RU2803531C2 - Method and device for encoding and decoding video - Google Patents

Abstract

FIELD: video encoding and decoding.

SUBSTANCE: invention relates to a method for incrementally encoding or decoding an entire area in an image over a plurality of images associated with an image. A method of encoding and decoding is proposed using gradual update comprising decoding, from the sequence header in the bitstream, a flag indicating whether gradual update is allowed; decoding the identification information to identify the first picture in the sequence to which the incremental update has been applied and determine the value of a picture order counter (POC) of the first picture; decoding the group size information to identify the group of pictures associated with the first picture to which the gradual update has been applied; determining a POC value of a second image corresponding to the last image belonging to the group based on the group size information; and determining a group of pictures associated with the first picture using the POC value of the first picture and the POC value of the second picture, where the identification information indicates that the gradual update is not applied to the first picture in the sequence, based on a flag indicating that the gradual update is not allowed.

EFFECT: increasing the decoding efficiency.

12 cl, 22 dwg

Description

Field of technology to which the invention relates

[1] The present disclosure relates to video encoding and decoding, and more specifically, to a method for incrementally encoding or decoding an entire region in an image across multiple images associated with an image.

State of the art

[2] Since the volume of video data is larger than the volume of speech data or still image data, storing or transmitting video data without processing for compression requires a lot of hardware resources, including a storage device. Accordingly, when storing or transmitting video data, the video data is typically compressed using an encoder for storage or transmission. The decoder then receives the compressed video data, decompresses and plays back the video data. Compression procedures for such video include H.264/AVC and High Efficiency Video Coding (HEVC), which improves encoding efficiency over H.264/AVC by approximately 40%.

[3] However, video size, resolution, and frame rate are gradually increasing, and accordingly, the amount of data that needs to be encoded is also increasing. Therefore, a new compression procedure having better coding efficiency and higher image quality than the existing compression procedure is required.

[4] To compress video data, each of the image blocks can be predictively encoded. Typically, prediction of the current block is performed using an intra-prediction procedure (using data from the image containing the current block) or an inter-prediction procedure (using data from the image that was encoded before the image containing the current block). Inter-prediction includes both unidirectional and bidirectional prediction.

[5] The first picture included in the video bitstream, or a random access picture that provides random access at a random position, such as an instant decoding update (IDR) picture or a pure random access (CRA) picture, is encoded using intra-prediction. In general, encoding an I- (intra) image in which the entire image region is predicted using intra-prediction requires a large number of bits compared to a P- (predicted) or B- (bidirectional) image that allows inter-prediction . This can cause problems with frequency control and buffer control from a maintenance perspective. In particular, this trend may occur more frequently as video size, resolution, and frame rate gradually increase.

Disclosure of the invention

[6] The present disclosure is directed to a procedure for incrementally encoding or decoding an entire image area across a plurality of images associated with a specified image.

[7] In accordance with one aspect of the present disclosure, a video decoding method is provided for decoding a sequence of images using incremental updating. The method includes decoding, from a sequence header in the bitstream, a flag indicating whether incremental updating is enabled; decoding identification information to identify a first picture to which incremental updating has been applied in the sequence and determining a picture order counter (POC) value of the first picture; decoding group size information to identify a group of pictures associated with the first picture to which the gradual update has been applied; determining a POC value of a second image corresponding to the last image belonging to the group based on the group size information; and determining a group of images associated with the first image using the POC value of the first image and the POC value of the second image.

According to another aspect of the present disclosure, a video decoding apparatus for decoding a sequence of images using incremental updating is provided. The apparatus includes one or more processors configured to decode the bitstream to reconstruct images in sequence; and one or more storage elements configured to store the recovered images. One or more processors are configured to decode, from a sequence header in the bit stream, a flag indicating whether incremental updating is enabled; decoding identification information to identify a first image to which incremental updating has been applied in the sequence and determining a picture order counter (POC) value of the first image; decoding the group size information to identify a group of pictures associated with the first picture to which the incremental update has been applied; determining a POC value of a second image corresponding to the last image belonging to the group based on the group size information; and determining a group of images associated with the first image using the POC value of the first image and the POC value of the second image. Brief description of drawings

[8] FIG. 1 is an exemplary block diagram of a video encoding apparatus configured to implement the procedures of the present disclosure.

[9] FIG. 2 is a diagram illustrating blocking using the QTBTTT structure.

[10] FIG. 3 is a diagram illustrating a variety of intra-prediction modes.

[11] FIG. 4 is an exemplary block diagram of a video decoding apparatus configured to implement the procedures of the present disclosure.

[12] FIG. 5A-5B are exemplary diagrams illustrating video encoding or decoding according to an aspect of the present disclosure.

[13] FIG. 6 is an example diagram illustrating a method for generating an image by combining update regions decoded from images belonging to an IR group according to an aspect of the present disclosure.

[14] FIG. 7A-7B are exemplary diagrams illustrating a method for storing and managing images belonging to a decoded IR group in a storage device according to an aspect of the present disclosure.

[15] FIG. 8A-8C are exemplary diagrams illustrating another method of storing and managing images belonging to a decoded IR group in a storage device according to an aspect of the present disclosure.

[16] FIG. 9 is an example diagram illustrating another method of generating an image by combining update regions decoded from images belonging to an IR group, according to an aspect of the present disclosure.

[17] FIG. 10 is a flow diagram illustrating a method for identifying an IR group in a sequence of pictures for video decoding using incremental update, according to an aspect of the present disclosure.

[18] FIG. 11 is an example diagram illustrating a method for post-processing decoded images in an IR group according to an aspect of the present disclosure.

[19] FIG. 12A-12B are exemplary diagrams illustrating another method of post-processing decoded images in an IR group according to an aspect of the present disclosure.

[20] FIG. 13 is an exemplary block diagram of a memory control apparatus for controlling a tile-based or tile group-based storage device according to an aspect of the present disclosure.

[21] FIG. 14A-14B are exemplary diagrams illustrating a method for controlling storage in tile units or tile groups by a storage control device according to an aspect of the present disclosure.

[22] FIG. 15A-15B are exemplary diagrams illustrating scalability supported by a storage device management method according to an aspect of the present disclosure.

Carrying out the invention

[23] Next, an embodiment of the present disclosure will be described in detail with reference to the accompanying drawings. It should be noted that in assigning reference numerals to constituent elements in the respective drawings, the same reference numerals are used to designate like elements even though the elements are shown in different drawings. Moreover, in the following description of the present disclosure, a detailed description of the known functions and configurations included herein will be omitted in order to avoid obscuring the subject matter of the present disclosure.

[24] FIG. 1 is an exemplary block diagram of a video encoding apparatus configured to implement the procedures of the present disclosure. Next, the video encoding device and elements of the device will be described with reference to FIG. 1.

[25] The video encoding apparatus includes a block separator 110, a predictor 120, a subtractor 130, a converter 140, a quantizer 145, a rearrangement unit 150, an entropy encoder 155, an inverse quantizer 160, an inverse converter 165, an adder 170, a filtering unit 180, and a memory device. 190.

