may indicate a scale factor used to determine the source picture interval of the corresponding consecutive pictures in output order in CLVS whose TemporalId is less than or equal to i. If spti_sublayer_source_picture_interval_scale_factor[i] is 0, it may be used to indicate that the source picture corresponding to the currently decoded output picture is the same as the source picture corresponding to the previously decoded output picture.

[0138] If spti_sublayer_synthesized_picture_flag[i] exists and its value is 1, it may indicate that the decoded output picture belonging to the i-th temporal sub-layer has been synthesized and does not match the unmodified original source picture. If the value of spti_sublayer_synthesized_picture_flag[i] is 0, this indication may not be provided. If spti_sublayer_synthesized_picture_flag[i] does not exist, the value of spti_sublayer_synthesized_picture_flag[i] may be inferred to be 0.

[0139] Hereinafter, a video encoding / decoding method according to various embodiments of the present disclosure will be described in detail.

[0140] In the existing SPTI SEI message design, the syntax elements spti_max_sublayers_minus1, spti_sublayer_source_picture_interval_scale_factor[i], and spti_sublayer_synthesized_picture_flag[i] can be signaled regardless of the persistence of the SEI message. If the SEI message persists for only one picture (i.e., a picture in the same AU that contains the SEI message), these syntax elements may not be needed. In addition, if the persistence of the SPTI SEI message applies only to the current picture, the calculation of SourcePictureInterval[] and SourcePictureTime[] may not be necessary. To address this issue, the present disclosure proposes the following four solutions.

[0141] 1. Signal spti_sublayer_source_picture_interval_scale_factor[i] and spti_sublayer_synthesized_picture_flag[i] only when the value of spti_persistence_flag is 1.

[0142] 2. Update the description related to SourcePictureInterval[ i ] and SourcePictureTime[ n ] to apply only when the value of spti_persistence_flag is 1.

[0143] 3. If the persistence of the SPTI SEI message applies only to the current picture, set SourcePictureInterval to be equal to ElementalSourcePictureInterval.

[0144] 4. If spti_sublayer_source_picture_interval_scale_factor[i] does not exist, its value is limited to 1.

[0145] Example 1

[0146] In order to present solutions 1 to 3 of the four solutions described above, Embodiment 1 proposes to update the SPTI SEI message syntax structure as shown in Table 3 below. The SPTI SEI message syntax structure proposed in this embodiment is as shown in Table 3 below.

[0147]

[0148] Referring to Table 3, spti_max_sublayers_minus1 can be signaled only when the value of spti_persistence_flag is 1. The value of spti_max_sublayers_minus_1 plus 1 can represent the maximum number of temporal sublayers that exist in the CLVS. If spti_max_sublayers_minus_1 does not exist and the value of spti_persistence_flag is 0, the value of spti_max_sublayers_minus_1 can be inferred to be 0.

[0149] spti_sublayer_source_picture_interval_scale_factor[i] may indicate a scale factor used to determine the source picture interval of corresponding consecutive pictures in output order in the CLVS having TemporalId less than or equal to i. spti_sublayer_source_picture_interval_scale_factor[i] having a value of 0 may indicate that the source picture corresponding to the currently decoded output picture is the same as the source picture corresponding to the previously decoded output picture.

[0150] If the value of spti_persistence_flag is 1, the process in Table 4 below can be performed.

[0151]

[0152] spti_sublayer_synthesized_picture_flag[i] having a value of 1 may indicate that the decoded output pictures belonging to the ith temporal sublayer are synthesized and do not correspond to the unmodified original source pictures. spti_sublayer_synthesized_picture_flag[i] having a value of 0 may indicate that such an indication does not exist. That is, spti_sublayer_synthesized_picture_flag[i] having a value of 0 may indicate that such a restriction does not exist. If spti_sublayer_synthesized_picture_flag[i] does not exist, its value may be inferred to be 0.

[0153] Example 2

[0154] Example 2 is an embodiment that embodies solution number 4 of the four solutions described above. Example 2 proposes updating the SPTI SEI message as shown in Table 5 below.

[0155]

[0156] According to Embodiment 2, spti_sublayer_source_picture_interval_scale_factor[i] may indicate a scale factor used to determine the source picture interval of corresponding consecutive pictures in output order in CLVS having TemporalId less than or equal to i. spti_sublayer_source_picture_interval_scale_factor[i] having a value of 0 may indicate that the source picture corresponding to the currently decoded output picture is the same as the source picture corresponding to the previously decoded output picture. If spti_sublayer_source_picture_interval_scale_factor[i] does not exist, its value may be inferred to be 1.

[0157] FIG. 5 is a flowchart of a video encoding method according to the present disclosure. According to FIG. 5, a video encoding device (100) can encode video information regarding a current picture (S510). Thereafter, the video encoding device (100) can transmit a bitstream including the video information (S530). That is, the video encoding device (100) can transmit a bitstream including the video information to a video decoding device (200).

