TMP fusion information derivation

Abstract

A video coder (encoder or decoder) obtains, from a bitstream, an indication that a block is coded using a fusion intra-template matching prediction (IntraTMP) mode. The video coder further derives, from a plurality of groups of block vector prediction (BVP) candidates for the block and based on cost metrics of the plurality of groups for at least one fusion model of the fusion IntraTMP mode, a fusion group of BVP candidates for coding the block. The video coder decodes the block based on the derived fusion group of BVP candidates.

Description

Docket No.: 24-2041PCTTITLETMP Fusion Information DerivationCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Application No. 63 / 708,436, filed October 17, 2024, which is hereby incorporated by reference in its entirety.BRIEF DESCRIPTION OF THE DRAWINGS

[0002] Some features are shown by way of example, and not by limitation, in the accompanying drawings. In the drawings, like numerals reference similar elements.

[0003] FIG. 1 illustrates an example video coding / decoding system in which embodiments of the present disclosure may be implemented.

[0004] FIG. 2 illustrates an example encoder in which embodiments of the present disclosure may be implemented.

[0005] FIG. 3 illustrates an example decoder in which embodiments of the present disclosure may be implemented.

[0006] FIG. 4 illustrates an example quadtree partitioning of a coding tree block (CTB).

[0007] FIG. 5 illustrates an example quadtree corresponding to the example quadtree partitioning of the CTB inFIG. 4.

[0008] FIG. 6 illustrates examples of binary tree and ternary tree partitions.

[0009] FIG. 7A shows an example of combined quadtree and multi-type tree partitioning of a CTB.

[0010] FIG. 7B shows an example tree corresponding to the combined quadtree and multi-type tree partitioning of the CTB shown in FIG. 7A.

[0011] FIG. 8 shows an example of partitioning modes in AV1.

[0012] FIG. 9 illustrates an example set of reference samples determined for intra prediction of a current block.

[0013] FIG. 10A, FIG. 10B, and FIG. 10C show example intra prediction modes.

[0014] FIG. 11 illustrates an example of a current block and corresponding reference samples.

[0015] FIG. 12 illustrates an example of applying an intra prediction mode (e.g., an angular mode) for prediction of a current block.

[0016] FIG. 13A illustrates an example of inter prediction performed for a current block in a current picture.

[0017] FIG. 13B illustrates an example motion vector.

[0018] FIG. 14 illustrates an example of bi-prediction performed for a current block.

[0019] FIG. 15A illustrates example spatial candidate neighboring blocks relative to a current block being coded.

[0020] FIG. 15B illustrates example locations of two temporal, co-located blocks relative to a current block.

[0021] FIG. 16 illustrates an example of intra block copy (IBC).

[0022] FIG. 17 illustrates, for an example current block, a reference region or search area of reconstructed samples within which in Intra Template Match Prediction (IntraTMP) a search is performed for a candidate reference block of which the template best matches the template of the current block.Docket No.: 24-2041PCT

[0023] FIG. 18 illustrates a current block in a current CTU, and the reference region with the corresponding IntraTMP search regions R1-R6 identified.

[0024] FIG. 19A illustrates the sparse search stage of IntraTMP.

[0025] FIG. 19B illustrates a block vector according to IntraTMP where the block vector's refinement window is clipped at the boundary of a search region.

[0026] FIG. 20 illustrates an example of the top-template type that can be used in IntraTMP.

[0027] FIG. 21 illustrates an example of the left-template type that can be used in IntraTMP.

[0028] FIG. 22 illustrates an example of the L-shape template type that can be used in IntraTMP.

[0029] FIG. 23A and FIG. 23B illustrate sample positions for determining adjacent blocks and non-adjacent blocks for determining block vector candidates.

[0030] FIG. 24A illustrates an example of IntraTMP with merge candidates process, according to some embodiments.

[0031] FIG. 24B illustrates another example of IntraTMP with merge candidates process, according to some embodiments.

[0032] FIG. 25 illustrates example refinement windows for sparse block vector candidates and merge block vector candidates, according to some embodiments.

[0033] FIG. 26 shows an example of regular IntraTMP submode, according to some embodiments.

[0034] FIG. 27 shows an example of a regular TMP mode used by a neighboring block of a current block which can be used to generate a TMP list for the current block, according to some embodiments.

[0035] FIG. 28 shows an example of three TMP fusion groups generated for the final TMP list shown in FIG. 26, according to some embodiments.

[0036] FIG. 29 depicts an example of fusion prediction blocks for a TMP fusion group shown in FIG. 28, according to some embodiments.

[0037] FIG. 30 shows one example of the fusion of five TMP fusion prediction blocks selected from the refined TMP list shown in FIG. 26, according to some embodiments.

[0038] FIG. 31 shows an example of the signaling of TMP-related flags and the decision flow for various TMP flags, according to some embodiments.

[0039] FIG. 32 shows an example of a process for deriving the fusion group used in the TMP fusion mode for a given fusion model, according to some embodiments.

[0040] FIG. 33 shows an example of a process for deriving both the fusion group and the fusion model used in the TMP fusion mode for a block, according to some embodiments.

[0041] FIG. 34 shows an example of a process for deriving the fusion model used in the TMP fusion mode for a block for a given fusion group, according to some embodiments.

[0042] FIG. 35A illustrates an example of signaling or decoding of TMP-related flags, according to some embodiments.Docket No.: 24-2041PCT

[0043] FIG. 35B illustrates another example of the signaling or decoding of TMP-related flags, according to some embodiments.

[0044] FIG. 35C illustrates yet another example of the signaling or decoding of TMP-related flags, according to some embodiments.

[0045] FIG. 36 shows a flowchart illustrating an example of a process for encoding a current block using an IntraTMP fusion mode, according to some embodiments.

[0046] FIG. 37 shows a flowchart illustrating another example of a process for encoding a current block using an IntraTMP fusion mode, according to some embodiments.

[0047] FIG. 38 shows a flowchart illustrating yet another example of a process for encoding a current block using an IntraTMP fusion mode, according to some embodiments.

[0048] FIG. 39 shows a flowchart illustrating an example of a process for decoding a current block using an IntraTMP fusion mode, according to some embodiments.

[0049] FIG. 40 shows a flowchart illustrating another example of a process for decoding a current block using an IntraTMP fusion mode, according to some embodiments.

[0050] FIG. 41 shows a flowchart illustrating yet another example of a process for decoding a current block using an IntraTMP fusion mode, according to some embodiments.

[0051] FIG. 42 shows a flowchart illustrating an example of a process for encoding a current block using an IntraTMP fusion mode with fusion group reordering, according to some embodiments.

[0052] FIG. 43 shows a flowchart illustrating an example of a process for decoding a current block using an IntraTMP fusion mode with fusion group reordering, according to some embodiments.

[0053] FIG. 44 illustrates a block diagram of an example computer system in which embodiments of the present disclosure may be implemented.DETAILED DESCRIPTION

[0054] In the following description, numerous specific details are set forth in order to provide a thorough understanding of the disclosure. However, it will be apparent to those skilled in the art that the disclosure, including structures, systems, and methods, may be practiced without these specific details. The description and representation herein are the common means used by those experienced or skilled in the art to most effectively convey the substance of their work to others skilled in the art. In other instances, well-known methods, procedures, components, and circuitry have not been described in detail to avoid unnecessarily obscuring aspects of the disclosure

[0055] References in the specification to “one embodiment,” “an embodiment,” “an example embodiment,” etc., indicate that the embodiment described may include a particular feature, structure, or characteristic, but every embodiment may not necessarily include the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted that it is within the knowledge of one skilled in the art toDocket No.: 24-2041PCT affect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described.

[0056] Also, it is noted that individual embodiments may be described as a process which is depicted as a flowchart, a flow diagram, a data flow diagram, a structure diagram, or a block diagram. Although a flowchart may describe the operations as a sequential process, many of the operations can be performed in parallel or concurrently. In addition, the order of the operations may be re-arranged. A process is terminated when its operations are completed, but could have additional steps not included in a figure. A process may correspond to a method, a function, a procedure, a subroutine, a subprogram, etc. When a process corresponds to a function, its termination can correspond to a return of the function to the calling function or the main function.

[0057] The term “computer-readable medium’’ includes, but is not limited to, portable or non-portable storage devices, optical storage devices, and various other mediums capable of storing, containing, or carrying instruction(s) and / or data. A computer-readable medium may include a non-transitory medium in which data can be stored and that does not include carrier waves and / or transitory electronic signals propagating wirelessly or over wired connections. Examples of a non-transitory medium may include, but are not limited to, a magnetic disk or tape, optical storage media such as compact disk (CD) or digital versatile disk (DVD), flash memory, memory or memory devices. A computer-readable medium may have stored thereon code and / or machine-executable instructions that may represent a procedure, a function, a subprogram, a program, a routine, a subroutine, a module, a software package, a class, or any combination of instructions, data structures, or program statements. A code segment may be coupled to another code segment or a hardware circuit by passing and / or receiving information, data, arguments, parameters, or memory contents. Information, arguments, parameters, data, etc may be passed, forwarded, or transmitted via any suitable means including memory sharing, message passing, token passing, network transmission, or the like.

[0058] Furthermore, embodiments may be implemented by hardware, software, firmware, middleware, microcode, hardware description languages, or any combination thereof. When implemented in software, firmware, middleware or microcode, the program code or code segments to perform the necessary tasks (e.g., a computer-program product) may be stored in a computer-readable or machine-readable medium. A processor(s) may perform the necessary tasks.

[0059] A video sequence, comprising multiple pictures / frames, may be represented in digital form for storage and / or transmission. Representing a video sequence in digital form may require a large quantity of bits. Large data sizes that may be associated with video sequences may require significant resources for storage and / or transmission. Video encoding may be used to compress a size of a video sequence for more efficient storage and / or transmission. Video decoding may be used to decompress a compressed video sequence for display and / or other forms of consumption.

[0060] FIG. 1 shows an example video coding / decoding system 100 in which embodiments of the present disclosure may be implemented. Video coding / decoding system 100 comprises a source device 102, a transmission medium 104, and a destination device 106. Source device 102 encodes a video sequence 108 into a bitstream 110 for more efficient storage and / or transmission. Source device 102 may store and / or send / transmit bitstream 110 toDocket No.: 24-2041PCT destination device 106 via transmission medium 104. Destination device 106 decodes bitstream 110 to display video sequence 108. Destination device 106 may receive bitstream 110 from source device 102 via transmission medium 104. Source device 102 and / or destination device 106 maybe any of a plurality of different devices (e.g., a desktop computer, laptop computer, tablet computer, smart phone, wearable device, television, camera, video gaming console, set-top box, video streaming device, etc.).

[0061] Source device 102 may comprise (e.g., for encoding video sequence 108 into bitstream 110) one or more of a video source 112, an encoder 114, and / or an output interface 116. Video source 112 may provide and / or generate video sequence 108 based on a capture of a natural scene and / or a synthetically generated scene. A synthetically generated scene may be a scene comprising computer generated graphics and / or screen content. Video source 112 may comprise a video capture device (e.g., a video camera), a video archive comprising previously captured natural scenes and / or synthetically generated scenes, a video feed interface to receive captured natural scenes and / or synthetically generated scenes from a video content provider, and / or a processor to generate synthetic scenes.

[0062] A video sequence, such as video sequence 108, may comprise a series of pictures (also referred to as frames). A video sequence may achieve an impression of motion based on successive presentation of pictures of the video sequence using a constant time interval or variable time intervals between the pictures. A picture may comprise one or more sample arrays of intensity values. The intensity values maybe taken (e.g., measured, determined, provided) at a series of regularly spaced locations within a picture. A color picture may comprise (e.g., typically comprises) a luminance sample array and two chrominance sample arrays. The luminance sample array may comprise intensity values representing the brightness (e.g., luma component, Y) of a picture. The chrominance sample arrays may comprise intensity values that respectively represent the blue and red components of a picture (e.g., chroma components, Cb and Cr) separate from the brightness. Other color picture sample arrays may be possible based on different color schemes (e.g., a red, green, blue (RGB) color scheme). A pixel, in a color picture, may refer to / comprise / be associated with all intensity values (e.g., luma component, chroma components), for a given location, in the sample arrays (e.g., three sample arrays are used for one luma component and two chroma components, respectively) used to represent color pictures. A monochrome picture may comprise a single, luminance sample array. A pixel, in a monochrome picture, may refer to / comprise / be associated with the intensity value (e.g., luma component) at a given location in the single, luminance sample array used to represent monochrome pictures.

[0063] Encoder 114 may encode video sequence 108 into bitstream 110. Encoder 114 may apply / use (e.g., to encode video sequence 108) one or more prediction techniques to reduce redundant information in video sequence 108. Redundant information is information that may be predicted at a decoder and need not be transmitted to the decoder for accurate decoding of video sequence 108. For example, encoder 114 may apply spatial prediction (e.g., intra-frame or intra prediction), temporal prediction (e.g., inter-frame prediction or inter prediction), inter-layer prediction, and / or other prediction techniques to reduce redundant information in video sequence 108. Encoder 114 may partition pictures comprising video sequence 108 into rectangular regions referred to as blocks, for example,Docket No.: 24-2041PCT before applying one or more prediction techniques. Encoder 114 may then encode a block using the one or more of the prediction techniques.

[0064] For temporal prediction, encoder 114 may search fora block similar to the block being encoded in another picture (e.g., referred to as a reference picture) of video sequence 108. The block determined during the search (e.g., referred to as a prediction block) may then be used to predict the block being encoded. For spatial prediction, encoder 114 may form a prediction block based on data from reconstructed neighboring samples of the block to be encoded within the same picture of video sequence 108. A reconstructed sample refers to a sample that was encoded and then decoded. Encoder 114 may determine a prediction error (e.g., also referred to as a residual) based on the difference between a block being encoded and a prediction block. The prediction error may represent non-redundant information that may be sent / transmitted to a decoder for accurate decoding of video sequence 108.

[0065] Encoder 114 may apply a transform to the prediction error (e.g using a discrete cosine transform (DCT), or any other transform) to generate transform coefficients. Encoder 114 may form bitstream 110 based on the transform coefficients and other information used to determine prediction blocks using / based on prediction types, motion vectors, and / or prediction modes. Encoder 114 may perform one or more of quantization and entropy coding of the transform coefficients and / or the other information used to determine the prediction blocks, for example, before forming bitstream 110. The quantization and / or the entropy coding may further reduce the quantity of bits needed to store and / or transmit video sequence 108.

[0066] Output interface 116 maybe configured to write and / or store bitstream 110 onto transmission medium 104 for transmission to destination device 106. In addition or alternatively, output interface 116 may be configured to send / transmit, upload, and / or stream bitstream 110 to destination device 106 via transmission medium 104. Output interface 116 may comprise a wired and / or a wireless transmitter configured to send / transmit, upload, and / or stream bitstream 110 in accordance with one or more proprietary, open-source, and / or standardized communication protocols (e.g., Digital Video Broadcasting (DVB) standards, Advanced Television Systems Committee (ATSC) standards, Integrated Services Digital Broadcasting (ISDB) standards, Data Over Cable Service Interface Specification (DOCSIS) standards, 3rd Generation Partnership Project (3GPP) standards, Institute of Electrical and Electronics Engineers (IEEE) standards, Internet Protocol (IP) standards, Wireless Application Protocol (WAP) standards, and / or any other communication protocol).

[0067] Transmission medium 104 may comprise wireless, wired, and / or computer readable medium. For example, transmission medium 104 may comprise one or more wires, cables, air interfaces, optical discs, flash memory, and / or magnetic memory. In addition or alternatively, transmission medium 104 may comprise one or more networks (e.g., the internet) or file servers configured to store and / or send / transmit encoded video data.

[0068] Destination device 106 may decode bitstream 110 into video sequence 108 for display. Destination device 106 may comprise one or more of an input interface 118, a decoder 120, and / or a video display 122. Input interface 118 may be configured to read bitstream 110 stored on transmission medium 104 by source device 102. In addition or alternatively, input interface 118 maybe configured to receive, download, and / or stream bitstream 110 from sourceDocket No.: 24-2041PCT device 102 via transmission medium 104. Input interface 118 may comprise a wired and / or a wireless receiver configured to receive, download, and / or stream bitstream 110 in accordance with one or more proprietary, open- source, standardized communication protocols, and / or any other communication protocol (e.g., such as referenced herein).

[0069] Decoder 120 may decode video sequence 108 from encoded bitstream 110. The decoder 120 may generate prediction blocks for pictures of video sequence 108 in a similar manner as encoder 114 and determine the prediction errors for the blocks, for example, to decode video sequence 108. Decoder 120 may generate the prediction blocks using / based on prediction types, prediction modes, and / or motion vectors received in bitstream 110. Decoder 120 may determine the prediction errors using the transform coefficients received in bitstream 110. Decoder 120 may determine the prediction errors by weighting transform basis functions using the transform coefficients. Decoder 120 may combine the prediction blocks and the prediction errors to decode video sequence 108. Video sequence 108 at the destination device 106 may be, or may not necessarily be, the same video sequence sent, such as video sequence 108 as sent by the source device 102. Decoder 120 may decode a video sequence that approximates video sequence 108, for example, because of lossy compression of video sequence 108 by encoder 114 and / or errors introduced into encoded bitstream 110 during transmission to destination device 106.

[0070] Video display 122 may display video sequence 108 to a user. Video display 122 may comprise a cathode rate tube (CRT) display, a liquid crystal display (LCD), a plasma display, a light emitting diode (LED) display, and / or any other display device suitable for displaying video sequence 108.

[0071] Video coding / decoding system 100 is merely an example and video encoding / decoding systems different from the video coding / decoding system 100 and / or modified versions of the video coding / decoding system 100 may similarly perform the methods and processes as described herein. For example, the video coding / decoding system 100 may comprise other components and / or arrangements. For example, video source 112 may be external to source device 102. Similarly, video display 122 may be external to destination device 106 or omitted altogether (e.g., if video sequence 108 is intended for consumption by a machine and / or storage device). In an example, source device 102 may further comprise a video decoder and destination device 106 may further comprise a video encoder. For example, source device 102 may be configured to further receive an encoded bitstream from destination device 106 to support two-way video transmission between the devices.

[0072] Encoder 114 and / or decoder 120 may operate according to one or more proprietary or industry video coding standards. For example, encoder 114 and / or decoder 120 may operate in accordance with one or more proprietary, open-source, and / or standardized protocols (e.g., International Telecommunications Union Telecommunication Standardization Sector (ITU-T) H.263, ITU-T H.264 and Moving Picture Expert Group (MPEG)-4 Visual (also known as Advanced Video Coding (AVC)), ITU-T H.265 and MPEG-H Part 2 (also known as High Efficiency Video Coding (HEVC)), ITU-T H.265 and MPEG-I Part 3 (also known as Versatile Video Coding (WC)), the WebM VP8 and VP9 codecs, and / or AO Media Video 1 (AV1), and / or any other video coding protocol).Docket No.: 24-2041PCT

[0073] FIG. 2 shows an example encoder. Encoder 200 as shown in FIG. 2 may implement one or more processes described herein. Encoder 200 may encode a video sequence 202 into a bitstream 204 for more efficient storage and / or transmission. Encoder 200 may be implemented in video coding / decoding system 100 as shown in FIG. 1 (e.g., as encoder 114) or in any computing, communication, or electronic device (e.g., desktop computer, laptop computer, tablet computer, smartphone, wearable device, television, camera, video gaming console, set-top box, video streaming device, etc.). Encoder 200 may comprise one or more of an inter prediction unit 206, an intra prediction unit 208, combiners 210 and 212, a transform and quantization unit (TR + Q) 214, an inverse transform and quantization unit (iTR + iQ) 216, an entropy coding unit 218, one or more filters 220, and / or a buffer 222.

[0074] Encoder 200 may partition pictures (e.g., frames) of (e.g., comprising) video sequence 202 into blocks and encode video sequence 202 on a block-by-block basis. Encoder 200 may perform / apply a prediction technique on a block being encoded using either inter prediction unit 206 or intra prediction unit 208. Inter prediction unit 206 may perform inter prediction by searching for a block similar to the block being encoded in another, reconstructed picture (e.g., a reference picture) of video sequence 202. A reconstructed picture refers to a picture that was encoded and then decoded. The block determined during the search (e.g., referred to as a prediction block) may then be used to predict the block being encoded to remove redundant information. Inter prediction unit 206 may exploit temporal redundancy or similarities in scene content from picture to picture in video sequence 202 to determine the prediction block. For example, scene content between pictures of video sequence 202 may be similar except for differences due to motion and / or affine transformation of the screen content over time.

[0075] Intra prediction unit 208 may perform intra prediction by forming a prediction block based on data from reconstructed neighboring samples of the block to be encoded within the same picture of video sequence 202. A reconstructed sample refers to a sample that was encoded and then decoded. Intra prediction unit 208 may exploit spatial redundancy or similarities in scene content within a picture of video sequence 202 to determine the prediction block. For example, the texture of a region of scene content in a picture may be similar to the texture in the immediate surrounding area of the region of the scene content in the same picture.

