Method, apparatus, and program for video coding

Abstract

To provide a method and an apparatus for video coding.SOLUTION: There is provided a method and an apparatus for video encoding / decoding according to an embodiment of the present disclosure. In some examples, an apparatus for video decoding includes a processing circuit. For example, the processing circuit decodes prediction information for the current block from an encoded video bitstream. The prediction information indicates that the prediction of the current block is at least partially based on inter prediction. The processing circuit then reconstructs at least the samples of the current block as a combination of the results from the inter prediction and neighboring samples of the block selected on the basis of the position of the samples.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This application claims the benefit of priority to U.S. Provisional Application No. 62 / 800,400, entitled "ENHANCEMENT FOR POSITION DEPENDENT PREDICTION COMBINATION," filed February 1, 2019, which claims the benefit of priority to U.S. Patent Application No. 16 / 777,339, entitled "METHOD AND APPARATUS FOR VIDEO CODING," filed January 30, 2020. The entire disclosure of the prior application is incorporated herein by reference in its entirety.

[0002] This disclosure describes embodiments generally related to video coding. [Background technology]

[0003] The background art discussion provided herein is intended to generally present the context for the present disclosure. The inventors' work, to the extent that it is described in this background art section, and aspects of the description that may not be admitted as prior art at the time of filing, are not admitted expressly or implicitly as prior art to the present disclosure.

[0004] Video encoding and decoding can be performed using inter-picture prediction with motion compensation. Uncompressed digital video may include a series of pictures, each having spatial dimensions of, for example, 1920 x 1080 luminance samples and associated chrominance samples. The series of pictures may have a fixed or variable picture rate (also informally called a frame rate), for example, 60 pictures per second or 60 Hz. Uncompressed video has significant bitrate requirements. For example, 1080p60 4:2:0 video (1920 x 1080 luminance sample resolution at a 60 Hz frame rate) with 8 bits per sample requires a bandwidth approaching 1.5 Gbit / s. One hour of such video requires more than 600 GB of storage space.

[0005] One goal of video encoding and decoding can be to reduce redundancy in an input video signal through compression. Compression can help reduce the aforementioned bandwidth or storage requirements by two or more orders of magnitude, in some cases. Both lossless and lossy compression, as well as combinations of them, can be used. Lossless compression refers to techniques that allow an exact replica of the original signal to be reconstructed from a compressed version. When using lossy compression, the reconstructed signal may not be identical to the original signal, but the distortion between the original and reconstructed signal is small enough that the reconstructed signal is useful for the intended application. For video, lossy compression is widely adopted. The amount of acceptable distortion varies depending on the application. For example, users of certain consumer streaming applications may tolerate higher distortion than users of television distribution applications. The achievable compression ratio may reflect that higher tolerance / tolerance distortion results in higher compression ratios.

[0006] Video encoders and decoders can utilize techniques in several broad categories, such as motion compensation, transforms, quantization, and entropy coding.

[0007] Video coding techniques can include a technique known as intra-coding. In intra-coding, sample values ​​are represented without reference to other data from samples or previously reconstructed reference pictures. In some video coding, pictures are spatially subdivided into blocks of samples. If all blocks of samples are coded in intra mode, the picture may be an intra-picture. Intra-pictures and their derivatives, such as independent decoder refresh pictures, can be used to reset the decoder state and therefore can be used as the first picture in a coded video bitstream and video session, or as a still image. Samples of intra-blocks may be subjected to a transform, and the transform coefficients may be quantized before entropy coding. Intra-prediction can be a technique that minimizes sample values ​​in the pre-transform domain. In some cases, the smaller the DC value and AC coefficients after the transform, the fewer bits required for a given quantization step size to represent the block after entropy coding.

[0008] Conventional intra-coding, such as that known from MPEG-2 generation coding techniques, does not use intra-prediction. However, some newer video compression techniques include techniques that rely on, for example, surrounding sample data and / or metadata obtained during the encoding / decoding of spatially adjacent and preceding blocks of data in decoding order. Such techniques are hereinafter referred to as "intra-prediction" techniques. Note that, at least in some cases, intra-prediction uses only reference data from the current picture being reconstructed, and not from reference pictures.

[0009] Intra prediction can take many different forms. If two or more such techniques can be used in a given video coding technique, the technique in use can be coded as an intra prediction mode. In some cases, a mode can have sub-modes and / or parameters, which can be coded separately or included in a mode codeword. The codeword used for a given mode / sub-mode / parameter combination can affect the coding efficiency gain via intra prediction, and so can the entropy coding technique used to convert the codeword into a bitstream.

[0010] Certain modes of intra prediction were introduced in H.264, improved in H.265, and further refined in new coding techniques such as the Joint Search Model (JEM), General Video Coding (VVC), and Benchmark Set (BMS). A predictor block can be formed using neighboring sample values ​​belonging to already available samples. The sample values ​​of the neighboring samples are copied to the predictor block according to their direction. A reference to the direction in use can be coded in the bitstream or can itself be predicted. Summary of the Invention [Means for solving the problem]

[0011] Aspects of the present disclosure provide methods and apparatuses for video encoding / decoding. In some examples, the apparatus for video decoding includes a processing circuit. For example, the processing circuit decodes prediction information for a current block from an encoded video bitstream. The prediction information indicates that prediction of the current block is based at least in part on inter-prediction. Then, the processing circuit reconstructs at least samples of the current block as a combination of results from the inter-prediction and neighboring samples of the block selected based on the sample's location.

[0012] In one embodiment, the prediction information indicates an intra-inter prediction mode that uses a combination of intra and inter prediction for the current block, and the processing circuit excludes bidirectional optical flow based motion refinement from the inter prediction for the current block.

[0013] In some embodiments, the processing circuit determines the use of position-dependent prediction combining (PDPC) for inter prediction based on the prediction information, and reconstructs the samples in response to the determination of the use of PDPC for inter prediction. In one example, the processing circuit receives a flag indicating the use of PDPC.

[0014] In some examples, the processing circuit decodes a first flag for an intra-inter prediction mode that uses a combination of intra prediction and inter prediction for the current block, and decodes a second flag that indicates use of PDPC if the first flag indicates true for the intra-inter prediction mode. In one example, the processing circuit decodes the second flag that indicates use of PDPC based on a context model of entropy coding.

[0015] In one embodiment, the processing circuitry applies a filter to neighboring samples of the current block and reconstructs the samples of the current block as a combination of the results from inter prediction and the filtered neighboring samples of the current block.

[0016] In other embodiments, the processing circuitry reconstructs the samples of the current block using neighboring samples of the current block without applying a filter to the neighboring samples.

[0017] In some examples, the processing circuit determines whether the current block satisfies a block size condition that limits the application of the PDPC in the reconstruction of the current block, and if the block size condition is satisfied, precludes the application of the PDPC in the reconstruction of at least one sample of the current block. In one example, the block size condition depends on the size of the virtual processing data unit.

[0018] In some examples, the processing circuitry ignores neighboring samples in the combination calculation if the distance of the neighboring samples to the sample is greater than a threshold.

[0019] In some embodiments, the processing circuitry combines the results from the inter prediction with neighboring samples selected based on the location of the sample and reconstructed based on the inter prediction.

[0020] In one example, the processing circuit decodes a flag indicating use of PDPC when the prediction information indicates merge mode.

[0021] In another example, the processing circuit decodes a second flag indicating the use of PDPC if the first flag indicates a non-zero residual for the current block.

[0022] Aspects of the present disclosure also provide a non-transitory computer-readable medium storing instructions that, when executed by a computer, cause the computer to perform a method for video decoding.

[0023] Further features, nature and various advantages of the disclosed subject matter will become more apparent from the following detailed description and accompanying drawings. [Brief explanation of the drawings]

[0024] [Figure 1] FIG. 1 is a simplified block diagram schematic of a communication system (100) according to one embodiment. [Figure 2] FIG. 2 is a simplified block diagram schematic of a communication system (200) according to one embodiment. [Figure 3] FIG. 2 is a schematic diagram of a simplified block diagram of a decoder according to one embodiment. [Figure 4] FIG. 2 is a schematic diagram of a simplified block diagram of an encoder according to one embodiment. [Figure 5] FIG. 10 is a block diagram of an encoder according to another embodiment. [Figure 6]FIG. 10 is a block diagram of a decoder according to another embodiment. [Figure 7] 1 shows a diagram of exemplary intra-prediction directions and intra-prediction modes. [Figure 8] 1 shows diagrams of exemplary intra-prediction directions and intra-prediction modes in some examples. [Figure 9A] 10 illustrates weights for predicting samples according to some embodiments. [Figure 9B] 10 illustrates weights for predicting samples according to some embodiments. [Figure 10] FIG. 10 is a diagram illustrating an example of an extended CU region in a BDOF. [Figure 11] The diagonal division of the CU and the anti-diagonal division of the CU are shown. [Figure 12] 1 is a flowchart outlining an example process according to some embodiments. [Figure 13] FIG. 1 is a schematic diagram of a computer system according to one embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0025] FIG. 1 illustrates a simplified block diagram of a communication system (100) according to an embodiment of the present disclosure. The communication system (100) includes multiple terminal devices capable of communicating with each other, e.g., via a network (150). For example, the communication system (100) includes a first pair of terminal devices (110) and (120) interconnected via the network (150). In the example of FIG. 1, the first pair of terminal devices (110) and (120) engage in unidirectional transmission of data. For example, the terminal device (110) may encode video data (e.g., a stream of video pictures captured by the terminal device (110)) for transmission to another terminal device (120) via the network (150). The encoded video data may be transmitted in the form of one or more coded video bitstreams. The terminal device (120) may receive the coded video data from the network (150), decode the coded video data to reconstruct the video pictures, and display the video pictures according to the reconstructed video data. One-way data transmission may be common, such as in media serving applications.

[0026] In another example, the communication system (100) includes a second pair of terminal devices (130) and (140) that engage in bidirectional transmission of encoded video data, such as may occur during a video conference. For the bidirectional transmission of data, in one example, each of the terminal devices (130) and (140) may encode video data (e.g., a stream of video pictures captured by the terminal device) for transmission to the other of the terminal devices (130) and (140) over the network (150). Each of the terminal devices (130) and (140) may also receive the encoded video data transmitted by the other of the terminal devices (130) and (140), decode the encoded video data to recover the video pictures, and display the video pictures on an accessible display device according to the recovered video data.

