On boundary gradient minimization

Abstract

Some aspects of the disclosure provide a method of video decoding. For example, a bitstream is received, the bitstream includes coded information of a sequence of pictures in a video. Further, to apply a coding tool on a current block in a current picture in the sequence of pictures is determined, the coding tool is based on boundary' gradient computation. Direction information of the current block is determined, and at least a boundary gradient associated with a sample of the current block is computed based on the direction information of the current block. A reconstructed block of the current block is generated by applying the coding tool that is based on at least the boundary gradient associated with the sample.

Description

Docket No: 043380.02116 1ON BOUNDARY GRADIENT MINIMIZATIONINCORPORATION BY REFERENCE

[0001] The present application claims the benefit of priority to U.S. Patent Application No. 19 / 466,760, filed on February 2, 2026, which claims the benefit of priority to U.S.Provisional Application No. 63 / 756,099, filed on February 8, 2025. The entire disclosures of the prior applications are hereby incorporated by reference in their entirety.TECHNICAL FIELD

[0002] The present disclosure describes aspects generally related to video coding.BACKGROUND

[0003] The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent the work is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.

[0004] Image / video compression can help transmit image / video data across different devices, storage and networks with minimal quality degradation. In some examples, video codec technology can compress video based on spatial and temporal redundancy. In an example, a video codec can use techniques referred to as intra prediction that can compress an image based on spatial redundancy. For example, the intra prediction can use reference data from the current picture under reconstruction for sample prediction. In another example, a video codec can use techniques referred to as inter prediction that can compress an image based on temporal redundancy. For example, the inter prediction can predict samples in a current picture from a previously reconstructed picture with motion compensation. The motion compensation can be indicated by a motion vector (MV).SUMMARY

[0005] Aspects of the disclosure include bitstreams, methods and apparatuses for video encoding / decoding. In some examples, an apparatus for video encoding / decoding includes processing circuitry.

[0006] Some aspects of the disclosure provide a method of video decoding. For example, a bitstream is received, the bitstream includes coded information of a sequence of pictures in aDocket No: 043380.02116 2video. Further, to apply a coding tool on a current block in a current picture in the sequence of pictures is determined, the coding tool is based on boundary’ gradient computation. Direction information of the current block is determined, and at least a boundary gradient associated with a sample of the current block is computed based on the direction information of the current block. A reconstructed block of the current block is generated by applying the coding tool that is based on at least the boundary gradient associated with the sample.

[0007] Some aspects of the disclosure provide a method for video encoding. In some examples, to apply a coding tool on a current block in a current picture within a sequence of pictures of a video is determined, the coding tool is based on boundary gradient computation. Further, direction information of the current block is determined. At least a boundary' gradient associated with a sample is computed based on the direction information of the current block. The current block is encoded into coded information in a bitstream by applying the coding tool that is based on at least the boundary gradient associated with the sample.

[0008] Aspects of the disclosure also provide an apparatus for video decoding. The apparatus for video encoding including processing circuitry configured to implement any of the described methods for video decoding.

[0009] Aspects of the disclosure also provide an apparatus for video encoding. The apparatus for video encoding including processing circuitry' configured to implement any of the described methods for video encoding.

[0010] Aspects of the disclosure also provide a non-transitory computer-readable medium storing instructions which, when executed by a computer, cause the computer to perform any of the described methods for video decoding / encoding.BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Further features, the nature, and various advantages of the disclosed subject matter will be more apparent from the following detailed description and the accompanying drawings in which:

[0012] FIG. 1 is a schematic illustration of an example of a block diagram of a communication system (100).

[0013] FIG. 2 is a schematic illustration of an example of a block diagram of a decoder.

[0014] FIG. 3 is a schematic illustration of an example of a block diagram of an encoder.

[0015] FIG. 4 show s a diagram for computing boundary gradient in a related example.

[0016] FIG. 5 shows an example of integer directions of intra mode defined in some examples.Docket No: 043380.02116 3

[0017] FIG. 6 shows a diagram of boundary gradient computation according to an aspect of the disclosure.

[0018] FIG. 7 shows an example of non-linear direction for boundary gradient computation according to an aspect of the disclosure

[0019] FIG. 8 shows a flow chart outlining a decoding process according to some aspects of the disclosure.

[0020] FIG. 9 shows a flow chart outlining an encoding process according to some aspects of the disclosure.

[0021] FIG. 10 is a schematic illustration of a computer system in accordance w ith an aspect.DETAILED DESCRIPTION

[0022] FIG. 1 shows a block diagram of a video processing system (100) in some examples. The video processing system (100) is an example of an application for the disclosed subject matter, a video encoder and a video decoder in a streaming environment. The disclosed subject matter can be equally applicable to other video enabled applications, including, for example, video conferencing, digital TV, streaming services, storing of compressed video on digital media including CD, DVD, memory stick and the like, and so on.

[0023] The video processing system (100) includes a capture subsystem (113), that can include a video source (101), for example a digital camera, creating for example a stream of video pictures (102) that are uncompressed. In an example, the stream of video pictures (102) includes samples that are taken by the digital camera. The stream of video pictures (102), depicted as a bold line to emphasize a high data volume when compared to encoded video data (104) (or coded video bitstreams), can be processed by an electronic device (120) that includes a video encoder (103) coupled to the video source (101). The video encoder (103) can include hardware, software, or a combination thereof to enable or implement aspects of the disclosed subject matter as described in more detail below. The encoded video data (104) (or encoded video bitstream), depicted as a thin line to emphasize the lower data volume when compared to the stream of video pictures (102). can be stored on a streaming server (105) for future use. One or more streaming client subsystems, such as client subsystems (106) and (108) in FIG. 1 can access the streaming server (105) to retrieve copies (107) and (109) of the encoded video data (104). A client subsystem (106) can include a video decoder (110), for example, in an electronic device (130). The video decoder (110) decodes the incoming copy (107) of the encoded video data and creates an outgoing stream of video pictures (111) that can be rendered on a displayDocket No: 043380.02116 4(112) (e.g., display screen) or other rendering device (not depicted). In some streaming systems, the encoded video data (104), (107). and (109) (e.g., video bitstreams) can be encoded according to certain video coding / compression standards. Examples of those standards include ITU-T Recommendation H.265. In an example, a video coding standard under development is informally known as Versatile Video Coding (VVC). The disclosed subject matter may be used in the context of VVC.

[0024] It is noted that the electronic devices (120) and (130) can include other components (not shown). For example, the electronic device (120) can include a video decoder (not shown) and the electronic device (130) can include a video encoder (not show n) as well.

[0025] FIG. 2 show s an example of a block diagram of a video decoder (210). The video decoder (210) can be included in an electronic device (230). The electronic device (230) can include a receiver (231) (e.g., receiving circuitry). The video decoder (210) can be used in the place of the video decoder (110) in the FIG. 1 example.