[0076] Combiner 210 may determine a prediction error (e.g., referred to as a residual) based on the difference between the block being encoded and the prediction block. The prediction error may represent non-redundant information that may be sent / transmitted to a decoder for accurate decoding of video sequence 202.

[0077] Transform and quantization unit (TR + Q) 214 may transform and quantize the prediction error. Transform and quantization unit 214 may transform the prediction error into transform coefficients by applying, for example, a DCT to reduce correlated information in the prediction error. Transform and quantization unit 214 may quantize the coefficients by mapping data of the transform coefficients to a predefined set of representative values. Transform and quantization unit 214 may quantize the coefficients to reduce irrelevant information in bitstream 204. The irrelevant information refers to information that may be removed from the coefficients without producing visible and / or perceptible distortion in video sequence 202 after decoding (e.g., at a receiving device).Docket No.: 24-2041PCT

[0078] Entropy coding unit 218 may apply one or more entropy coding methods to the quantized transform coefficients to further reduce the bit rate. For example, entropy coding unit 218 may apply context adaptive variable length coding (CAVLC), context adaptive binary arithmetic coding (CABAC), and / or syntax-based context-based binary arithmetic coding (SBAC). The entropy coded coefficients may be packed to form bitstream 204.

[0079] Inverse transform and quantization unit (iTR + iQ) 216 may inverse quantize and inverse transform the quantized transform coefficients to determine a reconstructed prediction error. Combiner 212 may combine the reconstructed prediction error with the prediction block to form a reconstructed block. Filter(s) 220 may filter the reconstructed block, for example, using a deblocking filter, a sample-adaptive offset (SAG) filter, constrained directional enhancement filters (CDEFs), and / or loop restoration (LR) filters. Buffer 222 may store the reconstructed block for prediction of one or more other blocks in the same and / or different picture of video sequence 202.

[0080] Encoder 200 may further comprise an encoder control unit. The encoder control unit may be configured to control one or more units of encoder 200 as shown in FIG. 2. The encoder control unit may control the one or more units of encoder 200 such that bitstream 204 may be generated in conformance with the requirements of one or more proprietary coding protocols, industry video coding standards, and / or any other video cording protocol. For example, the encoder control unit may control the one or more units of encoder 200 such that bitstream 204 may be generated in conformance with one or more of ITU-T H.263, AVC, HEVC, WC, VP8, VP9, AV1, and / or any other video coding standard / format.

[0081] The encoder control unit may be configured to attempt to minimize (or reduce) the bitrate of bitstream 204 and / or maximize (or increase) the reconstructed video quality (e.g ., within the constraints of a proprietary coding protocol, industry video coding standard, and / or any other video cording protocol) For example, the encoder control unit may be configured to attempt to minimize or reduce the bitrate of bitstream 204 such that the reconstructed video quality does not fall below a certain level / threshold, and / or to maximize or increase the reconstructed video quality such that the bitrate of bitstream 204 does not exceed a certain level / threshold. The encoder control unit may determine / control one or more of: partitioning of the pictures of video sequence 202 into blocks, whether a block is inter predicted by inter prediction unit 206 or intra predicted by intra prediction unit 208, a motion vector for inter prediction of a block, an intra prediction mode among a plurality of intra prediction modes for intra prediction of a block, filtering performed by filter(s) 220, and / or one or more transform types and / or quantization parameters applied by transform and quantization unit 214. The encoder control unit may determine / control one or more of the above based on a rate-distortion measure for a block or picture being encoded The encoder control unit may determine / control one or more of the above to reduce the rate-distortion measure for a block or picture being encoded.

[0082] The prediction type used to encode a block (intra or inter prediction), prediction information of the block (intra prediction mode if intra predicted, motion vector, etc.), and / or transform and / or quantization parameters, may be sent to entropy coding unit 218 to be further compressed (e.g., to reduce the bitrate). For example, entropy coding unit 218 may apply context adaptive variable length coding (CAVLC), context adaptive binary arithmetic coding (CABAC),Docket No.: 24-2041PCT syntax-based context-based binary arithmetic coding (SBAC), and / or symbol-to-symbol adaptive multi-symbol (nonbinary) arithmetic coding to achieve further compression. The prediction type, prediction information, and / or transform and / or quantization parameters may be packed with the prediction error to form bitstream 204.

[0083] Encoder 200 is merely an example and encoders different from encoder 200 and / or modified versions of encoder 200 may perform the methods and processes as described herein. For example, encoder 200 may comprise other components and / or arrangements. One or more of the components shown in FIG. 2 may be optionally included in encoder 200 (e.g., entropy coding unit 218 and / or filters(s) 220).

[0084] FIG. 3 shows an example decoder. A decoder 300 as shown in FIG. 3 may implement one or more processes described herein. Decoder 300 may decode a bitstream 302 into a decoded video sequence 304 for display and / or some other form of consumption. Decoder 300 may be implemented in video coding / decoding system 100 in FIG. 1 and / or in a computing, communication, or electronic device (e.g., desktop computer, laptop computer, tablet computer, smart phone, wearable device, television, camera, video gaming console, set-top box, and / or video streaming device). Decoder 300 may comprise an entropy decoding unit 306, an inverse transform and quantization (iTR + iQ) unit 308, a combiner 310, one or more filters 312, a buffer 314, an inter prediction unit 316, and / or an intra prediction unit 318.

[0085] Decoder 300 may comprise a decoder control unit configured to control one or more units of decoder 300. The decoder control unit may control the one or more units of decoder 300 such that bitstream 302 is decoded in conformance with the requirements of one or more proprietary coding protocols, industry video coding standards, and / or any other communication protocol. For example, the decoder control unit may control the one or more units of decoder 300 such that the bitstream 302 is decoded in conformance with one or more of ITU-T H.263, AVC, HEVC, WC, VP8, VP9, AV1, and / or any other video coding standard / format.

[0086] The decoder control unit may determine / control one or more of: whether a block is inter predicted by inter prediction unit 316 or intra predicted by intra prediction unit 318, a motion vector for inter prediction of a block, an intra prediction mode among a plurality of intra prediction modes for intra prediction of a block, filtering performed by filter(s) 312, and / or one or more inverse transform types and / or inverse quantization parameters to be applied by inverse transform and quantization unit 308. One or more of the control parameters used by the decoder control unit may be packed in bitstream 302.

[0087] Entropy decoding unit 306 may entropy decode the bitstream 302. For example, entropy decoding unit 306 may apply context adaptive variable length coding (CAVLC), context adaptive binary arithmetic coding (CABAC), and syntax-based context-based binary arithmetic coding (SBAC) to decompress the prediction type used to encode a block (intra or inter prediction), prediction information of the block (intra prediction mode if intra predicted, motion vector, etc.), and transform and quantization parameters. Inverse transform and quantization unit 308 may inverse quantize and / or inverse transform the quantized transform coefficients to determine a decoded prediction error. Combiner 310 may combine the decoded prediction error with a prediction block to form a decoded block The prediction block may be generated by intra prediction unit 318 or inter prediction unit 316 (e.g., as described aboveDocket No.: 24-2041PCT with respect to encoder 200 in FIG 2). Filter(s) 312 may filter the decoded block, for example, using a deblocking filter, a sample-adaptive offset (SAG) filter, constrained directional enhancement filters (CDEFs), and / or loop restoration (LR) filters. Buffer 314 may store the decoded block for prediction of one or more other blocks in the same and / or different picture of the video sequence in bitstream 302. Decoded video sequence 304 may be output from filter(s) 312 as shown in FIG. 3.

[0088] Decoder 300 is merely an example and decoders different from decoder 300 and / or modified versions of decoder 300 may perform the methods and processes as described herein. For example, decoder 300 may have other components and / or arrangements. One or more of the components shown in FIG. 3 may be optionally included in decoder 300 (e.g., entropy decoding unit 306 and / or filters(s) 312).

[0089] Although not shown in FIGS. 2 and 3, each of encoder 200 and decoder 300 may further comprise an intra block copy unit in addition to inter prediction and intra prediction units The intra block copy unit may perform / operate similar to an inter prediction unit but may predict blocks within the same picture. For example, the intra block copy unit may exploit repeated patterns that appear in screen content. The screen content may include computer generated text, graphics, animation, etc.

[0090] Video encoding and / or decoding may be performed on a block-by-block basis. The process of partitioning a picture into blocks may be adaptive based on the content of the picture. For example, larger block partitions may be used in areas of a picture with higher levels of homogeneity to improve coding efficiency.

[0091] A picture (e.g., in HEVC, or any other coding standard / format) may be partitioned into non-overlapping square blocks, which may be referred to as coding tree blocks (CTBs). The CTBs may comprise samples of a sample array. A CTB may have a size of 2nx2n samples, where n may be specified by a parameter of the encoding system. For example, n may be 4, 5, 6, or any other value. A CTB may have any other size. A CTB may be further partitioned by a recursive quadtree partitioning into coding blocks (CBs) of half vertical and half horizontal size. The CTB may form the root of the quadtree. A CB that is not split further as part of the recursive quadtree partitioning may be referred to as a leaf CB of the quadtree, and otherwise may be referred to as a non-leaf CB of the quadtree. A CB may have a minimum size specified by a parameter of the encoding system. For example, a CB may have a minimum size of 4x4, 8x8, 16x16, 32x32, 64x64 samples, or any other minimum size. A CB may be further partitioned into one or more prediction blocks (PBs) for performing inter and / or intra prediction. A PB may be a rectangular block of samples on which the same prediction type / mode may be applied. A CB may also be further partitioned into intra subpartitions (ISP) where the reconstructed samples of each sub-partition are available to generate the prediction of the next sub-partition. For example, a CB may be split into 2 to 4 sub-partitions. For transformations, a CB may be partitioned into one or more transform blocks (TBs). A TB may be a rectangular block of samples that may determine / indicate an applied transform size.

[0092] FIG. 4 shows an example quadtree partitioning of a CTB 400. FIG. 5 shows an example quadtree 500 corresponding to the example quadtree partitioning of CTB 400 in FIG. 4. As shown in the examples of FIGS. 4 and 5, CTB 400 may first be partitioned into four CBs of half vertical and half horizontal size. Three of the resulting CBs ofDocket No.: 24-2041PCT the first level partitioning of CTB 400 are leaf CBs. The three leaf CBs of the first level partitioning of CTB 400 are respectively labeled 7, 8, and 9 in FIGS. 4 and 5. The non-leaf CB of the first level partitioning of CTB 400 is partitioned into four sub-CBs of half vertical and half horizontal size. Three of the resulting sub-CBs of the second level partitioning of CTB 400 are leaf CBs. The three leaf CBs of the second level partitioning of CTB 400 are respectively labeled 0, 5, and 6 in FIGS. 4 and 5. Finally, The non-leaf CB of the second level partitioning of CTB 400 is partitioned into four leaf CBs of half vertical and half horizontal size. The four leaf CBs are respectively labeled 1 , 2, 3, and 4 in FIGS. 4 and 5.

[0093] The example CTB 400 of FIG. 4 is partitioned into 10 leaf CBs respectively labeled 0-9, but maybe partitioned into other quantities of leaf CBs. The 10 leaf CBs may correspond to 10 CB leaf nodes (e.g ., 10 CB leaf nodes of quadtree 500 as shown in FIG. 5). In other examples, a CTB may be partitioned into a different number of leaf CBs. The resulting quadtree partitioning of CTB 400 may be scanned using a z-scan (e.g., left-to-right, top-to- bottom) to form the sequence order for encoding / decoding the CB leaf nodes. A numeric label (e.g., indicator, index) of each CB leaf node in FIGS. 4 and 5 may correspond to the sequence order for encoding / decoding. For example, CB leaf node 0 may be encoded / decoded first and CB leaf node 9 may be encoded / decoded last. Although not shown in FIGS. 4 and 5, each CB leaf node may comprise one or more PBs and / or TBs.

[0094] A picture, in WC (or in any other coding standard / format), may be partitioned in a similar manner (such as in HEVC). A picture may be first partitioned into non-overlapping square CTBs. The CTBs may then be partitioned, using a recursive quadtree partitioning, into CBs of half vertical and half horizontal size. A quadtree leaf node (e.g., in WC) may be further partitioned by a binary tree or ternary tree partitioning (or any other partitioning) into CBs of unequal sizes.

[0095] FIG. 6 shows example binary tree and ternary tree partitions. A binary tree partition may divide a parent block in half in either a vertical direction 602 or a horizontal direction 604. The resulting partitions may be half in size as compared to the parent block. In other examples, the resulting partitions may correspond to sizes that are less than and / or greater than half of the parent block size. A ternary tree partition may divide a parent block into three parts in either a vertical direction 606 or a horizontal direction 608. FIG. 6 shows an example in which the middle partition may be twice as large as the other two end partitions in the ternary tree partitions. In other examples, partitions may be of other sizes relative to each other and to the parent block. Binary and ternary tree partitions are examples of multi-type tree partitioning. Multi-type tree partitions may comprise partitioning a parent block into other quantities of smaller blocks. The block partitioning strategy (e.g., in WC) may be referred to as a combination of quadtree and multi-type tree partitioning (quadtree + multi-type tree partitioning) because of the addition of binary and / or ternary tree partitioning to quadtree partitioning.

[0096] FIG. 7A shows an example of combined quadtree and multi-type tree partitioning of a CTB 700A. FIG. 7B shows an example tree 700B corresponding to the combined quadtree and multi-type tree partitioning of CTB 700A shown in FIG. 7A. In both FIGS. 7A and 7B, quadtree splits are shown in solid lines and multi-type tree splits are shown in dashed lines. For ease of explanation, CTB 700A is shown with the same quadtree partitioning as the CTBDocket No.: 24-2041PCT400 described in FIG. 4, and a description of the quadtree partitioning of CTB 700A, which is similar to that for CTB 400, is omitted. The quadtree partitioning of the CTB 700A is merely an example and a CTB may be quadtree partitioned in a manner different from the CTB 700A. Additional multi-type tree partitions of CTB 700A may be made relative to three leaf CBs shown in FIG. 4. The three leaf CBs in FIG. 4 that are shown in FIG. 7A as being further partitioned may be leaf CBs 5, 8, and 9. The three leaf CBs may be further partitioned using one or more binary and / or ternary tree partitions.

[0097] The leaf CB 5 of FIG. 4 may be partitioned into two CBs based on a vertical binary tree partitioning. The two resulting CBs may be leaf CBs respectively labeled 5 and 6 in FIGS. 7A and 7B. The leaf CB 8 of FIG. 4 may be partitioned into three CBs based on a vertical ternary tree partition. Two of the three resulting CBs may be leaf CBs respectively labeled 9 and 14 in FIGS. 7A and 7B. The remaining, non-leaf CB may be partitioned first into two CBs based on a horizontal binary tree partition. One of the two CBs maybe a leaf CB labeled 10. The other of the two CBs may be further partitioned into three CBs based on a vertical ternary tree partition. The resulting three CBs may be leaf CBs respectively labeled 11, 12, and 13 in FIGS. 7A and 7B. The leaf CB 9 of FIG. 4 may be partitioned into three CBs based on a horizontal ternary tree partition. Two of the three CBs may be leaf CBs respectively labeled 15 and 19 in FIGS. 7Aand 7B. The remaining, non-leaf CB may be partitioned into three CBs based on another horizontal ternary tree partition. The resulting three CBs may all be leaf CBs respectively labeled 16, 17, and 18 in FIGS. 7A and 7B.

[0098] Altogether, CTB 700A may be partitioned into 20 leaf CBs respectively labeled 0-19. The 20 leaf CBs may correspond to 20 leaf nodes (e.g., 20 leaf nodes of tree 700B shown in FIG. 7B). The resulting combination of quadtree and multi-type tree partitioning of the CTB 700A maybe scanned using a z-scan (left-to-right, top-to-bottom) to form the sequence order for encoding / decoding the CB leaf nodes. A numeric label of each CB leaf node in FIGS. 7A and 7B may correspond to the sequence order for encoding / decoding, with CB leaf node 0 encoded / decoded first and CB leaf node 19 encoded / decoded last. Although not shown in FIGS. 7A and 7B, it should be noted that each CB leaf node may comprise one or more PBs and / or TBs.

[0099] A coding standard / format (e.g., HEVC, VVC, or any other coding standard / format) may define various units (e.g., in addition to specifying various blocks (e.g., CTBs, CBs, PBs, TBs)). Blocks may comprise a rectangular area of samples in a sample array. Units may comprise the collocated blocks of samples from the different sample arrays (e.g., luma and chroma sample arrays) that form a picture as well as syntax elements and prediction data of the blocks. A coding tree unit (CTU) may comprise the collocated CTBs of the different sample arrays and may form a complete entity in an encoded bitstream. A coding unit (CU) may comprise the collocated CBs of the different sample arrays and syntax structures used to code the samples of the CBs. A prediction unit (PU) may comprise the collocated PBs of the different sample arrays and syntax elements used to predict the PBs. A transform unit (TU) may comprise TBs of the different samples arrays and syntax elements used to transform the TBs.

[0100] In some implementations of partitioning (e.g., AV1), a picture can be partitioned into multiple coding blocks. The largest coding blocks are also referred to as superblocks having sizes of either 128x128 or 64x64. SuperblocksDocket No.: 24-2041PCT can be partitioned into smaller coding blocks which can be performed in nine partitioning modes. FIG. 8 shows the nine partitioning modes among which only PARTITION_SPLIT allows recursive partitioning. In addition, PARTITION_VERT_4 and PARTITION_HORZ_4 modes are notallowed for 8x8 or 128x128 coding blocks, and T- shaped partitioning modes are not allowed for 8x8 coding blocks. The minimum coding block size is 4x4. Intra and inter coding blocks can be further partitioned into transform blocks and the partitioning depth is up to two levels.

[0101] A block may refer to any of a CTB, CB, PB, TB, CTU, CU, PU, and / or TU (e.g. , in the context of HEVC, VVC, or any other coding format / standard) . A block may be used to refer to similar data structures in the context of any video coding format / standard / protocol. For example, a block may refer to a macroblock in the AVC standard, a macroblock or a sub-block in the VP8 coding format, a superblock or a sub-block in the VP9 coding format, and / or a superblock or a sub-block (coding block or transform block) in the AV1 coding format.

[0102] In intra prediction, samples of a block to be encoded (e.g., also referred to as a current block) may be predicted from samples in a line of samples immediately adjacent to the current block. For example, the line of samplel s may include samples of the column immediately adjacent to the left-most column of the current block and samples of the row immediately adjacent to the top-most row of the current block. The samples from the immediately adjacent column and row may be jointly referred to as reference samples. Each sample of the current block may be predicted (e.g., in an intra prediction mode) by projecting the position of the sample in the current block in a given direction to a point along the reference samples. The sample may be predicted by interpolating between the two closest reference samples of the projection point if the projection does not fall directly on a reference sample. A prediction error (e.g., referred to as a residual) may be determined for the current block based on differences between the predicted sample values and the original sample values of the current block.

[0103] Predicting samples and determining a prediction error based on a difference between the predicted samples and original samples may be performed (e.g., at an encoder) for a plurality of different intra prediction modes (e.g., including non-directional intra prediction modes). The encoder may select one of the plurality of intra prediction modes and its corresponding prediction error to encode the current block. The encoder may send an indication of the selected prediction mode and its corresponding prediction error to a decoder for decoding of the current block. The decoder may decode the current block by predicting the samples of the current block, using the intra prediction mode indicated by the encoder, and / or combining the predicted samples with the prediction error.

[0104] FIG. 9 shows an example set of reference samples 902 determined for intra prediction of a current block 904. Current block 904 may correspond to a block being encoded and / or decoded. Current block 904 may correspond to block 3 of partitioned CTB 700 as shown in FIG. 7A. As described herein, the numeric labels 0-19 of the blocks of partitioned CTB 700A may correspond to the sequence order for encoding / decoding the blocks and may be used as such in the example of FIG. 9.

[0105] In some embodiments, reference samples 902 may include a line of samples immediately adjacent to current block 904 and include samples from a column and a row immediately adjacent to current block 904. For example, the line of samples may include reference samples to the left and / or above current block 904. In someDocket No.: 24-2041PCT embodiments, reference samples 902 may be obtained (or selected) from a reference line of multiple reference lines (MRL), which may include a line of samples adjacent to current block 904 and also a line of non-adjacent samples. The MRL may include reference lines identified by corresponding reference line indices that indicate an i-th line of samples adjacent to current block 904 such that the O-th line indicates the reference line immediate adjacent (or closest) to current block 904 and a higher numbered i-th line indicates a line of samples further away from current block 904. An encoder may select a reference line from a set of MRL and signal an MLR index in the bitstream to indicate the selected reference line. For example, the encoder may signal a codeword encoding the MRL index. The decoder may decode the codeword to determine the MRL index that identifies a specific reference line used in intra prediction of current block 904.

