Coding and decoding video data using adaptive affine block prediction

Abstract

An example apparatus for decoding video data includes a memory configured to store video data; and a processing system comprising one or more processors implemented in a circuit, the processing system configured to: determine whether motion information of a block of video data is for a sub-block of the block greater than each pixel of the block or for each pixel of the block, the block being associated with data indicating that the block is to be predicted using affine motion compensation; in response to determining that the motion information of the block is used for the sub-block, performing sub-block-based affine motion compensation to form a prediction block of the block; in response to determining that the motion information is used for each pixel, performing pixel-based affine motion compensation to form a prediction block of the block; and decoding the block using the prediction block.

Description

[0001] This application claims priority to U.S. Patent Application No. 18 / 481,055, filed on October 4, 2023, the entire contents of which are incorporated herein by reference. U.S. Patent Application No. 18 / 481,055, filed on October 4, 2023, claims the benefit of U.S. Provisional Application No. 63 / 379,043, filed on October 11, 2022. Technical Field

[0002] The present disclosure relates to video coding and decoding, including video encoding and video decoding. Background Art

[0003] Digital video capabilities may be incorporated into various types of devices, including digital televisions, digital live 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 game devices, video game consoles, cellular or satellite radio telephones, so-called "smart phones", video teleconferencing devices, video streaming devices, etc. Digital video devices implement video codec technologies, 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 Codec (AVC), ITU-T H.265 / High Efficiency Video Codec (HEVC), ITU-T H.266 / Versatile Video Codec (VVC), and extensions of such standards, as well as proprietary video codecs / formats, such as AOMedia Video 1 (AV1) developed by the Alliance for Open Media. Video devices may more efficiently send, receive, encode, decode, and / or store digital video information by implementing such video codec technologies.

[0004] Video coding techniques include spatial (intra-picture) prediction and / or temporal (inter-picture) prediction to reduce or remove redundancy inherent in video sequences. For block-based video coding, a video slice (e.g., a video picture or a portion of a video picture) may be partitioned into video blocks, which may 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 relative to reference samples in neighboring blocks in the same picture. Video blocks in an inter-coded (P or B) slice of a picture may use spatial prediction relative to reference samples in neighboring blocks in the same picture or temporal prediction relative to reference samples in other reference pictures. Pictures may be referred to as frames, and reference pictures may be referred to as reference frames. Summary of the invention

[0005] In general, the present disclosure describes techniques related to video codecs using affine motion compensation. Affine motion compensation is an inter-frame prediction technique that includes the use of motion information (e.g., two or three motion vectors). In some cases, affine motion compensation may be applied on a sub-block basis, and in some cases, affine motion compensation may be applied on a per-pixel basis. When applied on a sub-block basis, it is assumed that the sub-block has a size greater than a single pixel. According to the techniques of the present disclosure, when a block of video data is to be predicted using affine motion information, it may be determined whether the motion information of the block is applied to the sub-block or to each pixel. When motion information is used for a sub-block (having a size greater than each pixel), a video codec (encoder or decoder) may perform affine motion compensation on a sub-block basis, and when motion information is used for each pixel, the video codec may perform affine motion compensation on a per-pixel basis.

[0006] To determine whether motion information is for a sub-block or a pixel, the video decoder may determine whether overlapped block motion compensation (OBMC) is to be applied to the block. In this manner, processing tasks associated with sub-blocks that are larger than individual pixels but not the individual pixels themselves may be implicitly disabled, such as by not encoding or decoding syntax elements that indicate whether the processing tasks are enabled or disabled. Thus, processing efficiency may be improved and a bit rate associated with a bitstream including encoded video data may be reduced.

[0007] In one example, a method of decoding video data includes: determining whether motion information of a block of the video data is for a sub-block of a block larger than individual pixels of the block or for individual pixels, the block being associated with data indicating that affine motion compensation is to be used to predict the block; in response to determining that the motion information of the block is for the sub-block, performing sub-block-based affine motion compensation to form a prediction block for the block; in response to determining that the motion information is for individual pixels, performing pixel-based affine motion compensation to form a prediction block for the block; and decoding the block using the prediction block.

[0008] In another example, an apparatus for decoding video data includes: a memory configured to store video data; and a processing system including one or more processors implemented in circuitry, the processing system configured to: determine whether motion information for a block of the video data is for a sub-block of a block larger than individual pixels of the block or for individual pixels, the block being associated with data indicating that affine motion compensation is to be used to predict the block; in response to determining that the motion information for the block is for the sub-block, perform sub-block-based affine motion compensation to form a predicted block for the block; in response to determining that the motion information is for individual pixels, perform pixel-based affine motion compensation to form a predicted block for the block; and decode the block using the predicted block.

[0009] In another example, an apparatus for decoding video data includes: an apparatus module for determining whether motion information of a block of the video data is for a sub-block of a block larger than individual pixels of the block or for individual pixels, the block being associated with data indicating that affine motion compensation is to be used to predict the block; an apparatus module for performing sub-block-based affine motion compensation to form a prediction block for the block in response to determining that the motion information of the block is for a sub-block; an apparatus module for performing pixel-based affine motion compensation to form a prediction block for the block in response to determining that the motion information is for individual pixels; and an apparatus module for decoding the block using the prediction block.

[0010] The details of one or more examples are set forth in the accompanying drawings and the description below.Other features, objects, and advantages will be apparent from the description, drawings, and claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 is a block diagram illustrating an example video encoding and decoding system that may perform the techniques of this disclosure.

[0012] Figure 2A and 2B is a conceptual diagram showing an example of a control point motion vector (CPMV) for affine motion compensation.

[0013] Figure 3 is a conceptual diagram illustrating an example motion compensation process.

[0014] Figure 4 A conceptual diagram illustrating another example motion compensation process.

[0015] Figure 5 is a block diagram illustrating an example video encoder that may perform the techniques of this disclosure.

[0016] Figure 6 is a block diagram illustrating an example video decoder that may perform the techniques of this disclosure.

[0017] Figure 7 is a flowchart illustrating an example method for encoding a current block according to the techniques of this disclosure.

[0018] Figure 8 is a flowchart illustrating an example method for decoding a current block according to the techniques of this disclosure.

[0019] Fig. 9 1 is a flowchart illustrating an example method for encoding a current block using sub-block based affine motion compensation or individual pixel based affine motion compensation according to the techniques of this disclosure.

[0020] Fig.101 is a flowchart illustrating an example method for decoding a current block using sub-block based affine motion compensation or individual pixel based affine motion compensation according to the techniques of this disclosure. DETAILED DESCRIPTION

[0021] In general, the present disclosure relates to various techniques that can be used in conjunction with affine motion compensation for video codecs. In particular, sub-block based affine motion compensation or pixel / sample based affine motion compensation can be used to predict blocks of video data. Various other techniques, such as prediction refinement with optical flow (PROF), overlapped block motion compensation (OBMC), local illumination compensation (LIC), and / or multiple hypothesis prediction, can also be performed in conjunction with sub-block or pixel / sample based affine motion compensation.

[0022] Certain combinations of these additional techniques in conjunction with affine motion compensation may outperform other techniques, or result in better or worse performance. Thus, the present disclosure describes various constraints on when to perform certain additional techniques in conjunction with affine motion compensation and with each other. By limiting certain techniques to be used together and / or ensuring that other techniques are used together, the techniques of the present disclosure can reduce the amount of testing required to determine which techniques to enable or disable. Likewise, the techniques used in conjunction can reduce the bit rate of the encoded video bitstream.

[0023] Figure 1 1 is a block diagram illustrating an example video encoding and decoding system 100 that may perform the techniques of the present disclosure. The techniques of the present disclosure generally relate to encoding and decoding (encoding and / or decoding) video data. Generally, video data includes any data used to process video. Thus, video data may include original, unencoded video, encoded video, decoded (e.g., reconstructed) video, and video metadata, such as signaling data.

[0024] like Figure 1 , 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 computer-readable medium 110. Source device 102 and destination device 116 may comprise any of various types of devices, including desktop computers, notebook (i.e., laptop) computers, mobile devices, tablet computers, set-top boxes, telephone handsets such as smart phones, televisions, cameras, display devices, digital media players, video game consoles, video streaming devices, broadcast receiver devices, etc. In some cases, source device 102 and destination device 116 may be equipped for wireless communication, and thus may be referred to as wireless communication devices.

[0025] exist Figure 1In the example of , the source device 102 includes a video source 104, a memory 106, a video encoder 200, and an output interface 108. The destination device 116 includes an input interface 122, a video decoder 300, the memory 120, and a display device 118. According to the present disclosure, the video encoder 200 of the source device 102 and the video decoder 300 of the destination device 116 may be configured to apply a technique for encoding and decoding video data using affine motion compensation. Therefore, the source device 102 represents an example of a video encoding device, and the destination device 116 represents an example of a video decoding device. In other examples, the source device and the destination device may include other components or arrangements. For example, the source device 102 may receive video data from an external video source (such as an external camera). Similarly, the destination device 116 may interface with an external display device rather than including an integrated display device.

[0026] like Figure 1 The system 100 shown is only one example. In general, any digital video encoding and / or decoding device may perform techniques for encoding and decoding video data using affine motion compensation. The source device 102 and the destination device 116 are only examples of such codec devices in which the source device 102 generates encoded video data for transmission to the destination device 116. The present disclosure refers to a "codec" device as a device that performs encoding and decoding (encoding and / or decoding) of data. Therefore, the video encoder 200 and the video decoder 300 represent examples of codec devices, in particular video encoders and video decoders, respectively. In some examples, the source device 102 and the destination device 116 may operate in a substantially symmetrical manner, such that each of the source device 102 and the destination device 116 includes video encoding and decoding components. Therefore, the system 100 may support one-way or two-way video transmission between the source device 102 and the destination device 116, such as for video streaming, video playback, video broadcasting, or video telephony.

[0027] Typically, video source 104 represents a source of video data (i.e., raw, unencoded video data) and provides a series of consecutive pictures (also referred to as "frames") of video data to video encoder 200, which encodes the data of the pictures. Video source 104 of source device 102 may include a video capture device, such as a camera, a video archive containing previously captured raw video, and / or a video feed interface for receiving video from a video content provider. As another alternative, video source 104 may generate computer graphics-based data as source video, or a combination of live video, archived video, and computer-generated video. In each case, video encoder 200 encodes captured, pre-captured, or computer-generated video data. Video encoder 200 may rearrange pictures from the order in which they are received (sometimes referred to as "display order") into a codec order for encoding and decoding. Video encoder 200 may generate a bitstream including encoded video data. Source device 102 may then output the encoded video data onto computer-readable medium 110 via output interface 108 for receipt and / or retrieval by input interface 122 , such as destination device 116 .

[0028] The memory 106 of the source device 102 and the memory 120 of the destination device 116 represent general purpose memories. In some examples, the memories 106, 120 may store raw video data, such as raw video from the video source 104 and raw decoded video data from the video decoder 300. Additionally or alternatively, the memories 106, 120 may store software instructions that may be executed by, for example, the video encoder 200 and the video decoder 300, respectively. Although the memories 106 and 120 are shown separately from the video encoder 200 and the video decoder 300 in this example, it should be understood that the video encoder 200 and the video decoder 300 may also include internal memory for functionally similar or equivalent purposes. In addition, the memories 106, 120 may store encoded video data, such as output from the video encoder 200 and input to the video decoder 300. In some examples, portions of the memories 106, 120 may be allocated as one or more video buffers, such as to store raw, decoded, and / or encoded video data.

[0029] The computer-readable medium 110 may represent any type of medium or device capable of transmitting the encoded video data from the source device 102 to the destination device 116. In one example, the computer-readable medium 110 represents a communication medium that enables the source device 102 to send the encoded video data directly to the destination device 116 in real time, for example, via a radio frequency network or a computer-based network. According to a communication standard (such as a wireless communication protocol), the output interface 108 can modulate a transmission signal including the encoded video data, and the input interface 122 can demodulate the received transmission signal. The communication medium may include any wireless or wired communication medium, such as a radio frequency (RF) spectrum or one or more physical transmission lines. The communication medium may 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 may include a router, a switch, a base station, or any other device that can be used to facilitate communication from the source device 102 to the destination device 116.

[0030] In some examples, source device 102 may output the encoded data from output interface 108 to storage device 112. Similarly, destination device 116 may access the encoded data from storage device 112 via input interface 122. Storage device 112 may 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.

[0031] In some examples, source device 102 may output the encoded video data to a file server 114 or another intermediate storage device that may store the encoded video data generated by source device 102. Destination device 116 may access the stored video data from file server 114 via streaming or download.

[0032] The file server 114 may be any type of server device capable of storing encoded video data and sending the encoded video data to the destination device 116. The file server 114 may represent a web server (e.g., for a website), a server configured to provide a file transfer protocol service (such as the File Transfer Protocol (FTP) or the File Transfer over Unidirectional Transport (FLUTE) protocol), a content delivery network (CDN) device, a hypertext transfer protocol (HTTP) server, a Multimedia Broadcast Multicast Service (MBMS) or an enhanced MBMS (eMBMS) server, and / or a network attached storage (NAS) device. The file server 114 may additionally or alternatively implement one or more HTTP streaming protocols, such as HTTP Dynamic Adaptive Streaming (DASH), HTTP Live Streaming (HLS), Real-Time Streaming Protocol (RTSP), HTTP Dynamic Streaming, etc.

[0033] Destination device 116 may access the encoded video data from file server 114 through any standard data connection, including an Internet connection. This may include a wireless channel (e.g., a Wi-Fi connection), a wired connection (e.g., a digital subscriber line (DSL), a cable modem, etc.), or a combination of both, suitable for accessing the encoded video data stored on file server 114. Input interface 122 may be configured to operate according to any one or more of the various protocols discussed above for retrieving or receiving media data from file server 114 or other such protocols for retrieving media data.

[0034] Output interface 108 and input interface 122 may represent wireless transmitters / receivers, modems, wired networking components (e.g., Ethernet cards), wireless communication components that operate according to any of the various IEEE 802.11 standards, or other physical components. In examples where output interface 108 and input interface 122 include wireless components, output interface 108 and input interface 122 may be configured to transmit data (such as encoded video data) according to a cellular communication standard (such as 4G, 4G-LTE (Long Term Evolution), LTE Advanced, 5G, etc.). In some examples where output interface 108 includes a wireless transmitter, output interface 108 and input interface 122 may be configured to transmit data (such as encoded video data) according to other wireless standards (e.g., IEEE 802.11 specifications, IEEE 802.15 specifications (e.g., ZigBee TM ), Bluetooth TM 108). In some examples, source device 102 and / or destination device 116 may include respective system-on-chip (SoC) devices. For example, source device 102 may include a SoC device for performing functions attributed to video encoder 200 and / or output interface 108, and destination device 116 may include a SoC device for performing functions attributed to video decoder 300 and / or input interface 122.

[0035] The techniques disclosed herein may be applied to support video encoding and decoding for 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 Dynamic Adaptive Streaming (DASH)), digital video encoded onto data storage media, decoding of digital video stored on data storage media, or other applications.

[0036] The input interface 122 of the destination device 116 receives the encoded video bitstream from the computer-readable medium 110 (e.g., a communication medium, a storage device 112, a file server 114, etc.). The encoded video bitstream may include signaling information defined by the video encoder 200, which is also used by the video decoder 300, such as syntax elements with values ​​describing characteristics and / or processing of video blocks or other coding units (e.g., slices, pictures, groups of pictures, sequences, etc.). The display device 118 displays decoded pictures of the decoded video data to a 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.

