METHODS AND DEVICES WITH INTRA BLOCK COPY

CROSS-REFERENCE TO RELATED APPLICATION

[0001] The present application is based upon and claims priority to U.S. Provisional Application No. 63/414,895, entitled “Methods and Devices with Intra Block Copy,” filed on October 10, 2022, the entirety of which is incorporated by reference for all purposes.

FIELD

[0002] The present disclosure is related to video coding and compression, and in particular but not limited to, methods and apparatus on improving the coding efficiency of intra block copy (IBC).

BACKGROUND

[0003] Digital video is supported by a variety of electronic devices, such as digital televisions, laptop or desktop computers, tablet computers, digital cameras, digital recording devices, digital media players, video gaming consoles, smart phones, video teleconferencing devices, video streaming devices, etc. The electronic devices transmit and receive or otherwise communicate digital video data across a communication network, and/or store the digital video data on a storage device. Due to a limited bandwidth capacity of the communication network and limited memory resources of the storage device, video coding may be used to compress the video data according to one or more video coding standards before it is communicated or stored. For example, video coding standards include Versatile Video Coding (VVC), Joint Exploration test Model (JEM), High-Efficiency Video Coding (HEVC/H.265), Advanced Video Coding (AVC/H.264), Moving Picture Expert Group (MPEG) coding, or the like. Video coding generally utilizes prediction methods (e.g., inter-prediction, intra-prediction, or the like) that take advantage of redundancy inherent in the video data. Video coding aims to compress video data into a form that uses a lower bit rate, while avoiding or minimizing degradations to video quality.

SUMMARY

[0004] The present disclosure provides examples of techniques relating to improving the Intra Block Copy method in a video encoding or decoding process.

[0005] According to a first aspect of the present disclosure, there is provided a method for video decoding. In the method, a decoder may obtain a current coding unit (CU) that is coded based on IBC mode combined with Geometric Partitioning Mode (GPM). Additionally, the decoder may obtain a prediction for the current CU based on the IBC mode combined with GPM.

[0006] According to a second aspect of the present disclosure, there is provided a method for video encoding. In the method, an encoder may encode a current CU based on IBC mode combined with GPM. Additionally, the encoder may transmit the current CU that is coded based on the IBC mode combined with GPM to a decoder.

[0007] According to a third aspect of the present disclosure, there is provided a method for video decoding. In the method, a decoder may obtain a first prediction for a current CU, where the first prediction is associated with IBC mode. Additionally, the decoder may obtain a second prediction for the current CU, where the second prediction is associated with one of intra mode or inter mode. Furthermore, the decoder may obtain a final prediction for the current CU based on the first prediction and the second prediction.

[0008] According to a fourth aspect of the present disclosure, there is provided a method for video encoding. In the method, an encoder may obtain a first prediction for a current CU, where the first prediction is associated with IBC mode. Additionally, the encoder may obtain a second prediction for the current CU, where the second prediction is associated with one of intra mode or inter mode. Furthermore, the encoder may obtain a final prediction for the current CU based on the first prediction and the second prediction.

[0009] According to a fifth aspect of the present disclosure, there is provided a method for video decoding. In the method, a decoder may obtain a plurality of block vectors for a current CU based on IBC mode. Additionally, the decoder may obtain a final prediction for the current CU based on the plurality of block vectors.

[0010] According to a sixth aspect of the present disclosure, there is provided a method for video encoding. In the method, an encoder may obtain a plurality of block vectors for a current CU based on IBC mode. Additionally, the encoder may obtain a final prediction for the current CU based on the plurality of block vectors.

[0011] According to a seventh aspect of the present disclosure, there is provided an apparatus for video decoding. The apparatus may include one or more processors and a memory coupled to the one or more processors and configured to store instructions executable by the one or more processors. Furthermore, the one or more processors, upon execution of the instructions, are configured to perform the method according to the first aspect, the third aspect, or the fifth aspect. [0012] According to an eighth aspect of the present disclosure, there is provided an apparatus for video encoding. The apparatus may include one or more processors and a memory coupled to the one or more processors and configured to store instructions executable by the one or more processors. Furthermore, the one or more processors, upon execution of the instructions, are configured to perform the method according to the second aspect, the fourth aspect, or the sixth aspect.

[0013] According to a ninth aspect of the present disclosure, there is provided a non-transitory computer-readable storage medium for storing computer-executable instructions that, when executed by one or more computer processors, cause the one or more computer processors to perform the method according to the first aspect, the third aspect, or the fifth aspect.

[0014] According to a tenth aspect of the present disclosure, there is provided a non-transitory computer-readable storage medium for storing computer-executable instructions that, when executed by one or more computer processors, cause the one or more computer processors to perform the method according to the second aspect, the fourth aspect, or the sixth aspect.

[0015] According to an eleventh aspect of the present disclosure, there is provided a non-transitory computer-readable storage medium for storing a bitstream to be decoded by the method according to the first aspect, the third aspect, or the fifth aspect.

[0016] According to a twelfth aspect of the present disclosure, there is provided a non-transitory computer-readable storage medium for storing a bitstream generated by the method according to the second aspect, the fourth aspect, or the sixth aspect.

BRIEF DESCRIPTION OF THE DRAWINGS

[0017] A more particular description of the examples of the present disclosure will be rendered by reference to specific examples illustrated in the appended drawings. Given that these drawings depict only some examples and are not therefore considered to be limiting in scope, the examples will be described and explained with additional specificity and details through the use of the accompanying drawings.

[0018] FIG. 1A is a block diagram illustrating a system for encoding and decoding video blocks in accordance with some examples of the present disclosure.

[0019] FIG. IB shows a quad-tree data structure illustrating the end result of the partition process of the CTU 400 as depicted in FIG. IE in accordance with some examples of the present disclosure. [0020] FIG. 1C shows an encoded representation of a frame by first partitioning the frame into a set of CTUs in accordance with some examples of the present disclosure.

[0021] FIG. ID shows a CTU including one CTB of luma samples, two corresponding coding tree blocks of chroma samples, and syntax elements used to code the samples of the coding tree blocks in accordance with some examples of the present disclosure.

[0022] FIG. 2 is a block diagram illustrating an exemplary video encoder in accordance with some examples of the present disclosure

[0023] FIG. 3 is a block diagram illustrating an exemplary video decoder in accordance with some examples of the present disclosure.

[0024] FIG. 4A is a diagram illustrating block partitions in a multi-type tree structure in accordance with some examples of the present disclosure.

[0025] FIG. 4B is a diagram illustrating block partitions in a multi-type tree structure in accordance with some examples of the present disclosure.

[0026] FIG. 4C is a diagram illustrating block partitions in a multi-type tree structure in accordance with some examples of the present disclosure.

[0027] FIG. 4D is a diagram illustrating block partitions in a multi-type tree structure in accordance with some examples of the present disclosure.

[0028] FIG. 4E is a diagram illustrating block partitions in a multi-type tree structure in accordance with some examples of the present disclosure.

[0029] FIG. 5 illustrates a diagram of positions of spatial candidates in accordance with some examples of the present disclosure.

[0030] FIG. 6 illustrates a diagram of candidate pairs considered for redundancy check of spatial candidates in accordance with some examples of the present disclosure.

[0031] FIG. 7 illustrates a diagram of scaling of a motion vector for a temporal candidate in accordance with some examples of the present disclosure.

[0032] FIG. 8 illustrates a diagram of candidate positions for a temporal candidate in accordance with some examples of the present disclosure.

[0033] FIG. 9 illustrates a diagram of Merge mode with Motion Vector Difference (MMVD) search points in accordance with some examples of the present disclosure.

[0034] FIG. 10 illustrates uni -prediction motion vector selection for Geometric Partitioning Mode (GPM) in accordance with some examples of the present disclosure. [0035] FIG. 11 illustrates top and left neighboring blocks used in CIIP weight derivation in accordance with some examples of the present disclosure.

[0036] FIG. 12 illustrates current CTU processing order and its available reference samples in current and left CTU in accordance with some examples of the present disclosure.

[0037] FIG. 13 illustrates padding candidates for the replacement of the zero-vector in the IBC list in accordance with some examples of the present disclosure.

[0038] FIG. 14 illustrates reference area for IBC when CTU (m,n) is coded in accordance with some examples of the present disclosure.

[0039] FIG. 15 illustrates IBC reference area for camera-captured content in accordance with some examples of the present disclosure.

[0040] FIGS. 16A-16B illustrate the division method for angular modes in accordance with some examples of the present disclosure.

[0041] FIGS. 17A-17D illustrate GPM with inter and intra prediction in accordance with some examples of the present disclosure.

[0042] FIG. 18 illustrates the edge on templates in accordance with some examples of the present disclosure.

[0043] FIG. 19 is a diagram illustrating a computing environment coupled with a user interface, according to some implementations of the present disclosure.

[0044] FIG. 20 is a flow chart illustrating a method for video decoding in accordance with some examples of the present disclosure.

[0045] FIG. 21 is a flow chart illustrating a method for video encoding corresponding to the method for video decoding as shown in FIG. 20 in accordance with some examples of the present disclosure.

[0046] FIG. 22 is a flow chart illustrating a method for video decoding in accordance with some examples of the present disclosure.

[0047] FIG. 23 is a flow chart illustrating a method for video encoding corresponding to the method for video decoding as shown in FIG. 22 in accordance with some examples of the present disclosure.

[0048] FIG. 24 is a flow chart illustrating a method for video decoding in accordance with some examples of the present disclosure. [0049] FIG. 25 is a flow chart illustrating a method for video encoding corresponding to the method for video decoding as shown in FIG. 24 in accordance with some examples of the present disclosure.

DETAILED DESCRIPTION

[0050] Reference will now be made in detail to specific implementations, examples of which are illustrated in the accompanying drawings. In the following detailed description, numerous nonlimiting specific details are set forth in order to assist in understanding the subject matter presented herein. But various alternatives may be used without departing from the scope of claims and the subject matter may be practiced without these specific details. For example, the subject matter presented herein can be implemented on many types of electronic devices with digital video capabilities.

[0051] Terms used in the disclosure are only adopted for the purpose of describing specific embodiments and not intended to limit the disclosure. “A/an,” “said,” and “the” in a singular form in the disclosure and the appended claims are also intended to include a plural form, unless other meanings are clearly denoted throughout the disclosure. It is also to be understood that term “and/or” used in the disclosure refers to and includes one or any or all possible combinations of multiple associated items that are listed.

[0052] Reference throughout this specification to “one embodiment,” “an embodiment,” “an example,” “some embodiments,” “some examples,” or similar language means that a particular feature, structure, or characteristic described is included in at least one embodiment or example. Features, structures, elements, or characteristics described in connection with one or some embodiments are also applicable to other embodiments, unless expressly specified otherwise.

[0053] Throughout the disclosure, the terms “first,” “second,” “third,” etc. are all used as nomenclature only for references to relevant elements, e.g., devices, components, compositions, steps, etc., without implying any spatial or chronological orders, unless expressly specified otherwise. For example, a “first device” and a “second device” may refer to two separately formed devices, or two parts, components, or operational states of a same device, and may be named arbitrarily.

[0054] The terms “module,” “sub-module,” “circuit,” “sub-circuit,” “circuitry,” “sub-circuitry,” “unit,” or “sub-unit” may include memory (shared, dedicated, or group) that stores code or instructions that can be executed by one or more processors. A module may include one or more circuits with or without stored code or instructions. The module or circuit may include one or more components that are directly or indirectly connected. These components may or may not be physically attached to, or located adjacent to, one another.

[0055] As used herein, the term “if” or “when” may be understood to mean “upon” or “in response to” depending on the context. These terms, if appear in a claim, may not indicate that the relevant limitations or features are conditional or optional. For example, a method may comprise steps of: i) when or if condition X is present, function or action X’ is performed, and ii) when or if condition Y is present, function or action Y’ is performed. The method may be implemented with both the capability of performing function or action X’ , and the capability of performing function or action Y’ . Thus, the functions X’ and Y’ may both be performed, at different times, on multiple executions of the method.

[0056] A unit or module may be implemented purely by software, purely by hardware, or by a combination of hardware and software. In a pure software implementation, for example, the unit or module may include functionally related code blocks or software components, that are directly or indirectly linked together, so as to perform a particular function.

[0057] FIG. 1A is a block diagram illustrating an exemplary system 10 for encoding and decoding video blocks in parallel in accordance with some implementations of the present disclosure. As shown in FIG. 1A, the system 10 includes a source device 12 that generates and encodes video data to be decoded at a later time by a destination device 14. The source device 12 and the destination device 14 may include any of a wide variety of electronic devices, including cloud servers, server computers, desktop or laptop computers, tablet computers, smart phones, set-top boxes, digital televisions, cameras, display devices, digital media players, video gaming consoles, video streaming device, or the like. In some implementations, the source device 12 and the destination device 14 are equipped with wireless communication capabilities.

[0058] In some implementations, the destination device 14 may receive the encoded video data to be decoded via a link 16. The link 16 may include any type of communication medium or device capable of moving the encoded video data from the source device 12 to the destination device 14. In one example, the link 16 may include a communication medium to enable the source device 12 to transmit the encoded video data directly to the destination device 14 in real time. The encoded video data may be modulated according to a communication standard, such as a wireless communication protocol, and transmitted to the destination device 14. The communication medium may include any wireless or wired communication medium, such as a Radio Frequency (RF) spectrum or one or more physical transmission lines. The communication medium may form part of a packet-based network, such as a local area network, a wide-area network, or a global network such as the Internet. The communication medium may include routers, switches, base stations, or any other equipment that may be useful to facilitate communication from the source device 12 to the destination device 14.