[26] Each element of a video encoding device may be implemented as hardware or software, or a combination of hardware and software. The functions of the corresponding elements may be implemented as software, and the microprocessor may be implemented to perform the software functions corresponding to the corresponding elements.

[27] One video includes many images. Each image is divided into multiple regions, and coding is performed for each region. For example, one image is divided into one or more mosaic elements and/or fragments. In particular, one or more tiles may be defined as a group of tiles. Each tile or fragment is divided into one or more coding tree units (CTUs). And each CTU is divided into one or more coding units (CUs) with a tree structure. Information applied to each CU is encoded as CU syntax, and information applied to CUs included in one common CTU is encoded as CTU syntax. In addition, information typically applied to all blocks in a single tile is encoded as tile header syntax, and information applied to all blocks composing one image is encoded in a picture parameter set (PPS) or image header. In addition, the information to which a plurality of pictures relate is encoded in a Sequence Parameter Set (SPS). In addition, the information relied upon by one or more common SPSs is encoded in a video parameter set (VPS). Information typically applied to a single tile or group of tiles may be encoded as tile or group of tile header syntax.

[28] Block separator 110 is configured to determine the size of a coding tree unit (CTU). CTU unit size information (CTU size) is encoded as SPS or PPS syntax and sent to the video decoding device.

[29] The block divider 110 is configured to divide each image constituting a video into a plurality of CTUs having a predetermined size, and then recursively divide the CTUs using a tree structure. In a tree structure, a leaf node serves as a coding unit (CU), which is the basic coding unit.

[30] The tree structure can be QuadTree (QT), in which a node (or parent node) is divided into four subnodes (or child nodes) of equal size, BinaryTree (BT), in which a node is divided into two subnodes, TernaryTree (TT), in which a node is divided into three sub-nodes in a 1:2:1 ratio, or a structure formed by a combination of two or more of a QT structure, a BT structure, and a TT structure. For example, a structure including a quadtree and a binary tree (QTBT) or a structure including a quadtree and a ternary tree binary tree (QTBTTT) may be used. In particular, the VTTT may be collectively referred to as a multiple type tree (MTT).

[31] FIG. 2 shows the tree structure of the QTBTTT partition as an example. As shown in FIG. 2, CTU can be initially divided into QT structure. QT splitting can be repeated until the split block size reaches the minimum block size (MinQTSize) of a leaf node allowed in QT. The first flag (QT_split_flag) indicating whether each node of the QT structure is divided into four lower-level nodes is encoded by the entropy encoder 155 and signaled to the video decoding apparatus. If a leaf node QT is less than or equal to the maximum block size (MaxBTSize) of the root node allowed in the BT, it can be further divided into any one or more BT structures or TT structures. The BT structure and/or the CT structure can have multiple division directions. For example, there may be two directions, namely the direction in which the node block is divided horizontally and the direction in which the block is divided vertically. As shown in FIG. 2, when MTT splitting begins, a second flag (mtt_split_flag) indicating whether the nodes are split, a flag indicating the direction of splitting (vertical or horizontal) in case of splitting, and/or a flag indicating the type of splitting (binary or ternary) are encoded by the entropy encoder 155 and are signaled to the video decoding device. Alternatively, before encoding the first flag (QT_split_flag) indicating whether each node is split into four lower-level nodes, a CU split flag (split_cu_flag) may be encoded indicating whether the node is split or not. When the value of the CU split flag (split_cu_flag) indicates that the split has not been completed, the node block becomes a leaf node in the split tree structure and serves a coding unit (CU), which is the basic coding unit. When the value of the CU split flag (split_cu_flag) indicates that splitting has been completed, the video encoding device is configured to begin encoding the flags in the manner described above, starting with the first flag.

[32] When QTBT is used as another example of a tree structure, there can be two types of partitioning, which are a type of horizontal partitioning of a block into two blocks of equal size (i.e. symmetrical horizontal partitioning) and a type of vertical partitioning of a block into two blocks of equal size (i.e. symmetrical vertical division). A split flag (split_flag) indicating whether each node of the VT structure is divided into a lower-layer block, and split type information indicating the type of division, are encoded by the entropy encoder 155 and transmitted to the video decoding device. An additional type of division of the node block into two asymmetric blocks is possible. The asymmetrical division type may include a block division type into two rectangular blocks with an aspect ratio of 1:3, or a node block diagonal division type.

[33] In particular, the CUs may have different sizes according to the division of the CTU into QTBT or QTBTTT. In the following, the block corresponding to the CU (i.e., the QTBTTT end node) to be encoded or decoded is called the “current block”. Because QTBTTT partitioning is used, the shape of the current block can be square or rectangular.

[34] Predictor 120 is configured to predict the current block to generate a prediction block. Predictor 120 includes intra-predictor 122 and inter-predictor 124.

[35] The intra-prediction unit 122 is configured to predict pixels in the current block using pixels (reference pixels) located around the current block in the current image, including the current block. There are many intra-prediction modes according to the prediction directions. For example, as shown in FIG. 3, the plurality of intra-prediction modes may include two omnidirectional modes, which include planar mode and DC mode, and 65 directional modes. The neighboring pixels and the equation used are determined differently for each prediction mode.

[36] The intra-prediction module 122 may be configured to determine the intra-prediction mode used when encoding the current block. In some examples, intra-prediction module 122 may be configured to encode the current block using multiple intra-prediction modes and select from the tested modes the appropriate intra-prediction mode to use. For example, intra-prediction block 122 may be configured to calculate frequency distortion values using frequency-distortion ratio analysis of several tested intra-prediction modes and select the intra-prediction mode that has the best frequency-distortion characteristics among the tested modes.

[37] The intra-prediction unit 122 is configured to select one intra-prediction mode from a plurality of intra-prediction modes and predict the current block using neighboring pixels (reference pixels) and an equation determined in accordance with the selected intra-prediction mode. Information about the selected intra-prediction mode is encoded by the entropy encoder 155 and transmitted to the video decoding device.

[38] The inter-prediction unit 124 is configured to generate a prediction unit for the current block by motion compensation. The inter-prediction module 124 is configured to search for a block most similar to a current block in a reference picture that was encoded and decoded earlier than the current picture, and generate a prediction block for the current block using the found block. The inter-predictor is then configured to generate a motion vector corresponding to an offset between the current block in the current image and the prediction block in the reference image. In general, motion estimation is performed on the luminance component, and a motion vector calculated based on the luminance component is used for both the luminance component and the chrominance component.

[39] Motion information including reference image information and motion vector information used for predicting the current block is encoded by the entropy encoder 155 and transmitted to the video decoding apparatus. Inter-predictor 124 may be configured to interpolate on a reference image or reference block to improve prediction accuracy. In other words, subpixels between whole pixels are interpolated using whole pixels. When the process of searching for a block that is most similar to the current block for an interpolated reference image is performed, the motion vector may not be expressed in whole-pixel precision, but in sub-unit pixel precision. The precision or resolution of the motion vector can be set differently for each target area unit to be encoded, for example, as a fragment, tile, CTU or CU.

