Motion vector prediction with motion information acquisition buffer

Abstract

An example device for encoding and decoding video data includes: a memory configured to store video data; and one or more processors implemented in a circuit and configured to: determine that a size of a current block of video data is less than a threshold, the current block being a two-dimensional array of samples representing a portion of a picture; determine a set of motion vector prediction candidates for the current block based on the determination that the size of the current block is less than the threshold; a motion vector predictor that selects the motion vector prediction candidates for the current block; encode and decode motion information of the current block using the motion vector predictor; and encode and decode the current block using the motion information.

Description

[0001] This application claims priority to U.S. Patent Application No. 16 / 924,884, filed on July 9, 2020, U.S. Provisional Patent Application No. 62 / 873,162, filed on July 11, 2019, and U.S. Provisional Patent Application No. 62 / 873,661, filed on July 12, 2019, the entire contents of each of which are incorporated herein by reference. Technical Field

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

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

[0004] Video coding techniques include spatial (intra-picture) prediction and / or temporal (inter-picture) prediction to reduce or eliminate redundancy inherent in video sequences. For block-based video coding, a video slice (e.g., a video picture or a portion of a video picture) may be partitioned into video blocks, which may also be referred to as codec tree units (CTUs), codec units (CUs), and / or codec nodes. For video blocks in an intra-frame codec (I) slice of a picture, spatial prediction relative to reference samples in adjacent blocks in the same picture may be used for encoding. For video blocks in an inter-frame codec (P or B) slice of a picture, spatial prediction relative to reference samples in adjacent blocks in the same picture or temporal prediction relative to reference samples in other reference pictures may be used. 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] In general, this disclosure describes techniques related to decoder-side motion vector refinement (DMVR). These techniques can be applied to any existing video codec, such as HEVC (High Efficiency Video Codec) or the upcoming VVC (Versatile Video Codec). These techniques can also provide efficient encoding and decoding tools for future video codec standards.

[0006] In one example, a method for encoding and decoding video data includes: determining that a size of a current block of video data is less than a threshold, the current block being a two-dimensional array of sample points representing a portion of a picture; determining a set of motion vector prediction candidates for the current block based on the determination that the size of the current block is less than the threshold; selecting a motion vector predictor for the motion vector prediction candidate for the current block; encoding and decoding motion information of the current block using the motion vector predictor; and encoding and decoding the current block using the motion information.

[0007] In another example, a device for encoding and decoding video data includes: a memory configured to store video data; and one or more processors implemented in a circuit and configured to: determine that a size of a current block of video data is less than a threshold, the current block being a two-dimensional array of samples representing a portion of a picture; determine a set of motion vector prediction candidates for the current block based on the determination that the size of the current block is less than the threshold; a motion vector predictor that selects the motion vector prediction candidates for the current block; encode and decode motion information of the current block using the motion vector predictor; and encode and decode the current block using the motion information.

[0008] In another example, a computer-readable storage medium having instructions stored thereon, which when executed cause a processor to: determine that a size of a current block of video data is less than a threshold, the current block being a two-dimensional array of samples representing a portion of a picture; determine a set of motion vector prediction candidates for the current block based on the determination that the size of the current block is less than the threshold; select a motion vector predictor for the motion vector prediction candidate for the current block; encode and decode motion information of the current block using the motion vector predictor; and encode and decode the current block using the motion information.

[0009] In another example, a device for encoding and decoding video data includes: a component for determining that a size of a current block of video data is less than a threshold, the current block being a two-dimensional array of samples representing a portion of a picture; a component for determining a set of motion vector prediction candidates for the current block based on the determination that the size of the current block is less than the threshold; a component for selecting a motion vector predictor for the motion vector prediction candidate for the current block; a component for encoding and decoding motion information of the current block using the motion vector predictor; and a component for encoding and decoding the current block using the motion information.

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

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

[0012] Figure 2A and Figure 2B is a conceptual diagram showing examples of spatial neighboring motion vector (MV) candidates for merge mode and advanced motion vector prediction (AMVP) mode.

[0013] Figure 3A and Figure 3B is an example of a conceptual diagram of a temporal motion vector prediction (TMVP) candidate and scaling the MV of the TMVP candidate.

[0014] Figure 4 A conceptual diagram illustrating an example process by which non-adjacent spatial merge candidates may be obtained.

[0015] Figure 5A-Figure 5C is a conceptual diagram illustrating an example of an alternative motion vector prediction design.

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

[0017] Figure 7 is a block diagram illustrating an example video decoder that may perform the techniques of this disclosure.

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

[0019] Fig. 9 is a flow chart illustrating an example method for decoding a current block according to the techniques of this disclosure.

[0020] Fig.10 is a flowchart illustrating an example method for encoding video data according to the techniques of this disclosure.

[0021] Fig.11 is a flow chart illustrating an example method for decoding video data according to the techniques of this disclosure. DETAILED DESCRIPTION

[0022] Video codec standards include ITU-T H.261, ISO / IEC MPEG-1 Visual, ITU-T H.262 or ISO / IEC MPEG-2 Visual, ITU-T H.263, ISO / IEC MPEG-4 Visual, and ITU-T H.264 (also known as ISO / IEC MPEG-4 AVC), including its Scalable Video Codec (SVC) and Multi-view Video Codec (MVC) extensions.

[0023] In addition, the Joint Collaborative Team on Video Coding (JCT-VC) and the Joint Collaborative Team on 3D Video Coding Extensions (JCT-3V) of the ITU-T Video Coding Experts Group (VCEG) and the ISO / IEC Moving Picture Experts Group (MPEG) have developed High Efficiency Video Coding (HEVC) or ITU-T H.265, including its range extension, multi-view extension (MV-HEVC) and scalable extension (SHVC). The HEVC specification, hereinafter referred to as "HEVC WD", is available at phenix.int-evry.fr / jct / doc_end_user / documents / 14_Vienna / wg11 / JCTVC-N1003-v1.zip.

[0024] ITU-T VCEG (Q6 / 16) and ISO / IEC MPEG (JTC 1 / SC 29 / WG11) are investigating potential requirements for the standardization of future video codecs with compression capabilities significantly exceeding the current HEVC standard (including its current extensions and near-term extensions to the screen content codec and the high dynamic range codec). The groups are working together on this exploration activity in a joint collaborative effort known as the Joint Video Exploration Team (JVET) to evaluate compression technology designs proposed by their experts in the field. The JVET held its first meeting between October 19 and 21, 2015. A version of the reference software, the Joint Exploration Model 7 (JEM7), is available from jvet.hhi.fraunhofer.de / svn / svn_HMJEMSoftware / tags / HM-16.6-JEM-7.0 / . A draft of the VVC standard is described in Bross et al., "Versatile Video Coding (Draft 5)", ITU-T SG 16 WP3 and ISO / IEC JTC 1 / SC 29 / WG 11 Joint Video Experts Group (JVET), 14th Meeting: Geneva, Switzerland, March 19-27, 2019, JVET-N1001-v3 (hereinafter referred to as "VVC Draft 5"). However, the techniques of the present disclosure are not limited to any particular codec standard.

[0025] In HEVC, the largest codec unit in a slice is called a codec tree block (CTB) or codec tree unit (CTU). The CTB contains a quadtree whose nodes are codec units. In the HEVC Main Profile, the size of the CTB varies from 16×16 to 64×64 according to HEVC (although 8×8 CTB size is technically supported). According to HEVC, the codec unit (CU) can be the same size as the CTB or as small as 8×8. Each codec unit is coded and decoded with one prediction mode (i.e., inter or intra). When the CU is inter-coded, it can be further split into 2 or 4 prediction units (PUs), or just one PU when no further splitting is applied. When two PUs exist in a CU, they can be half-sized rectangles or two rectangles with sizes of 1 / 4 and 3 / 4 of the CU respectively. When the CU is inter-coded, each PU has a motion information set that can be derived with a unique inter prediction mode.

[0026] In HEVC, there are two inter prediction modes for prediction units (PUs), called merge mode (skip is considered a special case of merge mode) and advanced motion vector prediction (AMVP) mode. In AMVP mode or merge mode, the video codec maintains a motion vector (MV) candidate list for multiple motion vector predictors. The video codec generates the motion vector of the current PU and the reference index in merge mode by extracting a candidate from the MV candidate list.

[0027] According to HEVC, the MV candidate list contains up to 5 candidates for merge mode and only two candidates for AMVP mode. The merge candidate may contain a set of motion information, for example, motion vectors corresponding to both reference picture lists (list 0 and list 1) and reference indices. If the merge candidate is identified by a merge index, the reference picture used for prediction of the current block and the associated motion vector are determined. On the other hand, in AMVP mode, for each potential prediction direction from list 0 or list 1, since the AMVP candidate only contains motion vectors, the reference index is explicitly signaled to the MV candidate list together with the MV predictor (MVP) index. In AMVP mode, the predicted motion vector can be further refined. Candidates for both modes are similarly derived from the same spatial and temporal neighboring blocks.

[0028] Retrieving motion information of neighboring blocks of a current block to predict motion information of the current block may be costly in terms of the number of processor operations performed and memory bandwidth used. The present disclosure recognizes that for small block sizes, such as 4×4, 4×8, or 8×4, the number of such operations may be considerable, especially when compounded by many small blocks in a strip or picture. Therefore, according to the techniques of the present disclosure, a video codec may use a reduced number of motion information candidates to predict motion information for small-sized blocks relative to the number of motion information candidates for larger blocks. By reducing the number of candidates for small blocks, fewer operations may be performed and memory bandwidth may be increased, thereby improving the performance of the video codec without negatively affecting the bit rate of the encoded video bitstream and without negatively affecting video fidelity when decoding and displaying video data of the encoded video bitstream.

[0029] Figure 1 1 is a block diagram illustrating an example video encoding and decoding system 100 that may perform the techniques of the present disclosure. The techniques of the present disclosure are generally directed to encoding and decoding (encoding and / or decoding) video data. Generally, video data includes any data used to process video. Thus, video data may include original unencoded video, encoded video, decoded (e.g., reconstructed) video, and video metadata (such as signaling data).

[0030] 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 target device 116. Specifically, source device 102 provides the video data to target device 116 via computer-readable medium 110. Source device 102 and target device 116 may include any of a variety of devices, including desktop computers, notebook (i.e., laptop) computers, tablet computers, set-top boxes, handheld phones (such as smart phones), televisions, cameras, display devices, digital media players, video game consoles, video streaming devices, etc. In some cases, source device 102 and target device 116 may be equipped for wireless communication and, therefore, may be referred to as wireless communication devices.

[0031] exist Figure 1In the example of, source device 102 comprises video source 104, memory 106, video encoder 200 and output interface 108. Target device 116 comprises input interface 122, video decoder 300, memory 120 and display device 118. According to the present disclosure, the video encoder 200 of source device 102 and the video decoder 300 of target device 116 can be configured to apply the technology for performing motion vector prediction according to the present disclosure. Thus, source device 102 represents an example of video encoding device, and target device 116 represents an example of video decoding device. In other examples, source device and target device can include other components or arrangements. For example, source device 102 can receive video data from an external video source such as an external camera. Similarly, target device 116 can interface with an external display device without including an integrated display device.

[0032] like Figure 1 The system 100 shown is only an example. Generally, any digital video encoding and / or decoding device can perform the technology for performing motion vector prediction according to the present disclosure. The source device 102 and the target device 116 are only examples of such codec devices, wherein the source device 102 generates codec video data for transmission to the target device 116. The present disclosure represents the "codec" device as a device that performs data coding (coding and / or decoding). Thus, the video encoder 200 and the video decoder 300 represent examples of codec devices, specifically, video encoders and video decoders, respectively. In some examples, the device 102 and the device 116 can operate in a substantially symmetrical manner so that each of the devices 102 and 116 includes a video encoding and decoding component. Thus, the system 100 can support one-way or two-way video transmission between the video devices 102 and 116, such as for video streaming, video playback, video broadcasting or video telephony.

[0033] Generally, the video source 104 represents a source of video data (i.e., original, unencoded video data), and provides a sequence of continuous pictures (also referred to as "frames") of the video data to the video encoder 200, which encodes the data of the pictures. The video source 104 of the source device 102 may include a video capture device, such as a camera, a video archive including previously captured original video, and / or a video feed interface for receiving video from a video content provider. As a further alternative, the video source 104 may generate computer graphics-based data as a source video, or a combination of live video, archived video, and computer-generated video. In each case, the video encoder 200 encodes the captured, pre-captured, or computer-generated video data. The video encoder 200 may rearrange the pictures from the receiving order (sometimes referred to as "display order") to the encoding and decoding order for encoding and decoding. The video encoder 200 may generate a bitstream including the encoded video data. Then, the source device 102 may output the encoded video data to the computer-readable medium 110 via the output interface 108, for example, for reception and / or retrieval by the input interface 122 of the target device 116.

