A video processing method, device and recording medium

Abstract

Several techniques for video encoding and decoding are described. One example method involves performing a conversion between a sub-picture in a video frame and the video bitstream based on a rule. This rule specifies that, when a sub-picture is considered a video frame for conversion, cross-layer alignment constraints are applied to fewer than all layers, including the current layer containing the sub-picture and a subset of layers associated with the current layer.

Description

[0001] Cross-reference to related applications

[0002] This application is based on International Patent Application No. PCT / CN2021 / 082029, filed on March 22, 2021, which claims priority and interest in International Patent Application No. PCT / CN2020 / 080533, filed on March 21, 2020. All of the aforementioned patent applications are incorporated herein by reference in their entirety. Technical Field

[0003] This patent document relates to image and video encoding and decoding. Background Technology

[0004] Digital video consumes the largest share of bandwidth in the internet and other digital communication networks. As the number of connected user devices capable of receiving and displaying video increases, the bandwidth demand for digital video is expected to continue to grow. Summary of the Invention

[0005] This paper discloses techniques that can be used by video encoders and decoders to process the codec representation of video using control information useful for decoding the codec representation.

[0006] In one example aspect, a video processing method is disclosed. This method includes performing a conversion between a current image of the video and the video bitstream according to rules. The rules specify multiple syntax elements for specifying the use of a reference image resampling tool that resamples a reference image with a different resolution than the current image for use in the conversion.

[0007] In another example, a video processing method is disclosed. This method includes performing a conversion between a current image of a video and a bitstream of the video according to rules. The rules specify syntax elements with non-binary values ​​for specifying (1) a reference image resampling tool that resamples a reference image with a different resolution than the current image, and (2) the use of image resolution changes within a codec layer video sequence (CLVS).

[0008] In another example, a video processing method is disclosed. This method includes performing a conversion between a video comprising multiple layers and a video bitstream according to rules. The rules specify that, when a sub-image is considered a video image for conversion, cross-layer alignment constraints are applied to fewer than all layers, including the current layer containing the sub-image and a subset of layers associated with the current layer. The cross-layer alignment constraints include restrictions on at least one dimension of the video image, the number of sub-images within the video image, the position of at least one sub-image, or the identifier of the sub-image.

[0009] In another example, a video processing method is disclosed. This method includes performing a transformation between the current layer of a video and the video bitstream according to a rule. The rule specifies that cross-layer alignment constraints are applied to all layers in the dependency tree associated with the current layer, regardless of whether any layer among all layers is an output layer in the output layer set. The cross-layer alignment constraints include restrictions on at least one dimension of the video picture, the number of sub-pictures within the video picture, the position of at least one sub-picture, or the identifier of the sub-picture. All layers in the dependency tree include the current layer, all layers that have the current layer as a reference layer, and all reference layers of the current layer.

[0010] In another example, a video processing method is disclosed. This method includes performing a conversion between a current image of a video and the video bitstream according to a rule. This rule specifies that resampling of a reference image in the same layer as the current image is enabled, regardless of the value of a syntax element specifying whether changes in image resolution are allowed in a codec layer video sequence (CLVS).

[0011] In another example, a video processing method is disclosed. This method includes performing a conversion between a current image of a video comprising multiple layers and a bitstream of the video, according to a rule. The rule specifies one of the following: (1) juxtaposing a reference image of the current image is not allowed, or (2) if the reference image of the current image is juxtaposed, a motion vector pointing to the reference image is used during a conversion where the current image is not scaled.

[0012] In another example, a video processing method is disclosed. This method includes performing a conversion between a video and a video bitstream according to a rule. The rule specifies that the scaling window offset parameter is identical for any two video images of the same dimension, represented by the number of luminance samples, from the same codec layer video sequence (CLVS) or codec video sequence (CVS).

[0013] In another example, a video processing method is disclosed. This method includes performing a conversion between a current image of a video and the video bitstream according to a rule. The rule specifies that, in response to the current image having a resolution different from at least one other image in the same access unit of the current image, an inter-frame layer predictive codec tool is enabled only if the current image is an intra-frame random access point (IRAP) image.

[0014] In another example, a video processing method is disclosed. This method includes performing a conversion between videos comprising one or more video images, wherein the encoding / decoding representation conforms to a format rule; wherein the format rule specifies that two or more syntax fields in a sequence parameter set control the reference image resolution (RPR) change in the video.

[0015] In another example, a different video processing method is disclosed. This method includes performing a conversion between videos comprising one or more video images, wherein the codec representation conforms to a format rule; wherein the format rule specifies that a single syntax field in a sequence parameter set controls changes in the reference image resolution (RPR) in the video; and wherein the format rule specifies that resampling of the inter-frame layer reference image is permitted for the conversion, regardless of the value of the single syntax field.

[0016] In another example, a different video processing method is disclosed. This method includes performing a transformation between videos comprising one or more layers, each layer including one or more video frames containing one or more sub-pictures, wherein the codec representation conforms to a format rule; wherein the format rule specifies either a first constraint on cross-layer alignment or a second constraint on a combination of sub-pictures and scalability of inter-frame layer pictures.

[0017] In another example, a different video processing method is disclosed. This method includes performing a transformation between videos comprising one or more layers, each layer including one or more video images containing one or more sub-images, wherein the transformation conforms to a format rule that specifies that inter-frame layer reference images or long-term reference images are not allowed as juxtaposed images of the current image used for the transformation.

[0018] In another example, a different video processing method is disclosed. This method includes performing a conversion between a video comprising multiple images and a codec representation of the video, wherein the conversion conforms to the same rule for any two images within the same codec layer video sequence or codec video sequence that have the same values ​​for pic_width_in_luma_samples and pic_height_in_luma_samples.

[0019] In another example, a different video processing method is disclosed. This method includes performing a conversion between a video comprising multiple images and a codec representation of the video, wherein the conversion conforms to a rule specifying that inter-frame layer prediction is allowed only when the current image is an intra-frame random access point image, provided that the image resolution or scaling window differs for the current image and other images in the same access unit.

[0020] In yet another example, a video encoder apparatus is disclosed. The video encoder includes a processor configured to implement the methods described above.

[0021] In yet another example, a video decoder apparatus is disclosed. The video decoder includes a processor configured to implement the methods described above.

[0022] In yet another example, a computer-readable medium storing code is disclosed. This code embodies one of the methods described herein in the form of processor-executable code.

[0023] These and other features will be described in this document. Attached Figure Description

[0024] Figure 1 An example of raster scan strip segmentation of an image is shown, in which the image is divided into 12 slices and 3 raster scan strips.

[0025] Figure 2 An example of rectangular strip segmentation of an image is shown, where the image is divided into 24 slices (6 slice columns and 4 slice rows) and 9 rectangular strips.

[0026] Figure 3 An example of an image divided into slices and rectangular strips is shown, where the image is divided into 4 slices (2 slice columns and 2 slice rows) and 4 rectangular strips.

[0027] Figure 4 The image is shown as being divided into 18 slices, 24 strips, and 24 sub-images.

[0028] Figure 5 This is a block diagram of an example video processing system.

[0029] Figure 6 This is a block diagram of a video processing device.

[0030] Figure 7 This is a flowchart of an example method for video processing.

[0031] Figure 8 A block diagram of a video encoding / decoding system according to some embodiments of the present disclosure is shown.

[0032] Figure 9 A block diagram of an encoder according to some embodiments of the present disclosure is shown.

[0033] Figure 10 A block diagram of a decoder according to some embodiments of the present disclosure is shown.

[0034] Figure 11 This illustrates an example of a typical sub-picture-based viewport-dependent 360° video encoding / decoding scheme.

[0035] Figure 12A viewport-dependent 360° video encoding and decoding scheme based on sub-pictures and spatial scalability is presented.

[0036] Figure 13 This is a flowchart representation of a method for video processing according to the present technology.

[0037] Figure 14 This is a flowchart representation of another method for video processing according to the present technology.

[0038] Figure 15 This is a flowchart representation of another method for video processing according to the present technology.

[0039] Figure 16 This is a flowchart representation of another method for video processing according to the present technology.

[0040] Figure 17 This is a flowchart representation of another method for video processing according to the present technology.

[0041] Figure 18 This is a flowchart representation of another method for video processing according to the present technology.

[0042] Figure 19 This is a flowchart representation of another method for video processing according to the present technology.

[0043] Figure 20 This is a flowchart representation of another method for video processing according to the present technology. Detailed Implementation

[0044] Chapter headings are used in this document for ease of understanding, not to limit the applicability of the techniques and embodiments disclosed in each chapter to that chapter only. Furthermore, H.266 terminology is used in some descriptions merely for ease of understanding, not to limit the scope of the disclosed techniques. Therefore, the techniques described herein are also applicable to other video codec protocols and designs. In this document, regarding the current draft of the VVC specification, edited changes to the text are shown by strikethrough indicating undoing and highlighting indicating addition (including bold and italic).

[0045] 1. Overview

[0046] This article relates to video codec techniques. Specifically, it concerns 1) the use of two or more of the following in video codecs: Reference Picture Resampling (RPR), subpictures, and scalability; 2) the use of RPR between the current picture and the reference picture, which have the same spatial resolution; and 3) the combination of long-term reference pictures and juxtaposed pictures. This idea can be applied, alone or in various combinations, to any standard or non-standard video codec that supports multi-layered video codecs, such as the Multi-Functional Video Codec (VVC) currently under development.

[0047] 2. Abbreviations

[0048] APS Adaptive Parameter Set

[0049] AU Access Unit

[0050] AUD Access Unit Separator

[0051] AVC Advanced Video Codec

[0052] CLVS codec layer video sequence

[0053] CPB image buffer

[0054] CRA Fully Random Access

[0055] CTU (Codec Tree Unit)

[0056] CVS codec video sequence

[0057] DCI decoding capability information

[0058] DPB Decoding Image Buffer

[0059] End of EOB bitstream

[0060] End of EOS sequence

[0061] GDR gradually decoded and refreshed

[0062] HEVC High-Efficiency Video Encoding and Decoding

[0063] HRD Assumption Reference Decoder

[0064] IDR Instant Decoding and Refresh

[0065] ILP Inter-Frame Prediction

[0066] ILRP Inter-Frame Layer Reference Image

[0067] IRAP Intra-Frame Random Access Images

[0068] JEM Joint Exploration Model

[0069] LTRP Long-Term Reference Image

[0070] MCTS Motion Restraint Piece Set

[0071] NAL Network Abstraction Layer

[0072] OLS Output Layer Set

[0073] PH image header

[0074] PPS Image Parameter Set

[0075] PTL profile, layer, and level

[0076] PU Image Unit

[0077] RAP Random Access Point

[0078] RBSP raw byte sequence payload

[0079] SEI Assist Enhancement Information

[0080] SPS Sequence Parameter Set

[0081] STRP Short-Term Reference Image

[0082] SVC Scalable Video Codec

[0083] VCL (Video Codec Layer)

[0084] VPS Video Parameter Set

[0085] VTM VVC Test Model

[0086] VUI Video Availability Information

[0087] VVC Multi-Functional Video Encoding and Decoding

[0088] 3. Preliminary Discussion

[0089] Video codec standards are primarily developed from well-known ITU-T and ISO / IEC standards. ITU-T developed H.261 and H.263, while ISO / IEC developed MPEG-1 and MPEG-4 video standards. These two organizations jointly developed the H.262 / MPEG-2 video standard, the H.264 / MPEG-4 Advanced Video Coding (AVC) standard, and the H.265 / HEVC standard. Starting with H.262, video codec standards are based on a hybrid video codec architecture, which uses temporal prediction plus transform coding. To explore future video codec technologies beyond HEVC, VCEG and MPEG jointly established the Joint Video Exploration Team (JVET) in 2015. Since then, JVET has adopted many new methods and incorporated them into reference software called the Joint Exploration Model (JEM). JVET meetings are held quarterly, and the goal of the new codec standards is to reduce the bitrate by 50% compared to HEVC. The new video codec standard was officially named Multifunctional Video Codec (VVC) at the JVET meeting in April 2018, and the first version of the VVC Test Model (VTM) was also released at that time. Due to ongoing efforts to standardize VVC, new codec technologies have been adopted into the VVC standard at every JVET meeting. The VVC working draft and the VTM test model are updated after each meeting. The current goal of the VVC project is to achieve Technical Finalization (FDIS) at the meeting in July 2020.

[0090] 3.1. Image Segmentation Schemes in HEVC

[0091] HEVC includes four different image segmentation schemes: regular striping, dependent striping, slice, and wavefront parallel processing (WPP). These can be applied to maximum transmission unit (MTU) size matching, parallel processing, and reduced end-to-end latency.

[0092] Regular slices are similar to those in H.264 / AVC. Each regular slice is encapsulated in its own NAL unit, and intra-picture prediction (intra-sample prediction, motion information prediction, and encoding / decoding mode prediction) and entropy encoding / decoding dependencies across slice boundaries are disabled. Therefore, regular slices can be reconstructed independently of other regular slices within the same picture (although they may still have interdependencies due to loop filtering operations).