[0106] For current block 904 that is w x h samples in size, reference samples 902 may comprise: 2w samples (or any other quantity of samples) of an i-th row (e.g., indicated by an MRL index) adjacent to the top-most row of current block 904, 2h samples (or any other quantity of samples) of the i-th column adjacent to the left-most column of current block 904, and the top left neighboring corner sample(s) extending from the i-th column and i-th row with respect to current block 904. Current block 904 may be square, such that w = h = s. In other examples, a current block need not be square, such that w t h. Available samples from neighboring blocks of current block 904 may be used for constructing the set of reference samples 902. Samples may not be available for constructing the set of reference samples 902, for example, if the samples lie outside the picture of the current block, the samples are part of a different slice of the current block (e.g., if the concept of slices is used), and / or the samples belong to blocks that have been inter coded and constrained intra prediction is indicated. Intra prediction may not be dependent on inter predicted blocks, for example, if constrained intra prediction is indicated

[0107] Samples that may not be available for constructing the set of reference samples 902 may comprise samples in blocks that have not already been encoded and reconstructed at an encoder and / or decoded at a decoder based on the sequence order for encoding / decoding. Restriction of such samples from inclusion in the set of reference samples 902 may allow identical prediction results to be determined at both the encoder and decoder. In the example of FIG. 9, samples from neighboring blocks 0, 1, 2, and 8 may be available to construct reference samples 902 given that these blocks are encoded and reconstructed at an encoder and decoded at a decoder prior to coding of current block 904. The samples from neighboring blocks 0, 1, 2, and 8 may be available to construct reference samples 902, for example, if there are no other issues (e.g., as mentioned above) preventing the availability of the samples from the neighboring blocks 0, 1 , 2, and 8. The portion of reference samples 902 from neighboring block 6 may not be available due to the sequence order for encoding / decoding (e.g., because the block 6 may not have already been encoded and reconstructed at the encoder and / or decoded at the decoder based on the sequence order for encoding / decoding).

[0108] In some examples, unavailable samples from reference samples 902 may be filled with one or more of the available reference samples 902. For example, an unavailable reference sample may be filled with a nearest available reference sample. The nearest available reference sample may be determined by moving in a clock-wiseDocket No.: 24-2041PCT direction through reference samples 902 from the position of the unavailable reference. The reference samples 902 may be filled with the mid-value of the dynamic range of the picture being coded, for example, if no reference samples are available.

[0109] Samples of current block 904 may be intra predicted based on reference samples 902, for example, based on (e.g., after) determination and (optionally) filtering of reference samples 902. In some examples, a filtering scheme (e.g., a filtering algorithm) may be applied to reference samples 902 to improve prediction accuracy. The filtering scheme may be one of a plurality of filter types including at least: a smoothing filter (or reference sample smoothing filter) or an interpolation filter. In some examples, if reference samples of a given block are to be filtered, only one of the plurality of filter types is selected (e.g., activated) to be applied to the reference samples. For example, if the smoothing filter is selected (e.g., activated), the interpolation filter is not selected (e.g., disabled) or vice versa.

[0110] Many encoders / decoders may support a plurality of intra prediction modes in accordance with one or more video coding standards. For example, HEVC supports 35 intra prediction modes, including a planar mode, a direct current (DC) mode, and 33 angular modes. WC supports 67 intra prediction modes, including a planar mode, a DC mode, and 65 angular modes. Planar and DC modes may be used to predict smooth and gradually changing regions of a picture. Angular modes may be used to predict directional structures in regions of a picture. Any quantity of intra prediction modes may be supported.

[0111] FIGS. 10A-B show example intra prediction modes. FIG. 10A shows 35 intra prediction modes, such as supported by HEVC. The 35 intra prediction modes may be indicated / identified by indices 0 to 34. Prediction mode 0 may correspond to planar mode. Prediction mode 1 may correspond to DC mode. Prediction modes 2-34 may correspond to angular modes. Prediction modes 2-18 may be referred to as horizontal prediction modes because the principal source of prediction is in the horizontal direction. Prediction modes 19-34 may be referred to as vertical prediction modes because the principal source of prediction is in the vertical direction.

[0112] FIG. 10B shows 67 intra prediction modes, such as supported by WC. The 67 intra prediction modes may be indicated / identified by indices 0 to 66. Prediction mode 0 may correspond to planar mode. Prediction mode 1 corresponds to DC mode. Prediction modes 2-66 may correspond to angular modes. Prediction modes 2-34 may be referred to as horizontal prediction modes because the principal source of prediction is in the horizontal direction. Prediction modes 35-66 may be referred to as vertical prediction modes because the principal source of prediction is in the vertical direction. Some of the intra prediction modes illustrated in FIG. 10B may be adaptively replaced by wide-angle directions because blocks in WC need not be squares.

[0113] In some implementations of intra prediction modes (e.g., as supported by AV1), the angular modes can be defined by specifying a set of nominal modes and a set of angle delta offsets can be defined around each of the nominal modes. For example, there may be eight nominal angular prediction modes each having a set of angle delta offsets indexed between -3 and +3 with the nominal angle located at 0. FIG. 10C shows the eight nominal modes (in solid arrows) and the set of angle delta offsets around the D67_PRED nominal angle (in dotted arrows). The prediction angle can be derived by adding the offset to the associated nominal angle. As a result, there are 56Docket No.: 24-2041PCT angular modes in AV1. Note that for small blocks, such as 4x4, 4x8, and 8x4, only nominal angular modes are applied In addition to the 56 angular modes, there are five non-angular intra-prediction modes in AV1, including DC_PRED mode (averaging samples from reconstructed neighboring blocks), SMOOTH_V AND SMOOTH_H modes (using quadratic interpolation along the vertical and horizontal directions, respectively), SMOOTH mode (averaging the quadratic interpolation results along both directions), and Paeth mode (predicting each sample from its top, left and top left reference samples). Recursive intra-prediction modes may also be used where a coding block is divided into sub-blocks and each intra-predicted sub-block can be used to intra-predict the next sub-block.

[0114] FIG. 11 shows a current block 904 and corresponding reference samples 902 from FIG. 9. To further describe how intra prediction modes are applied to determine a prediction (e.g., a prediction block) of current block 904, FIG. 11 shows current block 904 and reference samples 902, from a reference line among a set of multiple reference lines (MRL) 908-912, in a two-dimensional x, y plane, where a sample may be referenced as p [x] [y], To simplify the prediction process, reference samples 902 may be placed in two, one-dimensional arrays. The reference samples 902 belonging to a reference line I from the set of MRL 908-912, above the current block 904, maybe placed in the one-dimensional array re [x] : re / j[x] = p[~ + *][- / ], (x- 0)' (1)The reference samples 902 belonging to reference line I, to the left of current block 904, may be placed in the onedimensional array re fa [y]: refa[y] = PH]H + yL (y «)■ (2)The variable / represents how many lines away the selected reference line is from current block. For example, if reference line #0908 is selected, then / is set to 1 to indicate the reference line adjacent to current block 904. For example, if reference line #1 910 is selected, then / is set to 2. For example, if reference line #2912 is selected, then I is set to 3.

[0115] In some examples, if MRL is not activated or selected, then reference samples 902 may be from reference line #0908 that is immediately adjacent to current block 904. In this example, the variable I in Equations (1) and (2) is set to 1.

[0116] The prediction process may comprise determination of a predicted sample p [x] [y] (e.g., a predicted value) at a location [x] [y] in current block 904. For planar mode, a sample at the location [x] [y] in current block 904 may be predicted by determining / calculating the mean of two interpolated values. The first of the two interpolated values may be based on a horizontal linear interpolation at the location [x] [y] in current block 904. The second of the two interpolated values may be based on a vertical linear interpolation at location [x] [y] in current block 904. The predicted sample p [x] [y] in current block 904 may be determined / calculated as:where / i[x] [y] = (s - x - 1) ■ re fa [y] + (x + 1) ■ re fa [s] (4)Docket No.: 24-2041PCT may be the horizonal linear interpolation at the location [x] [y] in current block 904 and v[x][y] = (s - y - 1) ■ re / jfx] + (y + 1) ■ re2[s] (5) may be the vertical linear interpolation at the location [x] [y] in current block 904. s may be equal to a length of a side (e.g. , a number of samples on a side) of the current block 904.

[0117] For DC mode, a sample at a location [x] [y] in current block 904 may be predicted by the mean of the reference samples 902. The predicted sample p [x] [y ] in current block 904 may be determi ned / calculated as:

[0118] For angular modes, a sample at a location [x] [y] in current block 904 may be predicted by projecting the location [x] [y] in a direction specified by a given angular mode to a point on the horizontal or vertical line of samples comprising reference samples 902. The sample at the location [x] [y] may be predicted by interpolating between the two closest reference samples of the projection point if the projection does not fall directly on a reference sample. The direction specified by the angular mode may be given by an angle q> defined relative to the y-axis for vertical prediction modes (e.g., modes 19-34 in HEVC and modes 35-66 in VVC). The direction specified by the angular mode may be given by an angle q> defined relative to the x-axis for horizontal prediction modes (e.g., modes 2-18 in HEVC and modes 2-34 in WC).

[0119] FIG. 12 shows an example of applying an intra prediction mode (e.g., an angular mode such as vertical prediction mode 906) for prediction of a current block 904. FIG. 12 specifically shows prediction of a sample at a location [x] [y] in current block 904 for a vertical prediction mode 906. Vertical prediction mode 906 may be given by an angle q> with respect to the vertical axis. The location [x] [y] in current block 904, in vertical prediction modes, may be projected to a point (e.g., referred to as a projection point) on the horizontal line of reference samples re / j[x]. The reference samples 902 are only partially shown in FIG. 12 and shown as being from a reference line with reference line index of 0 for ease of illustration. Reference samples 902 may be from another reference line of the set of MRL, as explained in FIG. 9. As shown in FIG. 12, the projection point on the horizontal line of reference samples ref [x] may not be exactly on a reference sample. A predicted sample p [x] [y] in current block 904 may be determi ned / calculated by linearly interpolating between the two reference samples, for example, if the projection point falls at a fractional sample position between two reference samples. The predicted sample p [x] [y] may be determined / calculated as: p[x][y] = (1 - if■ refi [x -F i;+ 1] + if■ ref^x + i;+ 2], (7) i;may be the integer part of the horizontal displacement of the projection point relative to the location [x][y], i, may be determined / calculated as a function of the tangent of the angle c of the vertical prediction mode 906 as: i; = L(y + 1) - tan ^J. (8) ifmay be the fractional part of the horizontal displacement of the projection point relative to the location [x] [y] and may be determined / calculated as:Docket No.: 24-2041PCT if = ((y + 1) ■ tan <p) - L(y + 1) ■ tan ^pj, (9) where [ ■ ] is the integer floor function.

[0120] For horizontal prediction modes, a location [x][y] of a sample in current block 904 may be projected onto the vertical line of reference samples ref2[y]. A predicted sample p [x] [y]for horizontal prediction modes may be determined / calculated as: p[x][y] = (1 - if) - ref2\y + it+ 1] + if- ref2[y + it+ 2], (10) izmay be the integer part of the vertical displacement of the projection point relative to the location [x][y], i;may be determined / calculated as a function of the tangent of the angle cp of the horizontal prediction mode as: if = [(x + 1) ■ tan <pj. (11) if may be the fractional part of the vertical displacement of the projection point relative to the location [x] [y ] . ifmay be determined / calculated as: if = ((x + 1) ■ tan <p) - [(x + 1) ■ tan <pj, (12) where [ ■ ] is the integer floor function.

[0121] The interpolation functions given by Equations (7) and (10) may be implemented by an encoder and / or a decoder (e.g., encoder 200 in FIG. 2 and / or decoder 300 in FIG. 3). The interpolation functions may be implemented by finite impulse response (FIR) filters. For example, the interpolation functions may be implemented as a set of two- tap FIR filters. The coefficients of the two-tap FIR filters may be respectively given by (1 -if) and if. The predicted sample p [x] [y] , in angular intra prediction, may be calculated with some predefined level of sample accuracy (e.g., 1 / 32 sample accuracy, or accuracy defined by any other metric). For 1 / 32 sample accuracy, the set of two-tap FIR interpolation filters may comprise up to 32 different two-tap FIR interpolation filters — one for each of the 32 possible values of the fractional part of the projected displacement if. In other examples, different levels of sample accuracy may be used.

[0122] In some examples, the FIR filters may be used for predicting chroma samples and / or luma samples. For example, the two-tap interpolation FIR filter may be used for predicting chroma samples and a same and / or a different interpolation technique / filter may be used for luma samples. For example, a four-tap FIR filter may be used to determine a predicted value of a luma sample. Coefficients of the four tap FIR filter may be determined based on if(e.g., similar to the two-tap FIR filter). For 1 / 32 sample accuracy, a set of 32 different four-tap FIR filters may comprise up to 32 different four-tap FIR filters — one for each of the 32 possible values of the fractional part of the projected displacement if. In other examples, different levels of sample accuracy may be used. The set of four-tap FIR filters may be stored in a look-up table (LUT) and referenced based on if. A predicted sample p [x] [y] , for vertical prediction modes, may be determined based on the four-tap FIR filter as:3(13) p M ty] = y fT [i] ■ ref [x + ildx + i], i=ODocket No.: 24-2041PCT where fTp], = 0. . .3, may be the filter coefficients, and / dx is integer displacement. A predicted sample p [x] [y] , for horizontal prediction modes, may be determined based on the four-tap FIR filter as:

[0123] Supplementary reference samples may be determined / constructed if the location [x] [y] of a sample in current block 904 to be predicted is projected to a negative x coordinate. The location [x] [y] of a sample may be projected to a negative x coordinate, for example, if negative vertical prediction angles q> are used. The supplementary reference samples may be determined / constructed by projecting the reference samples in ref2[y] in the vertical line of reference samples 902 to the horizontal line of reference samples 902 using the negative vertical prediction angle cp. Supplementary reference samples may be similarly determined / constructed, for example, if the location [x] [y] of a sample in current block 904 to be predicted is projected to a negative y coordinate. The location [x] [y ] of a sample may be projected to a negative y coordinate, for example, if negative horizontal prediction angles tp are used. The supplementary reference samples may be determined / constructed by projecting the reference samples in ref [x] on the horizontal line of reference samples 902 to the vertical line of reference samples 902 using the negative horizontal prediction angle cp.

[0124] An encoder may determine / predict samples of a current block being encoded (e.g. , current block 904) for a plurality of intra prediction modes (e.g., using one or more of the functions described herein). For example, an encoder may determine / predict samples of a current block for each of 35 intra prediction modes in HEVC and / or 67 intra prediction modes in VVC and / or including extended intra prediction modes from WAIP for rectangular blocks. The encoder may determine, for each intra prediction mode applied, a corresponding prediction error for the current block based on a difference (e.g., sum of squared differences (SSD), sum of absolute differences (SAD), or sum of absolute transformed differences (SATD)) between the prediction samples, generated from reference samples 902 of a reference line (e.g., from a set of MRL), determined for the intra prediction mode and the original samples of the current block. The encoder may determine / select one of the intra prediction modes to encode the current block based on the determined prediction errors. For example, the encoder may determine / select one of the intra prediction modes that results in the smallest prediction error for the current block. In some examples, the encoder may determine / select the intra prediction mode and the associated reference line to encode the current block based on a rate-distortion measure (e.g., Lagrangian rate-distortion cost) determined using the prediction errors. The encoder may signal, in the bitstream to a decoder for decoding of the current block, an indication of the determined / selected intra prediction mode and an indication of the associated MRL index (which may indicate a reference line index). The encoder may also signal in the bitstream to the decoder a corresponding prediction error (e.g., residual) of the intra prediction mode.

[0125] A decoder may determine / predict samples of a current block being decoded (e.g., current block 904) for an intra prediction mode. For example, a decoder may receive an indication of a reference line (e.g., a reference line index or an MRL index associated with the reference line index) and an intra prediction mode (e.g., an angular intraDocket No.: 24-2041PCT prediction mode) from an encoder for a current block. The decoder may retrieve a set of reference samples and perform intra prediction based on the MRL index and the intra prediction mode indicated by the encoder for the current block in a similar manner (e.g. , as described above for the encoder). For example, the decoder may obtain the reference samples from a reference line indicated / identified by the decoded MRL index. In some examples, when MRL is not enabled / activated / selected, the reference line has reference line index 0 and is immediately adjacent to the current block. In these examples, no indication of MRL index is signaled.

[0126] The decoder may add predicted values of the samples (e.g., determined based on the intra prediction mode) of the current block to a residual of the current block to reconstruct the current block. In some examples, a decoder need not receive an indication of an angular intra prediction mode from an encoder for a current block. Instead, the decoder may determine an intra prediction mode through other decoder-side means (e.g., by applying templatebased intra mode derivation (TIMD) tool / technique).

[0127] While various examples herein correspond to intra prediction modes in HEVC and WC, the methods, devices, and systems as described herein may be applied to / used for other intra prediction modes (e.g., as used in other video coding standards / formats, such as VP8, VP9, AV1, etc.).

[0128] Intra prediction may exploit correlations between spatially neighboring samples in the same picture of a video sequence to perform video compression. Inter prediction is another coding tool that may be used to perform video compression. Inter prediction may exploit correlations in the time domain between blocks of samples in different pictures of a video sequence. For example, an object may be seen across multiple pictures of a video sequence. The object may move (e.g., by some translation and / or affine motion) or remain stationary across the multiple pictures. A current block of samples in a current picture being encoded may have / be associated with a corresponding block of samples in a previously decoded picture. The corresponding block of samples may accurately predict the current block of samples. The corresponding block of samples may be displaced from the current block of samples, for example, due to movement of the object, represented in both blocks, across the respective pictures of the blocks. The previously decoded picture may be a reference picture. The corresponding block of samples in the reference picture may be a reference block for motion compensated prediction. An encoder may use a block matching technique to estimate the displacement (or motion) of the object and / or to determine the reference block in the reference picture.

[0129] Similar to intra prediction, an encoder may determine a difference between a current block and a prediction for a current block. An encoder may determine a difference, for example, based on / after determining / generating a prediction for a current block (e g., using inter prediction). The difference may be a prediction error (e.g , a residual). The encoder may store and / or send (e.g., signal), in / via a bitstream, the prediction error and / or other related prediction information. The prediction error and / or other related prediction information may be used for decoding and / or other forms of consumption. A decoder may decode the current block by predicting the samples of the current block (e.g., by using the related prediction information) and combining the predicted samples with the prediction error.

[0130] FIG. 13A shows an example of inter prediction. The inter prediction may be performed for a current block 1300 in a current picture 1302 being encoded. An encoder (e.g., encoder 200 as shown in FIG. 2) may perform interDocket No.: 24-2041PCT prediction to determine and / or generate a reference block 1304 in a reference picture 1306. Reference block 1304 may be used to predict the current block 1300. Reference pictures (e.g., reference picture 1306) may be prior decoded pictures available at the encoder and / or a decoder. Availability of a prior decoded picture may depend / be based on whether the prior decoded picture is available in a decoded picture buffer, at the time, current block 1300 is being encoded and / or decoded. The encoder may search the one or more reference pictures 1306 for a block (e.g., a candidate reference block) that is similar (or substantially similar) to current block 1300. The encoder may determine the best matching block from the blocks (e.g., candidate reference blocks) tested during the searching process. The best matching block may be a reference block 1304. The encoder may determine that reference block 1304 is the best matching reference block based on one or more cost criteria. The one or more cost criteria may comprise a ratedistortion criterion (e.g., Lagrangian rate-distortion cost). The one or more cost criteria may be based on a difference (e.g., SSD, SAD, and / or SATD) between prediction samples of reference block 1304 and original samples of current block 1300.

[0131] The encoder may search for reference block 1304 within a reference region (e.g., a search range 1308). The reference region (e.g., a search range 1308) may be positioned around a collocated block (or position) 1310, of current block 1300, in reference picture 1306. Collocated block 1310 may have a same position in the reference picture 1306 as the current block 1300 in the current picture 1302. The reference region (e.g., search range 1308) may at least partially extend outside of reference picture 1306. Constant boundary extension may be used, for example, if the reference region (e.g., search range 1308) extends outside of reference picture 1306. The constant boundary extension may be used such that values of the samples in a row or a column of reference picture 1306, immediately adjacent to a portion of the reference region (e.g., search range 1308) extending outside of reference picture 1306, may be used for sample locations outside of reference picture 1306. A subset of potential positions, or all potential positions, within the reference region (e.g., search range 1308) may be searched for reference block 1304. The encoder may utilize one or more search implementations to determine and / or generate the reference block 1304. For example, the encoder may determine a set of candidate search positions based on motion information of neighboring blocks (e.g., a motion vector 1312) to the current block 1300.

[0132] One or more reference pictures maybe searched by the encoder during inter prediction to determine and / or generate the best matching reference block. The reference pictures searched by the encoder may be included in (e.g., added to) one or more reference picture lists. For example, in HEVC and WC (and / or in one or more other communication protocols), two reference picture lists may be used (e.g., a reference picture list 0 and a reference picture list 1). A reference picture list may include one or more pictures. The reference picture 1306 of reference block 1304 maybe indicated by a reference index pointing into a reference picture list comprising reference picture 1306. The reference frames can include different types of frames. For example, in some implementations (e.g., such as in AV1 ), up to seven frames can be used as reference frames and there are four types of frames, including LAST frame (a frame that was displayed in the near past), BWD frame ( a frame that will be displayed in the future), GOLDEN frame (a frame that was displayed in the distant past), and ARF frame (a frame from either the past or the future).Docket No.: 24-2041PCT

[0133] FIG. 13B shows an example motion vector. A displacement between reference block 1304 and current block 1300 maybe interpreted as an estimate of the motion between reference block 1304 and current block 1300 across their respective pictures. The displacement maybe represented by a motion vector 1312. For example, motion vector 1312 maybe indicated by a horizontal component (MVx) and a vertical component (MVy) relative to the position of current block 1300. A motion vector (e.g., motion vector 1312) may have fractional or integer resolution. A motion vector with fractional resolution may point between two samples in a reference picture to provide a better estimation of the motion of current block 1300. For example, a motion vector may have 1 / 2, 1 / 4, 1 / 8, 1 / 16, 1 / 32, or any other fractional sample resolution. Interpolation between the two samples at integer positions may be used to generate a reference block and its corresponding samples at fractional positions, for example, if a motion vector points to a noninteger sample value in the reference picture. The interpolation may be performed by a filter with two or more taps.

