Derivation process for chain motion vector prediction in video coding

Abstract

An example video coder is configured to determine that a current block of video data is coded using bi-directional matching merge mode. The video coder is configured to determine a first chain motion vector prediction (CMVP) candidate based on a first source candidate and determine that the first source candidate satisfies one or more bi-directional matching conditions. The video coder is configured to insert the first CMVP candidate into a bi-directional matching merge list. The video coder is configured to determine a second CMVP candidate based on a second source candidate and determine that the second source candidate does not satisfy the one or more bi-directional matching conditions. The video coder is configured to insert the second CMVP candidate into a second list. The video coder is configured to decode the current block using at least one of the bi-directional matching merge list or the second list.

Description

[0001] This application claims priority to U.S. Patent Application No. 19 / 043,678, filed February 3, 2025, and U.S. Provisional Patent Application No. 63 / 567,828, filed March 20, 2024, the entire contents of each of which are incorporated herein by reference. U.S. Patent Application No. 19 / 043,678, filed February 3, 2025, claims the benefit of U.S. Provisional Application No. 63 / 567,828, filed March 20, 2024. Technical Field

[0002] This disclosure relates to video encoding and video decoding. Background Technology

[0003] Digital video capabilities can be incorporated into a wide variety of devices, including digital televisions, digital live broadcast systems, wireless broadcasting systems, personal digital assistants (PDAs), laptops or desktop computers, tablets, e-book readers, digital cameras, digital recording devices, digital media players, video game devices, video game consoles, cellular or satellite wireless phones (so-called "smartphones"), video conferencing equipment, video streaming devices, and more. Digital video devices implement video decoding technologies, such as those defined by MPEG-2, MPEG-4, ITU-T H.263, ITU-T H.264 / MPEG-4 (Part 10, Advanced Video Decoding (AVC)), ITU-T H.265 / High Efficiency Video Decoding (HEVC), ITU-T H.266 / Variety Video Decoding (VVC) and extensions to these standards, as well as proprietary video codecs / formats such as AOMedia Video1 (AV1) developed by the Open Media Alliance. By implementing such video decoding technologies, video devices can more efficiently send, receive, encode, decode, and / or store digital video information.

[0004] Video decoding 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 decoding, video slices (e.g., video pictures or portions of video pictures) can be divided into video blocks, which may also be referred to as decoding tree units (CTUs), decoding units (CUs), and / or decoding nodes. Video blocks in a slice after intra-frame decoding (I) of a picture are encoded using spatial prediction relative to reference samples in neighboring blocks within the same picture. Video blocks in a slice after inter-frame decoding (P or B) of a picture can use spatial prediction relative to reference samples in neighboring blocks within the same picture or temporal prediction relative to reference samples in other reference pictures. A picture may be referred to as a frame, and a reference picture may be referred to as a reference frame. Summary of the Invention

[0005] Generally, this disclosure describes techniques for decoding video data, including techniques for Chained Motion Vector Prediction (CMVP). This disclosure also describes various techniques (e.g., template types, fusion) and syntaxes used in template matching (TM) related tools. The techniques of this disclosure can be applied to any of the existing video codecs (such as HEVC (High Efficiency Video Decoding), VVC (Various Video Decoding), and EVC (Essential Video Decoding)), or can be efficient decoding tools in future video decoding standards (e.g., ECM (Enhanced Compression Model)). Certain CMVP implementations and standards may not be the optimal efficient way to decode video data. The CMVP techniques of this disclosure can improve the efficiency of video decoding and / or the quality of video data. Improving the efficiency of video decoding can reduce the processing and / or power consumption requirements of the video decoder.

[0006] Example methods include: determining to decode the current block of video data using a bilateral matching merge mode; determining a first chained motion vector prediction (CMVP) candidate based on a first source candidate; determining that the first source candidate satisfies one or more bilateral matching conditions; inserting the first CMVP candidate into a bilateral matching merge list based on the first source candidate satisfying one or more bilateral matching conditions; determining a second CMVP candidate based on a second source candidate; determining that the second source candidate does not satisfy one or more bilateral matching conditions; inserting the second CMVP candidate into a second list based on the second source candidate not satisfying one or more bilateral matching conditions; and decoding the current block using at least one of the bilateral matching merge list or the second list.

[0007] An example device includes: one or more memories configured to store video data; and one or more processors communicatively coupled to the one or more memories, the processors being configured to: determine a current block of video data to be decoded using a bilateral match-merge mode; determine a first chained motion vector prediction (CMVP) candidate based on a first source candidate; determine that the first source candidate satisfies one or more bilateral match conditions; insert the first CMVP candidate into a bilateral match-merge list based on the first source candidate satisfying one or more bilateral match conditions; determine a second CMVP candidate based on a second source candidate; determine that the second source candidate does not satisfy one or more bilateral match conditions; insert the second CMVP candidate into a second list based on the second source candidate not satisfying one or more bilateral match conditions; and decode the current block using at least one of the bilateral match-merge list or the second list.

[0008] Another example device includes: one or more memories configured to store video data; and one or more processors communicatively coupled to the one or more memories, the processors being configured to: determine a current block of video data to be encoded using a bilateral matching merge mode; determine a first chained motion vector prediction (CMVP) candidate based on a first source candidate; determine that the first source candidate satisfies one or more bilateral matching conditions; insert the first CMVP candidate into a bilateral matching merge list based on the first source candidate satisfying one or more bilateral matching conditions; determine a second CMVP candidate based on a second source candidate; determine that the second source candidate does not satisfy one or more bilateral matching conditions; insert the second CMVP candidate into a second list based on the second source candidate not satisfying one or more bilateral matching conditions; and encode the current block using at least one of the bilateral matching merge list or the second list.

[0009] Details of one or more examples are set forth in the accompanying drawings and the following description. Other features, objects, and advantages will be apparent from the description, drawings, and claims. Attached Figure Description

[0010] Figure 1 This is a block diagram illustrating an example video encoding and decoding system that can perform the techniques of this disclosure.

[0011] Figure 2A This is a conceptual diagram illustrating example space motion vector candidates used for merging patterns.

[0012] Figure 2B This is a conceptual diagram illustrating example space motion vector candidates for an Advanced Motion Vector Prediction (AMVP) pattern.

[0013] Figure 3A This is a conceptual diagram illustrating an example of a candidate time motion vector.

[0014] Figure 3B This is a conceptual diagram illustrating an example of motion vector scaling.

[0015] Figure 4 An example of template matching performed over the search region around the initial motion vector is shown.

[0016] Figure 5 An example of bilateral matching prediction is shown, in which the two motion vectors are proportional based on the time distance.

[0017] Figure 6 An example of bilateral matching prediction is shown, in which the two motion vectors are mirror images regardless of their temporal distance.

[0018] Figure 7An example of a 3×3 square search pattern in the search range [-8, 8] is shown.

[0019] Figure 8 An example of decoder-side motion vector refinement is shown.

[0020] Figure 9 An example export of a Chained Motion Vector Prediction (CMVP) candidate is shown.

[0021] Figure 10 This example demonstrates how to track motion vectors by referencing the source and destination in a CMVP.

[0022] Figure 11 An example of tracking CMVP motion with a depth of one is shown.

[0023] Figure 12 This is a flowchart illustrating an example of a chain motion vector prediction technique according to one or more aspects of this disclosure.

[0024] Figure 13 This is a flowchart illustrating another example of a chain motion vector prediction technique according to one or more aspects of this disclosure.

[0025] Figure 14 This is a block diagram illustrating an example video encoder that can perform the techniques of this disclosure.

[0026] Figure 15 This is a block diagram illustrating an example video decoder that can perform the techniques of this disclosure.

[0027] Figure 16 This is a flowchart illustrating an example method for encoding the current block according to the technology of this disclosure.

[0028] Figure 17 This is a flowchart illustrating an example method for decoding the current block according to the technology of this disclosure. Detailed Implementation

[0029] This disclosure describes techniques for decoding video data, including techniques for Chained Motion Vector Prediction (CMVP). Certain CMVP implementations and standards may not be the optimal, efficient way to decode video data. The CMVP techniques disclosed herein can improve the efficiency of video decoding and / or the quality of video data. Improving the efficiency of video decoding can reduce the processing and / or power consumption requirements of the video decoder.

[0030] Figure 1This is a block diagram illustrating an example video encoding and decoding system 100 capable of performing the techniques of this disclosure. The techniques of this disclosure generally relate to decoding (encoding and / or decoding) video data. Generally speaking, video data includes any data used for processing video. Thus, video data may include unencoded raw video, encoded video, decoded (e.g., reconstructed) video, and video metadata, such as signaling data.

[0031] like Figure 1 As shown, in this example, system 100 includes a source device 102 that provides encoded video data to be decoded and displayed by a destination device 116. Specifically, source device 102 provides video data to destination device 116 via computer-readable medium 110. Source device 102 and destination device 116 can be or may include any of a wide range of devices, such as desktop computers, laptop computers, mobile devices, tablet computers, set-top boxes, mobile phones (such as smartphones), 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 configured for wireless communication and are therefore referred to as wireless communication devices.

[0032] exist Figure 1 In the example, source device 102 includes a video source 104, memory 106, video encoder 200, and output interface 108. Destination device 116 includes an input interface 122, video decoder 300, memory 120, and display device 118. According to this disclosure, the video encoder 200 of source device 102 and the video decoder 300 of destination device 116 can be configured to apply techniques for chained motion vector prediction. Thus, source device 102 represents an example of a video encoding device, while destination device 116 represents an example of a video decoding device. In other examples, the source device and destination device may include other components or arrangements. For example, source device 102 may receive video data from an external video source such as an external camera. Similarly, destination device 116 may interface with an external display device, rather than including an integrated display device.

[0033] like Figure 1The system 100 shown is merely an example. Generally, any digital video encoding and / or decoding device can perform techniques for chained motion vector prediction. Source device 102 and destination device 116 are merely examples of such decoding devices, where source device 102 generates decoded video data for transmission to destination device 116. This disclosure refers to a “decoding” device as a device that performs the decoding (e.g., encoding and / or decoding) of data. Thus, video encoder 200 and video decoder 300 represent examples of decoding devices, specifically, a video encoder and a video decoder, respectively. In some examples, source device 102 and destination device 116 may operate in a substantially symmetrical manner, such that each of source device 102 and destination device 116 includes video encoding and decoding components. Therefore, system 100 may support one-way or two-way video transmission between source device 102 and destination device 116, for example, for video streaming, video playback, video broadcasting, or video telephony.

[0034] Generally, video source 104 represents the source of video data (i.e., unencoded raw video data) and provides a sequential series of pictures (also referred to as "frames") of video data to video encoder 200, which encodes the data for the pictures. Video source 104 of source device 102 may include video capture devices such as cameras, video archives containing previously captured raw video, and / or video feed interfaces for receiving video from video content providers. Alternatively, video source 104 may generate computer graphics-based data as source video, or a combination of live video, archived video, and computer-generated video. In each case, video encoder 200 encodes the captured, pre-captured, or computer-generated video data. Video encoder 200 may rearrange the pictures from the received order (sometimes referred to as "display order") to a decoding order for decoding. Video encoder 200 may generate a bitstream comprising the encoded video data. Then, the source device 102 can output the encoded video data to the computer-readable medium 110 via the output interface 108 for reception and / or retrieval by, for example, the input interface 122 of the destination device 116.

[0035] The memory 106 of source device 102 and the memory 120 of destination device 116 represent general-purpose memory. In some examples, memories 106 and 120 may store raw video data, such as raw video from video source 104 and raw decoded video data from video decoder 300. Additionally or alternatively, memories 106 and 120 may store software instructions executable by, for example, video encoder 200 and video decoder 300. Although memories 106 and 120 are shown separately from video encoder 200 and video decoder 300 in this example, it should be understood that video encoder 200 and video decoder 300 may also include internal memory for functionally similar or equivalent purposes. Furthermore, memories 106 and 120 may store encoded video data, such as output from video encoder 200 and input to video decoder 300. In some examples, portions of memories 106 and 120 may be allocated as one or more video buffers, for example, to store raw decoded and / or encoded video data.

[0036] Computer-readable medium 110 may represent any type of medium or device capable of transmitting encoded video data from source device 102 to destination device 116. In one example, computer-readable medium 110 represents a communication medium that enables source device 102 to directly transmit encoded video data to 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, output interface 108 may modulate the transmitted signal including the encoded video data, and input interface 122 may demodulate the received transmitted signal. The communication medium may include any wireless or wired communication medium, such as 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, switch, base station, or any other equipment that may be useful for facilitating communication from source device 102 to destination device 116.

[0037] In some examples, source device 102 can output encoded data from output interface 108 to storage device 112. Similarly, destination device 116 can access encoded data from storage device 112 via input interface 122. Storage device 112 may include any data storage medium of various distributed or locally accessed data storage media, such as hard disk drives, Blu-ray discs, DVDs, CD-ROMs, flash memory, volatile or non-volatile memory, or any other suitable digital storage medium for storing encoded video data.

[0038] In some examples, source device 102 can output encoded video data to file server 114 or another intermediate storage device that can store the encoded video data generated by source device 102. Destination device 116 can access the stored video data from file server 114 via streaming or download.

[0039] File server 114 can be any type of server device capable of storing encoded video data and sending the encoded video data to destination device 116. File server 114 may represent a web server (e.g., for a website), a server configured to provide file transfer protocol services (such as File Transfer Protocol (FTP) or FLUTE-based file delivery protocol), a Content Delivery Network (CDN) device, a Hypertext Transfer Protocol (HTTP) server, a Multimedia Broadcast Multicast Service (MBMS) or Enhanced MBMS (eMBMS) server, and / or a Network Attached Storage (NAS) device. File server 114 may additionally or alternatively implement one or more HTTP streaming protocols, such as HTTP-based Dynamic Adaptive Streaming (DASH), HTTP Live Streaming (HLS), Real-Time Streaming Protocol (RTSP), HTTP Dynamic Streaming, etc.

[0040] Destination device 116 can access encoded video data from file server 114 via any standard data connection, including an internet connection. This may include a wireless channel (e.g., Wi-Fi connection), a wired connection (e.g., digital subscriber line (DSL), cable modem, etc.), or a combination of both, suitable for accessing encoded video data stored on file server 114. Input interface 122 can be configured to operate according to any 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.

[0041] Output interface 108 and input interface 122 can represent a wireless transmitter / receiver, a modem, a wired networking component (e.g., an Ethernet card), a wireless communication component operating according to any of the various IEEE 802.11 standards, or other physical components. In examples where output interface 108 and input interface 122 include wireless components, output interface 108 and input interface 122 can be configured to transmit data, such as encoded video data, according to cellular communication standards such as 4G, 4G-LTE (Long Term Evolution), Advanced LTE, 5G, etc. In some examples where output interface 108 includes a wireless transmitter, output interface 108 and input interface 122 can be configured to comply with other wireless standards such as the IEEE 802.11 specification, the IEEE 802.15 specification (e.g., ZigBee), etc.™ ),Bluetooth ™ Standards are used to transmit data, such as encoded video data. In some examples, source device 102 and / or destination device 116 may include corresponding system-on-chip (SoC) devices. For example, source device 102 may include an SoC device for performing functions belonging to video encoder 200 and / or output interface 108, and destination device 116 may include an SoC device for performing functions belonging to video decoder 300 and / or input interface 122.

[0042] The technology disclosed herein can be applied to video decoding to support any multimedia application in a variety of multimedia applications, such as over-the-air television broadcasting, cable television transmission, satellite television transmission, internet streaming video transmission (such as HTTP-based Dynamic Adaptive Streaming (DASH)), digital video encoded onto data storage media, decoding of digital video stored on data storage media, or other applications.

