METHOD, DEVICE, AND MEDIUM FOR VIDEO PROCESSING

Embodiments of the present disclosure provide a method for video processing. The method comprises: applying, during a conversion between a target block of a video and a bitstream of the video, a gradient-based position dependent pre-diction combination to the target block in a coding mode, a gradient of a number of neighboring samples of the target block being used in the gradient-based position dependent prediction combination; and performing the conversion based on the applying.

FIELD

Embodiments of the present disclosure relates generally to video coding techniques, and more particularly, to applying a gradient-based position dependent prediction combination.

BACKGROUND

In nowadays, digital video capabilities are being applied in various aspects of peoples' lives. Multiple types of video processing technologies, such as motion picture expert group (MPEG)-2, MPEG-4, ITU-TH.263, international telecom union—telecommunication standardization sector (ITU-T) H.264/MPEG-4 Part 10 advanced video coding (AVC), ITU-T H.265 high efficiency video coding (HEVC) standard, versatile video coding (VVC) standard, have been proposed for video encoding/decoding. However, some aspects of the video processing technologies still need to be improved.

SUMMARY

Embodiments of the present disclosure provide solutions for applying a gradient-based position dependent prediction combination.

In a first aspect, a method for video processing is proposed. The method comprises applying, during a conversion between a target block of a video and a bitstream of the video, a gradient-based position dependent prediction combination to the target block in a coding mode, a gradient of a number of neighboring samples of the target block being used in the gradient-based position dependent prediction combination. The method also comprises performing the conversion based on the applying. The method in accordance with the first aspect of the present disclosure applies a gradient of a number of neighboring samples of the target block in the gradient-based position dependent prediction combination, which enhances the flexibility of use gradient-based position dependent prediction combination and the improves the quality of the conversion.

In a second aspect, another method for video processing is proposed. The method comprises determining, during a conversion between a target block of a video and a bitstream of the video, based on one or more neighboring prediction or reconstruction samples outside the target block, one or more hypotheses of the target block by using a prediction mode with more than one hypothesis. The method also comprises performing the conversion based on the one or more hypotheses. The method in accordance with the second aspect of the present disclosure applies improper coding information of the target block in the gradient-based position dependent prediction combination, which enhances the flexibility of use gradient-based position dependent prediction combination and the improves the quality of the conversion.

In a third aspect, an apparatus for processing video data is proposed. The apparatus comprises a processor and a non-transitory memory with instructions thereon, wherein the instructions upon execution by the processor, cause the processor to perform a method in accordance with the first or second aspect of the present disclosure.

In a fourth aspect, a non-transitory computer-readable storage medium is proposed. The non-transitory computer-readable storage medium stores instructions that cause a processor to perform a method in accordance with the first or second aspect of the present disclosure.

In a fifth aspect, a non-transitory computer-readable storage medium is proposed. The non-transitory computer-readable storage medium stores a bitstream of a video which is generated by a method performed by a video processing apparatus, wherein the method comprises: applying a gradient-based position dependent prediction combination to a target block of the video in a coding mode, a gradient of a number of neighboring samples of the target block being used in the gradient-based position dependent prediction combination; and generating the bitstream based on the applying of the gradient-based position dependent prediction combination.

In a sixth aspect, a method for storing bitstream of a video is proposed. The method comprises: applying a gradient-based position dependent prediction combination to a target block of the video in a coding mode, a gradient of a number of neighboring samples of the target block being used in the gradient-based position dependent prediction combination; generating the bitstream based on the applying of the gradient-based position dependent prediction combination; and storing the bitstream in a non-transitory computer-readable recording medium.

In a seventh aspect, a non-transitory computer-readable recording medium is proposed. The non-transitory computer-readable recording medium stores a bitstream of a video which is generated by a method performed by a video processing apparatus, wherein the method comprises: determining, based on one or more neighboring prediction or reconstruction samples outside a target block of the video, one or more hypotheses of the target block by using a prediction mode with more than one hypothesis; and generating the bitstream based on the one or more hypotheses of the target block.

In an eighth aspect, a method for storing bitstream of a video is proposed. The method comprises: determining, based on one or more neighboring prediction or reconstruction samples outside a target block of the video, one or more hypotheses of the target block by using a prediction mode with more than one hypothesis; generating the bitstream based on the one or more hypotheses of the target block; and storing the bitstream in a non-transitory computer-readable recording medium.

Throughout the drawings, the same or similar reference numerals usually refer to the same or similar elements.

DETAILED DESCRIPTION

Example Environment

FIG.1is a block diagram that illustrates an example video coding system100that may utilize the techniques of this disclosure. As shown, the video coding system100may include a source device110and a destination device120. The source device110can be also referred to as a video encoding device, and the destination device120can be also referred to as a video decoding device. In operation, the source device110can be configured to generate encoded video data and the destination device120can be configured to decode the encoded video data generated by the source device110. The source device110may include a video source112, a video encoder114, and an input/output (I/O) interface116.

The video source112may include a source such as a video capture device. Examples of the video capture device include, but are not limited to, an interface to receive video data from a video content provider, a computer graphics system for generating video data, and/or a combination thereof.

The video data may comprise one or more pictures. The video encoder114encodes the video data from the video source112to generate a bitstream. The bitstream may include a sequence of bits that form a coded representation of the video data. The bitstream may include coded pictures and associated data. The coded picture is a coded representation of a picture. The associated data may include sequence parameter sets, picture parameter sets, and other syntax structures. The I/O interface116may include a modulator/demodulator and/or a transmitter. The encoded video data may be transmitted directly to destination device120via the I/O interface116through the network130A. The encoded video data may also be stored onto a storage medium/server130B for access by destination device120.

The destination device120may include an I/O interface126, a video decoder124, and a display device122. The I/O interface126may include a receiver and/or a modem. The I/O interface126may acquire encoded video data from the source device110or the storage medium/server130B. The video decoder124may decode the encoded video data. The display device122may display the decoded video data to a user. The display device122may be integrated with the destination device120, or may be external to the destination device120which is configured to interface with an external display device.

The video encoder114and the video decoder124may operate according to a video compression standard, such as the High Efficiency Video Coding (HEVC) standard, Versatile Video Coding (VVC) standard and other current and/or further standards.

FIG.2is a block diagram illustrating an example of a video encoder200, which may be an example of the video encoder114in the system100illustrated inFIG.1, in accordance with some embodiments of the present disclosure.

The video encoder200may be configured to implement any or all of the techniques of this disclosure. In the example ofFIG.2, the video encoder200includes a plurality of functional components. The techniques described in this disclosure may be shared among the various components of the video encoder200. In some examples, a processor may be configured to perform any or all of the techniques described in this disclosure.

In some embodiments, the video encoder200may include a partition unit201, a predication unit202which may include a mode select unit203, a motion estimation unit204, a motion compensation unit205and an intra-prediction unit206, a residual generation unit207, a transform unit208, a quantization unit209, an inverse quantization unit210, an inverse transform unit211, a reconstruction unit212, a buffer213, and an entropy encoding unit214.

In other examples, the video encoder200may include more, fewer, or different functional components. In an example, the predication unit202may include an intra block copy (IBC) unit. The IBC unit may perform predication in an IBC mode in which at least one reference picture is a picture where the current video block is located.

Furthermore, although some components, such as the motion estimation unit204and the motion compensation unit205, may be integrated, but are represented in the example ofFIG.2separately for purposes of explanation.

The partition unit201may partition a picture into one or more video blocks. The video encoder200and the video decoder300may support various video block sizes.

The mode select unit203may select one of the coding modes, intra or inter, e.g., based on error results, and provide the resulting intra-coded or inter-coded block to a residual generation unit207to generate residual block data and to a reconstruction unit212to reconstruct the encoded block for use as a reference picture. In some examples, the mode select unit203may select a combination of intra and inter predication (CIIP) mode in which the predication is based on an inter predication signal and an intra predication signal. The mode select unit203may also select a resolution for a motion vector (e.g., a sub-pixel or integer pixel precision) for the block in the case of inter-predication.

To perform inter prediction on a current video block, the motion estimation unit204may generate motion information for the current video block by comparing one or more reference frames from buffer213to the current video block. The motion compensation unit205may determine a predicted video block for the current video block based on the motion information and decoded samples of pictures from the buffer213other than the picture associated with the current video block.

The motion estimation unit204and the motion compensation unit205may perform different operations for a current video block, for example, depending on whether the current video block is in an I-slice, a P-slice, or a B-slice. As used herein, an “I-slice” may refer to a portion of a picture composed of macroblocks, all of which are based upon macroblocks within the same picture. Further, as used herein, in some aspects, “P-slices” and “B-slices” may refer to portions of a picture composed of macroblocks that are not dependent on macroblocks in the same picture.

In some examples, the motion estimation unit204may output a full set of motion information for decoding processing of a decoder. Alternatively, in some embodiments, the motion estimation unit204may signal the motion information of the current video block with reference to the motion information of another video block. For example, the motion estimation unit204may determine that the motion information of the current video block is sufficiently similar to the motion information of a neighboring video block.

In one example, the motion estimation unit204may indicate, in a syntax structure associated with the current video block, a value that indicates to the video decoder300that the current video block has the same motion information as the another video block.

As discussed above, video encoder200may predictively signal the motion vector. Two examples of predictive signaling techniques that may be implemented by video encoder200include advanced motion vector predication (AMVP) and merge mode signaling.

The intra prediction unit206may perform intra prediction on the current video block. When the intra prediction unit206performs intra prediction on the current video block, the intra prediction unit206may generate prediction data for the current video block based on decoded samples of other video blocks in the same picture. The prediction data for the current video block may include a predicted video block and various syntax elements.

In other examples, there may be no residual data for the current video block for the current video block, for example in a skip mode, and the residual generation unit207may not perform the subtracting operation.

After the transform processing unit208generates a transform coefficient video block associated with the current video block, the quantization unit209may quantize the transform coefficient video block associated with the current video block based on one or more quantization parameter (QP) values associated with the current video block.

The inverse quantization unit210and the inverse transform unit211may apply inverse quantization and inverse transforms to the transform coefficient video block, respectively, to reconstruct a residual video block from the transform coefficient video block. The reconstruction unit212may add the reconstructed residual video block to corresponding samples from one or more predicted video blocks generated by the predication unit202to produce a reconstructed video block associated with the current video block for storage in the buffer213.

After the reconstruction unit212reconstructs the video block, loop filtering operation may be performed to reduce video blocking artifacts in the video block.

The entropy encoding unit214may receive data from other functional components of the video encoder200. When the entropy encoding unit214receives the data, the entropy encoding unit214may perform one or more entropy encoding operations to generate entropy encoded data and output a bitstream that includes the entropy encoded data.

FIG.3is a block diagram illustrating an example of a video decoder300, which may be an example of the video decoder124in the system100illustrated inFIG.1, in accordance with some embodiments of the present disclosure.

In the example ofFIG.3, the video decoder300includes an entropy decoding unit301, a motion compensation unit302, an intra prediction unit303, an inverse quantization unit304, an inverse transformation unit305, and a reconstruction unit306and a buffer307. The video decoder300may, in some examples, perform a decoding pass generally reciprocal to the encoding pass described with respect to video encoder200.

The entropy decoding unit301may retrieve an encoded bitstream. The encoded bitstream may include entropy coded video data (e.g., encoded blocks of video data). The entropy decoding unit301may decode the entropy coded video data, and from the entropy decoded video data, the motion compensation unit302may determine motion information including motion vectors, motion vector precision, reference picture list indexes, and other motion information. The motion compensation unit302may, for example, determine such information by performing the AMVP and merge mode. AMVP is used, including derivation of several most probable candidates based on data from adjacent PBs and the reference picture. Motion information typically includes the horizontal and vertical motion vector displacement values, one or two reference picture indices, and, in the case of prediction regions in B slices, an identification of which reference picture list is associated with each index. As used herein, in some aspects, a “merge mode” may refer to deriving the motion information from spatially or temporally neighboring blocks.

The motion compensation unit302may use the interpolation filters as used by the video encoder200during encoding of the video block to calculate interpolated values for sub-integer pixels of a reference block. The motion compensation unit302may determine the interpolation filters used by the video encoder200according to the received syntax information and use the interpolation filters to produce predictive blocks.

The motion compensation unit302may use at least part of the syntax information to determine sizes of blocks used to encode frame(s) and/or slice(s) of the encoded video sequence, partition information that describes how each macroblock of a picture of the encoded video sequence is partitioned, modes indicating how each partition is encoded, one or more reference frames (and reference frame lists) for each inter-encoded block, and other information to decode the encoded video sequence. As used herein, in some aspects, a “slice” may refer to a data structure that can be decoded independently from other slices of the same picture, in terms of entropy coding, signal prediction, and residual signal reconstruction. A slice can either be an entire picture or a region of a picture.

The intra prediction unit303may use intra prediction modes for example received in the bitstream to form a prediction block from spatially adjacent blocks. The inverse quantization unit304inverse quantizes, i.e., de-quantizes, the quantized video block coefficients provided in the bitstream and decoded by entropy decoding unit301. The inverse transform unit305applies an inverse transform.

The reconstruction unit306may obtain the decoded blocks, e.g., by summing the residual blocks with the corresponding prediction blocks generated by the motion compensation unit302or intra-prediction unit303. If desired, a deblocking filter may also be applied to filter the decoded blocks in order to remove blockiness artifacts. The decoded video blocks are then stored in the buffer307, which provides reference blocks for subsequent motion compensation/intra predication and also produces decoded video for presentation on a display device.