[0034] The memory 106 of the source device 102 and the memory 120 of the target device 116 represent general purpose memory. In some examples, the memories 106, 120 can store original video data, such as original video from the video source 104 and original decoded video data from the video decoder 300. Additionally or alternatively, the memories 106, 120 can store software instructions that can be executed by, for example, the video encoder 200 and the video decoder 300, respectively. Although shown separately from the video encoder 200 and the video decoder 300 in this example, it should be understood that the video encoder 200 and the video decoder 300 can also include internal memory for functionally similar or equivalent purposes. Further, the memories 106, 120 can store, for example, encoded video data output from the video encoder 200 and input to the video decoder 300. In some examples, some portions of the memories 106, 120 can be allocated as one or more video buffers, for example, to store original decoded and / or encoded video data.

[0035] The computer-readable medium 110 may represent any type of medium or device capable of transmitting the encoded video data from the source device 102 to the target device 116. In one example, the computer-readable medium 110 represents a communication medium to enable the source device 102 to transmit the encoded video data directly to the target device 116 in real time, for example, via a radio frequency network or a computer-based network. According to a communication standard such as a wireless communication protocol, the output interface 108 may modulate a transmission signal including the encoded video data, and the input interface 122 may demodulate the received transmission signal. The communication medium may include any wireless or wired communication medium, such as a radio frequency (RF) spectrum or one or more physical transmission lines. The communication medium may form part of a packet-based network, such as a local area network, a wide area network, or a global network such as the Internet. The communication medium may include a router, a switch, a base station, or any other equipment that facilitates communication from the source device 102 to the target device 116.

[0036] In some examples, source device 102 may output the encoded data from output interface 108 to storage device 112. Similarly, target device 116 may access the encoded data from storage device 112 via input interface 122. Storage device 112 may include any of a variety of distributed or locally accessed data storage media, such as a hard disk, Blu-ray disc, DVD, CD-ROM, flash memory, volatile or non-volatile memory, or any other suitable digital storage medium for storing encoded video data.

[0037] In some examples, source device 102 may output encoded video data to file server 114 or another intermediate storage device that may store encoded video generated by source device 102. Target device 116 may access the stored video data from file server 114 via streaming or downloading. File server 114 may be any type of server device capable of storing encoded video data and sending the encoded video data to target device 116. File server 114 may represent a web server (e.g., for a website), a file transfer protocol (FTP) server, a content delivery network device, or a network attached storage (NAS) device. Target device 116 may access the encoded video data from file server 114 through any standard data connection including an Internet connection. This may include a wireless channel (e.g., a Wi-Fi connection), a wired connection (e.g., a digital subscriber line (DSL), a cable modem, etc.), or a combination of the two suitable for accessing encoded video data stored on file server 114. File server 114 and input interface 122 may be configured to operate according to a streaming protocol, a downloading transmission protocol, or a combination thereof.

[0038] Output interface 108 and input interface 122 may represent wireless transmitters / receivers, modems, wired networking components (e.g., Ethernet cards), wireless communication components that operate according to any of the various IEEE 802.11 standards, or other physical components. In examples where output interface 108 and input interface 122 include wireless components, output interface 108 and input interface 122 may be configured to transmit data, such as encoded video data, according to a cellular communication standard such as 4G, 4G-LTE (Long Term Evolution), LTE Advanced, 5G, or the like. In certain examples where output interface 108 includes a wireless transmitter, output interface 108 and input interface 122 may be configured to transmit data, such as encoded video data, according to other wireless standards, such as the IEEE 802.11 specification, the IEEE 802.15 specification (e.g., ZigBee 5G). TM ),Bluetooth TM Standards, etc. to transmit data such as encoded video data. In some examples, source device 102 and / or target device 116 may include respective system-on-chip (SoC) devices. For example, source device 102 may include a SoC device to perform functions attributed to video encoder 200 and / or output interface 108, and target device 116 may include a SoC device to perform functions attributed to video decoder 300 and / or input interface 122.

[0039] The technology disclosed herein can be applied to video encoding and decoding to support any of a variety of multimedia applications, such as over-the-air television broadcasting, cable television transmission, satellite television transmission, Internet streaming video transmission such as Dynamic Adaptive Streaming over HTTP (DASH), digital video encoded to a data storage medium, decoding of digital video stored on a data storage medium, or other applications.

[0040] The input interface 122 of the target device 116 receives the encoded video bitstream from the computer-readable medium 110 (e.g., the storage device 112, the 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 characteristics and / or processing of video blocks or other codec units (e.g., slices, pictures, groups of pictures, sequences, etc.). The display device 118 displays decoded pictures of the decoded video data to a user. The display device 118 may represent any of a variety of display devices, such as a cathode ray tube (CRT), a liquid crystal display (LCD), a plasma display, an organic light emitting diode (OLED) display, or another type of display device.

[0041] Although not in Figure 1, but in some examples, the video encoder 200 and the video decoder 300 may each be integrated with an audio encoder and / or an audio decoder and may include appropriate MUX-DEMUX units or other hardware and / or software to process multiplexed streams including audio and video in a common data stream. If applicable, the MUX-DEMUX unit may conform to the ITU H.223 multiplexer protocol or other protocols such as the User Datagram Protocol (UDP).

[0042] The video encoder 200 and the video decoder 300 can each be implemented as any of a variety of suitable encoder and / or decoder circuits, such as one or more microprocessors, digital signal processors (DSPs), application specific integrated circuits (ASICs), field programmable gate arrays (FPGAs), discrete logic, software, hardware, firmware, or any combination thereof. When the technology is partially implemented in software, the device can store instructions for the software in a suitable non-temporary computer-readable medium and use one or more processors to execute the instructions in hardware to perform the technology of the present disclosure. Each of the video encoder 200 and the video decoder 300 can be included in one or more encoders or decoders, either of which can be integrated as part of a combined encoder / decoder (CODEC) in each device. The device including the video encoder 200 and / or the video decoder 300 may include an integrated circuit, a microprocessor, and / or a wireless communication device such as a cellular phone.

[0043] The video encoder 200 and the video decoder 300 may operate according to a video codec standard such as ITU-T H.265, also known as High Efficiency Video Codec (HEVC) or an extension thereof such as a multi-view and / or scalable video codec extension. Alternatively, the video encoder 200 and the video decoder 300 may operate according to other proprietary or industry standards such as the Joint Exploration Test Model (JEM) or ITU-T H.266 (also known as Versatile Video Codec (VVC)).

[0044] Generally, the video encoder 200 and the video decoder 300 can perform block-based encoding and decoding of pictures. The term "block" generally refers to a structure that includes data to be processed (e.g., to be encoded, to be decoded, or otherwise used in the encoding and / or decoding process). For example, a block may include a two-dimensional sample matrix of luminance and / or chrominance data. Generally, the video encoder 200 and the video decoder 300 can encode and decode video data represented in YUV (e.g., Y, Cb, Cr) format. That is, the video encoder 200 and the video decoder 300 can encode and decode luminance and chrominance components, where the chrominance components may include both red and blue hue components, instead of encoding and decoding red, green and blue (RGB) data of the samples of the picture. In some examples, the video encoder 200 converts the received RGB format data into a YUV representation before encoding, and the video decoder 300 converts the YUV representation into an RGB format. Alternatively, a pre-processing and post-processing unit (not shown) can perform these conversions.

[0045] The present disclosure generally relates to the encoding and decoding of pictures (e.g., encoding and decoding) to include the process of encoding or decoding picture data. Similarly, the present disclosure may relate to the encoding and decoding of blocks of pictures to include the process of encoding or decoding the data of the blocks, such as prediction and / or residual encoding and decoding. The encoded video bitstream generally includes a series of values ​​of syntax elements used to represent codec decisions (e.g., codec mode) and the partitioning of pictures into blocks. Thus, references to encoding and decoding pictures or blocks should generally be understood as encoding and decoding the values ​​of syntax elements that form pictures or blocks.

[0046] HEVC defines various blocks, including codec units (CUs), prediction units (PUs), and transform units (TUs). According to HEVC, a video codec (such as video encoder 200) partitions a codec tree unit (CTU) into CUs according to a quadtree structure. That is, the video codec partitions the CTU and CU into four equal non-overlapping squares, and each node of the quadtree has zero or four child nodes. A node without a child node may be referred to as a "leaf node", and the CU of such a leaf node may include one or more PUs and / or one or more TUs. The video codec may further partition the PU and TU. For example, in HEVC, a residual quadtree (RQT) represents the partitioning of a TU. In HEVC, a PU represents inter-frame prediction data, and a TU represents residual data. An intra-predicted CU includes intra-frame prediction information, such as an intra-frame mode indication.

[0047] As another example, the video encoder 200 and the video decoder 300 can be configured to operate according to JEM or VVC. According to JEM or VVC, a video codec (such as the video encoder 200) partitions a picture into multiple codec tree units (CTUs). The video encoder 200 can partition the CTU according to a tree structure such as a quadtree-binary tree (QTBT) structure or a multi-type tree (MTT) structure. The QTBT structure eliminates the concept of multiple partition types, such as the separation between CU, PU, ​​and TU of HEVC. The QTBT structure includes two levels: a first level partitioned according to quadtree partitioning, and a second level partitioned according to binary tree partitioning. The root node of the QTBT structure corresponds to the CTU. The leaf nodes of the binary tree correspond to codec units (CUs).

[0048] In the MTT segmentation structure, blocks can be segmented using quadtree (QT) segmentation, binary tree (BT) segmentation, and one or more types of ternary tree (TT) segmentation. Ternary tree segmentation is a segmentation method that divides a block into three sub-blocks. In some examples, ternary tree segmentation divides a block into three sub-blocks without dividing the original block by the center. The segmentation types in MTT (e.g., QT, BT, and TT) can be symmetric or asymmetric.

[0049] 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 corresponding chroma components).

[0050] The video encoder 200 and the video decoder 300 may be configured to use quadtree segmentation, QTBT segmentation, MTT segmentation, or other segmentation structures in accordance with HEVC. For illustrative purposes, a description of the technology of the present disclosure is presented with respect to QTBT segmentation. However, it should be understood that the technology of the present disclosure may also be applied to video codecs configured to use quadtree segmentation or other types of segmentation.

[0051] Blocks (e.g., CTUs or CUs) may be grouped in a picture in various ways. As an example, a brick may refer to a rectangular area of ​​a CTU row in a particular slice in a picture. A slice may be a rectangular area of ​​a CTU in a particular slice column and a particular slice row in a picture. A slice column refers to a rectangular area of ​​a CTU having a height equal to the picture height and a width specified by a syntax element (e.g., such as in a picture parameter set). A slice row refers to a rectangular area of ​​a CTU having a height specified by a syntax element (e.g., such as in a picture parameter set) and a width equal to the picture width.

[0052] In some examples, a slice may be partitioned into multiple bricks, each of which may include one or more CTU rows in the slice. A slice that is not partitioned into multiple bricks may also be referred to as a brick. However, a brick that is a proper subset of a slice cannot be referred to as a slice.

[0053] Bricks in a picture can also be arranged in slices. A slice can be an integer number of bricks of a picture that can be contained exclusively in a single Network Abstraction Layer (NAL) unit. In some examples, a slice includes multiple complete slices or only a contiguous sequence of complete bricks of a slice.

[0054] This disclosure may use "N×N" and "N by N" interchangeably to refer to the sample dimensions of a block (such as a CU or other video block) in the vertical and horizontal dimensions, for example, 16×16 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 generally has N samples in the vertical direction and N samples in the horizontal direction, where N represents a non-negative integer value. The samples in a CU may be arranged in rows and columns. In addition, a CU does not necessarily have the same number of samples in the horizontal direction as in the vertical direction. For example, a CU may contain N×M samples, where M is not necessarily equal to N.

[0055] The video encoder 200 encodes the video data of the CU representing prediction and / or residual information and other information. The prediction information indicates how the CU will be predicted in order to form a prediction block for the CU. The residual information generally represents the sample-by-sample difference between the samples of the CU before encoding and the prediction block.