[0037] although Figure 1 Not shown, but in some examples, video encoder 200 and video decoder 300 may each be integrated with an audio encoder and / or audio decoder, and may include appropriate MUX-DEMUX units or other hardware and / or software to process a multiplexed stream including both audio and video in a common data stream.

[0038] The video encoder 200 and the video decoder 300 may each be implemented as any of a variety of suitable encoder and / or decoder circuits, such as one or more microprocessors, digital signal processors (DSPs) application specific integrated circuits (ASICs) field programmable gate arrays (FPGAs), discrete logic, software, hardware, firmware, or any combination thereof. When the technology is implemented partially in software, the device may store instructions for the software in a suitable non-transitory computer-readable medium and use one or more processors to execute the instructions in hardware to perform the technology of the present disclosure. Each of the video encoder 200 and the video decoder 300 may be included in one or more encoders or decoders, any of which may be integrated as part of a combined encoder / decoder (CODEC) in the corresponding device. A device including the video encoder 200 and / or the video decoder 300 may include an integrated circuit, a microprocessor, and / or a wireless communication device, such as a cellular phone.

[0039] The video encoder 200 and the video decoder 300 may operate according to a video coding standard such as ITU-T H.265, also known as high-efficiency video coding (HEVC) or an extension thereof, such as multi-view and / or scalable video coding extension. Alternatively, the video encoder 200 and the video decoder 300 may operate according to other proprietary or industry standards such as ITU-T H.266, also known as universal video coding (VVC). In other examples, the video encoder 200 and the video decoder 300 may operate according to a proprietary video codec / format such as AOMedia Video 1 (AV1), an extension of AV1, and / or a successor version of AV1 (e.g., AV2). In other examples, the video encoder 200 and the video decoder 300 may operate according to other proprietary formats or industry standards. However, the technology of the present disclosure is not limited to any particular codec standard or format. In general, the video encoder 200 and the video decoder 300 may be configured to perform the technology of the present disclosure in conjunction with any video codec technology that encodes and decodes video data using affine motion compensation.

[0040] Typically, the video encoder 200 and the video decoder 300 may perform block-based encoding of a picture. The term "block" generally refers to a structure that includes data to be processed (e.g., encoded, decoded, or otherwise used in an encoding and / or decoding process). For example, a block may include a two-dimensional matrix of samples of luminance and / or chrominance data. Typically, the video encoder 200 and the video decoder 300 may encode video data represented in a YUV (e.g., Y, Cb, Cr) format. That is, the video encoder 200 and the video decoder 300 may encode luminance components and chrominance components instead of encoding red, green, and blue (RGB) data of samples of a picture, wherein the chrominance components may include both red hue chrominance components and blue hue chrominance components. In some examples, the video encoder 200 converts the received RGB formatted data to a YUV representation before encoding, and the video decoder 300 converts the YUV representation to an RGB format. Alternatively, a pre-processing and post-processing unit (not shown) may perform these conversions.

[0041] The present disclosure may generally refer to the encoding and decoding of a picture (e.g., encoding and decoding) to include the process of encoding or decoding the data of a picture. Similarly, the present disclosure may refer to the encoding and decoding of a block of a picture to include the process of encoding or decoding the data of the block, such as prediction and / or residual encoding and decoding. The encoded video bitstream generally includes a series of values ​​for syntax elements that represent codec decisions (e.g., codec mode) and partitioning of the picture into blocks. Therefore, references to encoding and decoding a picture or a block should generally be understood to be encoding and decoding the values ​​of the syntax elements that form the picture or block.

[0042] HEVC defines various blocks, including coding units (CUs), prediction units (PUs), and transform units (TUs). According to HEVC, a video codec (such as the video encoder 200) divides a coding tree unit (CTU) into CUs according to a quadtree structure. That is, the video codec partitions the CTU and the CU into four equal, non-overlapping squares, and each node of the quadtree has zero or four child nodes. A node without child nodes may be referred to as a "leaf node", and the CU of such a leaf node may include one or more PUs and / or one or more TUs. The video codec may further partition the PU and the TU. For example, in HEVC, a residual quadtree (RQT) represents the partitioning of a TU. In HEVC, a PU represents inter-frame prediction data, and a TU represents residual data. An intra-predicted CU includes intra-frame prediction information, such as an intra-frame mode indication.

[0043] As another example, the video encoder 200 and the video decoder 300 may be configured to operate according to VVC. According to VVC, a video encoder (such as the video encoder 200) divides a picture into a plurality of coding tree units (CTUs). The video encoder 200 may partition the CTU according to a tree structure (e.g., a quadtree-binary tree (QTBT) structure or a multi-type tree (MTT) structure). The QTBT structure removes the concept of multiple partition types, such as the separation between CU, PU, ​​and TU of HEVC. The QTBT structure includes two levels: a first level partitioned according to quadtree partitioning and a second level partitioned according to binary tree partitioning. The root node of the QTBT structure corresponds to the CTU. The leaf nodes of the binary tree correspond to coding units (CUs).

[0044] In the MTT partitioning structure, blocks can be partitioned using quadtree (QT) partitioning, binary tree (BT) partitioning, and one or more types of ternary tree (TT) (also known as ternary tree (TT)) partitioning. A ternary tree or ternary tree partition is a partition in which a block is split into three sub-blocks. In some examples, the ternary tree or ternary tree partition divides the block into three sub-blocks without dividing the original block through the center. The partition types in MTT (e.g., QT, BT, and TT) can be symmetric or asymmetric.

[0045] When operating according to the AV1 codec, the video encoder 200 and the video decoder 300 may be configured to encode video data in blocks. In AV1, the largest codec block that can be processed is called a super block. In AV1, a super block may be 128×128 luma samples or 64×64 luma samples. However, in subsequent video codec formats (e.g., AV2), super blocks may be defined by different (e.g., larger) luma sample sizes. In some examples, the super block is the top level of the block quadtree. The video encoder 200 may also divide the super block into smaller codec blocks. The video encoder 200 may divide the super block and other codec blocks into smaller blocks using square or non-square partitioning. Non-square blocks may include N / 2×N, N×N / 2, N / 4×N, and N×N / 4 blocks. The video encoder 200 and the video decoder 300 may perform separate prediction and transform processing on each codec block.

[0046] AV1 also defines tiles of video data. A tile is a rectangular array of super blocks that can be encoded and decoded independently of other tiles. That is, the video encoder 200 and the video decoder 300 can encode and decode the codec blocks within the tile, respectively, without using video data from other tiles. However, the video encoder 200 and the video decoder 300 can perform filtering across tile boundaries. The size of the tile can be uniform or non-uniform. Tile-based encoding can enable parallel processing and / or multi-threading for encoder and decoder implementations.

[0047] In some examples, the video encoder 200 and the video decoder 300 may use a single QTBT or MTT structure to represent each of the luma component and the chroma components, while in other examples, the video encoder 200 and the video decoder 300 may use two or more QTBT or MTT structures, such as one QTBT / MTT structure for the luma component and another QTBT / MTT structure for the two chroma components (or two QTBT / MTT structures for each chroma component).

[0048] The video encoder 200 and the video decoder 300 may be configured to use quadtree partitioning, QTBT partitioning, MTT partitioning, super block partitioning, or other partitioning structures.

[0049] In some examples, a CTU includes a codec tree block (CTB) of luma samples, two corresponding CTBs of chroma samples for a picture with three sample arrays, or a CTB of samples for a monochrome picture or a picture encoded using three separate color planes and a syntax structure for encoding and decoding samples. A CTB may be an N×N block of samples for some value of N, such that the division of a component into a CTB is a partition. A component may be an array or a single sample of one of the three arrays (luminance and two chroma) for a picture in 4:2:0, 4:2:2, or 4:4:4 color format, or an array or a single sample of an array for a picture in monochrome format. In some examples, a codec block is an M×N block of samples for some values ​​of M and N, such that the division of a CTB into a codec block is a partition.

[0050] Blocks (e.g., CTUs or CUs) may be grouped in a picture in various ways. As an example, a block may refer to a rectangular region of a CTU row within a particular tile in a picture. A tile may be a rectangular region of a CTU within a particular tile column and a particular tile row in a picture. A tile column refers to a rectangular region of a CTU having a height equal to the height of the picture and a width specified by a syntax element (such as in a picture parameter set). A tile row refers to a rectangular region of a CTU having a height specified by a syntax element (such as in a picture parameter set) and a width equal to the width of the picture.

[0051] In some examples, a tile may be partitioned into multiple bricks, each of which may include one or more CTU rows within the tile. Tiles that are not partitioned into multiple bricks may also be referred to as bricks. However, bricks that are true subsets of tiles may not be referred to as tiles. Bricks in a picture may also be arranged in slices. A slice may be an integer number of bricks of a picture, which may be exclusively included in a single network abstraction layer (NAL) unit. In some examples, a slice includes a continuous sequence of several complete tiles or only complete bricks of one tile.

[0052] This disclosure may use "N×N" and "N by N" interchangeably to refer to the sample dimensions of a block (e.g., a CU or other video block) in terms of vertical and horizontal dimensions, such as 16×16 samples or 16 by 16 samples. Typically, a 16×16 CU will have 16 samples in the vertical direction (y=16) and 16 samples in the horizontal direction (x=16). Likewise, an N×N CU typically has N samples in the vertical direction and N samples in the horizontal direction, where N represents a non-negative integer value. The samples in a CU may be arranged in rows and columns. Furthermore, a CU does not necessarily need to have the same number of samples in the horizontal direction as in the vertical direction. For example, a CU may include N×M samples, where M is not necessarily equal to N.

[0053] The video encoder 200 encodes the video data of the CU representing the prediction and / or residual information and other information. The prediction information indicates how to predict the CU in order to form the prediction block of the CU. The residual information generally indicates the sample-by-sample difference between the samples of the CU before encoding and the prediction block.

[0054] In order to predict a CU, the video encoder 200 may typically form a prediction block for the CU by inter-frame prediction or intra-frame prediction. Inter-frame prediction generally refers to predicting a CU from data of a previously coded picture, while intra-frame prediction generally refers to predicting a CU from previously coded data of the same picture. In order to perform inter-frame prediction, the video encoder 200 may use one or more motion vectors to generate a prediction block. The video encoder 200 may typically perform a motion search to identify a reference block that closely matches the CU, for example, in terms of the difference between the CU and the reference block. The video encoder 200 may calculate a difference metric using the sum of absolute differences (SAD), the sum of squared differences (SSD), the mean absolute difference (MAD), the mean squared difference (MSD), or other such difference calculations to determine whether the reference block closely matches the current CU. In some examples, the video encoder 200 may use unidirectional prediction or bidirectional prediction to predict the current CU.

[0055] Some examples of VVC also provide an affine motion compensation mode, which can be considered an inter-prediction mode. In the affine motion compensation mode, the video encoder 200 can determine two or more motion vectors representing non-translational motion, such as zooming in or out, rotation, perspective motion, or other irregular motion types.

[0056] According to the techniques of the present disclosure, the video encoder 200 may determine that affine motion compensation will be used to predict a block of video data. For example, the video encoder 200 may test various prediction and encoding schemes on a block (or region of a frame) and determine that affine motion compensation produces the best performance in the tested prediction mode of the block. The video encoder 200 may further determine whether affine motion compensation should be performed on a sub-block basis for the block, or on an individual pixel basis for the block. That is, the video encoder 200 may form motion information for the block, and the motion information may be used for sub-blocks that are larger in size than individual pixels (i.e., larger than 1×1), or for individual pixels.

[0057] In general, video encoder 200 may encode data representing motion information for a block. For example, video encoder 200 may encode data representing whether two, three, or another number of motion vectors will be used to predict a block, such as described below with respect to Figure 2A and Figure 2BDiscussed in more detail. The video encoder 200 may further determine whether to perform sub-block based affine motion compensation or to perform affine motion compensation based on individual pixels. In the case of sub-block based affine motion compensation, the video encoder 200 may calculate the corresponding motion vector of each sub-block of the block from the determined motion vector, as discussed in more detail below. In addition, the video encoder 200 may perform overlapped block motion compensation (OBMC) when performing sub-block based affine motion compensation, and encode the value of the OBMC syntax element (e.g., OBMC flag) of the block to indicate that the motion information is applied to the sub-block of the block and that both OBMC will be performed for the block during decoding. In the case of affine motion compensation based on individual pixels, the video encoder 200 may avoid performing OBMC and may encode the value of the OBMC syntax element to indicate that the motion information is applied to the individual pixels of the block and that both OBMC will not be performed on the block during decoding. Then, the video encoder 200 may generate a prediction block using affine motion compensation with or without OBMC as described above.

[0058] To perform intra prediction, the video encoder 200 may select an intra prediction mode to generate a prediction block. Some examples of VVC provide sixty-seven intra prediction modes, including various directional modes, as well as a plane mode and a DC mode. Typically, the video encoder 200 selects an intra prediction mode that describes neighboring samples of a current block (e.g., a block of a CU), where the samples of the current block are predicted according to the intra prediction mode. Assuming that the video encoder 200 encodes CTUs and CUs in a raster scan order (from left to right, from top to bottom), such samples may typically be at the top, upper left, or left side of the current block in the same picture as the current block.

[0059] The video encoder 200 encodes data representing the prediction mode of the current block. For example, for inter-frame prediction mode, the video encoder 200 may encode data indicating which of various available inter-frame prediction modes is used and motion information of the corresponding mode. For example, for unidirectional or bidirectional inter-frame prediction, the video encoder 200 may encode motion vectors using advanced motion vector prediction (AMVP) or merge mode. The video encoder 200 may use a similar mode to encode motion vectors for affine motion compensation mode.

[0060] AV1 includes two conventional techniques for encoding and decoding codec blocks of video data. The two conventional techniques are intra prediction (e.g., intra prediction or spatial prediction) and inter prediction (e.g., inter prediction or temporal prediction). In the context of AV1, when predicting a block of a current video data frame using an intra prediction mode, the video encoder 200 and the video decoder 300 do not use video data from other video data frames. For most intra prediction modes, the video encoder 200 encodes a block of the current frame based on the difference between the sample values ​​in the current block and the predicted values ​​generated from the reference samples in the same frame. The video encoder 200 determines the predicted values ​​generated from the reference samples based on the intra prediction mode.

[0061] After prediction of a block (such as intra-frame prediction or inter-frame prediction of the block), the video encoder 200 may calculate residual data for the block. The residual data (such as a residual block) represents the sample-by-sample difference between the block and the predicted block of the block formed using the corresponding prediction mode. The video encoder 200 may apply one or more transforms to the residual block to generate transform data in a transform domain rather than a sample domain. For example, the video encoder 200 may apply a discrete cosine transform (DCT), an integer transform, a wavelet transform, or a conceptually similar transform to the residual video data. In addition, the video encoder 200 may apply a secondary transform after the first transform, such as a mode-dependent non-separable secondary transform (MDNSST), a signal-dependent transform, a Karhunen-Loeve transform (KLT), etc. The video encoder 200 generates transform coefficients after applying one or more transforms.

[0062] As described above, after any transform to produce transform coefficients, the video encoder 200 may perform quantization of the transform coefficients. Quantization generally refers to the process of quantizing the transform coefficients to potentially reduce the amount of data used to represent the transform coefficients, thereby providing further compression. By performing the quantization process, the video encoder 200 may reduce the bit depth associated with some or all of the transform coefficients. For example, the video encoder 200 may round down an n-bit value to an m-bit value during quantization, where n is greater than m. In some examples, to perform quantization, the video encoder 200 may perform a bitwise right shift of the value to be quantized.