[0059] In some other implementations, the encoded video data may be transmitted from an output interface 22 to a storage device 32. Subsequently, the encoded video data in the storage device 32 may be accessed by the destination device 14 via an input interface 28. The storage device 32 may include any of a variety of distributed or locally accessed data storage media such as a hard drive, Blu-ray discs, Digital Versatile Disks (DVDs), Compact Disc Read-Only Memories (CD-ROMs), flash memory, volatile or non-volatile memory, or any other suitable digital storage media for storing the encoded video data. In a further example, the storage device 32 may correspond to a file server or another intermediate storage device that may hold the encoded video data generated by the source device 12. The destination device 14 may access the stored video data from the storage device 32 via streaming or downloading. The file server may be any type of computer capable of storing the encoded video data and transmitting the encoded video data to the destination device 14. Exemplary file servers include a web server (e.g., for a website), a File Transfer Protocol (FTP) server, Network Attached Storage (NAS) devices, or a local disk drive. The destination device 14 may access the encoded video data through any standard data connection, including a wireless channel (e.g., a Wireless Fidelity (Wi-Fi) connection), a wired connection (e.g., Digital Subscriber Line (DSL), cable modem, etc.), or a combination of both that is suitable for accessing encoded video data stored on a file server. The transmission of the encoded video data from the storage device 32 may be a streaming transmission, a download transmission, or a combination of both.

[0060] As shown in FIG. 1A, the source device 12 includes a video source 18, a video encoder 20 and the output interface 22. The video source 18 may include a source such as a video capturing device, e.g., a video camera, a video archive containing previously captured video, a video feeding interface to receive video from a video content provider, and/or a computer graphics system for generating computer graphics data as the source video, or a combination of such sources. As one example, if the video source 18 is a video camera of a security surveillance system, the source device 12 and the destination device 14 may form camera phones or video phones. However, the implementations described in the present application may be applicable to video coding in general, and may be applied to wireless and/or wired applications.

[0061] The captured, pre-captured, or computer-generated video may be encoded by the video encoder 20. The encoded video data may be transmitted directly to the destination device 14 via the output interface 22 of the source device 12. The encoded video data may also (or alternatively) be stored onto the storage device 32 for later access by the destination device 14 or other devices, for decoding and/or playback. The output interface 22 may further include a modem and/or a transmitter.

[0062] The destination device 14 includes the input interface 28, a video decoder 30, and a display device 34. The input interface 28 may include a receiver and/or a modem and receive the encoded video data over the link 16. The encoded video data communicated over the link 16, or provided on the storage device 32, may include a variety of syntax elements generated by the video encoder 20 for use by the video decoder 30 in decoding the video data. Such syntax elements may be included within the encoded video data transmitted on a communication medium, stored on a storage medium, or stored on a file server.

[0063] In some implementations, the destination device 14 may include the display device 34, which can be an integrated display device and an external display device that is configured to communicate with the destination device 14. The display device 34 displays the decoded video data to a user, and may include any of a variety of display devices such as a Liquid Crystal Display (LCD), a plasma display, an Organic Light Emitting Diode (OLED) display, or another type of display device.

[0064] The video encoder 20 and the video decoder 30 may operate according to proprietary or industry standards, such as VVC, HEVC, MPEG -4, Part 10, A VC, or extensions of such standards. It should be understood that the present application is not limited to a specific video encoding/decoding standard and may be applicable to other video encoding/decoding standards. It is generally contemplated that the video encoder 20 of the source device 12 may be configured to encode video data according to any of these current or future standards. Similarly, it is also generally contemplated that the video decoder 30 of the destination device 14 may be configured to decode video data according to any of these current or future standards. [0065] The video encoder 20 and the video decoder 30 each may be implemented as any of a variety of suitable encoder and/or decoder circuitry, such as one or more microprocessors, Digital Signal Processors (DSPs), Application Specific Integrated Circuits (ASICs), Field Programmable Gate Arrays (FPGAs), discrete logic, software, hardware, firmware or any combinations thereof. When implemented partially in software, an electronic device may store instructions for the software in a suitable, non-transitory computer-readable medium and execute the instructions in hardware using one or more processors to perform the video encoding/decoding operations disclosed in the present disclosure. Each of the video encoder 20 and the video decoder 30 may be included in one or more encoders or decoders, either of which may be integrated as part of a combined encoder/decoder (CODEC) in a respective device.

[0066] In some implementations, at least a part of components of the source device 12 (for example, the video source 18, the video encoder 20 or components included in the video encoder 20 as described below with reference to FIG. 1G, and the output interface 22) and/or at least a part of components of the destination device 14 (for example, the input interface 28, the video decoder 30 or components included in the video decoder 30 as described below with reference to FIG. 3, and the display device 34) may operate in a cloud computing service network which may provide software, platforms, and/or infrastructure, such as Software as a Service (SaaS), Platform as a Service (PaaS), or Infrastructure as a Service (laaS). In some implementations, one or more components in the source device 12 and/or the destination device 14 which are not included in the cloud computing service network may be provided in one or more client devices, and the one or more client devices may communicate with server computers in the cloud computing service network through a wireless communication network (for example, a cellular communication network, a short-range wireless communication network, or a global navigation satellite system (GNSS) communication network) or a wired communication network (e g., a local area network (LAN) communication network or a power line communication (PLC) network). In an embodiment, at least a part of operations described herein may be implemented as cloud-based services provided by one or more server computers which are implemented by the at least a part of the components of the source device 12 and/or the at least a part of the components of the destination device 14 in the cloud computing service network; and one or more other operations described herein may be implemented by the one or more client devices. In some implementations, the cloud computing service network may be a private cloud, a public cloud, or a hybrid cloud. The terms such as “cloud,” “cloud computing,” “cloud-based” etc. herein may be used interchangeably as appropriate without departing from the scope of the present disclosure. It should be understood that the present disclosure is not limited to being implemented in the cloud computing service network described above. Instead, the present disclosure may also be implemented in any other type of computing environments currently known or developed in the future.

[0067] FIGS. 4A-4E are schematic diagrams illustrating multi-type tree splitting modes in accordance with some implementations of the present disclosure. FIGS. 4A-4E respectively show five splitting types including quaternary partitioning (FIG. 4A), vertical binary partitioning (FIG. 4B), horizontal binary partitioning (FIG. 4C), vertical ternary partitioning (FIG. 4D), and horizontal ternary partitioning (FIG. 4E).

[0068] FIG. 2 is a block diagram illustrating another exemplary' video encoder 20 in accordance with some implementations described in the present application. The video encoder 20 may perform intra and inter predictive coding of video blocks within video frames. Intra predictive coding relies on spatial prediction to reduce or remove spatial redundancy in video data within a given video frame or picture. Inter predictive coding relies on temporal prediction to reduce or remove temporal redundancy in video data within adjacent video frames or pictures of a video sequence. It should be noted that the term “frame” may be used as synonyms for the term “image” or “picture” in the field of video coding.

[0069] As shown in FIG. 2, the video encoder 20 includes a video data memory 40, a prediction processing unit 41, a Decoded Picture Buffer (DPB) 64, a summer 50, a transform processing unit 52, a quantization unit 54, and an entropy encoding unit 56. The prediction processing unit 41 further includes a motion estimation unit 42, a motion compensation unit 44, a partition unit 45, an intra prediction processing unit 46, and an intra Block Copy (BC) unit 48. In some implementations, the video encoder 20 also includes an inverse quantization unit 58, an inverse transform processing unit 60, and a summer 62 for video block reconstruction. An in-loop fdter 63, such as a deblocking filter, may be positioned between the summer 62 and the DPB 64 to filter block boundaries to remove blockiness artifacts from reconstructed video. Another in-loop filter, such as Sample Adaptive Offset (SAO) filter, Cross Component Sample Adaptive Offset (CCSAO) filter and/or Adaptive in-Loop Filter (ALF), may also be used in addition to the deblocking filter to filter an output of the summer 62. It should be illustrated that for the CCSAO technique, the present application is not limited to the embodiments described herein, and instead, the application may be applied to a situation where an offset is selected for any of a luma component, a Cb chroma component and a Cr chroma component according to any other of the luma component, the Cb chroma component and the Cr chroma component to modify said any component based on the selected offset. Further, it should also be illustrated that a first component mentioned herein may be any of the luma component, the Cb chroma component and the Cr chroma component, a second component mentioned herein may be any other of the luma component, the Cb chroma component and the Cr chroma component, and a third component mentioned herein may be a remaining one of the luma component, the Cb chroma component and the Cr chroma component. In some examples, the in-loop filters may be omitted, and the decoded video block may be directly provided by the summer 62 to the DPB 64. The video encoder 20 may take the form of a fixed or programmable hardware unit or may be divided among one or more of the illustrated fixed or programmable hardware units.

[0070] The video data memory 40 may store video data to be encoded by the components of the video encoder 20. The video data in the video data memory ⁷ 40 may be obtained, for example, from the video source 18 as shown in FIG. 1A. The DPB 64 is a buffer that stores reference video data (for example, reference frames or pictures) for use in encoding video data by the video encoder 20 (e.g., in intra or inter predictive coding modes). The video data memory 40 and the DPB 64 may be formed by any of a variety of memory devices. In various examples, the video data memory 40 may be on-chip with other components of the video encoder 20, or off-chip relative to those components.

[0071] As shown in FIG. 2, after receiving the video data, the partition unit 45 within the prediction processing unit 41 partitions the video data into video blocks. This partitioning may also include partitioning a video frame into slices, tiles (for example, sets of video blocks), or other larger Coding Units (CUs) according to predefined splitting structures such as a Quad-Tree (QT) structure associated with the video data. The video frame is or may be regarded as a two- dimensional array or matrix of samples with sample values. A sample in the array may also be referred to as a pixel or a pel. A number of samples in horizontal and vertical directions (or axes) of the array or picture define a size and/or a resolution of the video frame. The video frame may be divided into multiple video blocks by, for example, using QT partitioning. The video block again is or may be regarded as a two-dimensional array or matrix of samples with sample values, although of smaller dimension than the video frame. A number of samples in horizontal and vertical directions (or axes) of the video block define a size of the video block. The video block may further be partitioned into one or more block partitions or sub-blocks (which may form again blocks) by, for example, iteratively using QT partitioning, Binary-Tree (BT) partitioning or TripleTree (TT) partitioning or any combination thereof. It should be noted that the term “block” or “video block” as used herein may be a portion, in particular a rectangular (square or non- square) portion, of a frame or a picture. With reference, for example, to HEVC and VVC, the block or video block may be or correspond to a Coding Tree Unit (CTU), a CU, a Prediction Unit (PU) or a Transform Unit (TU) and/or may be or correspond to a corresponding block, e.g., a Coding Tree Block (CTB), a Coding Block (CB), a Prediction Block (PB) or a Transform Block (TB) and/or to a sub-block.

[0072] The prediction processing unit 41 may select one of a plurality of possible predictive coding modes, such as one of a plurality of intra predictive coding modes or one of a plurality of inter predictive coding modes, for the current video block based on error results (e.g., coding rate and the level of distortion). The prediction processing unit 41 may provide the resulting intra or inter prediction coded block to the summer 50 to generate a residual block and to the summer 62 to reconstruct the encoded block for use as part of a reference frame subsequently. The prediction processing unit 41 also provides syntax elements, such as motion vectors, intra-mode indicators, partition information, and other such syntax information, to the entropy encoding unit 56.

[0073] In order to select an appropriate intra predictive coding mode for the current video block, the intra prediction processing unit 46 within the prediction processing unit 41 may perform intra predictive coding of the current video block relative to one or more neighbor blocks in the same frame as the current block to be coded to provide spatial prediction. The motion estimation unit 42 and the motion compensation unit 44 within the prediction processing unit 41 perform inter predictive coding of the current video block relative to one or more predictive blocks in one or more reference frames to provide temporal prediction. The video encoder 20 may perform multiple coding passes, e.g., to select an appropriate coding mode for each block of video data.

[0074] In some implementations, the motion estimation unit 42 determines the inter prediction mode for a current video frame by generating a motion vector, which indicates the displacement of a video block within the current video frame relative to a predictive block within a reference video frame, according to a predetermined pattern within a sequence of video frames. Motion estimation, performed by the motion estimation unit 42, is the process of generating motion vectors, which estimate motion for video blocks. A motion vector, for example, may indicate the displacement of a video block within a current video frame or picture relative to a predictive block within a reference frame relative to the current block being coded within the current frame. The predetermined pattern may designate video frames in the sequence as P frames or B frames. The intra BC unit 48 may determine vectors, e.g., block vectors, for intra BC coding in a manner similar to the determination of motion vectors by the motion estimation unit 42 for inter prediction, or may utilize the motion estimation unit 42 to determine the block vector.

[0075] A predictive block for the video block may be or may correspond to a block or a reference block of a reference frame that is deemed as closely matching the video block to be coded in terms of pixel difference, which may be determined by Sum of Absolute Difference (SAD), Sum of Square Difference (SSD), or other difference metrics. In some implementations, the video encoder 20 may calculate values for sub-integer pixel positions of reference frames stored in the DPB 64. For example, the video encoder 20 may interpolate values of one-quarter pixel positions, one- eighth pixel positions, or other fractional pixel positions of the reference frame. Therefore, the motion estimation unit 42 may perform a motion search relative to the full pixel positions and fractional pixel positions and output a motion vector with fractional pixel precision.

[0076] The motion estimation unit 42 calculates a motion vector for a video block in an inter prediction coded frame by comparing the position of the video block to the position of a predictive block of a reference frame selected from a first reference frame list (List 0) or a second reference frame list (List 1), each of which identifies one or more reference frames stored in the DPB 64. The motion estimation unit 42 sends the calculated motion vector to the motion compensation unit 44 and then to the entropy encoding unit 56.