[0158] Here, the image information may include a SPTI SEI message regarding the temporal distance between source pictures related to corresponding decoded pictures. The SPTI SEI message may include persistence information indicating whether the SPTI SEI message applies only to the current decoded picture. Here, the persistence information may be spti_persistence_flag.

[0159] Additionally, the SPTI SEI message may include at least one of first information indicating a maximum number of temporal sublayers, second information indicating a scale factor used to determine a temporal interval between source pictures corresponding to decoded pictures, or third information indicating whether a current decoded picture belonging to a temporal sublayer has been synthesized. Here, the first information may be spti_max_sublayers_minus1. The second information may be spti_sublayer_source_pictue_interval_scale_factor[i]. The third information may be spti_sublayer_synthesized_picture_flag[i].

[0160] According to one embodiment of the present disclosure, the first information, the second information, and / or the third information may be signaled based on whether the SPTI SEI message applies only to the current decoded picture. Specifically, the first information, the second information, and / or the third information may be signaled when the SPTI SEI message does not apply only to the current decoded picture.

[0161] According to one embodiment of the present disclosure, the second information and / or the third information may be signaled further based on the maximum number of temporal sub-layers. If the value of the scale factor used to determine the temporal interval between source pictures corresponding to the decoded picture is 1, signaling of the second information may be omitted.

[0162] According to one embodiment of the present disclosure, if the SPTI SEI message is applied only to the current decoded picture, the source picture spacing may be equal to the elemental source picture spacing.

[0163] FIG. 6 is a flowchart of a video decoding method according to the present disclosure. According to FIG. 6, a video decoding device (200) can receive a bitstream containing video information (S610). Thereafter, the video decoding device (200) can generate a restored picture by restoring the current picture based on the video information (S630).

[0164] Here, the image information may include a SPTI SEI message regarding the temporal distance between source pictures related to corresponding decoded pictures. In addition, the SPTI SEI message may include persistence information indicating whether the SPTI SEI message applies only to the current decoded picture. Here, the persistence information may be spti_persistence_flag.

[0165] Additionally, the SPTI SEI message may include at least one of first information indicating a maximum number of temporal sublayers, second information indicating a scale factor used to determine a temporal interval between source pictures corresponding to decoded pictures, or third information indicating whether a current decoded picture belonging to a temporal sublayer has been synthesized. Here, the first information may be spti_max_sublayers_minus1. The second information may be spti_sublayer_source_pictue_interval_scale_factor[i]. The third information may be spti_sublayer_synthesized_picture_flag[i].

[0166] According to one embodiment of the present disclosure, the first information, the second information, and / or the third information may be obtained based on the value of the persistence information. For example, the first information, the second information, and / or the third information may be obtained based on the persistence information indicating that the SPTI SEI message does not apply only to the current decoded picture.

[0167] According to one embodiment of the present disclosure, the second information and / or the third information may be acquired further based on the value of the first information. If the second information is not acquired, the value of the second information may be inferred as 1.

[0168] According to one embodiment of the present disclosure, the source picture spacing may be equal to the elemental source picture spacing, based on the persistence information indicating that the SPTI SEI message applies only to the current decoded picture.

[0169] While the exemplary methods of this disclosure are presented as a series of operations for clarity of description, this is not intended to limit the order in which the steps are performed, and individual steps may be performed simultaneously or in different orders, if desired. To implement a method according to this disclosure, additional steps may be included in addition to the steps illustrated, some steps may be excluded and the remaining steps included, or some steps may be excluded and additional steps included.

[0170] In the present disclosure, an image encoding device (100) or an image decoding device (200) that performs a predetermined operation (step) may perform an operation (step) that confirms a condition or situation for performing the corresponding operation (step). For example, if it is described that a predetermined operation is performed when a predetermined condition is satisfied, the image encoding device (100) or the image decoding device (200) may perform an operation for confirming whether the predetermined condition is satisfied, and then perform the predetermined operation.

[0171] The various embodiments of the present disclosure are not intended to list all possible combinations but rather to illustrate representative aspects of the present disclosure, and the matters described in the various embodiments may be applied independently or in combination of two or more.

[0172] Additionally, various embodiments of the present disclosure may be implemented by hardware, firmware, software, or a combination thereof. In the case of hardware implementation, the embodiments may be implemented by one or more Application Specific Integrated Circuits (ASICs), Digital Signal Processors (DSPs), Digital Signal Processing Devices (DSPDs), Programmable Logic Devices (PLDs), Field Programmable Gate Arrays (FPGAs), general processors, controllers, microcontrollers, microprocessors, etc.