[0027] In the example of FIG. 1 , the terminal devices 110, 120, 130, and 140 may be depicted as servers, personal computers, and smartphones, although the principles of the present disclosure are not so limited. Embodiments of the present disclosure find application in laptop computers, tablet computers, media players, and / or dedicated videoconferencing equipment. The network 150 represents any number of networks that convey encoded video data between the terminal devices 110, 120, 130, and 140, including, for example, wired (cabled) and / or wireless communication networks. The communication network 150 may exchange data over circuit-switched and / or packet-switched channels. Exemplary networks include telecommunications networks, local area networks, wide area networks, and / or the Internet. For purposes of this discussion, the architecture and topology of the network 150 may not be important to the operation of the present disclosure, unless otherwise described herein.

[0028] 2 shows the arrangement of a video encoder and a video decoder in a streaming environment as an example of an application for the disclosed subject matter. The disclosed subject matter may be equally applicable to other video-enabled applications including, for example, video conferencing, digital TV, storage of compressed video on digital media including CDs, DVDs, memory sticks, etc.

[0029] The streaming system may include a capture subsystem (213), which may include a video source (201), such as a digital camera, that creates a stream of uncompressed video pictures (202). In one example, the stream of video pictures (202) includes samples captured by the digital camera. The stream of video pictures (202), shown as a thick line to emphasize its high data volume compared to the encoded video data (204) (or encoded video bitstream), may be processed by an electronic device (220) that includes a video encoder (203) coupled to the video source (201). The video encoder (203) may include hardware, software, or a combination thereof to enable or implement aspects of the disclosed subject matter, as described in more detail below. The encoded video data (204) (or encoded video bitstream (204)), shown as a thin line to emphasize its low data volume compared to the stream of video pictures (202), may be stored on a streaming server (205) for future use. One or more streaming client subsystems, such as the client subsystems (206) and (208) of FIG. 2, can access the streaming server (205) to obtain copies (207) and (209) of the encoded video data (204). The client subsystem (206) can include, for example, a video decoder (210) within an electronic device (230). The video decoder (210) decodes an input copy (207) of the encoded video data and creates an output stream (211) of video pictures that can be rendered on a display (212) (e.g., a display screen) or other rendering device (not shown). In some streaming systems, the encoded video data (204), (207), and (209) (e.g., a video bitstream) can be encoded according to a particular video coding / compression standard. Examples of these standards include ITU-T Recommendation H.265.In one example, a video coding standard under development is informally known as Universal Video Coding (VVC), and the disclosed subject matter may be used in the context of VVC.

[0030] It should be noted that the electronic devices (220) and (230) may include other components (not shown). For example, the electronic device (220) may include a video decoder (not shown), and the electronic device (230) may also include a video encoder (not shown).

[0031] 3 shows a block diagram of a video decoder (310) according to an embodiment of the present disclosure. The video decoder (310) may be included in an electronic device (330). The electronic device (330) may include a receiver (331) (e.g., receiving circuitry). The video decoder (310) may be used in place of the video decoder (210) in the example of FIG. 2.

[0032] The receiver (331) can receive one or more coded video sequences to be decoded by the video decoder (310), and in the same or other embodiments, can receive one coded video sequence at a time, with the decoding of each coded video sequence being independent of the other coded video sequences. The coded video sequences can be received from a channel (301), which can be a hardware / software link to a storage device that stores the coded video data. The receiver (331) can receive the coded video data along with other data, such as coded audio data and / or auxiliary data streams, that can be forwarded to a respective using entity (not shown). The receiver (331) can separate the coded video sequences from other data. To combat network jitter, a buffer memory (315) can be coupled between the receiver (331) and the entropy decoder / parser (320) (hereinafter, "parser (320)"). In certain applications, the buffer memory (315) is part of the video decoder (310). In other cases, it may be external to the video decoder (310) (not shown). In still others, there may be a buffer memory (not shown) external to the video decoder (310), for example, to combat network jitter, and another buffer memory (315) internal to the video decoder (310), for example, to handle playback timing. If the receiver (331) is receiving data from a store-and-forward device with sufficient bandwidth and controllability, or from an equivalent synchronous network, the buffer memory (315) may not be needed or may be small. For use with best-effort packet networks such as the Internet, the buffer memory (315) may be needed, may be relatively large, advantageously adaptively sized, and may be implemented at least in part in an operating system or similar element (not shown) external to the video decoder (310).

[0033] The video decoder (310) may include a parser (320) for reconstructing symbols (321) from the encoded video sequence. These symbol categories include information used to manage the operation of the video decoder (310) and, potentially, information for controlling a rendering device, such as a rendering device (312) (e.g., a display screen) that is not an integral part of the electronic device (330) but can be coupled to the electronic device (330), as shown in FIG. 3. The rendering device control information may be in the form of a supplemental enhancement information (SEI) message or a video usability information (VUI) parameter set fragment (not shown). The parser (320) can parse / entropy decode the received encoded video sequence. The encoding of the encoded video sequence may follow a video coding technique or video coding standard and may follow various principles, including variable-length coding, Huffman coding, arithmetic coding with or without context sensitivity, etc. The parser (320) can extract from the coded video sequence a set of subgroup parameters for at least one of the subgroups of pixels in the video decoder based on at least one parameter corresponding to the group. The subgroups may include Group of Pictures (GOPs), pictures, tiles, slices, macroblocks, coding units (CUs), blocks, transform units (TUs), prediction units (PUs), etc. The parser (320) can also extract from the coded video sequence information such as transform coefficients, quantization parameter values, motion vectors, etc.

[0034] The parser (320) can perform entropy decoding / parsing operations on the video sequence received from the buffer memory (315) to create symbols (321).

[0035] The reconstruction of the symbols (321) may involve several different units, depending on the type of coded video picture or portion thereof (e.g., inter-picture and intra-picture, inter-block and intra-block, etc.), and other factors. The units involved and how they are involved may be controlled by subgroup control information parsed from the coded video sequence by the parser (320). The flow of such subgroup control information between the parser (320) and the following units is not shown for clarity.

[0036] In addition to the functional blocks already mentioned, the video decoder (310) may be conceptually subdivided into several functional units, as described below. In an actual implementation operating under commercial constraints, many of these units may interact closely with each other and may be at least partially integrated with each other. However, for purposes of describing the disclosed subject matter, the following conceptual subdivision into functional units is appropriate.

[0037] The first unit is a scalar / inverse transform unit (351), which receives quantized transform coefficients and control information from the parser (320) as symbols (321), including the transform to use, block size, quantization coefficients, quantization scaling matrix, etc. The scalar / inverse transform unit (351) may output blocks containing sample values ​​that may be input to an aggregator (355).

[0038] In some cases, the output samples of the scaler / inverse transform (351) may relate to intra-coded blocks, i.e., blocks that do not use prediction information from a previously reconstructed picture but can use prediction information from a previously reconstructed portion of the current picture. Such prediction information may be provided by an intra-picture prediction unit (352). In some cases, the intra-picture prediction unit (352) generates blocks of the same size and shape as the block being reconstructed using surrounding, already reconstructed information fetched from a current picture buffer (358). The current picture buffer (358), for example, buffers partially reconstructed and / or fully reconstructed current pictures. The aggregator (355) optionally adds, on a sample-by-sample basis, the prediction information generated by the intra-prediction unit (352) to the output sample information provided by the scaler / inverse transform unit (351).

[0039] In other cases, the output samples of the scalar / inverse transform unit (351) may relate to an inter-coded, potentially motion-compensated block. In such cases, the motion-compensated prediction unit (353) may access a reference picture memory (357) to fetch samples used for prediction. After motion-compensating the fetched samples according to the symbols (321) associated with the block, these samples may be added by an aggregator (355) to the output of the scalar / inverse transform unit (351) to generate output sample information (in this case, referred to as residual samples or residual signals). The addresses in the reference picture memory (357) from which the motion-compensated prediction unit (353) fetches prediction samples may be controlled by motion vectors available to the motion-compensated prediction unit (353), for example, in the form of symbols (321) that may have X, Y, and reference picture components. Motion compensation may also include interpolation of sample values ​​fetched from the reference picture memory (357) when sub-sample accurate motion vectors are used, as well as motion vector prediction mechanisms.

[0040] The output samples of the aggregator (355) may be subjected to various loop filtering techniques in the loop filter unit (356). Video compression techniques can include in-loop filtering techniques controlled by parameters contained in the coded video sequence (also referred to as the coded video bitstream) and available to the loop filter unit (356) as symbols (321) from the parser (320), but can also depend on meta-information obtained during decoding of a coded picture or previous portion (in decoding order) of the coded video sequence, or on previously reconstructed and loop-filtered sample values.

[0041] The output of the loop filter unit (356) may be a sample stream that can be output to a rendering device (312) as well as stored in a reference picture memory (357) for use in future inter-picture prediction.

[0042] Once a coded picture is fully reconstructed, it can be used as a reference picture for future prediction. For example, once the coded picture corresponding to the current picture is fully reconstructed and identified as a reference picture for the coded picture (e.g., by the parser (320)), the current picture buffer (358) can become part of the reference picture memory (357), and a fresh current picture buffer can be reallocated before starting reconstruction of the next coded picture.

[0043] The video decoder (310) can perform decoding operations according to a predetermined video compression technique in a standard, such as ITU-T Rec. H.265. An encoded video sequence may conform to the syntax specified by the video compression technique or standard being used, in the sense that the encoded video sequence conforms to both the syntax of the video compression technique or standard and the profile documented in the video compression technique or standard. Specifically, a profile may select certain tools from all tools available in the video compression technique or standard as the only tools usable under that profile. Compliance also requires that the complexity of the encoded video sequence be within a range defined by the level of the video compression technique or standard. In some cases, the level limits the maximum picture size, maximum frame rate, maximum reconstructed sample rate (e.g., measured in megasamples per second), maximum reference picture size, etc. The limits set by the level may, in some cases, be further limited by the specification of a hypothetical reference decoder (HRD) and HRD buffer management metadata signaled in the encoded video sequence.

