Sub-picture extraction and constraint in video coding

Abstract

Example techniques and apparatus for decoding video data are disclosed. An example apparatus includes a memory configured to store video data and one or more processors implemented in a circuit and communicatively coupled to the memory. The one or more processors are configured to extract a current sub-picture from a bitstream of the video data and parse a virtual boundary syntax element indicating a virtual boundary of the current picture, where the current sub-picture is associated with the current picture. The one or more processors are configured to: update the virtual boundary based at least in part on the virtual boundary syntax element; and decoding the current sub-picture based on the updated virtual boundary.

Description

[0001] This application is a divisional application of patent application No. 202180028077.8, filed on May 10, 2021, entitled "Sub-image Extraction and Constraint in Video Decoding". Cross-reference to related applications

[0002] This application claims priority to U.S. Patent Application No. 17 / 314,959, filed May 7, 2021, and U.S. Provisional Patent Application No. 63 / 023,044, filed May 11, 2020, the entire contents of each of which are incorporated herein by reference. U.S. Patent Application No. 17 / 314,959, filed May 7, 2021, claims the benefit of U.S. Provisional Patent Application No. 63 / 023,044, filed May 11, 2020. Technical Field

[0003] This disclosure relates to video encoding and video decoding. Background Technology

[0004] Digital video functionality can be incorporated into a wide variety of devices, including: digital televisions, digital live broadcast systems, wireless broadcasting systems, personal digital assistants (PDAs), laptops or desktop computers, tablets, e-book readers, digital cameras, digital recording devices, digital media players, video game devices, video game consoles, cellular or satellite wireless phones, so-called "smartphones," video conferencing equipment, video streaming devices, and so on. Digital video devices can implement video decoding technologies, such as those described in standards defined in MPEG-2, MPEG-4, ITU-T H.263, ITU-T H.264 / MPEG-4 Part 10, Advanced Video Decoding (AVC), ITU-T H.265 / High-Efficiency Video Decoding (HEVC), and extensions to these standards. By implementing such video decoding technologies, video devices can more efficiently send, receive, encode, decode, and / or store digital video information.

[0005] Video decoding techniques include spatial (intra-picture) prediction and / or temporal (inter-picture) prediction to reduce or remove inherent redundancy in video sequences. For block-based video decoding, video slices (e.g., video pictures or portions of video pictures) can be divided into video blocks, which may also be referred to as decoding tree units (CTUs), decoding units (CUs), and / or decoding nodes. Video blocks in intra-decoded (I) slices of a picture are encoded using spatial prediction relative to reference samples in adjacent blocks within the same picture. Video blocks in inter-decoded (P or B) slices of a picture can use spatial prediction relative to reference samples in adjacent blocks within the same picture, or temporal prediction relative to reference samples in other reference pictures. A picture may be referred to as a frame, and a reference picture may be referred to as a reference frame. Summary of the Invention

[0006] In summary, this disclosure describes techniques for decoding video data, specifically sub-image extraction, sub-image reference picture list (RPL) constraints, and sub-image reordering constraints.

[0007] When extracting sub-images from an image with virtual boundaries, the virtual boundaries can lie outside the sub-images. This can lead to decoding errors that may negatively impact decoding quality.

[0008] In one example, a method includes: extracting a current sub-image from a bitstream of video data; parsing a virtual boundary syntax element indicating a virtual boundary of the current sub-image associated with the current image; updating the virtual boundary at least in part based on the virtual boundary syntax element; and decoding the current sub-image based on the updated virtual boundary.

[0009] In another example, a device includes: a memory configured to store the video data; and one or more processors implemented in circuitry and communicatively coupled to the memory, the processors being configured to: extract a current sub-image from a bitstream of the video data; parse a virtual boundary syntax element indicating a virtual boundary of the current image, wherein the current sub-image is associated with the current image; update the virtual boundary at least in part based on the virtual boundary syntax element; and decode the current sub-image based on the updated virtual boundary.

[0010] In another example, a non-transitory computer-readable storage medium is encoded with instructions that, when executed, cause one or more processors to: extract a current sub-picture from a bitstream of the video data; parse a virtual boundary syntax element indicating a virtual boundary of the current picture, wherein the current sub-picture is associated with the current picture; update the virtual boundary at least in part based on the virtual boundary syntax element; and decode the current sub-picture based on the updated virtual boundary.

[0011] In another example, the device includes: a unit for extracting a current sub-image from a bitstream of the video data; a unit for parsing a virtual boundary syntax element indicating a virtual boundary of the current image, wherein the current sub-image is associated with the current image; a unit for updating the virtual boundary at least in part based on the virtual boundary syntax element; and a unit for decoding the current sub-image based on the updated virtual boundary.

[0012] Details of one or more examples are set forth in the accompanying drawings and the description below. Other features, objectives, and advantages will be apparent from the specification, drawings, and claims. Attached Figure Description

[0013] Figure 1 This is a block diagram illustrating an example video encoding and decoding system that can perform the techniques described in this disclosure.

[0014] Figure 2 This is a block diagram illustrating an example video encoder that can perform the techniques described in this disclosure.

[0015] Figure 3 This is a block diagram illustrating an example video decoder that can perform the techniques described in this disclosure.

[0016] Figure 4 This is a block diagram illustrating another example video encoding and decoding system that can perform the techniques described in this disclosure.

[0017] Figure 5 This is a flowchart illustrating the example sub-image extraction technique used in this disclosure.

[0018] Figure 6 This is a flowchart illustrating an example of video encoding.

[0019] Figure 7 This is a flowchart illustrating an example of video decoding. Detailed Implementation

[0020] Some sample devices and draft video decoding standards may support the use of virtual boundaries for images and may support treating sub-images as images (e.g., treating them as images). When a sub-image is treated as an image (e.g., treated as an image), the video decoder can extract and decode the sub-image independently of another sub-image within the same image. When the video decoder extracts a sub-image from an image with virtual boundaries, the virtual boundaries may be outside the sub-image. This can lead to decoding errors, which may negatively impact the quality of the decoded video.

[0021] Furthermore, some draft video decoding standards include reference image list constraints. These reference image list constraints may not be suitable for use cases where an image with multiple sub-images is predicted from an inter-layer reference image that has only one sub-image.

[0022] Furthermore, some draft video decoding standards do not require that sub-images be treated as images when sub-image reordering occurs. This can lead to decoding mismatches, which may negatively impact the quality of the decoded video.

[0023] According to the technology disclosed herein, when extracting sub-images of an image with virtual boundaries, the virtual boundaries of the image can be updated. Furthermore, the reference image list constraints can be modified to accommodate use cases where an image with multiple sub-images is predicted from an inter-layer reference image that has only one sub-image. Additionally, constraints can be added such that sub-images are treated as images when they are reordered. Such techniques can improve decoding quality and / or decoding performance.

[0024] Figure 1 This is a block diagram illustrating an example video encoding and decoding system 100 capable of performing the techniques described in this disclosure. In general, the techniques of this disclosure relate to decoding (encoding and / or decoding) video data. In general, video data includes any data used for processing video. Therefore, video data can include raw, unencoded video, encoded video, decoded (e.g., reconstructed) video, and video metadata, such as signaling data.

[0025] like Figure 1As shown, in this example, system 100 includes a source device 102 that provides encoded video data to be decoded and displayed by a destination device 116. Specifically, source device 102 provides video data to destination device 116 via computer-readable medium 110. Source device 102 and destination device 116 can include any of a variety of devices, including desktop computers, laptop computers, mobile devices, tablet computers, set-top boxes, handset telephones (e.g., smartphones), televisions, cameras, display devices, digital media players, video game consoles, video streaming devices, broadcast receivers, and so on. In some cases, source device 102 and destination device 116 may be equipped for wireless communication and therefore may be referred to as wireless communication devices.

[0026] exist Figure 1 In the example, source device 102 includes a video source 104, memory 106, video encoder 200, and output interface 108. Destination device 116 includes an input interface 122, video decoder 300, memory 120, and display device 118. According to this disclosure, the video encoder 200 of source device 102 and the video decoder 300 of destination device 116 can be configured to apply techniques for sub-picture extraction, sub-picture reference picture list (RPL) constraints, and sub-picture reordering constraints. Therefore, source device 102 represents an example of a video encoding device, while destination device 116 represents an example of a video decoding device. In other examples, the source and destination devices may include other components or arrangements. For example, source device 102 may receive video data from an external video source such as an external camera. Similarly, destination device 116 may interface with an external display device, rather than including an integrated display device.

[0027] Figure 1The system 100 shown is merely an example. In general, any digital video encoding and / or decoding device can perform techniques for sub-picture extraction, sub-picture RPL constraints, and sub-picture reordering constraints. Source device 102 and destination device 116 are merely examples of such decoding devices, where source device 102 generates decoded video data for transmission to destination device 116. This disclosure refers to a “decoding” device as a device that performs the decoding (encoding and / or decoding) of data. Thus, video encoder 200 and video decoder 300 represent examples of decoding devices, specifically a video encoder and a video decoder, respectively. In some examples, source device 102 and destination device 116 can operate in a substantially symmetrical manner, such that each of source device 102 and destination device 116 includes video encoding and decoding components. Therefore, system 100 can support one-way or two-way video transmission between source device 102 and destination device 116, for example, for video streaming, video playback, video broadcasting, or video telephony.

[0028] Typically, video source 104 represents the source of video data (i.e., raw, unencoded video data) and provides a series of sequential pictures (also referred to as “frames”) of the video data to video encoder 200, which encodes the data of the pictures. Video source 104 of source device 102 may include a video capture device (e.g., a camera, a video archive containing previously captured raw video, and / or a video feed interface) to receive video from a video content provider. Alternatively, video source 104 may generate computer graphics-based data as source video, or a combination of live video, archived video, and computer-generated video. In each case, video encoder 200 encodes the captured, pre-captured, or computer-generated video data. Video encoder 200 may rearrange the images from the order of reception (sometimes referred to as “display order”) to a decoding order for decoding. Video encoder 200 may generate a bitstream comprising the encoded video data. Source device 102 may then output the encoded video data to computer-readable medium 110 via output interface 108 for reception and / or retrieval via input interface 122 of destination device 116, for example.

[0029] The memory 106 of source device 102 and the memory 120 of destination device 116 represent general-purpose memory. In some examples, memories 106 and 120 may store raw video data, such as raw video from video source 104 and raw, decoded video data from video decoder 300. Additionally or alternatively, memories 106 and 120 may store software instructions executable by, for example, video encoder 200 and video decoder 300. Although memories 106 and 120 are shown separately from video encoder 200 and video decoder 300 in this example, it should be understood that video encoder 200 and video decoder 300 may also include internal memory for functionally similar or equivalent purposes. Furthermore, memories 106 and 120 may store encoded video data, such as encoded video data output from video encoder 200 and input to video decoder 300. In some examples, portions of memories 106 and 120 may be allocated as one or more video buffers, for example, to store raw, decoded, and / or encoded video data.

[0030] Computer-readable medium 110 can represent any type of medium or device capable of transmitting encoded video data from source device 102 to destination device 116. In one example, computer-readable medium 110 represents a communication medium enabling source device 102 to transmit encoded video data directly to destination device 116 in real time, for example, via a radio frequency network or a computer-based network. Output interface 108 can demodulate the transmitted signal including the encoded video data according to a communication standard (e.g., a wireless communication protocol), and input interface 122 can demodulate the received transmitted signal. The communication medium can include any wireless or wired communication medium, such as radio frequency (RF) spectrum or one or more physical transmission lines. The communication medium can form part of a packet-based network, such as a local area network, a wide area network, or a global network such as the Internet. The communication medium can include a router, switch, base station, or any other device that facilitates communication from source device 102 to destination device 116.

[0031] In some examples, source device 102 can output encoded data from output interface 108 to storage device 112. Similarly, destination device 116 can access encoded data from storage device 112 via input interface 122. Storage device 112 can include any of a variety of distributed or locally accessed data storage media, such as hard disk drives, Blu-ray discs, DVDs, CD-ROMs, flash memory, volatile or non-volatile memory, or any other suitable digital storage medium for storing encoded video data.

[0032] In some examples, source device 102 may output encoded video data to file server 114 or another intermediate storage device that may store the encoded video data generated by source device 102. Destination device 116 may access the stored video data from file server 114 via streaming or downloading. File server 114 may be any type of server device capable of storing encoded video data and sending it to destination device 116. File server 114 may represent a web server (e.g., for a website), a file transfer protocol (FTP) server, a content delivery network device, or a network attached storage (NAS) device. Destination device 116 may access the encoded video data from file server 114 via any standard data connection, including an internet connection. This may include a wireless channel (e.g., a Wi-Fi connection), a wired connection (e.g., a digital subscriber line (DSL), a cable modem, etc.), or a combination of both, suitable for accessing the encoded video data stored on file server 114. File server 114 and input interface 122 may be configured to operate according to a streaming protocol, a download protocol, or a combination thereof.

