Reference subpicture scaling ratio for subpicture in video coding

Abstract

A video decoder can be configured to determine that a first subpicture of a current picture has an associated scaling parameter; responsive to determining that the first subpicture of the current picture has the associated scaling parameter, receive the associated scaling parameter for the first subpicture of the current picture; determine motion information for a block of the first subpicture of the current picture that identifies a subpicture of a reference picture; locate a prediction block for the block of the first subpicture of the current picture in the subpicture of the reference picture; and scale the prediction block based on the associated scaling parameter for the first subpicture of the current picture.

Description

[0001] This application claims priority to U.S. Application No. 17 / 125,225 filed December 17, 2020, which claims benefit of U.S. Provisional Patent Application No. 62 / 953,015 filed December 23, 2019; and U.S. Provisional Patent Application No. 62 / 954,273 filed December 27, 2019, the entire contents of each of which are incorporated herein by reference. TECHNICAL FIELD

[0002] The present disclosure relates to video encoding and video decoding. BACKGROUND

[0003] Digital video capabilities can be incorporated into a wide range of devices, including digital televisions, digital direct broadcast systems, wireless broadcast systems, personal digital assistants (PDAs), laptop or desktop computers, tablet computers, e-book readers, digital cameras, digital recording devices, digital media players, video gaming devices, video game consoles, cellular or satellite radio telephones, so-called “smart phones,” video teleconferencing devices, video streaming devices, and the like. Digital video devices implement video coding techniques, such as those described in the standards defined by MPEG-2, MPEG-4, ITU-T H.263, ITU-T H.264 / MPEG-4, Part 10, Advanced Video Coding (AVC), ITU-T H.265 High Efficiency Video Coding (HEVC), and extensions of such standards. The video devices can implement video coding techniques to transmit, receive, encode, decode, and / or store digital video information more efficiently.

[0004] Video coding techniques include spatial (intra-picture) prediction and / or temporal (inter-picture) prediction to reduce or remove redundancy of video sequences. For block-based video coding, a video slice (e.g., a video picture or a portion of a video picture) can be partitioned into video blocks, which can also be referred to as coding tree units (CTUs), coding units (CUs), and / or coding nodes. Video blocks in an intra-coded (I) slice of a picture are encoded using spatial prediction with respect to reference samples in a same picture. Video blocks in an inter-coded (P or B) slice of a picture can use spatial prediction with respect to reference samples in a same picture or temporal prediction with respect to reference samples in other reference pictures. Pictures can be referred to as frames, and reference pictures can be referred to as reference frames. SUMMARY

[0005] To support 360-degree video, the Versatile Video Coding (VVC) standard supports sub-pictures. This disclosure describes techniques that enable a video coder (e.g., a video encoder or a video decoder) to support reference picture scaling ratios for sub-pictures. This disclosure also describes techniques that enable a video coder to support both reference picture resampling and sub-pictures.

[0006] As explained in more detail below, sub-pictures can have different resolutions, e.g., have different numbers of samples in the sub-pictures. There is currently no mechanism for a video coder to use reference blocks in sub-pictures having different resolutions to properly inter-predict a current block. This disclosure introduces techniques that can enable a video coder to receive scaling parameters for a sub-picture of a current picture and scale a prediction block based on the scaling parameters to enable a current block to be inter-predicted from a reference sub-picture having a different resolution than the first sub-picture. For example, a video coder can determine a scaling ratio based on a ratio of a window of a sub-picture of a reference picture to a window of a first sub-picture of a current picture. By scaling a prediction block based on the associated scaling parameters for the first sub-picture of the current picture, a video coder can advantageously inter-predict a current block of one sub-picture from a sub-picture having a different resolution, which can improve overall coding quality. Moreover, by determining a scaling ratio based on a scaling window rather than an entire sub-picture, the techniques of this disclosure can account for changes in perspective (e.g., zooming in or out) that occur between a current sub-picture and a reference picture, which can further advantageously improve overall coding quality by generating more accurate prediction blocks.

[0007] According to examples of the disclosure, a method includes determining that a first sub-picture of a current picture has an associated scaling parameter, receiving the associated scaling parameter for the first sub-picture of the current picture in response to determining that the first sub-picture of the current picture has the associated scaling parameter, determining motion information for a block of the first sub-picture of the current picture, wherein the motion information identifies a sub-picture of a reference picture, locating a prediction block for the block of the first sub-picture of the current picture in the sub-picture of the reference picture, and scaling the prediction block based on the associated scaling parameter for the first sub-picture of the current picture.

[0008] According to another example of the disclosure, an apparatus for decoding video data includes a memory configured to store video data, and one or more processors implemented in circuitry and configured to: determine that a first subpicture of a current picture has an associated scaling parameter; responsive to determining that the first subpicture of the current picture has the associated scaling parameter, receive the associated scaling parameter for the first subpicture of the current picture; determine motion information for a block of the first subpicture of the current picture, wherein the motion information identifies a subpicture of a reference picture; locate a prediction block for the block of the first subpicture of the current picture in the subpicture of the reference picture; and scale the prediction block based on the associated scaling parameter for the first subpicture of the current picture.

[0009] According to another example of the disclosure, a computer-readable storage medium stores instructions that, when executed by one or more processors, cause the one or more processors to: determine that a first subpicture of a current picture has an associated scaling parameter; responsive to determining that the first subpicture of the current picture has the associated scaling parameter, receive the associated scaling parameter for the first subpicture of the current picture; determine motion information for a block of the first subpicture of the current picture, wherein the motion information identifies a subpicture of a reference picture; locate a prediction block for the block of the first subpicture of the current picture in the subpicture of the reference picture; and scale the prediction block based on the associated scaling parameter for the first subpicture of the current picture.

[0010] According to another example of the disclosure, an apparatus for coding video data includes: means for determining that a first subpicture of a current picture has an associated scaling parameter; means for receiving, responsive to determining that the first subpicture of the current picture has the associated scaling parameter, the associated scaling parameter for the first subpicture of the current picture; means for determining motion information for a block of the first subpicture of the current picture, wherein the motion information identifies a subpicture of a reference picture; means for locating a prediction block for the block of the first subpicture of the current picture in the subpicture of the reference picture; and means for scaling the prediction block based on the associated scaling parameter for the first subpicture of the current picture.

[0011] The details of one or more examples are set forth in the accompanying drawings and the description below. Other features, objects, and advantages will become apparent from the description, drawings, and claims. BRIEF DESCRIPTION OF DRAWINGS

[0012] Figure 1 FIG. 1 is a block diagram illustrating an example video encoding and decoding system that can perform the techniques of this disclosure.

[0013] Figure 2A and Figure 2B FIG. 1 is a block diagram illustrating an example video encoding and decoding system that can perform the techniques of this disclosure.

[0014] Figure 3 An example of subpicture size with the same corresponding subpicture ID in the reference picture and the current picture is shown.

[0015] Figure 4 An example of a scaled window within a reference picture and a current picture is shown.

[0016] Figure 5 An example of a scaled window is shown.

[0017] Figure 6 An example of a reference block pointed to by a motion vector from a current coding block is shown.

[0018] Figure 7 FIG. 1 is a conceptual diagram illustrating the concept of adaptive streaming in an open group of pictures (GOP) structure.

[0019] Figure 8 FIG. 3 is a conceptual diagram illustrating a reference picture and a current picture with reference picture resampling (RPR) and subpictures enabled, where the subpicture IDs are not reordered.

[0020] Figure 9 FIG. 4 is a conceptual diagram illustrating a reference picture and a current picture with RPR and subpictures enabled, where the subpicture IDs are reordered.

[0021] Figure 10 FIG. 5 is a block diagram illustrating an example video encoder that can perform the techniques of this disclosure.

[0022] Figure 11 FIG. 6 is a block diagram illustrating an example video decoder that can perform the techniques of this disclosure.

[0023] Figure 12 FIG. 7 is a flowchart representing an example process for encoding a current block of video data.

[0024] Figure 13 FIG. 8 is a flowchart representing an example process for decoding a current block of video data.

[0025] Figure 14 FIG. 9 is a flowchart representing an example process for coding a current block of video data. DETAILED DESCRIPTION

[0026] Video coding (e.g., video encoding and / or video decoding) typically involves predicting blocks of video data from either already coded blocks of video data in the same picture (e.g., intra prediction) or already coded blocks of video data in different pictures (e.g., inter prediction). In some cases, a video encoder also computes residual data by comparing a predicted block to an original block. Thus, the residual data represents a difference between samples of the predicted block and samples of the original block. To reduce the number of bits needed to signal the residual data, the video encoder transforms and quantizes the residual data and signals the transformed and quantized residual data in an encoded bitstream. The compression achieved by the transform and quantization process can be lossy, meaning that the transform and quantization process can introduce distortion into decoded video data.

[0027] A video decoder decodes the residual data and adds it to the predicted block to produce a reconstructed video block that more closely matches the original video block than the predicted block itself. Due to the loss introduced by the transform and quantization of the residual data, the first reconstructed block can have distortion or artifacts. To further improve the quality of decoded video, the video decoder can perform one or more filtering operations on the reconstructed video block.

[0028] Video is coded as a series of pictures, where each picture is divided into one or more slices. A slice can include an integer number of blocks, e.g., coding tree units (CTUs). In some examples, blocks within a slice can be grouped into tiles or some other such grouping. For some applications, like two-dimensional movies or television, a picture typically corresponds to a single, continuous scene. For other types of applications, such as 360-degree video, a picture can include multiple sub-pictures, where each sub-picture can correspond to a single continuous scene, while the picture as a whole does not. A sub-picture generally refers to a rectangular region composed of one or more slices within a picture. As one example use case, in some implementations, a 360-degree picture can be tiled according to 96 different sub-pictures. The 96 different sub-pictures can be continuous or discontinuous between boundaries. When streaming 360-degree video, a user can receive only certain ones of the sub-pictures.

[0029] To support 360-degree video, the Versatile Video Coding (VVC) standard supports sub-pictures. This disclosure describes techniques that enable a video coder (e.g., a video encoder or a video decoder) to support reference picture scaling ratios for sub-pictures. This disclosure also describes techniques that enable a video coder to support both reference picture resampling and sub-pictures.

[0030] As explained in more detail below, sub-pictures can have different resolutions, e.g., have different numbers of samples in the sub-pictures. There currently does not exist a mechanism for a video coder to use reference blocks in sub-pictures having different resolutions to properly inter-predict a current block. This disclosure introduces techniques that can enable a video coder to receive scaling parameters for sub-pictures of a current picture, and scale a prediction block based on the scaling parameters to enable a current block to be inter-predicted from a reference sub-picture having a different resolution than a first sub-picture. For example, a video coder can determine a scaling ratio based on a ratio of a window of a sub-picture of a reference picture to a window of a first sub-picture of a current picture. By scaling a prediction block based on an associated scaling parameter for a first sub-picture of a current picture, a video coder can advantageously inter-predict a current block of one sub-picture from a sub-picture having a different resolution, which can improve overall coding quality. Moreover, by determining a scaling ratio based on a scaling window rather than an entire sub-picture, the techniques of this disclosure can account for changes in perspective (e.g., zooming in or out) that occur between a current sub-picture and a reference picture, which can further advantageously improve overall coding quality by generating more accurate prediction blocks.

[0031] Figure 1 FIG. 1 is a block diagram illustrating an example video encoding and decoding system 100 that can perform the techniques of this disclosure. The techniques of this disclosure generally relate to coding (encoding and / or decoding) video data. In general, video data includes any data for processing video. Thus, video data can include raw, unencoded video, encoded video, decoded (e.g., reconstructed) video, and video metadata, such as signaling data.

[0032] As Figure 1 shown, in this example, system 100 includes a source device 102 that provides encoded video data to be decoded and displayed by a destination device 116. In particular, source device 102 provides the video data to destination device 116 via a computer- readable medium 110. Source device 102 and destination device 116 can comprise any of a wide variety of devices, including desktop computers, notebook (i.e., laptop) computers, mobile devices, tablet computers, set-top boxes, telephone handsets such as smartphones, televisions, cameras, display devices, digital media players, video gaming consoles, video streaming devices, broadcast receiver devices, and the like. In some cases, source device 102 and destination device 116 can be equipped for wireless communication, and thus can be referred to as wireless communication devices.

[0033] In Figure 1In the example of FIG. 1, source device 102 includes video source 104, memory 106, video encoder 200, and output interface 108. Destination device 116 includes input interface 122, video decoder 300, memory 120, and display device 118. In accordance with this disclosure, video encoder 200 of source device 102 and video decoder 300 of destination device 116 can be configured to apply the techniques for reference subpicture scaling. Thus, source device 102 represents an example of a video encoding device, while destination device 116 represents an example of a video decoding device. In other examples, a source device and a destination device can include other components or arrangements. For example, source device 102 can receive video data from an external video source, such as an external camera. Likewise, destination device 116 can interface with an external display device, rather than include an integrated display device.

[0034] As Figure 1 System 100 of FIG. 1 is merely one example. In general, any digital video encoding and / or decoding device can perform the techniques for reference subpicture scaling. Source device 102 and destination device 116 are merely examples of such coding devices in which source device 102 generates coded video data for transmission to destination device 116. This disclosure refers to a “coding” device as a device that performs coding (encoding and / or decoding) of data. Thus, video encoder 200 and video decoder 300 represent examples of coding devices, in particular, examples of a video encoder and a video decoder, respectively. In some examples, source device 102 and destination device 116 can operate in a substantially symmetrical manner, such that each of source device 102 and destination device 116 includes video encoding and decoding components. Hence, system 100 can support one-way or two-way video transmission between source device 102 and destination device 116, e.g., for video streaming, video playback, video broadcasting, or video telephony.

[0035] In general, video source 104 represents a source of video data (i.e., raw, unencoded video data) and provides a continuous series of pictures (also referred to as “frames”) of the video data to video encoder 200, which encodes data for the pictures. Video source 104 of source device 102 can include a video capture device, such as a video camera, a video archive containing previously captured raw video, and / or a video feed interface to receive video from a video content provider. As a further alternative, video source 104 can generate computer graphics-based data as the source video, or a combination of live video, archived video, and computer-generated video. In each case, video encoder 200 encodes the captured, pre-captured, or computer-generated video data. Video encoder 200 can rearrange the pictures from received order (sometimes referred to as “display order”) into coding order for coding. Video encoder 200 can generate a bitstream including encoded video data. Source device 102 can then output the encoded video data via output interface 108 onto computer-readable medium 110 for reception and / or retrieval by, for example, input interface 122 of destination device 116.

[0036] Memory 106 of source device 102 and memory 120 of destination device 116 represent general purpose memories. In some examples, memories 106, 120 can store raw video data, e.g., raw video from video source 104 and raw, decoded video data from video decoder 300. Additionally or alternatively, memories 106, 120 can store software instructions executable by, e.g., video encoder 200 and video decoder 300, respectively. Although memory 106 and memory 120 are shown separately from video encoder 200 and video decoder 300 in this example, it should be understood that video encoder 200 and video decoder 300 can also include internal memories for a functionally similar or equivalent purpose. Furthermore, memories 106, 120 can store encoded video data, e.g., that is output from video encoder 200 and input to video decoder 300. In some examples, portions of memories 106, 120 can be allocated as one or more video buffers, e.g., to store raw, decoded, and / or encoded video data.

[0037] Computer-readable medium 110 can represent any type of medium or device capable of storing encoded video data from source device 102 and communicating that encoded video data to destination device 116. In one example, computer-readable medium 110 represents a communication medium to enable source device 102 to transmit encoded video data directly to destination device 116 in real-time, e.g., via a radio frequency network or computer-based network. Output interface 108 can modulate a transmission signal including the encoded video data, and input interface 122 can demodulate received transmission signals, according to a communication standard, such as a wireless communication protocol. The communication medium can comprise any wireless or wired communication medium, such as a radio frequency (RF) spectrum or one or more physical transmission lines. The communication medium can form part of a packet-based network, such as a local area network, a wide-area network, or a global network such as the Internet. The communication medium can include routers, switches, base stations, or any other equipment that can be useful to facilitate communication from source device 102 to destination device 116.

[0038] In some examples, source device 102 can output encoded data from output interface 108 to storage device 112. Similarly, destination device 116 can access encoded data from storage device 112 via input interface 122. Storage device 112 can include any of a variety of distributed or locally accessed data storage media such as a hard drive, Blu-ray discs, DVDs, CD-ROMs, flash memory, volatile or non-volatile memory, or any other suitable digital storage media for storing encoded video data.

[0039] In some examples, source device 102 can output encoded video data to a file server 114 or another intermediate storage device that can store encoded video data generated by source device 102. Destination device 116 can access stored video data from file server 114 via streaming or download.

[0040] The file server 114 can be any type of server device capable of storing encoded video data and transmitting that encoded video data to the destination device 116. The file server 114 can represent a web server (e.g., for a website), a server configured to provide file transfer protocol services, such as the File Transfer Protocol (FTP) or File Delivery over Unidirectional Transport (FLUTE) protocol, a content delivery network (CDN) device, a hypertext transfer protocol (HTTP) server, a multimedia broadcast multicast service (MBMS) or enhanced MBMS (eMBMS) server, and / or a network attached storage (NAS) device. The file server 114 can additionally or alternatively implement one or more HTTP streaming protocols, such as Dynamic Adaptive Streaming over HTTP (DASH), HTTP Live Streaming (HLS), Real Time Streaming Protocol (RTSP), HTTP Dynamic Streaming, and the like.

[0041] The destination device 116 can access encoded video data from the file server 114 through any standard data connection, including an internet connection. This can include a wireless channel (e.g., a Wi-Fi connection), a wired connection (e.g., a digital subscriber line (DSL), a cable modem, or the like), or a combination of both that is suitable for accessing encoded video data stored on the file server 114. The input interface 122 can be configured to operate according to any one or more of the protocols discussed above for retrieving or receiving media data from the file server 114, or other such protocols for retrieving media data.

[0042] The output interface 108 and the input interface 122 can represent wireless transmitters / receivers, modems, wired networking components (e.g., Ethernet cards), wireless communication components that operate according to any of a variety of IEEE 802.11 standards, or other physical components. In examples where the output interface 108 and the input interface 122 include wireless components, the output interface 108 and the input interface 122 can be configured to transfer data, such as encoded video data, according to a cellular communication standard, such as 4G, 4G-LTE (Long-Term Evolution), LTE Advanced, 5G, or the like. In some examples where the output interface 108 includes a wireless transmitter, the output interface 108 and the input interface 122 can be configured to transfer data, such as encoded video data, according to other wireless standards, such as an IEEE 802.11 specification, an IEEE 802.15 specification (e.g., ZigBee), a Bluetooth TM TM ​The source device 102 and / or destination device 116 may include corresponding system-on-chip (SoC) devices. For example, source device 102 may include an SoC device for performing functions attributed to video encoder 200 and / or output interface 108, while destination device 116 may include an SoC device for performing functions attributed to video decoder 300 and / or input interface 122.

[0043] The techniques disclosed herein can be applied to video decoding in any of a variety of multimedia applications such as: over-the-air television broadcasting, cable television transmission, satellite television transmission, internet streaming video transmission such as HTTP-based Dynamic Adaptive Streaming (DASH), digital video encoded onto a data storage medium, decoding of digital video stored on a data storage medium, or other applications.

[0044] The input interface 122 of the destination device 116 receives an encoded video bitstream from a computer-readable medium 110 (e.g., a communication medium, storage device 112, file server 114, etc.). The encoded video bitstream may include signaling notification information defined by the video encoder 200 and also used by the video decoder 300, such as syntax elements having values ​​describing the characteristics and / or processing of video blocks or other decoded units (e.g., slices, pictures, picture groups, sequences, etc.). The display device 118 displays a decoded image of the decoded video data to the user. The display device 118 may represent any of a variety of display devices, such as a liquid crystal display (LCD), a plasma display, an organic light-emitting diode (OLED) display, or another type of display device.

[0045] although Figure 1 Not shown, but in some examples, the video encoder 200 and video decoder 300 may each be integrated with the audio encoder and / or audio decoder, and may include appropriate MUX-DEMUX units or other hardware and / or software to handle multiplexed streams of both audio and video in a common data stream. Where applicable, the MUX-DEMUX unit may conform to the ITU H.223 multiplexer protocol or other protocols, such as User Datagram Protocol (UDP).

[0046] Video encoder 200 and video decoder 300 each can be implemented as any of a variety of suitable encoder and / or decoder circuitry, such as one or more microprocessors, digital signal processors (DSPs), application specific integrated circuits (ASICs), field programmable gate arrays (FPGAs), discrete logic, software, hardware, firmware or any combinations thereof. When the techniques are implemented partially in software, a device can store instructions for the software in a suitable, non- transitory computer-readable medium and execute the instructions in hardware using one or more processors to perform the techniques of this disclosure. Each of video encoder 200 and video decoder 300 can be included in one or more encoders or decoders, either of which can be integrated as part of a combined encoder / decoder (CODEC) in a respective device. A device including video encoder 200 and / or video decoder 300 can comprise an integrated circuit, a microprocessor, and / or a wireless communication device, such as a cellular telephone.