[0044] In one embodiment, the receiver (331) can receive additional (redundant) data along with the encoded video. The additional data may be included as part of the encoded video sequence. The additional data may be used by the video decoder (310) to properly decode the data and / or more accurately reconstruct the original video data. The additional data may be in the form of, for example, temporal, spatial, or signal-to-noise ratio (SNR) enhancement layers, redundant slices, redundant pictures, forward error correction codes, etc.

[0045] 4 shows a block diagram of a video encoder (403) according to an embodiment of the present disclosure. The video encoder (403) is included in an electronic device (420). The electronic device (420) includes a transmitter (440) (e.g., a transmission circuit). The video encoder (403) can be used in place of the video encoder (203) in the example of FIG. 2.

[0046] The video encoder (403) can receive video samples from a video source (401) (not part of the electronic device (420) in the example of FIG. 4) that can capture video images to be encoded by the video encoder (403). In other examples, the video source (401) is part of the electronic device (420).

[0047] The video source (401) may provide a source video sequence to be encoded by the video encoder (403) in the form of a digital video sample stream, which may be of any suitable bit depth (e.g., 8-bit, 10-bit, 12-bit, etc.), any color space (e.g., BT.601 YCrCB, RGB, etc.), and any suitable sampling structure (e.g., YCrCb 4:2:0, YCrCb 4:4:4). In a media serving system, the video source (401) may be a storage device that stores previously prepared video. In a video conferencing system, the video source (401) may be a camera that captures local picture information as a video sequence. The video data may be provided as multiple individual pictures that, when viewed sequentially, impart motion. The picture itself may be organized as a spatial array of pixels, each of which may contain one or more samples, depending on the sampling structure, color space, etc., in use. Those skilled in the art will readily understand the relationship between pixels and samples. The following discussion will focus on samples.

[0048] According to one embodiment, the video encoder (403) may encode and compress pictures of a source video sequence into an encoded video sequence (443) in real time or under any other time constraints, as required by the application. Enforcing the appropriate encoding rate is one function of the controller (450). In some embodiments, the controller (450) controls and is functionally coupled to other functional units, as described below. For clarity, coupling is not depicted. Parameters set by the controller (450) may include rate control-related parameters (e.g., picture skip, quantization, lambda value for rate-distortion optimization techniques), picture size, group of pictures (GOP) layout, maximum motion vector search range, etc.). The controller (450) may be configured to have other appropriate functions for the video encoder (403) optimized for a particular system design.

[0049] In some embodiments, the video encoder (403) is configured to operate in an encoding loop. As an overly simplified explanation, in one example, the encoding loop can include a source coder (430) (e.g., responsible for generating symbols, such as a symbol stream, based on an input picture to be encoded and a reference picture) and a (local) decoder (433) embedded in the video encoder (403). The decoder (433) reconstructs the symbols to create sample data in a manner similar to that of the (remote) decoder (since any compression between the symbols and the encoded video bitstream is lossless in the video compression techniques considered in the disclosed subject matter). The reconstructed sample stream (sample data) is input to a reference picture memory (434). Because decoding of the symbol stream yields bit-accurate results regardless of the decoder's location (local or remote), the contents of the reference picture memory (434) are also bit-accurate between the local encoder and the remote encoder. In other words, the prediction part of the encoder "sees" the exact same sample values ​​in the reference picture that the decoder "sees" when using the prediction during decoding. This basic principle of reference picture synchrony (and the drift that occurs when synchrony cannot be maintained, for example, due to channel errors) is also used in several related technologies.

[0050] The operation of the "local" decoder (433) may be the same as the operation of the "remote" decoder (310), such as the video decoder, already described in detail above in connection with Figure 3. However, briefly referring also to Figure 3, because symbols are available and the encoding / decoding of the symbols into an encoded video sequence by the entropy coder (445) and parser (320) may be lossless, the entropy decoding portion of the video decoder (310), including the buffer memory (315) and parser (320), may not be fully implemented in the local decoder (433).

[0051] An observation that can be made at this point is that any decoder techniques other than parsing / entropy decoding present in a decoder must necessarily be present in the corresponding encoder in substantially identical functional form. For this reason, the disclosed subject matter focuses on the operation of the decoder. A description of the encoder techniques may be omitted, as they are the reverse of the decoder techniques described generically. Only in certain areas is more detailed description necessary and is provided below.

[0052] In some examples, during operation, the source coder (430) may perform motion-compensated predictive coding, which predictively codes an input picture with reference to one or more previously coded pictures from a video sequence designated as “reference pictures.” In this way, the coding engine (432) codes differences between pixel blocks of the input picture and pixel blocks of reference pictures that may be selected as predictive references for the input picture.

[0053] The local video decoder (433) may decode the coded video data of images that may be designated as reference pictures based on the symbols created by the source coder (430). The operation of the coding engine (432) may advantageously be a lossy process. When the coded video data is decoded by a video decoder (not shown in FIG. 4), the reconstructed video sequence may be a replica of the source video sequence, typically with some errors. The local video decoder (433) may replicate the decoding process that may be performed by the video decoder on the reference pictures and store the reconstructed reference pictures in a reference picture cache (434). In this way, the video encoder (403) may locally store copies of reconstructed reference pictures that have common content with reconstructed reference pictures obtained by the far-end video decoder (without transmission errors).

[0054] The predictor (435) may perform the predictive search of the coding engine (432). That is, for a new picture to be coded, the predictor (435) may search the reference picture memory (434) for sample data (as candidate reference pixel blocks) or specific metadata that serve as appropriate predictive references for the new picture, such as the reference picture's motion vectors, block shape, etc. The predictor (435) may operate on a sample block-pixel block basis to find appropriate predictive references. In some cases, as determined by the search results obtained by the predictor (435), the input picture may have predictive references drawn from multiple reference pictures stored in the reference picture memory (434).

[0055] The controller (450) may manage the encoding operations of the source coder (430), including, for example, setting the parameters and subgroup parameters used to encode the video data.

[0056] The output of all the aforementioned functional units may undergo entropy coding in an entropy coder (445), which converts the symbols produced by the various functional units into an encoded video sequence by losslessly compressing the symbols according to techniques such as Huffman coding, variable length coding, or arithmetic coding.

[0057] The transmitter (440) can buffer the encoded video sequence created by the entropy coder (445) and prepare it for transmission over a communication channel (460), which can be a hardware / software link to a storage device that stores the encoded video data. The transmitter (440) can merge the encoded video data from the video encoder (403) with other data to be transmitted, such as encoded audio data and / or auxiliary data streams (sources not shown).

[0058] The controller (450) may manage the operation of the video encoder (403). During encoding, the controller (450) may assign a particular coded picture type to each coded picture, which may affect the coding technique that may be applied to the respective picture. For example, in many cases, pictures may be assigned as one of the following picture types:

[0059] An intra-picture (I-picture) is one that can be coded and decoded without using other pictures in a sequence as a source of prediction. Some video coding may use various types of intra-pictures, such as Independent Decoder Refresh ("IDR") pictures. Those skilled in the art are aware of these variations of I-pictures and their respective uses and characteristics.

[0060] A predicted picture (P picture) may be one that can be coded and decoded using intra- or inter-prediction, which uses at most one motion vector and reference index to predict the sample values ​​of each block.

[0061] Bidirectionally predicted pictures (B-pictures) may be those that can be coded and decoded using intra- or inter-prediction, which uses up to two motion vectors and reference indices to predict the sample values ​​of each block. Similarly, multiple predicted pictures may use more than two reference pictures and associated metadata to reconstruct a single block.

[0062] A source picture is typically spatially subdivided into multiple sample blocks (e.g., blocks of 4x4, 8x8, 4x8, or 16x16 samples each) and may be coded block by block. Blocks may be predictively coded with reference to other (already coded) blocks, as determined by the coding assignment applied to the block's respective picture. For example, blocks of an I-picture may be non-predictively coded, or they may be predictively coded with reference to already coded blocks of the same picture (spatial prediction or intra-prediction). Pixel blocks of a P-picture may be predictively coded via spatial prediction or via temporal prediction with reference to one previously coded reference picture. Blocks of a B-picture may be predictively coded via spatial prediction or via temporal prediction with reference to one or two previously coded reference pictures.

[0063] The video encoder (403) may perform encoding operations according to a predetermined video encoding technique or standard, such as ITU-T Rec. H.265. In its operations, the video encoder (403) may perform various compression operations, including predictive encoding operations that exploit temporal and spatial redundancies in the input video sequence. Thus, the encoded video data may conform to a syntax specified by the video encoding technique or standard being used.

[0064] In one embodiment, the transmitter (440) may transmit additional data along with the encoded video. The source coder (430) may include such data as part of the encoded video sequence. The additional data may include temporal / spatial / SNR enhancement layers, other forms of redundant data such as redundant pictures and slices, SEI messages, VUI parameter set fragments, etc.

[0065] Video may be captured in time sequence as multiple source pictures (video pictures). Intra-picture prediction (often abbreviated as intra-prediction) exploits spatial correlation within a given picture, while inter-picture prediction exploits correlation (temporal or otherwise) between pictures. In one example, a particular picture being encoded / decoded, called the current picture, is divided into blocks. When a block in the current picture is similar to a reference block in a previously encoded and still buffered reference picture in the video, the block in the current picture may be coded by a vector called a motion vector. The motion vector points to a reference block in the reference picture and may have a third dimension that identifies the reference picture if multiple reference pictures are used.

[0066] In some embodiments, bi-prediction techniques may be used for inter-picture prediction. According to bi-prediction techniques, two reference pictures, such as a first reference picture and a second reference picture, are used, both of which are before the decoding order of a current picture in a video (although their display orders may be past and future, respectively). A block in the current picture may be coded by a first motion vector that points to a first reference block in the first reference picture and a second motion vector that points to a second reference block in the second reference picture. A block may be predicted by a combination of the first reference block and the second reference block.

[0067] Furthermore, merge mode techniques can be used for inter-picture prediction to improve coding efficiency.