[0077] Motion compensation, performed by the motion compensation unit 44, may involve fetching or generating the predictive block based on the motion vector determined by the motion estimation unit 42. Upon receiving the motion vector for the current video block, the motion compensation unit 44 may locate a predictive block to which the motion vector points in one of the reference frame lists, retrieve the predictive block from the DPB 64, and forward the predictive block to the summer 50. The summer 50 then forms a residual video block of pixel difference values by subtracting pixel values of the predictive block provided by the motion compensation unit 44 from the pixel values of the current video block being coded. The pixel difference values forming the residual video block may include luma or chroma component differences or both. The motion compensation unit 44 may also generate syntax elements associated with the video blocks of a video frame for use by the video decoder 30 in decoding the video blocks of the video frame. The syntax elements may include, for example, syntax elements defining the motion vector used to identify the predictive block, any flags indicating the prediction mode, or any other syntax information described herein. Note that the motion estimation unit 42 and the motion compensation unit 44 may be highly integrated, but are illustrated separately for conceptual purposes.

[0078] In some implementations, the intra BC unit 48 may generate vectors and fetch predictive blocks in a manner similar to that described above in connection with the motion estimation unit 42 and the motion compensation unit 44, but with the predictive blocks being in the same frame as the current block being coded and with the vectors being referred to as block vectors as opposed to motion vectors. In particular, the intra BC unit 48 may determine an intra-prediction mode to use to encode a current block. In some examples, the intra BC unit 48 may encode a current block using various intra-prediction modes, e.g., during separate encoding passes, and test their performance through rate-distortion analysis. Next, the intra BC unit 48 may select, among the various tested intra-prediction modes, an appropriate intra-prediction mode to use and generate an intra-mode indicator accordingly. For example, the intra BC unit 48 may calculate rate -distortion values using a rate-distortion analysis for the various tested intra-prediction modes, and select the intra-prediction mode having the best rate -distortion characteristics among the tested modes as the appropriate intra-prediction mode to use. Rate-distortion analysis generally determines an amount of distortion (or error) between an encoded block and an original, unencoded block that was encoded to produce the encoded block, as well as a bitrate (i.e., a number of bits) used to produce the encoded block. Intra BC unit 48 may calculate ratios from the distortions and rates for the various encoded blocks to determine which intra-prediction mode exhibits the best rate -distortion value for the block.

[0079] In other examples, the intra BC unit 48 may use the motion estimation unit 42 and the motion compensation unit 44, in whole or in part, to perform such functions for Intra BC prediction according to the implementations described herein. In either case, for Intra block copy, a predictive block may be a block that is deemed as closely matching the block to be coded, in terms of pixel difference, which may be determined by SAD, SSD, or other difference metrics, and identification of the predictive block may include calculation of values for sub-integer pixel positions.

[0080] Whether the predictive block is from the same frame according to intra prediction, or a different frame according to inter prediction, the video encoder 20 may form a residual video block by subtracting pixel values of the predictive block from the pixel values of the current video block being coded, forming pixel difference values. The pixel difference values forming the residual video block may include both luma and chroma component differences.

[0081] The intra prediction processing unit 46 may intra-predict a current video block, as an alternative to the inter-prediction performed by the motion estimation unit 42 and the motion compensation unit 44, or the intra block copy prediction performed by the intra BC unit 48, as described above. In particular, the intra prediction processing unit 46 may determine an intra prediction mode to use to encode a current block. To do so, the intra prediction processing unit 46 may encode a current block using various intra prediction modes, e.g., during separate encoding passes, and the intra prediction processing unit 46 (or a mode selection unit, in some examples) may select an appropriate intra prediction mode to use from the tested intra prediction modes. The intra prediction processing unit 46 may provide information indicative of the selected intraprediction mode for the block to the entropy encoding unit 56. The entropy encoding unit 56 may encode the information indicating the selected intra-prediction mode in the bitstream.

[0082] After the prediction processing unit 41 determines the predictive block for the current video block via either inter prediction or intra prediction, the summer 50 forms a residual video block by subtracting the predictive block from the current video block. The residual video data in the residual block may be included in one or more TUs and is provided to the transform processing unit 52. The transform processing unit 52 transforms the residual video data into residual transform coefficients using a transform, such as a Discrete Cosine Transform (DCT) or a conceptually similar transform.

[0083] The transform processing unit 52 may send the resulting transform coefficients to the quantization unit 54. The quantization unit 54 quantizes the transform coefficients to further reduce the bit rate. The quantization process may also reduce the bit depth associated with some or all of the coefficients. The degree of quantization may be modified by adjusting a quantization parameter. In some examples, the quantization unit 54 may then perform a scan of a matrix including the quantized transform coefficients. Alternatively, the entropy encoding unit 56 may perform the scan. [0084] Following quantization, the entropy encoding unit 56 entropy encodes the quantized transform coefficients into a video bitstream using, e.g., Context Adaptive Variable Length Coding (CAVLC), Context Adaptive Binary Arithmetic Coding (CABAC), Syntax-based context- adaptive Binary Arithmetic Coding (SBAC), Probability Interval Partitioning Entropy (PIPE) coding or another entropy encoding methodology or technique. The encoded bitstream may then be transmitted to the video decoder 30 as shown in FIG. 1A, or archived in the storage device 32 as shown in FIG. 1A for later transmission to or retrieval by the video decoder 30. The entropy encoding unit 56 may also entropy encode the motion vectors and the other syntax elements for the current video frame being coded.

[0085] The inverse quantization unit 58 and the inverse transform processing unit 60 apply inverse quantization and inverse transformation, respectively, to reconstruct the residual video block in the pixel domain for generating a reference block for prediction of other video blocks. As noted above, the motion compensation unit 44 may generate a motion compensated predictive block from one or more reference blocks of the frames stored in the DPB 64. The motion compensation unit 44 may also apply one or more interpolation filters to the predictive block to calculate subinteger pixel values for use in motion estimation.

[0086] The summer 62 adds the reconstructed residual block to the motion compensated predictive block produced by the motion compensation unit 44 to produce a reference block for storage in the DPB 64. The reference block may then be used by the intra BC unit 48, the motion estimation unit 42 and the motion compensation unit 44 as a predictive block to inter predict another video block in a subsequent video frame.

[0087] FIG. 3 is a block diagram illustrating another exemplar}' video decoder 30 in accordance with some implementations of the present application. The video decoder 30 includes a video data memory 79, an entropy decoding unit 80, a prediction processing unit 81, an inverse quantization unit 86, an inverse transform processing unit 88, a summer 90, and a DPB 92. The prediction processing unit 81 further includes a motion compensation unit 82, an intra prediction unit 84, and an intra BC unit 85. The video decoder 30 may perform a decoding process generally reciprocal to the encoding process described above with respect to the video encoder 20 in connection with FIG. 2. For example, the motion compensation unit 82 may generate prediction data based on motion vectors received from the entropy decoding unit 80, while the intra-prediction unit 84 may generate prediction data based on intra-prediction mode indicators received from the entropy decoding unit 80.

[0088] In some examples, a unit of the video decoder 30 may be tasked to perform the implementations of the present application. Also, in some examples, the implementations of the present disclosure may be divided among one or more of the units of the video decoder 30. For example, the intra BC unit 85 may perform the implementations of the present application, alone, or in combination with other units of the video decoder 30, such as the motion compensation unit 82, the intra prediction unit 84, and the entropy decoding unit 80. In some examples, the video decoder 30 may not include the intra BC unit 85 and the functionality of intra BC unit 85 may be performed by other components of the prediction processing unit 81, such as the motion compensation unit 82.

[0089] The video data memory 79 may store video data, such as an encoded video bitstream, to be decoded by the other components of the video decoder 30. The video data stored in the video data memory 79 may be obtained, for example, from the storage device 32, from a local video source, such as a camera, via wired or wireless network communication of video data, or by accessing physical data storage media (e.g., a flash drive or hard disk). The video data memory 79 may include a Coded Picture Buffer (CPB) that stores encoded video data from an encoded video bitstream. The DPB 92 of the video decoder 30 stores reference video data for use in decoding video data by the video decoder 30 (e.g., in intra or inter predictive coding modes). The video data memory 79 and the DPB 92 may be formed by any of a variety of memory devices, such as dynamic random access memory (DRAM), including Synchronous DRAM (SDRAM), Magnetoresistive RAM (MRAM), Resistive RAM (RRAM), or other types of memory devices. For illustrative purpose, the video data memory 79 and the DPB 92 are depicted as two distinct components of the video decoder 30 in FIG. 3. But it will be apparent to one skilled in the art that the video data memory 79 and the DPB 92 may be provided by the same memory device or separate memory devices. In some examples, the video data memory 79 may be on-chip with other components of the video decoder 30, or off-chip relative to those components.

[0090] During the decoding process, the video decoder 30 receives an encoded video bitstream that represents video blocks of an encoded video frame and associated syntax elements. The video decoder 30 may receive the syntax elements at the video frame level and/or the video block level. The entropy decoding unit 80 of the video decoder 30 entropy decodes the bitstream to generate quantized coefficients, motion vectors or intra-prediction mode indicators, and other syntax elements. The entropy decoding unit 80 then forwards the motion vectors or intra-prcdiction mode indicators and other syntax elements to the prediction processing unit 81.

[0091] When the video frame is coded as an intra predictive coded (I) frame or for intra coded predictive blocks in other types of frames, the intra prediction unit 84 of the prediction processing unit 81 may generate prediction data for a video block of the current video frame based on a signaled intra prediction mode and reference data from previously decoded blocks of the current frame.

[0092] When the video frame is coded as an inter-predictive coded (i.e. , B or P) frame, the motion compensation unit 82 of the prediction processing unit 81 produces one or more predictive blocks for a video block of the current video frame based on the motion vectors and other syntax elements received from the entropy decoding unit 80. Each of the predictive blocks may be produced from a reference frame within one of the reference frame lists. The video decoder 30 may construct the reference frame lists, List 0 and List 1, using default construction techniques based on reference frames stored in the DPB 92.

[0093] In some examples, when the video block is coded according to the intra BC mode described herein, the intra BC unit 85 of the prediction processing unit 81 produces predictive blocks for the current video block based on block vectors and other syntax elements received from the entropy decoding unit 80. The predictive blocks may be within a reconstructed region of the same picture as the current video block defined by the video encoder 20.

[0094] The motion compensation unit 82 and/or the intra BC unit 85 determines prediction information for a video block of the current video frame by parsing the motion vectors and other syntax elements, and then uses the prediction information to produce the predictive blocks for the current video block being decoded. For example, the motion compensation unit 82 uses some of the received syntax elements to determine a prediction mode (e.g., intra or inter prediction) used to code video blocks of the video frame, an inter prediction frame type (e.g., B or P), construction information for one or more of the reference frame lists for the frame, motion vectors for each inter predictive encoded video block of the frame, inter prediction status for each inter predictive coded video block of the frame, and other information to decode the video blocks in the current video frame. [0095] Similarly, the intra BC unit 85 may use some of the received syntax elements, e.g., a flag, to determine that the current video block was predicted using the intra BC mode, construction information of which video blocks of the frame are within the reconstructed region and should be stored in the DPB 92, block vectors for each intra BC predicted video block of the frame, intra BC prediction status for each intra BC predicted video block of the frame, and other information to decode the video blocks in the current video frame.

[0096] The motion compensation unit 82 may also perform interpolation using the interpolation filters as used by the video encoder 20 during encoding of the video blocks to calculate interpolated values for sub-integer pixels of reference blocks. In this case, the motion compensation unit 82 may determine the interpolation filters used by the video encoder 20 from the received syntax elements and use the interpolation filters to produce predictive blocks.

[0097] The inverse quantization unit 86 inverse quantizes the quantized transform coefficients provided in the bitstream and entropy decoded by the entropy decoding unit 80 using the same quantization parameter calculated by the video encoder 20 for each video block in the video frame to determine a degree of quantization. The inverse transform processing unit 88 applies an inverse transform, e.g., an inverse DCT, an inverse integer transform, or a conceptually similar inverse transform process, to the transform coefficients in order to reconstruct the residual blocks in the pixel domain.

[0098] After the motion compensation unit 82 or the intra BC unit 85 generates the predictive block for the current video block based on the vectors and other syntax elements, the summer 90 reconstructs decoded video block for the current video block by summing the residual block from the inverse transform processing unit 88 and a corresponding predictive block generated by the motion compensation unit 82 and the intra BC unit 85. An in-loop filter 91 such as deblocking filter, SAO filter, CCSAO filter and/or ALF may be positioned between the summer 90 and the DPB 92 to further process the decoded video block. In some examples, the in-loop filter 91 may be omitted, and the decoded video block may be directly provided by the summer 90 to the DPB 92. The decoded video blocks in a given frame are then stored in the DPB 92, which stores reference frames used for subsequent motion compensation of next video blocks. The DPB 92, or a memory device separate from the DPB 92, may also store decoded video for later presentation on a display device, such as the display device 34 of FIG. 1A. [0099] In a typical video coding process, a video sequence typically includes an ordered set of frames or pictures. Each frame may include three sample arrays, denoted SL, SCb, and SCr. SL is a two-dimensional array of luma samples. SCb is a two-dimensional array of Cb chroma samples. SCr is a two-dimensional array of Cr chroma samples. In other instances, a frame may be monochrome and therefore includes only one two-dimensional array of luma samples.

[00100] As shown in FIG. 1C, the video encoder 20 (or more specifically a partition unit in a prediction processing unit of the video encoder 20) generates an encoded representation of a frame by first partitioning the frame into a set of CTUs. A video frame may include an integer number of CTUs ordered consecutively in a raster scan order from left to right and from top to bottom. Each CTU is a largest logical coding unit and the width and height of the CTU are signaled by the video encoder 20 in a sequence parameter set, such that all the CTUs in a video sequence have the same size being one of 128x128, 64x64, 32x32, and 16x16. But it should be noted that the present application is not necessarily limited to a particular size. As shown in FIG. ID, each CTU may include one CTB of luma samples, two corresponding coding tree blocks of chroma samples, and syntax elements used to code the samples of the coding tree blocks. The syntax elements describe properties of different types of units of a coded block of pixels and how the video sequence can be reconstructed at the video decoder 30, including inter or intra prediction, intra prediction mode, motion vectors, and other parameters. In monochrome pictures or pictures having three separate color planes, a CTU may include a single coding tree block and syntax elements used to code the samples of the coding tree block. A coding tree block may be an NxN block of samples.

