Method and apparatus for video filtering

Abstract

Various aspects of the present disclosure provide methods and apparatus for video encoding / decoding. In some examples, the apparatus for video decoding includes processing circuitry. The processing circuitry determines decoupled encoding information for a first color component and a second color component of a block based on decoded information in an encoded video stream. The processing circuitry then reconstructs a first sample of the first color component at a location in the block based on a first loop filter configuration, and reconstructs a second sample of the second color component at the location in the block based on a second loop filter configuration, the second loop filter configuration being different from the first loop filter configuration.

Description

[0001] Incorporation by reference

[0002] This application claims the benefit of priority to U.S. Patent Application No. 17 / 360,761, filed on June 28, 2021, entitled “METHOD AND APPARATUS FOR VIDEOFILTERING,” which claims the benefit of priority to U.S. Provisional Application No. 63 / 126,423, filed on December 16, 2020, entitled “HARMONIZED SCHEME BETWEEN SEMIDECOUPLED PARTITIONING AND LOOP FILTER.” The entire disclosure of the prior application is incorporated herein by reference in its entirety. Technical Field

[0003] This disclosure describes embodiments generally related to video encoding. Background Art

[0004] The background description provided herein is for the purpose of generally presenting the context of the present disclosure. To the extent described in this background section, the works of the presently named inventors and aspects of this description that might not otherwise qualify as prior art at the time of filing are neither explicitly nor implicitly admitted to be prior art to the present disclosure.

[0005] Video encoding and decoding can be performed using inter-picture prediction with motion compensation. An uncompressed digital video may comprise a series of pictures, each picture having a spatial size of, for example, 1920×1080 luma samples and associated chroma samples. The series of pictures may have a fixed or variable picture rate (also informally referred to as a frame rate) of, for example, 60 pictures per second or 60 Hz. Uncompressed video has specific bitrate requirements. For example, 1080p60 4:2:0 video with 8 bits per sample (a resolution of 1920×1080 luma samples at a 60 Hz frame rate) requires a bandwidth of nearly 1.5 Gbit / s. One hour of such video requires over 600 GB of storage space.

[0006] One purpose of video encoding and decoding can be to reduce redundancy in the input video signal through compression. Compression can help reduce the bandwidth and / or storage space requirements mentioned above, in some cases by two orders of magnitude or more. Lossless compression and lossy compression, as well as combinations thereof, can be used. Lossless compression refers to techniques that can reconstruct an exact replica of the original signal from the compressed original signal. When lossy compression is used, the reconstructed signal may not be the same as the original signal, but the distortion between the original and the reconstructed signal is small enough to make the reconstructed signal usable for the intended application. In the case of video, lossy compression is widely used. The amount of distortion that can be tolerated depends on the application; for example, users of some consumer streaming applications can tolerate higher distortion than users of television contribution applications. The achievable compression rate can reflect that higher allowable / tolerable distortion results in higher compression rates.

[0007] Video encoders and decoders may utilize techniques from several broad categories including, for example, motion compensation, transforms, quantization, and entropy coding.

[0008] Video codec techniques may include a technique known as intra-frame coding. In intra-frame 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 sample blocks are encoded in intra-frame mode, the picture can be an intra-frame picture. Intra-frame pictures and their derivatives (such as independent decoder refresh pictures) can be used to reset the decoder state and can therefore be used as the first picture in an encoded video stream and video session, or as a still image. The samples of an intra-frame block can be transformed, and the transform coefficients can be quantized before entropy coding. Intra-frame prediction can be a technique that minimizes the sample values ​​in the domain before the transform. In some cases, the smaller the DC value after the transform and the smaller the AC coefficients, the fewer bits are required to represent the block after entropy coding at a given quantization step size.

[0009] Traditional intra-frame coding, known from coding techniques such as MPEG-2, does not use intra-frame prediction. However, some newer video compression techniques include techniques that attempt to derive a block of data from, for example, surrounding sample data and / or metadata that was obtained during spatially adjacent encoding / decoding and preceded in decoding order. Such techniques are hereinafter referred to as "intra-frame prediction" techniques. It should be noted that, at least in some cases, intra-frame prediction uses only reference data from the current picture being reconstructed, and not reference data from reference pictures.

[0010] Intra-frame prediction can take many different forms. When more than one such technique can be used in a given video coding technique, the technique in use can be encoded in an intra-frame prediction mode. In some cases, a mode may have sub-modes and / or parameters, and these sub-modes and / or parameters may be encoded separately or included in a mode codeword. Which codeword is used for a given mode / sub-mode / parameter combination may affect the coding efficiency gain through intra-frame prediction, and therefore may affect the entropy coding technique used to convert the codeword into the bitstream.

[0011] H.264 introduced an intra-frame prediction mode, which was refined in H.265 and further refined in newer coding techniques such as the Joint Exploration Model (JEM), Versatile Video Coding (VVC), and the Benchmark Set (BMS). A predictor block is formed using the values ​​of neighboring samples belonging to already available samples. Sample values ​​from neighboring samples are copied into the predictor block based on the direction. A reference to the used direction can be encoded in the bitstream, or it can be predicted itself.

[0012] Referring to FIG1A , a subset of 9 prediction directions known from the 33 possible prediction directions of H.265 (corresponding to the 33 angular modes of the 35 intra modes) is depicted at the bottom right. The point (101) where the arrows converge represents the sample being predicted. The arrows represent the direction along which the sample is predicted. For example, arrow (102) indicates that sample (101) is predicted based on one or more samples to the upper right at an angle of 45 degrees to the horizontal. Similarly, arrow (103) indicates that sample (101) is predicted based on one or more samples to the lower left of sample (101) at an angle of 22.5 degrees to the horizontal.

[0013] Still referring to FIG1A , a square block (104) of 4×4 samples is depicted in the upper left (indicated by the dashed bold line). The square block (104) includes 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 in the Y dimension (from the top) and the first sample in the X dimension (from the left). Similarly, sample S44 is the fourth sample in the block (104) in both the Y and X dimensions. Since the size of the block is 4×4 samples, S44 is located in the lower right corner. Reference samples are also shown 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 H.264 and H.265, the prediction samples are adjacent to the block being reconstructed; therefore, there is no need to use negative values.

[0014] Intra-picture prediction works by copying reference sample values ​​from neighboring samples, appropriately following the signaled prediction direction. For example, assume the encoded video stream includes signaling that indicates a prediction direction for the block consistent with arrow (102), i.e., predicting samples based on one or more prediction samples located to the upper right and at a 45-degree angle to the horizontal. In that case, samples S41, S32, S23, and S14 are predicted based on the same reference sample R05. Sample S44 is then predicted based on reference sample R08.

[0015] In some cases, the values ​​of multiple reference samples may be combined, such as by interpolation, to calculate the reference sample; in particular, when the direction is not divisible by 45 degrees.

[0016] As video coding technology has developed, the number of possible directions has increased. In H.264 (2003), nine different directions can be represented. In H.265 (2013), this increased to 33 directions, 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 some techniques in entropy coding are used to represent those possible directions with a small number of bits, accepting a certain cost for less likely directions. In addition, the direction itself can sometimes be predicted based on the adjacent directions used in the adjacent blocks that have already been decoded.

[0017] FIG1B shows a schematic diagram (180) depicting 65 intra prediction directions according to JEM to illustrate the increase in the number of prediction directions over time.

[0018] The mapping of the intra-prediction direction bits representing the direction in the coded video stream may vary depending on the video coding technique; for example, it can range from a simple direct mapping of the prediction direction to the intra-prediction mode, to a mapping of the prediction direction to a codeword, to complex adaptive schemes involving the most probable mode, and similar techniques. However, in all cases, there may be some directions that are statistically less likely to appear in the video content than some other directions. Since the goal of video compression is to reduce redundancy, in a well-performing video coding technique, those less likely directions will be represented by a larger number of bits than more likely directions.

[0019] Motion compensation can be a lossy compression technique and can involve the following technique: a block of sample data from a previously reconstructed picture or portion thereof (reference picture) is used to predict a newly reconstructed picture or picture portion after being spatially shifted in a direction indicated by a motion vector (hereinafter referred to as MV). In some cases, the reference picture can be the same as the picture currently being reconstructed. The MV can have two dimensions, X and Y, or three dimensions, with the third dimension being an indication of the reference picture being used (the latter can indirectly be a temporal dimension).

[0020] In some video compression techniques, the MV applicable to a region of sample data can be predicted based on other MVs, such as an MV related to another region of sample data that is spatially adjacent to the region being reconstructed and precedes the MV in decoding order. This can significantly reduce the amount of data required to encode the MV, thereby eliminating redundancy and increasing compression. MV prediction works effectively, for example, because when encoding input video signals obtained from a camera (referred to as natural video), there is a statistical probability that regions larger than the region for which a single MV applies will move in a similar direction. Therefore, in some cases, similar motion vectors derived from MVs in neighboring regions can be used to predict this larger region. This allows the MV found for a given region to be similar or identical to the MV predicted from surrounding MVs. Consequently, after entropy coding, the MV found for the given region can be represented using a smaller number of bits than would be used if the MV were encoded directly. In some cases, MV prediction can be an example of lossless compression of a signal (i.e., an MV) derived from the original signal (i.e., a sample stream). In other cases, MV prediction can be inherently lossy, for example due to rounding errors when calculating the predicted value from multiple surrounding MVs.

[0021] Various MV prediction mechanisms are described in H.265 / HEVC (ITU-T Recommendation H.265, "High Efficiency Video Coding," December 2016). Among the various MV prediction mechanisms provided by H.265, this article describes a technique referred to as "spatial merging."

[0022] Referring to Figure 2, the current block (201) includes samples that have been found by the encoder during the motion search process, which can be predicted from a previous block of the same size that has been spatially offset. Instead of encoding the MV directly, the MV can be derived from metadata associated with one or more reference pictures, for example using the MV associated with any of the five surrounding samples labeled A0, A1 and B0, B1, B2 (202 to 206, respectively), which is derived from the nearest reference picture (in decoding order). In H.265, MV prediction can use prediction values ​​from the same reference picture being used by neighboring blocks. Summary of the Invention

[0023] Various aspects of the present disclosure provide methods and apparatus for video encoding / decoding. In some examples, the apparatus for video decoding includes processing circuitry. The processing circuitry determines decoupled encoding information for a first color component and a second color component of a block based on decoded information in an encoded video stream. The processing circuitry then reconstructs a first sample of the first color component at a location in the block based on a first loop filter configuration, and reconstructs a second sample of the second color component at the location in the block based on a second loop filter configuration, the second loop filter configuration being different from the first loop filter configuration.

[0024] In some embodiments, the decoupled coding information includes an enable / disable difference of intra block copy modes for the luma component and the chroma component. In some embodiments, the decoupled coding information includes a decoupled partitioning structure for the luma component and the chroma component.

[0025] In some embodiments, the processing circuitry enables at least one of a deblocking filter, a constrained directional enhancement filter (CDEF), a loop recovery filter, a local sample offset (LSO) filter, and a cross-component sample offset (CCSO) filter in one of a first loop filter configuration and a second loop filter configuration; and disables the deblocking filter, the constrained directional enhancement filter (CDEF), the loop recovery filter, the local sample offset (LSO) filter, and the cross-component sample offset (CCSO) filter in the other of the first loop filter configuration and the second loop filter configuration.

[0026] In one embodiment, the processing circuitry enables, in a second loop filter configuration associated with the chroma component, a deblocking filter, a constrained directional enhancement filter (CDEF), a loop restoration filter, a local sample offset (LSO) filter, and a cross-component sample offset (CCSO) filter in response to disabling the intra block copy mode for the chroma component and enabling the intra block copy mode for the luma component.

[0027] In another embodiment, the processing circuit enables, in a second loop filter configuration associated with the chroma component, one of a local sample offset (LSO) filter and a cross-component sample offset (CCSO) filter in response to disabling the intra block copy mode for the chroma component and enabling the intra block copy mode for the luma component.

[0028] In another embodiment, the processing circuit enables a constrained directional enhancement filter (CDEF) and a cross-component sample offset (CCSO) filter in a second loop filter configuration associated with the chroma component in response to disabling the intra block copy mode for the chroma component and enabling the intra block copy mode for the luma component.

[0029] In some examples, the processing circuit determines decoupled encoding information for the first color component and the second color component in the block based on corresponding enable / disable signals for the first color component and the second color component, and the corresponding enable / disable signals adopt at least one of the block level, video parameter set (VPS), sequence parameter set (SPS), picture parameter set (PPS), adaptation parameter set (APS), slice header and tile header.

[0030] In some examples, the processing circuit decodes a first enable / disable flag associated with a luma component from an encoded video stream, and decodes a second enable / disable flag associated with a chroma component from the encoded video stream. The processing circuit then determines decoupled coding information for the luma component and the chroma component based on the first enable / disable flag and the second enable / disable flag.

[0031] In some examples, the processing circuit decodes a first enable / disable flag associated with a luma component from the encoded video stream, decodes a second enable / disable flag associated with a first chroma component from the encoded video stream, and decodes a third enable / disable flag associated with a second chroma component from the encoded video stream. The processing circuit then determines decoupled coding information for the luma component, the first chroma component, and the second chroma component based on the first enable / disable flag, the second enable / disable flag, and the third enable / disable flag.

[0032] In some embodiments, the processing circuitry decodes a flag associated with a particular loop filter from a syntax higher than a block; and applies the particular loop filter to the luma component in response to the flag being true, without regard to decoupling coding information or intra block copy mode.

[0033] Aspects of the present disclosure also provide a non-transitory computer-readable medium storing instructions that, when executed by a computer for video decoding, cause the computer to perform any method for video decoding. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0035] FIG1A is a schematic illustration of an exemplary subset of intra prediction modes.

[0036] FIG. 1B is a diagram of exemplary intra prediction directions.

[0037] FIG2 is a schematic diagram of a current block and its surrounding spatial merging candidates in an example.

[0038] Figure 3is a schematic illustration of a simplified block diagram of a communication system (300) according to one embodiment.

[0039] Figure 4 is a schematic illustration of a simplified block diagram of a communication system (400) according to one embodiment.

[0040] Figure 5 is a schematic illustration of a simplified block diagram of a decoder according to one embodiment.

[0041] Figure 6 is a schematic illustration of a simplified block diagram of an encoder according to one embodiment.

[0042] Figure 7 A block diagram of an encoder according to another embodiment is shown.

[0043] Figure 8 A block diagram of a decoder according to another embodiment is shown.

[0044] Figure 9 An example of a filter shape according to an embodiment of the present disclosure is shown.

[0045] 10A to 10D An example of sub-sampling positions for calculating gradients according to an embodiment of the present disclosure is shown.

[0046] Figure 11A and Figure 11B An example of a virtual boundary filtering process according to an embodiment of the present disclosure is shown.

[0047] 12A to 12F An example of a symmetric fill operation at a virtual boundary according to an embodiment of the present disclosure is shown.

[0048] Figure 13 An example of segmentation of a picture according to some embodiments of the present disclosure is shown.

[0049] Figure 14 In some examples, a quadtree splitting pattern of a picture is shown.

[0050] Figure 15 A cross-component filter according to one embodiment of the present disclosure is shown.

[0051] Figure 16 An example of a filter shape according to one embodiment of the present disclosure is shown.

[0052] Figure 17 An example of syntax for cross-component filters according to some embodiments of the present disclosure is shown.

[0053] Figure 18A and Figure 18BShown are exemplary positions of chroma samples relative to luma samples, according to an embodiment of the present disclosure.

[0054] Figure 19 An example of direction search according to one embodiment of the present disclosure is shown.

[0055] Figure 20 Examples illustrating subspace projections in some examples are shown.

[0056] Figure 21 A table showing multiple sample adaptive offset (SAO) types according to one embodiment of the present disclosure is shown.

[0057] Figure 22 Examples of patterns of pixel classification in edge offsets are shown in some examples.

[0058] Figure 23 A table showing pixel classification rules for edge offset in some examples is shown.

[0059] Figure 24 An example of syntax that may be signaled is shown.

[0060] Figure 25 Examples of filter support regions according to some embodiments of the present disclosure are shown.

[0061] Figure 26 An example of another filter support region according to some embodiments of the present disclosure is shown.

[0062] Figures 27A to 27C A table with 81 combinations according to one embodiment of the present disclosure is shown.

[0063] Figure 28 Examples of coding tree structures for luma and chroma components are shown.

[0064] Figure 29 A flowchart outlining a process according to one embodiment of the present disclosure is shown.

[0065] Figure 30 is a schematic diagram of a computer system according to one embodiment. DETAILED DESCRIPTION

[0066] Figure 3 3 is a simplified block diagram of a communication system (300) according to an embodiment disclosed herein. The communication system (300) includes a plurality of terminal devices that can communicate with each other via, for example, a network (350). For example, the communication system (300) includes a terminal device (310) and a terminal device (320) interconnected via the network (350). Figure 3In an embodiment, the terminal device (310) and the terminal device (320) perform unidirectional data transmission. For example, the terminal device (310) may encode video data (e.g., a video picture stream collected by the terminal device (310)) for transmission to another terminal device (320) via the network (350). The encoded video data is transmitted in the form of one or more encoded video streams. The terminal device (320) may receive the encoded video data from the network (350), decode the encoded video data to restore the video data, and display the video picture based on the restored video data. Unidirectional data transmission is more common in applications such as media services.