Some exemplary embodiments of the present disclosure will be described in detailed hereinafter. It should be understood that section headings are used in the present document to facilitate ease of understanding and do not limit the embodiments disclosed in a section to only that section. Furthermore, while certain embodiments are described with reference to

Versatile Video Coding or other specific video codecs, the disclosed techniques are applicable to other video coding technologies also. Furthermore, while some embodiments describe video coding steps in detail, it will be understood that corresponding steps decoding that undo the coding will be implemented by a decoder. Furthermore, the term video processing encompasses video coding or compression, video decoding or decompression and video transcoding in which video pixels are represented from one compressed format into another compressed format or at a different compressed bitrate.

The present disclosure is related to video coding technologies. Specifically, it is about inter/intra prediction techniques in image/video coding. It may be applied to the existing video coding standard like HEVC, VVC, and etc. 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 [1] standards. Since H.262, the video coding standards are based on the hybrid video coding structure wherein temporal prediction plus transform coding are utilized. To explore the future video coding technologies beyond HEVC, the Joint Video Exploration Team (JVET) was founded by VCEG and MPEG jointly in 2015. The JVET meeting is concurrently held once every quarter, and the new video coding standard was officially named as Versatile Video Coding (VVC) in the April 2018 JVET meeting, and the first version of VVC test model (VTM) was released at that time. The VVC working draft and test model VTM are then updated after every meeting. The VVC project achieved technical completion (FDIS) at the July 2020 meeting.

2.1. Coding Tools

In one specific example embodiments, the coding tools is extracted from such as JVET-R2002.

2.1.1.1. Intra Mode Coding with 67 Intra Prediction Modes

FIG.4illustrates a schematic diagram400of intra prediction modes. To capture the arbitrary edge directions presented in natural video, the number of directional intra modes in VVC is extended from 33, as used in HEVC, to 65. The new directional modes not in HEVC are depicted as arrows inFIG.4without reference index, and the planar and DC modes remain the same. These denser directional intra prediction modes apply for all block sizes and for both luma and chroma intra predictions.

In VVC, several conventional angular intra prediction modes are adaptively replaced with wide-angle intra prediction modes for the non-square blocks.

In HEVC, every intra-coded block has a square shape and the length of each of its side is a power of 2. Thus, no division operations are required to generate an intra-predictor using DC mode. In VVC, blocks can have a rectangular shape that necessitates the use of a division operation per block in the general case. To avoid division operations for DC prediction, only the longer side is used to compute the average for non-square blocks.

2.1.1.2. Intra Mode Coding

To keep the complexity of the most probable mode (MPM) list generation low, an intra mode coding method with 6 MPMs is used by considering two available neighboring intra modes.

The following three aspects are considered to construct the MPM list:Default intra modesNeighbouring intra modesDerived intra modes

A unified 6-MPM list is used for intra blocks irrespective of whether MRL and ISP coding tools are applied or not. The MPM list is constructed based on intra modes of the left and above neighboring block. Suppose the mode of the left is denoted as Left and the mode of the above block is denoted as Above, the unified MPM list is constructed as follows:When a neighboring block is not available, its intra mode is set to Planar by default.If both modes Left and Above are non-angular modes:MPM list→Planar, DC, V, H, V−4, V+4}If one of modes Left and Above is angular mode, and the other is non-angular:Set a mode Max as the larger mode in Left and AboveMPM list→Planar, Max, DC, Max−1, Max+1, Max−2}If Left and Above are both angular and they are different:Set a mode Max as the larger mode in Left and Aboveif the difference of mode Left and Above is in the range of 2 to 62, inclusiveMPM list→Planar, Left, Above, DC, Max−1, Max+1}OtherwiseMPM list→Planar, Left, Above, DC, Max−2, Max+2}If Left and Above are both angular and they are the same:MPM list→Planar, Left, Left−1, Left+1, DC, Left−2}

Besides, the first bin of the mpm index codeword is CABAC context coded. In total three contexts are used, corresponding to whether the current intra block is MRL enabled, ISP enabled, or a normal intra block.

During 6 MPM list generation process, pruning is used to remove duplicated modes so that only unique modes can be included into the MPM list. For entropy coding of the 61 non-MPM modes, a Truncated Binary Code (TBC) is used.

Conventional angular intra prediction directions are defined from 45 degrees to −135 degrees in clockwise direction. In VVC, several conventional angular intra prediction modes are adaptively replaced with wide-angle intra prediction modes for non-square blocks. The replaced modes are signalled using the original mode indexes, which are remapped to the indexes of wide angular modes after parsing. The total number of intra prediction modes is unchanged, i.e., 67, and the intra mode coding method is unchanged.

To support these prediction directions, the top reference with length 2W+1, and the left reference with length 2H+1, are defined as shown inFIG.5.FIG.5illustrates a schematic diagram500of reference samples for wide-angular intra prediction.

The number of replaced modes in wide-angular direction mode depends on the aspect ratio of a block. The replaced intra prediction modes are illustrated in Table 2-1

FIG.6illustrates a schematic diagram600of a wide-angle intra prediction. As shown inFIG.6, two vertically-adjacent predicted samples may use two non-adjacent reference samples in the case of wide-angle intra prediction. Hence, low-pass reference samples filter and side smoothing are applied to the wide-angle prediction to reduce the negative effect of the increased gap Δpα. If a wide-angle mode represents a non-fractional offset. There are 8 modes in the wide-angle modes satisfy this condition, which are [−14, −12, −10, −6, 72, 76, 78, 80]. When a block is predicted by these modes, the samples in the reference buffer are directly copied without applying any interpolation. With this modification, the number of samples needed to be smoothing is reduced. Besides, it aligns the design of non-fractional modes in the conventional prediction modes and wide-angle modes.

In VVC, 4:2:2 and 4:4:4 chroma formats are supported as well as 4:2:0. Chroma derived mode (DM) derivation table for 4:2:2 chroma format was initially ported from HEVC extending the number of entries from 35 to 67 to align with the extension of intra prediction modes. Since HEVC specification does not support prediction angle below −135 degree and above 45 degree, luma intra prediction modes ranging from 2 to 5 are mapped to 2. Therefore chroma DM derivation table for 4:2:2: chroma format is updated by replacing some values of the entries of the mapping table to convert prediction angle more precisely for chroma blocks.

Four-tap intra interpolation filters are utilized to improve the directional intra prediction accuracy. In HEVC, a two-tap linear interpolation filter has been used to generate the intra prediction block in the directional prediction modes (i.e., excluding Planar and DC predictors).

In VVC, simplified 6-bit 4-tap Gaussian interpolation filter is used for only directional intra modes. Non-directional intra prediction process is unmodified. The selection of the 4-tap filters is performed according to the MDIS condition for directional intra prediction modes that provide non-fractional displacements, i.e. to all the directional modes excluding the following: 2, HOR_IDX, DIA_IDX, VER_IDX, 66.

Depending on the intra prediction mode, the following reference samples processing is performed:The directional intra-prediction mode is classified into one of the following groups:vertical or horizontal modes (HOR_IDX, VER_IDX),diagonal modes that represent angles which are multiple of 45 degree (2, DIA_IDX, VDIA_IDX),remaining directional modes;If the directional intra-prediction mode is classified as belonging to group A, then then no filters are applied to reference samples to generate predicted samples;Otherwise, if a mode falls into group B, then a [1, 2, 1] reference sample filter may be applied (depending on the MDIS condition) to reference samples to further copy these filtered values into an intra predictor according to the selected direction, but no interpolation filters are applied;Otherwise, if a mode is classified as belonging to group C, then only an intra reference sample interpolation filter is applied to reference samples to generate a predicted sample that falls into a fractional or integer position between reference samples according to a selected direction (no reference sample filtering is performed).

2.1.1.5. Position Dependent Intra Prediction Combination

In VVC, the results of intra prediction of DC, planar and several angular modes are further modified by a position dependent intra prediction combination (PDPC) method. PDPC is an intra prediction method which invokes a combination of the un-filtered boundary reference samples and HEVC style intra prediction with filtered boundary reference samples. PDPC is applied to the following intra modes without signalling: planar, DC, horizontal, vertical, bottom-left angular mode and its eight adjacent angular modes, and top-right angular mode and its eight adjacent angular modes.

The prediction sample pred(x′,y′) is predicted using an intra prediction mode (DC, planar, angular) and a linear combination of reference samples according to the Equation 3-8 as follows:

where Rx,−1, R−1,yrepresent the reference samples located at the top and left boundaries of current sample (x, y), respectively, and R−1,−1represents the reference sample located at the top-left corner of the current block.

If PDPC is applied to DC, planar, horizontal, and vertical intra modes, additional boundary filters are not needed, as required in the case of HEVC DC mode boundary filter or horizontal/vertical mode edge filters. PDPC process for DC and Planar modes is identical and clipping operation is avoided. For angular modes, pdpc scale factor is adjusted such that range check is not needed and condition on angle to enable pdpc is removed (scale>=0 is used). In addition, PDPC weight is based on 32 in all angular mode cases. The PDPC weights are dependent on prediction modes and are shown in Table 2-2. PDPC is applied to the block with both width and height greater than or equal to 4.

FIGS.7A-7Dillustrate schematic diagrams (700,720,740and760) of a definition of samples used by PDPC applied to diagonal and adjacent angular intra modes.FIGS.7A-7Dillustrate the definition of reference samples (Rx,−1, R−1,yand R−1,−1) for PDPC applied over various prediction modes. The prediction sample pred(x′,y′) is located at (x′,y′) within the prediction block. As an example, the coordinate x of the reference sample Rx,−1is given by: x=x′+y′+1, and the coordinate y of the reference sample R−1,yis similarly given by: y=x′+y′+1 for the diagonal modes. For the other annular mode, the reference samples Rx,−1and R−1,ycould be located in fractional sample position. In this case, the sample value of the nearest integer sample location is used.

2.1.1.6. Multiple Reference Line (MRL) Intra Prediction

Multiple reference line (MRL) intra prediction uses more reference lines for intra prediction.FIG.8illustrates a schematic diagram800of an example of four reference lines neighbouring to a prediction block. InFIG.8, an example of 4 reference lines is depicted, where the samples of segments A and F are not fetched from reconstructed neighbouring samples but padded with the closest samples from Segment B and E, respectively. HEVC intra-picture prediction uses the nearest reference line (i.e., reference line 0). In MRL, 2 additional lines (reference line 1 and reference line 3) are used.

The index of selected reference line (mrl_idx) is signalled and used to generate intra predictor. For reference line idx, which is greater than 0, only include additional reference line modes in MPM list and only signal mpm index without remaining mode. The reference line index is signalled before intra prediction modes, and Planar mode is excluded from intra prediction modes in case a nonzero reference line index is signalled.

MRL is disabled for the first line of blocks inside a CTU to prevent using extended reference samples outside the current CTU line. Also, PDPC is disabled when additional line is used. For MRL mode, the derivation of DC value in DC intra prediction mode for non-zero reference line indices is aligned with that of reference line index 0. MRL requires the storage of 3 neighboring luma reference lines with a CTU to generate predictions. The Cross-Component Linear Model (CCLM) tool also requires 3 neighboring luma reference lines for its downsampling filters. The definition of MLR to use the same 3 lines is aligned as CCLM to reduce the storage requirements for decoders.

The intra sub-partitions (ISP) divides luma intra-predicted blocks vertically or horizontally into 2 or 4 sub-partitions depending on the block size. For example, minimum block size for ISP is 4×8 (or 8×4). If block size is greater than 4×8 (or 8×4) then the corresponding block is divided by 4 sub-partitions. It has been noted that the M×128 (with M≤64) and 128×N (with N≤64) ISP blocks could generate a potential issue with the 64×64 VDPU. For example, an M×128 CU in the single tree case has an M×128 luma TB and two corresponding M/2×64 chroma TBs. If the CU uses ISP, then the luma TB will be divided into four M×32 TBs (only the horizontal split is possible), each of them smaller than a 64×64 block. However, in the current design of ISP chroma blocks are not divided. Therefore, both chroma components will have a size greater than a 32×32 block. Analogously, a similar situation could be created with a 128×N CU using ISP. Hence, these two cases are an issue for the 64×64 decoder pipeline. For this reason, the CU sizes that can use ISP is restricted to a maximum of 64×64.FIGS.9A and9Bshow examples of the two possibilities900and950. All sub-partitions fulfill the condition of having at least 16 samples.

In ISP, the dependence of 1×N/2×N subblock prediction on the reconstructed values of previously decoded 1×N/2×N subblocks of the coding block is not allowed so that the minimum width of prediction for subblocks becomes four samples. For example, an 8×N (N>4) coding block that is coded using ISP with vertical split is split into two prediction regions each of size 4×N and four transforms of size 2×N. Also, a 4×N coding block that is coded using ISP with vertical split is predicted using the full 4×N block; four transform each of 1×N is used. Although the transform sizes of 1×N and 2×N are allowed, it is asserted that the transform of these blocks in 4×N regions can be performed in parallel. For example, when a 4×N prediction region contains four 1×N transforms, there is no transform in the horizontal direction; the transform in the vertical direction can be performed as a single 4×N transform in the vertical direction Similarly, when a 4×N prediction region contains two 2×N transform blocks, the transform operation of the two 2×N blocks in each direction (horizontal and vertical) can be conducted in parallel. Thus, there is no delay added in processing these smaller blocks than processing 4×4 regular-coded intra blocks.