[40] Subtractor 130 is configured to subtract a prediction block generated by intra-predictor 122 or inter-predictor 124 from the current block to generate a residual block. Converter 140 may be configured to divide the residual block into one or more transform blocks and apply a transform to the one or more transform blocks, thereby converting the transform block residuals from the pixel domain to the frequency domain. In the frequency domain, transformed blocks are called coefficient blocks containing one or more transform coefficient values. The two-dimensional transformation kernel can be used for transformation, and the one-dimensional transformation kernels can be used for horizontal transformation and vertical transformation, respectively. The transform kernels may be based on discrete cosine transform (DCT), discrete sine transform (DST), or the like.

[41] Converter 140 may be configured to convert residual signals in a residual block using the entire size of the residual block as a conversion unit. Alternatively, the residual block can be divided into a plurality of sub-blocks, and the residual signals in the sub-block can be converted using the sub-block as a conversion unit.

[42] The converter 140 may be configured to individually convert the residual block in the horizontal direction and the vertical direction. Various types of transformation functions or transformation matrices can be used for transformation. For example, a pair of transform functions for transforming in the horizontal direction and vertical direction may be defined as a multiple transform set (MTS). Converter 140 may be configured to select one pair of transform functions having the greatest conversion efficiency in the MTS, and transform the residual block in the horizontal and vertical directions, respectively. Information (nits_idx) about the transform function pair selected from the MTS is encoded by the entropy encoder 155 and signaled to the video decoding device.

[43] Quantizer 145 is configured to quantize transform coefficients output from transformer 140 and output the quantized transform coefficients to entropy encoder 155. For some blocks or frames, quantizer 145 may be configured to directly quantize the associated residual block without transform.

[44] Rearrangement module 150 may be configured to reorganize coefficient values for the quantized residual value. Rearrangement module 150 may be configured to change a 2-dimensional array of coefficients into a 1-dimensional sequence of coefficients by scanning the coefficients. For example, rearrangement module 150 may be configured to scan coefficients from a DC coefficient to a high-frequency domain coefficient using a zigzag scan or a diagonal scan to output a 1-dimensional sequence of coefficients. Depending on the size of the transform unit and the intra-prediction mode, instead of zigzag scanning, vertical scanning may be used, in which a two-dimensional array of coefficients is scanned in the column direction, or horizontal scanning, in which two-dimensional block coefficients are scanned in the row direction. In other words, the scanning mode used can be determined among zigzag scanning, diagonal scanning, vertical scanning and horizontal scanning according to the size of the transformation unit and the intra-prediction mode.

[45] Entropy encoder 155 is configured to encode one-dimensional quantized transform coefficients output from rearrangement module 150 using various encoding techniques such as context-sensitive adaptive binary arithmetic code (CABAC) and exponential Golomb code to generate a bitstream.

[46] The entropy encoder 155 is configured to encode information such as CTU size, CU partition flag, QT partition flag, MTT partition type, and MTT partition direction, which is associated with block partitioning, so that the video decoding apparatus can partition the block in the same manner. as in a video encoder. In addition, the entropy encoder 155 is configured to encode prediction type information indicating whether the current block is encoded by intra-prediction or inter-prediction, and encodes intra-prediction information (i.e., intra-prediction mode information) or inter-prediction information. inter-prediction (reference image index and motion vector information) according to the prediction type.

[47] The inverse quantizer 160 is configured to inversely quantize the transform coefficients output from the quantizer 145 to generate transform coefficients. The inverse converter 165 is configured to convert the conversion coefficients output from the inverse quantizer 160 from the frequency domain to the spatial domain and restore the residual block.

[48] The adder 170 is configured to add the reconstructed residual block to the prediction block generated by the prediction module 120 to recover the current block. The pixels in the reconstructed current block are used as reference pixels when performing intra-prediction of the next block. The filtering module 180 is configured to filter the reconstructed pixels to reduce blocking artifacts, false outlining artifacts, and blur artifacts generated due to block-based prediction and transform/quantization. Filtering module 180 may include a deblocking filter 182 and an adaptive pixel offset (SAO) filter 184.

[49] The deblocking filter 180 is configured to filter the boundary between reconstructed blocks to remove the blocking artifact caused by block-by-block encoding/decoding, and the SAO filter 184 further performs deblocking filtering on the filtered image. The SAO 184 filter is a filter used to compensate for the difference between the reconstructed pixel and the original pixel caused by lossy encoding. The reconstructed block is filtered through the deblocking filter 182 and the SAO filter 184 and stored in the memory 190. When all the blocks in one image are reconstructed, the reconstructed image can be used as a reference image for inter-prediction of blocks in the next image to be encoded.

[50] FIG. 4 is an exemplary functional block diagram of a video decoding apparatus configured to implement the procedures of the present disclosure. Next, the video decoding device and elements of the device will be described with reference to FIG. 4. The video decoding apparatus may include an entropy decoder 410, a rearranger 415, an inverse quantizer 420, an inverse transformer 430, a predictor 440, an adder 450, a filtering unit 460, and a memory 470.

[51] Similar to the video encoding apparatus of FIG. 1, each element of a video decoding apparatus may be implemented as hardware or software, or a combination of hardware and software. In addition, the function of each element may be implemented as software, and a microprocessor may be implemented to execute the software function corresponding to each element.

[52] The entropy decoder 410 is configured to determine the current block to be decoded by decoding the bitstream generated by the video encoding apparatus and extracting block division related information and extracting prediction information and residual signal information and the like. , necessary to restore the current block.

[53] Entropy decoder 410 is configured to extract CTU size information from a sequence parameter set (SPS) or picture parameter set (PPS), determines the size of the CTU, and splits the image into CTUs of a certain size. The decoder is then configured to determine the CTU as the topmost level, that is, the root node of the tree structure, and retrieve partitioning information about the CTU to partition the CTU using the tree structure.

[54] For example, when a CTU is split using the QTBTTT structure, the first flag (QT_split_flag) associated with the QT split is retrieved to split each node into four sublayer nodes. For a node corresponding to a QT leaf node, a second flag (MTT_split_flag) and split direction (vertical/horizontal) and/or split type (binary/ternary) information related to the MTT split are retrieved to split the corresponding leaf node in the MTT structure. Thus, each node below the leaf node QT is recursively divided into a BT or TT structure.

[55] As another example, when a CTU is split using the QTBTTT structure, a CU split flag (split_cu_flag) may be retrieved indicating whether the CU should be split. When the corresponding block is split, the first flag (QT_split_flag) can be retrieved. In a split operation, zero or more recursive MTT splits may occur for each node after zero or more recursive QT splits. For example, a CTU may directly undergo MTT cleavage without QT cleavage or repeatedly undergo QT cleavage alone.

[56] As another example, when a CTU is split using the QTBT structure, the first flag (QT_split_flag) associated with the QT split is retrieved and each node is split into four lower-level nodes. Then, a split flag (split_flag) indicates whether the node corresponding to the leaf node QT is further split in the VT, and the split direction information is retrieved.