[0047] Video encoder 200 and video decoder 300 can operate according to a video coding standard, such as ITU-T H.265, also referred to as High Efficiency Video Coding (HEVC), or extensions thereof, such as the multi-view and / or scalable video coding extensions. Alternatively, video encoder 200 and video decoder 300 can operate according to other proprietary or industry standards, such as ITU-T H.266, also referred to as Versatile Video Coding (VVC). A draft of the VVC standard is described in Bross, et al., “Versatile Video Coding (Draft 7),” Joint Video Team (JVT) of ITU-T SG 16 WP 3 and ISO / IEC JTC 1 / SC 29 / WG 11, 16th Meeting: Geneva, Switzerland, 1-11 October 2019, JVET-P2001-v14 (hereinafter “VVC Draft 7”). The techniques of this disclosure, however, are not limited to any particular coding standard.

[0048] In general, video encoder 200 and video decoder 300 can perform block-based coding of pictures. The term “block” generally refers to a structure comprising data that is processed (e.g., encoded, decoded, or otherwise used in the encoding and / or decoding process) as a unit. For example, a block can include a two-dimensional matrix of samples of luma and / or chroma data. In general, video encoder 200 and video decoder 300 can code video data represented in a YUV (e.g., Y, Cb, Cr) format. That is, rather than coding red, green, and blue (RGB) data for samples of a picture, video encoder 200 and video decoder 300 can code luma and chroma components, where the chroma components can include both red hue and blue hue chroma components. In some examples, video encoder 200 converts received RGB formatted data to a YUV representation prior to encoding, and video decoder 300 converts the YUV representation to the RGB format. Alternatively, pre- and post-processing units (not shown) can perform these conversions.

[0049] This disclosure can generally relate to coding (e.g., encoding and decoding) of pictures, intended to include processes of encoding or decoding data of pictures. Similarly, this disclosure can refer to coding of blocks of pictures as including processes of encoding or decoding data for the blocks, e.g., prediction and / or residual coding. An encoded video bitstream generally includes a series of values for syntax elements that represent coding decisions (e.g., coding modes) and partitioning of pictures into blocks. Thus, references to coding a picture or block should generally be understood to code values for syntax elements that form the picture or block.

[0050] HEVC defines various blocks, including coding units (CUs), prediction units (PUs), and transform units (TUs). According to HEVC, a video coder, such as video encoder 200, partitions a coding tree unit (CTU) into CUs according to a quadtree structure. That is, the video coder partitions CTUs and CUs into four equal, non overlapping squares, and each node of the quadtree has either zero or four child nodes. Nodes with zero child nodes can be referred to as “leaf nodes,” and CUs of such leaf nodes can include one or more PUs and / or one or more TUs. The video coder can further partition PUs and TUs. For example, in HEVC, a residual quadtree (RQT) represents partitioning of TUs. In HEVC, PUs represent inter-predicted data, while TUs represent residual data. Intra-predicted CUs include intra-prediction information, such as an intra-mode indication.

[0051] As another example, video encoder 200 and video decoder 300 can be configured to operate according to VVC. According to VVC, a video coder, such as video encoder 200, partitions a picture into a plurality of coding tree units (CTUs). Video encoder 200 can partition a CTU according to a tree structure such as a quad-tree binary tree (QTBT) structure or a multi-type tree (MTT) structure. The QTBT structure removes the concepts of multiple partition types, such as the separation between CUs, PUs, and TUs of HEVC. The QTBT structure includes two levels: a first level partitioned according to quad-tree partitioning, and a second level partitioned according to binary tree partitioning. A root node of the QTBT structure corresponds to a CTU. Leaf nodes of the binary trees correspond to coding units (CUs).

[0052] In the MTT partitioning structure, a block can be partitioned using quad-tree (QT) partitioning, binary tree (BT) partitioning, and one or more types of ternary tree (TT) (also referred to as ternary tree (TT)) partitioning. Ternary tree or ternary tree partitioning is a partitioning in which a block is split into three sub-blocks. In some examples, a ternary tree or ternary tree partitioning divides a block into three sub-blocks rather than dividing the original block through the center. The partitioning types (e.g., QT, BT, and TT) in the MTT can be symmetric or asymmetric.

[0053] In some examples, video encoder 200 and video decoder 300 can use a single QTBT structure or MTT structure to represent each of luma and chroma components, while in other examples, video encoder 200 and video decoder 300 can use two or more QTBT structures or MTT structures, such as one QTBT / MTT structure for luma components and another QTBT / MTT structure for two chroma components (or two QTBT / MTT structures for respective chroma components).

[0054] Video encoder 200 and video decoder 300 can be configured to use quad-tree partitioning, QTBT partitioning, MTT partitioning, or other partitioning structures in accordance with HEVC. For purposes of explanation, the description of the techniques of this disclosure is presented with respect to QTBT partitioning. However, it should be understood that the techniques of this disclosure can also be applied to video coders configured to use quad-tree partitioning or other types of partitioning.

[0055] In certain examples, a CTU includes a coding tree block (CTB) of luma samples, two corresponding CTBs of chroma samples of a picture having three arrays of samples, or a CTB of samples of a monochrome picture or a picture coded using three separate color planes and syntax structures for coding samples. A CTB can be an NxN block of samples for some value N, such that the partitioning of components to CTBs is a one-level partitioning. A component is an array or a single sample from one of three arrays (luma and two chroma) that make up a picture in a 4:2:0, 4:2:2, or 4:4:4 color format, or an array or a single sample of an array that make up a picture in a monochrome format. In certain examples, a coding block is an MxN block of samples for some values M and N, such that the partitioning of CTBs to coding blocks is a one-level partitioning.

[0056] A block (e.g., a CTU or CU) can be grouped in various ways in a picture. As one example, a brick can refer to a rectangular region of CTU rows within a particular tile in a picture. A tile can be a rectangular region of CTUs within a particular tile column and a particular tile row in a picture. A tile column refers to a rectangular region of CTUs having a height equal to a height of the picture and a width specified by a syntax element (e.g., such as in a picture parameter set). A tile row refers to a rectangular region of CTUs having a height specified by a syntax element (e.g., such as in a picture parameter set) and a width equal to a width of the picture.

[0057] In certain examples, a tile can be partitioned into multiple bricks, where each brick can include one or more CTU rows within the tile. A tile that is not partitioned into multiple bricks can also be referred to as a brick. However, a brick that is a true subset of a tile can not be referred to as a tile.

[0058] Bricks in a picture can also be arranged in slices. A slice can be an integer number of bricks of a picture that can be exclusively contained in a single network abstraction layer (NAL) unit. In certain examples, a slice includes multiple complete tiles or a contiguous sequence of complete bricks of only one tile.

[0059] The present disclosure can interchangeably use “NxN” and “N by N” to refer to the sample dimensions of a block (such as a CU or other video block) in terms of vertical and horizontal dimensions, e.g., 16x16 samples or 16 by 16 samples. In general, a 16x16 CU will have 16 samples in the vertical direction (y = 16) and 16 samples in the horizontal direction (x = 16). Likewise, an NxN CU will generally have N samples in the vertical direction and N samples in the horizontal direction, where N represents a nonnegative integer value. The samples in a CU can be arranged in rows and columns. Moreover, a CU need not necessarily have the same number of samples in the horizontal direction as in the vertical direction. For example, a CU can comprise NxM samples, where M is not necessarily equal to N.

[0060] Video encoder 200 encodes video data representing prediction and / or residual information for a CU, among other information. Prediction information indicates how to predict the CU in order to form a prediction block for the CU. Residual information generally represents a sample-by-sample difference between samples of the CU prior to encoding and the prediction block.

[0061] To predict a CU, video encoder 200 can generally form a prediction block for the CU through inter-prediction or intra-prediction. Inter-prediction generally refers to predicting the CU from data of a previously coded picture, whereas intra-prediction generally refers to predicting the CU from previously coded data of the same picture. To perform inter-prediction, video encoder 200 can use one or more motion vectors to generate the prediction block. Video encoder 200 can generally perform a motion search to identify a reference block that closely matches the CU, e.g., according to a difference between the CU and the reference block. Video encoder 200 can calculate a difference metric using a sum of absolute difference (SAD), sum of squared difference (SSD), mean absolute difference (MAD), mean squared difference (MSD), or other such difference calculations to determine whether a reference block closely matches a current CU. In some examples, video encoder 200 can use uni -prediction or bi-prediction to predict a current CU.

[0062] Certain examples of VVC also provide an affine motion compensation mode, which can be considered a type of inter-prediction mode. In the affine motion compensation mode, video encoder 200 can determine two or more motion vectors representing non-translational motion, such as scaling or zooming, rotation, perspective motion, or other irregular types of motion.

[0063] To perform intra prediction, video encoder 200 can select an intra prediction mode to generate the prediction block. Certain examples of VVC provide sixty-seven intra prediction modes, including various directional modes, as well as a planar mode and a DC mode. Generally, video encoder 200 selects an intra prediction mode that describes neighboring samples of the current block (e.g., a block of a CU) to predict samples of the current block. Assuming that video encoder 200 is coding CTUs and CUs in a raster scan order (left to right, top to bottom), such samples can generally be located above, above and to the left, or to the left of the current block in the same picture as the current block.

[0064] Video encoder 200 encodes data that represents the prediction mode used for the current block. For example, for inter prediction modes, video encoder 200 can encode data that indicates which of the various available inter prediction modes is used, as well as motion information for the corresponding mode. For example, for uni- or bi-prediction, video encoder 200 can encode motion vectors using advanced motion vector prediction (AMVP) or merge mode. For affine motion compensation mode, video encoder 200 can encode motion vectors using a similar mode.

[0065] Following prediction of a block, such as after intra or inter prediction of a block, video encoder 200 can calculate residual data for the block. Residual data, such as a residual block, represents sample-by-sample differences between the block and a prediction block for the block that is formed using the corresponding prediction mode. Video encoder 200 can apply one or more transforms to the residual block to produce transformed data in a transform domain rather than the sample domain. For example, video encoder 200 can apply a discrete cosine transform (DCT), an integer transform, a wavelet transform, or a conceptually similar transform. In addition, video encoder 200 can apply a secondary transform following a primary transform, such as a mode-dependent non-separable secondary transform (MDNSST), a signal-dependent transform, a Karhunen-Loeve transform (KLT), or the like. Video encoder 200 produces transform coefficients following application of the transform(s).

[0066] As described above, following any transforms to produce transform coefficients, video encoder 200 can perform quantization of the transform coefficients. Quantization generally refers to a process in which transform coefficients are quantized to possibly reduce the amount of data used to represent the transform coefficients, providing further compression. By performing the quantization process, video encoder 200 can reduce the bit depth of certain or all of the transform coefficients associated with the transform coefficients. For example, video encoder 200 can round n-bit values down to m-bit values during quantization, with n greater than m. In some examples, to perform quantization, video encoder 200 can perform a bitwise right-shift of the values to be quantized.

[0067] After quantization, video encoder 200 can scan the transform coefficients, producing a one-dimensional vector from the two-dimensional matrix including the quantized transform coefficients. The scan can be designed to place higher energy (and hence lower frequency) transform coefficients at the front of the vector and lower energy (and hence higher frequency) transform coefficients at the back of the vector. In some examples, video encoder 200 can utilize a predefined scan order to scan the quantized transform coefficients to produce a serialized vector, and subsequently entropy encode the quantized transform coefficients of the vector. In other examples, video encoder 200 can perform an adaptive scan. After scanning the quantized transform coefficients to form a one-dimensional vector, video encoder 200 can entropy encode the one-dimensional vector, e.g., according to context adaptive binary arithmetic coding (CABAC). Video encoder 200 can also entropy encode values for syntax elements that describe metadata associated with the encoded video data for use in decoding the video data by video decoder 300.

[0068] To perform CABAC, video encoder 200 can assign a context within a context model to a symbol to be transmitted. The context can relate to, for example, whether neighboring values of the symbol are zero-valued or not. The probability determination can be based on the context assigned to the symbol.

[0069] Video encoder 200 can further generate, e.g., in a picture header, a block header, a slice header, block-based syntax data, picture-based syntax data, and sequence-based syntax data, or other syntax data such as sequence parameter sets (SPSs), picture parameter sets (PPSs), or video parameter sets (VPSs), to video decoder 300. Video decoder 300 can likewise decode such syntax data to determine how to decode corresponding video data.

[0070] In this way, video encoder 200 can produce a bitstream including encoded video data, e.g., syntax elements describing partitioning of a picture into blocks (e.g., CUs) and prediction and / or residual information for the blocks. Ultimately, video decoder 300 can receive the bitstream and decode the encoded video data.

[0071] In general, video decoder 300 performs a reciprocal process to that performed by video encoder 200 to decode encoded video data of the bitstream. For example, video decoder 300 can decode values for syntax elements in the bitstream using CABAC in a manner substantially similar to, although reciprocal to, the CABAC encoding process by video encoder 200. The syntax elements can define partitioning information for partitioning of a picture into CTUs, as well as partitioning of each CTU according to a corresponding partition structure, such as a QTBT structure, to define CUs of the CTU. The syntax elements can further define prediction and residual information for blocks (e.g., CUs) of video data.

[0072] The residual information can be represented by, for example, quantized transform coefficients. Video decoder 300 can inverse quantize and inverse transform the quantized transform coefficients of a block to reproduce a residual block for the block. Video decoder 300 forms a prediction block for the block using the signaled prediction mode (intra- or inter-prediction) and related prediction information (e.g., motion information for inter-prediction). Video decoder 300 can then combine (on a sample-by-sample basis) the prediction block and the residual block to reproduce the original block. Video decoder 300 can perform additional processing, such as performing a deblocking process to reduce visual artifacts along boundaries of the blocks.

[0073] This disclosure can generally relate to “signaling” certain information, such as syntax elements. The term “signaling” can generally relate to communication of values for syntax elements and / or other data used for decoding encoded video data. That is, video encoder 200 can signal values for syntax elements in the bitstream. In general, signaling involves generating the values in the bitstream. As described above, source device 102 can transmit the bitstream to destination device 116 in substantially real-time or non-real time, such as can occur when storing the syntax elements to storage device 112 for later retrieval by destination device 116.

[0074] Figure 2A and Figure 2Bis a conceptual diagram illustrating an example quad-tree binary tree (QTBT) structure 130, as well as a corresponding coding tree unit (CTU) 132. Solid lines represent quad-tree splitting, while dashed lines indicate binary-tree splitting. In each split (i.e., non-leaf) node of the binary tree, a flag is signaled to indicate which type of split is used (i.e., horizontal or vertical), where 0 indicates a horizontal split and 1 indicates a vertical split in this example. For quad-tree splitting, the split type does not need to be indicated because quad-tree nodes split a block horizontally and vertically into 4 equally sized sub-blocks. Accordingly, video encoder 200 can encode and video decoder 300 can decode syntax elements (such as split information) for the region tree hierarchy (i.e., solid lines) of QTBT structure 130 as well as syntax elements (such as split information) for the prediction tree hierarchy (i.e., dashed lines) of QTBT structure 130. Video encoder 200 can encode and video decoder 300 can decode video data such as prediction and transform data for CUs represented by terminal leaf nodes of QTBT structure 130.

[0075] In general, Figure 2B CTU 132 can be associated with parameters defining sizes of blocks corresponding to nodes in the first and second levels of QTBT structure 130. These parameters can include a CTU size (representing the size of CTU 132 in samples), a minimum quad-tree size (MinQTSize, representing a minimum allowed quad-tree leaf node size), a maximum binary tree size (MaxBTSize, representing a maximum allowed binary tree root node size), a maximum binary tree depth (MaxBTDepth, representing a maximum allowed binary tree depth), and a minimum binary tree size (MinBTSize, representing a minimum allowed binary tree leaf node size).

[0076] The root node of the QTBT structure corresponding to a CTU can have four child nodes at the first level of the QTBT structure, each of which can be partitioned according to quadtree partitioning. That is, nodes of the first level are either leaf nodes (having no child nodes) or have four child nodes. The example of the QTBT structure 130 represents such nodes as including parent and child nodes with solid lines for branches. If a node of the first level is not larger than a maximum allowed binary tree root node size (MaxBTSize), the node can be further partitioned by a corresponding binary tree. The binary tree split of a node can be iterated until the split results in a node that reaches a minimum allowed binary tree leaf node size (MinBTSize) or a maximum allowed binary tree depth (MaxBTDepth). The example of the QTBT structure 130 represents such nodes as having dashed lines for branches. Binary tree leaf nodes are referred to as coding units (CUs), which are used for prediction (e.g., intra- or inter-prediction) and transform without any further partitioning. As noted above, a CU can also be referred to as a “video block” or “block.”

[0077] In one example of a QTBT partitioning structure, the CTU size is set to 128x128 (luma samples and two corresponding 64x64 chroma samples), MinQTSize is set to 16x16, MaxBTSize is set to 64x64, MinBTSize (for both width and height) is set to 4, and MaxBTDepth is set to 4. Quadtree partitioning is first applied to the CTU to generate quadtree leaf nodes. A quadtree leaf node can have a size from 16x16 (i.e., MinQTSize) to 128x128 (i.e., the CTU size). If a quadtree leaf node is 128x128, the leaf quadtree node will not be further split by a binary tree because the size exceeds MaxBTSize (i.e., 64x64 in this example). Otherwise, the quadtree leaf node will be further partitioned by a binary tree. Thus, the quadtree leaf node is also a root node for the binary tree, and has a binary tree depth of 0. When the binary tree depth reaches MaxBTDepth (4 in this example), no further split is allowed. A binary tree node having a width equal to MinBTSize (4 in this example) means that no further vertical split (i.e., division of the width) of the binary tree node is allowed. Similarly, a binary tree node having a height equal to MinBTSize means that no further horizontal split (i.e., division of the height) of the binary tree node is allowed. As noted above, leaf nodes of the binary tree are referred to as CUs, and are further processed according to prediction and transform without further partitioning.

[0078] The present disclosure includes potential improvements to the following sections of VVC Draft 7. The following reproduces Section 7.3.2.3 of VVC Draft 7.

[0079]

[0080]

[0081] According to Section 7.4.3.3 in VVC Draft 7, the syntax elements in the above syntax table have the following definitions:

[0082] ref_pic_resampling_enabled_flag equal to 1 specifies that reference picture resampling can be applied when decoding pictures in a CLVS referring to the SPS.

[0083] ref_pic_resampling_enabled_flag equal to 0 specifies that reference picture resampling is not applied when decoding pictures in a CLVS referring to the SPS.

[0084] pic_width_max_in_luma_samples specifies the maximum width, in luma samples, of each decoded picture referring to the SPS. pic_width_max_in_luma_samples shall not be equal to 0 and shall be an integer multiple of Max(8, MinCbSizeY).

[0085] pic_height_max_in_luma_samples specifies the maximum height, in luma samples, of each decoded picture referring to the SPS. pic_height_max_in_luma_samples shall not be equal to 0 and shall be an integer multiple of Max(8, MinCbSizeY).

[0086] subpics_present_flag equal to 1 specifies that subpicture parameters are present in the SPS RBSP syntax. subpics_present_flag equal to 0 specifies that subpicture parameters are not present in the SPS RBSP syntax.

[0087] NOTE 2 - When the bitstream is the result of a sub-bitstream extraction process and contains only a subset of the subpictures of the input bitstream of the sub-bitstream extraction process, it can be necessary to set the value of subpics_present_flag to equal to 1 in the RBSP of the SPS.

[0088] sps_num_subpics_minus1 plus 1 specifies the number of subpictures.

[0089] sps num subpics minusl shall be in the range of 0 to 254. When not present, the value of sps num subpics minusl is inferred to be equal to 0.

[0090] subpic_ctu_top_left_x[ i ] specifies the horizontal positioning of the top-left CTU of the i-th subpicture in CtbSizeY units. The length of this syntax element is

[0091] Ceil( Log2( pic width max in luma samples / CtbSizeY ) ) bits. When not present, the value of subpic_ctu_top_left_x[ i ] is inferred to be equal to 0.

[0092] subpic_ctu_top_left_y[ i ] specifies the vertical positioning of the top-left CTU of the i-th subpicture in CtbSizeY units. The length of this syntax element is

[0093] Ceil( Log2( pic height max in luma samples / CtbSizeY ) ) bits. When not present, the value of subpic_ctu_top_left_y[ i ] is inferred to be equal to 0.

[0094] subpic_width_minusl[ i ] plus 1 specifies the width of the i-th subpicture in CtbSizeY units.

[0095] The length of this syntax element is

[0096] Ceil( Log2( pic width max in luma samples / CtbSizeY ) ) bits. When not present, the value of subpic_width_minusl[ i ] is inferred to be equal to Ceil( pic width max in luma samples / CtbSizeY ) - 1.

[0097] subpic_height_minusl[ i ] plus 1 specifies the height of the i-th subpicture in CtbSizeY units.

[0098] The length of this syntax element is

[0099] Ceil( Log2( pic_height_max_in_luma_samples / CtbSizeY ) ) bits. When not present, the value of subpic_width_minus1[ i ] is inferred to be equal to Ceil( pic_width_max_in_luma_samples / CtbSizeY ) - 1.