[0173] In addition, the video decoding device (200) and the video encoding device (100) to which the embodiments of the present disclosure are applied may be included in a multimedia broadcasting transmission / reception device, a mobile communication terminal, a home cinema video device, a digital cinema video device, a surveillance camera, a video conversation device, a real-time communication device such as a video communication, a mobile streaming device, a storage medium, a camcorder, a video-on-demand (VoD) service providing device, an OTT video (Over the top video) device, an Internet streaming service providing device, a three-dimensional (3D) video device, a video phone video device, and a medical video device, and may be used to process a video signal or a data signal. For example, the OTT video (Over the top video) device may include a game console, a Blu-ray player, an Internet-connected TV, a home theater system, a smartphone, a tablet PC, a DVR (Digital Video Recorder), and the like.

[0174] FIG. 7 is a diagram illustrating an example of a content streaming system to which an embodiment according to the present disclosure can be applied.

[0175] 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.

[0176] The encoding server compresses content input from multimedia input devices such as smartphones, cameras, and camcorders into digital data, generates a bitstream, and transmits it to the streaming server. Alternatively, if multimedia input devices such as smartphones, cameras, and camcorders directly generate bitstreams, the encoding server may be omitted.

[0177] The above bitstream can be generated by an image encoding method and / or an image encoding device (100) to which an embodiment of the present disclosure is applied, and the streaming server can temporarily store the bitstream during the process of transmitting or receiving the bitstream.

[0178] The streaming server transmits multimedia data to a user device based on a user request via a web server, and the web server can act as an intermediary to inform the user of available services. When a user requests a desired service from the web server, the web server transmits the request to the streaming server, and the streaming server can transmit 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 may control commands / responses between each device within the content streaming system.

[0179] The streaming server can receive content from a media repository and / or 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 smooth streaming service, the streaming server can store the bitstream for a certain period of time.

[0180] Examples of the user devices may include mobile phones, smart phones, laptop computers, digital broadcasting terminals, personal digital assistants (PDAs), portable multimedia players (PMPs), navigation devices, slate PCs, tablet PCs, ultrabooks, wearable devices (e.g., smartwatches, smart glasses, HMDs), digital TVs, desktop computers, digital signage, etc.

[0181] Each server within the above content streaming system can be operated as a distributed server, in which case data received from each server can be processed in a distributed manner.

[0182] The scope of the present disclosure includes software or machine-executable instructions (e.g., operating systems, applications, firmware, programs, etc.) that cause operations according to the methods of various embodiments to be executed on a device or a computer, and a non-transitory computer-readable medium having such software or instructions stored thereon and executable on the device or computer.

[0183] Embodiments according to the present disclosure can be used to encode / decode images.

Claims

1. In a video decoding method performed in a video decoding device, the video decoding method, A step of receiving a bitstream including image information; and A step of generating a restored picture by restoring the current picture based on the above image information is included, The above image information includes a SPTI (Source Picture Timing Information) SEI message regarding the temporal distance between source pictures related to corresponding decoded pictures. How to decrypt video.

2. In paragraph 1, The SPTI SEI message includes persistence information indicating whether the SPTI SEI message applies only to the current decoded picture. How to decrypt video.

3. In paragraph 2, The SPTI SEI message includes at least one of first information indicating a maximum number of temporal sub-layers, second information indicating a scale factor used to determine a temporal interval between source pictures corresponding to a decoded picture, or third information indicating whether the current decoded picture belonging to a temporal sub-layer has been synthesized. How to decrypt video.

4. In paragraph 3, The first information, second information and third information are obtained based on the persistence information. How to decrypt video.

5. In paragraph 4, The first information, the second information and the third information are obtained based on the persistence information indicating that the SPTI SEI message is not only applied to the current decoded picture. How to decrypt video.

6. In paragraph 4, The second information and the third information are obtained based on the value of the first information. How to decrypt video.

7. In paragraph 4, Based on the fact that the second information is not obtained, the value of the second information is inferred to be 1. How to decrypt video.

8. In paragraph 1, Based on the above persistence information indicating that the SPTI SEI message applies only to the current decoded picture, the source picture interval is equal to the elemental source picture interval. How to decrypt video.

9. In a video encoding method performed in a video encoding device, the video encoding method comprises: A step of generating image information about the current picture; and Comprising a step of encoding a bitstream including the above image information, The above image information includes a SPTI (Source Picture Timing Information) SEI message regarding the temporal distance between source pictures related to corresponding decoded pictures. How to decrypt video.

10. A computer-readable recording medium storing a bitstream generated by the image encoding method of Article 9.

11. In a method for transmitting a bitstream generated by an image encoding method, the image encoding method comprises: A step of generating image information about the current picture; and Comprising a step of encoding a bitstream including the above image information, The above image information includes a SPTI (Source Picture Timing Information) SEI message regarding the temporal distance between source pictures related to corresponding decoded pictures. Bitstream transmission method.

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