[0056] In order to predict a CU, the video encoder 200 can generally form a prediction block of the CU by inter-frame prediction or intra-frame prediction. Inter-frame prediction generally refers to predicting a CU from data of a previously coded picture, while intra-frame prediction generally refers to predicting a CU from previously coded data of the same picture. In order to perform inter-frame prediction, the video encoder 200 can use one or more motion vectors to generate a prediction block. The video encoder 200 can generally perform a motion search to identify a reference block that closely matches the CU, for example, in terms of the difference between the CU and the reference block. The video encoder 200 can use the sum of absolute differences (SAD), the sum of squared differences (SSD), the mean absolute difference (MAD), the mean square difference (MSD), or other such difference calculations to calculate a difference metric to determine whether the reference block closely matches the current CU. In some examples, the video encoder 200 can use unidirectional prediction or bidirectional prediction to predict the current CU.

[0057] Some examples of JEM and VVC also provide an affine motion compensation mode, which can be considered an inter-prediction mode. In the affine motion compensation mode, the video encoder 200 can determine two or more motion vectors representing non-translational motion, such as enlargement or reduction, rotation, perspective motion, or other irregular motion types.

[0058] In order to perform intra prediction, the video encoder 200 can select an intra prediction mode to generate a prediction block. Some examples of JEM and VVC provide sixty-seven intra prediction modes, including various directional modes as well as planar modes and DC modes. Generally, the video encoder 200 selects an intra prediction mode that describes the neighboring samples of the current block (e.g., a block of a CU), from which the prediction samples of the current block are predicted. The current block can be a two-dimensional array of samples representing a portion of a picture. Assuming that the video encoder 200 encodes and decodes CTUs and CUs in a raster scan order (from left to right, from top to bottom), such samples can typically be above, on the left, or on the left of the current block in the same picture as the current block.

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

[0060] Specifically, when encoding motion information such as a motion vector, the video encoder 200 may predict a motion vector from a motion vector prediction candidate. Such a motion vector prediction candidate may be selected from one or more neighboring blocks of the current block. In general, HEVC and VVC indicate a certain set of neighboring blocks of the current block from which the motion vector prediction candidate is selected. However, according to the technology of the present disclosure, the video encoder 200 and the video decoder 300 may use different numbers of neighboring blocks of the current block to select motion vector prediction candidates from these neighboring blocks based on the size of the current block.

[0061] For example, if the current block has a size greater than a threshold, the video encoder 200 and the video decoder 300 may select motion vector prediction candidates from a first number of neighboring blocks, and if the current block has a size less than the threshold, the video encoder 200 and the video decoder 300 may select motion vector prediction candidates from a second number of neighboring blocks, the second number being less than the first number. For example, when the current block has a size less than 8×8, the video encoder 200 and the video decoder 300 may select motion vector prediction candidates from up to 15 neighboring blocks, and if the current block has a size greater than or equal to 8×8, the video encoder 200 and the video decoder 300 may select motion vector prediction candidates from up to 23 neighboring blocks.

[0062] In some examples, the neighboring blocks of the current block may be spatial neighboring blocks. In order to ensure that the checked neighboring blocks are spaced apart from each other, the video encoder 200 and the video decoder 300 may skip checking different numbers of spatial neighboring blocks based on the size of the current block for use as motion vector prediction candidates. For example, when the current block has a size less than 8×8, the video encoder 200 and the video decoder 300 may use a first skip value number greater than 4, and if the current block has a size greater than or equal to 8×8, the video encoder 200 and the video decoder 300 may use a second skip value number of 4. Therefore, the number of skips for smaller blocks may be greater than the number of skips for larger blocks. Specifically, the video encoder 200 and the video decoder 300 may subsample the historical buffer information according to the skip offset. Similarly, the video encoder 200 and the video decoder 300 may determine a set of motion vector prediction candidates from a motion information buffer generated from a source other than the current picture including the current block. The source may be, for example, a picture other than the current picture, a different resolution level, a different view, a different strip, a different slice, or a different fragment.

[0063] After constructing the set of motion vector predictors, the video encoder 200 may determine one of the motion vector predictors that most accurately represents the motion vector of the current block. The video encoder 200 may encode an index identifying a motion vector prediction candidate that includes a motion vector predictor that most accurately represents the motion vector of the current block. If the video encoder 200 encodes motion information in AMVP mode, the video encoder 200 may further encode motion vector difference information and other motion information such as a reference picture list indicator and a reference picture index. The video decoder 300 may decode such information to determine the motion vector predictor and reconstruct the motion information of the current block.

[0064] After prediction (such as intra-frame prediction or inter-frame prediction of a block), the video encoder 200 can calculate residual data for the block. The residual data (such as a residual block) represents the sample-by-sample difference between the block and a prediction block for the block, which is formed using a corresponding prediction mode. The video encoder 200 can apply one or more transforms to the residual block to generate transform data in a transform domain rather than a sample domain. For example, the video encoder 200 can apply a discrete cosine transform (DCT), an integer transform, a wavelet transform, or a conceptually similar transform to the residual video data. In addition, the video encoder 200 can apply a secondary transform after a primary transform, such as a mode-dependent non-separable secondary transform (MDNSST), a signal-dependent transform, a Karhunen-Loeve transform (KLT), etc. The video encoder 200 generates transform coefficients after applying one or more transforms.

[0065] As described above, after performing any transforms to produce transform coefficients, the video encoder 200 can perform quantization on the transform coefficients. Quantization generally refers to the process of quantizing the transform coefficients to possibly reduce the amount of data used to represent the coefficients, thereby providing further compression. By performing the quantization process, the video encoder 200 can reduce the bit depth associated with some or all of the coefficients. For example, the video encoder 200 can round down an n-bit value to an m-bit value during quantization, where n is greater than m. In some examples, to perform quantization, the video encoder 200 can perform a bitwise right shift of the value to be quantized.

[0066] After quantization, the video encoder 200 can scan the transform coefficients to generate a one-dimensional vector from a two-dimensional matrix including the quantized transform coefficients. The scan can be designed to place coefficients with higher energy (and therefore lower frequency) in front of the vector and transform coefficients with lower energy (and therefore higher frequency) in the back of the vector. In some examples, the video encoder 200 can scan the quantized transform coefficients using a predefined scan order to generate a serialized vector, and then entropy encode the quantized transform coefficients of the vector. In other examples, the video encoder 200 can perform adaptive scanning. After scanning the quantized transform coefficients to form a one-dimensional vector, the video encoder 200 can entropy encode the one-dimensional vector, for example, according to context adaptive binary arithmetic coding (CABAC). The video encoder 200 can also entropy encode the values ​​of syntax elements, which describe metadata associated with the encoded video data used by the video decoder 300 in decoding the video data.

[0067] To perform CABAC, the video encoder 200 may assign context within a context model to a symbol to be transmitted. For example, the context may relate to whether the neighboring values ​​of the symbol are zero values. The probability determination may be based on the context assigned to the symbol.

[0068] The video encoder 200 may further generate syntax data, such as block-based syntax data, picture-based syntax data, and sequence-based syntax data, to the video decoder 300, for example, in a picture header, a block header, a slice header, or generate other syntax data, such as a sequence parameter set (SPS), a picture parameter set (PPS), or a video parameter set (VPS). The video decoder 300 may similarly decode such syntax data to determine how to decode the corresponding video data.

[0069] In this way, the video encoder 200 can generate a bitstream including the encoded video data, such as syntax elements describing the partitioning of a picture into blocks (eg, CUs) and prediction and / or residual information of the blocks. Finally, the video decoder 300 can receive the bitstream and decode the encoded video data.

[0070] In general, the video decoder 300 performs the reverse process performed by the video encoder 200 to decode the encoded video data of the bitstream. For example, the video decoder 300 may use CABAC to decode the values ​​of the syntax elements of the bitstream in a manner substantially similar to (although reversed from) the CABAC encoding process of the video encoder 200. The syntax elements may define partitioning information regarding partitioning of a picture into CTUs and partitioning each CTU according to a corresponding partitioning structure such as a QTBT structure to define CUs of the CTU. The syntax elements may further define prediction and residual information for a block (e.g., a CU) of video data.

[0071] For example, the residual information may be represented by quantized transform coefficients. The video decoder 300 may inverse quantize and inverse transform the quantized transform coefficients of the block to reproduce a residual block for the block. The video decoder 300 uses the signaled prediction mode (intra-frame or inter-frame prediction) and related prediction information (e.g., motion information for inter-frame prediction) to form a prediction block for the block. The video decoder 300 may then combine the prediction block and the residual block (on a sample-by-sample basis) to reproduce the original block. The video decoder 300 may perform additional processing (such as performing a deblocking process) to reduce visual artifacts along block boundaries.

[0072] In general, the present disclosure may involve "signaling" certain information, such as syntax elements. The term "signaling" may generally refer to the communication of values ​​for syntax elements and / or other data used to decode encoded video data. That is, the video encoder 200 may signal the values ​​of syntax elements in a bitstream. In general, signaling refers to generating values ​​in a bitstream. As described above, the source device 102 may transmit the bitstream to the target device 116 in substantially real time (or non-real time, such as may occur when storing syntax elements to the storage device 112 for later retrieval by the target device 116).

[0073] Figure 2A and 2B is a conceptual diagram showing an example of spatial neighboring motion vector (MV) candidates for merge mode and advanced motion vector prediction (AMVP) mode. Figure 2A In the example of FIG. 1 , the spatial domain MV candidates of PU0 130 are shown, and Figure 2B In the example of FIG. 1 , the spatial domain MV candidates of PU0 132 are shown. Specifically, Figure 2A 130 for merge mode, and Figure 2B 132 for AMVP mode. In HEVC, for a particular PU (PU0), the spatial MV candidates are Figure 2A and Figure 2B The candidates are derived from the neighboring blocks shown, although the technique used to generate candidates from blocks is different for merge mode and AMVP mode.

[0074] In merge mode, up to four spatial MV candidates may be derived for PU0 130 in the following order: Figure 2A Indicated by serial numbers, and in accordance with HEVC order as follows: left (0, A1), top (1, B1), right (2, B0), bottom left (3, A0) and top left (4, B2), as shown in FIG. Figure 2A shown.

[0075] In AVMP mode, according to HEVC, such as Figure 2B As shown, the neighboring blocks of PU0 132 are divided into two groups: the left group includes blocks 0 and 1, and the upper group includes blocks 2, 3, and 4. For each group, a potential candidate among the neighboring blocks of PU0 132 has the highest priority to be selected to form the final candidate of the group, which potential candidate refers to the same reference picture as indicated by the signaled reference index. It is possible that all neighboring blocks do not contain motion vectors pointing to the same reference picture. Therefore, if such a candidate cannot be found, the first available candidate will be scaled to form the final candidate, so that the temporal distance difference can be compensated.

[0076] Figure 3A and 3B is a conceptual diagram example of a temporal motion vector prediction (TMVP) candidate and scaling the MV of the TMVP candidate. Specifically, Figure 3A shows example locations of TMVP candidates for PU0 134, and Figure 3B Techniques related to scaling motion vectors of TMVP candidates are shown.

[0077] In HEVC, if enabled and available, TMVP candidates are added to the MV candidate list after the spatial motion vector candidates. The motion vector derivation process for TMVP candidates is the same for both merge mode and AMVP mode. However, in merge mode, the target reference index of the TMVP candidate is always set to 0 (as per HEVC).

[0078] The main block position for TMVP candidate derivation is the lower right block outside the collocated PU, such as Figure 3A 136 to compensate for the bias of the upper and left blocks used to generate spatial neighboring candidates. However, if the block is outside the current CTB row or the motion information of the block is not available (e.g., as shown by block T 138), the block is replaced by the center block of the PU (i.e., block T 140).

[0079] The video codec can derive the motion vector of the TMVP candidate of the current PU 142 from the co-located PU 144 of the co-located picture indicated in the slice level. The motion vector of the co-located PU 144 is called the co-located MV. Similar to the temporal direct mode in AVC, in order to derive the TMVP candidate motion vector, the co-located MV needs to be scaled to compensate for the temporal distance difference, such as Figure 3B shown.