For each sub-partition, reconstructed samples are obtained by adding the residual signal to the prediction signal. Here, a residual signal is generated by the processes such as entropy decoding, inverse quantization and inverse transform. Therefore, the reconstructed sample values of each sub-partition are available to generate the prediction of the next sub-partition, and each sub-partition is processed repeatedly. In addition, the first sub-partition to be processed is the one containing the top-left sample of the CU and then continuing downwards (horizontal split) or rightwards (vertical split). As a result, reference samples used to generate the sub-partitions prediction signals are only located at the left and above sides of the lines. All sub-partitions share the same intra mode. The followings are summary of interaction of ISP with other coding tools.Multiple Reference Line (MRL): if a block has an MRL index other than 0, then the ISP coding mode will be inferred to be 0 and therefore ISP mode information will not be sent to the decoder.Entropy coding coefficient group size: the sizes of the entropy coding subblocks have been modified so that they have 16 samples in all possible cases, as shown in Table 2-3. Note that the new sizes only affect blocks produced by ISP in which one of the dimensions is less than 4 samples. In all other cases coefficient groups keep the 4×4 dimensions.CBF coding: it is assumed to have at least one of the sub-partitions has a non-zero CBF. Hence, if n is the number of sub-partitions and the first n−1 sub-partitions have produced a zero CBF, then the CBF of the n-th sub-partition is inferred to be 1.MPM usage: the MPM flag will be inferred to be one in a block coded by ISP mode, and the MPM list is modified to exclude the DC mode and to prioritize horizontal intra modes for the ISP horizontal split and vertical intra modes for the vertical one.Transform size restriction: all ISP transforms with a length larger than 16 points uses the DCT-II.PDPC: when a CU uses the ISP coding mode, the PDPC filters will not be applied to the resulting sub-partitions.MTS flag: if a CU uses the ISP coding mode, the MTS CU flag will be set to 0 and it will not be sent to the decoder. Therefore, the encoder will not perform RD tests for the different available transforms for each resulting sub-partition. The transform choice for the ISP mode will instead be fixed and selected according the intra mode, the processing order and the block size utilized. Hence, no signalling is required. For example, let tHand tVbe the horizontal and the vertical transforms selected respectively for the w×h sub-partition, where w is the width and h is the height. Then the transform is selected according to the following rules:If w=1 or h=1, then there is no horizontal or vertical transform respectively.If w=2 or w>32, tH=DCT-IIIf h=2 or h>32, tV=DCT-IIOtherwise, the transform is selected as in Table 2-4.

In ISP mode, all 67 intra modes are allowed. PDPC is also applied if corresponding width and height is at least 4 samples long. In addition, the condition for intra interpolation filter selection doesn't exist anymore, and Cubic (DCT-IF) filter is always applied for fractional position interpolation in ISP mode.

Matrix weighted intra prediction (MIP) method is a newly added intra prediction technique into VVC. For predicting the samples of a rectangular block of width W and height H, matrix weighted intra prediction (MIP) takes one line of H reconstructed neighbouring boundary samples left of the block and one line of W reconstructed neighbouring boundary samples above the block as input. If the reconstructed samples are unavailable, they are generated as it is done in the conventional intra prediction. The generation of the prediction signal is based on the following three steps, which are averaging, matrix vector multiplication and linear interpolation as shown inFIG.10.FIG.10illustrates a schematic diagram1000of a matrix weighted intra prediction process.

2.1.1.9. Averaging Neighboring Samples

Among the boundary samples, four samples or eight samples are selected by averaging based on block size and shape. Specifically, the input boundaries bdrytopand bdryleftare reduced to smaller boundaries bdryredtopand bdryredleftby averaging neighboring boundary samples according to predefined rule depends on block size. Then, the two reduced boundaries bdryredtopand bdryredleftare concatenated to a reduced boundary vector bdryredwhich is thus of size four for blocks of shape 4×4 and of size eight for blocks of all other shapes. If mode refers to the MIP-mode, this concatenation is defined as follows:

A matrix vector multiplication, followed by addition of an offset, is carried out with the averaged samples as an input. The result is a reduced prediction signal on a subsampled set of samples in the original block. Out of the reduced input vector bdryreda reduced prediction signal predred, which is a signal on the downsampled block of width Wredand height Hredis generated. Here, Wredand Hredare defined as:

The reduced prediction signal predredis computed by calculating a matrix vector product and adding an offset:

Here, A is a matrix that has Wred·Hredrows and 4 columns if W=H=4 and 8 columns in all other cases. b is a vector of size Wred·Hred. The matrix A and the offset vector b are taken from one of the sets S0, S1, S2. One defines an index idx=idx(W,H) as follows:

Here, each coefficient of the matrix A is represented with 8 bit precision. The set S0consists of 16 matrices A0i, i∈{0, . . . , 15} each of which has 16 rows and 4 columns and 16 offset vectors b0i, i∈{0, . . . , 16} each of size 16. Matrices and offset vectors of that set are used for blocks of size 4×4. The set S1consists of 8 matrices A1i, i∈{0, . . . , 7}, each of which has 16 rows and 8 columns and 8 offset vectors b1i, i∈{0, . . . , 7} each of size 16. The set S2consists of 6 matrices A2i, i∈{0, . . . , 5}, each of which has 64 rows and 8 columns and of 6 offset vectors b2i, i∈{0, . . . , 5} of size 64.

The prediction signal at the remaining positions is generated from the prediction signal on the subsampled set by linear interpolation which is a single step linear interpolation in each direction. The interpolation is performed firstly in the horizontal direction and then in the vertical direction regardless of block shape or block size.

2.1.1.12. Signaling of MIP Mode and Harmonization with Other Coding Tools

For each Coding Unit (CU) in intra mode, a flag indicating whether an MIP mode is to be applied or not is sent. If an MIP mode is to be applied, MIP mode (predModeIntra) is signaled. For an MIP mode, a transposed flag (isTransposed), which determines whether the mode is transposed, and MIP mode Id (modeId), which determines which matrix is to be used for the given MIP mode is derived as follows

MIP coding mode is harmonized with other coding tools by considering following aspects:LFNST is enabled for MIP on large blocks. Here, the LFNST transforms of planar mode are usedThe reference sample derivation for MIP is performed exactly as for the conventional intra prediction modesFor the upsampling step used in the MIP-prediction, original reference samples are used instead of downsampled onesClipping is performed before upsampling and not after upsamplingMIP is allowed up to 64×64 regardless of the maximum transform sizeThe number of MIP modes is 32 for sizeId=0, 16 for sizeId=1 and 12 for sizeId=2

For each inter-predicted CU, motion parameters consisting of motion vectors, reference picture indices and reference picture list usage index, and additional information needed for the new coding feature of VVC to be used for inter-predicted sample generation. The motion parameter can be signalled in an explicit or implicit manner When a CU is coded with skip mode, the CU is associated with one PU and has no significant residual coefficients, no coded motion vector delta or reference picture index. A merge mode is specified whereby the motion parameters for the current CU are obtained from neighbouring CUs, including spatial and temporal candidates, and additional schedules introduced in VVC. The merge mode can be applied to any inter-predicted CU, not only for skip mode. The alternative to merge mode is the explicit transmission of motion parameters, where motion vector, corresponding reference picture index for each reference picture list and reference picture list usage flag and other needed information are signalled explicitly per each CU.

Beyond the inter coding features in HEVC, VVC includes a number of new and refined inter prediction coding tools listed as follows:Extended merge predictionMerge mode with MVD (MMVD)Symmetric MVD (SMVD) signallingAffine motion compensated predictionSubblock-based temporal motion vector prediction (SbTMVP)Adaptive motion vector resolution (AMVR)Motion field storage: 1/16thluma sample MV storage and 8×8 motion field compressionBi-prediction with CU-level weight (BCW)Bi-directional optical flow (BDOF)Decoder side motion vector refinement (DMVR)Geometric partitioning mode (GPM)Combined inter and intra prediction (CIIP)

The following text provides the details on those inter prediction methods specified in VVC.

2.1.2.1. Extended Merge Prediction

In VVC, the merge candidate list is constructed by including the following five types of candidates in order:1) Spatial MVP from spatial neighbour CUs2) Temporal MVP from collocated CUs3) History-based MVP from an FIFO table4) Pairwise average MVP5) Zero MVs.

The size of merge list is signalled in sequence parameter set header and the maximum allowed size of merge list is 6. For each CU code in merge mode, an index of best merge candidate is encoded using truncated unary binarization (TU). The first bin of the merge index is coded with context and bypass coding is used for other bins.

The derivation process of each category of merge candidates is provided in this session. As done in HEVC, VVC also supports parallel derivation of the merging candidate lists for all CUs within a certain size of area.

2.1.2.2. Spatial Candidates Derivation

The derivation of spatial merge candidates in VVC is same to that in HEVC except the positions of first two merge candidates are swapped. A maximum of four merge candidates are selected among candidates located in the positions depicted inFIG.11.FIG.11illustrates a schematic diagram1100of positions of spatial merge candidate. The order of derivation is B0, A0, B1, A1and B2. Position B2is considered only when one or more than one CUs of position B0, A0, B1, A1are not available (e.g. because it belongs to another slice or tile) or is intra coded. After candidate at position A1is 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. To reduce computational complexity, not all possible candidate pairs are considered in the mentioned redundancy check. Instead only the pairs linked with an arrow inFIG.12are considered and a candidate is only added to the list if the corresponding candidate used for redundancy check has not the same motion information.FIG.12illustrates a schematic diagram1200of candidate pairs considered for redundancy check of spatial merge candidates.

In this step, only one candidate is added to the list. Particularly, in the derivation of this temporal merge candidate, a scaled motion vector is derived based on co-located CU belonging to the collocated reference picture. The reference picture list to be used for derivation of the co-located CU is explicitly signalled in the slice header.FIG.13illustrates a schematic diagram1300of an illustration of motion vector scaling for temporal merge candidate. The scaled motion vector for temporal merge candidate is obtained as illustrated by the dotted line inFIG.13, which is scaled from the motion vector of the co-located CU using the POC distances, tb and td, where tb is defined to be the POC difference between the reference picture of the current picture and the current picture and td is defined to be the POC difference between the reference picture of the co-located picture and the co-located picture. The reference picture index of temporal merge candidate is set equal to zero.

FIG.14illustrates a schematic diagram1400of candidate positions for temporal merge candidate. The position for the temporal candidate is selected between candidates C0and C1, as depicted inFIG.14. If CU at position C0is not available, is intra coded, or is outside of the current row of CTUs, position C1is used. Otherwise, position C0is used in the derivation of the temporal merge candidate.

The history-based MVP (HMVP) merge candidates are added to merge list after the spatial MVP and TMVP. In this method, the motion information of a previously coded block is stored in a table and used as MVP for the current CU. The table with multiple HMVP candidates is maintained during the encoding/decoding process. The table is reset (emptied) when a new CTU row is encountered. Whenever there is a non-subblock inter-coded CU, the associated motion information is added to the last entry of the table as a new HMVP candidate.

The HMVP table size S is set to be 6, which indicates up to 6 History-based MVP (HMVP) candidates may be added to the table. When inserting a new motion candidate to the table, a constrained first-in-first-out (FIFO) rule is utilized wherein redundancy check is firstly applied to find whether there is an identical HMVP in the table. If found, the identical HMVP is removed from the table and all the HMVP candidates afterwards are moved forward, HMVP candidates could be used in the merge candidate list construction process. The latest several HMVP candidates in the table are checked in order and inserted to the candidate list after the TMVP candidate. Redundancy check is applied on the HMVP candidates to the spatial or temporal merge candidate.

To reduce the number of redundancy check operations, the following simplifications are introduced:1. Number of HMPV candidates is used for merge list generation is set as (N<=4 )? M: (8−N), wherein N indicates number of existing candidates in the merge list and M indicates number of available HMVP candidates in the table.2. Once the total number of available merge candidates reaches the maximally allowed merge candidates minus 1, the merge candidate list construction process from HMVP is terminated.

Pairwise average candidates are generated by averaging predefined pairs of candidates in the existing merge candidate list, and the predefined pairs are defined as {(0, 1), (0, 2), (1, 2), (0, 3), (1, 3), (2, 3)}, where the numbers denote the merge indices to the merge candidate list.

The averaged motion vectors are calculated separately for each reference list. If both motion vectors are available in one list, these two motion vectors are averaged even when they point to different reference pictures; if only one motion vector is available, use the one directly; if no motion vector is available, keep this list invalid.

When the merge list is not full after pair-wise average merge candidates are added, the zero MVPs are inserted in the end until the maximum merge candidate number is encountered.

2.1.2.6. Merge Estimation Region

Merge estimation region (MER) allows independent derivation of merge candidate list for the CUs in the same merge estimation region (MER). A candidate block that is within the same MER to the current CU is not included for the generation of the merge candidate list of the current CU. In addition, the updating process for the history-based motion vector predictor candidate list is updated only if (xCb+cbWidth)>>Log2ParMrgLevel is greater than xCb>>Log2ParMrgLevel and (yCb+cbHeight)>>Log2ParMrgLevel is great than (yCb>>Log2ParMrgLevel) and where (xCb, yCb) is the top-left luma sample position of the current CU in the picture and (cbWidth, cbHeight) is the CU size. The MER size is selected at encoder side and signalled as log2_parallel_merge_level_minus2 in the sequence parameter set.