[0026] The receiver (231) may receive one or more coded video sequences, included in a bitstream for example, to be decoded by the video decoder (210). In an aspect, one coded video sequence is received at a time, where the decoding of each coded video sequence is independent from the decoding of other coded video sequences. The coded video sequence may be received from a channel (201), which may be ahardware / software link to a storage device which stores the encoded video data. The receiver (231) may receive the encoded video data with other data, for example, coded audio data and / or ancillary data streams, that may be forwarded to their respective using entities (not depicted). The receiver (231) may separate the coded video sequence from the other data. To combat netw ork jitter, a buffer memory (215) may be coupled in between the receiver (231) and an entropy decoder / parser (220) ("parser (220)" henceforth). In certain applications, the buffer memory (215) is part of the video decoder (210). In others, it can be outside of the video decoder (210) (not depicted). In still others, there can be a buffer memory (not depicted) outside of the video decoder (210), for example to combat netw ork jitter, and in addition another buffer memory' (215) inside the video decoder (210), for example to handle playout timing. When the receiver (231) is receiving data from a store / forward device of sufficient bandwidth and controllability, or from an isosynchronous network, the buffer memory (215) may not be needed, or can be small. For use on best effort packet networks such as the Internet, the buffer memory (215) may be required, can be comparatively large and can be advantageously of adaptive size, and may at least partially be implemented in an operating system or similar elements (not depicted) outside of the video decoder (210).Docket No: 043380.02116 5

[0027] The video decoder (210) may include the parser (220) to reconstruct symbols (221) from the coded video sequence. Categories of those symbols include information used to manage operation of the video decoder (210), and potentially information to control a rendering device such as a render device (212) (e.g., a display screen) that is not an integral part of the electronic device (230) but can be coupled to the electronic device (230), as show n in FIG. 2. The control information for the rendering device(s) may be in the form of Supplemental Enhancement Information (SEI) messages or Video Usability Information (VU1) parameter set fragments (not depicted). The parser (220) may parse / entropy -decode the coded video sequence that is received. The coding of the coded video sequence can be in accordance with a video coding technology or standard, and can follow7various principles, including variable length coding, Huffman coding, arithmetic coding with or without context sensitivity, and so forth. The parser (220) may extract from the coded video sequence, a set of subgroup parameters for at least one of the subgroups of pixels in the video decoder, based upon at least one parameter corresponding to the group. Subgroups can include Groups of Pictures (GOPs), pictures, tiles, slices, macroblocks, Coding Units (CUs), blocks, Transform Units (TUs), Prediction Units (PUs) and so forth. The parser (220) may also extract from the coded video sequence information such as transform coefficients, quantizer parameter values, motion vectors, and so forth.

[0028] The parser (220) may perform an entropy decoding / parsing operation on the video sequence received from the buffer memory (215), so as to create symbols (221).

[0029] Reconstruction of the symbols (221) can involve multiple different units depending on the type of the coded video picture or parts thereof (such as: inter and intra picture, inter and intra block), and other factors. Which units are involved, and how7, can be controlled by subgroup control information parsed from the coded video sequence by the parser (220). The flow of such subgroup control information between the parser (220) and the multiple units below is not depicted for clarity.

[0030] Beyond the functional blocks already mentioned, the video decoder (210) can be conceptually subdivided into a number of functional units as described below7. In a practical implementation operating under commercial constraints, many of these units interact closely w ith each other and can, at least partly, be integrated into each other. However, for the purpose of describing the disclosed subject matter, the conceptual subdivision into the functional units below is appropriate.

[0031] A first unit is the scaler / inverse transform unit (251). The scaler I inverse transform unit (251) receives a quantized transform coefficient as well as control information, including which transform to use, block size, quantization factor, quantization scaling matrices.Docket No: 043380.02116 6etc. as symbol(s) (221) from the parser (220). The scaler / inverse transform unit (251) can output blocks comprising sample values, that can be input into aggregator (255).

[0032] In some cases, the output samples of the scaler / inverse transform unit (251) can pertain to an intra coded block. The intra coded block is a block that is not using predictive information from previously reconstructed pictures, but can use predictive information from previously reconstructed parts of the current picture. Such predictive information can be provided by an intra picture prediction unit (252). In some cases, the intra picture prediction unit (252) generates a block of the same size and shape of the block under reconstruction, using surrounding already reconstructed information fetched from the current picture buffer (258). The current picture buffer (258) buffers, for example, partly reconstructed current picture and / or fully reconstructed current picture. The aggregator (255). in some cases, adds, on a per sample basis, the prediction information the intra prediction unit (252) has generated to the output sample information as provided by the scaler / inverse transform unit (251).

[0033] In other cases, the output samples of the scaler / inverse transform unit (251) can pertain to an inter coded, and potentially motion compensated, block. In such a case, a motion compensation prediction unit (253) can access reference picture memory (257) to fetch samples used for prediction. After motion compensating the fetched samples in accordance with the symbols (221) pertaining to the block, these samples can be added by the aggregator (255) to the output of the scaler / inverse transform unit (251) (in this case called the residual samples or residual signal) so as to generate output sample information. The addresses within the reference picture memory (257) from where the motion compensation prediction unit (253) fetches prediction samples can be controlled by motion vectors, available to the motion compensation prediction unit (253) in the form of symbols (221) that can have, for example X, Y, and reference picture components. Motion compensation also can include interpolation of sample values as fetched from the reference picture memory (257) when sub-sample exact motion vectors are in use, motion vector prediction mechanisms, and so forth.

[0034] The output samples of the aggregator (255) can be subject to various loop filtering techniques in the loop filter unit (256). Video compression technologies can include in-loop filter technologies that are controlled by parameters included in the coded video sequence (also referred to as coded video bitstream) and made available to the loop filter unit (256) as symbols (221) from the parser (220). Video compression can also be responsive to meta-information obtained during the decoding of previous (in decoding order) parts of the coded picture or coded video sequence, as well as responsive to previously reconstructed and loop-filtered sample values.Docket No: 043380.02116 7

[0035] The output of the loop filter unit (256) can be a sample stream that can be output to the render device (212) as well as stored in the reference picture memory’ (257) for use in future inter-picture prediction.

[0036] Certain coded pictures, once fully reconstructed, can be used as reference pictures for future prediction. For example, once a coded picture corresponding to a current picture is fully reconstructed and the coded picture has been identified as a reference picture (by. for example, the parser (220)), the current picture buffer (258) can become a part of the reference picture memory (257), and a fresh current picture buffer can be reallocated before commencing the reconstruction of the following coded picture.

[0037] The video decoder (210) may perform decoding operations according to a predetermined video compression technology or a standard, such as ITU-T Rec. H.265. The coded video sequence may conform to a syntax specified by the video compression technology' or standard being used, in the sense that the coded video sequence adheres to both the syntax of the video compression technology or standard and the profiles as documented in the video compression technology or standard. Specifically, a profile can select certain tools as the only tools available for use under that profile from all the tools available in the video compression technology^ or standard. Also necessary for compliance can be that the complexity of the coded video sequence is within bounds as defined by the level of the video compression technology’ or standard. In some cases, levels restrict the maximum picture size, maximum frame rate, maximum reconstruction sample rate (measured in, for example megasamples per second), maximum reference picture size, and so on. Limits set by levels can, in some cases, be further restricted through Hypothetical Reference Decoder (HRD) specifications and metadata for HRD buffer management signaled in the coded video sequence.

[0038] In an aspect, the receiver (231) may receive additional (redundant) data with the encoded video. The additional data may be included as part of the coded video sequence(s). The additional data may be used by the video decoder (210) to properly decode the data and / or to more accurately reconstruct the original video data. Additional data can be in the form of, for example, temporal, spatial, or signal noise ratio (SNR) enhancement layers, redundant slices, redundant pictures, forward error correction codes, and so on.

[0039] FIG. 3 shows an example of a block diagram of a video encoder (303). The video encoder (303) is included in an electronic device (320). The electronic device (320) includes a transmitter (340) (e.g., transmitting circuitry). The video encoder (303) can be used in the place of the video encoder (103) in the FIG. 1 example.Docket No: 043380.02116 8

[0040] The video encoder (303) may receive video samples from a video source (301) (that is not part of the electronic device (320) in the FIG. 3 example) that may capture video image(s) to be coded by the video encoder (303). In another example, the video source (301) is a part of the electronic device (320).

[0041] The video source (301) may provide the source video sequence to be coded by the video encoder (303) in the form of a digital video sample stream that can be of any suitable bit depth (for example: 8 bit, 10 bit, 12 bit, ... ), any colorspace (for example, BT.601 Y CrCB, RGB, ...), and any suitable sampling structure (for example Y CrCb 4:2:0, Y CrCb 4:4:4). In a media serving system, the video source (301) may be a storage device storing previously prepared video. In a videoconferencing system, the video source (301) may be a camera that captures local image information as a video sequence. Video data may be provided as a plurality of individual pictures that impart motion when viewed in sequence. The pictures themselves may be organized as a spatial array of pixels, wherein each pixel can comprise one or more samples depending on the sampling structure, color space, etc. in use. The description below focuses on samples.