[0033] Output interface 108 and input interface 122 may represent a wireless transmitter / receiver, a modem, a wired network component (e.g., an Ethernet card), a wireless communication component operating according to any of the various IEEE 802.11 standards, or other physical components. In examples where output interface 108 and input interface 122 include wireless components, output interface 108 and input interface 122 may be configured to transmit data (e.g., encoded video data) according to cellular communication standards (e.g., 4G, 4G-LTE (Long Term Evolution), Advanced LTE, 5G, etc.). In some examples where output interface 108 includes a wireless transmitter, output interface 108 and input interface 122 may be configured to transmit data (e.g., encoded video data) according to other wireless standards (e.g., the IEEE 802.11 specification, the IEEE 802.15 specification (e.g., ZigBee™), the Bluetooth™ standard, etc.). In some examples, source device 102 and / or destination device 116 may include their respective system-on-chip (SoC) devices. For example, source device 102 may include a SoC device to perform functions that contribute to video encoder 200 and / or output interface 108, and destination device 116 may include a SoC device to perform functions that contribute to video decoder 300 and / or input interface 122.

[0034] The technology disclosed herein can be applied to video decoding that supports any of a variety of multimedia applications, such as over-the-air television broadcasting, cable television transmission, satellite television transmission, internet streaming video transmission, such as Dynamic Adaptive Streaming (DASH) over HTTP, digital video encoded to a data storage medium, decoding digital video stored on a data storage medium, or other applications.

[0035] The input interface 122 of the destination device 116 receives an encoded video bitstream from a computer-readable medium 110 (e.g., a communication medium, storage device 112, file server 114, etc.). The encoded video bitstream may include signaling information defined by the video encoder 200, which is also used by the video decoder 300, such as syntax elements having values ​​describing the characteristics and / or processing of video blocks or other encoded units (e.g., slices, pictures, picture groups, sequences, etc.). The display device 118 displays a decoded image of the decoded video data to the user. The display device 118 may represent any of a variety of display devices, such as a liquid crystal display (LCD), a plasma display, an organic light-emitting diode (OLED) display, or another type of display device.

[0036] Although not in Figure 1 As shown, but in some examples, the video encoder 200 and video decoder 300 may be integrated with the audio encoder and / or audio decoder, respectively, and may include appropriate MUX-DEMUX units or other hardware and / or software for processing multiplexed streams that include both audio and video in a common data stream. Where applicable, the MUX-DEMUX unit may conform to the ITU H.223 multiplexer protocol or other protocols, such as User Datagram Protocol (UDP).

[0037] The video encoder 200 and video decoder 300 can each be implemented as any of a variety of suitable encoder and / or decoder circuits, such as one or more microprocessors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), discrete logic units, software, hardware, firmware, or any combination thereof. When these technologies are implemented in part in software, the device may store instructions for the software in a suitable non-transitory computer-readable medium and use one or more processors to execute the instructions in hardware to perform the technologies of this disclosure. Each of the video encoder 200 and video decoder 300 may be included in one or more encoders or decoders, any of which may be integrated as part of a combined encoder / decoder (CODEC) in the respective device. Devices including the video encoder 200 and / or video decoder 300 may include integrated circuits, microprocessors, and / or wireless communication devices, such as cellular phones.

[0038] The video encoder 200 and video decoder 300 can operate according to video decoding standards such as ITU-T H.265, also known as High Efficiency Video Coding (HEVC) or its extensions, such as Multi-View and / or Adjustable Video Coding Extensions. Alternatively, the video encoder 200 and video decoder 300 can operate according to other proprietary or industry standards such as ITU-T H.266, also known as Versatile Video Coding (VVC). The latest draft of the VVC standard is described in “Versatile Video Coding (Draft 9)” by Bross et al., ITU-T SG 16 WP 3 and the Joint Video Experts Group (JVET) of ISO / IEC JTC 1 / SC 29 / WG 11, 18th Meeting, Teleconference, April 15-24, 2020, JVET-R2001-v8 (hereinafter referred to as “VVC Draft 9”). However, the technology of this disclosure is not limited to any particular decoding standard.

[0039] Typically, video encoder 200 and video decoder 300 can perform block-based decoding of images. The term "block" generally refers to a structure that includes data to be processed (e.g., data to be encoded and / or decoded, or otherwise to be used during encoding and / or decoding). For example, a block may include a two-dimensional matrix of samples of luminance and / or chrominance data. Typically, video encoder 200 and video decoder 300 can decode video data represented in YUV (e.g., Y, Cb, Cr) format. That is, video encoder 200 and video decoder 300 can decode luminance and chrominance components, rather than decoding the red, green, and blue (RGB) data sampled from the image, where the chrominance components may include red and blue chrominance components. In some examples, video encoder 200 converts the received RGB format data to a YUV representation before encoding, and video decoder 300 converts the YUV representation to RGB format. Alternatively, preprocessing and post-processing units (not shown) can perform these conversions.

[0040] This disclosure may generally refer to the decoding of images (e.g., encoding and decoding) to include the process of encoding or decoding the data of an image. Similarly, this invention may refer to the decoding of blocks of images to include the process of encoding or decoding the data of blocks, such as prediction and / or residual decoding. Encoded video bitstreams typically include a series of values ​​for syntax elements that represent decoding decisions (e.g., decoding modes) and the division of images into blocks. Therefore, references to decoding images or blocks should generally be understood as decoding the values ​​of the syntax elements that form the images or blocks.

[0041] HEVC defines various blocks, including decoding units (CUs), prediction units (PUs), and transform units (TUs). According to HEVC, a video decoder (e.g., a video encoder 200) divides the decoding tree unit (CTU) into CUs according to a quadtree structure. That is, the video decoder divides the CTU and CU into four equal, non-overlapping squares, and each node of the quadtree has zero or four child nodes. Nodes without child nodes can be called "leaf nodes," and the CU of such leaf nodes can include one or more PUs and / or one or more TUs. The video decoder can further divide the PUs and TUs. For example, in HEVC, a residual quadtree (RQT) represents the partitioning of TUs. In HEVC, PUs represent inter-prediction data, while TUs represent residual data. Intra-prediction CUs include intra-prediction information, such as intra-mode indicators.

[0042] As another example, video encoder 200 and video decoder 300 can be configured to operate according to VVC. According to VVC, the video decoder (e.g., video encoder 200) partitions the image into multiple decoding tree units (CTUs). Video encoder 200 can partition the CTUs according to a tree structure (e.g., a quadtree-binary tree (QTBT) structure or a multi-type tree (MTT) structure). The QTBT structure eliminates the concept of multiple partition types, such as the separation between CUs, PUs, and TUs in HEVC. The QTBT structure includes two levels: a first level partitioned according to quadtree partitioning, and a second level partitioned according to binary tree partitioning. The root node of the QTBT structure corresponds to a CTU. The leaf nodes of the binary tree correspond to decoding units (CUs).

[0043] In the MTT partitioning structure, blocks can be divided using quadtree (QT) partitioning, binary tree (BT) partitioning, and one or more types of ternary tree (TT) partitioning (also known as triplet tree (TT)). A ternary tree or triplet tree partition is a partitioning method that divides a block into three sub-blocks. In some examples, a ternary tree or triplet tree partition divides a block into three sub-blocks instead of partitioning the original block by a center. Partition types in MTT (e.g., QT, BT, and TT) can be symmetric or asymmetric.

[0044] In some examples, the video encoder 200 and the video decoder 300 may use a single QTBT or MTT structure to represent each of the luma and chroma components, while in other examples, the video encoder 200 and the video decoder 300 may use two or more QTBT or MTT structures, for example, one QTBT / MTT structure for the luma component and another QTBT / MTT structure for the two chroma components (or two QTBT / MTT structures for the respective chroma components).

[0045] The video encoder 200 and video decoder 300 can be configured to use quadtree partitioning for each HEVC, QTBT, MTT, or other partitioning structure. For illustrative purposes, a description of the techniques of this disclosure is given for QTBT partitioning. However, it should be understood that the techniques of this disclosure can also be applied to video decoders configured to use quadtree partitioning or other types of partitioning.

[0046] In some examples, a CTU includes a decoded tree block (CTB) for luminance sampling, two corresponding CTBs for chrominance sampling of an image with three sampled arrays, or a CTB for sampling of a monochrome image or an image decoded using three separate color planes and a syntax structure for decoding the samples. A CTB can be an NxN sampled block for some value of N, such that partitioning the components into CTBs is a partition. A component is an array or a single sample from one of the three arrays (luminance and two chrominance) that make up an image in a 4:2:0, 4:2:2, or 4:4:4 color format, or an array or a single sample from an array that makes up a monochrome image. In some examples, a decoded block is an MxN sampled block for some values ​​of M and N, such that partitioning the CTB into decoded blocks is a partition.

[0047] Blocks (e.g., CTUs or CUs) can be grouped within an image in various ways. As an example, a brick can refer to a rectangular area within a row of CTUs in an image, specifically within a tile. A tile can be a rectangular area of ​​a CTU within a specific tile column or row. A tile column is a rectangular area of ​​a CTU with a height equal to the image height and a width specified by a syntax element (e.g., as specified in the image parameter set). A tile row is a rectangular area of ​​a CTU with a height specified by a syntax element (e.g., as in the image parameter set) and a width equal to the image width.

[0048] In some examples, a tile can be divided into multiple bricks, each brick potentially including one or more CTU rows within the tile. A tile that is not divided into multiple bricks can also be referred to as a brick. However, a brick that is a true subset of a tile cannot be referred to as a tile.

[0049] The bricks in an image can also be arranged as slices. A slice can be an integer number of bricks in the image, which can be exclusively contained within a single Network Abstraction Layer (NAL) unit. In some examples, a slice consists of multiple complete tiles or a consecutive sequence of complete bricks consisting of only one tile.

[0050] This disclosure uses "NxN" and "N by N" interchangeably to refer to the sampling dimensions of a block (e.g., a CU or other video block) in both the vertical and horizontal dimensions, such as 16x16 samples or 16 by 16 samples. Typically, a 16x16 CU will have 16 samples in the vertical direction (y = 16) and 16 samples in the horizontal direction (x = 16). Similarly, an NxN CU typically has N samples in the vertical direction and N samples in the horizontal direction, where N represents a non-negative integer value. Samples in a CU can be arranged in rows and columns. Furthermore, a CU does not necessarily have the same number of samples in the horizontal direction as it does in the vertical direction. For example, a CU may include N×M samples, where M is not necessarily equal to N.

[0051] The video encoder 200 encodes video data of the CU (Cubic Containment Unit), which represents prediction and / or residual information, as well as other information. The prediction information indicates how the CU will be predicted to form a prediction block for the CU. The residual information typically represents the sample-by-sample difference between the CU samples before encoding and the prediction block.

[0052] To predict the Cubic Frame (CU), the video encoder 200 typically forms prediction blocks for the CU using either inter-prediction or intra-prediction. Inter-prediction generally refers to predicting the CU based on data from previously decoded images, while intra-prediction generally refers to predicting the CU based on data from previously decoded images of the same image. To perform inter-prediction, the video encoder 200 can use one or more motion vectors to generate prediction blocks. The video encoder 200 can typically perform motion search to identify, for example, reference blocks that closely match the CU in terms of differences between the CU and reference blocks. The video encoder 200 can use sum of absolute differences (SAD), sum of squared differences (SSD), mean absolute difference (MAD), mean squared difference (MSD), or other such differences to calculate difference metrics to determine whether the reference block closely matches the current CU. In some examples, the video encoder 200 can use unidirectional or bidirectional prediction to predict the current CU.

[0053] Some examples of VVC also provide an affine motion compensation mode, which can be viewed as an inter-prediction mode. In the affine motion compensation mode, the video encoder 200 can determine two or more motion vectors representing non-translational motion (such as zooming in or out, rotation, perspective motion, or other irregular motion types).

[0054] To perform intra-prediction, the video encoder 200 can select an intra-prediction mode to generate prediction blocks. Some examples of VVC provide 67 intra-prediction modes, including various orientation modes as well as planar and DC modes. Typically, the video encoder 200 selects an intra-prediction mode that describes the samples adjacent to the current block (e.g., the block of the CU), predicting samples of the current block from these adjacent samples. Assuming the video encoder 200 decodes the CTU and CU in raster scan order (from left to right, from top to bottom), such samples can typically be above, above left, or to the left of the current block in the same picture as the current block.

[0055] The video encoder 200 encodes data representing the prediction mode of the current block. For example, for inter-prediction modes, the video encoder 200 may encode data indicating which of the various available inter-prediction modes is used, as well as the motion information of the corresponding mode. For unidirectional or bidirectional inter-prediction, for example, the video encoder 200 may use Advanced Motion Vector Prediction (AMVP) or merging modes to encode motion vectors. The video encoder 200 may use similar modes to encode motion vectors for affine motion compensation modes.

[0056] After prediction (e.g., intra-block or inter-block prediction), the video encoder 200 can compute residual data for that block. The residual data (e.g., a residual block) represents the sample-by-sample difference between that block and the predicted block formed using the corresponding prediction mode. The video encoder 200 can apply one or more transforms to the residual block to produce transformed data in the transform domain rather than the sampling domain. For example, the video encoder 200 can apply a Discrete Cosine Transform (DCT), an integer transform, a wavelet transform, or a conceptually similar transform to the residual video data. Additionally, the video encoder 200 can apply a secondary transform after the first transform, such as a mode-dependent inseparable secondary transform (MDNSST), a signal-dependent transform, a Karhunen-Loeve transform (KLT), etc. The video encoder 200 produces transform coefficients after applying one or more transforms.

