WO2020114517A1 - Décalage sur des paramètres affines - Google Patents

Décalage sur des paramètres affines Download PDF

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Publication number
WO2020114517A1
WO2020114517A1 PCT/CN2019/124048 CN2019124048W WO2020114517A1 WO 2020114517 A1 WO2020114517 A1 WO 2020114517A1 CN 2019124048 W CN2019124048 W CN 2019124048W WO 2020114517 A1 WO2020114517 A1 WO 2020114517A1
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block
current block
basic block
affine
motion vector
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PCT/CN2019/124048
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English (en)
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Kai Zhang
Li Zhang
Hongbin Liu
Jizheng Xu
Yue Wang
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Beijing Bytedance Network Technology Co., Ltd.
Bytedance Inc.
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Priority to CN201980080911.0A priority Critical patent/CN113170159B/zh
Publication of WO2020114517A1 publication Critical patent/WO2020114517A1/fr

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
    • H04N19/50—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using predictive coding
    • H04N19/503—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using predictive coding involving temporal prediction
    • H04N19/51—Motion estimation or motion compensation
    • H04N19/537—Motion estimation other than block-based
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
    • H04N19/10—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding
    • H04N19/102—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding characterised by the element, parameter or selection affected or controlled by the adaptive coding
    • H04N19/103—Selection of coding mode or of prediction mode
    • H04N19/109—Selection of coding mode or of prediction mode among a plurality of temporal predictive coding modes
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
    • H04N19/10—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding
    • H04N19/169—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding characterised by the coding unit, i.e. the structural portion or semantic portion of the video signal being the object or the subject of the adaptive coding
    • H04N19/17—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding characterised by the coding unit, i.e. the structural portion or semantic portion of the video signal being the object or the subject of the adaptive coding the unit being an image region, e.g. an object
    • H04N19/176—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding characterised by the coding unit, i.e. the structural portion or semantic portion of the video signal being the object or the subject of the adaptive coding the unit being an image region, e.g. an object the region being a block, e.g. a macroblock
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
    • H04N19/50—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using predictive coding
    • H04N19/503—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using predictive coding involving temporal prediction
    • H04N19/51—Motion estimation or motion compensation
    • H04N19/513—Processing of motion vectors
    • H04N19/517—Processing of motion vectors by encoding
    • H04N19/52—Processing of motion vectors by encoding by predictive encoding

Definitions

  • This patent document relates to image and video coding and decoding.
  • Digital video accounts for the largest bandwidth use on the internet and other digital communication networks. As the number of connected user devices capable of receiving and displaying video increases, it is expected that the bandwidth demand for digital video usage will continue to grow.
  • the disclosed techniques may be used by video decoder or encoder embodiments during video decoding or encoding using control point motion vectors and affine coding.
  • a method of processing video includes associating, with a current video block, a first group of motion vectors (MVs) for determining inherited motion information of other video blocks, a second group of MVs for deriving MVs of sub-blocks of the current video block and a third group of MVs that is included in a bitstream representation of the current video block, and performing a conversion between the current video block and the bitstream representation using the first group of MVs, the second group of MVs or the third group of MVs.
  • MVs motion vectors
  • another method of video processing includes performing a conversion between a current block and a bitstream representation of the current block using affine inherited motion vectors (MVs) for the current block, wherein the affine inherited MVs are derived from (1) MVs stored for an adjacent neighboring basic block, denoted as Badj, or (2) an affine history list.
  • MVs affine inherited motion vectors
  • another method of video processing includes performing a conversion between a current block and a bitstream representation of the current block using affine inherited motion vectors (MVs) for the current block, wherein the affine inherited MVs are derived from a first MV stored in a first basic block adjacently neighboring the current block and a second MV stored in a second basic block that is offset from the first building block by an offset.
  • MVs affine inherited motion vectors
  • another method of video processing includes associating a first group of control point motion vectors (CPMVs) for determining inherited motion information of blocks coded after a first block, with a second group of CPMVs for deriving MVs of sub-blocks of the first block or a third group of CPMVs that is signaled for the first block, wherein the first group of CPMVs is not identical with the second group of CPMVs or the third group of CPMVs; determining inherited motion information for a second block, which is coded after the first block, based on the first group of CPMVs, and performing a conversation between the second block and a bitstream representation of the second block by using the inherited motion information.
  • CPMVs control point motion vectors
  • another method of video processing includes deriving, for a conversion between a first block of video and a bitstream representation of the first block, affine inherited motion vectors (MVs) for the first block based on stored motion vectors (MVs) ; and performing the conversion by using the affine inherited MVs.
  • MVs affine inherited motion vectors
  • another method of video processing includes deriving, for a conversion between a current block of video and a bitstream representation of the current block, affine inherited motion vectors (MVs) for the current block based on a first stored motion vector (MV) and a second stored MV different from the first stored MV, wherein the first stored MV is stored in a first basic block neighbouring to the current block, and the second stored MV is stored in a second basic block with an offset to the first basic block; and performing the conversion by using the affine inherited MVs for the current block.
  • MVs affine inherited motion vectors
  • another method of video processing includes deriving, for a conversion between a current block and a bitstream representation of the current block, one or more parameters of a set of affine model parameters associated with affine model for the current block; shifting the one or more parameters; and storing the shifted one or more parameters.
  • a video encoder apparatus includes a processor that is configured to implement a method described herein.
  • a video decoder apparatus includes a processor that is configured to implement a method described herein.
  • a computer readable medium having code stored thereupon having code stored thereupon.
  • the code when executed by a processor, causes the processor to implement a method described in the present document.
  • FIG. 1 shows an example of derivation process for merge candidate 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. 4A-4B show 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 candidate positions for temporal merge candidate, C0 and C1.
  • FIG. 7 shows example of combined bi-predictive merge candidate.
  • FIG. 8 summarizes derivation process for motion vector prediction candidate.
  • FIG. 9 is an example illustration of motion vector scaling for spatial motion vector candidate.
  • FIG. 10 shows an example of alternative motion vector predictor (ATMVP) motion prediction for a coding unit CU.
  • ATMVP alternative motion vector predictor
  • FIG. 11 shows example of one CU with four sub-blocks (A-D) and its neighbouring blocks (a–d) .
  • FIG. 12 shows an example flowchart of encoding with different MV precision.
  • FIG. 13A-13B show respectively 4 and 6 parameter simplified affine motion models.
  • FIG. 14 shows an example of Affine MVF per sub-block.
  • FIG. 15A shows an example of a 4-paramenter affine model.
  • FIG. 15B shows an example of a 6-parameter affine model.
  • FIG. 16 shows an example of an MVP for AF_INTER for inherited affine candidates.
  • FIG. 17 shows example MVP for AF_INTER for constructed affine candidates.
  • FIG. 18A shows an example of candidates for AF_MERGE in a five neighboring block scenario.
  • FIG. 18B shows an example flow of a CPMV predictor derivation process.
  • FIG. 19 shows example Candidates position for affine merge mode.
  • FIG. 20 shows an example of affine inheritance at CTU-row.
  • FIG. 21 shows examples of MV stored in adjacent neighbouring basic blocks
  • FIG. 22 shows positions in a 4 ⁇ 4 basic block.
  • FIG. 23 shows examples of MVs of two adjacent neighbouring blocks.
  • FIG. 24 shows an example of MVs used for affine inheritance crossing CTU rows.
  • FIG. 25 is a flowchart for an example of a video processing method.
  • FIG. 26 is a block diagram of an example of a video processing apparatus.
  • FIG. 27 shows an exemplary flowchart to find the first basic block and the second basic block (rectangular block indicates the termination of the whole process) .
  • FIG. 28 shows another exemplary flowchart to find the first basic block and the second basic block (rectangular block indicates the termination of the whole process) .
  • FIG. 29 is a flowchart for an example of a video processing method.
  • FIG. 30 is a flowchart for an example of a video processing method.
  • FIG. 31 is a flowchart for an example of a video processing method.
  • FIG. 32 is a flowchart for an example of a video processing method.
  • the present document provides various techniques that can be used by a decoder of video bitstreams to improve the quality of decompressed or decoded digital video or images. Furthermore, a video encoder may also implement these techniques during the process of encoding in order to reconstruct decoded frames used for further encoding.
  • Section headings are used in the present document for ease of understanding and do not limit the embodiments and techniques to the corresponding sections. As such, embodiments from one section can be combined with embodiments from other sections.
  • This patent document is related to video coding technologies. Specifically, it is related to motion vector coding 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.
  • 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 neighbouring 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 differences (MVD) 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.
  • MDV motion vector differences
  • 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.
  • inter prediction is used to denote prediction derived from data elements (e.g., sample values or motion vectors) of reference pictures other than the current decoded picture.
  • data elements e.g., sample values or motion vectors
  • a picture can be predicted from multiple reference pictures.
  • the reference pictures that are used for inter prediction are organized in one or more reference picture lists.
  • the reference index identifies which of the reference pictures in the list should be used for creating the prediction signal.
  • a single reference picture list, List 0 is used for a P slice and two reference picture lists, List 0 and List 1 are used for B slices. It should be noted reference pictures included in List 0/1 could be from past and future pictures in terms of capturing/display order.
  • 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. 4A-4B depict 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.
  • FIG. 2 shows positions of spatial merge candidates.
  • FIG. 3 shows candidate pairs considered for redundancy check of spatial merge candidates.
  • FIG. 4A-4B show positions for the second PU of N ⁇ 2N and 2N ⁇ N partitions.
  • a scaled motion vector is derived based on co-located PU belonging to the picture which has the smallest POC difference with current picture within the given reference picture list.
  • the reference picture list to be used for derivation of the co-located PU is explicitly signalled in the slice header.
  • the scaled motion vector for temporal merge candidate is obtained as illustrated by the dotted line in FIG.
  • 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.
  • FIG. 5 is an example illustration of motion vector scaling for temporal merge candidate.
  • 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 coding tree unit (CTU aka. LCU, largest coding unit) row, position C1 is used. Otherwise, position C0 is used in the derivation of the temporal merge candidate.
