Method and apparatus for video coding

Abstract

To provide a method for a video encoding / decoding, an apparatus, and a non-transitory computer readable storage medium.SOLUTION: An apparatus includes processing circuitry that decodes prediction information of a current block that is a part of a current picture in a video bitstream. The prediction information indicates a reference block for the current block. The processing circuitry generates filter coefficients of a filter operation based on neighboring reconstructed samples of the current block and neighboring reconstructed samples of the reference block that are co-located with the neighboring reconstructed samples of the current block. The filter operation compensates local changes to the current picture, such as illumination change or motion blur. The processing circuitry determines a prediction block for the current block based on the filter operation being performed on the reference block of the current block. The processing circuitry reconstructs the current block based on the prediction block of the current block.SELECTED DRAWING: Figure 13

Description

[Technical field]

[0001] Incorporation by Reference This application claims benefit of priority to U.S. Provisional Application No. 63 / 164,620, entitled "LOCAL BLUR AND ILLUMINATION COMPENSATION," filed March 23, 2021, which claims benefit of priority to U.S. Provisional Application No. 17 / 482,102, entitled "METHOD AND APPARATUS FOR VIDEO CODING," filed September 22, 2021. The disclosures of the prior applications are hereby incorporated by reference in their entirety into this application.

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

[0003] The discussion of the background art provided herein is intended to provide a general context for the present disclosure. The work of the inventors named herein is not admitted, expressly or impliedly, as prior art to the present disclosure to the extent that their work is described in this Background section, and aspects of the description that may not otherwise qualify as prior art at the time of filing.

[0004] Video coding and decoding can be performed using inter-picture prediction with motion compensation. Uncompressed digital video may include a sequence of pictures, each with spatial dimensions of, for example, 1920x1080 luminance samples and associated chrominance samples. The sequence of pictures may have a fixed or variable picture rate (also informally known as frame rate), for example, 60 pictures per second or 60 Hz. Uncompressed video has significant bitrate requirements. For example, 1080p60 4:2:0 video (1920x1080 luminance sample resolution at a frame rate of 60 Hz) with 8 bits per sample requires a bandwidth approaching 1.5 Gbit / s. One hour of such video requires more than 600 Gbytes of storage space.

[0005] One goal of video coding and decoding can be the reduction of redundancy in the input video signal through compression. Compression can help reduce the aforementioned bandwidth or storage space requirements, in some cases by more than two orders of magnitude. Both lossless and lossy compression, as well as combinations of these, can be used. Lossless compression refers to techniques where an exact copy of the original signal can be reconstructed from the compressed original signal. With lossy compression, the restored signal may not be identical to the original signal, but the distortion between the original and restored signals is small enough to make the restored signal useful for the intended application. For video, lossy compression has been widely adopted. The amount of acceptable distortion depends on the application, for example, a user of a particular consumer streaming application may tolerate higher distortion than a user of a television distribution application. The achievable compression ratio may reflect that a higher acceptable / tolerable distortion may result in a higher compression ratio.

[0006] Video encoders and decoders can utilize techniques from a number of broad categories, including, for example, motion compensation, transform, quantization, and entropy coding.

[0007] Video codec technology can include a technique known as intra-coding. In intra-coding, sample values ​​are represented without reference to samples or other data from previously reconstructed reference pictures. In some video codecs, a picture is spatially subdivided into blocks of samples. When 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 an intra block may be subjected to a transform, and the transform coefficients may be quantized before entropy coding. Intra prediction may be a technique that minimizes sample values ​​in the pre-transform domain. In some cases, the smaller the DC value after the transform and the smaller the AC coefficients, the fewer bits are required at a given quantization step size to represent the block after entropy coding.

[0008] Conventional intra-coding, for example as known from MPEG-2 generation coding techniques, does not use intra-prediction. However, some newer video compression techniques include techniques that attempt to predict from surrounding sample data and / or metadata obtained during encoding and / or decoding of a data block that is, for example, spatially adjacent and preceding in decoding order. Such techniques are hereafter referred to as "intra-prediction" techniques. It should be noted that, at least in some cases, intra-prediction uses only reference data from the current picture being reconstructed, and not from a reference picture.

[0009] Intra prediction may take many different forms. When two or more of such techniques may be used in a given video coding technique, the technique in use may be coded in an intra prediction mode. In certain cases, a mode may have sub-modes and / or parameters that may be coded separately or included in the codeword of the mode. Which codeword is used for a given mode, sub-mode, and / or parameter combination may affect the coding efficiency gains via intra prediction, and so may the entropy coding technique used to convert the codeword into a bitstream.

[0010] A specific mode of intra prediction was introduced in H.264, improved in H.265, and further improved in newer coding techniques such as Joint Search Model (JEM), Versatile 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 the direction. The reference to the direction in use can be coded in the bitstream or it can be predicted itself.

[0011] Referring to FIG. 1A, depicted at the bottom right is a subset of 9 predictor directions known from the 33 possible predictor directions (corresponding to the 33 angle modes of the 35 intra modes) of H.265. The point (101) where the arrows converge represents the sample being predicted. The arrows represent the direction from which the sample is predicted. For example, arrow (102) indicates that sample (101) is predicted from one or more samples to the upper right at an angle of 45 degrees from the horizontal. Similarly, arrow (103) indicates that sample (101) is predicted from one or more samples to the lower left of sample (101) at an angle of 22.5 degrees from the horizontal.

[0012] 1A, at the top left is depicted a square block (104) of 4×4 samples (indicated by a thick dashed line). The square block (104) contains 16 samples, each labeled with "S", its position in the Y dimension (e.g., row index), and its position in the X dimension (e.g., column index). For example, sample S21 is the second sample (from the top) in the Y dimension and the first sample (from the left) in the X dimension. Similarly, sample S44 is the fourth sample in both the Y and X dimensions in the block (104). Since the block is 4×4 samples in size, S44 is at the bottom right. Also shown are reference samples that follow a similar numbering scheme. The reference samples are labeled with R, their Y position (e.g., row index), and X position (column index) relative to the block (104). In both H.264 and H.265, the predicted samples are adjacent to the block being reconstructed, so negative values ​​do not need to be used.

[0013] Intra-picture prediction can work by copying reference sample values ​​from adjacent samples as assigned by the signaled prediction direction. For example, assume that the coded video bitstream includes signaling indicating a prediction direction that coincides with the arrow (102) for this block, i.e., the sample is predicted from one or more prediction samples located at an angle of 45 degrees from the horizontal and to the upper right. In that case, samples S41, S32, S23, and S14 are predicted from the same reference sample R05. Then, sample S44 is predicted from reference sample R08.

[0014] In certain cases, especially when the orientation is not evenly divisible by 45 degrees, the values ​​of multiple reference samples may be combined, for example by interpolation, to calculate the reference sample.

[0015] The number of possible directions has increased as video coding techniques have developed. In H.264 (2003), nine different directions could be represented. In H.265 (2013), this increased to 33, and at the time of this disclosure, JEM / VVC / BMS can support up to 65 directions. Experiments have been conducted to identify the most likely directions, and certain techniques of entropy coding are used to represent those likely directions with a small number of bits, accepting a certain penalty for the less likely directions. Furthermore, the direction itself can sometimes be predicted from neighboring directions used in adjacent already decoded blocks.

[0016] FIG. 1B shows a schematic diagram (105) showing 65 intra prediction directions with JEM to illustrate the increasing number of prediction directions over time.

[0017] The mapping of intra-prediction direction bits in a coded video bitstream that represent the direction may vary from one video coding technique to another, and can range, for example, from a simple direct mapping of prediction directions to intra-prediction modes, to complex adaptation schemes involving codewords, most likely modes, and similar techniques. In all cases, however, there may be certain directions that are statistically less likely to occur in the video content than certain other directions. Because the goal of video compression is to reduce redundancy, these less likely directions are represented by a greater number of bits than more likely directions in well-performing video coding techniques.

[0018] Motion compensation may be a lossy compression technique, and may refer to a technique in which blocks of sample data from a previously reconstructed picture or part thereof (reference picture) are used to predict a newly reconstructed picture or part of a picture after being spatially shifted in a direction indicated by a motion vector (hereafter MV). In some cases, the reference picture may be the same as the picture currently being reconstructed. The MV may have two dimensions X and Y, or three dimensions, with the third dimension being an indication of the reference picture in use (the latter may indirectly be a temporal dimension).

[0019] In some video compression techniques, the MV applicable to a particular region of sample data can be predicted from other MVs, e.g., from an MV associated with another region of sample data that is spatially adjacent to the region being restored and precedes that MV in decoding order. Doing so can significantly reduce the amount of data required to code the MV, resulting in the elimination of redundancy and increased compression. For example, when coding an input video signal derived from a camera (known as natural video), MV prediction can work effectively because there is a statistical likelihood that regions larger than the region to which a single MV is applicable move in similar directions and therefore, in some cases, can be predicted using similar MVs derived from MVs of neighboring regions. This makes the MV found for a given region similar or the same as the MV predicted from the surrounding MVs, and as a result, after entropy coding, it can be represented with fewer bits than would be used if coding the MV directly. In some cases, MV prediction can be an example of lossless compression of a signal (i.e., MV) derived from the original signal (i.e., sample stream). In other cases, the MV prediction itself can be lossy, e.g., due to rounding errors when computing a predictor from several surrounding MVs.

[0020] Various MV prediction mechanisms are described in H.265 / HEVC (ITU-T Rec. H.265, “High Efficiency Video Coding”, December 2016). Among the many MV prediction mechanisms offered by H.265, a technique hereafter referred to as “spatial merging” is described herein.