[00101] To achieve a better performance, the video encoder 20 may recursively perform tree partitioning such as binary-tree partitioning, ternary-tree partitioning, quad-tree partitioning or a combination thereof on the coding tree blocks of the CTU and divide the CTU into smaller CUs. FIGS. 1B-1E are block diagrams illustrating how a frame is recursively partitioned into multiple video blocks of different sizes and shapes in accordance with some implementations of the present disclosure. As depicted in FIG. IE, the 64x64 CTU 400 is first divided into four smaller CUs, each having a block size of 32x32. Among the four smaller CUs, CU 410 and CU 420 are each divided into four CUs of 16x16 by block size. The two 16x16 CUs 430 and 440 are each further divided into four CUs of 8x8 by block size. FIG. IB depicts a quad-tree data structure illustrating the end result of the partition process of the CTU 400 as depicted in FIG. IE, each leaf node of the quadtree corresponding to one CU of a respective size ranging from 32x32 to 8x8. Like the CTU depicted in FIG. ID, each CU may include a CB of luma samples and two corresponding coding blocks of chroma samples of a frame of the same size, and syntax elements used to code the samples of the coding blocks. In monochrome pictures or pictures having three separate color planes, a CU may include a single coding block and syntax structures used to code the samples of the coding block. It should be noted that the quad-tree partitioning depicted in FIGS. IE and IB is only for illustrative purposes and one CTU can be split into CUs to adapt to varying local characteristics based on quad/ternary/binary-tree partitions. In the multi-type tree structure, one CTU is partitioned by a quad-tree structure and each quad-tree leaf CU can be further partitioned by a binary and ternary tree structure. As shown in FIGS. 4A-4E, there are five possible partitioning types of a coding block having a width W and a height H, i.e., quaternary partitioning, horizontal binary partitioning, vertical binary partitioning, horizontal ternary partitioning, and vertical ternary partitioning.

[00102] In some implementations, the video encoder 20 may further partition a coding block of a CU into one or more MxN PBs. A PB is a rectangular (square or non-square) block of samples on which the same prediction, inter or intra, is applied. A PU of a CU may include a PB of luma samples, two corresponding PBs of chroma samples, and syntax elements used to predict the PBs. In monochrome pictures or pictures having three separate color planes, a PU may include a single PB and syntax structures used to predict the PB. The video encoder 20 may generate predictive luma, Cb, and Cr blocks for luma, Cb, and Cr PBs of each PU of the CU.

[00103] The video encoder 20 may use intra prediction or inter prediction to generate the predictive blocks for a PU. If the video encoder 20 uses intra prediction to generate the predictive blocks of a PU, the video encoder 20 may generate the predictive blocks of the PU based on decoded samples of the frame associated with the PU. If the video encoder 20 uses inter prediction to generate the predictive blocks of a PU, the video encoder 20 may generate the predictive blocks of the PU based on decoded samples of one or more frames other than the frame associated with the PU.

[00104] After the video encoder 20 generates predictive luma, Cb, and Cr blocks for one or more PUs of a CU, the video encoder 20 may generate a luma residual block for the CU by subtracting the CU’s predictive luma blocks from its original luma coding block such that each sample in the CU’s luma residual block indicates a difference between a luma sample in one of the CU's predictive luma blocks and a corresponding sample in the CU's original luma coding block. Similarly, the video encoder 20 may generate a Cb residual block and a Cr residual block for the CU, respectively, such that each sample in the CU's Cb residual block indicates a difference between a Cb sample in one of the CU's predictive Cb blocks and a corresponding sample in the CU's original Cb coding block and each sample in the CU's Cr residual block may indicate a difference between a Cr sample in one of the CU's predictive Cr blocks and a corresponding sample in the CU's original Cr coding block.

[00105] Furthermore, as illustrated in FIG. IE, the video encoder 20 may use quad-tree partitioning to decompose the luma, Cb, and Cr residual blocks of a CU into one or more luma, Cb, and Cr transform blocks respectively. A transform block is a rectangular (square or non-square) block of samples on which the same transform is applied. A TU of a CU may include a transform block of luma samples, two corresponding transform blocks of chroma samples, and syntax elements used to transform the transform block samples. Thus, each TU of a CU may be associated with a luma transform block, a Cb transform block, and a Cr transform block. In some examples, the luma transform block associated with the TU may be a sub-block of the CU's luma residual block. The Cb transform block may be a sub-block of the CU's Cb residual block. The Cr transform block may be a sub-block of the CU's Cr residual block. In monochrome pictures or pictures having three separate color planes, a TU may include a single transform block and syntax structures used to transform the samples of the transform block.

[00106] The video encoder 20 may apply one or more transforms to a luma transform block of a TU to generate a luma coefficient block for the TU. A coefficient block may be a two-dimensional array of transform coefficients. A transform coefficient may be a scalar quantity. The video encoder 20 may apply one or more transforms to a Cb transform block of a TU to generate a Cb coefficient block for the TU. The video encoder 20 may apply one or more transforms to a Cr transform block of a TU to generate a Cr coefficient block for the TU.

[00107] After generating a coefficient block (e.g., a luma coefficient block, a Cb coefficient block or a Cr coefficient block), the video encoder 20 may quantize the coefficient block. Quantization generally refers to a process in which transform coefficients are quantized to possibly reduce the amount of data used to represent the transform coefficients, providing further compression. After the video encoder 20 quantizes a coefficient block, the video encoder 20 may entropy encode syntax elements indicating the quantized transform coefficients. For example, the video encoder 20 may perform CABAC on the syntax elements indicating the quantized transform coefficients. Finally, the video encoder 20 may output a bitstream that includes a sequence of bits that forms a representation of coded frames and associated data, which is either saved in the storage device 32 or transmitted to the destination device 14.

[00108] After receiving a bitstream generated by the video encoder 20, the video decoder 30 may parse the bitstream to obtain syntax elements from the bitstream. The video decoder 30 may reconstruct the frames of the video data based at least in part on the syntax elements obtained from the bitstream. The process of reconstructing the video data is generally reciprocal to the encoding process performed by the video encoder 20. For example, the video decoder 30 may perform inverse transforms on the coefficient blocks associated with TUs of a current CU to reconstruct residual blocks associated with the TUs of the current CU. The video decoder 30 also reconstructs the coding blocks of the current CU by adding the samples of the predictive blocks for PUs of the current CU to corresponding samples of the transform blocks of the TUs of the current CU. After reconstructing the coding blocks for each CU of a frame, video decoder 30 may reconstruct the frame.

[00109] As noted above, video coding achieves video compression using primarily two modes, i.e., intra-frame prediction (or intra-prediction) and inter-frame prediction (or inter-prediction). It is noted that IBC could be regarded as either intra-frame prediction or a third mode. Between the two modes, inter-frame prediction contributes more to the coding efficiency than intra-frame prediction because of the use of motion vectors for predicting a current video block from a reference video block.

[00110] But with the ever improving video data capturing technology and more refined video block size for preserving details in the video data, the amount of data required for representing motion vectors for a current frame also increases substantially. One way of overcoming this challenge is to benefit from the fact that not only a group of neighboring CUs in both the spatial and temporal domains have similar video data for predicting purpose but the motion vectors between these neighboring CUs are also similar. Therefore, it is possible to use the motion information of spatially neighboring CUs and/or temporally co-located CUs as an approximation of the motion information (e.g., motion vector) of a current CU by exploring their spatial and temporal correlation, which is also referred to as “Motion Vector Predictor (MVP)” of the current CU. [00111] Instead of encoding, into the video bitstream, an actual motion vector of the current CU determined by the motion estimation unit as described above in connection with FIG. 2, the motion vector predictor of the current CU is subtracted from the actual motion vector of the current CU to produce a Motion Vector Difference (MVD) for the current CU. By doing so, there is no need to encode the motion vector determined by the motion estimation unit for each CU of a frame into the video bitstream and the amount of data used for representing motion information in the video bitstream can be significantly decreased.

[00112] Like the process of choosing a predictive block in a reference frame during inter-frame prediction of a code block, a set of rules need to be adopted by both the video encoder 20 and the video decoder 30 for constructing a motion vector candidate list (also known as a “merge list”) for a current CU using those potential candidate motion vectors associated with spatially neighboring CUs and/or temporally co-located CUs of the current CU and then selecting one member from the motion vector candidate list as a motion vector predictor for the current CU. By doing so, there is no need to transmit the motion vector candidate list itself from the video encoder 20 to the video decoder 30 and an index of the selected motion vector predictor within the motion vector candidate list is sufficient for the video encoder 20 and the video decoder 30 to use the same motion vector predictor within the motion vector candidate list for encoding and decoding the current CU.

[00113] In general, the basic inter prediction scheme applied in VVC is almost kept the same as that of HEVC, except that several prediction tools are further extended, added and/or improved, e.g., extended merge prediction, MMVD, and GPM.

Extended merge prediction

[00114] With the ever improving video data capturing technology and more refined video block size for preserving details in the video data, an amount of data required for representing motion vectors for a current picture also increases substantially. One way of overcoming this challenge is to use motion information (e.g., a motion vector) of a spatially neighboring CU, a temporally collocated CU etc. of a current CU as an approximation (e.g., prediction) of motion information of the current CU, which is also referred to as “Motion Vector Predictor (MVP)” of the current CU. [00115] Like a process of choosing a predictive block in a reference picture during inter-prediction of a coding block, a set of rules need to be adopted by both the video encoder 20 and the video decoder 30 for constructing an MVP candidate list for a current CU and then selecting one MVP candidate from the MVP candidate list as an MVP for the current CU. By doing so, there is no need to transmit the MVP candidate list itself between the video encoder 20 and the video decoder 30, and an index of the MVP candidate selected from the MVP candidate list is sufficient for the video encoder 20 and the video decoder 30 to use the same MVP candidate selected from the MVP candidate list for encoding and decoding the current CU.

[00116] In VVC, the MVP candidate list is constructed by including the following five types of MVPs in order:

[00117] — Spatial MVP from spatially neighboring CUs (i.e., spatial candidates);

[00118] — Temporal MVP from temporally collocated CUs (i.e., temporal candidates);

[00119] — History-based MVP (HMVP) from a First-In-First-Out (FIFO) table;

[00120] — Pairwise average MVP; and

[00121] —Zero MVPs.

[00122] A size of the MVP candidate list is signalled in a sequence parameter set header and a maximum allowed size of the MVP candidate list is 6. For each CU coded in merge mode, an index of the best MVP candidate is encoded using truncated unary binarization. A first bin of the index is coded with contexts and bypass coding is used for other bins of the index.

[00123] A derivation process of each type of MVPs is provided as follows. As in HEVC, VVC also supports parallel derivation of MVP candidate lists for all CUs within a certain size of area. Derivation of MVPs from spatial candidates

[00124] The derivation of MVPs from spatial candidates (for example, CUs neighboring a current CU 101 in FIG. 5) in VVC is the same as that in HEVC except that positions of first two spatial candidates are swapped. A maximum of four spatial candidates are selected from spatial candidates located at positions depicted in FIG. 5, that is, a top position B0, a left position A0, a top-right position Bl, a bottom-left position Al and a top-left position B2. The derivation is performed in an order of CUs at the positions B0, A0, Bl, Al and B2. A CU at the position B2 is considered only when one or more CUs at the positions B0, A0, Bl and Al are not available (for example, because said one or more CUs belong to other slices or tiles) or is intra coded.

[00125] After a CU at the position B0 is added as a candidate to a merge candidate list, the addition of the remaining candidates to the merge candidate list is subject to redundancy check, which ensures that candidates with the same motion information are excluded from the merge candidate list, so that coding efficiency is improved. To reduce computational complexity, not all possible candidate pairs are considered in the redundancy check. Instead, only pairs linked using a line with an arrow in FIG. 6 are considered and a candidate is added to the merge candidate list only if a candidate in a corresponding pair used for the redundancy check has not the same motion information as that of the candidate to be added. Spatial MVPs derived from the candidates in the merge candidate list are added to the MVP candidate list.

Derivation of MVPs from temporal candidates

[00126] During the derivation of MVPs from temporal candidates, only one temporal candidate is added to the merge candidate list. Particularly, in the derivation of an MVP from this temporal candidate, a scaled motion vector is derived based on a collocated CU (for example, col_CU 301 in FIG. 7) as the temporal candidate belonging to a collocated picture (for example, col _pic 302 in FIG. 7) for a current CU (for example, curr CU 303 in FIG. 7), and is added as a temporal MVP candidate to the MVP candidate list. A reference picture list and a reference picture index to be used for derivation of the collocated CU are explicitly signalled in a slice header. The scaled motion vector is obtained (i.e., scaled) from a motion vector of the collocated CU using Picture Order Count (POC) distances, i.e., tb and td, as illustrated in FIG. 7, where tb is defined to be a POC difference between a reference picture (for example, curr ref 305 in FIG. 7) of the current picture (for example, curr_pic 304 in FIG. 7) and the current picture and td is defined to be a POC difference between a reference picture (for example, col ref 306 in FIG. 7) of the collocated picture and the collocated picture. A reference picture index of the temporal candidate is set equal to zero. [00127] A position for the temporal candidate (i.e., the collocated CU) in the current CU 401 is selected between positions Co and Ci, as depicted in FIG. 8. If a CU at position Co in the collocated picture is not available, is intra coded, or is outside of a current row of CTUs, a CU at position Ci is used as the collocated CU for the derivation of the temporal MVP candidate. Otherwise, a CU at position Co is used as the collocated CU for the derivation of the temporal MVP candidate.

