WO2020049512A1 - Inter-prédiction en deux étapes - Google Patents

Inter-prédiction en deux étapes Download PDF

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Publication number
WO2020049512A1
WO2020049512A1 PCT/IB2019/057520 IB2019057520W WO2020049512A1 WO 2020049512 A1 WO2020049512 A1 WO 2020049512A1 IB 2019057520 W IB2019057520 W IB 2019057520W WO 2020049512 A1 WO2020049512 A1 WO 2020049512A1
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motion
block
current block
motion vector
prediction
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PCT/IB2019/057520
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English (en)
Inventor
Hongbin Liu
Li Zhang
Kai Zhang
Yue Wang
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Beijing Bytedance Network Technology Co., Ltd.
Bytedance Inc.
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Publication of WO2020049512A1 publication Critical patent/WO2020049512A1/fr

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
    • H04N19/10—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding
    • H04N19/134—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding characterised by the element, parameter or criterion affecting or controlling the adaptive coding
    • H04N19/157—Assigned coding mode, i.e. the coding mode being predefined or preselected to be further used for selection of another element or parameter
    • H04N19/159—Prediction type, e.g. intra-frame, inter-frame or bidirectional frame prediction
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
    • H04N19/50—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using predictive coding
    • H04N19/503—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using predictive coding involving temporal prediction
    • H04N19/51—Motion estimation or motion compensation
    • H04N19/523—Motion estimation or motion compensation with sub-pixel accuracy
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
    • H04N19/10—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding
    • H04N19/102—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding characterised by the element, parameter or selection affected or controlled by the adaptive coding
    • H04N19/103—Selection of coding mode or of prediction mode
    • H04N19/109—Selection of coding mode or of prediction mode among a plurality of temporal predictive coding modes
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
    • H04N19/10—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding
    • H04N19/102—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding characterised by the element, parameter or selection affected or controlled by the adaptive coding
    • H04N19/117—Filters, e.g. for pre-processing or post-processing
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
    • H04N19/10—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding
    • H04N19/102—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding characterised by the element, parameter or selection affected or controlled by the adaptive coding
    • H04N19/119—Adaptive subdivision aspects, e.g. subdivision of a picture into rectangular or non-rectangular coding blocks
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
    • H04N19/10—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding
    • H04N19/169—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding characterised by the coding unit, i.e. the structural portion or semantic portion of the video signal being the object or the subject of the adaptive coding
    • H04N19/17—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding characterised by the coding unit, i.e. the structural portion or semantic portion of the video signal being the object or the subject of the adaptive coding the unit being an image region, e.g. an object
    • H04N19/176—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding characterised by the coding unit, i.e. the structural portion or semantic portion of the video signal being the object or the subject of the adaptive coding the unit being an image region, e.g. an object the region being a block, e.g. a macroblock
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
    • H04N19/50—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using predictive coding
    • H04N19/503—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using predictive coding involving temporal prediction
    • H04N19/51—Motion estimation or motion compensation
    • H04N19/513—Processing of motion vectors
    • H04N19/517—Processing of motion vectors by encoding
    • H04N19/52—Processing of motion vectors by encoding by predictive encoding
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
    • H04N19/50—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using predictive coding
    • H04N19/503—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using predictive coding involving temporal prediction
    • H04N19/51—Motion estimation or motion compensation
    • H04N19/537—Motion estimation other than block-based
    • H04N19/54—Motion estimation other than block-based using feature points or meshes
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
    • H04N19/50—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using predictive coding
    • H04N19/503—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using predictive coding involving temporal prediction
    • H04N19/51—Motion estimation or motion compensation
    • H04N19/577—Motion compensation with bidirectional frame interpolation, i.e. using B-pictures
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
    • H04N19/50—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using predictive coding
    • H04N19/59—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using predictive coding involving spatial sub-sampling or interpolation, e.g. alteration of picture size or resolution
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
    • H04N19/70—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals characterised by syntax aspects related to video coding, e.g. related to compression standards

Definitions

  • This patent document relates to video coding techniques, devices and systems.
  • Devices, systems and methods related to digital video coding, and specifically, motion refinement based on updated motion vectors that are generated based on two-step inter prediction are described.
  • the described methods may be applied to both the existing video coding standards (e.g., High Efficiency Video Coding (HEVC)) and future video coding standards or video codecs.
  • HEVC High Efficiency Video Coding
  • a video processing method comprising: determining original motion information for a current block; scaling original motion vectors of the original motion information and derived motion vectors derived based on the original motion vectors to a same target precision; generating updated motion vectors from the scaled original and derived motion vectors; and performing a conversion between the current block and the bitstream representation of a video including the current block, based on the updated motion vectors.
  • a video processing method comprising: determining original motion information for a current block; updating original motion vectors of the original motion information for the current block based on a refining method; clipping the updated motion vectors to be within a range; and performing a conversion between the current block and a bitstream representation of a video including the current block, based on the clipped updated motion vectors.
  • the disclosed technology may be used to provide a method for video processing, comprising: determining original motion information associated with a current block; generating updated motion information based on specific prediction mode; and performing, based on the updated motion information, a conversion between the current block and a bitstream representation of a video data including the current block, wherein the specific prediction mode includes one or more of bi-directional optical flow (BIO) refinement, a decoder-side motion vector refinement (DMVR), frame-rate up conversion (FRUC) techniques or a template matching technique.
  • BIO bi-directional optical flow
  • DMVR decoder-side motion vector refinement
  • FRUC frame-rate up conversion
  • a video processing method comprising: determining a motion vector difference (MVD) precision for a current block processed with affine mode from an MVD precision set; performing, based on the determined MVD precision, a conversion between the current block and a bitstream representation of a video including the current block.
  • MVD motion vector difference
  • a video processing method comprising: determining non-updated motion information associated with a current block;
  • DMVD decoder-side motion vector derivation
  • a video processing method comprising: generating, for a current block, intermediate predictions based on a first motion information associated with the current block; updating the first motion information to a second motion information based on the intermediate predictions; and generating a final prediction for the current block based on the second motion information.
  • the disclosed technology may be used to provide a method for video coding.
  • This method includes receiving a bitstream representation of a current block of video data, generating updated first and second reference motion vectors based on a weighted sum of a first scaled motion vector and first and second scaled reference motion vectors, respectively, where a first motion vector is derived based on a first reference motion vector from a first reference block and a second reference motion vector from a second reference block, where the current block is associated with the first and second reference blocks with the first scaled motion vector being generated by scaling the first motion vector to a target precision, and the first and second scaled reference motion vectors being generated by scaling the first and second reference motion vectors to the target precision, respectively, and processing the bitstream representation based on the updated first and second reference motion vectors to generate the current block.
  • the disclosed technology may be used to provide a method for video coding.
  • This method includes generating, for a current block, an intermediate prediction based on a first motion information associated with the current block, updating the first motion information to a second motion information, and generating a final prediction for the current block based on the intermediate prediction or the second motion information.
  • the disclosed technology may be used to provide a method for video coding.
  • This method includes receiving a bitstream representation of a current block of video data, generating intermediate motion information based on motion information associated with the current block, generating updated first and second reference motion vectors based on first and second reference motion vectors, respectively, where the current block is associated with first and second reference blocks, and where the first and second reference motion vectors are associated with the first and second reference blocks, respectively, and processing the bitstream representation based on the intermediate motion information or the updated first and second reference motion vectors to generate the current block.
  • the disclosed technology may be used to provide a method for video coding. This method includes generating, for a current block, an intermediate prediction based on a first motion information associated with the current block, updating the first motion information to a second motion information, and generating a final prediction for the current block based on the intermediate prediction or the second motion information. [0015] In yet another representative aspect, the disclosed technology may be used to provide a method for video coding.
  • This method includes receiving a bitstream representation of a current block of video data, generating intermediate motion information based on motion information associated with the current block, generating updated first and second reference motion vectors based on first and second reference motion vectors, respectively, where the current block is associated with first and second reference blocks, and where the first and second reference motion vectors are associated with the first and second reference blocks, respectively, and processing the bitstream representation based on the intermediate motion information or the updated first and second reference motion vectors to generate the current block.
  • the disclosed technology may be used to provide a method for video coding.
  • This method includes generating, for a current block, an intermediate prediction based on a first motion information associated with the current block, updating the first motion information to a second motion information, and generating a final prediction for the current block based on the intermediate prediction or the second motion information.
  • the disclosed technology may be used to provide a method for video coding.
  • This method includes receiving a bitstream representation of a current block of video data, generating intermediate motion information based on motion information associated with the current block, generating updated first and second reference motion vectors based on first and second reference motion vectors, respectively, where the current block is associated with first and second reference blocks, and where the first and second reference motion vectors are associated with the first and second reference blocks, respectively, and processing the bitstream representation based on the intermediate motion information or the updated first and second reference motion vectors to generate the current block.
  • the disclosed technology may be used to provide a method for video coding.
  • This method includes generating, for a bitstream representation of a current block, an updated reference block by modifying a reference block associated with the current block, calculating, based on the updated reference block, a temporal gradient for a bi directional optical flow (BIO) motion refinement, and performing, based on the temporal gradient, a conversion, which includes the BIO motion refinement, between the bitstream representation and the current block.
  • BIO bi directional optical flow
  • the disclosed technology may be used to provide a method for video coding.
  • This method includes generating, for a bitstream representation of a current block, a temporal gradient for a bi-directional optical flow (BIO) motion refinement, generating an updated temporal gradient by subtracting a difference of a first mean value and a second mean value from the temporal gradient, where the first mean value is a mean value for a first reference block, the second mean value is a mean value for a second reference block, and the first and second reference blocks are associated with the current block, and performing, based on the updated temporal gradient, a conversion, which includes the BIO motion refinement, between the bitstream representation and the current block.
  • BIO bi-directional optical flow
  • the above- described method is embodied in the form of processor-executable code and stored in a computer-readable program medium.
  • a device that is configured or operable to perform the above-described method.
  • the device may include a processor that is
  • a video decoder apparatus may implement a method as described herein.
  • a video encoder apparatus may implement a method as described herein.
  • FIG. 1 shows an example of constructing a merge candidate list.
  • FIG. 2 shows an example of positions of spatial candidates.
  • FIG. 3 shows an example of candidate pairs subject to a redundancy check of spatial merge candidates.
  • FIGS. 4A and 4B show examples of the position of a second prediction unit (PU) based on the size and shape of the current block.
  • FIG. 5 shows an example of motion vector scaling for temporal merge candidates.
  • FIG. 6 shows an example of candidate positions for temporal merge candidates.
  • FIG. 7 shows an example of generating a combined bi-predictive merge candidate.
  • FIG. 8 shows an example of constructing motion vector prediction candidates.
  • FIG. 9 shows an example of motion vector scaling for spatial motion vector candidates.
  • FIG. 10 shows an example of motion prediction using the alternative temporal motion vector prediction (ATMVP) algorithm for a coding unit (CU).
  • ATMVP alternative temporal motion vector prediction
  • FIG. 11 shows an example of a coding unit (CU) with sub-blocks and neighboring blocks used by the spatial-temporal motion vector prediction (STMVP) algorithm.
  • CU coding unit
  • STMVP spatial-temporal motion vector prediction
  • FIGS. 12A and 12B show example snapshots of sub-block when using the overlapped block motion compensation (OBMC) algorithm.
  • OBMC overlapped block motion compensation
  • FIG. 13 shows an example of neighboring samples used to derive parameters for the local illumination compensation (LIC) algorithm.
  • LIC local illumination compensation
  • FIG. 14 shows an example of a simplified affine motion model.
  • FIG. 15 shows an example of an affine motion vector field (MVF) per sub-block.
  • FIG. 16 shows an example of motion vector prediction (MVP) for the AF INTER affine motion mode.
  • FIGS. 17A and 17B show example candidates for the AF MERGE affine motion mode.
  • FIG. 18 shows an example of bilateral matching in pattern matched motion vector derivation (PMMVD) mode, which is a special merge mode based on the frame-rate up conversion (FRUC) algorithm.
  • PMMVD pattern matched motion vector derivation
  • FRUC frame-rate up conversion
  • FIG. 19 shows an example of template matching in the FRUC algorithm.
  • FIG. 20 shows an example of unilateral motion estimation in the FRUC algorithm.
  • FIG. 21 shows an example of an optical flow trajectory used by the bi-directional optical flow (BIO) algorithm.
  • FIGS. 22A and 22B show example snapshots of using of the bi-directional optical flow (BIO) algorithm without block extensions.
  • FIG. 23 shows an example of the decoder-side motion vector refinement (DMVR) algorithm based on bilateral template matching.
  • FIG. 24 shows an example of a template definition used in transform coefficient context modelling.
  • FIG. 25 shows different examples of motion vector scaling.
  • FIGS. 26A and 26B show examples of inner and boundary sub-blocks in a PU/CU.
  • FIG. 27 shows a flowchart of an example method for video coding in accordance with the presently disclosed technology.
  • FIG. 28 shows a flowchart of another example method for video coding in accordance with the presently disclosed technology.
  • FIG. 29 shows a flowchart of another example method for video coding in accordance with the presently disclosed technology.
  • FIG. 30 shows a flowchart of another example method for video coding in accordance with the presently disclosed technology.
  • FIG. 31 shows a flowchart of another example method for video coding in accordance with the presently disclosed technology.
  • FIG. 32 shows an example of deriving motion vector in bi-directional optical flow based video encoding.
  • FIG. 33 shows a flowchart of another example method for video coding in accordance with the presently disclosed technology.