[57] Once the current block to be decoded is determined by partitioning in the tree structure, the entropy decoder 410 is configured to extract prediction type information indicating whether the current block is predicted using intra-prediction or inter-prediction. When the prediction type information indicates intra-prediction, the entropy decoder 410 is configured to extract a syntax element for the intra-prediction information (intra-prediction mode) of the current block. When the prediction type information indicates inter-prediction, the entropy decoder 410 is configured to extract a syntax element for the inter-prediction information, that is, information indicating a motion vector and a reference image on which the motion vector is based.

[58] Entropy decoder 410 is also configured to extract information about the quantized transform coefficients of the current block as residual signal information. Rearrangement module 415 may be configured to change the sequence of one-dimensional quantized transform coefficients entropy decoded by entropy decoder 410 into a two-dimensional coefficient array (ie, block) in the reverse order of the coefficient scan performed by the video encoding device.

[59] Inverse quantizer 420 is configured to inversely quantize the quantized transform coefficients. The inverse converter 430 is configured to inversely convert the inversely quantized transform coefficients from the frequency domain to the spatial domain, thereby generating a reconstructed residual block for the current block. In addition, when MTS is applied, the inverter 430 is configured to determine a transform function or transform matrix to be applied in the horizontal and vertical directions, respectively, based on the MTS information (rats_idx) signaled from the video encoding device, and inversely converts the transform coefficients to transformation block in the horizontal and vertical directions based on a specific transformation function.

[60] Predictor 440 may include intra predictor 442 and inter predictor 444. Itra predictor 442 is activated when the prediction type of the current block is intra prediction, and inter predictor 444 is activated when the prediction type of the current block is inter-prediction. prediction. The intra predictor 442 is configured to determine the intra prediction mode of the current block among the plurality of intra prediction modes based on the syntax element for the intra prediction mode extracted from the entropy decoder 410, and to predict the current block using reference pixels around the current block in accordance with intra-prediction mode.

[61] The inter-predictor 444 is configured to determine a motion vector of the current block and a reference image on which the motion vector is based, using a syntax element for inter-prediction information extracted from the entropy decoder 410, and predict the current block based on the motion vector and the reference Images. The adder 450 is configured to reconstruct the current block by adding the output of the residual block from the inverse transformer and the prediction block output from the inter-predictor or intra-predictor. The pixels in the reconstructed current block are used as reference pixels in intra-prediction of the next block to be decoded.

[62] Filtering module 460 may include a deblocking filter 462 and an SAO filter 464 . A deblocking filter 462 filters the boundary between reconstructed blocks to remove blocking artifacts caused by block-by-block decoding. The SAO filter 464 performs additional filtering on the reconstructed block after the deblocking filtering so as to compensate for the difference between the reconstructed pixel and the original pixel caused by lossy encoding. The reconstructed block is filtered through the deblocking filter 182 and the SAO filter 184 and stored in the memory 190. When all the blocks in one image are reconstructed, the reconstructed image is used as a reference image for inter-prediction of blocks in the next image to be encoded.

[63] As described above, a video encoding apparatus or a video decoding apparatus encodes and decodes one image in units of blocks. Images can be classified into an I (intra) image in which only intra-prediction is allowed, a P (prediction) image in which inter-prediction and intra-prediction are allowed together, or a B (dual-prediction) image in which bi-directional inter-prediction is allowed. prediction. The first picture in a video bitstream or a random access picture, such as an instant decoding update (IDR) picture or a pure random access (CRA) picture, that allows random access at a random position is an I picture. Typically, a significant number of bits are required to encode an I (intra) image, in which the entire image region is predicted by intra-prediction.

[64] As the coding efficiency of P or B pictures increases by relying on inter-pictures, i.e. inter-prediction, due to the development of encoding and decoding technology, the difference in the number of bits between I and P or B pictures may increase, which may increase problems regarding frequency control, buffer management and the like. from a service point of view. In addition, when an error occurs due to the environment of the transport channel over which the bit stream is transmitted, the error may be concentrated in the I-picture. In particular, this effect may occur more frequently as video size, resolution, and frame rate gradually increase.

[65] The following disclosure presents a method for incrementally encoding or decoding an entire image area across a plurality of images associated with an image to solve the above-mentioned problems. The video encoding device can encode a sequence of images, and the video decoding device can decode the sequence of images using the above-described method. An image (the first image) in a sequence may form one group in connection with multiple images. Each image in the group includes an update area. As the pictures in the group are decoded, the update regions can be gradually decoded. Once all update regions are decoded, a complete image with all updated regions can be generated. The complete image with all the updated regions can be the last image (second image) belonging to the group. In other words, individual regions are gradually updated across multiple images belonging to the group, such that all regions in the images are updated when the second image is reached.

[66] Hereinafter, a group of multiple images associated with a first image may be called an IR (intra-refresh) group or a Gradual Random Access (GRA) group. In addition, the update area in each picture belonging to a group may be called an intra-update unit (IRU) or a gradual random access unit (GRU). In addition, the first image may be called an IR image or a GRA image.

[67] The video decoding apparatus may be configured to correctly or more accurately decode all pictures from the last picture (second picture) of a group in decoding order. The last picture (second picture) in a group may serve as a reference picture for one or more encoded subsequent pictures following the group in decoding order. In addition, a group or the last picture in a group may serve as a random access picture for one or more encoded subsequent pictures following the group in decoding order.

[68] Next, the procedure according to the present disclosure will be described in detail with reference to the drawings.

[69] FIG. 5A-5B are exemplary diagrams illustrating a procedure according to the present disclosure.

[70] FIG. 5A shows a sequence of images. The video encoding apparatus sequentially encodes each image for each block according to the encoding order and transmits it to the video decoding apparatus. The video decoding apparatus decodes each picture for each block according to the decoding order. The sequence of images may include images belonging to a group (IR group or GRA group) of images to which gradual updating is applied. Information or a flag indicating whether incremental updating can be applied to a sequence of images may be reported in the sequence header, ie, in the SPS. For example, when the flag indicates the first value (eg, 1), images to which incremental updating applies may be present in the sequence. When the flag specifies the second value (for example, 0), there are no images in the sequence to which incremental updating applies.

[71] When the flag indicates that incremental update is applicable to the sequence, information to identify the IR group in the sequence is signaled. For example, when the time interval at which an IR group appears in a sequence is constant and the group size, that is, the number of images belonging to the group, is constant, information about the interval between IR groups and the size of the IR groups may be reported once per sequence unit.

[72] In another example, IR groups may not be regularly present in the sequence. In particular, information is required to identify each IR group in the sequence. This information may be signaled for each picture, ie, as picture header syntax, and may include information indicating whether the picture is an IR picture, and the size of the IR group. As an example, the video decoding apparatus obtains identification information indicating whether the corresponding picture is an image to which incremental updating is applied by decoding header information of the corresponding picture. When the identification information indicates that incremental updating has been applied to the corresponding picture, the video decoding apparatus decodes information indicating the size of a group of pictures associated with the corresponding picture, that is, an IR group. Identification information and information indicating the size of the IR group may be included in the first image representing the initial image of the IR group.