[0057] As described above, after performing any transformation to produce transform coefficients, the video encoder 200 can perform quantization of the transform coefficients. Quantization typically refers to the process of quantizing the transform coefficients to potentially reduce the amount of data used to represent them, thereby providing further compression. By performing the quantization process, the video encoder 200 can reduce the bit depth associated with some or all of the transform coefficients. For example, the video encoder 200 can round down an n-bit value to an m-bit value during quantization, where n is greater than m. In some examples, to perform quantization, the video encoder 200 can perform a bitwise right shift of the value to be quantized.

[0058] After quantization, the video encoder 200 can scan the transform coefficients to generate a one-dimensional vector from a two-dimensional matrix including the quantized transform coefficients. The scan can be designed to place higher-energy (and therefore lower-frequency) transform coefficients at the beginning of the vector and lower-energy (and therefore higher-frequency) transform coefficients at the end. In some examples, the video encoder 200 can utilize a predefined scan order to scan the quantized transform coefficients to produce a serialized vector, and then entropy-encode the quantized transform coefficients of the vector. In other examples, the video encoder 200 can perform adaptive scanning. After scanning the quantized transform coefficients to form a one-dimensional vector, the video encoder 200 can entropy-encode the one-dimensional vector, for example, according to context-adaptive binary arithmetic decoding (CABAC). The video encoder 200 can also entropy-encode the values ​​of syntax elements that describe metadata associated with the encoded video data for use by the video decoder 300 when decoding the video data.

[0059] To perform CABAC, the video encoder 200 can assign context within a context model to the symbols to be transmitted. The context may involve, for example, whether the neighboring values ​​of a symbol are zero. Probability determination can be based on the context assigned to the symbol.

[0060] The video encoder 200 can also generate syntax data for the video decoder 300, for example, in image headers, block headers, slice headers, or other syntax data (such as sequence parameter sets (SPS), picture parameter sets (PPS), or video parameter sets (VPS)). Examples of syntax data include block-based syntax data, image-based syntax data, and sequence-based syntax data. The video decoder 300 can similarly decode such syntax data to determine how to decode the corresponding video data.

[0061] In this manner, the video encoder 200 can generate a bitstream including encoded video data, such as syntax elements describing the division of images into blocks (e.g., CUs) and prediction and / or residual information for each block. Finally, the video decoder 300 can receive the bitstream and decode the encoded video data.

[0062] Typically, the video decoder 300 performs a process that is the reverse of that performed by the video encoder 200 to decode the encoded video data of the bitstream. For example, the video decoder 300 can use CABAC to decode the values ​​of the syntax elements of the bitstream in a manner substantially similar to (albeit the reverse of) the CABAC encoding process of the video encoder 200. Syntax elements can define partitioning information for dividing images into CTUs, and partitioning each CTU according to a corresponding partitioning structure (e.g., a QTBT structure) to define the CUs of the CTUs. Syntax elements can also define prediction and residual information for blocks (e.g., CUs) of video data.

[0063] The residual information can be represented, for example, by quantized transform coefficients. The video decoder 300 can inversely quantize and inverse transform the quantized transform coefficients of the block to reproduce the residual block of that block. The video decoder 300 uses the prediction pattern (intra-prediction or inter-prediction) conveyed by the signal and associated prediction information (e.g., motion information for inter-prediction) to form a prediction block for that block. The video decoder 300 can then combine the prediction block and the residual block (sample-by-sample) to reproduce the original block. The video decoder 300 can perform additional processing, such as performing a deblocking process to reduce visual artifacts along the block boundaries.

[0064] Some example devices (such as video encoder 200 and video decoder 300) and draft video decoding standards may support the use of virtual boundaries for images and may support treating sub-images as images (e.g., processing or decoding as images, such as encoding or decoding). When a sub-image is treated as an image (e.g., processed or decoded as an image, such as encoding or decoding), the video decoder can extract and decode the sub-image independently of another sub-image within the same image. When the video decoder extracts a sub-image from an image with virtual boundaries, the virtual boundaries may be outside the sub-image. This can lead to decoding errors, which may negatively impact the quality of the decoded video.

[0065] According to the technology of this disclosure, a method includes: extracting a current sub-image from a bitstream of video data; parsing a virtual boundary syntax element indicating a virtual boundary of the current image, the current sub-image being associated with the current image; updating the virtual boundary at least in part based on the virtual boundary syntax element; and decoding the current sub-image based on the updated virtual boundary.

[0066] According to the technology of this disclosure, an apparatus includes: a memory configured to store the video data; and one or more processors implemented in circuitry and communicatively coupled to the memory, the one or more processors being configured to: extract a current sub-image from a bitstream of the video data; parse a virtual boundary syntax element indicating a virtual boundary of the current image, wherein the current sub-image is associated with the current image; update the virtual boundary at least in part based on the virtual boundary syntax element; and decode the current sub-image based on the updated virtual boundary.

[0067] According to the technology of this disclosure, a non-transitory computer-readable storage medium is encoded with instructions that, when executed, cause one or more processors to: extract a current sub-picture from a bitstream of video data; parse a virtual boundary syntax element indicating a virtual boundary of the current picture, wherein the current sub-picture is associated with the current picture; update the virtual boundary at least in part based on the virtual boundary syntax element; and decode the current sub-picture based on the updated virtual boundary.

[0068] According to the technology disclosed herein, an apparatus includes: a unit for extracting a current sub-image from a bitstream of video data; a unit for parsing a virtual boundary syntax element indicating a virtual boundary of the current image, wherein the current sub-image is associated with the current image; a unit for updating a virtual boundary at least in part based on the virtual boundary syntax element; and a unit for decoding the current sub-image based on the updated virtual boundary.

[0069] This disclosure may be used broadly to refer to the "signaling" of certain information, such as syntax elements. The term "signaling" generally refers to the communication of values ​​for syntax elements and / or other data used to decode encoded video data. That is, the video encoder 200 can signal the values ​​of syntax elements in the bitstream. Typically, signaling refers to generating values ​​in the bitstream. As described above, the source device 102 can transmit the bitstream to the destination device 116 substantially in real time or not in real time, for example, when storing syntax elements in storage device 112 for later retrieval by the destination device 116.

[0070] Figure 2 This is a block diagram illustrating an example video encoder 200 capable of performing the techniques described in this disclosure. Figure 2 This disclosure is for illustrative purposes and should not be construed as limiting the techniques extensively illustrated and described herein. For illustrative purposes, this disclosure describes a video encoder 200 based on VVC (ITU-T H.266 under development) and HEVC (ITU-TH.265) technologies. However, the techniques of this disclosure can be implemented by video encoding devices configured for other video decoding standards.

[0071] exist Figure 2In the example, the video encoder 200 includes a video data memory 230, a mode selection unit 202, a residual generation unit 204, a transform processing unit 206, a quantization unit 208, an inverse quantization unit 210, an inverse transform processing unit 212, a reconstruction unit 214, a filter unit 216, a decoded picture buffer (DPB) 218, and an entropy coding unit 220. Any one or all of the video data memory 230, mode selection unit 202, residual generation unit 204, transform processing unit 206, quantization unit 208, inverse quantization unit 210, inverse transform processing unit 212, reconstruction unit 214, filter unit 216, DPB 218, and entropy coding unit 220 can be implemented in one or more processors or in processing circuitry. For example, the units of the video encoder 200 can be implemented as one or more circuit or logic elements as part of hardware circuitry, or as part of a processor, ASIC, or FPGA. Furthermore, the video encoder 200 may include additional or alternative processors or processing circuitry to perform these and other functions.

[0072] The video data storage device 230 can store video data to be encoded by the components of the video encoder 200. The video encoder 200 can obtain data from, for example, a video source 104 (…). Figure 1 The video encoder 200 receives video data stored in video data memory 230. DPB 218 can be used as a reference image memory, storing reference video data for use by the video encoder 200 when predicting subsequent video data. Video data memory 230 and DPB 218 can be formed from any of a variety of memory devices, such as dynamic random access memory (DRAM), including synchronous DRAM (SDRAM), magnetoresistive RAM (MRAM), resistive RAM (RRAM), or other types of memory devices. Video data memory 230 and DPB 218 can be provided by the same memory device or separate memory devices. In various examples, video data memory 230 can be on-chip along with other components of the video encoder 200, as shown, or off-chip relative to those components.

[0073] In this disclosure, unless so specifically described, references to video data memory 230 should not be construed as being limited to memory internal to video encoder 200; or, unless so specifically described, references to video data memory 230 should not be construed as being limited to memory external to video encoder 200. Rather, references to video data memory 230 should be understood as reference memory storing video data received by video encoder 200 for encoding (e.g., video data for the current block to be encoded). Figure 1 The memory 106 can also provide temporary storage for the outputs of the various units of the video encoder 200.

[0074] It shows Figure 2 The various units help to understand the operations performed by the video encoder 200. These units can be implemented as fixed-function circuits, programmable circuits, or a combination thereof. A fixed-function circuit is a circuit that provides a specific function and is pre-configured for the operations that can be performed. A programmable circuit is a circuit that can be programmed to perform various tasks and provides flexible functionality in the operations that can be performed. For example, a programmable circuit can execute software or firmware that causes the programmable circuit to operate in a manner defined by software or firmware instructions. A fixed-function circuit can execute software instructions (e.g., to receive or output parameters), but the type of operation performed by a fixed-function circuit is generally immutable. In some examples, one or more of these units can be different circuit blocks (fixed-function or programmable), and in some examples, one or more of these units can be integrated circuits.

[0075] The video encoder 200 may include an arithmetic logic unit (ALU), an essential function unit (EFU), digital circuitry, analog circuitry, and / or a programmable core formed from programmable circuitry. In an example where the operation of the video encoder 200 is performed using software executed by programmable circuitry, memory 106 ( Figure 1 The video encoder 200 may store instructions (e.g., object code) of the software received and executed by the video encoder 200, or another memory (not shown) within the video encoder 200 may store these instructions.

[0076] The video data storage unit 230 is configured to store received video data. The video encoder 200 can retrieve images of the video data from the video data storage unit 230 and provide the video data to the residual generation unit 204 and the mode selection unit 202. The video data in the video data storage unit 230 can be the raw video data to be encoded.

[0077] The mode selection unit 202 includes a motion estimation unit 222, a motion compensation unit 224, and an intraprediction unit 226. The mode selection unit 202 may include additional functional units to perform video prediction based on other prediction modes. As an example, the mode selection unit 202 may include a palette unit, an intra-block copy unit (which may be part of the motion estimation unit 222 and / or the motion compensation unit 224), an affine unit, a linear model (LM) unit, and so on.

[0078] Mode selection unit 202 typically coordinates multiple coding paths to test combinations of coding parameters and the resulting rate distortion values ​​for these combinations. Coding parameters may include dividing the CTU into CUs, the prediction mode for the CUs, the transform type for the residual data of the CUs, the quantization parameters for the residual data of the CUs, and so on. Mode selection unit 202 can ultimately select a combination of coding parameters that has a better rate distortion value than other tested combinations.

[0079] The video encoder 200 can divide images retrieved from the video data storage 230 into a series of CTUs and encapsulate one or more CTUs within a slice. The mode selection unit 202 can divide the image into CTUs according to a tree structure (such as the QTBT structure or quadtree structure of HEVC described above). As mentioned above, the video encoder 200 can form one or more CUs by dividing CTUs according to a tree structure. Such CUs can also generally be referred to as "video blocks" or "blocks".

[0080] In summary, the mode selection unit 202 also controls its components (e.g., motion estimation unit 222, motion compensation unit 224, and intraprediction unit 226) to generate predicted blocks for the current block (e.g., the current CU, or, in HEVC, the overlapping portion of PU and TU). For interprediction of the current block, the motion estimation unit 222 may perform a motion search to identify one or more closely matching reference blocks in one or more reference images (e.g., one or more previously encoded images stored in DPB 218). Specifically, the motion estimation unit 222 may calculate values ​​representing the similarity between the potential reference block and the current block, for example, based on sum of absolute differences (SAD), sum of squared differences (SSD), mean absolute difference (MAD), mean squared difference (MSD), etc. The motion estimation unit 222 may typically perform these calculations using sample-wise differences between the current block and the considered reference blocks. The motion estimation unit 222 may identify reference blocks with the lowest values ​​produced by these calculations, the lowest value indicating the reference block that most closely matches the current block.