  • FIG. 34 shows a flowchart of another example method for video coding in accordance with the presently disclosed technology.
  • FIG. 35 shows a flowchart of another example method for video coding in accordance with the presently disclosed technology.
  • FIG. 36 shows a flowchart of another example method for video coding in accordance with the presently disclosed technology.
  • FIG. 37 is a block diagram of an example of a hardware platform for implementing a visual media decoding or a visual media encoding technique described in the present document.
  • FIG. 38 shows a flowchart of another example method for video processing in accordance with the presently disclosed technology.
  • FIG. 39 shows a flowchart of another example method for video processing in accordance with the presently disclosed technology.
  • FIG. 40 shows a flowchart of another example method for video processing in accordance with the presently disclosed technology.
  • FIG. 41 shows a flowchart of another example method for video processing in accordance with the presently disclosed technology.
  • FIG. 42 shows a flowchart of another example method for video processing in accordance with the presently disclosed technology.
  • FIG. 43 shows a flowchart of another example method for video processing in accordance with the presently disclosed technology.
  • Video codecs typically include an electronic circuit or software that compresses or decompresses digital video, and are continually being improved to provide higher coding efficiency.
  • a video codec converts uncompressed video to a compressed format or vice versa.
  • the compressed format usually conforms to a standard video compression specification, e.g., the High Efficiency Video Coding (HEVC) standard (also known as H.265 or MPEG-H Part 2), the Versatile Video Coding standard to be finalized, or other current and/or future video coding standards.
  • HEVC High Efficiency Video Coding
  • MPEG-H Part 2 the Versatile Video Coding standard to be finalized, or other current and/or future video coding standards.
  • Embodiments of the disclosed technology may be applied to existing video coding standards (e.g., HEVC, H.265) and future standards to improve compression performance.
  • existing video coding standards e.g., HEVC, H.265
  • future standards e.g., HEVC, H.265
  • Video coding standards have significantly improved over the years, and now provide, in part, high coding efficiency and support for higher resolutions.
  • Recent standards such as HEVC and H.265 are based on the hybrid video coding structure wherein temporal prediction plus transform coding are utilized.
  • Each inter-predicted PU has motion parameters for one or two reference picture lists.
  • motion parameters include a motion vector and a reference picture index.
  • the usage of one of the two reference picture lists may also be signaled using inter _predjdc.
  • motion vectors may be explicitly coded as deltas relative to predictors.
  • a merge mode is specified whereby the motion parameters for the current PU are obtained from neighboring PUs, including spatial and temporal candidates.
  • the merge mode can be applied to any inter-predicted PU, not only for skip mode.
  • the alternative to merge mode is the explicit transmission of motion parameters, where motion vector, corresponding reference picture index for each reference picture list and reference picture list usage are signaled explicitly per each PU.
  • the PU is produced from one block of samples. This is referred to as‘uni-prediction’. Uni-prediction is available both for P-slices and B-slices.
  • the PU is produced from two blocks of samples. This is referred to as‘bi-prediction’. Bi-prediction is available for B-slices only.
  • Step 1 Initial candidates derivation
  • Step 1.1 Spatial candidates derivation
  • Step 1.2 Redundancy check for spatial candidates
  • Step 1.3 Temporal candidates derivation
  • Step 2 Additional candidates insertion
  • Step 2.1 Creation of bi-predictive candidates
  • Step 2.2 Insertion of zero motion candidates
  • FIG. 1 shows an example of constructing a merge candidate list based on the sequence of steps summarized above.
  • For spatial merge candidate derivation a maximum of four merge candidates are selected among candidates that are located in five different positions.
  • temporal merge candidate derivation a maximum of one merge candidate is selected among two candidates. Since constant number of candidates for each PU is assumed at decoder, additional candidates are generated when the number of candidates does not reach to maximum number of merge candidate (MaxNumMergeCand) which is signalled in slice header. Since the number of candidates is constant, index of best merge candidate is encoded using truncated unary binarization (TU). If the size of CU is equal to 8, all the PUs of the current CU share a single merge candidate list, which is identical to the merge candidate list of the 2Nx2N prediction unit.
  • TU truncated unary binarization
  • adding this candidate may lead to two prediction units having the same motion information, which is redundant to just have one PU in a coding unit. Similarly, position Bi is not considered when the current PU is partitioned as 2NxN.
  • FIG. 5 shows an example of the derivation of the scaled motion vector for a temporal merge candidate (as the dotted line), which is scaled from the motion vector of the co-located PU using the POC distances, tb and td, where tb is defined to be the POC difference between the reference picture of the current picture and the current picture and td is defined to be the POC difference between the reference picture of the co-located picture and the co-located picture.
  • the reference picture index of temporal merge candidate is set equal to zero. For a B-slice, two motion vectors, one is for reference picture list 0 and the other is for reference picture list 1, are obtained and combined to make the bi-predictive merge candidate.
  • the position for the temporal candidate is selected between candidates Co and Ci, as depicted in FIG. 6. If PU at position Co is not available, is intra coded, or is outside of the current CTU, position Ci is used. Otherwise, position Co is used in the derivation of the temporal merge candidate.
  • merge candidates there are two additional types of merge candidates: combined bi-predictive merge candidate and zero merge candidate.
  • Combined bi- predictive merge candidates are generated by utilizing spatio-temporal merge candidates.
  • Combined bi-predictive merge candidate is used for B-Slice only.
  • the combined bi-predictive candidates are generated by combining the first reference picture list motion parameters of an initial candidate with the second reference picture list motion parameters of another. If these two tuples provide different motion hypotheses, they will form a new bi-predictive candidate.
  • FIG. 7 shows an example of this process, wherein two candidates in the original list (710, on the left), which have mvLO and refldxLO or mvLl and refldxLl, are used to create a combined bi-predictive merge candidate added to the final list (720, on the right).
  • Zero motion candidates are inserted to fill the remaining entries in the merge candidates list and therefore hit the MaxNumMergeCand capacity. These candidates have zero spatial displacement and a reference picture index which starts from zero and increases every time a new zero motion candidate is added to the list. The number of reference frames used by these candidates is one and two for uni- and bi-directional prediction, respectively. In some embodiments, no redundancy check is performed on these candidates.
  • motion estimation can be performed in parallel whereby the motion vectors for all prediction units inside a given region are derived
  • a motion estimation region may be defined.
  • the size of the MER may be signaled in the picture parameter set (PPS) using the “log2_parallel_merge_level_minus2” syntax element.
  • AMVP advanced motion vector prediction
  • AMVP exploits spatio-temporal correlation of motion vector with neighboring PUs, which is used for explicit transmission of motion parameters. It constructs a motion vector candidate list by firstly checking availability of left, above temporally neighboring PU positions, removing redundant candidates and adding zero vector to make the candidate list to be constant length. Then, the encoder can select the best predictor from the candidate list and transmit the corresponding index indicating the chosen candidate. Similarly with merge index signaling, the index of the best motion vector candidate is encoded using truncated unary. The maximum value to be encoded in this case is 2 (see FIG. 8). In the following sections, details about derivation process of motion vector prediction candidate are provided.
  • FIG. 8 summarizes derivation process for motion vector prediction candidate, and may be implemented for each reference picture list with refidx as an input.
  • motion vector candidate two types are considered: spatial motion vector candidate and temporal motion vector candidate.
  • spatial motion vector candidate derivation two motion vector candidates are eventually derived based on motion vectors of each PU located in five different positions as previously shown in FIG. 2.
  • one motion vector candidate is selected from two candidates, which are derived based on two different co-located positions. After the first list of spatio-temporal candidates is made, duplicated motion vector candidates in the list are removed. If the number of potential candidates is larger than two, motion vector candidates whose reference picture index within the associated reference picture list is larger than 1 are removed from the list. If the number of spatio-temporal motion vector candidates is smaller than two, additional zero motion vector candidates is added to the list. 1.2.2 Constructing spatial motion vector candidates
  • the no-spatial-scaling cases are checked first followed by the cases that allow spatial scaling. Spatial scaling is considered when the POC is different between the reference picture of the neighbouring PU and that of the current PU regardless of reference picture list. If all PUs of left candidates are not available or are intra coded, scaling for the above motion vector is allowed to help parallel derivation of left and above MV candidates. Otherwise, spatial scaling is not allowed for the above motion vector.
  • the motion vector of the neighbouring PU is scaled in a similar manner as for temporal scaling.
  • One difference is that the reference picture list and index of current PU is given as input; the actual scaling process is the same as that of temporal scaling.
  • the reference picture index is signaled to the decoder.
  • JEM Joint Exploration Model
  • affine prediction alternative temporal motion vector prediction
  • STMVP spatial-temporal motion vector prediction
  • BIO bi directional optical flow
  • FRUC Frame-Rate Up Conversion
  • LAMVR Locally Adaptive Motion Vector Resolution
  • OBMC Overlapped Block Motion Compensation
  • LIC Local Illumination Compensation
  • DMVR Decoder-side Motion Vector Refinement
  • each CU can have at most one set of motion parameters for each prediction direction.
  • two sub-CU level motion vector prediction methods are considered in the encoder by splitting a large CU into sub- CUs and deriving motion information for all the sub-CUs of the large CU.
  • Alternative temporal motion vector prediction (ATMVP) method allows each CU to fetch multiple sets of motion information from multiple blocks smaller than the current CU in the collocated reference picture.
  • STMVP spatial-temporal motion vector prediction
  • motion vectors of the sub-CUs are derived recursively by using the temporal motion vector predictor and spatial neighbouring motion vector.
  • the motion compression for the reference frames may be disabled.
  • the temporal motion vector prediction (TMVP) method is modified by fetching multiple sets of motion information (including motion vectors and reference indices) from blocks smaller than the current CU.
  • FIG. 10 shows an example of ATMVP motion prediction process for a CU 1000
  • the ATMVP method predicts the motion vectors of the sub-CUs 1001 within a CU 1000 in two steps.
  • the first step is to identify the corresponding block 1051 in a reference picture 1050 with a temporal vector.
  • the reference picture 1050 is also referred to as the motion source picture.
  • the second step is to split the current CU 1000 into sub-CUs 1001 and obtain the motion vectors as well as the reference indices of each sub-CU from the block corresponding to each sub-CU.
  • a reference picture 1050 and the corresponding block is determined by the motion information of the spatial neighboring blocks of the current CU 1000
  • the first merge candidate in the merge candidate list of the current CU 1000 is used.
  • the first available motion vector as well as its associated reference index are set to be the temporal vector and the index to the motion source picture. This way, the corresponding block may be more accurately identified, compared with TMVP, wherein the corresponding block (sometimes called collocated block) is always in a bottom-right or center position relative to the current CU.
  • a corresponding block of the sub-CU 1051 is identified by the temporal vector in the motion source picture 1050, by adding to the coordinate of the current CU the temporal vector.
  • the motion information of its corresponding block e.g., the smallest motion grid that covers the center sample
  • the motion information of a corresponding NxN block is identified, it is converted to the motion vectors and reference indices of the current sub-CU, in the same way as TMVP of HEVC, wherein motion scaling and other procedures apply.
  • the decoder checks whether the low-delay condition (e.g.
  • motion vector MVx e.g., the motion vector corresponding to reference picture list X
  • motion vector MVy e.g., with X being equal to 0 or 1 and Y being equal to l-X
  • FIG. 11 shows an example of one CU with four sub-blocks and neighboring blocks.
  • 8x8 CU 1100 that includes four 4x4 sub-CUs A (1101), B (1102), C (1103), and D (1104).
  • the neighboring 4x4 blocks in the current frame are labelled as a (1111), b (1112), c (11 13), and d (1114).
  • the motion derivation for sub-CU A starts by identifying its two spatial neighbors.
  • the first neighbor is the NxN block above sub-CU A 1101 (block e l l 13). If this block c (1113) is not available or is intra coded the other NxN blocks above sub-CU A (1101) are checked (from left to right, starting at block c 1113).
  • the second neighbor is a block to the left of the sub- CU A 1101 (block b 1112). If block b (1112) is not available or is intra coded other blocks to the left of sub-CU A 1101 are checked (from top to bottom, staring at block b 1112).
  • the motion information obtained from the neighboring blocks for each list is scaled to the first reference frame for a given list.
  • temporal motion vector predictor (TMVP) of sub-block A 1101 is derived by following the same procedure of TMVP derivation as specified in HEVC.
  • the motion information of the collocated block at block D 1104 is fetched and scaled accordingly.
  • all available motion vectors are averaged separately for each reference list. The averaged motion vector is assigned as the motion vector of the current sub-CU.
  • the sub-CU modes are enabled as additional merge candidates and there is no additional syntax element required to signal the modes.
  • Two additional merge candidates are added to merge candidates list of each CU to represent the ATMVP mode and STMVP mode. In other embodiments, up to seven merge candidates may be used, if the sequence parameter set indicates that ATMVP and STMVP are enabled.
  • the encoding logic of the additional merge candidates is the same as for the merge candidates in the HM, which means, for each CU in P or B slice, two more RD checks may be needed for the two additional merge candidates.
  • all bins of the merge index are context coded by CABAC (Context-based Adaptive Binary Arithmetic Coding). In other embodiments, e.g., HEVC, only the first bin is context coded and the remaining bins are context by-pass coded.
  • CABAC Context-based Adaptive Binary Arithmetic Coding
  • motion vector differences (between the motion vector and predicted motion vector of a PU) are signalled in units of quarter luma samples when use integer mv flag is equal to 0 in the slice header.
  • MVDs motion vector differences
  • LAMVR locally adaptive motion vector resolution
  • MVD can be coded in units of quarter luma samples, integer luma samples or four luma samples.