[0100] subpic_treated_as_pic_flag[ i ] equal to 1 specifies that the i-th subpicture of each coded picture in the CLVS is treated as a picture in the decoding process except for in-loop filtering operations.

[0101] subpic_treated_as_pic_flag[ i ] equal to 0 specifies that the i-th subpicture of each coded picture in the CLVS is not treated as a picture in the decoding process except for in-loop filtering operations. When not present, the value of subpic_treated_as_pic_flag[ i ] is inferred to be equal to 0.

[0102] sps_subpic_id_present_flag equal to 1 specifies that subpicture ID mapping is present in the SPS.

[0103] sps_subpic_id_present_flag equal to 0 specifies that subpicture ID mapping is not present in the SPS.

[0104] sps_subpic_id_signalling_present_flag equal to 1 specifies that subpicture ID mapping is signaled in the SPS. sps_subpic_id_signalling_present_flag equal to 0 specifies that subpicture ID mapping is not signaled in the SPS. When not present, the value of sps_subpic_id_signalling_present_flag is inferred to be equal to 0.

[0105] sps_subpic_id_len_minus1 plus 1 specifies the number of bits used to represent the syntax element sps_subpic_id[ i ]. The value of sps_subpic_id_len_minus1 shall be in the range of 0 to 15, inclusive.

[0106] sps_subpic_id[ i ] specifies the subpicture ID of the i-th subpicture. The length of sps_subpic_id[ i ] syntax element is sps_subpic_id_len_minus1 + 1 bits. When not present and when sps_subpic_id_present_flag is equal to 0, the value of sps_subpic_id[ i ] is inferred to be equal to i for each i in the range of 0 to sps_num_subpics_minus1, inclusive.

[0107] The following reproduces section 7.3.2.4 of VVC Draft 7.

[0108]

[0109] According to section 7.4.3.4 in VVC Draft 7, the syntax elements in the above syntax table have the following definitions:

[0110] pic_width_in_luma_samples specifies the width of each decoded picture referring to the PPS in units of luma samples. pic_width_in_luma_samples shall not be equal to 0, shall be an integer multiple of Max(8, MinCbSizeY), and shall be less than or equal to pic_width_max_in_luma_samples.

[0111] When subpics_present_flag is equal to 1 or ref_pic_resampling_enabled_flag is equal to 0, the value of pic_width_in_luma_samples shall be equal to pic_width_max_in_luma_samples.

[0112] pic_height_in_luma_samples specifies the height of each decoded picture referring to the PPS in units of luma samples. pic_height_in_luma_samples shall not be equal to 0, shall be an integer multiple of Max(8, MinCbSizeY), and shall be less than or equal to pic_height_max_in_luma_samples.

[0113] When subpics_present_flag is equal to 1 or ref_pic_resampling_enabled_flag is equal to 0, the value of pic_height_in_luma_samples shall be equal to pic_height_max_in_luma_samples.

[0114] Let refPicWidthInLumaSamples and refPicHeightInLumaSamples be pic_width_in_luma_samples and pic_height_in_luma_samples of the reference picture of the current picture referring to this PPS. The requirement for bitstream conformance is that all of the following conditions are met:

[0115] - pic_width_in_luma_samples * 2 shall be greater than or equal to refPicWidthInLumaSamples.

[0116] - pic_height_in_luma_samples * 2 shall be greater than or equal to refPicHeightInLumaSamples.

[0117] - pic_width_in_luma_samples shall be less than or equal to refPicWidthInLumaSamples * 8.

[0118] - pic_height_in_luma_samples shall be less than or equal to refPicHeightInLumaSamples * 8.

[0119] scaling_window_flag equal to 1 specifies that scaling window offset parameters are present in the PPS. scaling_window_flag equal to 0 specifies that scaling window offset parameters are not present in the PPS. When ref_pic_resampling_enabled_flag is equal to 0, the value of scaling_window_flag shall be equal to 0.

[0120] scaling_win_left_offset, scaling_win_right_offset, scaling_win_top_offset, and scaling_win_bottom_offset specify, in luma samples, the offsets applied to the picture size for scaling ratio calculation. When scaling_window_flag is equal to 0, 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 0.

[0121] The value of scaling_win_left_offset + scaling_win_right_offset shall be less than pic_width_in_luma_samples, and the value of scaling_win_top_offset + scaling_win_bottom_offset shall be less than pic_height_in_luma_samples.

[0122] The variables PicOutputWidthL and PicOutputHeightL are derived as follows:

[0123] PicOutputWidthL = pic_width_in_luma_samples - (scaling_win_right_offset + scaling_win_left_offset) (74)

[0124] PicOutputHeightL = pic_height_in_luma_samples - (scaling_win_bottom_offset + scaling_win_top_offset) (75)

[0125] pps_subpic_id_signalling_present_flag equal to 1 specifies that subpicture IDs are signaled in the PPS. pps_subpic_id_signalling_present_flag equal to 0 specifies that subpicture IDs are not signaled in the PPS. When sps_subpic_id_present_flag is 0 or pps_subpic_id_signalling_present_flag is equal to 1, pps_subpic_id_signalling_present_flag shall be equal to 0.

[0126] pps_num_subpics_minus1 plus 1 specifies the number of subpictures in the coded picture referring to the PPS.

[0127] The requirement for bitstream conformance is that the value of pps_num_subpic_minus1 shall be equal to sps_num_subpics_minus1.

[0128] pps_subpic_id_len_minus1 plus 1 specifies the number of bits used to represent the syntax element pps_subpic_id[ i ]. The value of pps_subpic_id_len_minus1 shall be in the range of 0 to 15, inclusive.

[0129] It is a requirement of bitstream conformance that the value of pps_subpic_id_len_minus1 shall be the same for all PPS referred to by the coded pictures in a CLVS.

[0130] pps_subpic_id[ i ] specifies the subpicture ID of the i-th subpicture. The length of the pps_subpic_id[ i ] syntax element is pps_subpic_id_len_minus1 + 1 bits.

[0131] The following reproduces Section 7.3.2.6 of VVC Draft 7.

[0132]

[0133]

[0134] According to Section 7.4.3.6 in VVC Draft 7, the syntax elements in the above syntax table have the following definitions:

[0135] ph_subpic_id_signalling_present_flag equal to 1 specifies that subpicture ID mapping is signaled in the PH. ph_subpic_id_signalling_present_flag equal to 0 specifies that subpicture ID mapping is not signaled in the PH.

[0136] ph_subpic_id_len_minus1 plus 1 specifies the number of bits used to represent the syntax element ph_subpic_id[ i ]. The value of pic_subpic_id_len_minus1 shall be in the range of 0 to 15, inclusive.

[0137] It is a requirement of bitstream conformance that the value of ph_subpic_id_len_minus1 shall be the same for all PH referred to by the coded pictures in a CLVS.

[0138] ph_subpic_id[ i ] specifies the subpicture ID of the i-th subpicture. The length of the ph_subpic_id[ i ] syntax element is ph_subpic_id_len_minus1 + 1 bits.

[0139] The list SubpicIdList[ i ] is derived as follows:

[0140] for(i = 0; i <= sps num subpics minusl; i++) SubpicldList[i] = sps subpic id present flag? (76)

[0141] (sps subpic id signalling present flag? sps subpic id[i] : (ph subpic id signalling present flag? ph subpic id[i] : pps subpic id[i])) : i

[0142] The following reproduces section 7.3.7.1 of VVC Draft 7.

[0143]

[0144] According to section 7.4.8.1 in VVC Draft 7, the syntax elements in the above syntax table have the following definitions:

[0145] slice subpic id specifies the subpicture identifier of the subpicture containing the slice. If slice subpic id is present, the value of the variable SubPicldx is derived so that SubpicldList[SubPicldx] is equal to slice subpic id. Otherwise (slice subpic id is not present), the variable SubPicldx is derived to be equal to 0. The length of slice subpic id, in bits, is derived as follows:

[0146] - If sps subpic id signalling present flag is equal to 1, the length of slice subpic id is equal to sps subpic id len minusl + 1.

[0147] - Otherwise, if ph subpic id signalling present flag is equal to 1, the length of slice subpic id is equal to ph subpic id len minusl + 1.

[0148] - Otherwise, if pps subpic id signalling present flag is equal to 1, the length of slice subpic id is equal to pps subpic id len minusl + 1.

[0149] - Otherwise, the length of slice_subpic_id is equal to Ceil( Log2( sps_num_subpics_minus1 + 1 ) ).

[0150] The variables SubPicLeftBoundaryPos, SubPicTopBoundaryPos, SubPicRightBoundaryPos, and SubPicBotBoundaryPos are derived as follows:

[0151] if( subpic_treated_as_pic_flag[ SubPicIdx ] ) { SubPicLeftBoundaryPos = subpic_ctu_top_left_x[ SubPicIdx ] * CtbSizeY SubPicRightBoundaryPos = Min( pic_width_max_in_luma_samples - 1,

[0152] ( subpic_ctu_top_left_x[ SubPicIdx ] + subpic_width_minus1[ SubPicIdx ] + 1 ) * CtbSizeY - 1 )

[0153] SubPicTopBoundaryPos = subpic_ctu_top_left_y[ SubPicIdx ] * CtbSizeY (116)

[0154] SubPicBotBoundaryPos = Min( pic_height_max_in_luma_samples - 1, ( subpic_ctu_top_left_y[ SubPicIdx ] + subpic_height_minus1[ SubPicIdx ] + 1 ) * CtbSizeY - 1 )

[0155] The following reproduces section 8.3.2 of VVC Draft 7.

[0156] The reference picture lists RefPicList[0] and RefPicList[1], the reference picture scaling ratios RefPicScale[i][j][0] and RefPicScale[i][j][1], and the reference picture scaling flags RefPicIsScaled[0] and RefPicIsScaled[1] are constructed as follows:

[0157]

[0158]

[0159] The disclosure also describes potential improvements to the decoder-side motion vector refinement described in section 8.5.3 of VVC Draft 7 and to the decoder process for inter blocks in section 8.5.6 of VVC Draft 7.

[0160] The sections of VVC Draft 7 introduced above can have several issues that can be addressed by the techniques of the disclosure. The disclosure describes several changes to VVC Draft 7. The techniques of the disclosure can be used individually or in various combinations.

[0161] In an example from VVC Draft 7, subpicture IDs can change within a coded layer video sequence (CLVS). A video source can stream in a particular subpicture using the same subpicture ID, such that, for example, only one subpicture of pictures is rendered or displayed at any given time. As Figure 3 and Figure 5 illustrated, separate source contents can stream in three respective subpictures. If the current subpicture is considered a picture, the video decoder 300, for example, can consider the other subpictures as non-existent. In such cases, the current subpicture should refer to the reference subpicture with the same subpicture ID. However, as Figure 3 illustrated, this can result in different resolutions between the reference subpicture and the current subpicture. There is no reference subpicture scaling process in VVC Draft 7 to scale the reference subpicture to the current subpicture. According to the techniques of the disclosure, when the subpicture ID can change within a CLVS and reference picture resampling (RPR) is disabled (i.e., ref_pic_resampling_enabled_flag is set equal to 0), the video encoder 200 and the video decoder 300 can be configured to handle the subpicture scaling ratio process using techniques such as scaling window, derived scaling ratio, range of scaling ratio, and integer positioning for interpolation filtering.

[0162] Figure 3 Examples of subpictures with the same size and subpictures with different sizes between a reference picture and a current picture with the same corresponding subpicture ID are illustrated. In Figure 3 the current picture 136 includes subpictures with IDs 1, 2, and 3, while the reference picture 138 also includes subpictures with IDs 1, 2, and 3. In Figure 3 the example, the subpictures with IDs 1 and 2 in the current picture 136 have different sizes from the subpictures with IDs 1 and 2 in the reference picture 138, but the subpicture with ID 3 in the current picture 136 has the same size as the subpicture with ID 3 in the reference picture 138.

[0163] According to the techniques of this disclosure, video encoder 200 and video decoder 300 can be configured to utilize sub-picture based scaling windows. In VVC Draft 7, a reference picture scaling process is used when the reference picture size is different from the current picture size. VVC Draft 7 Section 8.3.2 describes this process as follows:

[0164] RefPicScale[i][j][0] = ((fRefWidth « 14) + (PicOutputWidthL » 1)) / PicOutputWidthL

[0165] where fRefWidth and fRefHeight are set equal to PicOutputWidthL and PicOutputHeightL (in luma samples) of the reference picture RefPicList[i][j], respectively. As shown in Figure 4 PicOutputWidthL and PicOutputHeightL are the scaling window width and height, and are cropped from the picture width and height as follows:

[0166] PicOutputWidthL = pic_width_in_luma_samples - (scaling_win_right_offset + scaling_win_left_offset)

[0167] PicOutputHeightL = pic_height_in_luma_samples - (scaling_win_bottom_offset + scaling_win_top_offset)

[0168] Figure 4 An example of scaling windows within a reference picture and a current picture is shown. Video encoder 200 and video decoder 300 can determine scaling ratios based on the reference scaling window 142 and the current scaling window 144, rather than determining scaling factors based on the sizes of the reference picture and the current picture. The scaling windows can be used to avoid position misalignment due to scaling or shifting between the temporal instance of the reference picture and the current picture in the reference picture scaling process.

[0169] Video encoder 200 and video decoder 300 can be configured to utilize scaling windows for scaling reference pictures and current pictures, as described above. Video encoder 200 and video decoder 300 can be configured to utilize scaling windows for scaling reference pictures and current pictures, as described above. Figure 4The same reference picture resampling process applies to sub-pictures with the same ID but different sizes. Video encoder 200 and video decoder 300 can apply the scaling window to the current sub-picture in scenarios where the sub-pictures are considered as scenes of a picture, e.g., when only one sub-picture of a picture is being decoded or displayed. According to the techniques of this disclosure, video encoder 200 and video decoder 300 can be configured to perform the following techniques, which will be described as modifications with respect to VVC Draft 7:

[0170] • For each sub-picture, video encoder 200 and video decoder 300 can code a scaling window flag (e.g., pps_scaling_window_flag[i]). If the ith flag pps_scaling_window_flag[i] is equal to 1, the scaling window offsets pps_scaling_win_left_offset[i], pps_scaling_win_right_offset[i], pps_scaling_win_top_offset[i], and pps_scaling_win_bottom_offset[i] are signaled for the ith sub-picture.

[0171] • Video encoder 200 and video decoder 300 can be configured to signal the number of sub-pictures in a CLVS in the PPS before the group of scaling window parameters are signaled.

[0172] • Video encoder 200 and video decoder 300 can be configured to infer the value of pps_scaling_window_flag[i] to be 0 to avoid accidental activation of the reference picture resampling process if at least one of the following conditions is true:

[0173] o ref_pic_resampling_enabled_flag is equal to 0 and subpics_present_flag is equal to 0 (e.g., both the RPR functionality and the sub-picture functionality are disabled);

[0174] o ref_pic_resampling_enabled_flag is equal to 0 and sps_subpic_id_present_flag is equal to 0 (e.g., the RPR functionality is disabled, and the sub-picture ID list is not reordered in the CLVS);

[0175] o ref_pic_resampling_enabled_flag is equal to 0 and sps_subpic_id_signalling_present_flag is equal to 1 (e.g., RPR functionality is disabled and the subpicture ID list is not reordered in the CLVS);

[0176] o subpics_present_flag is equal to 1 and subpic_treated_as_pic_flag[ i ] is equal to 0 (e.g., subpicture functionality is enabled and the ith subpicture is not treated as a picture); or

[0177] o ref_pic_resampling_enabled_flag is equal to 1 and subpics_present_flag is equal to 1 (e.g., RPR functionality and subpicture functionality cannot be enabled at the same time).

[0178] • pps_scaling_win_left_offset[ i ] + pps_scaling_win_right_offset[ i ] <= subpic_width_in_luma_samples[ i ], where subpic_width_in_luma_samples[ i ] is the width for the ith subpicture.

[0179] • pps_scaling_win_top_offset[ i ] + pps_scaling_win_bottom_offset[ i ] <= subpic_height_in_luma_samples[ i ], where subpic_height_in_luma_samples[ i ] is the height for the ith subpicture.

[0180] • The sub-picture based scaling window parameters are signaled in both PPS (e.g., pps_scaling_win_left_offset[i], pps_scaling_win_right_offset[i], pps_scaling_win_top_offset[i], and pps_scaling_win_bottom_offset[i]) and PH (e.g., ph_scaling_win_left_offset[i], ph_scaling_win_right_offset[i], ph_scaling_win_top_offset[i], and ph_scaling_win_bottom_offset[i]). Based on the scaling window flag in PH, i.e., ph_scaling_window_flag[i], the parameters in PH can override the parameters in PPS, e.g., scaling_win_left_offset[i] = (ph_scaling_window_flag[i])? ph_scaling_win_left_offset[i] : pps_scaling_win_left_offset[i].

[0181] o In some examples, the sub-picture based scaling window parameters can be signaled only in PPS.

[0182] o In some examples, the sub-picture based scaling window parameters can be signaled only in PH.

[0183] • The video encoder 200 and the video decoder 300 can be configured to derive the scaling window width and height for the i-th sub-picture by clipping the i-th sub-picture with the i-th scaling window offset as follows:

[0184] PicOutputWidthL[i] = subpic_width_in_luma_samples[i] - (scaling_win_right_offset[i] + scaling_win_left_offset[i])

[0185] PicOutputHeightL[i] = subpic_height_in_luma_samples[i] - (scaling_win_bottom_offset[i] + scaling_win_top_offset[i])

[0186] The following shows the modifications described in this disclosure to section 7.3.2.4 in VVC Draft 7. The syntax changes to VVC Draft 7 are shown in the following table. The label “ <add>" shows the start of an addition, while the tag< / add> ” shows the end of those additions. The label “ <del>" shows the start of a deletion (i.e., text removal), while the tag< / del> ” shows the end of those deletions.

[0187]

[0188]

[0189] The following shows the modifications to section 7.4.3.4 in VVC Draft 7.

[0190] pic_width_in_luma_samples specifies the width of each decoded picture referring to the PPS in units of luma samples. pic_width_in_luma_samples shall not be equal to 0, shall be an integer multiple of Max(8, MinCbSizeY), and shall be less than or equal to pic_width_max_in_luma_samples.

[0191] When subpics_present_flag is equal to 1 or ref_pic_resampling_enabled_flag is equal to 0, the value of pic_width_in_luma_samples shall be equal to pic_width_max_in_luma_samples.

[0192] pic_height_in_luma_samples specifies the height of each decoded picture referring to the PPS in units of luma samples. pic_height_in_luma_samples shall not be equal to 0, shall be an integer multiple of Max(8, MinCbSizeY), and shall be less than or equal to pic_height_max_in_luma_samples.

[0193] When subpics_present_flag is equal to 1 or ref_pic_resampling_enabled_flag is equal to 0, the value of pic_height_in_luma_samples shall be equal to pic_height_max_in_luma_samples.

[0194] <del>

[0195] scaling_window_flag equal to 1 specifies that scaling window offset parameters are present in the PPS. scaling_window_flag equal to 0 specifies that scaling window offset parameters are not present in the PPS. When ref_pic_resampling_enabled_flag is equal to 0, the value of scaling_window_flag shall be equal to 0.

[0196] scaling_win_left_offset, scaling_win_right_offset, scaling_win_top_offset, and scaling_win_bottom_offset specify, in units of luma samples, offsets applied to the picture size for scaling ratio calculation. When scaling_window_flag is equal to 0, 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 0.

[0197] The value of scaling_win_left_offset + scaling_win_right_offset shall be less than pic_width_in_luma_samples, and the value of scaling_win_top_offset + scaling_win_bottom_offset shall be less than pic_height_in_luma_samples.

[0198] < / del>

[0199] <add>

[0200] pps num subpics minusl plus 1 specifies the number of sub-pictures in the coded picture referring to the PPS.

[0201] The requirement of bitstream conformance is that the value of pps num subpics minusl shall be equal to sps num subpics minusl.

[0202] pps scaling window flag[ i ] equal to 1 specifies that scaling window offset parameters for the i-th sub-picture are present in the PPS. pps scaling window flag[ i ] equal to 0 specifies that scaling window offset parameters for the i-th sub-picture are not present in the PPS.

[0203] The value of pps scaling window flag[ i ] shall be inferred to be 0 if one of the following conditions is true:

[0204] - ref_pic_resampling_enabled_flag is equal to 0 and subpics_present_flag is equal to 0

[0205] - ref_pic_resampling_enabled_flag is equal to 0 and sps_subpic_id_present_flag is equal to 0

[0206] - ref_pic_resampling_enabled_flag is equal to 0 and sps_subpic_id_signalling_present_flag is equal to 1

[0207] - subpics_present_flag is equal to 1 and subpic_treated_as_pic_flag[ i ] is equal to 0

[0208] - ref_pic_resampling_enabled_flag is equal to 1 and subpics_present_flag is equal to 1

[0209] pps_scaling_win_left_offset[ i ], pps_scaling_win_right_offset[ i ], pps_scaling_win_top_offset[ i ], and pps_scaling_win_bottom_offset[ i ] specify, in units of luma samples, the offsets applied to the picture size for scaling ratio calculation for the i-th subpicture. When pps_scaling_window_flag[ i ] is equal to 0, the values of pps_scaling_win_left_offset[ i ], pps_scaling_win_right_offset[ i ], pps_scaling_win_top_offset[ i ], and pps_scaling_win_bottom_offset[ i ] are inferred to be equal to 0.