[0081] Motion estimation unit 222 can generate one or more motion vectors (MVs) that define the position of a reference block in a reference image relative to the position of the current block in the current image. Motion estimation unit 222 can then provide the motion vectors to motion compensation unit 224. For example, for one-way inter-prediction, motion estimation unit 222 can provide a single motion vector, while for two-way inter-prediction, motion estimation unit 222 can provide two motion vectors. Motion compensation unit 224 can then use the motion vectors to generate prediction blocks. For example, motion compensation unit 224 can use the motion vectors to retrieve data for the reference blocks. As another example, if the motion vectors have fractional sampling precision, motion compensation unit 224 can interpolate the values ​​of the prediction blocks according to one or more interpolation filters. Furthermore, for two-way inter-prediction, motion compensation unit 224 can retrieve data for two reference blocks identified by corresponding motion vectors and combine the retrieved data (e.g., by sample-wise averaging or weighted averaging).

[0082] As another example, for intraprediction or intraprediction decoding, intraprediction unit 226 can generate a prediction block based on samples adjacent to the current block. For example, in directional mode, intraprediction unit 226 can typically mathematically combine the values ​​of adjacent samples and fill these calculated values ​​into the current block along a defined direction to generate a prediction block. As another example, in DC mode, intraprediction unit 226 can calculate the average of adjacent samples up to the current block and generate a prediction block to include this resulting average for each sample of the prediction block.

[0083] Mode selection unit 202 provides a prediction block to residual generation unit 204. Residual generation unit 204 receives the original uncoded version of the current block from video data memory 230 and the prediction block from mode selection unit 202. Residual generation unit 204 calculates the sample-by-sample difference between the current block and the prediction block. The resulting sample-by-sample difference defines the residual block for the current block. In some examples, residual generation unit 204 may also determine the difference between sampled values ​​in the residual block to generate the residual block using residual differential pulse code modulation (RDPCM). In some examples, one or more subtractor circuits performing binary subtraction may be used to form residual generation unit 204.

[0084] In the example where mode selection unit 202 divides a CU into PUs, each PU can be associated with a luminance prediction unit and a corresponding chrominance prediction unit. Video encoder 200 and video decoder 300 can support PUs of various sizes. As mentioned above, the size of a CU can refer to the size of its luminance decoding block, while the size of a PU can refer to the size of the luminance prediction unit of the PU. Assuming a particular CU has a size of 2Nx2N, video encoder 200 can support PU sizes of 2Nx2N or NxN for intra-prediction, and symmetrical PU sizes of 2Nx2N, 2NxN, Nx2N, NxN, or similar for inter-prediction. Video encoder 200 and video decoder 300 can also support asymmetric partitioning of PU sizes of 2NxnU, 2NxnD, nLx2N, and nRx2N for inter-prediction.

[0085] In instances where the mode selection unit 202 does not further divide the CU into PUs, each CU can be associated with a luma decoding block and a corresponding chroma decoding block. As mentioned above, the size of the CU can refer to the size of the luma encoding block of the CU. The video encoder 200 and the video decoder 300 can support CU sizes of 2N×2N, 2N×N, or N×2N.

[0086] For other video decoding techniques (e.g., intra-block copy mode decoding, affine mode decoding, and linear model (LM) mode decoding, to name a few), mode selection unit 202 generates a prediction block for the current block being encoded via various units associated with the decoding technique. In some examples (e.g., palette mode decoding), mode selection unit 202 may not generate a prediction block, but instead generate syntax elements indicating how the block will be reconstructed based on the selected palette. In such a mode, mode selection unit 202 can provide these syntax elements to entropy coding unit 220 for encoding.

[0087] As described above, the residual generation unit 204 receives video data of the current block and the corresponding prediction block. The residual generation unit 204 then generates a residual block for the current block. To generate the residual block, the residual generation unit 204 calculates the sample-by-sample difference between the prediction block and the current block.

[0088] Transform processing unit 206 applies one or more transformations to the residual block to generate a block of transform coefficients (referred to herein as a "transform coefficient block"). Transform processing unit 206 can apply various transformations to the residual block to form the transform coefficient block. For example, transform processing unit 206 can apply a Discrete Cosine Transform (DCT), direction transformation, Karhunen-Loeve Transform (KLT), or conceptually similar transformations to the residual block. In some examples, transform processing unit 206 can perform multiple transformations on the residual block, such as primary and secondary transformations, such as rotation transformations. In some examples, transform processing unit 206 does not apply any transformations to the residual block.

[0089] Quantization unit 208 can quantize the transform coefficients in the transform coefficient block to produce a quantized transform coefficient block. Quantization unit 208 can quantize the transform coefficients of the transform coefficient block based on the quantization parameter (QP) value associated with the current block. Video encoder 200 (e.g., via mode selection unit 202) can adjust the degree of quantization applied to the transform coefficient block associated with the current block by adjusting the QP value associated with the CU. Quantization may result in information loss; therefore, the accuracy of the quantized transform coefficients may be lower than the accuracy of the original transform coefficients generated by transform processing unit 206.

[0090] The inverse quantization unit 210 and the inverse transform processing unit 212 can apply inverse quantization and inverse transform to the quantized transform coefficient block, respectively, to reconstruct the residual block from the transform coefficient block. The reconstruction unit 214 can generate a reconstructed block corresponding to the current block based on the reconstructed residual block and the prediction block generated by the mode selection unit 202 (although it may have some degree of distortion). For example, the reconstruction unit 214 can add samples of the reconstructed residual block to corresponding samples of the prediction block generated by the mode selection unit 202 to generate the reconstructed block.

[0091] Filter unit 216 can perform one or more filtering operations on the reconstructed block. For example, filter unit 216 can perform a deblocking operation to reduce blocky artifacts along the edges of the CU. In some examples, the operation of filter unit 216 can be skipped.

[0092] The video encoder 200 stores the reconstructed blocks in the DPB 218. For example, in an example where the operation of the filter unit 216 is not required, the reconstruction unit 214 can store the reconstructed blocks in the DPB 218. In an example where the operation of the filter unit 216 is required, the filter unit 216 can store the filtered reconstructed blocks in the DPB 218. The motion estimation unit 222 and the motion compensation unit 224 can retrieve a reference image formed by the reconstructed (and possibly filtered) blocks from the DPB 218 to perform inter-block prediction for the subsequently encoded image. Furthermore, the intra-prediction unit 226 can use the reconstructed blocks in the DPB 218 of the current image to perform intra-block prediction for other blocks in the current image.

[0093] Typically, entropy coding unit 220 can entropy-encode syntax elements received from other functional components of video encoder 200. For example, entropy coding unit 220 can entropy-encode quantized transform coefficient blocks from quantization unit 208. As another example, entropy coding unit 220 can entropy-encode predictive syntax elements (e.g., motion information for inter-prediction or intra-prediction information for intra-prediction) from mode selection unit 202. Entropy coding unit 220 can perform one or more entropy coding operations on syntax elements, another example of video data, to generate entropy-coded data. For example, entropy coding unit 220 can perform context-adaptive variable-length coding (CAVLC), CABAC, variable-to-variable (V2V) length coding, syntax-based context-adaptive binary arithmetic coding (SBAC), probability interval partitioning entropy (PIPE) coding, exponential Golomb coding, or another entropy coding operation on the data. In some examples, entropy coding unit 220 can operate in a bypass mode where syntax elements are not entropy-encoded.

[0094] The video encoder 200 can output a bitstream containing the entropy-coded syntax elements required to reconstruct slices or images. In particular, the entropy coding unit 220 can output a bitstream.

[0095] The above operations are described for blocks. Such descriptions should be understood as operations applied to the luma decoding block and / or chroma decoding block. As mentioned above, in some examples, the luma decoding block and chroma decoding block are the luma and chroma components of the CU. In some examples, the luma decoding block and chroma decoding block are the luma and chroma components of the PU.

[0096] In some examples, it is not necessary to repeat the operations performed for the luma decoding block for the chroma decoding block. As an example, it is not necessary to repeat the operations used to identify the motion vector (MV) and reference image for the luma decoding block to identify the MV and reference image for the chroma block. Instead, the MV for the luma decoding block can be adjusted to determine the MV for the chroma block, and the reference image can be the same. As another example, the intraprediction process can be the same for both the luma and chroma decoding blocks.

[0097] Figure 3 This is a block diagram illustrating an example video decoder 300 capable of performing the techniques described in this disclosure. Figure 3 This disclosure is for illustrative purposes and does not limit the techniques broadly illustrated and described herein. For illustrative purposes, this disclosure describes a video decoder 300 based on VVC (ITU-T H.266 under development) and HEVC (ITU-T H.265) technologies. However, the techniques of this disclosure can be implemented by video decoding devices configured for other video decoding standards.

[0098] exist Figure 3 In the example, the video decoder 300 includes an encoded picture buffer (CPB) memory 320, an entropy decoding unit 302, a prediction processing unit 304, an inverse quantization unit 306, an inverse transform processing unit 308, a reconstruction unit 310, a filter unit 312, and a decoded picture buffer (DPB) 314. Any one or all of the CPB memory 320, entropy decoding unit 302, prediction processing unit 304, inverse quantization unit 306, inverse transform processing unit 308, reconstruction unit 310, filter unit 312, and DPB 314 can be implemented in one or more processors or in processing circuitry. For example, units of the video decoder 300 can be implemented as one or more circuit or logic elements as part of hardware circuitry, or as part of a processor, ASIC, or FPGA. Furthermore, the video decoder 300 may include additional or alternative processors or processing circuitry to perform these and other functions.

[0099] The prediction processing unit 304 includes a motion compensation unit 316 and an intra-prediction unit 318. The prediction processing unit 304 may include additional units to perform predictions based on other prediction modes. As an example, the prediction processing unit 304 may include a palette unit, an intra-block copy unit (which may form part of the motion compensation unit 316), an affine unit, a linear model (LM) unit, and so on. In other examples, the video decoder 300 may include more, fewer, or different functional components.

[0100] CPB memory 320 can store video data (e.g., encoded video bitstream) that will be decoded by components of video decoder 300. This data can be stored, for example, from computer-readable medium 110 (…). Figure 1 The video decoder 300 obtains video data stored in the CPB memory 320. The CPB memory 320 may include a CPB storing encoded video data (e.g., syntax elements) from the encoded video bitstream. Furthermore, the CPB memory 320 may store video data other than the syntax elements of the decoded picture, such as temporary data representing the output from various units of the video decoder 300. The DPB 314 typically stores decoded pictures, which the video decoder 300 may output and / or use as reference video data when decoding subsequent data or pictures of the encoded video bitstream. The CPB memory 320 and DPB 314 may be formed from any of a variety of storage devices (e.g., DRAM (including SDRAM), MRAM, RRAM, or other types of storage devices). The CPB memory 320 and DPB 314 may be provided by the same memory device or separate memory devices. In various examples, the CPB memory 320 may be on-chip along with other components of the video decoder 300, or off-chip relative to those components.

[0101] Additionally or alternatively, in some examples, the video decoder 300 can be generated from the memory 120 ( Figure 1 The decoded video data is retrieved. That is, memory 120 can store data as discussed above for CPB memory 320. Similarly, when some or all of the functions of video decoder 300 are implemented in software to be executed by the processing circuitry of video decoder 300, memory 120 can store instructions to be executed by video decoder 300.

[0102] It shows Figure 3 The various units help understand the operations performed by the video decoder 300. These units can be implemented as fixed-function circuits, programmable circuits, or a combination thereof. Figure 2 Similarly, a fixed-function circuit is a circuit that provides a specific function and is pre-configured for the operations it can perform. A programmable circuit is a circuit that can be programmed to perform various tasks and provides flexible functionality in the operations it can perform. For example, a programmable circuit can execute software or firmware that causes it to operate in a manner defined by software or firmware instructions. A fixed-function circuit can execute software instructions (e.g., to receive or output parameters), but the type of operation performed by a fixed-function circuit is typically immutable. In some examples, one or more of these units may be different circuit blocks (fixed-function or programmable), and in some examples, one or more of these units may be integrated circuits.

[0103] The video decoder 300 may include an ALU, an EFU, digital circuitry, analog circuitry, and / or a programmable core formed by programmable circuitry. In an example where the operation of the video decoder 300 is performed by software executed on the programmable circuitry, on-chip or off-chip memory may store instructions (e.g., object code) of the software received and executed by the video decoder 300.

[0104] Entropy decoding unit 302 can receive encoded video data from the CPB and perform entropy decoding on the video data to reproduce the syntax elements. Prediction processing unit 304, inverse quantization unit 306, inverse transform processing unit 308, reconstruction unit 310, and filter unit 312 can generate decoded video data based on the syntax elements extracted from the bitstream.

[0105] Typically, the video decoder 300 reconstructs the image block by block. The video decoder 300 can perform the reconstruction operation on each block individually (where the block currently being reconstructed, i.e., decoded, can be referred to as the "current block").

[0106] Entropy decoding unit 302 can entropy decode syntax elements that define the following: quantized transform coefficients of a quantized transform coefficient block, and transform information such as quantization parameters (QP) and / or transform mode indications. Inverse quantization unit 306 can determine the quantization degree using the QP associated with the quantized transform coefficient block, and similarly, determine the inverse quantization degree for application by inverse quantization unit 306. Inverse quantization unit 306 can, for example, perform a bitwise left shift operation to inverse quantize the quantized transform coefficients. Inverse quantization unit 306 can thus form a transform coefficient block including the transform coefficients. In some examples, entropy decoding unit 302 can extract the current sub-picture from the bitstream of video data and parse virtual boundary syntax elements indicating virtual boundaries of the picture.