[0080] It is assumed that the value of the motion vector is proportional to the distance of the picture in the presentation time domain. The motion vector associates two pictures: the reference picture and the picture containing the motion vector (i.e., the containing picture). When a motion vector is used to predict another motion vector, the distance between the containing picture and the reference picture is calculated based on the picture order count (POC) value. For the motion vector to be predicted, its associated containing picture and reference picture can be different. Therefore, a new distance (based on POC) is calculated. And the motion vector is scaled based on these two POC distances. For a spatial neighboring candidate, the containing pictures of the two motion vectors are the same, but the reference pictures are different. In HEVC, motion vector scaling applies to both TMVP and AMVP for spatial and temporal neighboring candidates.

[0081] If the motion vector candidate list is incomplete, artificial motion vector candidates can be generated and inserted at the end of the list until the list has all the required candidates. In HEVC's merge mode, there are two types of artificial MV candidates: combined candidates derived only for B slices; and zero candidates used only for AMVP if the first type does not provide enough artificial candidates.

[0082] For each candidate pair that is already in the candidate list and has the necessary motion information, a bidirectional combined motion vector candidate is derived by combining the motion vector of the first candidate referring to the picture in reference list 0 and the motion vector of the second candidate referring to the picture in reference list 1.

[0083] Candidates from different blocks may happen to be the same, which reduces the efficiency of merge / AMVP candidate lists. According to HEVC, a pruning process is applied to solve this problem. According to the pruning process, the video codec compares one candidate in the current candidate list with other candidates to avoid inserting the same candidate to a certain extent. To reduce complexity, only a limited number of pruning processes are applied instead of comparing each potential candidate with all other existing candidates.

[0084] Figure 4 1 shows a conceptual diagram of an example process by which non-adjacent spatial merge candidates can be obtained. Specifically, the video encoder 200 or the video decoder 300 can obtain non-adjacent blocks of the current block 150, wherein the non-current block 150 includes, for example, a block V N and H N and block A J To H N and block B K To V N The other blocks between Figure 4In VVC, there are several inter-frame coding tools to derive or refine the candidate list of motion vector prediction or merge prediction for the current block.

[0085] History-based motion vector prediction (HMVP) (described in "CE4-realted: History-based motion vector prediction" by Zhang et al., Joint Video Exploration Group of ITU-T SG 16WP 3 and ISO / IEC JTC 1 / SC 29 / WG 11, July 2018, document JVET-K0104) is a history-based method that allows the video codec to find an MV predictor for each block from a list of MVs decoded in the past, except for those MVs in the immediate causal neighboring motion fields. A table with multiple HMVP candidates is maintained during the encoding / decoding process. The table is cleared when a new slice is encountered. Whenever there is an inter-coded block, the associated motion information is inserted into the table as a new HMVP candidate in a first-in-first-out (FIFO) manner. Then, the FIFO constraint rule can be applied. When an HMVP is inserted into the table, a redundancy check is first applied to find if the same HMVP exists in the table. If found, that particular HMVP is deleted from the table and then all HMVP candidates are moved.

[0086] HMVP candidates can be used in the merge candidate list construction process. According to VVC, all HMVP candidates from the last entry to the first entry in the table are inserted after the TMVP candidate. Pruning is applied to the HMVP candidates. Once the total number of available merge candidates reaches the maximum allowed merge candidates notified by signaling, the merge candidate list construction process can be terminated.

[0087] Similarly, HMVP candidates can also be used in the construction process of the AMVP candidate list. The motion vectors of the last K HMVP candidates in the table can be inserted after the TMVP candidate. HMVP candidates with the same reference picture as the AMVP target reference picture can be used to construct the AMVP candidate list. Pruning can be applied to HMVP candidates.

[0088] The construction of non-adjacent spatial merge candidates (described in Joint Video Exploration Group of ITU-T SG 16WP 3 and ISO / IEC JTC 1 / SC 29 / WG11, July 2, 2018, document JVET-K0228, Yu et al., "CE 4-2.1: Adding non-adjacent spatial merge candidates") involves selecting non-adjacent spatial merge candidates from two non-adjacent neighboring positions (i.e., from the non-adjacent block closest to the left / above, such as Figure 4 New spatial candidates are derived from the decoded blocks 150 as shown in the figure. These blocks are constrained to be within a maximum distance of 1 CTU from the current block 150. Distance 152 represents an example vertical backtracking distance, while distance 154 represents an example horizontal backtracking distance. The extraction process of non-neighboring candidates starts by tracing the previously decoded blocks in the vertical direction. The vertical backtracking stops when an inter-frame block is encountered or the backtracking distance reaches 1 CTU size.

[0089] The extraction process then tracks the previously decoded blocks in the horizontal direction. The criterion for stopping the horizontal extraction process depends on whether a vertical non-adjacent candidate is successfully extracted. If no vertical non-adjacent candidate is extracted, the horizontal extraction process stops when an inter-frame predicted block is encountered or the traceback distance exceeds a CTU size threshold. If a vertical non-adjacent candidate is extracted, the horizontal extraction process stops when an inter-frame predicted block containing a different MV from the vertical non-adjacent candidate is encountered or the traceback distance exceeds a CTU size threshold. The extracted non-adjacent neighboring candidate is added before the TMVP candidate in the merge candidate.

[0090] Figure 5A-Figure 5C is a conceptual diagram showing an example of an alternative motion vector prediction design. For example, this alternative design for spatial and temporal S / T-MVP prediction can be used according to VVC.

[0091] For example, in some implementations of merge mode (which may be referred to as skip mode or direct mode in some terminology), the following spatial and temporal MVP candidates may be visited in a given order to populate the MVP list. Figure 5A An example of the MVP candidate positions of the current blocks 160, 162 is shown. That is, Figure 5A The positions of spatial neighboring blocks of the current block 160 and the positions of temporal neighboring blocks of the current block 162 are shown, wherein the neighboring blocks can be used for MV prediction. Figure 5B An example access order for the S-MVP of the current block 164 is shown. Figure 5C An example spatial inversion pattern is shown that replaces the current block 166 .

[0092] Spatial neighbors used as MVP candidates may include blocks A, B, (C, A1|B1), A0, B2. The selection of neighboring blocks can be performed using a two-stage process, with the order of visit being Figure 5B In this example:

[0093] Group 1 (in Figure 5B shown in dark grey shading):

[0094] o A, B, and C (co-located with B0 in HEVC representation)

[0095] o A1 or B1, depending on the availability of MVP in the C position and the type of block split

[0096] Group 2 (in Figure 5B shown without shading):

[0097] A0 and B2

[0098] The temporally co-located neighbors used as MVP candidates include blocks co-located at the center of the current block 162 (in Figure 5A The unshaded C in the figure) and the block at the bottom right position outside the current block (in Figure 5A Marked as H).

[0099] FIG5 also shows an example group 3, which includes:

[0100] C and H

[0101] If H is found outside the same image, then Figure 5A The other H' positions in can be used as alternate positions.

[0102] In some implementations, depending on the block segmentation and encoding order used, such as Figure 5C The reverse S-MVP candidate order shown in Figure 5B The S-MVC candidate order.

[0103] The history-based MVP technology of VVC adopts the following process, in which a redundancy check is performed on each motion vector candidate stored in a history buffer of size MAX_HISTORY_BUFFER_SIZE against any motion vector candidate that already exists in the merge list (MERGE_LIST_SIZE). This redundancy check introduces a certain degree of complexity, which increases with the increase in size. The worst-case complexity problem (e.g., the check of MAX_HISTORY_BUFFER_SIZE x MERGE_LIST_SIZE) increases with the increase in the history buffer size and the merge list size. This complexity can be multiplied by the worst-case complexity of the block size, such as 4×4 or 4×8, or num_samples_in_block < N, where N can take any integer value of a certain size, such as 32.

[0104] The following shows an example specification defining the HMVP MV check in italics.

[0105] For the derivation process based on historical merge candidates

[0106] The inputs to this process are:

[0107] - The merge candidate list mergeCandList,

[0108] - The number of available merge candidates in the list numCurrMergeCand,

[0109] - The history-based motion information table HmvpCandList,

[0110] - The maximum number of elements in MergeCandList mLSize.

[0111] The outputs of this process are:

[0112] - The modified merge candidate list mergeCandList,

[0113] - The number of modified merge candidates in the list numCurrMergeCand,

[0114] The variable numOrigMergeCand is set to be equal to numCurrMergeCand. The variable hmvpStop is set to FALSE. The variable NumHmvpCand is set to the number of motion entries in HmvpCandList.

[0115] The variable maxNumCheckedHistory is set equal to (((NumHmvpCand+1)>>2)<<2)–1.

[0116] For each candidate in HmvpCandList with hMvpIdx=0..min(maxNumCheckedHistory, MAX_HISTORY_BUFFER_SIZE), repeat the following ordered steps until hmvpStop equals TRUE

[0117] 1. The variable sameMotion is exported as follows:

[0118] -sameMotion is set to FALSE

[0119] -sameMotion is set to TRUE if HMVPCandList[NumHmvpCand-hMvpIdx] has the same motion vector and the same reference index as any mergeCandList[i] where i is 0…numOrigMergeCand-1

[0120] 2. When sameMotion is equal to false, the candidate HmvpCandList[NumHmvpCand-

[0121] hMvpIdx] is added to the merge candidate list:

[0122] mergeCandList[numCurrMergeCand++]=HmvpCandList[NumHmvpCand-hMvpIdx](8-303)

[0123] 3. If numCurrMergeCand is equal to mLSize, hmvpStop is set to TRUE.

[0124] According to the technology of the present disclosure, for small block sizes, the video encoder 200 and the video decoder 300 can be configured to limit the maximum number of check entries in the history buffer. An example of such a limit is marked in italics in the following specification code:

[0125] 1. The number of check entries in the history buffer is affected by the size of the block currently being processed

[0126] a. For smaller block sizes (e.g., 4×4 size or other), the video encoder 200 and the video decoder 300 may check a smaller number (SIZE_SMALL) of entries from the history buffer compared to larger block sizes (SIZE_NORMAL). With this restriction, the video encoder 200 and the video decoder 300 may only check MVPs from close-area neighborhoods.

[0127] b. In another example, the video encoder 200 and the video decoder 300 may modify the skipping step (subsampling of the history buffer information) for each block size, and the video encoder 200 and the video decoder 300 may use a larger skipping offset for the smaller block size SKIP_NUMBER_SMALL than the skipping offset used for the larger block size (SKIP_NUMBER_NORMAL). In this way, the video encoder 200 and the video decoder 300 may check the full length of the buffer for the smaller block size, but access the data at a specific subsampling rate, thereby accessing the data at a coarser granularity of the information stored in the history buffer.

[0128] 2. In some examples, the video encoder 200 and the video decoder 300 may determine the motion vector prediction candidates from a history buffer, however in other examples this may be a motion information buffer that is not in the current picture but is generated by another source (e.g., MV information collected in another frame, or another resolution level (e.g., in the case of multi-resolution scalable coding), view, slice, slice, or fragment of the coded picture).

[0129] 3. In some examples, video encoder 200 and video decoder 300 may process a motion vector candidate before including it in a merge list, for example, by:

[0130] a. For example, in case of another POC distance due to different POC values ​​of the same block or difference in reference picture index, MV is rescaled

[0131] b. In case the MVC is extracted from a buffer collected from another (not matching the current picture) resolution level or picture, MV rescaling is performed.

[0132] c. For example, in case of multi-view video data representation, since the source of MV information is extracted from another view, MV disparity shift / compensation or MV rescaling is performed.

[0133] Example implementations of these techniques are described below, with certain changes relative to Enhanced Video Coding (EVC) indicated in italics.

[0134] Used for the derivation process based on historical merge candidates:

[0135] The inputs to this process are:

[0136] -merge candidate list mergeCandList,

[0137] - the number of available merge candidates in the list numCurrMergeCand,

[0138] -HmvpCandList, a table of historical sports information,

[0139] - The maximum number of elements in the MergeCandList is mLSize.

[0140] The output of this process is:

[0141] -The modified merge candidate list mergeCandList,

[0142] - the number of modified merge candidates in the list numCurrMergeCand,

[0143] The variable numOrigMergeCand is set equal to numCurrMergeCand. The variable hmvpStop is set to FALSE. The variable NumHmvpCand is set to the number of motion entries in HmvpCandList.

[0144] The variable maxNumCheckedHistory is set equal to (((NumHmvpCand+1)>>2)<<2)–1.

[0145] The variable SKIP_NUMBER is set equal to (mLSize=4)?SKIP_NUMBER_SMALL:SKIP_NUMBER_NORMAL.