[0043] The input interface 122 of the destination device 116 receives an encoded video bitstream from a computer-readable medium 110 (e.g., a communication medium, storage device 112, file server 114, etc.). The encoded video bitstream may include signaling information defined by the video encoder 200 and also used by the video decoder 300, such as syntax elements having values ​​describing the characteristics and / or processing of video blocks or other decoded units (e.g., slices, pictures, picture groups, sequences, etc.). The display device 118 displays a decoded picture of the decoded video data to the user. The display device 118 may represent any of a variety of display devices, such as a liquid crystal display (LCD), a plasma display, an organic light-emitting diode (OLED) display, or another type of display device.

[0044] Despite Figure 1Not shown, but in some examples, both the video encoder 200 and the video decoder 300 may be integrated with the audio encoder and / or audio decoder (e.g., audio codec), and may include appropriate MUX-DEMUX units or other hardware and / or software to process multiplexed streams that include both audio and video in a common data stream. Example audio codecs may include AAC, AC-3, AC-4, ALAC, ALS, AMBE, AMR, AMR-WB (G.722.2), AMR-WB+, aptX (various versions), ATRAC, BroadVoice (BV16, BV32), CELT, Enhanced AC-3 (E-AC-3), EVS, FLAC, G.711, G.722, G.722.1, G.722.2 (AMR-WB), G.723.1, G.726, G.728, G.729, G.729.1, GSM-FR, HE-AAC, iLBC, iSAC, LA Lyra, Monkey's Audio, MP1, MP2 (MPEG-1, 2 Audio Layer II), MP3, Musepack, Nellymoser Asao, OptimFROG, Opus, Sac, Satin, SBC, SILK, Siren 7, Speex, SVOPC, True Audio (TTA), TwinVQ, USAC, Vorbis (Ogg), WavPack and Windows Media Aud.

[0045] Both the video encoder 200 and the video decoder 300 can be implemented as any of a variety of suitable encoder and / or decoder circuits comprising a processing system, 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 in part in software, the device may store instructions for the software in a suitable non-transitory computer-readable medium and execute the instructions in hardware using one or more processors to perform the technology of this disclosure. Each of the video encoder 200 and the video decoder 300 may be included in one or more encoders or decoders, either of which may be integrated as part of a combined encoder / decoder (CODEC) in the respective device. Devices including the video encoder 200 and / or the video decoder 300 may implement the video encoder 200 and / or the video decoder 300 in processing circuitry such as integrated circuits and / or microprocessors. Such devices may be wireless communication devices (such as cellular phones) or any other type of device described herein.

[0046] The video encoder 200 and video decoder 300 may operate according to a video decoding standard such as ITU-T H.265 (also known as High Efficiency Video Decoding (HEVC)) or its extensions (such as Multi-View and / or Scalable Video Decoding Extensions)). Alternatively, the video encoder 200 and video decoder 300 may operate according to other proprietary or industry standards such as ITU-T H.266 (also known as Multi-Functional Video Decoding (VVC)). In other examples, the video encoder 200 and video decoder 300 may operate according to proprietary video codecs / formats such as AOMedia Video 1 (AV1), extensions to AV1, and / or subsequent versions of AV1 (e.g., AV2)). In other examples, the video encoder 200 and video decoder 300 may operate according to other proprietary formats or industry standards. However, the technology disclosed herein is not limited to any particular decoding standard or format. Generally speaking, the video encoder 200 and the video decoder 300 can be configured to perform the techniques of this disclosure in conjunction with any video decoding technique that uses chained motion vector prediction.

[0047] Generally, the video encoder 200 and video decoder 300 perform block-based decoding of images. The term "block" typically refers to a structure that includes data to be processed (e.g., encoded, decoded, or otherwise used during encoding and / or decoding). For example, a block may include a two-dimensional matrix of samples of luminance and / or chrominance data. Generally, the video encoder 200 and video decoder 300 decode video data represented in YUV (e.g., Y, Cb, Cr) format. That is, instead of decoding the red, green, and blue (RGB) data used for images, the video encoder 200 and video decoder 300 decode both the luminance and chrominance components, where the chrominance components may include both red and blue hue chrominance components. In some examples, the video encoder 200 converts the received RGB format data to a YUV representation before encoding, and the video decoder 300 converts that YUV representation to RGB format. Alternatively, preprocessing and postprocessing units (not shown) may perform these conversions.

[0048] This disclosure generally relates to the decoding (e.g., encoding and decoding) of images to include processes of encoding or decoding data of the image. Similarly, this disclosure may relate to the decoding of blocks of images to include processes of encoding or decoding data used for the blocks (e.g., prediction and / or residual decoding). Encoded video bitstreams typically include a series of values ​​for syntax elements representing decoding decisions (e.g., decoding modes) and the partitioning of images into blocks. Therefore, references to the decoding of images or blocks should generally be understood as the decoded values ​​of the syntax elements that form the images or blocks.

[0049] HEVC defines various blocks, including decoding units (CUs), prediction units (PUs), and transform units (TUs). According to HEVC, a video decoder (such as a video encoder 200) divides the decoding tree unit (CTU) into CUs based on a quadtree structure. That is, the video decoder divides the CTU and CU into four equal, non-overlapping squares, and each node of the quadtree has zero or four child nodes. Nodes without child nodes are called "leaf nodes," and the CU of such leaf nodes may include one or more PUs and / or one or more TUs. The video decoder may further divide the PUs and TUs. For example, in HEVC, a residual quadtree (RQT) represents the partitioning of the TU. In HEVC, the PU represents inter-frame prediction data, while the TU represents residual data. The CU after intra-frame prediction includes intra-frame prediction information, such as intra-frame mode indication.

[0050] As another example, video encoder 200 and video decoder 300 can be configured to operate according to VVC. According to VVC, the video decoder (such as video encoder 200) partitions the image into multiple CTUs. Video encoder 200 can partition the CTUs according to a tree structure (such as 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 CUs, PUs, and TUs in HEVC. The QTBT structure includes two levels: a first level partitioned according to quadtree partitioning, and a second level partitioned according to binary tree partitioning. The root node of the QTBT structure corresponds to a CTU. The leaf nodes of the binary tree correspond to CUs.

[0051] In the MTT partitioning structure, blocks can be divided using quadtree (QT) partitioning, binary tree (BT) partitioning, and one or more types of ternary tree (TT) partitioning (also known as triplet tree (TT)). A ternary tree or triplet tree partition is a partition in which a block is divided into three sub-blocks. In some examples, a ternary tree or triplet tree partition divides a block into three sub-blocks without dividing the original block through the center. Partition types in MTT (e.g., QT, BT, and TT) can be symmetric or asymmetric.

[0052] When operating according to the AV1 codec, the video encoder 200 and video decoder 300 can be configured to decode video data in blocks. In AV1, the largest decoded block that can be processed is called a superblock. In AV1, a superblock can be 128x128 luminance samples or 64x64 luminance samples. However, in subsequent video decoding formats (e.g., AV2), superblocks can be defined by different (e.g., larger) luminance sample sizes. In some examples, the superblock is the top level of a block quadtree. The video encoder 200 can further divide the superblock into smaller decoded blocks. The video encoder 200 can use square or non-square partitions to divide the superblock and other decoded blocks into smaller blocks. Non-square blocks can include N / 2xN blocks, NxN / 2 blocks, N / 4xN blocks, and NxN / 4 blocks. The video encoder 200 and video decoder 300 can perform separate prediction and transform processing on each decoded block within the decoded block.

[0053] AV1 also defines video data tiles. A tile is a rectangular array of superblocks that can be decoded independently of other tiles. That is, the video encoder 200 and video decoder 300 can encode and decode the decoding blocks within a tile separately without using video data from other tiles. However, the video encoder 200 and video decoder 300 can perform filtering across tile boundaries. The tile size can be uniform or non-uniform. Tile-based decoding enables parallel processing and / or multithreading in the encoder and decoder implementations.

[0054] In some examples, the video encoder 200 and the video decoder 300 may use a single QTBT or MTT structure to represent each of the luma and chroma components, while in other examples, the video encoder 200 and the video decoder 300 may use two or more QTBT or MTT structures, 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 the respective chroma components).

[0055] The video encoder 200 and the video decoder 300 can be configured to use quadtree partitioning, QTBT partitioning, MTT partitioning, superblock partitioning or other partitioning structures.

[0056] In some examples, a CTU includes a decoded tree block (CTB) of luminance samples, two corresponding CTBs of chrominance samples of an image with three sample arrays, or a CTB of samples of an image decoded using three separate color planes and a syntax structure for decoding the samples. A CTB can be an NxN sample block of some value N, such that a partitioning method divides the components into CTBs. A component is an array or a single sample from one of the three arrays (luminance and two chrominance) constituting a 4:2:0, 4:2:2, or 4:4:4 color format image, or an array or a single sample constituting an array or array constituting a monochrome format image. In some examples, a decoded block is an MxN sample block of values ​​M and N, such that a partitioning method divides the CTB into decoded blocks.

[0057] Blocks (e.g., CTUs or CUs) can be grouped in various ways within an image. As an example, a brick can refer to a rectangular area of ​​a row of CTUs within a specific tile in an image. A tile can be a rectangular area of ​​CTUs within a specific tile column and a specific tile row in an image. A tile column refers to a rectangular area of ​​a CTU having a height equal to the height of the image and a width specified by syntax elements (e.g., such as in an image parameter set). A tile row refers to a rectangular area of ​​a CTU having a height specified by syntax elements (e.g., such as in an image parameter set) and a width equal to the width of the image.

[0058] In some examples, a tile can be divided into multiple bricks, each of which may include one or more CTU rows within the tile. A tile that is not divided into multiple bricks can also be called a brick. However, bricks that are a true subset of a tile cannot be called a tile. Bricks in an image can also be arranged in slices. A slice can be an integer number of bricks in an image that can be uniquely contained within a single Network Abstraction Layer (NAL) unit. In some examples, a slice includes multiple complete tiles or a continuous sequence of complete bricks that include only one tile.

[0059] This disclosure uses "N×N" and "N by N" interchangeably to refer to the sample size of a block (such as a CU or other video block) in the vertical and horizontal dimensions, for example, 16x16 samples or 16 by 16 samples. Generally, a 16×16 CU will have 16 samples in the vertical direction (y=16) and 16 samples in the horizontal direction (x=16). Similarly, 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. Samples in a CU can 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 it does in the vertical direction. For example, a CU may include N×M samples, where M is not necessarily equal to N.

[0060] The video encoder 200 encodes video data representing prediction and / or residual information, as well as other information, for use in the control unit (CU). The prediction information indicates how the CU should be predicted to form a prediction block for the CU. The residual information typically represents the sample-by-sample difference between a sample of the CU before encoding and the prediction block.

[0061] To predict the Cubic Frame (CU), the video encoder 200 typically forms prediction blocks for the CU through inter-frame prediction or intra-frame prediction. Inter-frame prediction typically refers to predicting the CU from data in a previously decoded image, while intra-frame prediction typically refers to predicting the CU from data in a previously decoded image within the same frame. To perform inter-frame prediction, the video encoder 200 can use one or more motion vectors to generate prediction blocks. The video encoder 200 can typically perform a motion search to identify reference blocks that closely match the CU, for example, based on the differences between the CU and a reference block. The video encoder 200 can use sum of absolute differences (SAD), sum of squared differences (SSD), mean absolute difference (MAD), mean squared difference (MSD), or other such difference calculations to compute difference metrics to determine whether a reference block closely matches the current CU. In some examples, the video encoder 200 can use unidirectional or bidirectional prediction to predict the current CU.

[0062] Some examples of VVC also provide an affine motion compensation mode, which can be viewed as an inter-frame prediction mode. In 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.

[0063] To perform intra-frame prediction, the video encoder 200 can select an intra-frame prediction mode to generate prediction blocks. Some examples of VVC provide sixty-seven intra-frame prediction modes, including various directional modes, as well as planar and DC modes. Generally, the video encoder 200 selects an intra-frame prediction mode that describes the neighboring samples of the current block (e.g., the block of the CU) and predicts samples of the current block from them. Assuming the video encoder 200 decodes the CTU and CU in raster scan order (from left to right, from top to bottom), such samples can typically be located above, to the upper left, or to the left of the current block in the same image as the current block.

[0064] The video encoder 200 encodes data representing the prediction mode of the current block. For example, for inter-frame prediction modes, the video encoder 200 may encode data indicating which of the various available inter-frame prediction modes is used, as well as the motion information for 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 merging modes. The video encoder 200 may use similar modes to encode motion vectors used for affine motion compensation modes.

[0065] AV1 includes two common techniques for encoding and decoding blocks of video data. These two common techniques are intra-frame prediction (e.g., intra-frame prediction or spatial prediction) and inter-frame prediction (e.g., inter-frame prediction or temporal prediction). In the context of AV1, when using intra-frame prediction modes to predict blocks of video data for the current frame, the video encoder 200 and video decoder 300 do not use video data from other frames of the video data. For most intra-frame prediction modes, the video encoder 200 encodes blocks of the current frame based on the difference between sample values ​​in the current block and predicted values ​​generated from reference samples in the same frame. The video encoder 200 determines the predicted values ​​generated from the reference samples based on the intra-frame prediction mode.

[0066] After prediction (such as intra-frame or inter-frame prediction for a block), the video encoder 200 can compute residual data for the block. The residual data (such as a residual block) represents the sample-wise difference between the block and the prediction block used to form the block, which is formed using the corresponding prediction mode. The video encoder 200 can apply one or more transforms to the residual block to produce transformed data in the transform domain rather than the sample domain. For example, the video encoder 200 can apply a Discrete Cosine Transform (DCT), an integer transform, a wavelet transform, or a conceptually similar transform to the residual video data. Additionally, the video encoder 200 can apply a secondary transform after the first transform, such as a Mode Correlated Inseparable Secondary Transform (MDNSST), a Signal Correlation Transform, a Karhunen-Loeve Transform (KLT), etc. The video encoder 200 produces transform coefficients after applying one or more transforms.

[0067] As noted above, after any transformation that produces the transform coefficients, the video encoder 200 may perform quantization on the transform coefficients. Quantization generally refers to the process in which the transform coefficients are quantized to reduce the amount of data used to represent them, 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 quantize the transform coefficients during quantization. n The place value is rounded down to m Bit value, where n Greater than m In some examples, in order to perform quantization, the video encoder 200 may perform a bit-by-bit right shift of the value to be quantized.

[0068] After quantization, the video encoder 200 can scan the transform coefficients to generate a one-dimensional vector from a two-dimensional matrix containing the quantized transform coefficients. The scan can be designed to place higher-energy (and therefore lower-frequency) transform coefficients before the vector and lower-energy (and therefore higher-frequency) transform coefficients after the vector. In some examples, the video encoder 200 can utilize a predefined scan order to scan the quantized transform coefficients to produce a serialized vector, and then entropy-encode the quantized transform coefficients of that vector. In other examples, the video encoder 200 can perform an adaptive scan. After scanning the quantized transform coefficients to form a one-dimensional vector, the video encoder 200 can entropy-encode the one-dimensional vector, for example, according to context-adaptive binary arithmetic decoding (CABAC). The video encoder 200 can also entropy-encode the values ​​of syntax elements describing metadata associated with the encoded video data, which is used by the video decoder 300 when decoding the video data.