Derivation of HMVP candidates

[00128] HMVP candidates are added to the MVP candidate list after the spatial MVPs and the temporal MVP. Motion information of a previously coded block is stored in an HMVP table and used as an MVP for the current CU. The table with multiple HMVP candidates is maintained during the encoding/decoding process. The table is reset (emptied) when a new row of CTUs is encountered. Whenever there is a non-subblock inter-coded CU, associated motion information is added to a last entry of the HMVP table as a new HMVP candidate. [00129] A size of the HMVP table is set to 6. When a new HMVP candidate is inserted into the HMVP table, a constrained FIFO rule is utilized, wherein redundancy check is firstly applied to find whether there is an identical HMVP in the HMVP table. If found, the identical HMVP is removed from the HMVP table and all the HMVP candidates afterwards are moved forward, and the identical HMVP is added to the last entry of the HMVP table.

[00130J HMVP candidates may be used in the MVP candidate list construction process. The latest several HMVP candidates in the HMVP table are checked in order and inserted into the MVP candidate list after the temporal MVP candidate. Redundancy check is applied on the HMVP candidates relative to the spatial candidates and/or temporal MVP candidate.

[00131] To reduce a number of redundancy check operations, the following simplifications are introduced:

[00132] — Last two entries in the HMVP table are redundancy checked relative to spatial MVP candidates derived from the spatial candidates at the positions Al and B l, respectively; and [00133] — Once a total number of available MVP candidates reaches the maximum allowed size of the MVP candidate list minus 1, the MVP candidate list construction process from HMVP candidates is terminated.

Derivation of pairwise average MVP candidates

[00134] Pairwise average MVP candidates are generated by averaging MVPs derived using a predefined pair of first two merge candidates in the existing merge candidate list. A first merge candidate in the predefined pair may be defined as pOCand and a second merge candidate in the predefined pair may be defined as plCand. Averaged motion vectors are calculated according to availability of motion vectors of pOCand and plCand separately for each reference picture list. If both motion vectors are available for one reference picture list, these two motion vectors are averaged even when they point to different reference pictures, and a reference picture of the averaged motion vector is set to a reference picture of pOCand; if only one motion vector is available for one reference picture list, the motion vector is used directly; if no motion vector is available for one reference picture list, the motion vector and the reference picture index for this reference picture list are kept invalid.

Zero MVPs

[00135] When the MVP candidate list is not full after the pairwise average MVP candidates are added, zero MVPs are inserted at the end of the MVP candidate list until the maximum allowed size of the MVP candidate list is reached.

MMVD

[00136] As described above, in the merge mode, motion information (i.e., an MVP candidate) is implicitly derived from an MVP candidate list constructed for a current CU and is directly used as an MV of the current CU for generation of prediction samples of the current CU, which may result in a certain error between an actual MV of the current CU and the implicitly derived MVP. In order to increase the accuracy of an MV of the current CU, MMVD is introduced in VVC where a Motion Vector Difference (MVD) of the current CU is added to the implicitly derived MVP to obtain the MV of the current CU. An MMVD flag is signalled after a regular merge flag is transmitted to specify whether an MMVD mode is used for the current CU.

[00137] In the MMVD mode, after an MVP candidate is selected from first two MVP candidates in the MVP candidate list, MMVD information is signalled, wherein the MMVD information includes an MMVD candidate flag which is used to specify which one of the first two MVP candidates is selected to be used as an MV basis, a distance index for indication of motion magnitude information of the MVD, and a direction index for indication of motion direction information of the MVD.

[00138] The distance index, which specifies the motion magnitude information of the MVD, indicates a pre-defined offset from a starting point (represented by, for example, a dotted circle in FIG. 9) in a reference picture (for example, L0 reference picture 501 or LI reference picture 503 in FIG. 9) of the current CU to which the selected MVP candidate points, and the MVD may be derived from the offset and may be added to the selected MVP candidate. A relation between distance indexes and pre-defined offsets is specified in Table 1 below.

Table 1

[00139] The direction index specifies a sign of the MVD, which represents a direction of the MVD relative to the starting point. Table 2 specifies a relation between direction indexes and pre-defined signs. In some examples, the meaning of a sign of the MVD may be variant according to information of the selected MVP candidate. When the selected MVP candidate is an un-prediction MV or bi-prediction MVs with both MVs pointing to the same side of the current picture (i.e., POCs of two reference pictures (for example, reference pictures of list 0 and list 1, which are also referred to as LO reference picture and LI reference picture respectively) of the current picture are both greater than a POC of the current picture, or are both less than the POC of the current picture), the sign in Table 2 specifies the sign of the MVD added to the selected MVP candidate. When the selected MVP candidate is bi-prediction MVs with both MVs pointing to different sides of the current picture (i.e. a POC of one reference picture of the current picture is greater than the POC of the current picture, and a POC of the other reference picture of the current picture is less than the POC of the current picture), if a POC distance for LO reference picture (i.e., a POC distance between the LO reference picture and the current picture) is greater than a POC distance for LI reference picture (i.e., a POC distance between the LI reference picture and the current picture), the sign in Table 2 specifies a sign of an MVD for list 0 MVDO added to an MVP for list 0 MVPO of the selected MVP candidate and a sign of an MVD for list 1 MVD1 added to an MVP for list 1 MVP1 of the selected MVP candidate is opposite to the sign in Table 2; otherwise, if the POC distance for LI reference picture is greater than the POC distance for LO reference picture, the sign in Table 2 specifies the sign of MVD 1 added to MVP1 and the sign of MVDO added to MVPO is opposite to the sign in Table 2.

Table 2

[00140] The MVD is scaled according to the POC distances. If the POC distances for both LO reference picture and LI reference picture are the same, no scaling is needed for the MVD. Otherwise, if the POC distance for LO reference picture is greater than the POC distance for LI reference picture, MVD1 is scaled. If the POC distance for LI reference picture is greater than the POC distance for LO reference picture, MVDO is scaled.

GPM

[00141] In VVC, GPM is supported for inter prediction. The GPM is signalled using a CU-level flag as one kind of merge mode, with other merge modes including the regular merge mode, the MMVD mode, the CUP mode and the subblock merge mode. A total of 64 partitions are supported by GPM for each possible CU size W x H (W = 2 ^m and H = 2 ⁿ , with m, n G {3, 4, 5, 6}) excluding 8x64 and 64x8.

[00142J When the GPM is used, a CU is split into two parts by a geometrically located straight line. The position of the splitting line is mathematically derived from angle and offset parameters of a specific partition. Each part of the CU obtained by the geometrical partitioning is interpredicted using its own motion; and only uni -prediction is allowed for each partition, that is, each part has one motion vector and one reference index. The uni-prediction motion constraint is applied to ensure that like the conventional bi-prediction, only two motion compensated predictions are needed for each CU.

[00143] If the GPM is used for the current CU, then a geometric partition index indicating a partition mode of the geometric partitioning (indicating an angle and an offset of the geometric partitioning), and two merge indexes (one for each partition) are further signalled.

[00144] A uni -prediction candidate list is derived directly from a merge candidate list constructed according to the extended merge prediction process described above. Denote n as an index of a uni -prediction motion vector in the uni -prediction candidate list. An LX motion vector of an n ^,h merge candidate in the merge candidate list, with X equal to a parity of n, is used as the n ^th uniprediction motion vector for the GPM. These motion vectors are marked with “x” in FIG. 10. In a case that a corresponding LX motion vector of the n ^th merge candidate in the merge candidate list does not exist, an L(1 - X) motion vector of the same merge candidate is used instead as the uniprediction motion vector for the GPM.

CIIP

[00145] In VVC, when a CU is coded in a merge mode, if the CU contains at least 64 luma samples (that is, a width of CU times a height of the CU is equal to or larger than 64), and if both the width and the height of the CU are less than 128 luma samples, an additional flag is signalled to indicate if a CIIP mode is applied to the current CU. In the CIIP mode, a prediction signal is obtained by combining an inter prediction signal with an intra prediction signal. The inter prediction signal in the CIIP mode is derived using the same inter prediction process as that applied in the regular merge mode; and the intra prediction signal in the CIIP mode is derived following the regular intra prediction process with a planar mode. Then, the intra prediction signal and the inter prediction signal are combined using weighted averaging, where a weight value is calculated depending on coding modes of top and left neighboring blocks of the current CU 1601 (as shown in FIG. 11) as follows:

[00146] — If the top neighboring block is available and is intra coded, then isIntraTop is set to 1, otherwise isIntraTop is set to 0;

[00147] — If the left neighboring block is available and is intra coded, then isIntraLeft is set to 1, otherwise isIntraLeft is set to 0;

[00148] — If (isIntraLeft + isIntraTop) is equal to 2, then the weight value is set to 3;

[00149] — Otherwise, if (isIntraLeft + isIntraTop) is equal to 1, then the weight value is set to 2;

[00150] — Otherwise, the weight value is set to 1.

[00151] — The prediction signal P _CI]P in the CIIP mode is derived as follows:

[00152] Where Pi _nter is the inter prediction signal in the CIIP mode, Pi _ntr a is the intra prediction signal in the CIIP mode, wt is the weight value, and » represents a right shift operation.

Intra block copy in Versatile Video Coding (VVC)

[00153] Intra block copy (IBC) is a tool adopted in HEVC extensions on SCC. The IBC significantly improves the coding efficiency of screen content materials. Since IBC mode is implemented as a block level coding mode, block matching (BM) is performed at the encoder to find the optimal block vector (or motion vector) for each CU. Here, a block vector is used to indicate the displacement from the current block to a reference block, which is already reconstructed inside the current picture. The luma block vector of an IBC-coded CU is in integer precision. The chroma block vector rounds to integer precision as well. When combined with AMVR, the IBC mode can switch between 1-pel and 4-pel motion vector precisions. An IBC- coded CU is treated as the third prediction mode other than intra or inter prediction modes. The IBC mode is applicable to the CUs with both width and height smaller than or equal to 64 luma samples.

[00154] At the encoder side, hash-based motion estimation is performed for IBC. The encoder performs RD check for blocks with either width or height no larger than 16 luma samples. For non-merge mode, the block vector search is performed using hash-based search first. If hash search does not return valid candidate, block matching based local search will be performed.

[00155] In the hash-based search, hash key matching (32-bit CRC) between the current block and a reference block is extended to all allowed block sizes. The hash key calculation for every position in the current picture is based on 4x4 subblocks. For the current block of a larger size, a hash key is determined to match that of the reference block when all the hash keys of all 4*4 subblocks match the hash keys in the corresponding reference locations. If hash keys of multiple reference blocks are found to match that of the current block, the block vector costs of each matched reference are calculated and the one with the minimum cost is selected.

[00156J In block matching search, the search range is set to cover both the previous and current CTUs.

[00157] At CU level, IBC mode is signalled with a flag and it can be signaled as IBC AMVP mode or IBC skip/merge mode as follows:

[00158] IBC skip/merge mode: a merge candidate index is used to indicate which of the block vectors in the list from neighboring candidate IBC coded blocks is used to predict the current block. The merge list consists of spatial, HMVP, and pairwise candidates.

[00159] IBC AMVP mode: block vector difference is coded in the same way as a motion vector difference. The block vector prediction method uses two candidates as predictors, one from left neighbor and one from above neighbor (if IBC coded). When either neighbor is not available, a default block vector will be used as a predictor. A flag is signaled to indicate the block vector predictor index.

IBC reference region

[00160] To reduce memory consumption and decoder complexity, the IBC in VVC allows only the reconstructed portion of the predefined area including the region of current CTU and some region of the left CTU. FIG. 12 illustrates the reference region of IBC Mode, where each block represents 64x64 luma sample unit.

[00161] Depending on the location of the current coding CU location within the current CTU, the following applies:

[00162] If current block falls into the top-left 64x64 block of the current CTU, then in addition to the already reconstructed samples in the current CTU, it can also refer to the reference samples in the bottom-right 64x64 blocks of the left CTU, using CPR mode. The current block can also refer to the reference samples in the bottom-left 64x64 block of the left CTU and the reference samples in the top-right 64x64 block of the left CTU, using CPR mode.

[00163] If current block falls into the top-right 64x64 block of the current CTU, then in addition to the already reconstructed samples in the current CTU, if luma location (0, 64) relative to the current CTU has not yet been reconstructed, the current block can also refer to the reference samples in the bottom-left 64x64 block and bottom-right 64x64 block of the left CTU, using CPR mode; otherwise, the current block can also refer to reference samples in bottom-right 64x64 block of the left CTU.

[00164] If current block falls into the bottom-left 64x64 block of the current CTU, then in addition to the already reconstructed samples in the current CTU, if luma location (64, 0) relative to the current CTU has not yet been reconstructed, the current block can also refer to the reference samples in the top-right 64x64 block and bottom-right 64x64 block of the left CTU, using CPR mode. Otherwise, the current block can also refer to the reference samples in the bottom-right 64x64 block of the left CTU, using CPR mode.

[00165] If current block falls into the bottom-right 64x64 block of the current CTU, it can only refer to the already reconstructed samples in the current CTU, using CPR mode.

[00166] This restriction allows the IBC mode to be implemented using local on-chip memory for hardware implementations.

IBC interaction with other coding tools

[00167] The interaction between IBC mode and other inter coding tools in VVC, such as pairwise merge candidate, history based motion vector predictor (HMVP), combined intra/inter prediction mode (CIIP), merge mode with motion vector difference (MMVD), and geometric partitioning mode (GPM) are as follows:

[00168] IBC can be used with pairwise merge candidate and HMVP. A new pairwise IBC merge candidate can be generated by averaging two IBC merge candidates. For HMVP, IBC motion is inserted into history buffer for future referencing.

[00169] IBC cannot be used in combination with the following inter tools: affine motion, CIIP, MMVD, and GPM.

[00170] IBC is not allowed for the chroma coding blocks when DUAL TREE partition is used.

[00171] Unlike in the HEVC screen content coding extension, the current picture is no longer included as one of the reference pictures in the reference picture list 0 for IBC prediction. The derivation process of motion vectors for IBC mode excludes all neighboring blocks in inter mode and vice versa. The following IBC design aspects are applied:

[00172] IBC shares the same process as in regular MV merge including with pairwise merge candidate and history -based motion predictor, but disallows TMVP and zero vector because they are invalid for IBC mode.