[0146] For each candidate in HmvpCandList with hMvpIdx=START, START+SKIP_NUMBER, min(maxNumCheckedHistory, (mLSize=4)?SIZE_SMALL:SIZE_NORMAL), repeat the following ordered steps until hmvpStop equals TRUE

[0147] 1. The variable sameMotion is exported as follows:

[0148] -sameMotion is set to FALSE

[0149] -sameMotion is set to TRUE if HMVPCandList[NumHmvpCand-hMvpIdx] has the same motion vector and the same reference index as any mergeCandList[i] where i is 0…numOrigMergeCand-1

[0150] 2. When sameMotion is equal to false, add the candidate HmvpCandList[NumHmvpCand-hMvpIdx] to the merge candidate list as follows:

[0151] mergeCandList[numCurrMergeCand++]=HmvpCandList[NumHmvpCand-hMvpIdx](8-303)

[0152] If numCurrMergeCand is equal to mLSize, hmvpStop is set to TRUE.

[0153] Figure 6 is a block diagram illustrating an example video encoder 200 that may perform the techniques of this disclosure. Figure 6 For purposes of explanation and should not be considered limiting of the techniques broadly exemplified and described in this disclosure. For purposes of illustration, this disclosure describes the video encoder 200 in the context of video codec standards such as the H.265 / HEVC video codec standard and the developing H.266 / VVC video codec standard. However, the techniques of this disclosure are not limited to these video codec standards and are generally applicable to video encoding and decoding.

[0154] exist Figure 6 In the example of , the video encoder 200 includes a video data memory 230, a mode selection unit 202, a residual generation unit 204, a transform processing unit 206, a quantization unit 208, an inverse quantization unit 210, an inverse transform processing unit 212, a reconstruction unit 214, a filter unit 216, a decoded picture buffer (DPB) 218, and an entropy coding unit 220. Any or all of the video data memory 230, the mode selection unit 202, the residual generation unit 204, the transform processing unit 206, the quantization unit 208, the inverse quantization unit 210, the inverse transform processing unit 212, the reconstruction unit 214, the filter unit 216, the DPB 218, and the entropy coding unit 220 may be implemented in one or more processors or in processing circuits. In addition, the video encoder 200 may include additional or alternative processors or processing circuits to perform these and other functions.

[0155] The video data memory 230 may store video data to be encoded by the components of the video encoder 200. The video encoder 200 may receive video data from, for example, the video source 104 ( Figure 1 ) receives video data stored in video data memory 230. DPB 218 can be used as a reference picture memory, and its memory stores reference video data for use by video encoder 200 when predicting subsequent video data. Video data memory 230 and DPB 218 can be formed by any of a variety of storage devices, such as dynamic random access memory (DRAM), including synchronous DRAM (SDRAM), magnetoresistive RAM (MRAM), resistive RAM (RRAM) or other types of storage devices. Video data memory 230 and DPB218 can be provided by the same storage device or a separate storage device. In various examples, video data memory 230 can be placed on-chip with other components of video encoder 200, as shown, or placed off-chip relative to those components.

[0156] In the present disclosure, references to the video data memory 230 should not be interpreted as limited to a memory inside the video encoder 200 (unless specifically stated otherwise) or a memory outside the video encoder 200 (unless specifically stated otherwise). Of course, references to the video data memory 230 should be understood as a reference memory that stores video data received by the video encoder 200 for encoding (e.g., video data of a current block to be encoded). Figure 1 The memory 106 may also provide temporary storage for outputs from the various units of the video encoder 200 .

[0157] Shown Figure 6 The various units are used to help understand the operations performed by the video encoder 200. These units can be implemented as fixed-function circuits, programmable circuits, or a combination thereof. Fixed-function circuits refer to circuits that provide specific functions and are preset on the operations that can be performed. Programmable circuits refer to circuits that can be programmed to perform various tasks and provide flexible functions in the operations that can be performed. For example, a programmable circuit can execute software or firmware that causes the programmable circuit to operate in a manner defined by the instructions of the software or firmware. Fixed-function circuits can execute software instructions (for example, to receive parameters or output parameters), but the type of operation performed by the fixed-function circuit is generally immutable. In some examples, one or more units may be different circuit blocks (fixed function or programmable), and in some examples, one or more units may be integrated circuits.

[0158] The video encoder 200 may include an arithmetic logic unit (ALU), an elementary function unit (EFU), a digital circuit, an analog circuit, and / or a programmable core formed by a programmable circuit. In an example where the operation of the video encoder 200 is performed using software executed by a programmable circuit, the memory 106 ( Figure 1 ) may store object code for software received and executed by the video encoder 200, or another memory (not shown) within the video encoder 200 may store such instructions.

[0159] The video data memory 230 is configured to store received video data. The video encoder 200 may retrieve a picture of video data from the video data memory 230 and provide the video data to the residual generation unit 204 and the mode selection unit 202. The video data in the video data memory 230 may be original video data to be encoded.

[0160] The mode selection unit 202 includes a motion estimation unit 222, a motion compensation unit 224, and an intra prediction unit 226. The mode selection unit 202 may include additional functional units for performing video prediction according to other prediction modes. As an example, the mode selection unit 202 may include a palette unit, an intra block copy unit (which may be part of the motion estimation unit 222 and / or the motion compensation unit 224), an affine unit, a linear model (LM) unit, etc.

[0161] Generally, the mode selection unit 202 coordinates multiple encoding passes to test combinations of encoding parameters and derive rate-distortion values ​​of such combinations. The encoding parameters may include the partitioning of CTUs into CUs, the prediction mode of the CUs, the transform type of the residual data of the CUs, the quantization parameter of the residual data of the CUs, etc. The mode selection unit 202 may ultimately select a combination of encoding parameters that has a better rate-distortion value than other tested combinations.

[0162] The video encoder 200 may partition a picture retrieved from the video data memory 230 into a series of CTUs and encapsulate one or more CTUs in a slice. The mode selection unit 202 may partition the CTUs of the picture according to a tree structure (such as the QTBT structure or quadtree structure of HEVC described above). As described above, the video encoder 200 may form one or more CUs by partitioning the CTUs according to the tree structure. Such CUs may also be generally referred to as "video blocks" or "blocks".

[0163] In general, the mode selection unit 202 also controls its components (e.g., the motion estimation unit 222, the motion compensation unit 224, and the intra prediction unit 226) to generate a prediction block for the current block (e.g., the overlapping portion of the current CU or PU and TU in HEVC). In order to inter-predict the current block, the motion estimation unit 222 can perform a motion search to identify one or more closely matching reference blocks in one or more reference pictures (e.g., one or more previously coded pictures stored in the DPB 218). Specifically, the motion estimation unit 222 can calculate a value indicating how similar the potential reference block is to the current block based on, for example, the sum of absolute differences (SAD), the sum of squared differences (SSD), the mean absolute difference (MAD), the mean squared difference (MSD), etc. The motion estimation unit 222 can typically perform these calculations using the sample-by-sample differences between the current block and the reference block under consideration. The motion estimation unit 222 can identify the reference block with the lowest value generated by these calculations, which indicates the reference block that most closely matches the current block.

[0164] The motion estimation unit 222 may form one or more motion vectors (MVs) that define the position of a reference block in a reference picture relative to a current block in a current picture. The motion estimation unit 222 may then provide the motion vectors to the motion compensation unit 224. For example, for unidirectional inter prediction, the motion estimation unit 222 may provide a single motion vector, while for bidirectional inter prediction, the motion estimation unit 222 may provide two motion vectors. The motion compensation unit 224 may then use the motion vectors to generate a prediction block. For example, the motion compensation unit 224 may use the motion vectors to retrieve data for the reference block. As another example, if the motion vectors have fractional sample precision, the motion compensation unit 224 may interpolate the prediction block according to one or more interpolation filters. In addition, for bidirectional inter prediction, the motion compensation unit 224 may retrieve data for two reference blocks identified by respective motion vectors and combine the retrieved data (e.g., by sample-by-sample averaging or weighted averaging).

[0165] In the case where the mode selection unit 202 selects the inter-frame prediction mode for the current block, the video encoder 200 may further encode the motion information including the motion vector for the current block. For example, the entropy coding unit 220 may entropy encode the motion information in the merge mode or the AMVP mode. In the merge mode or the AMVP mode, the entropy coding unit 220 may determine the motion vector prediction candidate from the set of motion vector prediction candidates. According to the technology of the present disclosure, the entropy coding unit 220 may construct the set of motion vector prediction candidates to have a number of candidates corresponding to the size of the current block.

[0166] Specifically, in some examples, the entropy coding unit 220 may construct a set of motion vector prediction candidates to have a first number of candidates when the size of the current block is less than a threshold, and a second number of candidates when the size of the current block is greater than the threshold, wherein the second number is greater than the first number. In some examples, the entropy coding unit 220 may use a skip offset determined according to the size of the current block to sequentially skip several motion vector prediction candidates when constructing the set of motion vector prediction candidates. The skip offset for a block less than the threshold may be greater than the skip offset for a block greater than the threshold.

[0167] The entropy coding unit 220 may also select one of the motion vector prediction candidates from the set of motion vector prediction candidates to be used as a motion vector predictor, and then encode the motion information of the current block using the selected motion vector predictor. In the AMVP mode, the entropy coding unit 220 may also entropy encode the motion vector difference information, the reference picture list indicator, and the reference picture index identifying the reference picture in the reference picture list.

[0168] As another example, for intra prediction or intra prediction codec, the intra prediction unit 226 can generate a prediction block based on samples adjacent to the current block. For example, for directional mode, the intra prediction unit 226 can generally mathematically combine the values ​​of adjacent samples and fill these calculated values ​​along a defined direction on the current block to generate a prediction block. As another example, for DC mode, the intra prediction unit 226 can calculate the average value of adjacent samples of the current block and generate a prediction block to include the obtained average value for each sample of the prediction block.

[0169] The mode selection unit 202 provides the prediction block to the residual generation unit 204. The residual generation unit 204 receives the original uncoded version of the current block from the video data memory 230 and receives the prediction block from the mode selection unit 202. The residual generation unit 204 calculates the sample-by-sample difference between the current block and the prediction block. The resulting sample-by-sample difference defines a residual block for the current block. In some examples, the residual generation unit 204 may also use residual differential pulse code modulation (RDPCM) to determine the difference between the sample values ​​in the residual block to generate the residual block. In some examples, the residual generation unit 204 may be formed using one or more subtractor circuits that perform binary subtraction.

[0170] In the example where the mode selection unit 202 partitions the CU into PUs, each PU may be associated with a luma prediction unit and a corresponding chroma prediction unit. The video encoder 200 and the video decoder 300 may support PUs of various sizes. As described above, the size of the CU may refer to the size of the luma codec block of the CU, and the size of the PU may refer to the size of the luma prediction unit of the PU. Assuming that the size of a particular CU is 2N×2N, the video encoder 200 may support PU sizes of 2N×2N or N×N for intra-frame prediction, and symmetric PU sizes of 2N×2N, 2N×N, N×2N, N×N or similar for inter-frame prediction. The video encoder 200 and the video decoder 300 may also support asymmetric partitioning of PU sizes of 2N×nU, 2N×nD, nL×2N, and nR×2N for inter-frame prediction.

[0171] In an example where the mode selection unit does not further split the CU into PUs, each CU may be associated with a luma codec block and a corresponding chroma codec block. As described above, the size of a CU may refer to the size of the luma codec block of the CU. The video encoder 200 and the video decoder 300 may support a CU size of 2N×2N, 2N×N, or N×2N.

[0172] For other video codec techniques, such as intra block copy mode codec, affine mode codec, and linear model (LM) mode codec as some examples, the mode selection unit 202 generates a prediction block for the current block being encoded via a corresponding unit associated with the codec technique. In some examples, such as palette mode codec, the mode selection unit 202 may not generate a prediction block, but instead generate syntax elements indicating how to reconstruct the block based on the selected palette. In such a mode, the mode selection unit 202 may provide these syntax elements to the entropy coding unit 220 for encoding.

[0173] As described above, the residual generation unit 204 receives video data of a current block and a corresponding prediction block. Then, the residual generation unit 204 generates a residual block for the current block. To generate the residual block, the residual generation unit 204 calculates the sample-by-sample difference between the prediction block and the current block.