[0042] According to an aspect, the video encoder (303) may code and compress the pictures of the source video sequence into a coded video sequence (343) in real time or under any other time constraints as required. Enforcing appropriate coding speed is one function of a controller (350). In some aspects, the controller (350) controls other functional units as described below and is functionally coupled to the other functional units. The coupling is not depicted for clarity. Parameters set by the controller (350) can include rate control related parameters (picture skip, quantizer, lambda value of rate-distortion optimization techniques, ... ), picture size, group of pictures (GOP) layout, maximum motion vector search range, and so forth. The controller (350) can be configured to have other suitable functions that pertain to the video encoder (303) optimized for a certain system design.

[0043] In some aspects, the video encoder (303) is configured to operate in a coding loop. As an oversimplified description, in an example, the coding loop can include a source coder (330) (e.g., responsible for creating symbols, such as a symbol stream, based on an input picture to be coded, and a reference picture(s)), and a (local) decoder (333) embedded in the video encoder (303). The decoder (333) reconstructs the symbols to create the sample data in a similar manner as a (remote) decoder also would create. The reconstructed sample stream (sample data) is input to the reference picture memory (334). As the decoding of a symbol stream leads to bit-exact results independent of decoder location (local or remote), the content in the reference picture memory (334) is also bit exact between the local encoder and remote encoder. In otherDocket No: 043380.02116 9words, the prediction part of an encoder "sees" as reference picture samples exactly the same sample values as a decoder would "see" when using prediction during decoding. This fundamental principle of reference picture synchronicity (and resulting drift, if synchronicity cannot be maintained, for example because of channel errors) is used in some related arts as well.

[0044] The operation of the "local" decoder (333) can be the same as a "remote" decoder, such as the video decoder (210), which has already been described in detail above in conjunction with FIG. 2. Briefly referring also to FIG. 2, however, as symbols are available and encoding / decoding of symbols to a coded video sequence by an entropy coder (345) and the parser (220) can be lossless, the entropy decoding parts of the video decoder (210), including the buffer memory (215), and parser (220) may not be fully implemented in the local decoder (333).

[0045] In an aspect, a decoder technology except the parsing / entropy decoding that is present in a decoder is present, in an identical or a substantially identical functional form, in a corresponding encoder. Accordingly, the disclosed subject matter focuses on decoder operation. The description of encoder technologies can be abbreviated as they are the inverse of the comprehensively described decoder technologies. In certain areas a more detail description is provided below.

[0046] During operation, in some examples, the source coder (330) may perform motion compensated predictive coding, which codes an input picture predictively with reference to one or more previously coded picture from the video sequence that were designated as "reference pictures.’7In this manner, the coding engine (332) codes differences between pixel blocks of an input picture and pixel blocks of reference picture(s) that may be selected as prediction reference(s) to the input picture.

[0047] The local video decoder (333) may decode coded video data of pictures that may be designated as reference pictures, based on symbols created by the source coder (330).Operations of the coding engine (332) may advantageously be lossy processes. When the coded video data may be decoded at a video decoder (not shown in FIG. 3), the reconstructed video sequence typically may be a replica of the source video sequence with some errors. The local video decoder (333) replicates decoding processes that may be performed by the video decoder on reference pictures and may cause reconstructed reference pictures to be stored in the reference picture memory (334). In this manner, the video encoder (303) may store copies of reconstructed reference pictures locally that have common content as the reconstructed reference pictures that will be obtained by a far-end video decoder (absent transmission errors).

[0048] The predictor (335) may perform prediction searches for the coding engine (332). That is, for anew picture to be coded, the predictor (335) may search the reference pictureDocket No: 043380.02116 10memory' (334) for sample data (as candidate reference pixel blocks) or certain metadata such as reference picture motion vectors, block shapes, and so on, that may serve as an appropriate prediction reference for the new pictures. The predictor (335) may operate on a sample block-by-pixel block basis to find appropriate prediction references. In some cases, as determined by search results obtained by the predictor (335), an input picture may have prediction references drawn from multiple reference pictures stored in the reference picture memory (334).

[0049] The controller (350) may manage coding operations of the source coder (330), including, for example, setting of parameters and subgroup parameters used for encoding the video data.

[0050] Output of all aforementioned functional units may be subjected to entropy coding in the entropy coder (345). The entropy coder (345) translates the symbols as generated by the various functional units into a coded video sequence, by applying lossless compression to the symbols according to technologies such as Huffman coding, variable length coding, arithmetic coding, and so forth.

[0051] The transmitter (340) may buffer the coded video sequence(s) as created by the entropy coder (345) to prepare for transmission via a communication channel (360), which may be a hardware / software link to a storage device which would store the encoded video data. The transmitter (340) may merge coded video data from the video encoder (303) with other data to be transmitted, for example, coded audio data and / or ancillary data streams (sources not shown).

[0052] The controller (350) may manage operation of the video encoder (303). During coding, the controller (350) may assign to each coded picture a certain coded picture ty pe, which may affect the coding techniques that may be applied to the respective picture. For example, pictures often may be assigned as one of the following picture types:

[0053] An Intra Picture (I picture) may be coded and decoded without using any other picture in the sequence as a source of prediction. Some video codecs allow for different types of intra pictures, including, for example Independent Decoder Refresh (“IDR”) Pictures.

[0054] A predictive picture (P picture) may be coded and decoded using intra prediction or inter prediction using a motion vector and reference index to predict the sample values of each block.

[0055] A bi-directionally predictive picture (B Picture) may be coded and decoded using intra prediction or inter prediction using 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 for the reconstruction of a single block.Docket No: 043380.02116 11

[0056] Source pictures commonly may be subdivided spatially into a plurality of sample blocks (for example, blocks of 4x4, 8x8. 4x8, or 16x16 samples each) and coded on a block-by-block basis. Blocks may be coded predictively with reference to other (already coded) blocks as determined by the coding assignment applied to the blocks' respective pictures. For example, blocks of I pictures may be coded non-predictively or they may be coded predictively with reference to already coded blocks of the same picture (spatial prediction or intra prediction). Pixel blocks of P pictures may be coded predictively, via spatial prediction or via temporal prediction with reference to one previously coded reference picture. Blocks of B pictures may be coded predictively, via spatial prediction or via temporal prediction wi th reference to one or two previously coded reference pictures.

[0057] The video encoder (303) may perform coding operations according to a predetermined video coding technology or standard, such as ITU-T Rec. H.265. In its operation, the video encoder (303) may perform various compression operations, including predictive coding operations that exploit temporal and spatial redundancies in the input video sequence. The coded video data, therefore, may conform to a syntax specified by the video coding technology or standard being used.

[0058] In an aspect, the transmitter (340) may transmit additional data with the encoded video. The source coder (330) may include such data as part of the coded video sequence.Additional data may comprise temporal / spatial / SNR enhancement layers, other forms of redundant data such as redundant pictures and slices, SEI messages, VUI parameter set fragments, and so on.

[0059] A video may be captured as a plurality of source pictures (video pictures) in a temporal sequence. Intra-picture prediction (often abbreviated to intra prediction) makes use of spatial correlation in a given picture, and inter-picture prediction makes uses of the (temporal or other) correlation between the pictures. In an example, a specific picture under encoding / decoding, which is referred to as a current picture, is partitioned into blocks. When a block in the current picture is similar to a reference block in a previously coded and still buffered reference picture in the video, the block in the current picture can be coded by a vector that is referred to as a motion vector. The motion vector points to the reference block in the reference picture, and can have a third dimension identifying the reference picture, in case multiple reference pictures are in use.