[0069] To perform CABAC, the video encoder 200 can assign context within a context model to the symbols to be transmitted. Context may involve, for example, whether the neighboring values ​​of a symbol are zero. Probability determination can be based on the context assigned to the symbols.

[0070] The video encoder 200 may further generate syntax data for the video decoder 300, such as block-based syntax data, image-based syntax data, and sequence-based syntax data, for example, in image headers, block headers, and slice headers, or generate other syntax data such as sequence parameter sets (SPS), image parameter sets (PPS), or video parameter sets (VPS). The video decoder 300 may also decode such syntax data to determine how to decode the corresponding video data.

[0071] In this way, the video encoder 200 can generate a bitstream that includes encoded video data, such as syntax elements describing the partitioning of images 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.

[0072] Generally, the video decoder 300 performs the reverse process of the video encoder 200 to decode the encoded video data of the bitstream. For example, the video decoder 300 can use CABAC to decode the values ​​of syntax elements used for the bitstream in a manner substantially similar to but reversed by the CABAC encoding process of the video encoder 200. Syntax elements can define partitioning information for dividing a picture into CTUs and defining the CUs of each CTU according to a corresponding partitioning structure such as a QTBT structure. Syntax elements can further define prediction and residual information for video data blocks (e.g., CUs).

[0073] The residual information can be represented, for example, by quantized transform coefficients. The video decoder 300 can inversely quantize and inverse transform the quantized transform coefficients of the block to reconstruct the residual block for the block. The video decoder 300 uses a signaling prediction mode (intra-frame prediction or inter-frame prediction) and associated prediction information (e.g., motion information for inter-frame prediction) to form a prediction block for the block. The video decoder 300 can then combine the prediction block and the residual block (on a sample-by-sample basis) to reconstruct the original block. The video decoder 300 can perform additional processing, such as performing a deblocking process to reduce visual artifacts along the block boundaries.

[0074] This disclosure may generally relate to "signaling" certain information (such as syntax elements). The term "signaling" can generally refer to the communication of values ​​and / or other data of syntax elements used to decode encoded video data. That is, video encoder 200 may signal the values ​​of syntax elements in the bitstream. Generally speaking, signaling refers to generating values ​​in the bitstream. As noted above, source device 102 may transmit the bitstream to destination device 116 substantially in real time or not in real time (such as when syntax elements are stored in storage device 112 for later retrieval by destination device 116).

[0075] Generally, this disclosure describes techniques for decoding video data, including techniques for Chained Motion Vector Prediction (CMVP). This disclosure describes different techniques (e.g., template types, fusion) and syntaxes used in template matching (TM) related tools. The techniques of this disclosure can be applied to any of the existing video codecs, such as HEVC (High Efficiency Video Decoding), VVC (Various Video Decoding), and Basic Video Decoding (EVC), or can be efficient decoding tools in future video decoding standards (e.g., ECM (Enhanced Compression Model)). In the following sections, work related to the techniques of this disclosure in HEVC, Joint Exploratory Model (JEM) techniques, and VVC will be reviewed.

[0076] Now we will discuss the CU structure and motion vector prediction in HEVC. In HEVC, the largest decoding unit in a slice is the CTB (also known as the CTU). The CTB contains a quadtree, and the nodes of this quadtree are CUs. In the HEVC master profile, the size of the CTB typically ranges from 16×16 to 64×64, but in some scenarios, an 8×8 CTB size is also supported. The size of the CU ranges from the same size as the CTB to as small as 8×8. Each CU is encoded using a decoding mode, such as inter-frame or intra-frame. When a CU is inter-frame decoded, it can be further divided into 2 or 4 PUs, or if no further division is applied, it becomes a single PU. When two PUs exist in a CU, these two PUs can be rectangles half the size of the CU or two rectangles with a size of 1 / 4 or 3 / 4 of the CU.

[0077] When the CU is inter-frame decoded, each PU has a set of motion information derived using a unique inter-frame prediction mode.

[0078] Now, let's describe motion vector prediction. In the HEVC standard, there are two inter-frame prediction modes for the PU: merge mode (where skip mode is considered a special case of merge mode) and AMVP mode.

[0079] In AMVP or merge mode, the video encoder 200 and video decoder 300 can be configured to maintain a list of motion vector (MV) candidates, which includes multiple motion vector predictors. The video encoder 200 and video decoder 300 can be configured to generate motion vectors for the current PU and a reference index in merge mode by selecting candidates from the MV candidate list.

[0080] In HEVC, the MV candidate list contains up to five candidates for merge mode and only two candidates for AMVP mode. Merge candidates may contain a set of motion information, such as motion vectors corresponding to both the reference picture list (list 0 and list 1) and the reference index. If the merge candidates are identified by the merge index, the video encoder 200 and video decoder 300 can be configured to determine the reference picture and associated motion vector for prediction of the current block based on the selected candidates. Conversely, in AMVP mode, for each potential prediction direction from list 0 or list 1, the reference index is explicitly signaled along with the MV predictor (MVP) index of the MV candidate list (e.g., signaled by the video encoder 200 to the video decoder 300). In AMVP mode, the predicted motion vectors can be further refined, for example, by receiving motion vector differences that can be added to the MVP. The candidates in the candidate lists in both modes can be similarly derived from the same spatially and temporally neighboring blocks.

[0081] Now we describe the spatial proximity candidates. Figure 2A This is a conceptual diagram illustrating an example of spatially neighboring motion vector candidates for the merge mode. The video decoder 300 generates a candidate list by adding motion information from spatially neighboring candidates to the candidate list. Although the process for generating candidates from neighboring blocks may differ for merge mode and AMVP mode, as... Figure 2A and Figure 2B As shown, for a specific PU (PU0), spatial MV candidates are derived from these blocks. In merge mode, it is possible to Figure 2A The order shown derives a maximum of five space MV candidates for block 140 (PU0). The order is as follows: left (0), top (1), top right (2), bottom left (3), and top left (4), as... Figure 2A As shown.

[0082] Figure 2B This is a conceptual diagram illustrating an example of spatial proximity motion vector candidates for AMVP. In AMVP mode, the neighboring blocks of block 142 (PU0) are divided into two groups: a left group, which includes blocks 0 and 1; and an upper group, which includes blocks 2, 3, and 4, as shown below. Figure 3B As shown. For each group, potential candidates in neighboring blocks that reference the same reference image as the reference image indicated by the signaling reference are prioritized to form the final candidates for the group. All neighboring blocks may not contain motion vectors pointing to the same reference image. Therefore, if no such candidates can be found, the first available candidates can be scaled to form the final candidates, thus allowing compensation for temporal distance differences.

[0083] Temporal motion vector prediction in HEVC is now described. After adding spatial motion vector candidates, the video encoder 200 and video decoder 300 can be configured to add Temporal Motion Vector Predictor (TMVP) candidates (if enabled and available) to the MV candidate list. The motion vector derivation process for TMVP candidates can be the same for both merge mode and AMVP mode. However, in HEVC, the target reference index of the TMVP candidate can be set to 0 in merge mode.

[0084] Figure 3A This is a conceptual diagram illustrating an example of a TMVP candidate. The principal block position derived from the TMVP candidate of block 144 (PU0) is the lower right block juxtaposed outside PU (which is in Figure 3A The block is shown as "T" to compensate for the bias in the upper and left blocks used to generate spatial proximity candidates. However, if the block is located outside the current CTB column (e.g., image block 145), or motion information is unavailable (e.g., image block 143), the block is replaced by the center block 147 of the PU.

[0085] The video decoder 300 can derive motion vectors for TMVP candidates from the juxtaposition PUs of the juxtaposed images indicated at the slice level. The motion vectors of the juxtaposition PUs are called juxtaposition MVs. For example, if a block in the reference image and the current block each include at least one pixel corresponding to the same relative position in the reference image and the current image, then the block in the reference image can be considered, for example, as juxtaposed with a block in the current image.

[0086] Figure 3B This is a conceptual diagram illustrating an example of the motion vector scaling process 146. Similar to the direct temporal mode in AVC, to derive TMVP candidate motion vectors, the video decoder 300 can scale and juxtapose MV to compensate for temporal distance differences, such as... Figure 3B As shown.

[0087] Now, let's describe other aspects of motion prediction in HEVC. Motion vector scaling typically assumes that the value of a motion vector is proportional to the distance between images during rendering time. A motion vector associates a reference image with the image containing the motion vector (i.e., the containing image). When using motion vectors to predict other motion vectors, the distance between the containing and reference images is typically calculated based on the Picture Order Count (POC) value.

[0088] For a predicted motion vector, the associated containing image and reference image can be different. Therefore, a new distance based on the point of view (POC) can be calculated, and the motion vector is scaled based on the two POC distances. For spatial proximity candidates, the containing images of the two motion vectors are the same, while the reference images are different. In HEVC, motion vector scaling is applied to both TMVP and AMVP for spatial and temporal proximity candidates.

[0089] The video encoder 200 and video decoder 300 can be configured to perform artificial motion vector candidate generation. If the motion vector candidate list is incomplete (e.g., the motion vector candidate list contains fewer than a predetermined number of candidates), artificial motion vector candidates can be generated and inserted at the end of the list until the list has a specified number of candidates.

[0090] In the merge mode, there are two types of artificial motion vector candidates: combined candidates, which are derived only for B slices; and zero motion vector candidates, which are used for AMVP if the first type does not provide enough artificial candidates.

[0091] For each pair of candidates that is already in the candidate list and has the necessary motion information, the bidirectional combined motion vector candidate can be derived by combining the motion vector of the first candidate in the image in reference list 0 and the motion vector of the second candidate in the image in reference list 1.

[0092] The video encoder 200 and video decoder 300 can be configured to perform a pruning process for candidate insertion. Candidates from different blocks may happen to be the same, which reduces the efficiency of merging / AMVP candidate lists. A pruning process can be applied to address this problem. The pruning process compares a candidate with other candidates in the current candidate list to avoid inserting the same candidate to some extent. For example, to reduce complexity, only a limited number of pruning processes are applied instead of comparing every potential candidate with all other existing candidates.

[0093] Template matching prediction is now described. Video encoder 200 and video decoder 300 can be configured to perform template matching (TM) prediction. TM prediction is a special merging mode based on frame rate up conversion (FRUC) technology. In this mode, block motion information is not signaled (e.g., by video encoder 200), but is derived at the decoder side (e.g., by video decoder 300). TM prediction can be applied to both AMVP mode and regular merging mode. In AMVP mode, MVP candidate selection is determined based on template matching to identify candidates that result in the minimum difference between the current block template and the reference block template. In regular merging mode, a TM mode flag can be signaled to indicate the use of TM, and then TM can be applied to merging candidates indicated by the merging index for MV refinement.

[0094] Figure 4 An example of template matching performed over the search region around the initial motion vector is shown. Figure 4 As shown, the video encoder 200 and video decoder 300 can be configured to use template matching to derive motion information of the current CU by finding the closest match between the current template 148 (the top and / or left neighboring block of the current CU) in the current image 150 and the template within the reference template 152 of the reference block in the reference image 154 (which may be of the same size as the current template 148). Utilizing AMVP candidates selected based on the initial matching error, the video encoder 200 and video decoder 300 can refine the MVP using template matching. Using the merge candidates indicated by the merge index signaled by the signaling, the merged MV corresponding to L0 and L1 can be independently refined via template matching. Then, the less accurate merged MV can be further refined based on the more accurate merged MV.

[0095] The video encoder 200 and video decoder 300 can be configured to implement the cost function. Motion-compensated interpolation may be required when the motion vector points to the location of a fractional sample. To reduce complexity, bilinear interpolation can be used instead of conventional 8-tap DCT-IF interpolation for both template matching methods to generate a template in the reference image. Example matching cost for template matching. The calculation can be performed as follows: , in It is a weighting factor set to 4 based on experience. and These represent the current MV and the initial MV (e.g., the MVP candidate in AMVP mode, or the merged MV in merge mode). SAD is used as the matching cost for template matching.

[0096] When using TM, the video encoder 200 and video decoder 300 can be configured to refine the MV (e.g., the initial MV) using only luma samples. However, the MV determined based on the refinement can be used for both luma and chroma predictions in motion compensation (MC) inter-frame prediction. After determining the MV, the final MC can be performed using an 8-tap interpolation filter for luma and a 4-tap interpolation filter for chroma.

[0097] Video encoder 200 and video decoder 300 can be configured to implement the search process. MV refinement may include a pattern-based MV search process with a template matching cost criterion and utilizing a hierarchical structure. Two search modes are supported—diamond search and cross search for MV refinement. The hierarchical structure specifies the iterative process for refining the MV, starting with a coarse MV precision (e.g., quarter-pel) and ending with a finer precision (e.g., 1 / 8-pel). For example, quarter-pel MV precision implies performing a template matching process over a search area around the initial MV to identify the refined MV, where the search step size uses one-quarter (or resolution) of the luminance sample distance as the motion vector difference (MVD) precision (between the initial MV and the refined MV). The MV is searched directly using a diamond pattern with a quarter-luminance sample MVD precision, followed by a cross pattern search with a quarter-luminance sample MVD precision, and then a refined search using a cross pattern with an eighth-luminance sample MVD precision. The search range for MV refinement is set to be equal to (-8, +8) luminance samples around the initial MV. When the current block is a bidirectional prediction (e.g., a bidirectional prediction block), both MVs are refined independently and then the best one (in terms of matching cost) is set as the prior (e.g., the basis) to further refine the other MV using bidirectional prediction with CU hierarchical weight (BCW) weight values.

[0098] Bilateral matching prediction is now described. Video encoder 200 and video decoder 300 can be configured to perform bilateral matching prediction. Bilateral matching (also known as bidirectional merging) prediction is another merging mode based on the FRUC technique. When the BM mode is applied to a block, video encoder 200 and video decoder 300 can use signaled merge candidate indices to derive two initial motion vectors MV0 and MV1 to select merge candidates from an already constructed merge list. During bilateral matching, video encoder 200 and video decoder 300 search around MV0 and MV1 and derive the final MV0' and MV1' based on the minimum bilateral matching cost.

[0099] The motion vector differences MVD0 (denoted as MV0'–MV0) and MVD1 (denoted as MV1'–MV1) pointing to two reference blocks can be proportional to the temporal distance (TD) between the current image and the two reference images (e.g., TD0 and TD1). Figure 5 An example of bilateral matching prediction is shown, where the two motion vectors are proportional based on their temporal distance. Figure 5 In this example, the distance (TD1) between the current image 156 and the reference image 158 is four times the distance (TD0) between the current image 156 and the reference image 160. MVD0 and MVD1 are proportional based on time distance.

[0100] However, there is an optional design in which MVD0 and MVD1 are mirror images regardless of the time distance between TD0 and TD1. Figure 6 An example of bilateral matching prediction is shown, where the two motion vectors are mirror images regardless of their temporal distance. Figure 6 In this diagram, MVD0 and MVD1 are shown as mirror images, regardless of the time distance (TD1) between the current image 162 and the reference image 164, and the time distance (TD0) between the current image 162 and the reference image 166. For example, Figure 6 An example of mirrored MVD0 and MVD1 is shown, where TD1 is 4 times that of TD0.