[00173] Separate HMVP buffer (5 candidates each) is used for conventional MV and IBC.

[00174] Block vector constraints are implemented in the form of bitstream conformance constraint, the encoder needs to ensure that no invalid vectors are present in the bitstream, and merge shall not be used if the merge candidate is invalid (out of range or 0). Such bitstream conformance constraint is expressed in terms of a virtual buffer as described below.

[00175] For deblocking, IBC is handled as inter mode.

[00176] If the current block is coded using IBC prediction mode, AMVR does not use quarter-pel; instead, AMVR is signaled to only indicate whether MV is inter-pel or 4 integer-pel.

[00177] The number of IBC merge candidates can be signalled in the slice header separately from the numbers of regular, subblock, and geometric merge candidates.

[00178] A virtual buffer concept is used to describe the allowable reference region for IBC prediction mode and valid block vectors. Denote CTU size as ctbSize, the virtual buffer, ibcBuf, has width being wlbcBuf = 128xl28/ctbSize and height hlbcBuf = ctbSize. For example, for a CTU size of 128x128, the size of ibcBuf is also 128x128; for a CTU size of 64x64, the size of ibcBuf is 256x64; and a CTU size of 32x32, the size of ibcBuf is 512x32.

[00179] The size of a VPDU is min(ctbSize, 64) in each dimension, Wv = min(ctbSize, 64).

[00180] The virtual IBC buffer, ibcBuf is maintained as follows.

[00181] At the beginning of decoding each CTU row, refresh the whole ibcBuf with an invalid value -1.

[00182] At the beginning of decoding a VPDU (xVPDU, yVPDU) relative to the top-left comer of the picture, set the ibcBuf[ x ][ y ] = -1, with x = xVPDU%wIbcBuf, .. . , xVPDU% wlbcBuf + W _v - 1; y = yVPDU%ctbSize, . . ., yVPDU%ctbSize + W _v - 1.

[00183] After decoding a CU contains (x, y) relative to the top-left comer of the picture, set ibcBuff x % wlbcBuf ][ y % ctbSize ] = recSample[ x ][ y ]

[00184] For a block covering the coordinates (x, y), if the following is true for a block vector bv = (bv[0], bv[l]), then it is valid; otherwise, it is not valid:

[00185] ibcBuf[ (x + bv[0])% wlbcBuf] [ (y + bv[l]) % ctbSize ] shall not be equal to -1.

Intra block copy in Enhanced Compression Model (ECM) [00186] In ECM, IBC is improved from below aspects. IBC merge/ AMVP list construction

[00187] The IBC merge/ AMVP list construction is modified as follows:

[00188] Only if an IBC merge/ AMVP candidate is valid, it can be inserted into the IBC merge/ AMVP candidate list.

[00189] Above-right, bottom-left, and above-left spatial candidates and one pairwise average candidate can be added into the IBC merge/ AMVP candidate list.

[00190] Template based adaptive reordering (ARMC-TM) is applied to IBC merge list.

[00191] The HMVP table size for IBC is increased to 25. After up to 20 IBC merge candidates are derived with full pruning, they are reordered together. After reordering, the first 6 candidates with the lowest template matching costs are selected as the final candidates in the IBC merge list.

[00192] The zero vectors’ candidates to pad the IBC Merge/ AMVP list are replaced with a set of BVP candidates located in the IBC reference region. A zero vector is invalid as a block vector in IBC merge mode, and consequently, it is discarded as BVP in the IBC candidate list.

[00193] Three candidates are located on the nearest corners of the reference region, and three additional candidates are determined in the middle of the three sub-regions (A, B, and C), whose coordinates are determined by the width, and height of the current block and the AX and AY parameters, as is depicted in FIG. 13.

IBC with Template Matching

[00194] Template Matching is used in IBC for both IBC merge mode and IBC AMVP mode.

[00195] The IBC-TM merge list is modified compared to the one used by regular IBC merge mode such that the candidates are selected according to a pruning method with a motion distance between the candidates as in the regular TM merge mode. The ending zero motion fulfillment is replaced by motion vectors to the left (-W, 0), top (0, -H) and top-left (-W, -H), where W is the width and H the height of the current CU.

[00196] In the IBC-TM merge mode, the selected candidates are refined with the Template Matching method prior to the RDO or decoding process. The IBC-TM merge mode has been put in competition with the regular IBC merge mode and a TM-merge flag is signaled.

[00197] In the IBC-TM AMVP mode, up to 3 candidates are selected from the IBC-TM merge list. Each of those 3 selected candidates are refined using the Template Matching method and sorted according to their resulting Template Matching cost. Only the 2 first ones are then considered in the motion estimation process as usual. [00198] The Template Matching refinement for both IBC-TM merge and AMVP modes is quite simple since IBC motion vectors are constrained (i) to be integer and (ii) within a reference region as shown in FIG. 12. So, in IBC-TM merge mode, all refinements are performed at integer precision, and in IBC-TM AMVP mode, they are performed either at integer or 4-pel precision depending on the AMVR value. Such a refinement accesses only to samples without interpolation. In both cases, the refined motion vectors and the used template in each refinement step must respect the constraint of the reference region.

IBC reference area

[00199] The reference area for IBC is extended to two CTU rows above. FIG. 14 illustrates the reference area for coding CTU (m,n). Specifically, for CTU (m,n) to be coded, the reference area includes CTUs with index (m-2,n-2). . . (W,n-2),(0,n-l). .. (W,n-l),(0,n). . . (m,n), where W denotes the maximum horizontal index within the current tile, slice or picture. This setting ensures that for CTU size being 128, IBC does not require extra memory in the current ETM platform. The persample block vector search (or called local search) range is limited to [-(C « 1), C » 2] horizontally and [-C, C » 2] vertically to adapt to the reference area extension, where C denotes the CTU size.

IBC merge mode with block vector differences

[00200] IBC merge mode with block vector differences is adopted in ECM. The distance set is { 1- pel, 2-pel, 4-pel, 8-pel, 12-pel, 16-pel, 24-pel, 32-pel, 40-pel, 48-pel, 56-pel, 64-pel, 72-pel, 80- pel, 88-pel, 96-pel, 104-pel, 112-pel, 120-pel, 128-pel}, and the BVD directions are two horizontal and two vertical directions.

[00201] The base candidates are selected from the first five candidates in the reordered IBC merge list. And based on the SAD cost between the template (one row above and one column left to the current block) and its reference for each refinement position, all the possible MBVD refinement positions (20x4) for each base candidate are reordered. Finally, the top 8 refinement positions with the lowest template SAD costs are kept as available positions, consequently for MBVD index coding.

IBC adaptation for camera-captured content

[00202] When adapt IBC for camera-captured content, IBC reference range is reduced from 2 CTU rows to 2x128 rows as shown in FIG. 15. At encoder side to reduce the complexity, the local search range is set to [-8,8] horizontally and [-8,8] vertically centered at the first block vector predictor of the current CU. This encoder modification is not applied to SCC sequences. Combination of CIIP with TIMD and TM merge

[00203] In CIIP mode, the prediction samples are generated by weighting an inter prediction signal predicted using CIIP-TM merge candidate and an intra prediction signal predicted using TIMD derived intra prediction mode. The method is only applied to coding blocks with an area less than or equal to 1024.

[00204] The TIMD derivation method is used to derive the intra prediction mode in CIIP. Specifically, the intra prediction mode with the smallest SATD values in the TIMD mode list is selected and mapped to one of the 67 regular intra prediction modes.

[00205] In addition, it is also proposed to modify the weights (wlntra, winter) for the two tests if the derived intra prediction mode is an angular mode. For near-horizontal modes (2 <= angular mode index < 34), the current block is vertically divided as shown in FIG. 16A; for near-vertical modes (34 <= angular mode index <= 66), the current block is horizontally divided as shown in FIG. 16B.

[00206] The (wlntra, winter) for different sub-blocks are shown in Table 3.

[00207] With CIIP-TM, a CIIP-TM merge candidate list is built for the CIIP-TM mode. The merge candidates are refined by template matching. The CIIP-TM merge candidates are also reordered by the ARMC method as regular merge candidates. The maximum number of CIIP-TM merge candidates is equal to two.

Multi-hypothesis prediction (MHP)

[00208] In the multi -hypothesis inter prediction mode, one or more additional motion- compensated prediction signals are signaled, in addition to the conventional bi prediction signal. The resulting overall prediction signal is obtained by sample-wise weighted superposition. With the bi prediction signal p _bi and the first additional inter prediction signal/hypothesis h ₃ , the resulting prediction signal p ₃ is obtained as follows: p ₃ = (1 - a)p _bi + ah ₃ (2)

[00209] The weighting factor a is specified by the new syntax element add_hyp_weight_idx, according to the mapping presented in Table 4:

Table 4. The mapping between add hyp weight idx and a.

[00210] Analogously to above, more than one additional prediction signal can be used. The resulting overall prediction signal is accumulated iteratively with each additional prediction signal.

Pn+1 (1 _n +i)Pn 4" n+l -n+1 (3)

[00211] The resulting overall prediction signal is obtained as the last p _n (i.e., the p _n having the largest index n). Within this mode, up to two additional prediction signals can be used (i.e., n is limited to 2).

[00212] The motion parameters of each additional prediction hypothesis can be signaled either explicitly by specifying the reference index, the motion vector predictor index, and the motion vector difference, or implicitly by specifying a merge index. A separate multi-hypothesis merge flag distinguishes between these two signalling modes.

[00213] For inter AMVP mode, MHP is only applied if non-equal weight in BCW is selected in bi-prediction mode.

[00214] Combination of MHP and BDOF is possible, however the BDOF is only applied to the bi-prediction signal part of the prediction signal (i.e., the ordinary first two hypotheses).

Geometric Partitioning Mode (GPM) in ECM

[00215] GPM with merge motion vector differences (MMVD)

[00216] GPM in VVC is extended by applying motion vector refinement on top of the existing GPM uni-directional MVs. A flag is first signalled for a GPM CU, to specify whether this mode is used. If the mode is used, each geometric partition of a GPM CU can further decide whether to signal MVD or not. If MVD is signalled for a geometric partition, after a GPM merge candidate is selected, the motion of the partition is further refined by the signalled MVDs information. All other procedures are kept the same as in GPM. [00217] The MVD is signaled as a pair of distance and direction, similar as in MMVD There are nine candidate distances (%-pel, 1 -pel, 1-pel, 2-pel, 3-pel, 4-pel, 6-pel, 8-pel, 16-pel), and eight candidate directions (four horizontal/vertical directions and four diagonal directions) involved in GPM with MMVD (GPM-MMVD). In addition, when pic fpel mmvd enabled flag is equal to 1, the MVD is left shifted by 2 as in MMVD.

[00218J GPM with template matching (TM)

[00219] Template matching is applied to GPM. When GPM mode is enabled for a CU, a CU-level flag is signaled to indicate whether TM is applied to both geometric partitions. Motion information for each geometric partition is refined using TM. When TM is chosen, a template is constructed using left, above or left and above neighboring samples according to partition angle, as shown in Table 5. The motion is then refined by minimizing the difference between the current template and the template in the reference picture using the same search pattern of merge mode with half-pel interpolation filter disabled.

Table 5. Template for the 1st and 2nd geometric partitions, where A represents using above samples, L represents using left samples, and L+A represents using both left and above samples. [00220] A GPM candidate list is constructed as follows:

[00221] 1. Interleaved List-0 MV candidates and List-1 MV candidates are derived directly from the regular merge candidate list, where List-0 MV candidates are higher priority than List-1 MV candidates. A pruning method with an adaptive threshold based on the current CU size is applied to remove redundant MV candidates.

[00222] 2. Interleaved List-1 MV candidates and List-0 MV candidates are further derived directly from the regular merge candidate list, where List-1 MV candidates are higher priority than List-0 MV candidates. The same pruning method with the adaptive threshold is also applied to remove redundant MV candidates.

[00223] 3. Zero MV candidates are padded until the GPM candidate list is full. [00224] The GPM-MMVD and GPM-TM are exclusively enabled to one GPM CU. This is done by firstly signaling the GPM-MMVD syntax. When both two GPM-MMVD control flags are equal to false (i.e., the GPM-MMVD are disabled for two GPM partitions), the GPM-TM flag is signaled to indicate whether the template matching is applied to the two GPM partitions. Otherwise (at least one GPM-MMVD flag is equal to true), the value of the GPM-TM flag is inferred to be false.

[00225J GPM with inter and intra prediction

[00226] In GPM with inter and intra prediction, the final prediction samples are generated by weighting inter predicted samples and intra predicted samples for each GPM-separated region. The inter predicted samples are derived by inter GPM whereas the intra predicted samples are derived by an intra prediction mode (IPM) candidate list and an index signaled from the encoder. The IPM candidate list size is pre-defined as 3. The available IPM candidates are the parallel angular mode against the GPM block boundary (Parallel mode), the perpendicular angular mode against the GPM block boundary (Perpendicular mode), and the Planar mode as shown FIGS. 17A-17D, respectively. Furthermore, GPM with intra and intra prediction as shown FIG. 17D is restricted to reduce the signaling overhead for IPMs and avoid an increase in the size of the intra prediction circuit on the hardware decoder. In addition, a direct motion vector and IPM storage on the GPM- blending area is introduced to further improve the coding performance.

[00227] In DIMD and neighboring mode based IPM derivation Parallel mode is registered first. Therefore, max two IPM candidates derived from the decoder-side intra mode derivation (DIMD) method and/or the neighboring blocks can be registered if there is not the same IPM candidate in the list. As for the neighboring mode derivation, there are five positions for available neighboring blocks at most, but they are restricted by the angle of GPM block boundary as shown in Table 6, which are already used for GPM with template matching (GPM-TM).