[0067] In another embodiment, a communication system (300) includes terminal devices (330) and (340) that perform bidirectional transmission of encoded video data, which bidirectional transmission can occur, for example, during a video conference. For bidirectional data transmission, each of the terminal device (330) and the terminal device (340) can encode video data (e.g., a video picture stream collected by the terminal device) for transmission to the other terminal device (330) and the terminal device (340) via a network (350). Each of the terminal device (330) and the terminal device (340) can also receive the encoded video data transmitted by the other terminal device (330) and the terminal device (340), and can decode the encoded video data to restore the video data, and can display the video picture on an accessible display device based on the restored video data.

[0068] exist Figure 3 In the embodiment of the present invention, the terminal device (310), the terminal device (320), the terminal device (330) and the terminal device (340) may be servers, personal computers and smart phones, but the principles disclosed in the present application may not be limited thereto. The embodiments disclosed in the present application are applicable to laptop computers, tablet computers, media players and / or dedicated video conferencing equipment. The network (350) represents any number of networks that transmit encoded video data between the terminal device (310), the terminal device (320), the terminal device (330) and the terminal device (340), including, for example, wired (wired) and / or wireless communication networks. The communication network (350) can exchange data in circuit switching and / or packet switching channels. The network may include a telecommunications network, a local area network, a wide area network and / or the Internet. For the purposes of this application, unless explained below, the architecture and topology of the network (350) may be irrelevant to the operations disclosed in the present application.

[0069] As an example, Figure 4The video encoder and video decoder are shown in a streaming environment. The subject matter disclosed in this application is equally applicable to other video-enabled applications, including, for example, video conferencing, digital TV, storing compressed video on digital media including CDs, DVDs, memory sticks, etc.

[0070] The streaming system may include an acquisition subsystem (413), which may include a video source (401) such as a digital camera, which creates an uncompressed video picture stream (402). In an embodiment, the video picture stream (402) includes samples captured by the digital camera. The video picture stream (402) is depicted as a thick line to emphasize the high data volume of the video picture stream compared to the encoded video data (404) (or encoded video code stream), and the video picture stream (402) can be processed by an electronic device (420) that includes a video encoder (403) coupled to the video source (401). The video encoder (403) may include hardware, software, or a combination of hardware and software to implement or implement various aspects of the disclosed subject matter as described in more detail below. Compared to the video picture stream (402), the encoded video data (404) (or the encoded video code stream (404)) is depicted as a thin line to emphasize the lower amount of data of the encoded video data (404) (or the encoded video code stream (404)), which can be stored on the streaming server (405) for future use. One or more streaming client subsystems, such as Figure 4 The client subsystem (406) and the client subsystem (408) in the streaming server (405) can access the streaming server (405) to retrieve the copy (407) and the copy (409) of the encoded video data (404). The client subsystem (406) can include, for example, a video decoder (410) in the electronic device (430). The video decoder (410) decodes the incoming copy (407) of the encoded video data and produces an output video picture stream (411) that can be presented on a display (412) (e.g., a display screen) or another presentation device (not depicted). In some streaming systems, the encoded video data (404), the video data (407), and the video data (309) (e.g., a video bitstream) can be encoded according to certain video encoding / compression standards. Examples of such standards include ITU-T H.265. In an embodiment, the video coding standard under development is informally referred to as Versatile Video Coding (VVC), and the present application can be used in the context of the VVC standard.

[0071] It should be noted that the electronic device (420) and the electronic device (430) may include other components (not shown). For example, the electronic device (420) may include a video decoder (not shown), and the electronic device (430) may also include a video encoder (not shown).

[0072] Figure 5 1 is a block diagram of a video decoder (510) according to an embodiment disclosed in the present application. The video decoder (510) may be provided in an electronic device (530). The electronic device (530) may include a receiver (531) (e.g., a receiving circuit). The video decoder (510) may be used to replace Figure 4 A video decoder (510) of an embodiment.

[0073] A receiver (531) may receive one or more encoded video sequences to be decoded by a video decoder (510); in the same or another embodiment, one encoded video sequence is received at a time, wherein each encoded video sequence is decoded independently of the other encoded video sequences. The encoded video sequence may be received from a channel (501), which may be a hardware / software link to a storage device storing the encoded video data. The receiver (531) may receive the encoded video data as well as other data, such as encoded audio data and / or auxiliary data streams, which may be forwarded to their respective consuming entities (not shown). The receiver (531) may separate the encoded video sequence from the other data. To prevent network jitter, a buffer memory (515) may be coupled between the receiver (531) and the entropy decoder / parser (520) (hereinafter referred to as "parser (520)"). In some applications, the buffer memory (515) is part of the video decoder (510). In other cases, the buffer memory (515) may be provided external to the video decoder (510) (not shown). In other cases, a buffer memory (not shown) is provided external to the video decoder (510) to, for example, mitigate network jitter, and another buffer memory (515) may be provided internally to the video decoder (510) to, for example, handle broadcast timing. Furthermore, when the receiver (531) receives data from a store / forward device with sufficient bandwidth and controllability or from an isochronous network, the buffer memory (515) may not be required, or the buffer memory may be smaller. Of course, for use on a traffic packet network such as the Internet, the buffer memory (515) may also be required. The buffer memory may be relatively large and have an adaptive size, and may be at least partially implemented in an operating system or similar component (not shown) external to the video decoder (510).

[0074] The video decoder (510) may include a parser (520) for reconstructing symbols (521) from the encoded video sequence. The types of symbols include information for managing the operation of the video decoder (510) and potential information for controlling a display device such as a display device (512) (e.g., a display screen) that is not part of the electronic device (530) but can be coupled to the electronic device (530), such as Figure 5 As shown in . The control information for the display device may be a parameter set fragment (not shown) of Supplemental Enhancement Information (SEI message) or Video Usability Information (VUI). The parser (520) may parse / entropy decode the received coded video sequence. The coding of the coded video sequence may be performed according to a video coding technique or standard and may follow various principles, including variable length coding, Huffman coding, arithmetic coding with or without context sensitivity, and the like. The parser (520) may extract a subgroup parameter set for at least one subgroup of the subgroups of pixels in the video decoder from the coded video sequence based on at least one parameter corresponding to the group. The subgroup may include a Group of Pictures (GOP), a picture, a tile, a slice, a macroblock, a Coding Unit (CU), a block, a Transform Unit (TU), a Prediction Unit (PU), and the like. The parser (520) may also extract information from the encoded video sequence, such as transform coefficients, quantizer parameter values, motion vectors, and so on.

[0075] The parser (520) may perform entropy decoding / parsing operations on the video sequence received from the buffer memory (515), thereby creating symbols (521).

[0076] Depending on the type of coded video picture or portion of a coded video picture (e.g., inter-frame and intra-frame pictures, inter-frame blocks and intra-frame blocks) and other factors, the reconstruction of the symbol (521) may involve multiple different units. Which units are involved and how they are involved can be controlled by subgroup control information parsed from the coded video sequence by the parser (520). For the sake of brevity, the flow of such subgroup control information between the parser (520) and the multiple units below is not described.

[0077] In addition to the functional blocks already mentioned, the video decoder (510) can be conceptually broken down into several functional units as described below. In practical embodiments operating under commercial constraints, many of these units interact closely with each other and may be integrated with each other. However, for the purposes of describing the disclosed subject matter, the conceptual breakdown into the following functional units is appropriate.

[0078] The first unit is a scaler / inverse transform unit (551). The scaler / inverse transform unit (551) receives quantized transform coefficients as symbols (521) from the parser (520) along with control information, including which transform method to use, block size, quantization factor, quantization scaling matrix, etc. The scaler / inverse transform unit (551) may output a block comprising sample values, which may be input to an aggregator (555).

[0079] In some cases, the output samples of the scaler / inverse transform unit (551) may belong to an intra-coded block; that is, a block that does not use predictive information from a previously reconstructed picture, but may use predictive information from a previously reconstructed portion of the current picture. Such predictive information may be provided by the intra-picture prediction unit (552). In some cases, the intra-picture prediction unit (552) uses reconstructed information extracted from the current picture buffer (558) to generate surrounding blocks of the same size and shape as the block being reconstructed. For example, the current picture buffer (558) buffers partially reconstructed current pictures and / or fully reconstructed current pictures. In some cases, the aggregator (555) adds the prediction information generated by the intra-prediction unit (552) to the output sample information provided by the scaler / inverse transform unit (551) on a per-sample basis.

[0080] In other cases, the output samples of the scaler / inverse transform unit (551) may belong to inter-frame coded and potentially motion compensated blocks. In this case, the motion compensated prediction unit (553) may access the reference picture memory (557) to extract samples for prediction. After the extracted samples are motion compensated according to the symbols (521), these samples may be added to the output of the scaler / inverse transform unit (551) (in this case referred to as residual samples or residual signal) by the aggregator (555) to generate output sample information. The retrieval of the predicted samples by the motion compensated prediction unit (553) from the address in the reference picture memory (557) may be controlled by a motion vector, and the motion vector is provided to the motion compensated prediction unit (553) in the form of the symbol (521), which may include, for example, X, Y and reference picture components. Motion compensation may also include interpolation of sample values ​​extracted from the reference picture memory (557) when using sub-sample accurate motion vectors, motion vector prediction mechanisms, etc.

[0081] The output samples of the aggregator (555) may be used by various loop filtering techniques in a loop filter unit (556). The video compression techniques may include in-loop filtering techniques that are controlled by parameters included in the coded video sequence (also referred to as the coded video bitstream) and that are available to the loop filter unit (456) as symbols (521) from the parser (520). However, in other embodiments, the video compression techniques may also be responsive to meta-information obtained during decoding of a coded picture or a previous (in decoding order) portion of the coded video sequence, as well as to previously reconstructed and loop filtered sample values.

[0082] The output of the loop filter unit (556) may be a sample stream that may be output to a display device (512) and stored in a reference picture memory (557) for subsequent inter-picture prediction.

[0083] Once fully reconstructed, certain coded pictures can be used as reference pictures for future prediction. For example, once the coded picture corresponding to the current picture is fully reconstructed and the coded picture is identified as a reference picture (e.g., by the parser (520)), the current picture buffer (558) can become part of the reference picture memory (557) and a new current picture buffer can be reallocated before starting to reconstruct a subsequent coded picture.

[0084] The video decoder (510) may perform decoding operations according to a predetermined video compression technique, such as that in the ITU-T H.265 standard. A coded video sequence may conform to the syntax specified by the video compression technique or standard used, in the sense that the coded video sequence follows the syntax of the video compression technique or standard and a profile documented in the video compression technique or standard. Specifically, the profile may select certain tools from all the tools available in the video compression technique or standard as the only tools available for use under the profile. Compliance also requires that the complexity of the coded video sequence be within the limits defined by the hierarchy of the video compression technique or standard. In some cases, the hierarchy limits the maximum picture size, maximum frame rate, maximum reconstruction sampling rate (measured in, for example, megasamples per second), maximum reference picture size, etc. In some cases, the limits set by the hierarchy may be further defined by the Hypothetical Reference Decoder (HRD) specification and metadata about the HRD buffer management signaled in the coded video sequence.

[0085] In an embodiment, a receiver (531) may receive additional (redundant) data along with the encoded video. The additional data may be part of the encoded video sequence. The additional data may be used by the video decoder (510) to properly decode the data and / or more accurately reconstruct the original video data. The additional data may be in the form of, for example, temporal, spatial, or signal-to-noise ratio (SNR) enhancement layers, redundant slices, redundant pictures, forward error correction codes, and the like.

[0086] Figure 6 1 is a block diagram of a video encoder (603) according to an embodiment disclosed in the present application. The video encoder (603) is provided in an electronic device (620). The electronic device (620) includes a transmitter (640) (e.g., a transmission circuit). The video encoder (603) can be used to replace Figure 4 A video encoder (403) in an embodiment.

[0087] The video encoder (603) can be used to generate a video from a video source (601) (not Figure 6 In another embodiment, the video source (601) is a part of the electronic device (620) to receive video samples, and the video source can capture video images to be encoded by the video encoder (603). In another embodiment, the video source (601) is a part of the electronic device (620).

[0088] The video source (601) may provide a source video sequence in the form of a stream of digital video samples to be encoded by the video encoder (603), the digital video sample stream having 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 (601) may be a storage device storing previously prepared videos. In a video conferencing system, the video source (601) may be a camera that captures local image information as a video sequence. The video data may be provided as a plurality of individual pictures that are given motion when viewed sequentially. The pictures themselves may be constructed as a spatial array of pixels, where each pixel may include one or more samples depending on the sampling structure, color space, etc. used. The relationship between pixels and samples may be readily understood by those skilled in the art. The following description focuses on samples.

[0089] According to an embodiment, the video encoder (603) may encode and compress pictures of a source video sequence into an encoded video sequence (643) in real time or under any other time constraints required by the application. Implementing an appropriate encoding speed is a function of the controller (650). In some embodiments, the controller (650) controls other functional units as described below and is functionally coupled to these units. For the sake of simplicity, the coupling is not shown in the figure. The parameters set by the controller (650) may include rate control related parameters (picture skipping, quantizer, lambda value of rate-distortion optimization technology, etc.), picture size, group of pictures (GOP) layout, maximum motion vector search range, etc. The controller (650) can be used to have other suitable functions that are related to the video encoder (603) optimized for a certain system design.

[0090] In some embodiments, the video encoder (603) operates in a coding loop. As a simplified description, in some embodiments, the coding loop may include a source encoder (630) (e.g., responsible for creating symbols, such as a symbol stream, based on the input picture to be encoded and the reference pictures) and a (local) decoder (633) embedded in the video encoder (603). The decoder (633) reconstructs the symbols to create sample data in a manner similar to how the (remote) decoder creates sample data (because in the video compression techniques considered in this application, any compression between the symbols and the encoded video code stream is lossless). The reconstructed sample stream (sample data) is input to a reference picture memory (634). Since the decoding of the symbol stream produces bit-accurate results regardless of the decoder location (local or remote), the contents of the reference picture memory (634) are also bit-accurate between the local encoder and the remote encoder. In other words, the reference picture samples "seen" by the prediction portion of the encoder are exactly the same sample values ​​that the decoder will "see" when using the prediction during decoding. This basic principle of reference picture synchronization (and the resulting drift when synchronization cannot be maintained, eg due to channel errors) is also used in some related techniques.

[0091] The operation of the "local" decoder (633) can be combined with the operation of Figure 5 The "remote" decoder described in detail for the video decoder (510) is identical. However, additional brief reference is made to Figure 5 , when symbols are available and the entropy encoder (645) and parser (520) are capable of losslessly encoding / decoding the symbols into an encoded video sequence, the entropy decoding portion of the video decoder (510), including the buffer memory (515) and the parser (520), may not be fully implemented in the local decoder (633).

[0092] At this point, it can be observed that any decoder technology other than parsing / entropy decoding present in the decoder must also be present in a substantially identical functional form in the corresponding encoder. For this reason, this application focuses on the decoder operation. The description of the encoder technology can be simplified because the encoder technology is mutually inverse to the decoder technology described comprehensively. A more detailed description is only required in certain areas and is provided below.

[0093] During operation, in some embodiments, the source encoder (630) may perform motion-compensated predictive coding. This motion-compensated predictive coding predictively encodes an input picture with reference to one or more previously encoded pictures in the video sequence, designated as "reference pictures." In this manner, the encoding engine (632) encodes the differences between pixel blocks of the input picture and pixel blocks of a reference picture that may be selected as a prediction reference for the input picture.

[0094] The local video decoder (633) may decode the coded video data of a picture that may be designated as a reference picture based on the symbols created by the source encoder (630). The operation of the encoding engine (632) may be a lossy process. When the coded video data is available at the video decoder ( Figure 6 When decoded at a remote location (not shown), the reconstructed video sequence may typically be a copy of the source video sequence with some errors. The local video decoder (633) replicates the decoding process that the video decoder may perform on the reference picture and may cause the reconstructed reference picture to be stored in the reference picture cache (634). In this way, the video encoder (603) may locally store a copy of the reconstructed reference picture that has common content (absent transmission errors) with the reconstructed reference picture that will be obtained by the remote video decoder.

[0095] The predictor (635) may perform a prediction search for the encoding engine (632). That is, for a new picture to be encoded, the predictor (635) may search the reference picture memory (634) for sample data (as candidate reference pixel blocks) or certain metadata, such as reference picture motion vectors, block shapes, etc., that may serve as suitable prediction references for the new picture. The predictor (635) may operate on a pixel-by-pixel-block basis based on sample blocks to find a suitable prediction reference. In some cases, based on the search results obtained by the predictor (635), it may be determined that the input picture may have prediction references taken from multiple reference pictures stored in the reference picture memory (634).