  • the MVD resolution is controlled at the coding unit (CU) level, and MVD resolution flags are conditionally signalled for each CU that has at least one non- zero MVD components.
  • a first flag is signalled to indicate whether quarter luma sample MV precision is used in the CU.
  • the first flag (equal to 1) indicates that quarter luma sample MV precision is not used, another flag is signalled to indicate whether integer luma sample MV precision or four luma sample MV precision is used.
  • the quarter luma sample MV resolution is used for the CU.
  • the MVPs in the AMVP candidate list for the CU are rounded to the corresponding precision.
  • CU-level RD checks are used to determine which MVD resolution is to be used for a CU. That is, the CU-level RD check is performed three times for each MVD resolution. To accelerate encoder speed, the following encoding schemes are applied in the JEM:
  • the motion information of the current CU (integer luma sample accuracy) is stored.
  • the stored motion information (after rounding) is used as the starting point for further small range motion vector refinement during the RD check for the same CU with integer luma sample and 4 luma sample MVD resolution so that the time-consuming motion estimation process is not duplicated three times.
  • RD check of a CU with 4 luma sample MVD resolution is conditionally invoked.
  • RD cost integer luma sample MVD resolution is much larger than that of quarter luma sample MVD resolution
  • the RD check of 4 luma sample MVD resolution for the CU is skipped.
  • motion vector accuracy is one-quarter pel (one-quarter luma sample and one-eighth chroma sample for 4:2:0 video).
  • JEM the accuracy for the internal motion vector storage and the merge candidate increases to 1/16 pel.
  • the higher motion vector accuracy (1/16 pel) is used in motion compensation inter prediction for the CU coded with skip/merge mode.
  • the integer-pel or quarter-pel motion is used for the CU coded with normal AMVP mode.
  • HEVC motion compensation interpolation filters are used as motion compensation interpolation filters for the additional fractional pel positions.
  • the chroma component motion vector accuracy is 1/32 sample in the JEM, the additional interpolation filters of 1/32 pel fractional positions are derived by using the average of the filters of the two neighbouring 1/16 pel fractional positions.
  • OBMC overlapped block motion compensation
  • OBMC can be switched on and off using syntax at the CU level.
  • the OBMC is performed for all motion compensation (MC) block boundaries except the right and bottom boundaries of a CU. Moreover, it is applied for both the luma and chroma components.
  • an MC block corresponds to a coding block.
  • sub-CU mode includes sub-CU merge, affine and FRUC mode
  • each sub block of the CU is a MC block.
  • sub-block size is set equal to 4x4, as shown in FIGS. 12A and 12B.
  • FIG. 12A shows sub-blocks at the CU/PU boundary, and the hatched sub-blocks are where OBMC applies.
  • FIG. 12B shows the sub-Pus in ATMVP mode.
  • Prediction block based on motion vectors of a neighboring sub-block is denoted as PN, with N indicating an index for the neighboring above, below, left and right sub-blocks and prediction block based on motion vectors of the current sub-block is denoted as PC.
  • PN is based on the motion information of a neighboring sub-block that contains the same motion information to the current sub-block, the OBMC is not performed from PN. Otherwise, every sample of PN is added to the same sample in PC, i.e., four rows/columns of PN are added to PC.
  • weighting factors ⁇ 1/4, 1/8, 1/16, 1/32 ⁇ are used for PN and the weighting factors ⁇ 3/4, 7/8, 15/16, 31/32 ⁇ are used for PC.
  • the exception are small MC blocks, (i.e., when height or width of the coding block is equal to 4 or a CU is coded with sub-CU mode), for which only two rows/columns of PN are added to PC.
  • weighting factors ⁇ 1/4, 1/8 ⁇ are used for PN and weighting factors ⁇ 3/4, 7/8 ⁇ are used for PC.
  • For PN generated based on motion vectors of vertically (horizontally) neighboring sub-block samples in the same row (column) of PN are added to PC with a same weighting factor.
  • a CU level flag is signaled to indicate whether OBMC is applied or not for the current CU.
  • OBMC is applied by default.
  • the prediction signal formed by OBMC using motion information of the top neighboring block and the left neighboring block is used to compensate the top and left boundaries of the original signal of the current CU, and then the normal motion estimation process is applied.
  • LIC is based on a linear model for illumination changes, using a scaling factor a and an offset b. And it is enabled or disabled adaptively for each inter-mode coded coding unit (CU).
  • CU inter-mode coded coding unit
  • FIG. 13 shows an example of neighboring samples used to derive parameters of the IC algorithm. Specifically, and as shown in FIG. 13, the subsampled (2: 1 subsampling) neighbouring samples of the CU and the corresponding samples (identified by motion information of the current CU or sub-CU) in the reference picture are used. The IC parameters are derived and applied for each prediction direction separately.
  • the LIC flag is copied from neighboring blocks, in a way similar to motion information copy in merge mode; otherwise, an LIC flag is signaled for the CU to indicate whether LIC applies or not.
  • LIC When LIC is enabled for a picture, an additional CU level RD check is needed to determine whether LIC is applied or not for a CU.
  • MR-SAD mean- removed sum of absolute difference
  • MR-SATD mean-removed sum of absolute Hadamard- transformed difference
  • LIC is disabled for the entire picture when there is no obvious illumination change between a current picture and its reference pictures. To identify this situation, histograms of a current picture and every reference picture of the current picture are calculated at the encoder. If the histogram difference between the current picture and every reference picture of the current picture is smaller than a given threshold, LIC is disabled for the current picture; otherwise, LIC is enabled for the current picture.
  • FIG. 14 shows an example of an affine motion field of a block 1400 described by two control point motion vectors Vo and Vi.
  • the motion vector field (MVF) of the block 1400 can be described by the following equation:
  • (v 0x , vo y ) is motion vector of the top-left corner control point
  • (vi x , vi y ) is motion vector of the top-right corner control point.
  • sub-block based affine transform prediction can be applied.
  • the sub block size MxN is derived as follows:
  • MvPre is the motion vector fraction accuracy (e.g., 1/16 in JEM).
  • (v 2x , v 2y ) is motion vector of the bottom-left control point, calculated according to Eq. (1).
  • M and N can be adjusted downward if necessary to make it a divisor of w and h, respectively.
  • FIG. 15 shows an example of affine MVF per sub-block for a block 1500.
  • the motion vector of the center sample of each sub-block can be calculated according to Eq. (1), and rounded to the motion vector fraction accuracy (e.g., 1/16 in JEM).
  • the motion compensation interpolation filters can be applied to generate the prediction of each sub-block with derived motion vector.
  • the high accuracy motion vector of each sub-block is rounded and saved as the same accuracy as the normal motion vector.
  • AF INTER mode there are two affine motion modes: AF INTER mode and AF MERGE mode.
  • AF INTER mode can be applied.
  • An affine flag in CU level is signaled in the bitstream to indicate whether AF INTER mode is used.
  • AF INTER mode a candidate list with motion vector pair ⁇ (v 0 , v x )
  • v 0 a candidate list with motion vector pair ⁇ (v 0 , v x )
  • v 0
  • FIG. 16 shows an example of motion vector prediction (MVP) for a block 1600 in the AF INTER mode.
  • vo is selected from the motion vectors of the sub-block A, B, or C.
  • the motion vectors from the neighboring blocks can be scaled according to the reference list.
  • the motion vectors can also be scaled according to the relationship among the Picture Order Count (POC) of the reference for the neighboring block, the POC of the reference for the current CU, and the POC of the current CU.
  • POC Picture Order Count
  • the approach to select vi from the neighboring sub-block D and E is similar. If the number of candidate list is smaller than 2, the list is padded by the motion vector pair composed by duplicating each of the AMVP candidates.
  • the candidates can be firstly sorted according to the neighboring motion vectors (e.g., based on the similarity of the two motion vectors in a pair candidate). In some implementations, the first two candidates are kept.
  • a Rate Distortion (RD) cost check is used to determine which motion vector pair candidate is selected as the control point motion vector prediction (CPMVP) of the current CU.
  • An index indicating the position of the CPMVP in the candidate list can be signaled in the bitstream. After the CPMVP of the current affine CU is determined, affine motion estimation is applied and the control point motion vector (CPMV) is found. Then the difference of the CPMV and the CPMVP is signaled in the bitstream.
  • CPMV control point motion vector
  • FIG. 17A shows an example of the selection order of candidate blocks for a current CU 1700. As shown in FIG. 17A, the selection order can be from left (1701), above (1702), above right (1703), left bottom (1704) to above left (1705) of the current CU 1700.
  • FIG. 17B shows another example of candidate blocks for a current CU 1700 in the AF MERGE mode. If the neighboring left bottom block 1701 is coded in affine mode, as shown in FIG.
  • the motion vectors v 2 , vi and v 4 of the top left corner, above right corner, and left bottom corner of the CU containing the sub-block 1701 are derived.
  • the motion vector vo of the top left corner on the current CU 1700 is calculated based on v2, v3 and v4.
  • the motion vector vl of the above right of the current CU can be calculated accordingly.
  • the MVF of the current CU can be generated.
  • an affine flag can be signaled in the bitstream when there is at least one neighboring block is coded in affine mode.
  • the PMMVD mode is a special merge mode based on the Frame-Rate Up Conversion (FRUC) method. With this mode, motion information of a block is not signaled but derived at decoder side.
  • FRUC Frame-Rate Up Conversion
  • a FRUC flag can be signaled for a CU when its merge flag is true.
  • a merge index can be signaled and the regular merge mode is used.
  • an additional FRUC mode flag can be signaled to indicate which method (e.g., bilateral matching or template matching) is to be used to derive motion information for the block.
  • the decision on whether using FRUC merge mode for a CU is based on RD cost selection as done for normal merge candidate. For example, multiple matching modes (e.g., bilateral matching and template matching) are checked for a CU by using RD cost selection. The one leading to the minimal cost is further compared to other CU modes. If a FRUC matching mode is the most efficient one, FRUC flag is set to true for the CU and the related matching mode is used.
  • multiple matching modes e.g., bilateral matching and template matching
  • motion derivation process in FRUC merge mode has two steps: a CU-level motion search is first performed, then followed by a Sub-CU level motion refinement.
  • CU level an initial motion vector is derived for the whole CU based on bilateral matching or template matching.
  • a list of MV candidates is generated and the candidate that leads to the minimum matching cost is selected as the starting point for further CU level refinement.
  • a local search based on bilateral matching or template matching around the starting point is performed.
  • the MV results in the minimum matching cost is taken as the MV for the whole CU.
  • the motion information is further refined at sub-CU level with the derived CU motion vectors as the starting points.
  • the following derivation process is performed for a W X H CU motion information derivation.
  • MV for the whole W x H CU is derived.
  • the CU is further split into M x M sub-CUs.
  • the value of M is calculated as in Eq. (3), D is a predefined splitting depth which is set to 3 by default in the JEM.
  • the MV for each sub- CU is derived.
  • FIG. 18 shows an example of bilateral matching used in the Frame-Rate Up
  • the bilateral matching is used to derive motion information of the current CU by finding the closest match between two blocks along the motion trajectory of the current CU (1800) in two different reference pictures (1810, 1811).
  • the motion vectors MVO (1801) and MV1 (1802) pointing to the two reference blocks are proportional to the temporal distances, e.g., TD0 (1803) and TD1 (1804), between the current picture and the two reference pictures.
  • the bilateral matching becomes mirror based bi-directional MV.
  • FIG. 19 shows an example of template matching used in the Frame-Rate Up
  • Template matching can be used to derive motion information of the current CU 1900 by finding the closest match between a template (e.g., top and/or left neighboring blocks of the current CU) in the current picture and a block (e.g., same size to the template) in a reference picture 1910. Except the aforementioned FRUC merge mode, the template matching can also be applied to AMVP mode. In both JEM and HEVC, AMVP has two candidates. With the template matching method, a new candidate can be derived. If the newly derived candidate by template matching is different to the first existing AMVP candidate, it is inserted at the very beginning of the AMVP candidate list and then the list size is set to two (e.g., by removing the second existing AMVP candidate). When applied to AMVP mode, only CU level search is applied.
  • a template e.g., top and/or left neighboring blocks of the current CU
  • a block e.g., same size to the template
  • the MV candidate set at CU level can include the following: (1) original AMVP candidates if the current CU is in AMVP mode, (2) all merge candidates, (3) several MVs in the interpolated MV field (described later), and top and left neighboring motion vectors.
  • each valid MV of a merge candidate can be used as an input to generate a MV pair with the assumption of bilateral matching.
  • one valid MV of a merge candidate is (MVa, ref a ) at reference list A.
  • the reference picture reft of its paired bilateral MV is found in the other reference list B so that reft and reft are temporally at different sides of the current picture. If such a reft is not available in reference list B, reft is determined as a reference which is different from reft and its temporal distance to the current picture is the minimal one in list B.
  • MVb is derived by scaling MVa based on the temporal distance between the current picture and reft, reft.
  • four MVs from the interpolated MV field can also be added to the CU level candidate list. More specifically, the interpolated MVs at the position (0, 0),
  • the original AMVP candidates are also added to CU level MV candidate set.
  • 15 MVs for AMVP CUs and 13 MVs for merge CUs can be added to the candidate list.
  • the MV candidate set at sub-CU level includes an MV determined from a CU-level search, (2) top, left, top-left and top-right neighboring MVs, (3) scaled versions of collocated MVs from reference pictures, (4) one or more ATMVP candidates (e.g., up to four), and (5) one or more STMVP candidates (e.g., up to four).