[0093] Regular stripes are the only tool available for parallelization, and they are also available in almost the same form in H.264 / AVC. Parallelization based on regular stripes requires minimal inter-frame processor or inter-frame kernel communication (except for inter-frame processor or inter-frame kernel data sharing for motion compensation when decoding predictive encoded / decoded images, which is generally much more difficult than inter-frame processor or inter-frame kernel data sharing due to intra-image prediction). However, for the same reason, using regular stripes can lead to significant encoding / decoding overhead due to the bit cost of the stripe header and the lack of prediction across stripe boundaries. Furthermore, due to the intra-image independence of regular stripes and the fact that each regular stripe is encapsulated in its own NAL unit, regular stripes (compared to other tools mentioned below) also serve as a key mechanism for bitstream segmentation to match MTU size requirements. In many cases, the goals of parallelization and MTU size matching present conflicting requirements for stripe layout within images. This recognition led to the development of the parallelization tools mentioned below.

[0094] Dependency striping has a short stripe header and allows the bitstream to be split at tree block boundaries without disrupting arbitrary intra-picture predictions. Essentially, dependency striping provides the option to segment a regular stripe into multiple NAL units to offer reduced end-to-end latency by allowing a portion of the regular stripe to be transmitted before the entire regular stripe's encoding is complete.

[0095] In WPP, images are segmented into single-row codec tree blocks (CTBs). Entropy decoding and prediction are allowed to use data from CTBs in other segments. Parallel processing is possible through parallel decoding of CTB rows, where the start of decoding a CTB row is delayed by two CTBs, ensuring that data related to the CTBs above and to the right of the main CTB is available before the main CTB is decoded. Using this staggered start (which looks like a wavefront when graphically represented), parallelization is possible with as many processors / cores as the image containing CTB rows. Because intra-image prediction between adjacent tree block rows within an image is permitted, the inter-processor / inter-core communication required to implement intra-image prediction can be substantial. WPP segmentation does not result in the generation of additional NAL units compared to when it is not applied, therefore WPP is not a tool for MTU size matching. However, if MTU size matching is required, regular striping can be used with WPP, with some encoding / decoding overhead.

[0096] A slice defines the horizontal and vertical boundaries that divide an image into slice columns and slice rows. Slice columns extend from the top to the bottom of the image. Similarly, slice rows extend from the left to the right of the image. The number of slices in an image can be simply derived as the number of slice columns multiplied by the number of slice rows.

[0097] Before decoding the top-left CTB of the next slice in the order of slice raster scans of the image, the scan order of the CTBs is changed to be local within the slice (in the order of slice CTB raster scans). Similar to regular stripes, slices break the intra-image prediction dependency and the entropy decoding dependency. However, they do not need to be included in separate NAL units (the same as WPP in this respect); therefore, slices cannot be used for MTU size matching. Each slice can be processed by one processor / core, and the inter-processor / inter-core communication required for intra-image prediction between processing units decoding adjacent slices is limited to transmitting the shared slice header when the slice spans more than one slice, and loop filtering related to the sharing of reconstructed samples and metadata. When a slice includes more than one slice or WPP segment, the entry point byte offset of each slice or WPP segment in the slice, except for the first one, is signaled in the slice header.

[0098] For simplicity, restrictions on the application of the four different image segmentation schemes have been specified in HEVC. A given codec video sequence cannot simultaneously include slices and wavefronts of most of the levels specified in HEVC. For each strip and slice, one or both of the following conditions must be met: 1) All codec tree blocks in a strip belong to the same slice; 2) All codec tree blocks in a slice belong to the same strip. Ultimately, a wavefront segment contains exactly one CTB line, and when using WPP, if a strip starts within a CTB line, it must end within the same CTB line.

[0099] With the recent revision of HEVC, HEVC specifies three types of MCTS-related SEI messages: i.e., domain MCTS SEI messages, MCTS extracted information set SEI messages, and MCTS extracted information nested SEI messages.

[0100] The temporal MCTS SEI message indicates the presence of an MCTS in the bitstream, and signaling notifies the MCTS. For each MCTS, motion vectors are restricted to pointing to full-sample locations within the MCTS and fractional-sample locations that require interpolation only from full-sample locations within the MCTS, and motion vector candidates derived from blocks outside the MCTS for temporal motion vector prediction are not allowed. In this way, each MCTS can be decoded independently, and there are no slices not included in the MCTS.

[0101] The MCTS Extraction Information Set (SEI) message provides auxiliary information (specified as part of the semantics of the SEI message) that can be used in MCTS sub-bitstream extraction to generate a consistent bitstream of the MCTS set. This information consists of multiple extraction information sets, each defining multiple MCTS sets and containing RBSP bytes for replacing the VPS, SPS, and PPS to be used during the MCTS sub-bitstream extraction process. When extracting sub-bitstreams according to the MCTS sub-bitstream extraction process, the parameter sets (VPS, SPS, and PPS) need to be rewritten or replaced, and the slice header needs to be slightly updated because one or all slice address-related syntax elements (including first_slice_segment_in_pic_flag and slice_segment_address) typically need to have different values.

[0102] 3.2. Image Segmentation in VVC

[0103] In VVC, an image is divided into one or more slice rows and one or more slice columns. A slice is a sequence of CTUs covering a rectangular area of ​​the image. The CTUs within a slice are scanned in raster scan order within that slice.

[0104] A strip consists of an integer number of consecutive complete CTU lines within an integer number of complete slices or images.

[0105] Two stripe modes are supported: raster scan stripe mode and rectangular stripe mode. In raster scan stripe mode, a stripe contains a complete sequence of stripes in a sheet raster scan of an image. In rectangular stripe mode, a stripe contains multiple complete sheets that together form a rectangular area of ​​the image, or multiple consecutive complete CTU rows of a single sheet that together forms a rectangular area of ​​the image. Sheets within a rectangular stripe are scanned in the sheet raster scan order within the rectangular area corresponding to that stripe.

[0106] A sub-image contains one or more stripes that collectively cover a rectangular area of ​​the image.

[0107] Figure 1 An example of raster scan strip segmentation of an image is shown, in which the image is divided into 12 slices and 3 raster scan strips.

[0108] Figure 2 An example of rectangular strip segmentation of an image is shown, where the image is divided into 24 slices (6 slice columns and 4 slice rows) and 9 rectangular strips.

[0109] Figure 3 An example of an image divided into slices and rectangular strips is shown, where the image is divided into 4 slices (2 slice columns and 2 slice rows) and 4 rectangular strips.

[0110] Figure 4 An example of sub-image segmentation of an image is shown, where the image is segmented into 18 slices, with the 12 slices on the left each covering a strip of 4×4 CTU, and the 6 slices on the right each covering two vertically stacked strips of 2×2 CTU, resulting in a total of 24 strips and 24 sub-images of different dimensions (each strip being a sub-image).

[0111] 3.3. Changes in image resolution within a sequence

[0112] In AVC and HEVC, the spatial resolution of an image cannot be changed unless a new sequence with a new SPS begins with an IRAP image. VVC enables intra-sequence image resolution changes at locations where an IRAP image is not encoded; this IRAP image is always intra-coded. This feature is sometimes called Reference Image Resampling (RPR) because it requires resampling of the reference image used for inter-frame prediction when the reference image has a different resolution than the current image being decoded.

[0113] The scaling factor is limited to greater than or equal to 1 / 2 (2x downsampling from the reference image to the current image) and less than or equal to 8 (8x upsampling). Three sets of resampling filters with different frequency cutoffs are specified to handle various scaling factors between the reference and current images. The three sets of resampling filters are applied to scaling factors ranging from 1 / 2 to 1 / 1.75, from 1 / 1.75 to 1 / 1.25, and from 1 / 1.25 to 8, respectively. Each set of resampling filters has 16 phases for luma and 32 phases for chroma, similar to motion-compensated interpolation filters. In fact, the normal MC interpolation process is a special case of the resampling process where the scaling factor ranges from 1 / 1.25 to 8. The horizontal and vertical scaling factors are derived based on the image width and height, as well as the left, right, top, and bottom scaling offsets specified for the reference and current images.

[0114] Other aspects of the VVC design that support this feature that differ from HEVC include: i) Picture resolution and the corresponding consistency window are signaled in the PPS instead of the SPS, where the maximum picture resolution is signaled in the SPS. ii) For a single-layer bitstream, each picture storage (the time slot in the DPB used to store one decoded picture) occupies the buffer size required to store the decoded picture with the maximum picture resolution.

[0115] 3.4. Overview and Scalable Video Codec (SVC) in VVC

[0116] Scalable video codec (SVC, sometimes also called scalability in video codec) refers to video codec using a base layer (BL) (sometimes called a reference layer (RL)) and one or more scalable enhancement layers (EL). In SVC, the base layer can carry video data with a basic quality level. One or more enhancement layers can carry additional video data to support, for example, higher spatial, temporal, and / or signal-to-noise ratio (SNR) levels. Enhancement layers can be defined relative to previously encoded layers. For example, the bottom layer can act as a BL, while the top layer can act as an EL. Intermediate layers can act as either an EL or an RL, or both. For example, an intermediate layer (e.g., a layer that is neither the lowest nor the highest layer) can be an EL of a layer below the intermediate layer (such as a base layer or any inter-layer enhancement layer) and simultaneously act as an RL of one or more enhancement layers above the intermediate layer. Similarly, in the multi-view or 3D extension of the HEVC standard, there can be multiple views, and information from one view can be used to codec (e.g., encode or decode) information from another view (e.g., motion estimation, motion vector prediction, and / or other redundancy).

[0117] In SVC, parameters used by the encoder or decoder are grouped into parameter sets based on the codec level at which they can be utilized (e.g., video level, sequence level, picture level, stripe level, etc.). For example, parameters available for one or more codec video sequences at different layers in a bitstream can be included in the Video Parameter Set (VPS), and parameters available for one or more pictures in a codec video sequence can be included in the Sequence Parameter Set (SPS). Similarly, parameters utilized for one or more stripes in a picture can be included in the Picture Parameter Set (PPS), and additional parameters for a single strip can be included in the stripe header. Likewise, indications of which parameter set(s) a specific layer uses at a given time can be provided at various codec levels.

[0118] Because of VVC's support for Reference Picture Resampling (RPR), it's possible to design support for bitstreams containing multiple layers (e.g., two layers in VVC with SD and HD resolutions) without requiring any additional signal processing level codecs, as the upsampling needed for spatial scalability support can be achieved using only RPR upsampling filters. However, scalability support requires higher-level syntax changes (compared to no scalability support). Scalability support was specified in VVC version 1. Unlike scalability support in any earlier video codec standards (including in extensions to AVC and HEVC), VVC's scalability is designed to be as friendly as possible to single-layer decoder designs. The decoding capability of multi-layer bitstreams is specified as if there were only a single layer in the bitstream. For example, decoding capabilities, such as DPB size, are specified in a way that is independent of the number of layers in the bitstream to be decoded. Essentially, decoders designed for single-layer bitstreams do not require many changes to decode multi-layer bitstreams. Compared to the multi-layer extensions of AVC and HEVC, the HLS aspect is significantly simplified at the expense of some flexibility. For example, the IRAP AU is required to contain an image of each layer present in CVS.

[0119] 3.5. Sub-image-based viewport-dependent 360° video streaming

[0120] In 360° video (also known as omnidirectional video) streaming, at any given moment, only a subset of the entire omnidirectional video sphere (e.g., the current viewport) is presented to the user, who can change their viewing orientation at any time by turning their head, thus changing the current viewport. While it is desirable to have at least some lower-quality representation of areas not covered by the current viewport available at the client, ready to be presented to the user in case they suddenly change their viewing orientation to any location on the sphere, the high-quality representation of the omnidirectional video is only needed for the current viewport being presented to the user at that moment. This optimization is achieved by dividing the high-quality representation of the entire omnidirectional video into sub-pictures with appropriate granularity. Using VVC, these two representations can be encoded as two independent layers.

[0121] exist Figure 11 The diagram illustrates a typical sub-picture-based viewport-dependent 360° video delivery scheme, where a higher-resolution representation of the full video consists of sub-pictures, while a lower-resolution representation of the full video does not use sub-pictures and can be encoded and decoded using less dense random access points in the higher-resolution representation. The client receives the lower-resolution full video, and for the higher-resolution video, it only receives and decodes the sub-pictures covering the current viewport.

[0122] 3.6. Parameter Set

[0123] AVC, HEVC, and VVC specify parameter sets. Parameter set types include SPS, PPS, APS, and VPS. AVC, HEVC, and VVC all support SPS and PPS. VPS was introduced with HEVC and is included in both HEVC and VVC. APS is not included in AVC or HEVC, but it is included in the latest VVC draft text.