[0210] The width and height of the i-th subpicture are derived as follows:

[0211] subpic_width_in_luma_samples[ i ] = Min( pic_width_in_luma_samples, ( subpic_ctu_top_left_x[ i ] + subpic_width_minusl[ i ] + 1 ) * CtbSizeY ) - subpic_ctu_top_left_x[ i ] * CtbSizeY

[0212] subpic_height_in_luma_samples[ i ] = Min( pic_height_in_luma_samples, ( subpic_ctu_top_left_y[ i ] + subpic_height_minusl[ i ] + 1 ) * CtbSizeY ) - subpic_ctu_top_left_y[ i ] * CtbSizeY

[0213] The values of pps_scaling_win_left_offset[ i ] + pps_scaling_win_right_offset[ i ] shall be less than subpic_width_in_luma_samples[ i ], and the values of pps_scaling_win_top_offset[ i ] + pps_scaling_win_bottom_offset[ i ] shall be less than subpic_height_in_luma_samples[ i ].

[0214] < / add>

[0215] The following shows the modification to section 7.3.2.6 in VVC Draft 7.

[0216]

[0217]

[0218] The following shows the modification to section 7.4.3.6 in VVC Draft 7.

[0219] <add>ph scaling window flag [ i ] equal to 1 specifies that scaling window offset parameters for the i-th subpicture are present in the PH. ph scaling window flag [ i ] equal to 0 specifies that scaling window offset parameters for the i-th subpicture are not present in the PH. If not present, the value of ph scaling window flag [ i ] shall be inferred to be 0.

[0220] ph scaling win left offset [ i ], ph scaling win right offset [ i ], ph scaling win top offset [ i ] and ph scaling win bottom offset [ i ] specify, in units of luma samples, offsets applied to the picture size of the i-th subpicture for scaling ratio calculation. When ph scaling window flag [ i ] is equal to 0, the values of ph scaling win left offset [ i ], ph scaling win right offset [ i ], ph scaling win top offset [ i ] and ph scaling win bottom offset [ i ] are inferred to be equal to 0.

[0221] The value of ph scaling win left offset [ i ] + ph scaling win right offset [ i ] shall be less than subpic width in luma samples [ i ], and the value of ph scaling win top offset [ i ] + ph scaling win bottom offset [ i ] shall be less than subpic height in luma samples [ i ].

[0222] The variables scaling win left offset [ i ], scaling win right offset [ i ], scaling win top offset [ i ] and scaling win bottom offset [ i ] are derived as follows:

[0223] scaling win left offset [ i ] = ph scaling window flag [ i ]? ph scaling win left offset [ i ] : pps scaling win left offset [ i ]

[0224] scaling_win_right_offset[ i ] = ph_scaling_window_flag[ i ]? ph_scaling_win_right_offset[ i ] : pps_scaling_win_right_offset[ i ]

[0225] scaling_win_top_offset[ i ] = ph_scaling_window_flag[ i ]? ph_scaling_win_top_offset[ i ] : pps_scaling_win_top_offset[ i ]

[0226] scaling_win_bottom_offset[ i ] = ph_scaling_window_flag[ i ]? ph_scaling_win_bottom_offset[ i ] : pps_scaling_win_bottom_offset[ i ]

[0227] The variables PicOutputWidthL[ i ] and PicOutputHeightL[ i ] are derived as follows:

[0228] PicOutputWidthL[ i ] = subpic_weight_in_luma_samples[ i ] - ( scaling_win_right_offset[ i ] + scaling_win_left_offset[ i ] ) PicOutputHeightL[ i ] = subpic_height_in_luma_samples[ i ] - ( scaling_win_bottom_offset[ i ] + scaling_win_top_offset[ i ] )< / add>

[0229] Based on the following example processes, which can include only one condition or at least two conditions as shown below, the video decoder 300 can be configured to infer the value of pps_scaling_window_flag[i] as zero:

[0230] • ref_pic_resampling_enabled_flag is equal to 0 and subpics_present_flag is equal to 0 (both RPR functionality and subpicture functionality are disabled)

[0231] • ref_pic_resampling_enabled_flag is equal to 0 and sps_subpic_id_present_flag is equal to 0 (RPR functionality is disabled, and the subpicture ID list is not reordered in the CLVS)

[0232] • ref_pic_resampling_enabled_flag is equal to 0 and sps_subpic_id_signalling_present_flag is equal to 1 (RPR functionality is disabled, and the subpicture ID list is not reordered in the CLVS)

[0233] • subpics_present_flag is equal to 1 and subpic_treated_as_pic_flag[i] is equal to 0 (subpicture functionality is enabled and the ith subpicture is not treated as a picture)

[0234] • ref_pic_resampling_enabled_flag is equal to 1 and subpics_present_flag is equal to 1 (both RPR functionality and subpicture functionality cannot be enabled at the same time)

[0235] • ref_pic_resampling_enabled_flag is equal to 1, sps_subpic_id_present_flag is equal to 1, and sps_subpic_id_signalling_present_flag is equal to 0 (RPR functionality and subpicture ID reordering functionality cannot be enabled simultaneously)

[0236] In certain examples of the disclosure, the video decoder 300 can use only the following four conditions to infer that the value of pps_scaling_window_flag[ i ] is zero:

[0237] • If at least one of the following conditions is true, the value of pps_scaling_window_flag[ i ] shall be inferred to be 0 to avoid unexpected activation of the reference picture scaling process

[0238] o ref_pic_resampling_enabled_flag is equal to 0 and subpics_present_flag is equal to 0 (both RPR functionality and subpicture functionality are disabled)

[0239] o ref_pic_resampling_enabled_flag is equal to 0 and sps_subpic_id_present_flag is equal to 0 (RPR functionality is disabled, and the subpicture ID list is not reordered in the CLVS)

[0240] o ref_pic_resampling_enabled_flag is equal to 0 and sps_subpic_id_signalling_present_flag is equal to 1 (RPR functionality is disabled, and the subpicture ID list is not reordered in the CLVS)

[0241] o subpics_present_flag is equal to 1 and subpic_treated_as_pic_flag[ i ] is equal to 0 (subpicture functionality is enabled and the i-th subpicture is not treated as a picture)

[0242] • Note that this example can also be applied to the case where the subpicture ID can change within the CLVS and reference picture resampling (RPR) is enabled (i.e., ref_pic_resampling_enabled_flag is set equal to 1).

[0243] In certain examples, only the following five conditions can be used to infer that the value of pps_scaling_window_flag[ i ] is zero:

[0244] • If at least one of the following conditions is true, the value of pps_scaling_window_flag[ i ] shall be inferred to be 0 to avoid unexpected activation of the reference picture scaling process

[0245] o ref_pic_resampling_enabled_flag is equal to 0 and subpics_present_flag is equal to 0 (both RPR functionality and subpicture functionality are disabled)

[0246] o ref_pic_resampling_enabled_flag is equal to 0 and sps_subpic_id_present_flag is equal to 0 (RPR functionality is disabled and the subpicture ID list is not reordered in the CLVS)

[0247] o ref_pic_resampling_enabled_flag is equal to 0 and sps_subpic_id_signalling_present_flag is equal to 1 (RPR functionality is disabled and the subpicture ID list is not reordered in the CLVS)

[0248] o subpics_present_flag is equal to 1 and subpic_treated_as_pic_flag[ i ] is equal to 0 (subpicture functionality is enabled and the i-th subpicture is not treated as a picture)

[0249] o ref_pic_resampling_enabled_flag is equal to 1, sps_subpic_id_present_flag is equal to 1, and sps_subpic_id_signalling_present_flag is equal to 0 (RPR functionality and subpicture ID reordering functionality cannot be enabled at the same time)

[0250] • Note that this example can also be applied to the case where the subpicture ID does not change within the CLVS and reference picture resampling (RPR) is enabled (i.e., ref_pic_resampling_enabled_flag is set equal to 1).

[0251] In some examples, video encoder 200 can signal original picture scaling window parameters, scaling_win_left_offset[i], scaling_win_right_offset[i], scaling_win_top_offset[i], and scaling_win_bottom_offset[i], in the PPS and signal sub-picture based scaling window parameters, pps_scaling_win_left_offset[i], pps_scaling_win_right_offset[i], pps_scaling_win_top_offset[i], pps_scaling_win_bottom_offset[i], ph_scaling_win_left_offset[i], ph_scaling_win_right_offset[i], ph_scaling_win_top_offset[i], and ph_scaling_win_bottom_offset[i], in the above manner. The original picture scaling window parameters can be used for scaling process between a reference picture and a current picture, while the sub-picture based scaling window is used for scaling process of a reference sub-picture and a current sub-picture. This design can be applied when sub-picture ID can change within a CLVS and reference picture resampling (RPR) is enabled (i.e., ref_pic_resampling_enabled_flag is set to 1). The syntax can be as follows:

[0252]

[0253]

[0254] Video encoder 200 and video decoder 300 can be configured to perform derivation of reference sub-picture scaling ratios. As shown in FIG. 8, the same derivation of scaling ratios for reference pictures can be applied to the sub-picture design described herein by adding sub-picture index to the design of VVC Draft 7: Figure 5

[0255] ​fRefWidth and fRefHeight are defined as PicOutputWidthL[RefSubPicIdx] and PicOutputWidthL[RefSubPicIdx] (in luma samples) of the reference picture RefPicList[i][j], respectively, where RefSubPicIdx is derived such that SubpicIdList[RefSubPicIdx] of the reference picture RefPicList[i][j] is equal to slice_subpic_id of the current slice. The scaling ratios are then derived as follows:

[0256] RefPicScale[i][j][0] = ((fRefWidth « 14) + (PicOutputWidthL[SubPicIdx] » 1)) / PicOutputWidthL[SubPicIdx]

[0257] RefPicScale[i][j][1] = ((fRefHeight « 14) + (PicOutputHeightL[SubPicIdx] » 1)) / PicOutputHeightL[SubPicIdx]

[0258] where SubPicIdx is derived such that SubpicIdList[SubPicIdx] of the current picture is equal to slice_subpic_id of the current slice

[0259] Figure 5 A scaling window 150 with fRefWidth and fRefHeight for a reference subpicture and a scaling window 152 with PicOutputWidthL[1] and PicOutputHeightL[1] for the current subpicture are shown. Figure 1

[0260] If at least one of the following conditions is true, the video decoder 300 can be configured to infer that the values of the scaling ratios RefPicScale[i][j][0] and RefPicScale[i][j][1] are equal to 1 « 14 to avoid accidental activation of the reference picture scaling process

[0261] • ref_pic_resampling_enabled_flag is equal to 0 and subpics_present_flag is equal to 0 (both RPR functionality and subpicture functionality are disabled)​

[0262] • ref_pic_resampling_enabled_flag is equal to 0 and sps_subpic_id_present_flag is equal to 0 (RPR functionality is disabled and the subpicture ID list is not reordered in the CLVS)

[0263] • ref_pic_resampling_enabled_flag is equal to 0 and sps_subpic_id_signalling_present_flag is equal to 1 (RPR functionality is disabled and the subpicture ID list is not reordered in the CLVS)

[0264] • subpics_present_flag is equal to 1 and subpic_treated_as_pic_flag[ i ] is equal to 0 (subpicture functionality is enabled and the ith subpicture is not treated as a picture)

[0265] • ref_pic_resampling_enabled_flag is equal to 1 and subpics_present_flag is equal to 1 (RPR functionality and subpicture functionality cannot be enabled at the same time)

[0266] The syntax changes to VVC Draft 7 are shown in the following table. The label “ <add>" shows the start of an addition, while the tag< / add> ” shows the end of those additions. The label “ <del>" shows the start of a deletion (i.e., text removal), while the tag< / del> ” shows the end of those deletions. The reference picture lists RefPicList[0] and RefPicList[1], the reference picture scaling ratios RefPicScale[ i ][ j ][ 0 ] and RefPicScale[ i ][ j ][ 1 ], and the reference picture scaling flags RefPicIsScaled[0] and RefPicIsScaled[1] are constructed as follows:

[0267]

[0268]

[0269]

[0270]

[0271] According to another example, only one condition or at least two conditions as shown below can be used to infer that the values of the scaling ratios RefPicScale[ i ][ j ][ 0 ] and RefPicScale[ i ][ j ][ 1 ] are zero:

[0272] • ref_pic_resampling_enabled_flag is equal to 0 and subpics_present_flag is equal to 0 (both RPR and subpicture functionalities are disabled)

[0273] • ref_pic_resampling_enabled_flag is equal to 0 and sps_subpic_id_present_flag is equal to 0 (RPR functionality is disabled and the subpicture ID list is not reordered in the CLVS)

[0274] • ref_pic_resampling_enabled_flag is equal to 0 and sps_subpic_id_signalling_present_flag is equal to 1 (RPR functionality is disabled and the subpicture ID list is not reordered in the CLVS)

[0275] • subpics_present_flag is equal to 1 and subpic_treated_as_pic_flag[ i ] is equal to 0 (subpicture functionality is enabled and the i-th subpicture is not treated as a picture)

[0276] • ref_pic_resampling_enabled_flag is equal to 1 and subpics_present_flag is equal to 1 (both RPR and subpicture functionalities cannot be enabled at the same time)

[0277] • ref_pic_resampling_enabled_flag is equal to 1, sps_subpic_id_present_flag is equal to 1, and sps_subpic_id_signalling_present_flag is equal to 0 (both RPR and subpicture ID reordering functionalities cannot be enabled at the same time).

[0278] In certain examples of the disclosure, only the first four conditions can be used to infer that the values of the scaling ratios RefPicScale[ i ][ j ][ 0 ] and RefPicScale[ i ][ j ][ 1 ] are zero:

[0279] According to examples of the disclosure, if at least one of the following conditions is true, the scaling ratios RefPicScale[ i ][ j ][ 0 ] and RefPicScale[ i ][ j ][ 1 ] can be inferred to be equal to 1 « 14 to avoid unexpected activation of the reference picture resampling process

[0280] • ref_pic_resampling_enabled_flag is equal to 0 and sps_subpic_id_present_flag is equal to 0 (RPR functionality is disabled, and the subpicture ID list is not reordered in the CLVS)

[0281] • ref_pic_resampling_enabled_flag is equal to 0 and sps_subpic_id_present_flag is equal to 0 (RPR functionality is disabled, and the subpicture ID list is not reordered in the CLVS)

[0282] • ref_pic_resampling_enabled_flag is equal to 0 and sps_subpic_id_signalling_present_flag is equal to 1 (RPR functionality is disabled, and the subpicture ID list is not reordered in the CLVS)

[0283] • subpics_present_flag is equal to 1 and subpic_treated_as_pic_flag[ i ] is equal to 0 (subpicture functionality is enabled and the ith subpicture is not treated as a picture)

[0284] In certain examples of the disclosure, only the first four conditions and the sixth condition can be used to infer that the values of the scaling ratios RefPicScale[ i ][ j ][ 0 ] and RefPicScale[ i ][ j ][ 1 ] are zero:

[0285] In certain examples of the disclosure, if at least one of the following conditions is true, the scaling ratios RefPicScale[ i ][ j ][ 0 ] and RefPicScale[ i ][ j ][ 1 ] can be inferred to be equal to 1 « 14 to avoid unexpected activation of the reference picture resampling process

[0286] • ref_pic_resampling_enabled_flag is equal to 0 and sps_subpic_id_present_flag is equal to 0 (RPR functionality and subpicture functionality are both disabled)

[0287] • ref_pic_resampling_enabled_flag is equal to 0 and sps_subpic_id_present_flag is equal to 0 (RPR functionality is disabled, and the subpicture ID list is not reordered in the CLVS)

[0288] • ref_pic_resampling_enabled_flag is equal to 0 and sps_subpic_id_signalling_present_flag is equal to 1 (RPR functionality is disabled and the subpicture ID list is not reordered in the CLVS)

[0289] • subpics_present_flag is equal to 1 and subpic_treated_as_pic_flag[ i ] is equal to 0 (subpicture functionality is enabled and the i-th subpicture is not treated as a picture)

[0290] • ref_pic_resampling_enabled_flag is equal to 1, sps_subpic_id_present_flag is equal to 1, and sps_subpic_id_signalling_present_flag is equal to 0 (RPR functionality and subpicture ID reordering functionality cannot be enabled at the same time)

[0291] Video encoder 200 and video decoder 300 can be configured to utilize a range of reference subpicture scaling ratios. In VVC Draft 7, the range of reference picture scaling ratios shall be in the range of 1 / 8 to 2 (inclusive), and there is a bitstream conformance constraint to apply this range to the picture width and height between a reference picture and a current picture as follows:

[0292] Let refPicWidthInLumaSamples and refPicHeightInLumaSamples be pic width in luma samples and pic height in luma samples of a reference picture of a current picture referring to this PPS. There can be a requirement of bitstream conformance that all of the following conditions are met:

[0293] - pic width in luma samples * 2 shall be greater than or equal to refPicWidthInLumaSamples.

[0294] - pic height in luma samples * 2 shall be greater than or equal to refPicHeightInLumaSamples.

[0295] - pic width in luma samples shall be less than or equal to refPicWidthInLumaSamples * 8.

[0296] - pic height in luma samples shall be less than or equal to refPicHeightInLumaSamples * 8.

[0297] Since the reference picture scaling ratio is derived by the scaling window width and height of each subpicture ID in the reference subpicture and the current subpicture (i.e., PicOutputWidthL[SubPicIdx], PicOutputHeightL[SubPicIdx], PicOutputWidthL[RefSubPicIdx], and PicOutputHeightL[RefSubPicIdx]), the scaling ratio can be out of range if there is no limit on the values of PicOutputWidthL[m] and PicOutputHeightL[m], where RefSubPicIdx is derived such that SubpicIdList[RefSubPicIdx] of the reference picture is equal to slice_subpic_id referring to the current slice header of the current picture. Therefore, the video encoder 200 and the video decoder 300 can be configured to apply this range to the subpicture-based scaling window width and height between the reference picture and the current picture as follows:

[0298] RefSubPicIdx is derived such that SubpicIdList[RefSubPicIdx] of the reference picture is equal to slice_subpic_id referring to the current slice header of the current picture. Bitstream conformance is required to satisfy all the following conditions:

[0299] - PicOutputWidthL[SubPicIdx] * A shall be greater than or equal to PicOutputWidthL[RefSubPicIdx].

[0300] - PicOutputHeightL[SubPicIdx] * A shall be greater than or equal to PicOutputHeightL[RefSubPicIdx].

[0301] - PicOutputWidthL[SubPicIdx] shall be less than or equal to PicOutputWidthL[RefSubPicIdx] * B.

[0302] - PicOutputHeightL[SubPicIdx] shall be less than or equal to PicOutputHeightL[RefSubPicIdx] * B.

[0303] where parameters A and B can be any non-zero positive number, and B > A. One example is A = 2, and B = 8.

[0304] Figure 6 An example of a reference block 160 pointed by a motion vector 162 from a current coding block 164 is shown. The current picture 166 includes sub-pictures with IDs 1, 2, and 3, while the reference picture 168 also includes sub-pictures with IDs 1, 2, and 3. Video encoder 200 and video decoder 300 can be configured to perform integer positioning derivation for interpolation filtering. As shown, sub-pictures can stream the same video source using the same sub-picture ID 1. As shown, Figure 6 Figure 6 If the current sub-picture is considered as a picture, the coding block in the current sub-picture ID 1 can refer to the block in the reference sub-picture ID 1 to fetch the same source content for prediction. However, VVC Draft 7 only supports the coding block in the current sub-picture ID 1 to refer to the block in the reference sub-picture ID 2.

[0305] The present disclosure also describes techniques for adding sub-picture indexing to scaling window offsets, which can align to the above-mentioned sub-picture-based scaling windows, described in U.S. Provisional Patent Application 62 / 951,709, filed on December 20, 2019. The described changes are summarized as follows:

[0306] • Consider the left displacement from the scaling window of the current sub-picture to the scaling window of the reference sub-picture, the general formula is refPos = curPos - (curSubPicLeftBoundaryPos + cur_scaling_win_left_offset[SubPicIdx]) + (refSubPicLeftBoundaryPos + ref_scaling_win_left_offset[RefSubPicIdx])

[0307] o refPos: the top-left position of the scaling window in the reference sub-picture

[0308] o curPos: the top-left position of the scaling window in the current sub-picture

[0309] o curSubPicLeftBoundaryPos: the left boundary position in the current sub-picture, i.e., the derived SubPicLeftBoundaryPos in the current sub-picture

[0310] o refSubPicLeftBoundaryPos: the left boundary position in the reference sub-picture, i.e., the derived SubPicLeftBoundaryPos in the reference sub-picture

[0311] ​`οcur_scaling_win_left_offset[SubPicIdx]`: The `scaling_win_left_offset[SubPicIdx]` of the current subgraph.