[0068] According to some embodiments of the present disclosure, prediction, such as inter-picture prediction and intra-picture prediction, is performed block-by-block. For example, according to the HEVC standard, pictures in a sequence of video pictures are divided into coding tree units (CTUs) for compression, and the CTUs within a picture have the same size, such as 64x64 pixels, 32x32 pixels, or 16x16 pixels. Generally, a CTU includes three coding tree blocks (CTBs), one luma CTB and two chroma CTBs. Each CTU can be recursively quadtree-decomposed into one or more coding units (CUs). For example, a 64x64 pixel CTU can be divided into one CU of 64x64 pixels, four CUs of 32x32 pixels, or 16 CUs of 16x16 pixels. In one example, each CU is analyzed to determine the CU's prediction type, such as inter prediction or intra prediction. A CU is divided into one or more prediction units (PUs) according to temporal and / or spatial predictability. Generally, each PU includes a luma prediction block (PB) and two chroma PBs. In one embodiment, prediction operations in encoding (encoding / decoding) are performed in units of prediction blocks. Using a luma prediction block as an example of a prediction block, the prediction block includes a matrix of pixel values ​​(e.g., luma values) of 8x8 pixels, 16x16 pixels, 8x16 pixels, 16x8 pixels, etc.

[0069] 5 shows a diagram of a video encoder (503) according to another embodiment of this disclosure. The video encoder (503) is configured to receive a processed block of sample values ​​(e.g., a predictive block) in a current video picture in a sequence of video pictures and encode the processed block into a coded picture that is part of the coded video sequence. In one example, the video encoder (503) is used in place of the video encoder (203) of the example of FIG. 2.

[0070] In an HEVC example, the video encoder (503) receives a matrix of sample values ​​for a processing block, such as a predictive block of 8x8 samples. The video encoder (503) determines whether the processing block is best coded using intra-mode, inter-mode, or bi-predictive mode, for example, using rate-distortion optimization. If the processing block is coded in intra-mode, the video encoder (503) may use intra-prediction techniques to code the processing block into a coded picture. When the processing block is to be coded in inter-mode or bi-predictive mode, the video encoder (503) may use inter-prediction or bi-prediction techniques, respectively, to code the processing block into a coded picture. In some video coding techniques, merge mode may be an inter-picture prediction sub-mode in which motion vectors are derived from one or more motion vector predictors without the benefit of coded motion vector components outside the predictors. In some other video coding techniques, there may be motion vector components applicable to the current block. In one example, the video encoder (503) includes other components, such as a mode decision module (not shown) for determining the mode of the processing blocks.

[0071] In the example of FIG. 5, the video encoder (503) includes an inter-encoder (530), an intra-encoder (522), a residual calculator (523), a switch (526), ​​a residual encoder (524), a general controller (521), and an entropy encoder (525), coupled together as shown in FIG. 5.

[0072] The inter-encoder (530) is configured to receive samples of a current block (e.g., a processing block), compare the block to one or more reference blocks in reference pictures (e.g., blocks in previous and subsequent pictures), generate inter-prediction information (e.g., inter-coding techniques, motion vectors, description of redundant information through merge mode information), and calculate inter-prediction results (e.g., predicted blocks) based on the inter-prediction information using any suitable techniques. In some examples, the reference picture is a decoded reference picture that is decoded based on the coded video information.

[0073] The intra encoder (522) is configured to receive samples of a current block (e.g., a processing block), optionally compare the block with blocks already coded in the same picture, generate quantized coefficients after transformation, and optionally also generate intra prediction information (e.g., intra prediction direction information according to one or more intra coding techniques). In one example, the intra encoder (522) calculates an intra prediction result (e.g., a prediction block) based on the intra prediction information and a reference block in the same picture.

[0074] The general controller (521) is configured to determine general control data and control other components of the video encoder (503) based on the general control data. In one example, the general controller (521) determines the mode of the block and provides a control signal to the switch (526) based on the mode. For example, if the mode is intra mode, the general controller (521) controls the switch (526) to select an intra mode result for the residual calculator (523) to use, and controls the entropy encoder (525) to select intra prediction information for inclusion in the bitstream. If the mode is inter mode, the general controller (521) controls the switch (526) to select an inter prediction result for the residual calculator (523) to use, and controls the entropy encoder (525) to select inter prediction information for inclusion in the bitstream.

[0075] The residual calculator (523) calculates the difference (residual data) between the received block and a prediction result selected from the intra-encoder (522) or inter-encoder (530). The residual encoder (524) is configured to operate on the residual data to encode the residual data to generate transform coefficients. In one example, the residual encoder (524) is configured to transform the residual data from the spatial domain to the frequency domain to generate transform coefficients. The transform coefficients then undergo a quantization process to obtain quantized transform coefficients. In various embodiments, the video encoder (503) also includes a residual decoder (528). The residual decoder (528) is configured to perform an inverse transform and generate decoded residual data. The decoded residual data is suitable for use in the intra-encoder (522) and the inter-encoder (530). For example, the inter-encoder (530) may generate decoded blocks based on the decoded residual data and inter-prediction information, and the intra-encoder (522) may generate decoded blocks based on the decoded residual data and intra-prediction information. In some examples, the decoded blocks are appropriately processed to generate decoded pictures, which may be buffered in a memory circuit (not shown) and used as reference pictures.

[0076] The entropy encoder (525) is configured to format a bitstream to include the coded block. The entropy encoder (525) is configured to include various information in accordance with an appropriate standard, such as the HEVC standard. In one example, the entropy encoder (525) is configured to include general control data, selected prediction information (e.g., intra-prediction information or inter-prediction information), residual information, and other appropriate information in the bitstream. It should be noted that, according to the disclosed subject matter, when coding a block in a merged sub-mode of either an inter-mode or a bi-prediction mode, no residual information is present.

[0077] 6 shows a diagram of a video decoder (610) according to another embodiment of the present disclosure. The video decoder (610) is configured to receive coded pictures that are part of a coded video sequence and decode the coded pictures to generate reconstructed pictures. In one example, the video decoder (610) is used in place of the video decoder (210) of the example of FIG. 2.

[0078] In the example of Figure 6, the video decoder (610) includes an entropy decoder (671), an inter decoder (680), a residual decoder (673), a reconstruction module (674), and an intra decoder (672), which are coupled together as shown in Figure 6.

[0079] The entropy decoder (671) may be configured to reconstruct, from the coded picture, specific symbols representing syntax elements that make up the coded picture. Such symbols may include, for example, prediction information (e.g., intra-prediction information, inter-prediction information, etc.) that can identify the mode in which the block is coded (e.g., intra-mode, inter-mode, bi-prediction mode, the latter two being merged or separate submodes), specific samples or metadata used for prediction by the intra decoder (672) or inter decoder (680), respectively, residual information, e.g., in the form of quantized transform coefficients, etc. In one example, if the prediction mode is an inter-prediction mode or a bi-prediction mode, the inter-prediction information is provided to the inter decoder (680). If the prediction type is an intra-prediction type, the intra-prediction information is provided to the intra decoder (672). The residual information may undergo inverse quantization and be provided to the residual decoder (673).

[0080] The inter decoder (680) is configured to receive the inter prediction information and to generate inter prediction results based on the inter prediction information.

[0081] The intra decoder (672) is configured to receive intra prediction information and to generate a prediction result based on the intra prediction information.

[0082] The residual decoder (673) is configured to perform inverse quantization to extract dequantized transform coefficients and process the dequantized transform coefficients to transform the residual from the frequency domain to the spatial domain. The residual decoder (673) may also require certain control information (to include quantizer parameters (QP)), which may be provided by the entropy decoder (671). (The data path not shown may be low-volume control information only.)

[0083] The reconstruction module (674) is configured to combine, in the spatial domain, the residual as output by the residual decoder (673) and the prediction result (possibly as output by an inter- or intra-prediction module) to form a reconstructed block that may be part of a reconstructed picture, which may be part of a reconstructed video. It should be noted that other appropriate operations, such as a deblocking operation, may be performed to improve visual quality.

[0084] It should be noted that the video encoders (203), (403), and (503) and the video decoders (210), (310), and (610) may be implemented using any suitable technology. In one embodiment, the video encoders (203), (403), and (503) and the video decoders (210), (310), and (610) may be implemented using one or more integrated circuits. In other embodiments, the video encoders (203), (403), and (403) and the video decoders (210), (310), and (610) may be implemented using one or more processors executing software instructions.

[0085] Aspects of this disclosure provide enhancements for position-dependent prediction combining. In various embodiments, this disclosure provides an enhanced scheme for a set of advanced video coding techniques, particularly for intra-prediction modes.

[0086] Figure 7 shows a diagram of exemplary intra-prediction directions and intra-prediction modes used in HEVC. HEVC has a total of 35 intra-prediction modes (modes 0 to 34). Modes 0 and 1 are omnidirectional modes, mode 0 is planar mode, and mode 1 is DC mode. Modes 2 to 34 are directional modes, mode 10 is horizontal mode, mode 26 is vertical mode, and modes 2, 18, and 34 are diagonal modes. In some examples, intra-prediction modes are signaled by three most-probable modes (MPMs) and 32 remaining modes.

[0087] 8 shows a diagram of exemplary intra-prediction directions and intra-prediction modes in some examples (e.g., VVC). There are a total of 87 intra-prediction modes (mode -10 to mode 76), of which mode 18 is a horizontal mode, mode 50 is a vertical mode, and modes 2, 34, and 66 are diagonal modes. Modes -1 to -10 and modes 67 to 76 are referred to as wide-angle intra-prediction (WAIP) modes.

[0088] In some examples, HEVC-style intra prediction is based on filtered reference samples. For example, when the intra prediction mode is neither DC mode nor PLANAR mode, a filter is applied to the boundary reference samples, and the filtered reference samples are used to predict values ​​within the current block based on the intra prediction mode.

[0089] In some examples, PDPC combines boundary reference samples with HEVC-style intra prediction. In some embodiments, PDPC is applied to the following intra modes without signaling: PLANAR, DC, WAIP mode, horizontal, vertical, bottom-left angle mode (mode 2) and its eight adjacent angle modes (modes 3-10), and top-right angle mode (mode 66) and its eight adjacent angle modes (modes 58-65).