  • CTU current coding tree unit
  • FIG. 6 shows an example of candidate positions for temporal merge candidate, C0 and C1.
  • 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. Finally, no redundancy check is performed on these candidates.
  • AMVP exploits spatio-temporal correlation of motion vector with neighbouring 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 neighbouring 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) .
  • FIG. 8 summarizes derivation process for motion vector prediction candidate.
  • 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 neighbouring PU and that of the current PU regardless of reference picture list. If all PUs of left candidates are not available or are intra coded, scaling for the above motion vector is allowed to help parallel derivation of left and above MV candidates. Otherwise, spatial scaling is not allowed for the above motion vector.
  • FIG. 9 is an illustration of motion vector scaling for spatial motion vector candidate.
  • the motion vector of the neighbouring PU is scaled in a similar manner as for temporal scaling, as depicted in 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.
  • FIG. 10 shows an example of ATMVP motion prediction for a CU.
  • 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.
  • a reference picture and the corresponding block is determined by the motion information of the spatial neighbouring 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 neighbouring 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 neighbouring 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.
  • FIG. 11 shows an example of one CU with four sub-blocks (A-D) and its neighbouring blocks (a–d) .
  • 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.
  • AMVR Adaptive motion vector difference resolution
  • TPM Triangular prediction mode
  • GPI Generalized Bi-Prediction
  • BIO Bi-directional Optical flow
  • QuadTree/BinaryTree/MulitpleTree (QT/BT/TT) structure is adopted to divide a picture into square or rectangle blocks.
  • separate tree (a.k.a. Dual coding tree) is also adopted in VVC for I-frames.
  • VVC VVC
  • the coding block structure are signaled separately for the luma and chroma components.
  • 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 (i.e., 1/4-pel, 1-pel, 4-pel) .
  • the MVD resolution is controlled at the coding unit (CU) level, and MVD resolution flags are conditionally signalled for each CU that has at least one non-zero MVD components.
  • a first flag is signalled to indicate whether quarter luma sample MV precision is used in the CU.
  • the first flag (equal to 1) indicates that quarter luma sample MV precision is not used, another flag is signalled to indicate whether integer luma sample MV precision or four luma sample MV precision is used.
  • the quarter luma sample MV resolution is used for the CU.
  • the MVPs in the AMVP candidate list for the CU are rounded to the corresponding precision.
  • CU-level RD checks are used to determine which MVD resolution is to be used for a CU. That is, the CU-level RD check is performed three times for each MVD resolution. To accelerate encoder speed, the following encoding schemes are applied in the JEM.
  • the motion information of the current CU (integer luma sample accuracy) is stored.
  • the stored motion information (after rounding) is used as the starting point for further small range motion vector refinement during the RD check for the same CU with integer luma sample and 4 luma sample MVD resolution so that the time-consuming motion estimation process is not duplicated three times.
  • ⁇ RD check of a CU with 4 luma sample MVD resolution is conditionally invoked.
  • RD cost integer luma sample MVD resolution is much larger than that of quarter luma sample MVD resolution
  • the RD check of 4 luma sample MVD resolution for the CU is skipped.
  • the encoding process is shown in FIG. 12. First, 1/4 pel MV is tested and the RD cost is calculated and denoted as RDCost0, then integer MV is tested and the RD cost is denoted as RDCost1. If RDCost1 ⁇ th *RDCost0 (wherein th is a positive value) , then 4-pel MV is tested; otherwise, 4-pel MV is skipped. Basically, 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.
  • FIG. 12 is a flowchart of encoding with different MV precision.
  • HEVC high definition motion model
  • MCP motion compensation prediction
  • a simplified affine transform motion compensation prediction is applied with 4-parameter affine model and 6-parameter affine model.
  • FIGS. 13A-13B the affine motion field of the block is described by two control point motion vectors (CPMVs) for the 4-parameter affine model and 3 CPMVs for the 6-parameter affine model.
  • CPMVs control point motion vectors
  • the motion vector field (MVF) of a block is described by the following equations with the 4-parameter affine model (wherein the 4-parameter are defined as the variables a, b, e and f) in equation (1) and 6-parameter affine model (wherein the 4-parameter are defined as the variables a, b, c, d, e and f) in equation (2) respectively:
  • control point motion vectors (CPMV)
  • (x, y) represents the coordinate of a representative point relative to the top-left sample within current block
  • (mv h (x, y) , mv v (x, y) ) is the motion vector derived for a sample located at (x, y) .
  • the CP motion vectors may be signaled (like in the affine AMVP mode) or derived on-the-fly (like in the affine merge mode) .
  • w and h are the width and height of the current block.
  • the division is implemented by right-shift with a rounding operation.
  • the representative point is defined to be the center position of a sub-block, e.g., when the coordinate of the left-top corner of a sub-block relative to the top-left sample within current block is (xs, ys) , the coordinate of the representative point is defined to be (xs+2, ys+2) .
  • the representative point is utilized to derive the motion vector for the whole sub-block.
  • sub-block based affine transform prediction is applied.
  • the motion vector of the center sample of each sub-block is calculated according to Equation (1) and (2) , and rounded to 1/16 fraction accuracy.
  • the motion compensation interpolation filters for 1/16-pel are applied to generate the prediction of each sub-block with derived motion vector.
  • the interpolation filters for 1/16-pel are introduced by the affine mode.
  • FIG. 14 shows example of Affine MVF per sub-block.
  • the high accuracy motion vector of each sub-block is rounded and saved as the same accuracy as the normal motion vector.
  • AFFINE_INTER Similar to the translational motion model, there are also two modes for signaling the side information due affine prediction. They are AFFINE_INTER and AFFINE_MERGE modes.
  • 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.
  • an affine AMVP candidate list is constructed with three types of affine motion predictors in the following order, wherein each candidate includes the estimated CPMVs of the current block.
  • the differences of the best CPMVs found at the encoder side (such as mv 0 mv 1 mv 2 in FIG. 17) and the estimated CPMVs are signalled.
  • the index of affine AMVP candidate from which the estimated CPMVs are derived is further signalled.
  • the checking order is similar to that of spatial MVPs in HEVC AMVP list construction.
  • a left inherited affine motion predictor is derived from the first block in ⁇ A1, A0 ⁇ that is affine coded and has the same reference picture as in current block.
  • an above inherited affine motion predictor is derived from the first block in ⁇ B1, B0, B2 ⁇ that is affine coded and has the same reference picture as in current block.
  • the five blocks A1, A0, B1, B0, B2 are depicted in FIG. 16.
  • the CPMVs of the coding unit covering the neighboring block are used to derive predictors of CPMVs of current block. For example, if A1 is coded with non-affine mode and A0 is coded with 4-parameter affine mode, the left inherited affine MV predictor will be derived from A0. In this case, the CPMVs of a CU covering A0, as denoted by for the top-left CPMV and for the top-right CPMV in FIG.
  • top-left with coordinate (x0, y0)
  • top-right with coordinate (x1, y1)
  • bottom-right positions with coordinate (x2, y2)
  • a constructed affine motion predictor consists of control-point motion vectors (CPMVs) that are derived from neighboring inter coded blocks, as shown in FIG. 17, that have the same reference picture.
  • CPMVs control-point motion vectors
  • the number of CPMVs is 2, otherwise if the current affine motion model is 6-parameter affine, the number of CPMVs is 3.
  • the top-left CPMV is derived by the MV at the first block in the group ⁇ A, B, C ⁇ that is inter coded and has the same reference picture as in current block.
  • the top-right CPMV is derived by the MV at the first block in the group ⁇ D, E ⁇ that is inter coded and has the same reference picture as in current block.
  • the bottom-left CPMV is derived by the MV at the first block in the group ⁇ F, G ⁇ that is inter coded and has the same reference picture as in current block.
  • a constructed affine motion predictor is inserted into the candidate list only if both and are founded, that is, and are used as the estimated CPMVs for top-left (with coordinate (x0, y0) ) , top-right (with coordinate (x1, y1) ) positions of current block.
  • a constructed affine motion predictor is inserted into the candidate list only if and are all founded, that is, and are used as the estimated CPMVs for top-left (with coordinate (x0, y0) ) , top-right (with coordinate (x1, y1) ) and bottom-right (with coordinate (x2, y2) ) positions of current block.
  • FIG. 15A shows an example of a 4-paramenter affine model.
  • FIG. 15B shows an example of a 6-parameter affine model.
  • FIG. 16 shows an example of an MVP for AF_INTER for inherited affine candidates.
  • FIG. 17 shows an example of an MVP for AF_INTER for constructed affine candidates.
  • 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 FIGS. 15A-15B. 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.
  • 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. 18A (denoted by A, B, C, D, E in order) .
  • the neighbour left bottom block is coded in affine mode as denoted by A0 in FIG. 18B
  • the Control Point (CP) motion vectors mv 0 N , mv 1 N and mv 2 N of the top left corner, above right corner and left bottom corner of the neighbouring CU/PU which contains the block A are fetched.
  • the motion vector mv 0 C , mv 1 C and mv 2 C (which is only used for the 6-parameter affine model) of the top left corner/top right/bottom left on the current CU/PU is calculated based on mv 0 N , mv 1 N and mv 2 N .
  • sub-block e.g. 4 ⁇ 4 block in VTM
  • the sub-block located at the top-right corner may store mv1 if the current block is affine coded.
  • the sub-block located at the bottom-left corner stores mv2; otherwise (with the 4-parameter affine model) , LB stores mv2’.
  • Other sub-blocks stores the MVs used for MC.
  • 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. 18A shows example candidates for AF_MERGE in a 5 neighboring blocks case.
  • FIG. 18B shows an example of CPMV predictor derivation process.
  • Inherited affine candidate means that the candidate is derived from the affine motion model of its valid neighbor affine coded block.
  • the maximum two inherited affine candidates are derived from affine motion model of the neighboring blocks and inserted into the candidate list.
  • the scan order is ⁇ A0, A1 ⁇ ; for the above predictor, the scan order is ⁇ B0, B1, B2 ⁇ .
  • Constructed affine candidate means the candidate is constructed by combining the neighbor motion information of each control point.
