WO2020233600A1 - Compensation d'éclairage local simplifiée - Google Patents

Compensation d'éclairage local simplifiée Download PDF

Info

Publication number
WO2020233600A1
WO2020233600A1 PCT/CN2020/091299 CN2020091299W WO2020233600A1 WO 2020233600 A1 WO2020233600 A1 WO 2020233600A1 CN 2020091299 W CN2020091299 W CN 2020091299W WO 2020233600 A1 WO2020233600 A1 WO 2020233600A1
Authority
WO
WIPO (PCT)
Prior art keywords
samples
lic
block
video block
mode
Prior art date
Application number
PCT/CN2020/091299
Other languages
English (en)
Inventor
Na Zhang
Li Zhang
Kai Zhang
Hongbin Liu
Yue Wang
Original Assignee
Beijing Bytedance Network Technology Co., Ltd.
Bytedance Inc.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Beijing Bytedance Network Technology Co., Ltd., Bytedance Inc. filed Critical Beijing Bytedance Network Technology Co., Ltd.
Priority to CN202080037225.8A priority Critical patent/CN113841396B/zh
Publication of WO2020233600A1 publication Critical patent/WO2020233600A1/fr

Links

Images

Classifications

    • 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
    • H04N19/105—Selection of the reference unit for prediction within a chosen coding or prediction mode, e.g. adaptive choice of position and number of pixels used for 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
    • H04N19/10—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
    • H04N19/134—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
    • H04N19/136—Incoming video signal characteristics or properties
    • H04N19/137—Motion inside a coding unit, e.g. average field, frame or block difference
    • H04N19/139—Analysis of motion vectors, e.g. their magnitude, direction, variance or reliability
    • 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
    • H04N19/146—Data rate or code amount at the encoder output
    • H04N19/147—Data rate or code amount at the encoder output according to rate distortion criteria
    • 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
    • H04N19/10—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
    • H04N19/10—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
    • H04N19/182—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 a pixel
    • 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
    • H04N19/186—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 a colour or a chrominance component
    • 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
    • H04N19/583—Motion compensation with overlapping 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
    • H04N19/70—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