[0124] SPS is designed to carry sequence-level header information, and PPS is designed to carry infrequently changing image-level header information. Using SPS and PPS, infrequently changing information does not need to be repeated for each sequence or image, thus avoiding redundant signaling. Furthermore, the use of SPS and PPS enables out-of-band transmission of important header information, thus not only avoiding the need for redundant transmission but also improving fault tolerance.

[0125] A VPS is introduced to carry sequence-level header information common to all layers in a multi-layer bitstream.

[0126] APS is introduced to carry such image-level or strip-level information, which requires a considerable number of bits to encode and decode, can be shared by multiple images, and can have a considerable number of different variations in the sequence.

[0127] 4. The technical problem solved by the disclosed technical solution

[0128] The existing design in the latest VVC documentation has the following issues:

[0129] 1) such as Figure 11 As shown, the current VVC design supports typical codec schemes for 360° video. However, while the current VVC design supports scalability, it does not support features such as... Figure 12 The improved 360° video encoding / decoding scheme is shown. (Compared to...) Figure 11 The only difference between the methods shown is that inter-frame layer prediction (ILP) is applied to the method described above. Figure 12 The method shown in the figure. The following two places in the VVC draft do not allow the combination of sub-images and spatial scalability:

[0130] a. Spatial scalability design in VVC relies on RPR features. However, the combination of RPR and sub-images is currently not permitted by the following semantic constraints:

[0131] Therefore, the improved encoding and decoding scheme is not allowed because the above constraints do not allow setting subpic_info_present_flag to 1 (to use multiple subpics per picture) for the SPS referenced at higher levels, and at the same time set res_change_in_clvs_allowed_flag to 1 (to enable RPR, which is required to take advantage of the spatial scalability of ILP).

[0132] b. The current VVC draft imposes the following constraints on the combination of sub-images and scalability:

[0133]

[0134] Apart from the restricted combination of sub-images and SNR scalability, the above constraints essentially disallow any other combination of sub-images and scalability utilizing ILP, where each layer within the dependency tree must have the same spatial resolution and the same sub-image layout.

[0135] 2) When `subpic_treated_as_pic_flag[i]` equals 1, the subpicture boundary of the i-th subpicture will be considered as the picture boundary in motion compensation. In the VVC draft text, this is achieved by applying a specific cropping operation during the decoding process related to motion compensation. However, for... Figure 12 The improved encoding and decoding scheme shown in the figure does not require such cropping in this case, since the lower layers are fully available to the decoder and not just the region corresponding to the i-th sub-image, thus avoiding unnecessary encoding and decoding efficiency loss.

[0136] 3) Without considering the impact on Figure 12 With support for the improved encoding / decoding scheme shown, the existing constraints above (described in the description of Problem 1b) regarding the combination of sub-images and the scalability of ILP present the following problems:

[0137] a. This constraint should also apply when the layer containing the i-th sub-image is not an output layer of OLS. The entire constraint should be specified in a way that does not consider whether the layer is an output layer of OLS.

[0138] b. It should include the requirement that the value of subpic_treated_as_pic_flag[i] be aligned across layers, otherwise it would be impossible to extract subpicture sequences with the same index across layers.

[0139] c. The requirement for cross-layer alignment of the value of `loop_filter_across_subpic_enabled_flag[i]` should be excluded because regardless of the value of this flag, as long as `subpic_treated_as_pic_flag[i]` equals 1, the subpic sequence is extractable. The setting of the value of `loop_filter_across_subpic_enabled_flag[i]` should be left to the encoder to determine the trade-off between the quality of a single extractable subpic sequence and the quality of the set of extractable subpic sequences, just as these two flags are signaled independently of each other.

[0140] d. The entire constraint should only apply if sps_num_subpics_minus1 is greater than 0, to avoid all cases where a subpic of each subpic is unintentionally covered by the constraint.

[0141] e. It is necessary to explicitly specify the time domain range to which the constraints apply, such as the AU set.

[0142] f. This should include a requirement that the values ​​of each of the scaling window parameters scaling_win_left_offset, scaling_win_right_offset, scaling_win_top_offset, and scaling_win_bottom_offset be aligned across layers to ensure that ITRP's RPR is not needed when each image has multiple sub-images.

[0143] 4) Currently, the juxtaposed image of the current image can be a Long-Term Reference Image (LTRP) in the same layer as the current image, or it can be an Inter-Layer Reference Image (ILRP), such as a reference image in a different layer than the current image. However, in either case, motion vector-based scaling based on the Point of Contention (POC) is not applied, so encoding / decoding performance is expected to be very low due to this. Therefore, it is best to disallow the juxtaposed image of the current image to be either an LTRP or an ILRP.

[0144] 5) Currently, images with the same spatial resolution in CLVS are allowed to have different scaling windows. However, this should not be allowed; otherwise, the SPS flag and the general constraint flag of RPR would not be able to be used to completely disable the RPR tool.

[0145] 5. List of technical solutions and embodiments

[0146] To address the above and other issues, the following summarized methods are presented. These terms should be considered as examples for explaining general concepts, and not interpreted in a narrow way. Furthermore, these terms can be applied individually or combined in any way.

[0147] 1) To address issue 1a, multiple (such as two) SPS flags can be specified and / or signaled for controlling RPR, instead of just one SPS flag (e.g., res_change_in_clvs_allowed_flag as in the current VVC draft) for controlling RPR.

[0148] a. For example, the first flag (e.g., ref_pic_resampling_enabled_flag) specifies whether RPR may be needed to decode one or more images, while the second flag (e.g., res_change_in_clvs_allowed_flag) specifies whether the image resolution is allowed to be changed within CLVS.

[0149] b. Alternatively, the second flag may be signaled only if the first flag indicates that RPR may be needed to decode one or more images. Furthermore, when not signaled, the value of the second flag is inferred to specify a value that disallows changes to image resolution within the CLVS.

[0150] i. Alternatively, these two flags are signaled independently of each other.

[0151] c. Alternatively, another general constraint flag may be added, such that there is a general constraint flag for each of the first and second flags.

[0152] d. In addition, combinations of multiple sub-images per image are not allowed when res_change_in_clvs_allowed_flag is equal to 1, but combinations of multiple sub-images per image are allowed when ref_pic_resampling_enabled_flag is equal to 1.

[0153] e. Furthermore, the constraint on the value of scaling_window_explicit_signalling_flag based on the value of res_change_in_clvs_allowed_flag is changed to the value based on the value of ref_pic_resampling_enabled_flag, as follows: When When the value is 0, the value of scaling_window_explicit_signalling_flag should be 0.

[0154] f. Alternatively, signaling can be performed in the VPS instead of the SPS for any one or all of multiple (such as two) flags.

[0155] i. In one example, any one or all of the multiple (such as two) flags in the VPS apply to all tiers specified by the VPS.

[0156] ii. In another example, any one or all of a plurality of (such as two) flags in a VPS may each have multiple instances of signaling notification in the VPS, and each instance applies to all layers in a dependency tree.

[0157] g. In one example, l bits u(1) are used to encode each of the multiple flags into an unsigned integer.

[0158] h. Alternatively, a syntax element can be notified with a non-binary value (e.g., in SPS / VPS) signaling to specify the use of RPR during decoding and the permission for image resolution changes within CLVS.

[0159] i. In one example, when the value of the syntax element is equal to 0, it specifies that RPR is not required to decode one or more images.

[0160] ii. In one example, when the value of the syntax element is equal to 1, it specifies that RPR may be needed to decode one or more images, while the image resolution is not allowed to be changed within CLVS.

[0161] iii. In one example, when the value of the syntax element is equal to 2, it specifies that RPR may be needed to decode one or more images, while allowing the image resolution to be changed within CLVS.

[0162] iv. Alternatively, how signaling notification syntax elements are configured can depend on whether inter-frame layer prediction is allowed.

[0163] v. In one example, the syntax element is encoded and decoded using ue(v), which indicates the syntax element of the 0th order Exp-Golomb encoding of an unsigned integer with the left bit first.

[0164] vi. In another example, N bits u(N) (e.g., N equals 2) are used to encode and decode syntax elements into unsigned integers.

[0165] 2) Alternatively, in addition to item 1 used to address problem 1a, there may still be only one flag, such as res_change_in_clvs_allowed_flag, but the semantics can be changed so that resampling of the inter-layer reference image is allowed regardless of the value of the flag.

[0166] a. In one example, the semantics can be changed as follows: `res_change_in_clvs_allowed_flag` equal to 1 specifies that the image spatial resolution can be changed within the CLVS of the reference SPS. A value of 0 for `res_change_in_clvs_allowed_flag` indicates that the spatial resolution of the image remains unchanged within any CLVS of the reference SPS.

[0167] b. With this change, even when res_change_in_clvs_allowed_flag equals 0, decoding of sub-pictures / pictures can still use the RPR of the Inter-Frame Layer Reference Picture (ILRP).

[0168] 3) To address problem 1b, update the constraints on the combination of sub-images and the scalability of ILP, such that the constraints only impose cross-layer alignment restrictions on the current layer and all higher layers that depend on the current layer, and do not impose cross-layer alignment restrictions on higher layers that do not depend on the current layer or on lower layers.

[0169] a. Alternatively, update the constraints to apply cross-layer alignment constraints only to the current layer and all layers above the current layer.

[0170] b. Alternatively, update the constraints to apply cross-layer alignment constraints only to the current layer and all higher layers in each OLS that contains the current layer.

[0171] c. Alternatively, update the constraints to apply cross-layer alignment constraints only to the current layer and all lower layers that are reference layers to the current layer.

[0172] d. Alternatively, update the constraints to apply cross-layer alignment constraints only to the current layer and all layers below it.

[0173] e. Alternatively, update the constraints to apply cross-layer alignment constraints only to the current layer and all lower layers in each OLS that contains the current layer.

[0174] f. Alternatively, update the constraints to apply cross-layer alignment restrictions only to all layers below the highest layer.

[0175] g. Alternatively, update the constraints to apply cross-layer alignment restrictions only to all layers above the lowest layer.

[0176] 4) To address issue 2, in one or more decoding processes involving cropping operations in the inter-frame prediction correlation process used to handle sub-image boundaries as image boundaries in motion compensation / motion prediction (e.g., in the derivation of temporal luma motion vector prediction in clause 8.5.2.11, the luma sample bilinear interpolation process in 8.5.3.2.2, the derivation of sub-block-based temporal merge candidates in 8.5.5.3, the derivation of sub-block-based temporal merge basic motion data in 8.5.5.4, the derivation of affine control point motion vector merge candidates in 8.5.5.6, the derivation of luma sample interpolation filtering process in 8.5.6.3.3, the luma integer sample extraction process in 8.5.6.3.4, and the chroma sample interpolation process in 8.5.6.3.4), the following changes are applied:

[0177] a. In one example, the process is modified so that if subpic_treated_as_pic_flag[CurrSubpicIdx] equals 1 and the reference image refPicLX has a sps_num_subpics_minus1 greater than 0, then the cropping operation is applied; otherwise, the cropping operation is not applied.

[0178] i. Alternatively, when juxtaposing images is not allowed (ILRP), as described above, only the process of changing the reference image refPicLX is not a juxtaposed image.

[0179] Furthermore, without changing the reference image refPicLX, the process of juxtaposing images is performed.

[0180] b. In one example, the process is modified so that if subpic_treated_as_pic_flag[CurrSubpicIdx] equals 1 and the current stripe's nal_unit_type value is not equal to IDR_W_RADL, IDR_N_LP, or CRA_NUT, then a cropping operation is applied; otherwise, no cropping operation is applied. Additionally, ILP is only permitted for encoding and decoding IRAP images.

[0181] c. In one example, no changes are made to these decoding processes. For example, if subpic_treated_as_pic_flag[CurrSubpicIdx] equals 1, then the cropping operation is applied; otherwise, the cropping operation is not applied, which is the same as in the current VVC text.

[0182] 5) To address problem 3a, update the constraints on the sub-image and the combination of leveraging the scalability of ILP, such that the constraints impose cross-layer alignment restrictions on all layers in each dependency tree. The dependency tree contains a specific layer, all layers with that specific layer as a reference layer, and all reference layers of that specific layer, regardless of whether any of those layers is an output layer of OLS.

[0183] 6) To address problem 3b, update the constraint on the combination of subpic and the scalability of ILP, such that the constraint imposes a cross-layer alignment constraint on the value of subpic_treated_as_pic_flag[i].

[0184] 7) To address problem 3c, update the constraint on the combination of subpicks and the scalability of ILP so that the constraint does not impose cross-layer alignment restrictions on the value of loop_filter_across_subpic_enabled_flag[i].

[0185] 8) To address the 3D issue, update the constraints on the combination of subpics and the scalability of the ILP so that the constraints do not apply when sps_num_subpics_minus1 equals 0.

[0186] a. Alternatively, update the constraint so that it does not apply when subpic_info_present_flag equals 0.