[0063] After quantization, the video encoder 200 may scan the transform coefficients to produce a one-dimensional vector from a two-dimensional matrix including the quantized transform coefficients. The scan may be designed to place higher energy (and therefore lower frequency) transform coefficients at the front of the vector and lower energy (and therefore higher frequency) transform coefficients at the back of the vector. In some examples, the video encoder 200 may scan the quantized transform coefficients using a predefined scan order to produce a serialized vector, and then entropy encode the quantized transform coefficients of the vector. In other examples, the video encoder 200 may perform an adaptive scan. After scanning the quantized transform coefficients to form a one-dimensional vector, the video encoder 200 may entropy encode the one-dimensional vector, for example, according to context adaptive binary arithmetic coding (CABAC). The video encoder 200 may also entropy encode the values ​​of syntax elements describing metadata associated with the encoded video data for use by the video decoder 300 when decoding the video data.

[0064] To perform CABAC, video encoder 200 may assign context within a context model to a symbol to be sent. The context may relate to, for example, whether neighboring values ​​of the symbol are zero values. The probability determination may be based on the context assigned to the symbol.

[0065] The video encoder 200 may also generate syntax data, such as block-based syntax data, picture-based syntax data, and sequence-based syntax data, such as in a picture header, a block header, a slice header, or other syntax data, such as a sequence parameter set (SPS), a picture parameter set (PPS), or a video parameter set (VPS), to the video decoder 300. The video decoder 300 may also decode such syntax data to determine how to decode the corresponding video data.

[0066] In this way, the video encoder 200 can generate a bitstream including encoded video data, such as syntax elements describing the division of a picture into blocks (e.g., CUs) and prediction and / or residual information for the blocks. Finally, the video decoder 300 can receive the bitstream and decode the encoded video data.

[0067] In general, the video decoder 300 performs a process that is inverse to that performed by the video encoder 200 to decode the encoded video data of the bitstream. For example, the video decoder 300 may decode values ​​of syntax elements of the bitstream using CABAC in a manner substantially similar to, but inverse to, the CABAC encoding process of the video encoder 200. The syntax elements may define partitioning information for partitioning a picture into CTUs and partitioning each CTU according to a corresponding partitioning structure (such as a QTBT structure) to define CUs of the CTUs. The syntax elements may further define prediction and residual information for a block (e.g., a CU) of video data.

[0068] The residual information may be represented by, for example, quantized transform coefficients. The video decoder 300 may inverse quantize and inverse transform the quantized transform coefficients of the block to reproduce a residual block of the block. The video decoder 300 uses the signaled prediction mode (intra-frame or inter-frame prediction) and related prediction information (e.g., motion information for inter-frame prediction) to form a prediction block for the block.

[0069] The video decoder 300 may, for example, determine that affine motion compensation will be used to predict the current block. According to the technology of the present disclosure, the video decoder 300 may decode the motion information of the current block from the bitstream. The video decoder 300 may also determine whether the motion information is for a sub-block whose size is larger than each pixel of the block, or for each pixel itself. For example, the video decoder 300 may determine the value of an OBMC syntax element (e.g., an OBMC flag). If the OBMC flag has a value indicating that OBMC will be performed for the block, the video decoder 300 may implicitly determine that the motion information is for the sub-block, and if the OBMC flag has a value indicating that OBMS will not be performed for the block, the video decoder 300 may implicitly determine that the motion information is for each pixel. Then, the video decoder 300 may perform affine motion compensation for the determined sub-block or for each pixel with or without OBMC to generate a prediction block for the block.

[0070] The video decoder 300 may then combine the prediction block and the residual block (on a sample-by-sample basis) to reproduce the original block.The video decoder 300 may perform additional processing, such as performing a deblocking process to reduce visual artifacts along the boundaries of blocks.

[0071] The present disclosure may generally refer to "signaling" certain information, such as syntax elements. The term "signaling" may generally refer to the communication of values ​​of syntax elements and / or other data used to decode encoded video data. That is, video encoder 200 may signal the values ​​of syntax elements in a bitstream. Generally, signaling refers to producing the values ​​in the bitstream. As mentioned above, source device 102 may transmit the bitstream to destination device 116 in substantially real time or non-real time, such as may occur when storing syntax elements to storage device 112 for later retrieval by destination device 116.

[0072] Figure 2A and 2B is a conceptual diagram showing an example of a control point motion vector (CPMV) for affine motion compensation. In particular, Figure 2A Describe the three CPMV V to be used 0 、V 1 and V 2 The predicted current block 130, and Figure 2B Describe the four CPMVVs to be used 0 、V 1 、V2 and V 3 The predicted current block 132 .

[0073] The affine motion model can be described as:

[0074]

[0075] Where (v x ,v y ) is the motion vector at coordinate (x, y), and a, b, c, d, e, and f are six parameters. This affine motion model is called a 6-parameter affine motion model. In a typical video codec, a picture is divided into blocks for block-based coding and decoding. The affine motion model of a block can also be composed of 3 motion vectors (MV) at 3 different positions that are not in the same row Description. The three positions are often called control points, and the three motion vectors are called control point motion vectors (CPMV).

[0076] At the three control points located at Figure 2A In the case of the 3 corners of the block shown, the affine motion can be described as:

[0077]

[0078] Where blkW and blkH represent the width and height of the block respectively.

[0079] The simplified 4-parameter affine model (for scaling and rotational motion) can be described as:

[0080]

[0081] Similarly, the simplified 4-parameter affine model of the block can be obtained by the two CPMVs at the two corners of the block Description. The playing field can then be described as:

[0082]

[0083] Given an affine motion model for a block, a different motion vector may be derived for each pixel in the block. Thus, motion compensation may be performed pixel by pixel. However, to reduce complexity, sub-block based motion compensation may be used, where the block is partitioned into multiple sub-blocks (which have a smaller block size) and each sub-block is associated with one motion vector for motion compensation. That is, a block may have a single set of overhead data (which may, for example, indicate that the block is predicted using affine motion compensation), but each sub-block of the block may be predicted separately using corresponding motion information.

[0084] The (multiple) motion vectors for each sub - block can be derived using the representative coordinates of the sub - blocks. For example, the center position can be used. In one example, a block is divided into non - overlapping sub - blocks. The block width is blkW, the block height is blkH, the sub - block width is sbW and the sub - block height is sbH, resulting in blkH / sbH rows of sub - blocks and blkW / sbW sub - blocks in each row. For a six - parameter affine motion model, the motion vector of the sub - block (referred to as sub - block MV) at the i - th row (0 <= i < blkW / sbW) and the j - th column (0 <= j < blkH / sbH) can be derived as:

[0085]

[0086] After performing sub - block - based affine motion compensation, the prediction signal can be refined by adding an offset derived based on the gradients of per - pixel motion and the prediction signal, such as according to Prediction Refinement using Optical Flow (PROF). The offset at position (m,n) can be calculated as:

[0087] ΔI(m,n) = g x (m,n)*Δv x (m,n)+g y (m,n)*Δv y (m,n)

[0088] where g x (m,n) and g y (m,n) are the horizontal and vertical gradients of the prediction signal respectively. Δv x (m,n) and Δv y (m,n) are the differences in the x and y components between the motion vector calculated at the position pixel position (m,n) and the sub - block MV.

[0089] Let the coordinates of the top - left sample of the sub - block be (0,0), and the center of the sub - block be Given the affine motion parameters a, b, c, and d, Δv x (m,n) and Δv y (m,n) can be derived as:

[0090]

[0091] In a control - point - based affine motion model, the affine motion parameters a, b, c, and d can be calculated from CPMV as:

[0092]

[0093] When overlapped block motion compensation (OBMC) is applied, the top and left boundary pixels of the CU are refined using motion information of neighboring blocks using weighted prediction, as described in "CE10.2.1: OBMC" by Lin et al. (Joint Video Experts Team (JVET) of ITU-T SG 16WP 3 and ISO / IEC JTC 1 / SC 29 / WG 11, 12th Meeting: Macau, CN, Document No. JVET-L0101, October 3-12, 2018). According to JVET-L0101, when OBMC is disabled at the sequence parameter set (SPS) level, when the current block is predicted using intra mode or intra block copy (IBC) mode, when the current block is predicted using local illumination compensation (LIC), or when the current luma block area is less than or equal to 32, OBMC is not applied.

[0094] Sub-block boundary OBMC is performed by applying the same blending to the top, left, bottom, and right sub-block boundary pixels using the neighboring sub-block motion information. Sub-block boundary OBMC is enabled for sub-block based codec tools such as affine AMVP mode, affine merge mode, and sub-block based temporal motion vector prediction (SbTMVP) and sub-block based bilateral matching.

[0095] When OBMC mode is used in combined intra and inter prediction (CIIP) mode with luma mapping and chroma signaling (LMCS), inter blending may be performed before LMCS mapping of inter samples. LMCS may be applied to blended inter samples combined with intra samples to which LMCS is applied in CIIP mode as follows:

[0096]

[0097] Among them, Inter predY represents the samples predicted by the motion of the current block in the original domain, Intra predY Represents the sample predicted in the mapping domain, OBMC predY represents the samples predicted by the motion of the neighboring blocks in the original domain, and w 0 and w 1 is the weight.

[0098] Local illumination compensation (LIC) is an inter-prediction technique used to model the local illumination variation between the current block and its prediction block according to the local illumination variation between the current block template and the reference block template. The parameters of the function can be represented by a scale α and an offset β, which form a linear equation, i.e., α*p[x]+β, to compensate for illumination variation, where p[x] is the reference sample at position x on the reference picture pointed to by MV. Since α and β can be derived based on the current block template and the reference block template, no signaling overhead for them is required except for signaling the LIC flag for AMVP mode to indicate the use of LIC.

[0099] The local illumination compensation proposed in Seregin et al., "CE4-3.1a and CE4-3.1b: Unidirectional local illumination compensation with affine prediction" (Joint Video Experts Team (JVET) 15th Meeting of ITU-T SG 16WP 3 and ISO / IEC JTC 1 / SC 29 / WG 11: Gothenburg, SE, July 3-12, 2019, document number JVET-O0066) is used for unidirectionally predicted inter-CU with the following modifications: intra-frame neighboring samples can be used for LIC parameter derivation; LIC is disabled for blocks with less than 32 luma samples; and for both non-sub-block and affine modes, LIC parameter derivation is performed based on the template block samples corresponding to the current CU instead of the partial template block samples corresponding to the first upper left 16×16 unit. Samples of a reference block template may be generated using motion compensation (MC) with a block motion vector (MV) without rounding the MV to integer pixel (pel) precision.

[0100] In the multi-hypothesis inter prediction (MHP) mode, as described in Winken et al., "CE10: Multi-hypothesis inter prediction (Test 10.1.2)" (Joint Video Experts Team (JVET) 13th Meeting of ITU-T SG 16WP 3 and ISO / IEC JTC 1 / SC29 / WG 11: Marrakech, MA, January 9-18, 2019, Document No.: JVET-M0425), in addition to the traditional bidirectional prediction signal, one or more additional motion compensated prediction signals are signaled. The resulting overall prediction signal is obtained by sample-by-sample weighted superposition. Using the bidirectional prediction signal p bi and the first additional inter-frame prediction signal / hypothesis h 3 , the resulting prediction signal p is obtained as follows3 :

[0101] p 3 =(1-α)p bi +αh 3

[0102] The weighting factor α is specified by the syntax element add_hyp_weight_idx according to the following mapping:

[0103] add_hyp_weight_idx α 0 1 / 4 1 -1 / 8

[0104] Similar to the above, more than one additional prediction signal may be used. The resulting overall prediction signal is iteratively accumulated with each additional prediction signal as follows:

[0105] p n+1 =(1-α n+1 ) n +α n+1 h n+1

[0106] The resulting overall prediction signal is used as the final p n (i.e., the p with the largest index n n ) is obtained. A maximum of two additional prediction signals may be used (ie, n is limited to 2).

[0107] The motion parameters for each additional prediction hypothesis can be signaled explicitly by specifying the reference index, motion vector predictor index and motion vector difference, or implicitly by specifying the merge index. A separate multiple hypothesis merge flag distinguishes these two signaling modes.

[0108] For inter-AMVP mode, according to JVET-M0425, MHP is only applied if unequal weights in BCW are selected in bi-prediction mode.

[0109] A combination of MHP and Bidirectional Optical Flow (BDOF) is possible. However, according to JVET-M0425, BDOF is only applied to the bidirectional prediction signal part of the prediction signal (i.e., the ordinary first two hypotheses).

[0110] Figure 3 1 is a conceptual diagram illustrating an example motion compensation process 140. The affine prediction block may be derived by applying one or several methods, such as: pixel-based affine MC, block-based affine MC, PROF, LIC, weighted bidirectional prediction, OBMC, and MHP. In one coding model, Figure 3 The derived affine prediction blocks are shown, where dashed blocks are optionally applied.

[0111] Subblock-based affine MC has lower prediction accuracy than pixel-based affine MC, and subblock-based affine MC may encounter certain prediction problems at subblock boundaries within a codec block. OBMC is a method that can compensate for prediction inconsistencies at subblock boundaries; however, some video codecs consider OBMC optional to apply to codec blocks. For example, when an affine codec block will apply LIC, it may be implicitly determined that OBMC should not be applied to the codec block.

[0112] Figure 4 1 is a conceptual diagram illustrating another example motion compensation process 150. The present disclosure describes various techniques for deriving affine prediction blocks. The present disclosure includes several constraints on applying methods such as OBMC, MHP, and / or PROF to affine prediction blocks. The techniques of the present disclosure may be applied to both luma and chroma channels or only to the luma channel. The video encoder 200 and / or the video decoder 300 may be configured to perform any of the various techniques discussed below, alone or in any combination.

[0113] like Figure 4 As shown in , initially, a block to be affine motion compensated is predicted using sub-block based affine motion compensation or pixel based affine motion compensation. Figure 4 In the example of , if the block is to be predicted using sub-block based affine motion compensation, the video encoder 200 or the video decoder 300 may determine whether to apply PROF to the block. Then, the video encoder 200 or the video decoder 300 may determine to apply weighted bidirectional prediction, followed by OBMC or LIC, followed by MHP. On the other hand, according to Figure 4 For example, if a block is to be predicted using pixel-based affine motion compensation, the video encoder 200 or the video decoder 300 may determine to apply weighted bi-directional prediction followed by MHP or LIC followed by MHP without performing PROF.

[0114] In one example, the affine prediction block is derived by applying sub-block based affine MC or pixel based affine MC, and the pixel based affine MC is selected to be used when it is determined that OBMC is not applied to the affine prediction block.

[0115] In one example, the minimum sub-block size of the affine block is predetermined to be 1×1. When the motion difference between two pixels is small enough so that motion compensation using the same motion vector does not make a big difference, the two pixels can be grouped into larger sub-blocks. That is, the video encoder 200 can, for example, increase the sub-block size to M×N, where M is in the range of 1 to the block width and N is in the range of 1 to the block height, including the end values.

[0116] In one example, when pixel-based affine MC is applied, it is implicitly determined that PROF is not applied.

[0117] In one example, when the minimum sub-block width is less than K (eg, K equals 4), it is implicitly determined that PROF is not applied.

[0118] In one example, when the minimum sub-block height is less than K (eg, K equals 4), it is implicitly determined that PROF is not applied.

[0119] In one example, when it is determined that the affine prediction block applies MHP, it is implicitly determined that OBMC is not applied.