[0174] The transform processing unit 206 applies one or more transforms to the residual block to generate a block of transform coefficients (referred to herein as a "transform coefficient block"). The transform processing unit 206 may apply various transforms to the residual block to form a transform coefficient block. For example, the transform processing unit 206 may apply a discrete cosine transform (DCT), a directional transform, a Karhunen-Loeve transform (KLT), or a conceptually similar transform to the residual block. In some examples, the transform processing unit 206 may perform multiple transforms on the residual block, for example, a primary transform and a secondary transform such as a rotation transform. In some examples, the transform processing unit 206 does not apply a transform to the residual block.

[0175] The quantization unit 208 may quantize the transform coefficients in the transform coefficient block to produce a quantized transform coefficient block. The quantization unit 208 may quantize the transform coefficients of the transform coefficient block according to a quantization parameter (QP) value associated with the current block. The video encoder 200 (e.g., via the mode selection unit 202) may adjust the degree of quantization applied to the transform coefficient block associated with the current block by adjusting the QP value associated with the CU. Quantization may introduce information loss, and thus, the quantized transform coefficients may have lower precision than the original transform coefficients produced by the transform processing unit 206.

[0176] The inverse quantization unit 210 and the inverse transform processing unit 212 may apply inverse quantization and inverse transform, respectively, to the quantized transform coefficient block to reconstruct a residual block from the transform coefficient block. The reconstruction unit 214 may generate a reconstructed block corresponding to the current block (although 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 may add samples of the reconstructed residual block to corresponding samples from the prediction block generated by the mode selection unit 202 to generate a reconstructed block.

[0177] Filter unit 216 may perform one or more filter operations on the reconstructed block. For example, filter unit 216 may perform a deblocking operation to reduce blocking artifacts along the edges of the CU. In some examples, the operations of filter unit 216 may be skipped.

[0178] The video encoder 200 stores the reconstructed blocks in the DPB 218. For example, in examples where the operation of the filter unit 216 is not required, the reconstruction unit 214 can store the reconstructed blocks to the DPB 218. In examples where the operation of the filter unit 216 is required, the filter unit 216 can store the filtered reconstructed blocks to the DPB 218. The motion estimation unit 222 and the motion compensation unit 224 can retrieve a reference picture from the DPB 218, which is formed by the reconstructed (and potentially filtered) blocks, to perform inter-frame prediction on blocks of subsequently encoded pictures. In addition, the intra-frame prediction unit 226 can use the reconstructed blocks in the DPB 218 of the current picture to perform intra-frame prediction on other blocks in the current picture.

[0179] According to the technology of the present disclosure, DPB 218 may include one or more history buffers for storing motion information of previously coded blocks. Therefore, mode selection unit 202 may cause entropy coding unit 220 to select a motion vector predictor from the motion information of previously coded blocks in the history buffer. According to the technology of the present disclosure, when the current block is smaller than a threshold size, mode selection unit 202 may reduce the number of motion vector prediction candidates from which the motion vector predictor is selected from a first number to a second number smaller than the first number.

[0180] In general, the entropy coding unit 220 may entropy encode syntax elements received from other functional components of the video encoder 200. For example, the entropy coding unit 220 may entropy encode a block of quantized transform coefficients from the quantization unit 208. As another example, the entropy coding unit 220 may entropy encode a prediction syntax element (e.g., motion information for inter-frame prediction or intra-frame mode information for intra-frame prediction) from the mode selection unit 202. The entropy coding unit 220 may perform one or more entropy coding operations on syntax elements of another example of video data to generate entropy-encoded data. For example, the entropy coding unit 220 may perform a context-adaptive variable length coding (CAVLC) operation, a CABAC operation, a variable to variable (V2V) length coding operation, a syntax-based context-adaptive binary arithmetic coding (SBAC) operation, a probability interval partitioning entropy (PIPE) coding operation, an exponential-Golomb coding operation, or another type of entropy coding operation on the data. In some examples, the entropy coding unit 220 may operate in a bypass mode in which the syntax elements are not entropy encoded.

[0181] The video encoder 200 may output a bitstream including syntax elements of entropy coding required to reconstruct a block of a slice or a picture. Specifically, the entropy coding unit 220 may output the bitstream.

[0182] The above operations are described for blocks. Such descriptions should be understood as operations for luma codec blocks and / or chroma codec blocks. As described above, in some examples, the luma codec block and the chroma codec block are the luma and chroma components of the CU. In some examples, the luma codec block and the chroma codec block are the luma and chroma components of the PU.

[0183] In some examples, operations performed with respect to luma codec blocks do not need to be repeated for chroma codec blocks. As an example, operations for identifying motion vectors (MVs) and reference pictures for luma codec blocks do not need to be repeated to identify MVs and reference pictures for chroma blocks. Instead, the MVs of luma codec blocks may be scaled to determine the MVs of chroma blocks, and the reference pictures may be the same. As another example, the intra prediction process may be the same for luma coding blocks and chroma coding blocks.

[0184] The video encoder 200 represents an example of a device configured to encode video data, the device comprising: a memory configured to store the video data; and one or more processing units implemented in a circuit and configured to: determine that a size of a current block of the video data is less than a threshold, the current block being a two-dimensional array of samples representing a portion of a picture; determine a set of motion vector prediction candidates for the current block based on the determination that the size of the current block is less than the threshold; a motion vector predictor that selects the motion vector prediction candidates for the current block; encode motion information of the current block using the motion vector predictor; and encode the current block using the motion information.

[0185] Figure 7 is a block diagram illustrating an example video decoder 300 that may perform the techniques of this disclosure. Figure 7 It is for the purpose of explanation, not limitation, of the techniques widely exemplified and described in this disclosure. For the purpose of illustration, this disclosure describes a video decoder 300 according to the technical descriptions of JEM, VCC, and HEVC. However, the techniques of this disclosure may be performed by video codec devices configured for other video codec standards.

[0186] exist Figure 7In the example of , the video decoder 300 includes a codec picture buffer (CPB) memory 320, an entropy decoding unit 302, a prediction processing unit 304, an inverse quantization unit 306, an inverse transform processing unit 308, a reconstruction unit 310, a filter unit 312, and a decoded picture buffer (DPB) 314. Any or all of the CPB memory 320, the entropy decoding unit 302, the prediction processing unit 304, the inverse quantization unit 306, the inverse transform processing unit 308, the reconstruction unit 310, the filter unit 312, and the DPB 314 may be implemented in one or more processors or processing circuits. In addition, the video decoder 300 may include additional or alternative processors or processing circuits to perform these and other functions.

[0187] The prediction processing unit 304 includes a motion compensation unit 316 and an intra prediction unit 318. The prediction processing unit 304 may include additional units to perform predictions according to other prediction modes. As an example, the prediction processing unit 304 may include a palette unit, an intra block copy unit (which may form part of the motion compensation unit 316), an affine unit, a linear model (LM) unit, etc. In other examples, the video decoder 300 may include more, fewer, or different functional components.

[0188] CPB memory 320 may store video data, such as an encoded video bitstream, to be decoded by components of video decoder 300. For example, the video bitstream may be obtained from computer readable medium 110 ( Figure 1 ) obtains video data stored in CPB memory 320. CPB memory 320 may include a CPB that stores coded video data (e.g., syntax elements) from a coded video bitstream. Moreover, CPB memory 320 may store video data other than syntax elements of coded and decoded pictures, such as temporary data representing outputs from various units of video decoder 300. Generally, DPB 314 stores decoded pictures, which video decoder 300 may output and / or use as reference video data when decoding subsequent data or pictures of the coded video bitstream. CPB memory 320 and DPB 314 may be formed by any of a variety of storage devices, such as dynamic random access memory (DRAM), including synchronous DRAM (SDRAM), magnetoresistive RAM (MRAM), resistive RAM (RRAM), or other types of storage devices. CPB memory 320 and DPB 314 may be provided by the same storage device or a separate storage device. In various examples, CPB memory 320 may be placed on-chip with other components of video decoder 300, or off-chip relative to those components.

[0189] Additionally or alternatively, in some examples, video decoder 300 may retrieve the video from memory 120 ( Figure 1 ) to retrieve the encoded and decoded video data. That is, the memory 120 can store data together with the CPB memory 320 as discussed above. Similarly, when some or all of the functions of the video decoder 300 are implemented in software to be executed by the processing circuitry of the video decoder 300, the memory 120 can store instructions to be executed by the video decoder 300.

[0190] Show Figure 7 Various units are shown to aid in understanding the operations performed by the video decoder 300. These units may be implemented as fixed function circuits, programmable circuits, or a combination thereof. Figure 6 , fixed-function circuits refer to circuits that provide specific functions and are preset in the operations that can be performed. Programmable circuits refer to circuits that can be programmed to perform various tasks and provide flexible functions in the operations that can be performed. For example, a programmable circuit can execute software or firmware that causes the programmable circuit to operate in a manner defined by the instructions of the software or firmware. Fixed-function circuits can execute software instructions (for example, to receive parameters or output parameters), but the type of operation performed by the fixed-function circuit is generally immutable. In some examples, one or more units may be different circuit blocks (fixed function or programmable), and in some examples, one or more units may be integrated circuits.

[0191] The video decoder 300 may include an ALU, an EFU, a digital circuit, an analog circuit, and / or a programmable core formed by a programmable circuit. In an example where the operation of the video decoder 300 is performed by software executed on a programmable circuit, an on-chip or off-chip memory may store instructions (e.g., object code) of the software received and executed by the video decoder 300.

[0192] The entropy decoding unit 302 may receive the encoded video data from the CPB and entropy decode 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 may generate decoded video data based on the syntax elements extracted from the bitstream.

[0193] Generally, the video decoder 300 reconstructs a picture on a block-by-block basis. The video decoder 300 may perform a reconstruction operation on each block individually (where the block currently being reconstructed (ie, decoded) may be referred to as a "current block").

[0194] The entropy decoding unit 302 may entropy decode syntax elements defining the quantized transform coefficients of the quantized transform coefficient block and transform information such as a quantization parameter (QP) and / or (one or more) transform mode indications. The inverse quantization unit 306 may use the QP associated with the quantized transform coefficient block to determine a degree of quantization, and likewise, determine a degree of inverse quantization for the inverse quantization unit 306 to apply. The inverse quantization unit 306 may inverse quantize the quantized transform coefficients (e.g., performing a bitwise left shift operation). The inverse quantization unit 306 may thereby form a transform coefficient block including the transform coefficients.

[0195] 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 rotational transform, an inverse directional transform, or another inverse transform to the coefficient block.

[0196] In the case where the decoded value of the syntax element of the current block indicates that the current block is predicted using an inter-frame prediction mode, the video decoder 300 can further decode the motion information (including the motion vector) of the current block. For example, the entropy decoding unit 302 can entropy decode the motion information in a merge mode or an AMVP mode, for example, depending on the value of the syntax element. In the merge mode or the AMVP mode, the entropy decoding unit 302 can determine the motion vector prediction candidate from the set of motion vector prediction candidates. According to the technology of the present disclosure, the entropy decoding unit 302 can construct a set of motion vector prediction candidates to have a number of candidates corresponding to the size of the current block.

[0197] In some examples, the entropy decoding unit 302 may construct a set of motion vector prediction candidates to have a first number of candidates when the size of the current block is less than a threshold, and a second number of candidates when the size of the current block is greater than the threshold, wherein the second number is greater than the first number. In some examples, the entropy decoding unit 302 may use a skip offset determined according to the size of the current block to sequentially skip a number of motion vector prediction candidates when constructing the set of motion vector prediction candidates. The skip offset for blocks less than the threshold may be greater than the skip offset for blocks greater than the threshold.

[0198] The entropy decoding unit 302 may further decode a motion vector prediction candidate index that refers to one of the motion vector prediction candidates in the set of motion vector prediction candidates to be used as a motion vector prediction candidate for a motion vector predictor, and then decode the motion information of the current block using the selected motion vector predictor. In the AMVP mode, the entropy decoding unit 302 may also entropy decode motion vector difference information, a reference picture list indicator, and a reference picture index identifying a reference picture in a reference picture list.

[0199] Further, prediction processing unit 304 generates a prediction block based on the prediction information syntax element entropy decoded by entropy decoding unit 302. For example, if the prediction information syntax element indicates that the current block is inter-predicted, motion compensation unit 316 may generate the prediction block. In this case, the prediction information syntax element may indicate a reference picture in DPB 314 from which to retrieve the reference block, and a motion vector that identifies the position of the reference block in the reference picture relative to the current block in the current picture. Motion compensation unit 316 may generally generate a prediction block in the same manner as for motion compensation unit 224 ( Figure 6 ) is performed in a manner substantially similar to that described herein.