[0107] After the inverse quantization unit 306 forms the transform coefficient block, the inverse transform processing unit 308 can apply one or more inverse transforms to the transform coefficient block to generate a residual block associated with the current block. For example, the inverse transform processing unit 308 can apply an inverse DCT, an inverse integer transform, an inverse Karhunen-Loeve transform (KLT), an inverse rotation transform, an inverse direction transform, or another inverse transform to the transform coefficient block.

[0108] Furthermore, the prediction processing unit 304 generates a prediction block based on the prediction information syntax elements entropy-decoded by the entropy decoding unit 302. For example, if the prediction information syntax elements indicate that the current block is inter-predicted, the motion compensation unit 316 can generate the prediction block. In this case, the prediction information syntax elements may indicate a reference image from which a reference block is retrieved in the DPB 314, and a motion vector for identifying the position of the reference block in the reference image relative to the current block position in the current image. The motion compensation unit 316 can typically perform the inter-prediction process in a manner substantially similar to that described for the motion compensation unit 224. Figure 2 ).

[0109] As another example, if the prediction information syntax element indicates that the current block is intrapredictive, then intrapredictive unit 318 can generate a prediction block based on the intrapredictive pattern indicated by the prediction information syntax element. Again, intrapredictive unit 318 can typically be used in conjunction with intrapredictive unit 226 ( Figure 2 The intraprediction process is performed in a manner substantially similar to that described above. The intraprediction unit 318 can retrieve data from adjacent samples of the current block from the DPB 314.

[0110] Reconstruction unit 310 can reconstruct the current block using prediction blocks and residual blocks. For example, reconstruction unit 310 can add samples from the residual block to the corresponding samples from the prediction block to reconstruct the current block. In some examples, reconstruction unit 310 can decode the current sub-image based on updated virtual boundaries.

[0111] Filter unit 312 can perform one or more filtering operations on the reconstructed block. For example, filter unit 312 can perform a deblocking operation to reduce blocky artifacts along the edges of the reconstructed block. The operation of filter unit 312 is not necessarily performed in all examples.

[0112] The video decoder 300 can store reconstructed blocks in the DPB 314. For example, in an example where the filter unit 312 is not operated, the reconstruction unit 310 can store the reconstructed blocks in the DPB 314. In an example where the filter unit 312 is operated, the filter unit 312 can store the filtered reconstructed blocks in the DPB 314. As discussed above, the DPB 314 can provide reference information to the prediction processing unit 304, such as samples of the current image for intraprediction and previously decoded images for subsequent motion compensation. Furthermore, the video decoder 300 can output decoded images (e.g., decoded video) from the DPB 314 for subsequent display on a display device (e.g., [device name missing]). Figure 1 It is displayed on the display device 118.

[0113] In this manner, video decoder 300 represents an example of a video decoding device, comprising: a memory configured to store video data; and one or more processors implemented in circuitry and communicatively coupled to the memory, the one or more processors being configured to: extract a current sub-picture from a bitstream of video data; parse a virtual boundary syntax element indicating a virtual boundary of the current picture, wherein the current sub-picture is associated with the current picture; update the virtual boundary at least in part based on the virtual boundary syntax element; and decode the current sub-picture based on the updated virtual boundary.

[0114] Figure 4 This is a block diagram illustrating another example video encoding and decoding system that can perform the techniques described in this disclosure. Figure 4 Examples include source device 102, which includes video encoder 200; and destination device 136, which includes bitstream extractor 250 and video decoder 300. Bitstream extractor 250 can be configured to extract the current sub-picture from the bitstream of video data. In some examples, bitstream extractor 250 can be configured to parse virtual boundary syntax elements indicating the virtual boundaries of the current sub-picture associated with it. For example, bitstream extractor 250 may include entropy decoding unit 252 (shown as EDU 252), similar to entropy decoding unit 302 of video decoder 300, which can parse virtual boundary syntax elements. Virtual boundary update unit 254 (shown as UVBU 254) can update the virtual boundaries at least in part based on the virtual boundary syntax elements. Video decoder 300 can decode the current sub-picture based on the updated virtual boundaries.

[0115] In some examples, one or more of the techniques attributed to bitstream extractor 250 may be performed by video decoder 300. In some examples, the bitstream extractor may not be part of destination device 136, but may be part of a server. In some examples, for example, bitstream extractor 250 may be implemented as an application that can run on destination device 116, destination device 136, or a server.

[0116] In this manner, bitstream extractor 250 represents an example of a bitstream extractor device, comprising: a memory configured to store video data; and one or more processors implemented in circuitry and communicatively coupled to the memory, the one or more processors being configured to: extract a current sub-picture from the bitstream of video data; parse virtual boundary syntax elements indicating virtual boundaries of the current sub-picture associated with the current picture; and update the virtual boundaries at least in part based on the virtual boundary syntax elements.

[0117] As discussed above, some video decoding standard drafts (such as VVC draft 9) can support the use of virtual boundaries for images and can support treating sub-images as images. When a sub-image is treated as an image, the video decoder can extract and decode the sub-image independently of another sub-image within the same image. When the video decoder extracts a sub-image from an image with virtual boundaries, the virtual boundaries can be outside the sub-image. This can lead to decoding errors, which may negatively impact the quality of the decoded video.

[0118] Subpicks are a feature of some video decoding standards (e.g., VVC Draft 9). Subpicks can be specified as independently extractable and independently decodeable. Subpicks can be useful in viewport-dependent 360-degree video or region-of-interest applications. For example, when a person moves their head while watching viewport-dependent 360-degree video, the view may shift, allowing new subpicks to be extracted and decoded to be displayed in the viewport along with other pictures and / or subpicks.

[0119] Virtual boundaries can be used in adaptive loop filtering operations. When the adaptive loop filter is centered on the sample to be filtered and a portion of the filter extends beyond the virtual boundary, the filter can be modified so that samples not currently being filtered are not used on the other side of the virtual boundary. Therefore, if the virtual boundary is outside the current sub-image (e.g., not inside the current sub-image or at the true boundary of the current sub-image), the samples to be included in the filter template when applying adaptive loop filtering may be in other sub-images or images that may not be available for filtering. For example, another sub-image that may contain the virtual boundary may not have been decoded yet, and therefore samples from that other sub-image may not be available for filtering. Therefore, it may be necessary to move the virtual boundaries of the extracted sub-images.

[0120] Furthermore, some video decoding standard drafts (such as VVC draft 9) include reference picture list constraints. These reference picture list constraints may not be suitable for use cases where a picture with multiple sub-pictures is predicted from an inter-layer reference picture that has only one sub-picture.

[0121] Furthermore, some video decoding standard drafts (such as VVC draft 9) do not require that sub-pictures be treated as pictures when sub-picture reordering occurs. This can lead to decoding mismatches, which may negatively impact the quality of the decoded video.

[0122] VVC was developed by ITU-T and ISO / IEC JVET to achieve substantial compression capabilities beyond HEVC for a wider range of applications. VVC Draft 9 specifies the bitstream and picture formats, High-Level Syntax (HLS) and semantics, as well as the parsing and decoding processes. VVC Draft 9 also specifies profile / layer / level (PTL) constraints, byte stream formats, hypothetical reference decoders, and supplementary enhancement information (SEI) in its annex.

[0123] VVC Draft 9 inherits many advanced features from HEVC, such as the concepts of NAL cells and parameter sets, tile and wavefront parallel processing, layered decoding, and supplementary data signaling using SEI messages. Other advanced features introduced in VVC Draft 9 include the concepts of rectangular slices and subpictures, picture resolution adaptation, mixed NAL cell types, picture header (PH), gradient decode refresh (GDR) pictures, virtual boundaries, and a reference picture list (RPL) for reference picture management.

[0124] In VVC Draft 9, many signaling conditions or semantic constraints are specified for the parameter set syntax elements, and variables that can be derived from the syntax elements by the video decoder 300 are used by the video decoder 300 during the decoding process.

[0125] The following describes one or more potential issues in VVC Draft 9. Several sub-picture related issues are identified in VVC Draft 9 as follows: 1) VVC Draft 9 lacks a rewriting process for sub-picture ID mapping and sub-picture-based virtual boundaries during sub-picture sub-bitstream extraction; 2) Sub-picture-based RPL constraints should be updated to accommodate the use case where a picture with multiple sub-pictures is predicted from an inter-layer reference picture with only one sub-picture; 3) Treating sub-pictures as pictures is not required when sub-picture reordering occurs, which may lead to decoding mismatches. Constraints may be needed to avoid such mismatches.

[0126] Now we will discuss subpicture sub-bitstream extraction. VVC Draft 9 specifies a rewritten procedure for subpicture sub-bitstream extraction when the video decoder (e.g., video encoder 200 or video decoder 300) does not have an external unit to provide an alternative set of parameters (including general_level_idc, picture width and height, sps_num_subpics_minus1 and pps_num_subpics_minus1, subpicture position, tile / slice layout, and consistency window).

[0127] After the sub-image extraction process, there may be only one sub-image per layer. The sub-image ID mapped to the 0th sub-image in the inBitstream may not be equal to the sub-image ID of the extracted sub-image. As a result, the sub-image ID mapping may need to be rewritten to identify the extracted sub-bitstream slice NAL unit in the outBitstream. Furthermore, the sub-image virtual boundary positions signaled by the video encoder 200 in the inBitstream may not be aligned with the width and height of the new image, and some virtual boundary positions may be outside the boundaries of the new image. Therefore, when this information exists, it may be necessary to rewrite the SPS virtual boundary information.

[0128] To address this issue, the video encoder 200, bitstream extractor 250, or video decoder 300 may employ the following additional techniques:

[0129] 1) Remove the subpicture ID syntax elements (e.g., sps_subpic_id[j] and pps_subpic_id[j]) from the SPS and PPS in all referenced SPS and PPS NAL units for each j that is not equal to subpicIdx. In other words, for each j that is not equal to subpicIdx, sps_subpic_id[j] or pps_subpic_id[j] does not exist in the SPS or PPS, respectively, when the video decoder 300 rewrites or updates the SPS or PPS. For example, the video decoder 300 may rewrite the PPS associated with the current subpicture, wherein the rewritten PPS does not include the PPS subpicture identifier for subpictures other than the current subpicture. Similarly, the video decoder 300 may rewrite the SPS associated with the current subpicture, wherein the rewritten SPS does not include the SPS subpicture identifier for subpictures other than the current subpicture.

[0130] 2) The derivation of variables numVerVBs, subpicVBx, numHorVBs, and subpicVBy is as follows: numVerVBs = 0; for( i = 0; i <sps_num_ver_virtual_boundaries; i++) { if( sps_virtual_boundary_pos_x[ i ] > (sps_subpic_ctu_top_left_x[subpicIdx ] CtbSizeY / 8) &&sps_virtual_boundary_pos_x[ i ]<min( ( sps_subpic_ctu_top_left_x[ subpicIdx ] +sps_subpic_width_minus1[ subpicIdx ] + 1 ) CtbSizeY, pps_pic_width_in_luma_samples ) / 8 ) subpicVBx[ numVerVBs ++ ] = sps_virtual_boundary_pos_x[ i ] - sps_subpic_ctu_top_left_x[ subpicIdx ] CtbSizeY / 8 numHorVBs = 0; for( i = 0; i<sps_num_hor_virtual_boundaries; i++) { if( sps_virtual_boundary_pos_y[ i ] > (sps_subpic_ctu_top_left_y[subpicIdx ] CtbSizeY / 8) &&sps_virtual_boundary_pos_y[ i ]<min( ( sps_subpic_ctu_top_left_y[ subpicIdx ] + sps_subpic_height_minus1[ subpicIdx ] + 1 ) CtbSizeY, pps_pic_height_in_luma_samples ) / 8 ) subpicVBy[ numHorVBs ++ ] = sps_virtual_boundary_pos_y[ i ] - sps_subpic_ctu_top_left_y[ subpicIdx ] CtbSizeY / 8 ▪ When `sps_virtual_boundaries_present_flag` equals 1, the values ​​of `sps_num_ver_virtual_boundaries`, `sps_virtual_boundary_pos_x[]`, `sps_num_hor_virtual_boundaries`, and `sps_virtual_boundary_pos_y[]` in all referenced SPS NAL cells are rewritten to equal `numVerVBs`, `subpicVBx[i]`, `numHorVBs`, and `subpicVBy[j]`, where `i` is in the range of 0 to `numVerVB` (excluding endpoints), and `j` is in the range of 0 to `numHorVB` (excluding endpoints). Virtual boundaries outside the extracted sub-images are removed. When both numVerVB and numHorVB are equal to 0, the value of sps_virtual_boundaries_present_flag in all referenced SPS NAL units is rewritten to 0, and the syntax elements sps_num_ver_virtual_boundaries, sps_virtual_boundary_pos_x[i], sps_num_hor_virtual_boundaries, and sps_virtual_boundary_pos_y[i] are removed.