[0060] In some aspects, a bi-prediction technique can be used in the inter-picture prediction. According to the bi-prediction technique, two reference pictures, such as a first reference picture and a second reference picture that are both prior in decoding order to theDocket No: 043380.02116 12current picture in the video (but may be in the past and future, respectively, in display order) are used. A block in the current picture can be coded by a first motion vector that points to a first reference block in the first reference picture, and a second motion vector that points to a second reference block in the second reference picture. The block can be predicted by a combination of the first reference block and the second reference block.

[0061] Further, a merge mode technique can be used in the inter-picture prediction to improve coding efficiency.

[0062] According to some aspects of the disclosure, predictions, such as inter-picture predictions and intra-picture predictions, are performed in the unit of blocks. For example, according to the HEVC standard, a picture in a sequence of video pictures is partitioned into coding tree units (CTU) for compression, the CTUs in a picture have the same size, such as 64x64 pixels, 32x32 pixels, or 16x16 pixels. In general, a CTU includes three coding tree blocks (CTBs), which are one luma CTB and two chroma CTBs. Each CTU can be recursively quadtree split into one or multiple coding units (CUs). For example, a CTU of 64x64 pixels can be split into one CU of 64x64 pixels, or 4 CUs of 32x32 pixels, or 16 CUs of 16x16 pixels. In an example, each CU is analyzed to determine a prediction type for the CU, such as an inter prediction type or an intra prediction type. The CU is split into one or more prediction units (PUs) depending on the temporal and / or spatial predictability. Generally, each PU includes a luma prediction block (PB), and two chroma PBs. In an aspect, a prediction operation in coding (encoding / decoding) is performed in the unit of a prediction block. Using a luma prediction block as an example of a prediction block, the prediction block includes a matrix of values (e.g., luma values) for pixels, such as 8x8 pixels, 16x16 pixels, 8x16 pixels, 16x8 pixels, and the like.

[0063] It is noted that the video encoders (103) and (303), and the video decoders (110) and (210) can be implemented using any suitable technique. In an aspect, the video encoders (103) and (303) and the video decoders (110) and (210) can be implemented using one or more integrated circuits. In another aspect, the video encoders (103) and (303), and the video decoders (110) and (210) can be implemented using one or more processors that execute software instructions.

[0064] Aspects of the disclosure provide techniques on boundary gradient minimization.

[0065] According to some aspects, image and video coding standards can use a hybrid video coding framework. A hybrid video coding framework can include various modules, such as intra prediction, inter prediction, transform, quantization and in-loop filter.

[0066] According to some aspects, some video coding tools can use boundary gradients to guide the coding and hide some information (e.g., without explicitly signalling from theDocket No: 043380.02116 13encoder side to the decoder side). For example, a video coding tool of sign prediction can minimize the boundary gradient to hide sign bits.

[0067] Specifically, in an example, sample values in a current block are obtained via an inverse transform of transform coefficients. The magnitudes of one or more transform coefficients are signalled, but the signs of the one or more transform coefficients are not signalled. At the time of coding the cunent block, the neighbouring boundary samples around the current block, such as one or more rows above the current block, one or more left columns to the left of the current block and the like, are already reconstructed. In an example, the signs of the transform coefficients can be selected to minimize a boundary’ cost, such as the sum of absolute differences between the reconstructed block boundary and the neighbouring boundary samples (also referred to as the sum of absolute boundary gradients). The signs of one or more transform coefficients can be predicted, such that the reconstructed block’s boundary aligns smoothly with the already-reconstructed neighbouring boundary samples, thereby minimizing boundary discontinuities (gradients), and thus the bits needed to signal signs can be reduced.

[0068] In some examples, a confirmation bit can be signalled for the confirmation of the sign prediction of the signs for the one or more transform coefficients. For example, "T” indicates that the sign prediction of the signs is correct, and “0” indicates that the sign prediction of the signs is incorrect. In some examples, confirmation bits of blocks in a picture can be entropy coded, and continuous repeating values can be coded with high efficiency. Thus, in an example when boundary gradient is more accurately computed, the sign prediction can be better performed, and the confirmation bits can be encoded with high efficiency.

[0069] FIG. 4 shows a diagram for computing boundary gradient in a related example. At a time a current block (410) is under coding (encoding / decoding), neighbouring boundary samples 8-23 are reconstructed. In the related example, a boundary cost associated with a candidate set of signs is calculated based on a sum of absolute boundary gradients for the boundary7samples 1-7. The boundary gradient of boundary sample 1 is calculated based on reconstructed boundary7sample 1 (also referred to as predicted boundary7sample 1) under the candidate set of signs and the neighbouring boundary samples 8-9; the boundary gradient of boundary sample 2 is calculated based on reconstructed boundary sample 2 (also referred to as predicted boundary sample 2) under the candidate set of signs and the neighbouring boundary samples 10-11; the boundary7gradient of boundary' sample 3 is calculated based on reconstructed boundary sample 3 (also referred to as predicted boundary7sample 3) under the candidate set of signs and the neighbouring boundary7samples 12-13; the boundary gradient of boundary sample 4 is calculated based on reconstructed boundary sample 4 (also referred to as predicted boundary'Docket No: 043380.02116 14sample 4) under the candidate set of signs and the neighbouring boundary' samples 14-17; the boundary gradient of boundary’ sample 5 is calculated based on reconstructed boundary’ sample 5 (also referred to as predicted boundary’ sample 5) under the candidate set of signs and the neighbouring boundary’ samples 18-19; the boundary gradient of boundary sample 6 is calculated based on reconstructed boundary sample 6 (also referred to as predicted boundary' sample 6) under the candidate set of signs and the neighbouring boundary samples 20-21; the boundary¬ gradient of boundary sample 7 is calculated based on reconstructed boundary sample 7 (also referred to as predicted boundary sample 7) under the candidate set of signs and the neighbouring boundary’ samples 22-23.

[0070] Some aspects of the disclosure provide techniques for computing the boundary gradients, such as with additional or altered steps applied on input samples compared to the related example. Thus, the boundary gradients can be computed more accurately to improve the performance of the coding tools for sign prediction.

[0071] In some aspects, the direction information is considered when calculating the boundary gradient.

[0072] In an aspect, intra mode information (e.g., intra mode of the cunent block, intra mode of the neighboring block) or histogram of gradient (HoG) information (e.g., HoG of reconstructed samples in a template) can be used as the direction information for the boundary’ gradient estimation.

[0073] FIG. 5 shows an example of integer directions of intra mode defined in versatile video coding standard according to an aspect of the disclosure. Integer directions of diagonal (from bottom-left to top-right), horizontal, orthogonal diagonal (from top-left to bottom-right), vertical, and inverse diagonal (from top-right to bottom-left) are defined as intra mode 2, intra mode 18. intra mode 34, intra mode 50, intra mode 66 respectively. For different direction information, the boundary gradient can be calculated differently, for example by using samples from different locations.

[0074] FIG. 6 shows a diagram of boundary gradient computation according to an aspect of the disclosure.

[0075] In the FIG. 6 example, when the intra mode is horizontal mode (e.g., intra mode 18 in FIG. 5), the boundary gradient of sample A is estimated (calculated) as 2 x B_recon -C_recon - A_pred, where B_recon denotes the reconstructed sample value for sample B, C_recon denotes the reconstructed sample value for sample C, A_pred denotes a predicted sample value (e.g., a sum of a prediction with a residual) for sample A.Docket No: 043380.02116 15

[0076] In the FIG. 6 example, when the intra mode is diagonal mode (e.g., intra mode 2 in FIG. 5), the boundary gradient (associated with sample A) is estimated (calculated) as 2 x B’_recon - C’_recon - A_pred, where B’_recon denotes the reconstructed sample value for sample B’, C’_recon denotes the reconstructed sample value for sample C’, A_pred denotes a predicted sample value (e.g., a sum of a prediction with a residual) for sample A.

[0077] In some examples, the direction information can be derived, such as using decoder side intra mode derivation (D1MD) operation to determine the direction information.