[0090] In one example, the prediction sample pred'[x][y] located at position (x, y) is predicted according to Equation 1 using a linear combination of intra prediction modes (DC, PLANAR, Angular) and reference samples. pred'[x][y]=(wL×R(-1,y)+wT×R(x,-1)-wTL×R(-1,-1)+(64 wL-wT+wTL)×pred[x][y]+32)>>6 (Formula 1) In the formulas, R(x,-1) and R(-1,y) represent the (unfiltered) reference samples located above and to the left of the current sample (x,y), respectively, R(-1,-1) represents the reference sample located in the upper left corner of the current block, and wT, wL, and wTL represent weights. In DC mode, the weights are calculated by the following formulas: In formulas 2 to 5, width represents the width of the current block, and height represents the height of the current block. wT=32>>((y<<1)>>nScale) (Equation 2) wL=32>>((x<<1)>>nScale)(Formula 3) wTL = (wL>>4) + (wT>>4) (Equation 4) nScale=(log 2(width)+log 2(height)-2)>>2(Equation 5) In the formula, wT represents the weighting factor of the reference sample located on the top reference line with the same horizontal coordinate, wL represents the weighting factor of the reference sample located on the left reference line with the same vertical coordinate, wTL represents the weighting factor of the top-left reference sample of the current block, nScale specifies how quickly the weighting factor decreases along the axis (wL decreases from left to right, or wT decreases from top to bottom), i.e., the decrement rate of the weighting factor, which in the current design is the same along the x-axis (left to right) and y-axis (top to bottom). Also, 32 indicates the initial weighting factor of the neighboring sample, which is also the upper (left or top-left) weight assigned to the top-left sample in the current CB. The weighting factor of the neighboring sample in the PDPC processing must be less than or equal to this initial weighting factor.

[0091] For planar mode, wTL = 0, while for horizontal mode, wTL = wT, and for vertical mode, wTL = wL. The PDPC weights can be calculated using addition and shift operations. The values ​​of pred'[x][y] can be calculated in one step using Equation 1:

[0092] Figure 9A shows the weight of the predicted sample at (0,0) in DC mode. In the example of Figure 9A, the current block is a 4x4 block, with a width of 4 and a height of 4, so nScale is 0. Then, wT is 32, wL is 32, and -wTL is -4.

[0093] Figure 9B shows the weight of the predicted sample at (1,0) in DC mode. In the example of Figure 9B, the current block is a 4x4 block, with a width of 4 and a height of 4, so nScale is 0. Then, wT is 32, wL is 8, and -wTL is -2.

[0094] When PDPC is applied to DC, PLANAR, horizontal, and vertical intra modes, no additional boundary filters, such as the HEVC DC mode boundary filter or horizontal / vertical mode edge filter, are required. For example, PDPC combines unfiltered boundary reference samples with HEVC-style intra prediction with filtered boundary reference samples.

[0095] More generally, in some instances, the input to the PDPC process is Intra prediction mode represented by predModeIntra; The width of the current block expressed as nTbW; The height of the current block expressed in nTbH; the width of the reference sample represented by refW; the height of the reference sample represented by refH; Predicted samples from HEVC-style intra prediction, denoted by predSamples[x][y], where x=0..nTbW-1 and y=0..nTbH-1; The unfiltered reference (also called neighborhood) samples p[x][y] where x=-1, y=-1..refH-1, and x=0..refW-1, y=-1; and Contains the color components of the current block, represented by cIdx.

[0096] Furthermore, the output of the PDPC process is the modified predicted samples predSamples'[x][y], where x=0..nTbW-1, y=0..nTbH-1.

[0097] Then, the scaling factor nScale is calculated by Equation 6, which is similar to Equation 5. ((Log 2(nTbW)+Log 2(nTbH)-2)>>2)(Equation 6)

[0098] Furthermore, a reference sample array mainRef[x] with x=0..refW is defined as an array of unfiltered reference samples above the current block, and another reference sample array sideRef[y] with y=0..refH is defined as an array of unfiltered reference samples to the left of the current block according to Equations 7 and 8. mainRef[x]=p[x][-1] (Formula 7) sideRef[y]=p[-1][y] (Equation 8)

[0099] For each position (x, y) in the current block, the PDPC calculation uses a top reference sample, denoted as refT[x][y], a left reference sample, denoted as refL[x][y], and a reference sample at the corner p[-1,-1]. In some examples, the modified prediction sample is calculated according to Equation 9, and the result is appropriately clipped according to the cIdx variable, which indicates the color component. predSamples'[x][y]=(wL×refL(x,y)+wT×refT(x,y)-wTL×p(-1,-1)+(64 wL-wT+wTL)×predSamples[x][y]+32)>>6 (Equation 9)

[0100] The reference samples refT[x][y], refL[x][y] and the weights wL, wT, and wTL may be determined based on the intra-prediction mode predModelIntra.

[0101] In one example, when the intra prediction mode predModeIntra is equal to INTRA_PLANAR (e.g., 0, PLANAR mode, mode 0), INTRA_DC (e.g., 1, DC mode, mode 1), INTRA_ANGULAR 18 (e.g., 18, horizontal mode, mode 18 for 67 intra prediction mode), or INTRA_ANGULAR 50 (e.g., 50, vertical mode, mode 50 for 67 intra prediction mode), the reference samples refT[x][y], refL[x][y] and weights wL, wT, and wTL can be determined according to Equations 10 to 14. refL[x][y]=p[-1][y] (Equation 10) refT[x][y]=p[x][-1] (Equation 11) wT[y]=32>>((y<<1)>>nScale) (Equation 12) wL[x]=32>>((x<<1)>>nScale) (Equation 13) wTL[x][y]=(predModelntra==INTRA_DC)?((wL[x]>>4)+(wT[y]>>4)):0(Equation 14)

[0102] In another example, when the intra prediction mode predModeIntra is equal to INTRA_ANGULAR 2 (e.g., mode 2 for a 2,67 intra prediction mode) or INTRA_ANGULAR 66 (e.g., mode 66 for a 66,66 intra prediction mode), the reference samples refT[x][y], refL[x][y] and weights wL, wT, and wTL can be determined according to Equations 15 to 19. refL[x][y]=p[-1][x+y+1] (Equation 15) refT[x][y]=p[x+y+1][-1] (Equation 16) wT[y]=32>>((y<<1)>>nScale)(Equation 17) wL[x]=32>>((x<<1)>>nScale) (Equation 18) wTL[x][y]=0 (Equation 19)

[0103] In another example, if the intra-prediction mode predModeIntra is less than or equal to INTRA_ANGULAR 10 (e.g., mode 10 for 10,67 intra-prediction modes), for location(x, y), the variables dXPos[y], dXFrac[y], dXInt[y], and dX[y] are derived based on the variable invAngle, which is a function of the intra-prediction mode predModeIntra. In one example, invAngle may be determined based on a lookup table that stores invAngle values ​​corresponding to each intra-prediction mode, and then the reference samples refT[x][y], refL[x][y], and weights wL, wT, and wTL is determined based on the variables dXPos[y], dXFrac[y], dXInt[y] and dX[y].

[0104] For example, the variables dXPos[y], dXFrac[y], dXInt[y], and dX[y] are determined according to Equations 20 to 23. dXPos[y]=((y+1)×invAngle+2)>>2(Equation 20) dXFrac[y]=dXPos[y]&63(Equation 21) dXInt[y]=dXPos[y]>>6 (Equation 22) dX[y]=x+dXInt[y] (Equation 23)

[0105] Then, the reference samples refT[x][y] and refL[x][y] and the weights wL, wT, and wTL are determined according to Equations 24 to 28. refL[x][y]=0 (Equation 24) refT[x][y]=(dX[y]<refW-1)?((64-dXFrac[y])×mainRef[dX[y]]+dXFrac[y]×mainRef[dX[y]+1]+32> >6:0 (Formula 25) wT[y]=(dX[y]<refW-1)?32> >((y<<1)>>nScale):0 (Equation 26) wL[x]=0 (Equation 27) wTL[x][y]=0 (Equation 28)

[0106] In another example, if the intra-prediction mode predModeIntra is INTRA_ANGULAR 58 or greater (e.g., mode 58 for 67 intra-prediction modes), the variables dYPos[x], dYFrac[x], dYInt[x], and dY[x] are derived based on a variable invAngle, which is a function of the intra-prediction mode predModeIntra. In one example, invAngle can be determined based on a lookup table that stores invAngle values ​​corresponding to each intra-prediction mode, and then the reference samples refT[x][y], refL[x][y], and weights wL, wT, and wTL are determined based on the variables dYPos[x], dYFrac[x], dYInt[x], and dY[x].

[0107] For example, the variables dYPos[x], dYFrac[x], dYInt[x], and dY[x] are determined according to Equations 29 to 33. dYPos[x]=((x+1)×invAngle+2)>>2(Equation 29) dYFrac[x]=dYPos[x]&63(Equation 30) dYInt[x]=dYPos[x]>>6(Equation 31) dY[x]=x+dYInt[x] (Equation 32)

[0108] Then, the reference samples refT[x][y] and refL[x][y] and the weights wL, wT, and wTL are determined according to Equations 33 to 37. refL[x][y]=(dY[x]<refH-1)?((64-dYFrac[x])×sideRef[dY[x]]+dYFrac[x]×sideRef[dY[x]+1]+32)> >6:0 (Formula 33) refT[x][y]=0 (Equation 34) wT[y]=0 (Equation 35) wL[x]=(dY[x]<refH-1)?32> >((x<<1)>>nScale):0(Formula 36) wTL[x][y]=0 (Equation 37)

[0109] In some examples, if the variable predModeIntra is between 11 and 57, and not between 18 and 50, then refL[x][y], refT[x][y], wT[y], wL[y], and wTL[x][y] are all set equal to 0. Then, the values ​​of the filtered samples filtSamples[x][y], where x=0..nTbW-1, y=0..nTbH-1, are derived as follows: filtSamples[x][y]=clip 1Cmp((refL[x][y]×wL+refT[x][y]×wT-p[-1][-1]×wTL[x][y]+(64 wL[x]-wT[y]+wTL[x][y])×predsample[x][y]+32)>>6) (Equation 38)

[0110] Note that some PDPC processes include non-integer (e.g., floating-point) operations that increase the computational complexity. In some embodiments, the PDPC process includes relatively simple calculations for PLANAR mode (mode 0), DC mode (mode 1), vertical mode (e.g., mode 50 for 67 intra-prediction modes), horizontal mode (e.g., mode 18 for 67 intra-prediction modes), and diagonal mode (e.g., mode 2, mode 66, mode 34 for 67 intra-prediction modes), and the PDPC process includes relatively complex calculations for other modes.