[0120] In one example, when the block is determined to be an affine codec block, the OBMC flag is signaled as 0 or 1. Otherwise, the OBMC flag value is implicitly determined, for example, the OBMC flag value is equal to 1.

[0121] In one example, when the block is determined to be an affine coded block and not in merge prediction mode, the OBMC flag is signaled as 0 or 1. Otherwise, the OBMC flag value is implicitly determined, such as implicitly determined to be equal to 1.

[0122] In one example, when the block has a width equal to or greater than MAX_WIDTH_OBMC_ON_AFFINE (eg, 128) or a height equal to or greater than MAX_HEIGHT_OBMC_ON_AFFINE (eg, 128), it is determined that OBMC is not applied to the affine codec block.

[0123] In one example, when the POC distance between the reference picture and the current picture is greater than N (eg, N is equal to 1), pixel-based affine MC is applied to derive the prediction block.

[0124] In one example, the aforementioned technique(s) are only applied to non-low-latency pictures.

[0125] In one example, the OBMC flag is context-coded and different contexts are selected for use depending on whether the current picture is a low-delay picture or a non-low-delay picture.

[0126] In one example, the OBMC flag is context-coded and different contexts are selected to be used depending on whether the current block is an affine coded block or a non-affine coded block.

[0127] In one example, an affine codec block can be predicted by applying both LIC and OBMC. When LIC is applied to an affine block, OBMC is not applied to block boundaries (top block boundary and left block boundary), but OBMC is applied to sub-block boundaries.

[0128] Figure 5 is a block diagram illustrating an example video encoder 200 that may perform the techniques of this disclosure. Figure 5 The above description is provided for the purpose of explanation and should not be considered as limiting the techniques as broadly illustrated and described in this disclosure. For the purpose of explanation, this disclosure describes a video encoder 200 according to techniques of VVC (ITU-T H.266, under development) and HEVC (ITU-T H.265). However, the techniques of this disclosure may be performed by video encoding devices configured for other video codec standards and video codec formats, such as AV1 and successors of the AV1 video codec format.

[0129] exist Figure 5 In the example of , the video encoder 200 includes a video data memory 230, a mode selection unit 202, a residual generation unit 204, a transform processing unit 206, a quantization unit 208, an inverse quantization unit 210, an inverse transform processing unit 212, a reconstruction unit 214, a filter unit 216, a decoded picture buffer (DPB) 218, and an entropy coding unit 220. Any one or all of the video data memory 230, the mode selection unit 202, the residual generation unit 204, the transform processing unit 206, the quantization unit 208, the inverse quantization unit 210, the inverse transform processing unit 212, the reconstruction unit 214, the filter unit 216, the DPB 218, and the entropy coding unit 220 may be implemented in one or more processors or in processing circuits. For example, the units of the video encoder 200 may be implemented as one or more circuits or logic elements, as part of a hardware circuit, or as part of a processor, ASIC, or FPGA. In addition, the video encoder 200 may include additional or alternative processors or processing circuits to perform these and other functions.

[0130] Video data memory 230 may store video data to be encoded by components of video encoder 200. Video encoder 200 may receive video data from, for example, video source 104 ( Figure 1 ) receives video data stored in video data memory 230. DPB 218 may act as a reference picture memory that stores reference video data for predicting subsequent video data by video encoder 200. Video data memory 230 and DPB 218 may 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 may be provided by the same memory device or separate memory devices. In various examples, video data memory 230 may be on-chip with other components of video encoder 200 (as shown), or off-chip relative to those components.

[0131] In the present disclosure, references to the video data memory 230 should not be interpreted as limited to memory inside the video encoder 200, unless specifically described as such, or should not be interpreted as limited to memory outside the video encoder 200, unless specifically described as such. Instead, references to the video data memory 230 should be understood as a reference memory that stores video data received by the video encoder 200 for encoding (e.g., video data of a current block to be encoded). Figure 1 Memory 106 may also provide temporary storage of outputs from various units of video encoder 200 .

[0132] Figure 5 Various units are shown to help understand the operations performed by the video encoder 200. The units may be implemented as fixed-function circuits, programmable circuits, or a combination thereof. Fixed-function circuits refer to circuits that provide specific functionality and are preset on executable operations. Programmable circuits refer to circuits that can be programmed to perform various tasks and provide flexible functions in executable operations. For example, a programmable circuit may execute software or firmware that causes the programmable circuit to operate in a manner defined by instructions of the software or firmware. Fixed-function circuits may execute software instructions (e.g., to receive parameters or output parameters), but the type of operation performed by the fixed-function circuit is generally immutable. In some examples, one or more of the units may be different circuit blocks (fixed-function or programmable), and in some examples, one or more of the units may be integrated circuits.

[0133] The video encoder 200 may include an arithmetic logic unit (ALU), an elementary function unit (EFU), a digital circuit, an analog circuit, and / or a programmable core formed by a programmable circuit. In an example where the operation of the video encoder 200 is performed using software executed by a programmable circuit, the memory 106 ( Figure 1 ) may store instructions (eg, object code) for software received and executed by the video encoder 200, or another memory (not shown) within the video encoder 200 may store such instructions.

[0134] The video data memory 230 is configured to store received video data. The video encoder 200 may retrieve pictures of video data from the video data memory 230 and provide the video data to the residual generation unit 204 and the mode selection unit 202. The video data in the video data memory 230 may be original video data to be encoded.

[0135] Mode selection unit 202 includes motion estimation unit 222, motion compensation unit 224, and intra prediction unit 226. Mode selection unit 202 may include additional functional units for performing video prediction according to other prediction modes. As an example, mode selection unit 202 may include a palette unit, an intra-block copy unit (which may be part of motion estimation unit 222 and / or motion compensation unit 224), an affine unit, a linear model (LM) unit, etc. In some examples, motion compensation unit 224 may be configured to perform affine motion compensation according to any of the various techniques of this disclosure.

[0136] The mode selection unit 202 typically coordinates multiple encoding passes to test combinations of encoding parameters and the resulting rate-distortion values ​​of these combinations. The encoding parameters may include the partitioning of CTUs into CUs, the prediction mode of the CU, the transform type of the residual data of the CU, the quantization parameter of the residual data of the CU, etc. The mode selection unit 202 may ultimately select a combination of encoding parameters that has a better rate-distortion value than other tested combinations.

[0137] The video encoder 200 may partition the picture retrieved from the video data memory 230 into a series of CTUs and encapsulate one or more CTUs in a slice. The mode selection unit 202 may partition the CTUs of the picture according to a tree structure, such as an MTT structure, a QTBT structure, a super block structure, or a quadtree structure described above. As described above, the video encoder 200 may form one or more CUs by partitioning the CTUs according to the tree structure. Such CUs may also be generally referred to as "video blocks" or "blocks".

[0138] Typically, 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 the current block (e.g., the current CU, or in HEVC, the overlapping portion of the PU and TU). For inter prediction of the current block, the motion estimation unit 222 may perform a motion search to identify one or more closely matching reference blocks in one or more reference pictures (e.g., one or more previously coded pictures stored in the DPB 218). In particular, the motion estimation unit 222 may calculate values ​​representing how similar the potential reference blocks are to the current block, for example, based on the sum of absolute differences (SAD), the sum of squared differences (SSD), the mean absolute difference (MAD), the mean squared difference (MSD), etc. The motion estimation unit 222 may typically perform these calculations using the sample-by-sample differences between the current block and the reference block under consideration. The motion estimation unit 222 may identify the reference block having the lowest value resulting from these calculations (indicating the reference block that most closely matches the current block).

[0139] The motion estimation unit 222 may form one or more motion vectors (MVs) that define the position of a reference block in a reference picture relative to the position of a current block in a current picture. The motion estimation unit 222 may then provide the motion vectors to the motion compensation unit 224. For example, for unidirectional inter prediction, the motion estimation unit 222 may provide a single motion vector, while for bidirectional inter prediction, the motion estimation unit 222 may provide two motion vectors. The motion compensation unit 224 may then use the motion vectors to generate a prediction block. For example, the motion compensation unit 224 may use the motion vectors to retrieve data for the reference block. As another example, if the motion vector has fractional sample precision, the motion compensation unit 224 may interpolate the values ​​of the prediction block according to one or more interpolation filters. In addition, for bidirectional inter prediction, the motion compensation unit 224 may retrieve data for two reference blocks identified by the corresponding motion vectors and combine the retrieved data, for example, by sample-by-sample averaging or weighted averaging.

[0140] When operating according to the AV1 video codec format, the motion estimation unit 222 and the motion compensation unit 224 may be configured to encode codec blocks (e.g., both luma and chroma codec blocks) of the video data using translational motion compensation, affine motion compensation, overlapped block motion compensation (OBMC), and / or composite inter-intra prediction.

[0141] As another example, for intra prediction or intra prediction codec, the intra prediction unit 226 may generate a prediction block from samples adjacent to the current block. For example, for directional mode, the intra prediction unit 226 may generally mathematically combine the values ​​of adjacent samples and pad these calculated values ​​across the current block in a defined direction to generate a prediction block. As another example, for DC mode, the intra prediction unit 226 may calculate an average of adjacent samples of the current block and generate a prediction block to include the resulting average for each sample of the prediction block.

[0142] When operating according to the AV1 video coding format, the intra prediction unit 226 may be configured to encode codec blocks (e.g., luma and chroma codec blocks) of video data using directional intra prediction, non-directional intra prediction, recursive filter intra prediction, luma to chroma (CFL) prediction, intra block copy (IBC), and / or palette mode. The mode selection unit 202 may include additional functional units for performing video prediction according to other prediction modes.

[0143] The mode selection unit 202 provides the prediction block to the residual generation unit 204. The residual generation unit 204 receives the original uncoded version of the current block from the video data memory 230 and receives the prediction block from the mode selection unit 202. The residual generation unit 204 calculates the sample-by-sample difference between the current block and the prediction block. The resulting sample-by-sample difference defines a residual block for the current block. In some examples, the residual generation unit 204 may also determine the difference between the sample values ​​in the residual block to generate the residual block using residual differential pulse code modulation (RDPCM). In some examples, the residual generation unit 204 may be formed using one or more subtractor circuits that perform binary subtraction.

[0144] In the example where the mode selection unit 202 partitions the CU into PUs, each PU may be associated with a luma prediction unit and a corresponding chroma prediction unit. The video encoder 200 and the video decoder 300 may support PUs of various sizes. As indicated above, the size of the CU may refer to the size of the luma codec block of the CU, and the size of the PU may refer to the size of the luma prediction unit of the PU. Assuming that the size of a particular CU is 2N×2N, the video encoder 200 may support PU sizes of 2N×2N or N×N for intra-frame prediction, and symmetric PU sizes of 2N×2N, 2N×N, N×2N, N×N, or similar sizes for inter-frame prediction. The video encoder 200 and the video decoder 300 may also support asymmetric partitioning of PU sizes of 2N×nU, 2N×nD, nL×2N, and nR×2N for inter-frame prediction.

[0145] In an example where the mode selection unit 202 does not further partition a CU into PUs, each CU may be associated with a luma codec block and a corresponding chroma codec block. As described above, the size of a CU may refer to the size of the luma codec block of the CU. The video encoder 200 and the video decoder 300 may support CU sizes of 2N×2N, 2N×N, or N×2N.

[0146] For other video codec techniques, such as intra-block copy mode codec, affine mode codec, and linear model (LM) mode codec, as some examples, the mode selection unit 202 generates a prediction block for the current block being encoded via a corresponding unit associated with the codec technique. In some examples, such as palette mode codec, the mode selection unit 202 may not generate a prediction block, but instead generate syntax elements indicating how to reconstruct the block based on the selected palette. In such a mode, the mode selection unit 202 may provide these syntax elements to the entropy encoding unit 220 for encoding.

[0147] As described above, the residual generation unit 204 receives video data of a current block and a corresponding prediction block. Then, the residual generation unit 204 generates a residual block for the current block. To generate the residual block, the residual generation unit 204 calculates the sample-by-sample difference between the prediction block and the current block.

[0148] 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 may apply various transforms to the residual block to form a transform coefficient block. For example, transform processing unit 206 may apply a discrete cosine transform (DCT), a directional transform, a Karhunen-Loeve transform (KLT), or a conceptually similar transform to the residual block. In some examples, transform processing unit 206 may perform multiple transforms on the residual block, for example, a primary transform and a secondary transform, such as a rotation transform. In some examples, transform processing unit 206 does not apply a transform to the residual block.

[0149] When operating according to AV1, transform processing unit 206 may apply 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 may apply various transforms to the residual block to form a transform coefficient block. For example, transform processing unit 206 may apply a horizontal / vertical transform combination, which may include a discrete cosine transform (DCT), an asymmetric discrete sine transform (ADST), a flipped ADST (e.g., an ADST in reverse order), and an identity transform (IDTX). When an identity transform is used, a transform is skipped in one of the vertical or horizontal directions. In some examples, transform processing may be skipped.

[0150] Quantization unit 208 may quantize transform coefficients in a transform coefficient block to produce a quantized transform coefficient block. Quantization unit 208 may quantize the 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 selection unit 202) may adjust the degree of quantization applied to the transform coefficient block associated with the current block by adjusting the QP value associated with the CU. Quantization may introduce information loss, and therefore, the quantized transform coefficients may have lower precision than the original transform coefficients produced by transform processing unit 206.

[0151] The inverse quantization unit 210 and the inverse transform processing unit 212 may apply inverse quantization and inverse transform, respectively, to the quantized transform coefficient block to reconstruct a residual block from the transform coefficient block. The reconstruction unit 214 may generate a reconstructed block corresponding to the current block (although possibly with a certain degree of distortion) based on the reconstructed residual block and the prediction block generated by the mode selection unit 202. For example, the reconstruction unit 214 may add samples of the reconstructed residual block to corresponding samples from the prediction block generated by the mode selection unit 202 to generate a reconstructed block.

[0152] Filter unit 216 may perform one or more filter operations on the reconstructed block. For example, filter unit 216 may perform a deblocking operation to reduce blocking artifacts along the edges of the CU. In some examples, the operations of filter unit 216 may be skipped.

[0153] When operating according to AV1, filter unit 216 may perform one or more filter operations on the reconstructed block. For example, filter unit 216 may perform a deblocking operation to reduce blocking artifacts along the edges of the CU. In other examples, filter unit 216 may apply a constrained directional enhancement filter (CDEF), which may be applied after deblocking and may include applying a non-separable nonlinear low-pass directional filter based on an estimated edge direction. Filter unit 216 may also include a loop recovery filter applied after CDEF, and may include a separable symmetric normalized Wiener filter or a dual self-steering filter.

[0154] The video encoder 200 stores the reconstructed blocks in the DPB 218. For example, in an example where the operation of the filter unit 216 is not performed, the reconstruction unit 214 may store the reconstructed blocks to the DPB 218. In an example where the operation of the filter unit 216 is performed, the filter unit 216 may store the filtered reconstructed blocks to the DPB 218. The motion estimation unit 222 and the motion compensation unit 224 may retrieve a reference picture formed by the reconstructed (and potentially filtered) blocks from the DPB 218 to perform inter-frame prediction on blocks of subsequent encoded pictures. In addition, the intra-frame prediction unit 226 may use the reconstructed blocks in the DPB 218 of the current picture to perform intra-frame prediction on other blocks in the current picture.