[0078] In some examples, the number of maximal considered directions is pre-defined. For example, only the five directions as shown in FIG. 5 are allowed in an example. When an intra mode is not one of the pre-defined directions / intra modes, the intra mode is quantized to the closest integer direction in the predefined directions / intra modes.

[0079] In an aspect, when the direction is horizontal / vertical, only the boundary gradient from leftColumn / topRow is used. In an example that the boundary gradient is computed for sign prediction, only the leftColumn’s gradient is used when the direction is horizontal regardless of the existence of topRow. In an example, when the direction information indicates horizontal direction, only the boundary gradients for the boundary samples 1-4 in FIG. 4 are calculated and used to compute a boundary cost. In another example, when the direction information indicates vertical direction, only the boundary' gradients for the boundary' samples 5-8 in FIG. 4 are calculated and used to compute a boundary' cost.

[0080] In some aspects, a gradient filter with more taps can be used for boundary gradient estimation. In an example, a 5x5 Sobel filter is used for the boundary gradient estimation. In some examples, the gradient filter with same filter coefficients is used on the suitable sample positions. In some examples, the gradient filter with different filter coefficients can be used on different sample positions, thus gradient directions for different samples can be different.

[0081] In some aspects, the gradient minimization direction is the non-linear extension of current direction. In an example, when an edge is detected, the gradient minimization direction can be based on the direction of current edge. For example, the boundary gradient is calculated according to the non-linear extension of the current direction, and the calculated boundary gradients are used to predict the signs that minimize the boundary cost (the boundary cost is calculated based on the calculated boundary gradients).

[0082] FIG. 7 shows an example of non-linear direction for boundary' gradient computation according to an aspect of the disclosure. In the FIG. 7 example, an edge (701) in the local region is detected, the edge (701) has a shape of an arc. The gradient minimization direction can follow the edge (701) to minimize the difference. For example, the boundaryDocket No: 043380.02116 16gradient (associated with sample A) is estimated (calculated) as 2 * B’_recon - C’'_recon -A_pred, where B'_recon denotes the reconstructed sample value for sample B’, C”_recon denotes the reconstructed sample value for sample C”, A_pred denotes a predicted sample value for sample A (e.g., a sum of a prediction value and a residual value at sample A).

[0083] In some aspects, the input (e.g., reconstructed neighboring samples) for the boundary gradient estimation can be filtered before the gradient calculation.

[0084] In an example, a gaussian filter is applied to remove some noise.

[0085] In another example, whether to filter the boundary or not is based on a flag that is signaled inTU / CU / Slice / Tile / Picture etc. level.

[0086] In another example, whether to filter the boundary or not is inferred from the information available. In an example, whether to filter the boundary for the current block is determined (inherited) based on whether filtering is applied to a neighboring block of the current block in the boundary gradient calculation.

[0087] In some examples, the filter ty pe is selected from a filter candidate list. In an example, the filter selection is signaled based on an index signaled in TU / CU / Slice / Tile / Picture etc. level. In another example, the filter selection is inferred from the information available. In an example, the filter selection for current block is inferred (inherited) from a filter selection for a neighboring block of the current block.

[0088] In some aspects, interpolation filters are used on the boundary for the gradient calculation. In an example, a bilinear filter is used for fractional position. In some examples, when the direction of the boundary' gradient (also referred to as calculation direction of boundary' gradient, minimization direction of boundary gradient) is not vertical direction nor horizontal direction, the available sample data may not be on the integer positions along the direction, the sample data can be scaled for the boundary gradient calculation. In some examples, interpolation filters, such as a bilinear filter, are used to scale the sample data to the integer position along the direction of the boundary' gradient.

[0089] In some aspects, the current block can be either predicted block or reconstructed block. In some examples, the current block is the predicted block that is a combination of a prediction block and a residual block, and coding tools that are based on boundary gradient minimization are applied to generate the current block. In some examples, the coding tools that are based on boundary' gradient minimization are applied on an intermediate reconstructed block to generate a modified reconstructed block.

[0090] In some aspects, whether to apply the boundary gradient estimation techniques in the present disclosure can be based a flag signaled in TU / CU / Slice / Tile / Picture etc. level.Docket No: 043380.02116 17

[0091] In some aspects, whether to apply boundary gradient estimation techniques in the present disclosure can be based on information inferred from decoder. In an example, when the boundary gradient values calculated according to the related example are too large (e.g., larger than a threshold), the boundary gradient estimation techniques in the present disclosure are inferred to be applied. In another example, whether to apply boundary gradient estimation techniques in the present disclosure is determined based on block size.

[0092] FIG. 8 shows a flow chart outlining a process (800) according to an aspect of the disclosure. The process (800) can be used in a video decoder. In various aspects, the process (800) is executed by processing circuitry', such as the processing circuitry' that performs functions of the video decoder (110), the processing circuitry that performs functions of the video decoder (210), and the like. In some aspects, the process (800) is implemented in software instructions, thus when the processing circuitry executes the software instructions, the processing circuitry performs the process (800). The process starts at (S801) and proceeds to (S810).

[0093] At (S810), a bitstream is received. The bitstream includes coded information of a sequence of pictures in a video.

[0094] At (S820), to apply a coding tool on a current block in a current picture in the sequence of pictures is determined, the coding tool is based on boundary gradient computation.

[0095] At (S830), direction information of the current block is determined.

[0096] At (S840), at least a boundary' gradient associated with a sample is computed based on the direction information of the current block

[0097] At (S850), a reconstructed block of the current block is generated by applying the coding tool that is based on at least the boundary gradient associated with the sample.

[0098] According to an aspect of the disclosure, the direction information of the current block can include at least one of an intra prediction mode of the current block; an intra prediction mode that is derived by a decoder side intra mode derivation (DIMD) operation; histogram of gradient information that is obtained from a template of the current block; and histogram of gradient information that is obtained from a prediction block of the current block.

[0099] According to an aspect, positions of one or more neighboring samples for computing the boundary gradient associated with the sample are determined based on the direction information. In some examples, the positions of the one or more neighboring samples are determined along an extension line from the sample, the extension line extending according to the direction information.Docket No: 043380.02116 18

[0100] In some examples, the direction information is limited to one of a plurality of predefined directions. When a direction is not one of the plurality of predefined directions, the direction is quantized to a closest predefined direction in the plurality of predefined directions.

[0101] In some examples, a boundary cost of the current block is calculated based on boundary gradients of samples in a top row of the current block when the direction information of the current block indicates a vertical direction. Also, in some examples, a boundary cost of the current block is calculated based on boundary gradients of samples in a left column of the current block when the direction information of the current block indicates a horizontal direction.

[0102] According to an aspect, to compute the boundary gradient, a gradient filter with more than 3 taps is applied on the sample to compute the boundary gradient. In an example, the gradient filter comprises a 5x5 Sobel filter.

[0103] According to an aspect, the direction information indicates a direction at the sample and a gradient minimization direction that is a non-linear extension of the direction. The boundary gradient of the sample is computed according to samples along the non-linear extension of the direction.

[0104] According to an aspect, a filter is applied to input data for computing the boundary7gradient. In some examples, the filter includes at least one of a Gaussian filter, an interpolation filter, and a bilinear filter.

[0105] In an example, a flag is decoded from the bitstream, the flag indicates whether to apply the filter for computing the boundary gradient. In another example, whether to apply the filter for computing the boundary gradient is inferred from available information of the current block.

[0106] In some examples, a filter type for the filter is selected from a filter candidate list. In an example, the filter type is selected according to an index signal that is decoded from the bitstream. In another example, the filter t pe is inferred from decoded information available for the current block.

[0107] In some examples, the coding tool is applied during a reconstruction of the current block based on a prediction block and a residual block. In some examples, the coding tool is applied to an intermediate reconstructed block to generate the reconstructed block.

[0108] In an example, a flag is decoded from the bitstream, the flag indicates whether to use the direction information for computing the boundary7gradient. In another example, whether to use the direction information for computing the boundary7gradient is inferred from available information.