[73] In general, the bit stream contains information indicating the order counter (POC) of an image. This information may be included, for example, in the title of the image. Accordingly, the video decoding apparatus may be configured to determine a POC value of the first picture, which is the starting picture of the IR group. In addition, the POC of the second image, which corresponds to the last image of the IR group, can be determined using the size information of the IR group. For example, the POC value of the second image can be obtained by adding the POC value of the first image and the value specified in the group size information. The video decoding apparatus is configured to determine pictures having a POC value greater than or equal to the POC value of the first image and less than or equal to the POC value of the second image as an IR group.

[74] As shown in FIG. 5B, a group of images associated with the first image, that is, images belonging to the IR group, includes an update area and a non-update area. Specifically, the update region may be a region in which image data can be correctly and accurately encoded/decoded, and the non-updating region may be a region in which image data is not guaranteed to be correctly and more accurately encoded/decoded. For example, one picture to be encoded or decoded may be divided into a plurality of regions and distributed into a plurality of pictures belonging to an IR group. Image data corresponding to a plurality of areas is gradually encoded or decoded across the plurality of images. A set of images can be defined as an IR group. A plurality of regions that are respectively included in the images belonging to the IR group may be defined as updating regions, and another region of each image except the updating region may be defined as a non-refreshing region.

[75] A picture belonging to an IR group may be a 1-picture, a P-picture, a B-picture, or a random access picture such as IDR or CRA. However, not all images in an IR group can be random access images. The update region in each image belonging to an IR group may consist of a CU, a CTU, a tile, a group of tiles, a tile, or a group of tiles.

[76] The video decoding apparatus decodes the update area in the image belonging to the IR group. In general, the update region is encoded by intra-prediction, but is not limited to this. The video decoding apparatus reconstructs the update area by decoding the intra-prediction mode for each unit (CU) included in the update area and reconstructing each block according to the intra-prediction mode.

[77] The region without updating can be reconstructed through intra-prediction or inter-prediction. When a block in a non-updating region is predicted using inter-prediction, a prediction block can be generated by copying a predetermined value. For example, a prediction block may be filled with pixel values at the same position as a non-updating region in a previously generated reference image. In particular, the previously generated reference picture may be a reference picture shared between the encoding device and the decoding device. As an example, a previously generated reference picture may be an image having a POC closest to the POC of the image that is currently to be decoded. As another example, this could be an image augmented with a value derived from the pixel bit depth. For example, a value corresponding to half the maximum value expressed by the bit depth can be used as a padding value. When the bit depth is 8, the padding value is 128, which is half of 256, the maximum value that can be expressed in 8 bits. As another example, information about a reference picture on which the non-updating region is based may be signaled from the video encoding apparatus to the video decoding apparatus.

[78] Alternatively, only the update region of each picture belonging to the IR group may be decoded, and the decoding process for the non-update region may be skipped. After decoding of all the pictures belonging to the IR group from the first picture to the second picture is completed, the video decoding apparatus may be configured to generate one picture in which the picture update areas are combined, as shown in FIG. 6. The picture consisting only of the update areas is used as a reference picture for other pictures to be decoded subsequently after the IR group. An image containing an area without updating cannot be guaranteed to be correctly and accurately encoded/decoded. Therefore, a restriction may be required so that a picture including a region without updating is not used as a reference picture of other pictures to be decoded after the IR group.

[79] FIG. 7A to 7B are diagrams illustrating a method for storing and managing a decoded image of an IR group in a storage device. After decoding of the update areas and non-update areas of the pictures belonging to the IR group is completed, each picture may be stored in a storage device (eg, DPB, decoded picture buffer) with a different POC value assigned to it, as shown in FIG. 7A. When the second picture is set as a display picture or a picture on which other pictures to be decoded after the IR group are based, a picture having update areas in the IR group combined as shown in FIG. 6, is displayed or based on another image.

[80] As another example, as shown in FIG. 7B, the update area of the image that is decoded first among the pictures belonging to the IR group is stored in the storage device such that the decoded update area replaces the non-update area at the same position in the image to be decoded next. According to this method, the second image stored in the storage device becomes one image consisting only of update areas from each image belonging to the IR group. When the second picture is set as a display picture or a picture on which other pictures to be decoded after the IR group are based, the second picture may be displayed or based on the other pictures.

[81] A storage/memory storage management method described with reference to FIG. 7A-7B may include a restriction that display of other pictures in the IR group should not be allowed except for the second picture, which is the last picture. In other words, images having a POC value greater than or equal to the POC value of the first image, which is the starting image of the IR group, and less than that of the second image, which is the last image, are not allowed to be displayed.

[82] FIG. 8A to 8C show another example of a method for storing and managing a decoded image of an IR group in a storage device. Example in Fig. 8A-8C may be applied to, but is not limited to, the case where only the update region belonging to each picture in the IR group is decoded.

[83] As an example, as shown in FIG. 8A, only the update areas in the corresponding images belonging to the IR group may have different POC values when stored in the storage device. As another example, after decoding of all update areas is completed, the non-update area of each picture belonging to the IR group may be filled with an update area at the same position of another picture. In a storage device, as shown in FIG. 8B, the same images composed of update areas can be stored in a storage device with different POCs. As another example, as shown in FIG. 8C, after decoding of all update areas belonging to the IR group is completed, only an image consisting of only update areas can be stored in the storage device. Specifically, an image consisting only of update areas is stored in a storage device with a POC value of the second image.

[84] According to the example of FIG. 8A to 8C, pictures belonging to the IR group and stored in the storage device can be displayed individually and used as reference pictures for pictures to be decoded after the IR group.

[85] Position information for identifying positions of update areas in pictures belonging to an IR group may be signaled from the video encoding apparatus to the video decoding apparatus. The position information may be an index or coordinates identifying a CTU, a tile, or a group of tiles. As shown in FIG. 9, the position information may be set such that at least some of the update areas spatially overlap with each other. In particular, after decoding the update regions belonging to the IR group, the video decoding apparatus may be configured to apply filtering, such as weighted averaging, to the regions that overlap with each other, and store the filtered update regions or an image including the filtered update regions. The video decoding apparatus may be configured to perform filtering using a filter predetermined in connection with the video encoding apparatus. Alternatively, the video encoding device may signal filter coefficient information for filtering overlapping regions to the video decoding device, and the video decoding device may filter the overlapping regions based on the filter coefficient information.

[86] FIG. 10 is a flowchart illustrating a method for identifying an IR group in a sequence of pictures for video decoding using incremental update, according to an embodiment of the present disclosure.

[87] The video decoding apparatus is configured to receive a bit stream generated by encoding a sequence of pictures, and determine the first picture to which incremental updating in the sequence has been applied (S1010). For example, as described above, the first image to which gradual updating is applied can be identified by decoding, from the header of each picture in the sequence, identification information indicating whether the corresponding image is an image to which gradual updating is applied. Then, the POC value of the first image is determined (S1020). The POC value may be obtained from information in the bitstream, for example, POC information included in the header of the first picture.