[0312] `oref_scaling_win_left_offset[RefSubPicIdx]`: The scaling_win_left_offset[RefSubPicIdx] of the reference subgraph.

[0313] The same applies to the displacement from the zoom window in the current subgraph to the top of the zoom window in the reference subgraph.

[0314] The syntactic changes to VVC Draft 7 are shown in the table below. (Tag "...") <add>" shows the start of an addition, while the tag< / add> "Indicates the end of those added tags." <del>" shows the start of a deletion (i.e., text removal), while the tag< / del> "This indicates the end of those deletions."

[0315] <del>The variable fRefLeftOffset is set equal to (scaling_win_left_offset « 10), where scaling_win_left_offset is the scaling_win_left_offset for the reference picture.

[0316] The variable fRefTopOffset is set equal to (scaling_win_top_offset « 10), where scaling_win_top_offset is the scaling_win_top_offset for the reference picture.< / del>

[0317] <add>The variable leftBoundaryOffset is set equal to scaling_win_left_offset[ SubPicldx ], the variable topBoundaryOffset is set equal to scaling_win_top_offset[ SubPicldx ], and the variables refSubPicLeftBoundaryPos and refSubPicTopBoundaryPos are set equal to 0.

[0318] If subpic_treated_as_pic_flag[ SubPicldx ] is equal to 1, the following applies

[0319] leftBoundaryOffset += SubPicLeftBoundaryPos

[0320] topBoundaryOffset += SubPicTopBoundaryPos

[0321] RefSubPicldx is derived such that SubpicIdList[ RefSubPicldx ] of the reference picture is equal to slice_subpic_id.

[0322] refSubPicLeftBoundaryPos = subpic_ctu_top_left_x[ RefSubPicldx ] * CtbSizeY

[0323] refSubPicTopBoundaryPos = subpic_ctu_top_left_y[ RefSubPicldx ] * CtbSizeY

[0324] The variable fRefLeftOffset is set equal to (( scaling_win_left_offset[ RefSubPicldx ] + refSubPicLeftBoundaryPos ) << 10), where scaling_win_left_offset[ i ] is scaling_win_left_offset[ i ] for the reference picture.

[0325] The variable fRefTopOffset is set equal to ((scaling_win_top_offset[ RefSubPicIdx ] + refSubPicTopBoundaryPos ) « 10), where scaling_win_top_offset[ i ] is scaling_win_top_offset[ i ] for the reference picture.< / add> .

[0326] …

[0327] – If cIdx equals 0, then the following applies:

[0328] – For each luminance sample location within the predicted luminance sample array predSamplesLX

[0329] (x L =0..sbWidth-1+brdExtSize,

[0330] y L =0..sbHeight-1+brdExtSize), corresponding to the predicted brightness sample value.

[0331] predSamplesLX[x L ][y L The derivation is as follows:

[0332] – Let (refxSb) L ,refySb L ) and (refx L refy L ) is the motion vector

[0333] The brightness position pointed to by (refMvLX[0], refMvLX[1]), given in 1 / 16-sample units. The variable refxSb L refx L, refySb L and refy L are derived as follows:

[0334] refxSb L = (((xSb- <add>leftBoundaryOffset< / add> << 4) + refMvLX[0]) * scalingRatio[0] (937)

[0335] refx L = ((Sign(refxSb L ) * ((Abs(refxSb L ) + 128) » 8) + x L * ((scalingRatio[0] + 8) » 4)) + fRefLeftOffset + 32) » 6 (938)

[0336] refySb L = (((ySb- <add>topBoundaryOffset< / add> << 4) + refMvLX[1]) * scalingRatio[1] (939)

[0337] refy L = ((Sign(refySb L ) * ((Abs(refySb L ) + 128) » 8) + yL * ((scalingRatio[1] + 8) » 4)) + fRefTopOffset + 32) » 6 (940)

[0338] In implementing the above techniques, video decoder 300 can be configured to determine that a first sub-picture of a current picture has associated scaling parameters (e.g., pps_scaling_win_left_offset[i], pps_scaling_win_right_offset[i], pps_scaling_win_top_offset[i], and pps_scaling_win_bottom_offset[i]); responsive to determining that the first sub-picture of the current picture has the associated scaling parameters, receive the associated scaling parameters for the first sub-picture of the current picture; determine motion information for a block of the first sub-picture of the current picture that identifies a sub-picture of a reference picture; locate a prediction block for the block of the first sub-picture of the current picture in the sub-picture of the reference picture; and scale the prediction block based on the associated scaling parameters for the first sub-picture of the current picture.

[0339] According to techniques of this disclosure, a method includes determining whether a subpicture of video data is treated as a picture, scaling the subpicture as a picture based on the subpicture being treated as a picture, determining a subpicture scaling flag based on the subpicture not being treated as a picture, and coding the subpicture based on the scaling or the subpicture scaling flag.

[0340] According to techniques of this disclosure, a method includes determining whether a subpicture of video data is treated as a picture, determining a first scaling ratio based on the subpicture being treated as a picture, determining a second scaling ratio based on the subpicture not being treated as a picture, and coding the subpicture based on the first scaling ratio or the second scaling ratio.

[0341] According to techniques of this disclosure, a method includes limiting PicOutputWidthL * A to be greater than or equal to refPicOutputWidthL, limiting PicOutputHeightL * A to be greater than or equal to refPicOutputHeightL, limiting PicOutputWidthL to be less than or equal to refPicOutputWidthL * B, limiting PicOutputHeightL to be less than or equal to refPicOutputHeightL * B, and coding video data based on the limiting, where A is a non-zero positive number, B is a non-zero positive number, and B > A.

[0342] According to techniques of this disclosure, a method includes limiting PicOutputWidthL * A to be greater than or equal to refPicOutputWidthL, limiting PicOutputHeightL * A to be greater than or equal to refPicOutputHeightL, limiting PicOutputWidthL to be less than or equal to refPicOutputWidthL * B, limiting PicOutputHeightL to be less than or equal to refPicOutputHeightL * B, and coding video data based on the limiting, where A is a non-zero positive number, B is a non-zero positive number, and B > A.

[0343] According to techniques of this disclosure, a method includes determining a left displacement from a scaling window in a current subpicture of video data to a scaling window in a reference subpicture in the video data, determining an upper displacement from the scaling window in the current subpicture to the scaling window in the reference subpicture, and coding the current subpicture based on the left displacement and the upper displacement.

[0344] According to techniques of this disclosure, an apparatus includes a memory configured to store video data, coupled to one or more processors implemented in circuitry and configured to perform any of the techniques of this disclosure.

[0345] According to the techniques of this disclosure, a device includes one or more components for performing any of the techniques of this disclosure.

[0346] According to the techniques of this disclosure, a computer-readable storage medium is encoded with instructions that, when executed, cause a programmable processor to perform any of the techniques of this disclosure.

[0347] Video encoder 200 also represents an example of a device configured to encode video data, the device comprising a memory configured to store video data, and one or more processing units implemented in circuitry and configured to: determine whether a subpicture of the video data is treated as a picture, determine a first scaling ratio based on the subpicture being treated as the picture, determine a second scaling ratio based on the subpicture not being treated as the picture, and encode the subpicture based on the first scaling ratio or the second scaling ratio.

[0348] Video encoder 200 also represents an example of a device configured to encode video data, the device comprising a memory configured to store video data, and one or more processing units implemented in circuitry and configured to: determine whether a subpicture of the video data is treated as a picture, determine a first scaling ratio based on the subpicture being treated as the picture, determine a second scaling ratio based on the subpicture not being treated as the picture, and encode the subpicture based on the first scaling ratio or the second scaling ratio.

[0349] Video encoder 200 also represents an example of a device configured to encode video data, the device comprising a memory configured to store video data, and one or more processing units implemented in circuitry and configured to: limit PicOutputWidthL * A to be greater than or equal to refPicOutputWidthL, limit PicOutputHeightL * A to be greater than or equal to refPicOutputHeightL, limit PicOutputWidthL to be less than or equal to refPicOutputWidthL * B, limit PicOutputHeightL to be less than or equal to refPicOutputHeightL * B, and encode the video data based on the limiting, where A is a non-zero positive number, B is a non-zero positive number, and B > A.

[0350] Video encoder 200 also represents an example of a device configured to encode video data, the device comprising a memory configured to store the video data, and one or more processing units implemented in circuitry and configured to limit PicOutputWidthL*A to be greater than or equal to refPicOutputWidthL, limit PicOutputHeightL*A to be greater than or equal to refPicOutputHeightL, limit PicOutputWidthL to be less than or equal to refPicOutputWidthL*B, limit PicOutputHeightL to be less than or equal to refPicOutputHeightL*B, and encode the video data based on the limiting, where A is a non-zero positive number, B is a non-zero positive number, and B > A.

[0351] Video encoder 200 also represents an example of a device configured to encode video data, the device comprising a memory configured to store the video data, and one or more processing units implemented in circuitry and configured to determine a left displacement from a scaled window in a current subpicture of the video data to a scaled window in a reference subpicture in the video data, determine an upper displacement from the scaled window in the current subpicture to the scaled window in the reference subpicture, and encode the current subpicture based on the left displacement and the upper displacement.

[0352] In this way, video decoder 300 represents an example of a video decoding device, the device comprising a memory configured to store video data, and one or more processing units implemented in circuitry and configured to determine whether a subpicture of the video data is considered a picture, scale the subpicture to a picture based on the subpicture being considered a picture, determine a subpicture scaling flag based on the subpicture not being considered a picture, and decode the subpicture based on the scaling or the subpicture scaling flag.

[0353] Video decoder 300 also represents an example of a video decoding device, the device comprising a memory configured to store video data, and one or more processing units implemented in circuitry and configured to determine whether a subpicture of the video data is considered a picture, determine a first scaling ratio based on the subpicture being considered a picture, determine a second scaling ratio based on the subpicture not being considered a picture, and decode the subpicture based on the first scaling ratio or the second scaling ratio.

[0354] Video decoder 300 also represents an example of a video decoding device that includes a memory configured to store video data, and one or more processing units implemented in circuitry and configured to perform a method comprising limiting PicOutputWidthL * A to be greater than or equal to refPicOutputWidthL, limiting PicOutputHeightL * A to be greater than or equal to refPicOutputHeightL, limiting PicOutputWidthL to be less than or equal to refPicOutputWidthL * B, limiting PicOutputHeightL to be less than or equal to refPicOutputHeightL * B, and decoding the video data based on the limiting, where A is a non-zero positive number, B is a non-zero positive number, and B > A.

[0355] Video decoder 300 also represents an example of a video decoding device that includes a memory configured to store video data, and one or more processing units implemented in circuitry and configured to perform a method comprising limiting PicOutputWidthL * A to be greater than or equal to refPicOutputWidthL, limiting PicOutputHeightL * A to be greater than or equal to refPicOutputHeightL, limiting PicOutputWidthL to be less than or equal to refPicOutputWidthL * B, limiting PicOutputHeightL to be less than or equal to refPicOutputHeightL * B, and decoding the video data based on the limiting, where A is a non-zero positive number, B is a non-zero positive number, and B > A.

[0356] Video decoder 300 also represents an example of a video decoding device that includes a memory configured to store video data, and one or more processing units implemented in circuitry and configured to determine a left displacement from a scaling window in a current subpicture of the video data to a scaling window in a reference subpicture in the video data, determine an upper displacement from the scaling window in the current subpicture to the scaling window in the reference subpicture, and decode the current subpicture based on the left displacement and the upper displacement.

[0357] As Figure 7As shown, reference picture resampling (RPR) is incorporated into the VVC standard to support adaptive streaming in open group of pictures (GOP) prediction structure (starting from a CRA picture). Another subpicture function is also incorporated into the VVC standard to support extraction and merging of subpictures in 360 streaming, video conferencing, and other use cases. VVC Draft 7 only enables RPR in regular pictures. If the subpicture function is working, the RPR function is disabled. The present disclosure contemplates investigating enabling both RPR and subpicture at the same time. In other words, with the techniques of the present disclosure, video encoder 200 and video decoder 300 can enable both RPR and subpicture. This allows adaptive subpicture streaming in GOP prediction structure and shares the same benefits as RPR in regular picture use cases, which can achieve better compression performance and better subjective visual quality compared to traditional closed GOP prediction structure. Figure 8 and Figure 9 FIG. 1 illustrates a case of enabling both RPR and subpicture as described in the present disclosure.

[0358] The present disclosure describes subject matter other than U.S. Provisional Patent Application No. 62 / 953,015, filed on December 23, 2019, and which is hereby incorporated by reference in its entirety, where the techniques allow a reference subpicture scaling process for a current subpicture to upscale or downscale a reference subpicture using the same subpicture ID as shown above Figure 3 The present disclosure contemplates maintaining two categories of scaling processes, one using a scaling window and scaling ratio for regular pictures, and the other using a subpicture scaling window and subpicture scaling ratio for subpictures. For example, video encoder 200 and video decoder 300 can use a scaling window and scaling ratio for regular pictures, and use a subpicture scaling window and subpicture scaling ratio for subpictures.

[0359] Video encoder 200 and video decoder 300 can be configured to implement a subpicture-based scaling window. In VVC Draft 7, when the reference picture size and the current picture size are different, a reference picture scaling process is used, and the process is extracted from VVC Draft 7 Clause 8.3.2 as follows:

[0360] RefPicScale[i][j][0] = ((fRefWidth « 14) + (PicOutputWidthL » 1)) / PicOutputWidthL

[0361] RefPicScale[i][j][1] = ((fRefHeight « 14) + (PicOutputHeightL » 1)) / PicOutputHeightL

[0362] where fRefWidth and fRefHeight are set equal to PicOutputWidthL and PicOutputHeightL (in luma samples) of the reference picture RefPicList[i][j], respectively. As shown in FIG. 2, PicOutputWidthL and PicOutputHeightL are the scaled window width and height, and are cropped from the picture width and height as follows:

[0363] PicOutputWidthL = pic width in luma samples - (scaling win right offset + scaling win left offset)

[0364] PicOutputHeightL = pic height in luma samples - (scaling win bottom offset + scaling win top offset)

[0365] Video encoder 200 and video decoder 300 can use the scaling window to avoid position misalignment in the reference picture scaling process. Video encoder 200 and video decoder 300 can be configured to signal one scaling window for the regular picture scaling process and various subpicture scaling windows for the subpicture scaling process. For example, video encoder 200 can signal one scaling window for the regular picture scaling process and different subpicture scaling windows for the subpicture scaling process. Video decoder 300 can determine the signals by reading the signals. As shown in FIG. 2, the same reference picture scaling process is used for the current subpicture when the current subpicture is not treated as a picture. The subpicture scaling window is applied to the subpicture using the same ID when the current subpicture is treated as a picture. Accordingly, the modifications on top of the VVC Draft 7 specification are as follows: Figure 4

[0366] Each subpicture signals a scaling window flag, e.g., pps scaling window flag[i]. If the ith flag pps scaling window flag[i] is equal to 1, the scaling window offsets pps scaling win left offset[i], pps scaling win right offset[i], pps scaling win top offset[i], and pps scaling win bottom offset[i] are signaled for the ith subpicture.

[0367] ​The number of subpictures in a CLVS shall be signaled at the PPS before the set of subpicture scaling window parameters is signaled.

[0368] If at least one of the following conditions is true, the value of pps_scaling_window_flag[ i ] shall be inferred to be 0 to avoid unexpected activation of the subpicture scaling process

[0369] • subpics_present_flag is equal to 0 (subpicture functionality is disabled)

[0370] • ref_pic_resampling_enabled_flag is equal to 0 and sps_subpic_id_present_flag is equal to 0 (RPR functionality is disabled and the subpicture ID list is not reordered in the CLVS)

[0371] • ref_pic_resampling_enabled_flag is equal to 0 and sps_subpic_id_signalling_present_flag is equal to 1 (RPR functionality is disabled and the subpicture ID list is not reordered in the CLVS)

[0372] • subpics_present_flag is equal to 1 and subpic_treated_as_pic_flag[ i ] is equal to 0 (subpicture functionality is enabled and the i-th subpicture is not treated as a picture)

[0373] pps_scaling_win_left_offset[ i ] + pps_scaling_win_right_offset[ i ] <= subpic_width_in_luma_samples[ i ], where subpic_width_in_luma_samples[ i ] is the width for the i-th subpicture.

[0374] pps_scaling_win_top_offset[ i ] + pps_scaling_win_bottom_offset[ i ] <= subpic_height_in_luma_samples[ i ], where subpic_height_in_luma_samples[ i ] is the height for the i-th subpicture.

[0375] The sub-picture based scaling window parameters are signaled in both PPS (e.g., pps_scaling_win_left_offset[i], pps_scaling_win_right_offset[i], pps_scaling_win_top_offset[i], and pps_scaling_win_bottom_offset[i]) and PH (e.g., ph_scaling_win_left_offset[i], ph_scaling_win_right_offset[i], ph_scaling_win_top_offset[i], and ph_scaling_win_bottom_offset[i]). Based on the scaling window flag in PH, i.e., ph_scaling_window_flag[i], the parameters in PH can override the parameters in PPS, e.g., scaling_win_left_offset[i] = (ph_scaling_window_flag[i])? ph_scaling_win_left_offset[i] : pps_scaling_win_left_offset[i].

[0376] In one example, the sub-picture based scaling window parameters are only signaled by the video encoder 200 in PPS. In another example, the sub-picture based scaling window parameters are only signaled by the video encoder 200 in PH.

[0377] The scaling window width and height for the i-th sub-picture are derived by clipping the i-th sub-picture with the i-th scaling window offset as follows:

[0378] PicOutputWidthL[i] = subpic_width_in_luma_samples[i] - (scaling_win_right_offset[i] + scaling_win_left_offset[i])

[0379] PicOutputHeightL[i] = subpic_height_in_luma_samples[i] - (scaling_win_bottom_offset[i] + scaling_win_top_offset[i])

[0380] The syntax changes to VVC Draft 7 are shown in the following table. The additions are marked as <add>, and the end of an addition is marked as< / add> . The deletions are marked as <delete>, and the end of a deletion is marked as< / delete> .

[0381] Section 7.3.2.4 in VVC Draft 7:

[0382]

[0383]

[0384] Section 7.4.3.4 in VVC Draft 7 can be modified as follows:

[0385] pic_width_in_luma_samples specifies the width of each decoded picture referring to the PPS in units of luma samples. pic_width_in_luma_samples shall not be equal to 0, shall be an integer multiple of Max(8, MinCbSizeY), and shall be less than or equal to pic_width_max_in_luma_samples.

[0386] When subpics_present_flag is equal to 1 or ref_pic_resampling_enabled_flag is equal to 0, the value of pic_width_in_luma_samples shall be equal to pic_width_max_in_luma_samples.

[0387] pic_height_in_luma_samples specifies the height of each decoded picture referring to the PPS in units of luma samples. pic_height_in_luma_samples shall not be equal to 0, shall be an integer multiple of Max(8, MinCbSizeY), and shall be less than or equal to pic_height_max_in_luma_samples.

[0388] When subpics_present_flag is equal to 1 or ref_pic_resampling_enabled_flag is equal to 0, the value of pic_height_in_luma_samples shall be equal to pic_height_max_in_luma_samples.

[0389] scaling_win_left_offset, scaling_win_right_offset, scaling_win_top_offset, and scaling_win_bottom_offset specify, in units of luma samples, the offsets applied to the picture size for scaling ratio calculation. When scaling_window_flag is equal to 0,

[0390] 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 0.

[0391] The value of scaling win left offset + scaling win right offset shall be less than pic width in luma samples, and

[0392] The value of scaling win top offset + scaling win bottom offset shall be less than pic height in luma samples.

[0393] The variables PicOutputWidthL and PicOutputHeightL are derived as follows:

[0394]

[0395]

[0396] <add>pps num subpics minusl plus 1 specifies the number of sub-pictures in the coded picture referring to the PPS.

[0397] The requirement of bitstream conformance is that the value of pps num subpics minusl shall be equal to sps num subpics minusl.

[0398] pps scaling window flag[ i ] equal to 1 specifies that scaling window offset parameters for the i-th sub-picture are present in the PPS. pps scaling window flag[ i ] equal to 0 specifies that scaling window offset parameters for the i-th sub-picture are not present in the PPS. The value of pps scaling window flag[ i ] shall be inferred to be 0 if one of the following conditions is true:

[0399] - subpics present flag is equal to 0

[0400] - ref_pic_resampling_enabled_flag is equal to 0 and sps_subpic_id_present_flag is equal to 0

[0401] - ref_pic_resampling_enabled_flag is equal to 0 and sps_subpic_id_signalling_present_flag is equal to 1

[0402] - subpics present flag is equal to 1 and subpic treated as pic flag[ i ] is equal to 0 pps scaling win left offset[ i ], pps scaling win right offset[ i ], pps scaling win top offset[ i ] and pps scaling win bottom offset[ i ] specify, in units of luma samples, the offsets applied to the picture size for scaling ratio calculation for the i-th sub-picture. When pps scaling window flag[ i ] is equal to 0, the values of pps scaling win left offset[ i ], pps scaling win right offset[ i ], pps scaling win top offset[ i ] and pps scaling win bottom offset[ i ] are inferred to be equal to 0.