  • the present patent document relates to the field of video coding.
  • the present document provides techniques for incorporating simplified local illumination compensation in embodiments of video encoders or decoders.
  • a method of video processing includes making a decision, based on a coding mode of a current video block, regarding a selective application of a local illumination compensation (LIC) model on at least a portion of the current video block; and performing, based on the decision, a conversion between the current video block and a bitstream representation of the current video block.
  • LIC local illumination compensation
  • a method of video processing includes configuring, for a current video block comprising multiple sub-regions, each of the multiple sub-regions with a set of local illumination compensation (LIC) parameters; and performing, based on the configuring, a conversion between the current video block and a bitstream representation of the current video block.
  • LIC local illumination compensation
  • a method of video processing includes making a decision, for a current video block, regarding a selective enablement of a filtering process for the current video block based on a usage of a local illumination compensation (LIC) model on the current video block; and performing, based on the decision, a conversion between the current video block and a bitstream representation of the current video block.
  • LIC local illumination compensation
  • a method of video processing includes configuring, during a conversion between a current video block and a bitstream representation of the current video block, a local illumination compensation (LIC) model that is applied to the current video block, wherein a fixed number of one or more samples of neighboring blocks of the current video block are used to train the LIC model.
  • LIC local illumination compensation
  • a method of video processing includes deriving, for a conversion between a video block of a video and a bitstream representation of the video block, a motion candidate list, wherein a first candidate in the motion candidate list is set with a local illumination compensation (LIC) flag; and performing the conversion using the motion candidate list, wherein during the conversion, when the first candidate is selected from the motion candidate list, whether the LIC is enabled is determined based on the flag of the first candidate.
  • LIC local illumination compensation
  • a method of video processing includes determining, for a conversion between a video block of a video and a bitstream representation of the video block, at least one of : whether local illumination compensation (LIC) is enabled or disabled for at least a portion of the video block based on property of the video block, whether LIC is enabled for a reference picture list, and LIC parameters of at least one reference picture list; and performing the conversion based on the determination.
  • LIC local illumination compensation
  • a method of video processing includes determining, for a conversion between a video block of a video and a bitstream representation of the video block, whether to enable and/or how to apply in-loop filter process and/or post-reconstruction filtering process depend on usage of local illumination compensation (LIC) , wherein the in-loop filter process includes deblocking filter, a sample adaptive offset (SAO) , an adaptive loop filter (ALF) , and the post-reconstruction filtering process includes bilateral filter; and performing the conversion based on the determination.
  • LIC local illumination compensation
  • a method of video processing includes deriving, for a conversion between a video block of a video and a bitstream representation of the video block, local illumination compensation (LIC) parameters in a LIC model that is applied to the video block by using a fixed number of neighboring samples of the video block; and performing the conversion based on the LIC parameters.
  • LIC local illumination compensation
  • the various techniques described herein may be embodied as a computer program product stored on a non-transitory computer readable media.
  • the computer program product includes program code for carrying out the methods described herein.
  • a video decoder apparatus may implement a method as described herein.
  • FIG. 1 shows an example of a derivation process for merge candidates list construction.
  • FIG. 2 shows example positions of spatial merge candidates.
  • FIG. 3 shows examples of Candidate pairs considered for redundancy check of spatial merge candidates.
  • FIG. 4 shows example Positions for the second PU of N ⁇ 2N and 2N ⁇ N partitions.
  • FIG. 5 is an Illustration of motion vector scaling for temporal merge candidate.
  • FIG. 6 shows examples of Candidate positions for temporal merge candidate, C0 and C1.
  • FIG. 7 shows an example of combined bi-predictive merge candidate
  • FIG. 8 shows an example of a derivation process for motion vector prediction candidates.
  • FIG. 9 is an example illustration of motion vector scaling for spatial motion vector candidate.
  • FIG. 10 illustrates an example of advanced temporal motion vector predictor (ATMVP) for a Coding Unit (CU) .
  • ATMVP advanced temporal motion vector predictor
  • FIG. 11 shows an Example of one CU with four sub-blocks (A-D) and its neighboring blocks (a–d) .
  • FIG. 12 shows an example of a planar motion vector prediction process.
  • FIG. 13 is a flowchart of an example of encoding with different motion vector (MV) precision.
  • FIGS. 14A and 14B are examples of sub-blocks where OBMC applies.
  • FIG. 15 shows an example of neighboring samples used for deriving IC parameters.
  • FIG. 16 shows an example of the local illumination compensation (LIC) method for a 16 ⁇ 16 unit processing.
  • FIG. 17 is an illustration of splitting a coding unit (CU) into two triangular prediction units.
  • FIG. 18 shows an example of positions of neighboring blocks.
  • FIG. 19 shows an example in which a CU applies the 1 st weighting factor group.
  • FIG. 20 shows an example of motion vector storage implementation.
  • FIG. 21 shows an example of a simplified affine motion model.
  • FIG. 22 shows an example of affine MVF per sub-block.
  • FIG. 23 shows examples of (a) 4-paramenter affine model (b) and 6-parameter affine model.
  • FIG. 24 shows an example of a Motion Vector Predictor (MV) for AF_INTER mode.
  • MV Motion Vector Predictor
  • FIG. 25A-25B show examples of candidates for AF_MERGE mode.
  • FIG. 26 shows candidate positions for affine merge mode.
  • FIG. 27 shows example process for bilateral matching.
  • FIG. 28 shows example process of template matching.
  • FIG. 29 illustrates an implementation of unilateral motion estimation (ME) in frame rate upconversion (FRUC) .
  • FIG. 30 illustrates an embodiment of an Ultimate Motion Vector Expression (UMVE) search process.
  • UMVE Ultimate Motion Vector Expression
  • FIG. 31 shows examples of UMVE search points.
  • FIG. 32 shows an example of distance index and distance offset mapping.
  • FIG. 33 shows an example of an optical flow trajectory.
  • FIG. 34A-34B show examples of Bi-directional Optical flow (BIO) w/o block extension: a) access positions outside of the block; b) padding used in order to avoid extra memory access and calculation.
  • BIO Bi-directional Optical flow
  • FIG. 35 illustrates an example of using Decoder-side motion vector refinement (DMVR) based on bilateral template matching.
  • DMVR Decoder-side motion vector refinement
  • FIG. 36 shows an example of an architecture for luma mapping with chroma scaling (LMCS) .
  • FIG. 37 shows an example of locations of samples used for the derivation of parameters of the cross-component linear model (CCLM) mode.
  • CCLM cross-component linear model
  • FIGS. 38A and 38B show example locations of above neighboring row samples and left neighboring column samples, respectively.
  • FIG. 39 shows an example of a straight line between maximum and minimum luma values.
  • FIGS. 40A and 40B show examples of selected neighboring samples for deriving LIC parameters with 4 samples.
  • FIGS. 41A and 41 B show examples of selected neighboring samples for deriving LIC parameters with 8 samples.
  • FIGS. 42A and 42B show other examples of selected neighboring samples for deriving LIC parameters with 8 samples.
  • FIGS. 43A-43D show example methods for video processing.
  • FIG. 44 is a block diagram of a hardware platform for implementing the video coding or decoding techniques described in the present document.
  • FIG. 45 shows an example method for video processing.
  • FIG. 46 shows an example method for video processing.
  • FIG. 47 shows an example method for video processing.
  • FIG. 48 shows an example method for video processing.
  • This patent document is related to video coding technologies. Specifically, it is related to simplified local illumination compensation (LIC) in video coding. It may be applied to the existing video coding standard like HEVC, or the standard (Versatile Video Coding) to be finalized. It may be also applicable to future video coding standards or video codec.
  • LIC local illumination compensation
  • Video coding standards have evolved primarily through the development of the well-known ITU-T and ISO/IEC standards.
  • the ITU-T produced H. 261 and H. 263, ISO/IEC produced MPEG-1 and MPEG-4 Visual, and the two organizations jointly produced the H. 262/MPEG-2 Video and H. 264/MPEG-4 Advanced Video Coding (AVC) and H. 265/HEVC standards.
  • AVC H. 264/MPEG-4 Advanced Video Coding
  • H. 265/HEVC High Efficiency Video Coding
  • the video coding standards are based on the hybrid video coding structure wherein temporal prediction plus transform coding are utilized.
  • Joint Video Exploration Team JVET was founded by VCEG and MPEG jointly in 2015.
  • JVET Joint Exploration Model
  • 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. Usage of one of the two reference picture lists may also be signalled using inter_pred_idc. 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 (to be more precise, motion vector difference compared to a motion vector predictor) , corresponding reference picture index for each reference picture list and reference picture list usage are signalled explicitly per each PU.
  • Such a mode is named Advanced motion vector prediction (AMVP) in this disclosure.
  • the PU When signalling indicates that one of the two reference picture lists is to be used, 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.
  • Bi-prediction When signalling indicates that both of the reference picture lists are to be used, 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 1.2 Redundancy check for spatial candidates
  • steps are also schematically depicted in FIG. 1.
  • 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 obtained from step 1 does not reach the 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 2N ⁇ 2N prediction unit.
  • TU truncated unary binarization
  • a maximum of four merge candidates are selected among candidates located in the positions depicted in FIG. 2.
  • the order of derivation is A 1 , B 1 , B 0 , A 0 and B 2 .
  • Position B 2 is considered only when any PU of position A 1 , B 1 , B 0 , A 0 is not available (e.g. because it belongs to another slice or tile) or is intra coded.
  • candidate at position A 1 is added, the addition of the remaining candidates is subject to a redundancy check which ensures that candidates with same motion information are excluded from the list so that coding efficiency is improved.
  • a redundancy check To reduce computational complexity, not all possible candidate pairs are considered in the mentioned redundancy check. Instead only the pairs linked with an arrow in FIG.
  • FIG. 4 depicts the second PU for the case of N ⁇ 2N and 2N ⁇ N, respectively.
  • candidate at position A 1 is not considered for list construction. In fact, by adding this candidate will lead to two prediction units having the same motion information, which is redundant to just have one PU in a coding unit.
  • position B 1 is not considered when the current PU is partitioned as 2N ⁇ N.
  • tb is defined to be the POC difference between the reference picture of the current picture and the current picture
  • 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.
  • the position for the temporal candidate is selected between candidates C 0 and C 1 , as depicted in FIG. 6. If PU at position C 0 is not available, is intra coded, or is outside of the current CTU row, position C 1 is used. Otherwise, position C 0 is used in the derivation of the temporal merge candidate.
  • Zero merge candidate Combined bi-predictive merge candidates are generated by utilizing spatial and 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. As an example, FIG.
  • 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. Finally, no redundancy check is performed on these candidates.
  • HEVC defines the motion estimation region (MER) whose size is signalled in the picture parameter set using the “log2_parallel_merge_level_minus2” syntax element. When a MER is defined, merge candidates falling in the same region are marked as unavailable and therefore not considered in the list construction.
  • AMVP exploits spatio-temporal correlation of motion vector with neighboring PUs, which is used for explicit transmission of motion parameters.
  • a motion vector candidate list is constructed 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 signalling, 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) .
  • the maximum value to be encoded is 2 (see FIG. 8) .
  • 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 depicted 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.
  • a maximum of two candidates are considered among five potential candidates, which are derived from PUs located in positions as depicted in FIG. 2, those positions being the same as those of motion merge.
  • the order of derivation for the left side of the current PU is defined as A 0 , A 1 ,and scaled A 0 , scaled A 1 .
  • the order of derivation for the above side of the current PU is defined as B 0 , B 1 , B 2 , scaled B 0 , scaled B 1 , scaled B 2 .
  • the no-spatial-scaling cases are checked first followed by the spatial scaling. Spatial scaling is considered when the POC is different between the reference picture of the neighboring 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 neighboring PU is scaled in a similar manner as for temporal scaling, as depicted as FIG. 9.
  • the main 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.
  • 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
  • the motion compression for the reference frames is currently disabled.
  • the motion vectors temporal motion vector prediction is modified by fetching multiple sets of motion information (including motion vectors and reference indices) from blocks smaller than the current CU.
  • the sub-CUs are square N ⁇ N blocks (N is set to 4 by default) .
  • ATMVP predicts the motion vectors of the sub-CUs within a CU in two steps.
  • the first step is to identify the corresponding block in a reference picture with a so-called temporal vector.
  • the reference picture is called the motion source picture.
  • the second step is to split the current CU into sub-CUs and obtain the motion vectors as well as the reference indices of each sub-CU from the block corresponding to each sub-CU, as shown in FIG. 10.
  • a reference picture and the corresponding block is determined by the motion information of the spatial neighboring blocks of the current CU.