2.1.3. Merge Mode with MVD (MMVD)

In addition to merge mode, where the implicitly derived motion information is directly used for prediction samples generation of the current CU, the merge mode with motion vector differences (MMVD) is introduced in VVC. A MMVD flag is signalled right after sending a skip flag and merge flag to specify whether MMVD mode is used for a CU. In MMVD, after a merge candidate is selected, it is further refined by the signalled MVDs information. The further information includes a merge candidate flag, an index to specify motion magnitude, and an index for indication of motion direction. In MMVD mode, one for the first two candidates in the merge list is selected to be used as MV basis. The merge candidate flag is signalled to specify which one is used.

Distance index specifies motion magnitude information and indicate the pre-defined offset from the starting point.FIG.15illustrates a schematic diagram1500of a schematic diagram of MMVD search point. As shown inFIG.15, an offset is added to either horizontal component or vertical component of starting MV. The relation of distance index and pre-defined offset is specified in Table 2-5

Direction index represents the direction of the MVD relative to the starting point. The direction index can represent of the four directions as shown in Table 2-6. It's noted that the meaning of MVD sign could be variant according to the information of starting MVs. When the starting MVs is an un-prediction MV or bi-prediction MVs with both lists point to the same side of the current picture (i.e. POCs of two references are both larger than the POC of the current picture, or are both smaller than the POC of the current picture), the sign in Table 2-6 specifies the sign of MV offset added to the starting MV. When the starting MVs is bi-prediction MVs with the two MVs point to the different sides of the current picture (i.e. the POC of one reference is larger than the POC of the current picture, and the POC of the other reference is smaller than the POC of the current picture), the sign in Table 2-6 specifies the sign of MV offset added to the list0 MV component of starting MV and the sign for the list1 MV has opposite value.

TABLE 2-6Sign of MV offset specified by direction indexDirection IDX00011011x-axis+−N/AN/Ay-axisN/AN/A+−
2.1.3.1. Bi-prediction with CU-Level Weight (BCW)

In HEVC, the bi-prediction signal is generated by averaging two prediction signals obtained from two different reference pictures and/or using two different motion vectors. In VVC, the bi-prediction mode is extended beyond simple averaging to allow weighted averaging of the two prediction signals.

Five weights are allowed in the weighted averaging bi-prediction, w∈{−2, 3, 4, 5, 10}. For each bi-predicted CU, the weight w is determined in one of two ways: 1) for a non-merge CU, the weight index is signalled after the motion vector difference; 2) for a merge CU, the weight index is inferred from neighbouring blocks based on the merge candidate index. BCW is only applied to CUs with 256 or more luma samples (i.e., CU width times CU height is greater than or equal to 256). For low-delay pictures, all 5 weights are used. For non-low-delay pictures, only 3 weights (w∈{3,4,5}) are used.At the encoder, fast search algorithms are applied to find the weight index without significantly increasing the encoder complexity. These algorithms are summarized as follows. For further details readers are referred to the VTM software and document JVET-L0646. When combined with AMVR, unequal weights are only conditionally checked for 1-pel and 4-pel motion vector precisions if the current picture is a low-delay picture.When combined with affine, affine ME will be performed for unequal weights if and only if the affine mode is selected as the current best mode.When the two reference pictures in bi-prediction are the same, unequal weights are only conditionally checked.Unequal weights are not searched when certain conditions are met, depending on the POC distance between current picture and its reference pictures, the coding QP, and the temporal level.

The BCW weight index is coded using one context coded bin followed by bypass coded bins.

The first context coded bin indicates if equal weight is used; and if unequal weight is used, additional bins are signalled using bypass coding to indicate which unequal weight is used. Weighted prediction (WP) is a coding tool supported by the H.264/AVC and HEVC standards to efficiently code video content with fading. Support for WP was also added into the VVC standard. WP allows weighting parameters (weight and offset) to be signalled for each reference picture in each of the reference picture lists L0 and L1. Then, during motion compensation, the weight(s) and offset(s) of the corresponding reference picture(s) are applied. WP and BCW are designed for different types of video content. In order to avoid interactions between WP and BCW, which will complicate VVC decoder design, if a CU uses WP, then the BCW weight index is not signalled, and w is inferred to be 4 (i.e. equal weight is applied).For a merge CU, the weight index is inferred from neighbouring blocks based on the merge candidate index. This can be applied to both normal merge mode and inherited affine merge mode. For constructed affine merge mode, the affine motion information is constructed based on the motion information of up to 3 blocks. The BCW index for a CU using the constructed affine merge mode is simply set equal to the BCW index of the first control point MV.

In VVC, CLIP and BCW cannot be jointly applied for a CU. When a CU is coded with CIIP mode, the BCW index of the current CU is set to 2, e.g. equal weight.

The bi-directional optical flow (BDOF) tool is included in VVC. BDOF, previously referred to as BIO, was included in the JEM. Compared to the JEM version, the BDOF in VVC is a simpler version that requires much less computation, especially in terms of number of multiplications and the size of the multiplier.

BDOF is used to refine the bi-prediction signal of a CU at the 4×4 subblock level. BDOF is applied to a CU if it satisfies all the following conditions:The CU is coded using “true” bi-prediction mode, i.e., one of the two reference pictures is prior to the current picture in display order and the other is after the current picture in display orderThe distances (i.e. POC difference) from two reference pictures to the current picture are sameBoth reference pictures are short-term reference pictures.The CU is not coded using affine mode or the ATMVP merge modeCU has more than 64 luma samplesBoth CU height and CU width are larger than or equal to 8 luma samplesBCW weight index indicates equal weightWP is not enabled for the current CUCIIP mode is not used for the current CU

BDOF is only applied to the luma component. As its name indicates, the BDOF mode is based on the optical flow concept, which assumes that the motion of an object is smooth. For each 4×4 subblock, a motion refinement (vx, vy) is calculated by minimizing the difference between the L0 and L1 prediction samples. The motion refinement is then used to adjust the bi-predicted sample values in the 4×4 subblock. The following steps are applied in the BDOF process.

First, the horizontal and vertical gradients,

k=0,1, of the two prediction signals are computed by directly calculating the difference between two neighboring samples, i.e.,

where l(k) (i,j) are the sample value at coordinate (i,j) of the prediction signal in list k, k=0,1, and shift1 is calculated based on the luma bit depth, bitDepth, as shift1=max(6, bitDepth-6).

where Ω is a 6×6 window around the 4×4 subblock, and the values of naand nbare set equal to min(1, bitDepth-11) and min(4, bitDepth-8), respectively.

The motion refinement (vx,vy) is then derived using the cross- and auto-correlation terms using the following:

where

└⋅┘ is the floor function, and nS2=12.

Based on the motion refinement and the gradients, the following adjustment is calculated for each sample in the 4×4 subblock:

Finally, the BDOF samples of the CU are calculated by adjusting the bi-prediction samples as follows:

These values are selected such that the multipliers in the BDOF process do not exceed 15-bit, and the maximum bit-width of the intermediate parameters in the BDOF process is kept within 32-bit.

In order to derive the gradient values, some prediction samples l(k)(i,j) in list k (k=0,1) outside of the current CU boundaries need to be generated.FIG.16illustrates a schematic diagram1600of extended CU region used in BDOF. As depicted inFIG.16, the BDOF in VVC uses one extended row/column around the CU's boundaries. In order to control the computational complexity of generating the out-of-boundary prediction samples, prediction samples in the extended area (white positions) are generated by taking the reference samples at the nearby integer positions (using floor( ) operation on the coordinates) directly without interpolation, and the normal8-tap motion compensation interpolation filter is used to generate prediction samples within the CU (gray positions). These extended sample values are used in gradient calculation only. For the remaining steps in the BDOF process, if any sample and gradient values outside of the CU boundaries are needed, they are padded (i.e. repeated) from their nearest neighbors.

When the width and/or height of a CU are larger than 16 luma samples, it will be split into subblocks with width and/or height equal to 16 luma samples, and the subblock boundaries are treated as the CU boundaries in the BDOF process. The maximum unit size for BDOF process is limited to 16×16. For each subblock, the BDOF process could skipped. When the SAD of between the initial L0 and L1 prediction samples is smaller than a threshold, the BDOF process is not applied to the subblock. The threshold is set equal to (8*W*(H>>1), where W indicates the subblock width, and H indicates subblock height. To avoid the additional complexity of SAD calculation, the SAD between the initial L0 and L1 prediction samples calculated in DVMR process is re-used here.

If BCW is enabled for the current block, i.e., the BCW weight index indicates unequal weight, then bi-directional optical flow is disabled. Similarly, if WP is enabled for the current block, i.e., the luma_weight_lx_flag is 1 for either of the two reference pictures, then BDOF is also disabled. When a CU is coded with symmetric MVD mode or CIIP mode, BDOF is also disabled.

In VVC, besides the normal unidirectional prediction and bi-directional prediction mode MVD signalling, symmetric MVD mode for bi-predictional MVD signalling is applied (as showed inFIG.17.FIG.17illustrates a schematic diagram1700of an illustration for symmetrical MVD mode). In the symmetric MVD mode, motion information including reference picture indices of both list-0 and list-1 and MVD of list-1 are not signaled but derived.

The decoding process of the symmetric MVD mode is as follows:1) At slice level, variables BiDirPredFlag, RefIdxSymL0 and RefIdxSymL1 are derived as follows:If mvd_l1_zero_flag is 1, BiDirPredFlag is set equal to 0.Otherwise, if the nearest reference picture in list-0 and the nearest reference picture in list-1 form a forward and backward pair of reference pictures or a backward and forward pair of reference pictures, BiDirPredFlag is set to 1, and both list-0 and list-1 reference pictures are short-term reference pictures. Otherwise BiDirPredFlag is set to 0.2) At CU level, a symmetrical mode flag indicating whether symmetrical mode is used or not is explicitly signaled if the CU is bi-prediction coded and BiDirPredFlag is equal to 1.

When the symmetrical mode flag is true, only mvp_l0_flag, mvp_l1_flag and MVD0 are explicitly signaled. The reference indices for list-0 and list-1 are set equal to the pair of reference pictures, respectively. MVD1 is set equal to (−MVD0). The final motion vectors are shown in below formula.

In the encoder, symmetric MVD motion estimation starts with initial MV evaluation. A set of initial MV candidates comprising of the MV obtained from uni-prediction search, the MV obtained from bi-prediction search and the MVs from the AMVP list. The one with the lowest rate-distortion cost is chosen to be the initial MV for the symmetric MVD motion search.

2.1.5. Decoder Side Motion Vector Refinement (DMVR)

In order to increase the accuracy of the MVs of the merge mode, a bilateral-matching based decoder side motion vector refinement is applied in VVC. In bi-prediction operation, a refined MV is searched around the initial MVs in the reference picture list L01801and reference picture list L11803. The BM method calculates the distortion between the two candidate blocks in the reference picture list L0 and list L1.FIG.18illustrates a schematic diagram1800of decoding side motion vector refinement. As illustrated inFIG.18, the SAD between the block1810and block1812based on each MV candidate around the initial MV is calculated. The MV candidate with the lowest SAD becomes the refined MV and used to generate the bi-predicted signal.

In VVC, the DMVR can be applied for the CUs which are coded with following modes and features:CU level merge mode with bi-prediction MVOne reference picture is in the past and another reference picture is in the future with respect to the current picture1802The distances (i.e. POC difference) from two reference pictures to the current picture are sameBoth reference pictures are short-term reference picturesCU has more than 64 luma samplesBoth CU height and CU width are larger than or equal to 8 luma samplesBCW weight index indicates equal weightWP is not enabled for the current blockCIIP mode is not used for the current block

The refined MV derived by DMVR process is used to generate the inter prediction samples and also used in temporal motion vector prediction for future pictures coding. While the original MV is used in deblocking process and also used in spatial motion vector prediction for future CU coding.

The additional features of DMVR are mentioned in the following sub-clauses.

2.1.5.1. Searching Scheme

In DVMR, the search points are surrounding the initial MV and the MV offset obey the MV difference mirroring rule. In other words, any points that are checked by DMVR, denoted by candidate MV pair (MV0, MV1) obey the following two equations:

Where MV_offset represents the refinement offset between the initial MV and the refined MV in one of the reference pictures. The refinement search range is two integer luma samples from the initial MV. The searching includes the integer sample offset search stage and fractional sample refinement stage.

25 points full search is applied for integer sample offset searching. The SAD of the initial MV pair is first calculated. If the SAD of the initial MV pair is smaller than a threshold, the integer sample stage of DMVR is terminated. Otherwise SADs of the remaining 24 points are calculated and checked in raster scanning order. The point with the smallest SAD is selected as the output of integer sample offset searching stage. To reduce the penalty of the uncertainty of DMVR refinement, it is proposed to favor the original MV during the DMVR process. The SAD between the reference blocks referred by the initial MV candidates is decreased by ¼ of the SAD value.

The integer sample search is followed by fractional sample refinement. To save the calculational complexity, the fractional sample refinement is derived by using parametric error surface equation, instead of additional search with SAD comparison. The fractional sample refinement is conditionally invoked based on the output of the integer sample search stage. When the integer sample search stage is terminated with center having the smallest SAD in either the first iteration or the second iteration search, the fractional sample refinement is further applied.

In parametric error surface based sub-pixel offsets estimation, the center position cost and the costs at four neighboring positions from the center are used to fit a 2-D parabolic error surface equation of the following form

where (xmin,ymin) corresponds to the fractional position with the least cost and C corresponds to the minimum cost value. By solving the above equations by using the cost value of the five search points, the (xmin,ymin) is computed as:

The value of xminand yminare automatically constrained to be between −8 and 8 since all cost values are positive and the smallest value is E(0,0). This corresponds to half peal offset with 1/16th-pel MV accuracy in VVC. The computed fractional (xmin,ymin) are added to the integer distance refinement MV to get the sub-pixel accurate refinement delta MV.