[0101] Figure 7 An example of a 3×3 square search pattern in the search range [-8, 8] is shown. Figure 7 The search mode and search range can be used to achieve bilateral matching. When implementing bilateral matching, the video encoder 200 and video decoder 300 can be configured to perform a local search around the initial MV0 and MV1 to derive the final MV0' and MV1'. Figure 7In the example, the initial MV points to sample 170 and the final MV points to sample 172. The local search applies a 3×3 square search pattern to iterate through the search range [-8, 8]. Sample 174 represents an example of a sample within the search range surrounding samples 170, 172, and 176. Sample 176 represents an example of a sample corresponding to the MV determined during intermediate iterations of the search process. In each search iteration, the bilateral matching cost of the eight surrounding MVs in the search pattern is calculated and compared to the bilateral matching cost of the central MV. The MV with the minimum bilateral matching cost becomes the new central MV in the next search iteration. The local search terminates when the current central MV has the minimum cost within the 3×3 square search pattern or when the local search reaches a predefined maximum search iteration.

[0102] The bilateral matching AMVP-merging mode is now described. The bidirectional predictor consists of an AMVP predictor in one direction and a merge predictor in the other. The bilateral matching AMVP-merging mode can be enabled for the decoded block when the selected merge predictor and AMVP predictor satisfy the decoder-side motion vector refinement (DMVR) condition. This condition is characterized by at least one reference image from the past and one reference image from the future relative to the current image, and the distances from both reference images to the current image are equal. Bilateral matching MV refinement is applied to the merge MV candidate, with the AMVP MVP serving as the starting point. Otherwise, if template matching is enabled, template matching MV refinement is applied to either the merge predictor or the AMVP predictor, which has a higher template matching cost.

[0103] Signaling notifications to the bilateral matching AMVP-merge pattern AMVP portion is treated as a regular unidirectional AMVP, for example, signaling notifications to the reference index and MVD, and if template matching is used or when template matching is disabled, the signaling notification to the MVP index, then this AMVP portion has the derived MVP index.

[0104] For the AMVP direction LX, X can be 0 or 1. The merging portion in the other direction (1–LX) is implicitly derived by minimizing the bilateral matching cost between the AMVP predictor and the merging predictor (e.g., for a pair of AMVP and merging motion vectors). For each merging candidate in the merging candidate list that has a motion vector in the other direction (1–LX), the bilateral matching cost is computed using the merging candidate MV and the AMVP MV. The merging candidate with the minimum cost is selected. Starting with the selected merging candidate MV and AMVP MV, bilateral matching refinement is applied to the decoded block.

[0105] A third pass of the multi-pass DMVR is enabled for the AMVP-merged mode decoder block, which is the sub-PU bidirectional optical flow (BDOF) refinement of the multi-pass DMVR. The sub-PU size of the BDOF is adaptively selected based on width × height. For blocks smaller than 256, the sub-block size is 4×4; otherwise, 8×8 is used. Furthermore, the BDOF MV refinement parameters are derived using the following high-precision equations: ∑Gx.Gx vx +∑Gx.Gy vy =∑dI . Gx s1 vx + s2 vy = s3 ∑Gx.Gy vx +∑Gy.Gy vy =∑dI . Gy s2 vx + s5 vy = s6, Where Gx / Gy is the sum of the two horizontal / vertical gradients derived for each reference block. The sum (Σ) is a weighted sum, where the weights depend on the location Ω in the target region. In other cases, weights can also be applied to derive vx / vy.

[0106] The AMVP-merge mode for bilateral matching is indicated by a flag. If this mode is enabled, the AMVP direction LX is further indicated by a flag.

[0107] When the bilateral matching (BM) AMVP-merge mode is used for the current block and template matching is enabled, no signal is sent to the MVD. An additional pair of AMVP-merge MVPs is introduced. The merge candidate list is sorted in ascending order based on BM cost. A signaling index (0 or 1) (e.g., signaled by video encoder 200 to video decoder 300) is used to indicate which merge candidate in the sorted merge candidate list is to be used. When only one candidate exists in the merge candidate list, the pair of AMVPs and merge MVPs that do not have bilateral matching MV refinement are filled.

[0108] The adaptive decoder-side motion vector refinement is now described. The adaptive decoder-side motion vector refinement method is an extension of multi-pass DMVR, which includes two new merging modes to refine the MV only in one direction (L0 or L1) of the bidirectional prediction of the merging candidates that satisfy the DMVR conditions. The multi-pass DMVR process is applied to the selected merging candidates to refine the motion vectors; however, in the first pass (i.e., PU level) of the DMVR, MVD0 or MVD1 is set to zero. The video encoder 200 and the video decoder 300 can be configured to use adaptive decoder-side motion vector refinement.

[0109] The merge candidates for the new merging mode are derived from spatially adjacent decoded blocks, TMVPs, non-adjacent blocks, history-based motion vector predictors (HMVPs), and pairwise candidates, similar to the regular merging mode. The difference is that only those merge candidates that satisfy the DMVR conditions are added to the candidate list. Both new merging modes use the same merge candidate list. If the BM candidate list contains inherited BCW weights, the DMVR process remains unchanged, except that if the weights are unequal and bidirectional predictions are weighted with BCW weights, distortion is calculated using Mean Removed Absolute Difference Sum (MRSAD) or Mean Removed Transform Difference Sum (MRSATD). The merge index is decoded as in the regular merging mode.

[0110] Decoder-side Motion Vector Refinement (DMVR) is now described. Video encoder 200 and video decoder 300 can be configured to perform DMVR. In VVC, DMVR can be applied to increase the accuracy of the MV in the merged mode. In the bidirectional prediction operation, a refined MV is searched around the initial MV in reference image lists L0 and L1. The DMVR process calculates the distortion between two candidate blocks in reference image lists L0 and L1.

[0111] Figure 8 An example of decoder-side motion vector refinement is shown. For example... Figure 8 As illustrated, the video encoder 200 and video decoder 300 can be configured to compute the SAD between block 178 and block 180 based on each MV candidate surrounding the initial MV. The MV candidate with the lowest SAD becomes the refined MV and is used to generate the bidirectional prediction signal.

[0112] The refined MV derived from the DMVR process is used to generate inter-frame prediction samples and also for temporal motion vector prediction for future image decoding. The original MV is used during deblocking and also for spatial motion vector prediction in future CU decoding. DMVR is based on a sub-block merging pattern with a predefined maximum processing unit of 16×16 luma samples. When the width and / or height of a CU is greater than 16 luma samples, the CU can be further divided into sub-blocks with a width and / or height equal to 16 luma samples.

[0113] The search scheme is now described. The video encoder 200 and video decoder 300 can be configured to implement the search scheme. In the DMVR, the search point revolves around the initial MV and the MV offset follows the MV difference mirroring rule. In other words, any point examined by the DMVR, represented by the candidate MV pair (MV0, MV1), follows the following two equations: in This represents the refinement offset between the initial MV and the refined MV within a reference image. In DMVR, the refinement search range is two integer luminance samples from the initial MV. The search includes an integer sample offset search phase and a fractional sample refinement phase.

[0114] The video encoder 200 and video decoder 300 can be configured to apply a 25-point full search using integer sample offset search. First, the SAD of the initial MV pair is calculated. If the SAD of the initial MV pair is less than a threshold, the integer sample offset search phase of the DMVR terminates. Otherwise, the SAD of the remaining 24 points is calculated and checked according to the raster scan order. The point with the minimum SAD is selected as the output of the integer sample offset search phase. To reduce the loss due to the uncertainty of DMVR refinement, the video encoder 200 and video decoder 300 may favor the original MV during the DMVR process. The SAD between reference blocks referenced by the initial MV candidate references is reduced by 1 / 4 of the SAD value.

[0115] Following the integer sample search, the video encoder 200 and video decoder 300 can be configured to perform fractional sample refinement. To save computational complexity, fractional sample refinement is derived using the parametric error surface equation instead of an additional search via SAD comparison. Fractional sample refinement is conditionally invoked based on the output of the integer sample search phase. Fractional sample refinement is further applied when the integer sample search phase terminates at a center with the minimum SAD in either the first or second iteration search.

[0116] In subpixel offset estimation based on parametric error surfaces, the following 2-D parabolic error surface equation is fitted using the center localization cost and the costs of the four nearest localization points from the center: , in( This corresponds to the fractional location with the minimum cost, and C corresponds to the minimum cost value. The above equation is solved by using the cost values ​​of the five search points. The calculation is as follows: and The value is automatically constrained between -8 and 8 because all cost values ​​are positive and the minimum value is 8. This corresponds to a half-pel offset in VVC with 1 / 16-pel MV precision. The calculated fraction ( Added to integer distance refinement MV to obtain subpixel accurate refinement increment MV.

[0117] Bilinear interpolation and sample imputation are now described. The video encoder 200 and video decoder 300 can be configured to perform bilinear interpolation and sample imputation. In VVC, the maximum resolution of the MV is 1 / 16 of a luminance sample. An 8-tap interpolation filter is used to interpolate the samples at the fractional localization. In DMVR, the search point is offset by an integer sample around the initial fraction -pelMV, so it may be necessary to interpolate the samples at those fractional localizations for use in the DMVR search process. To reduce computational complexity, a bilinear interpolation filter can be used to generate fractional samples for the search process in DMVR. Another important effect of using a bilinear filter is that, compared to the normal motion compensation process, DMVR does not access more reference samples in the case of a 2-sample search range. After obtaining the refined MV using the DMVR search process, a normal 8-tap interpolation filter can be applied to generate the final prediction. To prevent the normal MC process from accessing too many reference samples, samples that are not needed by the interpolation process based on the original MV but are needed by the interpolation process based on the refined MV can be imputed from the available samples.

[0118] The enable conditions are now described. The video encoder 200 and video decoder 300 can be configured to implement one or more enable conditions for DMVR. In one example, the video encoder 200 and video decoder 300 can be configured to enable DMVR if all of the following conditions are met (e.g., exist or true).

[0119] • CU hierarchical merging mode with bidirectional predictive MV • A reference image is in the past and another reference image is in the future, relative to the current image. • The distances (e.g., POC difference) from the two reference images to the current image are the same. • The CU has more than 64 luminance samples. • Both the CU height and CU width are greater than or equal to 8 luminance samples. • BCW weight index indicates equal weights • Weighted prediction (WP) is not enabled for the current block. • Combined intra-frame and inter-frame prediction (CIIP) mode is not used for the current block. Chained Motion Vector Prediction (CMVP) will now be described. CMVP is a technique for deriving a list of inter-frame merge candidates. Video encoder 200 and video decoder 300 can be configured to use CMVP.

[0120] Figure 9 Example exports of CMVP candidates are shown. Figure 9As shown in the CMVP technique 900, CMVP candidates can be derived based on the MV pre-derived for the inter-frame merging candidate list, as an accumulation of the MV and block vectors (BV) of recursive tracking. For example, for a CMVP candidate, a set of motion vectors MV k / m and reference image RefPic k / m The following can be exported: MV k / m =MV k(0) + BV k(0) +MV k(1) +MV k(2) + … + MV k(m) , RefPic k / m =RefPic k(m) , Where k and m indicate the number of merged indices and tracking depths of the CMVP.

[0121] Figure 10 This example demonstrates how to track motion vectors from a source and destination in a CMVP. (In exporting the MV...) k / m At that time, MV k(m) This can be found by checking if there are MVs or BVs corresponding to all five positions of the current block in the MV / BV storage. Figure 10 As shown (e.g., the center, top left, top right, bottom left, and bottom right of the current block 1000).

[0122] When the pre-derived merge candidate for the CMVP candidate has two MVs, MV k / m Exported for each merge index, each list (i.e., L0 and L1), and each tracking depth. A maximum of two MVs can be exported for each list and each tracking depth, and the MV sets are inserted sequentially into the inter-frame merge candidate list.

[0123] Traceable reference images are only available within the reference image list. For regular merges and TM merges, CMVP candidates are inserted after HMVP candidates. When exporting CMVP candidates, hpelIfIdx, bcwIdx, licFlag, and mhpFlag are not inherited. CMVP candidates are not exported when TMVP is deprecated.

[0124] Figure 11 An example of tracking CMVP motion with a depth of one is shown. For example... Figure 11As shown, if the source motion is bidirectional prediction for the current block (currCU) 1100, two reference blocks RefBlkL0 1110 and RefBlkL1 11112 will be found. And if the two reference blocks RefBlkL0 1110 and RefBlkL1 1112 are also bidirectional prediction blocks, then up to 4 chain motion vectors can be tracked.

[0125] To improve the decoding efficiency of chained motion vector prediction, one or more of the following techniques can be used to derive chained motion vector prediction in different merging modes. The video encoder 200 and / or video decoder 300 can be configured to use any one or any combination of the following techniques.

[0126] The CMVP in the candidate list of bilateral matching merge patterns will now be discussed. In one example of this disclosure, the bilateral matching merge pattern candidates have at least one MV derived using the CMVP. In this example, at least one CMVP candidate of the BM candidate is derived from a source candidate that meets the BM pattern conditions. The BM pattern conditions may include one or more DMVR pattern conditions as described above. In some examples, the BM pattern conditions may be the same as the DMVR pattern conditions. In this example, at least one CMVP candidate of the BM candidate is derived from a source candidate that does not meet the BM pattern conditions. The source candidate is, for example, from spatial neighbors, temporal neighbors (tmvp), non-adjacent neighbors, etc.

[0127] In one example, a signal flag is sent to indicate whether the bilateral match merge mode is selected for that block. For example, video encoder 200 may signal the flag to video decoder 300 in the bitstream. If the bilateral match merge mode is selected, only bidirectional prediction candidates are inserted into the bilateral match merge list when exporting the merge candidate list.

[0128] In another example, when exporting the bilateral matching candidate list, only bidirectional prediction candidates whose two reference frames satisfy the following condition are inserted into the bilateral matching merge list: one of the reference frames is in the past and the other is in the future relative to the current frame.

[0129] In another example, when deriving the bilateral matching candidate list, only bidirectional prediction candidates whose two reference frames satisfy the following conditions are inserted into the bilateral matching merge list: one reference frame is in the past and the other is in the future relative to the current frame, and the POC difference from the two reference frames to the current frame is the same.

[0130] In another example, when exporting the bilateral matching merged candidate list, if a candidate meets the bilateral matching criteria, the candidate is inserted into the bilateral matching merged list. If a candidate does not meet the bilateral matching criteria, the candidate is inserted into a second list.

[0131] For example, video encoder 200 or video decoder 300 may determine to decode the current block of video data using a bilateral matching merge mode. Video encoder 200 or video decoder 300 may determine a first CMVP candidate based on a first source candidate. Video encoder 200 or video decoder 300 may determine that the first source candidate satisfies one or more bilateral matching conditions. Video encoder 200 or video decoder 300 may insert the first CMVP candidate into a bilateral matching merge list based on the first source candidate satisfying one or more bilateral matching conditions. Video encoder 200 or video decoder 300 may determine a second CMVP based on a second source candidate. Video encoder 200 or video decoder 300 may determine that the second source candidate does not satisfy one or more bilateral matching conditions. Video encoder 200 or video decoder 300 may insert the second CMVP into a second list based on the second source candidate not satisfying one or more bilateral matching conditions. Video encoder 200 or video decoder 300 may decode the current block using at least one of the bilateral matching merge list or the second list.

[0132] In another example, candidates from neighboring locations, non-neighboring locations, temporal locations, and the history buffer that do not meet the bilateral matching criteria will be inserted into a second list. For example, video encoder 200 or video decoder 300 may determine that at least one candidate from neighboring locations, non-neighboring locations, temporal locations, or the history buffer does not meet one or more bilateral matching criteria. Video encoder 200 or video decoder 300 may insert at least one candidate into the second list based on the fact that at least one candidate from neighboring locations, non-neighboring locations, temporal locations, or the history buffer does not meet one or more bilateral matching criteria.

[0133] In another example, only candidates that do not meet the criteria (e.g., candidates that do not meet the bilateral matching criteria) from neighboring locations, non-neighboring locations, and the history buffer will be inserted into the second list.