  • the first merge candidate in the merge candidate list of the current CU 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, in ATMVP, 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 is identified by the temporal vector in the motion source picture, by adding to the coordinate of the current CU the temporal vector.
  • the motion information of its corresponding block (the smallest motion grid that covers the center sample) is used to derive the motion information for the sub-CU.
  • the motion information of a corresponding N ⁇ N 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 (i.e.
  • motion vector MV x the motion vector corresponding to reference picture list X
  • motion vector MV y the motion vector corresponding to 0 or 1 and Y being equal to 1-X
  • FIG. 11 illustrates this concept. Let us consider an 8 ⁇ 8 CU which contains four 4 ⁇ 4 sub-CUs A, B, C, and D. The neighboring 4 ⁇ 4 blocks in the current frame are labelled as a, b, c, and d.
  • the motion derivation for sub-CU A starts by identifying its two spatial neighbours.
  • the first neighbour is the N ⁇ N block above sub-CU A (block c) . If this block c is not available or is intra coded the other N ⁇ N blocks above sub-CU A are checked (from left to right, starting at block c) .
  • the second neighbour is a block to the left of the sub-CU A (block b) . If block b is not available or is intra coded other blocks to the left of sub-CU A are checked (from top to bottom, staring at block b) .
  • 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 is derived by following the same procedure of TMVP derivation as specified in HEVC.
  • the motion information of the collocated block at location D is fetched and scaled accordingly.
  • all available motion vectors (up to 3) 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. Up to seven merge candidates are 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 is needed for the two additional merge candidates.
  • Pairwise average candidates are generated by averaging predefined pairs of candidates in the current merge candidate list, and the predefined pairs are defined as ⁇ (0, 1) , (0, 2) , (1, 2) , (0, 3) , (1, 3) , (2, 3) ⁇ , where the numbers denote the merge indices to the merge candidate list.
  • the averaged motion vectors are calculated separately for each reference list. If both motion vectors are available in one list, these two motion vectors are averaged even when they point to different reference pictures; if only one motion vector is available, use the one directly; if no motion vector is available, keep this list invalid.
  • the pairwise average candidates replace the combined candidates in HEVC standard.
  • Planar motion vector prediction is proposed.
  • FIG. 12 gives a brief description of the planar motion vector prediction process.
  • Planar motion vector prediction is achieved by averaging a horizontal and vertical linear interpolation on 4x4 block basis as follows.
  • W and H denote the width and the height of the block.
  • (x, y) is the coordinates of current sub-block relative to the above left corner sub-block. All the distances are denoted by the pixel distances divided by 4.
  • P (x, y) is the motion vector of current sub-block.
  • the horizontal prediction P h (x, y) and the vertical prediction P v (x, y) for location (x, y) are calculated as follows:
  • L (-1, y) and R (W, y) are the motion vectors of the 4x4 blocks to the left and right of the current block.
  • a (x, -1) and B (x, H) are the motion vectors of the 4x4 blocks to the above and bottom of the current block.
  • the reference motion information of the left column and above row neighbour blocks are derived from the spatial neighbour blocks of current block.
  • the reference motion information of the right column and bottom row neighbour blocks are derived as follows.
  • AR is the motion vector of the above right spatial neighbour 4x4 block
  • BR is the motion vector of the bottom right temporal neighbour 4x4 block
  • BL is the motion vector of the bottom left spatial neighbour 4x4 block.
  • the motion information obtained from the neighboring blocks for each list is scaled to the first reference picture for a given list.
  • 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.
  • 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.
  • 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.
  • the encoding process is shown in FIG. 13.
  • 1/4 pel MV is tested and the RD cost is calculated and denoted as RDCost0
  • integer MV is tested and the RD cost is denoted as RDCost1.
  • RDCost1 ⁇ th *RDCost0 (wherein th is a positive value)
  • 4-pel MV is tested; otherwise, 4-pel MV is skipped.
  • motion information and RD cost etc. are already known for 1/4 pel MV when checking integer or 4-pel MV, which can be reused to speed up the encoding process of integer or 4-pel MV.
  • motion vector accuracy is one-quarter pel (one-quarter luma sample and one-eighth chroma sample for 4: 2: 0 video) .
  • 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, as described in section 2.2.2.
  • SHVC upsampling interpolation filters which have same filter length and normalization factor as 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 neighboring 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.
  • a MC block is corresponding 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 4 ⁇ 4, as illustrated in FIG. 14.
  • motion vectors of four connected neighboring sub-blocks are also used to derive prediction block for the current sub-block. These multiple prediction blocks based on multiple motion vectors are combined to generate the final prediction signal of the current sub-block.
  • Prediction block based on motion vectors of a neighboring sub-block is denoted as P N , 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 P C .
  • P N 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 P N . Otherwise, every sample of P N is added to the same sample in P C , i.e., four rows/columns of P N are added to P C .
  • the weighting factors ⁇ 1/4, 1/8, 1/16, 1/32 ⁇ are used for P N and the weighting factors ⁇ 3/4, 7/8, 15/16, 31/32 ⁇ are used for P C .
  • 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 P N are added to P C .
  • weighting factors ⁇ 1/4, 1/8 ⁇ are used for P N and weighting factors ⁇ 3/4, 7/8 ⁇ are used for P C .
  • For P N generated based on motion vectors of vertically (horizontally) neighboring sub-block samples in the same row (column) of P N are added to P C with a same weighting factor.
  • a CU level flag is signalled 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 Local Illumination Compensation
  • CU inter-mode coded coding unit
  • a least square error method is employed to derive the parameters a and b by using the neighbouring samples of the current block and its reference block (identified by motion information of the current block or sub-CU) .
  • the number of samples should be a power of 2 so that the divisions are carried out with right shifting.
  • the maximum number of neighboring samples N used by LIC (in case both sides are available) :
  • minDim min (cuHeight, cuWidth)
  • minStepBit minDim > 8 ? 1 : 0;
  • cuHeight and cuWidth are the height and width of the current block.
  • the LIC flag is copied from spatial, HMVP, and uni-direction pairwise merge candidates, in a way similar to motion information copy in merge mode; otherwise, an LIC flag is signalled for the CU to indicate whether LIC applies or not.
  • LIC flag is included as a part of motion information in addition to MVs and reference indices.
  • LIC flag is inherited from the neighbor blocks for merge candidates, but LIC flag is not used for motion vector pruning for simplification purpose.
  • LIC flag is not stored in the motion vector buffer of the reference picture, so LIC flag is always set equal to false for TMVP. LIC flag is also set equal to false for bi-directional merge candidates, such as pair-wise average candidate, and zero motion candidates.
  • LIC flag is context coded with a single context, when LIC tool is not applicable, LIC flag is not signaled.
  • the inverse reshaping is applied to the neighbor samples of the current block prior to LIC parameter derivation, since the current block neighbors are in the reshaped domain, but the reference picture samples are in the original (non-reshaped) domain.
  • LIC When LIC is enabled for a picture, 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 uses reconstructed samples from inter coded neighbors only. If the neighbor reconstructed sample is intra, CIIP or IBC coded, it will be replaced by the corresponding reference sample.
  • FIG. 16 shows the proposed method for 16x16 unit processing.
  • LIC parameters are calculated at first 16x16 block in the current block with referring the neighboring samples of the 16x16 block only.
  • LIC parameters are shared with other 16x16 blocks in the current block.
  • cuWidth (cu. blocks [compID] . width > vpdu_blk_size) ? vpdu_blk_size : cu.blocks [compID] . width;
  • cuHeight (cu. blocks [compID] . height > vpdu_blk_size) ? vpdu_blk_size : cu.blocks [compID] . height;
  • minDim min (cuHeight, cuWidth)
  • minStepBit minDim > 8 ? 1 : 0;
  • Multi-hypothesis prediction is proposed, wherein hybrid intra and inter prediction is one way to generate multiple hypotheses.
  • multi-hypothesis prediction When the multi-hypothesis prediction is applied to improve intra mode, multi-hypothesis prediction combines one intra prediction and one merge indexed prediction.
  • a merge CU In a merge CU, one flag is signaled for merge mode to select an intra mode from an intra candidate list when the flag is true.
  • the intra candidate list is derived from 4 intra prediction modes including DC, planar, horizontal, and vertical modes, and the size of the intra candidate list can be 3 or 4 depending on the block shape.
  • horizontal mode is exclusive of the intra mode list and when the CU height is larger than the double of CU width, vertical mode is removed from the intra mode list.
  • One intra prediction mode selected by the intra mode index and one merge indexed prediction selected by the merge index are combined using weighted average.
  • DM is always applied without extra signaling.
  • the weights for combining predictions are described as follow. When DC or planar mode is selected, or the CB width or height is smaller than 4, equal weights are applied. For those CBs with CB width and height larger than or equal to 4, when horizontal/vertical mode is selected, one CB is first vertically/horizontally split into four equal-area regions.
  • (w_intra 1 , w_inter 1 ) is for the region closest to the reference samples and (w_intra 4 , w_inter 4 ) is for the region farthest away from the reference samples.
  • the combined prediction can be calculated by summing up the two weighted predictions and right-shifting 3 bits.
  • the intra prediction mode for the intra hypothesis of predictors can be saved for reference of the following neighboring CUs.
  • the concept of the triangular prediction unit mode is to introduce a new triangular partition for motion compensated prediction. As shown in FIG. 17, it splits a CU into two triangular prediction units (PUs) , in either diagonal or inverse diagonal direction. Each triangular prediction unit in the CU is inter-predicted using its own uni-prediction motion vector and reference frame index which are derived from a uni- prediction candidate list. An adaptive weighting process is performed to the diagonal edge after predicting the triangular prediction units. Then, the transform and quantization process are applied to the whole CU. It is noted that this mode is only applied to skip and merge modes.
  • the uni-prediction candidate list consists of five uni-prediction motion vector candidates. It is derived from seven neighboring blocks including five spatial neighboring blocks (1 to 5) and two temporal co-located blocks (6 to 7) , as shown in FIG. 18. The motion vectors of the seven neighboring blocks are collected and put into the uni-prediction candidate list according in the order of uni-prediction motion vectors, L0 motion vector of bi-prediction motion vectors, L1 motion vector of bi-prediction motion vectors, and averaged motion vector of the L0 and L1 motion vectors of bi-prediction motion vectors. If the number of candidates is less than five, zero motion vector is added to the list.
  • ⁇ 1 st weighting factor group ⁇ 7/8, 6/8, 4/8, 2/8, 1/8 ⁇ and ⁇ 7/8, 4/8, 1/8 ⁇ are used for the luminance and the chrominance samples, respectively;
  • One weighting factor group is selected based on the comparison of the motion vectors of two triangular prediction units.
  • the 2 nd weighting factor group is used when the reference pictures of the two triangular prediction units are different from each other or their motion vector difference is larger than 16 pixels. Otherwise, the 1 st weighting factor group is used. An example is shown in FIG. 19.
  • the motion vectors (Mv1 and Mv2 in FIG. 20) of the triangular prediction units are stored in 4 ⁇ 4 grids.
  • either uni-prediction or bi-prediction motion vector is stored depending on the position of the 4 ⁇ 4 grid in the CU.
  • uni-prediction motion vector either Mv1 or Mv2
  • a bi-prediction motion vector is stored for the 4 ⁇ 4 grid located in the weighted area.
  • the bi-prediction motion vector is derived from Mv1 and Mv2 according to the following rules:
  • Mv1 and Mv2 have motion vector from different directions (L0 or L1) , Mv1 and Mv2 are simply combined to form the bi-prediction motion vector.
  • Mv2 is scaled to the picture.
  • Mv1 and the scaled Mv2 are combined to form the bi-prediction motion vector.
  • Mv1 is scaled to the picture.
  • the scaled Mv1 and Mv2 are combined to form the bi-prediction motion vector.
  • HEVC high definition motion model
  • MCP motion compensation prediction
  • JEM JEM
  • affine transform motion compensation prediction is applied. As shown in FIG. 21, the affine motion field of the block is described by two control point motion vectors.
  • the motion vector field (MVF) of a block is described by the following equation:
  • Equation 2 M and N should be adjusted downward if necessary to make it a divisor of w and h, respectively.
  • the motion vector of the center sample of each sub-block is calculated according to Equation 1, and rounded to 1/16 fraction accuracy. Then the motion compensation interpolation filters mentioned in section 2.2.5 are 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.
  • affine motion modes 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 signalled in the bitstream to indicate whether AF_INTER mode is used.
  • v 0 is selected from the motion vectors of the block A, B or C.
  • the motion vector from the neighbour block is scaled according to the reference list and the relationship among the POC of the reference for the neighbour block, the POC of the reference for the current CU and the POC of the current CU. And the approach to select v 1 from the neighbour 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. When the candidate list is larger than 2, the candidates are firstly sorted according to the consistency of the neighboring motion vectors (similarity of the two motion vectors in a pair candidate) and only the first two candidates are kept. An 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.
  • CPMVP control point motion vector prediction
  • an index indicating the position of the CPMVP in the candidate list is signalled in the bitstream.