[0187] 9) To address problem 3e, update the constraints on the combination of sub-images and the scalability of ILP, such that the constraints impose cross-layer alignment restrictions on images in a specific target set of AU.

[0188] a. In one example, for each CLVS of the current layer of the reference SPS, let the target set of AUs, targetAuSet, be all AUs (inclusive) from the AU containing the first image of the CLVS in decoding order to the AU containing the last image of the CLVS in decoding order.

[0189] 10) To address problem 3f, update the constraints on the combination of sub-images and the scalability of the ILP, such that the constraints impose cross-layer alignment restrictions on the values ​​of each of the scaling window parameters scaling_win_left_offset, scaling_win_right_offset, scaling_win_top_offset, and scaling_win_bottom_offset.

[0190] 11) To solve problem 4, constrain the juxtaposed image of the current image to not be a long-term reference image (LTRP).

[0191] a. Alternatively, constrain the juxtaposed image of the current image to not be an inter-layer reference image (ILRP).

[0192] b. Alternatively, constrain the juxtaposed images of the current image to not be LTRP or ILRP.

[0193] c. Alternatively, if the juxtaposed image of the current image is LTRP or ILRP, scaling should not be applied to obtain the motion vector pointing to the juxtaposed image.

[0194] 12) To solve problem 5, the value of each of the constraints scaling_win_left_offset, scaling_win_right_offset, scaling_win_top_offset, and scaling_win_bottom_offset should be the same for any two images within the same CLVS that have the same values ​​of pic_width_in_luma_samples and pic_height_in_luma_samples, respectively.

[0195] a. Alternatively, replace “within the same CLVS” above with “within the same CVS”.

[0196] b. Alternatively, the constraint can be specified as follows:

[0197] Let ppsA and ppsB be any two PPSs referencing the same SPS. The requirement for bitstream consistency is that when ppsA and ppsB have the same values ​​for pic_width_in_luma_samples and pic_height_in_luma_samples, respectively, ppsA and ppsB should also have the same values ​​for scaling_win_left_offset, scaling_win_right_offset, scaling_win_top_offset, and scaling_win_bottom_offset, respectively.

[0198] c. Alternatively, the constraint can be specified as follows:

[0199] The values ​​of scaling_win_left_offset, scaling_win_right_offset, scaling_win_top_offset, and scaling_win_bottom_offset should be identical for any two images within the same CVS and satisfy all of the following conditions:

[0200] i. These two images have the same values ​​for pic_width_in_luma_samples and pic_height_in_luma_samples, respectively.

[0201] ii. These two images belong to the same layer or two layers (one layer is the reference layer of the other).

[0202] 13) It was proposed that when the image resolution / scaling window is different for the current image and other images in the same access unit, ILP should only be allowed if the current image is an IRAP image.

[0203] 14) In this document, image resolution may refer to the width and / or height of the image, or it may refer to the width and / or height and / or top-left corner position of the image's scaling window and / or consistency window.

[0204] 15) In this article, not using RPR means that any reference image of the current image has the same resolution as the current image.

[0205] 6. Example

[0206] The following are some example embodiments of aspects of the invention summarized in Section 5 above, which can be applied to the VVC specification. The most relevant parts that have been added or modified are... Underlined parts are used, and deleted parts are indicated by [[]].

[0207] 6.1. First Embodiment

[0208] This embodiment pertains to items 1, 1.a, 1.b, 1.c, 1.d, 3, 4.ai, 5, 6, 7, 8, 9, 9.a, 10, 11 and 12b.

[0209] 7.3.2.3 Sequence Parameter Set Syntax

[0210]

[0211]

[0212] 7.4.3.3 Sequence Parameter Set (RBSP) Semantics ...

[0214]

[0215] A value of 1 indicates that the image spatial resolution can be changed within the CLVS of the reference SPS. A value of 0 for res_change_in_clvs_allowed_flag indicates that the image spatial resolution will not be changed within any CLVS of the reference SPS. ...

[0217] A value of 1 indicates that the i-th subpic of each codec image in CLVS is considered a picture in the decoding process excluding loop filtering. A value of 0 indicates that the i-th subpic of each codec image in CLVS is not considered a picture in the decoding process excluding loop filtering. When it does not exist, the value of subpic_treated_as_pic_flag[i] is inferred to be equal to sps_independent_subpics_flag.

[0218] when When subpic_treated_as_pic_flag[i] equals 1 The requirement for bitstream consistency is that, All of the following conditions are true:

[0219] – All images should have the same value for pic_width_in_luma_samples and the same value for pic_height_in_luma_samples.

[0220] –

[0221] – All referenced SPSs should have the same value of sps_num_subpics_minus1, and for each value of j in the range from 0 to sps_num_subpics_minus1 (inclusive), it should have subpic_ctu_top_left_x[j], subpic_ctu_top_left_y[j], subpic_width_minus1[j], subpic_height_minus1[j], and subpic_ctu_top_left_y[j], respectively. The same value as [[loop_filter_across_subpic_enabled_flag[j]]].

[0222] For each value of j in the range from 0 to sps_num_subpics_minus1 (inclusive), All images should have the same value for SubpicIdVal[j]. ...

[0224] 7.4.3.4 Image Parameter Set RBSP Semantics ...

[0226] A value of 1 indicates that the scaling window offset parameter exists in PPS. A value of 0 indicates that the scaling window offset parameter does not exist in PPS. When [[res_change_in_clvs_allowed_flag]] equals 0, the value of scaling_window_explicit_signalling_flag should be equal to 0.

[0227] and Specifies the offsets applied to the image size for scaling calculations. When not present, the values ​​of scaling_win_left_offset, scaling_win_right_offset, scaling_win_top_offset, and scaling_win_bottom_offset are inferred to be equal to pps_conf_win_left_offset, pps_conf_win_right_offset, pps_conf_win_top_offset, and pps_conf_win_bottom_offset, respectively.

[0228] The value of SubWidthC*(scaling_win_left_offset+scaling_win_right_offset) should be less than pic_width_in_luma_samples, and the value of SubHeightC*(scaling_win_top_offset+scaling_win_bottom_offset) should be less than pic_height_in_luma_samples.

[0229]

[0230] The variables PicOutputWidthL and PicOutputHeightL are derived as follows:

[0231] PicOutputWidthL=pic_width_in_luma_samples- (78)

[0232] SubWidthC*(scaling_win_right_offset+scaling_win_left_offset)

[0233] PicOutputHeightL=pic_height_in_luma_samples- (79)

[0234] SubWidthC*(scaling_win_bottom_offset+scaling_win_top_offset)

[0235] Let refPicOutputWidthL and refPicOutputHeightL be the PicOutputWidthL and PicOutputHeightL of the reference image that references the current image of this PPS, respectively. Bitstream consistency requires that all of the following conditions be met:

[0236] –PicOutputWidthL*2 should be greater than or equal to refPicWidthInLumaSamples.

[0237] –PicOutputHeightL*2 should be greater than or equal to refPicHeightInLumaSamples.

[0238] –PicOutputWidthL should be less than or equal to refPicWidthInLumaSamples*8.

[0239] –PicOutputHeightL should be less than or equal to refPicHeightInLumaSamples*8.

[0240] –PicOutputWidthL*pic_width_max_in_luma_samples should be greater than or equal to refPicOutputWidthL*(pic_width_in_luma_samples-Max(8,MinCbSizeY)).

[0241] –PicOutputHeightL*pic_height_max_in_luma_samples should be greater than or equal to

[0242] refPicOutputHeightL*(pic_height_in_luma_samples-Max(8,MinCbSizeY)). ...

[0244] 7.3.3.2 General Constraint Information Syntax

[0245]

[0246]

[0247] 7.4.4.2 General Constraint Information Semantics ...

[0249]

[0250] A value of 1 indicates that `res_change_in_clvs_allowed_flag` should be equal to 0. A value of 0 for `no_res_change_in_clvs_constraint_flag` does not impose such a constraint.

[0251] 7.4.8.1 General Strip Header Semantics

[0252] An equal value of 1 indicates that the juxtaposed images used for temporal motion vector prediction are derived from reference image list 0. An equal value of 0 for slice_collocated_from_l0_flag indicates that the juxtaposed images used for temporal motion vector prediction are derived from reference image list 1.

[0253] When slice_type equals B or P, ph_temporal_mvp_enabled_flag equals 1, and slice_collocated_from_l0_flag does not exist, the following applies:

[0254] – If rpl_info_in_ph_flag equals 1, then slice_collocated_from_l0_flag is inferred to be equal to ph_collocated_from_l0_flag.

[0255] Otherwise (rpl_info_in_ph_flag equals 0 and slice_type equals P), the value of slice_collocated_from_l0_flag is inferred to be equal to 1.

[0256] Specify the reference index for the juxtaposed images used for temporal motion vector prediction.

[0257] When slice_type equals P, or when slice_type equals B and slice_collocated_from_l0_flag equals 1, slice_collocated_ref_idx refers to the entry in reference image list 0, and the value of slice_collocated_ref_idx should be in the range of 0 to NumRefIdxActive[0]-1 (inclusive of 0 and NumRefIdxActive[0]-1).

[0258] When slice_type equals B and slice_collocated_from_l0_flag equals 0, slice_collocated_ref_idx refers to the entry in reference image list 1, and the value of slice_collocated_ref_idx should be in the range of 0 to NumRefIdxActive[1]-1 (inclusive of 0 and NumRefIdxActive[1]-1).

[0259] When slice_collocated_ref_idx does not exist, the following applies:

[0260] – If rpl_info_in_ph_flag equals 1, then the value of slice_collocated_ref_idx is inferred to be equal to ph_collocated_ref_idx.

[0261] Otherwise (rpl_info_in_ph_flag equals 0), the value of slice_collocated_ref_idx is inferred to be equal to 0.

[0262] The requirement for bitstream consistency is that the image referenced by slice_collocated_ref_idx should be identical across all slices of the encoded and decoded image. .

[0263] The requirement for bitstream consistency is that the values ​​of pic_width_in_luma_samples and pic_height_in_luma_samples of the reference image referenced by slice_collocated_ref_idx should be equal to the values ​​of pic_width_in_luma_samples and pic_height_in_luma_samples of the current image, respectively, and RprConstraintsActive[slice_collocated_from_l0_flag? 0:1][slice_collocated_ref_idx] should be equal to 0. ...

[0265] 8.5.3.2.2 Bilinear Interpolation Process for Luminance Samples ...

[0267] For i = 0..1, the brightness position (xInt) in the full sample cell i ,yInt i The derivation is as follows:

[0268] – If subpic_treated_as_pic_flag[CurrSubpicIdx] equals 1

[0269] The following applies:

[0270] xInt i =Clip3(SubpicLeftBoundaryPos,SubpicRightBoundaryPos,xInt L +i) (640)

[0271] yInt i =Clip3(SubpicTopBoundaryPos,SubpicBotBoundaryPos,yInt L +i) (641)

[0272] Otherwise, (subpic_treated_as_pic_flag[CurrSubpicIdx] equals 0) Applicable to the following:

[0273] xInt i =Clip3(0,picW-1,refWraparoundEnabledFlag?ClipH((PpsRefWraparoundOffset)*MinCbSizeY,picW,(xInt L +i)):xInt L +i) (642)

[0274] yInt i =Clip3(0,picH-1,yInt) L +i) (643) ...

[0276] 8.5.6.3.2 Brightness Sample Interpolation and Filtering Process ...

[0278] – If subpic_treated_as_pic_flag[CurrSubpicIdx] equals 1 The following applies:

[0279] xInt i =Clip3(SubpicLeftBoundaryPos,SubpicRightBoundaryPos,xInt i (959)

[0280] yInt i =Clip3(SubpicTopBoundaryPos,SubpicBotBoundaryPos,yInt i (960)

[0281] Otherwise, (subpic_treated_as_pic_flag[CurrSubpicIdx] equals 0) Applicable to the following:

[0282] xInt i=Clip3(0,picW-1,refWraparoundEnabledFlag?ClipH((PpsRefWraparoundOffset)*MinCbSizeY,picW,xInt i ):xInt i (961)

[0283] yInt i =Clip3(0,picH-1,yInt) i (962) ...

[0285] 8.5.6.3.3 Brightness Integer Sample Extraction Process ...

[0287] The brightness position (xInt, yInt) in the full sample cell is derived as follows:

[0288] – If subpic_treated_as_pic_flag[CurrSubpicIdx] equals 1 The following applies:

[0289] xInt=Clip3(SubpicLeftBoundaryPos,SubpicRightBoundaryPos,xInt L (968)

[0290] yInt=Clip3(SubpicTopBoundaryPos,SubpicBotBoundaryPos,yInt L (969)

[0291] -otherwise Applicable to the following content:

[0292] xInt=Clip3(0,picW-1,refWraparoundEnabledFlag? (970)

[0293] ClipH((PpsRefWraparoundOffset)*MinCbSizeY,picW,xInt L ):xInt L )

[0294] yInt = Clip3(0, picH-1, yInt) L (971) ...