  • the motion information for the control points is derived firstly from the specified spatial neighbors and temporal neighbor shown in FIG. 19.
  • T is temporal position for predicting CP4.
  • 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.
  • FIG. 19 shows examples of candidate positions for affine merge mode.
  • 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.
  • T is used.
  • 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 two combinations ( ⁇ CP1, CP2 ⁇ , ⁇ CP1, CP3 ⁇ ) .
  • the two combinations will be converted to a 4-parameter motion model represented by top-left and top-right control points.
  • the reference indices of list X for each CP are checked, if they are all the same, then this combination has valid CPMVs for list X. If the combination does not have valid CPMVs for both list 0 and list 1, then this combination is marked as invalid. Otherwise, it is valid, and the CPMVs are put into the sub-block merge list.
  • FIG. 20 shows an example when the current CU is at the CTU row boundary.
  • the 4 ⁇ 4 block covering (x LE1 , y LE1 ) is selected to be inherited the affine model from, then the neighbouring CU covering (x LE1 , y LE1 ) is found.
  • the MVs of the bottom-left 4 ⁇ 4 block and bottom right block of the neighbouring CU are found (noted as vLE0 and vLE1 in the figure) .
  • the CPMVs of the current block are calculated as
  • control point vectors and of the current CU are derived by using the 4-parameter model, and by
  • control point vectors is derived by
  • CPMVs of neighbouring blocks out of the current CTU row are not required, CPMVs are not required to be stored in line-buffer. Moreover, the height and y-component of the coordinate of the top-left corner are not required to be stored in line-buffer. However, the width and the x-component of the coordinate of the top-left corner are still required to be stored in line-buffer.
  • FIG. 20 shows an example of affine inheritance at CTU-row.
  • affine inheritance it is proposed that the affine parameters a, b, c and d are stored for affine inheritance instead of storing CPMVs.
  • HMVP history motion vector prediction
  • the affine parameters a, b, c and d can be stored to generate a history motion vector prediction (HMVP) for affine merge or affine inter coding.
  • the buffer/table/list to store the history-based affine models is known as affine HMVP buffer/table/list.
  • control point vectors and of the current CU are derived by using the 4-parameter model, and by
  • control point vectors is derived by
  • (x LE1 , y LE1 ) and (x LE0 , y LE0 ) are used as a representative position of the bottom-right and bottom-left sample coordinate of a coding unit with affine mode, respectively.
  • v LE0 is assigned to the left-bottom position of the neighbouring CU denoted as (x E0 , y 0 ) .
  • v LE0 is assigned to the center position of the left-bottom sub-block of the neighbouring CU.
  • the sub-block covering (x LE0 , y LE0 ) is named as the first representative sub-block and the sub-block covering (x LE1 , y LE1 ) is named as the second representative sub-block. Therefore, additional line buffer is required to store the CU width, coordinate, etc.
  • Shift (x, n) (x+ offset0) >>n.
  • offset0 and/or offset1 are set to (1 ⁇ n) >>1 or (1 ⁇ (n-1) ) . In another example, offset0 and/or offset1 are set to 0.
  • Clip3 (min, max, x) is defined as
  • a first group of CPMVs (denoted as MV F 0, MV F 1 and MV F 2, at represented points (x F 0, y F 0) , (x F 1, y F 1) and (x F 2, y F 2) , respectively) of a block used to conduct affine inheritance for following blocks may be different from a second group of CPMVs (denoted as MV S 0, MV S 1 and MV S 2, at represented points (x S 0, y S 0) , (x S 1, y S 1) and (x S 2, y S 2) , respectively) of a block used to derive the MVs for each sub-block, or a third group of CPMVs (denoted as MV T 0, MV T 1 and MV T 2, at represented points (x T 0, y T 0) , (x T 1, y T 1) and (x T 2, y T 2) , respectively) signaled from the encoder to the decoder.
  • a third group of CPMVs (denoted as
  • the second group CPMVs are the same to the third group of CPMVs.
  • the first group of CPMVs are derived from the second or the third group of CPMVs.
  • the first group of CPMVs are stored after coding/decoder a block.
  • the represented points’ coordinator (such as (x F i, y F i) , (x S i, y S i) , (x T i, y T i) ) are defined as coordinators relative to one sub-block which is used in the affine motion compensation process.
  • the relative offset between the representative points of two CPMVs in the first group may not depend on the width or height of the block.
  • CPMVs of a block B denoted as MV F 0, MV F 1 and MV F 2 at representative points (x F 0, y F 0) , (x F 1, y F 1) and (x F 2, y F 2) , respectively, are stored.
  • CPMVs of a block B denoted as MV F 0 and MV F 1 at positions (x F 0, y F 0) and (x F 1, y F 1) are stored.
  • (x F 0, y F 0) , (x F 1, y F 1) and (x F 2, y F 2) may be inside block B, or they be outside of it.
  • y F 2 y F 1 + PW.
  • x F 2 x F 1
  • y F 2 y F 1 + PH.
  • PW and PH are integers.
  • PW 2 M .
  • PW may be equal to 4, 8 16, 32, 64 or 128.
  • PW -2 M .
  • PW may be equal to -4, -8 -16, -32, -64 or -128.
  • PH 2 M .
  • PH may be equal to 4, 8 16, 32, 64 or 128.
  • PH -2 M .
  • PH may be equal to -4, -8 -16, -32, -64 or -128.
  • VPS/SPS/PPS/Slice header/tile group header/tile/CTU are signaled in VPS/SPS/PPS/Slice header/tile group header/tile/CTU.
  • they may depend on the maximum CU size or/and minimum CU size of the slice/picture.
  • MV F 0, MV F 1 and MV F 2 are derived from MV S 0 and MV S 1 by Eq. (1) with (x F 0, y F 0) , (x F 1, y F 1) and (x F 2, y F 2) as the input coordinates.
  • MV F 0, MV F 1 and MV F 2 are derived from MV S 0, MV S 1 and MV S 2 by Eq. (2) with (x F 0, y F 0) , (x F 1, y F 1) and (x F 2, y F 2) as the input coordinates.
  • MV F 0, MV F 1 and MV F 2 are derived from MV T 0 and MV T 1 by Eq. (1) with (x F 0, y F 0) , (x F 1, y F 1) and (x F 2, y F 2) as the input coordinates.
  • MV F 0, MV F 1 and MV F 2 are derived from MV T 0, MV T 1 and MV T 2 by Eq. (2) with (x F 0, y F 0) , (x F 1, y F 1) and (x F 2, y F 2) as the input coordinates.
  • MV F 2 is only calculated if the current block is coded with the 6-parameter affine model.
  • MV F 2 is calculated no matter the current block is coded with the 6-parameter affine model or the 6-parameter affine model.
  • D1 MV F 1-MV F 0 is stored
  • D2 MV F 2-MV F 0 is stored
  • both D1 and D2 are stored;
  • D2 is stored only if the current block is coded with the 6-parameter affine model.
  • D2 is stored no matter the current block is coded with the 6-parameter affine model or the 6-parameter affine model.
  • the CPMVs and the differences between CPMVs may be stored together.
  • MV F 0, D1 and D2 are stored.
  • the stored CPMVs or differences between CPMVs may be shifted before being stored.
  • MV is a CPMV or the difference between CPMVs to be stored, then
  • MV’ (MV’x, MV’y) is stored instead of MV.
  • MV’ (MV’x, MV’y) is stored instead of MV.
  • n is an integer such as 2 or 4;
  • n depends on the motion precision.
  • ii. n may be different when CPMV is stored or the difference between CPMVs is stored.
  • the stored MV’ is left shift first before it is used in the affine inheritance.
  • the CPMVs or differences between CPMVs to be stored may be clipped before being stored.
  • MV is a CPMV or the difference between CPMVs to be stored, then
  • MV’ (MV’x, MV’y) is stored instead of MV.
  • i. K may be different depending on whether MV is a CPMV or a difference between CPMVs.
  • the stored MV’ is first shifted, then clipped before it is used in the affine inheritance.
  • the MV stored in an adjacent neighbouring basic block denoted as Badj is used to derive the affine inherited MVs of the current block.
  • FIG. 21 shows examples of MV stored in adjacent neighbouring basic blocks: L, A, LB, AR and AL.
  • a basic block is a 4 ⁇ 4 block.
  • MVa (mv h a , mv v a )
  • an affine inherited MV of the current block at position (x, y) denoted as (mv h (x, y) , mv v (x, y) ) is derived as
  • i. (x 0 , y 0 ) may be any position inside the basic block Badj.
  • FIG. 22 shows an example.
  • (x 0 , y 0 ) may be P22 in FIG. 22.
  • x 0 , y 0 may be any position outside or at the boundary of the basic block Badj.
  • (x 0 , y 0 ) may be any one of (xTL+i, yTL+j) with i may be -1, 0, Wb-1 or Wb; j may be -1, 0, Hb-1 or Hb.
  • i and j may depend on the width and height of the current block.
  • i and j may be signaled in VPS/SPS/PPS/Slice header/tile group header/tile/CTU/CU.
  • i and j may be different in different standard profiles/levels/tiers.
  • the position (x, y) may be in a sub-block of the current block, then the MV of a sub-block is inherited depending on MVa.
  • the position (x, y) may be a corner of the current block, then a CPMV of the current block is inherited depending on MVa.
  • the inherited CPMVs can be used to predict the signaled CPMVs of the affine inter-coded current block.
  • the inherited CPMVs can be directly used as CPMVs of the affine merge-coded current block.
  • Eq. (3) is applied if the current block uses the 4-paramter affine model.
  • Eq. (4) is applied if the current block uses the 6-paramter affine model.
  • Eq. (4) is applied no matter the current block uses the 4-paramter affine model or the 6-paramter affine model.
  • a, b, c and d are derived from stored CPMVs in the second or third group, as declared in bullet 1, of the CU covering the adjacent neighbouring basic block Badj.
  • the CU covering the adjacent neighbouring basic block Badj is block Z
  • mv t0 (mv h t0 , mv v t0 )
  • mv t1 (mv h t1 , mv v t1 )
  • mv t2 (mv h t2 , mv v t2 )
  • w t and h t are the width and height of block Z.