[0134] The encoder may determine a difference (eg., a corresponding sample-by-sample difference) between reference block 1304 and current block 1300. The encoder may determine the difference between reference block 1304 and current block 1300, for example, based on / after reference block 1304 is determined and / or generated, using inter prediction, for current block 1300. The difference may be a prediction error (e.g., a residual). The encoder may store and / or send (e.g., signal), in / via a bitstream, the prediction error and / or related motion information. The prediction error and / or the related motion information may be used for decoding (e.g., decoding current block 1300) and / or other forms of consumption. The motion information may comprise the motion vector 1312 and a reference indicator / index. The reference indicator may indicate the reference picture 1306 in a reference picture list. In other examples, the motion information may comprise an indication of motion vector 1312 and / or an indication of the reference indicator / index. The reference indicator may indicate reference picture 1306 in the reference picture list comprising reference picture 1306. A decoder may decode current block 1300 by determining and / or generating the reference block 1304, which may correspond to / form (e.g., be considered as) a prediction of the current block 1300. The decoder may determine and / or generate the reference block 1304, for example, based on the related motion information. The decoder may decode current block 1300 based on combining the prediction (e.g., a reference block) with the prediction error (e.g., a residual block).

[0135] Inter prediction, as shown in FIG. 13A, maybe performed using one reference picture 1306 as a source of a prediction for current block 1300. Inter prediction based on a prediction of a current block using a single picture may be referred to as uni-prediction or single reference inter prediction.

[0136] Inter prediction of a current block, using bi-prediction or compound prediction, may be based on two pictures (e.g., the source of prediction may be from the two pictures). Bi-prediction may be useful, for example, if a video sequence comprises fast motion, camera panning, zooming, and / or scene changes. Bi-prediction also may be useful to capture fade outs of one scene or fade outs from one scene to another, where two pictures may effectively be displayed simultaneously with different levels of intensity.

[0137] One or both of uni-prediction and bi-prediction may be avai lable / used for performing inter prediction (e.g., at an encoder and / or at a decoder). Performing a specific type of inter prediction (e.g., uni-prediction / single referenceDocket No.: 24-2041PCT prediction and / or bi-prediction / compound prediction) may depend on a slice type of current block. For example, for P slices, only uni-prediction may be available / used for performing inter prediction. For B slices, either uni-prediction or bi-prediction may be available / used for performing inter prediction. An encoder may determine and / or generate a reference block, for predicting a current block, from a reference picture list 0, for example, if the encoder is using uniprediction. An encoder may determine and / or generate a first reference block, for predicting a current block, from a reference picture list 0 and determine and / or generate a second reference block, for predicting the current block, from a reference picture list 1, for example, if the encoder is using bi-prediction.

[0138] FIG. 14 shows an example of bi-prediction / compound prediction. Two reference blocks 1402 and 1404 may be used to predict a current block 1400. For example, reference block 1402 may be in a reference picture of one of reference picture list 0 or reference picture list 1. Reference block 1404 may be in a reference picture of another one of reference picture list 0 or reference picture list 1. As shown in FIG. 14, reference block 1402 may be in a first picture that precedes (e.g., in time) a current picture of current block 1400, and the reference block 1404 may be in a second picture that succeeds (e.g., in time) the current picture of current block 1400. The first picture may precede the current picture in terms of a picture order count (POC) or a display order. The second picture may succeed the current picture in terms of the POC or the display order. In other examples, the reference pictures may both precede or both succeed the current picture in terms of POC or the display order. A POC may be / indicate an order in which pictures are output (e.g., from a decoded picture buffer). A POC may be / indicate an order in which pictures are generally intended to be displayed. Pictures that are output may not necessarily be displayed but may undergo different processing and / or consumption (e.g., transcoding). The two reference blocks determined and / or generated using / for bi-prediction may correspond to (e.g., be comprised in) a same reference picture. The reference picture may be included in both the reference picture list 0 and the reference picture list 1, for example, if the two reference blocks correspond to the same reference picture.

[0139] A configurable weight and / or offset value may be applied to one or more inter prediction reference blocks. An encoder may enable the use of weighted prediction using a flag in a picture parameter set (PPS) or a set of parameters at a similar level. The encoder may send / signal the weight and / or offset parameters in a slice segment header for current block 1400. Different weight and / or offset parameters may be sent / signaled for luma and / or chroma components.

[0140] The encoder may determine and / or generate the reference blocks 1402 and 1404 for the current block 1400 using inter prediction. The encoder may determine a difference between current block 1400 and each of reference blocks 1402 and 1404. The differences may be prediction errors or residuals. The encoder may store and / or send / signal, in / via a bitstream, the prediction errors and / or their respective related motion information. The prediction errors and their respective related motion information may be used for decoding and / or other forms of consumption.

[0141] The motion information for reference block 1402 may comprise a motion vector 1406 and / or a reference indicator / index. The reference indicator may indicate a reference picture, of the reference block 1402, in a reference picture list. In some examples, the motion information for reference block 1402 may comprise an indication of motionDocket No.: 24-2041PCT vector 1406 and / or an indication of the reference index. The reference index may indicate the reference picture, of reference block 1402, in the reference picture list.

[0142] The motion information for reference block 1404 may comprise a motion vector 1408 and / or a reference index / indicator. The reference indicator may indicate a reference picture, of the reference block 1404, in a reference picture list. The motion information for reference block 1404 may comprise an indication of motion vector 1408 and / or an indication of the reference index. The reference index may indicate the reference picture, of the reference block 1404, in the reference picture list.

[0143] A decoder may decode current block 1400 by determining and / or generating the reference blocks 1402 and 1404. The decoder may determine and / or generate the reference blocks 1402 and 1404, for example, based on the respective related motion information for the reference blocks 1402 and 1404. The reference blocks 1402 and 1404 may correspond to / form (e.g., be considered as) the prediction (e.g., used to generate a prediction block) of the current block 1400. The decoder may decode the current block 1400 based on combining the prediction with the prediction errors.

[0144] Motion information may be predictively coded, for example, before being stored and / or sent / signaled in / via a bit stream (e.g., in HEVC, WC, and / or other video coding standards / formats / protocols). The motion information for a current block may be predictively coded based on motion information of one or more blocks neighboring the current block. The motion information of the neighboring block(s) may often correlate with the motion information of the current block because the motion of an object represented in the current block is often the same as (or similar to) the motion of objects in the neighboring block(s). Motion information prediction techniques (such as those in HEVC and WC) may comprise advanced motion vector prediction (AMVP) and / or inter prediction block merging (e.g., merge mode).

[0145] An encoder (e.g., encoder 200 as shown in FIG. 2), may code a motion vector. The encoder may code the motion vector (e.g., using AMVP) as a difference between a motion vector of a current block being coded and a motion vector predictor (MVP). An encoder may determine / select the MVP from a list of candidate MVPs. The candidate MVPs may be / correspond to previously decoded motion vectors of neighboring blocks in the current picture of the current block, and / or blocks at or near the collocated position of the current block in other reference pictures. The encoder and / or a decoder may reciprocally generate and / or determine the list of candidate MVPs.

[0146] The encoder may determine / select an MVP from the list of candidate MVPs. Then, the encoder may send / signal, in / via a bitstream, an indication of the selected MVP and / or a motion vector difference (MVD). The encoder may indicate the selected MVP in the bitstream using an index / indicator. The index may indicate the selected MVP in the list of candidate MVPs. The MVD may be determined / calculated based on a difference between the motion vector of the current block and the selected MVP. For example, for a motion vector (e.g., comprising a horizontal component (MVx) and a vertical component (MVy)) that indicates a position relative to a position of the current block being coded, the MVD may be represented by two components MVD and MVDy. MVDXand MVDymay be determined / calculated as:Docket No.: 24-2041PCTMVDX= MV, - MVP,, (15)MVDy= MVy- MVPy(16)MVDx and MVDy may respectively represent horizontal and vertical components of the MVD. MVPx and MVPy may respectively represent horizontal and vertical components of the MVP.

[0147] A decoder (e.g . , decoder 300 as shown in FIG. 3) may decode the motion vector by adding the MVD to theMVP indicated in / via the bitstream. The decoder may decode the current block by determining and / or generating the reference block. The decoder may determine and / or generate the reference block, for example, based on the decoded motion vector. The reference block may correspond to / form (e.g., be considered as) the prediction of the current block (e.g., a prediction block). The decoder may decode the current block by combining the prediction with the prediction error.

[0148] The list of candidate MVPs (e.g., in HEVC, WC, and / or one or more other communication protocols), for AMVP, may comprise two or more candidates (e.g., candidates A and B). Candidates A and B may comprise: up to two (or any other quantity of) spatial candidate MVPs determined / derived from five (or any other quantity of) spatial neighboring blocks of a current block being coded; one (or any other quantity of) temporal candidate MVP determined / derived from two (or any other quantity of) temporal, co-located blocks (e.g., if both of the two spatial candidate MVPs are not available or are identical); and / or zero motion vector candidate MVPs (e.g., if one or both of the spatial candidate MVPs or temporal candidate MVPs are not available). Other quantities of spatial candidate MVPs, spatial neighboring blocks, temporal candidate MVPs, and / or temporal, co-located blocks may be used for the list of candidate MVPs.

[0149] FIG. 15A shows example spatial candidate neighboring blocks for a current block. For example, five (or any other quantity of) spatial candidate neighboring blocks may be located relative to a current block 1500 being encoded. The five spatial candidate neighboring blocks maybe A0, A1, B0, B1, and B2. FIG. 15B shows temporal, co-located blocks for the current block. For example, two (or any other quantity of) temporal, co-located blocks may be located relative to current block 1500 being coded. The two temporal, co-located blocks may be CO and C1. The two temporal, co-located blocks may be in one or more reference pictures that may be different from the current picture of current block 1500.

[0150] An encoder (e.g., encoder 200 as shown in FIG. 2) may code a motion vector using inter prediction block merging (e.g., a merge mode). For example, the encoder (e.g., using merge mode) may reuse the same motion information of a neighboring block (e.g., one of neighboring blocks A0, A1, B0, B1, and B2) for inter prediction of a current block. For example, the encoder (e.g., using merge mode) may reuse the same motion information of a temporal, co-located block (e.g., one of temporal, co-located blocks CO and C 1 ) for inter prediction of a current block. An MVD need not be sent (e.g., indicated, signaled) for the current block because the same motion information as that of a neighboring block or a temporal, co-located block may be used for the current block (e.g., at the encoder and / or a decoder). A signaling overhead for sending / signaling the motion information of the current block may be reduced because the MVD need not be indicated for the current block. The encoder and / or the decoder mayDocket No.: 24-2041PCT reciprocally generate a candidate list of motion information from neighboring blocks or temporal, co-located blocks of the current block (e.g in a manner similar to AMVP) The encoder may determine to use (e.g., inherit) motion information, of one neighboring block or one temporal, co-located block in the candidate list, for predicting motion information of the current block being coded. The encoder may signal / send, in / via a bitstream, an indication of the determined motion information from the candidate list. For example, the encoder may signal / send an indicator / index. The index may indicate the determined motion information in the list of candidate motion information. The encoder may signal / send the index to indicate the determined motion information.

[0151] A list of candidate motion information for merge mode (e.g., in HEVC, WC, or any other coding formats / standards / protocols) may comprise: up to four (or any other quantity of) spatial merge candidates derived / determined from five (or any other quantity of) spatial neighboring blocks (e.g., as shown in FIG. 15A); one (or any other quantity of) temporal merge candidate derived from two (or any other quantity of) temporal, co-located blocks (e.g., as shown in FIG. 15B); and / or additional merge candidates comprising bi-predictive candidates and zero motion vector candidates. In some examples, the spatial neighboring blocks and the temporal, co-located blocks used for merge mode may be the same as the spatial neighboring blocks and the temporal, co-located blocks used for AMVP.

[0152] In some examples (e.g., AV1), a list of derived MV predictors may be generated by pooling the spatial and temporal MV candidates and ranking them based on weightings determined by evaluating each of the candidates. Up to four candidates may be added to the list of MV predictors, which may also be referred to as the dynamic reference list (DRL). The DRL may be used in dynamic MV prediction modes.

[0153] Inter prediction may be performed in other ways and variants than those described herein. For example, motion information prediction techniques other than AMVP and merge mode may be used. While various examples herein correspond to inter prediction modes, such as used in HEVC and WC or AV1 , the methods, devices, and systems as described herein may be applied to / used for other inter prediction modes (e.g., as used for other video coding standards / formats such as VP8, VP9, etc.). History-based motion vector prediction (HMVP), combined intra / inter prediction mode (CIIP) or compound inter-intra prediction, warped motion compensation, overlapped block motion compensation (OBMC), and / or merge mode with motion vector difference (MMVD) (e.g., as described in WC) may be performed / used and are within the scope of the present disclosure.

[0154] A block matching operation (or technique) may be applied / used (e.g., in inter prediction) to determine a reference block in a different picture than that of a current block being coded (e.g., encoded and / or decoded). A block matching operation also may be applied / used to determine a reference block in a same picture as that of a current block being coded. The reference block, in a same picture as that of the current block, as determined using block matching may often not accurately predict the current block (e.g., for camera captured videos). Prediction accuracy for screen content videos may not be similarly impacted, for example, if a reference block in the same picture as that of the current block is used for encoding. Screen content videos may comprise, for example, computer generated text, graphics, animation, etc. Screen content videos may comprise (e.g., may often comprise) repeated patternsDocket No.: 24-2041PCT(e.g., repeated patterns of text and / or graphics) within the same picture. Using a reference block (e.g. , as determined using block matching), in a same picture as that of a current block being encoded, may provide efficient compression for screen content videos.

[0155] A prediction technique may be used (e.g., in HEVC, WC, AV1, and / or any other coding standards / formats / protocols) to exploit correlation between blocks of samples within a same picture (e.g., of screen content videos). The prediction technique may be intra block copy (IBC or IntraBC) or current picture referencing (CPR). An encoder may apply / use a block matching technique (e.g., similar to inter prediction) to determine a displacement vector (e.g., a block vector (BV)). The BV may indicate a relative position of a reference block (e.g., in accordance with intra block compensated prediction), that best matches the current block, from a position of the current block. For example, the relative position of the reference block may be a relative position of a top-left corner (or any other point / sample) of the reference block. The BV may indicate a relative displacement from the current block to the reference block that best matches the current block. The encoder may determine the best matching reference block from blocks tested during a searching process (e.g., in a manner similar to that used for inter prediction). The encoder may determine that a reference block is the best matching reference block based on one or more cost criteria. The one or more cost criteria may comprise a rate-distortion criterion (e.g., Lagrangian rate-distortion cost). The one or more cost criteria may be based on, for example, one or more differences (e.g., an SSD, an SAD, an SATD, and / or a difference determined based on a hash function) between the prediction samples of the reference block and the original samples of the current block. A reference block may correspond to / comprise prior decoded blocks of samples (e.g., reconstructed samples) of the current picture. The reference block may comprise decoded blocks of samples of the current picture prior to being processed by in-loop filtering operations (e.g., deblocking, SAO filtering, CDEFs, and / or LR filters). In some examples, the reference block may be restricted to a certain area. For example, in AV1, if the top-left pixel coordinate of a superblock is (xO, yO), IntraBC prediction is available at pixel position (x, y) only if the value of the vertical coordinate y is less than yO and the value of the horizontal coordinate x is less xO + 2(y0 - y). Further, due to hardware write-back delays, the immediate reconstructed area may not be accessible by IntraBC prediction.

[0156] FIG. 16 shows an example of IBC (e.g., an IBC mode or an IntraBC mode). The example shown in FIG. 16 may correspond to screen content. The rectangular portions / sections with arrows beginning at their boundaries may be the current blocks being encoded. The rectangular portions / sections that the arrows point to may be the reference blocks for predicting the respective current blocks.

[0157] A reference block may be determined and / or generated, for a current block, using IBC. The encoder may determine a difference (e.g., a corresponding sample-by-sample difference) between the reference block and the current block. The difference may be a prediction error or residual. The encoder may store and / or send / signal, in / via a bitstream the prediction error and / or related prediction information. The prediction error and / or the related prediction information may be used for decoding and / or other forms of consumption. The prediction information may comprise a BV. The prediction information may comprise an indication of the BV. A decoder (e.g., decoder 300 as shown in FIG.Docket No.: 24-2041PCT3), may decode the current block by determining and / or generating the reference block. The decoder may determine and / or generate the current block, for example, based on the prediction information (e.g., the BV). The reference block may correspond to / form (e.g., be considered as) the prediction (e.g., a prediction block) of the current block. The decoder may decode the current block by combining the prediction (e.g., prediction block) with the prediction error (e.g., residual or residual block).

[0158] A BV may be predictively coded (e.g., in HEVC, WC, and / or any other coding standards / formats / protocols) before being stored and / or sent / sig naled in / via a bitstream. For example, the BV for a current block may be predictively coded based on a BV of one or more blocks neighboring the current block. For example, an encoder may predictively code a BV using the merge mode (e.g., in a manner similar to as described herein for inter prediction), AMVP (e.g., as described herein for inter prediction), or a technique similar to AMVP. The technique similar to AMVP may be BV prediction and difference coding (or AMVP for IBC).

[0159] An encoder (e.g., encoder 200 as shown in FIG. 2) performing BV prediction and coding may code a BV as a difference between the BV of a current block being coded and a block vector predictor (BVP). An encoder may select / determine the BVP from a list of candidate BVPs. The candidate BVPs may comprise / correspond to previously decoded BVs of neighboring blocks in the current picture of the current block. The encoder and / or a decoder may reciprocally generate or determine the list of candidate BVPs.

[0160] The encoder may send / signal, in / via a bitstream, an indication of the selected BVP and a block vector difference (BVD). The encoder may indicate the selected BVP in the bitstream using an index / indicator. The index may indicate (e.g., point to) the selected BVP in the list of candidate BVPs. The BVD may be determined / calculated based on a difference between a BV of the current block and the selected BVP For example, for a BV (e.g., represented by a horizontal component (BVx) and a vertical component (BVy)) that indicates a position relative to a position of the current block being coded, the BVD may be represented by two components BVD and BVDy. BVD^. and BVDymay be determined / calculated as:BVD = BVX- BVP,, (17)BVDy = BVy - BVPy. (18)BVDx and BVDy may respectively represent horizontal and vertical components of the BVD. BVPx and BVPy may respectively represent horizontal and vertical components of the BVP. A decoder (e.g., decoder 300 as shown in FIG. 3), may decode the BV by adding the BVD to the BVP indicated in / via the bitstream. The decoder may decode the current block by determining and / or generating the reference block. The decoder may determine and / or generate the reference block, for example, based on the decoded BV. The reference block may correspond to / form (e.g., be considered as) the prediction (e.g , a prediction block) of the current block. The decoder may decode the current block by combining the prediction (e.g., the prediction block) with the prediction error (e.g., residual or residual block).

[0161] A same BV as that of a neighboring block may be used for the current block and a BVD need not be separately signaled / sent for the current block, such as in the merge mode. A BVP (in the candidate BVPs), which mayDocket No.: 24-2041PCT correspond to a decoded BV of the neighboring block, may itself be used as a BV for the current block. Not sending the BVD may reduce the signaling overhead.

[0162] A list of candidate BVPs (e.g., in HEVC, VVC, and / or any other coding standard / format / protocol) may comprise two (or more) candidates. The candidates may comprise candidates A and B. Candidates A and B may comprise: up to two (or any other quantity of) spatial candidate BVPs determined / derived from five (or any other quantity of) spatial neighboring blocks of a current block being encoded; and / or one or more of last two (or any other quantity of) coded BVs (e.g., if spatial neighboring candidates are not available). Spatial neighboring candidates may not be available, for example, if neighboring blocks are encoded using intra prediction or inter prediction. Locations of the spatial candidate neighboring blocks, relative to a current block, being encoded using IBC may be illustrated in a manner similar to spatial candidate neighboring blocks used for coding motion vectors in inter prediction (e.g., as shown in FIG. 15A). For example, five spatial candidate neighboring blocks of a current block being coded using IBC may be respectively denoted AO, A1, BO, B1 , and B2 as shown in FIG. 15A.