[0131] For example, bitstream extractor 250 or video decoder 300 can extract the current sub-image from the bitstream of video data. Bitstream extractor 250 or video decoder 300 can parse virtual boundary syntax elements that indicate the virtual boundaries of the current sub-image associated with it. For example, bitstream extractor 250 or video decoder 300 can parse `sps_num_ver_virtual_boundaries`, `sps_virtual_boundary_pos_x[i]`, `sps_num_hor_virtual_boundaries`, and `sps_virtual_boundary_pos_y[i]`. Bitstream extractor 250 or video decoder 300 can update virtual boundaries (e.g., for the current sub-image) at least in part based on the virtual boundary syntax elements. For example, bitstream extractor 250 or video decoder 300 can rewrite sps_num_ver_virtual_boundaries, sps_virtual_boundary_pos_x[], sps_num_hor_virtual_boundaries, and sps_virtual_boundary_pos_y[] as equal to numVerVBs, subpicVBx[i], numHorVBs, and subpicVBy[j], respectively, as described above. Video decoder 300 can decode the current subpic based on the updated virtual boundaries.

[0132] Now let's discuss the sub-image RPL constraint. In VVC Draft 9, when the current image is not an independent layer and has multiple sub-images, each sub-image can be predicted from a co-located sub-image with the same sub-image ID from a reference image with the same sub-image layout, or from an inter-layer reference image with only one sub-image, as shown below:

[0133] When vps_independent_layer_flag[GeneralLayerIdx[nuh_layer_id]] equals 0 and sps_num_subpics_minus1 is greater than 0, one of the following two conditions (but not both) may (e.g., should) be true: 1) The picture referenced by each active entry in RefPicList[0] or RefPicList[1] has the same subpicture layout as the current picture (e.g., the SPS referenced by that picture and the current picture have the same sps_num_subpics_minus1 value, and for 0 to sps_num_s Each j value within the range of ubpics_minus1 (including the endpoints) has the same values ​​for sps_subpic_ctu_top_left_x[j], sps_subpic_ctu_top_left_y[j], sps_subpic_width_minus1[j], and sps_subpic_height_minus1[j], respectively; or 2) the picture referenced by each active entry in RefPicList[0] or RefPicList[1] is the interlayer reference picture (ILRP) for which the value of sps_num_subpics_minus1 is equal to 0.

[0134] Furthermore, there are RPL constraints on the activity entries of the restricted sub-images, as shown below. The requirement for bitstream consistency applies to both of the following constraints: —For any two distinct values ​​of i and j in the range from 0 to sps_num_subpics_minus1 (inclusive), SubpicIdVal[i] should not be equal to SubpicIdVal[j]. —For each value of i in the range of 0 to sps_num_subpics_minus1 (inclusive), if the value of SubpicIdVal[i] of the current image is not equal to the value of SubpicIdVal[i] of the reference image, the active entry of the decoded slice RPL in the i-th sub-image of the current image should not include the reference image.

[0135] A reference layer with only one sub-image should be excluded from the above constraints because the entire image is used as a reference. For example, video encoder 200, bitstream extractor 250, or video decoder 300 can exclude the above constraints for reference layers with only one sub-image. For example, video encoder 200, bitstream extractor 250, or video decoder 300 can determine that a reference layer has more than one sub-image, wherein the rewriting of PPS and / or SPS is at least partially based on a reference layer with more than one sub-image. For example, video decoder 300 can determine that the reference image of the current image is an inter-layer reference image with only one sub-image, wherein the sub-image identifier of the co-located sub-image in the reference image and the sub-image identifier of the current sub-image have different values.

[0136] The RPL constraints can be updated as follows: <change> and< / change> The changes shown between these sections are from VVC Draft 9:

[0137] For each i value in the range 0 to sps_num_subpics_minus1 (inclusive), if <change> The reference image has more than one sub-image, and< / change> If the value of SubpicIdVal[i] of the current image is not equal to the value of SubpicIdVal[i] of the reference image, then the active entry of the RPL in the decoded slice of the i-th sub-image of the current image should not include the reference image.

[0138] For example, bitstream extractor 250 or video decoder 300 can determine whether a reference image of the current image has more than one sub-image, and, at least in part based on the fact that the reference image does not have more than one sub-image, add the reference image as an active entry in the list of reference images for the current sub-image. In this way, bitstream extractor 250 or video decoder 300 can avoid imposing constraints when the reference image has only one sub-image.

[0139] To address the scenario where both the current layer and the reference layer have only one sub-image but different sub-image IDs, this disclosure describes examples of applying this constraint only when the current layer image has more than one sub-image. For example, a video encoder 200, a bitstream extractor, or a video decoder 300 can apply the constraint only when the current layer image has more than one sub-image.

[0140] <change> If the current image has more than one sub-image, then< / change> For each i value in the range 0 to sps_num_subpics_minus1 (inclusive), if <change> The reference image has more than one sub-image, and< / change> If the value of SubpicIdVal[i] is not equal to the value of SubpicIdVal[i] of the reference image, then the active entry of the RPL in the decoded slice of the i-th sub-image of the current image should not include the reference image.

[0141] For example, video decoder 300 can determine whether a reference image of the current image has more than one sub-image and whether the current image has more than one sub-image. Based at least in part on the fact that the reference image does not have more than one sub-image, or the current image does not have more than one sub-image, or neither the reference image nor the current image has more than one sub-image, video decoder 300 can add the reference image as an active entry in the list of reference images for the current sub-image. In this way, video decoder 300 avoids applying constraints when the reference image, the current image, or both the reference image and the current image have only one sub-image.

[0142] In another example, for images within the same layer, the RPL constraint can be expressed as follows: for each i value (inclusive) in the range of 0 to sps_num_subpics_minus1, the value of SubpicIdVal[i] in the current image is not equal to <change> In the same layer< / change> Given the value of SubpicIdVal[i] of the reference image, the active entry of the RPL in the decoded slice of the i-th subpic of the current image should not include the reference image.

[0143] In some examples, any or all of the foregoing constraints may apply only to the case where a subpic of the current image is treated as an image, for example, when the associated `sps_subpic_treated_as_pic_flag[i]` equals 1. For example, video encoder 200, bitstream extractor 250, or video decoder 300 may determine that the current subpic will be treated as an image, wherein rewriting PPS and / or SPS is at least partially based on the current subpic being treated as an image. In some examples, video encoder 200, bitstream extractor 250, or video decoder 300 may determine that the current subpic will be treated as an image; and determine that the reference layer has more than one subpic, wherein rewriting PPS and / or SPS is based on the current subpic being treated as an image and the reference layer having more than one subpic. For example, video decoder 300 may determine that the current image has more than one subpic and determine that the current subpic will be treated as an image, wherein the subpicture identifier of the co-located subpic in the reference image of the current image has the same value as the subpicture identifier of the current subpic. For example, the video decoder 300 can determine that the current image has more than one sub-image and determine that the current sub-image will not be processed as an image, wherein the sub-image identifier of the co-located sub-image in the reference image of the current image has a different value than the sub-image identifier of the current sub-image.

[0144] In one example of one of the constraints mentioned above, the constraint can be expressed as follows: for each value of i in the range of 0 to sps_num_subpics_minus1 (inclusive), when <change> sps_subpic_treated_as_pic_flag[i] equals 1 and< / change>The value of SubpicIdVal[i] for the current image is not equal to <change> same floor< / change> The value of SubpicIdVal[i] of the reference image in the current image, the active entry of the decoded slice RPL in the i-th sub-image of the current image should not include the reference image.

[0145] For example, the video decoder 300 can determine whether the current sub-image will be processed as an image, and, at least in part based on the premise that the current sub-image will not be processed as an image, add a reference image as an active entry in the reference image list of the current sub-image. In this way, the video decoder 300 can avoid applying the constraint when the current sub-image is not processed as an image.

[0146] Now let's discuss subpicture reordering constraints. VVC Draft 9 allows subpicture reordering when a subpicture is not considered a picture (e.g., `sps_subpic_treated_as_pic_flag[i]` equals 0). Subpicture reordering can mean that the co-located subpicture ID in the reference picture is different from the current subpicture ID. If such references are allowed, then when a subpicture is reordered (e.g., reordered by video decoder 300), the reference may produce mismatches during reconstruction.

[0147] In one example, the following constraint is added: if the subpicks are reordered, for example, if co-located subpicks in the reference picture have different IDs, then the current subpick should be treated as a picture, for example, sps_subpic_treated_as_pic_flag[i] equals 1. For example, if the current subpicks are reordered, either video encoder 200 or video decoder 300 can treat the current subpick as a picture.

[0148] For example, the video decoder 300 can determine whether the current sub-image has been reordered, and at least in part based on the fact that the current sub-image has been reordered, treat the current sub-image as an image.

[0149] In one example, the constraint can be expressed as follows: for each i value in the range of 0 to sps_num_subpics_minus1 (inclusive), sps_subpic_treated_as_pic_flag[i] should be equal to 1 if the value of SubpicIdVal[i] of the current image is not equal to the value of SubpicIdVal[i] of the reference image in the same layer.

[0150] In another example, if an image contains at least one reordered sub-image, the constraint can require that all sub-images of the image be treated as images. For instance, if at least one sub-image of the current image is reordered, the video encoder 200 or video decoder 300 can treat all sub-images of the current image as images.

[0151] For example, when the current image includes more than one sub-image, the video decoder 300 may treat all sub-images of the current image as images, at least in part, based on the current sub-images being reordered.

[0152] In one example, the constraint can be expressed as follows: For any value of i in the range of 0 to sps_num_subpics_minus1 (inclusive), when the value of SubpicIdVal[i] of the current image is not equal to the value of SubpicIdVal[i] of the reference image in the same layer, for each value of j in the range of 0 to sps_num_subpics_minus1 (inclusive), sps_subpic_treated_as_pic_flag[j] should be equal to 1.

[0153] Additionally, in some examples, the above constraints may apply only to P-slices or B-slices within a sub-image. For instance, the video decoder 300 may determine whether a slice in the current sub-image is a P-slice or a B-slice; and further, based on whether the slice is a P-slice or a B-slice and the current sub-image being reordered, treat the current sub-image as an image.

[0154] Figure 5 This is a flowchart illustrating an example sub-image extraction technique of this disclosure. A video decoder 300 or a bitstream extractor 250 can extract the current sub-image (330) from the bitstream of video data. For example, the video decoder 300 can begin decoding the current sub-image, or the bitstream extractor 250 can extract the current sub-image from the bitstream.

[0155] The video decoder 300 or bitstream extractor 250 can parse the virtual boundary syntax elements that indicate the virtual boundaries of the current image, which is associated with the current sub-image (332). For example, the video decoder 300 or bitstream extractor 250 can parse sps_num_ver_virtual_boundaries, sps_virtual_boundary_pos_x[i], sps_num_hor_virtual_boundaries, and sps_virtual_boundary_pos_y[i].

[0156] The video decoder 300 or bitstream extractor 250 can update virtual boundaries (e.g., for the current sub-picture) at least in part based on virtual boundary syntax elements (334). For example, the video decoder 300 or bitstream extractor 250 can rewrite the values ​​of sps_num_ver_virtual_boundaries, sps_virtual_boundary_pos_x[i], sps_num_hor_virtual_boundaries, and sps_virtual_boundary_pos_y[i] to be equal to numVerVBs, subpicVBx[i], numHorVBs, and subpicVBy[j], respectively, as discussed above. This removes virtual boundaries outside the extracted current sub-picture.

[0157] The video decoder 300 can decode the current sub-image based on the updated virtual boundary (336). For example, the video decoder 300 can use the updated virtual boundary when decoding the current sub-image.

[0158] In some examples, the bitstream extractor 250 or the video decoder 300 may rewrite the PPS associated with the current subpicture, wherein the rewritten PPS does not include the PPS subpicture identifiers for subpictures other than the current subpicture. For example, the bitstream extractor 250 or the video decoder 300 may remove the PPS subpicture identifiers of other subpictures from the PPS for each j that is not equal to subpicIdx, such as pps_subpic_id[j].

[0159] In some examples, the bitstream extractor 250 or the video decoder 300 can determine that the current sub-image will be processed as an image; and determine that the reference layer has more than one sub-image, wherein the rewriting of PPS is based on the fact that the current sub-image is being processed as an image and that the reference layer has more than one sub-image.

[0160] In some examples, the bitstream extractor 250 or the video decoder 300 may rewrite the SPS associated with the current subpicture, wherein the rewritten SPS does not include the SPS subpicture identifiers of subpictures other than the current subpicture. For example, the bitstream extractor 250 or the video decoder 300 may remove the SPS subpicture identifiers of other subpictures from the SPS for each j that is not equal to subpicIdx, such as sps_subpic_id[j].

[0161] In some examples, the bitstream extractor 250 or the video decoder 300 can determine that the current sub-image will be processed as an image; and determine that the reference layer has more than one sub-image, wherein the SPS rewrite is based on the fact that the current sub-image is being processed as an image and the reference layer has more than one sub-image.