[0021] Referring to FIG. 1C, the current block (111) may include samples found by the encoder during a motion search process that are predictable from a previous block of the same size but spatially shifted. Instead of coding its MV directly, the MV may be derived from metadata associated with one or more reference pictures, e.g., the most recent reference picture (in decoding order), using MVs associated with any one of the five surrounding samples represented by A0, A1 and B0, B1, B2 (112 to 116, respectively). In H.265, MV prediction may use predictors from the same reference picture that neighboring blocks are using. Summary of the Invention [Means for solving the problem]

[0022] An aspect of the present disclosure provides an apparatus for video encoding / decoding. The apparatus includes a processing circuit that decodes prediction information for a current block that is part of a current picture in a video bitstream. The prediction information indicates a reference block for the current block. The processing circuit generates filter coefficients for a filter operation based on neighboring reconstructed samples of the current block and neighboring reconstructed samples of the reference block that are co-located with the neighboring reconstructed samples of the current block. The filter operation compensates for one or more local changes to the current picture. The one or more local changes include one of illumination changes and motion blur. The processing circuit determines a prediction block for the current block based on the filter operation being performed on the reference block of the current block. The processing circuit reconstructs the current block based on the prediction block of the current block.

[0023] In one embodiment, the filter operation includes one of a one-dimensional finite impulse response (FIR) filter and a two-dimensional FIR filter.

[0024] In one embodiment, the processing circuit generates a first plurality of filter coefficients based on one or more rows of adjacent reconstructed samples above the current block and one or more rows of adjacent reconstructed samples above the reference block.

[0025] In one embodiment, the processing circuit generates the first plurality of filter coefficients based on (i) one or more rows of adjacent reconstructed samples above the current block being available, and (ii) a width of the current block being greater than a threshold.

[0026] In one embodiment, the processing circuit generates a second plurality of filter coefficients based on one or more columns of left adjacent reconstructed samples of the current block and one or more columns of left adjacent reconstructed samples of the reference block.

[0027] In one embodiment, the processing circuit generates the second plurality of filter coefficients based on (i) one or more columns of adjacent reconstructed samples to the left of the current block being available, and (ii) the height of the current block being greater than a threshold.

[0028] In one embodiment, the processing circuit determines a prediction sample for a sample of the current block based on a co-located reference sample in a reference block of the current block and adjacent samples of the co-located reference sample.

[0029] In one embodiment, the processing circuit determines a plurality of filtered reference samples by multiplying each of the co-located reference sample and adjacent samples of the co-located reference sample by a respective filter coefficient of a filter operation. The processing circuit determines a sum of the plurality of filtered reference samples as a result of the filter operation. The processing circuit determines a predicted sample of the sample of the current block based on the sum of the result of the filter operation and an offset.

[0030] In one embodiment, each of the filter coefficients and offsets is expressed as a ratio of two integers.

[0031] In one embodiment, the denominator of each ratio is a power of two.

[0032] An aspect of the present disclosure provides a method for video encoding / decoding. The method may perform any one or combination of processes performed by an apparatus for video encoding / decoding. In the method, prediction information of a current block that is part of a current picture in a video bitstream is decoded. The prediction information indicates a reference block for the current block. Filter coefficients of a filter operation are generated based on neighboring reconstructed samples of the current block and neighboring reconstructed samples of a reference block co-located with the neighboring reconstructed samples of the current block. The filter operation compensates for one or more local changes to the current picture. The one or more local changes include one of illumination changes and motion blur. A prediction block is determined for the current block based on the filter operation being performed on the reference block of the current block. The current block is reconstructed based on the prediction block of the current block.

[0033] Aspects of the present disclosure also provide a non-transitory computer-readable medium storing instructions that, when executed by at least one processor, cause the at least one processor to perform any one or combination of methods for video encoding / decoding.

[0034] Further features, nature and various advantages of the disclosed subject matter will become more apparent from the following detailed description and the accompanying drawings. [Brief description of the drawings]

[0035] [Figure 1A] FIG. 2 is a schematic diagram of an example subset of intra-prediction modes. [Figure 1B] FIG. 2 is a diagram of an example intra-prediction direction. [Figure 1C] FIG. 2 is a schematic diagram of a current block and its surrounding spatial merge candidates in one example. [Diagram 2] FIG. 1 is a schematic diagram of a simplified block diagram of a communication system according to one embodiment. [Diagram 3] FIG. 1 is a schematic diagram of a simplified block diagram of a communication system according to one embodiment. [Figure 4] FIG. 2 is a schematic diagram of a simplified block diagram of a decoder according to one embodiment. [Diagram 5] FIG. 2 is a schematic diagram of a simplified block diagram of an encoder according to one embodiment. [Figure 6] 4 shows a block diagram of an encoder according to another embodiment; [Figure 7] 4 shows a block diagram of a decoder according to another embodiment; [Figure 8] 4 illustrates an example temporal prediction including a current block and its reference block indicated by a motion vector of the current block, according to one embodiment of the present disclosure. [Figure 9] FIG. 2 illustrates a current block with its template and a reference block with its template, according to one embodiment of the present disclosure. [Figure 10]FIG. 2 illustrates an exemplary template for a current block and an exemplary template for a reference block for the current block, according to one embodiment of the present disclosure. [Figure 11] FIG. 2 illustrates an exemplary dilation template for a current block and an exemplary dilation template for a reference block according to one embodiment of the present disclosure. [Figure 12] FIG. 13 illustrates another exemplary dilation template for a current block and another exemplary dilation template for a reference block according to one embodiment of the present disclosure. [Figure 13] FIG. 1 illustrates an exemplary flow chart according to one embodiment. [Figure 14] FIG. 1 is a schematic diagram of a computer system according to one embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0036] I. Video Decoder and Encoder Systems FIG. 2 shows a simplified block diagram of a communication system (200) according to one embodiment of the present disclosure. The communication system (200) includes a plurality of terminal devices that may communicate with each other, for example, via a network (250). For example, the communication system (200) includes a first pair of terminal devices (210) and (220) interconnected via the network (250). In the example of FIG. 2, the first pair of terminal devices (210) and (220) perform unidirectional transmission of data. For example, the terminal device (210) may code video data (e.g., a stream of video pictures captured by the terminal device (210)) for transmission to another terminal device (220) via the network (250). The encoded video data may be transmitted in the form of one or more coded video bitstreams. The terminal device (220) may receive the coded video data from the network (250), decode the coded video data to reconstruct the video pictures, and display the video pictures according to the reconstructed video data. Unidirectional data transmission may be common, such as in media serving applications.

[0037] In another example, the communication system (200) includes a second pair of terminal devices (230) and (240) performing bidirectional transmission of coded video data, which may occur, for example, during a video conference. For the bidirectional transmission of data, in one example, each of the terminal devices (230) and (240) may code video data (e.g., a stream of video pictures captured by the terminal device) for transmission to the other of the terminal devices (230) and (240) over the network (250). Each of the terminal devices (230) and (240) may also receive coded video data transmitted by the other of the terminal devices (230) and (240), decode the coded video data to reconstruct the video pictures, and display the video pictures on an accessible display device according to the reconstructed video data.

[0038] In the example of FIG. 2, the terminal devices (210), (220), (230), and (240) may be depicted as a server, a personal computer, and a smartphone, although the principles of the present disclosure may not be so limited. The embodiments of the present disclosure find application with laptop computers, tablet computers, media players, and / or dedicated video conferencing equipment. The network (250) represents any number of networks that convey coded video data between the terminal devices (210), (220), (230), and (240), including, for example, wired and / or wireless communication networks. The communication network (250) may exchange data over circuit-switched and / or packet-switched channels. Representative 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 (250) may not be important to the operation of the present disclosure unless otherwise described herein below.

[0039] 3 shows an arrangement of a video encoder and a video decoder in a streaming environment as an example of an application of 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, and the like.

[0040] The streaming system may include a video source (301) that creates a stream of uncompressed video pictures (302), a capture subsystem (313) that may include, for example, a digital camera. In one example, the stream of video pictures (302) includes samples taken by a digital camera. The stream of video pictures (302), shown as a thick line to emphasize the high amount of data compared to the encoded video data (304) (or coded video bitstream), may be processed by an electronic device (320) that includes a video encoder (303) coupled to the video source (301). The video encoder (303) 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 (304) (or encoded video bitstream (304)), shown as a thin line to emphasize the lower amount of data compared to the stream of video pictures (302), may be stored in a streaming server (305) for future use. One or more streaming client subsystems, such as the client subsystems (306) and (308) of FIG. 3, may access the streaming server (305) to retrieve copies (307) and (309) of the encoded video data (304). The client subsystem (306) may include a video decoder (310), for example within an electronic device (330). The video decoder (310) decodes an input copy (307) of the encoded video data and creates an output stream (311) of video pictures that may be rendered on a display (312) (e.g., a display screen) or other rendering device (not shown). In some streaming systems, the encoded video data (304), (307), and (309) (e.g., a video bitstream) may be encoded according to a particular video coding / compression standard. Examples of such standards include ITU-T Recommendation H.265.In one example, a video coding standard under development is informally known as Versatile Video Coding (VVC), and the disclosure may be used in the context of VVC.

[0041] It should be noted that the electronic devices (320) and (330) may include other components (not shown). For example, the electronic device (320) may include a video decoder (not shown), and the electronic device (330) may also include a video encoder (not shown).