[0134] In another example, only candidates that do not meet the criteria (e.g., candidates that do not meet the bilateral matching criteria) from neighboring locations, non-neighboring locations, and time locations will be inserted into the second list.

[0135] In another example, only candidates that do not meet the matching criteria from neighboring and non-neighboring locations (e.g., candidates that do not meet the bilateral matching criteria) will be inserted into the second list.

[0136] In another example, a second list export process is performed after the bilateral matching merge list export process is complete. For example, video encoder 200 or video decoder 300 may insert a second CMVP candidate into the second list after the bilateral matching merge list export or completion.

[0137] In another example, for each candidate in the second list, if the reference block from one of the prediction directions is bidirectional and the two chain motion vectors satisfy the bilateral matching condition, the bidirectional prediction chain motion will be inserted into the merge list (e.g., the bilateral matching merge list).

[0138] In another example, for each candidate in the second list, all available chained motion vectors with the maximum tracking depth *m* are examined and stored in the list. All combinations of two candidates within the list are attempted to form bidirectional prediction candidates. If either combination satisfies a bilateral matching condition, such combinations of candidates are inserted into a merge list (e.g., a bilateral matching merge list).

[0139] In another example, for each candidate in the second list, all available chained motion vectors with the maximum tracking depth *m* are examined and stored in the list along with the source motion. All combinations of two candidates within the list are attempted to form bidirectional prediction candidates. If any combination of candidates satisfies the bilateral matching condition, that combination of candidates is inserted into a merge list (e.g., a bilateral matching merge list).

[0140] For example, video encoder 200 or video decoder 300 can determine which candidates in a second list are available chained motion vectors with a predetermined maximum tracking depth. Video encoder 200 or video decoder 300 can store each candidate in the second list that is a available chained motion vector with a predetermined maximum tracking depth in a third list. Video encoder 200 or video decoder 300 can determine, for each combination of two stored candidates in the stored candidates in the third list, which corresponding combination satisfies one or more bilateral matching conditions. Video encoder 200 or video decoder 300 can insert each corresponding combination of candidates that satisfies one or more bilateral matching conditions into a bilateral matching merge list.

[0141] In another example, the tracking depth m is 1. For example, a predetermined depth could be equal to 1.

[0142] In another example, a second list export process is performed after the historical merge candidate export process is completed.

[0143] In another example, a second list export process is performed after the non-adjacent merge candidate export process is completed.

[0144] In another example, a second list export process is performed after the time-merging candidate export process is completed.

[0145] Now, we describe a bidirectional predictive chain of motion vector predictions for predicting source motion. In another example of this disclosure, if the source motion from an existing merge candidate is bidirectionally predicted, then at most 2 can be derived when the tracking depth is n. (n+1) There are bidirectional predicted chain motion vectors. For the existing merge candidates, at most m candidates can be inserted into the merge column.

[0146] In another example, the quantity m is limited to 2.

[0147] In another example, if there are more than m available combinations of chained motion vectors, a CMVP candidate selection process is performed to select m candidates to be inserted into the merge list.

[0148] In another example, bidirectional prediction of CMVP candidates is prioritized.

[0149] In another example, bidirectional prediction CMVP candidates with two reference frames pointing to different boxes are given priority.

[0150] In another example, bidirectional prediction CMVP candidates whose two reference frames point to the same box are given priority.

[0151] In another example, bidirectional prediction CMVP candidates that satisfy the bilateral matching condition between the two reference frames are given priority.

[0152] Bidirectional prediction chained motion vectors with adaptive tracking steps are now described. In another example of this disclosure, the bidirectional prediction CMVP candidate has a first MV on reference image A in reference list X, where the first MV is derived from the time trajectory using tracking steps N. The bidirectional prediction CMVP candidate has a second MV on reference image B in reference list (1–X), where the second MV is derived from the time trajectory using tracking steps M.

[0153] In one example, the first MV on reference image A in reference list X is derived from an N-step time trajectory, where N is the minimum traceable step order, for example, N equals 1.

[0154] In one example, the second MV is derived from the M-step time trajectory, where M is greater than 1, and M is the minimum trackable step when the second MV is located on reference image B in the reference list (1–X).

[0155] Chained motion vector prediction with time-scaled motion vectors will now be described. In the examples of this disclosure, the CMVP candidate has at least one motion vector, which is first derived from a time trajectory and then scaled to a reference image, which may be referred to as CmvpScaledRefPic.

[0156] In one example, CmvpScaledRefPic is predetermined, for example, the first reference image in the list of reference images X, where X is 0 or 1.

[0157] In one example, the CMVP candidate is a bidirectional prediction candidate, and the first MV is derived from the time trajectory and is located on reference image A in reference list X, where X is 0 or 1. The second MV is derived from the time trajectory and is located on reference image B in reference list X.

[0158] In one case, CmvpScaledRefPic is determined to be reference image C in the reference list (1–X), for example, reference image C is the first reference image in the reference list (1–X). The CMVP candidate has a first MV on reference image A and a second MV on CmvpScaledRefPic, where the second MV is obtained by time scaling image B to CmvpScaledRefPic.

[0159] In one case, CmvpScaledRefPic is determined to be reference image C in the reference list (1–X), for example, reference image C is the first reference image in the reference list (1–X). The CMVP candidate has a first MV on CmvpScaledRefPic and a second MV on reference image B, where the first MV is obtained by time scaling from image A to CmvpScaledRefPic.

[0160] In another case, CmvpScaledRefPic is determined as the reference image C in the reference list (1–X) and the minimum POC distance to the reference image A. The CMVP candidate has a first MV on the reference image A and a second MV on CmvpScaledRefPic, where the second MV is obtained by time scaling from image B to CmvpScaledRefPic.

[0161] In another case, CmvpScaledRefPic is determined as the reference image C in the reference list (1–X) and the minimum POC distance to the reference image B. The CMVP candidate has a first MV on CmvpScaledRefPic and a second MV on the reference image B, where the first MV is obtained by time scaling from image A to CmvpScaledRefPic.

[0162] Figure 12 This is a flowchart illustrating an example of a chained motion vector prediction technique according to one or more aspects of this disclosure. The video encoder 200 may determine (1200) to encode the current block of video data using a bilateral matching merge mode. For example, the video encoder 200 may determine that the most accurate and / or most efficient way to encode the current block is to encode it using a bilateral matching merge mode.

[0163] The video encoder 200 can determine a first CMVP candidate based on the first source candidate (1202). For example, the video encoder 200 can generate a first CMVP candidate based on the first source candidate.

[0164] The video encoder 200 can determine that the first source candidate satisfies one or more bilateral matching conditions (1204). For example, the video encoder 200 can determine whether the first source candidate satisfies one or more bilateral matching conditions (e.g., one or more DMVR conditions in DMVR conditions) and can determine that the first source candidate actually satisfies those one or more conditions.

[0165] The video encoder 200 may insert a first CMVP candidate into a bilateral matching merge list (1206) based on the first source candidate satisfying one or more bilateral matching conditions. The video encoder 200 may determine a second CMVP candidate based on a second source candidate (1208). For example, the video encoder 200 may generate a second CMVP candidate based on a second source candidate.

[0166] The video encoder 200 may determine that the second source candidate does not satisfy one or more bilateral matching conditions (1210). For example, the video encoder 200 may determine whether the second source candidate satisfies one or more bilateral matching conditions (e.g., one or more DMVR conditions of DMVR conditions) and may determine which one or more conditions the second source candidate does not satisfy (e.g., at least one of one or more conditions).

[0167] The video encoder 200 may insert a second CMVP candidate into a second list based on the second source candidate not satisfying one or more bilateral matching conditions (1212). The video encoder 200 may encode the current block using at least one of the bilateral matching merge list or the second list (1214). For example, the video encoder 200 may determine the candidates to be added to the second list of the bilateral matching merge list as described herein and use the bilateral matching merge list with the added candidates when encoding the current block.

[0168] In some examples, the video encoder 200 may determine that at least one candidate from neighboring locations, non-neighboring locations, temporal locations, or a history buffer does not satisfy one or more bilateral matching conditions. The video encoder 200 may insert at least one candidate into a second list based on the fact that at least one candidate from neighboring locations, non-neighboring locations, temporal locations, or a history buffer does not satisfy one or more bilateral matching conditions. In some examples, a second CMVP candidate is inserted into the second list after the bilateral matching merge list is exported.

[0169] In some examples, the video encoder 200 may determine which candidates in a second list are available chained motion vectors with a predetermined maximum tracking depth. The video encoder 200 may store each candidate from the second list that is a available chained motion vector with a predetermined maximum tracking depth in a third list. The video encoder 200 may determine, for each combination of two stored candidates in the third list, which corresponding combination satisfies one or more bilateral matching conditions. For example, the video encoder 200 may examine each possible combination of two stored candidates in the third list to determine which corresponding combination satisfies one or more bilateral matching conditions. The video encoder 200 may insert each corresponding combination that satisfies one or more bilateral matching conditions into a bilateral matching merge list.

[0170] In some examples, the predetermined depth is equal to 1. In some examples, as part of storing each of the determined candidates in a third list, the video encoder 200 may store the corresponding source motion of each of the determined candidates.

[0171] In some examples, the video encoder 200 may, for each candidate in the second list, determine whether the reference block from one of the two prediction directions is a bidirectional prediction reference block and whether the two chained motion vectors associated with the candidate satisfy one or more bilateral matching conditions. In some examples, the video encoder 200 may, for each candidate in the second list where the reference block from one of the two prediction directions is a bidirectional prediction reference block and the two chained motion vectors associated with the candidate satisfy one or more bilateral matching conditions, insert the corresponding bidirectional prediction chained motion vector prediction candidate into a bilateral matching merge list.

[0172] In some examples, the video encoder 200 may include a camera configured to capture video data.

[0173] Figure 13This is a flowchart illustrating another example of a chained motion vector prediction technique according to one or more aspects of this disclosure. The video decoder 300 can determine (1300) to decode the current block of video data using a bilateral match-and-merge pattern. For example, the video decoder 300 can parse a marker in the bitstream whose value indicates that the current block is being encoded using a bilateral match-and-merge pattern.

[0174] The video decoder 300 may determine a first CMVP candidate based on the first source candidate (1302). For example, the video decoder 300 may generate a first CMVP candidate based on the first source candidate.

[0175] The video decoder 300 can determine that the first source candidate satisfies one or more bilateral matching conditions (1304). For example, the video decoder 300 can determine whether the first source candidate satisfies one or more bilateral matching conditions (e.g., one or more DMVR conditions in DMVR conditions) and can determine that the first source candidate actually satisfies those one or more conditions.

[0176] The video decoder 300 may insert a first CMVP candidate into a bilateral matching merge list (1306) based on the first source candidate satisfying one or more bilateral matching conditions. The video decoder 300 may determine a second CMVP candidate based on a second source candidate (1308). For example, the video decoder 300 may generate a second CMVP candidate based on a second source candidate.

[0177] The video decoder 300 may determine that the second source candidate does not satisfy one or more bilateral matching conditions (1310). For example, the video decoder 300 may determine whether the second source candidate satisfies one or more bilateral matching conditions (e.g., one or more DMVR conditions in DMVR conditions) and may determine which one or more conditions the second source candidate does not satisfy (e.g., does not satisfy at least one of one or more conditions).

[0178] The video decoder 300 may insert a second CMVP candidate into a second list based on the second source candidate not satisfying one or more bilateral matching conditions (1312). The video decoder 300 may decode the current block using at least one of the bilateral matching merge list or the second list (1314). For example, the video decoder 300 may determine the candidates to be added to the second list of the bilateral matching merge list as described herein and use the bilateral matching merge list with the added candidates when decoding the current block.

[0179] In some examples, the video decoder 300 may determine that at least one candidate from neighboring locations, non-neighboring locations, temporal locations, or a history buffer does not satisfy one or more bilateral matching conditions. The video decoder 300 may insert at least one candidate into a second list based on the fact that at least one candidate from neighboring locations, non-neighboring locations, temporal locations, or a history buffer does not satisfy one or more bilateral matching conditions.

[0180] In some examples, a second CMVP candidate is inserted into a second list after the bilateral matching merge list is exported.

[0181] In some examples, the video decoder 300 may determine which candidates in a second list are available chained motion vectors with a maximum tracking depth of a predetermined depth. The video decoder 300 may store each candidate from the second list that is a available chained motion vector with a maximum tracking depth of a predetermined depth in a third list. The video decoder 300 may determine, for each combination of two stored candidates in the third list, which corresponding combination satisfies one or more bilateral matching conditions. The video decoder 300 may insert each corresponding combination that satisfies one or more bilateral matching conditions into a bilateral matching merge list. In some examples, the predetermined depth is equal to 1. In some examples, as part of storing each of the determined candidates in the third list, the video decoder 300 may store the corresponding source motion of each of the determined candidates.

[0182] In some examples, for each candidate in the second list, the video decoder 300 may determine whether the reference block from one of the two prediction directions is a bidirectional prediction reference block and whether the two chained motion vectors associated with the candidate satisfy one or more bilateral matching conditions. For each candidate in the second list where the reference block from one of the two prediction directions is a bidirectional prediction reference block and the two chained motion vectors associated with the candidate satisfy one or more bilateral matching conditions, the video decoder 300 may insert the corresponding bidirectional prediction chained motion vector prediction candidate into a bilateral matching merge list.

[0183] In some examples, the video decoder 300 includes a display configured to display decoded video data.

[0184] Figure 14 This is a block diagram illustrating an example video encoder 200 that can perform the techniques of this disclosure. Figure 14This disclosure is provided for illustrative purposes and should not be construed as a limitation on the techniques extensively illustrated and described herein. For illustrative purposes, this disclosure describes the video encoder 200 in accordance with the techniques of VVC and HEVC. However, the techniques of this disclosure can be performed by video encoding devices configured for other video decoding standards and video decoding formats, such as AV1 and subsequent formats of AV1 video decoding.

[0185] exist Figure 14 In the example, the video encoder 200 includes a video data memory 230, a mode selection unit 202, a residual generation unit 204, a transform processing unit 206, a quantization unit 208, an inverse quantization unit 210, an inverse transform processing unit 212, a reconstruction unit 214, a filter unit 216, a decoded picture buffer (DPB) 218, and an entropy coding unit 220. Any or all of the video data memory 230, mode selection unit 202, residual generation unit 204, transform processing unit 206, quantization unit 208, inverse quantization unit 210, inverse transform processing unit 212, reconstruction unit 214, filter unit 216, DPB 218, and entropy coding unit 220 may be implemented in one or more processors or in processing circuitry. For example, the units of the video encoder 200 may be implemented as one or more circuit or logic elements as part of hardware circuitry, or as part of a processor, ASIC, or FPGA. Furthermore, the video encoder 200 may include additional or alternative processors or processing circuitry to perform these and other functions.

[0186] Video data storage 230 is an example of a storage system capable of storing video data to be encoded by components of video encoder 200. Video encoder 200 can receive data from, for example, video source 104 (…). Figure 1 The video data memory 230 receives video data stored in the video data memory 230. The DPB 218 is an example of a memory system that can act as a reference picture memory, storing reference video data for use when the video encoder 200 predicts subsequent video data. The video data memory 230 and DPB 218 can each be formed from any of one or more memory devices or memory cells, such as dynamic random access memory (DRAM) (including synchronous DRAM (SDRAM)), magnetoresistive RAM (MRAM), resistive RAM (RRAM), or other types of memory devices. The video data memory 230 and DPB 218 can be provided by the same memory device or separate memory devices. In various examples, the video data memory 230 can be on-chip (as illustrated) with other components of the video encoder 200, or off-chip relative to those components.