[0163] The most probable mode (MPM) refers to the intra prediction mode (IPM) that is most likely to be the best mode for the current block being encoded or decoded. In current intra prediction techniques, the MPM is determined by analyzing the intra prediction modes of the neighboring CUs (e.g., also referred to as blocks) of a current block (or CU) to be coded (e.g., encoded or decoded). For example, a list of 6 MPMs (referred to as the "MPM list”) may be constructed for intra prediction. The MPM list is derived from the intra prediction modes of the neighboring CUs, and is updated as the encoder progresses through the video frame. When encoding a block, the encoder may determine if the current block is a candidate for any of the MPMs in the MPM list. If it is, the encoder then compares the prediction errors of the respective MPMs to determine which MPM from the MPM list is the best mode for the current block. If the current block is not a candidate for any of the MPMs in the MPM list, the encoder may then evaluate remaining intra prediction modes (e.g., from a total of 67 intra prediction modes which may include a planar mode, a DC mode, and 65 angular directional modes) to determine the best mode for the current block.

[0164] The use of MPMs can significantly improve the coding efficiency because the encoder does not need to explicitly signal the intra prediction mode for the current block if it is one of the MPMs. Instead, the decoder can infer the intra prediction mode for the current block from the corresponding MPM list identically generated at the decoder. Thus, signaling overhead in the bitstream may be reduced.

[0165] In some examples, three types of intra modes may be considered to construct the MPM list: default intra modes; neighboring intra modes; and derived intra modes. A unified 6 MPM list may be used for intra blocks irrespective of whether Multiple Reference Lines (MRL) and Intra Sub-Partitions (ISP) coding tools are applied. The MPM list for the current block is constructed based on intra modes of the left neighbor block (e.g., block corresponding to A1 in FIG. 15A) and the above neighbor block (e.g., block corresponding to B1 in FIG. 15A) of the current block. Suppose the mode of the left neighbor block is denoted as Left and the mode of the above neighbor block is denoted as Above, the unified MPM list may be constructed as follows: when a neighboring block is not available, its intra mode is set to planar mode by default; if both modes Left and Above are non-angular modes, thenDocket No.: 24-2041PCT the MPM list is set to include{planar, DC, V, H, V - 4, V + 4}, where "V” and “H” refer to vertical mode and horizontal mode, respectively; if one of modes Left and Above is an angular mode, and the other is non-angular, set a mode Max as the larger mode of Left and Above, and set MPM list to include {planar, Max, Max - 1 , Max + 1 , Max — 2, Max + 2}; if Left and Above are both angular and they are different, set a mode Max and a mode Min as the larger mode in Left and Above and as the smaller mode in Left and Above, respectively, and thereafter, if Max - Min is equal to 1 , then set MPM list to include {planar, Left, Above, Min - 1 , Max + 1 , Min - 2}, if Max - Min is greater than or equal to 62, then set MPM list to include {planar, Left, Above, Min + 1 , Max - 1 , Min + 2}, if Max - Min is equal to 2, set MPM list to include {planar, Left, Above, Min + 1, Min - 1, Max + 1}, or otherwise, set MPM list to include {planar, Left, Above, Min - 1 , -Min + 1 , Max - 1}; and if Left and Above are both angular and they are the same, set MPM list to include {planar, Left, Left - 1 , Left + 1 , Left - 2, Left + 2}.

[0166] The encoder may encode an MPM index in the bitstream to indicate the position of the selected intra prediction mode in the MPM list to the decoder. The encoder may represent the MPM index as a codeword and entropy encode the codeword into the bitstream. The decoder may derive the MPM list in a manner identical to the encoder, and use the MPM index obtained from the codeword decoded from bitstream to obtain the intra prediction mode from the MPM list derived at the decoder. In some instances, the first bin of codeword, representing the MPM index, is context coded using an arithmetic coder (e.g., CABAC) so as to achieve additional coding efficiencies. For example, three contexts may be used, corresponding to whether the current intra block is MRL enabled, ISP enabled, or a normal intra block.

[0167] In some examples, during the 6 MPM list generation process, pruning may be used to remove duplicated intra modes so that the MPM list includes only unique intra modes. For entropy coding of the 61 non-MPM modes (that is, the 67 modes in WC minus the 6 MPM), a truncated binary code (TBC) may be used.

[0168] In some implementations, the MPM list is extended to include 16 additional candidates, and is divided into two parts, the primary MPM (PMPM) (e.g., including 6 entries) and the secondary (SMPM) (e.g., including 16 entries). In some implementations, the first entry in the general MPM list is the planar mode. The remaining entries include the intra modes of the adjacent neighboring blocks corresponding to positions left (L), above (A), below-left (BL), aboveright (AR), and above-left (AL) (e.g., shown in FIG.15A as A1, B1, AO, BO, and B2), and decoder-side intra mode derivation (DIMD) modes which are sorted in ascending order of a cost such as, for example, SAD, SSD, SATD, etc. In some examples, up to a preconfigured / predetermined number of modes (e.g., 5) with the smallest costs are added to the MPM list. The cost for a respective MPM (e.g., an IPM corresponding to an entry in the MPM list) may be computed between the prediction of the reconstructed samples of the template of the current block and the reconstructed samples. For example, the prediction may be generated by applying the respective MPM for the template. Sorted directional modes are added into the general MPM list, and then the default modes, until the general MPM list with 22 entries is constructed. In some examples, if a CU block is vertically oriented, the order of neighboring blocks corresponds to A, L, BL, AR, AL; otherwise, it is L, A, AL, AR, BL.Docket No.: 24-2041PCT

[0169] Referring back to FIG. 16, in IBC mode applied for screen content, a reference block (RB) may be determined as a “best matching” reference block to a current block. For example, the arrows correspond to block vectors (BVs) that indicate respective displacements from respective current blocks (CBs) to respective reference blocks that best match the respective current blocks. In the examples shown in FIG. 16, the reference blocks match the respective current blocks and the calculated residuals would be small, if not zero. However, often, video content may be more efficiently encoded by considering symmetry properties. For example, it has been observed that symmetry is often present in video content, especially in text character regions and computer generated graphics in screen content video.

[0170] In some implementations, a Reconstruction-Reordered intra block copy IBC (RRIBC) mode (e.g., also referred to as I BC-Mirror Mode) is used for screen content video coding to take advantage of symmetry within video content to further improve the coding efficiency of IBC. In some examples, the RRIBC mode may be signaled based on IBC mode with an indication (or flag) indicating whether flipping is applied and if flipping is applied, further signaling an indication (or flag) indication a direction of flipping.

[0171] In some embodiments, when the RRIBC mode is indicated for encoding a current block, a residual for the current block may be calculated based on samples of a reference block (e.g., corresponding to an original reference block being encoded and decoded to form a reconstructed block) being flipped relative to the current block according to a flip direction indicated for the current block. In an example, at the encoder side, the current block (to be predicted) may be flipped before matching and residual calculation, while the reference block (used to predict the current block) may be derived without flipping. Similarly, at the decoder side, the current block (that was flipped at the encoder) may be determined based on the reference block and residual information, then flipped back to restore the original orientation of the current block before being flipped at the encoder side. In another example, instead of the current block being flipped, the reference block may be flipped instead such that the reference block is flipped to encode the current block (at the encoder) and flipped back (at the decoder) to restore the original orientation of the reference block at the encoder. As described in this specification, reference to flipping the current block may alternatively refer to flipping the reference block and not the current block such that the reference block and the current block are flipped in the direction with respect to each other.

[0172] In an example, in the RRIBC mode, the flip direction may include one of a horizontal direction (e.g., along an x-axis) or a vertical direction (e.g., along a y-axis) for RRIBC coded blocks. In an embodiment, for a current block coded in the RRIBC mode (e.g., an IBC advanced motion vector prediction (AMVP) coded block), a first indication (e.g., a first syntax flag) may indicate / signal whether to use flipping (e.g., also referred to as mirror flipping) to encode / decode the current block. Additionally, for the current block, a second indication (e.g., a second syntax flag) may indicate / signal the direction for flipping (e.g., vertical or horizontal). For IBC merge, the flip direction may be inherited from neighboring blocks, without syntax signaling. In an example, for RRIBC, flipping of a current block (or a reference block in an alternative embodiment) in a horizontal and a vertical direction can be represented in (19) and (20), respectively:Docket No.: 24-2041PCTReference^, y) = Sample(w - 1 - x,y) (19)Reference^, y) = Sample (x, h - 1 - y) (20) where w and h are the width and height of a current block, respectively. Sample(x,y) may indicate a sample value located in (x,y). Reference^, y) may indicate a corresponding reference sample value after flipping. In other words, for horizontal flipping, (19) shows that the current block is flipped in the horizontal direction by sampling from right to left. Similarly, for vertical flipping, (20) shows that the current block is flipped in the vertical direction by sampling the current block from down to up.

[0173] Considering the horizontal or vertical symmetry, the current block and the reference block are normally aligned horizontally or vertically, respectively. Therefore, in an example, based on the RRIBC mode and a flipping direction, the reference block may be determined from a reference region (including candidate reference blocks) aligned in the same flipping direction, as will be further described below. As a result, when flipping in a horizontal direction is applied / indicated, the vertical component (BVy) of the BV (indicating a displacement from the current block to the reference block) may not need to be signaled because it may be inferred to be equal to 0. Similarly, when flipping in a vertical direction is applied / indicated, the horizontal component (BVx) of the BV may not need to be signaled because it may be inferred to be equal to 0. In other words, in an example, only one component, aligned with the direction for flipping, of the BV may be encoded and signaled for the current block.

[0174] For a current block coded in IBC mode, a BV for the current block may be constrained to indicate a relative displacement from the current block to a reference block within an IBC reference region. In some examples, a BVP used to predicatively code a BV may be similarly constrained. This is because a BVP may be derived from a BV of a spatially neighboring block of the current block or a prior coded BV as explained above. Based on the BVP, a BVD may be determined as a difference between the BV and the BVP. This BVD may be encoded and transmitted along with an indication of the selected BVP in a bitstream to enable decoding of the current block, as described above.

[0175] Intra-template matching prediction (IntraTMP) is a special intra-prediction mode that selects a prediction block within a pre-determined reference region (RR) or search area from the reconstructed samples within the current frame. IntraTMP uses a pre-defined template of the current block to search for a candidate reference block of which the template best matches the template of the current block. FIG. 17 illustrates, for an example current block 1700, a reference region 1712 or search area from the reconstructed samples 1704 within which a search is performed for a candidate reference block 1706 of which the template 1708 (“candidate reference block template”) best matches the template 1702 (“current block template”) of the current block 1700. In this example the reference region is divided in four rectangular reference regions (R1, R2, R3, and R4).

[0176] By computing a cost function (e.g., SAD, SATD) between the template 1702 of the current block and the templates of several candidate reference blocks, N candidates with lower template costs (also referred to as “TMP costs” or “template matching costs”), each indicated by a corresponding block vector predictor (BVP) candidate 1710 (BVP candidate may also be referred to herein as block vector (BV) candidate), are stored in an intraTMP list and ranked by lower cost value (ascending cost). This process is performed by both encoder and decoder.Docket No.: 24-2041PCT

[0177] The residual blocks obtained as the difference between the samples of the current block 1700 and the candidate's reference blocks 1706 in the list are computed, and the reference block with the better rate-distortion performance is selected as the best IntraTMP reference block. An index indicating the position of the best BVP or BV candidate within the intraTM P list is signaled to the decoder in order to facilitate the block decoding using the IntraTMP prediction mode.

[0178] Due to the reference region having an irregular (non-rectangular) shape and to facilitate its hardware implementation, the template matching in the reference region 1712 is carried out in a set of rectangular sub-regions (R1 to R4 in the example of FIG. 17), whose dimensions are determined based on the current blocks' size and relative position inside the current CTU.

[0179] The global reference region 1712 dimensions comprising all sub-regions are determined by the SearchRange_w and SearchRangeJi parameters, which are set proportional to the current block 1700 dimension (CbWidth, CbHeight) using a multifactor parameter denoted as 'a', which controls the gain / complexity trade-off. In some implementations of IntraTMP, the multifactor parameter 'a' may be uniform and equal to 5 or may be determined by of the current block dimension.SearchRange_w = a * CbWidthSearchRangeJ = a * CbHeight

[0180] In some implementations of IntraTMP, the global RR for block dimensions 4 and 8 were extended to 64 pixels, according to the following equations:SearchRange_w = max (64, 5* CbWidth) SearchRangeJi = max (64, 5* CbHeight)

[0181] In practice, this has the effect of using a variable multifactor parameter 'a' based on the block dimensions, as shown in the following table:

[0182] FIG. 18 illustrates a current block 1800 in a current CTU 1804, and the reference region 1812 with example corresponding TMP search regions R1-R6 identified. An example reference block 1816, and reference block template 1818 and current block template 1808 are also illustrated.

[0183] In order to reduce the high computational burn of the exhaustive template matching searching in the whole RR, the searching process is split into 2 steps: a sparse search step, and a refinement search step.

[0184] The sparse search is illustrated in FIG. 19A. The sparse search in some implementations is carried out in a regular grid using a subsampling interval (e.g., 4 pixels or 3 pixels) in the horizontal and vertical directions. FIG. 19A shows an example candidate reference block 1916 in search region 4 (R4) and the corresponding reference templateDocket No.: 24-2041PCT1918. The template cost is computed for each reference block position within a search region (e.g., reference block position 1920 of reference block 1916), and the BVP candidates associated with the best (e.g., least cost) reference block are recorded in a sparse list and sorted in an ascending order based on the cost. The subsample positions are shown in the form of dark squares within the RR region, separately determined for each search region. In some implementations of IntraTMP, the size of the sparse list is set to 30.

[0185] The refinement search, the second step, is a refinement of the reference block candidates (correspondingly, BVP candidates) in the sparse list. In some implementations, the refinement is made in a window of a predetermined size (e.g., 5x5 pixels or 3x3 pixels) around the respective sparse BVP candidates using a sampling interval of 1. In other words, in addition to the sparse BVP, one or more additional BVP candidates can be generated within the refinement search window at the integer pixel positions. If the refinement window crosses into another search region, the refinement window is clipped to the region boundary to which the candidate belongs. FIG. 19B illustrates a current block 1906 and template 1908 located in a current CTU 1904 of a current frame 1900 (i.e., current picture), corresponding RR with respective search regions R1-R6, and an example BVP 1910 with its refinement search window 1912 being clipped where R5 (search region in which the BVP 1910 is located) borders R2 and R3. The 19 candidates with the lowest template costs (e.g., SAD costs) among the generated additional candidates and the sparse BVP candidates are selected to generate a "refined IntraTMP list.”

[0186] Once the encoder / decoder has constructed the refined IntraTMP list, the encoder / decoder can select among different IntraTMP sub-modes by checking the rate-distortion performance of each sub-mode. The IntraTMP submode is signaled to the decoder in combination with an index to the best candidate in the refined IntraTMP list or a cluster of candidates (e.g. the fusion mode). The IntraTMP sub-modes may be the single predictor sub-mode, the fusion sub-mode, the sub-pel precision sub-mode, and the linear filter mode sub-mode. In the single predictor submode, a single BVP candidate is selected from the refined IntraTMP list and signaled to the decoder. In the fusion sub-mode, multiple BVP candidates are blended to derive the final BV prediction block. The blending weights may be either computed from the template matching cost of each predictor or with a Wiener-filter-based weight derivation method. In the sub-pel precision sub-mode, when a single predictor is used, sub-pel precision can be used with 1 / 2- pel precision, 1 / 4-pel precision, and 3 / 4-pel precision, each with 8 possible directions. In the linear filter model submode, a linear filter can be learned between the reference and current templates and applied to the reference block. This mode can be used for a single predictor when sub-pel precision is not used and a single predictor is used.

[0187] In some implementations of IntraTMP, several types of template shapes may be used. Five types of templates have been proposed according to the current block location in the frame: top template, left template, L- shape template, an only top template type, and an only left template type.

[0188] The template type of top template may be used when only the current block's top samples are available, such as when the current block is located to the left boundary of the picture. Consequently, the TMP cost is computed using the top samples of the current and reference blocks. In some implementations, the top template is four samples in height.Docket No.: 24-2041PCT

[0189] The template type of left-template may be used when only the left samples of the current block are available, such as when the current block is located at the top boundary of the picture. Consequently, the TMP cost is computed using exclusively the left samples of both the current and the reference block. In some implementations, the left template is four samples in width.

[0190] The L-shape template type is used in the other cases (e.g., the current block is not located at the top or left boundary of the picture) where the samples surrounding the current block included in the L-shape are available. Consequently, the TMP cost is computed using the L-shape template of both the current and the reference block. In some implementations, the L-shape template is four samples in width and height.

[0191] The L-shape template introduces two more template types: the Only-Top (Only-T) and Only-Left (Only-L) templates. Therefore, in addition to the L-shape TMP cost, the TMP cost for the Only-T and Only-L templates are also computed, and the best N BV candidates are stored in different Only-T and Only-L lists.

[0192] FIG. 20 depicts an example of the top-template type. Only the top templates (e.g., template 2001 of current block and template 2000 of reference block 1816) are used for the TMP cost computation in 2003. The sparse search 2003 is computed using a sampling interval (SI) 2002 of three, and one Sparse List (sparse candidates list) 2004 is built using the best (lower cost) 30 BV candidates in some implementations. Those candidates are refined in 2006 using a 3x3 window 2005 with an SI of 1, and a Refined Candidates List 2007 is built.

[0193] For the left-template type, the same top-template type logic is applied, but the left templates (2100 and 2101) of reference and current blocks are used instead of the top templates illustrated in FIG. 21. The TMP cost calculation in search regions 2103, search intervals for sparse search 2102, sparse candidates list 2104, refinement of the sparse list 2116, refinement search windows 2105, and the refined candidates list 2107 of the Only-L process shown in FIG. 21 may be identical (except for the use of Only-L template instead of Only-T template) to 2003, 2002, 2004, 2006, 2005, and 2007, respectively, described in relation to FIG. 20.

[0194] FIG. 22 depicts an example of a current block that has available (e.g., reconstructed samples are available for) the L-shape template 2201 , and the L-shape template 2200 of the reference block is used to compute the L- shape TMP cost in all search regions, as it was described for the top-template and left-template type.

[0195] In addition to the L-shape cost, the Only-Top TMP and Only-Left TMP costs may also be computed. In some implementations, the sparse search builds three sparse lists, one sparse L-shape list with a size of 30 BV candidates, and two additional lists, the Only-T sparse list and Only-L sparse list, both with a length of 6 BV candidates.

[0196] These three sparse lists are refined by computing the respective template type cost using a window of 3x3 in some implementations. The best N BV candidates, which have obtained the lower TMP costs, are stored in three new refined lists: the refined L-shape list with a size of 19 BV candidates, the refined Only-T list with a length of 3 BV candidates and refined Only-L list with a size of 3 BV candidates. In some implementations, the final IntraTMP List has 19 candidates as the L-Shape List, but it is a combination of the BVs candidates in the L-Shape List, and the Refined Only-T and Only-L Lists.Docket No.: 24-2041PCT

[0197] In addition to the sparse BVP candidates obtained by TMP searching within the RR in IntraTMP, a set of merge BVP candidates is generated using another technique called "IntraTMP with merge candidates.” In some implementations, merge BVP candidates are a subset of the IBC merge candidates, including only the spatial candidates of the current block. In particular, the TMP merge BVP candidates may use the 5 adjacent BVs from the adjacent blocks and multiple (e.g., 20) non-adjacent BV candidates from the non-adjacent neighboring blocks encoded using an IBC or TMP mode. FIG. 23A illustrates an example of positions for identifying adjacent blocks of a block 2300 for determining block vector candidates. In this example, which is similar to the example shown in FIG.15A, a neighboring block is considered as an adjacent block (or adjacent neighboring block) of the current block 2300 if it contains one or more of the samples at positions indicated by aO, a1, bO, b2, and b2. In particular, a sample at a1 (left position) is the immediate left sample of the lower left sample of the block 2300. The sample at aO (below-left position) is one row below the sample at a1. The sample at b2 (above-left position) is at the top left of the top-left sample of the block 2300; the sample at bO (above-right position) is at the top right of the top-right sample of the block 2300; and the sample at b1 (above position) is the above sample of the top-right sample of the block 2300. FIG. 23B illustrates an example of positions for identifying non-adjacent blocks for a block in addition to the positions for identifying adjacent blocks shown in FIG. 23A. In FIG. 23B, a grid 2301 having a resolution as the size of the block 2300 is shown. The adjacent blocks are determined based on the positions represented by squares labelled with numbers 1 to 5. The non-adjacent blocks are determined based on the positions represented by squares labelled with numbers higher than 5. The numbers indicate the order of the positions being examined when determining the non- adjacent neighboring blocks. Fora position i (i > 5), a coding block containing the position / is identified as the non- adjacent neighboring block of the block 2300. Because a neighboring coding block may not have the same size as the current block 2300, one non-adjacent neighboring block may contain more than one position.