  • the scaled MVs from reference pictures are derived as follows. The reference pictures in both lists are traversed. The MVs at a collocated position of the sub-CU in a reference picture are scaled to the reference of the starting CU-level MV.
  • ATMVP and STMVP candidates can be the four first ones.
  • one or more MVs are added to the candidate list.
  • interpolated motion field Before coding a frame, interpolated motion field is generated for the whole picture based on unilateral ME. Then the motion field may be used later as CU level or sub-CU level MV candidates.
  • the motion field of each reference pictures in both reference lists is traversed at 4x4 block level.
  • FIG. 20 shows an example of unilateral Motion Estimation (ME) 2000 in the FRUC method.
  • ME Motion Estimation
  • the motion of the reference block is scaled to the current picture according to the temporal distance TD0 and TD1 (the same way as that of MV scaling of TMVP in HEVC) and the scaled motion is assigned to the block in the current frame. If no scaled MV is assigned to a 4x4 block, the block’s motion is marked as unavailable in the interpolated motion field.
  • the matching cost is a bit different at different steps.
  • the matching cost can be the absolute sum difference (SAD) of bilateral matching or template matching.
  • SAD absolute sum difference
  • the matching cost C of bilateral matching at sub-CU level search is calculated as follows:
  • w is a weighting factor. In some embodiments, w can be empirically set to 4.
  • MV and MV S indicate the current MV and the starting MV, respectively.
  • SAD may still be used as the matching cost of template matching at sub-CU level search.
  • MV is derived by using luma samples only. The derived motion will be used for both luma and chroma for MC inter prediction. After MV is decided, final MC is performed using 8-taps interpolation filter for luma and 4-taps interpolation filter for chroma.
  • MV refinement is a pattern based MV search with the criterion of bilateral matching cost or template matching cost.
  • two search patterns are supported - an unrestricted center-biased diamond search (UCBDS) and an adaptive cross search for MV refinement at the CU level and sub-CU level, respectively.
  • UMBDS center-biased diamond search
  • the MV is directly searched at quarter luma sample MV accuracy, and this is followed by one-eighth luma sample MV refinement.
  • the search range of MV refinement for the CU and sub-CU step are set equal to 8 luma samples.
  • bi-prediction is applied because the motion information of a CU is derived based on the closest match between two blocks along the motion trajectory of the current CU in two different reference pictures.
  • the encoder can choose among uni-prediction from listO, uni-prediction from listl, or bi prediction for a CU. The selection ca be based on a template matching cost as follows:
  • costBi ⁇ factor * min (costO, costl)
  • costO is the SAD of listO template matching
  • costl is the SAD of listl template matching
  • costBi is the SAD of bi-prediction template matching.
  • factor is equal to 1.25, it means that the selection process is biased toward bi-prediction.
  • the inter prediction direction selection can be applied to the CU-level template matching process.
  • BIO bi-directional optical flow
  • the first predictions are used to derive the spatial gradient, the temporal gradient and the optical flow of each sub-block/pixel within the block, which are then used to generate the second prediction, e.g., the final prediction of the sub- block/pixel.
  • the details are described as follows.
  • the bi-directional optical flow (BIO) method is a sample- wise motion refinement performed on top of block- wise motion compensation for bi-prediction.
  • the sample-level motion refinement does not use signaling.
  • prec I0 ]/2-( - ⁇ +7® +n c /2 ⁇ t i 3 ⁇ jdx-tb ⁇ jdc)+v y j2-[r l d ⁇ jd -tb ⁇ /dy)).
  • FIG. 21 shows an example optical flow trajectory in the Bi-directional Optical flow (BIO) method.
  • t 0 and t 1 denote the distances to the reference frames.
  • the motion vector field (v x , v y ) is determined by minimizing the difference D between values in points A and B.
  • FIGS. 9A-9B show an example of intersection of motion trajectory and reference frame planes.
  • Model uses only first linear term of a local Taylor expansion for D: [00182] All values in the above equation depend on the sample location, denoted as V ,j' ). Assuming the motion is consistent in the local surrounding area, D can be minimized inside the (2M+l)x(2M+l) square window W centered on the currently predicted point (i,j), where M is equal to 2:
  • the JEM uses a simplified approach making first a minimization in the vertical direction and then in the horizontal direction. This results in the following:
  • d is bit depth of the video samples.
  • FIG. 22A shows an example of access positions outside of a block 2200.
  • (2M+l)x(2M+l) square window W centered in currently predicted point on a boundary of predicted block needs to accesses positions outside of the block.
  • values of 7®, dl ⁇ / dx , dl (k) / dy outside of the block are set to be equal to the nearest available value inside the block.
  • BIO it is possible that the motion field can be refined for each sample.
  • a block-based design of BIO is used in the JEM.
  • the motion refinement can be calculated based on a 4x4 block.
  • the values of S n in Eq. (9) of all samples in a 4x4 block can be aggregated, and then the aggregated values of s n in are used to derived BIO motion vectors offset for the 4x4 block. More specifically, the following formula can used for block-based BIO derivation:
  • b k denotes the set of samples belonging to the k-th 4x4 block of the predicted block.
  • s n in Eq (9) and Eq (10) are replaced by (( s n,bk ) » 4 ) to derive the associated motion vector offsets.
  • MV regiment of BIO may be unreliable due to noise or irregular motion. Therefore, in BIO, the magnitude of MV regiment is clipped to a threshold value.
  • the threshold value is determined based on whether the reference pictures of the current picture are all from one direction. For example, if all the reference pictures of the current picture are from one direction, the value of the threshold is set to 12 x 2 14-d ; otherwise, it is set to 12 x 2 13-d .
  • Gradients for BIO can be calculated at the same time with motion compensation interpolation using operations consistent with HEVC motion compensation process (e.g., 2D separable Finite Impulse Response (FIR)).
  • the input for the 2D separable FIR is the same reference frame sample as for motion compensation process and fractional position (fracX, fracY) according to the fractional part of block motion vector.
  • fracX, fracY fractional position
  • Gradient filter BIOfilterG is then applied in horizontal direction corresponding to the fractional position fracX with de-scaling shift by 18 d.
  • a gradient filter is applied vertically using BIOfilterG corresponding to the fractional position fracY with de-scaling shift d 8.
  • the signal displacement is then performed using BlOfilterS in horizontal direction corresponding to the fractional position fracX with de-scaling shift by 18 d.
  • the length of interpolation filter for gradients calculation BIOfilterG and signal displacement BIOfilterF can be shorter (e.g., 6-tap) in order to maintain reasonable complexity.
  • Table 1 shows example filters that can be used for gradients calculation of different fractional positions of block motion vector in BIO.
  • Table 2 shows example interpolation filters that can be used for prediction signal generation in BIO.
  • BIO can be applied to all bi-predicted blocks when the two predictions are from different reference pictures.
  • BIO can be disabled.
  • BIO is applied for a block after normal MC process.
  • BIO may not be applied during the OBMC process. This means that BIO is applied in the MC process for a block when using its own MV and is not applied in the MC process when the MV of a neighboring block is used during the OBMC process.
  • DMVR decoder-side motion vector refinement
  • a bi-prediction operation for the prediction of one block region, two prediction blocks, formed using a motion vector (MV) of listO and a MV of listl , respectively, are combined to form a single prediction signal.
  • the two motion vectors of the bi-prediction are further refined by a bilateral template matching process.
  • the bilateral template matching applied in the decoder to perform a distortion-based search between a bilateral template and the reconstruction samples in the reference pictures in order to obtain a refined MV without transmission of additional motion information.
  • a bilateral template is generated as the weighted combination (i.e.
  • the template matching operation consists of calculating cost measures between the generated template and the sample region (around the initial prediction block) in the reference picture. For each of the two reference pictures, the MV that yields the minimum template cost is considered as the updated MV of that list to replace the original one.
  • nine MV candidates are searched for each list. The nine MV candidates include the original MV and 8 surrounding MVs with one luma sample offset to the original MV in either the horizontal or vertical direction, or both.
  • the two new MVs i.e., MV0' and MV1' as shown in FIG. 23, are used for generating the final bi-prediction results.
  • a sum of absolute differences (SAD) is used as the cost measure.
  • DMVR is applied for the merge mode of bi-prediction with one MV from a reference picture in the past and another from a reference picture in the future, without the transmission of additional syntax elements.
  • JEM when LIC, affine motion, FRUC, or sub-CU merge candidate is enabled for a CU, DMVR is not applied.
  • CABAC contains the following three major changes compared to the design in HEVC:
  • transform coefficients of a coding block are coded using non-overlapped coefficient groups (CGs), and each CG contains the coefficients of a 4x4 block of a coding block.
  • the CGs inside a coding block, and the transform coefficients within a CG, are coded according to pre-defmed scan orders.
  • the coding of transform coefficient levels of a CG with at least one non-zero transform coefficient may be separated into multiple scan passes. In the first pass, the first bin (denoted by binO, also referred as significant coejfi Jlag, which indicates the magnitude of the coefficient is larger than 0) is coded. Next, two scan passes for context coding the second/third bins (denoted by binl and bin2, respectively, also referred as
  • the context modeling for regular bins is changed.
  • the context index is dependent on the values of the z-th bins of previously coded coefficients in the neighbourhood covered by a local template. Specifically, the context index is determined based on the sum of the i-th bins of neighbouring coefficients.
  • the local template contains up to five spatial neighbouring transform coefficients wherein x indicates the position of current transform coefficient and xi (i being 0 to 4) indicates its five neighbours.
  • one coding block may be split into up to three regions and the splitting method is fixed regardless of the coding block sizes. For example, when coding binO of luma transform coefficients, as depicted in FIG. 24, one coding block is split into three regions marked with different colours, and the context index assigned to each region is listed. Luma and chroma components are treated in a similar way but with separate sets of context models. Moreover, the context model selection for binO (e.g., significant flags) of the luma component is further dependent on transform size.
  • the binary arithmetic coder is applied with a“multi-hypothesis” probability update model based on two probability estimates Po and Pi that are associated with each context model and are updated independently with different adaptation rates as follows:
  • the variable M (being 4, 5, 6, 7) is a parameter which controls the probability updating speed for the context model with index equal to i; and k represents the precision of probabilities (here it is equal to 15).
  • the probability estimate P used for the interval subdivision in the binary arithmetic coder is the average of the estimates from the two hypotheses:
  • Equation (15) the value of the parameter M, used in Equation (15) that controls the probability updating speed for each context model is assigned as follows:
  • the coded bins associated with each context model are recorded. After one slice is coded, for each context model with index equal to i, the rate costs of using different values of M, (being 4, 5, 6, 7) are calculated and the one that provides the minimum rate cost is selected. For simplicity, this selection process is performed only when a new combination of slice type and slice-level quantization parameter are encountered.
  • a 1 -bit flag is signalled for each context model i to indicate whether M is different from the default value 4. When the flag is 1, two bits are used to indicate whether M is equal to 5, 6, or 7.
  • the initial probability states of context models for inter-coded slices can be initialized by copying states from previously coded pictures. More specifically, after coding a centrally-located CTU of each picture, the probability states of all context models are stored for potential use as the initial states of the corresponding context models on later pictures. In the JEM, the set of initial states for each inter-coded slice is copied from the stored states of a previously coded picture that has the same slice type and the same slice-level QP as the current slice. This lacks loss robustness, but is used in the current JEM scheme for coding efficiency experiment purposes.
  • Methods related to the disclosed technology include extended LAMVR, wherein supported motion vector resolutions range from l/4-pel to 4-pel (l/4-pel, l/2-pel, l-pel, 2-pel and 4-pel). Information about the motion vector resolution is signaled at the CU level when MVD information is signaled.
  • MV motion vector
  • MVP motion vector predictor
  • MVD (MVD X , MVD y ) is also aligned to the resolution and, is signaled according to the resolution as follows:
  • motion vector resolution index indicates MVP index as well as the motion vector resolution.
  • the proposed method has no MVP index signaling.
  • the table shows what each value of MVR index represents.
  • AMVR has 3 modes for every resolution.
  • AMVR Bi- Index indicates whether MVD X , MVD y of each reference list (list 0 or list 1) are signaled or not.
  • AMVR Bi-Index An example of the AMVR Bi-Index is defined as in the table below.
  • the calculated MV between reference block/subblock in list 0 (denoted by refblkO) and reference block/subblock list 1 (refblkl), denoted by (v x , v y ), is only used for motion compensation of the current block/subblock, and are not used for motion prediction, deblocking, OBMC etc. of future coded blocks, which may be inefficient.
  • (v x , v y ) may be generated for each sub-block/pixel of the block, and Eq. (7) may be used to generate the second prediction of the sub-block/pixel.
  • (v x , v y ) is not used for motion compensation of the sub-block/pixel, which may also be inefficient.
  • BIO In another existing implementation that uses both DMVR and BIO for a bi-predicted PU, firstly, DMVR is performed. After that, motion information of the PU is updated. Then, BIO is performed with the updated motion information. That is to say, the input of BIO depends on the output of DMVR.
  • MVD is required to be coded, however, it can only be encoded in 1/4 pel precision, which may be inefficient.
  • Embodiments of the presently disclosed technology overcome the drawbacks of existing implementations, and provide additional solutions, thereby providing video coding with higher coding efficiencies.
  • the two-step inter-prediction, based on the disclosed technology, may enhance both existing and future video coding standards, is elucidated in the following examples described for various implementations.
  • the examples of the disclosed technology provided below explain general concepts, and are not meant to be interpreted as limiting. In an example, unless explicitly indicated to the contrary, the various features described in these examples may be combined.