  • a, b, c and d are derived from stored CPMVs in the first group, as declared in bullet 1, of the CU covering the adjacent neighbouring basic block Badj.
  • the CU covering the adjacent neighbouring basic block Badj is block Z
  • mv t0 (mv h t0 , mv v t0 )
  • mv t1 (mv h t1 , mv v t1 )
  • mv t2 (mv h t2 , mv v t2 )
  • w t and h t are PW and PH declared in bullet 2.
  • mv h t1 -mv h t0 , mv v t1 -mv v t0 , mv h t2 -mv h t0 , mv v t2 -mv v t0 are fetched from the storage directly as claimed in bullet 3.
  • FIG. 21 shows examples of MV stored in adjacent neighbouring basic blocks.
  • FIG. 22 shows positions in a 4 ⁇ 4 basic block.
  • a first MV stored in a first basic block adjacently neighbouring to the current block, and a second MV stored in a second basic block with a known offset to the first basic block, are used to derive the CPMVs of the current block.
  • an affine inherited MV of the current block at position (x, y) denoted as (mv h (x, y) , mv v (x, y) ) is derived by Eq. (3)
  • a, b are derived by Eq. (5) .
  • mv t0 and mv t1 in Eq. (5) are set equal to the MV stored in the first basic block and the MV stored in the second basic block, respectively.
  • w t is set to be the horizontal offset between the two basic blocks.
  • a, b are derived as
  • h t is set to be the horizontal offset between the two basic blocks.
  • w t and h t must be in a form of 2 N , such as 4, 8, 16..
  • the horizontal offset between the first basic block and the second basic block is defined as xLT1 -xLT0;
  • the vertical offset between the first basic block and the second basic block is defined as yLT1 -yLT0;
  • yLT1 -yLT0 must be equal to 0 when the first basic block is above the current block (such as block A, AL and AR in FIG. 23) .
  • xLT1 -xLT0 must be equal to 0. when the first basic block is left to the current block (such as block L, LB and AL in FIG. 23) .
  • How to choose the second basic block may depend on the position of the first block.
  • FIG. 23 shows examples of pairs of the first and second basic blocks: AL and AL’, A and A’, AR and AR’, L and L’, LB and LB’.
  • the second basic block may be selected from several candidate basic blocks.
  • the top-left positions of the M candidate basic block are denoted as (xC 0 , yC 0 ) , (xC 1 yC 1 ) , ... (xC M-1 , yC M-1 ) .
  • the M candidate basic block are checked in order, to find the one that is inter-coded, and has a MV referring to the same reference picture as the MV of the first basic block referring to. The found candidate is selected as the second basic block.
  • M 2.
  • Whether to and/or how to select the second basic block from candidate basic blocks may depend on the position of the first basic block and/or the position of the current block.
  • M 1.
  • yC 0 yLT0
  • xC 0 xLT0 + offset, where offset is a positive number such as 4, 8 or 16, if the first block is above-left to the current block (such as block AL in FIG. 23) .
  • M 2.
  • M 2.
  • M 2.
  • M 2.
  • M 2.
  • M 2.
  • M 2.
  • M 2.
  • whether and how to apply the methods in this bullet may depend on the position of the current block.
  • the methods in this bullet are applied only when the affine model is inherited from an above neighbouring block and it is not in the current CTU or CTU row.
  • the methods in this bullet are applied only when the affine model is inherited from an above or left neighbouring block and it is not in the current CTU.
  • BB may be A, AR or AL, the top-left position of BB is (xBB, yBB) , BB must be affine coded) , then BB is treated as the first adjacent neighboring basic block. And the following process applies to find the second adjacent neighboring basic block.
  • BBR is first checked, if BBR is affine coded, and it has the same reference index as BB for a given reference list, then BBR is treated as the second adjacent neighboring basic block. Otherwise, BBL is treated as the second adjacent neighboring basic block.
  • BBL is first checked, if BBL is affine coded, and it has the same reference index as BB for a given reference list, then BBL is treated as the second adjacent neighboring basic block. Otherwise, BBR is treated as the second adjacent neighboring basic block.
  • whether to find the second block from multiple candidates or from a predefined offset may depend on the position of the first block and/or the position of the current block.
  • BB may be A, AR or AL, the top-left position of BB is (xBB, yBB) , BB must be affine coded) , then BB is treated as the first adjacent neighbouring basic block. And the following process applies to find the second adjacent neighbouring basic block.
  • BB is AL and the left boundary of the current block is the left boundary of a CTU, then only the basic block BBR right to BB (AL”) is checked. if BBR is affine coded, and it has the same reference index as BB for a given reference list, then BBR is treated as the second adjacent neighbouring basic block. Otherwise, the affine model inherited from BB is unavailable.
  • BBR is affine coded, and it has the same reference index as BB for a given reference list, then BBR is treated as the second adjacent neighbouring basic block. Otherwise, BBL is treated as the second adjacent neighbouring basic block.
  • BBL is first checked, if BBL is affine coded, and it has the same reference index as BB for a given reference list, then BBL is treated as the second adjacent neighbouring basic block. Otherwise, BBR is treated as the second adjacent neighbouring basic block.
  • offset must be in a form of 2 K .
  • offset may depend on the minimum allowed CU width.
  • offset may depend on the minimum allowed CU height.
  • offset may depend on the basic block width.
  • offset may depend on the basic block height.
  • offset may depend on the minimum allowed width of a CU that affine coding is applicable.
  • offset may depend on the minimum allowed height of a CU that affine coding is applicable.
  • offset may be signaled from the encoder to the decoder.
  • P is not allowed to be the first block.
  • the second block can only be chosen from a basic unit left to P if Q is right to P.
  • the second block can only be chosen from a basic unit right to P if Q is left to P.
  • the second block can only be chosen from a basic unit above to P if Q is below to P.
  • the second block can only be chosen from a basic unit below to P if Q is above to P.
  • an adjacent neighbouring basic block may be on a row or column adjacent to the current block.
  • AL’ AR’, LB’ may also be regarded as adjacent neighbouring blocks.
  • a first basic block is considered as “valid” if it satisfies one, several or all of the following conditions:
  • whether a second basic block is considered as “valid” or not may depend on the information of the first basic block.
  • a second basic block is considered as “valid” if it satisfies one, several or all of the following conditions:
  • each candidate above neighbouring basic block such as AR, A and AL1 in FIG. 24, is checked in order to determine whether it is a valid first basic block.
  • the order may be AR, A, AL1 or A, AR AL1.
  • BB may be AR, A or AL1
  • BB is a valid first basic block
  • the basic block BBR right to BB is checked first.
  • An example of the detailed steps for the determination of first and second basic blocks are given as follows:
  • BBR is a valid second basic block
  • BB and BBR are output as the first basic block and second basic block
  • BBL is a valid second basic block, then BB and BBL are output as the first basic block and second basic block;
  • next basic block in order is checked to be the first basic block.
  • no valid first basic block and second basic block can be output.
  • BBL is a valid second basic block, then BB and BBL are output as the first basic block and second basic block;
  • BBR is a valid second basic block
  • BB and BBR are output as the first basic block and second basic block
  • next basic block in order is checked determine whether it is a valid first basic block.
  • BB may be AR, A or AL1
  • BB is a valid first basic block
  • An example of the detailed steps for the determination of first and second basic blocks are given as follows:
  • BBL is a valid second basic block, then BB and BBL are output as the first basic block and second basic block;
  • BB is not used as the first basic block and the next basic block in order is checked to determine whether it is a valid first basic block.
  • first and second basic blocks are given as follows:
  • BBR is a valid second basic block
  • BB and BBR are output as the first basic block and second basic block
  • BB is not used as the first basic block and the next basic block in order is checked to determine whether it is a valid first basic block.
  • FIG. 27 and FIG. 28 show two exemplary flowcharts of how to choose the first basic block and the second basic block.
  • neighbouring basic blocks may be checked for the determination of first basic blocks may depend on the position of the current block and/or sub-block sizes of affine motion compensation.
  • the candidate basic blocks are AR, A and AL” in FIG. 24.
  • the candidate basic blocks are AR, A and AL”; Otherwise, the candidates are AR, A and AL1.
  • Whether a basic block can be used as the first basic block may depend on the position of the current block.
  • the basic block AL1 in FIG. 24 cannot be used as the first basic block.
  • the basic block AL’ in FIG. 24 cannot be used as the first basic block.
  • the basic block AR in FIG. 24 cannot be used as the first basic block.
  • the basic block AR’ in FIG. 24 cannot be used as the first basic block.
  • Whether a basic block can be used as the second basic block may depend on the position of the current block.
  • the basic block AL1 in FIG. 24 cannot be used as the second basic block.
  • the basic block AL’ in FIG. 24 cannot be used as the second basic block.
  • the basic block AR in FIG. 24 cannot be used as the second basic block.
  • the basic block AR’ in FIG. 24 cannot be used as the second basic block.
  • the first basic block and the second basic block may be exchanged.
  • the output first and second basic blocks are firstly exchanged and then utilized for decoding one block.
  • first and second basic blocks mentioned above may be exchanged.
  • FIG. 23 shows examples of MVs of two adjacent neighbouring blocks.
  • the stored affine parameters may be shifted before being stored.
  • m (m may be a, b, c or d) is to be stored, then
  • m’ SatShift (m, n) .
  • m’ is stored instead of m.
  • m’ Shift (m, n) .
  • m’ is stored instead of m.
  • n is an integer such as 2 or 4;
  • n depends on the motion precision.
  • n may be different for different affine parameters.
  • n may be signaled in VPS/SPS/PPS/Slice header/tile group header/tile/CTU/CU.
  • n may be different in different standard profiles/levels/tiers.
  • the stored affine parameter is left shift first before it is used in the affine inheritance.
  • the stored m’ is first shifted, then clipped before it is used in the affine inheritance.
  • the CPMVs in the first group as disclosed in bullet 1 and bullet 2 may be stored into the affine HMVP buffer/table/list to represent one history-based candidate affine model.