[0096] The controller (650) can manage encoding operations of the source encoder (630), including, for example, setting parameters and subgroup parameters for encoding video data.

[0097] The outputs of all the above functional units may be entropy coded in an entropy encoder (645). The entropy encoder (645) losslessly compresses the symbols generated by the various functional units using techniques such as Huffman coding, variable length coding, arithmetic coding, etc., thereby converting the symbols into a coded video sequence.

[0098] The transmitter (640) can buffer the encoded video sequence created by the entropy encoder (645) in preparation for transmission over a communication channel (660), which can be a hardware / software link to a storage device where the encoded video data will be stored. The transmitter (640) can combine the encoded video data from the video encoder (603) with other data to be transmitted, such as encoded audio data and / or an auxiliary data stream (source not shown).

[0099] The controller (650) can manage the operation of the video encoder (603). During encoding, the controller (650) can assign a certain coded picture type to each coded picture, but this may affect the coding techniques that can be applied to the corresponding picture. For example, a picture can generally be assigned to any of the following picture types:

[0100] An intra picture (I picture) can be a picture that can be encoded and decoded without using any other picture in the sequence as a prediction source. Some video codecs allow different types of intra pictures, including, for example, Independent Decoder Refresh (IDR) pictures. Those skilled in the art are aware of the variations of I pictures and their corresponding applications and features.

[0101] A predictive picture (P picture) may be a picture that can be encoded and decoded using intra prediction or inter prediction, which uses at most one motion vector and a reference index to predict sample values ​​for each block.

[0102] Bidirectionally predictive pictures (B pictures) can be encoded and decoded using intra prediction or inter prediction, which uses up to two motion vectors and reference indices to predict the sample values ​​of each block. Similarly, multiple predictive pictures can use more than two reference pictures and associated metadata to reconstruct a single block.

[0103] A source picture is typically spatially subdivided into blocks of samples (e.g., blocks of 4×4, 8×8, 4×8, or 16×16 samples) and coded block by block. These blocks can be predictively coded with reference to other (already coded) blocks, determined according to the coding allocation applied to the block's corresponding picture. For example, a block of an I picture can be non-predictively coded, or the block can be predictively coded (spatial prediction or intra prediction) with reference to already coded blocks of the same picture. Pixel blocks of a P picture can be predictively coded using spatial prediction or temporal prediction with reference to a previously coded reference picture. Blocks of a B picture can be predictively coded using spatial prediction or temporal prediction with reference to one or two previously coded reference pictures.

[0104] The video encoder (603) may perform encoding operations according to a predetermined video coding technique or standard, such as ITU-T Recommendation H.265. In operation, the video encoder (603) may perform various compression operations, including predictive coding operations that exploit temporal and spatial redundancy in the input video sequence. Thus, the encoded video data may conform to the syntax specified by the video coding technique or standard used.

[0105] In an embodiment, the transmitter (640) may transmit additional data along with the encoded video. The source encoder (630) may include such data as part of the encoded video sequence. The additional data may include temporal / spatial / SNR enhancement layers, redundant pictures and slices, and other forms of redundant data, SEI messages, VUI parameter set fragments, and the like.

[0106] The captured video may be presented as a temporal sequence of multiple source pictures (video pictures). Intra-picture prediction (often shortened to intra prediction) exploits spatial correlation within a given picture, while inter-picture prediction exploits correlation (temporal or otherwise) between pictures. In an embodiment, a particular picture being encoded / decoded is divided into blocks, and the particular picture being encoded / decoded is referred to as the current picture. When a block in the current picture is similar to a reference block in a previously encoded and buffered reference picture in the video, the block in the current picture can be encoded using a vector called a motion vector. The motion vector points to the reference block in the reference picture, and when multiple reference pictures are used, the motion vector may have a third dimension that identifies the reference picture.

[0107] In some embodiments, bidirectional prediction techniques can be used for inter-picture prediction. According to bidirectional prediction techniques, two reference pictures are used, for example, a first reference picture and a second reference picture, both preceding the current picture in decoding order (but potentially in the past and future, respectively, in display order). A block in the current picture can be encoded using a first motion vector pointing to a first reference block in the first reference picture and a second motion vector pointing to a second reference block in the second reference picture. Specifically, the block can be predicted using a combination of the first and second reference blocks.

[0108] In addition, merge mode technology can be used in inter-picture prediction to improve coding efficiency.

[0109] According to some embodiments disclosed in the present application, predictions such as inter-picture prediction and intra-picture prediction are performed in units of blocks. For example, according to the HEVC standard, a picture in a video picture sequence is divided into coding tree units (CTUs) for compression, and the CTUs in the picture have the same size, such as 64×64 pixels, 32×32 pixels, or 16×16 pixels. Generally speaking, a CTU includes three coding tree blocks (CTBs), which are a luminance CTB and two chrominance CTBs. Furthermore, each CTU can be split into one or more coding units (CUs) using a quadtree. For example, a 64×64 pixel CTU can be split into a 64×64 pixel CU, or four 32×32 pixel CUs, or sixteen 16×16 pixel CUs. In an embodiment, each CU is analyzed to determine the prediction type used for the CU, such as an inter prediction type or an intra prediction type. In addition, depending on temporal and / or spatial predictability, the CU is split into one or more prediction units (PUs). Typically, each PU includes a luma prediction block (PB) and two chroma PBs. In an embodiment, the prediction operation in encoding (encoding / decoding) is performed in units of prediction blocks. Taking the luma prediction block as an example, the prediction block includes a matrix of pixel values ​​(e.g., luma values), such as 8×8 pixels, 16×16 pixels, 8×16 pixels, 16×8 pixels, and the like.

[0110] Figure 7 FIG2 is a diagram of a video encoder (703) according to another embodiment disclosed herein. The video encoder (703) is configured to receive a processed block (e.g., a prediction block) of sample values ​​within a current video picture in a sequence of video pictures and to encode the processed block into an encoded picture that is part of an encoded video sequence. In this embodiment, the video encoder (703) is configured to replace Figure 4A video encoder (403) in an embodiment.

[0111] In an HEVC embodiment, a video encoder (703) receives a matrix of sample values ​​for a processing block, such as a prediction block of 8×8 samples. The video encoder (703) uses, for example, rate-distortion (RD) optimization to determine whether to use intra mode, inter mode, or bi-prediction mode to encode the processing block. When encoding the processing block in intra mode, the video encoder (703) may use intra prediction techniques to encode the processing block into an encoded picture; and when encoding the processing block in inter mode or bi-prediction mode, the video encoder (703) may use inter prediction or bi-prediction techniques, respectively, to encode the processing block into an encoded picture. In some video coding techniques, merge mode may be an inter-picture prediction submode, in which motion vectors are derived from one or more motion vector predictors without resorting to coded motion vector components external to the predictor. In some other video coding techniques, there may be motion vector components applicable to the subject block. In an embodiment, the video encoder (703) includes other components, such as a mode decision module (not shown) for determining the processing block mode.

[0112] exist Figure 7 In an embodiment of the present invention, the video encoder (703) includes Figure 7 Shown are an inter-frame encoder (730), an intra-frame encoder (722), a residual calculator (723), a switch (726), a residual encoder (724), a general controller (721), and an entropy encoder (725) coupled together.

[0113] The inter-frame encoder (730) is configured to receive samples of a current block (e.g., a processing block), compare the current block with one or more reference blocks in a reference picture (e.g., blocks in a previous picture and a subsequent picture), generate inter-frame prediction information (e.g., redundant information description according to an inter-frame coding technique, motion vectors, merge mode information), and calculate an inter-frame prediction result (e.g., a predicted block) based on the inter-frame prediction information using any suitable technique. In some embodiments, the reference picture is a decoded reference picture decoded based on the encoded video information.

[0114] The intra-frame encoder (722) is configured to receive samples of a current block (e.g., a processing block), compare the block with previously encoded blocks in the same picture in some cases, generate quantized coefficients after transformation, and in some cases also generate intra-frame prediction information (e.g., intra-frame prediction direction information based on one or more intra-frame coding techniques). In an embodiment, the intra-frame encoder (722) further calculates an intra-frame prediction result (e.g., a predicted block) based on the intra-frame prediction information and a reference block in the same picture.

[0115] The general controller (721) is used to determine general control data and control other components of the video encoder (703) based on the general control data. In an embodiment, the general controller (721) determines the mode of the block and provides a control signal to the switch (726) based on the mode. For example, when the mode is intra mode, the general controller (721) controls the switch (726) to select the intra mode result for use by the residual calculator (723) and controls the entropy encoder (725) to select intra prediction information and add the intra prediction information to the bitstream; and when the mode is inter mode, the general controller (721) controls the switch (726) to select the inter prediction result for use by the residual calculator (723) and controls the entropy encoder (725) to select inter prediction information and add the inter prediction information to the bitstream.

[0116] The residual calculator (723) is used to calculate the difference (residual data) between the received block and the prediction result selected from the intra-frame encoder (722) or the inter-frame encoder (730). The residual encoder (724) is used to operate based on the residual data to encode the residual data to generate transform coefficients. In an embodiment, the residual encoder (724) is used to convert the residual data from the time domain to the frequency domain and generate transform coefficients. The transform coefficients are then quantized to obtain quantized transform coefficients. In various embodiments, the video encoder (703) also includes a residual decoder (728). The residual decoder (728) is used to perform an inverse transform and generate decoded residual data. The decoded residual data can be used appropriately by the intra-frame encoder (722) and the inter-frame encoder (730). For example, the inter-frame encoder (730) can generate a decoded block based on the decoded residual data and inter-frame prediction information, and the intra-frame encoder (722) can generate a decoded block based on the decoded residual data and intra-frame prediction information. The decoded blocks are appropriately processed to generate a decoded picture, and in some embodiments, the decoded picture may be buffered in memory circuitry (not shown) and used as a reference picture.

[0117] The entropy encoder (725) is used to format the codestream to produce encoded blocks. The entropy encoder (725) generates various information according to a suitable standard, such as the HEVC standard. In an embodiment, the entropy encoder (725) is used to obtain general control data, selected prediction information (e.g., intra-frame prediction information or inter-frame prediction information), residual information, and other suitable information from the codestream. It should be noted that according to the disclosed subject matter, when encoding a block in inter-frame mode or the merge sub-mode of bidirectional prediction mode, there is no residual information.

[0118] Figure 8FIG is a diagram of a video decoder (810) according to another embodiment disclosed herein. The video decoder (810) is configured to receive an encoded image as part of an encoded video sequence and decode the encoded image to generate a reconstructed picture. In an embodiment, the video decoder (810) is configured to replace Figure 4 A video decoder (410) of an embodiment.

[0119] exist Figure 8 In one embodiment, the video decoder (810) includes Figure 8 , an entropy decoder (871), an inter-frame decoder (880), a residual decoder (873), a reconstruction module (874), and an intra-frame decoder (872) coupled together are shown.

[0120] The entropy decoder (871) may be used to reconstruct certain symbols representing syntax elements constituting the coded picture from the coded picture. Such symbols may include, for example, the mode used to encode the block (e.g., intra mode, inter mode, bi-prediction mode, a combined sub-mode of the latter two, or another sub-mode), prediction information (e.g., intra prediction information or inter prediction information) that may identify certain samples or metadata for prediction by the intra decoder (872) or the inter decoder (880), respectively, residual information in the form of, for example, quantized transform coefficients, and the like. In an embodiment, when the prediction mode is inter or bi-prediction mode, the inter prediction information is provided to the inter decoder (880); and when the prediction type is intra prediction type, the intra prediction information is provided to the intra decoder (872). The residual information may be inverse quantized and provided to the residual decoder (873).

[0121] The inter-frame decoder (880) is used to receive inter-frame prediction information and generate an inter-frame prediction result based on the inter-frame prediction information.

[0122] The intra-frame decoder (872) is configured to receive intra-frame prediction information and generate a prediction result based on the intra-frame prediction information.

[0123] The residual decoder (873) is used to perform inverse quantization to extract dequantized transform coefficients and process the dequantized transform coefficients to convert the residual from the frequency domain to the spatial domain. The residual decoder (873) may also require certain control information (to obtain the quantizer parameter QP), and this information can be provided by the entropy decoder (871) (the data path is not shown because this is only low-level control information).

[0124] The reconstruction module (874) is used to combine the residual output by the residual decoder (873) with the prediction result (which may be output by the inter-frame prediction module or the intra-frame prediction module) in the spatial domain to form a reconstructed block. The reconstructed block can be part of a reconstructed picture, which in turn can be part of a reconstructed video. It should be noted that other suitable operations such as deblocking operations can be performed to improve visual quality.

[0125] It should be noted that the video encoder (403), video encoder (603), and video encoder (703), as well as the video decoder (410), video decoder (510), and video decoder (810) may be implemented using any suitable technology. In one embodiment, the video encoder (403), video encoder (603), and video encoder (703), as well as the video decoder (410), video decoder (510), and video decoder (810) may be implemented using one or more integrated circuits. In another embodiment, the video encoder (403), video encoder (603), and video encoder (703), as well as the video decoder (410), video decoder (510), and video decoder (810) may be implemented using one or more processors executing software instructions.

[0126] Aspects of the present disclosure provide filtering techniques for video encoding / decoding. Specifically, the filtering techniques are applied to a loop filter unit, such as a loop filter unit (556) in a prediction loop. For example, an image filtered by the loop filter unit (556) is stored in a buffer (e.g., a reference picture memory (557)) as a reference for further prediction. The loop filter unit can apply various loop filters to filter samples. In some examples, a loop filter configuration for the loop filter unit refers to the loop filter applied by the loop filter unit.

[0127] An adaptive loop filter (ALF) with block-based filter adaptation can be applied by the encoder / decoder to reduce artifacts. For the luma component, for example, one of multiple filters (e.g., 25 filters) can be selected for a 4×4 luma block based on the direction and activity of the local gradient.

[0128] The ALF can have any suitable shape and size. Figure 9, ALF (910)-(911) has a diamond shape, for example, ALF (910) has a 5×5 diamond shape, and ALF (911) has a 7×7 diamond shape. In ALF (910), elements (920)-(932) form a diamond shape and can be used in the filtering process. Seven values ​​(e.g., C0-C6) can be used for elements (920)-(932). In ALF (911), elements (940)-(964) form a diamond shape and can be used in the filtering process. 13 values ​​(e.g., C0-C12) can be used for elements (940)-(964).

[0129] refer to Figure 9 In some examples, two ALFs (910)-(911) having diamond filter shapes are used. A 5×5 diamond filter (910) may be applied to chroma components (e.g., chroma blocks, chroma CBs), and a 7×7 diamond filter (911) may be applied to luma components (e.g., luma blocks, luma CBs). Other suitable shapes and sizes may be used in the ALFs. For example, a 9×9 diamond filter may be used.

[0130] The filter coefficients at the positions indicated by the values ​​(e.g., C0-C6 in (910) or C0-C12 in (920)) may be non-zero. In addition, when the ALF includes a clipping function, the clipping values ​​at these positions may be non-zero.

[0131] For block classification of luma components, a 4×4 block (or luma block, luma CB) may be classified or categorized into one of a plurality of (e.g., 25) categories. The quantized values ​​of the direction parameter D and the activity value A may be used. The classification index C is derived using equation (1).

[0132]

[0133] In order to calculate the direction parameter D and the quantization value The gradient g in the vertical direction, horizontal direction, and two diagonal directions (e.g., d1 and d2) can be calculated using 1-D Laplacian v , g h , g d1 and g d2 ,as follows.

[0134]

[0135]

[0136]

[0137]

[0138] Where indices i and j refer to the coordinates of the top left sample within the 4×4 block, and R(k, l) indicates the reconstructed sample at coordinate (k, l). Directions (eg, d1 and d2) may refer to two diagonal directions.

[0139] In order to reduce the complexity of the above block classification, a subsampled 1-D Laplacian calculation may be applied. 10A to 10D The calculation methods for the vertical direction ( Figure 10A ), horizontal direction( Figure 10B ) and two diagonal directions d1( Figure 10C ) and d2( Figure 10D )’s gradient g v , g h , g d1 and g d2 The same subsampling position can be used for gradient calculation in different directions. Figure 10A The label 'V' shows the calculation of the vertical gradient g v The subsampling position of Figure 10B In the figure, the label 'H' shows the calculation of the horizontal gradient g h The subsampling position of Figure 10C In the figure, label 'd1' shows the calculation of the diagonal gradient g of d1. d1 The subsampling position of Figure 10D In the figure, label 'd2' shows the calculation of the diagonal gradient g of d2. d2 The subsampling position.

[0140] Horizontal gradient g h and the vertical gradient g v The maximum value and minimum value Can be set to:

[0141]

[0142] The gradient g in two diagonal directions d1 and g d2 The maximum value and minimum value Can be set to:

[0143]

[0144] The direction parameter D can be derived based on the above value and two thresholds t1 and t2 as follows.

[0145] Step 1: If (1) and (2) is true, D is set to 0.