  • RefO and Refl the reference picture of current picture from list 0 and list 1 is denoted RefO and Refl, respectively.
  • To POC(current) - POC(RefO)
  • ti POC(Refl) - POC(current)
  • refblkO and refblkl reference block of the current block from RefO and Refl respectively.
  • original MV of its corresponding sub block in refblkO pointing to refblkl is denoted by (v x , v y ).
  • MVs of the sub-block in RefO and Refl are denoted by (mvL0 x , mvL0 y ) and (mvLl x , mvLl y ) respectively.
  • Derived MVs derived from the original MVs in BIO are denoted by (v x , v y ).
  • the updated motion vector based methods for motion prediction may be extended, as described in this patent document, to existing and future video coding standards.
  • the target precision (to be scaled to) is set to be the higher (for better performance)/lower precision (for lower complexity) between MV (v x , v y ) and MV (mvLX x , mvLX y ).
  • the target precision (to be scaled to) is set to be a fixed value (e.g., 1/32 pel precision) regardless the precisions of these two MVs.
  • the original MV (mvLX x , mvLX y ) may be scaled to a higher precision before the adding operation, for example, it may be scaled from 1/4 pel precision to 1/16 pel precision.
  • mvLX x sign(mvLX x ) * (abs(mvLX x ) « N)
  • mvLX y sign(mvLX y ) * (abs(mvLX y ) « N)
  • function sign(-) returns the sign of an input parameter (shown below)
  • function abs( ) returns absolute value of an input parameter
  • N log2(curr_mv_precision/targ_mv_precision)
  • MV (v x , v y ) should be scaled to finer/coarser precision. For example, (mvLX x , mvLX y ) is with 1/16 pel precision, then (v x , v y ) is also scaled to 1/16 pel precision.
  • the updated MV is used for future motion prediction
  • the updated MV can only be used in motion prediction of its non-immediately following CU/PUs in decoding order.
  • the updated MV can only be used as TMVP in AMVP, merge or affine mode.
  • Example 2 instead of considering POC distances (e.g., in the computation of to and ti as described above), the scaling method of MVs invoked in BIO process may be simplified.
  • So and/or Si is set to 2. In one example, it is invoked under certain conditions, such as to > 0 and ti > 0.
  • offsets may be added during division process.
  • mvL0’ x (-v x +offset0) / So + mvL0 x
  • mvL0’ y -(v y + offsetO) / So + mvLO y
  • mvLl’ x (v x + offsetl) / Si + mvLl x
  • mvLl’ y (v y + offsetl) / Si + mvLl y .
  • offsetO is set to So/2 and offsetl is set to Si/2.
  • mvL0’ x ((-v x + l)»l) + mvL0 x
  • mvL0’ y (-(v y + (v y +
  • SFo is set to 2
  • SFi is set to 1.
  • it is invoked under certain conditions, such as t 0 > 0 and ti ⁇ 0 and t 0 >
  • mvL0’ x SFACTo*v x + mvL0 x
  • mvLO’ y SFACTo*v y + mvLO y
  • mvLl’ x SFACTi *v x + mvLl x
  • mvLl’ y SFACTi * v y + mvLl y .
  • SFACTo is set to 1
  • SFACTi is set to 2.
  • it is invoked under certain conditions, such as t 0 > 0 and t ⁇ ⁇ 0 and to ⁇
  • Example 3 Derivation of (v x , v y ) and update of (mvLX x , mvLX y ) may be done together when TO > 0 and t ⁇ > 0 to keep high precision.
  • K is an integer number, for example, K is equal to 1, 2, 3, -2, -1 or 0.
  • Example 4 Clipping operations may be further applied to the updated MVs employed in BIO and/or DMVR or other kinds of coding methods that may require MVs to be updated.
  • MVs e.g., clipped to be within a certain range compared to picture boundaries.
  • updated MVs are clipped to be within a certain range (or multiple ranges for different sub-blocks) compared to the MVs used in MC process. That is, the differences between the MV used in MC and updated MVs are clipped to be within a certain range (or multiple ranges for different sub-blocks).
  • Example 5 Usage of the updated MV invoked in BIO and/or other kinds of coding methods that may require MVs to be updated may be constrained.
  • the updated MV is used for future motion prediction (like in
  • updated MVs may be used for a first module but original MVs may be used for a second module.
  • the first module is motion prediction
  • the second module is deblocking.
  • future motion prediction refers to motion prediction in blocks to be coded/decoded after the current block in the current picture or slice.
  • future motion prediction refers to motion prediction in pictures or slices to be coded/decoded after the current picture or slice.
  • the updated MV can only be used in motion prediction of its non-immediately following CU/PUs in decoding order.
  • the updated MV can only be used as predictors for coding subsequent pictures/tiles/slices, such as TMVP in AMVP, and/or merge and/or affine mode.
  • the updated MV can only be used as predictors for coding subsequent pictures/tiles/slices, such as ATMVP and/or STMVP, etc. al.
  • Example 6 In one example, a two-step inter-prediction process is proposed wherein the first step is performed to generate some intermediate predictions (first predictions) based on the signaled/derived motion information associated with the current block and the second step is performed to derive final predictions of the current block (second predictions) based on updated motion information which may rely on the intermediate predictions.
  • the BIO procedure i.e., using signaled/derived motion information which is used to generate the first predictions and the spatial gradient, the temporal gradient and the optical flow of each sub-block/pixel within the block
  • the BIO procedure i.e., using signaled/derived motion information which is used to generate the first predictions and the spatial gradient, the temporal gradient and the optical flow of each sub-block/pixel within the block
  • the updated MV is then used to perform motion compensation and generate the second prediction (i.e., the final prediction) of each sub-block/pixel within the block.
  • shorter-tap filters like 6-tap filters, 4-tap filters or bilinear filters
  • 6-tap filters like 6-tap filters, 4-tap filters or bilinear filters
  • the filters (such as filter taps, filter coefficients) utilized in the first/second steps may be pre-defined.
  • the selected filter tap for the first and/or second step may depend on coded information, such as block sizes/block shapes (square, non square, etc. al)/slice types/prediction directions (uni or bi-prediction or multiple-hypothesis, forward or backward).
  • different block may choose different filters for the first/second steps.
  • one or more candidate sets of multiple filters may be pre-defined or signaled.
  • a block may select from the candidate sets.
  • the selected filter may be indicated by a signaled index or may be derived on-the-fly without being signaled.
  • a fractional MV is rounded to the closest integer MV.
  • the fractional MV is rounded to the closest integer MV that is no smaller than the fractional MV.
  • fractional MV is rounded to the closest integer
  • Usage of such a method may be signaled in SPS, PPS, Slice header, CTUs or
  • Usage of such a method may further depend on coded information, such as block sizes/block shapes (square, non-square, etc. al)/slice types/prediction directions (uni or bi prediction or multiple-hypothesis, forward or backward).
  • such a method may be automatically disallowed under certain conditions, for example, it may be disabled when the current block is coded with the affine mode.
  • such a method may be automatically applied under certain conditions, such as when the block is coded with bi-prediction and block size is larger than a threshold (e.g., more than 16 samples).
  • a threshold e.g., more than 16 samples.
  • Example 7 it is proposed that before calculating the temporal gradient in BIO, a reference block (or a prediction block) may be modified firstly, and the calculation of temporal gradient is based on the modified reference block.
  • (ii) Alternatively, for different reference picture list, it may decide whether to remove the mean or not. For example, for one reference block/sub-block, mean is removed before calculating temporal gradients, while for another one, mean is not removed.
  • different reference blocks may select whether to be modified firstly or not.
  • mean is defined as the average of selected samples in the reference block.
  • reference blocks may be firstly filtered before being used to derive temporal gradients.
  • smooth filtering methods may be first applied to reference blocks.
  • the pixels at block boundaries are first filtered.
  • OBMC Overlapped Block Motion Compensation
  • Illumination Compensation (IC) is first applied before deriving temporal gradients.
  • weighted prediction is first applied before deriving temporal gradients.
  • temporal gradient is calculated first and then is modified. For example, temporal gradient is further subtracted by the difference between MeanO and Meanl.
  • Example 8 whether to update MV for BIO coded blocks and/or use updated MV for future motion prediction and/or how to use updated MV for future motion prediction may be signaled from the encoder to the decoder, such as in Video Parameter Set (VPS), Sequence Parameter Set (SPS), Picture Parameter Set (PPS), Slice header, CTUs or CUs.
  • VPS Video Parameter Set
  • SPS Sequence Parameter Set
  • PPS Picture Parameter Set
  • Slice header CTUs or CUs.
  • Example 9 it is proposed to add a constraint to motion vectors utilized in the BIO process.
  • (v x , v y ) are constrained to given ranges, -M x ⁇ v x ⁇ N x , and/or
  • M x , N x , M y , N y are none-negative integers, and may be equal to 32, for example.
  • updated MVs of a BIO-coded sub-block/a BIO-coded block are constrained to given ranges, such as -MLO X ⁇ mvL0’ x ⁇ NLO X and/or -MLI X ⁇ mvLl’ x ⁇ NLI X , -
  • N LOY , Mu y , Nu y are none-negative integers, and may be equal to 1024, 2048 and so on, for example.
  • Example 10 It is proposed that for BIO, DMVR, FRUC, template matching or other methods that require to update MV (or motion information including MV and/or reference pictures) from those derived from the bitstream, usage of the updated motion information may be constrained.
  • updated and non-updated motion information may be stored differently for different subblocks.
  • the updated motion information of some subblocks may be stored and for the other remaining subblocks, the non-updated motion information are stored.
  • the updated MV are only stored for boundary subblocks.
  • the updated motion information from a neighbouring block is not used if the neighbouring block and the current block are not in the same CTU or the same region with a size such as 64x64 or 32x32.
  • a neighbouring block is treated as“unavailable” if the neighbouring block and the current block are not in the same CTFT or the same region with a size such as 64x64 or 32x32.
  • the motion information without the updating process is used by the current block if the neighbouring block and the current block are not in the same CTU or the same region with a size such as 64x64 or 32x32.
  • the updated MVs from a neighbouring block are not used if the neighbouring block and the current block are not in the same CTU row or the same row of regions with a size such as 64x64 or 32x32.
  • a neighbouring block is treated as“unavailable” if the neighbouring block and the current block are not in the same CTU row or the same row of regions with a size such as 64x64 or 32x32.
  • the motion information without the updating process is used by the current block if the neighbouring block and the current block are not in the same CTU row or the same row of regions with a size such as 64x64 or 32x32.
  • the motion information of a block is not updated if the bottom-most row of the block is the bottom-most row of a CTU or a region of a size such as 64x64 or 32x32.
  • the motion information of a block is not updated if the right most column of the block is the right-most column of a CTU or a region of a size such as 64x64 or 32x32.
  • CTU or top-left region are used for current CTU.
  • CTU or top-right region are used for current CTU.
  • region is of size such as 64x64 or 32x32.
  • Example 11 In one example, it is proposed that different MVD precisions maybe used in AF INTER mode and a syntax element may be signaled to indicate the MVD precision for each block/CU/PU.
  • the syntax element is present under further conditions, such as when there is non-zero MVD component of the block/CU/PU.
  • the MVD precision information is always signaled regardless whether there is any non-zero MVD component or not.
  • Example 12 it is proposed that different Decoder-side Motion Vector Derivation (DMVD) methods like BIO, DMVR, FRUC and template matching etc. work independently if more than one DMVD methods are performed for a block (e.g., PET), i.e., the input of a DMVD method does not depend on the output of another DMVD method.
  • DMVD Decoder-side Motion Vector Derivation
  • one prediction block and/or one set of updated motion information are generated from the multiple sets of motion information derived by the multiple DMVD methods.
  • motion compensation is performed using the derived motion information of each DMVD method, and they are averaged or weighted averaged or filtered (like by median filter) to generate the final prediction.
  • the derived motion information of all DMVD methods are averaged or weighted averaged or filtered (like by median filter) to generate the final motion information.
  • different priorities are assigned to different DMVD methods, and motion information derived by the method with the highest priority is selected as the final motion information. For example, when both BIO and DMVR are performed for a PU, then motion information generated by DMVR is used as the final motion information.
  • the DMVD methods are performed in a simultaneous way.
  • the updated MV of one DMVD method is not input as the start-point of the next DMVD method.
  • the non-updated MV is input as the searching start-point.
  • the DMVD methods are performed in a cascade way.
  • the updated MV of one DMVD method is input as the searching start-point of the next DMVD method.
  • the refined MVs may be used for motion vector prediction of following blocks within current slice/CTU row/tile, and/or filtering process (e.g., deblocking filter process) and/or motion vector prediction for blocks located at different pictures.
  • filtering process e.g., deblocking filter process
  • the derived motion vector pointing from the sub-block in reference block 0 to the sub-block in reference block 1, denoted by (DMV X , DMV y ), is used to further improve prediction of the current sub-block.
  • MVL0 x ' MVL0 x -
  • MVL0 y ' MVL0 y - (( DMV y + l) » l)
  • MVL1 X ' MVL1 X + (( DMV X + 1) » l)
  • MVLl y ' MVLl y + ( ⁇ DMV y + l) » l)
  • this method is employed only when the current CU is predicted from a preceding picture and a following picture, and therefore only works in the Random Access (RA) configuration.
  • RA Random Access
  • Example 13 The proposed method may be applied under certain conditions, such as block sizes, slice/picture/tile types.
  • Example 14 The above methods may be applied in a sub-block level.
  • BIO updating process or a two-step inter prediction process or a temporal gradient derivation method described in Example 7, may be invoked for each sub-block.