[0042] 4 shows a block diagram of a video decoder (410) according to one embodiment of the present disclosure. The video decoder (410) may be included in an electronic device (430). The electronic device (430) may include a receiver (431) (e.g., a receiving circuit). The video decoder (410) may be used in place of the video decoder (310) of the example of FIG. 3.

[0043] The receiver (431) may receive one or more coded video sequences to be decoded by the video decoder (410), in the same or another embodiment, one coded video sequence at a time, where the decoding of each coded video sequence is independent of the other coded video sequences. The coded video sequences may be received from a channel (401), which may be a hardware / software link to a storage device that stores the encoded video data. The receiver (431) may receive the encoded video data together with other data, such as a coded audio data stream and / or ancillary data stream, which may be forwarded to a respective using entity (not shown). The receiver (431) may separate the coded video sequences from the other data. To combat network jitter, a buffer memory (415) may be coupled between the receiver (431) and the entropy decoder / parser (420) (hereinafter "parser (420)"). In certain applications, the buffer memory (415) is part of the video decoder (410). In other applications, the buffer memory may be external to the video decoder (410) (not shown). In still other applications, there may be a buffer memory (not shown) external to the video decoder (410), e.g., to combat network jitter, plus another buffer memory (415) internal to the video decoder (410), e.g., to handle playout timing. If the receiver (431) is receiving data from a storage / forwarding device with sufficient bandwidth and controllability or from an isosynchronous network, the buffer memory (415) may not be needed or may be small. For use with best-effort packet networks such as the Internet, the buffer memory (415) may be needed and may be relatively large, preferably adaptively sized, and may be implemented at least in part in an operating system or similar element (not shown) external to the video decoder (410).

[0044] The video decoder (410) may include a parser (420) for reconstructing symbols (421) from the coded video sequence. These categories of symbols include information used to manage the operation of the video decoder (410) and, in some cases, information for controlling a rendering device (e.g., a display screen), such as a render device (412) that is not an integral part of the electronic device (430) but may be coupled to the electronic device (430) as shown in FIG. 4. The control information for the rendering device 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 (420) may parse / entropy decode the received coded video sequence. The coding of the coded video sequence may conform to a video coding technique or standard and may follow various principles including variable length coding, Huffman coding, and arithmetic coding with or without context dependency, etc. The parser (420) may 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 groups of pictures (GOPs), pictures, tiles, slices, macroblocks, coding units (CUs), blocks, transform units (TUs), prediction units (PUs), etc. The parser (420) may also extract from the coded video sequence information such as transform coefficients, quantizer parameter values, and MVs.

[0045] The parser (420) may perform an entropy decoding / parsing operation on the video sequence received from the buffer memory (415) to produce symbols (421).

[0046] The reconstruction of the symbols (421) may involve several different units depending on the type of coded video picture or portion thereof (inter-picture and intra-picture, inter-block and intra-block, etc.) as well as other factors. Which units are involved and how may be controlled by subgroup control information parsed from the coded video sequence by the parser (420). The flow of such subgroup control information between the parser (420) and the following units is not shown for clarity.

[0047] In addition to the functional blocks already mentioned, the video decoder (410) 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 disclosure, a conceptual subdivision into the following functional units is appropriate:

[0048] The first unit is a scalar / inverse transform unit (451), which receives quantized transform coefficients and control information from the parser (420) as symbols (421), including the transform to use, block size, quantization coefficients, quantization scaling matrix, etc. The scalar / inverse transform unit (451) may output blocks containing sample values ​​that may be input to an aggregator (455).

[0049] In some cases, the output samples of the scaler / inverse transform (451) may relate to intra-coded blocks, i.e., blocks that do not use prediction information from already reconstructed pictures but may use prediction information from already reconstructed parts of the current picture. Such prediction information may be provided by an intra-picture prediction unit (452). In some cases, the intra-picture prediction unit (452) generates a block of the same size and shape as the block being reconstructed using surrounding already reconstructed information fetched from a current picture buffer (458). The current picture buffer (458) buffers, for example, a partially reconstructed current picture and / or a fully reconstructed current picture. The aggregator (455) adds, possibly on a sample-by-sample basis, the prediction information generated by the intra-prediction unit (452) to the output sample information provided by the scaler / inverse transform unit (451).

[0050] In other cases, the output samples of the scaler / inverse transform unit (451) may relate to an inter-coded, possibly motion-compensated block. In such cases, the motion compensated prediction unit (453) may access a reference picture memory (457) to fetch samples used for prediction. After motion compensating the fetched samples according to the symbols (421) related to the block, these samples (in this case referred to as residual samples or residual signals) may be added to the output of the scaler / inverse transform unit (451) by an aggregator (455) to generate output sample information. The addresses in the reference picture memory (457) from which the motion compensated prediction unit (453) fetches the prediction samples may be controlled by the MVs available to the motion compensated prediction unit (453) in the form of symbols (421), which may have, for example, X, Y, and reference picture components. Motion compensation may also include interpolation of sample values ​​fetched from the reference picture memory (457) when sub-sample accurate MVs are used, MV prediction mechanisms, etc.

[0051] The output samples of the aggregator (455) may be subjected to various loop filtering techniques in a loop filter unit (456). The video compression techniques may include in-loop filter techniques that are controlled by parameters contained in the coded video sequence (also called the coded video bitstream) and made available to the loop filter unit (456) as symbols (421) from the parser (420), but may also be responsive to meta-information obtained during decoding of a coded picture or previous (in decoding order) part of the coded video sequence, as well as to previously reconstructed and loop filtered sample values.

[0052] The output of the loop filter unit (456) may be a sample stream that may be output to a render device (412) and may also be stored in a reference picture memory (457) for use in future inter-picture prediction.

[0053] Once a particular coded picture is fully reconstructed, it can be used as a reference picture for future prediction. For example, once a coded picture corresponding to a current picture is fully reconstructed and the coded picture is identified as a reference picture (e.g., by the parser (420)), the current picture buffer (458) can become part of the reference picture memory (457), and a new current picture buffer can be reallocated before beginning reconstruction of a subsequent coded picture.

[0054] The video decoder (410) may perform decoding operations according to a given video compression technique in a standard such as ITU-T Rec. H.265. The coded video sequence may conform to the syntax specified by the video compression technique or standard being used, in the sense that the coded video sequence adheres to both the syntax of the video compression technique or standard and the profile documented in the video compression technique. Specifically, the profile may select some tools from all tools available in the video compression technique or standard as the only tools available for use under that profile. Also, what is required for compliance may be that the complexity of the coded video sequence is 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 reconstruction sample rate (e.g., measured in megasamples per second), maximum reference picture size, etc. The limits set by the level may be further limited in some cases by the specification of a hypothetical reference decoder (HRD) and metadata for HRD buffer management signaled within the coded video sequence.

[0055] In one embodiment, the receiver (431) may receive additional (redundant) data along with the encoded video. The additional data may be included as part of the coded video sequence. The additional data may be used by the video decoder (410) to properly decode the data and / or to 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.

[0056] 5 shows a block diagram of a video encoder (503) according to one embodiment of the present disclosure. The video encoder (503) is included in an electronic device (520). The electronic device (520) includes a transmitter (540) (e.g., a transmission circuit). The video encoder (503) may be used in place of the example video encoder (303) of FIG.

[0057] The video encoder (503) may receive video samples from a video source (501) (which is not part of the electronic device (520) in the example of FIG. 5) that may capture video images to be coded by the video encoder (503). In other examples, the video source (501) is part of the electronic device (520).

[0058] The video source (501) may provide a source video sequence to be coded by the video encoder (503) 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, ...), any color space (e.g., BT.601 Y CrCB, RGB, ...), and any suitable sampling structure (e.g., Y CrCb 4:2:0, Y CrCb 4:4:4). In a media serving system, the video source (501) may be a storage device that stores already prepared video. In a video conferencing system, the video source (501) may be a camera that captures local image information as a video sequence. The video data may be provided as a number of individual pictures that convey motion when viewed in sequence. The pictures themselves 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 can easily understand the relationship between pixels and samples. The following description focuses on samples.

[0059] According to one embodiment, the video encoder (503) may code and compress pictures of a source video sequence into a coded video sequence (543) in real-time or under any other time constraint as required by the application. Enforcing an appropriate coding rate is one function of the controller (550). In some embodiments, the controller (550) controls and is operatively coupled to other functional units described below. For clarity, coupling is not shown. Parameters set by the controller (550) may include rate control related parameters (picture skip, quantizer, lambda value for rate distortion optimization techniques, ...), picture size, group of pictures (GOP) layout, and maximum MV allowed reference region, etc. The controller (550) may be configured with other appropriate functions associated with the video encoder (503) optimized for a particular system design.

[0060] In some embodiments, the video encoder (503) is configured to operate in a coding loop. As an oversimplified explanation, in one example, the coding loop may include a source coder (530) (e.g., responsible for creating symbols, such as a symbol stream, based on an input picture to be coded and a reference picture) and a (local) decoder (533) embedded in the video encoder (503). The decoder (533) reconstructs the symbols to create sample data in a manner similar to that of the (remote) decoder (when any compression between the symbols and the coded 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 (534). Since the decoding of the symbol stream produces bit-exact results regardless of the location of the decoder (local or remote), the contents of the reference picture memory (534) are also bit-exact between the local and remote encoders. In other words, the prediction part of the encoder "sees" exactly the same sample values ​​as the reference picture samples that the decoder "sees" when using prediction during decoding. This basic principle of reference picture synchrony (and the resulting drift when synchrony cannot be maintained, e.g., due to channel errors) is also used in several related technologies.