2.1.5.2. Bilinear-interpolation and sample padding

In VVC, the resolution of the MVs is 1/16 luma samples. The samples at the fractional position are interpolated using a 8-tap interpolation filter. In DMVR, the search points are surrounding the initial fractional-pel MV with integer sample offset, therefore the samples of those fractional position need to be interpolated for DMVR search process. To reduce the calculation complexity, the bi-linear interpolation filter is used to generate the fractional samples for the searching process in DMVR. Another important effect is that by using bi-linear filter is that with 2-sample search range, the DVMR does not access more reference samples compared to the normal motion compensation process. After the refined MV is attained with DMVR search process, the normal 8-tap interpolation filter is applied to generate the final prediction. In order to not access more reference samples to normal MC process, the samples, which is not needed for the interpolation process based on the original MV but is needed for the interpolation process based on the refined MV, will be padded from those available samples.

2.1.5.3. Maximum DMVR Processing Unit

When the width and/or height of a CU are larger than 16 luma samples, it will be further split into subblocks with width and/or height equal to 16 luma samples. The maximum unit size for DMVR searching process is limit to 16×16.

2.1.6. Combined Inter and Intra Prediction (CIIP)

In VVC, when a CU is coded in merge mode, if the CU contains at least 64 luma samples (that is, CU width times CU height is equal to or larger than 64), and if both CU width and CU height are less than 128 luma samples, an additional flag is signalled to indicate if the combined inter/intra prediction (CIIP) mode is applied to the current CU. As its name indicates, the CIIP prediction combines an inter prediction signal with an intra prediction signal. The inter prediction signal in the CIIP mode Pinteris derived using the same inter prediction process applied to regular merge mode; and the intra prediction signal Pintrais derived following the regular intra prediction process with the planar mode. Then, the intra and inter prediction signals are combined using weighted averaging, where the weight value is calculated depending on the coding modes of the top and left neighbouring blocks (depicted inFIG.19.FIG.19illustrates a schematic diagram1900of top and left neighboring blocks used in CIIP weight derivation) as follows:If the top neighbor is available and intra coded, then set isIntraTop to 1, otherwise set isIntraTop to 0;If the left neighbor is available and intra coded, then set isIntraLeft to 1, otherwise set isIntraLeft to 0;If (isIntraLeft+isIntraTop) is equal to 2, then wt is set to 3;Otherwise, if (isIntraLeft+isIntraTop) is equal to 1, then wt is set to 2;Otherwise, set wt to 1.

The CIIP prediction is formed as follows:

In VVC, a geometric partitioning mode is supported for inter prediction. The geometric partitioning mode is signalled using a CU-level flag as one kind of merge mode, with other merge modes including the regular merge mode, the MMVD mode, the CIIP mode and the subblock merge mode. In total 64 partitions are supported by geometric partitioning mode for each possible CU size w×h=2m×2nwith m, n∈{3 . . . 6} excluding 8×64 and 64×8.

When this mode is used, a CU is split into two parts by a geometrically located straight line (FIG.20illustrates a schematic diagram2000of examples of the GPM splits grouped by identical angles). The location of the splitting line is mathematically derived from the angle and offset parameters of a specific partition. Each part of a geometric partition in the CU is inter-predicted using its own motion; only uni-prediction is allowed for each partition, that is, each part has one motion vector and one reference index. The uni-prediction motion constraint is applied to ensure that same as the conventional bi-prediction, only two motion compensated prediction are needed for each CU.

If geometric partitioning mode is used for the current CU, then a geometric partition index indicating the partition mode of the geometric partition (angle and offset), and two merge indices (one for each partition) are further signalled. The number of maximum GPM candidate size is signalled explicitly in SPS and specifies syntax binarization for GPM merge indices. After predicting each of part of the geometric partition, the sample values along the geometric partition edge are adjusted using a blending processing with adaptive weights. This is the prediction signal for the whole CU, and transform and quantization process will be applied to the whole CU as in other prediction modes. Finally, the motion field of a CU predicted using the geometric partition modes is stored.

2.1.7.1. Uni-Prediction Candidate List Construction

The uni-prediction candidate list is derived directly from the merge candidate list constructed according to the extended merge prediction process. Denote n as the index of the uni-prediction motion in the geometric uni-prediction candidate list. The LX motion vector of the n-th extended merge candidate, with X equal to the parity of n, is used as the n-th uni-prediction motion vector for geometric partitioning mode. These motion vectors are marked with “x” inFIG.21, whereFIG.21illustrates a schematic diagram2100of uni-prediction MV selection for geometric partitioning mode. In case a corresponding LX motion vector of the n-the extended merge candidate does not exist, the L(1−X) motion vector of the same candidate is used instead as the uni-prediction motion vector for geometric partitioning mode.

2.1.7.2. Blending Along the Geometric Partitioning Edge

After predicting each part of a geometric partition using its own motion, blending is applied to the two prediction signals to derive samples around geometric partition edge. The blending weight for each position of the CU are derived based on the distance between individual position and the partition edge.

The distance for a position (x,y) to the partition edge are derived as:

where i,j are the indices for angle and offset of a geometric partition, which depend on the signaled geometric partition index. The sign of ρx,jand ρy,jdepend on angle index i. The weights for each part of a geometric partition are derived as following:

The partIdx depends on the angle index i. One example of weigh w0is illustrated inFIG.22.FIG.22illustrates a schematic diagram2200of exemplified generation of a bending weight w0 using geometric partitioning mode.

2.1.7.3. Motion Field Storage for Geometric Partitioning Mode

Mv1 from the first part of the geometric partition, Mv2 from the second part of the geometric partition and a combined Mv of Mv1 and Mv2 are stored in the motion filed of a geometric partitioning mode coded CU.

The stored motion vector type for each individual position in the motion filed are determined as:

where motionIdx is equal to d(4x+2, 4y+2), which is recalculated from equation (2-36). The partIdx depends on the angle index i.

If sType is equal to 0 or 1, Mv0 or Mv1 are stored in the corresponding motion field, otherwise if sType is equal to 2, a combined Mv from Mv0 and Mv2 are stored. The combined Mv are generated using the following process:1) If Mv1 and Mv2 are from different reference picture lists (one from L0 and the other from L1), then Mv1 and Mv2 are simply combined to form the bi-prediction motion vectors.2) Otherwise, if Mv1 and Mv2 are from the same list, only uni-prediction motion Mv2 is stored.

In one specific example embodiments, the MHP is described in such as JVET-U0100. The multi-hypothesis prediction previously proposed in JVET-M0425 is adopted in this contribution. Up to two additional predictors are signalled on top of inter AMVP mode, regular merge mode, and MMVD mode. The resulting overall prediction signal is accumulated iteratively with each additional prediction signal.

The weighting factor a is specified according to the following table:

For inter AMVP mode, MHP is only applied if non-equal weight in BCW is selected in bi-prediction mode.

2.2. On Prediction Blended from Multiple Compositions

The detailed embodiments below should be considered as examples to explain general concepts. These embodiments should not be interpreted in a narrow way. Furthermore, these embodiments can be combined in any manner

The terms ‘video unit’ or ‘coding unit’ or ‘block’ may represent a coding tree block (CTB), a coding tree unit (CTU), a coding block (CB), a CU, a PU, a TU, a PB, a TB. In the present discourse, regarding “a block coded with mode N”, here “mode N” may be a prediction mode (e.g., MODE_INTRA, MODE_INTER, MODE_PLT, MODE_IBC, and etc.), or a coding technique (e.g., AMVP, Merge, SMVD, BDOF, PROF, DMVR, AMVR, TM, Affine, CIIP, GPM, MMVD, BCW, HMVP, SbTMVP, and etc.).

As used herein, the expressions “a prediction mode with more than one hypothesis” and “a multiple hypothesis prediction mode” may be used changeable. Further, a “multiple hypothesis prediction” in the present discourse may refer to any coding tool that combining/blending more than one prediction/composition/hypothesis into one for later reconstruction process. For example, a composition/hypothesis may be INTER mode coded, INTRA mode coded, or any other coding mode/method like CIIP, GPM, MHP, and etc.

In the following discussion, a “base hypothesis” of a multiple hypothesis prediction block may refer to a first hypothesis/prediction with a first set of weighting values. In the following discussion, an “additional hypothesis” of a multiple hypothesis prediction block may refer to a second hypothesis/prediction with a second set of weighting values.

The Compositions of Multiple Hypothesis Prediction

1. In one example, mode X may NOT be allowed to generate a hypothesis of a multiple hypothesis prediction block coded with multiple hypothesis prediction mode Y.1) For example, a base hypothesis of a multiple hypothesis prediction block may not be allowed to be coded by mode X.2) For example, an additional hypothesis of a multiple hypothesis prediction block may not be allowed to be coded by mode X.3) For example, for an X-coded block, it may never signal any block level coding information related to mode Y.4) For example, X is a palette coded block (e.g., PLT mode).5) Alternatively, mode X may be allowed to be used to generate a hypothesis of a multiple hypothesis prediction block coded with mode Y.a) For example, X is a Symmetric MVD coding (e.g., SMVD) mode.b) For example, X is based on a template matching based technique.c) For example, X is based on a bilateral matching based technique.d) For example, X is a combined intra and inter prediction (e.g., CIIP) mode.e) For example, X is a geometric partition prediction (e.g., GPM) mode.6) Mode Y may be CIIP, GPM or MHP.2. CIIP may be used together with mode X (such as GPM, or MMVD, or affine) for a block.1) In one example, at least one hypothesis in GPM is a generated by CIIP. In other words, at least one hypothesis in GPM is generated as a weighted sum of at least one inter-prediction and one intra-prediction.2) In one example, at least one hypothesis in CIIP is a generated by GPM. In other words, at least one hypothesis in CIIP is generated as a weighted sum of at least two inter-predictions.3) In one example, at least one hypothesis in CIIP is a generated by MMVD.4) In one example, at least one hypothesis in CIIP is a generated by affine prediction.5) In one example, whether mode X can be used together with CIIP may depend on coding information such as block dimensions.6) In one example, whether mode X can be used together with CIIP may be signaled from the encoder to the decoder.a) In one example, the signaling may be conditioned by coding information such as block dimensions.3. In one example, one or more hypotheses of a multiple hypothesis prediction block may be generated based on position dependent prediction combination (e.g., PDPC).1) For example, prediction samples of a hypothesis may be processed by PDPC first, before it is used to generate the multiple hypothesis prediction block.2) For example, a predictor obtained based on PDPC which takes into account the neighboring sample values may be used to generate a hypothesis.3) For example, a predictor obtained based on gradient based PDPC which takes into account the gradient of neighboring samples may be used to generate a hypothesis.a) For example, a gradient based PDPC may be applied to an intra mode (Planar, DC, Horizontal, Vertical, or diagonal mode) coded hypothesis.4) For example, a PDPC predictor may be not based on a prediction sample inside the current block.a) For example, a PDPC predictor may be only based on prediction (or reconstruction) samples neighboring the current block.b) For example, a PDPC predictor may be based on both prediction (or reconstruction) samples neighboring the current block and inside the current block.4. In one example, a multiple hypothesis predicted block may be generated based on decoder side refinement techniques.1) For example, a decoder side refinement technique may be applied to one or more hypotheses of a multiple hypothesis prediction block.2) For example, a decoder side refinement technique may be applied to a multiple hypothesis prediction block.3) For example, the decoder side refinement technique may be based on decoder side template matching (e.g., TM), decoder side bilateral matching (e.g., DMVR), or decoder side bi-directional optical flow (e.g., BDOF) or Prediction Refinement with Optical Flow (PROF).4) For example, the multiple hypothesis predicted block may be coded with CIIP, MHP, GPM, or any other multiple hypothesis prediction modes.5) For example, the INTER prediction motion data of a multiple hypothesis block (e.g., CIIP) may be further refined by decoder side template matching (TM), and/or decoder side bilateral matching (DMVR), and/or decoder side bi-directional optical flow (BDOF).6) For example, the INTER prediction samples of a multiple hypothesis block (e.g., CIIP) may be further refined by decoder side template matching (TM), and/or decoder side bilateral matching (DMVR), and/or decoder side bi-directional optical flow (BDOF) or Prediction Refinement with Optical Flow (PROF).7) For example, the INTRA prediction part of a multiple hypothesis block (e.g., CIIP, MHP, and etc.) may be further refined by decoder side mode derivation (e.g., DIMD), decoder side intra template matching, and etc.8) The refined intra prediction mode/motion information of a multiple hypothesis block may be disallowed to predict the following blocks to be coded/decoded in the same slice/tile/picture/subpicture.9) Alternatively, decoder side refinement techniques may be NOT applied to a multiple hypothesis predicted block.a) For example, decoder side refinement techniques may be NOT allowed to an MHP coded block.

General Claims5. Whether to and/or how to apply the disclosed methods above may be signalled at sequence level/group of pictures level/picture level/slice level/tile group level, such as in sequence header/picture header/SPS/VPS/DPS/DCI/PPS/APS/slice header/tile group header.6. Whether to and/or how to apply the disclosed methods above may be signalled at PB/TB/CB/PU/TU/CU/VPDU/CTU/CTU row/slice/tile/sub-picture/other kinds of region contain more than one sample or pixel.7. Whether to and/or how to apply the disclosed methods above may be dependent on coded information, such as block size, colour format, single/dual tree partitioning, colour component, slice/picture type.