[0109] Then, the process proceeds to (S899) and terminates.Docket No: 043380.02116 19

[0110] The process (800) can be suitably adapted. Step(s) in the process (800) can be modified and / or omitted. Additional step(s) can be added. Any suitable order of implementation can be used.[OHl] FIG. 9 shows a flow chart outlining a process (900) according to an aspect of the disclosure. The process (900) can be used in a video encoder. In various aspects, the process (900) is executed by processing circuitry’, such as the processing circuitry that performs functions of the video encoder (103), the processing circuitry that performs functions of the video encoder (303), and the like. In some aspects, the process (900) is implemented in software instructions, thus when the processing circuitry’ executes the software instructions, the processing circuitry’ performs the process (900). The process starts at (S901) and proceeds to (S910).

[0112] At (S910), to apply a coding tool on a current block in a current picture within a sequence of pictures of a video is determined, the coding tool is based on boundary’ gradient computation.

[0113] At (S920), direction information of the current block is determined.

[0114] At (S930), at least a boundary gradient associated with a sample is computed based on the direction information of the current block

[0115] At (S940), the current block is encoded into coded information in a bitstream by applying the coding tool that is based on at least the boundary’ gradient associated with the sample.

[0116] According to an aspect of the disclosure, the direction information of the current block can include at least one of an intra prediction mode of the current block; an intra prediction mode that is derived by a decoder side intra mode derivation (DIMD) operation; histogram of gradient information that is obtained from a template of the current block; and histogram of gradient information that is obtained from a prediction block of the current block.

[0117] According to an aspect, positions of one or more neighboring samples for computing the boundary gradient associated with the sample are determined based on the direction information. In some examples, the positions of the one or more neighboring samples are determined along an extension line from the sample, the extension line extending according to the direction information.

[0118] In some examples, the direction information is limited to one of a plurality of predefined directions. When a direction is not one of the plurality' of predefined directions, the direction is quantized to a closest predefined direction in the plurality of predefined directions.

[0119] In some examples, a boundary cost of the current block is calculated based on boundary gradients of samples in a top row of the current block when the direction informationDocket No: 043380.02116 20of the current block indicates a vertical direction. Also, in some examples, a boundary cost of the current block is calculated based on boundary gradients of samples in a left column of the current block when the direction information of the current block indicates a horizontal direction.

[0120] According to an aspect, to compute the boundary gradient, a gradient filter with more than 3 taps is applied on the sample to compute the boundary gradient. In an example, the gradient filter comprises a 5x5 Sobel filter.

[0121] According to an aspect, the direction information indicates a direction at the sample and a gradient minimization direction that is a non-linear extension of the direction. The boundary' gradient of the sample is computed according to samples along the non-linear extension of the direction.

[0122] According to an aspect, a filter is applied to input data for computing the boundary gradient. In some examples, the filter includes at least one of a gaussian filter, an interpolation filter, and a bilinear filter.

[0123] In an example, a flag is encoded into the bitstream, the flag indicates whether to apply the filter for computing the boundary gradient.

[0124] In some examples, a filter type for the filter is selected from a filter candidate list. In an example, an index signal that indicates the filter ty pe is encoded into the bitstream.

[0125] In some examples, the coding tool is applied during a reconstruction of the current block based on a prediction block and a residual block. In some examples, the coding tool is applied to an intermediate reconstructed block to generate the reconstructed block.

[0126] In an example, a flag is encoded into the bitstream, the flag indicates whether to use the direction information for computing the boundary' gradient.

[0127] Then, the process proceeds to (S999) and terminates.

[0128] The process (900) can be suitably adapted. Step(s) in the process (900) can be modified and / or omitted. Additional step(s) can be added. Any suitable order of implementation can be used.

[0129] According to an aspect of the disclosure, a method of processing visual media data is provided. In the method, a conversion between a visual media file and a bitstream of visual media data is performed according to a format rule. For example, the bitstream may be a bitstream that is decoded / en coded in any of the decoding and / or encoding methods described herein. The format rule may specify one or more constraints of the bitstream and / or one or more processes to be performed by the decoder and / or encoder.

[0130] The techniques described above, can be implemented as computer software using computer-readable instructions and physically stored in one or more computer-readable media.Docket No: 043380.02116 21For example, FIG. 10 shows a computer system (1000) suitable for implementing certain aspects of the disclosed subject matter.

[0131] The computer software can be coded using any suitable machine code or computer language, that may be subject to assembly, compilation, linking, or like mechanisms to create code comprising instructions that can be executed directly, or through interpretation, micro-code execution, and the like, by one or more computer central processing units (CPUs), Graphics Processing Units (GPUs), and the like.

[0132] The instructions can be executed on various types of computers or components thereof, including, for example, personal computers, tablet computers, servers, smartphones, gaming devices, internet of things devices, and the like.

[0133] The components shown in FIG. 10 for computer system (1000) are examples and are not intended to suggest any limitation as to the scope of use or functionality of the computer software implementing aspects of the present disclosure. Neither should the configuration of components be interpreted as having any dependency or requirement relating to any one or combination of components illustrated in the example aspect of computer system (1000).

[0134] Computer system (1000) may include certain human interface input devices. Such a human interface input device may be responsive to input by one or more human users through, for example, tactile input (such as: keystrokes, swipes, data glove movements), audio input (such as: voice, clapping), visual input (such as: gestures), olfactory input (not depicted). The human interface devices can also be used to capture certain media not necessarily directly related to conscious input by a human, such as audio (such as: speech, music, ambient sound), images (such as: scanned images, photographic images obtain from a still image camera), video (such as two-dimensional video, three-dimensional video including stereoscopic video).

[0135] Input human interface devices may include one or more of (only one of each depicted): keyboard (1001), mouse (1002), trackpad (1003), touch screen (1010), data-glove (not shown), joystick (1005), microphone (1006), scanner (1007), camera (1008).

[0136] Computer system (1000) may also include certain human interface output devices. Such human interface output devices may be stimulating the senses of one or more human users through, for example, tactile output, sound, light, and smell / taste. Such human interface output devices may include tactile output devices (for example tactile feedback by the touch-screen (1010), data-glove (not shown), or joystick (1005), but there can also be tactile feedback devices that do not serve as input devices), audio output devices (such as: speakers (1009), headphones (not depicted)), visual output devices (such as screens (1010) to include CRT screens, LCD screens, plasma screens, OLED screens, each with or without touch-screen input capability, eachDocket No: 043380.02116 22with or without tactile feedback capability — some of which may be capable to output two dimensional visual output or more than three dimensional output through means such as stereographic output; virtual -reality glasses (not depicted), holographic displays and smoke tanks (not depicted)), and printers (not depicted).

[0137] Computer system (1000) can also include human accessible storage devices and their associated media such as optical media including CD / DVD ROM / RW (1020) with CD / DVD or the like media (1021), thumb-dnve (1022), removable hard drive or solid state drive (1023), legacy magnetic media such as tape and floppy disc (not depicted), specialized ROM / ASIC / PLD based devices such as security dongles (not depicted), and the like.

[0138] Those skilled in the art should also understand that term “computer readable media” as used in connection with the presently disclosed subject matter does not encompass transmission media, carrier waves, or other transitory signals.

[0139] Computer system (1000) can also include an interface (1054) to one or more communication networks (1055). Networks can for example be wireless, wireline, optical. Networks can further be local, wide-area, metropolitan, vehicular and industrial, real-time, delay-tolerant, and so on. Examples of networks include local area networks such as Ethernet, wireless LANs, cellular networks to include GSM, 3G, 4G, 5G, LTE and the like, TV wireline or wireless wide area digital networks to include cable TV, satellite TV, and terrestrial broadcast TV, vehicular and industrial to include CANBus, and so forth. Certain netw orks commonly require external network interface adapters that attached to certain general purpose data ports or peripheral buses (1049) (such as, for example USB ports of the computer system (1000)); others are commonly integrated into the core of the computer system (1000) by attachment to a system bus as described below (for example Ethernet interface into a PC computer system or cellular network interface into a smartphone computer system). Using any of these networks, computer system (1000) can communicate with other entities. Such communication can be uni-directional, receive only (for example, broadcast TV), uni-directional send-only (for example CANbus to certain CANbus devices), or bi-directional, for example to other computer systems using local or wide area digital networks. Certain protocols and protocol stacks can be used on each of those networks and network interfaces as described above.