[0061] The operation of the "local" decoder (533) may be the same as the operation of a "remote" decoder, such as the video decoder (410), already described in detail above in connection with Figure 4. However, with brief reference also to Figure 4, because symbols are available and the encoding / decoding of symbols into / from a coded video sequence by the entropy coder (545) and parser (420) may be lossless, the entropy decoding portion of the video decoder (410), including the buffer memory (415) and parser (420), may not be implemented entirely in the local decoder (533).

[0062] An observation that can be made at this point is that any decoder technology, except for parsing / entropy decoding, present in the decoder must also be present in substantially identical functional form in the corresponding encoder. For this reason, the disclosed subject matter focuses on the operation of the decoder. A description of the encoder technology can be omitted, since it is the inverse of the decoder technology described generically. Only in certain areas is a more detailed description required, which is provided below.

[0063] In operation, in some examples, the source coder (530) 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 manner, the coding engine (532) codes differences between pixel blocks of the input picture and pixel blocks of the reference pictures that may be selected as predictive references for the input picture.

[0064] The local video decoder (533) may decode the coded video data of pictures that may be designated as reference pictures based on the symbols created by the source coder (530). The operation of the coding engine (532) may preferably be a lossy process. When the coded video data may be decoded in a video decoder (not shown in FIG. 5), the reconstructed video sequence may usually be a replica of the source video sequence with some errors. The local video decoder (533) 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 (534). In this way, the video encoder (503) may locally store copies of reconstructed reference pictures that have common content with the reconstructed reference pictures obtained by the far-end video decoder (in the absence of transmission errors).

[0065] The predictor (535) may perform a prediction search for the coding engine (532). That is, for a new picture to be coded, the predictor (535) may search the reference picture memory (534) for sample data (as candidate reference pixel blocks) that may serve as suitable prediction references for the new picture, or for specific metadata such as reference picture MV and block shape. The predictor (535) may operate on a sample block-by-pixel block basis to find a suitable prediction reference. In some cases, as determined by the search results obtained by the predictor (535), the input picture may have a prediction reference drawn from among multiple reference pictures stored in the reference picture memory (534).

[0066] The controller (550) may manage the coding operations of the source coder (530), including, for example, setting the parameters and subgroup parameters used to encode the video data.

[0067] The output of all the aforementioned functional units may be subjected to entropy coding in an entropy coder (545), which converts the symbols produced by the various functional units into a coded video sequence by losslessly compressing the symbols according to techniques such as Huffman coding, variable length coding, and arithmetic coding.

[0068] The transmitter (540) may buffer the coded video sequence created by the entropy coder (545) to prepare it for transmission over a communication channel (560), which may be a hardware / software link to a storage device that stores the encoded video data. The transmitter (540) may merge the coded video data from the video coder (503) with other data to be transmitted, such as a coded audio data stream and / or an auxiliary data stream (source not shown).

[0069] The controller (550) may manage the operation of the video encoder (503). During coding, the controller (550) may assign a particular coded picture type to each coded picture, which may affect the coding techniques that may be applied to the respective picture. For example, pictures are often assigned as one of the following picture types:

[0070] An intra picture (I-picture) may be one that can be coded and decoded without using other pictures in a sequence as a source of prediction. Some video codecs allow various types of intra pictures, including, for example, independent decoder refresh ("IDR") pictures. Those skilled in the art are aware of variations of I-pictures and their respective uses and functions.

[0071] A predictive picture (P picture) may be one that can be coded and decoded using intra prediction or inter prediction, which uses at most one MV and a reference index to predict the sample values ​​of each block.

[0072] Bidirectionally predicted pictures (B-pictures) may be those that can be coded and decoded using intra- or inter-prediction that uses up to two MVs 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 for the reconstruction of a single block.

[0073] A source picture may generally be spatially subdivided into multiple sample blocks (e.g., blocks of 4x4, 8x8, 4x8, or 16x16 samples each) and 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 respective picture of the block. 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 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.

[0074] The video encoder (503) may perform coding operations according to a given video coding technique or standard, such as ITU-T Rec. H.265. In its operations, the video encoder (503) may perform various compression operations, including predictive coding operations that exploit temporal and spatial redundancy in the input video sequence. Thus, the coded video data may conform to a syntax specified by the video coding technique or standard being used.

[0075] In one embodiment, the transmitter (540) may transmit additional data along with the encoded video. The source coder (530) may include such data as part of the coded 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.

[0076] A video may be captured as multiple source pictures (video pictures) in a time sequence. Intra-picture prediction (often abbreviated as intra-prediction) exploits spatial correlation within a given picture, while inter-picture prediction exploits correlation (temporal or other) between pictures. In one example, a particular picture being encoded / decoded, called the current picture, is divided into blocks. If a block in the current picture is similar to a reference block in a previously coded and still buffered reference picture in the video, the block in the current picture may be coded by a vector, called a MV. The MV refers 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.

[0077] In some embodiments, inter-picture prediction may use a bi-prediction technique. According to the bi-prediction technique, two reference pictures, such as a first reference picture and a second reference picture, both of which are before the current picture in the video in decoding order (but may be past and future, respectively, in display order), are used. A block in the current picture may be coded by a first MV that points to a first reference block in the first reference picture and a second MV that points to a second reference block in the second reference picture. A block may be predicted by a combination of the first and second reference blocks.

[0078] Furthermore, merge mode techniques can be used in inter-picture prediction to improve coding efficiency.

[0079] According to some embodiments of the present disclosure, predictions such as inter-picture prediction and intra-picture prediction are performed on a block-by-block basis. For example, according to the HEVC standard, a picture in a sequence of video pictures is divided into coding tree units (CTUs) for compression, and the CTUs in a picture have the same size, such as 64×64 pixels, 32×32 pixels, or 16×16 pixels. In general, a CTU includes three coding tree blocks (CTBs), one luma CTB and two chroma CTBs. Each CTU may be recursively quadtree partitioned into one or more coding units (CUs). For example, a CTU of 64×64 pixels may be partitioned into one CU of 64×64 pixels, or four CUs of 32×32 pixels, or 16 CUs of 16×16 pixels. In one example, each CU is analyzed to determine the prediction type of the CU, such as an inter-prediction type or an intra-prediction type. A CU is divided into one or more prediction units (PUs) according to temporal and / or spatial predictability. In general, each PU includes one luma prediction block (PB) and two chroma PBs. In one embodiment, prediction operations in coding (encoding / decoding) are performed in units of prediction blocks. Taking luma prediction blocks as an example of prediction blocks, the prediction blocks include matrices of pixel values ​​(e.g., luma values) of 8×8 pixels, 16×16 pixels, 8×16 pixels, 16×8 pixels, etc.

[0080] 6 shows a diagram of a video encoder (603) according to another embodiment of the present disclosure. The video encoder (603) is configured to receive a processed block (e.g., a predictive block) of sample values ​​in a current video picture in a sequence of video pictures and to encode the processed block into a coded picture that is part of a coded video sequence. In one example, the video encoder (603) is used in place of the video encoder (303) of the example of FIG. 3.

[0081] In an HEVC example, the video encoder (603) receives a matrix of sample values ​​for a processing block, such as a predictive block, such as 8×8 samples. The video encoder (603) 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 to be coded in intra-mode, the video encoder (603) may use intra-prediction techniques to encode the processing block into a coded picture, and if the processing block is to be coded in inter-mode or bi-predictive mode, the video encoder (603) may use inter-prediction techniques or bi-prediction techniques, respectively, to encode the processing block into a coded picture. In certain video coding techniques, the merge mode may be an inter-picture prediction sub-mode, and the MV is derived from one or more MV predictors without the benefit of coded MV components outside the predictors. In certain other video coding techniques, there may be MV components applicable to the current block. In one example, the video encoder (603) includes other components, such as a mode decision module (not shown), to determine the mode of the processing block.

[0082] In the example of FIG. 6, the video encoder (603) includes an inter-encoder (630), an intra-encoder (622), a residual calculator (623), a switch (626), a residual encoder (624), a general controller (621), and an entropy encoder (625), which are coupled together as shown in FIG. 6.

[0083] The inter-encoder (630) is configured to receive samples of a current block (e.g., a processing block), compare the block with one or more reference blocks in a reference picture (e.g., blocks in a previous picture and a subsequent picture), generate inter-prediction information (e.g., description of redundant information by inter-encoding technique, MV, merge mode information), and calculate an inter-prediction result (e.g., a prediction block) based on the inter-prediction information using any suitable technique. In some examples, the reference picture is a decoded reference picture that is decoded based on the encoded video information.

[0084] The intra encoder (622) is configured to receive samples of a current block (e.g., a processing block), possibly compare the block with already coded blocks in the same picture, generate quantized coefficients after transformation, and possibly also generate intra prediction information (e.g., intra prediction direction information according to one or more intra encoding techniques). In one example, the intra encoder (622) also calculates intra prediction results (e.g., predicted blocks) based on the intra prediction information and reference blocks in the same picture.

[0085] The generic controller (621) is configured to determine generic control data and control other components of the video encoder (603) based on the generic control data. In one example, the generic controller (621) determines the mode of the block and provides a control signal to the switch (626) based on the mode. For example, if the mode is an intra mode, the generic controller (621) controls the switch (626) to select an intra mode result for use by the residual calculator (623) and controls the entropy encoder (625) to select intra prediction information and include the intra prediction information in the bitstream, and if the mode is an inter mode, the generic controller (621) controls the switch (626) to select an inter prediction result for use by the residual calculator (623) and controls the entropy encoder (625) to select inter prediction information and include the inter prediction information in the bitstream.