[0296] 8.5.6.3.4 Chromaticity Sample Interpolation Process ...

[0298] – If subpic_treated_as_pic_flag[CurrSubpicIdx] equals 1

[0299] The following applies:

[0300] xInt i =Clip3(SubpicLeftBoundaryPos / SubWidthC,SubpicRightBoundaryPos / SubWidthC,xInt i (977)

[0301] yInt i =Clip3(SubpicTopBoundaryPos / SubHeightC,SubpicBotBoundaryPos / SubHeightC,yInt i (978)

[0302] Otherwise, (subpic_treated_as_pic_flag[CurrSubpicIdx] equals 0) Applicable to the following:

[0303]

[0304] yInt i =Clip3(0,picH C -1,yInt i (980) ...

[0306] Alternatively, the highlighted part “and the reference image refPicLX’s sps_num_subpics_minus1 is greater than 0” can be replaced with “and if the reference image refPicLX is an ILRP with the same spatial resolution as the current image”.

[0307] Alternatively, the highlighted part “or the reference image refPicLX’s sps_num_subpics_minus1 equals 0” can be replaced with “or if the reference image refPicLX is an ILRP with a different spatial resolution than the current image”.

[0308] Alternatively, requirements for juxtaposed images, such as "bitstream consistency requirement, is that the image referenced by slice_collocated_ref_idx should be identical for all slices of the encoded / decoded image." "This can be replaced with "The requirement for bitstream consistency is that the image referenced by slice_collocated_ref_idx should be identical for all slices of the encoded and decoded image." .

[0309] Alternatively, requirements for juxtaposed images, such as "bitstream consistency requirement, is that the image referenced by slice_collocated_ref_idx should be identical for all slices of the encoded / decoded image." "This can be replaced with "The requirement for bitstream consistency is that the image referenced by slice_collocated_ref_idx should be identical for all slices of the encoded and decoded image." .

[0310] 6.2. Alternative Embodiments

[0311] In some alternative embodiments, the following constraints of the first embodiment are applied:

[0312] when When subpic_treated_as_pic_flag[i] equals 1 The requirement for bitstream consistency is that, All of the following conditions are true:

[0313] – All images should have the same value for pic_width_in_luma_samples and the same value for pic_height_in_luma_samples.

[0314] -

[0315] – All referenced SPSs should have the same value of sps_num_subpics_minus1, and for each value of j in the range from 0 to sps_num_subpics_minus1 (inclusive), it should have subpic_ctu_top_left_x[j], subpic_ctu_top_left_y[j], subpic_width_minus1[j], subpic_height_minus1[j], and subpic_ctu_top_left_y[j], respectively. The same value as [[loop_filter_across_subpic_enabled_flag[j]]].

[0316] For each value of j in the range from 0 to sps_num_subpics_minus1 (inclusive), All images should have the same value for SubpicIdVal[j].

[0317] Replace with one of the following:

[0318] 1) When When subpic_treated_as_pic_flag[i] equals 1 The requirement for bitstream consistency is that, All of the following conditions are true:

[0319] – All images should have the same value for pic_width_in_luma_samples and the same value for pic_height_in_luma_samples.

[0320] –

[0321] – All referenced SPSs should have the same value of SPS_num_subpics_minus1, and for each value of j in the range of 0 to SPS_num_subpics_minus1 (inclusive), it should have subpic_ctu_top_left_x[j], subpic_ctu_top_left_y[j], and subpic_width_minus1[j] respectively. The same value as subpic_height_minus1[j][[and loop_filter_across_subpic_enabled_flag[j]]].

[0322] For each value of j in the range from 0 to sps_num_subpics_minus1 (inclusive), All images should have the same value for SubpicIdVal[j].

[0323] 2) When When subpic_treated_as_pic_flag[i] equals 1 The requirement for bitstream consistency is that, All of the following conditions are true:

[0324] – All images should have the same value for pic_width_in_luma_samples and the same value for pic_height_in_luma_samples.

[0325] –

[0326] – All referenced SPSs should have the same value of sps_num_subpics_minus1, and for each value of j in the range of 0 to sps_num_subpics_minus1 (inclusive), they should have the same values ​​of subpic_ctu_top_left_x[j], subpic_ctu_top_left_y[j], subpic_width_minus1[j], subpic_height_minus1[j], and loop_filter_across_subpic_enabled_flag[j].

[0327] For each value of j in the range from 0 to sps_num_subpics_minus1 (inclusive), All images should have the same value for SubpicIdVal[j].

[0328] 3) When subpic_treated_as_pic_flag[i] equals 1, The requirement for bitstream consistency is that, All of the following conditions are true:

[0329] – All images should have the same value for pic_width_in_luma_samples and the same value for pic_height_in_luma_samples.

[0330] –

[0331] – All referenced SPSs should have the same value of sps_num_subpics_minus1, and for each value of j in the range from 0 to sps_num_subpics_minus1 (inclusive), it should have subpic_ctu_top_left_x[j], subpic_ctu_top_left_y[j], subpic_width_minus1[j], subpic_height_minus1[j], and subpic_ctu_top_left_y[j], respectively. The same value as [[loop_filter_across_subpic_enabled_flag[j]]].

[0332] For each value of j in the range from 0 to sps_num_subpics_minus1 (inclusive), All images should have the same value for SubpicIdVal[j].

[0333] 4) When When subpic_treated_as_pic_flag[i] equals 1 The requirement for bitstream consistency is that, All of the following conditions are true:

[0334] – All images should have the same value for pic_width_in_luma_samples and the same value for pic_height_in_luma_samples.

[0335] –

[0336] – All referenced SPSs should have the same value of sps_num_subpics_minus1, and for each value of j in the range from 0 to sps_num_subpics_minus1 (inclusive), it should have subpic_ctu_top_left_x[j], subpic_ctu_top_left_y[j], subpic_width_minus1[j], subpic_height_minus1[j], and subpic_ctu_top_left_y[j], respectively. Same value as loop_filter_across_subpic_enabled_flag[j].

[0337] For each value of j in the range from 0 to sps_num_subpics_minus1 (inclusive), All images should have the same value for SubpicIdVal[j].

[0338] Figure 5 This is a block diagram illustrating an example video processing system 1900 in which various techniques disclosed herein may be implemented. Various implementations may include some or all of the components of system 1900. System 1900 may include an input 1902 for receiving video content. The video content may be received in a raw or uncompressed format, such as 8 or 10-bit multi-component pixel values, or in a compressed or encoded format. Input 1902 may represent a network interface, a peripheral bus interface, or a storage interface. Examples of network interfaces include wired interfaces such as Ethernet and Passive Optical Network (PON) and wireless interfaces such as Wi-Fi or cellular interfaces.

[0339] System 1900 may include a codec component 1904 capable of implementing the various codec or encoding methods described herein. Codec component 1904 can reduce the average bit rate of the video from input 1902 to the output of codec component 1904 to produce a codec representation of the video. Codec techniques are therefore sometimes referred to as video compression or video transcoding techniques. The output of codec component 1904 may be stored or transmitted via a communication connection as indicated by component 1906. The stored or communicatively transmitted bitstream (or codec) representation of the video received at input 1902 can be used by component 1908 to generate pixel values ​​or transmit as displayable video to display interface 1910. The process of generating user-visual video from the bitstream representation is sometimes referred to as video decompression. Furthermore, although some video processing operations are referred to as “codec” operations or tools, it is understood that codec tools or operations are used at the encoder, and the corresponding decoding tools or operations that inversely represent the codec results will be performed by the decoder.

[0340] Examples of peripheral bus interfaces or display interfaces may include Universal Serial Bus (USB), High Definition Multimedia Interface (HDMI), or DisplayPort. Examples of storage interfaces include SATA (Serial Advanced Technology Accessory), PCI, IDE, etc. The technologies described herein can be found in a variety of electronic devices, such as mobile phones, laptops, smartphones, or other devices capable of performing digital data processing and / or video display.

[0341] Figure 6 This is a block diagram of a video processing apparatus 3600. Apparatus 3600 can be used to implement one or more methods described herein. Apparatus 3600 can be embodied in a smartphone, tablet, computer, Internet of Things (IoT) receiver, etc. Apparatus 3600 may include one or more processors 3602, one or more memories 3604, and video processing hardware 3606. The processors (multiple) 3602 can be configured to implement one or more methods described herein. The memories (multiple memories) 3604 can be used to store data and code for implementing the methods and techniques described herein. The video processing hardware 3606 can be used to implement some of the techniques described herein in a hardware circuit system.

[0342] Figure 8 This is a block diagram illustrating an example video codec system 100 that can utilize the techniques disclosed herein.

[0343] like Figure 8As shown, the video encoding / decoding system 100 may include a source device 110 and a target device 120. The source device 110 generates encoded video data, and this source device 110 may be referred to as a video encoding device. The target device 120 can decode the encoded video data generated by the source device 110, and this target device 120 may be referred to as a video decoding device.

[0344] The source device 110 may include a video source 112, a video encoder 114, and an input / output (I / O) interface 116.

[0345] Video source 112 may include sources such as video capture devices, interfaces for receiving video data from video content providers, and / or computer graphics systems for generating video data, or combinations of these sources. Video data may include one or more pictures. Video encoder 114 encodes the video data from video source 112 to generate a bitstream. The bitstream may include a sequence of bits forming a codec representation of the video data. The bitstream may include codec pictures and related data. A codec picture is a codec representation of a picture. Related data may include sequence parameter sets, picture parameter sets, and other syntax structures. I / O interface 116 may include a modulator / demodulator (modem) and / or a transmitter. Encoded video data may be transmitted directly to target device 120 via network 130a through I / O interface 116. Encoded video data may also be stored on storage medium / server 130b for access by target device 120.

[0346] The target device 120 may include an I / O interface 126, a video decoder 124, and a display device 122.

[0347] I / O interface 126 may include a receiver and / or a modem. I / O interface 126 may acquire encoded video data from source device 110 or storage medium / server 130b. Video decoder 124 may decode the encoded video data. Display device 122 may display the decoded video data to a user. Display device 122 may be integrated with target device 120 or may be external to target device 120 configured to interface with an external display device.

[0348] The video encoder 114 and the video decoder 124 can operate according to video compression standards, such as the High Efficiency Video Codec (HEVC) standard, the Multi-Functional Video Codec (VVM) standard, and other current and / or additional standards.

[0349] Figure 9 This is a block diagram illustrating an example of a video encoder 200, which may be... Figure 8 The video encoder 114 in the system 100 shown.

[0350] The video encoder 200 can be configured to perform any or all of the techniques disclosed herein. Figure 9 In the example, the video encoder 200 includes multiple functional components. The techniques described in this disclosure can be shared among the various components of the video encoder 200. In some examples, the processor can be configured to perform any or all of the techniques described in this disclosure.

[0351] The functional components of the video encoder 200 may include a segmentation unit 201, a prediction unit 202 (which may include a mode selection unit 203, a motion estimation unit 204, a motion compensation unit 205, and an intra-frame prediction unit 206), a residual generation unit 207, a transform unit 208, a quantization unit 209, an inverse quantization unit 210, an inverse transform unit 211, a reconstruction unit 212, a buffer 213, and an entropy coding unit 214.

[0352] In other examples, the video encoder 200 may include more, fewer, or different functional components. In one example, the prediction unit 202 may include an intra-block copy (IBC) unit. The IBC unit can perform prediction in IBC mode, where at least one reference picture is the picture containing the current video block.

[0353] Furthermore, some components, such as the motion estimation unit 204 and the motion compensation unit 205, can be highly integrated, but for interpretive purposes, in Figure 9 The example is represented separately.

[0354] The segmentation unit 201 can segment an image into one or more video blocks. The video encoder 200 and the video decoder 300 can support various video block sizes.

[0355] The mode selection unit 203 can select a coding / decoding mode (e.g., intra-frame or inter-frame) based on the error result, and provide the resulting intra-frame or inter-frame codec block to the residual generation unit 207 to generate residual block data, and to the reconstruction unit 212 to reconstruct the coded block for use as a reference picture. In some examples, the mode selection unit 203 can select a combination of intra-frame and inter-frame prediction modes (CIIP), where the prediction is based on the inter-frame prediction signal and the intra-frame prediction signal. In the case of inter-frame prediction, the mode selection unit 203 can also select a resolution of the motion vector for the block (e.g., a sub-pixel or pixel-precision integer).

[0356] To perform inter-frame prediction on the current video block, motion estimation unit 204 can generate motion information for the current video block by comparing one or more reference frames from buffer 213 with the current video block. Motion compensation unit 205 can determine the predicted video block for the current video block based on the motion information and decoded samples from images in buffer 213 other than the image associated with the current video block.

[0357] The motion estimation unit 204 and the motion compensation unit 205 can perform different operations on the current video block, for example, depending on whether the current video block is in an I-strip, P-strip, or B-strip.