  • the differences between CPMVs as disclosed in bullet 3 may be stored into the affine HMVP buffer/table/list to represent one history-based candidate affine model.
  • control point vectors and of the current CU are derived by using the 4-parameter model, and by
  • control point vectors is derived by
  • control point vectors and of the current CU are derived by using the 4-parameter model, and by
  • control point vectors is derived by
  • bullet 6 is applied to conduct affine inheritance not at the CTU row boundary.
  • An exemplary decoding process is specified as (the section numbers here refer to the current release of the VVC standard) :
  • variable availableFlagA is set equal to FALSE and the following applies for (xNbA k , yNbA k ) from (xNbA 0 , yNbA 0 ) to (xNbA 1 , yNbA 1 ) :
  • variable availableFlagA is set equal to TRUE
  • motionModelIdcA is set equal to MotionModelIdc [xNbA k ] [yNbA k ]
  • (xNb, yNb) is set equal to (CbPosX [xNbA k ] [yNbA k ] , CbPosY [xNbA k ] [yNbA k ] )
  • nbW is set equal to CbWidth [xNbA k ] [yNbA k ]
  • nbH is set equal to CbHeight [xNbA k ] [yNbA k ]
  • numCpMv is set equal to MotionModelIdc [xNbA k ] [yNbA k ] + 1.
  • predFlagLXA PredFlagLX [xNbA k ] [yNbA k ] (8-318)
  • refIdxLXA RefIdxLX [xNbAk] [yNbAk] (8-319)
  • variable availableFlagB is set equal to FALSE and the following applies for (xNbB k , yNbB k ) from (xNbB 0 , yNbB 0 ) to (xNbB 2 , yNbB 2 ) :
  • variable availableFlagB is set equal to TRUE
  • motionModelIdcB is set equal to MotionModelIdc [xNbB k ] [yNbB k ]
  • (xNb, yNb) is set equal to (CbPosX [xNbAB] [yNbB k ] , CbPosY [xNbB k ] [yNbB k ] )
  • nbW is set equal to CbWidth [xNbB k ] [yNbB k ]
  • nbH is set equal to CbHeight [xNbB k ] [yNbB k ]
  • numCpMv is set equal to MotionModelIdc [xNbB k ] [yNbB k ] + 1.
  • a luma location (xCb, yCb) specifying the top-left sample of the current luma coding block relative to the top-left luma sample of the current picture
  • a luma location (xNb, yNb) specifying the top-left sample of the neighbouring luma coding block relative to the top-left luma sample of the current picture
  • a luma location (xNbC, yNbC) specifying the center sample of the neighbouring luma coding sub-block relative to the top-left luma sample of the current picture
  • nNbW and nNbH specifying the width and the height of the neighbouring luma coding block
  • variable isCTUboundary is derived as follows:
  • isCTUboundary is set equal to TRUE:
  • isCTUboundary is set equal to FALSE.
  • log2NbW and log2NbH are derived as follows:
  • dHorX (MvLX [xNb + nNbW -1] [yNb + nNbH -1] [0] -MvLX [xNb] [yNb + n NbH -1] [0] ) ⁇ (7 -log2NbW) (8-373)
  • dHorX (CpMvLX [xNb + nNbW -1] [yNb] [1] [0] -CpMvLX [xNb] [yNb] [0] [0] ) ⁇ (7 -log2NbW) (8-377)
  • yNb is set equal to yCb. Then xNbC is set equal to xNb, yNbC is set equal to yNb.
  • cpMvLX [0] [0] (mvScaleHor + dHorX * (xCb -xNbC) + dHorY * (yCb -yNbC) ) (8-383)
  • cpMvLX [1] [0] (mvScaleHor + dHorX * (xCb + cbWidth -xNbC) + dHorY * (yCb -yNbC) ) (8-385)
  • cpMvLX [1] (mvScaleVer + dVerX * (xCb + cbWidth -xNbC) + dVerY * (yCb -yNbC) ) (8-386)
  • cpMvLX [2] [0] (mvScaleHor + dHorX * (xCb -xNbC) + dHorY * (yCb + cbHei ght -yNbC) ) (8-387)
  • cpMvLX [2] (mvScaleVer + dVerX * (xCb -xNbC) + dVerY * (yCb + cbHei ght -yNbC) ) (8-388)
  • the number of control point motion vector predictor candidates in the list numCpMvpCandLX is set equal to 0.
  • the sample locations (xNbA 0 , yNbA 0 ) , (xNbA 1 , yNbA 1 ) , (xNbA 2 , yNbA 2 ) , (xNbB 0 , yNbB 0 ) , (xNbB 1 , yNbB 1 ) , and (xNbB 2 , yNbB 2 ) are derived as follows:
  • the variable (xNb, yNb) is set equal to (CbPosX [xNbA k ] [yNbA k ] , CbPosY [xNbA k ] [yNbA k ] )
  • nbW is set equal to CbWidth [xNbA k ] [yNbA k ]
  • nbH is set equal to CbHeight [xNbA k ] [yNbA k ] .
  • variable availableFlagA is set equal to TRUE
  • numCpMvpCandLX numCpMvpCandLX + 1 (8-448)
  • variable availableFlagA is set equal to TRUE
  • numCpMvpCandLX numCpMvpCandLX + 1 (8-452)
  • the variable (xNb, yNb) is set equal to (CbPosX [xNbB k ] [yNbB k ] , CbPosY [xNbB k ] [yNbB k ] )
  • nbW is set equal to CbWidth [xNbB k ] [yNbB k ]
  • nbH is set equal to CbHeight [xNbB k ] [yNbB k ] .
  • variable availableFlagB is set equal to TRUE
  • numCpMvpCandLX numCpMvpCandLX + 1 (8-456)
  • variable availableFlagB is set equal to TRUE
  • numCpMvpCandLX numCpMvpCandLX + 1 (8-460)
  • FIG. 24 is a block diagram of a video processing apparatus 2600.
  • the apparatus 2600 may be used to implement one or more of the methods described herein.
  • the apparatus 2600 may be embodied in a smartphone, tablet, computer, Internet of Things (IoT) receiver, and so on.
  • the apparatus 2600 may include one or more processors 2602, one or more memories 2604 and video processing hardware 2606.
  • the processor (s) 2602 may be configured to implement one or more methods described in the present document.
  • the memory (memories) 2604 may be used for storing data and code used for implementing the methods and techniques described herein.
  • the video processing hardware 2606 may be used to implement, in hardware circuitry, some techniques described in the present document.
  • FIG. 25 is a flowchart for an example method 2500 of video processing.
  • the method 2500 includes associating (2502) , with a current video block, a first group of motion vectors (MVs) for determining inherited motion information of other video blocks, a second group of MVs for deriving MVs of sub-blocks of the current video block and a third group of MVs that is included in a bitstream representation of the current video block; and performing (2504) a conversion between the current video block and the bitstream representation using the first group of MVs, the second group of MVs or the third group of MVs.
  • MVs motion vectors
  • a method of video processing comprising:
  • MVs motion vectors
  • the first group of MVs comprises control point MVs (CPMVs) , MVF0, MVF1 and MVF2, at represented points (xF0, yF0) , (xF1, yF1) and (xF2, yF2) , respectively.
  • CPMVs control point MVs
  • MVF0, MVF1 and MVF2 at represented points (xF0, yF0) , (xF1, yF1) and (xF2, yF2) , respectively.
  • the second group of MVs comprises control point MVs (CPMVs) , denoted MVS0, MVS1 and MVS2, at represented points (xS0, yS0) , (xS1, yS1) and (xS2, yS2) , respectively.
  • CPMVs control point MVs
  • CPMVs control point MVs
  • MVT0, MVT1 and MVT2 at represented points (xT0, yT0) , (xT1, yT1) and (xT2, yT2) , respectively.
  • yF1 yF0
  • xF1 xF0 + PW
  • xF1 xF0
  • yF1 yF0 + PH
  • yF2 yF0
  • xF2 xF0 + PW
  • xF2 xF0
  • yF2 yF0 + PH
  • a method of video processing comprising: performing a conversion between a current block and a bitstream representation of the current block using affine inherited motion vectors (MVs) for the current block, wherein the affine inherited MVs are derived from (1) MVs stored for an adjacent neighboring basic block, denoted as Badj, or (2) an affine history list.
  • MVs affine inherited motion vectors
  • the MVs stored for Badj include: L (left) , A (above) , LB (left below) , AR (above right) and AL (above left) , and wherein Badj is a 4x4 size block.
  • a MV at a position (x, y) in the current block is computed using a motion vector MVa of Badj at a position (x0, y0) , wherein (x0, y0) is one of: (a) a position inside Badj, or (b) a position on outside or on boundary of Badj.
  • a method of video processing comprising: performing a conversion between a current block and a bitstream representation of the current block using affine inherited motion vectors (MVs) for the current block, wherein the affine inherited MVs are derived from a first MV stored in a first basic block adjacently neighboring the current block and a second MV stored in a second basic block that is offset from the first building block by an offset.
  • MVs affine inherited motion vectors
  • a video encoder apparatus comprising a processor configured to implement a method recited in any one or more of clauses 1-43.
  • a video decoder apparatus comprising a processor configured to implement a method recited in any one or more of clauses 1-43.
  • a computer program product stored on a non-transitory computer readable media the computer program product including program code for carrying out the method in any of clauses 1 to 43.
  • FIG. 29 is a flowchart for a method 2900 of processing video.
  • the method 2900 includes, associating (2902) a first group of control point motion vectors (CPMVs) for determining inherited motion information of blocks coded after a first block, with a second group of CPMVs for deriving MVs of sub-blocks of the first block or a third group of CPMVs that is signaled for the first block, wherein the first group of CPMVs is not identical with the second group of CPMVs or the third group of CPMVs; determining (2904) inherited motion information for a second block, which is coded after the first block, based on the first group of CPMVs, and performing (2906) a conversation between the second block and a bitstream representation of the second block by using the inherited motion information.
  • CPMVs control point motion vectors
  • the first group of CPMVs are derived from the second group of CPMVs or the third group of CPMVs.
  • the method further comprises: storing the first group of CPMVs after the conversion of the first block.