[0086] The residual calculator (623) calculates a difference (residual data) between the received block and a prediction result selected from the intra-encoder (622) or the inter-encoder (630). The residual encoder (624) is configured to operate on the residual data to encode the residual data to generate transform coefficients. In one example, the residual encoder (624) is configured to transform the residual data from the spatial domain to the frequency domain to generate transform coefficients. The transform coefficients are then subjected to a quantization process to obtain quantized transform coefficients. In various embodiments, the video encoder (603) also includes a residual decoder (628). The residual decoder (628) is configured to perform an inverse transform to generate decoded residual data. The decoded residual data may be used by the intra-encoder (622) and the inter-encoder (630) as appropriate. For example, the inter-encoder (630) may generate decoded blocks based on the decoded residual data and the inter-prediction information, and the intra-encoder (622) may generate decoded blocks based on the decoded residual data and the intra-prediction information. The decoded blocks are suitably processed to generate decoded pictures, which may be buffered in a memory circuit (not shown) and used as reference pictures in some examples.

[0087] The entropy encoder (625) is configured to format a bitstream to include the encoded block. The entropy encoder (625) is configured to include various information in accordance with an appropriate standard, such as HEVC. In one example, the entropy encoder (625) 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, no residual information is present when coding a block in a merged sub-mode of either an inter mode or a bi-prediction mode.

[0088] 7 shows a diagram of a video decoder (710) according to another embodiment of the present disclosure. The video decoder (710) is configured to receive coded pictures that are part of a coded video sequence and to decode the coded pictures to generate reconstructed pictures. In one example, the video decoder (710) is used in place of the video decoder (310) of the example of FIG. 3.

[0089] In the example of FIG. 7, the video decoder (710) includes an entropy decoder (771), an inter-decoder (780), a residual decoder (773), a reconstruction module (774), and an intra-decoder (772), which are coupled together as shown in FIG.

[0090] The entropy decoder (771) may be configured to reconstruct from the coded picture certain symbols that represent syntax elements that make up the coded picture. Such symbols may include, for example, the mode in which the block is coded (e.g., intra mode, inter mode, bi-predictive mode, etc., the latter two being merged or other submodes), prediction information (e.g., intra prediction information or inter prediction information, etc.) that may identify certain samples or metadata used for prediction by the intra decoder (772) or the inter decoder (780), respectively, and residual information, for example in the form of quantized transform coefficients. In one example, if the prediction mode is an inter mode or bi-predictive mode, the inter prediction information is provided to the inter decoder (780), and if the prediction type is an intra prediction type, the intra prediction information is provided to the intra decoder (772). The residual information may be subjected to inverse quantization and provided to the residual decoder (773).

[0091] The inter decoder (780) is configured to receive the inter prediction information and to generate inter prediction results based on the inter prediction information.

[0092] The intra decoder (772) is configured to receive intra prediction information and to generate a prediction result based on the intra prediction information.

[0093] The residual decoder (773) is configured to perform inverse quantization to extract inverse quantized transform coefficients, and process the inverse quantized transform coefficients to transform the residual from the frequency domain to the spatial domain. The residual decoder (773) may also require certain control information (to include Quantizer Parameters (QP)), which may be provided by the entropy decoder (771) (the data path not shown may be only low volume control information).

[0094] The reconstruction module (774) is configured to combine, in the spatial domain, the residual output by the residual decoder (773) and the prediction result (possibly output by the inter-prediction module or the intra-prediction module) to form a reconstructed block that may be part of a reconstructed picture, which may in turn be part of the reconstructed video. It should be noted that other suitable operations, such as deblocking operations, may be performed to improve visual quality.

[0095] It should be noted that the video encoders (303), (503), and (603) and the video decoders (310), (410), and (710) may be implemented using any suitable technology. In one embodiment, the video encoders (303), (503), and (603) and the video decoders (310), (410), and (710) may be implemented using one or more integrated circuits. In another embodiment, the video encoders (303), (503), and (603) and the video decoders (310), (410), and (710) may be implemented using one or more processors executing software instructions.

[0096] II. Local illumination compensation This disclosure includes embodiments that relate to prediction models that are applicable to multiple coding processes. For example, embodiments may include inter-prediction models that compensate for multiple coding processes such as local motion blur and local illumination changes.

[0097] This disclosure includes embodiments related to inter prediction in advanced video codecs. The inter prediction model can compensate for both local motion blur and local illumination changes. The Local Illumination Compensation (LIC) model is an inter prediction technique for uni-predictive inter CUs. In the LIC model, the local illumination variation between a current block and its reference block can be modeled as a function of the local illumination variation between the template of the current block and the template of the reference block.

[0098] FIG. 8 illustrates a current block (801) and its reference block (802) indicated by a motion vector (803) of the current block (801) according to one embodiment of the present disclosure. In FIG. 8, the reference block (802) is a temporal prediction of the current block (801) and is indicated by a motion vector (803) between the current block (801) and the reference block (802). Each of the reference block (802) and the current block (801) may have a respective template associated with the block, as shown in FIG. 9, where the sample regions (811) and (812) are templates of the current block (801) and the reference block (802), respectively. The reference block template (812) is a temporal prediction of the current block template (811) indicated by a motion vector (803) between the current block (801) and the reference block (802), as shown in FIG. 10.

[0099] According to an aspect of the present disclosure, the template of a block can include an upper template and a left template. For example, as shown in FIG. 9, the upper current block template (811-1) can include pixels adjacent to the upper side of the current block (801), and the left current block template (811-2) can include pixels adjacent to the left side of the current block (801). Similarly, the upper reference block template (812-1) can include pixels adjacent to the upper side of the reference block (802), and the left reference block template (812-2) can include pixels adjacent to the left side of the reference block (802).

[0100] In one example, as shown in FIG. 9, the upper template of a block can include one row of pixels immediately above the block, and the left template of the block can include one column of pixels immediately to the left of the block.

[0101] According to an aspect of the present disclosure, in the LIC model, for a current block having a width w and a height h, the prediction of the pixel y[i,j] in the current block

Equation

Equation

[0102] In Equation (1), 0 ≦ i < w, 0 ≦ j < h, α is a scaling coefficient, and β is an offset. Equation (1) can be used to compensate for changes in illumination in some related examples.

[0103] In some embodiments, the scaling factor α and offset β can be derived based on a current block template, such as the current block template (811) in Figure 9, and a reference block template, such as the reference block template (812), so that no signaling overhead is required for these parameters. In some cases, a LIC flag for advanced motion vector prediction (AMVP) mode can be signaled to indicate the use of the LIC model.

[0104] As mentioned above, the LIC model can be used to model the local illumination variation between a current block and its reference block as a function of the local illumination variation between the current block template and the reference block template. However, the LIC model used in some related examples is limited to compensating for local illumination changes. In some cases, it is desirable to compensate for some other changes, such as local motion blur, in addition to local illumination changes. Therefore, a more general prediction model that can compensate for multiple processes, such as both local illumination changes and other changes, such as local motion blur, is desirable.

[0105] III. Improved local illumination compensation The present disclosure includes a method for improving the LIC model. For example, a more generalized prediction model is provided to compensate for both local motion blur and local illumination changes. To generate a prediction of a current block, at least one filter operation can be applied to the neighborhood of a reference sample in a reference block of the current block, resulting in an improved LIC model that is not limited to compensation for local illumination changes.

[0106] According to some embodiments of the present disclosure, a prediction of pixel y[i,j] in the current block is

number

number

[0107] In equation 2,

number

[0108] To derive the 2D FIR filter h, the templates can be expanded. As shown in FIG. 11, for a 3×3 FIR filter, the upper current block template (1111) can be expanded to include the top four rows of the current block (1101), and the left current block template (1112) can be expanded to include the left four columns of the current block (1101). Similarly, the upper reference block template (1113) can be expanded to include the top four rows of the reference block (1102), and the left reference block template (1114) can be expanded to include the left four columns of the current block (1102). The filter coefficients of the FIR filter can be derived by minimizing the sum of the squared prediction errors of the pixels of the upper and left templates, excluding the pixels on the border of the templates.

[0109] Note that the templates can be expanded to include different numbers of rows and columns. For example, for a 3x3 FIR filter, the top current block template can be expanded to include the top 5 rows of the current block, and the left current block template can be expanded to include the left 5 columns of the current block. The reference block template can be expanded similarly.

[0110] In addition, the templates can be expanded based on the filter size. For example, for a 5x5 FIR filter, the top current block template can be expanded to include the top 6 rows of the current block, and the left current block template can be expanded to include the left 6 columns of the current block. The reference block template can be expanded similarly.

[0111] In one embodiment, an online training method such as a support vector machine (SVM) can be used to derive the filter coefficients of the FIR filter. The filter coefficients can be determined by minimizing the sum of squared prediction errors (called the online training error) in the online training method as follows:

number

[0112] In equation 5, T o contains pixel locations inside the top and left templates of the current block, as shown by gray sample areas (1121) and (1122) in Figure 11. Gray sample area (1121) is inside the top current block template (1111), and gray sample area (1122) is inside the left current block template (1112).

[0113] In one embodiment, the filter coefficients h[i,j] and the offset β may be determined by solving a set of linear equations, for example in a manner similar to solving ordinary least squares.