  • MVD In AF_INTER mode, when 4/6 parameter affine mode is used, 2/3 control points are required, and therefore 2/3 MVD needs to be coded for these control points, as shown in FIG. 23. It is proposed to derive the MV as follows, i.e., mvd 1 and mvd 2 are predicted from mvd 0 .
  • two motion vectors e.g., mvA (xA, yA) and mvB (xB, yB)
  • newMV mvA + mvB and the two components of newMV is set to (xA + xB) and (yA + yB) , respectively.
  • MV of 2 or 3 control points needs to be determined jointly. Directly searching the multiple MVs jointly is computationally complex. A fast affine ME algorithm is proposed and is adopted into VTM/BMS.
  • the fast affine ME algorithm is described for the 4-parameter affine model, and the idea can be extended to 6-parameter affine model.
  • the motion vectors can be rewritten in vector form as:
  • MVD of AF_INTER are derived iteratively.
  • MV i (P) the MV derived in the ith iteration for position P
  • dMV C i the delta updated for MV C in the ith iteration.
  • MSE MSE
  • a CU When a CU is applied in AF_MERGE mode, it gets the first block coded with affine mode from the valid neighbour reconstructed blocks. And the selection order for the candidate block is from left, above, above right, left bottom to above left as shown in FIG. 25A, the motion vectors v 2 , v 3 and v 4 of the top left corner, above right corner and left bottom corner of the CU which contains the block A are derived. And the motion vector v 0 of the top left corner on the current CU is calculated according to v 2 , v 3 and v 4 . Secondly, the motion vector v 1 of the above right of the current CU is calculated.
  • the MVF of the current CU is generated.
  • an affine flag is signalled in the bitstream when there is at least one neighbour block is coded in affine mode.
  • FIG. 25A and 25B show examples of candidates for AF_MERGE
  • An affine merge candidate list is constructed with following steps:
  • Inherited affine candidate means that the candidate is derived from the affine motion model of its valid neighbor affine coded block.
  • the scan order for the candidate positions is: A1, B1, B0, A0 and B2.
  • full pruning process is performed to check whether same candidate has been inserted into the list. If a same candidate exists, the derived candidate is discarded.
  • Constructed affine candidate means the candidate is constructed by combining the neighbor motion information of each control point.
  • the coordinates of CP1, CP2, CP3 and CP4 is (0, 0) , (W, 0) , (H, 0) and (W, H) , respectively, where W and H are the width and height of current block.
  • the motion information of each control point is obtained according to the following priority order:
  • the checking priority is B2->B3->A2.
  • B2 is used if it is available. Otherwise, if B2 is available, B3 is used. If both B2 and B3 are unavailable, A2 is used. If all the three candidates are unavailable, the motion information of CP1 cannot be obtained.
  • the checking priority is B1->B0.
  • the checking priority is A1->A0.
  • Motion information of three control points are needed to construct a 6-parameter affine candidate.
  • the three control points can be selected from one of the following four combinations ( ⁇ CP1, CP2, CP4 ⁇ , ⁇ CP1, CP2, CP3 ⁇ , ⁇ CP2, CP3, CP4 ⁇ , ⁇ CP1, CP3, CP4 ⁇ ) .
  • Combinations ⁇ CP1, CP2, CP3 ⁇ , ⁇ CP2, CP3, CP4 ⁇ , ⁇ CP1, CP3, CP4 ⁇ will be converted to a 6-parameter motion model represented by top-left, top-right and bottom-left control points.
  • Motion information of two control points are needed to construct a 4-parameter affine candidate.
  • the two control points can be selected from one of the following six combinations ( ⁇ CP1, CP4 ⁇ , ⁇ CP2, CP3 ⁇ , ⁇ CP1, CP2 ⁇ , ⁇ CP2, CP4 ⁇ , ⁇ CP1, CP3 ⁇ , ⁇ CP3, CP4 ⁇ ) .
  • Combinations ⁇ CP1, CP4 ⁇ , ⁇ CP2, CP3 ⁇ , ⁇ CP2, CP4 ⁇ , ⁇ CP1, CP3 ⁇ , ⁇ CP3, CP4 ⁇ will be converted to a 4-parameter motion model represented by top-left and top-right control points.
  • reference index X (X being 0 or 1) of a combination
  • the reference index with highest usage ratio in the control points is selected as the reference index of list X, and motion vectors point to difference reference picture will be scaled.
  • full pruning process is performed to check whether same candidate has been inserted into the list. If a same candidate exists, the derived candidate is discarded.
  • Pattern matched motion vector derivation (PMMVD) mode is a special merge mode based on Frame-Rate Up Conversion (FRUC) techniques. With this mode, motion information of a block is not signalled but derived at decoder side.
  • PMMVD Pattern matched motion vector derivation
  • FRUC Frame-Rate Up Conversion
  • a FRUC flag is signalled for a CU when its merge flag is true.
  • FRUC flag is false, a merge index is signalled and the regular merge mode is used.
  • FRUC flag is true, an additional FRUC mode flag is signalled to indicate which method (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. That is the two matching modes (bilateral matching and template matching) are both 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.
  • 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.
  • 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 which 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 and 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 ⁇ H CU motion information derivation.
  • MV for the whole W ⁇ H CU is derived.
  • the CU is further split into M ⁇ M sub-CUs.
  • the value of M is calculated as in (16)
  • D is a predefined splitting depth which is set to 3 by default in the JEM. Then the MV for each sub-CU is derived.
  • 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 in two different reference pictures.
  • the motion vectors MV0 and MV1 pointing to the two reference blocks shall be proportional to the temporal distances, i.e., TD0 and TD1, between the current picture and the two reference pictures.
  • the bilateral matching becomes mirror based bi-directional MV.
  • template matching is used to derive motion information of the current CU by finding the closest match between a template (top and/or left neighboring blocks of the current CU) in the current picture and a block (same size to the template) in a reference picture. Except the aforementioned FRUC merge mode, the template matching is also applied to AMVP mode.
  • AMVP has two candidates.
  • template matching method a new candidate is 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 (meaning remove the second existing AMVP candidate) .
  • AMVP mode only CU level search is applied.
  • the MV candidate set at CU level consists of:
  • each valid MV of a merge candidate is used as an input to generate a MV pair with the assumption of bilateral matching.
  • one valid MV of a merge candidate is (MVa, refa) at reference list A.
  • the reference picture refb of its paired bilateral MV is found in the other reference list B so that refa and refb are temporally at different sides of the current picture. If such a refb is not available in reference list B, refb is determined as a reference which is different from refa 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 refa, refb.
  • MVs from the interpolated MV field are also added to the CU level candidate list. More specifically, the interpolated MVs at the position (0, 0) , (W/2, 0) , (0, H/2) and (W/2, H/2) of the current CU are added.
  • the original AMVP candidates are also added to CU level MV candidate set.
  • the MV candidate set at sub-CU level consists of:
  • ATMVP and STMVP candidates are limited to the four first ones.
  • 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 4 ⁇ 4 block level.
  • 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 4 ⁇ 4 block, the block’s motion is marked as unavailable in the interpolated motion field.
  • 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.
  • the encoder can choose among uni-prediction from list0, uni-prediction from list1 or bi-prediction for a CU. The selection is based on a template matching cost as follows:
  • costBi ⁇ factor *min (cost0, cost1)
  • cost0 is the SAD of list0 template matching
  • cost1 is the SAD of list1 template matching
  • costBi is the SAD of bi-prediction template matching.
  • the value of factor is equal to 1.25, which means that the selection process is biased toward bi-prediction.
  • P TraditionalBiPred is the final predictor for the conventional bi-prediction
  • P L0 and P L1 are predictors from L0 and L1, respectively
  • RoundingOffset and shiftNum are used to normalize the final predictor.
  • GBI Generalized Bi-prediction
  • P GBi is the final predictor of GBi. (1-w 1 ) and w 1 are the selected GBI weights applied to the predictors of L0 and L1, respectively. RoundingOffset GBi and shiftNum GBi are used to normalize the final predictor in GBi.
  • the supported weights of w 1 is ⁇ -1/4, 3/8, 1/2, 5/8, 5/4 ⁇ .
  • One equal-weight set and four unequal-weight sets are supported.
  • the process to generate the final predictor is exactly the same as that in the conventional bi-prediction mode.
  • the number of candidate weight sets is reduced to three.
  • the weight selection in GBI is explicitly signaled at CU-level if this CU is coded by bi-prediction.
  • the weight selection is inherited from the merge candidate.
  • GBI supports DMVR to generate the weighted average of template as well as the final predictor for BMS-1.0.
  • the weighting factor ⁇ is specified by the syntax element add_hyp_weight_idx, according to the following mapping:
  • prediction list0/list1 is abolished, and instead one combined list is used.
  • This combined list is generated by alternatingly inserting reference frames from list0 and list1 with increasing reference index, omitting reference frames which have already been inserted, such that double entries are avoided.
  • more than one additional prediction signals can be used.
  • the resulting overall prediction signal is accumulated iteratively with each additional prediction signal.
  • inter prediction blocks using MERGE mode (but not SKIP mode)
  • additional inter prediction signals can be specified.
  • MERGE not only the uni/bi prediction parameters, but also the additional prediction parameters of the selected merging candidate can be used for the current block.
  • multi-hypothesis prediction When the multi-hypothesis prediction is applied to improve uni-prediction of AMVP mode, one flag is signaled to enable or disable multi-hypothesis prediction for inter_dir equal to 1 or 2, where 1, 2, and 3 represent list 0, list 1, and bi-prediction, respectively. Moreover, one more merge index is signaled when the flag is true. In this way, multi-hypothesis prediction turns uni-prediction into bi-prediction, where one motion is acquired using the original syntax elements in AMVP mode while the other is acquired using the merge scheme. The final prediction uses 1: 1 weights to combine these two predictions as in bi-prediction.
  • the merge candidate list is first derived from merge mode with sub-CU candidates (e.g., affine, alternative temporal motion vector prediction (ATMVP) ) excluded.
  • sub-CU candidates e.g., affine, alternative temporal motion vector prediction (ATMVP)
  • each candidate of multi-hypothesis prediction implies a pair of merge candidates, containing one for the 1 st merge indexed prediction and the other for the 2 nd merge indexed prediction.
  • the merge candidate for the 2 nd merge indexed prediction is implicitly derived as the succeeding merge candidate (i.e., the already signaled merge index plus one) without signaling any additional merge index. After removing redundancy by excluding those pairs, containing similar merge candidates and filling vacancy, the candidate list for multi-hypothesis prediction is formed.
  • a merge or skip CU with multi-hypothesis prediction enabled can save the motion information of the additional hypotheses for reference of the following neighboring CUs in addition to the motion information of the existing hypotheses.
  • sub-CU candidates e.g., affine, ATMVP
  • multi-hypothesis prediction is not applied to skip mode.
  • the worst-case bandwidth (required access samples per sample) for each merge or skip CU with multi-hypothesis prediction enabled is calculated in Table 1 and each number is less than half of the worst-case bandwidth for each 4x4 CU with multi-hypothesis prediction disabled.
  • UMVE Ultimate motion vector expression
  • UMVE re-uses merge candidate as same as using in VVC.
  • a candidate can be selected, and is further expanded by the proposed motion vector expression method.
  • UMVE provides a new motion vector expression with simplified signaling.
  • the expression method includes starting point, motion magnitude, and motion direction.
  • FIG. 30 shows an example of UMVE Search Process
  • FIG. 31 shows examples of UMVE Search Points.
  • This proposed technique uses a merge candidate list as it is. But only candidates which are default merge type (MRG_TYPE_DEFAULT_N) are considered for UMVE’s expansion.
  • Base candidate index defines the starting point.
  • Base candidate index indicates the best candidate among candidates in the list as follows.
  • Base candidate IDX is not signaled.
  • Distance index is motion magnitude information.
  • Distance index indicates the pre-defined distance from the starting point information. Pre-defined distance is as follows:
  • Direction index represents the direction of the MVD relative to the starting point.
  • the direction index can represent of the four directions as shown below.
  • UMVE flag is singnaled right after sending a skip flag and merge flag. If skip and merge flag is true, UMVE flag is parsed. If UMVE flage is equal to 1, UMVE syntaxes are parsed. But, if not 1, AFFINE flag is parsed. If AFFINE flag is equal to 1, that is AFFINE mode, But, if not 1, skip/merge index is parsed for VTM’s skip/merge mode.
  • UMVE is extended to affine merge mode, we will call this UMVE affine mode thereafter.
  • the proposed method selects the first available affine merge candidate as a base predictor. Then it applies a motion vector offset to each control point’s motion vector value from the base predictor. If there’s no affine merge candidate available, this proposed method will not be used.
  • the selected base predictor s inter prediction direction, and the reference index of each direction is used without change.
  • the current block’s affine model is assumed to be a 4-parameter model, only 2 control points need to be derived. Thus, only the first 2 control points of the base predictor will be used as control point predictors.
  • a zero_MVD flag is used to indicate whether the control point of current block has the same MV value as the corresponding control point predictor. If zero_MVD flag is true, there’s no other signaling needed for the control point. Otherwise, a distance index and an offset direction index is signaled for the control point.
  • a distance offset table with size of 5 is used as shown in the table below.
  • Distance index is signaled to indicate which distance offset to use.
  • the mapping of distance index and distance offset values is shown in FIG. 32.
  • FIG. 31 shows an example of distance index and distance offset mapping.
  • the direction index can represent four directions as shown below, where only x or y direction may have an MV difference, but not in both directions.
  • the signaled distance offset is applied on the offset direction for each control point predictor. Results will be the MV value of each control point.
  • MV (v x , v y ) MVP (v px , v py ) + MV (x-dir-factor *distance-offset, y-dir-factor *distance-offset) ;