[0146] Step 2: If Then proceed to step 3, otherwise proceed to step 4.

[0147] Step 3: If Then D is set to 2, otherwise D is set to 1.

[0148] Step 4: If Then D is set to 4, otherwise D is set to 3.

[0149] The activity value A can be calculated as:

[0150]

[0151] A can be further quantized to a range of 0 to 4 (inclusive), and the quantized value is expressed as

[0152] Block classification is not applied to the chroma components in a picture, so a single set of ALF coefficients may be applied to each chroma component.

[0153] The geometric transformation may be applied to the filter coefficients and the corresponding filter clipping values ​​(also referred to as clipping values). Before filtering a block (e.g., a 4x4 luma block), for example, based on the gradient values ​​(e.g., g v , g h , g d1 and / or g d2 ), geometric transformations such as rotation or diagonal and vertical flipping can be applied to the filter coefficients f(k, l) and the corresponding filter clipping values ​​c(k, l). The geometric transformation applied to the filter coefficients f(k, l) and the corresponding filter clipping values ​​c(k, l) can be equivalent to applying the geometric transformation to samples in the area supported by the filter. The geometric transformation can make different blocks more similar by aligning corresponding directions. ALF is applied to different blocks.

[0154] Three geometric transformations including diagonal flipping, vertical flipping, and rotation may be performed as described by equations (9)-(11), respectively.

[0155] f D (k,l)=f(l,k),c D (k, l) = c(l, k) Equation (9)

[0156] f V (k,l)=f(k,Kl-1),c V (k, l) = c(k, Kl-1) Equation (10)

[0157] f R (k,l)=f(Kl-1,k),c R (k, l) = c(Kl-1, k) Equation (11)

[0158] Where K is the size of the ALF or filter, and 0 ≤ k, l ≤ K-1 are the coordinates of the coefficients. For example, position (0, 0) is located in the upper left corner, and position (K-1, K-1) is located in the lower right corner of the filter f or the clipping value matrix (or clipping matrix) c. Based on the gradient values ​​calculated for the block, a transform can be applied to the filter coefficients f(k, l) and the clipping values ​​c(k, l). An example of the relationship between the transform and the four gradients is summarized in Table 1.

[0159] Table 1: Mapping of gradients computed for a block to transformations

[0160]

[0161]

[0162] In some embodiments, the ALF filter parameters are signaled in an adaptive parameter set (APS) for a picture. In the APS, one or more sets of luma filter coefficients and clipping value indices (e.g., up to 25 sets) may be signaled. In one example, a set in one or more sets may include luma filter coefficients and one or more clipping value indices. One or more sets of chroma filter coefficients and clipping value indices (e.g., up to 8 sets) may be signaled. To reduce signaling overhead, filter coefficients for different classifications (e.g., with different classification indices) for luma components may be merged. In the slice header, the index of the APS for the current slice may be signaled.

[0163] In one embodiment, a clipping value index (also referred to as a clipping index) may be decoded from the APS. The clipping value index may be used to determine the corresponding clipping value, for example, based on the relationship between the clipping value index and the corresponding clipping value. The relationship may be predefined and stored in the decoder. In one example, the relationship is described by a table such as a luminance table of the clipping value index and the corresponding clipping value (e.g., for a luminance CB), a chrominance table of the clipping value index and the corresponding clipping value (e.g., for a chrominance CB). The clipping value may depend on the bit depth B. The bit depth B may refer to an internal bit depth, a bit depth of reconstructed samples in the CB to be filtered, etc. In some examples, the table (e.g., luminance table, chrominance table) is obtained using equation (12).

[0164]

[0165] Where AlfClip is the clip value, B is the bit depth (e.g., bitDepth), N (e.g., N=4) is the number of allowed clip values, and (n-1) is the clip value index (also called clip index or clipIdx). Table 2 shows an example of a table obtained using equation (12) when N=4. In Table 2, the clip index (n-1) can be 0, 1, 2, and 3, and n can be 1, 2, 3, and 4. Table 2 can be used for luminance blocks or chrominance blocks.

[0166] Table 2 - AlfClip may depend on bit depth B and clipIdx

[0167]

[0168]

[0169] In the slice header of the current slice, one or more APS indices (e.g., up to 7 APS indices) may be signaled to specify the luma filter set that may be used for the current slice. The filtering process may be controlled at one or more appropriate levels (e.g., picture level, slice level, CTB level, etc.). In one embodiment, the filtering process may be further controlled at the CTB level. A flag may be signaled to indicate whether the ALF is applied to the luma CTB. The luma CTB may select a filter set from among multiple fixed filter sets (e.g., 16 fixed filter sets) and filter sets signaled in the APS (also referred to as signaled filter sets). A filter set index may be signaled to the luma CTB to indicate the filter set to be applied (e.g., from among multiple fixed filter sets and signaled filter sets). Multiple fixed filter sets may be predefined and hard-coded in the encoder and decoder and may be referred to as predefined filter sets.

[0170] For chroma components, the APS index can be signaled in the slice header to indicate the chroma filter set to be used for the current slice. At the CTB level, if there is more than one chroma filter set in the APS, the filter set index can be signaled to each chroma CTB.

[0171] The filter coefficients can be quantized using a norm equal to 128. To reduce multiplication complexity, codestream conformity can be applied so that the values ​​of coefficients in non-center positions can be in the range of -27 to 27-1 (inclusive). In one example, the center position coefficient is not signaled in the codestream and can be assumed to be equal to 128.

[0172] In some embodiments, the syntax and semantics of the slice index and slice value are defined as follows:

[0173] alf_luma_clip_idx[sfIdx][j] may be used to specify the clip index of the clip value to be used before multiplying the j-th coefficient of the luma filter signaled by sfIdx. Codestream compliance requirements may include: when sfIdx = 0 to alf_luma_num_filter_signal_minus 1 and j = 0 to 11, the value of alf_luma_clip_idx[sfIdx][j] shall be in the range of 0 to 3 (inclusive).

[0174] From bitDepth set equal to BitDepthY and clipIdx set equal to alf_luma_clip_idx[alf_luma_coeff_delta_idx[filtIdx]][j], the luma filter clipping value AlfClipL[adaption_parameter_set_id] with the elements AlfClipL[adaption_parameter_set_id][filtIdx][j] may be derived as specified in Table 2, where filtIdx = 0 to NumAlfFilters-1 and j = 0 to 11. alf_chroma_clip_idx[altIdx][j] may be used to specify the clipping index of the clipping value to be used prior to multiplication by the j-th coefficient of the alternative chroma filter with index altIdx. The codestream compliance requirement may include: when altIdx=0 to alf_chroma_num_alt_filters_minus 1 and j=0 to 5, the value of alf_chroma_clip_idx[altIdx][j] should be in the range of 0 to 3 (inclusive).

[0175] With bitDepth set equal to BitDepthC and clipIdx set equal to alf_chroma_clip_idx[altIdx]][j], the chroma filter clipping value AlfClipC[adaption_parameter_set_id][altIdx][j] may be derived as specified in Table 2, with alfIdx = 0 to alf_chroma_num_alt_filters_minus 1 and j = 0 to 5.

[0176] In one embodiment, the filtering process may be as follows. At the decoder side, when ALF is enabled for a CTB, the sample R(i, j) within the CU (or CB) may be filtered, thereby generating the filtered sample value R'(i, j) as shown below using equation (13). In one example, filtering is performed on each sample in the CU.

[0177]

[0178] Where f(k, l) indicates the decoded filter coefficients, K(x, y) is the clipping function, and c(k, l) indicates the decoded clipping parameter (or clipping value). The variables k and l can vary between -L / 2 and L / 2, where L indicates the filter length. The clipping function K(x, y) = min(y, max(-y, x)), which corresponds to the clipping function Clip3(-y, y, x). By including the clipping function K(x, y), the loop filtering method (e.g., ALF) becomes a nonlinear process and can be referred to as a nonlinear ALF.

[0179] In a nonlinear ALF, multiple clipping value sets can be provided as shown in Table 3. In one example, the luma set includes four clipping values ​​{1024, 181, 32, 6}, and the chroma set includes four clipping values ​​{1024, 161, 25, 4}. The four clipping values ​​in the luma set can be selected by splitting the full range of sample values ​​(e.g., 1024) of the luma block (encoded in 10 bits) approximately equally in the logarithmic domain. For the chroma set, the range can be from 4 to 1024.

[0180] Table 3 - Examples of limit values

[0181] Intra / Inter tile groups brightness {1024，181，32，6} Chroma {1024，161，25，4}

[0182] The selected clipping value may be encoded in the "alf_data" syntax element as follows: a suitable coding scheme (e.g., a Golomb coding scheme) may be used to encode the clipping index corresponding to the selected clipping value as shown in Table 3. The coding scheme may be the same coding scheme used to encode the filter set index.

[0183] In one embodiment, a virtual boundary filtering process may be used to reduce the line buffer requirements of the ALF. Thus, a modified block classification and filtering may be employed for samples close to a CTU boundary (e.g., a horizontal CTU boundary). Figure 11A As shown, the virtual boundary (1130) can be achieved by moving the horizontal CTU boundary (1120) by “N samples (N 样本 )” samples to define a line, where N samples Can be a positive integer. In one example, for the luminance component, N samplesis equal to 4, and for the chrominance component, N samples Equal to 2.

[0184] refer to Figure 11A , a modified block classification may be applied to the luma component. In one example, for the 1D Laplacian gradient calculation of the 4×4 block (1110) above the virtual boundary (1130), only samples above the virtual boundary (1130) are used. Similarly, referring to Figure 11B , for the 1D Laplacian gradient calculation of the 4×4 block (1111) below the virtual boundary (1131) shifted from the CTU boundary (1121), only the samples below the virtual boundary (1131) are used. Therefore, the quantization of the activity value A can be changed by considering reducing the number of samples used in the 1D Laplacian gradient calculation.

[0185] For the filtering process, symmetric padding operations at virtual boundaries can be used for luma and chroma components. 12A to 12F An example of this modified ALF filtering for the luma component at a virtual boundary is shown. When a filtered sample is below a virtual boundary, the adjacent samples above the virtual boundary may be padded. When a filtered sample is above a virtual boundary, the adjacent samples below the virtual boundary may be padded. Figure 12A , the adjacent sample C0 can be filled using the sample C2 located below the virtual boundary (1210). Figure 12B , the adjacent sample C0 can be filled with the sample C2 located above the virtual boundary (1220). Figure 12C , the adjacent samples C1-C3 can be filled with samples C5-C7 located below the virtual boundary (1230), respectively. Figure 12D , the adjacent samples C1-C3 can be filled with samples C5-C7 located above the virtual boundary (1240), respectively. Figure 12E , adjacent samples C4-C8 can be filled using samples C10, C11, C12, C11 and C10 located below the virtual boundary (1250), respectively. Figure 12F , adjacent samples C4-C8 may be filled using samples C10, C11, C12, C11, and C10 located above the virtual boundary (1260), respectively.

[0186] In some examples, when a sample and an adjacent sample are located to the left (or right) and to the right (or left) of a virtual boundary, the above description may be appropriately adjusted.

[0187] According to one aspect of the present disclosure, in order to improve coding efficiency, the picture can be segmented based on the filtering process. In some examples, the CTU is also referred to as the largest coding unit (LCU). In one example, the CTU or LCU may have a size of 64×64 pixels. In some embodiments, LCU-aligned picture quadtree splitting can be used for filtering-based segmentation. In some examples, an adaptive loop filter based on a coding unit synchronized picture quadtree can be used. For example, a luma picture can be split into several multi-level quadtree segmentations, and each segmentation boundary is aligned with the boundary of the LCU. Each segmentation has its own filtering process and is therefore called a filter unit (FU).

[0188] In some examples, a two-pass coded stream may be used. In the first pass of the two-pass coded stream, the quadtree splitting mode of the picture and the optimal filter for each FU may be determined. In some embodiments, the determination of the quadtree splitting mode of the picture and the determination of the optimal filter for the FU are based on filter distortion. During the determination process, filter distortion may be estimated using a fast filter distortion estimation (FFDE) technique. The picture is segmented using quadtree segmentation. Based on the determined quadtree splitting mode and the selected filters for all FUs, the reconstructed picture may be filtered.

[0189] At the second pass of the 2-pass coded stream, CU synchronous ALF on / off control is performed. According to the ALF on / off result, the first filtered picture is partially restored by the reconstructed picture.

[0190] Specifically, in some examples, a top-down splitting strategy is used to divide the picture into multiple levels of quadtree partitions using a rate-distortion criterion. Each partition is called a filter unit (FU). The splitting process aligns the quadtree partitions with LCU boundaries. The encoding order of the FUs follows the z-scan order.

[0191] Figure 13 An example of segmentation according to some embodiments of the present disclosure is shown. Figure 13 In the example of , the picture (1300) is split into 10 FUs, and the encoding order is FU0, FU1, FU2, FU3, FU4, FU5, FU6, FU7, FU8 and FU9.

[0192] Figure 14 A quadtree splitting pattern (1400) for a picture (1300) is shown. Figure 14 In the example of , the split flag is used to indicate the picture splitting mode. For example, "1" indicates that quadtree splitting is performed on the block; "0" indicates that the block is not further split. In some examples, the minimum size FU has the size of LCU, and the minimum size FU does not need a split flag. Figure 14 As shown, the split flags are encoded and transmitted in z-order.

[0193] In some examples, the filters for each FU are selected from two filter sets based on rate-distortion criteria. The first set has 1 / 2 symmetrical square filters and diamond filters derived for the current FU. The second set comes from a time-delayed filter buffer; the time-delayed filter buffer stores filters previously derived for the FU of the previous picture. The filter with the minimum rate-distortion cost of the two sets can be selected for the current FU. Similarly, if the current FU is not the minimum FU and can be further split into 4 sub-FUs, the rate-distortion cost of the 4 sub-FUs is calculated. By recursively comparing the rate-distortion costs of the split and non-split cases, the picture quadtree splitting mode can be determined.

[0194] In some examples, the maximum number of FUs can be limited using the maximum quadtree split level. In one example, when the maximum quadtree split level is 2, the maximum number of FUs is 16. Furthermore, during the quadtree split determination, the correlation values ​​used to derive the Wiener coefficients for the 16 FUs at the bottom quadtree level (the smallest FUs) can be reused. The remaining FUs can derive their Wiener filters based on the correlations of the 16 FUs at the bottom quadtree level. Therefore, in this example, only one frame buffer access is performed to derive the filter coefficients for all FUs.

[0195] After determining the quadtree splitting mode, CU-synchronized ALF on / off control can be performed to further reduce filtering distortion. By comparing the filtered and unfiltered distortion at each leaf CU, the leaf CU can explicitly turn the ALF on / off in its local region. In some examples, coding efficiency can be further improved by redesigning the filter coefficients based on the ALF on / off results.

[0196] The cross-component filtering process may apply a cross-component filter, such as a cross-component adaptive loop filter (CC-ALF). The cross-component filter may use the luma sample value of the luma component (e.g., luma CB) to refine the chroma component (e.g., the chroma CB corresponding to the luma CB). In one example, the luma CB and the chroma CB are included in a CU.

[0197] Figure 15 FIG. 1 shows a cross-component filter (e.g., CC-ALF) for generating chroma components according to one embodiment of the present disclosure. In some examples, Figure 15The filtering process for a first chroma component (e.g., a first chroma CB), a second chroma component (e.g., a second chroma CB), and a luma component (e.g., a luma CB) is shown. The luma component may be filtered by a sample adaptive offset (SAO) filter (1510) to generate an SAO-filtered luma component (1541). The SAO-filtered luma component (1541) may be further filtered by an ALF luma filter (1516) to become a filtered luma CB (1561) (e.g., 'Y').

[0198] The first chroma component may be filtered by an SAO filter (1512) and an ALF chroma filter (1518) to generate a first intermediate component (1552). In addition, the SAO filtered luma component (1541) may be filtered by a cross-component filter (e.g., CC-ALF) (1521) for the first chroma component to generate a second intermediate component (1542). Subsequently, a filtered first chroma component (1562) (e.g., 'Cb') may be generated based on at least one of the first intermediate component 1552 and the second intermediate component 1542. In one example, the filtered first chroma component (1562) (e.g., 'Cb') may be generated by combining the first intermediate component (1552) and the second intermediate component (1542) with an adder (1522). The cross-component adaptive loop filtering process for the first chroma component may include steps performed by the CC-ALF (1521) and steps performed by, for example, the adder (1522).

[0199] The above description may be applied to the second chroma component. The second chroma component may be filtered by the SAO filter (1514) and the ALF chroma filter (1518) to generate a third intermediate component (1553). In addition, the SAO filtered luma component (1541) may be filtered by a cross-component filter (e.g., CC-ALF) (1531) for the second chroma component to generate a fourth intermediate component (1543). Subsequently, a filtered second chroma component (1563) (e.g., 'Cr') may be generated based on at least one of the third intermediate component (1553) and the fourth intermediate component (1543). In one example, the filtered second chroma component (1563) (e.g., 'Cr') may be generated by combining the third intermediate component (1553) and the fourth intermediate component (1543) with an adder (1532). In one example, the cross-component adaptive loop filtering process of the second chroma component may include steps performed by a CC-ALF (1531) and steps performed by, for example, an adder (1532).