[0358] In some examples, motion estimation unit 204 can perform unidirectional prediction on the current video block, and can search for reference images in list 0 or list 1 for reference video blocks of the current video block. Motion estimation unit 204 can then generate a reference index indicating the reference image in list 0 or list 1, which contains the reference video block and a motion vector indicating the spatial displacement between the current video block and the reference video block. Motion estimation unit 204 can output the reference index, prediction direction indicator, and motion vector as motion information for the current video block. Motion compensation unit 205 can generate a predicted video block for the current block based on the reference video block indicated by the motion information of the current video block.

[0359] In other examples, motion estimation unit 204 can perform bidirectional prediction on the current video block. Motion estimation unit 204 can search for a reference video block for the current video block in the reference images in list 0, and can also search for another reference video block for the current video block in list 1. Motion estimation unit 204 can then generate a reference index indicating the reference images in lists 0 and 1 containing the reference video blocks, and a motion vector indicating the spatial displacement between the reference video blocks and the current video block. Motion estimation unit 204 can output the reference index and motion vector of the current video block as the motion information of the current video block. Motion compensation unit 205 can generate a predicted video block for the current video block based on the reference video blocks indicated by the motion information of the current video block.

[0360] In some examples, the motion estimation unit 204 can output a complete set of motion information for use in the decoder's decoding process.

[0361] In some examples, the motion estimation unit 204 may not output the complete set of motion information for the current video. Instead, the motion estimation unit 204 may refer to motion information signaling from another video block to inform the motion information of the current video block. For example, the motion estimation unit 204 may determine that the motion information of the current video block is sufficiently similar to the motion information of neighboring video blocks.

[0362] In one example, motion estimation unit 204 may indicate a value in the syntax structure associated with the current video block that indicates to video decoder 300 that the current video block has the same motion information as another video block.

[0363] In another example, motion estimation unit 204 can identify another video block and motion vector difference (MVD) in the syntax structure associated with the current video block. The motion vector difference indicates the difference between the motion vector of the current video block and the motion vector of the indicated video block. Video decoder 300 can use the motion vector of the indicated video block and the motion vector difference to determine the motion vector of the current video block.

[0364] As discussed above, the video encoder 200 can predictively signal motion vectors. Two examples of predictive signaling notification techniques that can be implemented by the video encoder 200 include Advanced Motion Vector Prediction (AMVP) and Merge Pattern Signaling Notification.

[0365] Intra-prediction unit 206 can perform intra-prediction on the current video block. When intra-prediction unit 206 performs intra-prediction on the current video block, it can generate prediction data for the current video block based on decoded samples from other video blocks in the same frame. The prediction data for the current video block can include the predicted video block and various syntax elements.

[0366] The residual generation unit 207 can generate residual data for the current video block by subtracting (e.g., indicated by a minus sign) multiple predicted video blocks from the current video block. The residual data for the current video block may include residual video blocks corresponding to different sample components of the samples in the current video block.

[0367] In other examples, such as in skip mode, there may be no residual data for the current video block, and the residual generation unit 207 may not perform the subtraction operation.

[0368] The transform processing unit 208 can generate one or more transform coefficient video blocks for the current video block by applying one or more transforms to the residual video blocks associated with the current video block.

[0369] After the transform processing unit 208 generates a transform coefficient video block associated with the current video block, the quantization unit 209 can quantize the transform coefficient video block associated with the current video block based on one or more quantization parameter (QP) values ​​associated with the current video block.

[0370] The inverse quantization unit 210 and the inverse transform unit 211 can apply inverse quantization and inverse transform to the transform coefficient video block, respectively, to reconstruct the residual video block from the transform coefficient video block. The reconstruction unit 212 can add the reconstructed residual video block to the corresponding samples of one or more predicted video blocks generated by the prediction unit 202 to produce a reconstructed video block associated with the current block, which is stored in the buffer 213.

[0371] After the video block is reconstructed by the reconstruction unit 212, a loop filtering operation can be performed to reduce video block artifacts in the video block.

[0372] Entropy encoding unit 214 can receive data from other functional components of video encoder 200. When entropy encoding unit 214 receives data, it can perform one or more entropy encoding operations to generate entropy encoded data and output a bit stream including the entropy encoded data.

[0373] Figure 10 This is a block diagram illustrating an example of a video decoder 300, which may be... Figure 8 The video decoder 114 in the system 100 shown.

[0374] The video decoder 300 can be configured to perform any or all of the techniques disclosed herein. Figure 10 In the example, the video decoder 300 includes multiple functional components. The techniques described in this disclosure can be shared among the various components of the video decoder 300. In some examples, the processor can be configured to perform any or all of the techniques described in this disclosure.

[0375] exist Figure 10 In the example, video decoder 300 includes an entropy decoding unit 301, a motion compensation unit 302, an intra-frame prediction unit 303, an inverse quantization unit 304, an inverse transform unit 305, a reconstruction unit 306, and a buffer 307. In some examples, video decoder 300 can perform functions typically associated with video encoder 200. Figure 9 The encoding process described is the opposite of the decoding process.

[0376] The entropy decoding unit 301 can retrieve the encoded bitstream. The encoded bitstream may include entropy-coded video data (e.g., encoded blocks of video data). The entropy decoding unit 301 can decode the entropy-coded video data, and from the entropy-coded video data, the motion compensation unit 302 can determine motion information including motion vectors, motion vector precision, reference image list index, and other motion information. The motion compensation unit 302 can determine such information, for example, by executing AMVP and Merge modes.

[0377] The motion compensation unit 302 can generate motion compensation blocks and can perform interpolation based on an interpolation filter. The identifier of the interpolation filter used at sub-pixel precision can be included in the syntax element.

[0378] The motion compensation unit 302 can use an interpolation filter, such as that used by the video encoder 200 during the encoding of a video block, to calculate the interpolation of sub-integer pixels of the reference block. The motion compensation unit 302 can determine the interpolation filter used by the video encoder 200 based on the received syntax information, and use the interpolation filter to generate the prediction block.

[0379] The motion compensation unit 302 may use some syntax information to determine the size of the blocks used to encode (multiple) frames and / or (multiple) stripes of the encoded video sequence, segmentation information describing how each macroblock of the image of the encoded video sequence is segmented, a pattern indicating how each segment is encoded, one or more reference frames (and a list of reference frames) for each inter-frame coded block, and other information for decoding the encoded video sequence.

[0380] Intra-prediction unit 303 can use, for example, an intra-prediction mode received in the bitstream to form prediction blocks from spatially adjacent blocks. Inverse quantization unit 303 performs inverse quantization, for example, dequantization, on the quantized video block coefficients provided in the bitstream and decoded by entropy decoding unit 301. Inverse transform unit 303 applies an inverse transform.

[0381] The reconstruction unit 306 can add the residual block to the corresponding prediction block generated by the motion compensation unit 202 or the intra-frame prediction unit 303 to form a decoded block. If necessary, a deblocking filter can also be applied to filter the decoded block to remove block artifacts. The decoded video block is then stored in the buffer 307 to provide a reference block for subsequent motion compensation / intra-frame prediction, and the decoded video is also generated for presentation on the display device.

[0382] The following is a list of preferred technical solutions for some embodiments.

[0383] The following technical solutions illustrate example embodiments of the techniques discussed in the previous section (e.g., item 1).

[0384] 1. A video processing method (e.g., Figure 7 The method 700 shown includes: performing a conversion between videos comprising one or more video pictures (702), wherein the encoding / decoding representation conforms to a format rule; wherein the format rule specifies that two or more syntax fields in a sequence parameter set control the reference picture resolution (RPR) change in the video.

[0385] 2. The method according to technical solution 1, wherein a first syntax field among two or more syntax fields indicates whether RPR is used for one or more images, and a second syntax field among two or more syntax fields indicates whether the image resolution is allowed to change in the sequence-level codec representation.

[0386] The following technical solutions illustrate example embodiments of the techniques discussed in the previous section (e.g., item 2).

[0387] 3. A video processing method, comprising: performing a conversion between videos including one or more video images, wherein the encoding / decoding representation conforms to a format rule; wherein the format rule specifies that a single syntax field in a sequence parameter set controls a change in the reference image resolution (RPR) in the video; and wherein the format rule specifies that resampling of the inter-frame layer reference image is permitted for the conversion regardless of the value of the single syntax field.

[0388] The following technical solutions illustrate example embodiments of the techniques discussed in the previous section (e.g., items 3, 5, 6, 7, 9, and 10).

[0389] 4. A video processing method comprising: performing a conversion between one or more layers of video, the one or more layers comprising one or more video images containing one or more sub-images, wherein the encoding / decoding representation conforms to a format rule; wherein the format rule specifies a first constraint on cross-layer alignment or a second constraint on a combination of sub-images and scalability of inter-frame layer images.

[0390] 5. The method according to technical solution 4, wherein the first constraint defines cross-layer alignment restrictions on the current layer and all higher layers that depend on the current layer, but does not impose alignment restrictions on lower layers of the current layer and all higher layers that do not depend on the current layer.

[0391] 6. The method according to technical solution 4, wherein the second constraint imposes cross-layer alignment restrictions on all layers in each dependency tree of a specific layer.

[0392] 7. The method according to technical solution 4, wherein the second constraint limits the value of subpic_treated_as_pic_flag[i] according to the cross-layer alignment constraint.

[0393] 8. The method according to technical solution 4, wherein the second constraint limits the value of loop_filter_across_subpic_enabled_flag[i] according to the cross-layer alignment constraint.

[0394] 9. The method according to any one of technical solutions 4 to 8, wherein the first constraint and / or the second constraint are specified for the target set of the access unit.

[0395] 10. The method according to technical solution 4, wherein the second constraint limits the value of each of the scaling window parameters scaling_win_left_offset, scaling_win_right_offset, scaling_win_top_offset and scaling_win_bottom_offset according to the cross-layer alignment constraint.

[0396] The following technical solutions illustrate example embodiments of the techniques discussed in the previous section (e.g., item 11).

[0397] 11. A video processing method, comprising: performing a conversion between videos comprising one or more layers, the one or more layers comprising one or more video pictures containing one or more sub-pictures, wherein the conversion conforms to a format rule that specifies that inter-frame layer reference pictures or long-term reference pictures are not allowed as juxtaposed pictures of the current picture used for the conversion.

[0398] The following technical solutions illustrate example embodiments of the techniques discussed in the previous section (e.g., item 12).

[0399] 12. A video processing method comprising: performing a conversion between a video comprising multiple images and a codec representation of the video, wherein the conversion conforms to the same rule for any two images within the same codec video sequence or codec video sequence having the same values ​​of pic_width_in_luma_samples and pic_height_in_luma_samples.

[0400] The following technical solutions illustrate example embodiments of the techniques discussed in the previous section (e.g., item 13).

[0401] 13. A video processing method, comprising: performing a conversion between a video comprising multiple images and a codec representation of the video, wherein the conversion conforms to a rule specifying that inter-frame layer prediction is allowed only when the current image is an intra-frame random access point image, provided that the image resolution or scaling window differs for the current image and other images in the same access unit.

[0402] 14. The method according to any one of technical solutions 1 to 13, wherein the conversion includes encoding the video into a codec representation.

[0403] 15. The method according to any one of technical solutions 1 to 13, wherein the conversion includes decoding the codec representation to generate pixel values ​​of the video.

[0404] 16. A video decoding apparatus, comprising a processor configured to implement one or more of the methods according to claims 1 to 15.

[0405] 17. A video encoding apparatus, comprising a processor configured to implement the method according to one or more of claims 1 to 15.

[0406] 18. A computer program product storing computer code, which, when executed by a processor, causes the processor to perform the method according to any one of claims 1 to 15.

[0407] 19. A method, apparatus or system described herein.

[0408] Figure 13 This is a flowchart representation of a method 1300 for video processing according to the present technology. Method 1300 includes operation 1310, performing a conversion between a current image of the video and the video bitstream according to rules. These rules specify multiple syntax elements for specifying the use of a reference image resampling tool. The reference image resampling tool is an encoding / decoding tool that resamples a reference image with a different resolution than the current image for use in the conversion.

[0409] In some embodiments, multiple syntax elements are included in a Sequence Parameter Set (SPS). In some embodiments, the multiple syntax elements include a first syntax element specifying whether a reference image resampling tool is enabled for the transformation, and a second syntax element specifying whether the resolution of the image is allowed to change within the Codec Layer Video Sequence (CLVS). In some embodiments, where the first syntax element specifies that the reference image resampling tool is enabled for the transformation, the second syntax element is included in the SPS. In some embodiments, where the second syntax element is not included in the SPS, the second syntax element is inferred to be equivalent to a value indicating that the resolution of the image is not allowed to change within the CLVS. In some embodiments, the first and second syntax elements are indicated independently of each other for the transformation.