[0140] Aforementioned human interface devices, human-accessible storage devices, and netw ork interfaces can be attached to a core (1040) of the computer system (1000).

[0141] The core (1040) can include one or more Central Processing Units (CPU) (1041), Graphics Processing Units (GPU) (1042), specialized programmable processing units in the form of Field Programmable Gate Areas (FPGA) (1043), hardware accelerators for certain tasksDocket No: 043380.02116 23(1044), graphics adapters (1050), and so forth. These devices, along with Read-only memory (ROM) (1045). Random-access memory (1046), internal mass storage such as internal non-user accessible hard drives, SSDs, and the like (1047), may be connected through a system bus (1048). In some computer systems, the system bus (1048) can be accessible in the form of one or more physical plugs to enable extensions by additional CPUs, GPU, and the like. The peripheral devices can be attached either directly to the core's system bus (1048), or through a peripheral bus (1049). In an example, the screen (1010) can be connected to the graphics adapter (1050). Architectures for a peripheral bus include PCI, USB, and the like.

[0142] CPUs (1041), GPUs (1042), FPGAs (1043), and accelerators (1044) can execute certain instructions that, in combination, can make up the aforementioned computer code. That computer code can be stored in ROM (1045) or RAM (1046). Transitional data can also be stored in RAM (1046), whereas permanent data can be stored for example, in the internal mass storage (1047). Fast storage and retrieve to any of the memory devices can be enabled through the use of cache memory, that can be closely associated with one or more CPU (1041), GPU (1042). mass storage (1047). ROM (1045), RAM (1046), and the like.

[0143] The computer readable media can have computer code thereon for performing various computer-implemented operations. The media and computer code can be those specially designed and constructed for the purposes of the present disclosure, or they can be of the kind well known and available to those having skill in the computer software arts.

[0144] As an example and not by way of limitation, the computer system having architecture (1000), and specifically the core (1040) can provide functionality as a result of processor(s) (including CPUs, GPUs, FPGA, accelerators, and the like) executing software embodied in one or more tangible, computer-readable media. Such computer-readable media can be media associated with user-accessible mass storage as introduced above, as well as certain storage of the core (1040) that are of non-transitory nature, such as core-internal mass storage (1047) or ROM (1045). The software implementing various aspects of the present disclosure can be stored in such devices and executed by core (1040). A computer-readable medium can include one or more memory devices or chips, according to particular needs. The software can cause the core (1040) and specifically the processors therein (including CPU. GPU, FPGA, and the like) to execute particular processes or particular parts of particular processes described herein, including defining data structures stored in RAM (1046) and modifying such data structures according to the processes defined by the software. In addition or as an alternative, the computer system can provide functionality as a result of logic hardwired or otherwise embodied in a circuit (for example: accelerator (1044)), which can operate in place of or together withDocket No: 043380.02116 24software to execute particular processes or particular parts of particular processes described herein. Reference to software can encompass logic, and vice versa, where appropriate.Reference to a computer-readable media can encompass a circuit (such as an integrated circuit (IC)) storing software for execution, a circuit embodying logic for execution, or both, where appropriate. The present disclosure encompasses any suitable combination of hardware and software.

[0145] The use of “at least one of’ or “one of’ in the disclosure is intended to include any one or a combination of the recited elements. For example, references to at least one of A, B, or C; at least one of A, B, and C; at least one of A, B, and / or C; and at least one of A to C are intended to include only A, only B, only C or any combination thereof. References to one of A or B and one of A and B are intended to include A or B or (A and B). The use of “one of’ does not preclude any combination of the recited elements when applicable, such as when the elements are not mutually exclusive.

[0146] While this disclosure has described several examples of aspects, there are alterations, permutations, and various substitute equivalents, which fall within the scope of the disclosure. It will thus be appreciated that those skilled in the art will be able to devise numerous systems and methods which, although not explicitly shown or described herein, embody the principles of the disclosure and are thus within the spirit and scope thereof.

[0147] The above disclosure also encompasses the features noted below. The features can be combined in various manners and are not limited to the combinations noted below.

[0148] (1). A method of video decoding, including: receiving a bitstream including coded information of a sequence of pictures in a video; determining that a coding tool that is based on boundary gradient computation is to be applied on a current block in a current picture in the sequence of pictures; determining direction information of the current block; computing at least a boundary gradient associated with a sample based on the direction information of the current block; and generating a reconstructed block of the current block by applying the coding tool that is based on at least the boundary gradient associated with the sample.

[0149] (2). The method of feature (1), in which the direction information of the current block includes at least one of: an intra prediction mode of the cunent block; an intra prediction mode that is derived by a decoder side intra mode derivation (DIMD) operation; histogram of gradient information that is obtained from a template of the current block; and histogram of gradient information that is obtained from a prediction block of the current block.Docket No: 043380.02116 25

[0150] (3). The method of any of features (1) to (2), in which the computing the boundary gradient includes: determining positions of one or more neighboring samples for computing the boundary gradient associated with the sample based on the direction information.

[0151] (4). The method of any of features (1) to (3), in which the determining the positions includes: determining the positions of the one or more neighboring samples along an extension line from the sample, the extension line extending according to the direction information.

[0152] (5). The method of any of features (1) to (4), in which the direction information is limited to one of a plurality of predefined directions, and the determining the direction information includes: quantizing a direction to a closest predefined direction in the plurality of predefined directions.

[0153] (6). The method of any of features (1) to (5), further including: computing a boundary cost of the current block based on boundary gradients of samples in a top row of the current block when the direction information of the current block indicates a vertical direction; and computing the boundary cost of the current block based on boundary gradients of samples in a left column of the current block when the direction information of the current block indicates a horizontal direction.

[0154] (7). The method of any of features (1) to (6), in which the computing the boundary gradient includes: applying a gradient filter with more than 3 taps on the sample to compute the boundary gradient.

[0155] (8). The method of any of features (1) to (7), in which the gradient filter includes a 5^5 Sobel filter.

[0156] (9). The method of any of features (1) to (8), in which the direction information indicates a direction at the sample and a gradient minimization direction that is a non-hnear extension of the direction, and the computing the boundary gradient includes: computing the boundary gradient of the sample according to sample values along the non-hnear extension of the direction.

[0157] (10). The method of any of features (1) to (9), in which the computing the boundary gradient includes: applying a filter to input data for computing the boundary gradient.

[0158] (11). The method of any of features (1) to (10), in which the filter includes at least one of: a Gaussian filter; an interpolation filter; and a bilinear filter.

[0159] (12). The method of any of features (1) to (11), further including at least one of: decoding a flag from the bitstream, the flag indicating whether to apply the filter for computingDocket No: 043380.02116 26the boundary gradient; and inferring whether to apply the filter for computing the boundary' gradient.

[0160] (13). The method of any of features (1) to (12), further including: selecting a filter type for the filter from a filter candidate list.

[0161] (14). The method of any of features (1) to (13), in which the selecting includes at least one of: selecting the filter type according to an index signal that is decoded from the bitstream; and inferring the filter type from decoded information available for the current block.

[0162] (15). The method of any of features (1) to (14), in which the generating the reconstructed block includes at least one of: applying the coding tool during a reconstruction of the current block based on a prediction block and a residual block; and applying the coding tool to an intermediate reconstructed block to generate the reconstructed block.

[0163] (16). The method of any of features (1) to (15), further including at least one of: decoding a flag from the bitstream, the flag indicating whether to use the direction information for computing the boundary gradient; and inferring whether to use the direction information for computing the boundary gradient.