[0187] In this disclosure, references to video data memory 230 should not be construed as limited to memory inside video encoder 200 (unless specifically described) or memory outside video encoder 200 (unless specifically described). Rather, references to video data memory 230 should be understood as a reference memory that stores video data received by video encoder 200 for encoding (e.g., video data for the current block to be encoded). Figure 1 The memory 106 can also provide temporary storage for the outputs from various units of the video encoder 200.

[0188] Examples Figure 14 Various units help understand the operations performed by the video encoder 200. Units can be implemented as fixed-function circuits, programmable circuits, or combinations thereof. Fixed-function circuits are circuits that provide specific functionality and are pre-configured for the operations that can be performed. Programmable circuits are circuits that can be programmed to perform various tasks and provide flexible functionality for the operations that can be performed. For example, a programmable circuit can execute software or firmware that causes the programmable circuit to operate in a manner defined by the instructions of the software or firmware. Fixed-function circuits can execute software instructions (e.g., to receive or output parameters), but the type of operation performed by a fixed-function circuit is generally immutable. In some examples, one or more units in the unit may be different circuit blocks (fixed-function or programmable), and in some examples, one or more units in the unit may be integrated circuits.

[0189] The video encoder 200 may include an arithmetic logic unit (ALU), an essential function unit (EFU), digital circuitry, analog circuitry, and / or a programmable core, all formed by programmable circuitry. In an example where the operation of the video encoder 200 is performed using software executed by programmable circuitry, memory 106 ( Figure 1 The video encoder 200 may store instructions (e.g., target code) of the software received and executed by the video encoder 200, or another memory (not shown) within the video encoder 200 may store such instructions.

[0190] The video data storage unit 230 is configured to store received video data. The video encoder 200 can retrieve images of the video data from the video data storage unit 230 and provide the video data to the residual generation unit 204 and the mode selection unit 202. The video data in the video data storage unit 230 can be raw video data to be encoded.

[0191] The mode selection unit 202 includes a motion estimation unit 222, a motion compensation unit 224, and an intra-frame prediction unit 226. The mode selection unit 202 may include additional functional units for performing video prediction based on other prediction modes. As an example, the mode selection unit 202 may include a palette unit, an intra-frame block copying unit (which may be part of the motion estimation unit 222 and / or the motion compensation unit 224), an affine unit, a linear model (LM) unit, etc.

[0192] Mode selection unit 202 typically coordinates multiple coding channels to test combinations of coding parameters and the resulting rate-distortion values ​​for such combinations. Coding parameters may include the CTU-CU partitioning, the prediction mode for the CU, the transformation type of the residual data for the CU, the quantization parameters of the residual data for the CU, etc. Mode selection unit 202 can ultimately select a combination of coding parameters that has a better rate-distortion value compared to other tested combinations.

[0193] The video encoder 200 can divide an image retrieved from the video data storage 230 into a series of CTUs and encapsulate one or more CTUs within a slice. The mode selection unit 202 can divide the image's CTUs according to the tree structure described above (such as an MTT structure, QTBT structure, superblock structure, or the quadtree structure described above). As described above, the video encoder 200 can form one or more CUs by dividing the CTUs according to the tree structure. Such CUs are also commonly referred to as "video blocks" or "blocks".

[0194] Generally, mode selection unit 202 also controls its components (e.g., motion estimation unit 222, motion compensation unit 224, and intra-prediction unit 226) to generate prediction blocks for the current block (e.g., the current CU, or, in HEVC, the overlapping portion of PU and TU). To perform inter-frame prediction for the current block, 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 decoded pictures stored in DPB 218). Specifically, motion estimation unit 222 may calculate values ​​representing the similarity between a potential reference block and the current block, for example, based on sum of absolute differences (SAD), sum of squared differences (SSD), mean absolute difference (MAD), mean squared difference (MSD), etc. Motion estimation unit 222 may typically perform these calculations using sample-by-sample differences between the current block and the reference blocks under consideration. Motion estimation unit 222 may identify reference blocks with the lowest values ​​produced by these calculations to indicate the reference block that best matches the current block.

[0195] Motion estimation unit 222 can generate one or more motion vectors (MVs) that define the location of a reference block in a reference image relative to the location of the current block in the current image. Motion estimation unit 222 can then provide the motion vectors to motion compensation unit 224. For example, for unidirectional inter-frame prediction, motion estimation unit 222 can provide a single motion vector, while for bidirectional inter-frame prediction, motion estimation unit 222 can provide two motion vectors. Motion compensation unit 224 can then use the motion vectors to generate a prediction block. For example, motion compensation unit 224 can use the motion vectors to retrieve data for the reference block. As another example, if the motion vectors have fractional sample accuracy, motion compensation unit 224 can interpolate the prediction block according to one or more interpolation filters. Furthermore, for bidirectional inter-frame prediction, motion compensation unit 224 can retrieve data for two reference blocks identified by corresponding motion vectors and combine the retrieved data, for example, by per-sample averaging or weighted averaging.

[0196] When operating according to the AV1 video decoding format, the motion estimation unit 222 and the motion compensation unit 224 can be configured to encode the decoded blocks of video data (e.g., both luma and chroma decoded blocks) using translational motion compensation, affine motion compensation, overlap block motion compensation (OBMC), and / or composite inter-intra-frame prediction.

[0197] As another example, for intra-prediction or intra-prediction decoding, intra-prediction unit 226 may generate a prediction block from samples neighboring the current block. For example, for directional mode, intra-prediction unit 226 may typically mathematically combine the values ​​of neighboring samples and fill these calculated values ​​across the current block in a defined direction to produce a prediction block. As another example, for DC mode, intra-prediction unit 226 may calculate the average of the neighboring samples of the current block and generate a prediction block to include that resulting average for each sample of the prediction block.

[0198] When operating according to the AV1 video decoding format, the intra-frame prediction unit 226 can be configured to encode decoded blocks of video data (e.g., both luma and chroma decoded blocks) using directional intra-frame prediction, non-directional intra-frame prediction, recursive filter intra-frame prediction, luma-chroma (CFL) prediction, intra-block copying (IBC), and / or palette modes. The mode selection unit 202 may include additional functional units for performing video prediction based on other prediction modes.

[0199] Mode selection unit 202 provides a prediction block to residual generation unit 204. Residual generation unit 204 receives an uncoded raw version of the current block from video data memory 230 and a prediction block from mode selection unit 202. Residual generation unit 204 calculates the sample-by-sample difference between the current block and the prediction block. The resulting sample-by-sample difference defines the residual block for the current block. In some examples, residual generation unit 204 may also determine the differences between sample values ​​in the residual block to generate the residual block using residual differential pulse decoding modulation (RDPCM). In some examples, residual generation unit 204 may be formed using one or more subtractor circuits performing binary subtraction.

[0200] In the example where mode selection unit 202 divides a CU into PUs, each PU can be associated with a luma prediction unit and a corresponding chroma prediction unit. Video encoder 200 and video decoder 300 can support PUs of various sizes. As noted above, the size of a CU can refer to the size of its luma decoding block, while the size of a PU can refer to the size of its luma prediction unit. Assuming a particular CU size is 2N×2N, video encoder 200 can 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 for inter-frame prediction. Video encoder 200 and video decoder 300 can also support asymmetric partitioning for PU sizes of 2N×nU, 2N×nD, nL×2N, and nR×2N for inter-frame prediction.

[0201] In an example where mode selection unit 202 does not further divide the CU into PUs, each CU can be associated with a luminance decoding block and a corresponding chrominance decoding block. As mentioned above, the size of the CU can refer to the size of the luminance decoding block of the CU. The video encoder 200 and the video decoder 300 can support CU sizes of 2N×2N, 2N×N, or N×2N.

[0202] For other video decoding techniques, such as intra-block copy mode decoding, affine mode decoding, and linear model (LM) mode decoding, as some examples, mode selection unit 202 generates a prediction block for the current block being encoded via a corresponding unit associated with the decoding technique. In some examples (such as palette mode decoding), mode selection unit 202 may not generate a prediction block, but instead generate syntax elements indicating how the block is reconstructed based on a selected palette. In such modes, mode selection unit 202 may provide these syntax elements to entropy coding unit 220 for encoding.

[0203] As described above, the residual generation unit 204 receives video data for the current block and the 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.

[0204] Transform processing unit 206 applies one or more transformations to the residual block to generate a block of transform coefficients (referred to herein as a "transform coefficient block"). Transform processing unit 206 may apply various transformations to the residual block to form the transform coefficient block. For example, transform processing unit 206 may apply a discrete cosine transform (DCT), direction transform, Karhunen-Loeve transform (KLT), or conceptually similar transformations to the residual block. In some examples, transform processing unit 206 may perform multiple transformations on the residual block, such as primary and secondary transformations (e.g., rotation transformations). In some examples, transform processing unit 206 does not apply any transformations to the residual block.

[0205] When operating according to AV1, transform processing unit 206 may apply one or more transforms to the residual block to generate 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 the transform coefficient block. For example, transform processing unit 206 may apply a combination of horizontal / vertical transforms, which may include the Discrete Cosine Transform (DCT), the Asymmetric Discrete Sine Transform (ADST), the Reversed ADST (e.g., ADST in reverse order), and the Identity Transform (IDTX). When using the Identity Transform, the transform is skipped in either the vertical or horizontal direction. In some examples, transform processing may be skipped entirely.

[0206] Quantization unit 208 quantizes the transform coefficients in a transform coefficient block to produce a quantized transform coefficient block. Quantization unit 208 quantizes the transform coefficients of the transform coefficient block according to the quantization parameter (QP) value associated with the current block. Video encoder 200 (e.g., via mode selection unit 202) can adjust the degree of quantization applied to the transform coefficient block associated with the current block by adjusting the QP value associated with the CU. Quantization may cause information loss, and therefore, the quantized transform coefficients may have lower accuracy compared to the original transform coefficients produced by transform processing unit 206.

[0207] The inverse quantization unit 210 and the inverse transform processing unit 212 can apply inverse quantization and inverse transform, respectively, to the quantized transform coefficient block to reconstruct the residual block based on the transform coefficient block. The reconstruction unit 214 can generate a reconstructed block corresponding to the current block (although potentially with some 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 can add samples of the reconstructed residual block to corresponding samples of the prediction block generated by the mode selection unit 202 to generate the reconstructed block.

[0208] Filter unit 216 may perform one or more filtering operations on the reconstructed block. For example, filter unit 216 may perform a deblocking operation to reduce block artifacts along the edges of the CU. In some examples, the operation of filter unit 216 may be skipped.

[0209] When operating according to AV1, filter unit 216 may perform one or more filtering operations on the reconstructed block. For example, filter unit 216 may perform a deblocking operation to reduce block artifacts along the edges of the CU. In other examples, filter unit 216 may apply a constrained direction enhancement filter (CDEF) after deblocking and may include the application of a non-separable, nonlinear, low-pass directional filter based on the 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-guided filter.

[0210] The video encoder 200 stores reconstructed blocks in the DPB 218. For example, in an example where the filter unit 216 is not operated, the reconstruction unit 214 may store reconstructed blocks in the DPB 218. In an example where the filter unit 216 is operated, the filter unit 216 may store filtered reconstructed blocks in the DPB 218. The motion estimation unit 222 and the motion compensation unit 224 may retrieve reference images formed by the reconstructed (and potentially filtered) blocks from the DPB 218 to perform inter-frame prediction for blocks of subsequent encoded images. Additionally, the intra-frame prediction unit 226 may use the reconstructed blocks of the current image in the DPB 218 to perform intra-frame prediction for other blocks in the current image.

[0211] Generally, entropy coding unit 220 can entropy code syntax elements received from other functional components of video encoder 200. For example, entropy coding unit 220 can entropy code quantized transform coefficient blocks from quantization unit 208. As another example, entropy coding unit 220 can entropy code predictive syntax elements (e.g., motion information for inter-frame prediction or intra-frame mode information for intra-frame prediction) from mode selection unit 202. Entropy coding unit 220 can perform one or more entropy coding operations on syntax elements (another example of video data) to generate entropy-coded data. For example, entropy coding unit 220 can perform context-adaptive variable-length decoding (CAVLC), CABAC, variable-to-variable (V2V) length decoding, syntax-based context-adaptive binary arithmetic decoding (SBAC), probability interval partitioning entropy (PIPE) decoding, exponential Golomb coding, or another type of entropy coding operation on the data. In some examples, entropy coding unit 220 can operate in a bypass mode where syntax elements are not entropy-coded.

[0212] The video encoder 200 can output a bitstream that includes the entropy coding syntax elements required to reconstruct slices or blocks of images. Specifically, the entropy coding unit 220 can output a bitstream.

[0213] According to AV1, entropy coding unit 220 can be configured as a symbol-to-symbol adaptive multi-symbol arithmetic decoder. The syntax elements in AV1 consist of an N-element alphabet, and the context (e.g., a probability model) consists of a set of N probabilities. Entropy coding unit 220 can store the probabilities as an n-bit (e.g., 15-bit) cumulative distribution function (CDF). Entropy coding unit 220 can perform recursive scaling using an update factor based on the alphabet size to update the context.

[0214] The operations described above are relative to blocks. This description should be understood as operations applied to luma decoding blocks and / or chroma decoding blocks. As described above, in some examples, the luma decoding block and chroma decoding block are the luma and chroma components of the CU. In some examples, the luma decoding block and chroma decoding block are the luma and chroma components of the PU.

[0215] In some examples, it is not necessary to repeat the operations performed relative to the luma decoder for the chroma decoder block. As an example, the operations for identifying the motion vector (MV) and reference image of the luma decoder block do not need to repeat the MV and reference image used to identify the chroma block. Instead, the MV used for the luma decoder block can be scaled to determine the MV used for the chroma block, and the reference image can be the same. As another example, the intra-frame prediction process can be the same for both the luma and chroma decoders.

[0216] Video encoder 200 represents an example of a device configured to encode video data, the device including: a memory configured to store video data; and one or more processing units implemented in circuitry and configured to perform any combination of the techniques of this disclosure for CMVP.

[0217] Figure 15 This is a block diagram illustrating an example video decoder 300 that can perform the techniques of this disclosure. Figure 15 This disclosure is provided for illustrative purposes and not for limiting the techniques extensively illustrated and described herein. For illustrative purposes, the video decoder 300 is described in accordance with VVC and HEVC techniques. However, the techniques of this disclosure can be implemented by video decoding devices configured for other video decoding standards.

[0218] exist Figure 15 In the example, the video decoder 300 includes a decoded 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 DPB 314. Any or all of the CPB memory 320, entropy decoding unit 302, prediction processing unit 304, inverse quantization unit 306, inverse transform processing unit 308, reconstruction unit 310, filter unit 312, and DPB 314 can be implemented in one or more processors or in processing circuitry. For example, the units of the video decoder 300 can be implemented as one or more circuit or logic elements as part of hardware circuitry, or as part of a processor, ASIC, or FPGA. Furthermore, the video decoder 300 may include additional or alternative processors or processing circuitry to perform these and other functions.

[0219] 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 based on other prediction modes. As an example, the prediction processing unit 304 may include a palette unit, an intra-block copying 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.

[0220] When operating according to AV1, motion compensation unit 316 can be configured to decode video data blocks (e.g., both luma and chroma blocks) using translational motion compensation, affine motion compensation, OBMC, and / or composite inter-intra-frame prediction, as described above. Intra-frame prediction unit 318 can be configured to decode video data blocks (e.g., both luma and chroma blocks) using directional intra-frame prediction, non-directional intra-frame prediction, recursive filter intra-frame prediction, CFL, IBC, and / or palette mode, as described above.