[0198] An example of the IntraTMP with merge candidates process is illustrated in FIG. 24A. In this example, a maximum of 50 BVP candidates including BVP candidates 2405 (maximum of 10) from the adjacent blocks and BVP candidates 2406 (maximum of 40) from non-adjacent blocks are obtained. In some examples, auto-relocated block vector prediction (AR-BVP), which will be discussed in more detail below, can be applied to the adjacent merge BVPs 2405 and the non-adjacent merge BVP 2406 to generate AR-BVP candidates 2409 using the BVPs in 2405 and 2406 as guiding BVs. Further, a sparse list 2404 is generated at 2403 for the current block, as described above in relation to IntraTMP. For example, the sparse list 2404 can be generated by calculating TMP costs for reference templates (e.g., L-shape reference templates) 2400 and the current block's template 2401 in search regions using a predetermined sampling interval 2402.

[0199] In some examples, a TMP BVP clustering 2700 is applied to the BVP candidates generated above, such as the adjacent merge BVP candidates 2405, the non-adjacent merge BVP candidates 2406, the sparse list 2404, and / or the AR-BVP candidates 2409. Each BVP candidate in the sparse list 2404, adjacent merge list 2405, non-adjacent merge BVP candidates 2406, and AR-BVP list 2409, is refined using a refinement window around the BVP (e.g., 3x3, 5x5, 7x7). Because the BVP candidates are not constrained, the refinement windows of two BVP candidates in theDocket No.: 24-2041PCT sparse list may overlap those of the BVP candidates in the other lists (adjacent, non-adjacent, and AR-BVP lists). The overlapping of refinement windows is inefficient because the same potential BVP candidates are evaluated several times. Moreover, the refined window overlapping reduces the diversity of these lists (adjacent, non-adjacent, and AR- BVP lists) because they include BVP candidates that may derivate similar BVP candidates. The BVPs clustering based on the refine windows overlapping, merges two BVP candidates in a new BVP candidate (e.g., selecting the BVP with less TMP cost) and determines a new refine window comprising the overlapped refine windows of each BVP candidate. As a result of the clustering, two lists are built: a sparse and merge list 3204 that includes BVP candidates from any of the lists 2404, 2405, 2406, 2409 and / or BVP candidates corresponding to enlarged refinement windows for any of the BVP candidates from the lists 2404, 2405, 2406, 2409 and a refinement window list 3206 comprising corresponding information (e.g., height and width of the refinement window or the top-left and bottom-right coordinates) of the corresponding refinement windows. It should be noted that in some embodiments, the refinement window information may be maintained in the same list as the corresponding BVP candidate information.

[0200] At 2407, the BVP candidates in list 2408 are reordered in ascendent TM cost of the BVP candidates (nonclustered BVP candidate, a new BVP candidate defined for the centroid of the clustered refinement search regions, or one of the BVP candidates whose refinement windows partially or fully overlap) and pruned to the best 30 candidates forming the updated sparse and merge list 2411. The refinement stage 2704 of BVP candidates of the updated sparse and merge list 2411 uses the refinement window list 2702 to apply the refinement search efficiently to respective BVP candidates in the updated sparse and merge list 2411 and to generate the refined list 2414. During the refinement search, similar to that described above in relation to the refinement stage of IntraTMP, for the respective refinement window of each BVP candidate in the list being considered, the candidate reference block that has the best TMP cost is determined and the BVP candidate corresponding to that candidate reference block is added to the refined list 2414.

[0201] FIG. 24B illustrates another example of IntraTMP with merge candidates process, according to some embodiments. Compared with FIG. 24A, the TMP merge clustering 2700 is performed on adjacent and non-adjacent merge BVPs to generate the merge list 2407 and refine window list 2701. While not shown in FIG. 24B, in some examples, AR-BVP candidates are also included in the TMP merge clustering process as in FIG. 24A. The sparse list 2404 is used to remove redundant merge BVP at 2419. The updated merge list 2410 is then compared with the sparse list 2404 to identify the sparse and merge list 2411. Further, the refinement window / search window is determined based on whether the BVP is a merge candidate or a sparse candidate. If the former, the refine window list 2702 is used int eh refinement process; if the latter, a search window of size 3x3 is used for refinement.

[0202] FIG. 25 depicts an example of refinement windows of 5 merge BVP candidates (BVP-M1 to BVP-M5) located outside of the regular TMP reference region, one merge BVP candidate (BVP-M6) located inside the regular TMP reference region, and one merge BVP candidate (BVP-M7) which is partially overlapping with the regular TMP reference region. FIG. 25 also shows an example of refinement windows of three sparse BVP candidates (BVP-S1 to BVP-S3) positioned within the regular TMP reference region.Docket No.: 24-2041PCT

[0203] As mentioned above, there are two IntraTMP submodes: regular IntraTMP submode and fusion IntraTMP submode. The regular IntraTMP selects only one BVP in the refined TMP list (e.g., the refined list 2414 containing 19 candidates) to derivate one prediction block for the current block. FIG. 26 depicts one example of this mode. In FIG. 26, the refined TMP list 2604 based on Only-T candidates and the refined TMP list 2605 based on Only-L candidates are combined with the refined TMP list 2600 based on L-shape candidates to generate the final TMP list 2606 which contains 19 candidates (e.g., as the refined list 2414). Each entry in the list represents one BVP candidate and includes an index 2601, a name of the candidate 2602, and the horizontal and vertical components 2603 of the BVP candidate. In the example regular IntraTMP submode shown in FIG. 26, the encoder has selected the BV at position 12 (TMP index = 12) 2607 as the BV to code the block.

[0204] The information related to the BV can be stored to allow this BV to be used for other blocks as a BV candidate. In particular, the TMP flag, the TMP index, and the BV candidate can be recorded to be available for subsequent blocks (e.g., neighboring blocks). FIG. 27 shows an example of the regular TMP mode used by a neighboring block of a current block which can be used to generate the TMP merge list 2710 for the current block. The final TMP list of the neighboring block is TMP list 2606 shown in FIG. 26 (also shown in FIG. 27). In this example, the BV (-24, -18) with the TMP index 8 is selected from the TMP list 2606 for the neighboring block to intra code the neighboring block. Because the regular TMP mode is used, the TMP flag is set to 1 and the TMP fusion flag is set to 0.

[0205] In some examples, when a merge or ARBVP list, such as list 270, is built for a current block, the information related to the TMP or IBC prediction mode used by the spatial adjacent blocks (e.g., BVP-IBCA or BVP-TMPA shown in FIG. 27) and non-adjacent blocks (e.g., BVP-IBCNA or BVP-TMPNAin FIG. 27) is retrieved. If such a neighbor block was encoded using the IBC or TMP mode, its respective BV may be used as a BV candidate in the merge list. In the example of FIG. 27, the TMP information 2714 is used to construct a merge list. The TMP BV is inserted in the last free position (B VP-TM PNAS) of the merge list, which has a total capacity of 20.

[0206] In the fusion IntraTMP submode (which may also be referred to as “IntraTMP fusion mode,” “TMP fusion mode,” or “fusion mode”), the encoder may select 5 BVs predictors from the final refined list (e.g., the final TMP list 2606). These BVs predictors may be blended to derive a final fused prediction block. In examples where the final refined list has a size of 19, three fusion groups each with 5 BV candidates are determined. FIG. 28 shows an example of 3 TMP fusion groups generated for the final TMP list 2606 shown in FIG. 26, namely, group 0 (2802), group 1 (2804), and group 2 (2806). These three groups are contiguous and are built starting from the first position in the TMP refined list 2606. If the refined list size is less than 15, some of the fusion groups may not be available, and some may have a size of less than 5 BV candidates.

[0207] In some examples, the TMP tools are signaled to the decoder as follows. If the IntraTMP tool is selected as the intra-mode for predicting the current block, the encoder signals a flag TmpFlag with value 1 ; otherwise, the encoder signals the flag T mpFlag with value 0. The flag T mpFlag may be context-encoded.Docket No.: 24-2041PCT

[0208] If the intra mode selected is the IntraTMP mode (e.g., TmpFlag = 1), further signaling is performed based on whether the TMP fusion mode is selected or not. If the TMP fusion mode is selected, a flag tmpFusionFlag can be signaled with value 1. Further, another flag is signaled to indicate the TMP fusion model used to derive the fusion weight parameters. As will be discussed below, there are two TMP fusion models that can be used to derive the fusion weight parameters: a cost-based model and a Gaussian solver model. If the TMP fusion model is the costbased model, a flag tmpFusionModel can be signaled with value 0. If the TMP fusion model is the Gaussian solver model, the flag tmpFusionModel can be signaled with value 1. Both the tmpFusionFlag and the tmpFusionModel may be context coded. Furthermore, a fusion index indicating one of the three TMP fusion groups can be signaled, for example, with one or two bins as shown in Table 1. In some examples, the first bin is context coded and the second bin is coded with equal probability (EP) via a bypass mode. In addition, a TMP LIC flag can be signaled to indicate if the local illumination compensation (LIC) mode uses the intra TMP candidates to predict the current block in the LIC mode. If so, the encoder signals tmpLicFlag = 1; otherwise, the encoder signals tmpLicFlag = 0. The flag tmpLicFlag can be context-encoded.Table 1 Fusion Index Signaling

[0209] If the TMP fusion is not selected, the tmpFusionFlag is signaled with value 0 to indicate that the regular TMP mode is used. The regular TMP index, Tmpldx with value between 0 and 18, can be signaled to indicate the BV candidate selected from the refined list (e.g., the final TMP list 2606). In this case, a tmpFImFlag flag can be signaled if the prediction block pointed to by the BV associated with the Tmpldx must be filtered using a linear model (FLM). If so, tmpFImFlag is signaled with value 1; otherwise, tmpFImFlag is signaled with value 0. If tmpFImFlag = 0, the LIC and fractional BV precision flags may be signaled.

[0210] It should be understood that the above flags and / or the values of these flags are examples and should not be construed as limiting. Other flags or other flag values may be used to signal the mode and tools used at the encoder.

[0211] FIG. 29 depicts an example of fusion prediction blocks for the TMP fusion group 2 shown in FIG. 28. In this example, three fusion BV candidates are TMP merge candidates outside the TMP search region (BVP-LS11 3201, BVP-LS123202, and BVP-T1 3204), and the other two fusion BV candidates (BVP-LS133203and BVP-T23205) are candidates derived from the TMP search region.

[0212] The positions indicated by the 5 fusion BVs include the 5 fusion prediction blocks (F-PB1 to F-PB5), which are blended to derive a final fused prediction block. The blending weights used for the fusion of the prediction blocks can be derived from the templates of the prediction blocks associated with the fusion candidates and the template ofDocket No.: 24-2041PCT the current block. FIG. 30 shows one example of the fusion of 5 TM P fusion prediction blocks (F-PB1 2906 to F-PB52910) selected from the refined TMP list 2606. Each prediction block is weighted by a fusion weight parameter (Wj), and the weighted blocks (F-WPB1 3006 to F-WPB53010) are blended to generate the fused prediction block (FPB3012) as follows:where n is the number of fusion prediction blocks (e.g., the number of blocks to be blended or fused). In the example of FIG. 30, n = 5. Fusion residual block 3013 is generated by subtracting the fused prediction block 3012 from the current block 3026.

[0213] In some examples, the fusion weight parameters (W 3011 may be derived using two models, referred to as fusion models or fusion weight models. In the first fusion model, the fusion weight parameters 3011 can be computed based on the template matching cost of each candidate prediction block, such as the SADs, according to the following:with n is the number of fusion prediction blocks. In some examples, the BV candidates are ranked according to an ascending cost order. Because the fusion weight parameters ( Wt) are inversely related to the TMP cost, the BV candidates are effectively ordered according to a decreasing order of the parameters.

[0214] In the second fusion model, the derivation of the fusion weight parameters, denoted as wn, is performed by solving a linear system obtained to determine a linear prediction equation between the template samples of the reference block and the current block template samples using a Gaussian solver method used in convolutional crosscomponent model (CCCM). For template samples of the fusion prediction block, denoted as tmpFusionn(x, y), and the samples of the current block's template, denoted as tmpCurrBlock(x, y), the linear equation is defined as follows: w0* tmpFusion0(x,y) + wt* tmpFusion1(x,y) + w2* tmpFusion2(x,y) + w3* tmpFusion3(x,y) + w4* tmpFusion4(x,y) + wN* midVai= tmpCurrBlock(x, y) where midVai is a global bias for all the samples. For samples using a bit-depth of 10-bits, midVai = 512(2b 1, b = bitdepth'). This model derives the fused prediction block from the N fusion candidates as follows:where fusedBlock represents samples of the final fused prediction block, and predBlocknrepresent the n-th of the N fusion prediction blocks. Table 2 shows an example of the fusion weight parameters wnderived for a block.Docket No.: 24-2041PCTTable 2. Fusion weight parameters wnderived for a blockAs can be seen from Table 2, in this fusion model, the fusion parameters wnare not inversely related to the TMP cost and, consequently, the wtmay not be sorted in a descending order of their absolute magnitudes. For example, w3which is ranked before w4has an absolute magnitude around 100 times smaller than that of w4. This means that the weight of the prediction block of the fourth BV candidate (index 3) is negligible compared to that of other candidates.

[0215] In some examples, if a block is encoded using the TMP fusion mode, the associated fusion information, including the fusion weight model and the fusion group used in the fusion mode, needs to be signaled. As a result, the number of bins or bits required to indicate the fusion weight model and the fusion group index is at least 2 bits and up to a maximum of 3 bits. Table 3 shows an example of the number of bins and the bin value for each group with different fusion weight models. In this example, a flag tmpFusionModelFlag is used to indicate the fusion model and a syntax tmpFusionldx is used to indicate the fusion group index. The tmpFusionModelFlag is coded in the first bin and the tmpFusionldx is coded using the second bin and, if needed, the third bin. The first two bins can be context- encoded and the third bin is coded with equal probability via a bypass mode. For instance, a “011” bin sequence can be used to indicate that the TMP fusion mode selects a cost-based fusion model and a fusion group with group index 2. FIG. 31 illustrates the signaling of TMP-related flags and details the decision flow for various TMP flags, including tmpFusion Flag , tmpFImFlag, tmpLicFlag, and tmpFracFlag. When the tmpFusion Flag is on, further parsing of tmpFusionModelFlag and tmpFusionldx is to be conducted. The extra bins / bits used to signal the fusion mode lead to a higher bitrate of the video and reduces the coding efficiency.Table 3Docket No.: 24-2041PCT

[0216] To solve this problem, the encoder and decoder can be configured to derive the TMP fusion information, or a portion thereof, based on cost metrics rather than explicitly signal or decode the information in the bitstream. For example, a cost metric of fused candidates for each fusion model and / or group can be calculated, and the fusion model and / or group with the lowest cost metric can be selected and used as the TMP fusion information. In this way, bits used to signal the TMP fusion information, or a portion thereof, can be saved and the bitrate of the encoded video can be reduced, thereby increasing the coding efficiency.

[0217] These and other features of the present disclosure are described further below.

[0218] FIG. 32 shows an example of a process for deriving the fusion group used in the TMP fusion mode for a given fusion model, according to some embodiments. In this example, three candidate fusion groups 3208-3210 (e.g., fusion groups 2802, 2804, and 2806) are evaluated. For each candidate fusion group (e.g., 3208), up to five BV candidates are used to generate a fused template (e.g., 3228) by applying the given fusion model to each group. For example, the given fusion model can be applied to the BV candidates in a group as discussed above with respect to FIG. 29 and 30 to generate the fusion weight parameters. The templates of the respective reference blocks (e.g., candidate prediction blocks) indicated by (e.g., pointed to by) the corresponding BV candidates can be combined based on the weight parameters (e.g., weighted combination) to generate the fused template for the group. This process can be repeated for other groups.

[0219] A cost metric, such as the template matching cost, can be calculated between the current template 2928 (or reconstructed template) of the current block 2926 and the fused template (e.g., 3228, 3229, 3230) for each fusion group. The fusion group with the lowest cost metric can be selected as the fusion group. The TMP fused prediction block 3212 can be generated by combining the prediction blocks (reference blocks) indicated (pointed to) by the BV candidates in the fusion group according to the fusion weight parameters. For the encoder, the TMP fusion residual block 3213 can be calculated by subtracting the TMP fused prediction block 3212 from the current block 2926. For the decoder, the TMP fusion residual block can be decoded from the bitstream and added to the TMP fused prediction block 3212 to reconstruct the current block.

[0220] In some examples, each candidate fusion group can be filtered before the corresponding fused template is generated. The filtering may remove one or more of the BV candidates in the group that have less impact on the fused template. For example, the filtering can be based on the template cost (e.g., SAD cost) associated with the BV candidates in the group. To do so, a reference cost value can be determined, and a threshold cost value can be set according to the reference cost. For instance, the reference cost can be the lowest template cost in the group and the threshold cost value can be set to p times of the reference cost, with p>1 (e.g., p=2). In this way, a BV candidate whose template cost is higher than the threshold cost value can be removed from the group. The remaining BV candidates in the group are used to determine the fused template as discussed above In the example shown in FIG. 32, TMP fusion group 1 3029 is the filtered group which has three BV candidates after the filtering. As such, theDocket No.: 24-2041PCT fusion weight 1 has three weights for the three BV candidates and is determined based on the three BV candidates in the group according to the fusion model.

[0221] FIG. 33 shows an example of a process for deriving both the fusion group and the fusion model used in the TMP fusion mode for a block, according to some embodiments. In this example, both the fusion group and the fusion model are derived based on the cost metrics. There are two possible fusion models and three candidate fusion groups. As such, two sets of fused templates are generated using two distinct fusion models, such as cost-based fusion model and Gaussian-based fusion model. Each set of fused templates includes three fused templates for the corresponding three candidate fusion groups. The fused templates can be generated in a similar way as described above with respect to FIG. 32. A cost metric (e.g template costs) can be computed between the current template 2908 (or reconstructed template) of the current block 2906 and the fused template for each candidate fusion group and fusion model combination. In the example shown in FIG. 33, there are six different combinations of fusion group and fusion model, and thus six fused templates 3328 are generated. The fused template with the lowest cost metric can be selected, and the fusion group and fusion model used to generate the selected fused template can be determined as the TMP fusion information for the block. Similar to the example shown in FIG. 32, the fused prediction block 3312 can be generated using the IntraTMP fusion mode with the determined fusion group and fusion model to encode or decode the block. In some examples, each of the candidate fusion groups may be filtered as described above before the corresponding fused template is generated.

[0222] FIG. 34 shows an example of a process for deriving the fusion model used in the TMP fusion mode for a block for a given fusion group, according to some embodiments. In this example, the fusion group is known (the fusion group 3408), and the fusion model is to be derived based on the cost metrics. The fusion group may be determined by extracting, from the bitstream, a syntax representing the fusion group index. Alternatively, or additionally, the fusion group index may be predetermined and known to both the encoder and decoder. As such, the fusion group index does not need to be signaled in the bitstream nor derived at the encoder and decoder. For example, the fusion group index can be fixed to be fusion group 0 because the BV candidates in fusion group 0 have lower costs than the BV candidates in other fusion groups. As such, the encoder and decoder only need to determine the fusion model to perform the coding using the TMP fusion mode.

[0223] In the example shown in FIG. 34, there are two possible fusion models, such as cost-based model and Gaussian-solver based model. As such, two fused templates are generated using these two fusion models for the given fusion group. The fused template for a fusion model can be generated in a similar way as described above with respect to FIG. 32. A cost metric (e.g., template costs) can be computed between the current template 2908 (or reconstructed template) of the current block 2906 and the fused templates for each fusion model. The fused template with the lowest cost metric can be selected, and the fusion model used to generate the selected fused template can be determined as the TMP fusion information for the block. Similar to the example shown in FIGS. 32 and 33, the fused prediction block 3412 can be generated using the IntraTMP fusion mode with the fusion model and the givenDocket No.: 24-2041PCT fusion group to encode or decode the block. In some examples, each of the candidate fusion groups may be filtered as described above before the corresponding fused template is generated

[0224] In the above examples, the filtered group(s) are used when determining the group index / fusion mode and when determining the fused prediction block. In other examples, the filtered groups are used when determining the group index and / or fusion mode, and the unfiltered groups are used when determining the fused prediction block. In further examples, the filtering is not used when determining the group index / fusion mode or when determining the fused prediction block.

[0225] FIG. 35A illustrates an example of signaling or decoding of TMP-related flags, according to some embodiments. In the example shown in FIG. 35A, if the TmpFlag has a value 1, which indicates that the IntraTMP tool is selected as the intra-mode for predicting the current block, the flag tmpFusion Flag is signaled or parsed to indicate whether the TMP fusion mode is selected. If the tmpFusionFlag is 0 (the fusion mode is not selected), the tmpFImFlag flag is signaled or parsed. As discussed above, the tmpFImFlag indicates whether the prediction block pointed to by the BV associated with the Tmpldx must be filtered using a linear model (FLM). If the tmpFImFlag has a value 1, no more TMP-related flags are signaled or parsed. Otherwise (tmpFImFlag has value 0), the LIC flag tmpLic Flag and the fractional BV precision flag tmpFracFlag may be signaled or parsed. The tmpLicFlag indicates if the local illumination compensation (LIC) mode uses the intra TMP candidates to predict the current block in the LIC mode. The tmpFracFlag indicates whether fractional BV precision is used or not.