  • the signaled distance offset is applied on the signaled offset direction for control point predictor’s L0 motion vector; and the same distance offset with opposite direction is applied for control point predictor’s L1 motion vector. Results will be the MV values of each control point, on each inter prediction direction.
  • MV L0 (v 0x , v 0y ) MVP L0 (v 0px , v 0py ) + MV (x-dir-factor *distance-offset, y-dir-factor *distance-offset ) ;
  • MV L1 (v 0x , v 0y ) MVP L1 (v 0px , v 0py ) + MV (-x-dir-factor *distance-offset, -y-dir-factor *distance-offset ) ;
  • Bi-directional Optical flow is sample-wise motion refinement which is performed on top of block-wise motion compensation for bi-prediction.
  • the sample-level motion refinement doesn’t use signalling.
  • the motion vector field (v x , v y ) is given by an equation
  • ⁇ 0 and ⁇ 1 denote the distances to the reference frames as shown in FIG. 33.
  • the motion vector field (v x , v y ) is determined by minimizing the difference ⁇ between values in points A and B (intersection of motion trajectory and reference frame planes on FIG. 33) .
  • Model uses only first linear term of a local Taylor expansion for ⁇ :
  • Equation 26 All values in Equation 26 depend on the sample location (i′, j′) , which was omitted from the notation so far. Assuming the motion is consistent in the local surrounding area, we minimize ⁇ inside the (2M+1) ⁇ (2M+1) square window ⁇ 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
  • d bit depth of the video samples.
  • I (k) In order to keep the memory access for BIO the same as for regular bi-predictive motion compensation, all prediction and gradients values, I (k) , are calculated only for positions inside the current block.
  • (2M+1) ⁇ (2M+1) square window ⁇ centered in currently predicted point on a boundary of predicted block needs to accesses positions outside of the block (as shown in FIG. 34A) .
  • values of I (k) , outside of the block are set to be equal to the nearest available value inside the block. For example, this can be implemented as padding, as shown in FIG. 34B.
  • BIO it’s 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 is calculated based on 4 ⁇ 4 block.
  • the values of s n in Equation 30 of all samples in a 4 ⁇ 4 block are aggregated, and then the aggregated values of s n in are used to derived BIO motion vectors offset for the 4 ⁇ 4 block. More specifically, the following formula is used for block-based BIO derivation:
  • Equations 28 and 29 are replaced by ( (s n, bk ) >> 4 ) to derive the associated motion vector offsets.
  • MV regiment of BIO might be unreliable due to noise or irregular motion. Therefore, in BIO, the magnitude of MV regiment is clipped to a threshold value thBIO.
  • the threshold value is determined based on whether the reference pictures of the current picture are all from one direction. If all the reference pictures of the current picture are from one direction, the value of the threshold is set to 12 ⁇ 2 14-d ; otherwise, it is set to 12 ⁇ 2 13-d .
  • Gradients for BIO are calculated at the same time with motion compensation interpolation using operations consistent with HEVC motion compensation process (2D separable FIR) .
  • the input for this 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.
  • gradient filter BIOfilterG is applied in horizontal direction corresponding to the fractional position fracX with de-scaling shift by 18-d.
  • Table 2 Filters for gradients calculation in BIO Fractional pel position Interpolation filter for gradient (BIOfilterG) 0 ⁇ 8, -39, -3, 46, -17, 5 ⁇ 1/16 ⁇ 8, -32, -13, 50, -18, 5 ⁇ 1/8 ⁇ 7, -27, -20, 54, -19, 5 ⁇ 3/16 ⁇ 6, -21, -29, 57, -18, 5 ⁇ 1/4 ⁇ 4, -17, -36, 60, -15, 4 ⁇ 5/16 ⁇ 3, -9, -44, 61, -15, 4 ⁇ 3/8 ⁇ 1, -4, -48, 61, -13, 3 ⁇ 7/16 ⁇ 0, 1, -54, 60, -9, 2 ⁇ 1/2 ⁇ -1, 4, -57, 57, -4, 1 ⁇
  • Fractional pel position Interpolation filter for prediction signal (BIOfilterS) 0 ⁇ 0, 0, 64, 0, 0, 0 ⁇ 1/16 ⁇ 1, -3, 64, 4, -2, 0 ⁇ 1/8 ⁇ 1, -6, 62, 9, -3, 1 ⁇ 3/16 ⁇ 2, -8, 60, 14, -5, 1 ⁇ 1/4 ⁇ 2, -9, 57, 19, -7, 2 ⁇ 5/16 ⁇ 3, -10, 53, 24, -8, 2 ⁇ 3/8 ⁇ 3, -11, 50, 29, -9, 2 ⁇ 7/16 ⁇ 3, -11, 44, 35, -10, 3 ⁇ 1/2 ⁇ 3, -10, 35, 44, -11, 3 ⁇
  • BIO is applied to all bi-predicted blocks when the two predictions are from different reference pictures.
  • BIO is disabled.
  • BIO is not applied during the OBMC process. This means that BIO is only 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.
  • bi-prediction operation for the prediction of one block region, two prediction blocks, formed using a motion vector (MV) of list0 and a MV of list1, respectively, are combined to form a single prediction signal.
  • MV motion vector
  • DMVR decoder-side motion vector refinement
  • 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. average) of the two prediction blocks, from the initial MV0 of list0 and MV1 of list1, respectively, as shown in FIG. 35.
  • 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. 35, are used for generating the final bi-prediction results.
  • a sum of absolute differences (SAD) is used as the cost measure.
  • SAD sum of absolute differences
  • 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.
  • the history-based MVP (HMVP) merge candidates are added to merge list after the spatial MVP and TMVP.
  • HMVP history-based MVP
  • the motion information of a previously coded block is stored in a table and used as MVP for the current block.
  • the table with multiple HMVP candidates is maintained during the encoding/decoding process.
  • the table is reset (emptied) when a new CTU row is encountered. Whenever there is a non- subblock inter-coded CU, the associated motion information is added to the last entry of the table as a new HMVP candidate.
  • HMVP table size S is set to be 6, which indicates up to 6 History-based MVP (HMVP) candidates may be added to the table.
  • HMVP History-based MVP
  • FIFO constrained first-in-first-out
  • HMVP candidates could be used in the merge candidate list construction process.
  • the latest several HMVP candidates in the table are checked in order and inserted to the candidate list after the TMVP candidate. Redundancy check is applied on the HMVP candidates to the spatial or temporal merge candidate.
  • LMCS luma mapping with chroma scaling
  • FIG. 36 shows the LMCS architecture from decoder’s perspective.
  • the light shaded blocks in FIG. 36 indicate where the processing is applied in the mapped domain; and these include the inverse quantization, inverse transform, luma intra prediction and adding of the luma prediction together with the luma residual.
  • LMCS LMCS functional blocks, including forward and inverse mapping of the luma signal and a luma-dependent chroma scaling process.
  • LMCS can be enabled/disabled at the sequence level using an SPS flag.
  • Intra block copy is a tool adopted in HEVC extensions on SCC. It is well known that it significantly improves the coding efficiency of screen content materials. Since IBC mode is implemented as a block level coding mode, block matching (BM) is performed at the encoder to find the optimal block vector (or motion vector) for each CU.Here, a motion vector is used to indicate the displacement from the current block to a reference block, which is already reconstructed inside the current picture.
  • the luma motion vector of an IBC-coded CU is in integer precision.
  • the chroma motion vector is clipped to integer precision as well.
  • the IBC mode can switch between 1-pel and 4-pel motion vector precisions.
  • An IBC-coded CU is treated as the third prediction mode other than intra or inter prediction modes.
  • the IBC in VTM4 allows only the reconstructed portion of the predefined area including current CTU to be used. This restriction allows the IBC mode to be implemented using local on-chip memory for hardware implementations.
  • hash-based motion estimation is performed for IBC.
  • the encoder performs RD check for blocks with either width or height no larger than 16 luma samples.
  • the block vector search is performed using hash-based search first. If hash search does not return valid candidate, block matching based local search will be performed.
  • the search range is set to be N samples to the left and on top of the current block within the current CTU.
  • the value of N is initialized to 128 if there is no temporal reference picture, and initialized to 64 if there is at least one temporal reference picture.
  • a hash hit ratio is defined as the percentage of samples in the CTU that found a match using hash-based search. While encoding the current CTU, if the hash hit ratio is below 5%, N is reduced by half.
  • IBC mode is signalled with a flag and it can be signaled as IBC AMVP mode or IBC skip/merge mode as follows:
  • ⁇ IBC skip/merge mode a merge candidate index is used to indicate which of the block vectors in the list from neighboring candidate IBC coded blocks is used to predict the current block.
  • the merge list consists of spatial, HMVP, and pairwise candidates.
  • ⁇ IBC AMVP mode block vector difference is coded in the same way as a motion vector difference.
  • the block vector prediction method uses two candidates as predictors, one from left neighbor and one from above neighbor (if IBC coded) . When either neighbor is not available, a default block vector will be used as a predictor. A flag is signaled to indicate the block vector predictor index.
  • CCLM cross-component linear model
  • C (i, j) represents the predicted chroma samples in a CU and rec L ′ (i, j) represents the downsampled reconstructed luma samples of the same CU for color formats 4: 2: 0 or 4: 2: 2 while rec L ′ (i, j) represents the reconstructed luma samples of the same CU for color format 4: 4: 4.
  • CCLM Parameters ⁇ and ⁇ are derived by minimizing the regression error between the neighbouring reconstructed luma and chroma samples around the current block as follows:
  • L (n) represents the down-sampled (for color formats 4: 2: 0 or 4: 2: 2) or original (for color format 4: 4: 4) top and left neighbouring reconstructed luma samples
  • C (n) represents the top and left neighbouring reconstructed chroma samples
  • value of Nis equal to twice of the minimum of width and height of the current chroma coding block.
  • This regression error minimization computation is performed as part of the decoding process, not just as an encoder search operation, so no syntax is used to convey the ⁇ and ⁇ values.
  • MDLM multi-directional LM
  • two additional CCLM modes areET proposed: LM-A, where the linear model parameters are derived only based on the top neighboring samples as shown in FIG. 38A, and LM-L, where the linear model parameters are derived only based on the left neighboring samples as shown in FIG. 38B.
  • the 2 points (couple of Luma and Chroma) (A, B) are the minimum and maximum values inside the set of neighboring Luma samples as depicted in FIG. 39.
  • CCLM parameters The derivation of CCLM parameters involves quite a lot of comparison operations, which are not desirable in hardware or software design.
  • ⁇ W’ W+H when LM-A mode is applied;
  • ⁇ H’ H+W when LM-L mode is applied
  • the four neighbouring luma samples at the selected positions are down-sampled and compared four times to find two smaller values: x 0 A and x 1 A , and two larger values: x 0 B and x 1 B .
  • Their corresponding chroma sample values are denoted as y 0 A , y 1 A , y 0 B and y 1 B .
  • x A , x B , y A and y B are derived as:
  • LIC part of the neighboring samples of either current block or the first 16x16 block in the current block are used for deriving LIC parameters. Although in most cases not all neighboring samples are used, the computation complexity is still high especially for large blocks.
  • LIC when one block is coded with a pairwise candidate, LIC shall be disabled.
  • the IC flag associated with the pairwise candidate may be set to true.
  • the IC flag associated with the pairwise candidate may be set to true.
  • the IC flag associated with the pairwise candidate may be set to false.
  • the IC flag associated with the pairwise candidate may be set to false.
  • how to set the LIC flag may depend on the LIC flags associated with other merge candidates.
  • the first merge candidate is associated with an IC flag equal to true, then it is set to true for the zero motion merge candidate.
  • LIC may be enabled for the ATMVP-coded blocks.
  • whether to enable LIC or not may depend on the spatial merge candidate derived from a neighboring block, such as ‘A1’ block, as depicted with FIG. 10.
  • one set of LIC parameters for each reference picture list may be derived for the whole block.
  • all sub-blocks may share the same LIC parameters, if LIC is enabled for the sub-block.
  • the sub-block may be the top-left sub-block.
  • the sub-block may be the center sub-block.
  • Different sub-blocks may be selected for different color components.
  • multiple sets of LIC parameters for each reference picture list may be derived, and each sub-block within the block may select one from the multiple sets.
  • the sub-region may be defined as the sub-block for blocks coded with sub-block-based technologies, such as ATMVP, Affine.
  • LIC may be enabled for one reference picture list but disabled for the other reference picture list.
  • two LIC flags may be stored.
  • LIC flags may be both inherited from each of the two merge candidates which are used to derive the pairwise candidate.
  • the LIC parameters may be derived once for the two reference picture lists.
  • a may be derived according to the motion information of one reference picture list.
  • the neighboring samples relative to the two reference pictures in the two reference picture lists may be both utilized.
  • how to select the neighboring samples relative to the two reference pictures in the two reference picture lists may be different for the two lists.
  • LIC may be enabled for some sub-regions within one block and disabled for the remaining sub-regions.
  • one sub-block e.g., one 8x8 block
  • another sub-block may disable LIC.
  • one sub-block e.g., one 8x8 block
  • another sub-block may disable LIC.
  • Whether to enable LIC may depend on the position of a block.
  • LIC may be disabled.
  • LIC and transform bypass (TransBypass) mode e.g., TS mode, QR-BDPCM
  • TS mode TS mode
  • QR-BDPCM transform bypass
  • TransBypass mode e.g., TS mode
  • the signaling of transform skip mode may be skipped.
  • Side information of LIC mode may be signaled conditionally depending on the indication of usage of transform skip mode.
  • the signaling of side information of LIC mode may be skipped.
  • Whether to enable and/or how to apply in-loop filter process may depend on the usage of LIC.
  • in-loop filter process such as deblocking filter, SAO, ALF
  • post-reconstruction filtering process e.g., bilateral filter
  • the edge between them may still be filtered.
  • LIC utilizes a fixed number of the neighboring (adjacent or non-adjacent) samples to train the linear model parameters.
  • LIC may use a fixed denominator or value for shifting in the linear model parameter derivation process.
  • How many neighboring samples are used for deriving the LIC parameters may depend on the availability of neighboring samples, or/and dimensions of the block.
  • the selected samples may be located at (x-1, y + offsetY + Ky*H/Fy) and/or (x + offsetX + Kx *W/Fx, y-1) , where Fx samples are selected from the above neighbouring row, Kx may be from 0 to Fx –1 and Fy samples are selected from the left neighbouring column, Ky may be from 0 to Fy –1.
  • SH samples of left column and SW samples of above row may be selected, where SH ⁇ H and SW ⁇ W.