[0403] The width and height of the ith subpicture are derived as follows:

[0404] subpic_width_in_luma_samples[i] = Min( pic_width_in_luma_samples, ( subpic_ctu_top_left_x[i] + subpic_width_minusl[i] + 1 ) * CtbSizeY ) - subpic_ctu_top_left_x[i] * CtbSizeY

[0405] subpic_height_in_luma_samples[i] = Min( pic_height_in_luma_samples, ( subpic_ctu_top_left_y[i] + subpic_height_minusl[i] + 1 ) * CtbSizeY ) - subpic_ctu_top_left_y[i] * CtbSizeY

[0406] The value of pps_scaling_win_left_offset[i] + pps_scaling_win_right_offset[i] shall be less than subpic_width_in_luma_samples[i], and the value of pps_scaling_win_top_offset[i] + pps_scaling_win_bottom_offset[i] shall be less than subpic_height_in_luma_samples[i].< / add>

[0407] Section 7.4.3.4 in VVC Draft 7 can be modified as follows:

[0408]

[0409]

[0410] Section 7.4.3.6 in VVC Draft 7 can be modified as follows:

[0411] <add>ph scaling window flag[i] equal to 1 specifies that scaling window offset parameters for the i-th subpicture are present in the PH. ph scaling window flag[i] equal to 0 specifies that scaling window offset parameters for the i-th subpicture are not present in the PH. If not present, scaling_win_left_offset[i], scaling_win_right_offset[i], scaling_win_top_offset[i] and scaling_win_bottom_offset[i] are inferred to be equal to 0.

[0412] The value of ph scaling window flag[i] shall be inferred to be 0.

[0413] ph scaling win left offset[i], ph scaling win right offset[i], ph scaling win top offset[i] and ph scaling win bottom offset[i] specify, in units of luma samples, the offsets applied to the picture size of the i-th subpicture for scaling ratio calculation. When ph scaling window flag[i] is equal to 0, the values of ph scaling win left offset[i], ph scaling win right offset[i], ph scaling win top offset[i] and ph scaling win bottom offset[i] are inferred to be equal to 0.

[0414] The value of ph scaling win left offset[i] + ph scaling win right offset[i] shall be less than subpic width in luma samples[i], and

[0415] The value of ph scaling win top offset[i] + ph scaling win bottom offset[i] shall be less than subpic height in luma samples[i].

[0416] The variables scaling_win_left_offset[i], scaling_win_right_offset[i], scaling_win_top_offset[i] and scaling_win_bottom_offset[i] are derived as follows:

[0417] scaling_win_left_offset[ i ] = ph_scaling_window_flag[ i ]? ph_scaling_win_left_offset[ i ] : pps_scaling_win_left_offset[ i ]

[0418] scaling_win_right_offset[ i ] = ph_scaling_window_flag[ i ]? ph_scaling_win_right_offset[ i ] : pps_scaling_win_right_offset[ i ]

[0419] scaling_win_top_offset[ i ] = ph_scaling_window_flag[ i ]? ph_scaling_win_top_offset[ i ] : pps_scaling_win_top_offset[ i ]

[0420] scaling_win_bottom_offset[ i ] = ph_scaling_window_flag[ i ]? ph_scaling_win_bottom_offset[ i ] : pps_scaling_win_bottom_offset[ i ]

[0421] The variables PicOutputWidthL[ i ] and PicOutputHeightL[ i ] are derived as follows:

[0422] PicOutputWidthL[ i ] = subpic_weight_in_luma_samples[ i ] - ( scaling_win_right_offset[ i ] + scaling_win_left_offset[ i ] )

[0423] PicOutputHeightL[ i ] = subpic_height_in_luma_samples[ i ] - ( scaling_win_bottom_offset[ i ] + scaling_win_top_offset[ i ] )< / add>

[0424] Video encoder 200 and video decoder 300 can be configured to perform derivation of a reference sub-picture scaling ratio. Video encoder 200 and video decoder 300 can be configured to derive two separate scaling ratios, e.g., one for regular pictures and another for sub-pictures. For example, video encoder 200 and video decoder 300 can use one scaling ratio for regular pictures and another scaling ratio for sub-pictures. When the current sub-picture is not considered as a picture, the current reference picture scaling process in VVC is targeted at the current picture or the current sub-picture. When the current sub-picture is considered as a picture, a sub-picture scaling window is applied as follows:

[0425] fRefWidth and fRefHeight are defined as PicOutputWidthL[ RefSubPicIdx ] and PicOutputWidthL[ RefSubPicIdx ] (in luma samples) of the reference picture RefPicList[ i ][ j ], respectively, where RefSubPicIdx is derived such that SubpicIdList[ RefSubPicIdx ] of the reference picture RefPicList[ i ][ j ] is equal to slice_subpic_id of the current slice. The scaling ratios are then derived as follows:

[0426] RefPicScale[ i ][ j ][ 0 ] = ( ( fRefWidth « 14 ) + ( PicOutputWidthL[ SubPicIdx ] » 1 ) ) / PicOutputWidthL[ SubPicIdx ]

[0427] where SubPicIdx is derived such that SubpicIdList[ SubPicIdx ] of the current picture is equal to slice_subpic_id of the current slice.

[0428] The syntax changes to VVC Draft 7 are shown in the following table. The additions are marked as <add>, and the end of an addition is marked as< / add> . The deletions are marked as <delete>, and the end of a deletion is marked as< / delete> .

[0429]

[0430]

[0431]

[0432]

[0433] The video encoder 200 and the video decoder 300 can be configured to limit the reference subpicture scaling ratios to be within a certain range.

[0434] In VVC Draft 7, the range of the reference picture scaling ratios shall be in the range of 1 / 8 to 2 (inclusive), and there is bitstream conformance to apply this range to the picture width and height between the reference picture and the current picture, as follows:

[0435] Let refPicWidthInLumaSamples and refPicHeightInLumaSamples be pic_width_in_luma_samples and pic_height_in_luma_samples of the reference picture of the current picture referring to this PPS. The requirement of bitstream conformance that can exist is that all the following conditions are met:

[0436] - pic_width_in_luma_samples * 2 shall be greater than or equal to refPicWidthInLumaSamples.

[0437] - pic_height_in_luma_samples * 2 shall be greater than or equal to refPicHeightInLumaSamples.

[0438] - pic_width_in_luma_samples shall be less than or equal to refPicWidthInLumaSamples * 8.

[0439] - pic_height_in_luma_samples shall be less than or equal to refPicHeightInLumaSamples * 8.

[0440] Since the reference picture scaling ratio is derived from the scaling window width and height of each regular picture (i.e., PicOutputWidthL and PicOutputHeightL), the scaling ratio can go out of range if there is no limit on PicOutputWidthL and PicOutputHeightL. VVC Draft 7 can be modified as follows.

[0441] Let refPicOutputWidthL and refPicOutputHeightL be PicOutputWidthL and PicOutputHeightL of the reference picture of the current picture referring to this PPS. The requirement of bitstream conformance that can exist is that all the following conditions are met:

[0442] - PicOutputWidthL * A shall be greater than or equal to refPicOutputWidthL.

[0443] - PicOutputHeightL * A shall be greater than or equal to refPicOutputHeightL.

[0444] - PicOutputWidthL shall be less than or equal to refPicOutputWidthL * B.

[0445] - PicOutputHeightL shall be less than or equal to refPicOutputHeightL * B.

[0446] - Where parameters A and B can be any non-zero positive number, and B > A. One example is A = 2, and B = 8.

[0447] For example, video encoder 200 and video decoder 300 code according to the above condition restrictions.

[0448] If there are no restrictions on PicOutputWidthL[m] and PicOutputHeightL[m], there is also a problem that the subpicture scaling ratio can be out of range. Therefore, video encoder 200 and video decoder 300 can be configured to apply this range to the subpicture-based scaling window width and height between the reference picture and the current picture, as follows:

[0449] RefSubPicIdx is derived such that SubpicIdList[RefSubPicIdx] of the reference picture is equal to slice_subpic_id referring to the current slice header of the current picture. Bitstream conformance is required to satisfy all the following conditions:

[0450] PicOutputWidthL[SubPicIdx] * A shall be greater than or equal to PicOutputWidthL[RefSubPicIdx].

[0451] PicOutputHeightL[SubPicIdx] * A shall be greater than or equal to PicOutputHeightL[RefSubPicIdx].

[0452] PicOutputWidthL[SubPicIdx] shall be less than or equal to PicOutputWidthL[RefSubPicIdx] * B.

[0453] PicOutputHeightL[SubPicIdx] shall be less than or equal to PicOutputHeightL[RefSubPicIdx] * B.

[0454] Where parameters A and B can be any non-zero positive number, and B > A. One example is A = 2, and B = 8.

[0455] For example, video encoder 200 and video decoder 300 restrict the coding according to the above conditions.

[0456] Video encoder 200 and video decoder 300 can be configured to perform integer positioning derivation for interpolation filtering.

[0457] The left and top displacements shall be derived to position the top-left integer position of the current block to the top-left integer position of the reference block. There are two cases: one is the displacement between regular pictures, and the other is the displacement between sub-pictures. The displacement between sub-pictures is only enabled when the current sub-picture is treated as a picture. U.S. Provisional Patent Application No. 62 / 951,709, filed on December 20, 2019, and U.S. Provisional Patent Application No. 62 / 953,015, filed on December 23, 2019, both of which are incorporated by reference herein in their entireties, address certain of the issues discussed. Displacement for regular pictures has already been provided in VVC, as follows:

[0458] Consider the left displacement from the scaling window of the current picture to the scaling window of the reference picture, the general formula is refPos = curPos - cur_scaling_win_left_offset + ref_scaling_win_left_offset

[0459] • refPos: the top-left position of the scaling window in the reference sub-picture

[0460] • curPos: the top-left position of the scaling window in the current sub-picture

[0461] • cur_scaling_win_left_offset: scaling_win_left_offset of the current sub-picture

[0462] • ref_scaling_win_left_offset: scaling_win_left_offset of the reference sub-picture

[0463] The same procedure can be used for the top displacement.

[0464] Video encoder 200 and video decoder 300 can be configured to determine the displacement for sub-pictures, as follows:

[0465] Considering the left displacement from the scaling window in the current subpicture to the scaling window in the reference subpicture, the general formula is refPos = curPos - (curSubPicLeftBoundaryPos + cur_scaling_win_left_offset[SubPicIdx]) + (refSubPicLeftBoundaryPos + ref_scaling_win_left_offset[RefSubPicIdx])

[0466] • refPos: the top-left position of the scaling window in the reference subpicture

[0467] • curPos: the top-left position of the scaling window in the current subpicture

[0468] • curSubPicLeftBoundaryPos: the left boundary position in the current subpicture, i.e., the derived SubPicLeftBoundaryPos in the current subpicture

[0469] • refSubPicLeftBoundaryPos: the left boundary position in the reference subpicture, i.e., the derived SubPicLeftBoundaryPos in the reference subpicture

[0470] • cur_scaling_win_left_offset[SubPicIdx]: scaling_win_left_offset[SubPicIdx] of the current subpicture

[0471] • ref_scaling_win_left_offset[RefSubPicIdx]: scaling_win_left_offset[RefSubPicIdx] of the reference subpicture

[0472] The same procedure can be used for the top displacement.

[0473] The syntax changes to VVC Draft 7 are shown in the following table. The added starts are marked as <add>, and the end of an addition is marked as< / add> .

[0474]

[0475]

[0476] The techniques discussed in this disclosure can be used individually or in any combination. For example, the following three examples can be used individually or in any combination.

[0477] Based on the first example, the reference image and the current image can be the same size. For example, as in... Figure 3 In the example, a scaling ratio is enabled for the current subgraph to scale the size of the reference subgraph to the size of the current subgraph. For example, video encoder 200 and video decoder 300 can scale the size of the reference subgraph to the size of the current subgraph.

[0478] According to the second example, the video encoder 200 and video decoder 300 can be configured to support scaling processes where the reference image and the current image are of different sizes, and the sub-image ID remains unchanged in CLVS. Figure 8 In the image, current image 180 includes subimages with IDs 1, 2, and 3, while reference image 182 also includes subimages with IDs 1, 2, and 3. Figure 8 An example is shown where the current image 180 and the reference image 182 have different sizes but the reference image ID remains the same. In such examples, the video encoder 200 and the video decoder 300 may not change the sub-image ID.

[0479] According to the third example, the video encoder 200 and video decoder 300 can be configured to support scaling processes where the reference image and the current image are of different sizes, and the sub-image ID changes in CLVS. Figure 9 In the image, current image 190 includes subimages with IDs 1, 2, and 3, while reference image 192 also includes subimages with IDs 1, 2, and 3. Figure 9 An example is shown where the current image 190 and the reference image 192 have different sizes and the reference image ID has been changed. In such examples, the video encoder 200 and the video decoder 300 can change the sub-image ID.

[0480] Figure 10 This is a block diagram illustrating an example video encoder 200 that can perform the techniques of this disclosure. Figure 10 This disclosure is provided for illustrative purposes and should not be construed as limiting the techniques extensively illustrated and described herein. For illustrative purposes, this disclosure describes the video encoder 200 in the context of video decoding standards such as the HEVC video decoding standard and the H.266 video decoding standard under development. However, the techniques of this disclosure are not limited to these video decoding standards and can be generally applied to video encoding and decoding.

[0481] exist Figure 10In the example of FIG. 2, video encoder 200 includes video data memory 230, mode select unit 202, residual generation unit 204, transform processing unit 206, quantization unit 208, inverse quantization unit 210, inverse transform processing unit 212, reconstruction unit 214, filter unit 216, decoded picture buffer (DPB) 218, and entropy encoding unit 220. Any or all of video data memory 230, mode select unit 202, residual generation unit 204, transform processing unit 206, quantization unit 208, inverse quantization unit 210, inverse transform processing unit 212, reconstruction unit 214, filter unit 216, DPB 218, and entropy encoding unit 220 can be implemented in one or more processors or in processing circuitry. For instance, the units of video encoder 200 can be implemented as one or more circuits or logic elements as part of hardware circuitry, or as part of a processor of a FPGA, ASIC, etc. Also, video encoder 200 can include an additional or alternative processor or processing circuitry to perform these and other functions.

[0482] Video data memory 230 can store video data to be encoded by the components of video encoder 200. Video encoder 200 can receive the video data stored in video data memory 230 from, for example, video source 104 Figure 1 DPB 218 can act as a reference picture memory that stores reference video data for use in prediction of subsequent video data by video encoder 200. Video data memory 230 and DPB 218 can be formed by any of a variety of memory devices, such as dynamic random access memory (DRAM) (including synchronous DRAM (SDRAM)), magnetoresistive RAM (MRAM), resistive RAM (RRAM), or other types of memory devices. Video data memory 230 and DPB 218 can be provided by the same memory device or separate memory devices. In various examples, video data memory 230 can be on-chip with other components of video encoder 200, as illustrated, or off-chip relative to those components.

[0483] In this disclosure, reference to video data memory 230 should not be interpreted as being limited to memory internal to video encoder 200, unless specifically so described, or memory external to video encoder 200, unless specifically so described. Rather, reference to video data memory 230 should be understood as reference memory that stores video data that video encoder 200 receives for encoding (e.g., video data for a current block that is to be encoded). Figure 1 Memory 106 of source device 102 can also provide temporary storage of outputs from the various units of video encoder 200.

[0484] Figure 10 The various units are shown as individual functional blocks for purposes of illustration only. In some implementations, the functions of the units can be performed by one or more integrated circuits. In some implementations, the functions of the units can be performed by the same integrated circuit or multiple integrated circuits. In some implementations, the functions of the units can be performed by different integrated circuits. In some implementations, the functions of the units can be performed by one or more processors executing software or firmware instructions. In some implementations, the functions of the units can be performed by one or more circuits dedicated for the functions.

[0485] Video encoder 200 can include an arithmetic logic unit (ALU), an elementary function unit (EFU), digital circuits, analog circuits, and / or programmable cores formed from programmable circuitry. In examples where operations of video encoder 200 are performed using software executed by the programmable circuitry, memory 106 Figure 1 ) can store instructions (e.g., object code) of the software that video encoder 200 receives and executes, or another memory within video encoder 200 (not shown) can store such instructions.

[0486] Video data memory 230 is configured to store video data to be encoded. Video encoder 200 can retrieve pictures of the video data from video data memory 230 and provide the video data to residual generation unit 204 and mode select unit 202. Video data in video data memory 230 can be raw video data that is to be encoded.

[0487] Mode select unit 202 includes motion estimation unit 222, motion compensation unit 224, and intra prediction unit 226. Mode select unit 202 can include additional functional units to perform video prediction according to other prediction modes. As examples, mode select unit 202 can include a palette unit, an intra block copy unit (which can be part of motion estimation unit 222 and / or motion compensation unit 224), an affine unit, a linear model (LM) unit, and so on.

[0488] The mode selection unit 202 generally coordinates multiple encoding passes to test combinations of encoding parameters and resulting rate-distortion values for such combinations. The encoding parameters can include partitioning of CTUs into CUs, prediction modes for CUs, transform types for residual data of CUs, quantization parameters for residual data of CUs, and so on. The mode selection unit 202 can ultimately select a combination of encoding parameters that has a better rate-distortion value than other tested combinations.

[0489] The video encoder 200 can partition a picture retrieved from the video data memory 230 into a series of CTUs, and encapsulate one or more CTUs within a slice. The mode selection unit 202 can partition the CTUs of the picture according to a tree structure such as the QTBT structure or the quad-tree structure of HEVC described above. As described above, the video encoder 200 can form one or more CUs by partitioning a CTU according to the tree structure. Such CUs can also be generally referred to as “video blocks” or “blocks.”

[0490] In general, the mode selection unit 202 also controls its components (e.g., the motion estimation unit 222, the motion compensation unit 224, and the intra prediction unit 226) to generate a prediction block for a current block (e.g., a current CU, or an overlapping portion of a PU and a TU in HEVC). For inter prediction of a current block, the motion estimation unit 222 can perform a motion search to identify one or more closely matching reference blocks in one or more reference pictures (e.g., one or more previously coded pictures that are stored in the DPB 218). Specifically, the motion estimation unit 222 can calculate, for example, a sum of absolute difference (SAD), a sum of squared difference (SSD), a mean absolute difference (MAD), a mean squared difference (MSD), and so on, that represent how similar a potential reference block is to the current block. The motion estimation unit 222 can generally perform these calculations using the sample-wise difference between the current block and the reference block under consideration. The motion estimation unit 222 can identify the reference block with the lowest value resulting from these calculations, which indicates the reference block that most closely matches the current block.

[0491] Motion estimation unit 222 can form one or more motion vectors (MVs) that define the positioning of a reference block in a reference picture relative to a current block in the current picture. Motion estimation unit 222 can then provide the motion vector(s) to motion compensation unit 224. For example, for single prediction, motion estimation unit 222 can provide a single motion vector, while for bi-prediction, motion estimation unit 222 can provide two motion vectors. Motion compensation unit 224 can then use the motion vector(s) to generate a predicted block. For example, motion compensation unit 224 can use the motion vector(s) to retrieve data for the reference block(s). As another example, if the motion vector(s) have fractional sample precision, motion compensation unit 224 can interpolate values for the predicted block according to one or more interpolation filters. Further, for bi-prediction, motion compensation unit 224 can retrieve data for two reference blocks identified by the respective motion vectors and combine the retrieved data, e.g., by sample-wise averaging or weighted averaging. As described above, when a block of a current subpicture is inter-predicted according to a reference subpicture having a different resolution, motion estimation unit 222 and motion compensation unit 224 may, for example, scale the predicted block from the reference subpicture based on the scaling parameters for the current subpicture. Motion estimation unit 222 and motion compensation unit 224 may, for example, determine scaling ratios using scaling windows according to the techniques described above.

[0492] As another example, for intra-prediction or intra-prediction coding, intra-prediction unit 226 can generate a predicted block from samples neighboring the current block. For example, for directional modes, intra-prediction unit 226 can mathematically combine values of the neighboring samples and fill these computed values across a defined direction of the current block to produce the predicted block. As another example, for a DC mode, intra-prediction unit 226 can compute an average of the neighboring samples for the current block and generate the predicted block to include this resulting average for each sample of the predicted block.

[0493] Mode selection unit 202 provides the predicted block to residual generation unit 204. Residual generation unit 204 receives the original, unencoded version of the current block from video data store 230 and the predicted block from mode selection unit 202. Residual generation unit 204 computes the sample-wise differences between the current block and the predicted block. The resulting sample-wise differences define a residual block for the current block. In some examples, residual generation unit 204 can also determine differences between sample values in the residual block to generate the residual block using residual differential pulse code modulation (RDPCM). In some examples, residual generation unit 204 can be formed using one or more subtractor circuits that perform binary subtraction.