[0155] In general, the entropy coding unit 220 may entropy encode syntax elements received from other functional components of the video encoder 200. For example, the entropy coding unit 220 may entropy encode a block of quantized transform coefficients from the quantization unit 208. As another example, the entropy coding unit 220 may entropy encode prediction syntax elements (e.g., motion information for inter-frame prediction or intra-frame mode information for intra-frame prediction) from the mode selection unit 202. The entropy coding unit 220 may perform one or more entropy coding operations on the syntax elements (which is another example of video data) to produce entropy-encoded data. For example, the entropy coding unit 220 may 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 some examples, the entropy coding unit 220 may operate in a bypass mode, in which the syntax elements are not entropy encoded.

[0156] The video encoder 200 may output a bitstream including entropy-encoded syntax elements required to reconstruct blocks of a slice or picture. In particular, the entropy encoding unit 220 may output a bitstream.

[0157] According to AV1, the entropy coding unit 220 may be configured as a symbol-to-symbol adaptive multi-symbol arithmetic codec. The syntax elements in AV1 include an alphabet of N elements, and the context (e.g., a probability model) includes a set of N probabilities. The entropy coding unit 220 may store the probabilities as an n-bit (e.g., 15-bit) cumulative distribution function (CDF). The entropy coding unit 22 may perform recursive scaling with an update factor based on the size of the alphabet to update the context.

[0158] The operations described above are described with respect to blocks. Such descriptions should be understood as operations for luma codec blocks and / or chroma codec blocks. As described above, in some examples, the luma codec block and the chroma codec block are the luma component and the chroma component of the CU. In some examples, the luma codec block and the chroma codec block are the luma component and the chroma component of the PU.

[0159] In some examples, operations performed with respect to luma codec blocks do not need to be repeated for chroma codec blocks. As an example, operations for identifying a motion vector (MV) and reference picture for a luma codec block do not need to be repeated to identify the MV and reference picture for a chroma block. In fact, the MV for the luma codec block may be scaled to determine the MV for the chroma block, and the reference picture may be the same. As another example, the intra prediction process may be the same for luma codec blocks and chroma codec blocks.

[0160] Figure 6 is a block diagram illustrating an example video decoder 300 that may perform the techniques of this disclosure. Figure 6 It is provided for the purpose of explanation and does not limit the techniques as extensively illustrated and described in this disclosure. For the purpose of explanation, this disclosure describes a video decoder 300 according to the techniques of VVC (ITU-T H.266, under development) and HEVC (ITU-T H.265). However, the techniques of this disclosure may be performed by video codec devices configured for other video codec standards.

[0161] exist Figure 6 In the example of , the video decoder 300 includes a coded picture buffer (CPB) memory 320, an entropy decoding unit 302, a prediction processing unit 304, an inverse quantization unit 306, an inverse transform processing unit 308, a reconstruction unit 310, a filter unit 312, and a decoded picture buffer (DPB) 314. Any or all of the CPB memory 320, the entropy decoding unit 302, the prediction processing unit 304, the inverse quantization unit 306, the inverse transform processing unit 308, the reconstruction unit 310, the filter unit 312, and the DPB 314 may be implemented in one or more processors or in processing circuits. For example, the units of the video decoder 300 may be implemented as one or more circuits or logic elements, as part of a hardware circuit, or as part of a processor, ASIC, or FPGA. In addition, the video decoder 300 may include additional or alternative processors or processing circuits to perform these and other functions.

[0162] The prediction processing unit 304 includes a motion compensation unit 316 and an intra prediction unit 318. The prediction processing unit 304 may include additional units that perform predictions according to other prediction modes. As an example, the prediction processing unit 304 may include a palette unit, an intra-block copy unit (which may form part of the motion compensation unit 316), an affine unit, a linear model (LM) unit, etc. In other examples, the video decoder 300 may include more, fewer, or different functional components. The motion compensation unit 316 may be configured to perform affine motion compensation according to any of the various techniques of this disclosure, alone or in any combination.

[0163] When operating according to AV1, the compensation unit 316 may be configured to decode codec blocks of video data (e.g., both luma and chroma codec blocks) using translational motion compensation, affine motion compensation, OBMC, and / or composite inter-intra prediction, as described above. The intra prediction unit 318 may be configured to decode codec blocks of video data (e.g., both luma and chroma codec blocks) using directional intra prediction, non-directional intra prediction, recursive filter intra prediction, CFL, intra block copy (IBC), and / or palette mode, as described above.

[0164] CPB memory 320 may store video data, such as an encoded video bitstream, to be decoded by components of video decoder 300. The video bitstream may be obtained, for example, from computer readable medium 110 ( Figure 1 ) obtains video data stored in CPB memory 320. CPB memory 320 may include a CPB that stores encoded video data (e.g., syntax elements) from an encoded video bitstream. In addition, CPB memory 320 may store video data other than syntax elements of encoded and decoded pictures, such as temporary data representing outputs from various units of video decoder 300. DPB 314 typically stores decoded pictures, which video decoder 300 may output and / or use as reference video data when decoding subsequent data or pictures of the encoded video bitstream. CPB memory 320 and DPB 314 may 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. CPB memory 320 and DPB 314 may be provided by the same memory device or a separate memory device. In various examples, CPB memory 320 may be on-chip with other components of video decoder 300, or off-chip relative to those components.

[0165] Additionally or alternatively, in some examples, video decoder 300 may retrieve the video from memory 120 ( Figure 1 ) retrieves the encoded and decoded video data. That is, memory 120 may store data, as described above with respect to CPB memory 320. Likewise, 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 may store instructions to be executed by video decoder 300.

[0166] Figure 6 The various units shown in FIG. 3 are shown to aid in understanding the operations performed by the video decoder 300. The units may be implemented as fixed function circuits, programmable circuits, or a combination thereof. Figure 5, fixed-function circuits refer to circuits that provide specific functionality and are preset in executable operations. Programmable circuits refer to circuits that can be programmed to perform various tasks and provide flexible functions in executable operations. For example, a programmable circuit can execute software or firmware that causes the programmable circuit to operate in a manner defined by the instructions of the software or firmware. Fixed-function circuits can execute software instructions (for example, to receive parameters or output parameters), but the type of operation performed by the fixed-function circuit is generally immutable. In some examples, one or more of the units may be different circuit blocks (fixed-function or programmable), and in some examples, one or more of the units may be integrated circuits.

[0167] The video decoder 300 may include an ALU, an EFU, a digital circuit, an analog circuit, and / or a programmable core formed by a programmable circuit. In an example where the operation of the video decoder 300 is performed by software executed on the programmable circuit, an on-chip or off-chip memory may store instructions (e.g., object code) of the software received and executed by the video decoder 300.

[0168] Entropy decoding unit 302 may 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 may generate decoded video data based on syntax elements extracted from the bitstream.

[0169] Typically, the video decoder 300 reconstructs a picture on a block-by-block basis. The video decoder 300 may perform a reconstruction operation on each block separately (where a block currently being reconstructed (ie, decoded) may be referred to as a "current block").

[0170] The entropy decoding unit 302 may entropy decode syntax elements defining quantized transform coefficients of the quantized transform coefficient block, as well as transform information, such as a quantization parameter (QP) and / or a transform mode indication. The inverse quantization unit 306 may use the QP associated with the quantized transform coefficient block to determine a degree of quantization, and likewise, determine a degree of inverse quantization to be applied by the inverse quantization unit 306. The inverse quantization unit 306 may, for example, perform a bitwise left shift operation to inverse quantize the quantized transform coefficients. The inverse quantization unit 306 may thereby form a transform coefficient block including the transform coefficients.

[0171] After inverse quantization unit 306 forms the transform coefficient block, inverse transform processing unit 308 may 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 may 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.

[0172] In addition, prediction processing unit 304 generates a prediction block based on 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 may generate the prediction block. In this case, the prediction information syntax elements may indicate a reference picture in DPB 314 from which to retrieve the reference block, and a motion vector identifying the position of the reference block in the reference picture relative to the position of the current block in the current picture. Motion compensation unit 316 may generally be substantially similar to the instructions for motion compensation unit 224 ( Figure 5 ) performs the inter-frame prediction process in the manner described.

[0173] As another example, if the prediction information syntax element indicates that the current block is intra-predicted, the intra-prediction unit 318 may generate a prediction block according to the intra-prediction mode indicated by the prediction information syntax element. Again, the intra-prediction unit 318 may generally be similar to the intra-prediction unit 226 ( Figure 5 The intra prediction process is performed in the manner described in the above description. The intra prediction unit 318 may retrieve data of neighboring samples of the current block from the DPB 314.

[0174] The reconstruction unit 310 may reconstruct the current block using the prediction block and the residual block. For example, the reconstruction unit 310 may add samples of the residual block to corresponding samples of the prediction block to reconstruct the current block.

[0175] The filter unit 312 may perform one or more filter operations on the reconstructed block. For example, the filter unit 312 may perform a deblocking operation to reduce blocking artifacts along the edges of the reconstructed block. The operations of the filter unit 312 may not necessarily be performed in all examples.

[0176] The video decoder 300 may store the reconstructed block in the DPB 314. For example, in an example where the operation of the filter unit 312 is not performed, the reconstruction unit 310 may store the reconstructed block to the DPB 314. In an example where the operation of the filter unit 312 is performed, the filter unit 312 may store the filtered reconstructed block to the DPB 314. As described above, the DPB 314 may provide reference information (such as samples of the current picture for intra-frame prediction and samples of previously decoded pictures for subsequent motion compensation) to the prediction processing unit 304. In addition, the video decoder 300 may output a decoded picture (e.g., a decoded video) from the DPB 314 for subsequent display on a display device (such as a Figure 1 is presented on a display device 118).

[0177] Figure 7 1 is a flowchart illustrating an example method for encoding a current block according to the techniques of the present disclosure. The current block may include a current CU. Although relative to the video encoder 200 ( Figure 1 and5 ), but it should be understood that other devices may be configured to perform similar Figure 7 method of method of method.

[0178] In this example, the video encoder 200 initially predicts a current block (350). For example, the video encoder 200 may form a prediction block for the current block based on affine motion compensation using any of the various techniques of the present disclosure, alone or in any combination. The video encoder 200 may then calculate a residual block for the current block (352). To calculate the residual block, the video encoder 200 may calculate the difference between the original, unencoded block and the prediction block for the current block. The video encoder 200 may then transform the residual block and quantize the transform coefficients of the residual block (354). Next, the video encoder 200 may scan the quantized transform coefficients of the residual block (356). During or after the scan, the video encoder 200 may entropy encode the transform coefficients (358). For example, the video encoder 200 may encode the transform coefficients using CAVLC or CABAC. The video encoder 200 may then output entropy encoded data for the block (360).

[0179] Video encoder 200 may also decode the current block after encoding the current block to use the decoded version of the current block as reference data for subsequent encoded data (e.g., in an inter-frame or intra-frame prediction mode). Accordingly, video encoder 200 may inverse quantize and inverse transform the coefficients to reproduce a residual block (362). Video encoder 200 may combine the residual block with the prediction block to form a decoded block (364). Video encoder 200 may then store the decoded block in DPB 218 (366).

[0180] Figure 8 1 is a flowchart illustrating an example method for decoding a current block of video data according to the techniques of the present disclosure. The current block may include a current CU. Although relative to the video decoder 300 ( Figure 1 and 6 ), but it should be understood that other devices may be configured to perform similar Figure 8 method of method of method.

[0181] The video decoder 300 may receive entropy encoded data for a current block, such as entropy encoded prediction information and entropy encoded data for transform coefficients of a residual block corresponding to the current block (370). The video decoder 300 may entropy decode the entropy encoded data to determine prediction information for the current block and reproduce transform coefficients of the residual block (372). The video decoder 300 may predict the current block (374) based on affine motion compensation, for example, using any of the various techniques of the present disclosure, alone or in any combination, to calculate a prediction block for the current block. The video decoder 300 may then inverse scan the reproduced transform coefficients (376) to create a quantized transform coefficient block. The video decoder 300 may then inverse quantize the transform coefficients and apply an inverse transform to the transform coefficients to produce a residual block (378). The video decoder 300 may ultimately decode the current block (380) by combining the prediction block and the residual block.

[0182] Fig. 9 1 is a flowchart illustrating an example method for encoding a current block using sub-block based affine motion compensation or individual pixel based affine motion compensation according to the techniques of the present disclosure. Figure 1 and Figure 5 Description of the video encoder 200 Fig. 9 However, other video encoding devices may be configured to perform such methods or similar methods consistent with the techniques of this disclosure.

[0183] Initially, video encoder 200 determines that affine motion compensation (MC) is to be used to predict a block (400). For example, video encoder 200 may test various prediction modes (e.g., inter prediction mode, intra prediction mode, and affine prediction mode) and determine that affine motion compensation produces the best rate-distortion optimization (RDO) value in the various tested modes. Video encoder 200 may then determine motion information for the block (402). For example, motion estimation unit 222 may determine a motion vector that, when used in affine motion compensation, identifies a reference block that best matches the block, e.g., using SAD, SSD, MAD, MSD, or other such difference metrics.

[0184] The video encoder 200 may also determine whether to perform sub-block based affine motion compensation (404). That is, the video encoder 200 may determine whether to modify the motion vector of the sub-block whose size is larger than the individual pixels, or whether to modify the motion vector of the individual pixels themselves. The determination may involve SAD, SSD, MAD, MSD or other such difference metrics, as well as RDO determination and / or processing time determination. In general, affine motion compensation based on individual pixels may be more computationally expensive, and therefore, when the performance (e.g., in terms of RDO or other such metrics) is greater than the performance of sub-block based affine motion compensation by a certain margin, the video encoder 200 may determine to use affine motion compensation based on individual pixels. In some examples, the margin may be determined according to the profile, hierarchy and / or level of the corresponding video coding standard. Otherwise, for example, when the performance of sub-block based affine motion compensation is comparable to the performance of sub-block based affine motion compensation, or when the margin is not overcome, the video encoder 200 may determine to use sub-block based affine motion compensation.

[0185] In the event that the video encoder 200 determines to perform sub-block based affine motion compensation ("yes" branch of 404), the video encoder 200 may determine motion information of the sub-block (406). For example, as discussed above with respect to formula (5), the video encoder 200 may modify the determined motion information of the block for each sub-block. The video encoder 200 may then predict each sub-block using the corresponding motion information (408). The video encoder 200 may also perform OBMC to form a predicted block for the block from the predicted sub-blocks (410). In addition, the video encoder 200 may encode a value of an OBMC flag indicating that OBMC is to be performed on the block (412).

[0186] On the other hand, in the event that the video encoder 200 determines not to perform sub-block based affine motion compensation (the "no" branch of 404), the video encoder 200 may determine motion information for each pixel (414). The process may be similar to the process described with respect to equation (5), except that the pixels are considered to be 1×1 sub-blocks, and therefore, the center pixel will be the pixel itself. Therefore, the video encoder 200 may use the motion information to predict each pixel to form a prediction block (416). Because each pixel is predicted separately in this case, OBMC does not need to be performed. Therefore, the video encoder 200 encodes an OBMC flag indicating that OBMC is not performed on the block (418).

[0187] Finally, video encoder 200 may then encode the block using the prediction block (420). Figure 7As discussed, the video encoder 200 may calculate a pixel-by-pixel difference between a prediction block and a block to be encoded to form a residual block, then quantize and transform the residual block to form a block of quantized transform coefficients, and then entropy encode each quantized transform coefficient.