[0114] In one embodiment, the filter coefficients may be quantized, and the quantized filter coefficients may be obtained by using an algorithm such as Cramer's rule for solving linear equations as divisions of two integers using fixed-point arithmetic with a scaling factor of 2^b and a lookup table that replaces divisions with multiplications.

[0115] In one embodiment, the quantized filter coefficients may be clipped to a predetermined range, and the quantized and clipped filter coefficients may then be used to determine a quantized value for the offset β that minimizes the online training error.

[0116] In one embodiment, filter h may be symmetric, i.e., filter h does not introduce phase distortion during the filtering process of (Equation 2).

[0117] According to some embodiments of the present disclosure, to reduce the generalization error of the LIC model, the locations of samples used in the online training method can be closer to the current block. For example, pixels at or adjacent to one or more boundaries of the template shared with the current block can be used to determine the filter coefficients of the FIR filter.

[0118] In some embodiments, a prediction of pixel y[i,j] in the current block is

number

number

[0119] In equation (6),

number

[0120] In one embodiment, the filter coefficients may be determined by least-squares minimization that minimizes the online training error as follows:

number

[0121] In (Equation 9), T' includes pixel locations as shown by the gray sample regions (1221) and (1222) in FIG. 12. As shown in FIG. 12, for a 3×3 FIR filter, the upper current block template (1211) can be expanded to include the top four rows of the current block (1201), and the left current block template (1212) can be expanded to include the left four columns of the current block (1201). Similarly, the upper reference block template (1213) can be expanded to include the top four rows of the reference block (1202), and the left reference block template (1214) can be expanded to include the left four columns of the current block (1202). The gray sample regions (1221) and (1222) are used in (Equation 9) to calculate the filter coefficients h[u,v]. Note that the gray sample region (1221) includes the row immediately above the current block (1201), and the gray sample region (1222) includes the column immediately to the left of the current block (1201). Thus, when computing the filter coefficients, the least-squares minimization can refer to pixels outside the template. For example, the prediction of sample (1231)

number

[0122] Note that the templates can be expanded to include different numbers of rows and columns. For example, for a 3x3 FIR filter, the upper current block template can be expanded to include the 5 rows above the current block. The 5 rows could include the row immediately above the current block. The left current block template can be expanded to include the 5 columns to the left of the current block. The 5 columns could include the column immediately to the left of the current block. The reference block template can be expanded similarly.

[0123] In addition, the templates can be expanded based on the filter size. For example, for a 5x5 FIR filter, the top current block template can be expanded to include the 6 rows above the current block, and the left current block template can be expanded to include the 6 columns to the left of the current block. The 6 rows can include the row immediately above the current block, and the 6 columns can include the column immediately to the left of the current block. The reference block template can be expanded similarly.

[0124] In one embodiment, filter h is symmetric, i.e., filter h does not introduce phase distortion during the filtering process of (Equation 6).

[0125] According to some embodiments of the present disclosure, a single row above the current block and / or a single column to the left of the current block can be used to compensate for multiple processes such as motion blur and lighting changes.

[0126] In some embodiments, the prediction of pixels in the current block may be a combination of upward and leftward prediction of pixels in the current block. In both upward and leftward prediction of pixels, a row of pixels is predicted from an upward template T A and one column of pixels is in the left template T L You can use the same template that is in

[0127] In one embodiment, the upward prediction of pixels in the current block can be expressed as:

number

[0128] In (Equation 10), the 2M+1 filter coefficients h A [u] can be determined by a least-squares minimization that minimizes the online training error in the upper template of the current block as follows:

number

[0129] In one embodiment, if the least squares minimization refers to a pixel outside the upper template, a padding value based on, for example, the closest pixel in the upper template can be used instead, which is used in some embodiments.

[0130] In one embodiment, M=1.

[0131] In one embodiment, the left prediction of a pixel can be expressed as:

number

[0132] In (Equation 12), the 2N+1 filter coefficients h L [v] can be determined by a least-squares minimization that minimizes the online training error in the left template of the current block as follows:

number

[0133] In one embodiment, if the least squares minimization refers to a pixel outside the left template, a padding value based on, for example, the closest pixel in the left template can be used instead, which is used in some embodiments.

[0134] In one embodiment, N=1.

[0135] According to some embodiments of the present disclosure, a prediction of pixel y[i,j] in the current block is

number

number

number

[0136] In one embodiment, a prediction of pixel y[i,j] in the current block is

number

number

[0137] (Condition 1) The upper template of the current block is available and the width of the upper template is greater than a predetermined width.

[0138] (Condition 2) The left template of the current block is available and the height of the upper template is greater than a predetermined height.

[0139] In one embodiment, a prediction of pixel y[i,j] in the current block is

number

number

[0140] (Condition 1) The upper template of the current block is available and the width of the upper template is greater than a predetermined width.

[0141] (Condition 2) The left template for the current block is not available, or the height of the left template is not greater than a predetermined height.

[0142] In one embodiment, a prediction of pixel y[i,j] in the current block is

number

number

[0143] (Condition 1) The upper template for the current block is not available, or the width of the upper template is not greater than a predetermined width.

[0144] (Condition 2) The left template of the current block is available and the height of the left template is greater than a predetermined height.

[0145] In one embodiment, a prediction of pixel y[i,j] in the current block is

number

number

[0146] (Condition 1) The upper template for the current block is not available, or the width of the upper template is not greater than a predetermined width.

[0147] (Condition 2) The left template for the current block is not available, or the height of the left template is not greater than a predetermined height.

[0148] In one embodiment, the predetermined width and / or the predetermined height is seven.

[0149] In one embodiment, the filter h A and h L Each of the filters h A does not introduce phase distortion during the filtering process of (Eq. 10), and the filter h L does not introduce phase distortion during the filtering process of (Eq. 12).

[0150] This disclosure includes a more general predictive model to compensate for more localized changes such as lighting changes and / or motion blur by using at least one filter, such as an FIR filter, and an offset.

[0151] In some embodiments, an online training method can be used to obtain model parameters of a predictive model based on pixels in the template immediately above the current block and pixels in the template immediately above the reference block of the current block when both upper templates are available. In one embodiment, when the online training method refers to pixels outside the upper template of the reference block, a padding value can be used instead. For example, the closest pixel in the upper template of the reference block can be used instead.

[0152] In some embodiments, an online training method can be used to obtain model parameters of the prediction model based on pixels in the template immediately to the left of the current block and pixels in the template immediately to the left of the reference block of the current block when both left templates are available. In one embodiment, when the online training refers to pixels outside the left template of the reference block, a padding value can be used instead. For example, the closest pixel in the left template of the reference block can be used instead.

[0153] In one embodiment, each of the at least one filter in the predictive model may be symmetric, i.e., each of the at least one filter does not introduce phase distortion during the filtering process, and therefore, due to the linear phase of the filter, all frequencies input to the filter may be delayed in the same way.

[0154] In some embodiments, each filter coefficient of at least one filter in the predictive model can be expressed as a ratio of two integers. In one embodiment, each filter coefficient of at least one filter can be expressed as a ratio of two integers, with the denominator of each ratio being a predetermined number that is a power of two. In one embodiment, each filter coefficient of at least one filter can be expressed as a ratio of two integers, with the denominator of all ratios being the same predetermined number that is a power of two.

[0155] In some embodiments, the offset in the predictive model may be expressed as a ratio of two integers. In one embodiment, the offset may be expressed as a ratio of two integers, where the denominator of the ratio is a predetermined number that is a power of two.

[0156] In some embodiments, the prediction model may be a combination of an up-down prediction model and a left-down prediction model.

[0157] The upper prediction model is based on the upper template of the current block and the upper template of the reference block. When the upper template is selected for the prediction model, the parameters of the upper prediction model are derived from the upper template. The upper template is selected for the prediction model only if the upper template is available and the width of each upper template is greater than a predetermined width. In one embodiment, the predetermined width is 7. In another embodiment, the predetermined width may be a different number, such as 3.

[0158] The left prediction model is based on the left template of the current block and the left template of the reference block. When a left template is selected for the prediction model, the parameters of the left prediction model are derived from the left template. A left template is selected for the prediction model only if a left template is available and the height of each left template is greater than a predetermined height. In one embodiment, the predetermined height is 7. In another embodiment, the predetermined height may be a different number, such as 3.

[0159] In one embodiment, if both an upper template and a left template are selected for a predictive model, the output of the predictive model may be the average of the prediction from the upper prediction model and the prediction from the left prediction model.

[0160] In one embodiment, if for a predictive model, the top template is selected and the left template is not selected, the output of the predictive model may be a prediction from the top predictive model.

[0161] In one embodiment, for a predictive model, if no top template is selected and a left template is selected, the output of the predictive model may be a prediction from the left predictive model.

[0162] In one embodiment, for a predictive model, if no top template is selected and no left template is selected, the output of the predictive model may be a reference block.

[0163] IV. Flowchart 13 shows a flow chart outlining an example process (1300) according to one embodiment of the disclosure. In various embodiments, the process (1300) is performed by processing circuitry within the terminal devices (210), (220), (230), and (240), processing circuitry performing the functions of the video encoder (303), processing circuitry performing the functions of the video decoder (310), processing circuitry performing the functions of the video encoder (503), etc. In some embodiments, the process (1300) is implemented with software instructions, and thus the processing circuitry performs the process (1300) when the processing circuitry executes the software instructions.

[0164] The process (1300) may generally begin at step (S1310), where the process (1300) decodes prediction information for a current block that is part of a current picture in a video bitstream. The prediction information indicates a reference block for the current block. The process (1300) then proceeds to step (S1320).