  • the block when a block with either width or height or both width and height are both larger than (or equal to ) a threshold L, the block may be split into multiple sub blocks. Each sub-block is treated in the same way as a normal coding block with size equal to the sub-block size.
  • Example 15 The threshold may be pre-defined or signaled in
  • the thresholds may be depend on certain coded information, such as block size, picture type, temporal layer index, etc.
  • FIG. 27 shows a flowchart of an exemplary method for video decoding.
  • the method 2700 includes, at step 2710, receiving a bitstream representation of a current block of video data.
  • the method 2700 includes, at step 2720, generating updated first and second reference motion vectors based on a weighted sum of a first scaled motion vector and first and second scaled reference motion vectors, respectively.
  • the first scaled motion vector is generated by scaling a first motion vector to a target precision
  • the first and second scaled reference motion vectors are generated by scaling first and second reference motion vectors to the target precision, respectively.
  • the first motion vector is derived based on the first reference motion vector from a first reference block and the second reference motion vector from a second reference block, and where the current block is associated with the first and second reference blocks.
  • an indication of the target precision is signaled in a Video Parameter Set (VPS), a Sequence Parameter Set (SPS), a Picture Parameter Set (PPS), a slice header, a coding tree unit (CTU) or a coding unit (CU).
  • VPS Video Parameter Set
  • SPS Sequence Parameter Set
  • PPS Picture Parameter Set
  • slice header a slice header
  • CTU coding tree unit
  • CU coding unit
  • the first motion vector has a first precision and the first and second reference motion vectors have a reference precision.
  • the first precision may be higher or lower than the reference precision.
  • the target precision may be set to either the first precision, the reference precision or a fixed (or predetermined) precision regardless of the first and reference precisions.
  • the first motion vector is derived based on a bi-directional optical flow (BIO) refinement using the first and second reference motion vectors.
  • BIO bi-directional optical flow
  • the method 2700 includes, at step 2730, processing the bitstream representation based on the updated first and second reference motion vectors to generate the current block.
  • the processing is based on a bi-directional optical flow (BIO) refinement or a decoder-side motion vector refinement (DMVR), and wherein the updated first and second reference motion vectors are clipped prior to the processing.
  • BIO bi-directional optical flow
  • DMVR decoder-side motion vector refinement
  • the processing is based on a bi-directional optical flow (BIO) refinement, and the updated first and second reference motion vectors are constrained to a predetermined range of values prior to the processing.
  • BIO bi-directional optical flow
  • the processing is based on a bi-directional optical flow (BIO) refinement, a decoder-side motion vector refinement (DMVR), frame-rate up conversion (FRUC) techniques or a template matching technique.
  • BIO bi-directional optical flow
  • DMVR decoder-side motion vector refinement
  • FRUC frame-rate up conversion
  • the updated first and second reference motion vectors are generated for inner sub-blocks that are not on a boundary of the current block.
  • the updated first and second reference motion vectors are generated for a subset of sub-blocks of the current block.
  • the processing is based on at least two techniques, which may include a bi-directional optical flow (BIO) refinement, a decoder-side motion vector refinement (DMVR), frame-rate up conversion (FRUC) techniques or a template matching technique.
  • BIO bi-directional optical flow
  • DMVR decoder-side motion vector refinement
  • FRUC frame-rate up conversion
  • the processing is performed for each of the at least two techniques to generate multiple sets of results, which may be averaged or filtered to generate the current block.
  • the processing is performed in a cascaded manner for each of the at least two techniques to generate the current block.
  • FIG. 28 shows a flowchart of an exemplary method for video decoding.
  • the method 2800 includes, at step 2810, generating, for a current block, an intermediate prediction based on a first motion information associated with the current block.
  • generating the intermediate prediction comprises a first interpolation filtering process.
  • the generating the intermediate prediction is further based on signaling in a sequence parameter set (SPS), a picture parameter set (PPS), a coding tree unit (CTU), a slice header, a coding unit (CU) or a group of CTUs.
  • SPS sequence parameter set
  • PPS picture parameter set
  • CTU coding tree unit
  • CU coding unit
  • group of CTUs a group of CTUs.
  • the method 2800 includes, at step 2820, updating the first motion information to a second motion information.
  • updating the first motion information comprises using a bi-directional optical flow (BIO) refinement.
  • BIO bi-directional optical flow
  • the method 2800 includes, at step 2830, generating a final prediction for the current block based on the intermediate prediction or the second motion information.
  • generating the final prediction comprises a second interpolation filtering process.
  • the first interpolation filtering process uses a first set of filters that are different from a second set of filters used by the second interpolation filtering process.
  • at least one filter tap of the first or second interpolation filtering process is based on a dimension, a prediction direction, or a prediction type of the current block.
  • FIG. 29 shows a flowchart of another exemplary method for video decoding. This example includes some features and/or steps that are similar to those shown in FIG. 28, and described above. At least some of these features and/or components may not be separately described in this section.
  • the method 2900 includes, at step 2910, receiving a bitstream representation of a current block of video data.
  • step 2910 includes receiving the bitstream representation from a memory location or buffer in a video encoder or decoder.
  • step 2910 includes receiving the bitstream representation over a wireless or wired channel at a video decoder.
  • step 2910 include receiving the bitstream representation from a different module, unit or processor, which may implement one or more methods as described in, but not limited to, the embodiments in the present document.
  • the method 2900 includes, at step 2920, generating intermediate motion information based on motion information associated with the current block.
  • the method 2900 includes, at step 2930, generating updated first and second reference motion vectors based on first and second reference motion vectors, respectively.
  • the current block is associated with first and second reference blocks.
  • the first and second reference motion vectors are associated with the first and second reference blocks, respectively.
  • the method 2900 includes, at step 2940, processing the bitstream representation based on the intermediate motion information or the updated first and second reference motion vectors to generate the current block.
  • the generating the updated first and second reference motion vectors is based on a weighted sum of a first scaled motion vector and first and second scaled reference motion vectors, respectively.
  • a first motion vector is derived based on the first reference motion vector and the second reference motion vector
  • the first scaled motion vector is generated by scaling the first motion vector to a target precision
  • the first and second scaled reference motion vectors are generated by scaling the first and second reference motion vectors to the target precision, respectively.
  • an indication of the target precision is signaled in a Video Parameter Set (VPS), a Sequence Parameter Set (SPS), a Picture Parameter Set (PPS), a slice header, a coding tree unit (CTU) or a coding unit (CU).
  • VPS Video Parameter Set
  • SPS Sequence Parameter Set
  • PPS Picture Parameter Set
  • slice header a slice header
  • CTU coding tree unit
  • CU coding unit
  • the first motion vector has a first precision and the first and second reference motion vectors have a reference precision.
  • the first precision may be higher or lower than the reference precision.
  • the target precision may be set to either the first precision, the reference precision or a fixed (or predetermined) precision regardless of the first and reference precisions.
  • the first motion vector is derived based on a bi-directional optical flow (BIO) refinement using the first and second reference motion vectors.
  • BIO bi-directional optical flow
  • the processing is based on a bi-directional optical flow (BIO) refinement, and the updated first and second reference motion vectors are constrained to a predetermined range of values prior to the processing.
  • the processing is based on a bi-directional optical flow (BIO) refinement or a decoder-side motion vector refinement (DMVR), and wherein the updated first and second reference motion vectors are clipped prior to the processing.
  • BIO bi-directional optical flow
  • DMVR decoder-side motion vector refinement
  • the processing is based on a bi-directional optical flow (BIO) refinement, a decoder-side motion vector refinement (DMVR), frame-rate up conversion (FRUC) techniques or a template matching technique.
  • BIO bi-directional optical flow
  • DMVR decoder-side motion vector refinement
  • FRUC frame-rate up conversion
  • the updated first and second reference motion vectors are generated for inner sub-blocks that are not on a boundary of the current block.
  • the updated first and second reference motion vectors are generated for a subset of sub-blocks of the current block.
  • the processing is based on at least two techniques, which may include a bi-directional optical flow (BIO) refinement, a decoder-side motion vector refinement (DMVR), frame-rate up conversion (FRUC) techniques or a template matching technique.
  • BIO bi-directional optical flow
  • DMVR decoder-side motion vector refinement
  • FRUC frame-rate up conversion
  • the processing is performed for each of the at least two techniques to generate multiple sets of results, which may be averaged or filtered to generate the current block.
  • the processing is performed in a cascaded manner for each of the at least two techniques to generate the current block.
  • FIG. 30 shows a flowchart of an exemplary method for video decoding.
  • the method 3000 includes, at step 3010, generating, for a current block, an intermediate prediction based on a first motion information associated with the current block.
  • generating the intermediate prediction comprises a first interpolation filtering process.
  • the generating the intermediate prediction is further based on signaling in a sequence parameter set (SPS), a picture parameter set (PPS), a coding tree unit (CTU), a slice header, a coding unit (CU) or a group of CTUs.
  • SPS sequence parameter set
  • PPS picture parameter set
  • CTU coding tree unit
  • CU coding unit
  • group of CTUs a group of CTUs.
  • the method 3000 includes, at step 3020, updating the first motion information to a second motion information.
  • updating the first motion information comprises using a bi-directional optical flow (BIO) refinement.
  • BIO bi-directional optical flow
  • the method 3000 includes, at step 3030, generating a final prediction for the current block based on the intermediate prediction or the second motion information.
  • generating the final prediction comprises a second interpolation filtering process.
  • the first interpolation filtering process uses a first set of filters that are different from a second set of filters used by the second interpolation filtering process.
  • at least one filter tap of the first or second interpolation filtering process is based on a dimension, a prediction direction, or a prediction type of the current block.
  • FIG. 31 shows a flowchart of another exemplary method for video decoding. This example includes some features and/or steps that are similar to those shown in FIG. 30, and described above. At least some of these features and/or components may not be separately described in this section.
  • the method 3100 includes, at step 3110, receiving a bitstream representation of a current block of video data.
  • step 3110 includes receiving the bitstream representation from a memory location or buffer in a video encoder or decoder.
  • step 3110 includes receiving the bitstream representation over a wireless or wired channel at a video decoder.
  • step 3110 include receiving the bitstream representation from a different module, unit or processor, which may implement one or more methods as described in, but not limited to, the embodiments in the present document.
  • the method 3100 includes, at step 3120, generating intermediate motion information based on motion information associated with the current block.
  • the method 3100 includes, at step 3130, generating updated first and second reference motion vectors based on first and second reference motion vectors, respectively.
  • the current block is associated with first and second reference blocks.
  • the first and second reference motion vectors are associated with the first and second reference blocks, respectively.
  • the method 3100 includes, at step 3140, processing the bitstream representation based on the intermediate motion information or the updated first and second reference motion vectors to generate the current block.
  • the generating the updated first and second reference motion vectors is based on a weighted sum of a first scaled motion vector and first and second scaled reference motion vectors, respectively.
  • a first motion vector is derived based on the first reference motion vector and the second reference motion vector
  • the first scaled motion vector is generated by scaling the first motion vector to a target precision
  • the first and second scaled reference motion vectors are generated by scaling the first and second reference motion vectors to the target precision, respectively.
  • an indication of the target precision is signaled in a Video Parameter Set (VPS), a Sequence Parameter Set (SPS), a Picture Parameter Set (PPS), a slice header, a coding tree unit (CTU) or a coding unit (CU).
  • VPS Video Parameter Set
  • SPS Sequence Parameter Set
  • PPS Picture Parameter Set
  • slice header a slice header
  • CTU coding tree unit
  • CU coding unit
  • the first motion vector has a first precision and the first and second reference motion vectors have a reference precision.
  • the first precision may be higher or lower than the reference precision.
  • the target precision may be set to either the first precision, the reference precision or a fixed (or predetermined) precision regardless of the first and reference precisions.
  • the first motion vector is derived based on a bi-directional optical flow (BIO) refinement using the first and second reference motion vectors.
  • BIO bi-directional optical flow
  • the processing is based on a bi-directional optical flow (BIO) refinement, and the updated first and second reference motion vectors are constrained to a predetermined range of values prior to the processing.
  • BIO bi-directional optical flow
  • the processing is based on a bi-directional optical flow (BIO) refinement or a decoder-side motion vector refinement (DMVR), and wherein the updated first and second reference motion vectors are clipped prior to the processing.
  • BIO bi-directional optical flow
  • DMVR decoder-side motion vector refinement
  • the processing is based on a bi-directional optical flow (BIO) refinement, a decoder-side motion vector refinement (DMVR), frame-rate up conversion (FRUC) techniques or a template matching technique.
  • BIO bi-directional optical flow
  • DMVR decoder-side motion vector refinement
  • FRUC frame-rate up conversion
  • the updated first and second reference motion vectors are generated for inner sub-blocks that are not on a boundary of the current block.
  • the updated first and second reference motion vectors are generated for a subset of sub-blocks of the current block.
  • the processing is based on at least two techniques, which may include a bi-directional optical flow (BIO) refinement, a decoder-side motion vector refinement (DMVR), frame-rate up conversion (FRUC) techniques or a template matching technique.
  • BIO bi-directional optical flow
  • DMVR decoder-side motion vector refinement
  • FRUC frame-rate up conversion
  • the processing is performed for each of the at least two techniques to generate multiple sets of results, which may be averaged or filtered to generate the current block.
  • the processing is performed in a cascaded manner for each of the at least two techniques to generate the current block.
  • FIG. 33 shows a flowchart of an exemplary method for video decoding.
  • the method 3300 includes, at step 3310, generating, for a current block, an intermediate prediction based on a first motion information associated with the current block.
  • generating the intermediate prediction comprises a first interpolation filtering process.