[0162] In some examples, the bitstream extractor 250 or the video decoder 300 may determine that the reference image of the current image does not have more than one sub-image, and at least in part based on the fact that the reference image does not have more than one sub-image, add the reference image as an active entry in the reference image list of the current sub-image. In such cases, the video decoder 300 may decode the current sub-image based on the updated virtual boundary and the reference image list. For example, the video decoder 300 may avoid applying the constraint that the reference image may not be an active entry in the reference image list of the current sub-image unless the reference image contains more than one sub-image. In some examples, the reference image and the current image are on the same layer.

[0163] In some instances, video decoder 300 can determine whether a reference image of the current image has more than one sub-image and whether the current image has more than one sub-image. Based at least in part on the premise that the reference image does not have more than one sub-image, the current image does not have more than one sub-image, or neither the reference image nor the current image has more than one sub-image, video decoder 300 can add the reference image as an active entry in the reference image list of the current sub-image. In such cases, video decoder 300 can decode the current sub-image based on the updated virtual boundary and the reference image list. For example, video decoder 300 can avoid applying the constraint that the reference image may not be an active entry in the reference image list of the current sub-image unless the reference image has more than one sub-image, the current image has more than one sub-image, or both the reference image and the current image have more than one sub-image.

[0164] In some examples, the video decoder 300 can determine whether the current subpicture is treated as an image; and, at least in part based on the premise that the current subpicture will not be treated as an image, add a reference image as an active entry in the reference image list of the current subpicture. In such cases, the video decoder 300 can decode the current subpicture based on the updated virtual boundary and the reference image list. In some examples, the video decoder 300 can parse `sps_subpic_treated_as_pic_flag[i]` to determine whether the current subpicture is considered an image. For example, the video decoder 300 can avoid applying the constraint that a reference image may not be an active entry in the reference image list of the current subpicture unless the current subpicture is considered an image. In some examples, the reference image and the current image are on the same layer.

[0165] In some examples, video decoder 300 can determine whether the current sub-image has been reordered. In some examples, as part of determining whether the current sub-image has been reordered, video decoder 300 can determine whether a co-located sub-image in a reference image has the same identifier as the current sub-image. Based at least in part on the fact that the current sub-image has been reordered, video decoder 300 can treat the current sub-image as an image.

[0166] In some examples, the image comprises more than one sub-image, and the video decoder 300 is at least partially reordered based on the current sub-image, allowing all sub-images of the current image to be treated as images.

[0167] In some examples, the video decoder 300 can determine whether the slice in the current sub-image is a P-slice or a B-slice, and further treat the current sub-image as an image based on whether the slice is a P-slice or a B-slice and the sub-images have been reordered.

[0168] In some examples, the video decoder 300 can determine that the current image has more than one sub-image and that the current sub-image will be processed as an image, wherein the sub-image identifier of the co-located sub-image in the reference image of the current image has the same value as the sub-image identifier of the current sub-image. In some examples, the video decoder 300 can determine that the reference image of the current image is an inter-layer reference image with only one sub-image, wherein the sub-image identifier of the co-located sub-image in the reference image and the sub-image identifier of the current sub-image have different values. In some examples, the video decoder 300 can determine that the current image has more than one sub-image and that the current sub-image will not be processed as an image, wherein the sub-image identifier of the co-located sub-image in the reference image of the current image and the sub-image identifier of the current sub-image have different values.

[0169] Figure 6 This is a flowchart illustrating an example method for encoding the current block. The current block may include the current CU. Although for video encoder 200 ( Figure 1 and Figure 2 The description is provided, but it should be understood that other devices can be configured to perform actions similar to... Figure 6 A similar approach.

[0170] In this example, the video encoder 200 initially predicts the current block (350). For example, the video encoder 200 may form a predicted block for the current block. The video encoder 200 may then compute a residual block for the current block (352). To compute the residual block, the video encoder 200 may compute the difference between the original uncoded block and the predicted block for the current block. The video encoder 200 may then transform the residual block and quantize the transform coefficients of the residual block (354). Next, the video encoder 200 may scan the quantized transform coefficients of the residual block (356). During or after the scan, the video encoder 200 may entropy-encode the transform coefficients (358). For example, the video encoder 200 may encode the transform coefficients using CAVLC or CABAC. The video encoder 200 may then output the entropy-encoded data for the block (360).

[0171] Figure 7 This is a flowchart illustrating an example method for decoding the current block of video data. The current block may include the current CU. Although for video decoder 300 ( Figure 1 and Figure 3 The description is provided, but it should be understood that other devices can be configured to perform actions similar to... Figure 7 A similar approach.

[0172] The video decoder 300 may receive entropy-coded data for the current block, such as entropy-coded prediction information and entropy-coded data of the transform coefficients of the residual block corresponding to the current block (370). The video decoder 300 may perform entropy decoding on the entropy-coded data to determine the prediction information for the current block and reproduce the transform coefficients of the residual block (372). In some instances, as part of the entropy-decoded data, the video decoder 300 may parse virtual boundary syntax elements indicating virtual boundaries of the current image, to which the current sub-image is associated.

[0173] The video decoder 300 may, for example, use an intra-prediction or inter-prediction mode indicated by prediction information for the current block to predict the current block (374) to compute a predicted block for the current block. The video decoder 300 may then perform an inverse scan of the reconstructed transform coefficients (376) to create a block of quantized transform coefficients. The video decoder 300 may then inverse-quantize the transform coefficients and apply the inverse transform to the transform coefficients to produce a residual block (378). The video decoder 300 may finally decode the current block by combining the predicted block and the residual block (380). In some examples, the video decoder 300 may perform [the following actions] while decoding the video data: Figure 5 One or more technologies.

[0174] By updating the virtual boundaries of an image when extracting sub-images of an image with virtual boundaries, modifying the RPL constraint to accommodate use cases that include images with multiple sub-images predicted from an inter-layer reference image that has only one sub-image, and adding the constraint that sub-images are treated as images when they are reordered, video decoding quality and / or video decoding performance can be improved.

[0175] This disclosure includes the following non-limiting examples.

[0176] Clause 1A, a method for decoding video data, the method comprising: removing a first sequence parameter set (SPS) sub-picture identifier (ID) syntax element from a referenced network abstraction layer (NAL) unit; removing a first PPS sub-picture ID syntax element from a referenced picture parameter set (PPS) NAL unit; determining whether a second SPS sub-picture ID syntax element is equal to a sub-picture index; removing a second SPS sub-picture ID syntax element from the SPS based on the second SPS sub-picture ID syntax element not being equal to the sub-picture index; determining whether a second PPS sub-picture ID syntax element is equal to the sub-picture index; removing a second PPS sub-picture ID syntax element from the PPS based on the second PPS sub-picture ID syntax element not being equal to the sub-picture index; avoiding signal transmission or parsing of the first SPS sub-picture ID syntax element, the first PPS sub-picture ID syntax element, the second SPS sub-picture ID syntax element, and the second PPS sub-picture ID syntax element; and decoding the video data.

[0177] Clause 2A, the method described in Clause 1A, further includes: removing virtual boundaries outside the extracted sub-images.

[0178] Clause 3A, a method for decoding video, the method comprising: determining whether a reference picture has more than one subpicture; avoiding constraints on a list of reference pictures (RPL) based on the fact that the reference picture has only one subpicture; and decoding the video data based on the RPL.

[0179] Clause 4A, the method described in Clause 3A, further includes: determining whether a sub-image of the current image is considered an image; and avoiding constraints on the RPL based on the fact that the sub-image is not considered an image.

[0180] Clause 5A, the method described according to Clause 3A or 4A, further includes: determining whether the current layer image has more than one sub-image; and avoiding constraints on the RPL based on the fact that the current layer image does not have more than one sub-image.

[0181] Clause 6A, a method for decoding video data, the method comprising: determining whether sub-images of a current image have been reordered; treating the sub-images as images based on the reordering of the sub-images; and decoding the video data based on the treating the sub-images as images.

[0182] Clause 7A, the method described in Clause 6A, wherein determining whether a sub-image has been reordered includes: determining whether co-located sub-images in the reference images have different IDs.

[0183] The method of any combination of Clause 8A, Clause 6A, or 7A further includes: sending or parsing a syntax element that indicates that the sub-picture is regarded as the picture.

[0184] The method described in Clause 9A, or any combination of Clauses 6A-8A, further includes: treating all sub-images of the current image as images based on the reordering of the sub-images.

[0185] The method described in Clause 10A, or any combination of Clauses 6A-9A, further comprises: determining whether a slice in the sub-image is a P-slice or a B-slice; and treating the sub-image as the image based on whether the slice is a P-slice or a B-slice and the sub-image being reordered.

[0186] Clause 11A, the method described in any combination of Clauses 1A-10A.

[0187] Clause 12A, the method described in any of the clauses 1A-11A, wherein decoding includes decoding.

[0188] Clause 13A, the method described under any of the clauses 1A-12A, wherein decoding includes encoding.

[0189] Clause 14A, an apparatus for decoding video data, said apparatus comprising one or more units for performing the method described in any of the clauses 1A-13A.

[0190] Clause 15A, the device described in Clause 14A, wherein the one or more units include one or more processors implemented in a circuit.

[0191] The device described in Clause 16A, or any of Clauses 14A and 15A, further includes a memory for storing the video data.

[0192] The device described in Clause 17A, or any of Clauses 14A-16A, also includes a display configured to display decoded video data.

[0193] Clause 18A, the device described in any of Clauses 14A-17A, wherein the device includes one or more of the following: camera, computer, mobile device, broadcast receiver device or set-top box.

[0194] Clause 19A, the device described in any of Clauses 14A-18A, wherein the device includes a video decoder.

[0195] Clause 20A, the device described in any of the clauses 14A-19A, wherein the device includes a video encoder.

[0196] Clause 21A. A computer-readable storage medium having instructions stored thereon, which, when executed, cause one or more processors to perform the method described in accordance with any one of Clauses 1-13.

[0197] Clause 1B, a method for decoding video data, the method comprising: extracting a current sub-image from a bitstream of the video data; parsing a virtual boundary syntax element indicating a virtual boundary of the current sub-image associated with the current image; updating the virtual boundary at least in part based on the virtual boundary syntax element; and decoding the current sub-image based on the updated virtual boundary.

[0198] Clause 2B, the method described in Clause 1B, further includes: rewriting the Picture Parameter Set (PPS) associated with the current sub-picture, wherein the rewritten PPS does not include the PPS sub-picture identifiers of sub-pictures other than the current sub-picture.

[0199] Clause 3B, the method according to Clause 1B, further includes: determining that the current sub-image will be processed as an image; and determining that the reference layer has more than one sub-image, wherein the rewriting of the PPS is based on the current sub-image being processed as an image and the reference layer having more than one sub-image.

[0200] Clause 4B, the method according to any combination of Clauses 1B-3B, further comprises: rewriting the sequence parameter set (SPS) associated with the current sub-image, wherein the rewritten SPS does not include the SPS sub-image identifiers of sub-images other than the current sub-image.

[0201] Clause 5B, the method according to Clause 4B, further includes: determining that the current sub-image will be processed as an image; and determining that the reference layer has more than one sub-image, wherein the rewriting of the SPS is based on the current sub-image being processed as an image and the reference layer having more than one sub-image.

[0202] The method described in Clause 6B, or any combination of Clauses 1B, 2B, or 4B, further includes: determining that a reference image of the current image does not have more than one sub-image; and adding the reference image as an active entry in the list of reference images of the current sub-image, at least in part based on the fact that the reference image does not have more than one sub-image.

[0203] Clause 7B, the method described in Clause 6B, wherein the reference image and the current image are on the same layer.

[0204] Clause 8B, the method according to any combination of Clauses 1B-7B, further includes: determining whether a reference image of the current image has more than one sub-image; determining whether the current image has more than one sub-image; and adding the reference image as an active entry in the reference image list of the current sub-image, at least in part based on the fact that the reference image does not have more than one sub-image, the current image does not have more than one sub-image, or both the reference image and the current image do not have more than one sub-image, wherein decoding the current sub-image includes: decoding the current sub-image based on the updated virtual boundary and the reference image list.

[0205] The method described in Clause 9B, or any combination of Clauses 1B-2B, 4B, or 6B-8B, further comprises: determining that the current sub-image will not be processed as an image; and adding a reference image as an active entry in the reference image list of the current sub-image, at least in part based on the fact that the current sub-image will not be processed as the image, wherein decoding the current sub-image comprises: decoding the current sub-image based on the updated virtual boundary and the reference image list.

[0206] Clause 10B, the method described in Clause 9B, wherein the reference image and the current image are on the same layer.

[0207] Clause 11B, the method according to any combination of Clauses 1B-10B, further includes: determining that the current sub-image has been reordered; and processing the current sub-image as an image based at least in part on the fact that the current sub-image has been reordered.

[0208] Clause 12B, the method according to Clause 11B, wherein determining that the current sub-image has been reordered includes: determining whether a co-located sub-image in a reference image has the same identifier as the current sub-image; and determining that the current sub-image has been reordered based on the fact that the co-located sub-image in the reference image has the same identifier as the current sub-image.