[0200] According to the techniques of the present disclosure, DPB 314 may include one or more history buffers for storing motion information of previously coded blocks. Thus, prediction processing unit 304 may cause motion compensation unit 316 to select a motion vector predictor from the motion information of previously coded blocks. According to the techniques of the present disclosure, when the current block is smaller than a threshold size, prediction processing unit 304 may reduce the number of motion vector prediction candidates from which a motion vector predictor is selected.

[0201] As another example, if the prediction information syntax element indicates that the current block is intra-predicted, the intra-prediction unit 318 may generate a prediction block according to the intra-prediction mode indicated by the prediction information syntax element. Again, the intra-prediction unit 318 may generally generate a prediction block in the same manner as for the intra-prediction unit 226 ( Figure 6 The intra prediction process is performed in a manner substantially similar to that described in the foregoing description. The intra prediction unit 318 may retrieve data of neighboring samples of the current block from the DPB 314.

[0202] The reconstruction unit 310 may reconstruct the current block using the prediction block and the residual block. For example, the reconstruction unit 310 may add samples of the residual block to corresponding samples of the prediction block to reconstruct the current block.

[0203] The filter unit 312 may perform one or more filter operations on the reconstructed block. For example, the filter unit 312 may perform a deblocking operation to reduce blocking artifacts along the edges of the reconstructed block. The operations of the filter unit 312 may not necessarily be performed in all examples.

[0204] The video decoder 300 may store the reconstructed blocks in the DPB 314. As described above, the DPB 314 may provide reference information to the prediction processing unit 304, such as samples of the current picture for intra prediction and previously decoded pictures for subsequent motion compensation. In addition, the video decoder 300 may output decoded pictures from the DPB 314 for subsequent presentation on a display such as a Figure 1 on a display device 118 of the display device.

[0205] In this way, the 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 a circuit and configured to: determine that a size of a current block of video data is less than a threshold, the current block being a two-dimensional array of samples representing a portion of a picture; determine a set of motion vector prediction candidates for the current block based on the determination that the size of the current block is less than the threshold; a motion vector predictor that selects a motion vector prediction candidate for the current block; decodes motion information of the current block using the motion vector predictor; and decodes the current block using the motion information.

[0206] Figure 8 2 is a flowchart illustrating an example method for encoding a current block according to the techniques of the present disclosure. The current block may include a current CU. Although the video encoder 200 ( Figure 1 and Figure 6 ), but it should be understood that other devices may be configured to perform similar Figure 8 method.

[0207] In this example, the video encoder 200 initially predicts the current block using inter-frame prediction (350). For example, the video encoder 200 may use motion information to form a prediction block for the current block. The video encoder 200 may then calculate a residual block for the current block (352). To calculate the residual block, the video encoder 200 may calculate the difference between the original unencoded block and the prediction block for the current block. The video encoder 200 may then transform and quantize the coefficients of the residual block (354). Next, the video encoder 200 may scan the quantized transform coefficients of the residual block (356). During or after the scan, the video encoder 200 may entropy encode the coefficients and motion information (358).

[0208] For example, the video encoder 200 may determine whether the size of the current block is less than a threshold. If the size is greater than or equal to the threshold, the video encoder 200 may select a first number of motion vector prediction candidates from which a motion vector predictor is ultimately selected to encode the motion information of the current block (e.g., using merge mode or AMVP mode). If the size of the current block is less than the threshold, the video encoder 200 may select a second, reduced number of motion vector prediction candidates that is less than the first number of motion vector prediction candidates from which a motion vector predictor is ultimately selected to encode the motion information of the current block (e.g., using merge or AMVP mode). The video encoder 200 may encode the coefficients and motion information using CAVLC or CABAC. The video encoder 200 may then output entropy-encoded data (360) for the block.

[0209] In this way, Figure 8 The method represents an example of a method for encoding video data, including: determining that a size of a current block of video data is less than a threshold, the current block being a two-dimensional array of samples representing a portion of a picture; determining a set of motion vector prediction candidates for the current block based on the determination that the size of the current block is less than the threshold; selecting a motion vector predictor for the motion vector prediction candidate for the current block; encoding motion information of the current block using the motion vector predictor; and encoding the current block using the motion information.

[0210] Fig. 9 1 is a flowchart illustrating an example method for decoding a current block according to the techniques of the present disclosure. The current block may include a current CU. Although the video decoder 300 ( Figure 1 and Figure 7 ), but it should be understood that other devices may be configured to perform similar Fig. 9 method.

[0211] The video decoder 300 may receive entropy coded data (370) of a current block, such as entropy coded prediction information and entropy coded data of coefficients of a residual block corresponding to the current block. The video decoder 300 may decode the entropy coded data to determine the prediction information of the current block and reproduce the coefficients of the residual block (372). For example, the video decoder 300 may determine whether the size of the current block is less than a threshold. If the size of the current block is less than the threshold, the video decoder 300 may select a reduced number of motion vector prediction candidates from which to ultimately select a motion vector predictor to decode the motion information of the current block (e.g., using a merge mode or an AMVP mode).

[0212] The video decoder 300 may predict the current block (374) (e.g., using motion information in an inter-prediction mode) to calculate a prediction block for the current block. The video decoder 300 may then inverse scan the reproduced coefficients (376) to create a block of quantized transform coefficients. The video decoder 300 may then inverse quantize and inverse transform the coefficients to produce a residual block (378). The video decoder 300 may ultimately decode the current block by combining the prediction block and the residual block (380).

[0213] In this way, Fig. 9 The method represents an example of a method, including: determining that a size of a current block of video data is less than a threshold, the current block being a two-dimensional array of samples representing a portion of a picture; determining a set of motion vector prediction candidates for the current block based on the determination that the size of the current block is less than the threshold; a motion vector predictor for selecting the motion vector prediction candidates for the current block; decoding motion information of the current block using the motion vector predictor; and decoding the current block using the motion information.

[0214] Fig.10 is a flowchart illustrating an example method for encoding video data according to the techniques of the present disclosure. Although the video encoder 200 ( Figure 1 and Figure 6 ), but it should be understood that other devices may be configured to perform similar Fig.10 method.

[0215] Initially, mode selection unit 202 of video encoder 200 may determine to inter-predict a current block of video data (390). For example, mode selection unit 202 may perform a rate-distortion optimization (RDO) process to compare rate-distortion values ​​of various prediction modes, block sizes, and other encoding parameters to ultimately determine that the current block will be predicted using an inter-prediction mode. During the RDO process, mode selection unit 202 may also cause motion estimation unit 222 to determine a motion vector for the current block (392), and mode selection unit 202 may determine a size of the current block (394).

[0216] The mode selection unit 202 may provide the motion vector and other prediction information (such as motion information and block size) of the block to the entropy coding unit 220. The entropy coding unit 220 may determine whether the size of the current block is less than a threshold value (396). If the size of the current block is less than the threshold value (the "yes" branch of 396), the entropy coding unit 220 may construct a set of motion vector prediction (MVP) candidates of a first size (398). If the size of the current block is not less than the threshold value (the "no" branch of 396), for example, greater than or equal to the threshold value, the entropy coding unit 220 may construct a set of MVP candidates of a second size (400), which is greater than the first size.

[0217] To construct a set of MVP candidates, the entropy coding unit 220 may be configured to select a first skip offset when the size of the current block is less than a threshold, and to select a second skip offset when the size of the current block is greater than or equal to the threshold. The entropy coding unit 220 may be configured to select a first skip offset when the size of the current block is less than a threshold, and to select a second skip offset when the size of the current block is greater than or equal to the threshold. Figure 5B Or the set of MVP candidates is constructed by adding adjacent candidates to the set of MVP candidates in the order specified by 5C, but a number of candidates between the additions equal to the determined skip offset may be skipped.

[0218] After constructing the set of MVP candidates, entropy coding unit 220 may select a MVP candidate from the set of MVP candidates (402). Then, entropy coding unit 220 may entropy encode motion information of the current block including the determined motion vector using the MVP candidate (404). For example, entropy coding unit 220 may entropy encode a merge candidate index for merge mode, or an AMVP candidate index in AMVP mode, motion vector difference data, a reference picture list identifier, and a reference picture list index.

[0219] In this way, Fig.10 The method represents an example of a method for encoding video data, including: determining that a size of a current block of video data is less than a threshold, the current block being a two-dimensional array of samples representing a portion of a picture; determining a set of motion vector prediction candidates for the current block based on the determination that the size of the current block is less than the threshold; selecting a motion vector predictor for the motion vector prediction candidate for the current block; encoding motion information of the current block using the motion vector predictor; and encoding the current block using the motion information.

[0220] Fig.11 is a flowchart illustrating an example method for decoding video data according to the techniques of the present disclosure. Although the video decoder 300 ( Figure 1 and Figure 7 ), but it should be understood that other devices may be configured to perform similar Fig.11 method.

[0221] Initially, the entropy decoding unit 302 of the video decoder 300 may determine an entropy decoded value of a syntax element indicating that a current block of video data is inter-predicted (410). The entropy decoding unit 302 may also entropy decode a value of a syntax element indicating a size of the current block (412). The entropy decoding unit 302 may then determine whether the size of the current block is less than a threshold (414). If the size of the current block is less than the threshold (the "yes" branch of 414), the entropy decoding unit 302 may construct a set of motion vector prediction (MVP) candidates of a first size (416). If the size of the current block is not less than the threshold (the "no" branch of 414), for example, greater than or equal to the threshold, the entropy decoding unit 302 may construct a set of MVP candidates of a second size (418), which is greater than the first size.

[0222] To construct a set of MVP candidates, the entropy decoding unit 302 may be configured to select a first skip offset when the size of the current block is less than a threshold, and to select a second skip offset when the size of the current block is greater than or equal to the threshold. The entropy decoding unit 302 may be configured to select a first skip offset when the size of the current block is less than a threshold, and to select a second skip offset when the size of the current block is greater than or equal to the threshold. Figure 5B Or the set of MVP candidates is constructed by adding adjacent candidates to the set of MVP candidates in the order specified by 5C, but a number of candidates between the additions equal to the determined skip offset may be skipped.

[0223] The entropy decoding unit 302 may also entropy decode the MVP candidate index into a set of MVP candidates (420). The entropy decoding unit 302 may use the MVP candidate index to determine one of the set of MVP candidates (422) (i.e., identified by the MVP candidate index) as the MVP candidate to be used for decoding the motion information of the current block. The entropy decoding unit 302 may then use the MVP candidate to decode and reconstruct the motion information (424). For example, for merge mode, the entropy decoding unit 302 may provide the motion vector to the motion compensation unit 316. For AMVP mode, the entropy decoding unit 302 may further decode the motion vector difference data, the reference picture index, and the reference picture list, and provide the information to the motion compensation unit 316.

[0224] In this way, Fig.11 The method represents an example of a method for decoding video data, including: determining that a size of a current block of video data is less than a threshold, the current block being a two-dimensional array of samples representing a portion of a picture; determining a set of motion vector prediction candidates for the current block based on the determination that the size of the current block is less than the threshold; selecting a motion vector predictor for the motion vector prediction candidate for the current block; decoding motion information of the current block using the motion vector predictor; and decoding the current block using the motion information.

[0225] The various techniques of this disclosure are summarized in the following example:

[0226] Example 1: A method for encoding and decoding video data, the method comprising: determining that a size of a current block of video data is less than a threshold; determining a set of motion vector prediction candidates for the current block based on the determination that the size of the current block is less than the threshold; selecting a motion vector predictor for the motion vector prediction candidate for the current block; encoding and decoding motion information of the current block using the motion vector predictor; and encoding and decoding the current block using the motion information.

[0227] Example 2: The method of Example 1, wherein determining the set of motion vector prediction candidates comprises: determining the number of candidates to be included in the set of motion vector prediction candidates based on a determination that the size of the current block is less than a threshold.

[0228] Example 3: The method of Example 2, wherein the number of candidates is less than the number of candidates to be included in the set of motion vector prediction candidates for blocks having a size greater than a threshold.

[0229] Example 4: A method of any one of Examples 1-3, wherein the current block includes a first block, the size of the first block includes a first size, the motion vector predictor includes a first motion vector predictor, and the set of motion vector prediction candidates includes a first set of motion vector prediction candidates having a first number of motion vector prediction candidates, the method further comprising: determining that a second size of a second block of video data is greater than the threshold; determining a second set of motion vector prediction candidates for the second block based on determining that the second size of the second block is greater than the threshold, the second set having a second number of motion vector prediction candidates, the second number being greater than the first number; and encoding and decoding motion information of the second block using the second motion vector predictor.