[0111] In some embodiments, for a chroma component of an intra-coded block, the encoder selects the best chroma prediction mode from among five modes, including PLANAR mode (mode index 0), DC mode (mode index 1), horizontal mode (mode index 18), vertical mode (mode index 50), diagonal mode (mode index 66), and a direct copy of the intra prediction mode of the associated luma component, i.e., DM mode. The mapping of intra prediction direction and intra prediction mode number for chroma is shown in Table 1.

[0112] [Table 1]

[0113] To avoid overlapping modes, in some embodiments, the four modes other than DM are assigned according to the intra-prediction mode of the associated luma component. If the intra-prediction mode number of a chroma component is 4, the intra-prediction direction of the luma component is used to generate intra-prediction samples for the chroma component. If the intra-prediction mode number of a chroma component is not 4 but is the same as the intra-prediction mode number of the luma component, intra-prediction direction 66 is used to generate intra-prediction samples for the chroma component.

[0114] According to some aspects of this disclosure, inter-picture prediction (also referred to as inter-prediction) includes merge mode and skip mode.

[0115] In merge mode for inter-picture prediction, motion data (e.g., motion vectors) of blocks are inferred instead of being explicitly signaled. In one example, a merge candidate list of candidate motion parameters is first constructed, and then an index identifying the candidate to be used is signaled.

[0116] In some embodiments, the merge candidate list includes a non-sub-CU merge candidate list and a sub-CU merge candidate list. The non-sub-CU merge candidates are constructed based on spatially neighboring motion vectors, co-located temporal motion vectors, and history-based motion vectors. The sub-CU merge candidate list includes affine merge candidates and ATMVP merge candidates. The sub-CU merge candidates are used to derive multiple motion vectors for the current CU, and different portions of samples within the current CU may have different motion vectors.

[0117] In skip mode, the motion data of a block is inferred instead of being explicitly signaled, and the prediction residual is 0, i.e., no transform coefficients are transmitted. At the beginning of each CU in an inter-picture predicted slice, a skip_flag is signaled, which indicates that merge mode is used to derive the motion data and that no residual data is present in the coded video bitstream.

[0118] According to some aspects of the present disclosure, intra prediction and inter prediction can be appropriately combined, such as multi-hypothesis intra-inter prediction. Multi-hypothesis intra-inter prediction combines one intra prediction and one merge-indexed prediction, and is referred to as an intra-inter prediction mode in this disclosure. In one example, when a CU is in merge mode, a specific flag for the intra mode is signaled. If the specific flag is true, an intra mode can be selected from an intra candidate list. For the luma component, an intra candidate list is derived from four intra prediction modes: DC mode, planar mode, horizontal mode, and vertical mode, and the size of the intra candidate list can be three or four depending on the block shape. In one example, if the CU width is greater than twice the CU height, horizontal mode is removed from the intra mode candidate list, and if the CU height is greater than twice the CU width, vertical mode is removed from the intra mode candidate list. In some embodiments, intra prediction is performed based on the intra prediction mode selected by the intra mode index, and inter prediction is performed based on the merge index. Intra and inter predictions are combined using a weighted average. For chroma components, in some instances, DM is always applied without extra signaling.

[0119] In some embodiments, the weights for combining intra prediction and inter prediction can be appropriately determined. In one example, when DC or PLANAR mode is selected, or when the width or height of the coding block (CB) is less than 4, equal weights are applied to inter prediction and intra prediction. In another example, for a CB with a CB width and CB height of 4 or more, when a horizontal / vertical mode is selected, the CB is first divided vertically / horizontally into four equal area regions. Each region is divided into four equal area regions, each of which is designated by (w_intra i ,w_inter i), where i ranges from 1 to 4. In one example, a first weight set (w_intra1, w_inter1) = (6, 2), a second weight set (w_intra2, w_inter2) = (5, 3), a third weight set (w_intra3, w_inter3) = (3, 5), and a fourth weight set (w_intra4, w_inter4) = (2, 6) may be applied to corresponding regions. For example, the first weight set (w_intra1, w_inter1) is for the region closest to the reference sample, and the fourth weight set (w_intra4, w_inter4) is for the region farthest from the reference sample. The two weighted predictions may then be summed and right-shifted by 3 bits to calculate a composite prediction.

[0120] Also, when intra-coding a neighboring CB, it is possible to save the intra-prediction mode for the intra-hypothesis of the predictor for intra-mode coding of the following neighboring CB.

[0121] According to some aspects of the present disclosure, a motion refinement technique called bidirectional optical flow (BDOF) mode is used in inter prediction. BDOF is also referred to as BIO in some examples. BDOF is used to refine the bi-predictive signal of a CU at the 4x4 sub-block level. BDOF is applied to a CU if the CU satisfies the following conditions: 1) the height of the CU is not 4 and the size of the CU is not 4x8; 2) the CU is not coded using affine mode or ATMVP merge mode; 3) the CU is coded using a "true" bi-predictive mode, i.e., one of the two reference pictures is before the current picture in display order, and the other is after the current picture in display order. In some examples, BDOF is applied only to the luma component.

[0122] Motion refinement in BDOF mode is based on the concept of optical flow, which assumes smooth object motion. For each 4x4 sub-block, motion refinement (v) is achieved by minimizing the difference between the L0 and L1 predicted samples. x ,v y ) is calculated. Then, motion refinement is used to adjust the bi-predictive sample values ​​within the 4x4 sub-block. In BDOF processing, the following steps are applied:

[0123] First, the horizontal and vertical gradients of the two prediction signals,

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number

number

[0124] Then the autocorrelations and crosscorrelations of the gradients S1, S2, S3, S5 and S6 are calculated as follows: S1=Σ (i,j)∈Ω ψ x (i,j), S3=Σ (i,j)∈Ω θ(i,j) ψ x (i,j) S2=Σ (i,j)∈Ω ψ x (i,j)·ψ y (i,j) S5=Σ (i,j)∈Ω ψ y (i,j)·ψ y (i,j)S6=Σ (i,j)∈Ω θ(i,j) ψ y (i,j)(Equation 40) where:

number

[0125] Then, motion refinement (v x ,v y ) is derived.

number

number

number

[0126] Based on the motion refinement and gradients, the following adjustments are calculated for each sample in the 4x4 sub-block:

number

[0127] Finally, the BDOF samples of the CU are calculated by adjusting the bi-predictive samples as follows: pred BDOF (x,y)=(I (0) (x,y)+I (1) (x,y)+b(x,y)+o offset )>>Shift (Equation 44)

[0128] In the above, n a , n b and

number

[0129] To derive the gradient value, we select some predicted samples I in list k (k=0, 1) outside the current CU boundary. (k) (i,j) can be generated.

[0130] FIG. 10 shows an example of an extended CU region within BDOF. In the example of FIG. 10, a 4×4 CU 1010 is shown as a shaded region. BDOF uses one extended row / column around the boundary of the CU, and the extended region is shown as a dashed 6×6 block 1020. To control the computational complexity of generating out-of-bounds predicted samples, a bilinear filter is used to generate predicted samples within the extended region (white positions), and a regular 8-tap motion compensation interpolation filter is used to generate predicted samples within the CU (gray positions). These extended sample values ​​are only used in gradient calculations. In the remaining steps of BDOF processing, when samples and gradient values ​​outside the CU boundary are needed, they are padded (i.e., repeated) from their nearest neighbors.

[0131] In some examples, triangular partitioning can be used for inter prediction. For example (e.g., VTM 3), a new triangular partitioning mode is introduced for inter prediction. The triangular partitioning mode only applies to CUs that are 8x8 or larger and are coded in skip or merge mode. For CUs that meet these conditions, a CU-level flag is signaled to indicate whether the triangular partitioning mode applies.

[0132] When the triangular partition mode is used, the CU is divided evenly into two triangular partitions using either diagonal or anti-diagonal partitioning.

[0133] Figure 11 shows diagonal and anti-diagonal partitioning of a CU. Each triangular partition within a CU has its own motion information and can be inter-predicted using its own motion. In one example, only uni-prediction is allowed for each triangular partition. Each partition has one motion vector and one reference index. Uni-prediction motion constraints are applied to ensure that only two motion-compensated predictions are required per CU, just like traditional bi-prediction. The uni-prediction motion for each partition is derived from a uni-prediction candidate list constructed using a process.

[0134] In some examples, if the CU-level flag indicates that the current CU is coded using a triangular partition mode, an index in the range of [0, 39] is further signaled. Using this triangular partition index, the direction of the triangular partition (diagonal or anti-diagonal) and the motion of each partition can be obtained via a lookup table. After predicting each triangular partition, the sample values ​​along the diagonal or anti-diagonal edge are adjusted using a blending process with adaptive weights. After the entire CU is predicted, the transform and quantization processes are applied to the entire CU, similar to other prediction modes. Finally, the motion field of the CU predicted using the triangular partition mode is stored in 4x4 units.

[0135] In some related examples of intra-prediction modes, PDPC is applied only to intra-predicted samples to improve video quality by reducing artifacts. In related examples, some artifacts for intra-predicted samples may still exist, which may not result in optimal video results.

[0136] The proposed methods may be used separately or combined in any order.

[0137] According to some aspects of the present disclosure, PDPC is applied to inter-predicted samples (or reconstructed samples of inter-coded CUs), and the use of PDPC filtering techniques in inter-prediction may be referred to as inter-PDPC mode. In one example, Equation 1 can be appropriately modified for the inter-PDPC mode. For example, pred[x][y] is modified to indicate the sample value of inter-prediction in the inter-PDPC mode.

[0138] In some examples, a flag referred to in this disclosure as interPDPCFlag (other suitable names can be used for the flag) is signaled to indicate whether PDPC is applied to inter-predicted samples. In one example, if the flag interPDPCFlag is true, the inter-predicted samples (or reconstructed samples of inter-coded CUs) are further modified in the PDPC process in a manner similar to the PDPC process for intra prediction.