[0221] CPB memory 320 is an example of a memory system capable of storing video data (such as encoded video bitstreams) to be decoded by components of video decoder 300. For example, it can be stored from computer-readable medium 110 ( Figure 1 The video data stored in the CPB memory 320 is obtained. The CPB memory 320 may include a CPB that stores encoded video data (e.g., syntax elements) from the encoded video bitstream. Furthermore, the CPB memory 320 may store video data other than the syntax elements of the decoded picture, such as temporary data representing the output from various units of the video decoder 300. The DPB 314 is an example of a memory system that typically stores decoded pictures, which the video decoder 300 may output, and / or uses as reference video data when decoding subsequent data or pictures of the encoded video bitstream. The CPB memory 320 and the DPB 314 may each be formed from any of various memory devices or memory cells, such as DRAM (including SDRAM), MRAM, RRAM, or other types of memory devices. The CPB memory 320 and the DPB 314 may be provided by the same memory device or separate memory devices. In various examples, the CPB memory 320 may be on-chip with other components of the video decoder 300, or off-chip relative to those components.

[0222] Additionally or alternatively, in some examples, the video decoder 300 may be from the memory 120 ( Figure 1 The decoded video data can be retrieved from the memory. In other words, memory 120 can utilize CPB memory 320 to store data as discussed above. Similarly, when some or all of the functionality of video decoder 300 is implemented in software to be executed by the processing circuitry of video decoder 300, memory 120 can store instructions to be executed by video decoder 300.

[0223] Examples Figure 15 The various units shown help to understand the operations performed by the video decoder 300. These units can be implemented as fixed-function circuits, programmable circuits, or a combination thereof. Similar to... Figure 14 Fixed-function circuits are circuits that provide specific functionality and are pre-configured for the operations they can perform. Programmable circuits are circuits that can be programmed to perform various tasks and provide flexible functionality for the operations they can perform. 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 (e.g., to receive or output parameters), but the type of operation performed by a fixed-function circuit is typically immutable. In some examples, one or more units in a cell may be different circuit blocks (fixed-function or programmable), and in some examples, one or more units in a cell may be integrated circuits.

[0224] The video decoder 300 may include an ALU, EFU, digital circuitry, analog circuitry, and / or a programmable core formed by programmable circuitry. In an example where the operation of the video decoder 300 is performed by software executed on programmable circuitry, on-chip or off-chip memory may store instructions (e.g., object code) of the software received and executed by the video decoder 300.

[0225] The entropy decoding unit 302 can receive encoded video data from the CPB and perform entropy decoding on the video data to reproduce the syntax elements. The prediction processing unit 304, the inverse quantization unit 306, the inverse transform processing unit 308, the reconstruction unit 310, and the filter unit 312 can generate decoded video data based on the syntax elements extracted from the bitstream.

[0226] Generally speaking, the video decoder 300 reconstructs the image block by block. The video decoder 300 can perform the reconstruction operation on each block individually (where the block currently being reconstructed (i.e., decoded) can be referred to as the "current block").

[0227] Entropy decoding unit 302 can entropy decode the syntax elements of the quantized transform coefficients defining the quantized transform coefficient block, as well as transform information (such as quantization parameters (QP) and / or transform mode indications). Inverse quantization unit 306 can use the QP associated with the quantized transform coefficient block to determine the degree of quantization, and similarly, determine the degree of inverse quantization to be applied by inverse quantization unit 306. Inverse quantization unit 306 can, for example, perform a bit-by-bit left shift operation to inverse quantize the quantized transform coefficients. Inverse quantization unit 306 can thereby form a transform coefficient block including the transform coefficients.

[0228] After the inverse quantization unit 306 forms the transform coefficient block, the inverse transform processing unit 308 may apply one or more inverse transforms to the transform coefficient block to generate a residual block associated with the current block. For example, the inverse transform processing unit 308 may apply an inverse DCT, an inverse integer transform, an inverse Karhunen-Loeve transform (KLT), an inverse rotation transform, an inverse direction transform, or another inverse transform to the transform coefficient block.

[0229] Furthermore, the prediction processing unit 304 generates a prediction block based on the prediction information syntax elements entropy decoded by the entropy decoding unit 302. For example, if the prediction information syntax elements indicate that the current block is an inter-frame prediction, the motion compensation unit 316 can generate the prediction block. In this case, the prediction information syntax elements may indicate the reference picture from which the reference block is to be retrieved in the DPB 314, 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. The motion compensation unit 316 may generally follow the same procedure as relative to the motion compensation unit 224 ( Figure 14 The method described is essentially the same as the method used to perform the inter-frame prediction process.

[0230] As another example, when the prediction information syntax element indicates that the current block is intra-predictive, intra-predictive unit 318 may generate a prediction block according to the intra-predictive mode indicated by the prediction information syntax element. Similarly, intra-predictive unit 318 may generally follow the same procedure as relative to intra-predictive unit 226 ( Figure 14 The intra-prediction process is performed in a manner substantially similar to that described above. The intra-prediction unit 318 can retrieve data of neighboring samples of the current block from the DPB 314.

[0231] Reconstruction unit 310 can use the prediction block and the residual block to reconstruct the current block. For example, reconstruction unit 310 can add samples from the residual block to the corresponding samples from the prediction block to reconstruct the current block.

[0232] Filter unit 312 can perform one or more filtering operations on the reconstructed block. For example, filter unit 312 can perform a deblocking operation to reduce block artifacts along the edges of the reconstructed block. The operation of filter unit 312 is not necessarily performed in all examples.

[0233] The video decoder 300 can store reconstructed blocks in the DPB 314. For example, in an example where the operation of the filter unit 312 is not performed, the reconstruction unit 310 can store the reconstructed blocks in the DPB 314. In an example where the operation of the filter unit 312 is performed, the filter unit 312 can store the filtered reconstructed blocks in the DPB 314. As discussed above, the DPB 314 can provide reference information (such as samples of the current image for intra-frame prediction and samples of previously decoded images for subsequent motion compensation) to the prediction processing unit 304. Furthermore, the video decoder 300 can output decoded images (e.g., decoded video) from the DPB 314 for use in applications such as... Figure 1 The subsequent presentation on display devices such as display device 118.

[0234] In this way, video decoder 300 represents an example of a video decoding device, which includes: a memory configured to store video data; and one or more processing units implemented in circuitry and configured to perform any combination of the techniques of this disclosure for CMVP.

[0235] Figure 16 This is a flowchart illustrating an example method for encoding the current block according to the technology of this disclosure. The current block may be or may include the current CU. Although this relates to video encoder 200 ( Figure 1 and Figure 14 This is a description, but it should be understood that other devices can be configured to perform similar actions. Figure 16 Similar to the method.

[0236] In this example, the video encoder 200 initially predicts the current block (400). For example, the video encoder 200 may form a prediction block for the current block. The video encoder 200 may then compute a residual block for the current block (402). To compute the residual block, the video encoder 200 may compute the difference between the unencoded original block for the current block and the prediction block. The video encoder 200 may then transform the residual block and quantize the transform coefficients of the residual block (404). Next, the video encoder 200 may scan the quantized transform coefficients of the residual block (406). During or after the scan, the video encoder 200 may entropy encode the transform coefficients (408). For example, the video encoder 200 may use CAVLC or CABAC to encode the transform coefficients. The video encoder 200 may then output the entropy-encoded data of the block (410).

[0237] Figure 17This is a flowchart illustrating an example method for decoding a current block of video data according to the technology of this disclosure. The current block may be or may include the current CU. Although this relates to video decoder 300 ( Figure 1 and Figure 15 This description is provided, but it should be understood that other devices can be configured to perform similar actions. Figure 17 Similar to the method.

[0238] The video decoder 300 may receive entropy-coded data of the current block, such as entropy-coded prediction information and entropy-coded data for the transform coefficients of the residual block corresponding to the current block (500). The video decoder 300 may entropy decode the entropy-coded data to determine the prediction information for the current block and reproduce the transform coefficients of the residual block (502). The video decoder 300 may predict the current block, for example, using an intra-frame prediction mode or inter-frame prediction mode indicated by the prediction information of the current block (504), to compute a prediction block for the current block. The video decoder 300 may then inverse scan the reproduced transform coefficients (506) to create a block of quantized transform coefficients. 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 (508). The video decoder 300 may finally decode the current block by combining the prediction block and the residual block (510).

[0239] The following numbered clauses illustrate one or more aspects of the devices and technologies described in this disclosure.

[0240] Aspect 1A. A method for decoding video data, the method comprising: deriving motion vectors for bilateral matching merge pattern candidates using chained motion vector prediction; adding the bilateral matching merge pattern candidates to a candidate list; and decoding blocks of video data using the candidate list.

[0241] Aspect 2A. A method for decoding video data, the method comprising: limiting the number of bidirectional prediction chain motion vectors of the merging candidate when the source motion of the merging candidate is bidirectional prediction.

[0242] Aspect 3A. A method for decoding video data, the method comprising: for a bidirectional predictive chain of motion vector predictor candidates, deriving a first motion vector on a reference image A in a reference list X from an N-step time trajectory, where N is the minimum trackable step order.

[0243] Aspect 4A. A method for decoding video data, the method comprising: deriving at least one motion vector from a time trajectory for a chained motion vector predictor candidate; and scaling the at least one motion vector to a reference image.

[0244] Aspect 5A. The method according to any one of Aspects 1A to 4A, wherein decoding includes decoding.

[0245] Aspect 6A. The method according to any one of aspects 1A to 4A, wherein decoding includes encoding.

[0246] Aspect 7A. An apparatus for decoding video data, the apparatus comprising one or more components for performing the method according to any one of aspects 1A to 6A.

[0247] Aspect 8A. The device according to aspect 7A, wherein the one or more components include one or more processors implemented in a circuit.

[0248] Aspect 9A. The device according to any one of Aspects 7A and 8A, the device further comprising: a memory for storing the video data.

[0249] Aspect 10A. The device according to any one of aspects 7A to 9A, the device further comprising a display configured to display decoded video data.

[0250] Aspect 11A. The device according to any one of Aspects 7A to 10A, wherein the device includes one or more of a camera, computer, mobile device, broadcast receiver device or set-top box.

[0251] Aspect 12A. The device according to any one of aspects 7A to 11A, wherein the device includes a video decoder.

[0252] Aspect 13A. The device according to any one of aspects 7A to 12A, wherein the device includes a video encoder.

[0253] Aspect 14A. A computer-readable storage medium having instructions stored thereon, which, when executed, cause one or more processors to perform the method according to any one of aspects 1A to 6A.

[0254] Aspect 1B. A method for decoding video data, the method comprising: determining to decode a current block of the video data using a bilateral matching merge pattern; determining a first chained motion vector prediction (CMVP) candidate based on a first source candidate; determining that the first source candidate satisfies one or more bilateral matching conditions; inserting the first CMVP candidate into a bilateral matching merge list based on the first source candidate satisfying the one or more bilateral matching conditions; determining a second CMVP candidate based on a second source candidate; determining that the second source candidate does not satisfy the one or more bilateral matching conditions; inserting the second CMVP candidate into a second list based on the second source candidate not satisfying the one or more bilateral matching conditions; and decoding the current block using at least one of the bilateral matching merge list or the second list.

[0255] Aspect 2B. The method according to aspect 1B, the method further comprising: determining that at least one candidate from a neighboring location, a non-neighboring location, a time location, or a history buffer does not satisfy the one or more bilateral matching conditions; and inserting the at least one candidate into the second list based on the fact that the at least one candidate from the neighboring location, the non-neighboring location, the time location, or the history buffer does not satisfy the one or more bilateral matching conditions.

[0256] Aspect 3B. The method according to any one of Aspects 1B to 2B, wherein the second CMVP candidate is inserted into the second list after the bilateral matching merge list is derived.

[0257] Aspect 4B. The method according to any one of Aspects 1B to 3B, the method further comprising: determining which candidates in the second list are available chained motion vectors with a maximum tracking depth having a predetermined depth; storing each candidate in the second list as a available chained motion vector with the maximum tracking depth having the predetermined depth in a third list; determining which corresponding combination satisfies the one or more bilateral matching conditions for each combination of two stored candidates in the stored candidates in the third list; and inserting each corresponding combination that satisfies the one or more bilateral matching conditions into the bilateral matching merge list.

[0258] Aspect 5B. The method according to aspect 4B, wherein the predetermined depth is equal to 1.

[0259] Aspect 6B. The method according to any one of Aspects 4B to 5B, wherein storing in the third list comprises: storing the corresponding source motion of each of the determined candidates.

[0260] Aspect 7B. The method according to Aspect 1B, the method further comprising: for each candidate in the second list, determining whether a reference block from one of the two prediction directions is a bidirectional prediction reference block and whether two chain motion vectors associated with the candidate satisfy the one or more bilateral matching conditions; and for each candidate in the second list where the reference block from one of the two prediction directions is a bidirectional prediction reference block and the two chain motion vectors associated with the candidate satisfy the one or more bilateral matching conditions, inserting the corresponding bidirectional prediction chain motion vector prediction candidate into the bilateral matching merge list.

[0261] Aspect 8B. The method according to any one of aspects 1B to 7B, wherein decoding includes decoding.

[0262] Aspect 9B. The method according to any one of aspects 1B to 7B, wherein decoding includes encoding.

[0263] Aspect 10B. An apparatus configured to decode video data, the apparatus comprising: one or more memories configured to store the video data; and one or more processors communicatively coupled to the one or more memories, the one or more processors configured to: determine a current block of the video data to be decoded using a bilateral matching merge mode; determine a first chained motion vector prediction (CMVP) candidate based on a first source candidate; determine that the first source candidate satisfies one or more bilateral matching conditions; insert the first CMVP candidate into a bilateral matching merge list based on the first source candidate satisfying the one or more bilateral matching conditions; determine a second CMVP candidate based on a second source candidate; determine that the second source candidate does not satisfy the one or more bilateral matching conditions; insert the second CMVP candidate into a second list based on the second source candidate not satisfying the one or more bilateral matching conditions; and decode the current block using at least one of the bilateral matching merge list or the second list.

[0264] Aspect 11B. The device according to aspect 10B, wherein the one or more processors are further configured to: determine that at least one candidate from a neighboring location, a non-neighboring location, a time location, or a history buffer does not satisfy the one or more bilateral matching conditions; and insert the at least one candidate into the second list based on the fact that the at least one candidate from the neighboring location, the non-neighboring location, the time location, or the history buffer does not satisfy the one or more bilateral matching conditions.

[0265] Aspect 12B. The device according to any one of aspects 10B to 11B, wherein the second CMVP candidate is inserted into the second list after the bilateral matching merge list is derived.

[0266] Aspect 13B. The device according to any one of Aspects 10B to 12B, wherein the one or more processors are further configured to: determine which candidates in the second list are available chained motion vectors with a maximum tracking depth having a predetermined depth; store each candidate in the second list as a candidate of the available chained motion vector with the maximum tracking depth having the predetermined depth in a third list; determine which corresponding combination satisfies the one or more bilateral matching conditions for each combination of two stored candidates in the third list; and insert each corresponding combination that satisfies the one or more bilateral matching conditions into the bilateral matching merge list.

[0267] Aspect 14B. The device according to aspect 13B, wherein the predetermined depth is equal to 1.