[0165] In step (S1320), the process (1300) generates filter coefficients for a filter operation based on adjacent reconstructed samples of the current block and adjacent reconstructed samples of a reference block co-located with the adjacent reconstructed samples of the current block. The filter operation compensates for one or more local changes to the current picture. The one or more local changes include one of illumination changes and motion blur. The process (1300) then proceeds to step (S1330).

[0166] In step (S1330), the process (1300) determines a prediction block for the current block based on a filter operation performed on the reference block of the current block. Then, the process (1300) proceeds to step (S1340).

[0167] In step (S1340), the process (1300) reconstructs the current block based on the predicted block of the current block.

[0168] The process (1300) then ends.

[0169] In one embodiment, the filter operation includes one of a one-dimensional FIR filter and a two-dimensional FIR filter.

[0170] In one embodiment, the process (1300) generates a first plurality of filter coefficients based on one or more rows of adjacent reconstructed samples above a current block and one or more rows of adjacent reconstructed samples above a reference block.

[0171] In one embodiment, the process (1300) generates a first plurality of filter coefficients based on (i) one or more rows of adjacent reconstructed samples above the current block being available, and (ii) the width of the current block being greater than a threshold.

[0172] In one embodiment, the process (1300) generates a second plurality of filter coefficients based on one or more columns of left adjacent reconstructed samples of the current block and one or more columns of left adjacent reconstructed samples of the reference block.

[0173] In one embodiment, the process (1300) generates a second plurality of filter coefficients based on (i) the availability of one or more adjacent columns of reconstructed samples to the left of the current block, and (ii) the height of the current block being greater than a threshold.

[0174] In one embodiment, the process (1300) determines a prediction sample for a sample of a current block based on a co-located reference sample in a reference block of the current block and adjacent samples of the co-located reference sample.

[0175] In one embodiment, the process (1300) determines a plurality of filtered reference samples by multiplying each of the co-located reference sample and adjacent samples of the co-located reference sample by a respective filter coefficient of a filter operation. The process (1300) determines a sum of a plurality of filtered reference samples as a result of the filter operation. The process (1300) determines a predicted sample of the sample of the current block based on the sum of the result of the filter operation and an offset.

[0176] In one embodiment, each of the filter coefficients and offsets is expressed as a ratio of two integers.

[0177] In one embodiment, the denominator of each ratio is a power of two.

[0178] V. Computer Systems The techniques described above may be implemented as computer software using computer-readable instructions physically stored on one or more computer-readable media. For example, Figure 14 illustrates a computer system (1400) suitable for implementing certain embodiments of the disclosed subject matter.

[0179] The computer software may be coded using any suitable machine code or computer language that may undergo assembly, compilation, linking, or similar mechanisms to produce code containing instructions that may be executed by one or more computer central processing units (CPUs) and graphics processing units (GPUs), etc., directly, or through interpretation and execution of microcode, etc.

[0180] 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.

[0181] 14 with respect to computer system (1400) 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 the embodiments of the present disclosure, nor should the arrangement of components be interpreted as having a dependency or requirement regarding any one or combination of components illustrated in the exemplary embodiment of computer system (1400).

[0182] The computer system (1400) may include certain human interface input devices. Such human interface input devices may be responsive to input by one or more human users, for example, via tactile input (keystrokes, swipes, data glove movements, etc.), audio input (voice, clapping, etc.), visual input (gestures, etc.), olfactory input (not shown). The human interface devices may also be used to capture certain media not necessarily directly associated with conscious human input, such as audio (speech, music, ambient sounds, etc.), images (scanned images, photographic images obtained from still image cameras, etc.), video (two-dimensional video, three-dimensional video including stereoscopic video, etc.).

[0183] The input human interface devices may include one or more (only one of each is shown) of a keyboard (1401), a mouse (1402), a trackpad (1403), a touch screen (1410), a data glove (not shown), a joystick (1405), a microphone (1406), a scanner (1407), and a camera (1408).

[0184] The computer system (1400) may also include certain human interface output devices. Such human interface output devices may stimulate one or more of the senses of a human user, for example, through haptic output, sound, light, and smell / taste. Such human interface output devices may include haptic output devices (e.g., haptic feedback via a touch screen (1410), data gloves (not shown), or joystick (1405), although there may also be haptic feedback devices that do not function as input devices), audio output devices (e.g., speakers (1409), headphones (not shown)), visual output devices (e.g., screens (1410), including CRT screens, LCD screens, plasma screens, OLED screens, each with or without touch screen input capability, each with or without haptic feedback capability, some of which may output two-dimensional visual output or three or more dimensional visual output through means such as stereoscopic output; virtual reality glasses (not shown), holographic displays, and smoke tanks (not shown)), and printers (not shown). These visual output devices (such as a screen (1410)) can be connected to the system bus (1448) through a graphics adapter (1450).

[0185] The computer system (1400) may also include human accessible storage devices and associated media such as optical media including CD / DVD ROM / RW (1420) with CD / DVD or similar media (1421), thumb drives (1422), removable hard drives or solid state drives (1423), legacy magnetic media such as tapes and floppy disks (not shown), and dedicated ROM / ASIC / PLD based devices (not shown) such as security dongles.

[0186] Also, those skilled in the art should understand that the term "computer-readable medium" as used in connection with the subject matter of this disclosure does not encompass transmission media, carrier waves, or other transitory signals.

[0187] The computer system (1400) may also include a network interface (1454) with one or more communication networks (1455). The one or more communication networks (1455) may be, for example, wireless, wired, optical. The one or more communication networks (1455) may further be local, wide area, metropolitan, vehicular and industrial, real-time, delay tolerant, etc. Examples of the one or more communication networks (1455) include local area networks such as Ethernet, wireless LAN, etc., cellular networks including GSM, 3G, 4G, 5G, LTE, etc., TV wired or wireless wide area digital networks including cable TV, satellite TV, and terrestrial TV, vehicular and industrial including CANBus, etc. Certain networks generally require an external network interface adapter connected to a particular general-purpose data port or peripheral bus (1449) (such as, for example, a USB port on the computer system (1400)), while others are generally integrated into the core of the computer system (1400) by connection 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 (1400) can communicate with other entities. Such communications may be unidirectional receive only (e.g., a TV broadcast), unidirectional transmit only (e.g., a CANbus to a particular CANbus device), or bidirectional, for example, with other computer systems using local or wide area digital networks. Specific protocols and protocol stacks may be used with each of those networks and network interfaces, as described above.

[0188] The aforementioned human interface devices, human accessible storage devices, and network interfaces may be connected to the core (1440) of the computer system (1400).

[0189] The cores (1440) may include one or more central processing units (CPUs) (1441), graphics processing units (GPUs) (1442), dedicated programmable processing units in the form of field programmable gate areas (FPGAs) (1443), hardware accelerators for specific tasks (1444), graphics adapters (1450), etc. These devices may be connected through a system bus (1448), along with read only memory (ROM) (1445), random access memory (1446), internal mass storage devices (1447) such as internal hard drives, SSDs, etc. that are not user accessible. In some computer systems, the system bus (1448) may be accessible in the form of one or more physical plugs to allow expansion with additional CPUs, GPUs, etc. Peripheral devices may be connected directly to the core's system bus (1448) or through a peripheral bus (1449). In one example, a screen (1410) may be connected to the graphics adapter (1450). Peripheral bus architectures include PCI, USB, and the like.

[0190] The CPU (1441), GPU (1442), FPGA (1443), and accelerator (1444) can execute certain instructions that, in combination, can constitute the aforementioned computer code. That computer code can be stored in ROM (1445) or RAM (1446). Persistent data can be stored, for example, in internal mass storage device (1447), while transitory data can also be stored in RAM (1446). Rapid storage and retrieval in any memory device is possible through the use of cache memory, which can be closely associated with one or more of the CPU (1441), GPU (1442), mass storage device (1447), ROM (1445), RAM (1446), etc.

[0191] The computer-readable medium may bear computer code for performing various computer-implemented operations. The medium and computer code may be those specially designed and constructed for the purposes of the present disclosure, or they may be of the type well known and available to those skilled in the computer software arts.

[0192] By way of example and not limitation, a computer system (1400) having an architecture, and specifically a core (1440), can provide functionality as a result of a processor (or processors) (including CPUs, GPUs, FPGAs, accelerators, etc.) executing software embodied in one or more tangible computer-readable media. Such computer-readable media can be user-accessible mass storage devices as introduced above, as well as media associated with specific storage of the core (1440) of a non-transitory nature, such as mass storage device (1447) internal to the core or ROM (1445). Software implementing various embodiments of the present disclosure can be stored in such devices and executed by the core (1440). The computer-readable media can include one or more memory devices or chips, depending on the particular needs. The software can cause the core (1440), and specifically the processors therein (including CPUs, GPUs, FPGAs, etc.) to perform certain processes, or certain portions of certain processes, described herein, including defining data structures stored in RAM (1446) and modifying such data structures according to the software-defined processes. Additionally or alternatively, a computer system may provide functionality as a result of logic hardwired or otherwise embodied in circuitry (e.g., accelerator (1444)) that may operate in place of or together with software to perform certain processes, or certain portions of certain processes, described herein. References to software may encompass logic, and vice versa, where appropriate. Where appropriate, references to computer-readable media may encompass circuitry (such as an integrated circuit (IC)) that stores software for execution, circuitry that embodies logic for execution, or both. The present disclosure encompasses any suitable combination of hardware and software.

[0193] While this disclosure has described several exemplary embodiments, there are modifications, substitutions, and various substitute equivalents that are 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.