[0494] In examples in which mode selection unit 202 partitions a CU into PUs, each PU can be associated with a luma prediction unit and corresponding chroma prediction units. Video encoder 200 and video decoder 300 can support PUs having various sizes. As described above, the size of a CU can refer to the size of the CU's luma coding block, while the size of a PU can refer to the size of the PU's luma prediction unit. Assuming that a particular CU has a size of 2Nx2N, video encoder 200 can support PUs having a size of 2Nx2N or NxN for intra-prediction, and symmetric PUs having a size of 2Nx2N, 2NxN, Nx2N, NxN, or similar for inter-prediction. Video encoder 200 and video decoder 300 can also support asymmetric partitioning for PUs having a size of 2NxnU, 2NxnD, nLx2N, and nRx2N for inter-prediction.

[0495] In examples in which mode selection unit 202 does not further partition a CU into PUs, each CU can be associated with a luma coding block and corresponding chroma coding blocks. As described above, the size of a CU can refer to the size of the CU's luma coding block. Video encoder 200 and video decoder 300 can support CUs having a size of 2Nx2N, 2NxN, or Nx2N.

[0496] For other video coding techniques, such as intra-block copy mode coding, affine mode coding, and linear model (LM) mode coding, as several examples, mode selection unit 202 generates, via a respective unit associated with the coding technique, a prediction block for the current block being encoded. In certain examples, such as palette mode coding, mode selection unit 202 can not generate a prediction block, but rather generate syntax elements that indicate a manner in which to reconstruct the block based on a selected palette. In such modes, mode selection unit 202 can provide these syntax elements to entropy encoding unit 220 for encoding.

[0497] As described above, residual generation unit 204 receives video data for a current block and a corresponding prediction block. Residual generation unit 204 then generates a residual block for the current block. To generate the residual block, residual generation unit 204 computes a sample-by-sample difference between the prediction block and the current block.

[0498] Transform processing unit 206 applies one or more transforms to the residual block to produce a block of transform coefficients (referred to herein as a "transform coefficient block"). Transform processing unit 206 can apply various transforms to the residual block to form the transform coefficient block. For example, transform processing unit 206 can apply a discrete cosine transform (DCT), a directional transform, a Karhunen-Loeve Transform (KLT), or a conceptually similar transform. In some examples, transform processing unit 206 can perform multiple transforms, e.g., a primary transform and a secondary transform such as a rotational transform, on the residual block. In some examples, transform processing unit 206 does not apply a transform to the residual block.

[0499] Quantization unit 208 can quantize the transform coefficients in the transform coefficient block to produce a quantized transform coefficient block. Quantization unit 208 can quantize transform coefficients of the transform coefficient block according to a quantization parameter (QP) value associated with the current block. Video encoder 200 (e.g., via mode select unit 202) can adjust the degree of quantization applied to the transform coefficient block associated with the current block by adjusting the QP value associated with the CU. Quantization can introduce loss of information, and thus, quantized transform coefficients can have lower precision than the original transform coefficients produced by transform processing unit 206.

[0500] Inverse quantization unit 210 and inverse transform processing unit 212 can apply inverse quantization and inverse transforms, respectively, to a quantized transform coefficient block to reconstruct a residual block from the transform coefficient block. Reconstruction unit 214 can produce a reconstructed block corresponding to the current block (albeit potentially with some degree of distortion) based on the reconstructed residual block and the prediction block generated by mode select unit 202. For example, reconstruction unit 214 can add samples of the reconstructed residual block to corresponding samples from the prediction block generated by mode select unit 202 to produce the reconstructed block.

[0501] Filter unit 216 can perform one or more filter operations on the reconstructed block. For example, filter unit 216 can perform a deblocking operation to reduce blocking artifacts along CU boundaries. In some examples, the operations of filter unit 216 can be skipped.

[0502] Video encoder 200 stores the reconstructed blocks in DPB 218. For example, in examples where the operations of filter unit 216 are not needed, reconstruction unit 214 can store the reconstructed blocks to DPB 218. In examples where the operations of filter unit 216 are needed, filter unit 216 can store the filtered reconstructed blocks to DPB 218. Motion estimation unit 222 and motion compensation unit 224 can retrieve reference pictures formed from the reconstructed (and possibly filtered) blocks in DPB 218 to inter-predict blocks of subsequent encoded pictures. In addition, intra-prediction unit 226 can use reconstructed blocks of the current picture in DPB 218 to intra-predict other blocks in the current picture.

[0503] In general, entropy encoding unit 220 can entropy encode syntax elements received from other functional components of video encoder 200. For example, entropy encoding unit 220 can entropy encode quantized transform coefficient blocks from quantization unit 208. As another example, entropy encoding unit 220 can entropy encode prediction syntax elements (e.g., motion information for inter-prediction or intra-mode information for intra-prediction) from mode select unit 202. Entropy encoding unit 220 can perform one or more entropy encoding operations on syntax elements, as another example of video data, to generate entropy encoded data. For example, entropy encoding unit 220 can perform a context- adaptive variable length coding (CAVLC) operation, a CABAC operation, a variable to variable (V2V) length coding operation, a syntax-based context-adaptive binary arithmetic coding (SBAC) operation, a Probability Interval Partitioning Entropy (PIPE) coding operation, an Exponential-Golomb coding operation, or another type of entropy coding operation on the data. In certain examples, entropy encoding unit 220 can operate in a bypass mode in which syntax elements are not entropy encoded.

[0504] Video encoder 200 can output a bitstream that includes the entropy encoded syntax elements needed to reconstruct blocks of a slice or picture. In particular, entropy encoding unit 220 can output the bitstream.

[0505] The operations described above are described with respect to blocks. Such descriptions should be understood to be operations for luma coding blocks and / or chroma coding blocks. As described above, in certain examples, luma coding blocks and chroma coding blocks are luma and chroma components of a CU. In certain examples, luma coding blocks and chroma coding blocks are luma and chroma components of a PU.

[0506] In some examples, operations performed with respect to the luma coding block need not be repeated for the chroma coding blocks. As one example, operations to identify a motion vector (MV) and reference picture for the luma coding block need not be repeated for identifying the MV and reference picture for the chroma coding blocks. Rather, the MV for the luma coding block can be scaled to determine the MV for the chroma blocks, while the reference picture can be the same. As another example, intra prediction processing can be the same for the luma coding block and the chroma coding blocks.

[0507] Figure 11 FIG. 3 is a block diagram illustrating an example video decoder 300 that can perform the techniques of this disclosure. Figure 11 The techniques of this disclosure are provided for purposes of explanation and are not limited to the techniques broadly illustrated and described. For purposes of explanation, this disclosure describes video decoder 300 according to the techniques of JEM, VVC, and HEVC. However, the techniques of this disclosure can be performed by video coding devices configured to other video coding standards.

[0508] In Figure 11 In the example of FIG. 3, video decoder 300 includes coded picture buffer (CPB) memory 320, entropy decoding unit 302, prediction processing unit 304, inverse quantization unit 306, inverse transform processing unit 308, reconstruction unit 310, filter unit 312, and decoded picture buffer (DPB) 314. Any or all of CPB memory 320, entropy decoding unit 302, prediction processing unit 304, inverse quantization unit 306, inverse transform processing unit 308, reconstruction unit 310, filter unit 312, and DPB 314 can be implemented in one or more processors or in processing circuitry. For instance, the units of video decoder 300 can be implemented as one or more circuits or logic elements as part of hardware circuitry, or as part of a processor of a FPGA, ASIC. Also, video decoder 300 can include additional or alternative processors or processing circuitry to perform these and other functions.

[0509] Prediction processing unit 304 includes motion compensation unit 316 and intra-prediction unit 318. Prediction processing unit 304 can include additional units to perform prediction according to other prediction modes. As examples, prediction processing unit 304 can include a palette unit, an intra-block copy unit (which can be part of motion compensation unit 316), an affine unit, a linear model (LM) unit, and so on. In other examples, video decoder 300 can include more, fewer, or different functional components.

[0510] CPB memory 320 can store video data, such as encoded video bitstreams, to be decoded by the components of video decoder 300. The video data stored in CPB memory 320 can be obtained, for example, from computer- readable medium 110 Figure 1 ). CPB memory 320 can include a CPB that stores encoded video data (e.g., syntax elements) from an encoded video bitstream. Also, CPB memory 320 can store video data other than syntax elements of coded pictures, such as temporary data representing outputs from the various units of video decoder 300. DPB 314 generally stores decoded pictures, which video decoder 300 can output and / or use as reference video data when decoding subsequent data or pictures of an encoded video bitstream. CPB memory 320 and DPB 314 can be formed by any of a variety of memory devices, such as DRAM, including SDRAM, MRAM, RRAM, or other types of memory devices. CPB memory 320 and DPB 314 can be provided by the same memory devices or separate memory devices. In various examples, CPB memory 320 can be on-chip with other components of video decoder 300, or off-chip relative to those components.

[0511] Additionally or alternatively, in some examples, video decoder 300 can retrieve coded video data from memory 120 Figure 1 ). That is, memory 120 can store data as discussed above in connection with CPB memory 320. Similarly, when some or all of the functionality of video decoder 300 is implemented in software to be executed by processing circuitry of video decoder 300, memory 120 can store the instructions to be executed by video decoder 300.

[0512] Figure 11 The various units illustrated in FIG. 3 are illustrated to assist with understanding the operations performed by video decoder 300. The units can be implemented as fixed- function circuits, programmable circuits, or a combination thereof. Similar to the units illustrated in FIG. 2, the units illustrated in FIG. 3 are not intended to limit the Figure 10 Circuits, like fixed-function circuits, refer to circuits that provide particular functionality and are preset in the operations that can be performed. Programmable circuits refer to circuits that can be programmed to perform various tasks and provide flexible functionality in the operations that can be performed. For instance, programmable circuits can execute software or firmware such that the programmable circuits operate in a manner defined by the instructions of the software or firmware. Fixed-function circuits can execute software instructions (e.g., to receive parameters or output parameters), but the types of operations that the fixed-function circuits perform are generally immutable. In some examples, one or more of the units can be distinct circuit blocks (fixed-function or programmable), while in some examples one or more of the units can be integrated circuits.

[0513] Video decoder 300 can include ALUs, EFUs, digital circuits, analog circuits, and / or programmable cores formed from programmable circuitry. In examples where the operations of video decoder 300 are performed by software executing on the programmable circuitry, on-chip or off-chip memory can store instructions (e.g., object code) of the software that video decoder 300 receives and executes.

[0514] Entropy decoding unit 302 can receive encoded video data from the CPB and entropy decode the video data to reproduce syntax elements. Prediction processing unit 304, inverse quantization unit 306, inverse transform processing unit 308, reconstruction unit 310, and filter unit 312 can generate decoded video data based on the syntax elements extracted from the bitstream.

[0515] In general, video decoder 300 reconstructs a picture on a block-by-block basis. Video decoder 300 can perform reconstruction operations individually for each block (where the block that is currently being reconstructed, i.e., decoded, can be referred to as the “current block”).

[0516] Entropy decoding unit 302 can entropy decode syntax elements defining quantized transform coefficient blocks of quantized transform coefficients, as well as transform information such as a quantization parameter (QP) and / or transform mode indication(s). Inverse quantization unit 306 can use a QP associated with a quantized transform coefficient block to determine a degree of quantization and, likewise, a degree of inverse quantization for inverse quantization unit 306 to apply. Inverse quantization unit 306 may, for example, perform a bitwise left shift operation to inverse quantize a quantized transform coefficient. Inverse quantization unit 306 may, thereby, form a transform coefficient block comprising transform coefficients.

[0517] After inverse quantization unit 306 forms a transform coefficient block, inverse transform processing unit 308 can apply one or more inverse transforms to the transform coefficient block to produce a residual block associated with the current block. For example, inverse transform processing unit 308 can apply an inverse DCT, an inverse integer transform, an inverse Karhunen-Loeve Transform (KLT), an inverse rotational transform, an inverse directional transform, or another inverse transform to the transform coefficient block.

[0518] Further, prediction processing unit 304 generates the prediction block from the prediction information syntax elements entropy decoded by entropy decoding unit 302. For example, if the prediction information syntax elements indicate that the current block is inter-predicted, motion compensation unit 316 can generate the prediction block. In such cases, the prediction information syntax elements can indicate a reference picture in the DPB 314 from which to retrieve a reference block, and a motion vector identifying a location of the reference block in the reference picture relative to a location of the current block in the current picture. Motion compensation unit 316 can generally use the motion vector to retrieve the reference block from the reference picture in a manner consistent with the motion vector. Motion compensation unit 316 may, in some examples, perform interpolation based on the motion vector to obtain the reference block if the reference block is not located at an integer pixel value. Figure 10The inter-frame prediction process is performed in a manner substantially similar to that described above. As mentioned, when performing inter-frame prediction on blocks of the current subgraph based on reference subgraphs with different resolutions, the motion compensation unit 316 can, for example, scale the predicted blocks from the reference subgraph based on scaling parameters used for the current subgraph. The motion compensation unit 316 can, for example, use a scaling window to determine the scaling ratio using the techniques described above.

[0519] As another example, if the prediction information syntax element indicates that the current block is intra-predictable, then intra-prediction unit 318 can generate a prediction block according to the intra-prediction mode indicated by the prediction information syntax element. Again, intra-prediction unit 318 can typically be used in conjunction with intra-prediction unit 226 ( Figure 10 The intra-prediction process is performed in a manner that is essentially similar to that described above. The intra-prediction unit 318 can retrieve data from the neighboring samples of the current block from the DPB 314.

[0520] Reconstruction unit 310 can reconstruct the current block using the prediction block and the residual block. For example, reconstruction unit 310 can add the samples of the residual block to the corresponding samples of the prediction block to reconstruct the current block.

[0521] Filter unit 312 can perform one or more filtering operations on the reconstructed block. For example, filter unit 312 can perform a deblocking operation to reduce block artifacts along the edges of the reconstructed block. The operation of filter unit 312 need not be performed in all examples.

[0522] The video decoder 300 can store reconstructed blocks in the DPB 314. For example, in an example where the operation of the filter unit 312 is not performed, the reconstruction unit 310 can store the reconstructed blocks in the DPB 314. In an example where the operation of the filter unit 312 is performed, the filter unit 312 can store the filtered reconstructed blocks in the DPB 314. As described above, the DPB 314 can provide reference information to the prediction processing unit 304, such as samples of the current image for intra-frame prediction and previously decoded images for subsequent motion compensation. Moreover, the video decoder 300 can output decoded images (e.g., decoded video) from the DPB 314 for applications such as... Figure 1 The subsequent presentation on the display device 118.

[0523] Figure 12 This is a flowchart illustrating an example process for encoding the current block. The current block may include the current CU. Although relative to video encoder 200 ( Figure 1 and Figure 7 This description is provided, but it should be understood that other devices can be configured to perform similar actions. Figure 6 Similar to the method.

[0524] In this example, initially, video encoder 200 predicts the current block (350). For example, video encoder 200 can form a prediction block for the current block. Video encoder 200 can then calculate a residual block for the current block (352). To calculate the residual block, video encoder 200 can calculate the difference between the original, unencoded block and the prediction block for the current block. Video encoder 200 can then transform and quantize the coefficients of the residual block (354). Next, video encoder 200 can scan the quantized transform coefficients of the residual block (356). During or after the scan, video encoder 200 can entropy encode the transform coefficients (358). For example, video encoder 200 can encode the transform coefficients using CAVLC or CABAC. Video encoder 200 can then output the entropy encoded data for the block (360).

[0525] Figure 13 is a flowchart illustrating an example process for decoding a current block of video data. The current block can include a current CU. Although described with respect to video decoder 300 Figure 1 and Figure 8 ), it should be understood that other devices can be configured to perform similar methods as the methods of Figure 13

[0526] Video decoder 300 can receive entropy encoded data for the current block, such as entropy encoded prediction information corresponding to the current block and entropy encoded data for the coefficients of a residual block (370). Video decoder 300 can entropy decode the entropy encoded data to determine prediction information for the current block and to reproduce the coefficients of the residual block (372). Video decoder 300 can predict the current block (374), e.g., using an intra prediction or inter prediction mode as indicated by the prediction information for the current block, to calculate a prediction block for the current block. Video decoder 300 can then inverse scan the reproduced coefficients (376) to create a block of quantized transform coefficients. Video decoder 300 can then inverse quantize and inverse transform the transform coefficients to produce a residual block (378). Video decoder 300 can finally decode the current block by combining the prediction block and the residual block (380).

[0527] Figure 14 is a flowchart illustrating an example process for decoding a current block of video data. The current block can include a current CU. Figure 14 The techniques of Figure 1 and Figure 7 ) or video decoder 300 Figure 1 and Figure 8 ​However, it should be understood that other devices can be configured to perform similar processes as Figure 14

[0528] The video coder determines that a first sub-picture of a current picture has an associated scaling parameter (400). The video coder may, for example, determine that the first sub-picture of the current picture has the associated scaling parameter by receiving, in a parameter set data structure for the current picture, a first instance of a first syntax element that indicates whether the first sub-picture of the current picture has an associated scaling parameter. The parameter set data structure may, for example, be a picture header, a PPS, or other such parameter set data structure.

[0529] The video coder receives the associated scaling parameter for the first sub-picture of the current picture in response to determining that the first sub-picture of the current picture has the associated scaling parameter (402). To receive the associated scaling parameter for the first sub-picture, the video coder can be configured to receive the associated scaling parameter for the first sub-picture in a parameter set data structure. The parameter set data structure may, for example, be a picture header, a PPS, or other such parameter set data structure. The video coder can also be configured to receive a second syntax element that indicates a number of sub-pictures in the current picture; for each of the sub-pictures in the current picture, receive an instance of a first syntax element that indicates whether a respective sub-picture of the current picture has an associated scaling parameter; and for each respective sub-picture that has an associated scaling parameter, receive the associated scaling parameter.

[0530] The associated scaling parameter may, for example, include one or more of: a left offset value that specifies, in units of luma samples, an offset between a left boundary of the first sub-picture and a left boundary of a scaling window in the first sub-picture; a right offset value that specifies, in units of luma samples, an offset between a right boundary of the first sub-picture and a right boundary of the scaling window in the first sub-picture; a top offset value that specifies, in units of luma samples, an offset between a top boundary of the first sub-picture and a top boundary of the scaling window in the first sub-picture; and a bottom offset value that specifies, in units of luma samples, an offset between a bottom boundary of the first sub-picture and a bottom boundary of the scaling window in the first sub-picture. The associated scaling parameter may, for example, include one or more of the pps_scaling_win_left_offset[i], pps_scaling_win_right_offset[i], pps_scaling_win_top_offset[i], and pps_scaling_win_bottom_offset[i] syntax elements described above.

[0531] ​The video coder determines motion information for a block of a first subpicture of the current picture that identifies a subpicture of a reference picture (404). The motion information may, for example, include one or more of a motion vector, a reference picture index, or a motion vector resolution. As described above, the video coder can use the motion information to inter-predict the block. The video coder locates a prediction block for the block of the first subpicture of the current picture in the subpicture of the reference picture (406).

[0532] The video coder scales the prediction block based on the associated scaling parameter for the first subpicture of the current picture (408). To scale the prediction block based on the associated scaling parameter for the first subpicture, the video coder may, for example, determine a window of the subpicture of the reference picture based on the associated scaling parameter for the first subpicture, where the window of the subpicture of the reference picture includes less than all of the subpicture of the reference picture; determine a window of the first subpicture of the current picture based on the associated scaling parameter for the first subpicture, where the window of the first subpicture of the current picture includes less than all of the first subpicture of the current picture; determine a scaling ratio based on a ratio of the window of the subpicture of the reference picture to the window of the first subpicture of the current picture; and scale the prediction block based on the determined scaling ratio. To scale the subpicture of the reference picture based on the associated scaling parameter for the first subpicture, the video coder may, for example, determine a scaling window in the first subpicture based on the associated scaling parameter for the first subpicture; determine a ratio of a height of the scaling window in the first subpicture to a height of the scaling window in the subpicture of the reference picture; determine a ratio of a width of the scaling window in the first subpicture to a width of the scaling window in the subpicture of the reference picture; and scale the prediction block based on the ratio of the height of the scaling window in the first subpicture to the height of the scaling window in the subpicture of the reference picture and the ratio of the width of the scaling window in the first subpicture to the width of the scaling window in the subpicture of the reference picture. The determined scaling ratio is in a range of 1 / 8 to 2, inclusive. The resolution of the scaled prediction block can be equal to the resolution of the block of the first subpicture of the current picture.

[0533] The video coder can output the decoded video data based on the scaled prediction block. The video coder may, for example, add residual data to the scaled prediction block to form a reconstructed block and output the reconstructed block, possibly after applying one or more filter operations. When the video coder is encoding video data, the video coder can output the decoded video data by storing the decoded video data for use when encoding a subsequent block or a subsequent picture. When the video coder is decoding video data, the video coder can output the decoded video by storing the decoded video data for use when decoding a subsequent block or a subsequent picture, or output the decoded video for display.