  • the second group of CPMVs are same as the third group of CPMVs.
  • multiple representative points’ coordinates of the first group of CPMVs, multiple representative points’ coordinates of the second group of CPMVs and/or multiple representative points’ coordinates of the third group of CPMVs are defined as coordinates relative to one block or sub-block which is used in an affine motion compensation process.
  • a relative offset between representative points of two CPMVs in the first group of CPMVs is independent of a width or a height of the first block.
  • representative points of the first group of CPMVs are inside of the first block or outside of the first block.
  • PW and PH are not stored.
  • PW and PH are fixed.
  • PW and PH are signaled in at least one of Sequence Parameter Set (SPS) , Video Parameter Set (VPS) , Picture Parameter Set (PPS) , slice header, tile group header, tile, or CTU.
  • SPS Sequence Parameter Set
  • VPS Video Parameter Set
  • PPS Picture Parameter Set
  • PW and PH are different in different standard profiles or levels or tiers.
  • PW and PH depend on maximum coding unit (CU) size or/and minimum CU size of slice or picture.
  • motion vectors MVF0, MVF1 and MVF2 in the first group of CPMVs are derived from motion vectors MVS0 and MVS1 in the second group of CPMVs by using a 4-parameter affine model with coordinates (xF0, yF0) , (xF1, yF1) and (xF2, yF2) as the input coordinates of the affine model.
  • motion vectors MVF0, MVF1 and MVF2 in the first group of CPMVs are derived from motion vectors MVS0, MVS1 and MVS2 in the second group of CPMVs by using a 6-parameter affine model with (xF0, yF0) , (xF1, yF1) and (xF2, yF2) as the input coordinates of the affine model.
  • motion vectors MVF0, MVF1 and MVF2 in the first group of CPMVs are derived from motion vectors MVT0 and MVT1 in the third group of CPMVs by using a 4-parameter affine model with (xF0, yF0) , (xF1, yF1) and (xF2, yF2) as the input coordinates of the affine model.
  • motion vectors MVF0, MVF1 and MVF2 in the first group of CPMVs are derived from motion vectors MVT0, MVT1 and MVT2 in the third group of CPMVs by using a 6-parameter affine model with (xF0, yF0) , (xF1, yF1) and (xF2, yF2) as the input coordinates of the affine model.
  • motion vectors MVF2 in the first group of CPMVs comprising motion vectors MVF0, MVF1 and MVF2 is only calculated if the first block is coded with a 6-parameter affine model, or motion vectors MVF2 in the first group of CPMVs comprising motion vectors MVF0, MVF1 and MVF2 is calculated no matter the first block is coded with a 4-parameter affine model or a 6-parameter affine model.
  • the method further comprises: storing one or more differences (D1, D2) between the CPMVs in the first group of CPMVs.
  • D2 is stored only when the first block is coded with a 6-parameter affine model.
  • D2 is stored when the first block is coded with the 6-parameter affine model or the 6-parameter affine model.
  • the method further comprises: storing the first group of CPMVs and one or more differences (D1, D2) between the CPMVs in the first group of CPMVs together.
  • the multiple CPMVs in the first group of CPMVs and/or one or more differences between the CPMVs in the first group of CPMVs are shifted with a shift function, and the shifted CPMVs and/or differences are stored.
  • the shift function SatShift (x, n) is defined as: wherein n is an integer, and offset0 and/or offset1 are set to (1 ⁇ n) >>1 or (1 ⁇ (n-1) ) , or ( (1 ⁇ n) >>1) -1, or offset0 and/or offset1 are set to 0.
  • n is 2 or 4, or n depends on the motion precision.
  • stored CPMV is left shift first before it is used in the affine inheritance of the blocks coded after the first block.
  • the multiple CPMVs in the first group of CPMVs and/or one or more differences between the CPMVs in the first group of CPMVs are clipped with a clip function, and the clipped CPMVs and/or the differences are stored.
  • the clip function Clip3 (min, max, x) is defined as:
  • Min is a lower threshold of the clip function
  • Max is a higher threshold of the clip function
  • K is an integer.
  • K is different depending on whether the CPMV or the difference is to be stored.
  • the multiple CPMVs in the first group of CPMVs and/or one or more differences between the CPMVs in the first group of CPMVs are processed with the shift function and the clip function sequentially, and the processed CPMVs and/or the differences are stored.
  • the multiple CPMVs in the first group of CPMVs are stored into an affine (History Motion Vector Prediction) HMVP buffer or table or list to represent one history-based candidate affine model.
  • affine History Motion Vector Prediction
  • the one or more differences between the CPMVs in the first group of CPMVs are stored into an affine (History Motion Vector Prediction) HMVP buffer or table or list to represent one history-based candidate affine model.
  • affine History Motion Vector Prediction
  • one or more CPMVs or one or more differences stored in the HMVP buffer or table or list are shifted with the shift function and/or clipped with the clip function.
  • FIG. 30 is a flowchart for a method 3000 of processing video.
  • the method 3000 includes, deriving (3002) , for a conversion between a current block of video and a bitstream representation of the current block, affine inherited motion vectors (MVs) for the first block based on stored motion vectors (MVs) ; performing (3004) the conversion by using the affine inherited MVs.
  • deriving (3002) for a conversion between a current block of video and a bitstream representation of the current block, affine inherited motion vectors (MVs) for the first block based on stored motion vectors (MVs) ; performing (3004) the conversion by using the affine inherited MVs.
  • MVs affine inherited motion vectors
  • the MVs are stored in an adjacent neighbouring basic block.
  • the MVs are stored in affine (History Motion Vector Prediction) HMVP buffer or table or list.
  • affine History Motion Vector Prediction
  • the MVs stored in the adjacent neighbouring basic block at least include: MV stored in a left adjacent neighbouring basic block (L) , MV stored in an above adjacent neighbouring basic block (A) , MV stored in a left-bottom adjacent neighbouring basic block (LB) , MV stored in an above-right adjacent neighbouring basic block (AR) and MV stored in an above left adjacent neighbouring basic block (AL) .
  • the adjacent neighbouring basic block is a 4x4 block
  • MVa (mv h a , mv v a )
  • the representative point (x 0 , y 0 ) is any position inside the basic block.
  • the representative point (x 0 , y 0 ) is any position outside or at the boundary of the basic block.
  • the coordinate of the representative point (x 0 , y 0 ) is determined based on the coordinate (xTL, yTL) of a top-left corner sample in the adjacent neighbouring basic block and additional information including two variables (i, j) .
  • a first variable (i) of the two variables depends on width of the basic block, and a second variable (j) of the two variables depends on height of the basic block.
  • the variables (i, j) depends on the position of the neighbouring basic block.
  • the coordinate of the representative point (x 0 , y 0 ) is determined based on the coordinate of top-left sample of the first block (xPos00, yPos00) , the coordinate of top-right sample of the first block (xPos10, yPos00) , and the coordinate of top-right sample of the first block (xPos00, yPos01) .
  • the coordinate of the representative point (x 0 , y 0 ) for the left adjacent neighbouring basic block L is (xPos00-2, yPos01-1) ; the coordinate of the representative point (x 0 , y 0 ) for the left-bottom adjacent neighbouring basic block (LB) is (xPos00-2, yPos01+3) ; the coordinate of the representative point (x 0 , y 0 ) for the above adjacent neighbouring basic block (A) is (xPos10-1, yPos00-2) ; the coordinate of the representative point (x 0 , y 0 ) for the above-right adjacent neighbouring basic block (AR) is (xPos10+3, yPos00-2) ; the coordinate of the representative point (x 0 , y 0 ) for the above left adjacent neighbouring basic block (AL) is (xPos00-2, yPos00-2) .
  • the additional information depends on the position of the adjacent neighbouring basic block or the adjacent neighbouring basic block, or the additional information is signaled in at least one of Sequence Parameter Set (SPS) , Video Parameter Set (VPS) , Picture Parameter Set (PPS) , slice header, tile group header, tile, coding tree unit (CTU) , CU.
  • SPS Sequence Parameter Set
  • VPS Video Parameter Set
  • PPS Picture Parameter Set
  • slice header slice header
  • tile group header tile group header
  • tile coding tree unit
  • CU coding tree unit
  • the additional information is different in different standard profiles or levels or tiers.
  • the affine inherited MV at a position (x, y) in a sub-block of the first block is derived by using a first MV of the adjacent neighbouring basic block (MVa) at a representative point (x 0 , y 0 ) based on an affine model with (x-x 0 , y-y 0 ) as the input coordinates of the affine model.
  • the affine inherited MV at a position (x, y) in a sub-block is used to perform motion compensation for the sub-block.
  • the affine inherited MV at a position (x, y) which is a corner of the first block, is derived as an inherited control point motion vector (CPMV) of the first block by using a first MV of the adjacent neighbouring basic block (MVa) at a representative point (x 0 , y 0 ) based on an affine model with (x-x 0 , y-y 0 ) as the input coordinates of the affine model.
  • CPMV inherited control point motion vector
  • the inherited CPMVs are used to predict signaled CPMVs of the first block which is affine inter-coded.
  • the inherited CPMVs are directly used as CPMVs of the first block which is affine merge-coded.
  • the affine model for deriving the affine inherited MV at a position (x, y) in the first block is:
  • a and b are variables of the affine model.
  • the affine model for deriving the affine inherited MV at a position (x, y) in the first block is:
  • a, b, c and d are variables of the affine model.
  • variable a, b, or variable a, b, c, d are calculated as:
  • mv t0 (mv h t0 , mv v t0 )
  • mv t1 (mv h t1 , mv v t1 )
  • mv t2 (mv h t2 , mv v t2 ) are CPMVs at three representative points, respectively, in a first group CPMVs for a second block covering the adjacent neighbouring basic block, and w t and h t depends on relative offsets between the representative points of the second block, wherein the first group CPMVs is used for determining inherited motion information of blocks coded after the second block.