[0139] In some embodiments, when the multi-hypothesis intra-inter prediction flag is true, one additional flag, such as interPDPCFlag in the present disclosure, is signaled to indicate whether to apply multi-hypothesis intra-inter prediction or apply PDPC to inter predicted samples. In one example, when interPDPCFlag is true, PDPC is directly applied to the inter predicted samples (or reconstructed samples of the inter coded CU) to generate the final inter predicted value (or reconstructed samples of the inter coded CU). Otherwise, in the example, multi-hypothesis intra-inter prediction is applied to the inter predicted samples (or reconstructed samples of the inter coded CU).

[0140] In one embodiment, a fixed context model is used for entropy coding of interPDPCFlag.

[0141] In other embodiments, the selection of the context model used for entropy coding of interPDPCFlag depends on coding information, including but not limited to whether the neighboring CU is an intra CU, an inter CU, or an intra mode, coding block size, etc. The block size may be measured by a block region size, a block width, a block height, a block width + height, a block width and height, etc.

[0142] For example, if none of the neighboring modes is an intra-coded CU, the first context model is used, otherwise, if at least one of the neighboring modes is an intra-coded CU, the second context model is used.

[0143] In another example, if none of the neighboring modes is an intra-coded CU, a first context model is used, if one of the neighboring modes is an intra-coded CU, a second context model is used, and if two or more of the neighboring modes are intra-coded CUs, a third context model is used.

[0144] In other embodiments, when PDPC is applied to an inter-predicted sample, a smoothing filter is applied to neighboring reconstructed (or predicted) samples.

[0145] In other embodiments, to apply PDPC to inter-predicted samples, neighboring reconstructed (or predicted) samples are used directly in the PDPC process without using smoothing or interpolation filters.

[0146] In other embodiments, if the block size of the current block is less than or equal to a threshold, the flag interPDPCFlag may be derived as false. The block size may be measured by a block area size, a block width, a block height, a block width + height, a block width and height, etc. In one example, if the block area size is less than 64 samples, the flag interPDPCFlag is derived as false.

[0147] In other embodiments, if the block size of the current block is larger than a threshold value, such as the size of a VPDU (a virtual processing data unit defined as a 64x64 block in the example), the flag interPDPCFlag is not signaled but can be inferred to be false.

[0148] In other embodiments, the PDPC scaling factor (e.g., nScale in this disclosure) or weighting factor (e.g., weight in Equation 1) is constrained so that PDPC (as a filtering technique) does not change the value of the current pixel if the distance (e.g., Equation 1) from the current pixel to the reconstructed pixel is greater than a certain threshold, such as the VPDU width / height.

[0149] In some embodiments, to apply PDPC to inter-predicted samples (or reconstructed samples of an inter-coded CU), a default intra-prediction mode is assigned to the current block, so that the associated parameters of the default mode, such as weighting factors and scaling factors, can be used for PDPC processing. In one example, the default intra-prediction mode may be PLANAR mode or DC mode. In another example, the default intra-prediction mode for chroma components is DM prediction mode. In another example, subsequent blocks may use this default intra-prediction mode for intra-mode coding and Most Probable Mode (MPM) derivation.

[0150] In other embodiments, in order to apply PDPC to inter-predicted samples, BDOF (also called BIO) is not applied in the process of generating inter-predicted samples.

[0151] In other embodiments, when PDPC is applied to inter-predicted samples, in one example, only neighboring reconstructed (or predicted) samples from inter-coded CUs may be used for PDPC processing.

[0152] In other embodiments, interPDPCFlag is signaled for coding blocks coded in merge mode. In other embodiments, PDPC is not applied to skip mode CUs or sub-block merge mode CUs. In other embodiments, PDPC is not applied to triangular partition mode coded CUs.

[0153] In other embodiments, interPDPCFlag is signaled at the TU level and is signaled only if the CBF (Coded Block Flag) of the current TU is not 0. In one example, the th flag interPDPCFlag is not signaled and can be inferred as 0 (false) when the CBF of the current TU is 0. In other examples, reconstructed samples in the neighborhood of the current TU (or current PU / CU) can be used for PDPC.

[0154] In other embodiments, to apply PDPC to inter-predicted samples, only uni-predictive motion vectors can be used to generate intra-predicted samples. If the motion vector of the current block is a bi-predictive motion vector, the motion vector needs to be converted to a uni-predictive motion vector. In one example, if the motion vector of the current block is a bi-predictive motion vector, the motion vectors in List 1 can be discarded and the motion vectors in List 0 can be used to generate intra-predicted samples.

[0155] In other embodiments, transform skip mode (TSM) is not applied or signaled to apply PDPC to inter-predicted samples.

[0156] In some embodiments, if intra-inter mode is true, BDOF is not applied to inter-predicted samples.

[0157] In some embodiments, when bi-prediction is applied, boundary filtering can be applied to both forward and backward predicted blocks using spatially neighboring samples in the corresponding reference picture. The bi-predictive block is then generated by averaging (or weighted summing) the forward and backward predicted blocks. In one example, boundary filtering is applied using a PDPC filter. In another example, neighboring samples of a forward (or backward) predicted block may include the above, left, below, and right of the spatially neighboring samples in the associated reference picture.

[0158] In some embodiments, when uni-prediction is applied, filtering is applied to the prediction block using its spatially neighboring samples in the reference picture. In one example, boundary filtering is applied using a PDPC filter. In another example, the neighboring samples of a forward (or backward) predicted block may include the spatially neighboring samples above, to the left, below, and to the right of the associated reference picture.

[0159] In some embodiments, PLANAR prediction is applied to an inter-predicted block using spatially neighboring samples in a corresponding reference picture. This process is called an inter-prediction sample refinement process. In one example, when bi-prediction is applied, after the inter-prediction refinement process, a bi-predicted block is generated by averaging (or weighted sum) the forward and backward refined prediction blocks. In another example, the neighboring samples used in the inter-prediction refinement process may include spatially neighboring samples above, left, below, and right in the associated reference picture.

[0160] FIG. 12 shows a flowchart outlining a process (1200) according to one embodiment of the present disclosure. The process (1200) can be used in block reconstruction to generate a prediction block for the block being reconstructed. In various embodiments, the process (1200) is performed by a processing circuit, such as the processing circuitry of the terminal devices (110), (120), (130), and (140), a processing circuit performing the functions of the video encoder (203), a processing circuit performing the functions of the video decoder (210), a processing circuit performing the functions of the video decoder (310), or a processing circuit performing the functions of the video encoder (403). In some embodiments, the process (1200) is implemented by software instructions, and thus, the processing circuit performs the process (1200) when the processing circuit executes the software instructions. The process starts at (S1201) and proceeds to (S1210).

[0161] At (S1210), prediction information for the current block is decoded from the coded video bitstream. The prediction information indicates a prediction of the current block that is based at least in part on inter prediction. In one example, the prediction information indicates an inter prediction mode, such as merge mode, skip mode, etc. In another example, the prediction information indicates an intra-inter prediction mode.

[0162] At (S1220), the use of PDPC for inter prediction is determined based on the prediction information of the current block. In one example, a flag such as interPDPCflag is received and decoded from the coded bitstream. In another example, the flag is derived.

[0163] At (S1230), samples of the current block are reconstructed. At least the samples of the current block are reconstructed as a combination of results from inter prediction and neighboring samples selected based on the sample's location. In one example, PDPC is applied to the results of inter prediction in the same way as PDPC for intra prediction. Then, the process proceeds to (S1299) and ends.

[0164] Note that in one example, the prediction information indicates an intra-inter prediction mode that uses a combination of intra and inter prediction for the current block, and then the bidirectional optical flow based motion refinement from the inter prediction for the current block can be excluded. In this example, (S1220) can be skipped, and the decoding is independent of the PDPC processing.

[0165] The techniques described above may be implemented as computer software using computer-readable instructions and may be physically stored on one or more computer-readable media. For example, Figure 13 illustrates a computer system (1300) suitable for implementing certain embodiments of the disclosed subject matter.

[0166] Computer software can be encoded using any suitable machine code or computer language and can be subjected to assembly, compilation, linking, or similar mechanisms to create code containing instructions that can be executed by one or more computer central processing units (CPUs), graphics processing units (GPUs), etc., directly, or through interpretation, execution of microcode, etc.

[0167] The instructions may be executed on various types of computers or components thereof, including, for example, personal computers, tablet computers, servers, smartphones, gaming devices, Internet of Things devices, and the like.

[0168] 13 for computer system (1300) are exemplary in nature and are not intended to suggest any limitation as to the scope of use or functionality of the computer software implementing embodiments of the present disclosure, nor should the arrangement of components be interpreted as having a dependency or requirement related to any one or combination of components illustrated in the exemplary embodiment of computer system (1300).

[0169] The computer system 1300 may include certain human interface input devices. Such human interface input devices may respond to input by one or more users, such as, for example, tactile input (e.g., keystrokes, swipes, data glove movements), audio input (e.g., voice, clapping), visual input (e.g., gestures), and olfactory input (not shown). The human interface devices may also be used to capture certain media that are not necessarily directly related to conscious human input, such as audio (e.g., speech, music, ambient sounds), pictures (e.g., scanned images, photographic images obtained from a still image camera), and images (e.g., two-dimensional video, three-dimensional video, including stereoscopic video).

[0170] The input human interface devices may include one or more (only one of each shown) of a keyboard (1301), a mouse (1302), a trackpad (1303), a touchscreen (1310), a data glove (not shown), a joystick (1305), a microphone (1306), a scanner (1307), and a camera (1308).

[0171] The computer system (1300) may also include certain human interface output devices. Such human interface output devices may stimulate one or more of the human user's senses, for example, through tactile output, sound, light, and smell / taste. Such human interface output devices may include haptic output devices (e.g., haptic feedback via a touchscreen (1310), data gloves (not shown), or joystick (1305), although some haptic feedback devices may not function as input devices), audio output devices (e.g., speakers (1309), headphones (not shown)), visual output devices (e.g., screens (1310), including CRT screens, LCD screens, plasma screens, and OLED screens, each with or without touchscreen input capability, each with or without haptic feedback capability, some capable of outputting two-dimensional visual output or three-dimensional or higher-dimensional output by means of stereographic output, virtual reality glasses (not shown), holographic displays, and smoke tanks (not shown)), and printers (not shown).