[0188] In this way, Fig. 9 The method represents an example of a method for encoding a block of video data, the method comprising determining whether motion information of the block of video data is for a sub-block of a block larger than individual pixels of the block or for individual pixels, the block being associated with data indicating that the block is to be predicted using affine motion compensation; in response to determining that the motion information of the block is for a sub-block, performing sub-block-based affine motion compensation to form a prediction block for the block; in response to determining that the motion information is for individual pixels, performing pixel-based affine motion compensation to form a prediction block for the block; and encoding the block using the prediction block.

[0189] Fig.10 1 is a flowchart illustrating an example method for decoding a current block using sub-block based affine motion compensation or individual pixel based affine motion compensation according to the techniques of the present disclosure. Figure 1 and Figure 6 The video decoder 300 is described Fig.10 However, other video encoding devices may be configured to perform such methods or similar methods consistent with the techniques of this disclosure.

[0190] Initially, the video decoder 300 may determine that a block is to be predicted using affine motion compensation (MC) (430). For example, the video decoder 300 may decode data in the bitstream indicating that the block is to be predicted using affine motion compensation. The video decoder 300 may further decode motion information for the block (432). For example, the video decoder 300 may decode data indicating the number of motion vectors to be used in affine mode and, for each motion vector, a merge index indicating the location of a candidate motion vector to be used, an AMVP index, and motion vector difference information, etc.

[0191] The video decoder 300 may also decode an OBMC flag for the block. The video decoder 300 may determine whether the value of the OBMC flag indicates whether OBMC is to be performed (434). In the event that the OBMC flag indicates that OBMC is to be performed (the "yes" branch of 434), the video decoder 300 may determine motion information for sub-blocks of the block (436), where the sub-blocks are larger than individual pixels of the block. For example, the video decoder 300 may modify the decoded motion information to fit each sub-block, such as discussed above with respect to equation (5). The video decoder 300 may then predict each sub-block using the corresponding motion information (438), and perform OBMC on the sub-blocks to form a predicted block (440).

[0192] Alternatively, if the OBMC flag indicates that OBMC is not to be performed (the "No" branch of 434), the video decoder 300 may determine motion information for each of the individual pixels of the block (442). The video decoder 300 may then use the corresponding motion information to predict the pixels to form a predicted block (444). In this case, the video decoder 300 may avoid performing OBMC because the individual pixels do not overlap with each other. Therefore, the video decoder 300 may use the OBMC flag as an indication of whether the motion information of the block to be predicted using affine motion compensation is applied to a sub-block larger than the individual pixels or to the individual pixels themselves.

[0193] Finally, the video decoder 300 may decode the block using the prediction block (446). For example, the video decoder 300 may entropy decode the quantized transform coefficients, inverse quantize and inverse transform the quantized transform coefficients, and reconstruct a residual block for the block. The video decoder 300 may then combine the pixels of the residual block with the pixels of the prediction block on a pixel-by-pixel basis to reconstruct the current block.

[0194] In this way, Fig.10 The method represents an example of a method of decoding video data, the method including determining whether motion information of a block of video data is for a sub-block of a block larger than individual pixels of the block or for individual pixels, the block being associated with data indicating that the block is to be predicted using affine motion compensation; in response to determining that the motion information of the block is for the sub-block, performing sub-block-based affine motion compensation to form a prediction block for the block; in response to determining that the motion information is for individual pixels, performing pixel-based affine motion compensation to form a prediction block for the block; and decoding the block using the prediction block.

[0195] Various examples of the techniques of the present disclosure are summarized in the following clauses:

[0196] Clause 1: A method for decoding video data, the method comprising: determining whether overlapped block motion compensation (OBMC) is applied to a video data block, the video data block being associated with data indicating that affine motion compensation is to be used to predict the video data block; in response to determining that OBMC is to be applied to the video data block, performing sub-block-based affine motion compensation to form a prediction block of the video data block; in response to determining that OBMC is not to be applied to the video data block, performing pixel-based affine motion compensation to form a prediction block of the video data block; and decoding the video data block using the prediction block.

[0197] Item 2: A method of decoding video data, the method comprising: determining that a block of video data will be predicted using pixel-based affine motion compensation; in response to determining that the block of video data will be predicted using pixel-based affine motion compensation, determining that prediction refinement using optical flow (PROF) will not be performed on the block of video data; forming a prediction block of the block of video data using pixel-based affine motion compensation and without performing PROF; and decoding the block of video data using the prediction block.

[0198] Clause 3: A method comprising a combination of the method of clause 1 and the method of clause 2.

[0199] Clause 4: The method of any of clauses 2 and 3, wherein determining that PROF is not to be performed comprises determining that PROF is not to be performed without encoding syntax elements related to PROF for the block of video data.

[0200] Clause 5: A method for decoding video data, the method comprising: dividing a video data block into a plurality of sub-blocks, the video data block being associated with data indicating that affine motion compensation will be used to predict the video data block; determining that prediction refinement (PROF) using optical flow will not be performed on the video data block when a smallest sub-block among the sub-blocks has a size less than a threshold; forming a prediction block for the video data block using affine motion compensation; and decoding the video data block using the prediction block.

[0201] Clause 6: A method comprising a combination of the method according to any one of clauses 1 to 4 and the method according to clause 5.

[0202] Clause 7: The method of any of clauses 5 and 6, wherein the size of the smallest sub-block corresponds to one dimension of the sub-block, and wherein the threshold is 4 samples.

[0203] Clause 8: The method of clause 7, wherein one dimension comprises one of a height of a smallest sub-block or a width of a smallest sub-block.

[0204] Clause 9: A method according to any of clauses 5-8, wherein determining that PROF is not to be performed comprises determining that PROF is not to be performed without encoding syntax elements related to PROF for the block of video data.

[0205] Item 10: A method for decoding video data, the method comprising: determining that affine motion compensation will be used to predict a video data block; in response to determining that a prediction block of the video data block will be formed using multiple hypothesis prediction (MHP), determining not to apply overlapped block motion compensation (OBMC) when forming the prediction block; forming a prediction block of the video data block; and decoding the video data block using the prediction block.

[0206] Clause 11: A method comprising a combination of the method according to any one of clauses 1 to 9 and the method according to clause 10.

[0207] Clause 12: The method of any of clauses 10 and 11, wherein determining that OBMC is not to be performed comprises determining that OBMC is not to be performed without decoding OBMC-related syntax elements for the block of video data.

[0208] Clause 13: A method of decoding video data, the method comprising: determining that affine motion compensation is to be used to predict a block of video data; decoding data indicating whether overlapped block motion compensation (OBMC) is applied to the block of video data; forming a prediction block for the block of video data; and decoding the block of video data using the prediction block.

[0209] Clause 14: A method comprising a combination of the method according to any one of clauses 1 to 9 and the method according to clause 13.

[0210] Clause 15: The method according to any one of clauses 13 and 14 further includes: determining that affine motion compensation will not be used to predict a second block of video data; in response to determining that affine motion compensation will not be used to predict the second block of video data, implicitly determining whether OBMC is applied to the second block of video data without decoding data indicating whether OBMC is applied to the second block of video data; forming a second prediction block for the second block of video data; and decoding the second block of video data using the second prediction block.

[0211] Clause 16: The method of any of clauses 13-15, further comprising determining that an affine motion compensation mode other than merge prediction mode is to be used to predict the block of video data.

[0212] Clause 17: A method according to any one of clauses 13-16, wherein encoding data indicating whether OBMC will be applied includes: determining a context for context encoding and decoding the data indicating whether OBMC will be applied based on whether a picture including a video data block is a low-latency picture or a non-low-latency picture; and context encoding and decoding the data indicating whether OBMC will be applied using the determined context.

[0213] Clause 18: A method according to any one of clauses 13-16, wherein decoding data indicating whether OBMC will be applied includes: determining a context for context encoding and decoding the data indicating whether OBMC will be applied based on a video data block predicted using affine motion compensation; and context encoding and decoding the data indicating whether OBMC will be applied using the determined context.

[0214] Item 19: A method for decoding video data, the method comprising: determining that affine motion compensation will be used to predict a video data block; determining whether the video data block has a size greater than a threshold; when the video data block has a size greater than the threshold, determining not to apply overlapped block motion compensation (OBMC) to the video data block; forming a prediction block for the video data block; and decoding the video data block using the prediction block.

[0215] Clause 20: A method comprising a combination of the method according to any one of clauses 1-9 and the method according to clause 19.

[0216] Clause 21: The method of any of clauses 19 and 20, wherein the size of the block of video data corresponds to a dimension of the block of video data, and wherein the threshold comprises 128 samples.

[0217] Clause 22: The method of clause 21, wherein one dimension comprises one of a width of the block of video data or a height of the block of video data.

[0218] Clause 23: A method for decoding video data, the method comprising: determining a block of a current picture of video data to be predicted using affine motion compensation relative to a reference picture of the video data; determining a difference between a picture order count (POC) of the current picture and a POC of the reference picture; when the difference between the POC of the current picture and the POC of the reference picture is greater than a threshold, forming a prediction block of the block of the current picture of the video data using pixel-based affine motion compensation; and decoding the block of video data using the prediction block.

[0219] Clause 24: A method comprising a combination of the method according to any one of clauses 1 to 22 and the method according to clause 23.

[0220] Clause 25: The method of any of clauses 23 and 24, wherein the threshold value is a value of 1.

[0221] Clause 26: A method of decoding video data, the method comprising: determining that a block of video data is to be predicted using affine motion compensation; forming a prediction block for the block of video data using both local illumination compensation (LIC) and overlapped block motion compensation (OBMC); and decoding the block of video data using the prediction block.

[0222] Clause 27: A method comprising a combination of the methods of any one of clauses 1-9, 13-18, and 23-26.

[0223] Clause 28: The method of any of clauses 26 and 27, wherein forming the prediction block comprises performing OBMC on sub-block boundaries within the block of video data and not performing OBMC on boundaries of the block of video data.

[0224] Clause 29: The method of clause 28, wherein the boundary of the video data block comprises an upper boundary of the video data block and a left boundary of the video data block.

[0225] Clause 30: A method according to any of clauses 1-29, wherein the block of video data is included in a non-low-delay picture.

[0226] Clause 31: The method of any one of clauses 1-30, further comprising encoding the current block before decoding the current block.

[0227] Clause 32: An apparatus for decoding video data, the apparatus comprising one or more means for performing the method according to any of clauses 1-31.

[0228] Clause 33: The apparatus of clause 32, wherein one or more of the means comprises one or more processors implemented in circuitry.

[0229] Clause 34: The apparatus of any of clauses 32 and 33, further comprising a display configured to display the decoded video data.

[0230] Clause 35: The device of any of clauses 32-34, wherein the device comprises one or more of a camera, a computer, a mobile device, a broadcast receiver device, or a set-top box.

[0231] Clause 36: The apparatus of clauses 32 to 35, further comprising a memory configured to store video data.

[0232] Clause 37: A computer-readable storage medium having stored thereon instructions which, when executed, cause a processor of a device for decoding video data to perform the method of any of clauses 1 to 31.

[0233] Item 38: A method for decoding video data, the method comprising: determining whether overlapped block motion compensation (OBMC) is applied to a video data block, the video data block being associated with data indicating that affine motion compensation is to be used to predict the video data block; in response to determining that OBMC is to be applied to the video data block, performing sub-block-based affine motion compensation to form a prediction block of the video data block; in response to determining that OBMC is not to be applied to the video data block, performing pixel-based affine motion compensation to form a prediction block of the video data block; and decoding the video data block using the prediction block.

[0234] Clause 39: A method for decoding video data, the method comprising: determining that a block of video data will be predicted using pixel-based affine motion compensation; in response to determining that the block of video data will be predicted using pixel-based affine motion compensation, determining that prediction refinement PROF using optical flow will not be performed on the block of video data; forming a prediction block of the block of video data using pixel-based affine motion compensation and without performing PROF; and decoding the block of video data using the prediction block.

[0235] Clause 40: The method of clause 39, wherein determining that PROF is not to be performed comprises determining that PROF is not to be performed without decoding syntax elements associated with PROF for the block of video data.

[0236] Item 41: A method for decoding video data, the method comprising: dividing a video data block into a plurality of sub-blocks, the video data block being associated with data indicating that affine motion compensation will be used to predict the video data block; determining that prediction refinement PROF using optical flow will not be performed on the video data block when a smallest sub-block among the sub-blocks has a size smaller than a threshold; forming a prediction block of the video data block using affine motion compensation; and decoding the video data block using the prediction block.

[0237] Clause 42: The method of clause 41, wherein the size of the smallest sub-block corresponds to a dimension of the sub-block, and wherein the threshold is 4 samples.

[0238] Clause 43: The method of clause 42, wherein one dimension comprises one of a height of a smallest sub-block or a width of a smallest sub-block.

[0239] Clause 44: The method of clause 41, wherein determining that PROF is not to be performed comprises determining that PROF is not to be performed without encoding and decoding syntax elements associated with PROF for the block of video data.

[0240] Item 45: A method for decoding video data, the method comprising: determining that affine motion compensation will be used to predict a video data block; in response to determining that a prediction block of the video data block will be formed using multi-hypothesis prediction (MHP), determining not to apply overlapped block motion compensation (OBMC) when forming the prediction block; forming a prediction block of the video data block; and decoding the video data block using the prediction block.

[0241] Clause 46: The method of clause 45, wherein determining that OBMC is not to be performed comprises determining that OBMC is not to be performed without encoding and decoding syntax elements associated with OBMC for the block of video data.

[0242] Clause 47: A method of decoding video data, the method comprising: determining that affine motion compensation is to be used to predict a block of video data; encoding and decoding data indicating whether overlapped block motion compensation (OBMC) is applied to the block of video data; forming a prediction block for the block of video data; and decoding the block of video data using the prediction block.

[0243] Clause 48: The method according to Clause 47 further includes: determining that affine motion compensation will not be used to predict a second block of video data; in response to determining that affine motion compensation will not be used to predict the second block of video data, implicitly determining whether OBMC is applied to the second block of video data without decoding data indicating whether OBMC is applied to the second block of video data; forming a second prediction block for the second block of video data; and decoding the second block of video data using the second prediction block.

[0244] Clause 49: The method of clause 47, further comprising determining that an affine motion compensation mode other than merge prediction mode is to be used to predict the block of video data.

[0245] Clause 50: A method according to Clause 47, wherein encoding and decoding data indicating whether OBMC will be applied includes: determining a context for context encoding and decoding the data indicating whether OBMC will be applied based on whether a picture including a video data block is a low-latency picture or a non-low-latency picture; and context encoding and decoding the data indicating whether OBMC will be applied using the determined context.

[0246] Clause 51: A method according to Clause 47, wherein encoding and decoding data indicating whether OBMC will be applied includes: determining a context for context encoding and decoding the data indicating whether OBMC will be applied based on predicting a video data block using affine motion compensation; and context encoding and decoding the data indicating whether OBMC will be applied using the determined context.

[0247] Item 52: A method for decoding video data, the method comprising: determining that affine motion compensation will be used to predict a video data block; determining whether the video data block has a size greater than a threshold; when the video data block has a size greater than the threshold, determining not to apply overlapped block motion compensation (OBMC) to the video data block; forming a prediction block for the video data block; and decoding the video data block using the prediction block.

[0248] Clause 53: The method of clause 52, wherein the size of the block of video data corresponds to a dimension of the block of video data, and wherein the threshold comprises 128 samples.

[0249] Clause 54: The method of clause 53, wherein one dimension comprises one of a width of the block of video data or a height of the block of video data.