  • H is larger than W.
  • H is smaller than W.
  • N is an integer such as numSteps. In another example, N may depend on W and/or H.
  • SW samples of above row may be selected, where SW ⁇ W.
  • the selected samples may be located at (suppose the top-left coordinate of the current block is (x, y) , the width and height of the current block is W and H, respectively. ) :
  • N is an integer such as numSteps. In another example, N may depend on W and/or H.
  • SH samples of left column may be selected, where SH ⁇ H;
  • the selected samples may be located at:
  • N is an integer such as numSteps. In another example, N may depend on W and/or H.
  • N is an integer such as numSteps. In another example, N may depend on W and/or H:
  • the selected samples may be located at (suppose the top-left coordinate of the current block is (x, y) , the width and height of the current block is W and H, respectively. ) :
  • N is an integer such as numSteps.
  • N may depend on W and/or H:
  • the selected samples may be located at:
  • N is an integer such as numSteps. In another example, N may depend on W and/or H:
  • a least square error method may be employed to derive the LIC parameters.
  • a two-point method may be employed to derive the LIC parameters.
  • the 2 points x A and x B are the minimum and maximum sample inside the set of selected neighboring samples of the current block as depicted in 4.11. d or 4.11. e. Their corresponding samples in the reference picture are denoted as y A and y B
  • x A (x 0 A + x 1 A + x 2 A +x 3 A + off) >>2;
  • x B (x 0 B + x 1 B + x 2 B +x 3 B +off) >>2;
  • ⁇ is derived using the averaged values, which are calculated inside the set of selected neighboring samples of the current block and the set of selected neighboring samples of its reference block as depicted in 4.11. d or 4.11. e, instead of minimum values (x A , y A )
  • the one-side selection may be invoked only when the current block is non-square.
  • d if the height is larger than the width, only use the left neighboring samples of current block and its reference block to train LIC parameters.
  • a neighboring sample of current block is coded with intra mode and/or hybrid intra and inter mode or/and IBC mode, it may be considered as “unavailable” and replaced by an “available” (e.g., samples coded with non-intra mode and/or non-CIIP mode or/and non-IBC mode) neighboring sample.
  • a “unavailable” sample may be replaced by its nearest “available” neighboring sample.
  • the nearest available sample is the sample coded with non-intra mode and/or non-CIIP mode or/and non-IBC mode before or after current “unavailable” sample with the shortest distance in the order of fetching for above neighboring samples if current “unavailable” sample is in the above; for the left neighboring sample case, it is similar.
  • LIC may be disabled depending on block dimensions.
  • LIC may be disabled for 4 ⁇ 4 blocks.
  • padding may be applied to replace the unavailable samples, such as copied from available samples.
  • the selected neighboring samples coded with intra mode and/or hybrid intra and inter mode or/and IBC mode are excluded from derivation of LIC parameters.
  • the neighboring samples coded with non-intra mode and/or non-CIIP mode or/and non-IBC mode may be included in the derivation of LIC parameters.
  • the block width and height of current block is W and H, respectively.
  • the top-left coordinate of current block is [0, 0] .
  • the least square error method is employed to derive the LIC parameters. Selection of neighboring samples to be used for the LIC parameter derivation is defined as follows:
  • the two above samples’ coordinates are [W/4, -1] and [3*W/4, -1] .
  • the two left samples’ coordinates are [-1, H/4] and [-1, 3*H/4] .
  • the selected samples are painted in black as depicted in FIG. 40A.
  • samples are only selected from the above row. Four samples are selected when W>2 and two samples are selected when W is equal to 2.
  • the four selected above samples’ coordinates are [W/8, -1] , [W/8 + W/4, -1] , [W/8 + 2*W/4, -1] , and [W/8 + 3*W/4 , -1] .
  • the selected samples are painted in black as depicted in FIG. 40B.
  • the block width and height of current block is W and H, respectively.
  • the top-left coordinate of current block is [0, 0] .
  • the least square error method is employed to derive the LIC parameters. Selection of neighboring samples to be used for the LIC parameter derivation is defined as follows:
  • the four above samples’ coordinates are [W/8, -1] , [W/8 + W/4, -1] , [W/8 +2*W/4, -1] , and [W/8 + 3*W/4 , -1] .
  • the four left samples’ coordinates are [-1, H/8] , [-1, H/8 + H/4] , [-1, H/8 +2*H/4] , and [-1, H/8 + 3*H/4 ] .
  • the selected samples are painted in black as depicted in FIG. 41A.
  • the eight selected above samples’ coordinates are [W/16, -1] , [W/16 + W/8, -1] , [W/16 + 2*W/8, -1] , [W/16 + 3*W/8 , -1] , [W/16 + 4*W/8, -1] , [W/16 + 5*W/8 , -1] , [W/16 + 6*W/8, -1] , [W/16 + 7*W/8 , -1] .
  • the selected samples are painted in black as depicted in FIG. 41B.
  • the eight selected left samples’ coordinates are [-1, H/16] , [-1, H/16 + H/8] , [-1, H/16 + 2*H/8] , [-1, H/16 + 3*H/8 ] , [-1, H/16 + 4*H/8] , [-1, H/16 + 5*H/8 ] , [-1, H/16 +6*H/8] , [-1, H/16 + 7*H/8 ] .
  • the block width and height of current block is W and H, respectively.
  • the top-left coordinate of current block is [0, 0] .
  • the least square error method is employed to derive the LIC parameters. Selection of neighboring samples to be used for the LIC parameter derivation is defined as follows:
  • W is 16 when the width of the current block is larger than 16
  • H is 16 when the height of the current block is larger than 16.
  • the four above samples’ coordinates are [W/8, -1] , [W/8 + W/4, -1] , [W/8 +2*W/4, -1] , and [W/8 + 3*W/4 , -1] .
  • the four left samples’ coordinates are [-1, H/8] , [-1, H/8 + H/4] , [-1, H/8 +2*H/4] , and [-1, H/8 + 3*H/4 ] .
  • the selected samples are painted in black as depicted in FIG. 42A.
  • the eight selected above samples’ coordinates are [W/16, -1] , [W/16 + W/8, -1] , [W/16 + 2*W/8, -1] , [W/16 + 3*W/8 , -1] , [W/16 + 4*W/8, -1] , [W/16 + 5*W/8 , -1] , [W/16 + 6*W/8, -1] , [W/16 + 7*W/8 , -1] .
  • the selected samples are painted in black as depicted in FIG. 42B.
  • the eight selected left samples’ coordinates are [-1, H/16] , [-1, H/16 + H/8] , [-1, H/16 + 2*H/8] , [-1, H/16 + 3*H/8 ] , [-1, H/16 + 4*H/8] , [-1, H/16 + 5*H/8 ] , [-1, H/16 +6*H/8] , [-1, H/16 + 7*H/8 ] .
  • FIG. 43A shows a flowchart of an exemplary method for video processing.
  • the method 4310 includes, at step 4312, making a decision, based on a coding mode of a current video block, regarding a selective application of a local illumination compensation (LIC) model on at least a portion of the current video block.
  • LIC local illumination compensation
  • the method 4310 includes, at step 4314, performing, based on the decision, a conversion between the current video block and a bitstream representation of the current video block.
  • the current video block is coded with a pairwise candidate, and wherein the application of the LIC model is disabled.
  • the current video block is coded based on a zero-motion merge candidate, and wherein the application of the LIC model is disabled.
  • the coding mode is an alternative temporal motion vector prediction (ATMVP) mode, and wherein the application of the LIC model is enabled.
  • ATMVP alternative temporal motion vector prediction
  • the decision is further based on a position of the current video block in a video unit.
  • the position of the current video block is a boundary of the video unit, wherein the video unit is a picture, slice, tile or brick, and wherein the application of the LIC model is disabled.
  • the coding mode is a transform bypass mode, and the application of the LIC model is disabled. In other embodiments, the coding mode excludes a transform bypass mode, and the application of the LIC model is enabled.
  • the transform bypass mode is a transform skip (TS) mode or a quantized residual block differential pulse-code modulation (QR-BDPCM) mode.
  • FIG. 43B shows a flowchart of an exemplary method for video processing.
  • the method 4320 includes, at step 4322, configuring, for a current video block comprising multiple sub-regions, each of the multiple sub-regions with a set of local illumination compensation (LIC) parameters.
  • LIC local illumination compensation
  • the method 4320 includes, at step 4324, performing, based on the configuring, a conversion between the current video block and a bitstream representation of the current video block.
  • the set of LIC parameters for one sub-region is different from the set of LIC parameters for any other sub-region of the multiple sub-regions.
  • each of the multiple sub-regions comprises a sub-block of the current video block that is coded with a sub-block-based mode.
  • an LIC model is enabled for a first of the multiple sub-regions, and wherein the LIC model is disabled for a second of the multiple sub-regions.
  • the current vide block is coded using an alternative temporal motion vector prediction (ATMVP) mode or an affine mode.
  • ATMVP alternative temporal motion vector prediction
  • FIG. 43C shows a flowchart of an exemplary method for video processing.
  • the method 4330 includes, at step 4332, making a decision, for a current video block, regarding a selective enablement of a filtering process for the current video block based on a usage of a local illumination compensation (LIC) model on the current video block.
  • LIC local illumination compensation
  • the method 4330 includes, at step 4334, performing, based on the decision, a conversion between the current video block and a bitstream representation of the current video block.
  • the filtering process comprises at least one of a deblocking filter, a sample adaptive offset (SAO) filter, an adaptive loop filter or a bilateral filter.
  • the filtering process is applied to an edge of the current video block with a neighboring block.
  • the usage of the LIC model for the current video block is enabled, and the usage of the LIC mode for the neighboring block is disabled.
  • the usage of the LIC model for the current video block is disabled, and the usage of the LIC mode for the neighboring block is enabled.
  • the usage of the LIC model for the current video block is enabled, and the usage of the LIC mode for the neighboring block is enabled.
  • FIG. 43D shows a flowchart of an exemplary method for video processing.
  • the method 4340 includes, at step 4342, configuring, during a conversion between a current video block and a bitstream representation of the current video block, a local illumination compensation (LIC) model that is applied to the current video block, wherein a fixed number of one or more samples of neighboring blocks of the current video block are used to train the LIC model.
  • LIC local illumination compensation
  • the fixed number is based on an availability of the one or more samples of neighboring blocks or at least one dimension of the current video block.
  • a size of the current video block is W ⁇ H
  • the one or more samples comprise samples with coordinates (x -1, y + offsetY + Ky ⁇ H /Fy) or (x + offsetX + Kx ⁇ W /Fx, y -1)
  • Fx samples are selected from an above neighboring row
  • Fy samples are selected from a left neighboring column
  • Kx ranges from 0 to (Fx-1)
  • Ky ranges from 0 to (Fy-1)
  • H, W, Kx, Ky, Fx, Fy, offsetX and offsetY are integers.
  • a size of the current video block is W ⁇ H
  • the one or more samples comprise SW ⁇ W samples of the above neighboring row and SH ⁇ H samples of the left neighboring column
  • SH, SW, H and W are integers.
  • a top-left coordinate of the current video block is denoted (x, y)
  • the one or more samples comprise (x + W/4, y -1) , (x + 3 ⁇ W/4, y -1) , (x -1, y + H/4) and (x -1, y + 3 ⁇ H/4) .
  • a top-left coordinate of the current video block is denoted (x, y)
  • the one or more samples comprise (x, y -1) , (x + W -max (1, W/H) , y -1) , (x -1, y) and (x -1, y + H –max (1, H/W) ) .
  • a top-left coordinate of the current video block is denoted (x, y)
  • the one or more samples comprise (x, y -1) , (x + W/4, y -1) , (x + 2 ⁇ W/4, y -1) and (x + 3 ⁇ W/4, y –1) .
  • a top-left coordinate of the current video block is denoted (x, y)
  • the one or more samples comprise (x + W/8, y -1) , (x + 3 ⁇ W/8, y -1) , (x + 5 ⁇ W/8, y -1) and (x + 7 ⁇ W/8, y -1) .
  • a top-left coordinate of the current video block is denoted (x, y)
  • the one or more samples comprise (x -1, y) , (x -1, y + H/4) , (x -1, y + 2 ⁇ H/4) and (x -1, y + 3 ⁇ H/4) .
  • a top-left coordinate of the current video block is denoted (x, y) , and wherein the one or more samples comprise (x -1, y + H/8) , (x -1, y + 3 ⁇ H/8) , (x -1, y + 5 ⁇ H/8) and (x -1, y + 7 ⁇ H/8) .
  • the method 4340 further includes the step of determining that one or more samples in both an above neighboring row and in a left neighboring column are available, where the one or more samples of neighboring blocks are selected from either the above neighboring row or the left neighboring column.
  • the current video block is non-square.
  • the one or more samples of neighboring blocks exclude samples coded with at least one of an intra mode, a hybrid intra and inter mode, or an intra block copy (IBC) mode.
  • an intra mode a hybrid intra and inter mode
  • IBC intra block copy
  • the one or more samples of neighboring blocks comprise samples coded with one or more of a non-intra mode, a non-CIIP (combined intra-inter prediction) mode, or a non-IBC (intra block copy) mode.
  • FIG. 44 is a block diagram of a video processing apparatus 4400.
  • the apparatus 4400 may be used to implement one or more of the methods described herein.
  • the apparatus 4400 may be embodied in a smartphone, tablet, computer, Internet of Things (IoT) receiver, and so on.
  • the apparatus 4400 may include one or more processors 4402, one or more memories 4404 and video processing hardware 4406.
  • the processor (s) 4402 may be configured to implement one or more methods (including, but not limited to, methods 4310, 4320, 4330 and 4340) described in the present document.
  • the memory (memories) 4404 may be used for storing data and code used for implementing the methods and techniques described herein.
  • the video processing hardware 4406 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. 44.
  • FIG. 45 shows a flowchart of an exemplary method for video processing.
  • the method 4500 includes, at step 4502, deriving, for a conversion between a video block of a video and a bitstream representation of the video block, a motion candidate list, wherein a first candidate in the motion candidate list is set with a local illumination compensation (LIC) flag; and at step 4504, performing the conversion using the motion candidate list, wherein during the conversion, when the first candidate is selected from the motion candidate list, whether the LIC is enabled is determined based on the flag of the first candidate.
  • LIC local illumination compensation
  • the LIC flag of the first candidate is set according to at least one of : a type of first candidate; a LIC flag of a second candidate which is used to derive the first candidate; a type of a second candidate in the motion candidate list which is used to derive the first candidate; LIC flags of other candidates in the motion candidate list.
  • the first candidate is a pairwise candidate in a merge candidate list for the video block.
  • the LIC flag associated with pairwise candidate is always set to be false.