  • the generating the intermediate prediction is further based on signaling in a sequence parameter set (SPS), a picture parameter set (PPS), a coding tree unit (CTU), a slice header, a coding unit (CU) or a group of CTUs.
  • SPS sequence parameter set
  • PPS picture parameter set
  • CTU coding tree unit
  • CU coding unit
  • the method 3300 includes, at step 3320, updating the first motion information to a second motion information.
  • updating the first motion information comprises using a bi-directional optical flow (BIO) refinement.
  • BIO bi-directional optical flow
  • the method 3300 includes, at step 3330, generating a final prediction for the current block based on the intermediate prediction or the second motion information.
  • generating the final prediction comprises a second interpolation filtering process.
  • the first interpolation filtering process uses a first set of filters that are different from a second set of filters used by the second interpolation filtering process.
  • at least one filter tap of the first or second interpolation filtering process is based on a dimension, a prediction direction, or a prediction type of the current block.
  • FIG. 34 shows a flowchart of another exemplary method for video decoding. This example includes some features and/or steps that are similar to those shown in FIG. 33, and described above. At least some of these features and/or components may not be separately described in this section.
  • the method 3400 includes, at step 3410, receiving a bitstream representation of a current block of video data.
  • step 3410 includes receiving the bitstream representation from a memory location or buffer in a video encoder or decoder.
  • step 3410 includes receiving the bitstream representation over a wireless or wired channel at a video decoder.
  • step 3410 include receiving the bitstream representation from a different module, unit or processor, which may implement one or more methods as described in, but not limited to, the embodiments in the present document.
  • the method 3400 includes, at step 3420, generating intermediate motion information based on motion information associated with the current block.
  • the method 3400 includes, at step 3430, generating updated first and second reference motion vectors based on first and second reference motion vectors, respectively.
  • the current block is associated with first and second reference blocks.
  • the first and second reference motion vectors are associated with the first and second reference blocks, respectively.
  • the method 3400 includes, at step 3440, processing the bitstream representation based on the intermediate motion information or the updated first and second reference motion vectors to generate the current block.
  • the generating the updated first and second reference motion vectors is based on a weighted sum of a first scaled motion vector and first and second scaled reference motion vectors, respectively.
  • a first motion vector is derived based on the first reference motion vector and the second reference motion vector
  • the first scaled motion vector is generated by scaling the first motion vector to a target precision
  • the first and second scaled reference motion vectors are generated by scaling the first and second reference motion vectors to the target precision, respectively.
  • an indication of the target precision is signaled in a Video Parameter Set (VPS), a Sequence Parameter Set (SPS), a Picture Parameter Set (PPS), a slice header, a coding tree unit (CTU) or a coding unit (CU).
  • VPS Video Parameter Set
  • SPS Sequence Parameter Set
  • PPS Picture Parameter Set
  • slice header a slice header
  • CTU coding tree unit
  • CU coding unit
  • the first motion vector has a first precision and the first and second reference motion vectors have a reference precision.
  • the first precision may be higher or lower than the reference precision.
  • the target precision may be set to either the first precision, the reference precision or a fixed (or predetermined) precision regardless of the first and reference precisions.
  • the first motion vector is derived based on a bi-directional optical flow (BIO) refinement using the first and second reference motion vectors.
  • BIO bi-directional optical flow
  • the processing is based on a bi-directional optical flow (BIO) refinement, and the updated first and second reference motion vectors are constrained to a predetermined range of values prior to the processing.
  • BIO bi-directional optical flow
  • the processing is based on a bi-directional optical flow (BIO) refinement or a decoder-side motion vector refinement (DMVR), and wherein the updated first and second reference motion vectors are clipped prior to the processing.
  • BIO bi-directional optical flow
  • DMVR decoder-side motion vector refinement
  • the processing is based on a bi-directional optical flow (BIO) refinement, a decoder-side motion vector refinement (DMVR), frame-rate up conversion (FRUC) techniques or a template matching technique.
  • BIO bi-directional optical flow
  • DMVR decoder-side motion vector refinement
  • FRUC frame-rate up conversion
  • the updated first and second reference motion vectors are generated for inner sub-blocks that are not on a boundary of the current block.
  • the updated first and second reference motion vectors are generated for a subset of sub-blocks of the current block.
  • the processing is based on at least two techniques, which may include a bi-directional optical flow (BIO) refinement, a decoder-side motion vector refinement (DMVR), frame-rate up conversion (FRUC) techniques or a template matching technique.
  • BIO bi-directional optical flow
  • DMVR decoder-side motion vector refinement
  • FRUC frame-rate up conversion
  • the processing is performed for each of the at least two techniques to generate multiple sets of results, which may be averaged or filtered to generate the current block.
  • the processing is performed in a cascaded manner for each of the at least two techniques to generate the current block.
  • FIG. 35 shows a flowchart of an exemplary method for video decoding.
  • the method 3500 includes, at step 3510, generating, for a bitstream representation of a current block, an updated reference block by modifying a reference block associated with the current block.
  • the method 3500 further includes the step of filtering the reference block using a smoothing filter.
  • the method 3500 further includes the step of filtering pixels at block boundaries of the reference block.
  • the method 3500 further includes the step of applying overlapped block motion compensation (OBMC) to the reference block.
  • OBMC overlapped block motion compensation
  • the method 3500 further includes the step of applying illumination compensation (IC) to the reference block.
  • IC illumination compensation
  • the method 3500 further includes the step of applying a weighted prediction to the reference block.
  • the method 3500 includes, at step 3520, calculating, based on the updated reference block, a temporal gradient for a bi-directional optical flow (BIO) motion refinement.
  • BIO bi-directional optical flow
  • the method 3500 includes, at step 3530, performing, based on the temporal gradient, a conversion, which includes the BIO motion refinement, between the bitstream representation and the current block.
  • the conversion generates the current block from the bitstream representation (e.g., as might be implemented in a video decoder).
  • the conversion generates the bitstream representation from the current block (e.g., as might be implemented in a video encoder).
  • the method 3500 further includes the steps of computing a mean value for the reference block, and subtracting the mean value from each pixel of the reference block.
  • computing the mean value is based on all pixels of the reference block.
  • computing the mean value is based on all pixels in a sub block of the reference block.
  • computing the mean value is based on a subset of pixels (in other words, not all the pixels) of the reference block.
  • the subset of pixels includes pixels in every fourth row or column of the reference block.
  • the subset of pixels includes four corner pixels.
  • the subset of pixels includes the four corner pixels and a center pixel.
  • FIG. 36 shows a flowchart of another exemplary method for video decoding. This example includes some features and/or steps that are similar to those shown in FIG. 35, and described above. At least some of these features and/or components may not be separately described in this section.
  • the method 3600 includes, at step 3610, generating, for a bitstream representation of a current block, a temporal gradient for a bi-directional optical flow (BIO) motion refinement.
  • BIO bi-directional optical flow
  • the method 3600 includes, at step 3620, generating an updated temporal gradient by subtracting a difference of a first mean value and a second mean value from the temporal gradient, where the first mean value is a mean value for a first reference block, the second mean value is a mean value for a second reference block, and the first and second reference blocks are associated with the current block.
  • the mean value is based on all pixels of the corresponding reference block (e.g., the first mean value is computed as the average of all the pixels of the first reference block). In another example, computing the mean value is based on all pixels in a sub block of the corresponding reference block.
  • the mean value is based on a subset of pixels (in other words, not all the pixels) of the corresponding reference block.
  • the subset of pixels includes pixels in every fourth row or column of the corresponding reference block.
  • the subset of pixels includes four corner pixels.
  • the subset of pixels includes the four corner pixels and a center pixel.
  • the method 3600 includes, at step 3630, performing, based on the updated temporal gradient, a conversion, which includes the BIO motion refinement, between the bitstream representation and the current block.
  • the conversion generates the current block from the bitstream representation (e.g., as might be implemented in a video decoder). In other embodiments, the conversion generates the bitstream representation from the current block (e.g., as might be implemented in a video encoder).
  • FIG. 38 shows a flowchart of an exemplary method for video processing.
  • the method 3800 includes, at step 3810, determining original motion information for a current block; at step 3820, scaling original motion vectors of the original motion information and derived motion vectors derived based on the original motion vectors to a same target precision; at step 3830, generating updated motion vectors from the scaled original and derived motion vectors; and at step 3840, performing a conversion between the current block and a bitstream representation of a video including the current block, based on the updated motion vectors.
  • FIG. 39 shows a flowchart of an exemplary method for video processing.
  • the method 3900 includes, at step 3910, determining original motion information for a current block; at step 3920, updating original motion vectors of the original motion information for the current block based on a refining method; at step 3930, clipping the updated motion vectors to be within a range; and at step 3940, performing a conversion between the current block and a bitstream representation of a video including the current block, based on the clipped updated motion vectors.
  • FIG. 40 shows a flowchart of an exemplary method for video processing.
  • the method 4000 includes, at step 4010, determining original motion information associated with a current block; at step 4020, generating updated motion information based on specific prediction mode; and at step 4030, performing, based on the updated motion information, a conversion between the current block and a bitstream representation of a video data including the current block, wherein the specific prediction mode includes one or more of bi-directional optical flow (BIO) refinement, a decoder-side motion vector refinement (DMVR), frame-rate up conversion (FRUC) techniques or a template matching technique.
  • BIO bi-directional optical flow
  • DMVR decoder-side motion vector refinement
  • FRUC frame-rate up conversion
  • FIG. 41 shows a flowchart of an exemplary method for video processing.
  • the method 4100 includes, at step 41 10, determining a motion vector difference (MVD) precision for a current block processed with affine mode from an MVD precision set; at step 4120, performing, based on the determined MVD precision, a conversion between the current block and a bitstream representation of a video including the current block.
  • FIG. 42 shows a flowchart of an exemplary method for video processing.
  • the method 4200 includes, at step 4210, determining non -updated motion information associated with a current block; at step 4220, updating the non-updated motion information based on multiple decoder-side motion vector derivation (DMVD) methods to generate updated motion information for the current block; at step 4230, performing, based on the updated motion information, a conversion between the current block and a bitstream representation of a video including the current block.
  • DMVD decoder-side motion vector derivation
  • FIG. 43 shows a flowchart of an exemplary method for video processing.
  • the method 4300 includes, at step 4310, generating, for a current block, intermediate predictions based on a first motion information associated with the current block; at step 4320, updating the first motion information to a second motion information based on the intermediate predictions; and at step 4330, generating a final prediction for the current block based on the second motion information.
  • FIG. 37 is a block diagram of a video processing apparatus 3700.
  • the apparatus 3700 may be used to implement one or more of the methods described herein.
  • the apparatus 3700 may be embodied in a smartphone, tablet, computer, Internet of Things (IoT) receiver, and so on.
  • the apparatus 3700 may include one or more processors 3702, one or more memories 3704 and video processing hardware 3706.
  • the processor(s) 3702 may be configured to implement one or more methods (including, but not limited to, methods 2700-3100, 3300-3600 and 3800-4200) described in the present document.
  • the memory (memories) 3704 may be used for storing data and code used for implementing the methods and techniques described herein.
  • the video processing hardware 3706 may be used to implement, in hardware circuitry, some techniques described in the present document.
  • the video coding methods may be implemented using an apparatus that is implemented on a hardware platform as described with respect to FIG. 37.
  • a video processing method comprising: determining original motion information for a current block; scaling original motion vectors of the original motion information and derived motion vectors derived based on the original motion vectors to a same target precision; generating updated motion vectors from the scaled original and derived motion vectors; and performing a conversion between the current block and a bitstream representation of a video including the current block, based on the updated motion vectors.
  • mvLX’ x sign(mvLX x ) * (abs(mvLX x ) « N)
  • mvLX’ y sign(mvLX y ) * (abs(mvLX y ) « N)
  • curr_mv_precision is the precision of the original motion vectors
  • targ_mv_precision is a precision of the derived motion vectors as the target precision
  • v’ x sign(v x ) * ((abs(v x ) + offset) » N)
  • v’ y sign(v y ) * ((abs(v y ) + offset) » N) [00457] when the derived motion vectors are to be right-shifted by N to achieve the target precision
  • (v x , v y ) are the derived motion vectors
  • (v’ x , v’ y ) are the scaled derived motion vectors
  • offset is an offset applied to the derived motion vectors to achieve the target precision
  • function sign(.) returns a sign of an input parameter
  • function abs(.) returns absolute value of an input parameter
  • N log2(curr_mv_precision/targ_mv_precision), wherein curr_mv_precision is the first precision, and targ_mv_precision is the second precision.
  • (mvL0 x , mvL0 y ) and (mvLl x , mvLl y ) are the original motion vectors
  • (mvLO’ x , mvLO’ y ) and (mvLl’ x , mvLl’ y ) are the updated motion vectors
  • (v x , v y ) are the derived motion vectors
  • So and Si are scaling factors.
  • (mvL0 x , mvL0 y ) and (mvLl x , mvLl y ) are the original motion vectors
  • (mvLO’ x , mvLO’ y ) and (mvLl’ x , mvLl’ y ) are the updated motion vectors
  • (v x , v y ) are the derived motion vectors
  • offsetO and offsetlare offsets and So and Si are scaling factors.
  • mvLO’ x ((-v x + l)»l) + mvLO x
  • mvLO’ y (-(v y + 1) »l) + mvL0 y
  • mvLl’ x ((v x + 1) »l) + mvLl x
  • mvLl’ y ((v y + l)»l)+ mvLl y
  • (mvL0 x , mvL0 y ) and (mvLl x , mvLl y ) are the original motion vectors
  • (mvLO’ x , mvLO’ y ) and (mvLl’ x , mvLl’ y ) are the updated motion vectors
  • (v x , v y ) are the derived motion vectors.