There are several issues in the existing video coding techniques, which would be further improved for higher coding gain.1) The current PDPC for intra Planar doesn't consider the gradient of neighboring samples, which may be improved.2) The existing MHP in JVET-U0100 doesn't consider coding information of neighboring samples, which would be further improved for higher coding gain.3) The existing methods explored applying motion refinement like template matching to a

GPM coded block. However, whether it is allowed to be applied is not dependent on the GPM partition mode/shape.4) The existing methods explored applying a template matching to a GPM coded block, either use one flag for the entire GPM block, or two flags each for one subpartition of a GPM block. The signalling of template matching based GPM coding can be further optimized.5) The existing methods explored applying a motion refinement to a video block, e.g., applying either template matching or MMVD to a GPM coded block, but never both. However, more than one motion refinement method may be applied to a video block such as GPM, CIIP, and etc.6) The existing methods code the merge index using a fixed cMax value. However, the binarization of the merge index coding may be dependent on the coding method used to the video unit, given that more than one coding method is allowed to be used to the video unit and each of them has its own maximum merge candidate number.7) Currently, a template matching related technique may be used to a video unit, and there is no signaling about different template styles, which may be modified.

The detailed descriptions below should be considered as examples to explain general concepts. These below embodiments should not be interpreted in a narrow way. Furthermore, these embodiments can be combined in any manner

The terms ‘video unit’ or ‘coding unit’ or ‘block’ may represent a coding tree block (CTB), a coding tree unit (CTU), a coding block (CB), a CU, a PU, a TU, a PB, a TB.

A “multiple hypothesis prediction” in the present disclosure may refer to any coding tool that combining/blending more than one prediction/composition/hypothesis into one for later reconstruction process. For example, a composition/hypothesis may be INTER mode coded, INTRA mode coded, or any other coding mode/method like CIIP, GPM, MHP, and etc.

In the following discussion, a “base hypothesis” of a multiple hypothesis prediction block may refer to a first hypothesis/prediction with a first set of weighting values.

In the following discussion, an “additional hypothesis” of a multiple hypothesis prediction block may refer to a second hypothesis/prediction with a second set of weighting values.

On Coding Techniques Using Coding Information of Neighboring Video Units

1. In one example, a gradient-based position dependent prediction combination (e.g., PDPC) may be applied to a mode-Y-coded block.1) For example, the gradient-based PDPC may take use of the gradient of neighboring available samples for coding the current block.a) For example, a gradient value may be calculated from sample values of a certain number (such as two) of neighboring samples.b) For example, several (such as two) available neighboring samples from above, above-right, left, bottom-left may be used to calculate the gradient.c) For example, for an angular prediction direction, several available neighboring samples along the same direction may be used to calculate the gradient.2) For example, Y is intra PLANAR.3) For example, Y is intra CCLM.4) For example, Y is an inter prediction mode.5) For example, beside the left and top neighbor samples, a gradient-based PDPC for intra PLANAR mode may take into account the top-left neighboring sample.6) For example, a gradient based PDPC for an inter prediction mode may take into account the top-left, and/or top, and/or left neighboring samples.2. In one example, one or more hypotheses of a multiple hypothesis prediction block may be generated based on neighboring prediction/reconstruction samples outside the current block.1) For example, the multiple hypothesis prediction block may be coded with MHP, GPM, or any other multiple hypothesis prediction modes.2) For example, besides intra PLANAR, other INTRA prediction mode (intra DC mode, intra angular prediction mode, intra DM mode, intra LM mode) taking use of neighboring samples, may be used to generate the multiple hypothesis predicted block.3) For example, INTER prediction mode taking use of neighboring prediction/reconstruction samples (inter LIC, inter OBMC, inter template matching, inter filtering using neighboring samples) may be used to generate the multiple hypothesis predicted block.3. In one example, whether and/or which neighboring samples are used to a video unit coded by multiple hypothesis prediction (e.g., MHP, GPM, CIIP, and etc.), may be depend on the coded information of the video unit.1) For example, different neighboring samples may be used for different video units dependent on the intra angular mode applied to the video unit.a) For example, the video unit may be a subblock, or a partition of the multiple hypothesis block.b) For example, the video unit may be one of the hypotheses of the multiple hypothesis block.2) For example, if the coded information (e.g., intra modes, and etc.) of a hypothesis indicates that the prediction direction is from left and/or above, more than one left and/or above neighboring sample may be grouped together to construct a template for generating prediction samples of the hypothesis.3) Additionally, whether neighboring samples are used to a video unit (a partition/subblock/hypothesis of an entire block, or an entire block), may be dependent on the availability of neighboring samples and/or the partitioning shape, and/or partition angle/direction regarding the video unit.a) For example, for a partition/subblock of a GPM coded block, whether left and/or above neighboring samples are used to generate prediction samples of a hypothesis may be dependent on the partitioning shape of the geometric partitioning merge mode (e.g., merge_gpm_partition_idx).b) For example, for a partition/subblock/hypothesis of a GPM coded block, whether left and/or above neighboring samples are used to generate prediction samples of a hypothesis may be dependent on the partition angle (e.g., angleIdx) which is derived from the partitioning shape of the geometric partitioning merge mode.c) For example, for a partition/subblock/hypothesis of a GPM coded block, whether left and/or above neighboring samples are used to generate prediction samples of a hypothesis may be dependent on the partition distance (e.g., distanceIdx) which is derived from the partitioning shape of the geometric partitioning merge mode.

General Rules of Motion Refinement on GPM Coded Blocks

8. In one example, whether a motion refinement (e.g., template matching, TM, MMVD, bilateral matching) is applied to a GPM coded video unit (e.g., a partition/subblock of an entire block, or an entire block) may be dependent on coding information, such as the partitioning shape of the geometric partitioning merge mode (e.g., merge_gpm_partition_idx).1) Alternatively, whether a motion refinement is applied to a GPM coded video unit may be dependent on the partition angle/direction (e.g., angleIdx) derived from the partitioning shape of the geometric partitioning merge mode.2) Alternatively, whether a partition angle/direction (e.g., angleIdx) derived from a partitioning shape of the geometric partitioning merge mode is applicable may be dependent on whether a motion refinement is applied to a GPM coded video unit.a) For example, signaling of partition angle/direction may depend on whether a motion refinement is applied to a GPM coded video unit.3) Alternatively, whether a motion refinement is applied to a GPM coded video unit is dependent on the partition distance (e.g., distanceIdx) derived from the partitioning shape of the geometric partitioning merge mode.4) For example, the signalling of motion refinement related syntax elements may be dependent on the partitioning shape, and/or partition angle, and/or partition distance of the geometric partitioning merge mode.a) For example, the motion refinement related syntax element may be a flag indicating whether a video unit is using motion refinement.b) For example, the motion refinement related syntax elements may be those syntax elements indicate how a video unit uses motion refinement.c) For example, for certain partitioning shapes (and/or certain partition angles, and/or certain partition distances), GPM motion refinement related syntax elements may be not allowed to be signalled for GPM coded blocks.9. In one example, in case that a motion refinement (e.g., template matching, TM, MMVD, bilateral matching) is allowed to be applied to a GPM coded block, the signaling of the usage of motion refinement may be follow a style of a two-level signaling.1) For example, the two-level signalling may be constructed from a first syntax element (e.g., a flag) indicating whether a motion refinement is applied to the whole GPM block, followed by a second syntax element (e.g., a flag) indicating whether a motion refinement is applied to the first part of the GPM block, and a third syntax element (e.g., a flag) indicating whether a motion refinement is applied to the second part of the GPM block.2) For example, the signalling of the second and the third syntax elements are conditioned based on the value of the first syntax element.a) For example, if the first syntax element indicates that a motion refinement is not applied to the GPM block, then the second and the third syntax elements are not signalled and inferred to be equal to a default value (e.g., equal to 0).3) For example, the signalling of the third syntax element is conditioned based on the value of the first and the second syntax elements.a) For example, if the first syntax element indicates that a motion refinement is applied to the GPM block and the second syntax element indicates that a motion refinement is not applied to the first part of the GPM block, then the third syntax elements is not signalled and inferred to be equal to a default value (e.g., equal to 0).10. Whether a motion refinement (e.g., template matching, TM, MMVD, bilateral matching) is allowed to be applied to a GPM coded block may be signaled in VPS/SPS/PPS/picture header/slice header or any other video unit higher than a block level.11. For example, if a pruning process is applied during a merge list construction (e.g., GPM merge list generation), new candidates may be filled to the merge list if the length of the merge list is shorter than a certain value (e.g., a signaled value, or, a predefined value).1) For example, a new candidate may be generated by a weighted sum of the first X (such as X=2) available candidates in the merge list.a) For example, average weighting may be used.b) For example, non-average weighting may be used.c) For example, the weighting factors may be pre-defined.d) For example, what weighting factors are used may be based on syntax elements (such as syntax flag or syntax variable).i. For example, K sets of weights are pre-defined, and a syntax variable is signaled for the video unit to specify which set of weights are used for the video unit.2) For example, a new candidate may be filled only if it is similar to its preceding M candidates in the merge list.a) For example, M is equal to all the available candidates in the merge list.b) For example, M is a fixed number, such as M=1.c) For example, “similar” means the difference of their motion vectors is smaller than a threshold.d) For example, “similar” means they are pointing to a same reference picture.e) For example, “similar” means identical (such as same motion vector to its preceding candidate, and/or same reference picture to its preceding candidate).3) Alternatively, a new candidate may be filled only if it is different to its preceding M candidates in the merge list.a) For example, “different” means the difference of their motion vectors is greater than a threshold.b) For example, “different” means they are pointing to different reference pictures.12. For example, in case that MMVD is applied to a video block, the relationship between a signalled MMVD step/distance/direction index and an interpreted/mapped MMVD step/distance/direction may follow one or more of below rules:1) For example, a larger MMVD step/distance index may not specify a longer mmvd step/distance.a) Similarly, a smaller MMVD step/distance index may not specify a shorter mmvd step/distance.2) For example, the mapping relationship between a signalled MMVD step/distance/direction index and an interpreted/mapped MMVD step/distance/direction may be defined by two-layer mapping table.a) For example, a first mapping table specifies the corresponding relationship between a signalled MMVD step/distance/direction index and a mapped MMVD step/distance/direction index, and a second mapping table specifies the corresponding relationship between a mapped MMVD step/distance/direction index and an interpreted/mapped MMVD step/distance/direction.3) For example, binarization of MMVD step/distance/direction index may be based on a converted MMVD step/distance/direction index.a) For example, the converted MMVD step/distance/direction index is decoded and then convert back to derive an interpreted/mapped MMVD step/distance/direction for latter use.b) For example, an MMVD step/distance/direction index equal to X may be converted to Y for binarization.c) For example, X and Y are integers.d) For example, not all of the possible MMVD step/distance/direction indexes are converted to another value for binarization.e) For example, the first K MMVD step/distance/direction indexes are converted to other values for binarization.f) For example, the value of K1-th MMVD step/distance/direction index and the value of K2-th MMVD step/distance/direction index are exchanged for binarization.

On Multiple Motion Refinements Allowable for a Video Unit

13. In one example, more than one motion refinement process (e.g., template matching, TM, or MMVD) may be applied to a video unit coded with a certain mode X.1) For example, the X is GPM.2) For example, the X is CIIP.3) For example, the X is intra mode.4) For example, the X is IBC.5) For example, SPS/PPS/PH/SH/slice level syntax elements may be signaled to indicate which kind of motion refinement process (e.g., TM or MMVD) is allowed to be applied to the video unit.6) For example, the syntax elements may be conditioned on the coded information of the video unit.a) For example, the coded information may be the Width and/or Height of the video unit.b) For example, if the Width and/or Height of the video unit meet a condition, then a first type motion refinement is applied, otherwise, a second type of motion refinement is applied.i. For example, the first type of motion refinement is template matching.ii. For example, the second type of motion refinement is MMVD.7) In one example, a syntax element may be signaled to indicate which kind of motion refinement process is used.14. In one example, the merge index coding of an INTER merge based coding mode may depend on which or whether a motion refinement (e.g., template matching, TM, MMVD, bilateral matching) is applied to the video unit.1) For example, the binarization of the merge index may be dependent on which motion refinement is used to the video unit.2) For example, in case that a merge candidate is allowed to be further refined by a motion refinement of any of {method_A, method_B, method_C, . . . }, the maximum allowed merge candidate numbers may be different from different refinement methods.a) For example, if a merge block is coded with method_A, the merge index is coded with a binarization cMax value equal to a number LEN_A; otherwise, if a merge block is coded with method_B, the merge index is coded with a binarization cMax value equal to a number LEN_B; otherwise, if a merge block is coded with method_C, the merge index is coded with a binarization cMax value equal to a number LEN_C; and etc.3) For example, in case that a merge candidate is allowed to be either coded with a motion refinement or without a motion refinement, the maximum allowed merge candidate numbers may be different from the coding methods (e.g., with or without motion refinement).a) For example, if a merge coded block is not using a motion refinement (e.g., a merge mode without template matching), the merge index is coded with a binarization cMax value equal to a number X1; otherwise (a merge coded block is coded using a template matching), the merge index is coded with a binarization cMax value equal to a number X 2, wherein X1!=X2.4) Alternatively, whether and/or how to apply motion refinement may depend on the merge index.15. In one example, in case that a template matching based motion refinement is allowed for a video unit, there may be more than one type of templates allowed for the video unit.1) For example, the type of templates may follow one or more of the following rules:a) A group of neighboring samples on the above side only.b) A group of neighboring samples on the left side only.c) A group of neighboring samples on both left and above sides.d) A group of neighboring samples coded with mode X.e) A group of neighboring samples coded with mode Y, wherein X!=Y.2) For example, which template is used for a video unit may be indicated by syntax elements.a) For example, a syntax variable may be signaled specifying which template of {Template_A, Template_B, Template_C, . . . } is used for a video block.b) For example, a syntax flag may be signalled specifying whether template A or template B is used for a video block.3) For example, which template is used for a video unit may be restricted by pre-defined rules.a) For example, the rule is dependent on the partitioning shape (and/or partition angle, and/or partition distance) of the geometric partitioning merge mode coded video unit.b) For example, the rule is dependent on the availability of neighboring samples.