[0200] The cross-component filters (e.g., CC-ALF (1521), CC-ALF (1531)) may operate by applying a linear filter having any suitable filter shape to the luma component (or luma channel) to refine each chroma component (e.g., a first chroma component, a second chroma component).

[0201] Figure 16 An example of a filter (1600) according to one embodiment of the present disclosure is shown. The filter (1600) may include non-zero filter coefficients and zero filter coefficients. The filter (1600) has a diamond shape (1620) (indicated by a circle with a black fill) formed by the filter coefficients (1610). In one example, the non-zero filter coefficients in the filter (1600) are included in the filter coefficients (1610), and the filter coefficients not included in the filter coefficients (1610) are zero. Therefore, the non-zero filter coefficients in the filter (1600) are included in the diamond shape (1620), and the filter coefficients not included in the diamond shape (1620) are zero. In one example, the number of filter coefficients of the filter (1600) is equal to the number of filter coefficients (1610), Figure 16 In the example shown, the number of filter coefficients is 18.

[0202] CC-ALF may include any suitable filter coefficients (also referred to as CC-ALF filter coefficients). Figure 15 , CC-ALF (1521) and CC-ALF (1531) may have the same filter shape, e.g. Figure 16 The diamond shape (1620) shown, and CC-ALF (1521) and CC-ALF (1531) may have the same number of filter coefficients. In one example, the values ​​of the filter coefficients in CC-ALF (1521) are different from the values ​​of the filter coefficients in CC-ALF (1531).

[0203] Typically, filter coefficients (e.g., non-zero filter coefficients) in CC-ALF can be transmitted in APS, for example. In one example, the filter coefficients can be multiplied by a factor (e.g., 2 10 ) scaling and may be rounded for a fixed point representation. The application of CC-ALF may be controlled with variable block sizes and signaled via a context coding flag (e.g., a CC-ALF enable flag) received for each block of samples. The context coding flag (e.g., a CC-ALF enable flag) may be signaled at any suitable level (e.g., a block level). For each chroma component, the block size and CC-ALF enable flag may be received together at the slice level. In some examples, block sizes (in chroma samples) of 16×16, 32×32, and 64×64 may be supported.

[0204] Figure 17 An example of syntax for CC-ALF according to some embodiments of the present disclosure is shown. Figure 17 In the example of , alf_ctb_cross_component_cb_idc[xCtb>>CtbLog2SizeY][yCtb>>CtbLog2SizeY] is an index used to indicate whether a cross-component Cb filter is used, and if used, indicates the index of the cross-component Cb filter. For example, when alf_ctb_cross_component_cb_idc[xCtb>>CtbLog2SizeY][yCtb>>CtbLog2SizeY] is equal to 0, the cross-component Cb filter is not applied to the block of Cb color component samples at luma position (xCtb, yCtb); when alf_ctb_cross_component_cb_idc[xCtb>>CtbLog2SizeY][yCtb>>CtbLog2SizeY] is not equal to 0, alf_ctb_cross_component_cb_idc[xCtb>>CtbLog2SizeY][yCtb>>CtbLog2SizeY] is the index of the filter to be applied. For example, the alf_ctb_cross_component_cb_idc[xCtb>>CtbLog2SizeY][yCtb>>CtbLog2SizeY]th cross-component Cb filter is applied to the block of Cb color component samples at luma location (xCtb, yCtb).

[0205] Further, in Figure 17In the example of , alf_ctb_cross_component_cr_idc[xCtb>>CtbLog2SizeY][yCtb>>CtbLog2SizeY] is used to indicate whether to use a cross-component Cr filter and the index of whether to use the cross-component Cr filter. For example, when alf_ctb_cross_component_cr_idc[xCtb>>CtbLog2SizeY][yCtb>>CtbLog2SizeY] is equal to 0, the cross-component Cr filter is not applied to the block of Cr color component samples at the luma position (xCtb, yCtb); when alf_ctb_cross_component_cr_idc[xCtb>>CtbLog2SizeY][yCtb>>CtbLog2SizeY] is not equal to 0, alf_ctb_cross_component_cr_idc[xCtb>>CtbLog2SizeY][yCtb>>CtbLog2SizeY] is the index of the cross-component Cr filter. For example, the alf_ctb_cross_component_cr_idc[xCtb>>CtbLog2SizeY][yCtb>>CtbLog2SizeY]th cross-component Cr filter may be applied to a block of Cr color component samples at luma location (xCtb, yCtb).

[0206] In some examples, a chroma subsampling technique is used, so the number of samples in each chroma block can be less than the number of samples in the luma block. The chroma subsampling format (also referred to as a chroma subsampling format, e.g., specified by chroma_format_idc) can indicate a chroma horizontal subsampling factor (e.g., SubWidthC) and a chroma vertical subsampling factor (e.g., SubHeightC) between each chroma block and the corresponding luma block. In one example, the chroma subsampling format is 4:2:0, so the chroma horizontal subsampling factor (e.g., SubWidthC) and the chroma vertical subsampling factor (e.g., SubHeightC) are 2, as shown in FIG. Figure 18A and Figure 18B In one example, the chroma subsampling format is 4:2:2, so the chroma horizontal subsampling factor (e.g., SubWidthC) is 2, and the chroma vertical subsampling factor (e.g., SubHeightC) is 1. In one example, the chroma subsampling format is 4:4:4, so the chroma horizontal subsampling factor (e.g., SubWidthC) and the chroma vertical subsampling factor (e.g., SubHeightC) are 1. The chroma sample type (also referred to as chroma sample position) may indicate the relative position of the chroma samples in the chroma block relative to the corresponding at least one luma sample in the luma block.

[0207] Figure 18A and Figure 18B illustratively shows exemplary positions of chroma samples relative to luma samples according to an embodiment of the present disclosure. Figure 18A , the brightness sample (1801) is located in rows (1811)-(1818). Figure 18A The luma sample (1801) shown may represent a portion of a picture. In one example, a luma block (e.g., luma CB) includes luma sample (1801). The luma block may correspond to two chroma blocks having a chroma subsampling format of 4:2:0. In one example, each chroma block includes a chroma sample (1803). Each chroma sample (e.g., chroma sample (1803(1)) corresponds to four luma samples (e.g., luma samples (1801(1))-(1801(4)). In one example, the four luma samples are an upper left sample (1801(1)), an upper right sample (1801(2)), a lower left sample (1801(3)), and a lower right sample (1801(4)). The chroma sample (e.g., (1803(1)) is located at the center left and is located between the upper left sample (1801(1)) and the lower right sample (1801(2)). 1(1)) and the lower left sample (1801(3)), the chroma sample type of the chroma block having the chroma sample (1803) may be referred to as chroma sample type 0. Chroma sample type 0 indicates a relative position 0 corresponding to a left center position located between the upper left sample (1801(1)) and the lower left sample (1801(3)). Four luma samples (e.g., (1801(1))-(1801(4))) may be referred to as adjacent luma samples of the chroma sample (1803)(1).

[0208] In one example, each chroma block includes a chroma sample (1804). The above description with reference to the chroma sample (1803) may be applicable to the chroma sample (1804), and thus a detailed description may be omitted for the sake of brevity. Each chroma sample (1804) may be located at a center position of four corresponding luma samples, and a chroma sample type of a chroma block having the chroma sample (1804) may be referred to as a chroma sample type 1. The chroma sample type 1 indicates a relative position 1 corresponding to the center position of four luma samples (e.g., (1801(1))-(1801(4))). For example, one chroma sample (1804) may be located at a center portion of the luma samples (1801(1))-(1801(4)).

[0209] In one example, each chroma block includes a chroma sample (1805). Each chroma sample (1805) may be located at an upper left position co-located with an upper left sample of four corresponding luma samples (1801), and the chroma sample type of the chroma block having the chroma sample (1805) may be referred to as chroma sample type 2. Therefore, each chroma sample (1805) is co-located with an upper left sample of four luma samples (1801) corresponding to the corresponding chroma sample. Chroma sample type 2 indicates a relative position of 2 corresponding to the upper left position of the four luma samples (1801). For example, one chroma sample (1805) may be located at an upper left position of luma samples (1801(1))-(1801(4)).

[0210] In one example, each chroma block includes a chroma sample (1806). Each chroma sample (1806) may be located at a top center position between a corresponding upper left sample and a corresponding upper right sample, and a chroma sample type of a chroma block having the chroma sample (1806) may be referred to as a chroma sample type 3. Chroma sample type 3 indicates a relative position 3 corresponding to a top center position between the upper left sample and the upper right sample. For example, one chroma sample (1806) may be located at a top center position of luma samples (1801(1))-(1801(4)).

[0211] In one example, each chroma block includes a chroma sample (1807). Each chroma sample (1807) may be located at a lower left position co-located with a lower left sample of four corresponding luma samples (1801), and the chroma sample type of the chroma block having the chroma sample (1807) may be referred to as chroma sample type 4. Thus, each chroma sample (1807) is co-located with a lower left sample of four luma samples (1801) corresponding to the corresponding chroma sample. Chroma sample type 4 indicates a relative position of 4 corresponding to the lower left position of the four luma samples (1801). For example, one chroma sample (1807) may be located at a lower left position of luma samples (1801(1))-(1801(4)).

[0212] In one example, each chroma block includes a chroma sample (1808). Each chroma sample (1808) is located at a bottom center position between a bottom left sample and a bottom right sample, and the chroma sample type of the chroma block having the chroma sample (1808) may be referred to as a chroma sample type 5. The chroma sample type 5 indicates a relative position 5 corresponding to a bottom center position between a bottom left sample and a bottom right sample of the four luma samples (1801). For example, one chroma sample (1808) may be located between the bottom left sample and the bottom right sample of the luma samples (1801(1))-(1801(4)).

[0213] In general, any suitable chroma sample type can be used for a chroma subsampling format. Chroma sample types 0-5 are exemplary chroma sample types described for the chroma subsampling format 4:2:0. Additional chroma sample types can be used for the chroma subsampling format 4:2:0. Furthermore, variations of chroma sample types 0-5 and / or other chroma sample types can be used for other chroma subsampling formats, such as 4:2:2, 4:4:4, etc. In one example, a chroma sample type combining chroma samples (1805) and (1807) is used for the chroma subsampling format 4:2:2.

[0214] In one example, a luma block is considered to have alternating rows, such as rows (1811)-(1812), which respectively include the top two samples (e.g., (1801(1))-(1801(2))) of the four luma samples (e.g., 1801(1))-(1801(4))) and the bottom two samples (e.g., 1801(3))-(1801(4))) of the four luma samples (e.g., 1801(1)-(1801(4))). Thus, rows (1811), (1813), (1815), and (1817) may be referred to as current rows (also referred to as a top field), and rows (1812), (1814), (1816), and (1818) may be referred to as next rows (also referred to as a bottom field). Four luma samples (e.g., (1801(1))-(1801(4))) are located at the current row (e.g., (1811)) and the next row (e.g., (1812)). Relative positions 2 and 3 are located in the current row, relative positions 0 and 1 are located between each current row and the corresponding next row, and relative positions 4 and 5 are located in the next row.

[0215] In each chroma block, chroma samples (1803), (1804), (1805), (1806), (1807), or (1808) are located in rows (1851)-(1854). The specific location of rows (1851)-(1854) may depend on the chroma sample type of the chroma samples. For example, for chroma samples (1803)-(1804) having chroma sample types 0 and 1, respectively, row (1851) is located between rows (1811)-(1812). For chroma samples (1805)-(1806) having chroma sample types 2 and 3, respectively, row (1851) is co-located with the current row (1811). For chroma samples (1807)-(1808) having chroma sample types 4 and 5, respectively, row (1851) is co-located with the next row (1812). The above description is applicable to rows (1852)-(1854) as appropriate, and a detailed description is omitted for the sake of brevity.

[0216] Any suitable scanning method may be used to display, store and / or transmit the above Figure 18A In one example, progressive scanning is used.

[0217] Interlaced scanning can be used, such as Figure 18B As shown. As described above, the chroma subsampling format is 4:2:0 (e.g., chroma_format_idc is equal to 1). In one example, the variable chroma location type (e.g., ChromaLocType) indicates the current row (e.g., ChromaLocType is chroma_sample_loc_type_top_field) or the next row (e.g., ChromaLocType is chroma_sample_loc_type_bottom_field). The current rows (1811), (1813), (1815), and (1817) and the next rows (1812), (1814), (1816), and (1818) may be scanned respectively. For example, the current rows (1811), (1813), (1815), and (1817) may be scanned first, and then the next rows (1812), (1814), (1816), and (1818) may be scanned. The current row may include luma samples (1801) and the next row may include luma samples (1802).

[0218] Similarly, the corresponding chroma blocks may be interlaced. Rows (1851) and (1853) including chroma samples (1803), (1804), (1805), (1806), (1807), or (1808) without fill may be referred to as current rows (or current chroma rows), and rows (1852) and (1854) including chroma samples (1803), (1804), (1805), (1806), (1807), or (1808) with gray fill may be referred to as next rows (or next chroma rows). In one example, during interlaced scanning, rows (1851) and (1853) are scanned first, and then rows (1852) and (1854) are scanned.

[0219] In some examples, constrained directional enhancement filtering techniques can be used. The use of an in-loop constrained directional enhancement filter (CDEF) can filter out coding artifacts while preserving image details. In one example (e.g., HEVC), the sample adaptive offset (SAO) algorithm can achieve similar goals by defining signal offsets for different pixel classes. Unlike SAO, CDEF is a nonlinear spatial filter. In some examples, CDEF can be constrained to be easily vectorized (i.e., implementable using single instruction multiple data (SIMD) operations). It should be noted that other nonlinear filters (e.g., median filter, bilateral filter) cannot be processed in the same manner.

[0220] In some cases, the amount of ringing artifacts in the encoded image tends to be roughly proportional to the quantization step size. The amount of detail is a property of the input image, but the smallest detail retained in the quantized image also tends to be proportional to the quantization step size. For a given quantization step size, the amplitude of the ringing is typically smaller than the amplitude of the detail.

[0221] CDEF can be used to identify the direction of each block and then adaptively filter along the identified direction and to a lesser extent along directions rotated 45 degrees from the identified direction. In some examples, the encoder can search for filter strengths and can explicitly signal the filter strengths, which allows for a high degree of control over blur.

[0222] Specifically, in some examples, a direction search is performed only on reconstructed pixels after the filter is deblocked. Since those pixels are available to the decoder, the direction can be searched by the decoder, so in one example, no direction signaling is required. In some examples, the direction search can operate on certain block sizes, such as 8×8 blocks, which are small enough to adequately handle non-straight edges while being large enough to reliably estimate the direction when applied to a quantized image. Furthermore, having a constant direction across an 8×8 area makes vectorization of the filter easier. In some examples, each block (e.g., 8×8) can be compared to a perfectly oriented block to determine the difference. A perfectly oriented block is one in which all pixels along a line in one direction have the same value. In one example, a difference measure, such as the sum of squared differences (SSD) or the root mean square (RMS) error, can be calculated between the block and each of the perfectly oriented blocks. The perfectly oriented block with the smallest difference (e.g., smallest SSD, smallest RMS, etc.) can then be determined, and the direction of the determined perfectly oriented block can be the direction that best matches the pattern in the block.

[0223] Figure 19 An example of a directional search according to one embodiment of the present disclosure is shown. In one example, the block (1910) is an 8×8 block that is reconstructed and output from the deblocking filter. Figure 19 In the example of , the direction search can determine one of the eight directions shown by (1920) for the block (1910). Eight perfectly oriented blocks (1930) are formed corresponding to the eight directions (1920), respectively. A perfectly oriented block corresponding to a direction is a block such that the pixels along the line of that direction have the same value. In addition, a difference measure such as SSD, RMS error, etc. can be calculated for each of the block (1910) and the perfectly oriented block (1930). Figure 19 In the example of , the RMS error is shown by (1940). As shown by (1943), the RMS error between block (1910) and the perfectly oriented block (1933) is the smallest, so direction (1923) is the direction that best matches the pattern in block (1910).

[0224] After identifying the direction of the block, a nonlinear low-pass directional filter can be determined. For example, the filter taps of the nonlinear low-pass directional filter can be aligned along the identified direction to reduce ringing while preserving directional edges or patterns. However, in some examples, directional filtering alone is sometimes not enough to reduce ringing. In one example, additional filter taps are also used for pixels that are not located in the identified direction. In order to reduce the risk of blur, the additional filter taps are handled more conservatively. To this end, CDEF includes a primary filter tap and a secondary filter tap. In one example, the complete 2-D CDEF filter can be expressed as equation (14):

[0225]

[0226] Where D represents the damping parameter, S (p) Indicates the strength of the main filter tap, S (s) Denotes the strength of the secondary filter tap, round(·) denotes the operation around the limit away from zero, w denotes the filter weight, and f(d, S, D) is a constraint function that operates on the difference between the filtered pixel and each adjacent pixel. In one example, for small differences, the function f(d, S, D) is equal to D, which makes the filter behave like a linear filter; when the difference is large, the function f(d, S, D) is equal to 0, which effectively ignores the filter tap.