  • mvLO’ x - SFo * v x + mvL0 x
  • mvL0’ y -v y * SFo + mvLO y
  • mvLl’ x - SFi* v x + mvLl x
  • mvLl’ y - SFi*v y + mvLl y
  • (mvL0 x , mvL0 y ) and (mvLl x , mvLl y ) are the original motion vectors
  • (mvLO’ x , mvLO’ y ) and (mvLl’ x , mvLl’ y ) are the updated motion vectors
  • (v x , v y ) are the derived motion vectors
  • SFo and SFi are scaling factors.
  • POC(Refo) POC(Refi) - POC(current)
  • POC(current), POC(Refo) and POC(Refi) are the picture order counts of the current block, a first reference block and a second reference block, respectively.
  • mvLO’ x SFACTo*v x + mvL0 x
  • mvL0’ y SFACTo*v y + mvL0 y
  • (mvL0 x , mvL0 y ) and (mvLl x , mvLl y ) are the original motion vectors
  • (mvLO’ x , mvLO’ y ) and (mvLl’ x , mvLl’ y ) are the updated motion vectors
  • (v x , v y ) are the derived motion vectors
  • SFACTo and SFACTi are scaling factors.
  • POC(Refo) POC(Refi) - POC(current)
  • POC(current), POC(Refo) and POC(Refi) are the picture order counts of the current block, a first reference block and a second reference block, respectively.
  • mvLO’ x ((-v x + offset) » (N + 1)) + mvL0 x
  • mvLO’ y ((-v y + offsetl) » (N + 1)) + mvLO y
  • mvLl’ x ((v x + offset) » (N + 1)) + mvLl x
  • mvLl’ y ((v y + offset2) » (N + 1)) + mvLl y ,
  • mvLO’ x -sign(v x ) * ((abs(v x ) + offsetO) » (N + 1)) + mvL0 x ,
  • mvLO’ y -sign(v y ) * ((abs(v y ) + offsetO) » (N + 1)) + mvLO y ,
  • mvLl’ x sign(v x ) * ((abs(v x ) + offsetl) » (N + 1)) + mvLl x ,
  • curr_mv_precision/targ_mv_precision is a precision of the original motion vectors
  • targ_mv_precision is a precision of the derived motion vector.
  • each of the first to fifth thresholds is pre-defined or signaled in sequence parameter set (SPS) level, or picture parameter set (PPS) level, or picture level, or slice level, or tile level.
  • SPS sequence parameter set
  • PPS picture parameter set
  • each of the first to fifth thresholds is defined depending on coded information including at least one of a block size, a picture type, and a temporal layer index.
  • An apparatus in a video system comprising a processor and a non-transitory memory with instructions thereon, wherein the instructions upon execution by the processor, cause the processor to implement the method in any one of examples 1.1 to 1.32.
  • a video processing method comprising: determining original motion information for a current block; updating original motion vectors of the original motion information for the current block based on a refining method; clipping the updated motion vectors to be within a range; and performing a conversion between the current block and a bitstream representation of a video including the current block, based on the clipped updated motion vectors.
  • the refining method comprises a bi directional optical flow (BIO) refinement, a decoder-side motion vector refinement (DMVR) , a frame-rate up conversion (FRUC) or a template matching.
  • BIO bi directional optical flow
  • DMVR decoder-side motion vector refinement
  • FRUC frame-rate up conversion
  • each of the first to fifth thresholds is pre-defined or signaled in sequence parameter set (SPS) level, or picture parameter set (PPS) level, or picture level, or slice level, or tile level.
  • SPS sequence parameter set
  • PPS picture parameter set
  • each of the first to fifth thresholds is defined depending on coded information including at least one of a block size, a picture type, and a temporal layer index.
  • 2.17 An apparatus in a video system comprising a processor and a non-transitory memory with instructions thereon, wherein the instructions upon execution by the processor, cause the processor to implement the method in any one of examples 2.1 to 2.16.
  • a computer program product stored on a non-transitory computer readable media including program code for carrying out the method in any one of examples 2.1 to 2.16.
  • a method for video processing comprising: determining original motion information associated with a current block; generating updated motion information based on specific prediction mode; and performing, based on the updated motion information, a conversion between the current block and a bitstream representation of a video data including the current block, wherein the specific prediction mode includes one or more of bi-directional optical flow (BIO) refinement, a decoder-side motion vector refinement (DMVR), frame-rate up conversion (FRUC) techniques or a template matching technique.
  • BIO bi-directional optical flow
  • DMVR decoder-side motion vector refinement
  • FRUC frame-rate up conversion
  • CTU or left region are used for the current CTU.
  • each of the first to fifth thresholds is pre-defined or signaled in sequence parameter set (SPS) level, or picture parameter set (PPS) level, or picture level, or slice level, or tile level.
  • SPS sequence parameter set
  • PPS picture parameter set
  • each of the first to fifth thresholds is defined depending on coded information including at least one of a block size, a picture type, and a temporal layer index.
  • a computer program product stored on a non-transitory computer readable media including program code for carrying out the method in any one of examples 3.1 to 3.45.
  • a video processing method comprising: determining a motion vector difference
  • MVD MVD precision for a current block processed with affine mode from an MVD precision set; performing, based on the determined MVD precision, a conversion between the current block and a bitstream representation of a video including the current block.
  • determining the MVD precision further comprises: determining the MVD precision for the current block based on a syntax element indicating the MVD precision.
  • each of the first to fifth thresholds is pre-defined or signaled in sequence parameter set (SPS) level, or picture parameter set (PPS) level, or picture level, or slice level, or tile level.
  • SPS sequence parameter set
  • PPS picture parameter set
  • each of the first to fifth thresholds is defined depending on coded information including at least one of a block size, a picture type, and a temporal layer index.
  • An apparatus in a video system comprising a processor and a non-transitory memory with instructions thereon, wherein the instructions upon execution by the processor, cause the processor to implement the method in any one of examples 4.1 to 4.33.
  • a computer program product stored on a non-transitory computer readable media including program code for carrying out the method in any one of examples 4.1 to 4.33.
  • a video processing method comprising: determining non-updated motion information associated with a current block; updating the non-updated motion information based on multiple decoder-side motion vector derivation (DMVD) methods to generate updated motion information for the current block; and performing, based on the updated motion information, a conversion between the current block and a bitstream representation of a video including the current block.
  • DMVD decoder-side motion vector derivation
  • the multiple DMVD methods include at least two of the followings: bi-directional optical flow (BIO) refinement, decoder-side motion vector refinement (DMVR), frame-rate up conversion (FRUC) technique, and template matching technique.
  • BIO bi-directional optical flow
  • DMVR decoder-side motion vector refinement
  • FRUC frame-rate up conversion
  • updating the non-updated motion information based on multiple decoder-side motion vector derivation (DMVD) methods to generate updated motion information for the current block further includes: deriving multiple sets of updated motion information by the multiple DMVD methods, generating a final set of updated motion information from the multiple sets of motion information.
  • DMVD decoder-side motion vector derivation
  • generating the final set of updated motion information from the multiple sets of motion information further includes: generating the final set of updated motion information based on an average or a weighted average of the multiple sets of motion information.
  • generating the final set of updated motion information from the multiple sets of motion information further includes: generating the final set of updated motion information by filtering the multiple sets of motion information using a median filter.
  • performing, based on the updated motion information, a conversion between the current block and a bitstream representation of a video including the current block further includes: performing motion compensation using multiple sets of updated motion information derived by the multiple DMVD method, respectively, to obtain multiple sets of motion compensation results, generating the current block based on an average or a weighted average of the multiple sets of motion compensation results.
  • performing, based on the updated motion information, a conversion between the current block and a bitstream representation of a video including the current block further includes: performing motion compensation using multiple sets of updated motion information derived by the multiple DMVD method, respectively, to obtain multiple sets of motion compensation results, generating the current block by filtering the multiple sets of motion compensation results using a median filter.
  • each of the first to fifth thresholds is pre-defined or signaled in sequence parameter set (SPS) level, or picture parameter set (PPS) level, or picture level, or slice level, or tile level.
  • SPS sequence parameter set
  • PPS picture parameter set
  • each of the first to fifth thresholds is defined depending on coded information including at least one of a block size, a picture type, and a temporal layer index.
  • An apparatus in a video system comprising a processor and a non-transitory memory with instructions thereon, wherein the instructions upon execution by the processor, cause the processor to implement the method in any one of examples 5.1 to 5.25.
  • a computer program product stored on a non-transitory computer readable media the computer program product including program code for carrying out the method in any one of examples 5.1 to 5.25.
  • a method of video processing comprising: generating, for a current block, intermediate predictions based on a first motion information associated with the current block; updating the first motion information to a second motion information based on the intermediate predictions; and generating a final prediction for the current block based on the second motion information.
  • coded information includes at least one of: a size of the current block, a shape of the current block, prediction directions, and a slice type.
  • coded information includes at least one of: a size of the current block, a shape of the current block, prediction directions, and a slice type.
  • each of the first to fifth thresholds is pre-defined or signaled in sequence parameter set (SPS) level, or picture parameter set (PPS) level, or picture level, or slice level, or tile level.
  • SPS sequence parameter set
  • PPS picture parameter set
  • each of the first to fifth thresholds is defined depending on coded information including at least one of a block size, a picture type, and a temporal layer index.
  • a computer program product stored on a non-transitory computer readable media including program code for carrying out the method in any one of examples 6.1 to 6.36.
  • a video decoding apparatus comprising a processor configured to implement a method recited in anyone of examples 6.1 to 6.36.
  • a video encoding apparatus comprising a processor configured to implement a method recited in anyone of examples 6.1 to 6.36.
  • video processing may refer to video encoding, video decoding, video compression or video decompression.
  • video compression algorithms may be applied during conversion from pixel representation of a video to a corresponding bitstream representation or vice versa.
  • Implementations of the subject matter and the functional operations described in this patent document can be implemented in various systems, digital electronic circuitry, or in computer software, firmware, or hardware, including the structures disclosed in this specification and their structural equivalents, or in combinations of one or more of them.
  • Implementations of the subject matter described in this specification can be implemented as one or more computer program products, i.e., one or more modules of computer program instructions encoded on a tangible and non-transitory computer readable medium for execution by, or to control the operation of, data processing apparatus.
  • the computer readable medium can be a machine- readable storage device, a machine-readable storage substrate, a memory device, a composition of matter effecting a machine-readable propagated signal, or a combination of one or more of them.
  • the term“data processing unit” or“data processing apparatus” encompasses all apparatus, devices, and machines for processing data, including by way of example a
  • the apparatus can include, in addition to hardware, code that creates an execution environment for the computer program in question, e.g., code that constitutes processor firmware, a protocol stack, a database management system, an operating system, or a combination of one or more of them.
  • a computer program (also known as a program, software, software application, script, or code) can be written in any form of programming language, including compiled or interpreted languages, and it can be deployed in any form, including as a stand-alone program or as a module, component, subroutine, or other unit suitable for use in a computing environment.
  • a computer program does not necessarily correspond to a file in a file system.
  • a program can be stored in a portion of a file that holds other programs or data (e.g., one or more scripts stored in a markup language document), in a single file dedicated to the program in question, or in multiple coordinated files (e.g., files that store one or more modules, sub programs, or portions of code).
  • a computer program can be deployed to be executed on one computer or on multiple computers that are located at one site or distributed across multiple sites and interconnected by a communication network.
  • Processors suitable for the execution of a computer program include, by way of example, both general and special purpose microprocessors, and any one or more processors of any kind of digital computer. Generally, a processor will receive instructions and data from a read only memory or a random access memory or both.
  • the essential elements of a computer are a processor for performing instructions and one or more memory devices for storing instructions and data.
  • a computer will also include, or be operatively coupled to receive data from or transfer data to, or both, one or more mass storage devices for storing data, e.g., magnetic, magneto optical disks, or optical disks.
  • mass storage devices for storing data, e.g., magnetic, magneto optical disks, or optical disks.
  • a computer need not have such devices.
  • Computer readable media suitable for storing computer program instructions and data include all forms of nonvolatile memory, media and memory devices, including by way of example semiconductor memory devices, e.g., EPROM, EEPROM, and flash memory devices.
  • semiconductor memory devices e.g., EPROM, EEPROM, and flash memory devices.
  • the processor and the memory can be supplemented by, or incorporated in, special purpose logic circuitry.

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  • Engineering & Computer Science (AREA)
  • Multimedia (AREA)
  • Signal Processing (AREA)
  • Compression Or Coding Systems Of Tv Signals (AREA)

Abstract

Des modes de réalisation de la présente invention concernent une inter-prédiction en deux étapes. L'invention concerne un procédé de traitement vidéo, comprenant les étapes consistant à : générer, pour un bloc courant, des prédictions intermédiaires sur la base d'une première information de mouvement associée au bloc courant; mettre à jour les premières informations de mouvement en une seconde information de mouvement sur la base des prédictions intermédiaires; et générer une prédiction finale pour le bloc actuel sur la base des secondes informations de mouvement.
PCT/IB2019/057520 2018-09-06 2019-09-06 Inter-prédiction en deux étapes WO2020049512A1 (fr)

Applications Claiming Priority (4)

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CN2018104301 2018-09-06
CNPCT/CN2018/104301 2018-09-06
CNPCT/CN2018/109250 2018-10-06
CN2018109250 2018-10-06

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CN110881124B (zh) 2023-07-25
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