  • the LIC flag is set to be false and LIC is disabled.
  • the LIC flag associated with pairwise candidate is set based on two merge candidates which are used to derive the pairwise candidate.
  • the LIC flag associated with the pairwise candidate is set to be true.
  • the LIC flag associated with the pairwise candidate is set to be true.
  • the LIC flag associated with pairwise candidate is set to false.
  • the LIC flag associated with pairwise candidate is set to false.
  • the first candidate is a zero motion merge candidate in a merge candidate list for the video block.
  • the LIC flag associated with zero motion merge candidate is always set to be false.
  • the LIC flag associated with zero motion merge candidate is set depending on LIC flags associated with other merge candidates in the merge candidate list.
  • the LIC flag associated with zero motion merge candidate is set to be true.
  • the specific merge candidate is the first merge candidate.
  • FIG. 46 shows a flowchart of an exemplary method for video processing.
  • the method 4600 includes, at step 4602, determining, for a conversion between a video block of a video and a bitstream representation of the video block, at least one of : whether local illumination compensation (LIC) is enabled or disabled for at least a portion of the video block based on property of the video block, whether LIC is enabled for a reference picture list, and LIC parameters of at least one reference picture list; and at step 4604, performing the conversion based on the determination.
  • LIC local illumination compensation
  • the property includes coding mode of the video block, and when the video block is coded with an alternative temporal motion vector prediction (ATMVP) mode, LIC is enabled.
  • ATMVP alternative temporal motion vector prediction
  • whether to enable LIC or not further depends on spatial merge candidate derived from a neighboring block of the video block.
  • one set of LIC parameters for each reference picture list is derived for the whole video block.
  • LIC if LIC is enabled for one sub-block of the video block, all sub-blocks share the same LIC parameters.
  • one or multiple motion vectors of one sub-block are used to identify neighboring reference samples of the whole video block, which are used to derive the LIC parameters for the whole video block.
  • the one sub-block is a top-left sub-block.
  • the one sub-block is a center sub-block.
  • different sub-blocks are selected for different color components.
  • LIC when LIC is enabled for the video block, different sub-regions within the video block use different LIC parameters.
  • multiple sets of LIC parameters for each reference picture list are derived, and each sub-region within the video block selects one from the multiple sets of LIC parameters.
  • the sub-region is a sub-block for blocks coded with sub-block-based technologies including at least one of ATMVP mode and affine mode.
  • LIC is enabled for one reference picture list but disabled for the other reference picture list.
  • LIC flags are stored for each video block.
  • LIC flags are both inherited from each of two merge candidates which are used to derive the pairwise candidate.
  • LIC parameters are derived once for two reference picture lists.
  • the LIC parameters are derived according to motion information of one reference picture list.
  • the LIC parameters are derived according to motion information of two reference picture lists.
  • neighboring samples relative to two reference pictures in the two reference picture lists are both utilized.
  • selecting of the neighboring samples relative to the two reference pictures in the two reference picture lists is different for the two reference picture lists.
  • LIC is enabled for partial sub-regions within the video block and disabled for the remaining sub-regions.
  • LLC when the video block is an ATMVP-coded block, LLC is enabled for one sub-block and is disabled for another sub-block.
  • LLC when the video block is an affine-coded block, LLC is enabled for one sub-block and is disabled for another sub-block.
  • the sub-block is 8x8 block.
  • the property includes position of the video block.
  • LIC when the video block is located at boundary of at least one of picture, slice, tile and brick, LIC is disabled.
  • the property includes coding mode.
  • LIC and transform bypass (TransBypass) mode including at least one of a Transform Skip (TS) mode and a quantized residual block differential pulse-code modulation (QR-BDPCM) mode are exclusively used.
  • TransBypass Transform bypass
  • QR-BDPCM quantized residual block differential pulse-code modulation
  • TransBypass mode including TS mode is disabled if the video block is coded with LIC mode.
  • TS mode if TS mode is disabled, signaling of TS mode is skipped.
  • side information of LIC mode is signaled conditionally depending on indication of usage of TS mode.
  • TS mode is enabled for the video block
  • signaling of side information of LIC mode is skipped.
  • FIG. 47 shows a flowchart of an exemplary method for video processing.
  • the method 4700 includes, at step 4702, determining, for a conversion between a video block of a video and a bitstream representation of the video block, whether to enable and/or how to apply in-loop filter process and/or post-reconstruction filtering process depend on usage of local illumination compensation (LIC) , wherein the in-loop filter process includes deblocking filter, a sample adaptive offset (SAO) , an adaptive loop filter (ALF) , and the post-reconstruction filtering process includes bilateral filter; and at step 4704, performing the conversion based on the determination.
  • LIC local illumination compensation
  • edge between the two adjacent blocks is filtered.
  • boundary strength is set to M, M being unequal to 0.
  • edge between the two adjacent blocks is filtered.
  • boundary strength is set to M, M being unequal to 0.
  • FIG. 48 shows a flowchart of an exemplary method for video processing.
  • the method 4800 includes, at step 4802, deriving, for a conversion between a video block of a video and a bitstream representation of the video block, local illumination compensation (LIC) parameters in a LIC model that is applied to the video block by using a fixed number of neighboring samples of the video block; and at step 4804, performing the conversion based on the LIC parameters.
  • LIC local illumination compensation
  • the neighboring samples include neighboring adjacent or non-adjacent samples.
  • the LIC mode uses a fixed denominator or value for shifting in the LIC parameter derivation process.
  • the number of neighboring samples that are selected for deriving the LIC parameters depends on availability of neighboring samples, or/and dimensions of the video block, wherein width of the video block is W and height of the video block is H, and top-left coordinate of the video block is (x, y) .
  • the selected samples are located at (x-1, y + offsetY +Ky*H/Fy) and/or (x + offsetX + Kx *W/Fx, y-1) , where Fx samples are selected from above neighbouring row, Kx is from 0 to Fx –1, and Fy samples are selected from left neighbouring column, Ky is from 0 to Fy –1, offsetX and offsetY are integers.
  • the fixed number is four.
  • SH samples of left column and SW samples of above row are selected, where SH and SW are integers, SH ⁇ H and SW ⁇ W.
  • the selected samples are located at one of the following positions:
  • the selected samples are located at one of the following positions:
  • f1 (K) ( (K *W ) >> dimShift )
  • f2 (K) ( (K *H) >> dimShift)
  • minDimBit Log2 [min (H, W) ]
  • minDim min (H, W)
  • minStepBit minDim > 8 ? 1 :
  • numSteps minDim >> minStepBit
  • dimShift minDimBit –minStepBit
  • K and N are integers.
  • N numSteps.
  • N depends on W and/or H.
  • SW samples of the above neighboring row are selected, where SW is an integer and SW ⁇ W.
  • selecting of the samples depends on the width/height.
  • the selected samples are located at one of the following positions:
  • the selected samples are located at one of the following positions:
  • f1 (K) ( (K *W ) >> dimShift )
  • f2 (K) ( (K *H) >> dimShift)
  • minDimBit Log2 [min (H, W) ]
  • minDim min (H, W)
  • minStepBit minDim > 8 ? 1: 0
  • numSteps minDim >> minStepBit
  • dimShift minDimBit –minStepBit
  • K and N are integers.
  • N numSteps.
  • the samples are only selected from the left neighboring column.
  • selecting of the samples depends on the width/height.
  • the selected samples are located at one of the following positions:
  • the selected samples are located at one of the following positions:
  • N numSteps.
  • N depends on W and/or H.
  • the fixed number is eight.
  • both left neighboring column and above neighboring row of the video block are available, four samples of left column and four samples of above row are selected.
  • the selected samples are located at one of the following positions:
  • the selected samples are located at one of the following positions:
  • f1 (K) ( (K *W ) >> dimShift )
  • f2 (K) ( (K *H) >> dimShift)
  • minDimBit Log2 [min (H, W) ]
  • minDim min (H, W)
  • minStepBit minDim > 8 ? 1: 0
  • numSteps minDim >> minStepBit
  • dimShift minDimBit –minStepBit
  • K and N are integers.
  • N numSteps.
  • N depends on W and/or H.
  • the samples are only selected from the above neighboring row.
  • SW samples of the above neighboring row are selected, where SW is an integer.
  • selecting of the samples depends on the width/height.
  • the selected samples are located at one of the following positions:
  • the selected samples are located at one of the following positions:
  • f1 (K) ( (K *W ) >> dimShift )
  • f2 (K) ( (K *H) >> dimShift)
  • minDimBit Log2 [min (H, W) ]
  • minDim min (H, W)
  • minStepBit minDim > 8 ? 1 :
  • numSteps minDim >> minStepBit
  • dimShift minDimBit –minStepBit
  • K and N are integers.
  • N numSteps.
  • N depends on W and/or H.
  • the selected neighboring samples have a pixel distance larger than or equal to S, S being an integer.
  • S 1.
  • W is set equal to 16
  • H is set equal to 16.
  • W is set equal to the width of the current video block
  • H is set equal to the height of the current video block
  • deriving the LIC parameters by using a least square error method deriving the LIC parameters by using a least square error method.
  • deriving the LIC parameters by using a two-point method deriving the LIC parameters by using a two-point method.
  • the 2 points x A and x B are the minimum and maximum sample inside a set of selected neighboring samples of the video block, and their corresponding samples in reference picture are denoted as y A and y B .
  • the four or eight neighboring samples of the video block at the selected positions are compared to find two smallest samples: x 0 A and x 1 A and two largest values: x 0 B and x 1 B , and their corresponding samples in the reference picture are denoted as y 0 A , y 1 A , y 0 B and y 1 B , wherein x A , x B , y A and y B are derived as:
  • the eight neighboring samples of the video block at the selected positions are compared to find four smaller samples: x 0 A , x 1 A , x 2 A , x 3 A , and four larger values: x 0 B , x 1 B , x 2 B , x 3 B , their corresponding samples in the reference picture are denoted as y 0 A , y 1 A , y 2 A , y 3 A , y 0 B , y 1 B , y 2 B , y 3 B , wherein x A , x B , y A and y B are derived as:
  • x A (x 0 A + x 1 A + x 2 A +x 3 A + off) >>2;
  • x B (x 0 B + x 1 B + x 2 B +x 3 B + off) >>2;
  • LIC parameter ⁇ is derived by using averaged values, which are calculated inside the set of selected neighboring samples of the video block and the set of selected neighboring samples of its reference block instead of minimum values (x A , y A ) .
  • one-side selection is involved in the LIC parameter derivation process, wherein either above neighboring samples or left neighboring samples are involved in the LIC parameter derivation process even both above neighboring samples and left neighboring samples are available.
  • the one-side selection is invoked only when the current video block is non-square.
  • selection of the one side depends on dimension of the video block, wherein the one side is above side or left side.
  • the height is smaller than the width of the video block, only the above neighboring samples of the video block and its reference block are used to derive the LIC parameters.
  • the height is larger than the width of the video block, only the left neighboring samples of the video block and its reference block are used to derive the LIC parameters.
  • a neighboring sample of the video block is coded with intra mode and/or hybrid intra and inter mode or/and IBC mode
  • the sample is considered as unavailable and replaced by an available neighboring sample which is selected from samples coded with a non-intra mode and/or a non-CIIP (combined intra-inter prediction) mode and/or a non-IBC (intra block copy) mode.
  • an unavailable sample is replaced by its nearest available neighboring sample.
  • the nearest available sample is the sample coded with non-intra mode and/or non-CIIP mode or/and non-IBC mode before or after the current unavailable sample with the shortest distance in the order of fetching for above neighboring samples.
  • the nearest available sample is the sample coded with non-intra mode and/or non-CIIP mode or/and non-IBC mode before or after the current unavailable sample with the shortest distance in the order of fetching for left neighboring samples.
  • an unavailable selected neighboring sample is replaced by its nearest available selected neighboring sample.
  • LIC mode is disabled depending on dimensions of the video block.
  • LIC when the video block is 4 ⁇ 4 block, LIC is disabled.
  • padding is applied to replace the unavailable samples.
  • the padding includes copying from available samples.
  • the neighboring samples coded with intra mode and/or hybrid intra and inter mode or/and IBC mode are excluded from derivation of LIC parameters.
  • one or multiple the samples fetched later are discard to make sure total 2N samples are obtained to solve the least square error.
  • the selected neighboring samples coded with intra mode and/or hybrid intra and inter mode or/and IBC mode are excluded from derivation process of the LIC parameters.
  • the neighboring samples coded with non-intra mode and/or non-CIIP mode or/and non-IBC mode are included in derivation process of the LIC parameters.
  • the conversion generates the video block of video from the bitstream representation.
  • the conversion generates the bitstream representation from the video block of video.
  • 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.
  • data processing unit or “data processing apparatus” encompasses all apparatus, devices, and machines for processing data, including by way of example a programmable processor, a computer, or multiple processors or computers.
  • 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.
  • the processes and logic flows described in this specification can be performed by one or more programmable processors executing one or more computer programs to perform functions by operating on input data and generating output.
  • the processes and logic flows can also be performed by, and apparatus can also be implemented as, special purpose logic circuitry, e.g., an FPGA (field programmable gate array) or an ASIC (application specific integrated circuit) .
  • 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.
  • 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.