[0227] In some examples, an in-loop recovery scheme is used in post-deblocking video encoding to substantially remove noise and enhance edge quality, in addition to the deblocking operation. In one example, the in-loop recovery scheme is switchable within a frame for each appropriately sized tile. The in-loop recovery scheme is based on a separable symmetric Wiener filter, a dual self-guided filter with subspace projection, and a domain transform recursive filter. Because content statistics can vary substantially within a frame, the in-loop recovery scheme is integrated into a switchable framework, where different schemes can be triggered in different regions of the frame.

[0228] A separable symmetric Wiener filter can be one of the in-loop restoration schemes. In some examples, each pixel in the degraded frame can be reconstructed as a non-causal filtered version of the pixels within a w×w window around each pixel, where w=2r+1 and w is an odd number for integer r. If the 2D filter taps are represented by column vectorized form w 2 × 1 element vector F, then direct LMMSE optimization results in the filter parameters being F = H -1 M is given, where H = E[XX T ] is x, w in a w×w window around the pixel 2 The autocovariance of the column vectorized version of the samples, and M = E[YX T] is the cross-correlation of x with the scalar source sample y to be estimated. In one example, the encoder can estimate H and M based on the implementation in the deblocked frame and source, and can send the resulting filter F to the decoder. However, this is not only in the case of sending w 2 The use of a single tap in the convolution operation results in a considerable bit rate cost, and non-separable filtering will make decoding very complex. In some embodiments, several additional constraints are imposed on the properties of F. For the first constraint, F is constrained to be separable, so that filtering can be implemented as separable horizontal and vertical w-tap convolutions. For the second constraint, each of the horizontal filter and the vertical filter is constrained to be symmetrical. For the third constraint, the sum of the horizontal filter coefficient and the vertical filter coefficient is assumed to be 1.

[0229] Double self-guided filtering with subspace projection can be one of the in-loop recovery schemes. Guided filtering is an image filtering technique where the local linear model is given by Equation (15):

[0230] y=Fx+G Equation (15)

[0231] A local linear model is used to compute the filtered output y from the unfiltered sample x, where F and G are determined based on the statistics of the guidance image and the degraded image near the filtered pixel. If the guidance image is identical to the degraded image, the resulting so-called self-guided filtering has the effect of edge-preserving smoothing. In one example, a specific form of self-guided filtering can be used. The specific form of self-guided filtering depends on two parameters: the radius r and the noise parameter e, and is listed as follows:

[0232] 1. Get the mean μ and variance σ of the pixels in the (2r+1)×(2r+1) window around each pixel 2 This step can be efficiently implemented using box filtering based on integral imaging.

[0233] 2. For each pixel, calculate: f = σ 2 / (σ 2 +e); g=(1-f)μ

[0234] 3. Calculate F and G for each pixel as the average of the f and g values ​​in a 3×3 window around the pixel being used.

[0235] The specific form of the self-guided filter is controlled by r and e, where higher r means higher spatial variance and higher e means higher range variance.

[0236] Figure 20 Examples illustrating subspace projections in some examples are shown. Figure 20As shown, even if the restored X1 and X2 are not close to the source Y, appropriate multipliers {α, β} can make X1 and X2 closer to the source Y as long as X1 and X2 are slightly moved to the right.

[0237] In some examples (e.g., HEVC), a filtering technique called sample adaptive offset (SAO) can be used. In some examples, SAO is applied to the reconstructed signal after filter deblocking. SAO can use an offset value given in the slice header. In some examples, for luma samples, the encoder can decide whether to apply (enable) SAO on the slice. When SAO is enabled, the current picture allows the coding unit to be recursively split into four sub-regions, and each sub-region can select an SAO type from multiple SAO types based on the characteristics of the sub-region.

[0238] Figure 21 A table (2100) is shown of multiple SAO types according to one embodiment of the present disclosure. In table (2100), SAO types 0-6 are shown. It should be noted that SAO type 0 is used to indicate that SAO is not applied. In addition, each of SAO types 1 to 6 includes multiple categories. SAO can classify reconstructed pixels of a sub-region into multiple categories and reduce distortion by adding an offset to pixels of each category in the sub-region. In some examples, edge attributes can be used for pixel classification in SAO types 1 to 4, and pixel intensity can be used for pixel classification in SAO types 5 and 6.

[0239] Specifically, in one embodiment, such as SAO types 5 and 6, a band offset (BO) can be used to classify all pixels of a sub-area into multiple bands. Each of the multiple bands includes pixels in the same intensity interval. In some examples, the intensity range is divided equally into multiple intervals, such as 32 intervals from zero to the maximum intensity value (e.g., 255 intervals for 8-bit pixels), and each interval is associated with an offset. In addition, in one example, the 32 bands are divided into two groups, such as a first group and a second group. The first group includes the central 16 bands (e.g., 16 intervals in the middle of the intensity range), while the second group includes the remaining 16 bands (e.g., 8 intervals on the low side of the intensity range and 8 intervals on the high side of the intensity range). In one example, only the offset of one of the two groups is transmitted. In some embodiments, when using the pixel classification operation in BO, the five most significant bits of each pixel can be directly used as a band index.

[0240] Furthermore, in one embodiment, edge offset (EO) may be used for pixel classification and offset determination, such as for SAO types 1 to 4. For example, edge direction information may be considered to determine pixel classification based on a 1-dimensional 3-pixel pattern.

[0241] Figure 22An example of a 3-pixel pattern for pixel classification for edge offset is shown in FIG. Figure 22 In the example, the first pattern (2210) (as shown by the three gray pixels) is called a 0-degree pattern (the horizontal direction is associated with the 0-degree pattern), the second pattern (2220) (as shown by the three gray pixels) is called a 90-degree pattern (the vertical direction is associated with the 90-degree pattern), the third pattern (2230) (as shown by the three gray pixels) is called a 135-degree pattern (the 135-degree diagonal direction is associated with the 135-degree pattern), and the fourth pattern (2240) (as shown by the three gray pixels) is called a 45-degree pattern (the 45-degree diagonal direction is associated with the 45-degree pattern). In one example, the edge direction information of the sub-region may be considered to select Figure 22 One of the four directional patterns shown is selected. In one example, the selection can be transmitted as auxiliary information in the encoded video stream. Pixels in the sub-region can then be classified into multiple categories by comparing each pixel with its two adjacent pixels in the direction associated with the directional pattern.

[0242] Figure 23 A table (2300) shows pixel classification rules for edge offset in some examples. Specifically, pixel c (also in Figure 22 Each pattern is shown) and two adjacent pixels (also Figure 22 The pixel c can be compared based on the comparison, according to Figure 23 The pixel classification rules shown are used to classify the pixels into one of categories 0 to 4.

[0243] In some embodiments, SAO on the decoder side can operate independently of the largest coding unit (LCU) (e.g., CTU), so that line buffers can be saved. In some examples, when the 90-degree, 135-degree, and 45-degree classification patterns are selected, the pixels in the top and bottom rows of each LCU are not SAO-processed; when the 0-degree, 135-degree, and 45-degree patterns are selected, the pixels in the leftmost and rightmost columns of each LCU are not SAO-processed.

[0244] Figure 24 An example of syntax that may need to be signaled to a CTU if parameters are not merged from neighboring CTUs is shown (2400). For example, the syntax element sao_type_idx[cIdx][rx][ry] may be signaled to indicate the SAO type of the sub-region. The SAO type may be BO (band offset) or EO (edge ​​offset). When sao_type_idx[cIdx][rx][ry] takes a value of 0, it indicates that SAO is OFF; a value of 1 to 4 indicates that one of the four EO categories corresponding to 0°, 90°, 135°, and 45° is used; a value of 5 indicates that BO is used. Figure 24 In the example of , each of the BO type and the EO type has four SAO offset values ​​(sao_offset[cIdx][rx][ry][0] to sao_offset[cIdx][rx][ry][3]) signaled.

[0245] like Figure 24 As shown, SAO is a filtering process that requires additional signaling overhead to indicate all relevant information required to perform SAO filtering, such as Figure 24 As shown, this can limit the potential of SAO.

[0246] Typically, a filtering process may use reconstructed samples of a first color component as input (e.g., Y or Cb or Cr, or R or G or B) to generate an output, and the output of the filtering process is applied to a second color component, which may be the same as the first color component or may be another color component different from the first color component.

[0247] In a related example of cross-component filtering (CCF), filter coefficients are derived based on some mathematical equations. From the encoder side to the decoder side, the derived filter coefficients are sent with a signal, and the derived filter coefficients are used to generate offsets using linear combinations. The generated offsets are then added to the reconstructed samples as a filtering process. For example, offsets are generated based on a linear combination of the filter coefficients and the luma samples, and the generated offsets are added to the reconstructed chroma samples. The related example of CCF is based on the assumption of a linear mapping relationship between the reconstructed luma sample values ​​and the delta values ​​between the original chroma samples and the reconstructed chroma samples. However, the mapping between the reconstructed luma sample values ​​and the delta values ​​between the original chroma samples and the reconstructed chroma samples does not necessarily follow a linear mapping process, so the coding performance of CCF can be limited under the assumption of a linear mapping relationship.

[0248] In some examples, nonlinear mapping techniques can be used for cross-component filtering and / or same-color component filtering without significant signaling overhead. In one example, nonlinear mapping techniques can be used for cross-component filtering to generate cross-component sample offsets. In another example, nonlinear mapping techniques can be used for same-color component filtering to generate local sample offsets.

[0249] For convenience, the filtering process using nonlinear mapping technology can be referred to as sample offset through nonlinear mapping (SO-NLM). In cross-component filtering, SO-NLM can be referred to as cross-component sample offset (CCSO). In same-color component filtering, SO-NLM can be referred to as local sample offset (LSO).

[0250] In one example, CCSO and LSO can be used as loop filters to reduce distortion of reconstructed samples. CCSO and LSO do not rely on the linear mapping assumption used in the related example CCF. For example, CCSO does not rely on the assumption of a linear mapping relationship between the reconstructed luma sample values ​​and the delta values ​​between the original chroma samples and the reconstructed chroma samples. Similarly, LSO does not rely on the assumption of a linear mapping relationship between the reconstructed sample values ​​of a color component and the delta values ​​between the original samples of the color component and the reconstructed samples of the color component.

[0251] In the following description, an SO-NLM filtering process is described, which uses reconstructed samples of a first color component as input (e.g., Y or Cb or Cr, or R or G or B) to generate an output, and the output of the filtering process is applied to a second color component. When the second color component is the same color component as the first color component, the description applies to LSO; and when the second color component is different from the first color component, the description applies to CCSO.

[0252] In SO-NLM, a nonlinear mapping is derived at the encoder. The nonlinear mapping is applied between the reconstructed samples of the first color component within the filter support region and the offset of the second color component added to the filter support region. When the second color component is the same as the first, the nonlinear mapping is used for LSO; when the second color component is different, the nonlinear mapping is used for CCSO. The domain of the nonlinear mapping is determined by the different combinations of processed input reconstructed samples (also known as possible combinations of reconstructed sample values).

[0253] The SO-NLM technique can be illustrated using a specific example. In the specific example, reconstructed samples from a first color component that are within a filter support region (also referred to as a "filter support region") are determined. The filter support region is the region to which a filter can be applied, and the filter support region can have any suitable shape.

[0254] Figure 25 An example of a filter support region (2500) according to some embodiments of the present disclosure is shown. The filter support region (2500) includes four reconstructed samples of the first color component: P0, P1, P2, and P3. Figure 25 In the example of FIG, the four reconstructed samples may form a cross shape in the vertical and horizontal directions, and the center position of the cross shape is the position of the sample to be filtered. The sample at the center position and having the same color component as P0-P3 is represented by C. The sample at the center position and having a second color component is represented by F. The second color component may be the same as or different from the first color component of P0-P3.

[0255] Figure 26 An example of another filter support region (2600) according to some embodiments of the present disclosure is shown. The filter support region (2600) includes four reconstructed samples P0, P1, P2, and P3 of the first color component, and the samples P0, P1, P2, and P3 form a square shape. Figure 26 In the example of FIG, the center position of the square shape is the position of the sample to be filtered. The sample at the center position and having the same color component as P0-P3 is represented by C. The sample at the center position and having a second color component is represented by F. The second color component can be the same as or different from the first color component of P0-P3.

[0256] The reconstructed samples are then processed appropriately to form the filter taps.In a specific example, the reconstructed samples are processed in the following two steps.

[0257] In the first step, the delta values ​​between P0-P3 and C are calculated respectively. For example, m0 represents the delta value between P0 and C; m1 represents the delta value between P1 and C; m2 represents the delta value between P2 and C; and m3 represents the delta value between P3 and C.

[0258] In the second step, the delta values ​​m0-m3 are further quantized, with the quantized values ​​being denoted as d0, d1, d2, and d3. In one example, the quantized value can be one of -1, 0, and 1 based on the quantization process. For example, when m is less than -N (N is a positive value and is referred to as the quantization step size), the value m can be quantized to -1; when m is within the range of [-N, N], the value m can be quantized to 0; and when m is greater than N, the value m can be quantized to 1. In some examples, the quantization step size N can be one of 4, 8, 12, 16, and so on.

[0259] In some embodiments, the quantized values ​​d0-d3 are filter taps and can be used to identify a combination in the filter domain. For example, the filter taps d0-d3 can form a combination in the filter domain. Each filter tap can have three quantized values, so when four filter taps are used, the filter domain includes 81 (3×3×3×3) combinations.

[0260] Figures 27A to 27CA table (2700) with 81 combinations according to one embodiment of the present disclosure is shown. Table (2700) includes 81 rows corresponding to the 81 combinations. In each row corresponding to a combination, the first column includes the index of the combination; the second column includes the value of the filter tap d0 of the combination; the third column includes the value of the filter tap d1 of the combination; the fourth column includes the value of the filter tap d2 of the combination; the fifth column includes the value of the filter tap d3 of the combination; and the sixth column includes an offset value associated with the combination of nonlinear mappings. In one example, when determining the filter taps d0-d3, the offset value (represented by s) associated with the combination of d0-d3 can be determined according to table (2700). In one example, the offset values ​​s0-s80 are integers, such as 0, 1, -1, 3, -3, 5, -5, -7, etc.

[0261] In some embodiments, the final filtering process of SO-NLM may be applied, as shown in equation (16):

[0262] f'=clip(F+s) Equation (16)

[0263] Where F is the reconstructed sample of the second color component to be filtered, s is an offset value determined based on the filter taps, and the filter taps are the result of processing the reconstructed samples of the first color component, for example, using table (2700). The sum of the reconstructed sample F and the offset value s is further clipped to a range associated with the bit depth to determine the final filtered sample f' of the second color component.

[0264] It should be noted that, in the case of LSO, the second color component in the above description is the same as the first color component; in the case of CCSO, the second color component in the above description may be different from the first color component.

[0265] It should be noted that the above description may be adapted for other embodiments of the present invention.

[0266] In some examples, on the encoder side, the encoding device may derive a mapping between reconstructed samples of a first color component in a filter support region and offsets to be added to reconstructed samples of a second color component. The mapping may be any suitable linear or nonlinear mapping. The filtering process may then be applied on the encoder side and / or decoder side based on the mapping. For example, the mapping may be appropriately notified to the decoder (e.g., the mapping is included in the encoded video stream sent from the encoder side to the decoder side), and the decoder may then perform the filtering process based on the mapping.

[0267] In some examples, a technique called semi-decoupled partitioning (SDP) may be used. In one example, an SDP technique uses a semi-decoupled tree (SDT). SDT technology is also called semi-independent tree (SST) or flexible block partitioning for chroma components. In SDT technology, the luma block and chroma block in a super block (SB) (for example, defined in AOMedia Video1 (AV1)) or a CTU (for example, defined in HEVC) may have the same or different block partitioning, and the block partitioning may depend on the luma coding block size or the luma tree depth. In one example, when the luma block area size is greater than a first threshold T1 or the coding tree split depth of the luma block is less than or equal to a second threshold T2, the chroma block uses the same coding tree structure as the luma. Otherwise, when the luma block area size is less than or equal to T1 or the luma split depth is greater than T2, the corresponding chroma block may have a different coding block partitioning from the luma component, which is called flexible block partitioning of the chroma component. In the above examples, T1 is a positive integer, such as 128 or 256; T2 is a positive integer, such as 1 or 2.

[0268] Figure 28 Examples of coding tree structures for luma and chroma components are shown. Figure 28 A first partitioning structure (2810) is shown for the luma component in a super-block, and a second partitioning structure (2850) is shown for the chroma components in a super-block. Figure 28 The 4:2:0 chroma subsampling scheme is used in the RGBA, but when other chroma subsampling schemes are used, the Figure 28 .exist Figure 28 , D1 in the block indicates that the coding tree splitting depth of the block is 1; D2 in the block indicates that the coding tree splitting depth of the block is 2; and D3 in the block indicates that the coding tree splitting depth of the block is 3.