Table 6. The position of available neighboring blocks for IPM candidate derivation based on the angle of GPM block boundary. A and L denotes the above and left side of the prediction block. [00228] GPM-intra can be combined with GPM with merge with motion vector difference (GPM- MMVD). TIMD is used for on IPM candidates of GPM-intra to further improve the coding performance. The Parallel mode can be registered first, then IPM candidates of TIMD, DIMD, and neighboring blocks.

[00229] Template matching based reordering for GPM split modes

[00230] In template matching based reordering for GPM split modes, given the motion information of the current GPM block, the respective TM cost values of GPM split modes are computed. Then, all GPM split modes are reordered in ascending ordering based on the TM cost values. Instead of sending GPM split mode, an index using Golomb-Rice code to indicate where the exact GPM split mode is located in the reordering list is signaled.

[00231] The reordering method for GPM split modes is a two-step process performed after the respective reference templates of the two GPM partitions in a coding unit are generated, as follows: [00232] • extending GPM partition edge into the reference templates of the two GPM partitions, resulting in 64 reference templates and computing the respective TM cost for each of the 64 reference templates;

[00233] • reordering GPM split modes based on their TM cost values in ascending order and marking the best 32 as available split modes.

[00234] The edge on the template is extended from that of the current CU, as FIG. 18 illustrates, but GPM blending process is not used in the template area across the edge.

[00235] After ascending reordering using TM cost, an index is signaled.

Currently, the IBC tool is not combined with the GPM tool, it is straightforward to combine them together, which may improve the prediction accuracy and improve the coding performance.

Currently, the coding block coded with IBC mode is not combined with the coding block coded with intra mode or inter mode, it is straightforward to combine them together, which may improve the prediction accuracy and improve the coding performance.

[00236] Currently, the block vector (BV) number in the IBC tool is singular, it is straightforward to increase the block vector (BV) number and the prediction results can be combined, which may improve the prediction accuracy and improve the coding performance.

[00237] In this disclosure, to address the issues as pointed out above, methods are provided to further improve the existing design of the IBC. In general, the main features of the proposed technologies in this disclosure are summarized as follows. 1. The IBC tool is combined with GPM tool, the combined form can be GPM with IBC and IBC prediction, GPM with IBC and Intra prediction or GPM with IBC and inter prediction.

2. As a simplified version of IBC tool combined with GPM tool, for a predefined direction (such as 45 degree), the upper left part is predicted with intra mode, the bottom right part is predicted with IBC mode, then they are average weighted to obtain the final prediction signal.

3. The IBC tool is combined with CUP tool, where the IBC prediction is combined with intra prediction mode, or the IBC prediction is combined with inter prediction mode.

4. The IBC tool is combined with MHP tool, where more than one BV prediction are obtained and they are weighted averaged to obtain the final prediction signal.

[00238] In some examples, the disclosed methods may be applied independently or jointly.

GPM with IBC and IBC prediction

[00239] According to the one or more embodiments of the disclosure, the IBC tool is combined with GPM tool in the form of GPM with IBC and IBC prediction. Different methods may be used to achieve this goal.

[00240] In the first method, both “inter” parts of GPM with inter and inter prediction method in VVC is replaced with IBC. That means that two IBC merge prediction results are weighted averaged with each other according to a splitting line in the coding block. The weight can be obtained referring to GPM with inter and inter prediction method in VVC.

[00241] In the second method, both “inter” parts of GPM with inter and inter prediction method in ECM is replaced with IBC, where some template matching tools can be utilized to further improve the coding performance.

GPM with IBC and intra prediction

[00242] According to the one or more embodiments of the disclosure, the IBC tool is combined with GPM tool in the form of GPM with IBC and intra prediction. Different methods may be used to achieve this goal.

[00243] In the first method, the “inter” part of GPM with inter and intra prediction method in ECM is replaced with IBC, where the IBC merge predicted results are weighted averaged with the intra prediction results to obtain the final prediction signal. GPM with IBC and inter prediction

[00244] According to the one or more embodiments of the disclosure, the IBC tool is combined with GPM tool in the form of GPM with IBC and inter prediction. Different methods may be used to achieve this goal.

[00245] In the first method, one “inter” part of GPM with inter and inter prediction method in VVC is replaced with IBC, where the IBC merge predicted results are weighted averaged with the inter merge prediction results to obtain the final prediction signal.

[00246] In the second method, one “inter” part of GPM with inter and inter prediction method in ECM is replaced with IBC, where some template matching tools can be utilized to further improve the coding performance.

Simplified IBC and intra prediction combination in GPM form

[00247] According to the one or more embodiments of the disclosure, the IBC tool is combined with GPM tool in the form of simplified GPM with IBC and intra prediction, such as IBC and intra prediction is combined at a certain splitting mode, which can save the bits overhead of the splitting representation. Different methods may be used to achieve this goal.

[00248] In the first method, aiming at one splitting line, such as 45 degree, the upper left parts of the coding block is coded with intra prediction mode, and the bottom right parts of the coding block is coded with IBC prediction mode, then they are averaged in GPM form to obtain the final prediction signal.

Combined IBC-intra/inter prediction

[00249] According to the one or more embodiments of the disclosure, the coding block coded with IBC mode are combined with the coding block coded with intra mode or inter mode. Different methods may be used to achieve this goal.

[00250] In the first method, the encoder/decoder may combine the coding block coded with IBC mode with the coding block coded with intra mode. Various methods can be utilized in this combination. In one example, similar to the CIIP technology in VVC, the coding block coded with IBC merge mode is regarded as the coding block coded with inter merge mode, and it is combined with the coding block coded with planar intra prediction mode. In another example, similar to the Combination of CIIP with TIMD and TM merge technology in ECM, the coding block coded with IBC merge-TM mode is combined with the coding block coded with TIMD derived intra prediction mode. [00251] In the second method, the encoder/decoder may combine the coding block coded with IBC mode with the coding block coded with inter mode. Various methods can be utilized in this combination. In one example, similar to the CIIP technology in VVC, the coding block coded with IBC merge mode is regarded as the coding block coded with planar intra mode, and it is combined with the coding block coded with inter merge mode. In another example, the coding block coded with IBC merge mode is regarded as the coding block coded with inter merge mode, and it is combined with the coding block coded with inter merge mode by equally averaging.

[00252] In the third method, the encoder/decoder may combine the coding block coded with IBC mode with the coding block coded with intra mode and the coding block coded with inter mode. Various methods can be utilized in this combination. In one example, the coding block coded with IBC mode, the coding block coded with intra mode, and the coding block coded with inter mode are directly combined by equally averaging. In another example, firstly the coding block coded with IBC mode is separately combined with the coding block coded with intra mode and inter mode as presented in the first and second method. Then, the separate combined results are combined by equally averaging.

Multiple hypothesis IBC prediction

[00253] According to the one or more embodiments of the disclosure, the block vector (BV) number in IBC tool is increased to 2 or more, and 2 or more hypothesis are combined to obtain the final prediction result. Different methods may be used to achieve this goal.

[00254] In the first method, the encoder/decoder may combine 2 hypothesis corresponding to 2 BVs to obtain the final prediction result. Various methods can be utilized to achieve this goal. In one example, the 2 BVs corresponding the smallest and the second smallest rate distortion metrics in IBC AMVP mode are equally averaged to obtain the final prediction result. In another example, the prediction result corresponding to IBC AMVP mode and the prediction result corresponding to IBC merge mode are equally averaged to obtain the final prediction result.

[00255] In the second method, the encoder/decoder may combine more hypothesis corresponding to more BVs to obtain the final prediction result. Various methods can be utilized to achieve this goal. In one example, the iterative accumulation method proposed in Multi -hypothesis prediction (MHP) technology is utilized to obtain the final prediction result. In another example, all the BVs corresponding the smallest, the second smallest, the third smallest, ... , rate distortion metrics in IBC AMVP mode are equally averaged to obtain the final prediction result. [00256] FIG. 19 shows a computing environment (or a computing device) 1610 coupled with a user interface 1650. The computing environment 1610 can be part of a data processing server. In some embodiments, the computing device 1610 can perform any of various methods or processes (such as encoding/decoding methods or processes) as described hereinbefore in accordance with various examples of the present disclosure. The computing environment 1610 includes a processor 1620, a memory 1630, and an Input/Output (I/O) interface 1640.

[00257] The processor 1620 typically controls overall operations of the computing environment 1610, such as the operations associated with display, data acquisition, data communications, and image processing. The processor 1620 may include one or more processors to execute instructions to perform all or some of the steps in the above-described methods. Moreover, the processor 1620 may include one or more modules that facilitate the interaction between the processor 1620 and other components. The processor may be a Central Processing Unit (CPU), a microprocessor, a single chip machine, a Graphical Processing Unit (GPU), or the like.

[00258] The memory 1630 is configured to store various types of data to support the operation of the computing environment 1610. The memory 1630 may include predetermined software 1632. Examples of such data includes instructions for any applications or methods operated on the computing environment 1610, video datasets, image data, etc. The memory 1630 may be implemented by using any type of volatile or non-volatile memory devices, or a combination thereof, such as a Static Random Access Memory (SRAM), an Electrically Erasable Programmable Read-Only Memory (EEPROM), an Erasable Programmable Read-Only Memory (EPROM), a Programmable Read-Only Memory (PROM), a Read-Only Memory (ROM), a magnetic memory, a flash memory, a magnetic or optical disk.

[00259] The I/O interface 1640 provides an interface between the processor 1620 and peripheral interface modules, such as a keyboard, a click wheel, buttons, and the like. The buttons may include but are not limited to, a home button, a start scan button, and a stop scan button. The I/O interface 1640 can be coupled with an encoder and decoder.

[00260] FIG. 20 is a flowchart illustrating a method for video decoding according to an example of the present disclosure. FIG. 20 illustrates methods of GPM with IBC and IBC prediction, GPM with IBC and intra prediction, GPM with IBC and inter prediction, and/or simplified IBC and intra prediction combination in GPM form. [00261] In Step 2001, the processor 1620, at the side of a decoder, may obtain a current CU that is coded based on IBC mode combined with GPM.

[00262] In Step 2002, the processor 1620 may obtain a prediction for the current CU based on the IBC mode combined with GPM.

[00263] In some examples, the current CU is partitioned into a first IBC-predicted part and a second IBC-predicted part.

[00264] In one or more examples, the current CU is partitioned into the two IBC-predicted parts following GPM with inter and inter prediction method in VVC. Both “inter” parts of GPM with inter and inter prediction method in VVC is replaced with IBC. That means that two IBC merge prediction results are weighted averaged with each other according to a splitting line in the coding block. The weight can be obtained referring to GPM with inter and inter prediction method in VVC. For example, the processor 1620 may obtain a first IBC merge prediction for the first IBC- predicted part and a second IBC merge prediction for the second IBC-predicted part, and obtain the prediction for the current CU based on the first IBC merge prediction and the second IBC merge prediction. The prediction for the current CU may be obtained by weighted-averaging the first IBC merge prediction and the second IBC merge prediction.

[00265] In one or more examples, the current CU is partitioned into the two IBC-predicted parts following GPM with inter and inter prediction method in ECM. Both “inter” parts of GPM with inter and inter prediction method in ECM is replaced with IBC, where some template matching tools can be utilized to further improve the coding performance. For example, the processor 1620 may obtain a first IBC-TM prediction for the first IBC-predicted part and a second IBC-TM prediction for the second IBC-predicted part, and obtain the prediction for the current CU based on the first IBC-TM prediction and the second IBC-TM prediction.

[00266] In some examples, the current CU is partitioned into a first IBC-predicted part and a second intra-predicted part. In these examples, the “inter” part of GPM with inter and intra prediction method in ECM is replaced with IBC, where the IBC merge predicted results are weighted averaged with the intra prediction results to obtain the final prediction signal. For example, the processor 1620 may obtain a first IBC merge prediction for the first IBC-predicted part and a second intra prediction for the second intra-predicted part, and obtain the prediction for the current CU by weighted-averaging the first IBC merge prediction and the second intra prediction. [00267] In some examples, the current CU is partitioned into a first IBC-predicted part and a second inter-predicted part. In these examples, one “inter” part of GPM with inter and inter prediction method in VVC or in ECM is replaced with IBC. For example, the processor 1620 may obtain a first IBC merge prediction for the first IBC-predicted part and a second inter prediction for the second inter-predicted part, and obtain the prediction for the current CU by weighted- averaging the first IBC merge prediction and the second inter prediction. For another example, the processor 1620 may obtain a first IBC-TM prediction for the first IBC-predicted part and a second inter prediction for the second inter-predicted part, and obtain the prediction for the current CU based on the first IBC TM prediction and the second inter prediction.

[00268] In some examples, the IBC tool may be combined with GPM tool in the form of simplified GPM with IBC and intra prediction. For example, the current CU is partitioned into a first part and a second part based on a predefined direction, corresponding to a certain splitting mode used in GPM. In these examples, the processor 1620 may obtain a first IBC prediction for the first part and a second intra prediction for the second part, and obtain the prediction for the current CU by averaging the first IBC prediction and the second intra prediction. In some examples, the predefined direction may be one splitting line at 45 degrees, the upper left parts of the coding block is coded with intra prediction mode, and the bottom right parts of the coding block is coded with IBC prediction mode, then they are averaged in GPM form to obtain the final prediction signal.

[00269] FIG. 21 is a flowchart illustrating a method for video encoding corresponding the method for video decoding as shown in FIG. 20.

[00270] In Step 2101, the processor 1620, at the side of an encoder, may encode a current CU based on IBC mode combined with GPM.

[00271] In Step 2102, the processor 1620 may transmit the current CU that is coded based on the IBC mode combined with GPM to a decoder.

[00272] In some examples, the current CU is partitioned into a first IBC-predicted part and a second IBC-predicted part.