Landscapes

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

Abstract

Compensation d'éclairage local (LIC) simplifiée. Un procédé de traitement vidéo illustratif consiste à dériver, pour une conversion entre un bloc vidéo d'une vidéo et une représentation en flux binaire du bloc vidéo, une liste de candidats de mouvement, un premier candidat de la liste de candidats de mouvement étant réglé avec un indicateur de compensation d'éclairage local (LIC) ; et effectuer la conversion à l'aide de la liste de candidats de mouvement ; au cours de la conversion, lorsque le premier candidat est sélectionné à partir de la liste de candidats de mouvement, on détermine, sur la base de l'indicateur du premier candidat, si la LlC est activée.
PCT/CN2020/091299 2019-05-20 2020-05-20 Compensation d'éclairage local simplifiée WO2020233600A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
CN202080037225.8A CN113841396B (zh) 2019-05-20 2020-05-20 简化的局部照明补偿

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
CN2019087620 2019-05-20
CNPCT/CN2019/087620 2019-05-20

Publications (1)

Publication Number Publication Date
WO2020233600A1 true WO2020233600A1 (fr) 2020-11-26

Family

ID=73458289

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/CN2020/091299 WO2020233600A1 (fr) 2019-05-20 2020-05-20 Compensation d'éclairage local simplifiée

Country Status (2)

Country Link
CN (1) CN113841396B (fr)
WO (1) WO2020233600A1 (fr)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2022162004A1 (fr) * 2021-02-01 2022-08-04 Interdigital Vc Holdings France, Sas Procédé et appareil de codage ou de décodage vidéo
WO2023034640A1 (fr) * 2021-09-06 2023-03-09 Beijing Dajia Internet Information Technology Co., Ltd. Dérivation de candidats pour un mode de fusion affine dans un codage vidéo
WO2023134452A1 (fr) * 2022-01-11 2023-07-20 Beijing Bytedance Network Technology Co., Ltd. Procédé, appareil et support de traitement vidéo
WO2023200561A1 (fr) * 2022-04-13 2023-10-19 Qualcomm Incorporated Procédés de signalisation adaptative de nombre maximal de candidats à la fusion dans une prédiction à hypothèses multiples
TWI851355B (zh) 2022-07-26 2024-08-01 大陸商杭州海康威視數字技術股份有限公司 一種編解碼方法、裝置及其設備

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2024037649A1 (fr) * 2022-08-19 2024-02-22 Douyin Vision Co., Ltd. Extension de compensation d'éclairage local
WO2024199245A1 (fr) * 2023-03-27 2024-10-03 Douyin Vision Co., Ltd. Procédé, appareil et support de traitement vidéo

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102215389A (zh) * 2010-04-09 2011-10-12 华为技术有限公司 一种局部亮度补偿的视频编解码方法及装置
CN107147911A (zh) * 2017-07-05 2017-09-08 中南大学 基于局部亮度补偿lic的快速帧间编码模式选择方法及装置
US20180063531A1 (en) * 2016-08-26 2018-03-01 Qualcomm Incorporated Unification of parameters derivation procedures for local illumination compensation and cross-component linear model prediction
CN108462873A (zh) * 2017-02-21 2018-08-28 联发科技股份有限公司 用于四叉树加二叉树拆分块的候选集决定的方法与装置
WO2019007697A1 (fr) * 2017-07-05 2019-01-10 Telefonaktiebolaget Lm Ericsson (Publ) Commande de filtrage de déblocage pour compensation d'éclairage
CN109644271A (zh) * 2016-09-06 2019-04-16 联发科技股份有限公司 用于二叉树分割块的确定候选集的方法及装置

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR100856411B1 (ko) * 2006-12-01 2008-09-04 삼성전자주식회사 조도 보상 방법 및 그 장치와 그 방법을 기록한 컴퓨터로 읽을 수 있는 기록매체
WO2014203726A1 (fr) * 2013-06-18 2014-12-24 シャープ株式会社 Dispositif de compensation d'éclairage, dispositif de prédiction lm, dispositif de décodage d'image, dispositif de codage d'image
US10356416B2 (en) * 2015-06-09 2019-07-16 Qualcomm Incorporated Systems and methods of determining illumination compensation status for video coding
JP6781340B2 (ja) * 2016-09-22 2020-11-04 エルジー エレクトロニクス インコーポレイティド 映像コーディングシステムにおける照度補償基盤インター予測方法及び装置
EP3468193A1 (fr) * 2017-10-05 2019-04-10 Thomson Licensing Procédé et appareil pour une compensation d'éclairage adaptative dans le codage et le décodage vidéo

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102215389A (zh) * 2010-04-09 2011-10-12 华为技术有限公司 一种局部亮度补偿的视频编解码方法及装置
US20180063531A1 (en) * 2016-08-26 2018-03-01 Qualcomm Incorporated Unification of parameters derivation procedures for local illumination compensation and cross-component linear model prediction
CN109644271A (zh) * 2016-09-06 2019-04-16 联发科技股份有限公司 用于二叉树分割块的确定候选集的方法及装置
CN108462873A (zh) * 2017-02-21 2018-08-28 联发科技股份有限公司 用于四叉树加二叉树拆分块的候选集决定的方法与装置
CN107147911A (zh) * 2017-07-05 2017-09-08 中南大学 基于局部亮度补偿lic的快速帧间编码模式选择方法及装置
WO2019007697A1 (fr) * 2017-07-05 2019-01-10 Telefonaktiebolaget Lm Ericsson (Publ) Commande de filtrage de déblocage pour compensation d'éclairage

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
BORDES，PHILIPPE: "Combination of post-reconstruction filtering and bi-directional LIC mutually exclusive", JOINT VIDEO EXPERTS TEAM (JVET) OF ITU-T SG 16 WP 3 AND ISO/IEC JTC 1/SC 29/WG 11 14TH MEETING: GENEVA， CH， 19–27 MARCH 2019, 28 March 2019 (2019-03-28), XP55756629, DOI: 20200805203524X *
TSAI，CHIA-MING ET AL.: "Simplification of local illumination compensation", JOINT VIDEO EXPERTS TEAM (JVET) OF ITU-T SG 16 WP 3 AND ISO/IEC JTC 1/SC 29/WG 11 13TH MEETING: MARRAKECH， MA， 9–18 JAN. 2019, 18 January 2019 (2019-01-18), XP030213336, DOI: 20200805202346A *

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2022162004A1 (fr) * 2021-02-01 2022-08-04 Interdigital Vc Holdings France, Sas Procédé et appareil de codage ou de décodage vidéo
WO2023034640A1 (fr) * 2021-09-06 2023-03-09 Beijing Dajia Internet Information Technology Co., Ltd. Dérivation de candidats pour un mode de fusion affine dans un codage vidéo
WO2023134452A1 (fr) * 2022-01-11 2023-07-20 Beijing Bytedance Network Technology Co., Ltd. Procédé, appareil et support de traitement vidéo
WO2023200561A1 (fr) * 2022-04-13 2023-10-19 Qualcomm Incorporated Procédés de signalisation adaptative de nombre maximal de candidats à la fusion dans une prédiction à hypothèses multiples
TWI851355B (zh) 2022-07-26 2024-08-01 大陸商杭州海康威視數字技術股份有限公司 一種編解碼方法、裝置及其設備

Also Published As

Publication number Publication date
CN113841396A (zh) 2021-12-24
CN113841396B (zh) 2022-09-13

Similar Documents

Publication Publication Date Title
US11889108B2 (en) Gradient computation in bi-directional optical flow
US11405607B2 (en) Harmonization between local illumination compensation and inter prediction coding
US11956465B2 (en) Difference calculation based on partial position
US11509927B2 (en) Weighted prediction in video coding
US12120340B2 (en) Constraints for usage of updated motion information
US11641467B2 (en) Sub-block based prediction
US11483550B2 (en) Use of virtual candidate prediction and weighted prediction in video processing
US20210227211A1 (en) Temporal gradient calculations in bio
WO2020147745A1 (fr) Listes de candidats au mouvement utilisant une compensation locale d'éclairage
WO2020084507A1 (fr) Compensation d'éclairage local harmonisée et codage par inter-prédiction modifié
WO2020084461A1 (fr) Restrictions sur une dérivation de vecteur de mouvement côté décodeur sur la base d'informations de codage
WO2020233600A1 (fr) Compensation d'éclairage local simplifiée
WO2020070729A1 (fr) Restriction de taille sur la base d'informations de mouvement

Legal Events

Date Code Title Description
121 Ep: the epo has been informed by wipo that ep was designated in this application

Ref document number: 20808664

Country of ref document: EP

Kind code of ref document: A1

NENP Non-entry into the national phase

Ref country code: DE

122 Ep: pct application non-entry in european phase

Ref document number: 20808664

Country of ref document: EP

Kind code of ref document: A1

32PN Ep: public notification in the ep bulletin as address of the adressee cannot be established

Free format text: NOTING OF LOSS OF RIGHTS PURSUANT TO RULE 112(1) EPC (EPO FORM 1205A DATED 23/03/2022)