  • variable a, b, or variable a, b, c, d are calculated as:
  • mv t0 (mv h t0 , mv v t0 )
  • mv t1 (mv h t1 , mv v t1 )
  • mv t2 (mv h t2 , mv v t2 ) are CPMVs at three representative points, respectively, in a second group CPMVs or a third group of CPMVs for a second block covering the adjacent neighbouring basic block
  • w t and h t are the width and height of the second block
  • the second group CPMVs are used to derive MVs for each sub-block of the second block
  • the third group CPMVs are signaled from encoder to decoder.
  • variable a, b, or variable a, b, c, d are calculated as:
  • mv t0 (mv h t0 , mv v t0 )
  • mv t1 (mv h t1 , mv v t1 )
  • mv t2 (mv h t2 , mv v t2 ) are CPMVs at three representative points, respectively, of a second block covering the adjacent neighbouring basic block
  • w t and h t are the width and height of the second block
  • mv h t1 -mv h t0 , mv v t1 -mv v t0 , mv h t2 -mv h t0 , mv v t2 -mv v t0 are fetched from a storage for storing difference between CPMVs of the blocks directly.
  • the conversion generates the first/second block of video from the bitstream representation.
  • the conversion generates the bitstream representation from the first/second block of video.
  • FIG. 31 is a flowchart for a method 3100 of processing video.
  • the method 3100 includes, deriving (3102) , for a conversion between a current block of video and a bitstream representation of the current block, affine inherited motion vectors (MVs) for the current block based on a first stored motion vector (MV) and a second stored MV different from the first stored MV, wherein the first stored MV is stored in a first basic block neighbouring to the current block, and the second stored MV is stored in a second basic block with an offset to the first basic block; and; performing (3104) the conversion by using the affine inherited MVs for the current block.
  • MVs affine inherited motion vectors
  • the first basic block neighbouring to the current block includes at least one of: a left neighbouring basic block (L) , an above neighbouring basic block (A) , a left-bottom neighbouring basic block (LB) , an above-right neighbouring basic block (AR, AR’) and an above left neighbouring basic block (AL, AL’, AL1, AL”) .
  • the parameters a and b are calculated as:
  • the parameters a and b are calculated as:
  • w t 2 N
  • h t 2 M , wherein N and M are integers.
  • the horizontal offset between the first basic block and the second basic block is defined as xLT1 -xLT0, and/or the vertical offset between the first basic block and the second basic block is defined as yLT1 -yLT0.
  • the vertical offset is 0.
  • the horizontal offset is 0.
  • the second basic block is selected depending on the position of the first basic block.
  • coordinates of top-left sample of the first basic block and the second basic block are (xLT0, yLT0) and (xLT1, yLT1) , respectively, and
  • M is an integer
  • coordinates of top-left sample of the first basic block and the second basic block are (xLT0, yLT0) and (xLT1, yLT1) , respectively, and
  • M is an integer
  • coordinates of top-left sample of the first basic block and the second basic block are (xLT0, yLT0) and (xLT1, yLT1) , respectively, and when the first block is above-left to the current block, or when the first block is above-left to the current block and left boundary of the current block is also the left boundary of a CTU, or when xLT0 –offset ⁇ xLT_AL, where xLT_AL is the top-left coordinate of a neighbouring basic block above-left to the current block, or when xLT0 –offset ⁇ xLT_AL, where xLT_AL is the top-left coordinate of a neighbouring basic block above-left to the current block and left boundary of the current block is also the left boundary of a CTU,
  • the second basic block is selected from M candidate basic blocks, M is an integer.
  • the second basic block is selected by checking the M candidate basic blocks in order so as to determine one of the M candidate basic blocks, which is inter-coded and has a MV referring to the same reference picture as the MV of the first basic block referring to, as the second basic block.
  • whether to and/or how to select the second basic block from the M candidate basic blocks depend on the position of the first basic block and/or the position of the current block.
  • the affine inherited motion vectors (MVs) for the current block cannot be derived from the first basic block.
  • whether to and/or how to derive the affine inherited motion vectors (MVs) for the current block depends on the position of the current block.
  • an affine model for the current block is inherited from an above neighbouring block of the current block in different ways depending on whether the neighbouring block is in a Coding Tree Unit (CTU) or CTU row where in the current block is located or not.
  • CTU Coding Tree Unit
  • the affine model for the current block is inherited from an above or left neighbouring block of the current block, which is not in a CTU or CTU row where in the current block is located
  • the affine inherited motion vectors (MVs) for the current block is derived based on the first stored motion vector (MV) and the second stored MV.
  • whether to and/or how to select the second basic block from multiple candidates or from a predefined offset depends on a position of the first block and/or a position of the current block, and wherein the second basic block is a second neighboring basic block.
  • an affine model for the current block is inherited from the first basic block neighboring the current block, which is affine coded and includes at least one of: an above neighbouring basic block (A) , an above-right neighbouring basic block (AR) and an above left neighbouring basic block (AL) , and wherein a top-left position of the first basic block is (xBB, yBB) .
  • the second neighboring basic block is selected by:
  • the second neighboring basic block is selected by:
  • the second neighboring basic block is selected by: only checking whether a basic block on the right of the first basic block is affine coded and has a reference index same as that of the first basic block for a given reference list; and if yes, selecting the basic block on the right of the first basic block as the second neighboring basic block, or otherwise, the affine model for the current block cannot be inherited from the first basic block.
  • the second neighboring basic block is selected by: checking whether a basic block on the right of the first basic block is affine coded and has a reference index same as that of the first basic block for a given reference list; and if yes, selecting the basic block on the right of the first basic block as the second neighboring basic block, or otherwise, selecting a basic block on the left of the first basic block as the second neighboring basic block.
  • the second neighboring basic block is selected by: checking whether a basic block on the left of the first basic block is affine coded and has a reference index same as that of the first basic block for a given reference list; and if yes, selecting the block on the left of the first basic block as the second neighboring basic block, or otherwise, selecting that a block on the right of the first basic block is the second neighboring basic block.
  • S is equal to 8
  • the offset between the first basic block and the second basic block is a positive integer.
  • the offset is in a form of 2 K , K is an integer, or depends on the minimum allowed CU width and/or height, or depend on width and/or height of the basic block, or depends on the minimum allowed width and/or height of a CU that affine coding is applicable, or is signaled from an encoder to a decoder.
  • the basic block Q is not allowed to be chosen as the second basic block when the basic block P is the first basic block in a second affine inheritance process.
  • the basic block P when a basic block P is chosen as the second basic block and when a basic block Q is the first basic block in a first affine inheritance process, the basic block P is not allowed to be the first basic block in the second affine inheritance process.
  • the second basic block in the second affine inheritance process can only be chosen from a basic block on the left of the basic block P if the basic block Q is on the right of the basic block P, or the second basic block can only be chosen from a basic block on the right of the basic block P if the basic block Q is on the left of the basic block P, or the second basic block can only be chosen from a basic block on the above of the basic block P if the basic block Q is on the below of the basic block P, or the second basic block can only be chosen from a basic block on the below of the basic block P if the basic block Q is on the above of the basic block P.
  • he neighbouring basic block is on a row or column adjacent to the current block.
  • the first basic block is determined as valid if it satisfies at least one of the following conditions: i. it is inter-coded; ii. it is not intra-block-copy coded; iii. it is affine-coded; iv. it is affine-merge coded; v. it is affine-inter coded.
  • whether the second basic block is determined as valid depends on information of the first basic block.
  • the second basic block is determined as valid if it satisfies at least one of the following conditions: i. it is inter-coded; ii. it is not intra-block-copy coded; iii. it is affine-coded; iv. it is affine-merge coded; v. it is affine-inter coded; vi. it has the same inter-prediction direction as the first basic block; vii. it has the same reference index for reference list 0 as the first basic block; viii. it has the same reference index for reference list 1 as the first basic block; ix. it has the same inter-prediction direction and same reference indices as the first basic block; x. it has the same picture-order-count (POC) value of the reference picture in reference list X as that for the first basic block, where X is 0 and/or 1.
  • POC picture-order-count
  • each basic block of above neighbouring basic blocks of the current block is checked in a predetermined order to determine whether it is a valid first basic block.
  • the above neighbouring basic blocks of the current block are checked in the order from left to right or from right to left.
  • the above neighbouring basic blocks include at least one of: an above neighbouring basic block (A) , an above-right neighbouring basic block (AR) and a first above left neighbouring basic block (AL1) .
  • one basic block (BB) of the above neighbouring basic blocks is a valid first basic block
  • a basic block on the left and/or right of the valid first basic block (BB) is checked to determine a corresponding second basic block.
  • the basic block (BBR) on the right of the valid first basic block (BB) is check first to determine whether it is a valid second basic block, and when the basic block (BBR) is the valid second basic block, the valid first basic block (BB) and the valid second basic block (BBR) are output as the first basic block and the second basic block.
  • the basic block (BBR) on the left of the valid first basic block (BB) is check to determine whether it is the valid second basic block, and when the basic block (BBL) is the valid second basic block, the valid first basic block (BB) and the valid second basic block (BBL) are output as the first basic block and the second basic block.
  • a next basic block left to the one basic block (BB) in order is checked to determine whether it is a valid first basic block.
  • the basic block (BBL) on the left of the valid first basic block (BB) is check first to determine whether it is a valid second basic block, and when the basic block (BBL) is the valid second basic block, the valid first basic block (BB) and the valid second basic block (BBL) are output as the first basic block and the second basic block.
  • the basic block (BBL) when the basic block (BBL) is not valid, the basic block (BBR) on the right of the valid first basic block (BB) is check to determine whether it is the valid second basic block, and when the basic block (BBR) is the valid second basic block, the valid first basic block (BB) and the valid second basic block (BBR) are output as the first basic block and the second basic block.
  • a next basic block right to the one basic block (BB) in order is checked to determine whether it is a valid first basic block.
  • only the basic block (BBR) on the right of the valid first basic block (BB) is check to determine whether it is a valid second basic block, and when the basic block (BBR) is the valid second basic block, the valid first basic block (BB) and the valid second basic block (BBR) are output as the first basic block and the second basic block.
  • the valid first basic block (BB) and the basic block (BBL) on the left of the valid first basic block are output as the first basic block and the second basic block.