[0534] Clause 1: A method of coding video data, comprising: determining whether a subpicture of the video data is treated as a picture; scaling the subpicture as the picture based on the subpicture being treated as the picture; determining a subpicture scaling flag based on the subpicture not being treated as the picture; and coding the subpicture based on the scaling or the subpicture scaling flag.

[0535] Clause 2: The method of clause 1, wherein the subpicture scaling flag is signaled in a picture parameter set (PPS).

[0536] Clause 3: The method of any combination of clauses 1-2, wherein the subpicture scaling flag is inferred to be 0 if: subpics_present_flag is equal to 0; ref_pic_resampling_enabled_flag is equal to 0 and sps_subpic_id_present_flag is equal to 0; ref_pic_resampling_enabled_flag is equal to 0 and sps_subpic_id_signalling_present_flag is equal to 1; or subpics_present_flag is equal to 1 and subpic_treated_as_pic_flag[i] is equal to 0.

[0537] Clause 4: The method of any combination of clauses 1-3, further comprising determining a subpicture scaling window parameter.

[0538] Clause 5: The method of clause 4, wherein the subpicture scaling window parameter is signaled in a PPS.

[0539] Clause 6: The method of any combination of clauses 4-5, wherein the subpicture scaling window parameter is signaled in a picture header (PH).

[0540] Clause 7: A method of coding video data, comprising: determining whether a subpicture of the video data is treated as a picture; determining a first scaling ratio based on the subpicture being treated as the picture; determining a second scaling ratio based on the subpicture not being treated as the picture; and coding the subpicture based on the first scaling ratio or the second scaling ratio.

[0541] Clause 8: A method of coding video data comprising: restricting PicOutputWidthL * A to be greater than or equal to refPicOutputWidthL; restricting PicOutputHeightL * A to be greater than or equal to refPicOutputHeightL; restricting PicOutputWidthL to be less than or equal to refPicOutputWidthL * B; restricting PicOutputHeightL to be less than or equal to refPicOutputHeightL * B; and coding the video data based on the restrictions, where A is a non-zero positive number, B is a non-zero positive number, and B > A.

[0542] Clause 9: A method of coding video data comprising: restricting PicOutputWidthL [SubPicldx] * A to be greater than or equal to PicOutputWidthL [RefSubPicldx]; restricting PicOutputHeightL [SubPicldx] * A to be greater than or equal to PicOutputHeightL [RefSubPicldx]; restricting PicOutputWidthL [SubPicldx] to be less than or equal to PicOutputWidthL [RefSubPicldx] * B; restricting PicOutputHeightL [SubPicldx] to be less than or equal to PicOutputHeightL [RefSubPicldx] * B; and coding the video data based on the restrictions, where A is a non-zero positive number, B is a non-zero positive number, and B > A.

[0543] Clause 10: A method of coding video data comprising: determining a left displacement from a scaling window in a current subpicture of the video data to a scaling window in a reference subpicture in the video data; determining an upper displacement from the scaling window in the current subpicture to the scaling window in the reference subpicture; and coding the current subpicture based on the left displacement and the upper displacement.

[0544] Clause 11: The method of any of clauses 1-10, wherein the reference picture and the current picture are the same size, and a scaling ratio is enabled for the current subpicture to scale a size of the reference subpicture to a size of the current subpicture.

[0545] Clause 12: The method of any of clauses 1-11, wherein the reference picture and the current picture are different sizes, and a subpicture ID is kept constant across a coded layer-wise video sequence (CLVS).

[0546] Clause 13: The method of any of clauses 1-12, wherein the reference picture and the current picture are different sizes, and the subpicture ID changes within the CLVS.

[0547] Clause 14: The method of any of clauses 1-13, wherein the coding comprises decoding.

[0548] Clause 15: The method of any of clauses 1-14, wherein the coding comprises encoding.

[0549] Clause 16: A device for coding video data, the device comprising one or more means for performing the method of any of clauses 1-15.

[0550] Clause 17: The device of clause 16, wherein the one or more means comprise one or more processors implemented in circuitry.

[0551] Clause 18: The device of any of clauses 16 and 17, further comprising a memory for storing video data.

[0552] Clause 19: The device of any of clauses 16-18, further comprising a display configured to display decoded video data.

[0553] Clause 20: The device of any of clauses 16-19, wherein the device comprises one or more of a camera, a computer, a mobile device, a broadcast receiver device, and a set-top box.

[0554] Clause 21: The device of any of clauses 16-20, wherein the device comprises a video decoder.

[0555] Clause 22: The device of any of clauses 16-21, wherein the device comprises a video encoder.

[0556] Clause 23. A computer-readable storage medium having stored thereon instructions that, when executed, cause one or more processors to perform the method of any of clauses 1-15.

[0557] Clause 24: A device for encoding video data, comprising means for performing any of the methods of the disclosure.

[0558] Clause 25: A method of coding video data, comprising: identifying a subpicture of a reference picture corresponding to a subpicture of a current picture; scaling the subpicture of the reference picture; and coding a block of the subpicture of the current picture based on the scaled subpicture of the reference picture.

[0559] Clause 26: The method of clause 25, wherein a resolution of the scaled subpicture of the reference picture is equal to a resolution of the subpicture of the current picture.

[0560] Clause 27: The method of clause 25 or 26, wherein scaling the sub- picture of the reference picture comprises determining a scaling window in the sub-picture of the reference picture.

[0561] Clause 28: The method of any of clauses 25-27, wherein coding comprises decoding.

[0562] Clause 29: The method of any of clauses 25-27, wherein coding comprises encoding.

[0563] Clause 30: An apparatus for coding video data, the apparatus comprising one or more means for performing the method of any of clauses 25-29.

[0564] Clause 31: The apparatus of clause 30, wherein the one or more means comprise one or more processors implemented in circuitry.

[0565] Clause 32: The apparatus of any of clauses 30 and 32, further comprising a memory for storing video data.

[0566] Clause 33: The apparatus of any of clauses 30-32, further comprising a display configured to display decoded video data.

[0567] Clause 34: The apparatus of any of clauses 30-33, wherein the apparatus comprises one or more of a camera, a computer, a mobile device, a broadcast receiver device, and a set-top box.

[0568] Clause 35: The apparatus of any of clauses 30-34, wherein the apparatus comprises a video decoder.

[0569] Clause 36: The apparatus of any of clauses 30-34, wherein the apparatus comprises a video encoder.

[0570] Clause 37. A computer-readable storage medium having stored thereon instructions that, when executed, cause one or more processors to perform the method of any of clauses 25-29.

[0571] It is recognized that depending on the example, certain acts or events of any of the techniques described herein can be performed in a different sequence, can be added, modified or omitted (e.g., not all described acts or events are necessary for the practice of the techniques), and / or can be performed concurrently in any desired fashion. Also, certain acts or events can be performed concurrently, e.g., through multi-threaded processing, interrupt processing, or multiple processors, rather than sequentially.

[0572] In one or more examples, the functions described can be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions can be stored on or transmitted over as one or more instructions or code on a computer-readable medium and executed by a hardware-based processing unit. Computer-readable media can include computer-readable storage media, which corresponds to a tangible medium such as data storage media, or communication media including any medium that facilitates transfer of a computer program from one place to another, e.g., according to a communication protocol. In this manner, computer- readable media generally can correspond to (1) tangible computer-readable storage media which is non-transitory or (2) a communication medium such as a signal or carrier wave. Data storage media can be any available media that can be accessed by one or more computers or one or more processors to retrieve instructions, code and / or data structures for implementation of the techniques described in this disclosure. A computer program product can include a computer-readable medium.

[0573] By way of example, and not limitation, such computer-readable storage media can include RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage, or other magnetic storage devices, flash memory, or any other storage medium that can be used to store desired program code in the form of instructions or data structures and that can be accessed by a computer. Also, any

[0574] Instructions can be executed by one or more processors, such as one or more digital signal processors (DSPs), general purpose microprocessors, application-specific integrated circuits (ASICs), field programmable gate arrays (FPGAs), or other equivalent integrated or discrete logic circuitry. Accordingly, the term "processor" as used herein can refer to any of the foregoing structure or any other structure suitable for implementation of the techniques described herein. In addition, in some aspects, the functionality described herein can be provided within dedicated hardware and / or software modules configured for encoding and decoding, or incorporated in a combined codec. Also, the techniques could be fully implemented in one or more circuits or logic elements.

[0575] The techniques of this disclosure can be implemented in a wide variety of devices or apparatuses, including a wireless handset, an integrated circuit (IC) or IC package (e.g., a chip set), among others. Various components, modules, or units are described herein as being stored in or on memory, which can include one or more types of memory such as volatile memory (e.g., dynamic random access memory, DRAM, or static RAM, SRAM) or nonvolatile memory (e.g., read only memory, ROM, electrically programmable read only memory, EPROM, electrically erasable programmable read only memory, EEPROM, or flash memory). In some examples, the memory can include one or more types of removable media and / or built-in memory controlled by a mobile processor or a desktop processor.

[0576] Various examples have been described. These and other examples are within the scope of the following claims.

Claims

1. A method of coding video data, the method comprising: determining that a first subpicture of a current picture has an associated scaling parameter; in response to determining that the first subpicture of the current picture has the associated scaling parameter, receiving the associated scaling parameter for the first subpicture of the current picture; determining motion information for a block of the first subpicture of the current picture, wherein the motion information identifies a subpicture of a reference picture; locating, in the subpicture of the reference picture, a prediction block for the block of the first subpicture of the current picture; and scaling the prediction block based on the associated scaling parameter for the first subpicture of the current picture, wherein scaling the prediction block based on the associated scaling parameter for the first subpicture comprises: when the first subpicture is not considered a picture, scaling the prediction block using a scaling window for a regular picture scaling process, and when the first subpicture is considered a picture, scaling the prediction block using a different subpicture scaling window for a subpicture scaling process.

2. The method of claim 1, wherein: determining that the first subpicture of the current picture has the associated scaling parameter comprises receiving, in a parameter set data structure for the current picture, a first instance of a first syntax element indicating whether the first subpicture of the current picture has the associated scaling parameter; and receiving the associated scaling parameter for the first subpicture comprises receiving the associated scaling parameter for the first subpicture in the parameter set data structure.

3. The method of claim 1, wherein scaling the prediction block using a different subpicture scaling window for a subpicture scaling process comprises: determining a scaling window for the subpicture of the reference picture based on the associated scaling parameter for the first subpicture, wherein the scaling window for the subpicture of the reference picture comprises less than all of the subpicture of the reference picture; determining a scaling window for the first subpicture of the current picture based on the associated scaling parameter for the first subpicture, wherein the scaling window for the first subpicture of the current picture comprises less than all of the first subpicture of the current picture; determining a scaling ratio based on a ratio of the scaling window for the subpicture of the reference picture to the scaling window for the first subpicture of the current picture; and scaling the prediction block based on the determined scaling ratio.

4. The method of claim 3, wherein the determined scaling ratio is in a range of 1 / 8 to 2, inclusive.

5. The method of claim 1, wherein a resolution of the scaled prediction block is equal to a resolution of the block of the first subpicture of the current picture.

6. The method of claim 1, further comprising: receiving a second syntax element indicating a number of subpictures in the current picture; for each of the subpictures in the current picture, receiving an instance of a first syntax element indicating whether a respective subpicture of the current picture has an associated scaling parameter; and ​ ​ ​ For each respective subpicture having an associated scaling parameter, the associated scaling parameter is received.

7. The method of claim 3, wherein scaling the prediction block using different subpicture scaling windows for a subpicture scaling process further comprises: determining a ratio of a height of the scaling window of the first subpicture of the current picture to a height of a scaling window of the subpicture of the reference picture; determining a ratio of a width of the scaling window of the first subpicture of the current picture to a width of the scaling window of the subpicture of the reference picture; scaling the prediction block based on the ratio of the height of the scaling window of the first subpicture of the current picture to the height of the scaling window of the subpicture of the reference picture and the ratio of the width of the scaling window of the first subpicture of the current picture to the width of the scaling window of the subpicture of the reference picture.

8. The method of claim 1, wherein the associated scaling parameter comprises: a left offset value specifying, in units of luma samples, an offset between a left boundary of the first subpicture and a left boundary of the scaling window in the first subpicture; a right offset value specifying, in units of the luma samples, an offset between a right boundary of the first subpicture and a right boundary of the scaling window in the first subpicture; an above offset value specifying, in units of the luma samples, an offset between an above boundary of the first subpicture and an above boundary of the scaling window in the first subpicture; and a below offset value specifying, in units of the luma samples, an offset between a below boundary of the first subpicture and a below boundary of the scaling window in the first subpicture.

9. The method of claim 1, wherein the method of coding the video data comprises a method of encoding the video data.

10. The method of claim 1, wherein the method of coding the video data comprises a method of decoding the video data.

11. A device for decoding video data, the device comprising: a memory configured to store video data; one or more processors implemented in circuitry and configured to: determine that a first subpicture of a current picture has an associated scaling parameter; in response to determining that the first subpicture of the current picture has the associated scaling parameter, receive the associated scaling parameter for the first subpicture of the current picture; determine motion information for a block of the first subpicture of the current picture, wherein the motion information identifies a subpicture of a reference picture; locate, in the subpicture of the reference picture, a prediction block for the block of the first subpicture of the current picture; and scale the prediction block based on the associated scaling parameter for the first subpicture of the current picture, wherein, to scale the prediction block based on the associated scaling parameter for the first subpicture, the one or more processors are further configured to: determine a scaling window for the prediction block based on the associated scaling parameter for the first subpicture of the current picture. ​ scaling the prediction block using a scaling window for a regular picture scaling process when the first subpicture is not considered a picture, and scaling the prediction block using a different subpicture scaling window for a subpicture scaling process when the first subpicture is considered a picture.

12. The device of claim 11, wherein: to determine that the first subpicture of the current picture has the associated scaling parameter, the one or more processors are further configured to receive, in a parameter set data structure for the current picture, a first instance of a first syntax element that indicates whether the first subpicture of the current picture has the associated scaling parameter; and to receive the associated scaling parameter for the first subpicture, the one or more processors are further configured to receive the associated scaling parameter for the first subpicture in the parameter set data structure.

13. The device of claim 11, wherein to scale the prediction block using a different subpicture scaling window for a subpicture scaling process, the one or more processors are further configured to: determine a scaling window of the subpicture of the reference picture based on the associated scaling parameter for the first subpicture, wherein the scaling window of the subpicture of the reference picture comprises less than all of the subpicture of the reference picture; determine a scaling window of the first subpicture of the current picture based on the associated scaling parameter for the first subpicture, wherein the scaling window of the first subpicture of the current picture comprises less than all of the first subpicture of the current picture; determine a scaling ratio based on a ratio of the scaling window of the subpicture of the reference picture to the scaling window of the first subpicture of the current picture; and scale the prediction block based on the determined scaling ratio.

14. The device of claim 11, wherein the determined scaling ratio is in a range of 1 / 8 to 2, inclusive.

15. The device of claim 11, wherein a resolution of the scaled prediction block is equal to a resolution of the block of the first subpicture of the current picture.

16. The device of claim 15, wherein the one or more processors are further configured to: receive a second syntax element that indicates a number of subpictures in the current picture; for each of the subpictures in the current picture, receive an instance of a first syntax element that indicates whether a respective subpicture of the current picture has an associated scaling parameter; and for each respective subpicture that has an associated scaling parameter, receive the associated scaling parameter.

17. The device of claim 13, wherein to scale the prediction block using a different subpicture scaling window for a subpicture scaling process, the one or more processors are further configured to: determine a ratio of a height of the scaling window of the first subpicture of the current picture to a height of a scaling window of the subpicture of the reference picture; a ratio of a width of the scaling window of the first sub-picture of the current picture to a width of the scaling window of the sub-picture of the reference picture; and scaling the prediction block based on the ratio of the height of the scaling window of the first sub-picture of the current picture to the height of the scaling window of the sub-picture of the reference picture and the ratio of the width of the scaling window of the first sub-picture of the current picture to the width of the scaling window of the sub-picture of the reference picture.

18. The device of claim 11, wherein the associated scaling parameters comprise: a left offset value specifying, in units of luma samples, an offset between a left boundary of the first sub-picture and a left boundary of the scaling window in the first sub-picture; a right offset value specifying, in units of the luma samples, an offset between a right boundary of the first sub-picture and a right boundary of the scaling window in the first sub-picture; an upper offset value specifying, in units of the luma samples, an offset between an upper boundary of the first sub-picture and an upper boundary of the scaling window in the first sub-picture; and a lower offset value specifying, in units of the luma samples, an offset between a lower boundary of the first sub-picture and a lower boundary of the scaling window in the first sub-picture.

19. The device of claim 11, wherein the device comprises a wireless communication device, further comprising a receiver configured to receive encoded video data.

20. The device of claim 19, wherein the wireless communication device comprises a telephone handset, and wherein the receiver is configured to demodulate a signal comprising the encoded video data according to a wireless communication standard.

21. The device of claim 11, further comprising: a display configured to display decoded video data.

22. The device of claim 11, wherein the device comprises a wireless communication device, a transmitter configured to modulate a signal comprising encoded video data according to a wireless communication standard.

23. The device of claim 11, further comprising: a camera configured to capture the video data.

24. A computer-readable storage medium storing instructions that, when executed by one or more processors, cause the one or more processors to: determine that a first sub-picture of a current picture has associated scaling parameters; in response to determining that the first sub-picture of the current picture has the associated scaling parameters, receive the associated scaling parameters for the first sub-picture of the current picture; determine motion information for a block of the first sub-picture of the current picture, wherein the motion information identifies a sub-picture of a reference picture; locate, in the sub-picture of the reference picture, a prediction block for the block of the first sub-picture of the current picture; and scale the prediction block based on the associated scaling parameters for the first sub-picture of the current picture, wherein scaling the prediction block based on the associated scaling parameters for the first sub-picture comprises: ​ ​ scaling the prediction block using a scaling window for a regular picture scaling process when the first subpicture is not considered a picture, and scaling the prediction block using a different subpicture scaling window for a subpicture scaling process when the first subpicture is considered a picture.

25. The computer-readable storage medium of claim 24, wherein: To determine that the first subpicture of the current picture has the associated scaling parameter, the instructions cause the one or more processors to: receive, in a parameter set data structure for the current picture, a first instance of a first syntax element that indicates whether the first subpicture of the current picture has the associated scaling parameter; and To receive the associated scaling parameter for the first subpicture, the instructions cause the one or more processors to: receive, in the parameter set data structure, the associated scaling parameter for the first subpicture.

26. The computer-readable storage medium of claim 24, wherein to scale the prediction block using a different subpicture scaling window for a subpicture scaling process, the one or more processors are further configured to: determine a scaling window of the subpicture of the reference picture based on the associated scaling parameter for the first subpicture, wherein the scaling window of the subpicture of the reference picture comprises less than all of the subpicture of the reference picture; determine a scaling window of the first subpicture of the current picture based on the associated scaling parameter for the first subpicture, wherein the scaling window of the first subpicture of the current picture comprises less than all of the first subpicture of the current picture; determine a scaling ratio based on a ratio of the scaling window of the subpicture of the reference picture to the scaling window of the first subpicture of the current picture; and scale the prediction block based on the determined scaling ratio.

27. The computer-readable storage medium of claim 24, wherein a resolution of the scaled prediction block is equal to a resolution of the block of the first subpicture of the current picture.

28. The computer-readable storage medium of claim 27, wherein the instructions cause the one or more processors to: receive a second syntax element that indicates a number of subpictures in the current picture; receive, for each of the subpictures in the current picture, an instance of a first syntax element that indicates whether a respective subpicture of the current picture has an associated scaling parameter; and receive, for each respective subpicture that has an associated scaling parameter, the associated scaling parameter.

29. The computer-readable storage medium of claim 26, wherein to scale the prediction block using a different subpicture scaling window for a subpicture scaling process, the instructions cause the one or more processors to: determine a ratio of a height of the scaling window of the first subpicture of the current picture to a height of a scaling window of the subpicture of the reference picture; determine a ratio of a width of the scaling window of the first subpicture of the current picture to a width of the scaling window of the subpicture of the reference picture; a ratio of the height of the scaling window of the first sub-picture of the current picture to the height of the scaling window of the sub-picture of the reference picture, and a ratio of the width of the scaling window of the first sub-picture of the current picture to the width of the scaling window of the sub-picture of the reference picture, scaling the prediction block.

30. The computer-readable storage medium of claim 24, wherein the associated scaling parameters comprise: a left offset value specifying, in units of luma samples, an offset between a left boundary of the first sub-picture and a left boundary of the scaling window in the first sub-picture; a right offset value specifying, in units of the luma samples, an offset between a right boundary of the first sub-picture and a right boundary of the scaling window in the first sub-picture; an upper offset value specifying, in units of the luma samples, an offset between an upper boundary of the first sub-picture and an upper boundary of the scaling window in the first sub-picture; and a lower offset value specifying, in units of the luma samples, an offset between a lower boundary of the first sub-picture and a lower boundary of the scaling window in the first sub-picture.

31. A device for coding video data, the device comprising means for performing the steps of the method of any of claims 1-10. ​

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