[0410] In some embodiments, one or more general constraint flags corresponding to each of a plurality of syntax elements are indicated for the transformation. In some embodiments, the rule specifies that the resolution of the image is not allowed to change within the codec layer video sequence (CLVS) when the current image comprises multiple sub-images. In some embodiments, the rule specifies that a reference image resampling tool is enabled for the transformation when the current image comprises multiple sub-images. In some embodiments, the constraint flag specifying whether the scaling window offset parameter exists in the image parameter set is determined based on the first syntax element. In some embodiments, where the first syntax element indicates that the reference image resampling tool is disabled for the transformation, the constraint flag specifies that the scaling window offset parameter is omitted in the image parameter set.

[0411] In some embodiments, multiple syntax elements are included in a video parameter set. In some embodiments, at least one of the multiple syntax elements applies to all layers specified by the video parameter set. In some embodiments, at least one of the multiple syntax elements has multiple instances indicated in the video parameter set, and each of the multiple instances applies to all layers in the dependency tree. In some embodiments, each of the multiple syntax elements is encoded or decoded using a unary encoding / decoding method utilizing one bit.

[0412] Figure 14 This is a flowchart representation of a method 1400 for video processing according to the present technology. Method 1400 includes operation 1410, which performs a conversion between a current picture of the video and a bitstream of the video according to a rule. The rule specifies a syntax element with a non-binary value for specifying (1) a reference picture resampling tool that resamples a reference picture with a different resolution than the current picture, and (2) the use of picture resolution changes within a codec layer video sequence (CLVS).

[0413] In some embodiments, a value of 0 for the syntax element indicates that the reference image resampling tool is disabled for the transformation. In some embodiments, a value of 1 for the syntax element indicates that the reference image resampling tool is enabled for the transformation, and changes in image resolution are not allowed within the codec layer video sequence (CLVS). In some embodiments, a value of 2 for the syntax element indicates that the reference image resampling tool is enabled for the transformation, and changes in image resolution are allowed within the codec layer video sequence (CLVS). In some embodiments, the indication of the syntax element is based on whether the inter-frame layer prediction codec is allowed for the transformation. In some embodiments, the syntax element is an unsigned integer 0-order Exp-Golobm codec syntax element. In some embodiments, the syntax element uses N bits to encode and decode into an unsigned integer, where N is an integer. In some embodiments, N equals 2.

[0414] Figure 15This is a flowchart representation of a method 1500 for video processing according to the present technology. Method 1500 includes operation 1510, performing a conversion between a video comprising multiple layers and a video bitstream according to a rule. The rule specifies that, when a sub-picture is considered a video picture for conversion, cross-layer alignment constraints are applied to fewer than all layers, including the current layer containing the sub-picture and a subset of layers associated with the current layer. The cross-layer alignment constraints include restrictions on at least one dimension of the video picture, the number of sub-pictures within the video picture, the position of at least one sub-picture, or the identification of the sub-picture.

[0415] In some embodiments, a subset of layers includes all higher layers that depend on the current layer. In some embodiments, a subset of layers excludes all lower layers of the current layer and higher layers that do not depend on the current layer. In some embodiments, a subset of layers includes all layers above the current layer. In some embodiments, a subset of layers includes all higher layers in the same set of output layers as the current layer. In some embodiments, a subset of layers includes all lower layers that serve as a reference layer for the current layer. In some embodiments, a subset of layers includes all layers below the current layer. In some embodiments, a subset of layers includes all lower layers in the same set of output layers as the current layer. In some embodiments, a subset of layers includes all layers below the highest layer. In some embodiments, a subset of layers includes all layers above the lowest layer.

[0416] Figure 16 This is a flowchart representation of a method 1600 for video processing according to the present technology. Method 1600 includes operation 1610, performing a conversion between the current layer of a video and the video bitstream according to a rule. The rule specifies that cross-layer alignment constraints are applied to all layers in the dependency tree associated with the current layer, regardless of whether any layer in the dependency tree is an output layer in the output layer set. Cross-layer alignment constraints include restrictions on at least one dimension of a video picture, the number of sub-pictures within a video picture, the position of at least one sub-picture, or the identifier of a sub-picture. All layers in the dependency tree include the current layer, all layers having the current layer as a reference layer, and all reference layers of the current layer.

[0417] In some embodiments, the cross-layer alignment constraint also includes a constraint regarding whether a sub-picture in a video picture is considered a picture that spans all layers. In some embodiments, the cross-layer alignment constraint does not limit whether a loop filtering operation is applied to the boundaries of a sub-picture within a video picture that spans all layers. In some embodiments, the rule also specifies that the cross-layer alignment constraint is not applied if a syntax element in the sequence parameter set indicates that a video picture includes a single sub-picture. In some embodiments, the rule also specifies that the cross-layer alignment constraint is not applied if a syntax element indicates that sub-picture information is omitted in the sequence parameter set. In some embodiments, the rule also specifies that the cross-layer alignment constraint is applied to pictures in the target set of access units. In some embodiments, for each CLVS of the current layer of the reference sequence parameter set, the target set of access units includes all access units from the first access unit including the first picture of the CLVS to the second access unit including the last picture of the CLVS, according to the decoding order.

[0418] In some embodiments, the cross-layer alignment constraint further includes a scaling window offset parameter, which includes at least one of the following: (1) a left offset of the scaling window, (2) a right offset of the scaling window, (3) a top offset of the scaling window, or (4) a bottom offset of the scaling window.

[0419] Figure 17 This is a flowchart representation of a method 1700 for video processing according to the present technology. Method 1700 includes operation 1710, which performs a conversion between a current image of the video and the video bitstream according to a rule. The rule specifies that resampling of a reference image in the same layer as the current image is enabled, regardless of the value of a syntax element specifying whether changes in image resolution are allowed in a codec layer video sequence (CLVS).

[0420] In some embodiments, where the syntax element indicates that changes to the image resolution are not allowed in CLVS, a reference image resampling tool is enabled for the reference image to be resampled with a different image resolution than the current image.

[0421] Figure 18 This is a flowchart representation of a method 1800 for video processing according to the present technology. Method 1800 includes operation 1810, performing a conversion between a current image of a video comprising multiple layers and a video bitstream according to a rule. The rule specifies one of the following: (1) juxtaposing a reference image of the current image is not allowed, or (2) if the reference image of the current image is juxtaposed, a motion vector pointing to the reference image is used during a conversion where the current image is not scaled. In some embodiments, the reference image is a long-term reference image. In some embodiments, the reference image is an inter-frame layer reference image.

[0422] Figure 19 This is a flowchart representation of a method 1900 for video processing according to the present technology. Method 1900 includes operation 1910, performing a conversion between video and video bitstreams according to a rule. The rule specifies that the scaling window offset parameter is identical for any two video images having the same dimension, expressed in terms of the number of luminance samples, in the same codec layer video sequence (CLVS) or codec video sequence (CVS).

[0423] In some embodiments, the scaling window offset parameter includes at least one of the following: (1) left offset of the scaling window, (2) right offset of the scaling window, (3) top offset of the scaling window, or (4) bottom offset of the scaling window. In some embodiments, this dimension includes the width or height of the image. In some embodiments, the rule also specifies that any two video images belong to the same layer. In some embodiments, the rule also specifies that any two video images belong to two layers, including a first layer and a second layer. The first layer is a reference layer for the second layer.

[0424] Figure 20 This is a flowchart representation of a method 2000 for video processing according to the present technology. Method 2000 includes operation 2010, which performs a conversion between a current frame of video and a video bitstream according to a rule. The rule specifies that, in response to the current frame's frame resolution differing from at least one other frame in the same access unit, the inter-frame layer predictive codec tool is enabled only if the current frame is an intra-frame random access point (IRAP) frame with the same value of NAL unit type for all Video Codec Layer (VCL) Network Abstraction Layer (NAL) units.

[0425] In some embodiments, a change in the image resolution of a reference image is not permitted to indicate that the image resolution of the reference image is the same as that of the current image. In some embodiments, the image resolution of a video image includes the width or height of the video image. In some embodiments, the image resolution of a video image includes the width, height, and / or top-left position of the zoom window or consistency window of the video image.

[0426] In some embodiments, the conversion includes encoding the video into a bitstream. In some embodiments, the conversion includes decoding the bitstream to generate a video.

[0427] In the technical solution described herein, the encoder can generate a codec representation that conforms to the format rules. In the technical solution described herein, the decoder can parse the syntax elements in the codec representation using the format rules, knowing whether or not the syntax elements exist, to generate the decoded video.

[0428] In this document, the term "video processing" can refer to video encoding, video decoding, video compression, or video decompression. For example, a video compression algorithm can be applied during the conversion from the pixel representation of a video to the corresponding bitstream representation, and vice versa. For example, the bitstream representation of the current video block can correspond to juxtaposed positions or bits propagated at different positions in the bitstream defined by the syntax. For example, a macroblock can be encoded based on the error residual value after transformation and encoding, and can also use bits in the header and other fields of the bitstream. Furthermore, during the conversion, the decoder can parse the bitstream based on this determination, knowing that some fields may or may not be present, as described in the above technical solutions. Similarly, the encoder can determine whether to include or exclude specific syntax fields, and generate the codec representation accordingly by including or excluding syntax fields from the codec representation.

[0429] The disclosed and other technical solutions, examples, embodiments, modules, and functional operations described herein can be implemented in digital electronic circuits or computer software, firmware, or hardware, including the structures disclosed herein and their structural equivalents, or combinations thereof. The disclosed embodiments and other embodiments can be implemented as one or more computer program products, i.e., one or more modules of computer program instructions encoded on a computer-readable medium for execution by or control of a data processing apparatus. The computer-readable medium can be a combination of a machine-readable storage device, a machine-readable storage substrate, a storage device, a substance that influences machine-readable propagated signals, or one or more such combinations. The term "data processing apparatus" includes all means, devices, and machines for processing data, including, for example, a programmable processor, a computer, or multiple processors or computers. In addition to hardware, the apparatus may also include code that creates an execution environment for a computer program, such as code constituting processor firmware, a protocol stack, a database management system, an operating system, or a combination thereof. The propagated signals are artificially generated signals, such as machine-generated electrical, optical, or electromagnetic signals, which are generated to encode information for transmission to a suitable receiver device.

[0430] Computer programs (also known as programs, software, software applications, scripts, or code) can be written in any programming language (including compiled or interpreted languages) and can be deployed in any form, including as standalone programs or as modules, components, subroutines, or other units suitable for use in a computing environment. A computer program does not necessarily correspond to a file in a file system. A program can be stored in a portion of a file that holds other programs or data (e.g., one or more scripts stored in a markup language file), in a single file dedicated to that program, or in multiple coordinating files (e.g., a file storing one or more modules, subroutines, or portions of code). Computer programs can be deployed and executed on one or more computers located at a single site or distributed across multiple sites and interconnected via a communication network.

[0431] The processing and logic flows described herein can be executed by one or more programmable processors that execute one or more computer programs to perform functions by manipulating input data and generating outputs. The processing and logic flows can also be executed by special-purpose logic circuitry, and the devices can be implemented as special-purpose logic circuitry, such as FPGAs (Field-Programmable Gate Arrays) or ASICs (Application-Specific Integrated Circuits).

[0432] For example, processors suitable for executing computer programs include general-purpose and special-purpose microprocessors, as well as one or more of any type of digital computer. Typically, the processor receives instructions and data from read-only memory or random access memory, or both. The basic components of a computer are a processor that executes instructions and one or more storage devices that store the instructions and data. Typically, a computer will also include one or more mass storage devices for storing data, such as magnetic disks, magneto-optical disks, or optical disks, or receive data from or transfer data to one or more mass storage devices via operative coupling, or both. However, a computer does not necessarily have such devices. Computer-readable media suitable for storing computer program instructions and data include all forms of non-volatile memory, media, and memory devices, including, for example, semiconductor memory devices such as EPROM, EEPROM, and flash memory devices; magnetic disks, such as intra-frame hard disks or removable hard disks; magneto-optical disks; and CD-ROMs and DVD-ROMs. The processor and memory may be supplemented by or incorporated into special-purpose logic circuitry.

[0433] While this patent document contains numerous details, it should not be construed as limiting any subject matter or scope of the claims, but rather as a description of features of specific embodiments of a particular technology. Certain features described in the context of individual embodiments may also be implemented in combination in a single embodiment. Conversely, various functions described in the context of a single embodiment may also be implemented individually in multiple embodiments, or in any suitable sub-combination. Furthermore, although the foregoing features may be described as functioning in certain combinations, or even initially claimed to be so, in some cases one or more features from a combination of claims may be removed from the combination, and a combination of claims may refer to a sub-combination or a variation of a sub-combination.

[0434] Similarly, although the operations are described in a specific order in the accompanying drawings, this should not be construed as requiring the specific order or sequence shown to perform such operations, or all the described operations, in order to obtain the desired result. Furthermore, the separation of various system components in the embodiments of this patent document should not be construed as requiring such separation in all embodiments.

[0435] Only some implementations and examples are described; other implementations, enhancements, and variations can be made based on the content described and illustrated in this patent document.