  • a next basic block right to the one basic block (BB) in order is checked to determine whether it is a valid first basic block.
  • only the basic block (BBL) on the left of the valid first basic block (BB) is check to determine whether it is a valid second basic block, and when the basic block (BBL) is the valid second basic block, the valid first basic block (BB) and the valid second basic block (BBL) are output as the first basic block and the second basic block.
  • the valid first basic block (BB) and the basic block (BBR) on the right of the valid first basic block are output as the first basic block and the second basic block.
  • a next basic block left to the one basic block (BB) in order is checked to determine whether it is a valid first basic block.
  • selection of candidate basic blocks from the above neighbouring basic blocks to be checked for the determination of the first basic blocks depends on the position of the current block and/or sub-block sizes of affine motion compensation.
  • the candidate basic blocks when the current block is at the left boundary of a CTU, includes at least one of: an above neighbouring basic block (A) , an above-right neighbouring basic block (AR) and a first above left neighbouring basic block (AL1) , and when the current block is not at the left boundary of a CTU, the candidate basic blocks includes at least one of: an above neighbouring basic block (A) , an above-right neighbouring basic block (AR) and a second above left adjacent neighbouring basic block (AL”) .
  • whether a candidate basic blocks from the above neighbouring basic blocks can be used as the first basic blocks depends on the position of the current block.
  • an above left neighbouring basic block (AL1, AL”) cannot be used as the first basic block.
  • an above-right neighbouring basic block (AR, AR’) cannot be used as the first basic block.
  • whether a candidate basic blocks from the above neighbouring basic blocks can be used as the second basic blocks depends on the position of the current block.
  • an above left neighbouring basic block (AL1, AL’) cannot be used as the first basic block.
  • an above-right neighbouring basic block (AR, AR’) cannot be used as the first basic block.
  • the first basic block and the second basic block are exchangeable.
  • the first basic block and second basic block are firstly exchanged, and the conversion of the current block is performed by using the exchanged first basic block and second basic block.
  • the determination process of the first basic block and the second basic block are exchangeable.
  • the conversion generates the current block of video from the bitstream representation.
  • the conversion generates the bitstream representation from the current block of video.
  • FIG. 32 is a flowchart for a method 3200 of processing video.
  • the method 3200 includes, deriving (3202) , for a conversion between a current block of video and a bitstream representation of the current block, one or more parameters of a set of affine model parameters associated with affine model for the current block; shifting (3204) the one or more parameters; and storing (3206) the shifted one or more parameters.
  • the shifting the one or more parameters further comprises shifting the one or more parameters with a first shift function SatShift (x, n) , which is defined as:
  • x is one of the one or more parameters
  • n is an integer
  • offset0 and/or offset1 are set to (1 ⁇ n) >>1 or (1 ⁇ (n-1) )
  • offset0 and/or offset1 are set to 0.
  • the shifting the one or more parameters further comprises shifting the one or more parameters with a second shift function Shift (x, n) , which is defined as:
  • x is one of the one or more parameters
  • n is an integer
  • offset0 is set to (1 ⁇ n) >>1 or (1 ⁇ (n-1) ) , or ( (1 ⁇ n) >>1) -1, or offset0 is set to 0.
  • n 2 or 4.
  • n depends on motion precision, or n is different for different parameters in the set of affine model parameters.
  • n is signaled in at least one of Sequence Parameter Set (SPS) , Video Parameter Set (VPS) , Picture Parameter Set (PPS) , slice header, tile group header, tile, coding tree unit (CTU) , coding unit (CU) .
  • SPS Sequence Parameter Set
  • VPS Video Parameter Set
  • PPS Picture Parameter Set
  • slice header tile group header
  • tile coding tree unit
  • CU coding unit
  • n is different in different standard profiles or levels or tiers.
  • the stored parameter is left shift first before it is used in affine inheritance of blocks coded after the current block.
  • the stored parameter is shift with a shift function and clipped with a clip function sequentially before it is used in affine inheritance of blocks coded after the current block.
  • a parameter a of the set of affine model parameters is calculated by where mv h 0 is a horizontal motion vector component of a top-left corner control point of the current block, mv h 1 is a horizontal motion vector component of a top-right corner control point of the current block, and w is a width of the current block.
  • a parameter b of the set of affine model parameters is calculated by where mv v 0 is a vertical motion vector component of a top-left corner control point of the current block, mv v 1 is a vertical motion vector component of a top-right corner control point of the current block, and w is a width of the current block.
  • a parameter c of the set of affine model parameters is calculated by where mv h 0 is a horizontal motion vector component of a top-left corner control point of the current block, mv h 2 is a horizontal motion vector component of a bottom-left corner control point of the current block, and h is a height of the current block.
  • a parameter d of the set of affine model parameters is calculated by where mv v 0 is a vertical motion vector component of a top-left corner control point of the current block, mv v 2 is a vertical motion vector component of a bottom-left corner control point of the current block, and h is a height of the current block.
  • a parameter e of the set of affine model parameters is calculated by where mv h 0 is a horizontal motion vector component of a top-left corner control point of the current block.
  • a parameter f of the set of affine model parameters is calculated by where mv v 0 is a vertical motion vector component of a top-left corner control point of the current block.
  • the width and height of the current block are noted as w and h are equal to 2 WB and 2 HB , where WB and HB are integers greater than one.
  • a parameter a of the set of affine model parameters is calculated by where P is an integer and represents a calculation precision, mv h 0 is a horizontal motion vector component of a top-left corner control point of the current block, and mv h 1 is a horizontal motion vector component of a top-right corner control point of the current block.
  • a parameter b of the set of affine model parameters is calculated by where P is an integer and represents a calculation precision, mv v 0 is a vertical motion vector component of a top-left corner control point of the current block, and mv v 1 is a vertical motion vector component of a top-right corner control point of the current block.
  • a parameter c of the set of affine model parameters is calculated by where P is an integer and represents a calculation precision, mv h 0 is a horizontal motion vector component of a top-left corner control point of the current block, and mv h 2 is a horizontal motion vector component of a bottom-left corner control point of the current block.
  • a parameter d of the set of affine model parameters is calculated by where P is an integer and represents a calculation precision, mv v 0 is a vertical motion vector component of a top-left corner control point of the current block, and mv v 2 is a vertical motion vector component of a bottom-left corner control point of the current block.
  • P is set to 7.
  • the method further comprises: clipping the one or more parameters, prior to the storing the one or more parameters.
  • X is a, b, c, d, e, or f.
  • K is equal to 8.
  • the set of affine model parameters comprises six variables (a, b, c, d, e, f) corresponding to a six-parameter affine model given by
  • mv h (x, y) is a horizontal component of a motion vector of the current block
  • mv v (x, y) is a vertical component of a motion vector of the current block
  • (x, y) represents the coordinate of a representative point relative to a top-left sample within the current block
  • (mv h 0 , mv v 0 ) is a motion vector of a top-left corner control point (CP)
  • (mv h 1 , mv v 1 ) is a motion vector of a top-right corner control point
  • (mv h 2 , mv v 2 ) is a motion vector of a bottom-left corner control point for the current block.
  • the one or more parameters comprise a, b, c, and d.
  • the set of affine model parameters comprises four variables (a, b, e, f) corresponding to a four-parameter affine model given by
  • mv h (x, y) is a horizontal component of a motion vector of the current block
  • mv v (x, y) is a vertical component of a motion vector of the current block
  • (x, y) represents the coordinate of a representative point relative to a top-left sample within the current block
  • (mv h 0 , m hv 0 ) is a motion vector of a top-left corner control point (CP)
  • (mv h 1 , mv v 1 ) is a motion vector of a top-right corner control point for the current block.
  • the one or more parameters comprise a and b.
  • the one or more parameters comprise a, b, e and f.
  • the parameter c -b, when the conversion between the current block and the bitstream representation of the current block is performed with a four-parameter affine mode.
  • the parameter d a, when the conversion between the current block and the bitstream representation of the current block is performed with a four-parameter affine mode.
  • the method further comprises: performing a conversion between a block coded after the current block and a bitstream representation of the block coded after the current block, based on the stored shifted one or more parameters.
  • the method further comprises: performing, based stored on the one or more parameters, the conversion between the current block and the bitstream representation of the current block.
  • the conversion generates the block coded after the current block from the bitstream representation.
  • the conversion generates the bitstream representation from the block coded after the current block.
  • Video blocks may be encoded into bitstream representations that include non-contiguous bits that are placed in various headers or in network adaption layer, and so on.
  • the disclosed and other solutions, examples, embodiments, modules and the functional operations described in this document can be implemented in digital electronic circuitry, or in computer software, firmware, or hardware, including the structures disclosed in this document and their structural equivalents, or in combinations of one or more of them.
  • the disclosed and other embodiments can be implemented as one or more computer program products, i.e., one or more modules of computer program instructions encoded on a 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 them.
  • 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 propagated signal is an artificially generated signal, e.g., a machine-generated electrical, optical, or electromagnetic signal, that is generated to encode information for transmission to suitable receiver apparatus.
  • 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 document 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 non-volatile memory, media and memory devices, including by way of example semiconductor memory devices, e.g., EPROM, EEPROM, and flash memory devices; magnetic disks, e.g., internal hard disks or removable disks; magneto optical disks; and CD ROM and DVD-ROM disks.
  • semiconductor memory devices e.g., EPROM, EEPROM, and flash memory devices
  • magnetic disks e.g., internal hard disks or removable disks
  • magneto optical disks e.g., CD ROM and DVD-ROM disks.
  • the processor and the memory can be supplemented by, or incorporated in, special purpose logic circuitry.

Abstract

L'invention concerne un décalage sur des paramètres affines. Un procédé donné à titre d'exemple consiste à : dériver, pour une conversion entre un bloc actuel et une représentation de flux binaire du bloc actuel, un ou plusieurs paramètres d'un ensemble de paramètres de modèle affine associés à un modèle affine pour le bloc actuel ; décaler le ou les paramètres ; et stocker le ou les paramètres décalés.
PCT/CN2019/124048 2018-12-08 2019-12-09 Décalage sur des paramètres affines WO2020114517A1 (fr)

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