[0250] Item 55: A method for decoding video data, the method comprising: determining a block of a current picture of video data to be predicted using affine motion compensation relative to a reference picture of the video data; determining a difference between a picture order count (POC) of the current picture and the POC of the reference picture; when the difference between the POC of the current picture and the POC of the reference picture is greater than a threshold, forming a prediction block of the block of the current picture of the video data using pixel-based affine motion compensation; and decoding the block of video data using the prediction block.

[0251] Clause 56: The method of clause 55, wherein the threshold value is a value of 1.

[0252] Clause 57: A method of decoding video data, the method comprising: determining that a block of video data is to be predicted using affine motion compensation; forming a prediction block for the block of video data using both local illumination compensation (LIC) and overlapped block motion compensation (OBMC); and decoding the block of video data using the prediction block.

[0253] Clause 58: The method of clause 57, wherein forming the prediction block comprises performing OBMC on sub-block boundaries within the block of video data and not performing OBMC on boundaries of the block of video data.

[0254] Clause 59: The method of clause 58, wherein the boundary of the video data block comprises an upper boundary of the video data block and a left boundary of the video data block.

[0255] Item 60: A device for decoding video data, the device comprising: a device module for determining whether to apply overlapped block motion compensation (OBMC) to a video data block, the video data block being associated with data indicating that affine motion compensation will be used to predict the video data block; a device module for performing sub-block based affine motion compensation to form a prediction block for the video data block in response to determining that OBMC will be applied to the video data block; a device module for performing pixel-based affine motion compensation to form a prediction block for the video data block in response to determining that OBMC is not applied to the video data block; and a device module for decoding the video data block using the prediction block.

[0256] Item 61: A device for decoding video data, the device comprising: a device module for determining that a video data block will be predicted using pixel-based affine motion compensation; a device module for determining that prediction refinement using optical flow (PROF) will not be performed on the video data block in response to determining that the video data block will be predicted using pixel-based affine motion compensation; a device module for forming a prediction block for the video data block using pixel-based affine motion compensation and without performing PROF; and a device module for decoding the video data block using the prediction block.

[0257] Item 62: A device for decoding video data, the device comprising: a device for dividing a video data block into a plurality of sub-blocks, the video data block being associated with data indicating that affine motion compensation will be used to predict the video data block; a device module for determining that prediction refinement PROF using optical flow will not be performed on the video data block when a smallest sub-block in the sub-blocks has a size less than a threshold; a device module for forming a prediction block for the video data block using affine motion compensation; and a device module for decoding the video data block using the prediction block.

[0258] Item 63: A device for decoding video data, the device comprising: a device module for determining that affine motion compensation will be used to predict a block of video data; a device module for determining not to apply overlapped block motion compensation (OBMC) when forming the prediction block in response to determining that multiple hypothesis prediction (MHP) will be used to form a prediction block for the block of video data; a device module for forming a prediction block for the block of video data; and a device module for decoding the block of video data using the prediction block.

[0259] Item 64: A device for decoding video data, the device comprising: a device module for determining that affine motion compensation will be used to predict a video data block; a device module for encoding and decoding data indicating whether overlapped block motion compensation (OBMC) will be applied to the video data block; a device module for forming a prediction block for the video data block; and a device module for decoding the video data block using the prediction block.

[0260] Item 65: A device for decoding video data, the device comprising: a device module for determining that affine motion compensation will be used to predict a video data block; a device module for determining whether the video data block has a size greater than a threshold; a device module for determining not to apply overlapped block motion compensation (OBMC) to the video data block when the video data block has a size greater than the threshold; a device module for forming a prediction block for the video data block; and a device module for decoding the video data block using the prediction block.

[0261] Item 66: A device for decoding video data, the device comprising: a device module for determining a block of a current picture of video data to be predicted using affine motion compensation relative to a reference picture of the video data; a device module for determining a difference between a picture order count (POC) of the current picture and the POC of the reference picture; a device module for forming a prediction block of the block of the current picture of the video data using pixel-based affine motion compensation when the difference between the POC of the current picture and the POC of the reference picture is greater than a threshold; and a device module for decoding a block of video data using the prediction block.

[0262] Item 67: A device for decoding video data, the device comprising: a device module for determining that affine motion compensation will be used to predict a block of video data; a device module for forming a prediction block for the block of video data using both local illumination compensation (LIC) and overlapped block motion compensation (OBMC); and a device module for decoding the block of video data using the prediction block.

[0263] Item 68: A method for encoding video data, the method comprising: determining that a motion difference between a first portion of a video data block and a second portion of the video data block is less than a threshold; grouping the first portion and the second portion into a single portion; forming prediction information of the single portion as a corresponding portion of a prediction block; and encoding the video data block using the prediction block.

[0264] Clause 69: The method of clause 68, further comprising encoding data indicating that the first portion and the second portion are to be grouped into a single portion.

[0265] Clause 70: The method of any of clauses 68 and 69, wherein the first portion is a first sample and the second portion is a second sample adjacent to the first sample.

[0266] Item 71: A method for decoding video data, the method comprising: determining whether motion information for a block of video data is for a sub-block of a block larger than individual pixels of the block or for individual pixels, the block being associated with data indicating that affine motion compensation is to be used to predict the block; in response to determining that the motion information of the block is for a sub-block, performing sub-block-based affine motion compensation to form a prediction block for the block; in response to determining that the motion information is for individual pixels, performing pixel-based affine motion compensation to form a prediction block for the block; and decoding the block using the prediction block.

[0267] Clause 72: The method of clause 71, wherein determining whether the motion information is for a sub-block or for individual pixels comprises determining whether overlapped block motion compensation (OBMC) is to be applied to the block.

[0268] Clause 73: The method of clause 72, further comprising, when applying OBMC, performing OBMC on internal sub-block boundaries of the sub-block and performing local illumination compensation (LIC) to form the prediction block without performing OBMC on external boundaries of the block.

[0269] Clause 74: The method of clause 72, wherein determining whether OBMC is to be applied to the block comprises: when multi-hypothesis prediction (MHP) is determined to be applied to the block, determining that OBMC is not to be applied to the block without decoding syntax elements related to OBMC for the block.

[0270] Clause 75: The method of clause 72, wherein determining whether OBMC is to be applied to the block comprises determining a value of an OBMC syntax element, the value of the OBMC syntax element indicating whether OBMC is to be applied to the block.

[0271] Clause 76: The method of clause 75, wherein the OBMC syntax element comprises an OBMC flag.

[0272] Clause 77: The method according to clause 75 further includes: determining a context for decoding the OBMC syntax element according to whether the picture including the video data block is a low-delay picture or a non-low-delay picture; and performing context-based decoding on the OBMC syntax element using the determined context.

[0273] Clause 78: The method of clause 75, further comprising: determining a context for decoding the OBMC syntax element based on data indicating that the block is to be predicted using affine motion compensation; and context-based decoding of the OBMC syntax element using the determined context.

[0274] Clause 79: The method of clause 72, wherein determining whether OBMC is to be applied to the block comprises determining not to apply OBMC to the block of video data when the block has a size greater than a threshold.

[0275] Clause 80: The method of clause 79, wherein the size of the block of video data corresponds to a dimension of the block of video data, and wherein the threshold comprises 128 samples along the one dimension.

[0276] Clause 81: The method of clause 80, wherein one dimension comprises one of a width of the block of video data or a height of the block of video data.

[0277] Clause 82: The method of clause 71, wherein the block comprises a luma block, the method further comprising performing pixel-based affine motion compensation on a chroma block corresponding to the luma block.

[0278] Clause 83: The method of clause 71, further comprising, in response to determining that motion information of the block is for respective pixels, determining that prediction refinement (PROF) using optical flow is not to be performed on the block.

[0279] Clause 84: The method of clause 83, wherein determining that PROF is not to be performed comprises determining that PROF is not to be performed without decoding PROF-related syntax elements for the block.

[0280] Clause 85: The method of clause 71, further comprising, in response to determining that the motion information of the block is for sub-blocks, determining that prediction refinement PROF using optical flow is not to be performed on the block when a smallest sub-block among the sub-blocks has a size less than a threshold.

[0281] Clause 86: The method of clause 85, wherein the size of the smallest sub-block corresponds to a dimension of the sub-block, and wherein the threshold is 4 samples.

[0282] Clause 87: The method of clause 86, wherein one dimension comprises one of a height of a smallest sub-block or a width of a smallest sub-block.

[0283] Clause 88: The method of clause 85, wherein determining that PROF is not to be performed comprises determining that PROF is not to be performed without decoding PROF-related syntax elements for the block.

[0284] Clause 89: A method according to clause 71, wherein the block includes a first block and the prediction block includes a first prediction block, the method further comprising: determining that a second block of video data will not be predicted using affine motion compensation; in response to determining that the second block of video data will not be predicted using affine motion compensation, implicitly determining whether overlapped block motion compensation (OBMC) is applied to the second block of video data without decoding data indicating whether OBMC is applied to the second block of video data; forming a second prediction block for the second block of video data; and decoding the second block of video data using the second prediction block.

[0285] Clause 90: The method of clause 71, wherein the data indicating that the block is to be predicted using affine motion compensation comprises data indicating that the block of video data is to be predicted using an affine motion compensation mode other than merge prediction mode.

[0286] Clause 91: A method according to clause 71, wherein the current picture includes a block and the motion information refers to a reference picture, and wherein determining whether the motion information is for a sub-block or for individual pixels comprises: determining a difference between a picture order count (POC) of the current picture and a POC of the reference picture; and when the difference between the POC of the current picture and the POC of the reference picture is greater than a threshold, determining that the motion information is for individual pixels.

[0287] Clause 92: The method of clause 91, wherein the threshold value is a value of 1.

[0288] Clause 93: The method of clause 71, wherein the block is included in a non-low-latency picture.

[0289] Clause 94: The method of clause 71, further comprising encoding the current block before decoding the current block.

[0290] Item 95: A device for decoding video data, the device comprising: a memory configured to store video data; and a processing system comprising one or more processors implemented in a circuit, the processing system being configured to: determine whether motion information for a block of video data is for a sub-block of a block larger than individual pixels of the block or for individual pixels, the block being associated with data indicating that affine motion compensation is to be used to predict the block; in response to determining that the motion information for the block is for a sub-block, perform sub-block-based affine motion compensation to form a prediction block for the block; in response to determining that the motion information is for individual pixels, perform pixel-based affine motion compensation to form a prediction block for the block; and decode the block using the prediction block.

[0291] Clause 96: The apparatus of clause 95, wherein to determine whether the motion information is for a sub-block or for individual pixels, the processing system is configured to determine whether overlapped block motion compensation (OBMC) is to be applied to the block.

[0292] Clause 97: The apparatus of clause 96, wherein the processing system is further configured to, when applying OBMC, perform OBMC on internal sub-block boundaries of the sub-block and perform local illumination compensation (LIC) to form the prediction block without performing OBMC on external boundaries of the block.

[0293] Clause 98: An apparatus according to clause 96, wherein to determine whether OBMC is to be applied to a block, the processing system is configured to determine that OBMC is not to be applied to the block without decoding syntax elements related to OBMC for the block when multiple hypothesis prediction (MHP) is determined to be applied to the block.

[0294] Clause 99: The apparatus of clause 96, wherein to determine whether OBMC is to be applied to the block, the processing system is configured to determine a value of an OBMC syntax element, the value of the OBMC syntax element indicating whether OBMC is to be applied to the block.

[0295] Clause 100: An apparatus according to clause 99, wherein the OBMC syntax element comprises an OBMC flag.

[0296] Clause 101: An apparatus according to clause 99, wherein the processing system is further configured to: determine a context for decoding an OBMC syntax element based on whether a picture including a video data block is a low-delay picture or a non-low-delay picture; and perform context-based decoding on the OBMC syntax element using the determined context.

[0297] Clause 102: The apparatus of clause 99, wherein the processing system is further configured to: determine a context for decoding the OBMC syntax element based on data indicating that the block is to be predicted using affine motion compensation; and perform context-based decoding of the OBMC syntax element using the determined context.

[0298] Clause 103: The apparatus of clause 96, wherein to determine whether OBMC is to be applied to the block, the processing system is configured to determine not to apply OBMC to the block when the block has a size greater than a threshold.

[0299] Clause 104: The device of clause 95, wherein the device comprises one or more of a camera, a computer, a mobile device, a broadcast receiver device, or a set-top box.

[0300] Item 105: A device for decoding video data, the device comprising: a device for determining whether motion information for a block of video data is for a sub-block of a block larger than individual pixels of the block or for individual pixels, the block being associated with data indicating that affine motion compensation is to be used to predict the block; a device module for performing sub-block-based affine motion compensation to form a prediction block for the block in response to determining that the motion information for the block is for a sub-block; a device module for performing pixel-based affine motion compensation to form a prediction block for the block in response to determining that the motion information is for individual pixels; and a device module for decoding the block using the prediction block.

[0301] Item 106: A method for decoding video data, the method comprising: determining whether motion information for a block of video data is for a sub-block of a block larger than individual pixels of the block or for individual pixels, the block being associated with data indicating that affine motion compensation is to be used to predict the block; in response to determining that the motion information of the block is for a sub-block, performing sub-block-based affine motion compensation to form a prediction block for the block; in response to determining that the motion information is for individual pixels, performing pixel-based affine motion compensation to form a prediction block for the block; and decoding the block using the prediction block.

[0302] Clause 107: The method of clause 106, wherein determining whether the motion information is for a sub-block or for individual pixels comprises determining whether overlapped block motion compensation (OBMC) is to be applied to the block.

[0303] Clause 108: The method of clause 107, further comprising, when applying OBMC, performing OBMC on internal sub-block boundaries of the sub-block and performing local illumination compensation (LIC) to form the prediction block without performing OBMC on external boundaries of the block.

[0304] Clause 109: A method according to any of clauses 107 and 108, wherein determining whether OBMC is to be applied to the block comprises: when determining that multiple hypothesis prediction (MHP) is to be applied to the block, determining not to apply OBMC to the block without decoding syntax elements related to OBMC for the block.

[0305] Clause 110: The method of any of clauses 107 and 108, wherein determining whether OBMC is to be applied to the block comprises determining a value of an OBMC syntax element, the value of the OBMC syntax element indicating whether OBMC is to be applied to the block.

[0306] Clause 111: The method of clause 110, wherein the OBMC syntax element comprises an OBMC flag.

[0307] Clause 112: The method according to any one of clauses 110 and 111 further includes: determining a context for decoding the OBMC syntax element based on whether the picture including the video data block is a low-delay picture or a non-low-delay picture; and performing context-based decoding on the OBMC syntax element using the determined context.

[0308] Clause 113: The method of any of clauses 110 and 111, further comprising: determining a context for decoding an OBMC syntax element based on data indicating that the block is to be predicted using affine motion compensation; and context-based decoding of the OBMC syntax element using the determined context.

[0309] Clause 114: The method of any of clauses 107-113, wherein determining whether OBMC is to be applied to the block comprises determining not to apply OBMC to the block of video data when the block has a size greater than a threshold.

[0310] Clause 115: The method of clause 114, wherein the size of the block of video data corresponds to a dimension of the block of video data, and wherein the threshold comprises 128 samples along the one dimension.

[0311] Clause 116: The method of clause 115, wherein the one dimension comprises one of a width of the block of video data or a height of the block of video data.

[0312] Clause 117: The method of any of clauses 106-116, wherein the block comprises a luma block, the method further comprising performing pixel-based affine motion compensation on a chroma block corresponding to the luma block.

[0313] Clause 118: The method of any of clauses 106-117, further comprising, in response to determining that the motion information of the block is for individual pixels, determining that prediction refinement (PROF) using optical flow is not to be performed on the block.