[0172] The computer system (1300) may also include human-accessible storage and associated media such as optical media (1321) such as CD / DVD ROM / RW (1320), including CDs / DVDs, thumb drives (1322), removable hard drives or solid state drives (1323), legacy magnetic media such as tape and floppy disks (not shown), and dedicated ROM / ASIC / PLD-based devices such as security dongles (not shown).

[0173] Those skilled in the art should also understand that the term "computer-readable medium" as used in connection with the subject matter disclosed herein does not encompass transmission media, carrier waves, or other transitory signals.

[0174] The computer system (1300) may also include interfaces to one or more communication networks. Networks may be, for example, wireless, wired, or optical. Furthermore, networks may be local, wide-area, metropolitan, vehicular, industrial, real-time, or delay-tolerant. Examples of networks include local area networks, such as Ethernet, WLAN, and cellular networks, including GSM, 3G, 4G, 5G, and LTE; TV wired or wireless wide-area digital networks, including cable, satellite, and terrestrial broadcast television; and vehicular and industrial networks, including CANbus. Certain networks generally require an external network interface adapter connected to a particular general data port or peripheral bus (1349) (e.g., a USB port (1300) on the computer system); others are generally integrated into the computer system core (1300) by connecting to a system bus, as described below (e.g., an Ethernet interface to a PC computer system or a cellular network interface to a smartphone computer system). Using any of these networks, the computer system (1300) can communicate with other entities. Such communication may be unidirectional, receive only (e.g., broadcast TV), unidirectional transmit only (e.g., from a CANbus to a particular CANbus device), or bidirectional, e.g., communication to other computer systems using local area digital networks or wide area digital networks. As noted above, specific protocols and protocol stacks may be used with each of these networks and network interfaces.

[0175] The aforementioned human interface devices, human-accessible storage devices, and network interfaces may be connected to the core (1340) of the computer system (1300).

[0176] A core (1340) may include specialized programmable processing devices in the form of one or more central processing units (CPUs) (1341), graphics processing units (GPUs) (1342), field programmable gate arrays (FPGAs) (1343), hardware accelerators for specific tasks (1344), etc. These devices may be connected via a system bus (1348), along with read-only memory (ROM) (1345), random access memory (1346), and internal mass storage devices (1347) such as a non-user-accessible internal hard drive or SSD. In some computer systems, the system bus (1348) may be accessible in the form of one or more physical plugs, allowing expansion with additional CPUs, GPUs, etc. Peripheral devices may be connected directly to the core's system bus (1348) or via a peripheral bus (1349). Peripheral bus architectures include PCI, USB, etc.

[0177] The CPU (1341), GPU (1342), FPGA (1343), and accelerator (1344) can execute specific instructions that, in combination, can constitute the aforementioned computer code. The computer code can be stored in ROM (1345) or RAM (1346). Transient data can also be stored in RAM (1346), while persistent data can be stored, for example, in internal mass storage (1347). The use of cache memory, which can be closely associated with one or more of the CPU (1341), GPU (1342), mass storage (1347), ROM (1345), RAM (1346), etc., allows for fast storage and retrieval of any memory device.

[0178] The computer-readable media may have computer code thereon for performing various computer-implemented operations. The media and computer code may be those specially designed and constructed for the purposes of the present disclosure, or they may be of the kind well known and available to those skilled in the computer software arts.

[0179] By way of example and not limitation, the architecture (1300), and in particular a computer system having a core (1340), can provide functionality as a result of a processor (including a CPU, GPU, FPGA, accelerator, etc.) executing software embodied in one or more tangible computer-readable media. Such computer-readable media may be the user-accessible mass storage devices introduced above, as well as media associated with specific storage of the core (1340) that is non-transitory in nature, such as the core's internal mass storage device (1347) or ROM (1345). Software implementing various embodiments of the present disclosure may be stored on such devices and executed by the core (1340). The computer-readable media may include one or more memory devices or chips according to particular needs. The software may cause the core (1340), and in particular the processor (including a CPU, GPU, FPGA, etc.) therein, to perform specific processes or portions of specific processes described herein, including defining data structures stored in RAM (1346) and modifying such data structures according to software-defined operations. Additionally, or alternatively, a computer system may provide functionality as a result of logic embedded in or otherwise implemented in circuitry (e.g., accelerator (1344)), which may operate in place of or together with software to perform particular processes or portions of particular processes described herein. References to software may include logic, and vice versa, as appropriate. References to computer-readable media may encompass circuitry (such as an integrated circuit (IC)) storing software for execution, circuitry embodying logic for execution, or both, as appropriate. The present disclosure encompasses any suitable combination of hardware and software. Appendix A: Acronyms JEM: Joint exploration model VVC: Versatile video coding General video coding BMS:benchmark set MV: Motion Vector HEVC: High Efficiency Video Coding SEI: Supplementary Enhancement Information VUI:Video Usability Information GOP:Group of Pictures Group of Pictures TU: Transform Units PU: Prediction Units CTU: Coding Tree Units CTB: Coding Tree Blocks PB: Prediction Blocks HRD: Hypothetical Reference Decoder SNR: Signal Noise Ratio CPU: Central Processing Units GPU: Graphics Processing Units CRT:Cathode Ray Tube LCD: Liquid-Crystal Display OLED: Organic Light-Emitting Diode CD:Compact Disc DVD: Digital Video Disc ROM: Read-Only Memory RAM: Random Access Memory ASIC: Application-Specific Integrated Circuit PLD: Programmable Logic Device LAN: Local Area Network GSM: Global System for Mobile communications LTE: Long-Term Evolution CANBus: Controller Area Network Bus USB: Universal Serial Bus PCI: Peripheral Component Interconnect FPGA: Field Programmable Gate Areas SSD: solid-state drive IC: Integrated Circuit CU: Coding Unit

[0180] While this disclosure has described several exemplary embodiments, there are alterations, permutations, and various substitute equivalents that fall within the scope of this disclosure. It will thus be appreciated that those skilled in the art will be able to devise numerous systems and methods that, although not explicitly shown or described herein, embody the principles of the present disclosure and are therefore within its spirit and scope. [Explanation of symbols]

[0181] 100 Communication Systems 110 Terminal Equipment 120 Terminal Equipment 130 Terminal Equipment 150 Network 200 Communication Systems 201 Video Sources 202 Video Picture Stream 203 Video Encoder 204 encoded video data 205 Streaming Server 206 Client Subsystem 207 copies 210 Video Decoder 211 Video Picture Output Stream 212 Display 213 Capture Subsystem 220 Electronic equipment 230 Electronic equipment 301 Channel 310 Video Decoder 312 Rendering Device 315 Buffer Memory 320 Entropy Decoder / Parser 321 Symbol 330 Electronic equipment 331 Receiver 351 Scaler / Descaler Unit 352 Intra-picture prediction unit 353 Motion Compensation Prediction Unit 355 Aggregator 356 Loop Filter Unit 357 Reference Picture Memory 358 Picture Buffer 401 Video Source 403 Video Encoder 420 Electronic equipment 430 Source Coder 432 encoding engine 433 Decoder 434 Reference Picture Memory 435 Predictor 440 Transmitter 443 coded video sequence 445 Entropy Coder 450 Controller 460 Communication Channels 503 Video Encoder 521 General Controller 522 Intra Encoder 523 Residual Calculator 524 Residual Encoder 525 Entropy Encoder 526 Switch 528 Residual Decoder 530 Inter-encoder 610 Video Decoder 671 Entropy Decoder 672 Intra Decoder 673 Residual Decoder 674 Reconstruction Module 680 Inter Decoder 1200 Processing 1300 Computer Systems 1301 Keyboard 1302 Mouse 1303 Trackpad 1305 Joystick 1306 Mike 1307 Scanner 1308 Camera 1309 Speaker 1310 Touchscreen 1321 Optical Media 1322 thumb drive 1323 Solid State Drive 1340 cores 1343 Field Programmable Gate Area (FPGA) 1344 Hardware Acceleration for Specific Tasks 1345 Read-Only Memory (ROM) 1346 Random Access Memory 1347 Internal mass storage 1348 system bus 1349 Peripheral Bus 1350 graphics adapter 1354 Network Interface

Claims

1. A method of video encoding performed by an encoder, comprising: encoding a first flag for an intra-inter prediction mode, the first flag indicating whether the current block uses a combination of intra prediction and inter prediction for the current block; excluding bidirectional optical flow-based motion refinement (BDOF) from the inter prediction of the current block; encoding at least the samples of the current block as a result of a combination of neighboring samples of the current block selected based on the result of the inter prediction and the position of the samples; Including, The method, wherein if the first flag is true, position-dependent prediction combining (PDPC) is applied directly to inter-predicted samples.

2. The BDOF is applied to the inter prediction when the following conditions are met: (1) the height of the current block is not 4 and the size is not 4x8; (2) the affine mode or ATMVP merge mode is not used for the current block; and (3) a first reference picture used for the inter prediction is before the current block in display order, and a second reference picture is after the current block in display order. The method of claim 1.

3. The BDOF is applied only to the luma component. The method of claim 2.

4. applying a filter to neighboring samples of the current block. The method of claim 1.

5. If the first flag is not true, multi-hypothesis intra-inter prediction is applied to the inter-predicted samples. The method of claim 1.

6. An apparatus for video encoding configured to perform a method according to any one of claims 1 to 5.

7. A computer program for causing a computer of a device for video encoding to execute a method according to any one of claims 1 to 5.

8. A computer-implemented method for storing a bitstream, comprising: generating an encoded bitstream, encoding a first flag for an intra-inter prediction mode, the first flag indicating whether the current block uses a combination of intra prediction and inter prediction for the current block; excluding bidirectional optical flow-based motion refinement (BDOF) from the inter prediction of the current block; encoding at least the samples of the current block as a result of a combination of neighboring samples of the current block selected based on the result of the inter prediction and the position of the samples; Including, generating an encoded bitstream in which position-dependent prediction combining (PDPC) is applied directly to inter-predicted samples if the first flag is true; storing the encoded bitstream on a computer-readable non-transitory medium. method.

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