[0226] If the tmpFusionFlag is 1 (the fusion mode is enabled), because the fusion information (e.g., the fusion model and fusion group) can be identically derived at the encoder and decoder, there is no need to signal the fusion model or fusion group as shown in FIG. 31. tmpLicFlag can be signaled or parsed as usual As a result, the signaling or parsing of tmpFusion Model Flag and timpFusionldx are skipped, which optimizes the signaling process and saves bits in the encoding process.

[0227] FIG. 35B illustrates another example of the signaling or decoding of TMP-related flags, according to some embodiments. In this example, the fusion group is identically derived by the encoder and decoder and the fusion model is signaled in or parse from the bitstream. As such, compared with FIG. 35A, FIG. 35B has an extra step of signaling or parsing the tmpFusion ModelFlag . This example saves the bit(s) for signaling the fusion model compared with FIG. 31.

[0228] FIG. 35C illustrates yet another example of the signaling or decoding of TMP-related flags, according to some embodiments. In this example, the fusion model is identically derived by the encoder and decoder and the fusion group index is signaled in or parsed from the bitstream. As such, compared with FIG. 35A, FIG. 35C has an extra step of signaling or parsing the tmpFusionldx. This example saves the bit(s) for signaling the fusion group index compared with FIG. 31.

[0229] FIG. 36 shows an example flowchart illustrating a process 3600 for encoding a current block using an IntraTMP fusion mode, according to some embodiments. Operations of process 3600 may be performed by an encoder, such as, for example, encoder 200 in FIG. 2.Docket No.: 24-2041PCT

[0230] At 3602, process 3600 involves deriving, based on block vector prediction (BVP) candidates for a block, a fusion model of a fusion intra-template matching prediction (IntraTMP) mode for coding the block. In some examples, deriving the fusion model is performed based on a cost metric. For example, deriving the fusion model can include generating a first fused template based on the at least one group of BVP candidates using a first fusion model, the first fused template having a first cost metric and generating a second fused template based on the at least one group of BVP candidates using a second fusion model, the second fused template having a second cost metric. The deriving can further include selecting the first fusion model as the fusion model based, at least in part, upon the first cost metric being lower than the second distortion metric.

[0231] In further examples, deriving the fusion model can include generating a plurality of fused templates using the plurality of fusion models for the at least one group of BVP candidates, each of the plurality of fused templates having a cost metric. The deriving can further include determining the fusion model of the fusion IntraTMP mode by selecting, from the plurality of fusion models, a fusion model used by a fused template that has a lower cost metric than another fused template of the plurality of fused templates. In some examples, the at least one group of BVP candidates includes a plurality of groups of BVP candidates and the encoder can determine, from the plurality of groups of BVP candidates, a group of BVP candidates from which the fused template having the lower cost metric is generated. Encoding the block may be further based on the group of BVP candidates by applying the IntraTMP mode with the derived fusion model to the group of BVP candidates.

[0232] In some examples, the cost metric can be a template matching cost determined based on the fused template and a template of the block.

[0233] At 3604, process 3600 involves generating, using the fusion model, a fused prediction block for the block. In some examples, the fused prediction block is generated based on reference blocks indicated by a group of BVP candidates. The group of BVP candidates can be selected from a list of BVP candidates of the block. For example, the list of BVP candidates of the block can include the BVP candidates in the refined TMP list (e.g., refined list 2414). In some examples, the list of BVP candidates can be used to generate a plurality of groups of BVP candidates. The group of BVP candidates can be selected from the plurality of groups based on a predetermined group index, such as group index 0. In alternative or additional examples, the group of BVP candidates cam be determined by determining a fused template for each group of the plurality of groups of BVP candidates and selecting, from the plurality of groups, one group of BVP candidates having a lower cost metric than another group as the group of BVP candidates. In this example, the cost metric is determined based on the fused template.

[0234] In some examples, determining a fused template for a group of BVP candidates can include determining fusion weights for respective BVP candidates in the group and generating the fused template as a weighted combination of templates of blocks indicated by the BVP candidates in the group based on the fusion weights. The fusion weight of a BVP candidate can be determined based on a template matching cost of a candidate prediction block indicated by the BVP candidate. For example, the fusion weight of a BVP candidate can be determined according to a Gaussian solver fusion model.Docket No.: 24-2041PCT

[0235] In some examples, a group of BVP candidates of the plurality of groups can be generated from the list of BVP candidates by selecting a set of BVP candidates from the list of BVP candidates and filtering the set of BVP candidates based on respective cost metrics associated with the set of BVP candidates. The group of BVP candidates can be determined as the filtered set of BVP candidates. In some examples, the cost metric associated with a BVP candidate is a template matching cost of the BVP candidate. Filtering the set of BVP candidates based on respective cost metrics associated with the set of BVP candidates can include, for example, determining a reference cost metric and removing, from the set of BVP candidates, BVP candidates whose respective cost metric is higher than a threshold value determined by the reference cost metric. In some examples, the reference cost metric can be the lowest cost metric among the cost metrics associated with the set of BVP candidates, and the threshold value can be determined as p times the reference cost metric with p>1.

[0236] In some examples, the fused prediction block can be generated by combining reference blocks indicated by the group of BVP candidates according to respective weights of the group of BVP candidates. In some examples, the weight of a BVP candidate used in generating the fused prediction block can be determined based on a template matching cost of a reference block indicated by the BVP candidate. In alternative or additional examples, the weight of a BVP candidate used in generating the fused prediction block can be determined according to a Gaussian solver fusion model.

[0237] At 3606, process 3600 involves encoding the block based on the fused prediction block. In some examples, the encoding includes encoding, in a bitstream, an indication that the block is coded using the fusion IntraTMP mode and the fusion model is to be derived by a decoder. In examples where deriving the fusion model is performed based on a cost metric, the indication further indicates the fusion model is to be derived by the decoder based on the decoder deriving the cost metric.

[0238] Encoding the block can further include determining a residual of the block based on the fused prediction block and encoding, in the bitstream, the residual of the block. The encoding may further include encoding, in the bitstream, a fusion group index representing the group of BVP candidates.

[0239] FIG. 37 shows another example flowchart illustrating a process 3700 for encoding a current block using an IntraTMP fusion mode, according to some embodiments. Operations of process 3600 may be performed by an encoder, such as, for example, encoder 200 in FIG. 2.

[0240] At 3702, process 3700 involves determining, based on block vector prediction (BVP) candidates for a block, a fusion group of BVP candidates used in a fusion intra-template matching prediction (IntraTMP) mode for coding the block. In some examples, determining the fusion group of BVP candidates is performed based on a cost metric. In some examples, determining the fusion group of BVP candidates includes determining a fused template for each group of BVP candidates of a plurality of BVP candidates and selecting, from the plurality of groups, a group of BVP candidates having a lower cost metric than another group as the fusion group of BVP candidates. The cost metric may be determined based on the fused template.Docket No.: 24-2041PCT

[0241] In some examples, determining a fused template for a group of BVP candidates includes determining fusion weights for respective BVP candidates in the group, and generating the fused template as a weighted combination of templates of blocks indicated by the BVP candidates in the group based on the fusion weights. The fusion weight of a BVP candidate may be determined based on a template matching cost of a candidate prediction block indicated by the BVP candidate. In alternative or additional examples, the fusion weight of a BVP candidate may be determined according to a Gaussian solver fusion model. The cost metric may be a template matching cost determined based on the fused template and a template of the block.

[0242] In some examples, the plurality of groups of BVP candidates are determined by selecting a set of BVP candidates from the BVP candidates for the block, filtering the set of BVP candidates based on respective cost metrics associated with the set of BVP candidates, and determining the filtered set of BVP candidates as a group of BVP candidates of the plurality of groups. In some examples, the cost metric associated with a BVP candidate is a template matching cost of the BVP candidate. In some examples, the filtering the set of BVP candidates based on respective cost metrics associated with the set of BVP candidates includes determining a reference cost metric and removing, from the set of BVP candidates, BVP candidates whose respective cost metric is higher than a threshold value determined by the reference cost metric. For examples, the reference cost metric can be a lowest cost metric among the cost metrics associated with the set of BVP candidates, and the threshold value is determined as p times the reference distortion metric with p>1.

[0243] At 3704, process 3700 involves generating, based on the fusion group of BVP candidates, a fused prediction block for the block. In some examples, the fused prediction block is generated by applying a determined fusion model to reference blocks indicated by the fusion group of BVP candidates. The encoding the block comprises determining a residual of the block based on the fused prediction block.

[0244] In some examples, the fusion model may be determined by generating a first fused template by applying a first fusion model to blocks indicated by the group of BVP candidates, the first fused template having a first cost metric and generating a second fused template by applying a second fusion model to blocks indicated by the group of BVP candidates, the second fused template having a second cost metric. The first fusion model can be selected as the fusion model based, at least in part, upon the first cost metric being lower than the second cost metric.

[0245] In some examples, the fused prediction block is generated by combining reference blocks indicated by the fusion group of BVP candidates according to respective weights of the fusion group of BVP candidates. The weight of a BVP candidate used in generating the fused prediction block can be determined based on a template matching cost of a reference block indicated by the BVP candidate. The weight of a BVP candidate used in generating the fused prediction block may be determined according to a Gaussian solver fusion model

[0246] At 3706, process 3700 involves encoding the block based on the fused prediction block, the encoding comprising encoding, in a bitstream, an indication that the block is coded using the IntraTMP mode and the fusion group is to be derived by a decoder. In examples where the fusion group of BVP candidates is performed based on aDocket No.: 24-2041PCT cost metric, the indication further indicates the fusion group of BVP candidates is to be derived by the decoder based on the decoder deriving the cost metric.

[0247] FIG. 38 shows yet another example flowchart illustrating a process 3800 for encoding a current block using an IntraTMP fusion mode, according to some embodiments. Operations of process 3600 may be performed by an encoder, such as, for example, encoder 200 in FIG. 2.

[0248] At 3802, process 3800 involves identifying a group of block vector prediction (BVP) candidates, used to encode the block using a fusion intra-template matching prediction (IntraTMP) mode, from a predetermined subset of a list of BVP candidates for the block. In some examples, identifying a group of BVP candidates includes selecting the predetermined subset of BVP candidates from the list of BVP candidates for the block, filtering the predetermined subset of BVP candidates based on respective cost metrics associated with the predetermined subset of BVP candidates, and determining the filtered subset of BVP candidates as the group of BVP candidates.

[0249] At 3804, process 3800 involves determining, for the group of BVP candidates, a fusion model of the fusion IntraTMP mode. Determining the fusion model may be performed according to any mechanism described above with respect to FIGS. 36-37 and other figures.

[0250] At 3806, process 3800 involves generating a fused prediction block by applying the fusion model to reference blocks indicated by the group of BVP candidates. Generating the fusion prediction block may be performed as described above with respect to FIGS. 36-37 and other figures.

[0251] At 3808, process 3800 involves encoding the block based on the fused prediction block, the encoding the block comprising encoding, in a bitstream, an indication that the block is coded using the IntraTMP mode and the predetermined group is to be derived by a decoder based on a preset parameter. In some examples, the preset parameter is one of a group index representing the predetermined group or an integer N indicating the predetermined group comprising first N BVPs of the list of BVP candidates. For example, the predetermined group index may be 0 indicating the predetermined subset of BVP candidates is group 0 of the BVP candidates.

[0252] FIG. 39 shows an example flowchart illustrating a process 3900 for decoding a current block using an IntraTMP fusion mode, according to some embodiments. Operations of process 3900 may be performed by a decoder, such as, for example, decoder 300 in FIG. 3.

[0253] At 3902, process 3900 involves obtaining, from a bitstream, an indication that a block is coded using a fusion intra-template matching prediction (IntraTMP) mode.

[0254] At 3904, process 3900 involves deriving, from a plurality of fusion models and based on cost metrics of the plurality of fusion models for at least one group of block vector prediction (BVP) candidates of the block, a fusion model of the fusion IntraTMP mode for coding the block. In some examples, deriving the fusion model of the fusion IntraTMP mode for coding the block includes generating a first fused template based on the at least one group of BVP candidates using a first fusion model, the first fused template having a first cost metric, generating a second fused template based on the at least one group of BVP candidates using a second fusion model, the second fused templateDocket No.: 24-2041PCT having a second cost metric, and selecting the first fusion model as the fusion model based, at least in part, upon the first cost metric being lower than the second distortion metric.

[0255] In some examples, deriving the fusion model of the fusion IntraTMP mode for coding the block includes generating a plurality of fused templates using the plurality of fusion models for the at least one group of BVP candidates, each of the plurality of fused templates having a cost metric, and determining the fusion model of the fusion IntraTMP mode by selecting, from the plurality of fusion models, a fusion model used by a fused template that has a lower cost metric than another fused template of the plurality of fused templates.

[0256] At 3906, process 3900 involves decoding the block based on the derived fusion model. In some examples, decoding the block includes generating a fused prediction block by applying the derived fusion model to reference blocks indicated by a group of BVP candidates of the at least one group of BVP candidates via combining the reference blocks based on respective weights of the group of BVP candidates and reconstructing the block based on the fused prediction block. Reconstructing the block is further based on a residual of the block obtained from a bitstream. The group of BVP candidates used to generate the fused prediction block of the block is determined from a list of BVP candidates of the block.

[0257] In some examples, the fused prediction block can be generated by combining reference blocks indicated by the group of BVP candidates according to respective weights of the group of BVP candidates. In some examples, the weight of a BVP candidate used in generating the fused prediction block is determined based on a template matching cost of a reference block indicated by the BVP candidate. In alternative or additional examples, the weight of a BVP candidate used in generating the fused prediction block is determined according to a Gaussian solver fusion model.

[0258] In some examples, the at least one group of BVP candidates includes a plurality of groups of BVP candidates and the process further includes determining, from the plurality of groups of BVP candidates, a group of BVP candidates from which the fused template having the lower cost metric is generated. The block may be decoded based on the group of BVP candidates.

[0259] In some examples, determining the group of BVP candidates includes obtaining, from the bitstream, a fusion group index of the group of BVP candidates, and determining the group of BVP candidates based on the fusion group index. In alternative or additional examples, determining the group of BVP candidates includes selecting, from a plurality of groups of BVP candidates, the group of BVP candidates based on a predetermined group index. For example, the predetermined group index may be 0.

[0260] In further examples, determining the group of BVP candidates includes determining, from the list of BVP candidates, a plurality of groups of BVP candidates, determining a fused template for each group, and selecting, from the plurality of groups, one group of BVP candidates having a lower cost metric than another group as the group of BVP candidates. The cost metric may be determined based on the fused template.

[0261] In some examples, determining, from the list of BVP candidates, a plurality of groups of BVP candidates includes selecting a set of BVP candidates from the list of BVP candidates, filtering the set of BVP candidates based on respective cost metrics associated with the set of BVP candidates, and determining the filtered set of BVPDocket No.: 24-2041PCT candidates as one group of BVP candidates of the plurality of groups. The cost metric associated with a BVP candidate can be a template matching cost of the BVP candidate. Filtering the set of BVP candidates based on respective cost metrics associated with the set of BVP candidates can include determining a reference cost metric, and removing, from the set of BVP candidates, BVP candidates whose respective cost metric is higher than a threshold value determined by the reference cost metric. For example, the reference cost metric can be the lowest cost metric among the cost metrics associated with the set of BVP candidates, and the threshold value is determined as p times the reference cost metric with p>1.

[0262] In some examples, determining a fused template for a group includes determining fusion weights for respective BVP candidates in the group, and generating the fused template as a weighted combination of templates of blocks indicated by the BVP candidates in the group based on the fusion weights. In some examples, the fusion weight of a BVP candidate is determined based on a template matching cost of a candidate prediction block indicated by the BVP candidate. In alternative or additional examples, the fusion weight of a BVP candidate is determined according to a Gaussian solver fusion model. The cost metric may be a template matching cost determined based on the fused template and a template of the block.

[0263] FIG. 40 shows another example flowchart illustrating a process 4000 for decoding a current block using an IntraTMP fusion mode, according to some embodiments. Operations of process 4000 may be performed by a decoder, such as, for example, decoder 300 in FIG. 3.

[0264] At 4002, process 4000 involves obtaining, from a bitstream, an indication that a block is coded using a fusion intra-template matching prediction (IntraTMP) mode.

[0265] At 4004, process 4000 involves deriving, from a plurality of groups of block vector prediction (BVP) candidates for the block and based on cost metrics of the plurality of groups for at least one fusion model of the fusion IntraTMP mode, a fusion group of BVP candidates for coding the block. In some examples, deriving the fusion group of BVP candidates includes determining a fused template for each group of BVP candidates, and selecting, from the plurality of groups, a group of BVP candidates having a lower cost metric than another group as the fusion group of BVP candidates, the cost metric determined based on the fused template.

[0266] In some examples, the plurality of groups of BVP candidates are determined by selecting a set of BVP candidates from the BVP candidates for the block, filtering the set of BVP candidates based on respective cost metrics associated with the set of BVP candidates, and determining the filtered set of BVP candidates as a group of BVP candidates of the plurality of groups. The cost metric associated with a BVP candidate may be a template matching cost of the BVP candidate. In some examples, filtering the set of BVP candidates based on respective cost metrics associated with the set of BVP candidates includes determining a reference cost metric, and removing, from the set of BVP candidates, BVP candidates whose respective cost metric is higher than a threshold value determined by the reference cost metric. For example, the reference cost metric can be the lowest cost metric among the cost metrics associated with the set of BVP candidates, and the threshold value can be determined as p times theDocket No.: 24-2041PCT reference distortion metric with p>1. The cost metric may be a template matching cost determined based on the fused template and a template of the block

[0267] In some examples, determining a fused template for each group includes determining fusion weights for respective BVP candidates in the group, and generating the fused template as a weighted combination of templates of blocks indicated by the BVP candidates in the group based on the fusion weights. In some examples, the fusion weight of a BVP candidate may be determined based on a template matching cost of a candidate prediction block indicated by the BVP candidate. In alternative or additional examples, the fusion weight of a BVP candidate is determined according to a Gaussian solver fusion model.

[0268] At 4006, process 4000 involves decoding the block based on the derived fusion group of BVP candidates. In some examples, the process further involves determining, from the at least one fusion model, a fusion model of the fusion IntraTMP mode. Decoding the block includes generating a fused prediction block based on blocks indicated by the group of BVP candidates using the fusion model, and reconstructing the block based on the fused prediction block. The process may further involves obtaining a residual of the block from a bitstream and reconstructing the block is further based on the obtained residual of the block.

[0269] In some examples, determining the fusion model includes obtaining, from the bitstream, a fusion model indication and determining the fusion model based on the fusion model indication. In further examples, determining the fusion model includes generating a first fused template by applying a first fusion model to blocks indicated by the group of BVP candidates, the first fused template having a first cost metric, generating a second fused template applying a second fusion model to blocks indicated by the group of BVP candidates, the second fused template having a second cost metric, and selecting the first fusion model as the fusion model based, at least in part, upon the first cost metric being lower than the second cost metric.

[0270] In some examples, the fused prediction block is generated by combining reference blocks indicated by the fusion group of BVP candidates according to respective weights of the fusion group of BVP candidates. In some examples, the weight of a BVP candidate used in generating the fused prediction block is determined based on a template matching cost of a reference block indicated by the BVP candidate. In alternative or additional examples, the weight of a BVP candidate used in generating the fused prediction block is determined according to a Gaussian solver fusion model.

[0271] FIG. 41 shows yet another example flowchart illustrating a process 4100 for decoding a current block using an IntraTMP fusion mode, according to some embodiments. Operations of process 4100 may be performed by a decoder, such as, for example, decoder 300 in FIG. 3.

[0272] At 4102, process 4100 involves obtaining, from a bitstream, an indication that a block is coded using a fusion intra-template matching prediction (IntraTMP) mode.

[0273] At 4104, process 4100 involves identifying a group of BVP candidates, used to generate a fused prediction block of the block, from a predetermined subset of a list of BVP candidates for the block. In some examples, identifying a group of BVP candidates includes selecting the predetermined subset of BVP candidates from the list ofDocket No.: 24-2041PCTBVP candidates for the block, filtering the predetermined subset of BVP candidates based on respective cost metrics associated with the predetermined subset of BVP candidates, and determining the filtered subset of BVP candidates as the group of BVP candidates. In some examples, the predetermined subset of the BVP candidates can include first N BVP candidates in the list, where N is a positive integer greater than 2. In some examples, the predetermined subset of BVP candidates has a predetermined group index. For instance, the predetermined group index can be 0 indicating the first group of BVP candidate is used as the predetermined subset of BVP candidates.

[0274] At 4106, process 4100 involves determining, for the group of BVP candidates for the block, a fusion model of the fusion IntraTMP mode for coding the block. In some examples, determining the fusion model can be performed as discussed above with respect to FIGS. 39-40 and other figures.

[0275] At 4108, process 4100 involves generating the fused prediction block by applying the fusing model to reference blocks indicated by the group of BVP candidates. In some examples, generating the fused prediction block can be performed as discussed above with respect to FIGS. 39-40 and other figures.

[0276] At 4110, process 4100 involves decoding the block based on the fused prediction block. Decoding the block may be performed as discussed above with respect to FIGS. 39-40 and other figures.