[0230] Example 5: The method of any one of Examples 1 to 4, wherein determining a set of motion vector prediction candidates comprises: selecting motion vector prediction candidates from a near region adjacent to the current block.

[0231] Example 6: The method of any one of Examples 1-4, wherein determining a set of motion vector prediction candidates comprises: subsampling the history buffer information according to a skip offset, the skip offset being determined based on a determination that a size of the block is less than a threshold.

[0232] Example 7: The method of any one of Examples 1-6, wherein determining a set of motion vector prediction candidates comprises: selecting the set of motion prediction candidates from a motion information buffer generated from a source other than a current picture including the current block.

[0233] Example 8: The method of Example 7 further includes: generating a motion information buffer from motion information collected from pictures other than the current picture, different resolution levels, different views, different slices, different pieces, or different fragments.

[0234] Example 9: The method of any one of Examples 1 to 8, wherein determining a set of motion vector prediction candidates comprises: modifying motion information of a neighboring block; and adding the modified motion information to the set of motion vector prediction candidates.

[0235] Example 10: The method of Example 9, wherein modifying the motion information comprises: scaling a motion vector of the motion information.

[0236] Example 11: The method of Example 10, wherein scaling comprises: scaling the motion vector to take into account a picture order count (POC) difference between a current picture including the current block, a reference picture for motion information of the current block, and a reference picture for motion information of a neighboring block.

[0237] Example 12: The method of Example 10, wherein scaling comprises scaling the motion vector according to a buffer comprising motion information of neighboring blocks.

[0238] Example 13: The method of Example 12, wherein the buffer stores motion information for one of different resolution levels, different pictures, or different views.

[0239] Example 14: The method of any one of Examples 1 to 13, wherein encoding and decoding the current block includes decoding the current block, including: forming a prediction block of the current block using motion information; decoding the residual block of the current block; and combining the prediction block with the residual block to reproduce the current block.

[0240] Example 15: The method of any one of Examples 1-14, wherein encoding and decoding the current block includes decoding the current block, including: forming a prediction block of the current block using motion information; subtracting the prediction block from the current block to generate a residual block of the current block; and encoding the residual block.

[0241] Example 16: A device for encoding and decoding video data, the device comprising one or more components for performing the method of any one of Examples 1-15.

[0242] Example 17: The device of Example 16, wherein the one or more components include one or more processors implemented in the circuit.

[0243] Example 18: The device of Example 16, further comprising a display configured to display the video data.

[0244] Example 19: The device of Example 16, wherein the device comprises one or more of: a camera, a computer, a mobile device, a broadcast receiver device, or a set-top box.

[0245] Example 20: The device of Example 16, further comprising a memory configured to store video data.

[0246] Example 21: The device of Example 16, further comprising a camera configured to capture video data.

[0247] Example 22: The device of Example 16, wherein the device comprises at least one of: an integrated circuit; a microprocessor; or a wireless communication device.

[0248] Example 23: A computer-readable storage medium having instructions stored thereon, which instructions, when executed, cause a processor to perform the method of any one of Examples 1-15.

[0249] Example 24: A device for decoding video data, the device comprising: a component for determining that a size of a current block of the video data is less than a threshold; a component for determining a set of motion vector prediction candidates for the current block based on the determination that the size of the current block is less than the threshold; a component for selecting a motion vector predictor for the motion vector prediction candidate for the current block; a component for encoding and decoding motion information of the current block using the motion vector predictor; and a component for encoding and decoding the current block using the motion information.

[0250] It should be appreciated that, according to examples, certain actions or events of any technology described herein may be performed in a different sequence, may be added, merged, or omitted together (e.g., not all described actions or events are necessary for the practice of the technology). In addition, in some examples, actions or events may be performed concurrently rather than sequentially, such as by multithreading, interrupt handling, or multiple processors.

[0251] In one or more examples, the described functions may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions may be stored on or transmitted through a computer-readable medium as one or more instructions or codes and executed by a hardware-based processing unit. Computer-readable media may include computer-readable storage media, which corresponds to tangible media such as data storage media, or communication media, including, for example, any media that facilitates the transfer of a computer program from one place to another according to a communication protocol. In this manner, a computer-readable medium may generally correspond to (1) a non-temporary tangible computer-readable storage medium, or (2) a communication medium such as a signal or carrier wave. A data storage medium may be any available medium that can be accessed by one or more computers or one or more processors to retrieve instructions, codes, and / or data structures to implement the techniques described in the present disclosure. A computer program product may include a computer-readable medium.

[0252] As an example and not limitation, such computer-readable storage media may include RAM, ROM, EEPROM, CD-ROM or other optical disk storage, disk storage or other magnetic storage devices, flash memory or any other medium that can be used to store the required program code in the form of instructions or data structures and can be accessed by a computer. Moreover, any connection is appropriately referred to as a computer-readable medium. For example, if a coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL) or wireless technology (such as infrared, radio and microwave) is used to send instructions from a website, server or other remote source, the definition of the medium includes coaxial cable, fiber optic cable, twisted pair, DSL or wireless technology (such as infrared, radio and microwave). However, it should be understood that computer-readable storage media and data storage media do not include connections, carriers, signals or other temporary media, but are directed to non-temporary tangible storage media. As used herein, disks and optical disks include compact disks (CDs), laser optical disks, optical optical disks, digital versatile disks (DVDs), floppy disks and blue-ray disks, wherein disks usually reproduce data magnetically, and optical disks reproduce data optically with lasers. The above combination should also be included in the scope of computer-readable media.

[0253] Instructions may be executed by one or more processors, such as one or more digital signal processors (DSPs), general-purpose microprocessors, application-specific integrated circuits (ASICs), field programmable gate arrays (FPGAs), or other equivalent integrated or discrete logic circuits. Therefore, the terms "processor" and "processing circuit" as used in this application may refer to any of the aforementioned structures or any other structure suitable for implementing the technology described in this application. In addition, in some aspects, the functions described in this application may be provided within dedicated hardware and / or software modules configured for encoding and decoding, or incorporated in a combined codec. Similarly, the technology may be fully implemented in one or more circuits or logic elements.

[0254] The techniques of the present disclosure may be implemented in a variety of devices or apparatuses including a wireless handset, an integrated circuit (IC), or a set of ICs (e.g., a chipset). Various components, modules, or units are described in the present disclosure to emphasize functional aspects of devices configured to perform the disclosed techniques, but do not necessarily need to be implemented by different hardware units. Instead, as described above, the various units may be combined in a codec hardware unit, or provided by a collection of interoperable hardware units, including one or more processors as described above in combination with appropriate software and / or firmware.

[0255] Various examples have been described. These and other examples are within the scope of the following claims.

Claims

1. A method for encoding and decoding video data, the method comprising: Determining that a size of a current block of the video data is less than a threshold, the current block being a two-dimensional array of samples representing a portion of a picture; Determining a set of motion vector prediction candidates for the current block according to the determination that the size of the current block is smaller than the threshold; selecting a motion vector predictor of the motion vector prediction candidate for the current block; encoding and decoding the motion information of the current block using the motion vector predictor; as well as Using the motion information to encode and decode the current block, Wherein, according to the determination that the size of the current block is less than the threshold, determining the set of motion vector prediction candidates for the current block includes: limiting the maximum number of candidates to be considered for inclusion in the set of motion vector prediction candidates in the table of history-based motion vector prediction HMVP candidates to a first maximum number of candidates, wherein the first maximum number of candidates is less than a second maximum number of candidates to be considered for block sizes greater than or equal to the threshold, and Determining that the size of the current block is smaller than a threshold includes determining that the size of the current block is smaller than 8×8 samples.

2. The method according to claim 1, wherein: The first maximum number of candidates is 15, and the second maximum number of candidates is 23.

3. The method according to claim 1, wherein: Determining a set of motion vector prediction candidates further includes: selecting the motion vector prediction candidate from a near area adjacent to the current block.

4. The method according to claim 1, wherein: Determining a set of motion vector prediction candidates further comprises: sub-sampling the candidates in the table of HMVP candidates according to a skip step size, wherein the skip step size is determined according to the determination that the size of the current block is smaller than the threshold value.

5. The method of claim 4, further comprising, in response to the determination that the size of the current block is less than the threshold, determining the skip step size to be greater than a skip step size determined for a block having a size greater than or equal to the threshold.

6. The method according to claim 1, wherein: Determining a set of motion vector prediction candidates further includes selecting the set of motion vector prediction candidates from a motion information buffer generated from a source other than a current picture including the current block.

7. The method according to claim 6, further comprising: The motion information buffer is generated by motion information collected from pictures other than the current picture, different resolution levels, different views, different slices, different slices, or different fragments.

8. The method according to claim 1, wherein: Determining the set of motion vector prediction candidates also includes: Modifying motion information of adjacent blocks; and The modified motion information is added to the set of motion vector prediction candidates.

9. The method according to claim 8, wherein: Modifying the motion information includes scaling a motion vector of the motion information.

10. The method according to claim 9, wherein: The scaling includes scaling the motion vector to take into account a picture order count (POC) difference between a current picture including the current block, a reference picture for motion information of the current block, and a reference picture for motion information of the neighboring block.

11. The method according to claim 9, wherein: Scaling includes: The motion vector is scaled according to a buffer including motion information of the neighboring blocks.

12. The method according to claim 11, wherein: The buffer stores motion information for one of different resolution levels, different pictures or different views.

13. The method according to claim 1, wherein: Encoding and decoding the current block includes decoding the current block, including: forming a prediction block of the current block using the motion information; Decoding the residual block of the current block; and The prediction block is combined with the residual block to reproduce the current block.

14. The method according to claim 1, wherein: Encoding and decoding the current block includes encoding the current block, including: forming a prediction block of the current block using the motion information; subtracting the prediction block from the current block to generate a residual block for the current block; and The residual block is encoded.

15. A device for encoding and decoding video data, the device comprising: a memory configured to store video data; as well as One or more processors implemented in circuitry and configured to: Determining that a size of a current block of the video data is less than a threshold, the current block being a two-dimensional array of samples representing a portion of a picture; Determining a set of motion vector prediction candidates for the current block according to the determination that the size of the current block is smaller than the threshold; selecting a motion vector predictor of the motion vector prediction candidate for the current block; encoding and decoding the motion information of the current block using the motion vector predictor; as well as Using the motion information to encode and decode the current block, In order to determine a set of motion vector prediction candidates for the current block according to the determination that the size of the current block is less than the threshold, the one or more processors are further configured to: limiting the maximum number of candidates in the table of history-based motion vector prediction (HMVP) candidates to be considered for inclusion in the set of motion vector prediction candidates to a first maximum number of candidates, wherein the first maximum number of candidates is less than a second maximum number of candidates to be considered for block sizes greater than or equal to the threshold, and In order to determine that the size of the current block is smaller than a threshold, the one or more processors are further configured to determine that the size of the current block is smaller than 8×8 samples. The apparatus of claim 15 , wherein the first maximum number of candidates is 15, and the second maximum number of candidates is 23.

17. The apparatus according to claim 15, wherein: The one or more processors are configured to: responsive to the determination that the size of the current block is less than the threshold, determining a skip step size that is greater than a skip step size determined for a block having a size greater than the threshold; as well as The candidates in the table of HMVP candidates are sub-sampled according to the skip step size to determine the set of motion vector prediction candidates.

18. The device according to claim 15, wherein, in order to encode and decode the current block, the one or more processors are configured to: forming a prediction block of the current block using the motion information; Decoding the residual block of the current block; and The prediction block is combined with the residual block to reproduce the current block.

19. The device according to claim 15, wherein, in order to encode and decode the current block, the one or more processors are configured to: forming a prediction block of the current block using the motion information; subtracting the prediction block from the current block to generate a residual block for the current block; and The residual block is encoded.

20. The device of claim 15, further comprising a display configured to display the video data.

21. The apparatus of claim 15, wherein: The device is a camera, a computer, a mobile device, a broadcast receiver device, a set-top box, an integrated circuit, a microprocessor, or a wireless communication device.

22. The device of claim 15, further comprising a camera configured to capture the video data.

23. A computer-readable storage medium having stored thereon instructions which, when executed, cause a processor to perform the method of any one of claims 1-14.

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