[0269] exist Figure 28 In the example shown in FIG2 , T2 is set to 1. Therefore, when the coding tree splitting depth is equal to 1, the first partitioning structure (2810) and the second partitioning structure (2850) have the same block partitioning structure. For example, the luma block area of ​​the super block is divided into (2811)-(2814) according to quadtree (QT) partitioning (e.g., a larger square block is divided into four smaller square blocks of equal size), and the corresponding chroma block area is divided into (2851)-(2854) according to QT partitioning.

[0270] When the coding tree split depth is greater than T2, the luma block region and the corresponding chroma block region may have different coding block partitioning structures. For example, vertical binary tree (BT) partitioning is used to partition the luma block region (2813) into (2821) and (2822) (e.g., a larger block is divided into two smaller blocks of equal size by a vertical line), and QT partitioning is used to partition the corresponding chroma block region (2853) into (2861)-(2864).

[0271] In addition, in another SDP technology, the luma component and the chroma component can share part of the tree structure starting from the root node of the super block, and the conditions related to the different tree partitioning starting from luma and chroma depend on the high-level syntax from the codestream or the partitioning information of the luma component.

[0272] Block-based compensation can be used for both inter-frame prediction and intra-frame prediction. For inter-frame prediction, block-based compensation from different pictures is called motion compensation. Block-based compensation can also be performed from previously reconstructed areas within the same picture. Block-based compensation from reconstructed areas within the same picture is called intra-picture block compensation, current picture reference (CPR), or intra-block copy (IntraBC). The displacement vector that indicates the offset between the current block and a reference block in the same picture based on which the current block can be encoded / decoded is called a block vector (BV). The motion vector in motion compensation can be any value (positive or negative in the x or y direction), and unlike the motion vector in motion compensation, the BV has several constraints to ensure that the reference block is available and reconstructed. In addition, in some examples, some reference areas such as tile boundaries, slice boundaries, or wavefront trapezoid boundaries are excluded for parallel processing.

[0273] A block vector (BV) can be encoded to specify the location of the prediction value block. The encoding of the block vector can be explicit or implicit. In explicit mode, the BV difference between the block vector and the predicted value of the block vector (also called the block vector predicted value) is signaled. In implicit mode, the block vector is recovered from the predicted value of the block vector (called the block vector predicted value) in a manner similar to the motion vector in merge mode, without using the BV difference. The explicit mode can be referred to as the non-merged BV prediction mode. The implicit mode can be referred to as the merged BV prediction mode.

[0274] In some implementations, the resolution of the block vectors is limited to integer positions. In other implementations, the block vectors are allowed to point to fractional positions.

[0275] In some examples, for the current block, a flag indicating whether the current block is in IntraBC mode (e.g., an IntraBC flag) is first sent in the coded video bitstream. Then, if the current block is in IntraBC mode, a BV difference (e.g., diff) is obtained by subtracting a reference BV (e.g., a block vector prediction value) from the current BV. The diff is then classified into four types based on the horizontal and vertical components of the diff. The type information needs to be sent in the bitstream, and then the diff values ​​of the two components can be signaled based on the type information.

[0276] According to one aspect of the present disclosure, in IntraBC mode, a prediction value block is formed based on reconstructed samples in the current picture, followed by loop filtering. In Inter prediction mode, a prediction value block is formed based on reconstructed samples in other pictures after loop filtering. Disabling the loop filter in IntraBC mode allows the picture buffer for reconstructed samples to be shared between IntraBC mode and Inter prediction, simplifying hardware design.

[0277] In some examples (e.g., AOMedia Video 1 (AV1)), when IntraBC mode is enabled, IntraBC mode is enabled for both luma and chroma components, and all loop filters are disabled for both luma and chroma components. Loop filters may include a deblocking filter, a constrained directional enhancement filter (CDEF), a loop recovery (LR) filter, and the like. However, in some examples, when SDP is on, IntraBC mode may be enabled for one color component, such as the luma component, but disabled for another color component, such as the chroma component. According to some aspects of the present disclosure, loop filters may be enabled or disabled for different color components, and better picture quality may be achieved by using loop filters in some color components. For example, when IntraBC mode is enabled only for the luma component, loop filters may be enabled / disabled differently for the luma and chroma components. For example, in response to enabling IntraBC mode for the luma component, loop filters may be disabled for the luma component, and in response to disabling IntraBC mode for the chroma components, loop filters may be enabled for the chroma components. Therefore, since the loop filter is disabled for the luma component, the picture buffer can be shared between the IntraBC mode and the inter prediction mode, and since the loop filter is used in the chroma component, better picture quality can be achieved.

[0278] In the following description, filters used in loop filtering are referred to as in-loop filters and may include any filter that operates on reconstructed samples within an accessible frame / slice / tile. In-loop filters include, but are not limited to, deblocking (DB) filters, CDEF filters, loop recovery filters, CCSO filters, LSO filters, and the like.

[0279] According to some aspects of the present disclosure, when the IntraBC mode is enabled for the luma component but disabled for the chroma components, at least one in-loop (in-) filter is allowed for the chroma components.

[0280] In some embodiments, when IntraBC mode is enabled for luma components but disabled for chroma components, all in-loop (in-loop) filters may be allowed for chroma components. In one example, when IntraBC mode is enabled for luma components but disabled for chroma components, DB filters, CDEF filters, LR filters, CCSO filters, and LSO filters are allowed for chroma components.

[0281] In some embodiments, when IntraBC mode is enabled for luma components but disabled for chroma components, either CCSO filters or LSO filters are allowed for chroma components.

[0282] In one embodiment, when the IntraBC mode is enabled for the luma component but disabled for the chroma components, the CCSO filter and the CDEF filter are allowed to be used for the chroma components.

[0283] In one embodiment, the enabling / disabling of IntraBC mode for different color components is signaled separately at the picture level.Then, if IntraBC mode is disabled for a color component at the picture level, at least one loop filter is allowed to be used for the color component in the picture.

[0284] In one example, two different picture-level flags are used to indicate whether the IntraBC mode is enabled / disabled for luma and chroma components at the picture level, respectively. For example, the first flag "cm->features.allow_intrabc_luma" is used to indicate whether the IntraBC mode is enabled / disabled for the luma component (also referred to as the luma channel), and the second flag "cm->features.allow_intrabc_chroma" is used to indicate whether the IntraBC mode is enabled / disabled for the chroma component (also referred to as the chroma channel). When the first flag "cm->features.allow_intrabc_luma" is turned on (e.g., has a value of "1") and the second flag "cm->features.allow_intrabc_chroma" is turned off (e.g., has a value of "0"), at least one loop filter is allowed to be used for the chroma component.

[0285] In another example, three different picture-level flags are used to indicate whether the IntraBC mode is enabled / disabled for the Y / Cb / Cr components, respectively. For example, the first flag "cm->features.allow_intrabc_y" is used to indicate whether the IntraBC mode is enabled / disabled for the Y component (also referred to as the luma component), the second flag "cm->features.allow_intrabc_cb" is used to indicate whether the IntraBC mode is enabled / disabled for the Cb component (also referred to as the first chroma component), and the third flag "cm->features.allow_intrabc_cr" is used to indicate whether the IntraBC mode is enabled / disabled for the Cr component (also referred to as the second chroma component). For example, when the first flag "cm->features.allow_intrabc_y" is turned on (e.g., has a value of "1"), the second flag "cm->features.allow_intrabc_cb" and the third flag "cm->features.allow_intrabc_cr" are turned off (both have a value of "0"), at least one loop filter is allowed to be used for the Cb component and the Cr component.

[0286] In one embodiment, if IntraBC mode is turned on for luma and chroma components, the luma block and the associated chroma block share the same block vector (BV), and in some examples, the loop filter is disabled for the luma and chroma blocks.

[0287] In some examples, whether to apply an in-loop filter to a color component (e.g., Y, Cb, Cr) depends on a flag indicating whether IntraBC mode is enabled / disabled for the color component. In one example, when the flag indicates that IntraBC mode is disabled for the color component (e.g., Y, Cb, Cr), the in-loop filter may be applied to the color component; and when the flag indicates that IntraBC mode is enabled for the color component (e.g., Y, Cb, Cr), the in-loop filter is disabled for the color component.

[0288] In some examples, whether to apply an in-loop filter to a color channel (luminance / chrominance) depends on a flag indicating whether IntraBC mode is enabled / disabled for that color channel. In one example, when the flag indicates that IntraBC mode is disabled for a color channel (e.g., luminance or chrominance), the in-loop filter may be applied to the color channel; and when the flag indicates that IntraBC mode is enabled for a color channel (e.g., luminance or chrominance), the in-loop filter is disabled for the color channel.

[0289] In some embodiments, the enable / disable of IntraBC mode for different color components is signaled separately at the block level. Then, if IntraBC mode is disabled for a color component at the block level, at least one loop filter is enabled for the current block in the color component. A block can be interpreted as a prediction block, a coding block, or a coding unit (CU), i.e., a CTU block or super block, or a filter unit (FU).

[0290] In one example, two different block-level flags are used to indicate whether the IntraBC mode is enabled / disabled for the luma component and the chroma component at the block level, respectively. For example, a first flag "mi_params->mi_grid_base[x]->allow_intrabc_luma" is used to indicate whether the IntraBC mode is enabled / disabled for the luma component at the block level, and a second flag "mi_params->mi_grid_base[x]->allow_intrabc_chroma" is used to indicate whether the IntraBC mode is enabled / disabled for the chroma component at the block level. For example, when the first flag "mi_params->mi_grid_base[x]->allow_intrabc_luma" is turned on (e.g., has a value of "1") and the second flag "mi_params->mi_grid_base[x]->allow_intrabc_chroma" is turned off (e.g., has a value of "0"), at least one loop filter is allowed to be used for the current chroma block.

[0291] In another example, three different block-level flags are used to indicate whether the IntraBC mode is enabled / disabled for Y / Cb / Cr blocks, respectively. For example, the first flag "mi_params->mi_grid_base[x]->allow_intrabc_y" is used to indicate whether the IntraBC mode is enabled / disabled for the Y block, the second flag "mi_params->mi_grid_base[x]->allow_intrabc_cb" is used to indicate whether the IntraBC mode is enabled / disabled for the Cb block, and the third flag "mi_params->mi_grid_base[x]->allow_intrabc_cr" is used to indicate whether the IntraBC mode is enabled / disabled for the Cr block. For example, when the first flag "mi_params->mi_grid_base[x]->allow_intrabc_y" is turned on (for example, has a value of "1"), the second flag "mi_params->mi_grid_base[x]->allow_intrabc_cb" and the third flag "mi_params->mi_grid_base[x]->allow_intrabc_cr" are turned off (for example, both have a value of "0"), at least one loop filter is allowed to be used for the current Cb block and the current Cr block.

[0292] In another embodiment, the enable / disable of IntraBC mode may be signaled using high-level syntax (HLS), such as adaptive parameter set (APS), slice header, frame header, picture parameter set (PPS), sequence parameter set (SPS), video parameter set (VPS), etc.

[0293] In some embodiments, when IntraBC mode is applied, whether a specific loop filter (e.g., DB filter, CDEF filter, LR filter, CCSO filter, LSO filter) can be applied depends on another flag signaled in the HLS (APS, slice header, frame header, PPS, SPS, VPS). In one embodiment, for the CDEF filter, a flag "slice_force_cdef_flag_luma" is signaled in the slice header. In one example, when the flag "slice_force_cdef_flag_luma" is signaled as true (e.g., having a value of "1") in the slice header of a slice, the CDEF filter will be applied to the luma component in the slice regardless of whether IntraBC mode is enabled. In another example, when the flag "slice_force_cdef_flag_luma" is signaled as false (e.g., having a value of "0") in the slice header of the slice, whether the CDEF filter will be applied to the luma component in the slice still depends on whether IntraBC mode is enabled.

[0294] In some embodiments, regardless of whether IntraBC mode is allowed for the current frame / slice / tile, at least one in-loop filter is allowed for chroma components.

[0295] In some embodiments, all in-loop (in-) filters may be allowed for chroma components regardless of whether IntraBC mode is enabled for the current frame / slice / tile.

[0296] In another embodiment, CCSO filter or LSO filter or CDEF filter is allowed to be used for chroma components regardless of whether IntraBC mode is enabled for the current frame / slice / tile.

[0297] According to some aspects of the present disclosure, SDP may be used to determine enabling / disabling of loop filters.When SDP is applied, at least one loop (in-) filter is allowed to be used for chroma components.

[0298] In some embodiments, when SDP is applied, all loop (in-loop) filters may be allowed to be used for chroma components. In one example, when SDP is applied, DB filters, CDEF filters, LR filters, CCSO filters, and LSO filters are all allowed to be used for chroma components.

[0299] In some embodiments, when SDP is applied, CCSO filters or LSO filters are allowed to be used for chroma components.

[0300] In one embodiment, when SDP is applied, both CCSO filters and CDEF filters are allowed to be used for chroma components.

[0301] Figure 29 A flowchart outlining a process (2900) according to one embodiment of the present disclosure is shown. The process (2900) may be used to reconstruct blocks in a picture of an encoded video sequence. The term block may be interpreted as a prediction block, a coding unit, a luma block, a chroma block, or the like. In various embodiments, the process (2900) is performed by a processing circuit such as a processing circuit in a terminal device (310), a terminal device (320), a terminal device (330), and a terminal device (340), a processing circuit that performs the functions of a video encoder (403), a processing circuit that performs the functions of a video decoder (410), a processing circuit that performs the functions of a video decoder (510), a processing circuit that performs the functions of a video encoder (603), or the like. In some embodiments, the process (2900) is implemented as software instructions, so that when the processing circuit executes the software instructions, the processing circuit performs the process (2900). The process starts at (S2901) and proceeds to (S2910).

[0302] At (S2910), decoupling coding information for a first color component and a second color component of a block is determined based on decoded information in the encoded video stream. In some examples, the decoupling coding information includes an enable / disable difference in intra-block copy mode for the luma component and the chroma component. For example, the intra-block copy mode is enabled for the luma component and disabled for the chroma component. In some examples, the decoupling coding information includes a decoupled partitioning structure for the luma component and the chroma component. In one example, SDP is applied so that the luma component and the chroma component have different partitioning structures in the block.

[0303] In some embodiments, decoupled coding information of the first color component and the second color component in the block is determined based on corresponding enable / disable signals of the first color component and the second color component, and the corresponding enable / disable signals adopt at least one of the block level, video parameter set (VPS), sequence parameter set (SPS), picture parameter set (PPS), adaptation parameter set (APS), slice header and tile header.

[0304] In some examples, a first enable / disable flag associated with a luma component is decoded from an encoded video stream, and a second enable / disable flag associated with a chroma component is decoded from the encoded video stream. Decoupled coding information for the luma component and the chroma component is determined based on the first enable / disable flag and the second enable / disable flag.

[0305] In some examples, a first enable / disable flag associated with the luma component is decoded from the coded video stream; a second enable / disable flag associated with the first chroma component is decoded from the coded video stream; and a third enable / disable flag associated with the second chroma component is decoded from the coded video stream. Decoupled coding information for the luma component, the first chroma component, and the second chroma component is then determined based on the first enable / disable flag, the second enable / disable flag, and the third enable / disable flag.

[0306] At (S2920), a first sample of a first color component is reconstructed at a location in the block based on a first loop filter configuration, and a second sample of a second color component is reconstructed at the location in the block based on a second loop filter configuration. The first loop filter configuration is different from the second loop filter configuration.

[0307] In some embodiments, at least one of a deblocking filter, a constrained directional enhancement filter (CDEF), a loop recovery filter, a local sample offset (LSO) filter, and a cross-component sample offset (CCSO) filter is enabled in one of the first loop filter configuration and the second loop filter configuration; and the deblocking filter, the constrained directional enhancement filter (CDEF), the loop recovery filter, the local sample offset (LSO) filter, and the cross-component sample offset (CCSO) filter is disabled in the other of the first loop filter configuration and the second loop filter configuration.

[0308] In one embodiment, in response to disabling the intra block copy mode for the chroma component and enabling the intra block copy mode for the luma component, in a second loop filter configuration associated with the chroma component, a deblocking filter, a constrained directional enhancement filter (CDEF), a loop restoration filter, a local sample offset (LSO) filter, and a cross-component sample offset (CCSO) filter are enabled.

[0309] In another embodiment, in response to disabling the intra block copy mode for the chroma component and enabling the intra block copy mode for the luma component, one of a local sample offset (LSO) filter and a cross-component sample offset (CCSO) filter is enabled in a second loop filter configuration associated with the chroma component.

[0310] In another embodiment, in response to disabling the intra block copy mode for the chroma component and enabling the intra block copy mode for the luma component, a constrained directional enhancement filter (CDEF) and a cross-component sample offset (CCSO) filter are enabled in a second loop filter configuration associated with the chroma component.