[88] Thereafter, the video decoding apparatus is configured to decode group size information (IR group) of pictures associated with the first picture to which incremental updating has been applied, and determine the IR group size (S1030). The size information can be extracted from the header of the first image. Then, the POC value of the second image corresponding to the last image of the IR group is determined based on the determined group size (S1040). The video decoding apparatus may be configured to determine a POC value of the second picture corresponding to the last picture in the IR group by adding the group size determined from the size information to the POC value of the first picture. The IR group can be defined as images having a POC value greater than or equal to the POC value of the first image and less than or equal to the POC value of the second image (S1050). The images in the IR group are decoded and stored in a memory device in the above-described manner. Since this operation has been described in detail above, further description will be omitted.

[89] Next, a method for post-processing decoded update areas after decoding update areas of images belonging to an IR group is described. Fig. 11 is an exemplary diagram illustrating a post-processing method of decoded IR group images according to the embodiment described in the present disclosure.

[90] As shown in FIG. 11, the video decoding apparatus may expand each of the update regions by padding a certain range beyond the boundary of the update region with reconstructed pixels near the boundary in the decoded update region. When update regions are combined to form a single reference image, the update regions overlap each other due to the filled regions. Accordingly, as described with reference to FIG. 9, after filtering the regions that overlap each other, the video decoding apparatus may be configured to store the filtered update regions or an image including the filtered update regions in a storage device. The size of the filled area may be a size shared between the video encoding apparatus and the video decoding apparatus, or may be signaled from the video encoding apparatus to the video decoding apparatus. This post-processing technique can be used to reduce artifacts that occur at the edge of the update region when combining update regions.

[91] FIG. 12A-12B are exemplary diagrams illustrating a post-processing method for decoded IR group images according to another embodiment described in the present disclosure. As shown in FIG. 12A, pictures in an IR group or an image generated by combining image update areas belonging to an IR group can be used as a reference picture for inter-prediction of other pictures to be decoded after the IR group.

[92] Images composed of update regions may have artifacts at the border between update regions. Thus, as shown in FIG. 12B, when an image consisting of update regions is used as a reference image for inter-prediction of a block in another image to be decoded after the IR group, artifacts may reduce the prediction accuracy, reduce the encoding efficiency, and degrade the subjective image quality of the displayed image. Therefore, in some embodiments of the present disclosure, when storing decoded images of an IR group in a storage device, displaying an image combining update areas of images belonging to the IR group, or using images belonging to an IR group or images combining update areas as a reference image, The video decoding device may perform filtering at the boundary between update areas.

[93] The video encoding apparatus may signal information or a flag indicating whether filtering is enabled at the boundaries of update regions to the video decoding apparatus via a high-level syntax such as SPS, IR group picture header, or update region header on the IR group picture. The video decoding apparatus may be configured to determine whether to apply filtering to the update region boundary in accordance with the signaled information.

[94] Alternatively, whether filtering is enabled at the boundaries of update regions can be adaptively determined based on at least one of luminance filtering applied to the update region, size information, or quantization parameter (QP) associated with the reference block , which is relied upon in the area of updating, the intra-prediction mode of the reference signal, the type of transform function applied to the reference signal, the precision of the motion vector difference, or the motion vector of the block currently intended for encoding/decoding. For example, when no luminance filter is applied to adjacent update regions, when the applied luminance filters are the same or similar, or when the difference in the quantization parameter between two blocks of an update region adjacent to the boundary between adjacent update regions is less than or equal to a preset threshold, filtering may not be performed. The video decoding apparatus may be configured to receive the information described above to determine whether to allow filtering from the previously recovered information. Accordingly, the video decoding apparatus may be configured to determine whether filtering is enabled without receiving additional information from the video encoding apparatus. In other words, no signaling is required for additional information indicating whether to enable filtering.

[95] Filtering information for filtering the boundary between update areas may be explicitly signaled from the video encoding apparatus to the video decoding apparatus. The filtering information may be included in a header of at least one of the target image currently being encoded/decoded, a tile or tile or CTU currently being encoded/decoded in the target image, an image relied upon in the group IR target image, or image update areas in an IR group. For example, the filter information may be signaled from the video encoding device to the video decoding device as the syntax of the last picture (the second picture in FIG. 5A) in the IR group. Alternatively, the filter information may be signaled as the syntax of a picture decoded after the IR group and based on a picture in the IR group (eg, a picture composed of update areas of corresponding pictures in the IR group).

[96] The filter information may be filter coefficient information or information for selecting one of a plurality of filters. When multiple filters are used, the plurality of filters may be predetermined between the video encoding apparatus and the video decoding apparatus. Alternatively, the video encoding apparatus may be configured to select one filter bank from the filter banks, each of which consists of one or more filters, and signal information indicative of the selected filter bank for the video decoding apparatus.

[97] Filter information may not be signaled, but may be obtained using various pieces of pre-decoded information. For example, it may be obtained by at least one of brightness filtering of the update region, a size of the reference block, QP information about each signal relied upon in the update region, an intra prediction mode of the reference signal, a type of transform function applied to the reference signal, reference mode, motion vector difference accuracy, motion vector accuracy, prediction block size, chrominance component type, or luma component range.

[98] As an example, the video encoding apparatus and the video decoding apparatus may adaptively determine a filter coefficient or a filter length using the luminance filtering value applied to the update region as a weight. Alternatively, the value of the filter coefficient or filter length can be determined adaptively in accordance with the type of transform function applied to the reference signal. Alternatively, the filtering strength may be determined adaptively in accordance with one or more of the size of the reference block or QP information about each reference signal, the shape of the reference block, or the motion vector difference precision or motion vector of the block that is currently to be decoded, and determine the filtration coefficient or filtration length according to the intensity.

[99] In addition, when the reference signal in the IR image is decoded by intra-prediction, the filtering direction can be determined according to the intra-prediction direction. Alternatively, filter information may be obtained from a neighboring block in accordance with the reference mode (unidirectional prediction, bidirectional prediction, etc.) of the current block or the relationship between the reference modes of the current block and the neighboring block. For example, the same filter may be used as for an adjacent block. Alternatively, a filtering index for selecting one of a plurality of filters may be obtained based on motion vector difference accuracy, motion vector accuracy, prediction block size, chroma component type, luminance component range, and the like.

[100] Thus, filtering information such as filter coefficient, filter length, filtering intensity and filtering direction can be obtained using a combination of one or more pieces of information described above as an example. Alternatively, the filter information obtained by the above method can be used as prediction information for a filter to actually be applied. In particular, the differential filtering information is signaled from the video encoding device to the video decoding device. The video decoding apparatus may be configured to obtain filtering information to actually be applied based on the received filtering information (prediction information) and differential filtering information.

[101] According to some embodiments of the present disclosure, different filtering may be applied to each of the update areas. In particular, filtering information such as a filter coefficient or an index indicating one of a plurality of filters is signaled for each update region constituting the IR group. Alternatively, assignment information may be signaled between the update area (or a block in the update area) and the filter index. The video decoding apparatus may be configured to determine a filter to be applied to each update area based on the filter index assigned to each update area.

[102] In another embodiment, the same filtering information may be shared by all update areas in an IR group. The video decoding apparatus may be configured to perform filtering by applying the same filtering information to all update regions in an IR group. Shared filtering information may be predetermined between the video encoding device and the decoding device.