[0268] Aspect 15B. The device according to any one of aspects 13B to 14B, wherein, as part of the storage in the third list, the one or more processors are configured to: store the corresponding source motion of each of the determined candidates.

[0269] Aspect 16B. The apparatus according to any one of Aspects 10B to 15B, wherein the one or more processors are further configured to: for each candidate in the second list, determine whether a reference block from one of the two prediction directions is a bidirectional prediction reference block and whether two chain motion vectors associated with the candidate satisfy the one or more bilateral matching conditions; and for each candidate in the second list where a reference block from one of the two prediction directions is a bidirectional prediction reference block and the two chain motion vectors associated with the candidate satisfy the one or more bilateral matching conditions, insert the corresponding bidirectional prediction chain motion vector prediction candidate into the bilateral matching merge list.

[0270] Aspect 17B. The device according to any one of aspects 10B to 16B, the device further comprising a display configured to display decoded video data.

[0271] Aspect 18B. A method for encoding video data, the method comprising: determining to encode a current block of the video data using a bilateral matching merge pattern; determining a first chained motion vector prediction (CMVP) candidate based on a first source candidate; determining that the first source candidate satisfies one or more bilateral matching conditions; inserting the first CMVP candidate into a bilateral matching merge list based on the first source candidate satisfying the one or more bilateral matching conditions; determining a second CMVP candidate based on a second source candidate; determining that the second source candidate does not satisfy the one or more bilateral matching conditions; inserting the second CMVP candidate into a second list based on the second source candidate not satisfying the one or more bilateral matching conditions; and encoding the current block using at least one of the bilateral matching merge list or the second list.

[0272] Aspect 19B. The method according to aspect 18B, the method further comprising: determining that at least one candidate from a neighboring location, a non-neighboring location, a time location, or a history buffer does not satisfy the one or more bilateral matching conditions; and inserting the at least one candidate into the second list based on the fact that the at least one candidate from the neighboring location, the non-neighboring location, the time location, or the history buffer does not satisfy the one or more bilateral matching conditions.

[0273] Aspect 20B. The method according to any one of Aspects 18B to 19B, wherein the second CMVP candidate is inserted into the second list after the bilateral matching merge list is derived.

[0274] Aspect 21B. The method according to any one of Aspects 18B to 20B, the method further comprising: determining which candidates in the second list are available chained motion vectors with a maximum tracking depth having a predetermined depth; storing each of the determined candidates in the second list as available chained motion vectors with the maximum tracking depth having the predetermined depth in a third list; determining which corresponding combination satisfies the one or more bilateral matching conditions for each combination of two stored candidates in the stored candidates in the third list; and inserting each corresponding combination that satisfies the one or more bilateral matching conditions into the bilateral matching merge list.

[0275] Aspect 22B. The method according to aspect 21B, wherein the predetermined depth is equal to 1.

[0276] Aspect 23B. The method according to any one of aspects 21B to 22B, wherein storing in the third list comprises: storing the corresponding source motion of each of the determined candidates.

[0277] Aspect 24B. The method according to any one of Aspects 18B to 23B, the method further comprising: for each candidate in the second list, determining whether a reference block from one of the two prediction directions is a bidirectional prediction reference block and whether two chain motion vectors associated with the candidate satisfy the one or more bilateral matching conditions; and for each candidate in the second list where the reference block from one of the two prediction directions is a bidirectional prediction reference block and the two chain motion vectors associated with the candidate satisfy the one or more bilateral matching conditions, inserting the corresponding bidirectional prediction chain motion vector prediction candidate into the bilateral matching merge list.

[0278] Aspect 25B. An apparatus configured to encode video data, the apparatus comprising: one or more memories configured to store the video data; and one or more processors communicatively coupled to the one or more memories, the one or more processors configured to: determine a current block of the video data to be encoded using a bilateral matching merge mode; determine a first chained motion vector prediction (CMVP) candidate based on a first source candidate; determine that the first source candidate satisfies one or more bilateral matching conditions; insert the first CMVP candidate into a bilateral matching merge list based on the first source candidate satisfying the one or more bilateral matching conditions; determine a second CMVP candidate based on a second source candidate; determine that the second source candidate does not satisfy the one or more bilateral matching conditions; insert the second CMVP candidate into a second list based on the second source candidate not satisfying the one or more bilateral matching conditions; and encode the current block using at least one of the bilateral matching merge list or the second list.

[0279] Aspect 26B. The device according to aspect 25B, wherein the one or more processors are further configured to: determine that at least one candidate from a neighboring location, a non-neighboring location, a time location, or a history buffer does not satisfy the one or more bilateral matching conditions; and insert the at least one candidate into the second list based on the fact that the at least one candidate from the neighboring location, the non-neighboring location, the time location, or the history buffer does not satisfy the one or more bilateral matching conditions.

[0280] Aspect 27B. The device according to any one of aspects 25B to 26B, wherein the second CMVP candidate is inserted into the second list after the bilateral matching merge list is derived.

[0281] Aspect 28B. The device according to any one of Aspects 25B to 27B, wherein the one or more processors are further configured to: determine which candidates in the second list are available chained motion vectors with a maximum tracking depth having a predetermined depth; store each candidate in the second list as an available chained motion vector with the maximum tracking depth having the predetermined depth in a third list; determine which corresponding combination satisfies the one or more bilateral matching conditions for each combination of two stored candidates in the stored candidates in the third list; and insert each corresponding combination that satisfies the one or more bilateral matching conditions into the bilateral matching merge list.

[0282] Aspect 29B. The device according to aspect 28B, wherein the predetermined depth is equal to 1.

[0283] Aspect 30B. The device according to any one of aspects 28B to 29B, wherein, as part of the storage in the third list, the one or more processors are configured to: store the corresponding source motion of each of the determined candidates.

[0284] Aspect 31B. The apparatus according to any one of Aspects 25B to 30B, wherein the one or more processors are further configured to: for each candidate in the second list, determine whether a reference block from one of the two prediction directions is a bidirectional prediction reference block and whether two chain motion vectors associated with the candidate satisfy the one or more bilateral matching conditions; and for each candidate in the second list where a reference block from one of the two prediction directions is a bidirectional prediction reference block and the two chain motion vectors associated with the candidate satisfy the one or more bilateral matching conditions, insert the corresponding bidirectional prediction chain motion vector prediction candidate into the bilateral matching merge list.

[0285] Aspect 32B. The device according to any one of aspects 25B to 31B, the device further comprising a camera configured to capture the video data.

[0286] It should be recognized that, based on the examples, certain actions or events of any technique described herein may be performed in a different sequence, and may be added, combined, or omitted entirely (e.g., not all actions or events described are necessary for implementing the technique). Furthermore, in some examples, actions or events may be performed concurrently (e.g., through multithreading, interrupt handling, or multiple processors) rather than sequentially.

[0287] In one or more examples, the described functionality may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functionality may be stored as one or more instructions or code on a computer-readable medium or transmitted via a computer-readable medium and executed by a hardware-based processing unit. A computer-readable medium may include a computer-readable storage medium (which corresponds to a tangible medium such as a data storage medium) or a communication medium, including, for example, any medium that facilitates the transfer of a computer program from one place to another according to a communication protocol. In this way, a computer-readable medium may generally correspond to (1) a non-transitory tangible computer-readable storage medium, or (2) a communication medium such as a signal or carrier wave. A data storage medium may be any available medium that can be accessed by one or more computers or one or more processors to retrieve instructions, code, and / or data structures for implementing the techniques described in this disclosure. Computer program products may include computer-readable media.

[0288] By way of example, and not limitation, such computer-readable storage media may include one or more of RAM, ROM, EEPROM, CD-ROM or other optical disc storage devices, magnetic disk storage devices or other magnetic storage devices, flash memory, or any other medium capable of storing desired program code in the form of instructions or data structures and accessible by a computer. Furthermore, any connection is appropriately referred to as a computer-readable medium. For example, if instructions are transmitted from a website, server, or other remote source using coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technology (such as infrared, radio, and microwave), then 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 transient media, but instead refer to non-transient tangible storage media. As used herein, disks and optical discs include compact optical discs (CDs), laser optical discs, optical discs, digital versatile optical discs (DVDs), floppy disks, and Blu-ray discs, where disks typically reproduce data magnetically, while optical discs use lasers to reproduce data optically. Combinations of these should also be included within the scope of computer-readable media.

[0289] Instructions can be executed by one or more processors, such as one or more DSPs, general-purpose microprocessors, ASICs, FPGAs, or other equivalent integrated or discrete logic circuits. Therefore, the terms "processor" and "processing circuit" as used herein can refer to any of the foregoing structures or any other structure suitable for implementing the techniques described herein. Additionally, in some aspects, the functionality described herein can be provided within dedicated hardware and / or software modules configured for encoding and decoding, or incorporated into combined codecs. Furthermore, these techniques can be fully implemented in one or more circuit or logic elements.

[0290] The techniques disclosed herein can be implemented in a wide variety of devices or apparatuses, including wireless mobile phones, integrated circuits (ICs), or IC sets (e.g., chipsets). Various components, modules, or units are described in this disclosure to emphasize functional aspects of a device configured to perform the disclosed techniques, but implementation by different hardware units is not necessarily required. Rather, as described above, various units can be combined in a codec hardware unit, or various units can be provided by a collection of interoperable hardware units (including one or more processors as described above) combined with appropriate software and / or firmware.

[0291] 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 comprising: Determine whether to use the bilateral matching merge mode to decode the current block of the video data; First chain motion vector prediction (CMVP) candidates are determined based on the first source candidates; The first source candidate is determined to satisfy one or more bilateral matching conditions; Based on the fact that the first source candidate satisfies one or more bilateral matching conditions, the first CMVP candidate is inserted into the bilateral matching merge list; The second CMVP candidate is determined based on the second source candidate; It is determined that the second source candidate does not satisfy the one or more bilateral matching conditions; Based on the fact that the second source candidate does not meet the one or more bilateral matching conditions, the second CMVP candidate is inserted into the second list; as well as The current block is decoded using at least one of the bilateral matching merge list or the second list.

2. The method according to claim 1, further comprising: Determine that at least one candidate from neighboring locations, non-neighboring locations, time locations, or history buffers does not satisfy the one or more bilateral matching conditions; as well as Based on the fact that at least one candidate from the neighboring location, the non-neighboring location, the time location, or the history buffer does not satisfy the one or more bilateral matching conditions, the at least one candidate is inserted into the second list.

3. The method of claim 1, wherein the second CMVP candidate is inserted into the second list after the bilateral matching merge list is exported.

4. The method according to claim 1, further comprising: Determine which candidates in the second list are available chain motion vectors with a maximum tracking depth of a predetermined depth; Each candidate in the second list that is a candidate for the maximum tracking depth with the predetermined depth is stored in a third list; For each combination of two stored candidates in the third list, determine which corresponding combination satisfies the one or more bilateral matching conditions; as well as Insert each corresponding combination that satisfies one or more bilateral matching conditions into the bilateral matching merge list.

5. The method according to claim 4, wherein the predetermined depth is equal to 1.

6. The method of claim 4, wherein storing in the third list comprises: Store the corresponding source motion for each of the identified candidates.

7. The method according to claim 1, further comprising: For each candidate in the second list, determine whether the reference block from one of the two prediction directions is a bidirectional prediction reference block and whether the two chain motion vectors associated with the candidate satisfy the one or more bilateral matching conditions; as well as For each candidate in the second list whose reference block from one of the two prediction directions is a bidirectional prediction reference block and whose two chain motion vectors associated with the candidate satisfy the one or more bilateral matching conditions, the corresponding bidirectional prediction chain motion vector prediction candidate is inserted into the bilateral matching merge list.

8. The method of claim 1, wherein decoding includes decoding.

9. The method of claim 1, wherein decoding includes encoding.

10. An apparatus configured to decode video data, the apparatus comprising: One or more memories, the one or more memories being configured to store the video data; and One or more processors, communicatively coupled to one or more memories, are configured to: Determine to use the bilateral matching merge mode to decode the current block of the video data; First chain motion vector prediction (CMVP) candidates are determined based on the first source candidates; The first source candidate is determined to satisfy one or more bilateral matching conditions; Based on the fact that the first source candidate satisfies one or more bilateral matching conditions, the first CMVP candidate is inserted into the bilateral matching merge list; The second CMVP candidate is determined based on the second source candidate; It is determined that the second source candidate does not satisfy the one or more bilateral matching conditions; Based on the fact that the second source candidate does not meet the one or more bilateral matching conditions, the second CMVP candidate is inserted into the second list; as well as The current block is decoded using at least one of the bilateral matching merge list or the second list.

11. The device of claim 10, wherein the one or more processors are further configured to: Determine that at least one candidate from neighboring locations, non-neighboring locations, time locations, or history buffers does not satisfy the one or more bilateral matching conditions; and Based on the fact that at least one candidate from the neighboring location, the non-neighboring location, the time location, or the history buffer does not satisfy the one or more bilateral matching conditions, the at least one candidate is inserted into the second list.

12. The device of claim 10, wherein the second CMVP candidate is inserted into the second list after the bilateral matching merge list is exported.

13. The device of claim 10, wherein the one or more processors are further configured to: Determine which candidates in the second list are available chain motion vectors with a maximum tracking depth of a predetermined depth; Each candidate in the second list that is a candidate for the maximum tracking depth with the predetermined depth is stored in a third list; For each combination of two stored candidates in the third list, determine which corresponding combination satisfies the one or more bilateral matching conditions; as well as Insert each corresponding combination that satisfies one or more bilateral matching conditions into the bilateral matching merge list.

14. The device of claim 13, wherein, as part of the storage in the third list, the one or more processors are configured to: store the corresponding source motion of each of the determined candidates.

15. The device of claim 10, further comprising a display configured to display decoded video data.

16. An apparatus configured to encode video data, the apparatus comprising: One or more memories, the one or more memories being configured to store the video data; and One or more processors, communicatively coupled to one or more memories, are configured to: Determine to encode the current block of the video data using a bilateral matching merge mode; First chain motion vector prediction (CMVP) candidates are determined based on the first source candidates; The first source candidate is determined to satisfy one or more bilateral matching conditions; Based on the fact that the first source candidate satisfies one or more bilateral matching conditions, the first CMVP candidate is inserted into the bilateral matching merge list; The second CMVP candidate is determined based on the second source candidate; It is determined that the second source candidate does not satisfy the one or more bilateral matching conditions; Based on the fact that the second source candidate does not meet the one or more bilateral matching conditions, the second CMVP candidate is inserted into the second list; as well as The current block is encoded using at least one of the bilateral matching merge list or the second list.

17. The device of claim 16, wherein the one or more processors are further configured to: Determine that at least one candidate from neighboring locations, non-neighboring locations, time locations, or history buffers does not satisfy the one or more bilateral matching conditions; and Based on the fact that at least one candidate from the neighboring location, the non-neighboring location, the time location, or the history buffer does not satisfy the one or more bilateral matching conditions, the at least one candidate is inserted into the second list.

18. The device of claim 16, wherein the second CMVP candidate is inserted into the second list after the bilateral matching merge list is exported.

19. The device of claim 16, wherein the one or more processors are further configured to: Determine which candidates in the second list are available chain motion vectors with a maximum tracking depth of a predetermined depth; Each candidate in the second list that is a candidate for the maximum tracking depth with the predetermined depth is stored in a third list; For each combination of two stored candidates in the third list, determine which corresponding combination satisfies the one or more bilateral matching conditions; as well as Insert each corresponding combination that satisfies one or more bilateral matching conditions into the bilateral matching merge list.

20. The device of claim 16, further comprising a camera configured to capture the video data.

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