[00273] In one or more examples, the current CU is partitioned into the two IBC-predicted parts following GPM with inter and inter prediction method in VVC. Both “inter” parts of GPM with inter and inter prediction method in VVC is replaced with IBC. That means that two IBC merge prediction results are weighted averaged with each other according to a splitting line in the coding block. The weight can be obtained referring to GPM with inter and inter prediction method in VVC. For example, the processor 1620 may obtain a first IBC merge prediction for the first IBC- predicted part and a second IBC merge prediction for the second IBC-predicted part, and obtain the prediction for the current CU based on the first IBC merge prediction and the second IBC merge prediction. The prediction for the current CU may be obtained by weighted-averaging the first IBC merge prediction and the second IBC merge prediction.

[00274J In one or more examples, the current CU is partitioned into the two IBC-predicted parts following GPM with inter and inter prediction method in ECM. Both “inter” parts of GPM with inter and inter prediction method in ECM is replaced with IBC, where some template matching tools can be utilized to further improve the coding performance. For example, the processor 1620 may obtain a first IBC-TM prediction for the first IBC-predicted part and a second IBC-TM prediction for the second IBC-predicted part, and obtain the prediction for the current CU based on the first IBC-TM prediction and the second IBC-TM prediction.

[00275] In some examples, the current CU is partitioned into a first IBC-predicted part and a second intra-predicted part. In these examples, the “inter” part of GPM with inter and intra prediction method in ECM is replaced with IBC, where the IBC merge predicted results are weighted averaged with the intra prediction results to obtain the final prediction signal. For example, the processor 1620 may obtain a first IBC merge prediction for the first IBC-predicted part and a second intra prediction for the second intra-predicted part, and obtain the prediction for the current CU by weighted-averaging the first IBC merge prediction and the second intra prediction.

[00276] In some examples, the current CU is partitioned into a first IBC-predicted part and a second inter-predicted part. In these examples, one “inter” part of GPM with inter and inter prediction method in VVC or in ECM is replaced with IBC. For example, the processor 1620 may obtain a first IBC merge prediction for the first IBC-predicted part and a second inter prediction for the second inter-predicted part, and obtain the prediction for the current CU by weighted- averaging the first IBC merge prediction and the second inter prediction. For another example, the processor 1620 may obtain a first IBC-TM prediction for the first IBC-predicted part and a second inter prediction for the second inter-predicted part, and obtain the prediction for the current CU based on the first IBC TM prediction and the second inter prediction.

[00277] In some examples, the IBC tool may be combined with GPM tool in the form of simplified GPM with IBC and intra prediction. For example, the current CU is partitioned into a first part and a second part based on a predefined direction, corresponding to a certain splitting mode used in GPM. In these examples, the processor 1620 may obtain a first IBC prediction for the first part and a second intra prediction for the second part, and obtain the prediction for the current CU by averaging the first IBC prediction and the second intra prediction. In some examples, the predefined direction may be one splitting line at 45 degrees, the upper left parts of the coding block is coded with intra prediction mode, and the bottom right parts of the coding block is coded with IBC prediction mode, then they are averaged in GPM form to obtain the final prediction signal.

[00278] FIG. 22 is a flowchart illustrating a method for video decoding according to an example of the present disclosure. FIG. 22 illustrates combined IBC-intra/inter prediction.

[00279] In Step 2201, the processor 1620, at the side of a decoder, may obtain a first prediction for a current CU, where the first prediction is associated with intra block copy (IBC) mode.

[00280] In Step 2202, the processor 1620, may obtain a second prediction for the current CU, where the second prediction is associated with one of intra mode or inter mode.

[00281] In Step 2203, the processor 1620, may obtain a final prediction for the current CU based on the first prediction and the second prediction.

[00282] In some examples, similar to the CIIP technology in VVC, the first prediction is associated with IBC merge mode and the second prediction is obtained based on planar intra prediction mode. [00283] In some examples, similar to the Combination of CIIP with TIMD and TM merge technology in ECM, the first prediction is obtained based on IBC merge- TM mode and the second prediction is obtained based on Template-based intra mode derivation (TIMD) derived intra prediction mode.

[00284] In some examples, similar to the CIIP technology in VVC, the first prediction is associated with IBC merge mode and the second prediction is obtained based on inter merge mode, and the final prediction is obtained by equally averaging the first prediction and the second prediction.

[00285] In some examples, the processor 1620 may combine the coding block coded with IBC mode with the coding block coded with intra mode and the coding block coded with inter mode.

[00286] For example, the processor 1620 may further obtain a third prediction for the current CU, where the third prediction is associated with the other of intra mode or inter mode and obtain the final prediction for the current CU by equally averaging the first prediction, the second prediction, and the third prediction. [00287] For another example, the processor 1620 may obtain a first intermediate prediction based on the first prediction and the second prediction and a second intermediate prediction based on the first prediction and the third prediction, and obtain final prediction for the current CU by equally averaging the first intermediate prediction and the second intermediate prediction.

[00288] FIG. 23 is a flowchart illustrating a method for video encoding corresponding the method for video decoding as shown in FIG. 22.

[00289] In Step 2301, the processor 1620, at the side of an encoder, may obtain a first prediction for a current CU, where the first prediction is associated with intra block copy (IBC) mode.

[00290] In Step 2302, the processor 1620, may obtain a second prediction for the current CU, where the second prediction is associated with one of intra mode or inter mode.

[00291] In Step 2303, the processor 1620, may obtain a final prediction for the current CU based on the first prediction and the second prediction.

[00292] In some examples, similar to the CIIP technology in VVC, the first prediction is associated with IBC merge mode and the second prediction is obtained based on planar intra prediction mode. [00293] In some examples, similar to the Combination of CIIP with TIMD and TM merge technology in ECM, the first prediction is obtained based on IBC merge- TM mode and the second prediction is obtained based on Template-based intra mode derivation (TIMD) derived intra prediction mode.

[00294] In some examples, similar to the CIIP technology in VVC, the first prediction is associated with IBC merge mode and the second prediction is obtained based on inter merge mode, and the final prediction is obtained by equally averaging the first prediction and the second prediction.

[00295] In some examples, the processor 1620 may combine the coding block coded with IBC mode with the coding block coded with intra mode and the coding block coded with inter mode. [00296] For example, the processor 1620 may further obtain a third prediction for the current CU, where the third prediction is associated with the other of intra mode or inter mode and obtain the final prediction for the current CU by equally averaging the first prediction, the second prediction, and the third prediction.

[00297] For another example, the processor 1620 may obtain a first intermediate prediction based on the first prediction and the second prediction and a second intermediate prediction based on the first prediction and the third prediction, and obtain final prediction for the current CU by equally averaging the first intermediate prediction and the second intermediate prediction. [00298] FIG. 24 is a flowchart illustrating a method for video decoding according to an example of the present disclosure. FIG. 24 illustrates multiple hypothesis IBC prediction.

[00299] In Step 2401, the processor 1620, at the side of a decoder, may obtain a plurality of block vectors for a current CU based on IBC mode.

[00300] In Step 2402, the processor 1620, at the side of the decoder, may obtain a final prediction for the current CU based on the plurality of block vectors.

[00301] In some examples, the plurality of block vectors may include two block vectors, i.e., a first block vector and a second block vector. The processor 1620 may obtain the first block vector based on a smallest rate distortion metric in IBC AMVP mode and the second block vector based on a second smallest rate distortion metric in the IBC AMVP mode, and obtain the final prediction for the current CU by equally averaging the prediction result of the first block vector and the prediction result of the second block vector.

[00302] In some examples, the plurality of block vectors may include two block vectors, i.e., a first block vector and a second block vector. The processor 1620 may obtain the first block vector based on a smallest rate distortion metric in IBC AMVP mode and the second block vector based on a smallest rate distortion metric in the IBC merge mode, and obtain the final prediction for the current CU by equally averaging the prediction result of the first block vector and the prediction result of the second block vector.

[00303] In some examples, the processor 1620 may obtain the plurality of block vectors based on distortion metrics in IBC AMVP mode and obtain the final prediction for the current CU by equally averaging the prediction results corresponding to the plurality of block vectors.

[00304] In some examples, the processor 1620 may obtain the plurality of block vectors. The iterative accumulation method in Multi-hypothesis prediction (MHP) technology may be utilized to obtain the final prediction result.

[00305] FIG. 25 is a flowchart illustrating a method for video encoding corresponding the method for video decoding as shown in FIG. 24.

[00306] In Step 2501, the processor 1620, at the side of an encoder, may obtain a plurality of block vectors for a current CU based on IBC mode.

[00307] In Step 2502, the processor 1620, at the side of the encoder, may obtain a final prediction for the current CU based on the plurality of block vectors. [00308] In some examples, the plurality of block vectors may include two block vectors, i.e., a first block vector and a second block vector. The processor 1620 may obtain the first block vector based on a smallest rate distortion metric in IBC AMVP mode and the second block vector based on a second smallest rate distortion metric in the IBC AMVP mode, and obtain the final prediction for the current CU by equally averaging the prediction result of the first block vector and the prediction result of the second block vector.

[00309] In some examples, the plurality of block vectors may include two block vectors, i.e., a first block vector and a second block vector. The processor 1620 may obtain the first block vector based on a smallest rate distortion metric in IBC AMVP mode and the second block vector based on a smallest rate distortion metric in the IBC merge mode, and obtain the final prediction for the current CU by equally averaging the prediction result of the first block vector and the prediction result of the second block vector.

[00310] In some examples, the processor 1620 may obtain the plurality of block vectors based on distortion metrics in IBC AMVP mode and obtain the final prediction for the current CU by equally averaging the prediction results corresponding to the plurality of block vectors.

[00311] In some examples, the processor 1620 may obtain the plurality of block vectors. The iterative accumulation method in Multi-hypothesis prediction (MHP) technology may be utilized to obtain the final prediction result.

[00312] In some examples, there is provided an apparatus for video coding. The apparatus includes a processor 1620 and a memory 1640 configured to store instructions executable by the processor; where the processor, upon execution of the instructions, is configured to perform any method as illustrated in FIGS. 20-25.

[00313] In an embodiment, there is also provided a non-transitory computer-readable storage medium comprising a plurality of programs, for example, in the memory 1630, executable by the processor 1620 in the computing environment 1610, for performing the above-described methods and/or storing a bitstream generated by the encoding method described above or a bitstream to be decoded by the decoding method described above. In one example, the plurality of programs may be executed by the processor 1620 in the computing environment 1610 to receive (for example, from the video encoder 20 in FIG. 2) a bitstream or data stream including encoded video information (for example, video blocks representing encoded video frames, and/or associated one or more syntax elements, etc.), and may also be executed by the processor 1620 in the computing environment 1610 to perform the decoding method described above according to the received bitstream or data stream. In another example, the plurality of programs may be executed by the processor 1620 in the computing environment 1610 to perform the encoding method described above to encode video information (for example, video blocks representing video frames, and/or associated one or more syntax elements, etc.) into a bitstream or data stream, and may also be executed by the processor 1620 in the computing environment 1610 to transmit the bitstream or data stream (for example, to the video decoder 30 in FIG. 3). Alternatively, the non-transitory computer-readable storage medium may have stored therein a bitstream or a data stream comprising encoded video information (for example, video blocks representing encoded video frames, and/or associated one or more syntax elements etc.) generated by an encoder (for example, the video encoder 20 in FIG. 2) using, for example, the encoding method described above for use by a decoder (for example, the video decoder 30 in FIG. 3) in decoding video data. The non- transitory computer-readable storage medium may be, for example, a ROM, a Random Access Memory (RAM), a CD-ROM, a magnetic tape, a floppy disc, an optical data storage device or the like.

[00314] In an embodiment, there is provided a bitstream generated by the encoding method described above or a bitstream to be decoded by the decoding method described above. In an embodiment, there is provided a bitstream comprising encoded video information generated by the encoding method described above or encoded video information to be decoded by the decoding method described above.

[00315] In an embodiment, the is also provided a computing device comprising one or more processors (for example, the processor 1620); and the non-transitory computer-readable storage medium or the memory 1630 having stored therein a plurality of programs executable by the one or more processors, where the one or more processors, upon execution of the plurality of programs, are configured to perform the above-described methods.

[00316] In an embodiment, there is also provided a computer program product having instructions for storage or transmission of a bitstream comprising encoded video information generated by the encoding method described above or encoded video information to be decoded by the decoding method described above. In an embodiment, there is also provided a computer program product comprising a plurality of programs, for example, in the memory 1630, executable by the processor 1620 in the computing environment 1610, for performing the above-described methods. For example, the computer program product may include the non-transitory computer-readable storage medium.

[00317] In an embodiment, the computing environment 1610 may be implemented with one or more ASICs, DSPs, Digital Signal Processing Devices (DSPDs), Programmable Logic Devices (PLDs), FPGAs, GPUs, controllers, micro-controllers, microprocessors, or other electronic components, for performing the above methods.

[00318] In an embodiment, there is also provided a method of storing a bitstream, comprising storing the bitstream on a digital storage medium, where the bitstream includes encoded video information generated by the encoding method described above or encoded video information to be decoded by the decoding method described above.

[00319] In an embodiment, there is also provided a method for transmitting a bitstream generated by the encoder described above. In an embodiment, there is also provided a method for receiving a bitstream to be decoded by the decoder described above.

[00320] The description of the present disclosure has been presented for purposes of illustration and is not intended to be exhaustive or limited to the present disclosure. Many modifications, variations, and alternative implementations will be apparent to those of ordinary skill in the art having the benefit of the teachings presented in the foregoing descriptions and the associated drawings.

[00321] Unless specifically stated otherwise, an order of steps of the method according to the present disclosure is only intended to be illustrative, and the steps of the method according to the present disclosure are not limited to the order specifically described above, but may be changed according to practical conditions. In addition, at least one of the steps of the method according to the present disclosure may be adjusted, combined or deleted according to practical requirements.

[00322] The examples were chosen and described in order to explain the principles of the disclosure and to enable others skilled in the art to understand the disclosure for various implementations and to best utilize the underlying principles and various implementations with various modifications as are suited to the particular use contemplated. Therefore, it is to be understood that the scope of the disclosure is not to be limited to the specific examples of the implementations disclosed and that modifications and other implementations are intended to be included within the scope of the present disclosure.