Claims

1. A video processing method, comprising: The conversion between the video and its bitstream, which includes multiple layers, is performed according to the rules. The rule specifies that, where the first syntax element included in the sequence parameter set indicates that the number of sub-images in the video image is greater than 1, and a sub-image with a first sub-image index is considered a video image used for the transformation, a cross-layer alignment constraint is applied to a subset of the current layer including the sub-image and the layers associated with the current layer, wherein the subset of the layers associated with the current layer includes one or more higher layers that depend on the current layer. The cross-layer alignment restriction includes restricting the current image containing the sub-image and the first image in the subset of the layer from having the same value for at least one of the following syntax elements: The value of the first syntax element, The value of the second syntax element that indicates the dimension of the video image. The value of the third syntax element indicating the dimension of the i-th sub-image. The value of the fourth syntax element indicating the position of the i-th sub-image, or The value of the index of the first sub-image.

2. The method according to claim 1, wherein, A subset of the layers associated with the current layer excludes all higher layers that do not depend on the current layer.

3. The method according to claim 1, wherein, A subset of the layers associated with the current layer excludes all lower layers of the current layer.

4. The method according to claim 1, wherein, The subset of the layers associated with the current layer is a subset of the dependency tree associated with the current layer. The dependency tree associated with the current layer includes the current layer, all layers that have the current layer as a reference layer, and all reference layers of the current layer.

5. The method according to claim 4, wherein, The subset of the layers associated with the current layer is the subset of the dependency tree, regardless of whether any of the subsets of the dependency tree is an output layer in the output layer set.

6. The method according to claim 1, wherein, The cross-layer alignment constraint also includes a constraint on the value of the fifth syntax element, and the current layer and a subset of the layers associated with the current layer have the same value of the fifth syntax element. The fifth syntax element specifies whether the sub-picture of each codec picture in the codec layer video sequence is considered a picture in the decoding process that excludes loop filtering operations.

7. The method according to claim 1, wherein, The cross-level alignment restriction excludes the value of the sixth syntax element. The sixth syntax element specifies whether to enable loop filtering across sub-image boundaries.

8. The method according to claim 1, wherein, The rule also specifies that the cross-layer alignment restriction should not be applied if the first syntax element indicates that the video image includes a single sub-image.

9. The method according to claim 1, wherein, The rule also specifies that the cross-layer alignment restriction should not be applied if the seventh syntax element included in the sequence parameter set indicates that the sub-image information is not present.

10. The method according to claim 1, wherein, The rule also specifies that the cross-layer alignment restriction is applied to images in the target set of the access unit.

11. The method according to claim 10, wherein, For each CLVS of the current layer of the reference sequence parameter set, the target set of the access units, according to the decoding order, includes all access units from the first access unit that includes the first picture of the CLVS to the second access unit that includes the last picture of the CLVS.

12. The method according to claim 1, wherein, The conversion includes encoding the video into the bitstream.

13. The method according to claim 1, wherein, The conversion includes decoding the bitstream to generate the video.

14. An apparatus for processing video data, comprising a processor and a non-transitory memory having instructions thereon, wherein the instructions, when executed by the processor, cause the processor to: The conversion between the video and its bitstream, which includes multiple layers, is performed according to the rules. in, The rule specifies that, where the first syntax element included in the sequence parameter set indicates that the number of sub-images in the video image is greater than 1, and a sub-image with a first sub-image index is considered a video image used for the transformation, a cross-layer alignment constraint is applied to a subset of the current layer including the sub-image and the layers associated with the current layer, wherein the subset of the layers associated with the current layer includes one or more higher layers that depend on the current layer. The cross-layer alignment restriction includes restricting the current image containing the sub-image and the first image in the subset of the layer from having the same value for at least one of the following syntax elements: The value of the first syntax element, The value of the second syntax element that indicates the dimension of the video image. The value of the third syntax element indicating the dimension of the i-th sub-image. The value of the fourth syntax element indicating the position of the i-th sub-image, or The value of the index of the first sub-image.

15. The apparatus according to claim 14, wherein, A subset of the layers associated with the current layer excludes all higher layers that do not depend on the current layer.

16. The apparatus according to claim 14, wherein, A subset of the layers associated with the current layer excludes all lower layers of the current layer.

17. A non-transitory computer-readable storage medium for storing instructions, said instructions causing a processor to: The conversion between the video and its bitstream, which includes multiple layers, is performed according to the rules. in, The rule specifies that, where the first syntax element included in the sequence parameter set indicates that the number of sub-images in the video image is greater than 1, and a sub-image with a first sub-image index is considered a video image used for the transformation, a cross-layer alignment constraint is applied to a subset of the current layer including the sub-image and the layers associated with the current layer, wherein the subset of the layers associated with the current layer includes one or more higher layers that depend on the current layer. The cross-layer alignment restriction includes restricting the current image containing the sub-image and the first image in the subset of the layer from having the same value for at least one of the following syntax elements: The value of the first syntax element, The value of the second syntax element that indicates the dimension of the video image. The value of the third syntax element indicating the dimension of the i-th sub-image. The value of the fourth syntax element indicating the position of the i-th sub-image, or The value of the index of the first sub-image.

18. A non-transitory computer-readable recording medium storing a bitstream of video generated by a method executed by a video processing apparatus and instructions, wherein, When the instruction is executed by the video processing device, the method is implemented, wherein the method includes: The bitstream of the video, comprising multiple layers, is generated according to rules. The rule specifies that, where the first syntax element included in the sequence parameter set indicates that the number of sub-images in the video image is greater than 1, and a sub-image with a first sub-image index is considered a video image used for the transformation, a cross-layer alignment constraint is applied to a subset of the current layer including the sub-image and the layers associated with the current layer, wherein the subset of the layers associated with the current layer includes one or more higher layers that depend on the current layer. The cross-layer alignment restriction includes restricting the current image containing the sub-image and the first image in the subset of the layer from having the same value for at least one of the following syntax elements: The value of the first syntax element, The value of the second syntax element that indicates the dimension of the video image. The value of the third syntax element indicating the dimension of the i-th sub-image. The value of the fourth syntax element indicating the position of the i-th sub-image, or The value of the index of the first sub-image.

19. A method for storing a bitstream of video, comprising: Generate a video bitstream comprising multiple layers according to rules. The bitstream is stored in a non-transitory computer-readable recording medium. in, The rule specifies that, where the first syntax element included in the sequence parameter set indicates that the number of sub-images in the video image is greater than 1, and a sub-image with a first sub-image index is considered for the generated video image, a cross-layer alignment constraint is applied to a subset of the current layer including the sub-image and the layers associated with the current layer, wherein the subset of the layers associated with the current layer includes one or more higher layers that depend on the current layer. The cross-layer alignment restriction includes restricting the current image containing the sub-image and the first image in the subset of the layer from having the same value for at least one of the following syntax elements: The value of the first syntax element, The value of the second syntax element that indicates the dimension of the video image. The value of the third syntax element indicating the dimension of the i-th sub-image. The value of the fourth syntax element indicating the position of the i-th sub-image, or The value of the index of the first sub-image.

20. A video processing method, comprising: The conversion between the video and its bitstream, which includes multiple layers, is performed according to the rules. The rule specifies that when a sub-image is considered a video image for the transformation, cross-layer alignment restrictions are applied to fewer than all layers, including the current layer containing the sub-image and a subset of layers associated with the current layer. The cross-layer alignment restrictions include restrictions on at least one dimension of the video image, the number of sub-images within the video image, the position of at least one sub-image, or the identifier of the sub-image.

21. The method according to claim 20, wherein, The subset of the layer includes all higher layers that depend on the current layer.

22. The method according to claim 20 or 21, wherein, The subset of the layer excludes all lower layers of the current layer and higher layers that do not depend on the current layer.

23. The method of claim 20, wherein, The subset of the layer includes all layers above the current layer.

24. The method of claim 20, wherein, The subset of the layer includes all higher layers in the same set of output layers as the current layer.

25. The method according to claim 20, wherein, The subset of the layer includes all lower layers that serve as the reference layer for the current layer.

26. The method of claim 20, wherein, The subset of the layer includes all layers below the current layer.

27. The method of claim 20, wherein, The subset of the layer includes all lower layers in the same set of output layers as the current layer.

28. The method according to claim 20, wherein, The subset of the layers includes all layers below the highest layer.

29. The method according to claim 20, wherein, The subset of the layers includes all layers above the lowest layer.

30. A video processing method, comprising: Perform the conversion between the current layer of the video and the bitstream of the video according to the rules. The rule specifies that cross-layer alignment constraints are applied to all layers in the dependency tree associated with the current layer, regardless of whether any of the layers is an output layer in the output layer set. The cross-layer alignment constraints include restrictions on at least one dimension of the video image, the number of sub-images within the video image, the position of at least one sub-image, or the identifier of the sub-image. The "all layers" in the dependency tree include the current layer, all layers that have the current layer as a reference layer, and all reference layers of the current layer.

31. The method according to claim 30, wherein, The cross-layer alignment restrictions also include restrictions on whether sub-images in a video image are considered images that span all said layers.

32. The method according to claim 30 or 31, wherein, The cross-layer alignment constraint does not limit whether a loop filtering operation is applied to the boundaries of sub-images within a video image spanning all layers.

33. The method according to claim 30, wherein, The rule also specifies that the cross-layer alignment restriction should not be applied if a syntax element in the sequence parameter set indicates that a video image comprises a single sub-image.

34. The method according to claim 30, wherein, The rule also specifies that the cross-layer alignment restriction should not be applied if the syntax element indicates that sub-image information is omitted in the sequence parameter set.

35. The method according to claim 30, wherein, The rule also specifies that the cross-layer alignment restriction is applied to images in the target set of the access unit.

36. The method according to claim 35, wherein, For each CLVS of the current layer of the reference sequence parameter set, the target set of the access units, according to the decoding order, includes all access units from the first access unit that includes the first picture of the CLVS to the second access unit that includes the last picture of the CLVS.

37. The method of claim 30, wherein, The cross-layer alignment constraint also includes a scaling window offset parameter, which includes at least one of the following: (1) left offset of the scaling window, (2) right offset of the scaling window, (3) top offset of the scaling window, or (4) bottom offset of the scaling window.

38. The method according to claim 20 or 30, wherein, The conversion includes encoding the video into the bitstream.

39. The method according to claim 20 or 30, wherein, The conversion includes decoding the bitstream to generate the video.

40. A method for storing a bitstream of video, comprising: The bitstream of the video is generated from multiple layers of the video according to the rules, and the bitstream of the video is stored. The rule specifies that when a sub-image is considered for use in the generated video image, cross-layer alignment restrictions are applied to fewer than all layers, including the current layer containing the sub-image and a subset of layers associated with the current layer. The cross-layer alignment restrictions include restrictions on at least one dimension of the video image, the number of sub-images within the video image, the position of at least one sub-image, or the identifier of the sub-image.

41. A method for storing a bitstream of video, comprising: Generate the bitstream of the video from the current layer of the video according to the rules, and store the bitstream of the video; The rule specifies that cross-layer alignment constraints are applied to all layers in the dependency tree associated with the current layer, regardless of whether any of the layers is an output layer in the output layer set. The cross-layer alignment constraints include restrictions on at least one dimension of the video image, the number of sub-images within the video image, the position of at least one sub-image, or the identifier of the sub-image. The "all layers" in the dependency tree include the current layer, all layers that have the current layer as a reference layer, and all reference layers of the current layer.

42. A video decoding apparatus comprising a processor configured to implement the method according to any one of claims 20 to 41.

43. A video encoding apparatus comprising a processor configured to implement the method according to any one of claims 20 to 41.

44. A non-transitory computer-readable recording medium storing a bitstream of video generated by a method executed by a video processing apparatus and instructions, wherein, When the instruction is executed by the video processing device, the method is implemented, wherein the method includes: The bitstream of the video is generated from multiple layers of the video according to the rules. The rule specifies that when a sub-image is considered a video image for the transformation, cross-layer alignment restrictions are applied to fewer than all layers, including the current layer containing the sub-image and a subset of layers associated with the current layer. The cross-layer alignment restrictions include restrictions on at least one dimension of the video image, the number of sub-images within the video image, the position of at least one sub-image, or the identifier of the sub-image.

45. A non-transitory computer-readable recording medium storing a bitstream of video generated by a method executed by a video processing apparatus and instructions, wherein, When the instruction is executed by the video processing device, the method is implemented, wherein the method includes: The bitstream of the video is generated from the current layer of the video according to the rules. The rule specifies that cross-layer alignment constraints are applied to all layers in the dependency tree associated with the current layer, regardless of whether any of the layers is an output layer in the output layer set. The cross-layer alignment constraints include restrictions on at least one dimension of the video image, the number of sub-images within the video image, the position of at least one sub-image, or the identifier of the sub-image. The "all layers" in the dependency tree include the current layer, all layers that have the current layer as a reference layer, and all reference layers of the current layer.

Images