[0277] In the above examples, the fusion mode (including the fusion group and / or the fusion model if there are multiple fusion models) is derived at the decoder in order to the save the bits used to signal the fusion group and / or fusion model. In some cases, the actual bits used to signal the fusion mode can be saved by reordering the fusion group before signaling the group index. For example, if the fusion model is fixed, the bits used to signal the selected fusion group can be saved by reordering the fusion groups. In the example shown in FIG. 32, the fusion group 0, fusion group 1 , and fusion group 2 can be reordered according to an increasing order of their cost metrics (of the fused templates). Because the cost metrics of the fused templates of the fusion groups are close estimates of the prediction costs of the fusion groups, a fusion group with a lower cost (and thus lower index in the reordered groups) is more likely to be selected as the fusion group for the current block. As a result, the number of bits used to signal the index of the selected fusion group is smaller.

[0278] For instance, an encoder may use the SATD cost (or other cost metrics) between the predicted block and the current block as the cost metric for selecting the fusion group. Alternatively, or additionally, the encoder may employ ratio distortion optimization (RDO) algorithm to select the fusion group. In either case, the selected fusion group is likely to be the fusion group with index 0 or fusion group 1 in the reordered groups (assuming the cost metrics of the fused templates are good estimates of the prediction errors of respective fusion groups). As a result, the selected fusion group can be signaled using only one bit in most cases, thereby reducing the bitrate of the video. To identify the selected fusion group, the decoder can perform the same process of reordering the fusion groups and selecting the fusion group based on the signaled index.

[0279] FIG. 42 shows a flowchart illustrating an example of a process for encoding a current block using an IntraTMP fusion mode with fusion group reordering, according to some embodiments. Operations of process 4200 may be performed by an encoder, such as, for example, encoder 200 in FIG. 2.Docket No.: 24-2041PCT

[0280] At 4202, process 4200 involves ordering, based on cost metrics of a plurality of groups of block vector prediction (BVP) candidates, the plurality of groups for a block coded using a fusion intra-template matching prediction (IntraTMP) mode. In some examples, ordering the plurality of groups of BVP candidates for the block comprises determining a fused template for each group of the plurality of groups of BVP candidates, determining a cost metric for each group of the plurality of groups of BVP candidates based on the fused template, and ordering the plurality of groups of BVP candidates according to an ascending order of the cost metrics.

[0281] In some examples, the plurality of groups of BVP candidates are determined by selecting a set of BVP candidates from BVP candidates for the block, filtering the set of BVP candidates based on respective cost metrics associated with the set of BVP candidates, and determining the filtered set of BVP candidates as a group of BVP candidates of the plurality of groups. In some examples, the cost metric associated with a BVP candidate is a template matching cost of the BVP candidate. Filtering the set of BVP candidates based on respective cost metrics associated with the set of BVP candidates can include determining a reference cost metric, and removing, from the set of BVP candidates, BVP candidates whose respective cost metric is higher than a threshold value determined by the reference cost metric. In some examples, the reference cost metric is a lowest cost metric among the cost metrics associated with the set of BVP candidates, and the threshold value is determined as p times the reference distortion metric with p>1.

[0282] In some examples, determining a fused template for each group comprises determining fusion weights for respective BVP candidates in the group, and generating the fused template as a weighted combination of templates of blocks indicated by the BVP candidates in the group based on the fusion weights. The fusion weight of a BVP candidate may be determined based on a template matching cost of a candidate prediction block indicated by the BVP candidate. The fusion weight of a BVP candidate may also be determined according to a Gaussian solver fusion model. The cost metric fora group is a template matching cost determined based on the fused template of the group and a template of the block.

[0283] At 4204, process 4200 involves determining, from the plurality of groups, a fusion group of BVP candidates for coding the block. In some examples, determining, from the plurality of groups, a fusion group of BVP candidates is performed based on a cost metric or a rate distortion optimization algorithm.

[0284] At 4206, process 4200 involves generating, based on the fusion group of BVP candidates, a fused prediction block for the block. In some examples, the fused prediction block is generated by applying a fusion model to reference blocks indicated by the fusion group of BVP candidates. In some examples, the fused prediction block is generated by combining reference blocks indicated by the fusion group of BVP candidates according to respective weights of the fusion group of BVP candidates. The weight of a BVP candidate used in generating the fused prediction block may be determined based on a template matching cost of a reference block indicated by the BVP candidate. The weight of a BVP candidate used in generating the fused prediction block may also be determined according to a Gaussian solver fusion model.Docket No.: 24-2041PCT

[0285] At 4208, process 4200 involves encoding the block based on the fused prediction block. In some examples, encoding comprising encoding, in a bitstream, an indication that the block is coded using the IntraTMP mode and a fusion group index of the fusion group in the ordered plurality of groups. In some examples, encoding the block further comprises determining a residual of the block based on the fused prediction block and encoding, in the bitstream, the residual of the block.

[0286] FIG. 43 shows a flowchart illustrating an example of a process for decoding a current block using an IntraTMP fusion mode with fusion group reordering, according to some embodiments. Operations of process 4300 may be performed by a decoder, such as, for example, decoder 300 in FIG. 3.

[0287] At 4302, process 4300 involves obtaining, from a bitstream, an indication that a block is coded using a fusion intra-template matching prediction (IntraTMP) mode and a fusion group index.

[0288] At 4304, process 4300 involves ordering a plurality of groups of block vector prediction (BVP) candidates for the block based on cost metrics of the plurality of groups for the fusion IntraTMP mode. In some examples, ordering the plurality of groups of BVP candidates for the block comprises determining a fused template for each group of the plurality of groups of BVP candidates, determining a cost metric for each group of the plurality of groups of BVP candidates based on the fused template, and ordering the plurality of groups of BVP candidates according to an ascending order of the cost metrics.

[0289] In some examples, the plurality of groups of BVP candidates are determined by selecting a set of BVP candidates from BVP candidates for the block, filtering the set of BVP candidates based on respective cost metrics associated with the set of BVP candidates, and determining the filtered set of BVP candidates as a group of BVP candidates of the plurality of groups. In some examples, the cost metric associated with a BVP candidate is a template matching cost of the BVP candidate. Filtering the set of BVP candidates based on respective cost metrics associated with the set of BVP candidates can include determining a reference cost metric, and removing, from the set of BVP candidates, BVP candidates whose respective cost metric is higher than a threshold value determined by the reference cost metric. In some examples, the reference cost metric is a lowest cost metric among the cost metrics associated with the set of BVP candidates, and the threshold value is determined as p times the reference distortion metric with p>1.

[0290] In some examples, determining a fused template for each group comprises determining fusion weights for respective BVP candidates in the group, and generating the fused template as a weighted combination of templates of blocks indicated by the BVP candidates in the group based on the fusion weights. The fusion weight of a BVP candidate may be determined based on a template matching cost of a candidate prediction block indicated by the BVP candidate. The fusion weight of a BVP candidate may also be determined according to a Gaussian solver fusion model. The cost metric fora group is a template matching cost determined based on the fused template of the group and a template of the block.

[0291] At 4306, process 4300 involves determining, from the plurality of groups of BVP candidates and according to the fusion group index, a fusion group of BVP candidates for coding the block.Docket No.: 24-2041PCT

[0292] At 4308, process 4300 involves decoding the block based on the fusion group of BVP candidates, in some examples, decoding the block comprises generating a fused prediction block based on blocks indicated by the group of BVP candidates using a fusion model, and reconstructing the block based on the fused prediction block. In some examples, the fused prediction block is generated by applying a fusion model to reference blocks indicated by the fusion group of BVP candidates. In some examples, the fused prediction block is generated by combining reference blocks indicated by the fusion group of BVP candidates according to respective weights of the fusion group of BVP candidates. The weight of a BVP candidate used in generating the fused prediction block may be determined based on a template matching cost of a reference block indicated by the BVP candidate. The weight of a BVP candidate used in generating the fused prediction block may also be determined according to a Gaussian solver fusion model.In some examples, process 4300 further involves obtaining a residual of the block from a bitstream and reconstructing the block is further based on the obtained residual of the block.

[0293] Embodiments of the present disclosure may be implemented in hardware using analog and / or digital circuits, in software, through the execution of instructions by one or more general purpose or special-purpose processors, or as a combination of hardware and software. Consequently, embodiments of the disclosure may be implemented in the environment of a computer system or other processing system. An example of such a computer system 4400 is shown in FIG. 44. Blocks depicted in the figures above, such as the blocks in FIGS. 1, 2, and 3, may execute on one or more computer systems 4400. Furthermore, each of the steps of the flowcharts depicted in this disclosure may be implemented on one or more computer systems 4400.

[0294] Computer system 4400 includes one or more processors, such as processor 4404. Processor 4404 may be, for example, a special purpose processor, general purpose processor, microprocessor, or digital signal processor. Processor 4404 may be connected to a communication infrastructure 4402 (for example, a bus or network). Computer system 4400 may also include a main memory 4406, such as random access memory (RAM), and may also include a secondary memory 4408.

[0295] Secondary memory 4408 may include, for example, a hard disk drive 4410 and / or a removable storage drive 4412, representing a magnetic tape drive, an optical disk drive, or the like. Removable storage drive 4412 may read from and / or write to a removable storage unit 4416 in a well-known manner. Removable storage unit 4416 represents a magnetic tape, optical disk, or the like, which is read by and written to by removable storage drive 4412. As will be appreciated by persons skilled in the relevant art(s), removable storage unit 4416 includes a computer usable storage medium having stored therein computer software and / or data.

[0296] In alternative implementations, secondary memory 4408 may include other similar means for allowing computer programs or other instructions to be loaded into computer system 4400. Such means may include, for example, a removable storage unit 4418 and an interface 4414. Examples of such means may include a program cartridge and cartridge interface (such as that found in video game devices), a removable memory chip (such as an EPROM or PROM) and associated socket, a thumb drive and USB port, and other removable storage units 4418 andDocket No.: 24-2041PCT interfaces 4414 which allow software and data to be transferred from removable storage unit 4418 to computer system 4400.

[0297] Computer system 4400 may also include a communications interface 4420. Communications interface 4420 allows software and data to be transferred between computer system 4400 and external devices. Examples of communications interface 4420 may include a modem, a network interface (such as an Ethernet card), a communications port, etc. Software and data transferred via communications interface 4420 are in the form of signals which may be electronic, electromagnetic, optical, or other signals capable of being received by communications interface 4420. These signals are provided to communications interface 4420 via a communications path 4422. Communications path 4422 carries signals and may be implemented using wire or cable, fiber optics, a phone line, a cellular phone link, an RE link, and other communications channels.

[0298] As used herein, the terms "computer program medium” and “computer readable medium” are used to refer to tangible storage media, such as removable storage units 4416 and 4418 or a hard disk installed in hard disk drive 4410. These computer program products are means for providing software to computer system 4400. Computer programs (also called computer control logic) may be stored in main memory 4406 and / or secondary memory 4408. Computer programs may also be received via communications interface 4420. Such computer programs, when executed, enable the computer system 4400 to implement the present disclosure as discussed herein. In particular, the computer programs, when executed, enable processor 4404 to implement the processes of the present disclosure, such as any of the methods described herein. Accordingly, such computer programs represent controllers of the computer system 4400.

[0299] In another embodiment, features of the disclosure may be implemented in hardware using, for example, hardware components such as application-specific integrated circuits (ASICs) and gate arrays. Implementation of a hardware state machine to perform the functions described herein will also be apparent to persons skilled in the art.

Claims

Docket No.: 24-2041PCTCLAIMSWhat is claimed is:

1. A method comprising: obtaining, from a bitstream, an indication that a block is coded using a fusion intra-template matching prediction (IntraTMP) mode; deriving, from a plurality of groups of block vector prediction ( BVP) candidates for the block and based on cost metrics of the plurality of groups for at least one fusion model of the fusion IntraTMP mode, a fusion group of BVP candidates for coding the block; and decoding the block based on the derived fusion group of BVP candidates.

2. The method of claim 1 , further comprising: determining, from the at least one fusion model, a fusion model of the fusion IntraTMP mode, wherein the decoding the block comprises: generating a fused prediction block based on blocks indicated by the group of BVP candidates using the fusion model; and reconstructing the block based on the fused prediction block.

3. The method of claim 2, further comprising: obtaining a residual of the block from a bitstream, wherein reconstructing the block is further based on the obtained residual of the block.

4. The method of claim 1 , wherein the deriving, from a plurality of groups of BVP candidates for the block and based on cost metrics of the plurality of groups for at least one fusion model of the fusion IntraTMP mode, a fusion group of BVP candidates comprises: determining a fused template for each group of BVP candidates; and selecting, from the plurality of groups, a group of BVP candidates having a lower cost metric than another group as the fusion group of BVP candidates, the cost metric determined based on the fused template.

5. A method comprising: determining, based on block vector prediction (BVP) candidates for a block, a fusion group of BVP candidates used in a fusion intra-template matching prediction (IntraTMP) mode for coding the block; generating, based on the fusion group of BVP candidates, a fused prediction block for the block; and encoding the block based on the fused prediction block, the encoding comprising encoding, in a bitstream, an indication that the block is coded using the IntraTMP mode and the fusion group is to be derived by a decoder.

6. The method of claim 5, further comprising: determining a fusion model of the fusion IntraTMP mode, wherein: the fused prediction block is generated by applying the fusion model to reference blocks indicated by the fusion group of BVP candidates; andDocket No.: 24-2041PCT the encoding the block comprises determining a residual of the block based on the fused prediction block7. The method of claim 6, further comprising: encoding, in the bitstream, the residual of the block.

8. The method of any one of claims 5-7, wherein the determining a fusion group of BVP candidates is performed based on a cost metric, wherein the indication further indicates the fusion group of BVP candidates is to be derived by the decoder based on the decoder deriving the cost metric.

9. The method of any one of claims 5-8, wherein the fusion group of BVP candidates is determined from a plurality of fusion groups of BVP candidates.

10. The method of claim 9, wherein the determining the fusion group of BVP candidates from the plurality of fusion groups of BVP candidates comprises: determining a fused template for each group of BVP candidates; and selecting, from the plurality of groups, a group of BVP candidates having a lower cost metric than another group as the fusion group of BVP candidates, the cost metric determined based on the fused template.

11. The method of any one of claims 1-4 or 9-10, wherein the plurality of groups of BVP candidates are determined by: selecting a set of BVP candidates from the BVP candidates for the block; filtering the set of BVP candidates based on respective cost metrics associated with the set of BVP candidates; and determining the filtered set of BVP candidates as a group of BVP candidates of the plurality of groups.

12. The method of claim 11 , wherein the cost metric associated with a BVP candidate is a template matching cost of the BVP candidate.

13. The method of any one of claims 11-12, wherein the filtering the set of BVP candidates based on respective cost metrics associated with the set of BVP candidates comprises: determining a reference cost metric; and removing, from the set of BVP candidates, BVP candidates whose respective cost metric is higher than a threshold value determined by the reference cost metric.

14. The method of claim 13, wherein the reference cost metric is a lowest cost metric among the cost metrics associated with the set of BVP candidates, and the threshold value is determined as p times the reference cost metric with p>1.

15. The method of any one of claims 4 or 10-14, wherein the determining a fused template for each group comprises: determining fusion weights for respective BVP candidates in the group; and generating the fused template as a weighted combination of templates of blocks indicated by the BVP candidates in the group based on the fusion weights.Docket No.: 24-2041PCT16. The method of claim 15, wherein the fusion weight of a BVP candidate is determined based on a template matching cost of a candidate prediction block indicated by the BVP candidate17. The method of claim 15, wherein the fusion weight of a BVP candidate is determined according to a Gaussian solver fusion model.

18. The method of any one of claims 4 or 10-17, wherein the cost metric is a template matching cost determined based on the fused template and a template of the block.

19. The method of any one of claims 2-4 or 5-18, wherein the fused prediction block is generated by combining reference blocks indicated by the fusion group of BVP candidates according to respective weights of the fusion group of BVP candidates.

20. The method of claim 19, wherein the weight of a BVP candidate used in generating the fused prediction block is determined based on a template matching cost of a reference block indicated by the BVP candidate.

21. The method of claim 19, wherein the weight of a BVP candidate used in generating the fused prediction block is determined according to a Gaussian solver fusion model.

22. A method comprising: obtaining, from a bitstream, an indication that a block is coded using a fusion intra-template matching prediction (IntraTMP) mode and a fusion group index; ordering a plurality of groups of block vector prediction (BVP) candidates for the block based on cost metrics of the plurality of groups for the fusion IntraTMP mode; determining, from the plurality of groups of BVP candidates and according to the fusion group index, a fusion group of BVP candidates for coding the block; and decoding the block based on the fusion group of BVP candidates.

23. The method of claim 22, wherein the decoding the block comprises: generating a fused prediction block based on blocks indicated by the group of BVP candidates using a fusion model; and reconstructing the block based on the fused prediction block.

24. The method of claim 23, further comprising: obtaining a residual of the block from a bitstream, wherein reconstructing the block is further based on the obtained residual of the block.

25. A method comprising: ordering, based on cost metrics of a plurality of groups of block vector prediction (BVP) candidates, the plurality of groups for a block coded using a fusion intra-template matching prediction (IntraTMP) mode; determining, from the plurality of groups, a fusion group of BVP candidates for coding the block; generating, based on the fusion group of BVP candidates, a fused prediction block for the block; andDocket No.: 24-2041PCT encoding the block based on the fused prediction block, the encoding comprising encoding, in a bitstream, an indication that the block is coded using the I ntraTMP mode and a fusion group index of the fusion group in the ordered plurality of groups.

26. The method of claim 25, wherein: the fused prediction block is generated by applying a fusion model to reference blocks indicated by the fusion group of BVP candidates; and the encoding the block further comprises determining a residual of the block based on the fused prediction block.

27. The method of claim 26, further comprising: encoding, in the bitstream, the residual of the block.

28. The method of any one of claims 25-27, wherein the determining, from the plurality of groups, a fusion group of BVP candidates is performed based on a cost metric or a rate distortion optimization algorithm.

29. The method of any one of claims 22-24 or 25-28, wherein the ordering the plurality of groups of BVP candidates for the block comprises: determining a fused template for each group of the plurality of groups of BVP candidates; determining a cost metric for each group of the plurality of groups of BVP candidates based on the fused template; and ordering the plurality of groups of BVP candidates according to an ascending order of the cost metrics.

30. The method of any one of claims 22-24 or 25-28, wherein the plurality of groups of BVP candidates are determined by: selecting a set of BVP candidates from BVP candidates for the block; filtering the set of BVP candidates based on respective cost metrics associated with the set of BVP candidates; and determining the filtered set of BVP candidates as a group of BVP candidates of the plurality of groups.

31. The method of claim 30, wherein the cost metric associated with a BVP candidate is a template matching cost of the BVP candidate.

32. The method of any one of claims 30-31 , wherein the filtering the set of BVP candidates based on respective cost metrics associated with the set of BVP candidates comprises: determining a reference cost metric; and removing, from the set of BVP candidates, BVP candidates whose respective cost metric is higher than a threshold value determined by the reference cost metric.

33. The method of claim 32, wherein the reference cost metric is a lowest cost metric among the cost metrics associated with the set of BVP candidates, and the threshold value is determined as p times the reference cost metric with p>134. The method of any one of claims 29-33, wherein the determining a fused template for each group comprises:Docket No.: 24-2041PCT determining fusion weights for respective BVP candidates in the group; and generating the fused template as a weighted combination of templates of blocks indicated by the BVP candidates in the group based on the fusion weights.

35. The method of claim 34, wherein the fusion weight of a BVP candidate is determined based on a template matching cost of a candidate prediction block indicated by the BVP candidate.

36. The method of claim 34, wherein the fusion weight of a BVP candidate is determined according to a Gaussian solver fusion model.

37. The method of any one of claims 29-36, wherein the cost metric for a group is a template matching cost determined based on the fused template of the group and a template of the block.

38. The method of any one of claims 23-24 or 25-37, wherein the fused prediction block is generated by combining reference blocks indicated by the fusion group of BVP candidates according to respective weights of the fusion group of BVP candidates.

39. The method of claim 38, wherein the weight of a BVP candidate used in generating the fused prediction block is determined based on a template matching cost of a reference block indicated by the BVP candidate.

40. The method of claim 38, wherein the weight of a BVP candidate used in generating the fused prediction block is determined according to a Gaussian solver fusion model.

41. A non-transitory computer-readable medium comprising instructions that, when executed by one or more processors of an apparatus, cause the apparatus to perform the method of any one of claims 1-40.

42. An encoder comprising: one or more processors; and memory storing instructions that, when executed by the one or more processors, cause the encoder to perform the method of any one of claim 5-21 and 25-40.

43. A non-transitory computer-readable recording medium storing a bitstream generated by the method for encoding a video according to any one of claims 5-21 and 25-40.

44. A decoder comprising: one or more processors; and memory storing instructions that, when executed by the one or more processors, cause the decoder to perform the method of any one of claims 1-4, 11-21, 22-24, and 29-40.

45. A non-transitory computer readable medium storing a bitstream, which, when decoded by a decoder, causes the decoder to perform the method according to any one of claims 11-4, 11-21, 22-24, and 29-40.

46. A bitstream generated according to any one of claims 5-21 and 25-40.

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