[103] In another embodiment, a flag indicating whether filtering information is shared among all update areas in an IR group may be signaled by the video encoding device. When filtering information is shared, the shared filtering information (eg, an index to indicate one of a plurality of filters, index output information, or coefficient information regarding a shared filter) may be signaled. The video decoding apparatus may be configured to perform filtering by applying the same filtering information to all update regions based on the shared filtering information. When the filtering information is not shared, the video decoding apparatus may be configured to decode the filtering information for each update area and apply different filtering to each update area as described above.

[104] Filtering operations may be performed on an image belonging to an IR group sequentially or simultaneously both within the update region and at the boundary of the update region. When filtering is performed sequentially, the video decoding apparatus first filters the inside of the update region as each update region is decoded. For example, deblocking or SAO filtering described above can be applied to the interior of the update region. Update region edge filtering may be performed when decoding of all update regions is completed, that is, when update regions included in the last IR group image are decoded. When filtering is performed simultaneously, filtering according to the present disclosure may be performed within the update region and at the edge of the update region at the time that the update region included in the last picture of the IR group is decoded.

[105] The video encoding apparatus may be configured to signal information indicating whether filtering according to the present disclosure is used to support an inter-image for inter-prediction or for display. The video decoding apparatus may be configured to apply filtering according to the present disclosure when performing one or more inter-image supports and display according to the information. For example, when filtering is used for both support and display, the video decoding apparatus is configured to store the filtered image in both the support memory and the display memory. When filtering is used for a support and is not used in a subsequent display step, the filtered image is stored in the support storage device rather than in the display storage device. Alternatively, the video decoding apparatus may be configured to store an unfiltered image. Filtering can be performed when the stored image is displayed in the future or used as a reference image.

[106] In another embodiment, the video encoding apparatus may be configured to signal, through a header of a starting picture (the first picture in FIG. 5A) or a header of an update region included in the starting picture, position information about the picture from which decoding begins based on the filtered IR group image. The video decoding apparatus is configured to decode pictures before the picture indicated by the position information among pictures decoded after decoding the IR group, relying on the unfiltered picture in the IR group. Then, decoding of the image specified in the position information and subsequent images is performed based on the filtered images of the IR group.

[107] As described above, the video decoding apparatus performs filtering based on information transmitted by the video encoding apparatus. However, it is obvious that the video encoding apparatus must also perform filtering in the same manner as the video decoding apparatus to ensure compatibility between the video encoding apparatus and the video decoding apparatus.

[108] Next, a method for managing a storage device based on a tile or a group of tiles will be described. As described above, update areas may consist of one or more tiles. Therefore, the storage device management method described below is naturally related to the storage and management of IR group images described above.

[109] FIG. 13 is an exemplary block diagram of a storage device control device for controlling a storage device based on tiles or on a group of tiles according to an embodiment of the present disclosure. When the storage device control is implemented in the video encoding device and video decoding device described above, it can be used to control DPB in the devices. Each component of a storage device control device may be implemented as hardware, software, or a combination of hardware and software. Moreover, the function of each component may be implemented as software, and a microprocessor may be implemented to execute the software function corresponding to each component.

[110] Memory module 1310 may include a plurality of memories for storing the reconstructed signal. The storage device manager 1320 is configured to store and manage the restored images in the storage device module 1310 using an image or a tile group consisting of one or more tiles as a storage unit. For example, as shown in FIG. 14A, the storage manager 1310 may be configured to divide the reconstructed image into groups or tiles and store the divided groups or tiles in the storage module 1310, or combine the reconstructed signals in the group or tile units into a single image, and store the combined image in the module 1310 storage device.

[111] The storage manager 1320 may be configured to determine a storage position depending on whether the target group of tiles to be stored are MCTs (Motion Restricted Tile Sets) that do not allow leaning between tiles at different positions . For example, when the target tile group is not an MCT, support between adjacent tile groups may be allowed. Accordingly, a target tile group is stored in the same storage device as adjacent MCTs to facilitate reference between tile groups. When the target tile group is an MCT, the target tile group is only allowed to rely on the group of co-located tiles in the previously decoded image. Accordingly, the target group of tiles is stored in the same storage device as the group of co-located tiles in the previously decoded image.

[112] Memory manager 1320 may also be configured to store the reconstructed signal in a memory device for each image. In particular, the storage device manager 1320 may be configured to store the reconstructed images in the same storage device based on the temporary layer, decoding order, or output order.

[113] In addition, when the reconstructed signal is stored in the memory device for each image, the memory manager 1320 may be configured to continuously store all samples in the image in the memory device or store all samples in the image at intervals of one or more samples between groups of tiles included in the image. When the reconstructed signal is stored in the memory device on a per-tile group basis, the memory manager 1320 may be configured to continuously store the tile groups in the memory device or store the tile groups with an interval of one or more samples between the tile groups. In particular, the predetermined value may be stored in a memory space corresponding to a sample interval between groups of tiles. For example, you could use a value such as 128. The specific value is determined by the bit depth of the pixel. For example, the predetermined value may be set to a value corresponding to half the maximum value expressed in bit depth. When the bit depth is 8, the preset value is 128, which is half of 256, the maximum value that can be expressed in 8 bits.

[114] Storage manager 1320 may be configured to remove stored reconstructed signals from storage on a per-image basis or on a group-of-tile basis, as shown in FIG. 14V. Storage manager 1320 may be configured to change the storage location of the reconstructed sample based on reference information received from the video encoding device. For example, when multiple tile groups are relied upon to generate prediction samples of a target block to be encoded or decoded, storage manager 1320 may be configured to identify the multiple tile groups from the index information in the multiple tile groups obtained from the video encoding device. , and storing the identified groups of tiles in the same storage device. Alternatively, it may identify multiple tile groups from a reference block position in the reference image specified in motion information (reference image index and motion vector) about the target block, and store the identified tile groups in the same storage device.

[115] The video reconfiguration module 1330 may be configured to receive reconstructed signals stored in a memory device as input and reconfigure an image to be output by the video output module 1340. For example, when reconstructed signals are input from a storage device on a per-tile group basis, the reconstructed signals may be output for each tile group, or the input tile groups may be reconfigured into one image for output on a per-image basis. The storage management method of the present disclosure can support temporal scalability and spatial scalability for each group of tiles in one image.

[116] FIG. 15A-15B are exemplary diagrams illustrating the scalability supported by a storage device management method according to the present disclosure. As shown in FIG. 15A, which illustrates temporal scalability, groups of tiles can be encoded and decoded at different frame rates. Tile tiles decoded at the same frame rate may be stored in the same storage device. For example, tile group 2 encoded at 30 frames per second may be stored in memory 1, and tile groups 1 and 3 encoded at 15 frames per second may be stored in memory 2. Video reconfiguration module 1330 may be configured to reconfigure tile group 1 stored in storage device 2 into a tile group having a frame rate of 30 frames per second by interpolation using co-located tile groups temporarily adjacent to tile group 1. Similarly, the tile group 3 can be reconfigured into a tile group having a frame rate of 30 frames per second. The video reconfiguration module can then combine groups of 1-3 tiles to output video at a frame rate of 30 frames per second.