[0311] In some embodiments, a flag associated with a particular loop filter is decoded from a syntax higher than a block; and the particular loop filter is applied to the luma component in response to the flag being true without regard to decoupling coding information.

[0312] The process (2900) proceeds to (S2999) and ends.

[0313] The process (2900) may be adjusted as appropriate. Steps in the process (2900) may be modified and / or omitted. Additional steps may be added. Any suitable order of implementation may be used.

[0314] The embodiments of the present disclosure may be used alone or in any combination. In addition, each of the method (or embodiment), encoder, and decoder may be implemented by a processing circuit (e.g., one or more processors or one or more integrated circuits). In one example, one or more processors execute a program stored in a non-transitory computer-readable medium.

[0315] The above technology can be implemented as computer software that uses computer-readable instructions and is physically stored in one or more computer-readable media. For example, Figure 30 A computer system (3000) suitable for implementing certain embodiments of the disclosed subject matter is shown.

[0316] Computer software may be encoded using any suitable machine code or computer language that may be subjected to assembly, compilation, linking, or similar mechanisms to create code comprising instructions that may be executed directly by one or more computer central processing units (CPUs), graphics processing units (GPUs), etc., or through interpretation, microcode execution, etc.

[0317] The instructions may be executed on various types of computers or components thereof, including, for example, personal computers, tablet computers, servers, smart phones, gaming devices, IoT devices, and the like.

[0318] Figure 30 The components of the computer system (3000) shown are exemplary in nature and are not intended to suggest any limitation on the scope of use or functionality of computer software implementing embodiments of the present disclosure. Neither should the configuration of the components be interpreted as having any dependency or requirement relating to any one or combination of components shown in the exemplary embodiment of the computer system (3000).

[0319] The computer system (3000) may include certain human interface input devices. Such human interface input devices may be responsive to input from one or more human users through, for example, tactile input (e.g., keystrokes, swipes, data glove movements), audio input (e.g., speech, hand clapping), visual input (e.g., gestures), and olfactory input (not depicted). The human interface devices may also be used to capture certain media that are not necessarily directly related to human conscious input, such as audio (e.g., speech, music, ambient sounds), images (e.g., scanned images, captured images from a still camera), and video (e.g., two-dimensional video, three-dimensional video including stereoscopic video).

[0320] The human-machine interface input device may include one or more of the following (only one of each is shown): keyboard (3001), mouse (3002), touchpad (3003), touch screen (3010), data gloves (not shown), joystick (3005), microphone (3006), scanner (3007), camera (3008).

[0321] The computer system (3000) may also include certain human-computer interface output devices. Such human-computer interface output devices may stimulate one or more human user senses, for example, through tactile output, sound, light, and smell / taste. Such human-computer interface output devices may include tactile output devices (e.g., tactile feedback of a touch screen (3010), a data glove (not shown), or a joystick (3005), but may also be a tactile feedback device that is not an input device), audio output devices (e.g., speakers (3009), headphones (not depicted)), visual output devices (e.g., screens (3010) including CRT screens, LCD screens, plasma screens, OLED screens, each with or without touch screen input capabilities, each with or without tactile feedback capabilities, some of which are capable of outputting two-dimensional visual output or output in more than three dimensions through devices such as stereoscopic image output, virtual reality glasses (not depicted), holographic displays, and smoke boxes (not depicted), and printers (not depicted).

[0322] The computer system (3000) may also include human-accessible storage devices and their associated media, such as optical media including CD / DVD ROM / RW (3020) including CD / DVD etc. media (3021), thumb drives (3022), removable hard drives or solid-state drives (3023), traditional magnetic media such as tapes and floppy disks (not depicted), dedicated ROM / ASIC / PLD based devices such as security dongles (not depicted), etc.

[0323] Those skilled in the art will also understand that the term "computer-readable medium" used in connection with the presently disclosed subject matter does not encompass transmission media, carrier waves, or other transitory signals.

[0324] The computer system (3000) may also include an interface (3054) to one or more communication networks (3055). The network may be, for example, a wireless network, a wired network, an optical network. The network may further be a local area network, a wide area network, a metropolitan area network, a vehicle and industrial network, a real-time network, a delay-tolerant network, etc. Examples of networks include local area networks such as Ethernet, wireless LANs, cellular networks including GSM, 3G, 4G, 5G, LTE, etc., television wired or wireless wide area digital networks including cable television, satellite television, and terrestrial broadcast television, vehicle and industrial networks including CANBus, etc. Some networks typically require an external network interface adapter attached to some common data port or peripheral bus (3049) (e.g., a USB port of the computer system (3000)); as described below, other network interfaces are typically integrated into the core of the computer system (3000) by attaching to the system bus (e.g., connecting to an Ethernet interface in a PC computer system or connecting to a cellular network interface in a smartphone computer system). The computer system (3000) can use any of these networks to communicate with other entities. Such communications can be one-way receive only (e.g., broadcast television), one-way send only (e.g., a CANbus connected to certain CANbus devices), or bidirectional, for example, connecting to other computer systems using a local area network or wide area network digital network. As described above, certain protocols and protocol stacks can be used on each of those networks and network interfaces.

[0325] The above-mentioned human interface device, human-accessible storage device and network interface may be attached to the kernel (3040) of the computer system (3000).

[0326] The core (3040) may include one or more central processing units (CPUs) (3041), graphics processing units (GPUs) (3042), specialized programmable processing units in the form of field programmable gate arrays (FPGAs) (3043), hardware accelerators (3044) for certain tasks, a graphics adapter (3050), and the like. These devices, as well as read-only memory (ROM) (3045), random access memory (3046), and internal mass storage (3047) such as internal non-user accessible hard drives, SSDs, and the like, may be connected via a system bus (3048). In some computer systems, the system bus (3048) may be accessed in the form of one or more physical plugs to enable expansion with additional CPUs, GPUs, and the like. Peripheral devices may be attached directly to the core's system bus (3048) or to the core's system bus (3048) via a peripheral bus (3049). In one example, a display (3010) may be connected to a graphics adapter (3050). Peripheral bus architectures include PCI, USB, and the like.

[0327] The CPU (3041), GPU (3042), FPGA (3043), and accelerator (3044) can execute certain instructions, which can be combined to form the above-mentioned computer code. The computer code can be stored in ROM (3045) or RAM (3046). Transient data can also be stored in RAM (3046), while permanent data can be stored, for example, in internal mass storage (3047). Fast storage and retrieval to any storage device can be achieved by using a cache, which can be closely associated with one or more of the CPU (3041), GPU (3042), mass storage (3047), ROM (3045), RAM (3046), etc.

[0328] The computer readable medium may have computer code thereon 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 a type well known and available to those skilled in the art of computer software.

[0329] As an example and not a limitation, a computer system having the architecture (3000), particularly the kernel (3040), may provide functionality due to one or more processors (including CPUs, GPUs, FPGAs, accelerators, etc.) executing software contained in one or more tangible computer-readable media. Such computer-readable media may be media associated with user-accessible mass storage as described above, as well as certain non-transitory kernel (3040) memories, such as kernel internal mass storage (3047) or ROM (3045). Software implementing various embodiments of the present disclosure may be stored in such devices and executed by the kernel (3040). Depending on specific needs, the computer-readable medium may include one or more storage devices or chips. The software may cause the kernel (3040), particularly the processors therein (including CPUs, GPUs, FPGAs, etc.), to perform specific processes or specific parts of specific processes described herein, including defining data structures stored in RAM (3046) and modifying such data structures according to processes defined by the software. Additionally or alternatively, the computer system may provide functionality due to logic hardwired or otherwise embodied in circuitry (e.g., accelerator (3044)), which may replace software or operate in conjunction with software to perform specific processes or specific portions of specific processes described herein. Where appropriate, references to software may include logic and vice versa. Where appropriate, references to computer-readable media may include circuitry (e.g., integrated circuits (ICs)) storing software for execution, circuitry embodying logic for execution, or both. The present disclosure includes any suitable combination of hardware and software.

[0330] Appendix A: Acronyms

[0331] JEM: Joint Exploration Model

[0332] VVC: Versatile Video Coding

[0333] BMS: Benchmark Set

[0334] MV: Motion Vector

[0335] HEVC: High Efficiency Video Coding

[0336] MPM: Most Probable Mode

[0337] WAIP: Wide Angle Intra Prediction

[0338] SEI: Supplementary Enhancement Information

[0339] VUI: Video Availability Information

[0340] GOP: Group of Pictures

[0341] TU: Transform Unit

[0342] PU: prediction unit

[0343] CTU: Coding Tree Unit

[0344] CTB: Coding Tree Block

[0345] PB: prediction block

[0346] HRD: Hypothetical Reference Decoder

[0347] SDR: Standard Dynamic Range

[0348] SNR: Signal-to-Noise Ratio

[0349] CPU: Central Processing Unit

[0350] GPU: Graphics Processing Unit

[0351] CRT: cathode ray tube

[0352] LCD: Liquid Crystal Display

[0353] OLED: Organic Light-Emitting Diode

[0354] CD: compact disc

[0355] DVD: Digital Video Disc

[0356] ROM: Read-Only Memory

[0357] RAM: Random Access Memory

[0358] ASIC: Application Specific Integrated Circuit PLD: Programmable Logic Device

[0359] LAN: Local Area Network

[0360] GSM: Global System for Mobile Communications

[0361] LTE: Long Term Evolution

[0362] CANBus: Controller Area Network Bus

[0363] USB: Universal Serial Bus

[0364] PCI: Peripheral Component Interconnect

[0365] FPGA: Field Programmable Gate Array

[0366] SSD: Solid State Drive

[0367] IC: integrated circuit

[0368] CU: Coding Unit

[0369] PDPC: Position Dependent Prediction Combination

[0370] ISP: Intra-frame sub-partitioning

[0371] SPS: Sequence parameter settings

[0372] Although the present disclosure has described a number of exemplary embodiments, there are modifications, permutations, and various alternative equivalents that fall within the scope of the present disclosure. Therefore, it should be understood that those skilled in the art will be able to devise many systems and methods that, although not explicitly shown or described herein, embody the principles of the present disclosure and therefore fall within the spirit and scope of the present disclosure.

Claims

1. A method for filtering in video decoding, comprising: Determining, by a processor, decoupled coding information of a luma component and a chroma component of a block based on decoded information in the coded video stream; Indicating, based on the decoupling encoding information, that the chroma component of the block disables an intra block copy mode and the luma component of the block enables the intra block copy mode, or that a decoupled partitioning structure is applied to the luma component and the chroma component of the block, enabling at least one loop filter of the chroma component; as well as Reconstructing, by the processor, a first sample of the luma component at a location in the block based on a first loop filter configuration that does not include the at least one loop filter, and reconstructing a second sample of the chroma component at the location in the block based on a second loop filter configuration that includes the at least one loop filter.

2. The method according to claim 1, wherein The decoupled encoding information indicates that a chroma component of the block disables an intra block copy mode and a luma component of the block enables the intra block copy mode.

3. The method according to claim 1, further comprising: enabling at least one of a deblocking filter, a constrained directional enhancement filter, a loop restoration filter, a local sample offset filter, and a cross-component sample offset filter in the second loop filter configuration; and The deblocking filter, the constrained directional enhancement filter, the loop restoration filter, the local sample offset filter, and the cross-component sample offset filter are disabled in the first loop filter configuration.

4. The method according to claim 3, further comprising: In response to disabling the intra block copy mode for the chroma component and enabling the intra block copy mode for the luma component, in a second loop filter configuration associated with the chroma component, enabling the deblocking filter, the constrained directional enhancement filter, the loop restoration filter, the local sample offset filter, and the cross-component sample offset filter.

5. The method according to claim 3, further comprising: In response to disabling the intra block copy mode for the chroma component and enabling the intra block copy mode for the luma component, in a second loop filter configuration associated with the chroma component, one of the local sample offset filter and the cross-component sample offset filter is enabled.

6. The method according to claim 3, further comprising: In response to disabling the intra block copy mode for the chroma component and enabling the intra block copy mode for the luma component, enabling the constrained directional enhancement filter and the cross-component sample offset filter in a second loop filter configuration associated with the chroma component.

7. The method according to claim 1, further comprising: Decoupled coding information of the luma component and the chroma component in the block is determined based on respective enable / disable signals of the luma component and the chroma component, wherein the respective enable / disable signals adopt at least one of a block level, a video parameter set (VPS), a sequence parameter set (SPS), a picture parameter set (PPS), an adaptation parameter set (APS), a slice header, and a tile header.

8. The method according to claim 1, further comprising: Decoding a first enable / disable flag associated with the luminance component from the encoded video stream; Decoding a second enable / disable flag associated with the chroma component from the encoded video stream; as well as Decoupled encoding information of the luma component and the chroma component is determined based on the first enable / disable flag and the second enable / disable flag.

9. The method according to claim 1, further comprising: Decoding a first enable / disable flag associated with the luminance component from the encoded video stream; Decoding a second enable / disable flag associated with a first chroma component from the encoded video stream; Decoding a third enable / disable flag associated with a second chroma component from the encoded video stream; as well as Decoupling encoding information of the luma component, the first chroma component, and the second chroma component is determined based on the first enable / disable flag, the second enable / disable flag, and the third enable / disable flag.

10. The method according to claim 1, wherein The decoupled encoding information indicates that the decoupled partitioning structure applies to the luma component of the block and the chroma components of the block.

11. An apparatus for filtering in video decoding, comprising a processing circuit configured to: Determining decoupled coding information of a luminance component and a chrominance component of a block based on decoded information in the coded video stream; Indicating, based on the decoupling encoding information, that the chroma component of the block disables an intra block copy mode and the luma component of the block enables the intra block copy mode, or that a decoupling partitioning structure is applied to the luma component and the chroma component representing the block, enabling at least one loop filter of the chroma component; as well as A first sample of the luma component is reconstructed at a location in the block based on a first loop filter configuration that does not include the at least one loop filter, and a second sample of the chroma component is reconstructed at the location in the block based on a second loop filter configuration that includes the at least one loop filter.

12. The device according to claim 11, wherein The decoupled encoding information indicates that a chroma component of the block disables an intra block copy mode and a luma component of the block enables the intra block copy mode.

13. The device according to claim 11, wherein The processing circuit is configured to: enabling at least one of a deblocking filter, a constrained directional enhancement filter, a loop restoration filter, a local sample offset filter, and a cross-component sample offset filter in the second loop filter configuration; and The deblocking filter, the constrained directional enhancement filter, the loop restoration filter, the local sample offset filter, and the cross-component sample offset filter are disabled in the first loop filter configuration.

14. The device according to claim 13, wherein The processing circuit is configured to: In response to disabling the intra block copy mode for the chroma component and enabling the intra block copy mode for the luma component, in a second loop filter configuration associated with the chroma component, enabling the deblocking filter, the constrained directional enhancement filter, the loop restoration filter, the local sample offset filter, and the cross-component sample offset filter.

15. The device according to claim 13, wherein The processing circuit is configured to: In response to disabling the intra block copy mode for the chroma component and enabling the intra block copy mode for the luma component, in a second loop filter configuration associated with the chroma component, one of the local sample offset filter and the cross-component sample offset filter is enabled.

16. The device according to claim 13, wherein The processing circuit is configured to: In response to disabling the intra block copy mode for the chroma component and enabling the intra block copy mode for the luma component, enabling the constrained directional enhancement filter and the cross-component sample offset filter in a second loop filter configuration associated with the chroma component.

17. The device according to claim 11, wherein The processing circuit is configured to: Decoupled coding information of the luma component and the chroma component in the block is determined based on respective enable / disable signals of the luma component and the chroma component, wherein the respective enable / disable signals adopt at least one of a block level, a video parameter set (VPS), a sequence parameter set (SPS), a picture parameter set (PPS), an adaptation parameter set (APS), a slice header, and a tile header.

18. The device according to claim 11, wherein The processing circuit is configured to: Decoding a first enable / disable flag associated with the luminance component from the encoded video stream; Decoding a second enable / disable flag associated with the chroma component from the encoded video stream; as well as Decoupled encoding information of the luma component and the chroma component is determined based on the first enable / disable flag and the second enable / disable flag.

19. The device according to claim 11, wherein The processing circuit is configured to: Decoding a first enable / disable flag associated with the luminance component from the encoded video stream; Decoding a second enable / disable flag associated with a first chroma component from the encoded video stream; Decoding a third enable / disable flag associated with a second chroma component from the encoded video stream; as well as Decoupling encoding information of the luma component, the first chroma component, and the second chroma component is determined based on the first enable / disable flag, the second enable / disable flag, and the third enable / disable flag.

20. The device according to claim 11, wherein The decoupled encoding information indicates that the decoupled partitioning structure applies to the luma component of the block and the chroma components of the block.

21. A computer-readable medium, characterized in that Instructions are stored, and when the instructions are executed, they are used to implement the method according to any one of claims 1 to 10.

Images