[0164] (17). A method of video encoding, including: determining to apply a coding tool on a current block in a current picture within a sequence of pictures of a video, the coding tool being based on boundary' gradient computation; determining direction information of the current block; computing at least a boundary gradient associated with a sample based on the direction information of the current block: and encoding the current block into coded information in a bitstream by applying the coding tool that is based on at least the boundary gradient associated with the sample.

[0165] (18). The method of feature (17), in which the direction information of the current block includes at least one of: an intra prediction mode of the cunent block; an intra prediction mode that is derived by a decoder side intra mode derivation (DIMD) operation; histogram of gradient information that is obtained from a template of the current block; and histogram of gradient information that is obtained from a prediction block of the current block.

[0166] (19). The method of any of features (17) to (18), in which the computing the boundary gradient includes: determining positions of one or more neighboring samples for computing the boundary gradient associated with the sample based on the direction information.

[0167] (20). The method of any of features (17) to (19), in which the determining the positions includes: determining the positions of the one or more neighboring samples along an extension line from the sample, the extension line extending according to the direction information.Docket No: 043380.02116 27

[0168] (21). The method of any of features (17) to (20), in which the direction information is limited to one of a plurality of predefined directions, and the determining the direction information includes: quantizing a direction to a closest predefined direction in the plurality of predefined directions.

[0169] (22). The method of any of features (17) to (21), further including: computing a boundary cost of the cunent block based on boundary gradients of samples in a top row of the current block when the direction information of the current block indicates a vertical direction; and computing the boundary cost of the current block based on boundary gradients of samples in a left column of the current block when the direction information of the current block indicates a horizontal direction.

[0170] (23). The method of any of features (17) to (22). in which the computing the boundary gradient includes: applying a gradient filter with more than 3 taps on the sample to compute the boundary gradient.

[0171] (24). The method of any of features (17) to (23), in which the gradient filter includes a 5x5 Sobel filter.

[0172] (25). The method of any of features (17) to (24), in which the direction information indicates a direction at the sample and a gradient minimization direction that is a non-linear extension of the direction, and the computing the boundary gradient includes: computing the boundary gradient of the sample according to sample values along the non-linear extension of the direction.

[0173] (26). The method of any of features (17) to (25), in which the computing the boundary gradient includes: applying a filter to input data for computing the boundary gradient.

[0174] (27). The method of any of features (17) to (26), in which the filter includes at least one of: a gaussian filter; an interpolation filter; and a bilinear filter.

[0175] (28). The method of any of features (17) to (27), further including: encoding a flag into the bitstream, the flag indicating whether to apply the filter for computing the boundary gradient.

[0176] (29). The method of any of features (17) to (28), further including: selecting a filter type for the filter from a filter candidate list.

[0177] (30). The method of any of features (17) to (29), in which the selecting includes at least one of: encoding an index signal into the bitstream, the index signal indicating the filter type in the filter candidate list.

[0178] (31). The method of any of features (17) to (30). further including at least one of: applying the coding tool during a reconstruction of the current block based on a predictionDocket No: 043380.02116 28block and a residual block: and applying the coding tool to an intermediate reconstructed block to generate a tuned reconstructed block.

[0179] (32). The method of any of features (17) to (31), further including at least one of: encoding a flag into the bitstream, the flag indicating whether to use the direction information for computing the boundary gradient.

[0180] (33). A non-transitory computer-readable storage medium storing instructions which when executed by a processor cause the processor to perform an encoding method, the encoding method including: determining to apply a coding tool on a current block in a current picture within a sequence of pictures of a video, the coding tool being based on boundary' gradient computation; determining direction information of the current block; computing at least a boundary gradient associated with a sample based on the direction information of the current block; encoding the current block into coded information in a bitstream by applying the coding tool that is based on at least the boundary gradient associated with the sample; and transmitting the bitstream.

[0181] (34). An apparatus for video decoding, including processing circuitry that is configured to perform the method of any of features (1) to (16).

[0182] (35). An apparatus for video encoding, including processing circuitry that is configured to perform the method of any of features (17) to (32).

[0183] (36). A non- transitory' computer-readable storage medium storing instructions which when executed by at least one processor cause the at least one processor to perform the method of any of features (1) to (32).

Claims

Docket No: 043380.02116 29WHAT IS CLAIMED IS:

1. A method of video decoding, comprising:receiving a bitstream comprising coded information of a sequence of pictures in a video; determining that a coding tool is to be applied on a current block in a current picture in the sequence of pictures, the coding tool being based on boundary gradient computation;determining direction information of the current block;computing at least a boundary gradient associated with a sample based on the direction information of the current block; andgenerating a reconstructed block of the current block by applying the coding tool that is based on at least the boundary gradient associated with the sample.

2. The method of claim 1, wherein the direction information of the current block comprises at least one of:an intra prediction mode of the current block;an intra prediction mode that is derived by a decoder side intra mode derivation (DIMD) operation;histogram of gradient information that is obtained from a template of the current block; andhistogram of gradient information that is obtained from a prediction block of the current block.

3. The method of claim 1, wherein the computing the boundary' gradient comprises: determining positions of one or more neighboring samples for computing the boundary gradient associated with the sample based on the direction information.

4. The method of claim 3. wherein the determining the positions comprises: determining the positions of the one or more neighboring samples along an extension line from the sample, the extension line extending according to the direction information.

5. The method of any one of claims 1 to 4, wherein the direction information is limited to one of a plurality of predefined directions, and the determining the direction information comprises:quantizing a direction to a closest predefined direction in the plurality of predefined directions.Docket No: 043380.02116 306. The method of any one of claims 1 to 5, further comprising:computing a boundary cost of the current block based on boundary gradients of samples in a top row of the cunent block when the direction information of the current block indicates a vertical direction; andcomputing the boundary7cost of the current block based on boundary7gradients of samples in a left column of the current block when the direction information of the current block indicates a horizontal direction.

7. The method of any one of claims 1 to 6, wherein the computing the boundary gradient comprises:applying a gradient filter with more than 3 taps on the sample to compute the boundary gradient.

8. The method of claim 7. wherein the gradient filter comprises a 5 *5 Sobel filter.

9. The method of any one of claims 1 to 8, wherein the direction information indicates a direction at the sample and a gradient minimization direction that is a non-linear extension of the direction, and the computing the boundary gradient comprises:computing the boundary gradient of the sample according to sample values along the nonlinear extension of the direction.

10. The method of any one of claims 1 to 9, wherein the computing the boundary gradient comprises:applying a filter to input data for computing the boundary gradient.

11. The method of claim 10, wherein the filter comprises at least one of:a gaussian filter;an interpolation filter; anda bilinear filter.

12. The method of claim 10, further comprising at least one of:decoding a flag from the bitstream, the flag indicating whether to apply the filter for computing the boundary gradient; andinferring whether to apply the filter for computing the boundary7gradient.Docket No: 043380.02116 3113. The method of claim 10, further comprising:selecting a filter type for the filter from a filter candidate list.

14. A method of video encoding, comprising:determining to apply a coding tool on a current block in a current picture within a sequence of pictures of a video, the coding tool being based on boundary gradient computation;determining direction information of the current block;computing at least a boundary gradient associated with a sample based on the direction information of the current block; andencoding the current block into coded information in a bitstream by applying the coding tool that is based on at least the boundary gradient associated with the sample.

15. A non-transitory computer-readable storage medium storing instructions which when executed by a processor cause the processor to perform an encoding method, the encoding method comprising:determining to apply a coding tool on a current block in a current picture \\ i thin a sequence of pictures of a video, the coding tool being based on boundary7gradient computation;determining direction information of the current block;computing at least a boundary gradient associated with a sample based on the direction information of the current block;encoding the current block into coded information in a bitstream by applying the coding tool that is based on at least the boundary7gradient associated with the sample; and transmitting the bitstream.

Images