[117] As shown in FIG. 15B, which illustrates spatial scalability, groups of tiles can be encoded and decoded at different spatial resolutions. Tile group 2 may be decoded at a first resolution and stored in memory 1, and tile groups 1 and 3 may be decoded at half the first resolution and stored in memory 2. Video reconfiguration unit 1330 may be configured to reconfiguring the tile groups stored in the storage device 2 into tile groups having a first resolution through interpolation between pixels. Thereafter, groups of 13 tiles having the same resolution can be combined to output video having the first resolution.

[118] In addition, MSTs do not allow for support between groups of tiles in different positions. Therefore, only inter-prediction related to a group of co-located tiles in the reference image is allowed for the target block to be encoded or decoded in the MCT. The present disclosure proposes a processing method used when a reference block indicated by a motion vector of a target block in an MCT is outside a group of co-located tiles in the reference image.

[119] In an embodiment, when at least a portion of the reference block indicated by the motion vector of the target block in the MCT is outside the group of aligned tiles, the pixels or samples in the outer region may be complemented by one or more samples within the aligned tile. For example, they can be supplemented with sample values adjacent to a boundary within a group of tiles.

[120] Alternatively, they may be padded with a predetermined value, for example 128. The predetermined value may be derived from the sample bit depth, as described above. Using a predetermined padding value as a prediction value can be easily implemented using the above-described storage device control method. For example, as described above, a plurality of tile groups constituting one image may be stored at intervals of several samples spaced between the tile groups. A predefined value such as 128 is stored in memory space between tile groups. Accordingly, when at least a portion of the reference block indicated by the motion vector of the target block in the MCT is outside the group of co-located tiles, the sample values in the outer region are automatically set to 128.

[121] In another embodiment, when at least a portion of the reference block, indicated by the motion vector of the target block in the MCT, is outside the region of the group of co-located tiles, the motion vector of the target block can be adjusted so that the reference block is completely contained in the group of co-located tiles mosaic elements. For example, the motion vector of the target block may be scaled so that the reference block is located within a group of co-located tiles.

[122] It should be understood that the exemplary embodiments described above may be implemented in a variety of different ways. The functions described in one or more examples may be implemented by hardware, software, firmware, or any combination thereof. It should be understood that the functional components described here are described as "modules" to further emphasize their implementation independence.

[123] Various functions or methods described in the present disclosure may be implemented by instructions stored on a non-transitory recording medium that can be read and executed by one or more processors. Non-transitory recording medium includes, for example, all types of recording devices in which data is stored in a form readable by a computer system. For example, non-transitory recording media includes media such as erasable programmable read-only memory (EPROM), flash drives, optical drives, magnetic hard disks, and solid-state drives (SSDs).

[124] Although exemplary embodiments have been described for illustrative purposes, those skilled in the art will appreciate that various modifications and changes are possible without departing from the concept and scope of the embodiments. Exemplary embodiments have been described for brevity and clarity. Accordingly, one skilled in the art will appreciate that the scope of the embodiments is not limited to the embodiments expressly described above, but includes the claims and their equivalents.

Cross reference to related application

This application claims priority to Patent Application No. 10-2019-0028371, filed on March 12, 2019 in Korea, Patent Application No. 10-2019-0030334, filed on March 18, 2019 in Korea, and Patent Application No. 10-. 2019-0056985, filed May 15, 2019 in Korea, the entire contents of which are incorporated herein by reference.

Claims (35)

1. A video decoding method for decoding a sequence of images using incremental updating, comprising: decoding, from the sequence header in the bit stream, a flag indicating whether incremental updating is enabled; decoding identification information to identify a first picture to which incremental updating has been applied in the sequence, and determining a picture order counter (POC) value of the first picture; decoding group size information to identify a group of pictures associated with the first picture to which the gradual update has been applied; determining a POC value of a second image corresponding to the last image belonging to the group based on the group size information and the POC value of the first image; And determining a group of images associated with the first image using the POC value of the first image and the POC value of the second image, wherein pictures having a POC value greater than or equal to the POC value of the first image and less than the POC value of the second image are not allowed to be displayed after decoding, wherein the identification information indicates that gradual updating is not applied to the first image in the sequence based on the flag indicating that gradual updating is not allowed. 2. The method of claim 1, wherein when a block in an image belonging to a group is predicted using inter-prediction, the block is allowed to be predicted using a reference block filled with a predetermined value. 3. The method of claim 2, wherein the predetermined value is obtained from the bit depth of the pixel values. 4. The method of claim 1, wherein each of the images belonging to a group of images associated with the first image includes update regions at different positions, the update regions being gradually decoded as corresponding images belonging to the group are decoded, and wherein all decoded update regions in a group of pictures associated with the first picture are combined to form a reference picture that will be available as a reference picture for another picture. 5. The method of claim 4, wherein only intra-prediction decoding is enabled for the update regions. 6. The method of claim 4, wherein both intra-prediction decoding and inter-prediction decoding are enabled for non-updating regions in each of the pictures belonging to the group of pictures associated with the first picture. 7. The method according to claim 4, additionally containing: decoding position information indicating positions of update areas in each of the pictures belonging to the group of pictures associated with the first picture. 8. The method according to claim 7, additionally containing: Overlapping region filtering, where image update regions overlap each other. 9. The method according to claim 8, additionally containing: decoding filter coefficient information to filter overlapping regions. 10. The method of claim 4, wherein when a reference image combining decoded update regions is used to inter-predict a target block to be decoded in said other image, the target block is predicted using the reference image after filtering the boundary between the decoded update regions. 11. A video encoding method for encoding a sequence of images using incremental updating, comprising: encoding, into a sequence header in the bitstream, a flag indicating that incremental updating is enabled; encoding identification information for identifying a first image to which incremental updating has been applied in the sequence, and a picture order counter (POC) value of the first image; determining a group of images associated with the first image to which incremental updating is applied, and encoding group size information to identify the group of images, wherein the group size information is used as information for obtaining a POC value of a second image corresponding to the last image belonging to the group; wherein pictures having a POC value greater than or equal to the POC value of the first image and less than the POC value of the second image are not allowed to be displayed after decoding, wherein the identification information indicates that gradual updating is not applied to the first image in the sequence based on the flag indicating that gradual updating is not allowed. 12. A method for storing a bitstream associated with video data, the method comprising: generating a bit stream by encoding video data; And storing the bitstream in a non-transitory machine-readable medium, in this case, the generation of the bit stream includes: encoding, into a sequence header in the bitstream, a flag indicating that incremental updating is enabled; encoding identification information for identifying a first picture to which incremental updating is applied in the sequence, and a picture order counter (POC) value of the first picture; determining a group of images associated with the first image to which incremental updating is applied, and encoding group size information to identify the group of images, wherein the group size information is used as information for obtaining a POC value of a second image corresponding to the last image belonging to the group; wherein pictures having a POC value greater than or equal to the POC value of the first image and less than the POC value of the second image are not allowed to be displayed after decoding, wherein the identification information indicates that gradual updating is not applied to the first image in the sequence based on the flag indicating that gradual updating is not allowed.