[0314] Clause 119: The method of clause 118, wherein determining that the PROF is not to be performed comprises determining that the PROF is not to be performed without decoding syntax elements associated with the PROF of the block.

[0315] Clause 120: The method of any of clauses 106-119, further comprising, in response to determining that the motion information of the block is for a sub-block, determining that prediction refinement (PROF) using optical flow is not to be performed on the block when a smallest sub-block of the sub-blocks has a size less than a threshold.

[0316] Clause 121: The method of clause 120, wherein the size of the smallest sub-block corresponds to a dimension of the sub-block, and wherein the threshold is 4 samples.

[0317] Clause 122: The method of clause 121, wherein one dimension comprises one of a height of a smallest sub-block or a width of a smallest sub-block.

[0318] Clause 123: The method of any of clauses 120-122, wherein determining that PROF is not to be performed comprises determining that PROF is not to be performed without decoding syntax elements related to PROF of the block.

[0319] Clause 124: A method according to any one of clauses 106 to 123, wherein the block includes a first block and the prediction block includes a first prediction block, the method further comprising: determining that a second block of video data will not be predicted using affine motion compensation; in response to determining that the second block of video data will not be predicted using affine motion compensation, implicitly determining whether overlapped block motion compensation (OBMC) is applied to the second block of video data without decoding data indicating whether OBMC is applied to the second block of video data; forming a second prediction block for the second block of video data; and decoding the second block of video data using the second prediction block.

[0320] Clause 125: The method of any of clauses 106-124, wherein the data indicating that the block is to be predicted using affine motion compensation comprises data indicating that the block of video data is to be predicted using an affine motion compensation mode other than merge prediction mode.

[0321] Clause 126: A method according to any one of clauses 106 to 125, wherein the current picture includes a block and the motion information refers to a reference picture, and wherein determining whether the motion information is for a sub-block or for individual pixels comprises: determining a difference between a picture order count (POC) of the current picture and a POC of the reference picture; and when the difference between the POC of the current picture and the POC of the reference picture is greater than a threshold, determining that the motion information is for individual pixels.

[0322] Clause 127: The method of clause 126, wherein the threshold is a value of 1.

[0323] Clause 128: The method of any of clauses 106-126, wherein the block is included in a non-low-latency picture.

[0324] Clause 129: The method of any of clauses 106-128, further comprising encoding the current block before decoding the current block.

[0325] Item 130: A device for decoding video data, the device comprising: a memory configured to store video data; and a processing system comprising one or more processors implemented in a circuit, the processing system being configured to: determine whether motion information for a block of video data is for a sub-block of a block larger than individual pixels of the block or for individual pixels, the block being associated with data indicating that affine motion compensation is to be used to predict the block; in response to determining that the motion information for the block is for a sub-block, perform sub-block-based affine motion compensation to form a prediction block for the block; in response to determining that the motion information is for individual pixels, perform pixel-based affine motion compensation to form a prediction block for the block; and decode the block using the prediction block.

[0326] Clause 131: The apparatus of clause 130, wherein to determine whether the motion information is for a sub-block or for individual pixels, the processing system is configured to determine whether overlapped block motion compensation (OBMC) is applied to the block.

[0327] Clause 132: The apparatus of clause 131, wherein the processing system is further configured to, when applying OBMC, perform OBMC on internal sub-block boundaries of the sub-block and perform local illumination compensation (LIC) to form the prediction block without performing OBMC on external boundaries of the block.

[0328] Clause 133: An apparatus according to any of clauses 131 and 132, wherein in order to determine whether OBMC is to be applied to a block, the processing system is configured to, when determining that multiple hypothesis prediction (MHP) is to be applied to the block, determine that OBMC is not to be applied to the block without decoding syntax elements related to OBMC for the block.

[0329] Clause 134: The apparatus of any of clauses 131 and 132, wherein to determine whether OBMC is to be applied to the block, the processing system is configured to determine a value of an OBMC syntax element, the value of the OBMC syntax element indicating whether OBMC is to be applied to the block.

[0330] Clause 135: An apparatus according to clause 134, wherein the OBMC syntax element comprises an OBMC flag.

[0331] Clause 136: An apparatus according to any one of clauses 134 and 135, wherein the processing system is further configured to: determine a context for decoding an OBMC syntax element based on whether a picture including a video data block is a low-delay picture or a non-low-delay picture; and perform context-based decoding of the OBMC syntax element using the determined context.

[0332] Clause 137: An apparatus according to any of clauses 134 and 135, wherein the processing system is further configured to: determine a context for decoding an OBMC syntax element based on data indicating that affine motion compensation will be used to predict a block; and perform context-based decoding of the OBMC syntax element using the determined context.

[0333] Clause 138: The apparatus of any of clauses 131-137, wherein to determine whether OBMC is to be applied to the block, the processing system is configured to determine not to apply OBMC to the block when the block has a size greater than a threshold.

[0334] Clause 139: The device of any of clauses 130-138, wherein the device comprises one or more of a camera, a computer, a mobile device, a broadcast receiver device, or a set-top box.

[0335] Clause 140: An apparatus for decoding video data, the apparatus comprising one or more means for performing the method of any of clauses 106-129.

[0336] It should be appreciated that, depending on the example, certain actions or events of any of the techniques described herein may be performed in a different order, may be added, combined, or omitted entirely (e.g., not all described actions or events are required to practice the techniques). Furthermore, in some examples, actions or events may be performed simultaneously rather than sequentially, such as through multithreading, interrupt processing, or multiple processors.

[0337] In one or more examples, the functions described may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions may be stored on or sent via a computer-readable medium as one or more instructions or codes and executed by a hardware-based processing unit. A computer-readable medium may include a computer-readable storage medium that corresponds to a tangible medium such as a data storage medium, or a communication medium that includes any medium that facilitates, for example, the transfer of a computer program from one place to another according to a communication protocol. In this manner, a computer-readable medium may generally correspond to (1) a non-transitory tangible computer-readable storage medium, or (2) a communication medium, such as a signal or carrier wave. A data storage medium may be any available medium that can be accessed by one or more computers or one or more processors to retrieve instructions, codes, and / or data structures for implementations of the technology described in the present disclosure. A computer program product may include a computer-readable medium.

[0338] By way of example and not limitation, such computer-readable storage media may include RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage, flash memory, or any other medium that can be used to store the desired program code in the form of instructions or data structures and can be accessed by a computer. In addition, any connection is appropriately referred to as a computer-readable medium. For example, if instructions are sent from a website, server or other remote source using a coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technology (such as infrared, radio, and microwave), the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technology (such as infrared, radio, and microwave) is included in the definition of medium. However, it should be understood that computer-readable storage media and data storage media do not include connections, carrier waves, signals, or other temporary media, but are actually directed to non-temporary tangible storage media. As used herein, disks and optical disks include compact disks (CDs), laser disks, optical disks, digital versatile disks (DVDs), floppy disks, and Blu-ray disks, where disks typically reproduce data magnetically, while optical disks reproduce data optically with lasers. Combinations of the above should also be included within the scope of computer-readable media.

[0339] Instructions may 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 circuits. Therefore, the terms "processor" and "processing circuitry" as used herein may refer to any of the aforementioned structures or any other structure suitable for implementation in the techniques described herein. In addition, in some aspects, the functionality described herein may be provided in dedicated hardware and / or software modules configured for encoding and decoding, or incorporated in a combined codec. In addition, these techniques may be fully implemented in one or more circuits or logic elements.

[0340] The techniques of the present disclosure may be implemented in a variety of devices or apparatuses, including wireless handsets, integrated circuits (ICs) or groups of ICs (e.g., chipsets). Various components, modules, or units are described in the present disclosure to emphasize functional aspects of devices configured to perform the disclosed techniques, but do not necessarily need to be implemented by different hardware units. In particular, as described above, the various units may be combined in a codec hardware unit in conjunction with appropriate software and / or firmware, or provided by a collection of interoperable hardware units (including one or more processors as described above).

[0341] Various examples have been described. These and other examples are within the scope of the following claims.

Claims

1. A method for decoding video data, the method include: determining whether motion information for a block of video data is for a sub-block of the block that is larger than individual pixels of the block or for the individual pixels, the block being associated with data indicating that the block is to be predicted using affine motion compensation; In response to determining that the motion information of the block is for the sub-block, performing sub-block-based affine motion compensation to form a prediction block for the block; In response to determining that the motion information is for the respective pixels, performing pixel-based affine motion compensation to form a prediction block for the block; as well as The block is decoded using the prediction block.

2. The method according to claim 1, in, Determining whether the motion information is for the sub-block or for the individual pixels includes determining whether overlapped block motion compensation (OBMC) is to be applied to the block.

3. The method according to claim 2, in, Determining whether OBMC is to be applied to the block includes: when multi-hypothesis prediction (MHP) is determined to be applied to the block, determining that OBMC is not to be applied to the block without decoding OBMC-related syntax elements for the block.

4. The method according to claim 3, in, Determining whether OBMC is to be applied to the block includes determining whether OBMC is to be applied to the block based on whether OBMC is to be applied to spatial neighbors of the block.

5. The method according to claim 2, in, Determining whether OBMC is to be applied to the block includes determining a value of an OBMC syntax element, the value of the OBMC syntax element indicating whether OBMC is to be applied to the block.

6. The method according to claim 5, in, The OBMC syntax element includes an OBMC flag.

7. The method according to claim 5, further comprising: include: determining a context for decoding the OBMC syntax element according to whether a picture including the block of the video data is a low-delay picture or a non-low-delay picture; as well as The OBMC syntax element is context-based decoded using the determined context.

8. The method according to claim 5, further comprising: include: determining a context for decoding the OBMC syntax element based on the data indicating that the block is to be predicted using affine motion compensation; as well as The OBMC syntax element is context-based decoded using the determined context.

9. The method according to claim 2, in, Determining whether OBMC is to be applied to the block includes determining not to apply OBMC to the block of the video data when the block has a size greater than a threshold.

10. The method according to claim 9, in, The size of the block of video data corresponds to a dimension of the block of video data, and wherein the threshold comprises 128 samples along the one dimension.

11. The method according to claim 10, in, The one dimension comprises one of a width of the block of video data or a height of the block of video data.

12. The method according to claim 1, in, The block includes a luma block, and the method further includes performing pixel-based affine motion compensation on a chroma block corresponding to the luma block.

13. The method according to claim 1, further comprising: include: In response to determining that the motion information of the block is for the respective pixels, it is determined that prediction refinement PROF using optical flow is not to be performed on the block.

14. The method according to claim 13, in, Determining that PROF is not to be performed includes determining that PROF is not to be performed without decoding PROF-related syntax elements for the block.

15. The method of claim 1, further comprising, in response to determining that the motion information of the block is for the sub-blocks, determining that prediction refinement PROF using optical flow is not to be performed on the block when a smallest sub-block among the sub-blocks has a size smaller than a threshold.

16. The method according to claim 15, in, The block includes a coding unit CU.

17. The method according to claim 15, in, The size of the minimum sub-block corresponds to a dimension of the sub-block, and wherein the threshold is 4 samples.

18. The method according to claim 17, in, The one dimension includes one of a height of the smallest sub-block or a width of the smallest sub-block.

19. The method according to claim 15, in, Determining that PROF is not to be performed includes determining that PROF is not to be performed without decoding PROF-related syntax elements for the block.

20. The method according to claim 1, in, The block comprises a first block and the prediction block comprises a first prediction block, the method further comprising: determining that affine motion compensation is not to be used to predict the second block of the video data; In response to determining that affine motion compensation is not to be used to predict the second block of the video data, implicitly determining whether to apply overlapped block motion compensation (OBMC) to the second block of the video data without decoding data indicating whether to apply OBMC to the second block of the video data; forming a second prediction block for a second block of the video data; and A second block of the video data is decoded using the second prediction block.

21. The method according to claim 1, in, The data indicating that the block is to be predicted using affine motion compensation comprises data indicating that the block of the video data is to be predicted using an affine motion compensation mode other than an affine merge mode.

22. The method according to claim 1, in, The current picture includes the block and the motion information refers to a reference picture, and wherein determining whether the motion information is for the sub-block or the individual pixels comprises: determining a difference between a picture order count (POC) of the current picture and a POC of the reference picture; and When a difference between the POC of the current picture and the POC of the reference picture is greater than a threshold, the motion information is determined to be used for the respective pixels.

23. The method according to claim 22, in, The threshold value is the value 1.

24. The method according to claim 1, in, The block is included in a non-low-latency picture.

25. The method according to claim 1, in, Also included is encoding the current block before decoding the current block.

26. A device for decoding video data, the device include: a memory configured to store video data; as well as A processing system, comprising one or more processors implemented in circuitry, the processing system being configured to: determining whether motion information for a block of the video data is for a sub-block of the block that is larger than individual pixels of the block or for the individual pixels, the block being associated with data indicating that the block is to be predicted using affine motion compensation; In response to determining that the motion information of the block is for the sub-block, performing sub-block-based affine motion compensation to form a prediction block for the block; In response to determining that the motion information is for the respective pixels, performing pixel-based affine motion compensation to form a prediction block for the block; as well as The block is decoded using the prediction block.

27. The device according to claim 26, in, In order to determine whether the motion information is for the sub-block or for the individual pixels, the processing system is configured to determine whether overlapped block motion compensation (OBMC) is to be applied to the block.

28. The device according to claim 27, in, To determine whether OBMC is to be applied to the block, the processing system is configured to determine that OBMC is not to be applied to the block without decoding OBMC-related syntax elements for the block when multi-hypothesis prediction (MHP) is determined to be applied to the block.

29. The device according to claim 28, in, To determine whether OBMC is to be applied to the block, the processing system is configured to determine whether OBMC is to be applied to spatial neighbors of the block.

30. The device according to claim 27, in, To determine whether OBMC is to be applied to the block, the processing system is configured to determine a value of an OBMC syntax element, the value of the OBMC syntax element indicating whether OBMC is to be applied to the block.

31. The device according to claim 30, in, The OBMC syntax element includes an OBMC flag.

32. The device according to claim 30, in, The processing system is also configured to: determining a context for decoding the OBMC syntax element according to whether a picture including the block of the video data is a low-delay picture or a non-low-delay picture; as well as The OBMC syntax element is context-based decoded using the determined context.

33. The device according to claim 30, in, The processing system is also configured to: determining a context for decoding the OBMC syntax element based on the data indicating that the block is to be predicted using affine motion compensation; as well as The OBMC syntax element is context-based decoded using the determined context.

34. The device according to claim 27, in, To determine whether OBMC is to be applied to the block, the processing system is configured to determine not to apply OBMC to the block when the block has a size greater than a threshold.

35. The device according to claim 26, in, The device includes one or more of a camera, a computer, a mobile device, a broadcast receiver device, or a set-top box.

36. A device for decoding video data, the device include: means for determining whether motion information for a block of the video data is for a sub-block of the block that is larger than individual pixels of the block or for the individual pixels, the block being associated with data indicating that the block is to be predicted using affine motion compensation; means for performing sub-block based affine motion compensation to form a prediction block for the block in response to determining that the motion information of the block is for the sub-block; means for performing pixel-based affine motion compensation to form a prediction block for the block in response to determining that the motion information is for the respective pixels; as well as Means for decoding the block using the prediction block.

37. The device according to claim 36, in, The means for determining whether the motion information is for the sub-block or for the individual pixels includes means for determining whether overlapped block motion compensation (OBMC) is to be applied to the block.

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