General Claims

16. Whether to and/or how to apply the disclosed methods above may be signalled at sequence level/group of pictures level/picture level/slice level/tile group level, such as in sequence header/picture header/SPS/VPS/DPS/DCl/PPS/APS/slice header/tile group header.17. Whether to and/or how to apply the disclosed methods above may be signalled at PB/TB/CB/PU/TU/CU/VPDU/CTU/CTU row/slice/tile/sub-picture/other kinds of region contains more than one sample or pixel.18. Whether to and/or how to apply the disclosed methods above may be dependent on coded information, such as block size, colour format, single/dual tree partitioning, colour component, slice/picture type.

The present disclosure relates to solutions of applying a gradient-based position dependent prediction combination to the target block in a coding mode.

FIG.23illustrates a flowchart of a method2300of processing video data in accordance with some embodiments of the present disclosure. As shown inFIG.23, the method2300starts at2310, where during a conversion between a target block of a video and a bitstream of the video, a gradient-based position dependent prediction combination is applied to the target block in a coding mode. A gradient of a number of neighboring samples of the target block are used in the gradient-based position dependent prediction combination. At2320, the conversion is performed based on the applying.

The method2300applies a gradient of a number of neighboring samples of the target block in the gradient-based position dependent prediction combination, which enhances the flexibility of use gradient-based position dependent prediction combination and the improves the quality of the conversion.

In some embodiments, a value of the gradient may be determined from values of the number of neighboring samples.

In some embodiments, the number is two. It is to be understand that the example number is only for the purpose of illustration without suggesting any limitations. The number may be any suitable value.

In some embodiments, the number of neighboring samples comprise one or more available neighboring samples from above of the target block. Alternatively or in addition, the number of neighboring samples comprise one or more available neighboring samples from above-right. the number of neighboring samples comprise one or more available neighboring samples from left of the target block. the number of neighboring samples comprise one or more available neighboring samples from bottom-left of the target block.

In some embodiments, the number of neighboring samples may comprise one or more available neighboring samples along an angular prediction direction.

In some embodiments, the coding mode may be an intra planar mode. Alternatively, the coding mode may be an intra cross-component linear model (CCLM) mode. Alternatively, the coding mode may be an inter prediction mode.

In some embodiments, the coding mode comprises an intra planar mode and the number of neighboring samples comprise left, top and top-left neighboring samples.

In some embodiments, the coding mode comprises an inter prediction mode and the number of neighboring samples comprise left, top and/or top-left neighboring samples.

In some embodiments, information of whether to and/or how to apply the gradient-based position dependent prediction combination is indicated at any suitable level. By way of example, the information is indicated at sequence level. Alternatively, the information also may be indicated at group of pictures level. Alternatively, the information also may be indicated at picture level. Alternatively, the information also may be indicated at slice level. Alternatively, the information also may be indicated at tile group level.

In some embodiments, information of whether to and/or how to apply the gradient-based position dependent prediction combination may be signalled/represented in any suitable forms. By way of examples, the information is included in a VPS. Alternatively, the information is included in an SPS. Alternatively, the information is included in a PPS. Alternatively, the information is included in a DPS. Alternatively, the information is included in a DCI. Alternatively, the information is included in an APS. Alternatively, the information is included in a sequence header. Alternatively, the information is included in a picture header. Alternatively, the information is included in a sub-picture header. Alternatively, the information is included in a slice header. Alternatively, the information is included in a tile group header.

In some embodiments, information of whether to and/or how to apply the gradient-based position dependent prediction combination may be indicated at any suitable region. By way of examples, the information is indicated at a PB. Alternatively, the information is indicated at a TB. Alternatively, the information is indicated at a CB. Alternatively, the information is indicated at a PU. Alternatively, the information is indicated at a TU. Alternatively, the information is indicated at a CU. Alternatively, the information is indicated at a VPDU. Alternatively, the information is indicated at a CTU.

Alternatively, the information is indicated at a CTU row. Alternatively, the information is indicated at a slice. Alternatively, the information is indicated at a tile. Alternatively, the information is indicated at a sub-picture.

In some embodiments, the method2300further comprises determining whether and/or how the gradient-based position dependent prediction combination is applied based on coded information of the target block. In some embodiments, the coded information may comprise any suitable information. In one example, the coded information is a block size. Alternatively, in a further example, the coded information is a colour format. In another example, the coded information is a single/dual tree partitioning. Alternatively, the information may be other suitable, such as, a colour component, a slice type, or a picture type.

In some embodiments, the conversion may include encoding the target block into the bitstream.

In some embodiments, the conversion may include decoding the target block from the bitstream.

FIG.24illustrates a flowchart of a method2400of processing video data in accordance with some embodiments of the present disclosure. As shown inFIG.24, the method2400starts at2410, where during a conversion between a target block of a video and a bitstream of the video, one or more hypotheses of the target block by using a prediction mode with more than one hypothesis is determined based on one or more neighboring prediction or reconstruction samples outside the target block. At block2420, the conversion is performed based on the one or more hypotheses.

The method2400applies improper coding information of the target block in the gradient-based position dependent prediction combination, which enhance the flexibility of use gradient-based position dependent prediction combination and the improve the quality of the conversion.

Implementations of the present disclosure can be described in view of the following clauses, the features of which can be combined in any reasonable manner.

In some embodiments, the prediction mode with more than one hypothesis may be a multi-hypothesis prediction (MHP) mode. Alternatively, the prediction mode with more than one hypothesis may be an overlapped block motion compensation (OBMC) mode. Alternatively, the prediction mode with more than one hypothesis may be a multi-hypothesis prediction (MHP) mode. Alternatively, the prediction mode with more than one hypothesis may be a geometric partitioning mode (GPM). Alternatively, the prediction mode with more than one hypothesis may be a combination of intra and inter predication (CIIP) mode.

In some embodiments, the one or more hypotheses of the target block may be determined in an intra prediction mode taking use of neighboring samples.

In some embodiments, the intra prediction mode may be an intra planar mode. Alternatively, the intra prediction mode may be an intra direct currency (DC) mode. Alternatively, the intra prediction mode may be an intra angular prediction mode. Alternatively, the intra prediction mode may be an intra derived mode (DM). Alternatively, the intra prediction mode may be an intra linear model (LM).

In some embodiments, the one or more hypotheses of the target block may be determined in an inter prediction mode taking use of neighboring prediction or reconstruction samples.

In some embodiments, the inter prediction mode comprises at least one of mode, including but not limited to, an inter local illumination compensation (LIC) mode, an inter overlapped block motion compensation (OBMC) mode, an inter template matching mode or an inter filtering mode using neighboring samples.

In some embodiments, the one or more hypotheses of the target block may comprise at least a hypothesis of a target unit of the target block.

In some embodiments, the method2400comprises determining the one or more neighboring samples to be used to obtain the hypothesis of the target unit based on coded information of the target unit.

In some embodiments, the coded information comprises an intra angular mode applied to the target unit, and the one or more neighboring samples comprise at least one neighboring sample to be used for the target unit. The at least one neighboring sample is different from neighboring samples for a further unit of the video other than the target block.

In some embodiments, the target unit may comprise a subblock or a partition of the target block.

In some embodiments, target unit may comprise a hypothesis of a plurality of hypotheses of the target block.

In some embodiments, the coded information of the targe unit may comprise coded information of the hypothesis of the target unit, the coded information of the hypothesis indicating that a prediction direction is from left and/or above, and the one or more neighboring samples may comprise more than one left and/or above neighboring sample grouped together to construct a template for prediction samples of the hypothesis.

In some embodiments, the hypothesis of the target unit may be determined in an intra mode.

In some embodiments, whether the one or more neighboring samples are used to obtain the hypothesis of the target unit may be determined based on coded information of the target unit.

In some embodiments, the coded information of the target unit comprises availability of the one or more neighboring samples. Alternatively or in addition, the coded information of the target unit comprises availability of the one or more neighboring samples. Alternatively or in addition, the coded information of the target unit comprises at least one of a partitioning shape, a partition angle or a direction associated with the target unit.

In some embodiments, the target unit may comprise a partition or subblock of the target block, a hypothesis of a plurality of hypotheses of the target block, or the target block.

In some embodiments, the target unit may comprise a partition or subblock of the target block or a hypothesis of a plurality of hypotheses of the target block in a geometric partitioning merge mode, and the one or more neighboring samples may comprise left and/or above neighboring samples.

In some embodiments, the coded information of the target unit may comprise a partitioning shape of the geometric partitioning merge mode, and whether the left and/or above neighboring samples are used for prediction samples of the hypothesis may be determined based on the partitioning shape of the geometric partitioning merge mode.

In some embodiments, the partitioning shape of the geometric partitioning merge mode may be indicated by an index for merge GPM partition, for example, merge_gpm_partition_idx.

In some embodiments, the coded information of the target unit may comprise a partition angle of the geometric partitioning merge mode, and whether the left and/or above neighboring samples are used for prediction samples of the hypothesis may be determined based on the partition angle of the geometric partitioning merge mode.

In some embodiments, the partition angle of the geometric partitioning merge mode may be derived from a partitioning shape of the geometric partitioning merge mode.

In some embodiments, the partition angle of the geometric partitioning merge mode may be indicated by an index for angle, such as angleIdx.

In some embodiments, the coded information of the target unit may comprise a partition distance of the geometric partitioning merge mode, and whether the left and/or above neighboring samples are used for prediction samples of the hypothesis may be determined based on the partition distance of the geometric partitioning merge mode.

In some embodiments, the partition distance of the geometric partitioning merge mode may be derived from a partitioning shape of the geometric partitioning merge mode.

In some embodiments, the partition distance of the geometric partitioning merge mode may be indicated by an index for distance, such as distanceIdx.

In some embodiments, information of whether to and/or how to obtain the one or more hypotheses of the target block based on the one or more neighboring samples may be signalled/represented in any suitable forms. By way of examples, the information is included in a VPS. In another example, the information is included in an SPS. In a still further example, the information is included in a PPS. Or, the information is included in a DPS. Alternatively, the information is included in a DCI. As a further alternative, the information is included in an APS. In some other alternative embodiments, the information may be included in some kinds of headers, for example, a sequence header, a picture header, a sub-picture header, a slice header, a tile group header, and/or the like.

In some embodiments, information of whether to and/or how to obtain the one or more hypotheses of the target block based on the one or more neighboring samples may be indicated at any suitable region. By way of examples, the information is indicated at a PB. Alternatively, the information is indicated at a TB. Alternatively, the information is indicated at a CB. Alternatively, the information is indicated at a PU. Alternatively, the information is indicated at a TU. Alternatively, the information is indicated at a CU. Alternatively, the information is indicated at a VPDU. Alternatively, the information is indicated at a CTU. Alternatively, the information is indicated at a CTU row. Alternatively, the information is indicated at a slice. Alternatively, the information is indicated at a tile. Alternatively, the information is indicated at a sub-picture.

In some embodiments, the method further comprises determining whether and/or how the one or more hypotheses of the target block are determined based on coded information of the target block. In some embodiments, the coded information may comprise any suitable information. In one example, the coded information is a block size. Alternatively, in a further example, the coded information is a colour format. In another example, the coded information is a single/dual tree partitioning. Alternatively, the information may be other suitable, such as, a colour component, a slice type, or a picture type.

In some embodiments, the conversion may include encoding the target block into the bitstream.

In some embodiments, the conversion may include decoding the target block from the bitstream.

Implementations of the present disclosure can be described in view of the following clauses, the features of which can be combined in any reasonable manner.

Clause 1. A method for video processing, comprising: applying, during a conversion between a target block of a video and a bitstream of the video, a gradient-based position dependent prediction combination to the target block in a coding mode, a gradient of a number of neighboring samples of the target block being used in the gradient-based position dependent prediction combination; and performing the conversion based on the applying.

Clause 2. The method of clause 1, wherein a value of the gradient is determined from values of the number of neighboring samples.

Clause 3. The method of clause 2, wherein the number is two.

Clause 4. The method of clause 1 or 2, wherein the number of neighboring samples comprise one or more available neighboring samples from above, above-right, left and/or bottom-left of the target block.

Clause 5. The method of clause 1 or 2, wherein the number of neighboring samples comprise one or more available neighboring samples along an angular prediction direction.

Clause 6. The method of any of clauses 1-5, wherein the coding mode is one of the following: an intra planar mode, an intra cross-component linear model (CCLM) mode, or an inter prediction mode.

Clause 7. The method of any of clauses 1 or 2, wherein the coding mode comprises

an intra planar mode, and the number of neighboring samples comprise left, top and top-left neighboring samples.

Clause 8. The method of clause 1 or 2, wherein the coding mode comprises an inter prediction mode, and the number of neighboring samples comprise left, top and/or top-left neighboring samples.

Clause 9. The method of any of clauses 1-8, wherein information of whether to and/or how to apply the gradient-based position dependent prediction combination is indicated at one of the following: a sequence level, a picture group level, a picture level, a slice level ,or a tile group level.