[0194] Appendix A: Acronyms ALF Adaptive Loop Filter AMVP Advanced Motion Vector Prediction APS Adaptation Parameter Set ASIC Application Specific Integrated Circuit ATMVP Alternative / Advanced Temporal Motion Vector Prediction AV1 AOMedia Video 1 AV2 AOMedia Video 2 BMS Benchmark Set BV Block Vector CANBus Controller Area Network Bus CB coding block CC-ALF Cross-Component Adaptive Loop Filter CD Compact Disc CDEF Constrained Directional Enhancement Filter CPR Current Picture Reference CPU Central Processing Unit CRT Braun tube CTB coding tree block CTU Coding Tree Unit CU coding unit DPB Decoder Picture Buffer DPCM Differential Pulse Code Modulation DPS Decoding Parameter Set DVD Digital Video Disc FPGA Field Programmable Gate Area JCCR Joint CbCr Residual Coding JVET Joint Video Exploration Team GOP Picture Group GPU Graphics Processing Unit GSM Global System for Mobile Communications HDR High Dynamic Range HEVC High Efficiency Video Coding HRD Hypothetical Reference Decoder IBC Intra Block Copy IC Integrated Circuit ISP Intra Subpartition JEM Collaborative Exploration Model LAN Local Area Network LCD Liquid Crystal Display LR Loop Recovery Filter LRU Loop Recovery Unit LTE Long Term Evolution MPM Most Accurate Mode MV Motion Vector OLED Organic Light Emitting Diode PBs predicted blocks PCI Peripheral Component Interconnect PDPC Position-dependent Prediction Combination PLD Programmable Logic Device PPS Picture Parameter Set PU Prediction Unit RAM Random Access Memory ROM Read Only Memory SAO pixel adaptive offset SCC Screen Content Coding SDR Standard Dynamic Range SEI Supplemental Extension Information SNR Signal to Noise Ratio SPS sequence parameter set SSD Solid State Drive TU Conversion Unit USB Universal Serial Bus VPS Video Parameter Set VUI Video Usability Information VVC Versatile Video Coding WAIP Wide-angle Intra Prediction [Explanation of symbols]

[0195] 101 Samples 102 Arrow 103 Arrow 104 Block 111 Current Block 200 Communication Systems 210 Terminal Devices 220 Terminal Devices 230 Terminal Devices 240 Terminal Devices 250 Network 301 Video Source 302 Video Picture Stream 303 Video Encoder 304 Video Data 305 Streaming Server 306 Client Subsystem 307 Video Data 308 Client Subsystem 309 Video Data 310 Video Decoder 311 Output Stream 312 Display 313 Capture Subsystem 320 Electronic Devices 330 Electronic Devices 401 Channel 410 Video Decoder 412 Render Device 415 Buffer Memory 420 Parser 421 Symbols 430 Electronic Devices 431 Receiver 451 Reverse conversion unit 452 Intra-picture Prediction Unit 453 Motion Compensation Prediction Unit 455 Aggregator 456 Loop Filter Unit 457 Reference Picture Memory 458 Picture Buffer 501 Video Sources 503 Video Encoder 520 Electronic Devices 530 Source Coder 532 Coding Engine 533 Local Decoder 534 Reference Picture Memory 535 Predictors 540 Transmitter 543 Video Sequences 545 Entropy Coder 550 Controller 560 Communication Channels 603 Video Encoder 621 General-purpose controller 622 Intra Encoder 623 Residual Calculator 624 Residual Encoder 625 Entropy Encoder 626 Switch 628 Residual Decoder 630 InterEncoder 710 Video Decoder 771 Entropy Decoder 772 Intra Decoder 773 Residual Decoder 774 Reconstruction Module 780 Inter Decoder 801 Current Block 802 Reference Block 803 Motion Vectors 811 Block Templates / Sample Area 812 Reference Block Template 1101 Current Block 1102 Reference Block 1111 Block Template 1112 Block Template 1113 Upper reference block template 1114 Left Reference Block Template 1121 Sample Area 1122 Sample Area 1201 Block 1202 Reference Block 1211 Block Template 1212 Block Template 1213 Reference Block Template 1214 Reference Block Template 1221 Gray Sample Area 1222 Gray sample area 1231 Samples 1232 Samples 1233 Samples 1400 Computer Systems 1401 Keyboard 1402 Mouse 1403 Trackpad 1405 Joystick 1406 Mike 1407 Scanner 1408 Camera 1409 Speaker 1410 Screen 1421 Medium 1422 Thumb Drive 1423 Solid State Drive 1440 cores 1441 CPU 1442 GPU 1443 FPGA 1444 Accelerator 1445 ROM 1446 Random Access Memory 1447 Mass Storage 1448 System Bus 1449 Surrounding Bus 1450 Graphics Adapter 1454 Network Interface 1455 Communication Network

Claims

1. A method of video encoding in an encoder, comprising: determining a reference block for a current block that is part of the current picture; generating prediction information indicative of the reference block for the current block; encoding the current picture and the prediction information into a video bitstream; The following steps: calculating filter coefficients of a filter operation based on reconstructed samples in the vicinity of the current block and reconstructed samples in the vicinity of the reference block, wherein the positions of the reconstructed samples in the vicinity of the current block relative to the current block are the same as the positions of the reconstructed samples in the vicinity of the reference block relative to the reference block; applying a filter operation using the filter coefficients to a plurality of reference samples in the reference block to generate a plurality of filtered reference samples, applying the filter operation to a reference sample in the reference block to generate a corresponding filtered reference sample, multiplying the one reference sample and neighboring samples of the one reference sample by the filter coefficients and generating a corresponding filtered reference sample by summing the multiplied one reference sample and the neighboring samples; determining a prediction block for the current block based on the plurality of filtered reference samples; the reference block is determined such that the current block is reconstructed based on the prediction block of the current block, method.

2. The method of claim 1, wherein the filter operation includes one of a one-dimensional finite impulse response (FIR) filter and a two-dimensional FIR filter.

3. The step of calculating calculating a first plurality of filter coefficients based on one or more rows of reconstructed samples in a neighborhood of information of the current block and one or more rows of reconstructed samples in a neighborhood of information of the reference block; or 3. The method of claim 1, further comprising: calculating a second plurality of filter coefficients based on one or more columns of reconstructed samples in a left neighborhood of the current block and one or more columns of reconstructed samples in a left neighborhood of the reference block.

4. The step of calculating includes the step of calculating the first plurality of filter coefficients; the step of calculating the first plurality of filter coefficients includes calculating the first plurality of filter coefficients based on (i) the one or more columns of reconstructed samples in an upper neighborhood of the current block being available, and (ii) a width of the current block being greater than a threshold. The method according to claim 3.

5. The method of claim 1, wherein the calculating step includes the step of calculating the second plurality of filter coefficients. the step of calculating the second plurality of filter coefficients includes calculating the second plurality of filter coefficients based on (i) the one or more columns of reconstructed samples in a left neighbor of the current block being available, and (ii) a height of the current block being greater than a threshold. The method according to claim 3.

6. The step of determining a prediction block, comprising:

6. The method according to claim 1, further comprising a step of determining a predicted sample of a sample of the current block based on a reference sample in the reference block and a sample in the vicinity of the reference sample, wherein a positional relationship of the sample to the current block is the same as a positional relationship of the reference sample to the reference block.

7. The step of determining a prediction sample comprising: The method of claim 6 , further comprising determining the prediction sample of the sample of the current block based on a sum of the corresponding filter reference sample and an offset.

8. A method according to claim 1, wherein each of the filter coefficients and offsets is expressed as a ratio of two integers.

9. The method of claim 8, wherein the denominator of each ratio is a power of two.

10. An apparatus comprising processing circuitry configured to carry out the method according to claim 1 or 2.

11. The processing circuitry comprises:

11. The apparatus of claim 10, configured to calculate a first plurality of filter coefficients based on one or more rows of reconstructed samples in an upper neighborhood of the current block and one or more rows of reconstructed samples in an upper neighborhood of the reference block.

12. The processing circuitry comprises:

12. The apparatus of claim 11 , configured to calculate the first plurality of filter coefficients based on (i) the one or more rows of reconstructed samples in an upper neighborhood of the current block being available, and (ii) a width of the current block being greater than a threshold.

13. The processing circuitry comprises:

11. The apparatus of claim 10, configured to calculate a second plurality of filter coefficients based on one or more columns of reconstructed samples in a left neighborhood of the current block and one or more columns of reconstructed samples in a left neighborhood of the reference block.

14. The processing circuitry comprises:

14. The apparatus of claim 13, configured to calculate the second plurality of filter coefficients based on (i) the one or more columns of reconstructed samples in a left neighbor of the current block being available, and (ii) a height of the current block being greater than a threshold.

15. The processing circuitry comprises:

15. The device according to claim 10, configured to determine a prediction sample of a sample of the current block based on a reference sample in the reference block and a sample in the vicinity of the reference sample, wherein a positional relationship of the sample to the current block is the same as a positional relationship of the reference sample to the reference block.

16. The processing circuitry comprises: The apparatus of claim 15 , configured to determine the prediction sample of the sample of the current block based on a sum of the corresponding filtered reference sample and an offset.

17. The apparatus of claim 10, wherein each of the filter coefficients and offsets is expressed as a ratio of two integers.

18. The apparatus of claim 17, wherein the denominator of each ratio is a power of two.

19. A computer program for causing a computer to carry out a method according to any one of claims 1 to 9.

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