[0209] Clause 13B, the method according to Clause 11B or 12B, wherein the current image comprises more than one sub-image, and wherein the method further comprises: processing all sub-images of the current image as images, at least in part based on the current sub-images being reordered.

[0210] Clause 14B, the method according to Clause 11B or 12B, further includes: determining whether a slice in the current sub-image is a P-slice or a B-slice; and further processing the current sub-image as an image based on whether the slice is a P-slice or a B-slice and the current sub-image being reordered.

[0211] The method described in Clause 15B, or any of Clauses 1B-8B or Clauses 11B-14B, further comprises: determining that the current image has more than one sub-image, and determining that the current sub-image will be treated as an image, wherein the sub-image identifier of the co-located sub-image in the reference images of the current image has the same value as the sub-image identifier of the current sub-image.

[0212] The method described in Clause 16B, or any of Clauses 1B-11B or Clauses 13B-14B, further includes: determining that the reference image of the current image is an interlayer reference image having only one sub-image, wherein the sub-image identifier of the co-located sub-image in the reference image and the sub-image identifier of the current sub-image have different values.

[0213] The method described under Clause 17B, or any of Clauses 1B-11B, 13B-14B, or 16B, further comprises: determining that the current image has more than one sub-image, and determining that the current sub-image will not be treated as an image, wherein the sub-image identifier of the co-located sub-image in the reference images of the current image has a different value than the sub-image identifier of the current sub-image.

[0214] Clause 18B, an apparatus for decoding video data, the apparatus comprising: a memory configured to store the video data; and one or more processors implemented in circuitry and communicatively coupled to the memory, wherein the one or more processors are configured to: extract a current sub-picture from a bitstream of the video data; parse a virtual boundary syntax element indicating a virtual boundary of the current picture, wherein the current sub-picture is associated with the current picture; update the virtual boundary at least in part based on the virtual boundary syntax element; and decode the current sub-picture based on the updated virtual boundary.

[0215] Clause 19B, the device as described in Clause 18B, wherein the one or more processors are further configured to: rewrite the Picture Parameter Set (PPS) associated with the current sub-picture, wherein the rewritten PPS does not include the PPS sub-picture identifiers of sub-pictures other than the current sub-picture.

[0216] Clause 20B, the device according to Clause 19B, wherein the one or more processors are further configured to: determine that the current sub-image will be processed as an image; and determine that the reference layer has more than one sub-image, wherein the one or more processors are configured to: rewrite the PPS based on the determination that the current sub-image will be processed as the image and the determination that the reference layer has more than one sub-image.

[0217] Clause 21B, the device according to any combination of clauses 18B-20B, wherein the one or more processors are further configured to: rewrite the sequence parameter set (SPS) associated with the current sub-image, wherein the rewritten SPS does not include the SPS sub-image identifiers of sub-images other than the current sub-image.

[0218] Clause 22B, the device according to Clause 21B, wherein the one or more processors are further configured to: determine that the current sub-image will be processed as an image; and determine that the reference layer has more than one sub-image, wherein the one or more processors rewrite the SPS based on the determination that the current sub-image will be processed as the image and the determination that the reference layer has more than one sub-image.

[0219] The device described in Clause 23B, or any combination of Clauses 18B, 19B, or 21B, wherein the one or more processors are further configured to: determine that a reference image of the current image does not have more than one sub-image; and, at least in part based on the determination that the reference image of the current image does not have more than one sub-image, add the reference image as an active entry in the list of reference images of the current sub-image.

[0220] Clause 24B, the device described in Clause 23B, wherein the reference image and the current image are on the same layer.

[0221] Clause 25B, the device according to any combination of clauses 18B-24B, wherein the one or more processors are further configured to: determine whether a reference image of the current image has more than one sub-image; determine whether the current image has more than one sub-image; and add the reference image as an active entry in the list of reference images of the current sub-image, at least in part based on the determination that the reference image of the current image has more than one sub-image and the determination that the current image has more than one sub-image reference image, wherein at least one of the reference image or the current image does not have more than one sub-image.

[0222] The device described in Clause 26B, or any combination of Clauses 18B-19B, 21B, or 23B-25B, wherein the one or more processors are further configured to: determine that the current sub-image will not be processed as an image; and add a reference image as an active entry in the reference image list of the current sub-image, at least in part based on the fact that the current sub-image will not be processed as an image, wherein the one or more processors are configured to: decode the current sub-image based on the updated virtual boundary and the reference image list.

[0223] Clause 27B, the device described in Clause 26B, wherein the reference image and the current image are on the same layer.

[0224] Clause 28B, the device according to any combination of clauses 18B-27B, wherein the one or more processors are further configured to: determine that the current sub-image has been reordered; and process the current sub-image as an image based at least in part on the determination that the current sub-image has been reordered.

[0225] Clause 29B, the device according to Clause 28B, wherein, to determine that the current sub-image has been reordered, the one or more processors are configured to: determine whether a co-located sub-image in a reference image has the same identifier as the current sub-image; and determine that the current sub-image has been reordered based on the fact that the co-located sub-image in the reference image has the same identifier as the current sub-image.

[0226] Clause 30B, the device described in Clause 28B or 29B, wherein the current image comprises more than one sub-image, and wherein the one or more processors are further configured to: process all sub-images of the current image as images, at least in part based on the determination that the current sub-images are reordered.

[0227] Clause 31B, the device according to Clause 28B or 29B, wherein the one or more processors are further configured to: determine whether a slice in the current sub-image is a P slice or a B slice; and further process the current sub-image as an image based on the determination that a slice in the current sub-image is a P slice or a B slice and the determination that the current sub-image has been reordered.

[0228] The device described in Clause 32B, or any of Clauses 18B-25B or 28B-31B, wherein the one or more processors are further configured to: determine that the current image has more than one sub-image, and determine that the current sub-image will be processed as an image, wherein the sub-image identifier of the co-located sub-image in the reference images of the current image has the same value as the sub-image identifier of the current sub-image.

[0229] The device described in Clause 33B, or any of Clauses 18B-28B or 30B-31B, wherein the one or more processors are further configured to: determine that a reference image of the current image is an interlayer reference image having only one sub-image, wherein the sub-image identifier of the co-located sub-image in the reference image and the sub-image identifier of the current sub-image have different values.

[0230] Clause 34B, the device described in any of Clauses 18B-28B, 30B-31B, or 33B, wherein the one or more processors are further configured to: determine that the current image has more than one sub-image, and determine that the current sub-image will not be processed as an image, wherein the sub-image identifier of the co-located sub-image in the reference images of the current image has a different value than the sub-image identifier of the current sub-image.

[0231] The device described in Clause 35B, or any of Clauses 18B-34B, further includes: a display configured to display the video data.

[0232] Clause 36B, the device described in any of the clauses 18B-35B, wherein the device includes a mobile phone.

[0233] Clause 37B, a non-transitory computer-readable storage medium storing instructions that, when executed, cause one or more processors to: extract a current sub-picture from a bitstream of video data; parse a virtual boundary syntax element indicating a virtual boundary of the current picture, wherein the current sub-picture is associated with the current picture; update the virtual boundary at least in part based on the virtual boundary syntax element; and decode the current sub-picture based on the updated virtual boundary.

[0234] Clause 38B, an apparatus for decoding video data, the apparatus comprising: a unit for extracting a current sub-picture from a bitstream of the video data; a unit for parsing a virtual boundary syntax element indicating a virtual boundary of the current picture, wherein the current sub-picture is associated with the current picture; a unit for updating the virtual boundary at least in part based on the virtual boundary syntax element; and a unit for decoding the current sub-picture based on the updated virtual boundary.

[0235] It should be recognized that, depending on the examples, certain actions or events of any of the techniques described herein may be performed in a different order, and may be added, combined, or omitted together (e.g., not all described actions are necessary for the implementation of the technique). Furthermore, in some examples, actions or events may be performed concurrently (e.g., through multithreading, interrupt handling, or multiprocessor) rather than sequentially.

[0236] In one or more examples, the described functionality may be implemented using hardware, software, firmware, or any combination thereof. If implemented in software, these functions may be stored as one or more instructions or code on a computer-readable medium, transmitted via a computer-readable medium, or executed by a hardware-based processing unit. A computer-readable medium may include a computer-readable storage medium, which corresponds to a tangible medium such as a data storage medium, or a communication medium (which includes, for example, any medium that facilitates the transfer of a computer program from one location to another according to a communication protocol). In this way, a computer-readable medium may generally correspond to (1) a non-transitory tangible computer-readable storage medium or (2) a communication medium (such as a signal or carrier wave). A data storage medium may be any available medium that can be accessed by one or more computers or one or more processors to retrieve instructions, code, and / or data structures used for the implementation of the techniques described in this disclosure. A computer program product may include a computer-readable medium.

[0237] By way of example, and not limitation, such computer-readable storage media may include RAM, ROM, EEPROM, CD-ROM or other optical disc storage, disk storage or other magnetic storage devices, flash memory, or any other medium that can be used to store desired program code in the form of instructions or data structures and that can be accessed by a computer. Furthermore, any connection may be appropriately referred to as a computer-readable medium. For example, if instructions are transmitted from a website, server, or other remote source using coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave, then coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave are included in the definition of medium. However, it should be understood that computer-readable storage media and data storage media do not include connections, carrier waves, signals, or other transient media, but rather refer to non-transient, tangible storage media. As used herein, disk and optical disc include compressed optical discs (CDs), laser optical discs, optical discs, digital versatile optical discs (DVDs), floppy disks, and Blu-ray discs, where disks typically magnetically copy data, while optical discs optically copy data using lasers. Combinations of the above items should also be included within the scope of computer-readable media.

[0238] Instructions can be processed by one or more processors, such as one or more digital signal processors (DSPs), general-purpose microprocessors, application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other equivalent integrated or discrete logic circuits. Therefore, as used herein, the terms "processor" and "processing circuitry" can refer to any of the foregoing structures or any other structures suitable for implementing the techniques described herein. Furthermore, in some aspects, the functions described herein can be provided in dedicated hardware and / or software modules configured for encoding and decoding or incorporated into combined codecs. Moreover, these techniques can be fully implemented in one or more circuit or logic units.

[0239] The technologies disclosed herein can be implemented in a variety of devices or apparatuses, including wireless handheld devices, integrated circuits (ICs), or a set of ICs (e.g., chipsets). Various components, modules, or units are described in this disclosure to emphasize functional aspects of a device configured to perform the disclosed technologies, but are not necessarily required to be implemented by different hardware units. Rather, as described above, the various units can be combined in a codec hardware unit or provided by a collection of interoperable hardware units, including one or more processors as described above combined with suitable software and / or firmware.

[0240] Examples have been described. These and other examples are within the scope of the following claims.

Claims

1. A method for decoding video data, the method comprising: Extract the current sub-image from the bitstream of the video data; The virtual boundary syntax element that indicates the virtual boundary of the current image is parsed, and the current sub-image is associated with the current image; The virtual boundary of the current sub-image is updated based at least in part on the virtual boundary syntax elements. The current sub-image is decoded based on the updated virtual boundary.

2. The method according to claim 1, wherein the update further comprises: Determine the number of vertical virtual boundaries of the current sub-image, the number of horizontal virtual boundaries of the current sub-image, the position of the vertical virtual boundary of the current sub-image, and the position of the horizontal virtual boundary of the current sub-image.

3. The method according to claim 2, wherein the update further comprises: The virtual boundary syntax element is rewritten using the determined number of vertical virtual boundaries of the current sub-image, the determined number of horizontal virtual boundaries of the current sub-image, the determined vertical virtual boundary position of the current sub-image, and the determined horizontal virtual boundary position of the current sub-image.

4. The method according to claim 2, further comprising: The horizontal virtual boundary position of the current sub-image is updated based on a comparison between the horizontal virtual boundary position indicated by the virtual boundary syntax element and the vertical position (y-position) of the top-left corner CTU of the current sub-image, and a comparison between the horizontal virtual boundary position indicated by the virtual boundary syntax element and the vertical position (y-position) of the top-left corner CTU of the current sub-image plus the height of the current sub-image.

5. The method according to claim 4, further comprising: The height of the current image is obtained by adding the vertical position (y-position) of the top-left corner CTU of the current sub-image to the height of the current image.

6. The method according to claim 2, further comprising: The vertical virtual boundary position of the current sub-image is updated based on a comparison between the vertical virtual boundary position indicated by the virtual boundary syntax element and the horizontal position (x position) of the top-left corner CTU of the current sub-image, and a comparison between the vertical virtual boundary position indicated by the virtual boundary syntax element and the horizontal position (x position) of the top-left corner CTU of the current sub-image plus the width of the current sub-image.

7. The method according to claim 6, further comprising: The width of the current image is cropped by adding the horizontal position (x position) of the top left corner CTU of the current sub-image to the width of the current image.

8. An apparatus for decoding video data, the apparatus comprising: A memory configured to store the video data; as well as One or more processors coupled to the memory, wherein the one or more processors are configured to perform the method according to any one of claims 1-7.

9. A non-transitory computer-readable storage medium storing instructions that, when executed, cause one or more processors to perform the method according to any one of claims 1-7.

Images