Clause 10. The method of any of clauses 1-8, wherein information of whether to and/or how to apply the gradient-based position dependent prediction combination is included in one of the following: a sequence header, a picture header, a sequence parameter set (SPS), a video parameter set (VPS), a dependency parameter set (DPS), a decoding capability information, a picture parameter set (PPS), an adaptation parameter sets (APS), a slice header, or a tile group header.

Clause 11. The method of any of clauses 1-8, wherein information of whether to and/or how to apply the gradient-based position dependent prediction combination is included in one of the following: a prediction block (PB), transform block (TB), coding block (CB), a prediction unit (PU), a transform unit (TU), a coding unit (CU), a a virtual pipeline data unit (vDU), a coding tree unit (CTU), a CTU row, a slice, a tile, a sub-picture, or a region containing more than one sample or pixel.

Clause 12. The method of any of clauses 1-11, further comprising: determining, based on coded information of the target block, whether and/or how the gradient-based position dependent prediction combination is applied, the coded information including at least one of the following: a block size, a colour format, a single and/or dual tree partitioning, a colour component, a slice, or a picture type.

Clause 13. The method of any of clauses 1-12, wherein the conversion includes encoding the target block into the bitstream.

Clause 14. The method of any of clauses 1-12, wherein the conversion includes decoding the target block from the bitstream.

Clause 15. A method for video processing, comprising: determining, during a conversion between a target block of a video and a bitstream of the video, based on one or more neighboring prediction or reconstruction samples outside the target block, one or more hypotheses of the target block by using a prediction mode with more than one hypothesis; and performing the conversion based on the one or more hypotheses.

Clause 16. The method of clause 15, wherein the prediction mode with more than one hypothesis is one of the following: an overlapped block motion compensation (OBMC) mode, a multi-hypothesis prediction (MHP) mode, a geometric partitioning mode (GPM), or a combination of intra and inter predication (CIIP) mode.

Clause 17. The method of clause 15 or 16, wherein the one or more hypotheses of the target block are determined in an intra prediction mode taking use of neighboring samples.

Clause 18. The method of clause 17, wherein the intra prediction mode comprises at least one of an intra planar mode, an intra direct currency (DC) mode, an intra angular prediction mode, an intra derived mode (DM) or an intra linear model (LM).

Clause 19. The method of clause 15 or 16, wherein the one or more hypotheses of the target block are determined in an inter prediction mode taking use of neighboring prediction or reconstruction samples.

Clause 20. The method of clause 19, wherein the inter prediction mode comprises at least one of an inter local illumination compensation (LIC) mode, an inter overlapped block motion compensation (OBMC) mode, an inter template matching mode or an inter filtering mode using neighboring samples.

Clause 21. The method of any of clauses 15-20, wherein the one or more hypotheses of the target block comprise at least a hypothesis of a target unit of the target block.

Clause 22. The method of clause 21, further comprising: determining, based on coded information of the target unit, the one or more neighboring samples to be used to obtain the hypothesis of the target unit.

Clause 23. The method of clause 22, wherein the coded information comprises an intra angular mode applied to the target unit, and the one or more neighboring samples comprise at least one neighboring sample to be used for the target unit, the at least one neighboring sample being different from neighboring samples for a further unit of the video other than the target block.

Clause 24. The method of any of clauses 21-23, wherein the target unit comprises a subblock or a partition of the target block.

Clause 25. The method of any of clauses 21-23, wherein the target unit comprises a hypothesis of a plurality of hypotheses of the target block.

Clause 26. The method of clause 22, wherein the coded information of the targe unit comprises coded information of the hypothesis of the target unit, the coded information of the hypothesis indicating that a prediction direction is from left and/or above, and the one or more neighboring samples comprise more than one left and/or above neighboring sample grouped together to construct a template for prediction samples of the hypothesis.

Clause 27. The method of clause 26, wherein the hypothesis of the target unit is determined in an intra mode.

Clause 28. The method of clause 21, wherein whether the one or more neighboring samples are used to obtain the hypothesis of the target unit is determined based on coded information of the target unit.

Clause 29. The method of clause 28, wherein the coded information of the target unit comprises at least one of the following: availability of the one or more neighboring samples , or at least one of a partitioning shape, a partition angle or a direction associated with the target unit.

Clause 30. The method of clause 29, wherein the target unit comprises a partition or subblock of the target block, a hypothesis of a plurality of hypotheses of the target block, or the target block.

Clause 31. The method of clause 29 or 30, wherein the target unit comprises a partition or subblock of the target block or a hypothesis of a plurality of hypotheses of the target block in a geometric partitioning merge mode, and the one or more neighboring samples comprise left and/or above neighboring samples.

Clause 32. The method of clause 31, wherein the coded information of the target unit comprises a partitioning shape of the geometric partitioning merge mode, and wherein whether the left and/or above neighboring samples are used for prediction samples of the hypothesis is determined based on the partitioning shape of the geometric partitioning merge mode.

Clause 33. The method of clause 32, wherein the partitioning shape of the geometric partitioning merge mode is indicated by an index for merge GPM partition.

Clause 34. The method of clause 31, wherein the coded information of the target unit comprises a partition angle of the geometric partitioning merge mode, and wherein whether the left and/or above neighboring samples are used for prediction samples of the hypothesis is determined based on the partition angle of the geometric partitioning merge mode.

Clause 35. The method of clause 34, wherein the partition angle of the geometric partitioning merge mode is derived from a partitioning shape of the geometric partitioning merge mode.

Clause 36. The method of clause 34, wherein the partition angle of the geometric partitioning merge mode is included in by an index for angle.

Clause 37. The method of clause 34, wherein the coded information of the target unit comprises a partition distance of the geometric partitioning merge mode, and wherein whether the left and/or above neighboring samples are used for prediction samples of the hypothesis is determined based on the partition distance of the geometric partitioning merge mode.

Clause 38. The method of clause 37, wherein the partition distance of the geometric partitioning merge mode is derived from a partitioning shape of the geometric partitioning merge mode.

Clause 39. The method of clause 37, wherein the partition distance of the geometric partitioning merge mode is indicated by an index for distance.

Clause 40. The method of any of clauses 15-39, wherein information of whether to and/or how to obtain the one or more hypotheses of the target block based on the one or more neighboring samples is included in a sequence header, a picture header, a sequence parameter set (SPS), a video parameter set (VPS), a DPS, a decoding capability information (DCI), a picture parameter set (PPS), an adaptation parameter sets (APS), a slice header and/or a tile group header.

Clause 41. The method of any of clauses 15-39, wherein information of whether to and/or how to obtain the one or more hypotheses of the target block based on the one or more neighboring samples is included in one of the following: a prediction block (PB), a transform block (TB), a coding block (CB), a prediction unit (PU), a transform unit (TU), a coding unit (CU), a virtual pipeline data unit (VPDU), a coding tree unit (CTU), a CTU row, a slice, a tile, a sub-picture, or a region containing more than one sample or pixel.

Clause 42. The method of any of clauses 15-41, further comprising: determining, based on coded information of the target block, whether and/or how the one or more hypotheses of the target block are determined, the coded information including at least one of the following: a block size, a colour format, a single and/or dual tree partitioning, a colour component, a slice, or a picture type.

Clause 43. The method of any of clauses 15-42, wherein the conversion includes encoding the target block into the bitstream.

Clause 44. The method of any of clauses 15-42, wherein the conversion includes decoding the target block from the bitstream.

Clause 45. An apparatus for processing video data comprising a processor and a non-transitory memory with instructions thereon, wherein the instructions upon execution by the processor, cause the processor to perform a clause in accordance with any of claims 1-14 or claims 15-44.

Clause 46. A non-transitory computer-readable storage medium storing instructions that cause a processor to perform a clause in accordance with any of claims 1-14 or claims 15-44.

Clause 47. A non-transitory computer-readable recording medium storing a bitstream of a video which is generated by a clause performed by a video processing apparatus, wherein the clause comprises: applying a gradient-based position dependent prediction combination to a target block of the video in a coding mode, a gradient of a number of neighboring samples of the target block being used in the gradient-based position dependent prediction combination; and generating the bitstream based on the applying of the gradient-based position dependent prediction combination.

Clause 48. A clause for storing a bitstream of a video, comprising: applying a gradient-based position dependent prediction combination to a target block of the video in a coding mode, a gradient of a number of neighboring samples of the target block being used in the gradient-based position dependent prediction combination; generating the bitstream based on the applying of the gradient-based position dependent prediction combination; and storing the bitstream in a non-transitory computer-readable recording medium.

Clause 49. A non-transitory computer-readable recording medium storing a bitstream of a video which is generated by a clause performed by a video processing apparatus, wherein the clause comprises: determining, based on one or more neighboring prediction or reconstruction samples outside a target block of the video, one or more hypotheses of the target block by using a prediction mode with more than one hypothesis; and generating the bitstream based on the one or more hypotheses of the target block.

Clause 50. A clause for storing a bitstream of a video, comprising: determining, based on one or more neighboring prediction or reconstruction samples outside a target block of the video, one or more hypotheses of the target block by using a prediction mode with more than one hypothesis; generating the bitstream based on the one or more hypotheses of the target block; and storing the bitstream in a non-transitory computer-readable recording medium.

Example Device

FIG.25illustrates a block diagram of a computing device2500in which various embodiments of the present disclosure can be implemented. The computing device2500may be implemented as or included in the source device110(or the video encoder114or200) or the destination device120(or the video decoder124or300).

It would be appreciated that the computing device2500shown inFIG.25is merely for purpose of illustration, without suggesting any limitation to the functions and scopes of the embodiments of the present disclosure in any manner.

As shown inFIG.25, the computing device2500includes a general-purpose computing device2500. The computing device2500may at least comprise one or more processors or processing units2510, a memory2520, a storage unit2530, one or more communication units2540, one or more input devices2550, and one or more output devices2560.

In some embodiments, the computing device2500may be implemented as any user terminal or server terminal having the computing capability. The server terminal may be a server, a large-scale computing device or the like that is provided by a service provider. The user terminal may for example be any type of mobile terminal, fixed terminal, or portable terminal, including a mobile phone, station, unit, device, multimedia computer, multimedia tablet, Internet node, communicator, desktop computer, laptop computer, notebook computer, netbook computer, tablet computer, personal communication system (PCS) device, personal navigation device, personal digital assistant (PDA), audio/video player, digital camera/video camera, positioning device, television receiver, radio broadcast receiver, E-book device, gaming device, or any combination thereof, including the accessories and peripherals of these devices, or any combination thereof. It would be contemplated that the computing device2500can support any type of interface to a user (such as “wearable” circuitry and the like).

The processing unit2510may be a physical or virtual processor and can implement various processes based on programs stored in the memory2520. In a multi-processor system, multiple processing units execute computer executable instructions in parallel so as to improve the parallel processing capability of the computing device2500. The processing unit2510may also be referred to as a central processing unit (CPU), a microprocessor, a controller or a microcontroller.

The computing device2500typically includes various computer storage medium. Such medium can be any medium accessible by the computing device2500, including, but not limited to, volatile and non-volatile medium, or detachable and non-detachable medium. The memory2520can be a volatile memory (for example, a register, cache, Random Access Memory (RAM)), a non-volatile memory (such as a Read-Only Memory (ROM), Electrically Erasable Programmable Read-Only Memory (EEPROM), or a flash memory), or any combination thereof. The storage unit2530may be any detachable or non-detachable medium and may include a machine-readable medium such as a memory, flash memory drive, magnetic disk or another other media, which can be used for storing information and/or data and can be accessed in the computing device2500.

The computing device2500may further include additional detachable/non-detachable, volatile/non-volatile memory medium. Although not shown inFIG.25, it is possible to provide a magnetic disk drive for reading from and/or writing into a detachable and non-volatile magnetic disk and an optical disk drive for reading from and/or writing into a detachable non-volatile optical disk. In such cases, each drive may be connected to a bus (not shown) via one or more data medium interfaces.

The communication unit2540communicates with a further computing device via the communication medium. In addition, the functions of the components in the computing device2500can be implemented by a single computing cluster or multiple computing machines that can communicate via communication connections. Therefore, the computing device2500can operate in a networked environment using a logical connection with one or more other servers, networked personal computers (PCs) or further general network nodes.

The input device2550may be one or more of a variety of input devices, such as a mouse, keyboard, tracking ball, voice-input device, and the like. The output device2560may be one or more of a variety of output devices, such as a display, loudspeaker, printer, and the like. By means of the communication unit2540, the computing device2500can further communicate with one or more external devices (not shown) such as the storage devices and display device, with one or more devices enabling the user to interact with the computing device2500, or any devices (such as a network card, a modem and the like) enabling the computing device2500to communicate with one or more other computing devices, if required. Such communication can be performed via input/output (I/O) interfaces (not shown).

The computing device2500may be used to implement video encoding/decoding in embodiments of the present disclosure. The memory2520may include one or more video coding modules2525having one or more program instructions. These modules are accessible and executable by the processing unit2510to perform the functionalities of the various embodiments described herein.

In the example embodiments of performing video encoding, the input device2550may receive video data as an input2570to be encoded. The video data may be processed, for example, by the video coding module2525, to generate an encoded bitstream. The encoded bitstream may be provided via the output device2560as an output2580.

In the example embodiments of performing video decoding, the input device2550may receive an encoded bitstream as the input2570. The encoded bitstream may be processed, for example, by the video coding module2525, to generate decoded video data. The decoded video data may be provided via the output device2560as the output2580.